MSD I - Final Group Report (Biomass-Powered Gas Disctrict Cooling Plant)

GROUP PROJECT REPORT MECHANICAL SYSTEM DESIGN 1 (MSD 1) JANUARY 2015 SEMESTER

BIOMASS-POWERED GAS DISTRICT COOLING PLANT DESIGN

SUPERVISOR: IR. KAMARUDDIN SHEHABUDDIN

GROUP MEMBERS

MATRIX ID

1. MUHAMMAD ZULFAQQAR BIN MOHD KASIM

14367

2. MUHAMMAD AMIR ADLI BIN NAZARUDIN

16831

3. RAZIN AKMAL B RUSLAN

16931

4. KU MUHAMMAD FAEZ BIN KU ARIFFIN

16917

5. CHOONG WENG HONG

16777

Table of Content Content 1.

2.

3.

Page

Introduction

1

1.1

Overview

1

1.2

Project Background

2

1.3

Problem Statement

3

1.4

Project Objectives

4

1.5

Scope of Project

4

1.5

Selected Datum – KLIA GDC plant

5

Methodology

9

2.1

10

Design Process Diagram

Concept Generation

11

3.1

Physical Decomposition of Biomass-powered GDC plant

11

3.2

Functional Decomposition of Biomass-powered GDC plant

12

3.3

Morphology Chart

13

3.4

Concept Generated (all members)

17

3.4.1

Design Concept (Concept 1: Zulfaqqar’s)

17

3.4.2

Justification of the chosen system (Concept 1: Zulfaqqar’s)

18

3.4.3

Concept sketch (Concept 1: Zulfaqqar’s)

20

3.5.1

Design Concept (Concept 2: Adli’s)

21

3.5.2

Justification of the chosen system (Concept 2: Adli’s)

22

3.5.3

Concept sketch (Concept 2: Adli’s)

24

3.6.1

Design Concept (Concept 1: Razin’s)

25

i

4.

3.6.2

Justification of the chosen system (Concept 2: Razin’s)

26

3.6.3

Concept sketch (Concept 2: Razin’s)

28

3.7.1

Design Concept (Concept 1: Faez’s)

29

3.7.2

Justification of the chosen system (Concept 2: Faez’s)

30

3.7.3


32

3.8.1

Design Concept (Concept 1: Choong’s)

33

3.8.2

Justification of the chosen system (Concept 2: Choong’s)

34

3.8.3


36

Concept Evaluation

11

4.1.1

37

Fuel Supply & Pre-Treatment System Objective Tree and Decision Matrix

4.1.2

Justification (Fuel Supply & Pre-Treatment system)

39

4.2.1

Co-combustion System Objective Tree and Decision Matrix

41

4.2.2

Justification (Co-combustion system)

43

4.3.1

Co-generation System Objective Tree and Decision Matrix

45

4.3.2

Justification (Co-generation system)

47

4.4.1

Heat Recovery System Objective Tree and Decision Matrix

48

4.4.2

Justification (Heat Recovery system)

50

4.5.1

Refrigeration System Objective Tree and Decision Matrix

51

4.5.2

Justification (Refrigeration system)

53

4.6.1

Heat Rejection System Objective Tree and Decision Matrix

55

4.6.2

Justification (Heat Rejection system)

57

ii

5.

6.

Selected Concept

59

5.1

Winning Concept

59

5.2

Winning concept’s sketch (Faez’s)

62

5.3

Subsystems for winning concept

63

Detailed Selected Concept’s Working Principle

65

6.1

Overall system’s working principle

65

6.2

Subsystem’s working principle

67

6.2.1

Working principle (Drying of Biomass)

67

6.2.2

Working principle (Indirect co-firing)

69

6.2.3

Working principle (Gas turbine)

71

6.2.4

Working principle (Heat Recovery Steam Generator)

72

6.2.5

Working principle (Absorption chiller)

74

6.2.6

Working principle (Induced Draft Cross Flow Cooling Tower)

76

6.3

7.

Peer evaluation of the selected concept 6.3.1

Zul’s evaluation

78

6.3.2

Adli’s evaluation

80

6.3.3

Razin’s evaluation

81

6.3.4

Faez’s evaluation

82

6.3.5

Choong’s evaluation

84

Governing Equation

86

7.1

Gasification

86

7.2

Closed-cycle Gas Turbine

86

7.3

Absorption Chiller

88

iii

8.

Conclusion

89

9.

References

91

List of Figures Figures

Page

Figure 1: KLIA GDC Plant (rear entrance)

7

Figure 2: KLIA GDC Plant (main entrance)

8

Figure 3: KLIA GDC Plant (storage tank and chimneys in view)

8

Figure 4: Physical Decomposition of the Biomass-powered GDC system

11

Figure 5: Functional Decomposition of the Biomass-powered GDC system

12

Figure 6: Rotary dryers operation flow for biomass drying

68

Figure 7: Schematic Diagram of Gasifier

69

Figure 8: Working principle of basic gas turbine

71

Figure 9: Components of HRSG

73

Figure 10: Absorption Chiller

74

Figure 11: Absorption Chiller process

75

Figure 12: Example of fill which being used in the cooling tower

76

Figure 13: Induced Draft Cross Flow Cooling Tower

76

Figure 14: Fan being setup on top of the cooling tower

77

iv

List of Tables Table

Page

Table 1: Output capacity and demand for KLIA GDC plant

6

Table 2: Main equipment details of the KLIA GDC plant

6

Table 3: Weighted decision matrix for Fuel Supply & Pre-Treatment System

38

Table 4: Weighted decision matrix for Co-Combustion System

42

Table 5: Weighted decision matrix for Co-Generation System

46

Table 6: Weighted decision matrix for Heat Recovery System

49

Table 7: Weighted decision matrix for Refrigeration System

52

Table 8: Weighted decision matrix for Heat Rejection System

56

Table 9: Concept Selection

59

v

1.

INTRODUCTION 1.1

Overview

District Cooling is a concept in which that the central source is utilised to supply cooling to a number of buildings instead of using multiple individual cooling systems. The concept of this system starts with the production of the chilled water in a centralized plant, and the chilled water will be then distributed through a district cooling system via underground pipelines to heat exchangers within buildings to provide air cooling [9]. It is very common for the District Cooling system to be coupled along with District Heating system or/and being integrated along with the Co-Generation system to produce outputs other than chilled water. District Energy System (DES) for instance, covers both District Cooling and also District Heating as well. This system will produce and distribute both steam, as well as chilled water from a centralized plant, to individual buildings to provide space heating and cooling, domestic hot water, and also industrial process energy [22]. By having DES, boilers and chillers will no longer have to be installed in individual buildings and hence could eliminate costs of installing and maintaining those individual chillers and boilers. This kind of system was widely used in countries/regions which are experiencing winter as well as summer season. Meanwhile, the Co-Generation system which also known as Combined Heat and Power (CHP) system produces both electric supply and also heat supply, from one fuel source [2]. The electrical output produced will be distributed via national grid network for domestic use or will be directly used by plants/facilities such as universities, airports, government buildings, etc. On the other hand, the heat produced by this Co-Generation system will then be used to generate steam via Heat Recovery Steam Generators (HRSGs) and the steam produced will be passed through the Absorption Chiller as part of the District Cooling system to produce chilled water. The chilled water produced will then be distributed to individual buildings for space cooling and air conditioning. This system is much more commonly used and existed in most District Cooling Plants. Depending on the type of turbine used, the Co-Generation system is quite flexible in terms of the usage of fuel. Gas turbines in the Co-Generation system is mainly utilising natural gas as its main fuel but it could also use other type of fuel as backup during emergency (fuel depletion) such as the Jet A1 fuel [17] and also Methane gas. 1

Biomass system meanwhile, is renewable and sustainable system which produces/utilizes fuel out of organic materials that are readily available such as the agricultural by-products, forest debris, and etc. [22]. The most common types of Biomass systems are; Direct-fire Biomass system, and also the Biomass Gasification system. For the Direct-fire Biomass system, the biomass fuel (from organic materials) will be burned in a boiler to produce a high-pressured steam which will then be used to power the steam turbinepowered electrical generator. There are also many other applications which utilizes the steam output from the Direct-fire Biomass system such as for space cooling, space heating, and also as the process heat for industrial purposes [19]. Differing to the Direct-fire Biomass system, the Biomass gasification system is basically a means to create fuel (in the form of flammable gas) out of the raw Biomass source. It starts by heating up the biomass in the environment in which the solid Biomass breaks down to form a flammable gas [11]. The flammable gas produced (i.e. Methane) will then could be used for domestic purposes such as cooking and heating, or as the fuel source for electric generation, or could also be used as the synthetic gas for producing a higher quality fuels or chemical products such as Methanol and Hydrogen.

1.2

Project Background

This project is mainly to propose a design of the GDC plant which utilizes Biomass as its main fuel source. The designed GDC plant is supposed to have two useful outputs which is the electricity and chilled water which will be used internally (not to be supplied to the outside grid network and also buildings outside the complex). As for the reference for this project (datum), Kuala Lumpur International Airport (KLIA) GDC plant under the care of Gas District Cooling (M) Sdn. Bhd. (subsidiary of PETRONAS) will be taken as datum, and the design will be made mostly in reference to it. All the design specifications and the design capacity will be referred to the datum chosen (KLIA GDC plant). Additionally, this project will also be comparing some advantages and disadvantages of having a Biomass-powered GDC to the gas-powered GDC plant and to the conventional individual, non-centralized cooling system. The comparison will cover the scopes of energy efficiency, cost efficiency, ease of maintainability, environmental effects and also the fuel availability (for Biomass GDC plant and conventional GDC plant). 2

Flexibility was given in deciding which components/subsystems to be incorporated inside the design of the plant in order to achieve the best ever solution in terms of cost and efficiency. The end product of the design will not necessarily be the same as the datum chosen earlier and it may have certain improvements in any form of aspects. In this project, each team members were given a chance to come up with their own concepts with their own justification, and later, the suggested designs will be evaluated using design concept generation tools to see which design is the best as a whole.

1.3

Problem Statement

For this project, there are several issues regarding the current conventional GDC plant and also the individual, non-centralized cooling system which we had found and will be taken into focus to set our design objectives. The issues are as follows; •

Maintenance issue In the individual, non-centralized cooling system, all the components for the cooling system were installed in the individual building, only for the usage of that particular building alone. If there are 20 buildings in the complex, it means that there will be 20 individual systems installed in each and every building. Having to maintain 20 separate cooling systems will costs a huge money, and massive waste of time and energy. So, to address this issue, a centralized cooling system needed to be utilized in the design.

•

Cost issue A conventional gas-powered GDC plant commonly use natural gas (Liquified Petroleum Gas) as the main source of fuel to power the plant. With ever increasing price of petroleum-based fuel and also the fact that it is non-renewable, the cost of running a conventional gas-powered GDC plant will be increasing by time to time. Hence, cheaper and renewable alternatives for the natural gas must be incorporated into the design of a GDC in order to provide a means of reducing the running cost of the currently available GDC plant and at the same time maintaining/improve the level efficiency of the GDC system.

3

•

Environmental effect Commonly, a conventional GDC plant will be using natural petroleum gas as the fuel to power up the gas turbine. It was known that the usage of natural petroleum gas will somehow contribute in the depletion of fossil fuel, especially within a plant which will consume a huge amount of fuel to produce power. On top of that, utilising a fossil fuel will produce by-products that are harmful to environment. Due to these concerns, it is very vital to have a design of GDC plant which utilizes alternative fuel that is clean and renewable as a source to generate power and to produce chilled water for cooling purposes.

1.4

Project objectives

There are several objectives set for this design project. Those objectives are; •

To produce a Biomass-powered GDC design that has a better or comparable output compared to conventional GDC.

•

To design a cost-efficient Biomass-powered GDC plant throughout its service in terms of maintenance costs and also in terms of fuel cost.

•

To produce a cleaner Biomass-powered GDC by utilising a renewable alternative source of fuel.

1.5

Scope of project

The project will be focusing on the usage of GDC within Malaysian region and all the requirements, supply and demand data, required specifications will be made according to the Malaysian environment. As mentioned earlier in Project Background part, KLIA GDC plant will be taken as the reference/datum for this design project, and all the outputs, projected performance and specifications of the Biomass-powered GDC plant to be designed will be referred and compared to it (KLIA GDC plant).

4

Due to time, knowledge and resource limitation, this project will only be focusing onto 6 out of many critical subsystems of the Biomass GDC Plant. There will be lists of options of subsystem types to be chosen as design concepts and all of the team members will be having their individual personal design concepts which will be justified accordingly according to the concept’s pro and cons. All the preliminary personal design concepts will be evaluated one after another until a decision can be made on which of the design concept the best is using the evaluation tool such as Pugh’s Evaluation matrix. The best Biomass GDC plant concept design will be chosen as the design of choice.

1.6

Selected datum – KLIA GDC Plant To design a GDC plant that is excellent in terms of its efficiency and reliability, a

datum of an established system must be taken into account as reference. Hence, this design project had chosen the Kuala Lumpur International Airport (KLIA) GDC plant as the datum. This GDC plant is owned, being managed, and being maintained by Gas District Cooling (M) Sdn. Bhd. which is one of the many Petroliam Nasional Berhad’s (PETRONAS) subsidiaries. Gas District Cooling (M) Sdn. Bhd. is also owns 7 other GDC plants which are serving high profile development areas within Klang Valley, Kuala Lumpur City Center (KLCC), and also in Malaysia’s Administrative centre, Putrajaya [8]. KLIA GDC plant’s customers that make use of the chilled water for their air conditioning needs include, Malaysia Airport (Sepang) Berhad (MAHB) – (For the main terminal, Administration Management Centre, Satellite A, Contact Pier, Car Park A, B, C &D complex, VVIP Engineering Complex and Custom Complex of the KLIA), Malaysia Airline System (MAS) – (Flight Crew Centre & MAS Complex), KL Airport Services (KLAS) – (KLAS Cargo & KLAS Kitchen), KL International Airport Berhad – (Air Traffic Controller), Air Asia Berhad – (Air Asia Simulator complex), Kuala Lumpur Airport Hotel Sdn. Bhd. – (Pan Pacific Hotel)[14]. Meanwhile, most of the electrical output produced by the GDC plant is being exported to the KLIA grid and small portion of it is being used internally for the plant’s equipment. All the plant’s output capacity, performance, equipment and specifications are listed at the following page.

5

Table 1: Output capacity and demand for KLIA GDC plant Type of output

Capacity

Chilled Water output

30000RT (Refrigeration Tonne – unit for cooling loading capacity) 40 MWe (34MW is distributed to the KLIA grid network and 6MW for the plant’s internal use) [10]

Electrical output

Table 2: Main equipment details of the KLIA GDC plant Equipments Co-Generation system General Electric (GE) LM2500 Gas Turbine

Remarks • 2 Units of this Gas turbine installed • Each Gas Turbines produces 20MW of power • Both Units combined produces total power of 40MW • Utilizes Natural Gas as main fuel • In case of emergency, Jet-A1 fuel can be utilized as back-up reserve fuel

Steam Generator System Heat Recovery Steam Generator (HRSG) manufactured and installed by Mechmar Sdn. Bhd.

• • • •

6

2 Units of this HRSG installed Each HRSG is capable of producing output of 40 Tonne/hr of 8 bar pressure of saturated steam Both units produces 80 Tonne/hr of saturated steam Steam produced by both HRSGs (and auxiliary boilers) is channelled to Steam Absorption Chillers to produce chilled water for cooling

Refrigeration System & Heat Rejection system Chiller plant, built by Shinryo International Corporation housing 12 units of absorption chillers, and 7 Cooling Towers

• • • • •

Single absorption chiller’s capacity is 2500 RT (12 x 2500 = 30240 RT) Produces chilled water outlet temperature of 7⁰C and the return water inlet 14⁰C Return water (from served building complexes) is reused again for steam generation Cooling Tower used is the Mechanical Towers type. The function of the cooling tower is to create condensate from the return water inlet which is used again for in HRSG for steam generation

Here are some of the pictures of the KLIA Gas District Cooling plant retrieved via Google Streetview and Google Maps;

Figure 1: KLIA GDC Plant (Rear Entrance) 7

Figure 2: KLIA GDC Plant (Main Entrance)

Figure 3: KLIA GDC Storage Tank and chimneys in view

8

2.

METHODOLOGY In carrying out the design process of the GDC plant, several methods and design tools

will be used. All of the methods and design tools are meant to assist system designers to make sure each and every aspect of design is thoroughly covered, without having anything left behind. Below are the methods and tool used in conducting the design process; a)

Taking a Datum/reference for this project This design project will be referring to an existing GDC plant, KLIA GDC plant as our datum. All of its output and specifications will be used as reference and will be compared with the Biomass-powered GDC plan to be designed. The details of the Datum chosen were presented in the part 1.6 – Selected Datum.

b)

Design Process Diagram Design process diagram functions as the reference of design steps which will be used in designing the Biomass-powered GDC plant. The Design Process Diagram will be included later in the end of this chapter.

c)

Physical and functional Decomposition of the overall system Physical Decomposition of the system will be used to help the understanding of the overall system by dividing the overall complex system into smaller chunks of subsystems or smaller group of components that are responsible to their respective functions.

d)

Morphological chart From the Physical and functional decomposition chart, lists of options of alternatives can be generated for all the subsystems determined earlier. From the lists of alternatives, several new forms of concepts of Biomass GDC plants could be made.

e)

Pugh’s Chart After having several design concepts of the Biomass GDC plants, all of the design concepts will be evaluated later on using Pugh’s Chart to determine which conceptual design is the best. The concepts generated will be compared datum set in all possible aspects to determine whether it is better or not compared to the datum.

9

2.1

Design Process Diagram (Conceptual Design)

START

Define problem: • • •

Setting problem statement Choosing the datum Determining the Plant Design Specification

Gather Information: •

Via multiple trusted sources; Internet, Patents, Technical articles, journals.

Concept Generation: • • • •

Brainstorming Functional & Physical decomposition Morphology chart Multiple individual concepts

Evaluation of Concept: • • •

Decision making Pugh Chart Decision matrix

END

10

3.

CONCEPT GENERATION

3.1

Physical Decomposition of Biomass-powered GDC system Based on the information gathered from the whole working system of the datum (KLIA GDC plant) and also from the requirement needs

for this project, decomposition of the plant was done. This decomposition will only include main systems of the plant which will be the concentrated more throughout this design project. Figure 4 and figure 5 are the physical and functional decomposition of the Biomass-powered GDC plant.

Biomass-powered GDC Plant

Fuel supply and Pretreatment system (Biomass)

Co-combustion system

Co-Generation system

(Biomass) Gas Turbine

Steam Generation system HRSG

Co-Firing Auxiliary Boiler

Figure 4: Physical Decomposition of the Biomass-powered GDC system

11

Refrigeration cycle system Absorption Chiller

Heat Rejection System Cooling Tower

Biomass

Functional Decomposition of Biomass-powered GDC

Biomass

Prepare and pretreat biomass

Combust biomass

Energy

Generate electricity and heat

Electricity

Heat

Steam Water

Steam

Generate steam

Chilled water Cooling Steam

Generate chilled water

Returned water Chilled water

Chilled water

3.2

Store and supply chilled water

Chilled water

Figure 5: Functional Decomposition of the Biomass-powered GDC system

12

3.3

Morphology chart After the physical and the functional decomposition of the whole Biomass-powered GDC system, a morphology chart was done in which

all the possible alternatives of components/systems that are possible to be included in the system is being grouped in its own subsystem classifications. All of the listed alternatives will be chosen to create several Biomass GDC plant concepts.

Subsystem Fuel Supply & Pre-Treatment System Pre-treatment of the biomass fuel (e.g.woody/herbac eous) produces upgraded quality of fuel which reduce in storage, transport and handling as well as removing impurities within the fuels.

Components & Equipment - Means/How 3

1

2

Pre-treatment of waste wood The waste wood is shredded and added with iron pieces later screened into mesh sizes. Results in wood waste with metals composition.

Balling of fuels Herbaceous fuels pressed into bales (with square or round size) using machines.

13

Pellets & Briquettes Compressing fuels into cylindrical shape by applying varying processes.

4

Drying of Biomass Reducing moisture contents of the fuels using different techniques.

5

Co-combustion system Combustion of different types of fuel (e.g coalbiomass) at the same time to improve on the combustion rate with lower emission.

Direct Co-firing Involves direct feeding of biomass to coal firing system or furnace.

Indirect Co-Firing Involves gasification of the biomass and the produced fuel gas is used for combustion in the furnace.

Parallel Co-Firing Involves combustion of biomass in different combustor and boiler. Produced steam is utilized for power generation systems.

Co-generation (CHP) system Generation of electricity and useful cooling/heating by utilizing heat engine or power station.

Steam turbines Power derived from expansion of steam to the engine driving electricity generator. Capacity power of (<120 MW).

Gas Turbines Combustion of fuel (natural gas) and air to generate power to drive electricity generator. High efficiency and capable of producing up to 120 MW.

Combined-Cycle Gas/ Steam Turbine Incorporates the gas turbine and steam turbine generating set. HRSG creates steam from exhaust gas to power steam turbine.

14

Stirling engines Main operation from cyclic compression or expansion of air/other gas to produce work. Small scale applications of 1kW to 100 kW.

Heat Recovery Steam Generators (HRSG) system Hot waste gases are passed through the heat exchanger which produces steam that is used for cogeneration or powering steam turbine.

Horizontal HRSG The gases flow horizontally with vertical coils providing natural circulation in the system. Simple design with more floor space.

Vertical HRSG The gas flow vertically with horizontal coils and has low air circulation rate that is assisted with water circulation. More compact in design.

Once-Through Steam Generators (OTSG) Advance version of HRSG without boiler drums. Water enters the coil and immediately converts to steam.

Refrigeration Cycle system Circulation of refrigerants through various cycles to absorb or reject heat creating low temperature condition.

Vapor CompressionCycle Chiller The compressor pumped the refrigerant to a condenser unit to reject heat from refrigerant to cooling water or air outside the system.

Absorption Chiller Mixture of liquid refrigerant water & absorbent with high pressure, directed to condenser which rejects heat.

Exhaust Gas Fired Chiller Double-effect (twostage absorption system) machine powered from hot exhaust gases and can be direct coupled to combustion engine.

15

Generator-Absorber Heat Exchange (GAX) cycle Heat Pump Gas-cooling by absorption of heat based on difference from high temperature end of absorber and the low temperature end of generator.

Heat Rejection System Removal of excess heat from a refrigeration system to the outside environment.

Natural Draft-Type Cooling Tower Inducing airflow from difference of density between the ambient air entering the bottom of tower and vapor mixture leaving the system.

Forced -Draft Cross Flow Cooling Tower Air is forced into the tower from axial flow fans. Hot water distribution system may be used at the bottom.

16

Forced-Draft Counter Flow Cooling Tower Axial or centrifugal fans mounted at low level forcing air to flow upwards. Enable reduction in overall height of tower.

Induced-Draft Cross Flow Cooling Tower More distribution of air through the tower from axial fans. Available in twin pack versions.

Induced-Draft Counter Flow Cooling Tower Air is circulated using axial flow fans. Input air comes from openings at the base of the tower.

3.4

Concepts generated (all members) 3.4.1

Design Concept (Concept 1: Zulfaqqar’s)

Subsystem

Alternatives 1

2

3

4

Fuel Supply & Pretreatment system

Pre-treatment of waste wood

Baling of fuels

Pellets & Briquettes

Drying of biomass

Co-combustion System

Direct Co-firing

Indirect Co-Firing

Parallel Co-Firing

Gas turbines

Combined-Cycle Gas Turbine/Steam Turbine

Vertical HRSG

Once-through Steam Generators (OTSG) Generator-Absorber Heat Exchange (GAX) Heat Pump Induced-Draft Cross Flow Cooling Tower

Co-generation System Heat Recovery Steam Generators (HRSG) System

Steam turbines

Horizontal HRSG

Refrigeration Cycle System

Vapor Compression Cycle Chiller

Absorption Chiller

Exhaust Gas Fired Chiller

Heat Rejection System

Natural-Draft Type Cooling Tower

Forced-Draft Cross Flow Cooling Tower

Forced-Draft Counter Flow Cooling Tower

17

5

Stirling engines

Induced-Draft Counter Flow Cooling Tower

3.4.2

Justification of the chosen system (Concept 1: Zulfaqqar’s)

a)

Fuel Supply and Pre-Treatment system. For this subsystem, the drying of Biomass raw materials was proposed as the means

of preparation of the Biomass fuel. Drying of Biomass process is very important in maximizing the energy efficiency of the whole Biomass process. This process is mainly to eliminate any moisture content that exists in the Biomass raw material before they can be used as fuel for the next stage; which is the direct co-firing process. By eliminating the moisture content of the raw Biomass material, the combustion of the fuel can be performed more efficiently, producing more heat energy.

b)

Co-combustion system. Meanwhile, for the co-combustion system, direct co-firing process was used for this

subsystem. This process is the faster means to consume the Biomass fuel and produce steam at much faster rate compared to then indirect co-firing system. This means that the waiting time for a system which adopted the direct co-firing system to start up is much less compared to the gasification process. Additionally, since this system will be producing steam as its output, the usage of Heat recovery steam generators (HRSGs) can be omitted from the whole system. This can be very helpful in reducing the maintenance bills. The less component to maintain, the cheaper the maintenance bill would be.

c)

Co-generation system Next, it was proposed that this particular subsystem will be using a steam turbine

instead of gas turbine. The main reason for it is since direct co-firing system was adopted in the design of the GDC system, the only type of turbine that is compatible is the steam turbine. On top of that, a steam turbine can help reducing the fuel cost as it will not be consuming any petroleum-based fuel. The price of Natural gas (one of the petroleum-based fuel) kept increasing, which had cause the cost of running a system with gas turbines also rising. To curb this, adopting the steam turbine as an alternative will be a very smart choice. Having a steam turbine adopted in the GDC system could also help in terms of maintenance costs. Since the process in the steam turbine does not involve any combustion process, there will be no carbon residue formed within the steam turbine system. This also means there will be no 18

reduction of efficiency due to ‘dirty’ turbine internals and there will be no need for maintenance to address this issue when steam turbine is adopted to the system.

d)

Refrigeration cycle system For this subsystem, absorption chiller was chosen. The main reason for the absorption

chiller to be used in the system is due to its energy efficiency. The absorption chiller consumes less electricity, which will be very helpful in reducing the electricity bill compared to the rest. Additionally, the absorption chiller was also known to be quiet and produces less vibration compared to the other type of chiller. This type of chiller will also be very useful in eliminating the CFC emission which will be produced by some other chiller system, making it a greener and cleaner chiller alternative to be used in any plant, particularly in a GDC plant.

e)

Heat rejection system This particular subsystem will be using the induced-draft cooling tower as the main

heat rejection system. The reason for this cooling tower to be chosen is because it is could sustain a constant airflow regardless of whatever the ambient temperature might be. On top of that, this type of cooling tower can be adapted to any water flow, slow of fast. This type of cooling tower is also able to adapt in the condition in which the thermal condition at that time is severe. (i.e. draught, extreme cold). By having the mentioned qualities above, it is clear that the induced-draft cooling tower is the best choice of component to be used in the Heat rejection system.

19

3.4.3

Concept sketch (Concept 1: Zulfaqqar’s)

20

3.5.1

Design Concept (Concept 2: Adli’s)

Subsystem Fuel Supply & Pre-treatment system Co-combustion System

Alternatives 1

2

3

4


Baling of fuels


Drying of biomass

Direct Co-firing

Indirect Co-Firing

Parallel Co-Firing

Stirling engines

Co-generation System

Steam turbines

Gas turbines


Heat Recovery System

Horizontal HRSG

Vertical HRSG

Once-through Steam Generators (OTSG)

Condenser Heat Recovery System



Absorption Chiller


Generator-Absorber Heat Exchange (GAX) Heat Pump





Induced-Draft Cross Flow Cooling Tower

21

5


3.5.2

Justification of the chosen system (Concept 2: Adli’s)

Fuel Supply & Pre-treatment System Pre-treatment of waste wood involves processing the waste wood obtained through logging from the forest. The waste wood is developed into biomass fuel through processing plant which have four main working steps. In the first step, the wood passes through the low speed shredder which include 100mm screen basket. Through this, an overband and magnetic roller remove the iron pieces from the composition of waste wood. Later, the waste wood is screened through 10mm mesh which separates the ferrous and non-ferrous metal wood. This results in wood waste which is free from other metal composition or impurities and produced for size between 10 and 100mm. The beneficial part of this waste wood processing involves a reduction of costs for ash disposal. It has been shown that pre-treated waste wood have lower amounts of ashes produced during combustion which result in less deposit formation in the furnace and the boiler. Therefore, the combustion plant will has better availability and reduced operating costs due to this initiative.

Co-Combustion System The indirect co-firing is based on the gasification of biomass where the produced fuel gas will be combusted directly in the coal-fired furnace. After the gas emitted from combustion of biomass fuel is passed through the gasifier, the product of the gasification process has low calorific value fuel gas (syngas) and similar property as natural gas. The gasifier installed in the indirect co-firing system has the function to process bio-fuel which termed as synthetic natural gas (SNG). This may acts as a substitute for natural gas as the main source of fuel to the gas turbine.

Co-generation System Combined cycle gas turbine & steam turbine incorporates the gas-turbine generator with heat recovery steam generator (HRSG) and steam-turbine generator, condenser and auxiliary system. The HRSG acts as the heat exchanger which provides steam from the hot exhaust gases of the gas turbine and later is used to power the steam turbine. Based on the cogeneration system, the heat recovered through the HRSG is projected as in the form of high-pressure steam which later injected to the steam cycles (in steam turbines) to produce additional power. It is beneficial to employ the combined cycle where the facility or plant has 22

large low or high-pressure steam load where the steam can be used for the intermediate stage of the steam turbine. Besides, additional electric power generated by the steam turbine can be used for mechanical drive service in smaller capacity applications. Mainly in facility plants or district heating/cooling plants this include the use of steam turbines to drive chillers, pumps and other related equipment. Conventional combined-cycle system is employed where power plants have medium-to-large scale of power production from 100 MW to 1000 MW. Further, combine-cycle system has high efficiency compared to conventional power plants and reduction in compensation cost to the society due to emission of pollution and other damaging externalities.

Heat Recovery System Horizontal HRSG design is incorporated with natural circulation under all conditions of operation. It composed of simple design with fewer platforms and light supporting structure. Usually, the stack is supported from the ground hence providing zero load acting on the structure which means greater stability. Basically, it requires pump assistance for blowoff and draining as the headers are low and the blow tanks are at higher level than the boiler system.

Refrigeration Cycle System Vapor Compression Chiller basically comprises of four primary components which are the compressor, evaporator, condenser and metering device. It is equipped with different types of compressor namely reciprocating, scroll, screw-driven and centrifugal powered by motors or gas turbines to pump refrigerant to the condenser unit which later rejects heat energy from the refrigerant to the cooling water or air outside the system. With evaporative cooling, the coefficient of performance (COP) for this type of chiller is quite high.

Heat Rejection System Induced-Draft Cross Flow Cooling Tower is equipped with axial fans to give more even distribution of air through the system but makes control of drift difficult. Due to distribution of air in the tower, it is able to maintain constant airflow throughout the operation. Besides, the tower is able to operates in any given operating condition regardless of ambient temperature (e.g. winter, summer) thus providing maximum performance output.

23

3.5.3

Concept sketch (Concept 2: Adli’s)

24

3.6.1

Design Concept (Concept 3: Razin’s)

Subsystem

Alternatives 1

2

3

4



Baling of fuels


Drying of biomass


Direct Co-firing

Indirect Co-Firing

Parallel Co-Firing

Gas turbines


Vertical HRSG



Steam turbines

Horizontal HRSG



Absorption Chiller






25

5

Stirling engines


3.6.2

Justification of the chosen system (Concept 3: Razin’s) Sub-System

Justification •

a) Fuel Supply and Pre-treatment system - Drying of biomass

Able

to

utilize

whole

Biomass

process as this process is mainly to eliminate any moisture content that exists in the Biomass raw material before they can be used as fuel for the next stage •

Eliminating the moisture content inside the biomass material, will help the in term of combustion process.

•

b) Co-combustion system. - Co - Firing

Co-firing process was choosen for this subsystem.

•

Able to produce steam steam faster rate because the biomass is feed directly to the firing system or furnace.

•

Output of the system is steam compare to indirect firing which is fuel gas.

•

Able to omitted HRSG from the system.

c) Co-generation system

•

Use steam to move the turbine.

- Steam turbine

•

Able to use steam directly from the co – firing system.

•

Less maintenance as no combustion and carbon deposited on the turbine.

•

Save cost as using easily obtainable renewable resources.

•

d) Refrigeration cycle system - Vapor Compression Cycle Chiller

The

vapor-compression

uses

a

circulating liquid refrigerant as the medium which absorbs and removes

26

heat from the space to be cooled and subsequently

rejects

that

heat

elsewhere from the system. •

Relatively inexpensive, so able to save in term of costing.

e) Heat rejection system

•

Efficient up to 60%.

•

Crossflow is a design in which the air

- Forced-Draft Cross Flow Cooling Tower

flow is directed perpendicular to the water flow. •

Gravity water distribution allows smaller pumps and maintenance while in use.

•

Typically lower initial and long-term cost,

mostly

requirements.

27

due

to

pump

3.6.3


28

3.7.1

Design Concept (Concept 4: Faez’s)

Subsystem

Alternatives 1

2

3

4



Baling of fuels


Drying of biomass


Direct Co-firing

Indirect Co-Firing

Parallel Co-Firing

Gas turbines


Vertical HRSG



Steam turbines

Horizontal HRSG



Absorption Chiller






29

5

Stirling engines


3.7.2

Justification of the chosen system (Concept 4: Faez’s)

Subsystem

Alternatives

Fuel Supply & Pre-

Drying of biomass

Justification

-

treatment system

Biomass can be burned efficiently and much faster due to low humidity level.

-

The amount of energy burnt from the dry biomass is much higher compare to other alternatives

-

Cheap, easily maintained with low capital cost.

Co-combustion

-

Indirect Co-Firing

System

Increase the energy produced in order to drive the turbine much faster.

-

Increase the efficiency of the burning process of the biomass product, thus reduce the energy wasted during the process.

Co-generation

-

Gas turbines

System

High efficiency in producing power, especially in electricity.

-

High power capacity produced.

-

Low time taken to generate electricity as the energy from combustion is enormous.

Heat Recovery

-

Vertical HRSG

Low space required, thus save some space for other equipment.

Steam Generators -

(HRSG) System

Easily maintained as it uses natural circulation, assisted with water flow during the process.

30

Refrigeration Cycle

-

Absorption Chiller

Environmental friendly, no CFC emission.

System -

Quiet operation, less vibration produced.

-

Lower electricity cost incurred.

-

Reliable, yet low in maintenance.

Heat Rejection

Induced-Draft Cross Flow

-

Induces hot moist air quickly.

System

Cooling Tower

-

Reducing the recirculation effect due to low input velocities and high output velocities.

-

Increase rate of cooling due to induced process.

31

3.7.3

Concept sketch (Concept 4: Faez’s)

32

3.8.1

Design Concept (Concept 5: Choong’s) Subsystem

1

2

Components & Equipments 3

4

Fuel Supply & PreTreatment System


Balling of fuels

Pellets & Briquettes Drying of Biomass

Co-combustion system

Direct Co-firing

Indirect Co-Firing

Parallel Co-Firing

Co-generation (CHP) system

Steam turbines

Gas Turbines

Combined-Cycle Gas/ Steam Turbine

Heat Recovery Steam Generators (HRSG) system

Horizontal HRSG

Vertical HRSG

Once-Through Steam Generators (OTSG)

Refrigeration Cycle system

Vapor CompressionCycle Chiller

Absorption Chiller



Natural Draft-Type Cooling Tower

Forced -Draft Cross Forced-Draft Flow Cooling Counter Flow Tower Cooling Tower

33

5

Stirling engines

GeneratorAbsorber Heat Exchange (GAX) cycle Heat Pump Induced-Draft Cross Flow Cooling Tower


3.8.2 i.

Justification of the chosen system (Concept 5: Choong’s) Fuel Supply and Pre-Treatment System

Fuel supply and pre-treatment system is functions to prepare the biomass before it is supplied for energy conversion process. For this subsystem, drying of biomass is chosen. For all biomass conversion technologies, biomass is heated in order to produce steam or hot gas. Therefore, the dryness of biomass has significant effect on the efficiency of biomass conversion process. Besides that, low moisture content of the biomass feedstock will result in higher energy efficiency of the conversion process. This is because moisture biomass needs more energy for heating and vaporizing the moisture content, this energy is lost in the stack. Hence, drying process of biomass is needed in the design for proper process function and control [21]. ii.

Co-Combustion System

Co-combustion system is functions to produce hot gas or steam and uses it to drive turbine generator. There are three different types of co-combustion system and in-direct firing has been selected in this design. In-direct firing system is also known as gasification. By comparing to the direct-firing system, gasification is more environmental friendly. Fuel contaminants are removed in gasification and it assists in reducing emissions [21]. iii.

Co-generation system

Gas turbine is chosen in co-generation system. The reason why gas turbine is chosen is that it generates high power up to 120MW. High power generation is needed in this design of GDC system because it is used to power up the plant and supplied to a district. The second reason is that gasification produce hot gas and it is commonly used to drive gas turbine. Thus, gas turbine is chosen. The benefits of gas turbine include high reliability and high power density, which makes it has lower operating cost and higher efficiency compare to steam turbine. In addition, the exhaust heat from gas turbine has high quality and usable. The heat produce can be used in other processes such as generate steam [15].

34

iv.

Heat Recovery Steam Generator (HRSG) system

HRSG system in this design is functions to convert the waste heat from the exhaust of gas turbine to steam. Once-through steam generator (OTSG) is picked in this system because it provides high degree of flexibility as the sections are allowed to grow or contract based on the heat load from gas turbine. In this design, the inlet feedwater follows continuous path without segmented sections for economizers, evaporators and superheater. Moreover, OTSG is a special type of HRSG which without drum, this characteristic allows for quick changes in steam production and fewer variables to control [18]. v.


Absorption chiller is chosen as the refrigeration cycle system in this design. The use of absorption chillers eliminates the high incremental cost of electric cooling. Furthermore, absorption chiller utilize the waste heat from the gas turbine that would otherwise be unused greatly increases the cost-effectiveness of the systems. Absorption chillers are also have several non-energy benefits which are environmental friendly and they are elimination the use of chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants, and also reduction in sound pollution due to its vibration free operation [21]. vi.


Natural draft cooling tower has selected as heat rejection system in this design concept. This type of cooling tower is particularly attractive as a cost-saving solution for larger power stations and industrial plants requiring greater quantities of cooling water. As this type of cooling tower operates without fans, the substantial amount of electric power otherwise required for large cooling tower systems is not needed. The required cooling air is conveyed through the tower by natural draft thus neither fan nor fan power is required [15].

35

3.8.3

Concept sketch (Concept 5: Choong’s)

36

4.

CONCEPT EVALUATION In this section, evaluation for all concepts will be done through the breakdown of each concept’s subsystems. All of the concept’s

subsystems will be evaluated through several primary and design criteria determined from the objective tree made before the subsystem’s evaluation. Evaluation will be done through Weighted Decision Matrix (WDM).

4.1.1

Fuel Supply & Pre-Treatment System Objective Tree and Decision Matrix

Fuel Supply & Pre-Treatment System 1.0

Cost 0.5

Operation (OPEX)

0.6

Design

Performance

0.2

0.3

Capital (CAPEX)

Quality 0.4

Productivity 0.6

Complexity 0.4

37

Reliability 0.5

0.5

Table 3: Weighted decision matrix for Fuel Supply & Pre-Treatment System

Primary Criterion

Cost (0.5)

Performanc e (0.3)

Design (0.2)

Design Criterion

Weight factor

Unit

Concept 1 – Drying of Biomass (Zulfaqqar) Mag.

Score

Rate

Concept 2 – PreTreatment of waste wood (Adli) Mag. Score Rate

Concept 3 – Drying of Biomass (Razin)

Concept 4 – Drying of Biomass (Faez)

Concept 5 – Drying of Biomass (Choong)

Mag.

Score

Rate

Mag.

Score

Rate

Mag.

Score

Rate

Operation (OPEX) (0.6)

0.30

Exp

Low

9

2.70

Medi um

6

1.80

Low

9

2.70

Low

9

2.70

Low

9

2.70

Capital (CAPEX) (0.4)

0.20

Exp

Medi um

7

1.40

High

3

0.60

Medi um

7

1.40

Medi um

7

1.40

Medi um

7

1.40

Quality of fuel (0.6)

0.18

Exp

Medi um

6

1.08

Very Good

8

1.44

Medi um

6

1.08

Medi um

6

1.08

Medi um

6

1.08

Productivity (0.4)

0.12

kg / hr

2000

8

0.96

1500 0

10

1.20

2000

8

0.96

2000

8

0.96

2000

8

0.96

Complexity (0.5)

0.10

Exp

Very Good

8

0.80

Good

7

0.70

Very Good

8

0.80

Very Good

8

0.80

Very Good

8

0.80

Reliability (0.5)

0.10

Exp

High

8

0.80

High

8

0.80

High

8

0.80

High

8

0.80

High

8

0.80

Total

7.74

6.54

38

7.74

7.74

7.74

4.1.2

Justification (Fuel Supply & Pre-Treatment system) Biomass fuels have varying quality and characteristics which are mainly dependent

of the types of biomass and pre-treatment technologies applied to these fuels. For example some of the characteristics of biomass fuels include moisture content which is important for storage durability and combustion effectiveness, net calorific value (NCV) or gross calorific value (GCV) that determines the fuel utilization as well as the ash content which provides information on dust emission, ash utilization or disposal and the combustion technology to be used. The fuel supply of biomass system consists of planting, harvesting, comminution, drying, storage as well as transport and handling. The fuel quality of biomass is usually an important considerations for the operation of biomass combustion plant as well as on realization of costs incurred from combustion to utilization of the fuels. The criteria which have been assigned for the Fuel Supply and Pre-Treatment system include cost, performance and design of the overall pre-treatment technologies. The cost of the system accounts for 0.5 of the initial weightage for the system as the operator must consider different circumstances on costs which relates to capital expenditure (CAPEX) as well as operation expenditure (OPEX) while maintaining profits. Whereas the performance of the system has been evaluated at 0.3 significance as this includes the quality of fuel as well as productivity. Further, the design of the system has been given at 0.2 as the complexity and reliability of the equipment in operation will provide a relation in manpower as well as maintenance costs. The operational costs (OPEX) for the system have been given a higher significance which is 0.6 as these costs are borne by the operator every year during operation of the system. These costs include maintenance, personnel and transportation costs. For the capital expenditure (CAPEX), a weightage of 0.4 is given to assess on the initial investment for the technologies. The magnitude of this criteria has been ranked from high to low based on 11point scoring system in which a lower cost incurred for the operation of the system is preferable. The ranking of each subsystem has been assigned where a score of 9 will be given for the lowest cost, score of 7 for the medium cost while score of 3 for the highest cost. These scores are given based on review from Processing Cost Analysis for Biomass Feedstock; Phillip Badger [2] and Report on Biomass Drying Technology; Wade Amos [3].

39

The quality of fuel is one of the important considerations for this pre-treatment system as this determines the amount of impurities within the fuel composition. It has been given a weightage of 0.6. The scoring is based on the level of fuel quality from Low, Medium to Very Good which is given depending on information from the book of Biomass Combustion & Co-firing [1]. While the productivity is a measure of output the system may attained in terms of kg per hour of operation and assessed to has 0.4 significance. The magnitude given which is 2000 kg/h is the rated output derived from Agromech, a company specialized on drum driers for biomass drying [16] while 15000 kg/h is the nominal capacity for breakers from Rudnick-Enners GmbH [4]. The complexity of the design is judged based on the equipments involves in each system and the operability of these equipments. It has been given a rating from Bad, Good to Very Good in which the information are derived from Biomass Combustion & Co-firing [1]. Drying of biomass can be done at the outside which reduces its moisture content and later transferred to drum dryers that are heated directly or indirectly. Whereas the pre-treatment of waste wood involves using magnetic roller, screening basket and wood breakers to obtain wood waste which has relatively low impurities contents. In terms of reliability, it has been given the same merit as complexity at 0.5 and rated based on operational duration of the system before maintenance or breakdown. All systems are given High consideration due to the operational data retrieved from Biomass Combustion & Co-firing [1].

40

4.2.1

Co-Combustion Objective Tree and Decision Matrix

Co-Combustion System 1

Cost

Quality of Service

0.4

Operation (OPEX)

0.6

Capital (CAPEX)

Environmental Effect 0.2 0.4 Contaminants Emission 1

0.4

Plant Efficiency

Versatility 0.6

0.4

41

Table 4: Weighted decision matrix for Co-Combustion System Primary Criterion

Design Criterion

Weight factor

Unit

Cost (0.40)

Operation (OPEX) (0.6) Capital (CAPEX) (0.4) Plant Overall Efficiency (0.70) Versatility (0.30) Contaminan ts Emission (1.00)

0.24

USD $/yr

0.16

Quality of Service (0.40)

Environmen tal Effect (0.20) Total

Concept 1 – Direct Co-Firing (Zulfaqqar) Mag. Score Rate 660K 8 1.92

Concept 2 – Indirect Co-Firing (Adli) Mag. Score Rate 955K 6 1.44

Concept 3 – Direct Co-Firing (Razin) Mag. Score Rate 660K 8 1.92

Concept 4 – Indirect Co-Firing (Faez) Mag. Score Rate 955K 6 1.44

Concept 5 – Indirect Co-Firing (Choong) Mag. Score Rate 955K 6 1.44

Exp

9610 K

8

1.28

1900 0K

6

0.96

9610 K

8

1.28

1900 0K

6

0.96

1900 0K

6

0.96

0.28

Exp

med.

6

1.68

high

7

1.96

med.

6

1.68

high

7

1.96

high

7

1.96

0.12

Exp

med.

5

0.60

high

7

0.84

med.

5

0.60

high

7

0.84

med.

7

0.84

0.20

Exp

med.

5

1.00

low

8

1.60

med

5

1.00

low

8

1.60

low

8

1.60

6.48

6.80

42

6.48

6.80

6.80

4.2.2

Justification (Co-Combustion System) Co-combustion system plays a vital role in biomass-based GDC plant and responsible

for driving turbine in order to generate electricity. Hence, it is important to select the most suitable components listed in the morphology chart based on the criteria shown in the objective tree that had been constructed. From the objective tree, one of the main criteria of selecting components for cocombustion system is cost and the weightage is rated as 0.4. There are two costs are taken into consideration under the criteria of cost and they are operational (including maintenance) and capital. Both costs have a weightage of 0.6 and 0.4 respectively. The reason why the weightage of operational cost is higher than the capital cost is that operational cost has long term effect on the plant, while capital cost is only taken into account during the initial expenses. Besides that, quality of service is also considered as one of the criteria in the objective tree. The weightage for quality of service is similar to the cost which is 0.4. Under the quality of service, there are two factors are taken into consideration and they are plant overall efficiency and versatility. Plant overall efficiency has a weightage of 0.7 while versatility has 0.3. This is because efficiency is the most important criteria in designing. Besides, versatility of the product produced from co-combustion system is important as the product may only suitable to drive only one turbine’s type or more. Thus, versatility is considered as one of the criteria. Furthermore, environmental effect is also one of the criteria of selecting the components and has a weightage of 0.2 which is lesser compared to cost and quality of service. In line with the objective of this project, the emission of contaminants from the cocombustion system is included as criteria in order to optimize the plant to be more environmental friendly. From the five concepts generated, only two components from the morphology chart are chosen and they are direct co-firing and indirect co-firing. By comparison, direct co-firing has lower operational and capital cost [21]. Hence, the score for direct co-firing is higher than indirect co-firing under cost criteria in Table 4.

43

However, in term of plant overall efficiency, indirect co-firing is greater than direct co-firing. Heat from the turbine exhaust can be recovered when fuel gas, also known as syngas, produced from indirect co-firing is used to power up gas turbine for generating electricity. With the heat recovery, the system efficiency can improve to 80% [21]. Moreover, the syngas produced from indirect co-firing can used to heat up boiler and produce steam. This makes indirect co-firing is more versatile since it can used to drive steam turbine and gas turbine. Thus, indirect co-firing has higher score under quality of service criteria in Table 4. In term of contaminants emission, direct co-firing produces by-products such as flying ash from the combustion of biomass and these by-products is harmful to environment. In addition, indirect co-firing emits lesser contaminants compared to direct co-firing [21]. Therefore, indirect co-firing is rated as 8 while direct co-firing rated as 5 for the score of environmental effect criteria in Table 4.

44

4.3.1

Co-Generation System Objective Tree and Decision Matrix

Co-Generation System 1

Cost Flexibility

0.4

0.3

Operation (OPEX)

0.6

Capital (CAPEX)

Maintenance

0.4

Control 0.6

0.4

Performance

Design 0.3

0.4

Efficiency

Reliability 0.5

Compatibility

Complexity 0.5

0.3

0.3

Size 45

0.4

Table 5: Weighted decision matrix for Co-Generation System

Primary Criterion

Cost (0.40)

Performance (0.40)

Flexibility (0.30)

Design (0.30)

Total

Design Criterion Operation (OPEX) (0.60) Capital (CAPEX) (0.40) Efficiency (0.50) Reliability (0.50) Maintenance (0.60) Control (0.40) Complexity (0.30) Size (0.40) Compatibility (0.30)

Weight Factor

0.24

Mag.

Score

Rate

Concept 2 Combined_Cycle Gas / Steam Turbine (Adli) Mag. Score Rate

15.00

6

1.44

13.20

7

1.68

15.00

6

1.44

7.30

9

2.16

7.30

9

2.16

Concept 1 Steam Turbine (Zulfaqqar)

Unit

USD $/kW -yr

Concept 5 Gas Turbine (Choong)

Concept 4 Gas Turbine (Faez)

Concept 3 Steam Turbine (Razin) Mag.

Score

Rate

Mag.

Score

Rate

Mag.

Score

Rate

0.16

USD $/kW

800

9

1.44

900

8

1.28

800

9

1.44

980

7

1.12

980

7

1.12

0.20

%

75

7

1.40

80

8

1.60

75

7

1.40

75

7

1.40

75

7

1.40

0.20

%

94

7

1.40

95

8

1.60

94

7

1.40

97

9

1.80

97

9

1.80

0.18

Exp

High

6

1.08

Med

7

1.26

High

6

1.08

Fair

8

1.44

Fair

8

1.44

0.12

Exp

High

6

0.72

Med

7

0.84

High

6

0.72

Fair

8

0.96

Fair

8

0.96

0.09

Exp

Med

7

0.63

High

6

0.54

Med

7

0.63

Fair

8

0.72

Fair

8

0.72

0.12

Exp

Med

8

0.96

Big

7

0.84

Med

8

0.96

Med

8

0.96

Med

8

0.96

0.09

Exp

Med

8

0.72

Med

8

0.72

Med

8

0.72

High

9

0.81

High

9

0.81

9.79

10.36

46

9.79

11.37

11.37

4.3.2

Justification (Co-Generation System) The co-generation system is important in the gas district cooling system as it

generates electricity and also useful heat simultaneously. Therefore, it is very important to choose the proper co-generation system to be run in the gas district cooling system. To determine and choose the best system, some criteria are listed in the objective tree diagram. Four main criterias are listed in which focused more on the cost, performance, flexibility and also the design of the system. The highest weightage in the objective tree diagram is more towards the cost and also the performance, in which rated as 0.4 as these two factors is the main objectives in the selection, which is to get an affordable system with a better performance. In the cost factor, the operational expenditures (OPEX) is weighed higher then capital expenditures (CAPEX) with the rating on 0.6 against 0.4. This is due to the annual cost that is need to be in higher considerations in which including the maintenance, parts replacement and also the client cost. Even so, the CAPEX also should be as low as possible in order to reduce the overall expenditures throughout the years. Other than that, the third and fourth factors are shared together; flexibility and its design which is rated as 0.3. Flexibility in this term means that how the system operates without too much hassle when the operator or working dealing with the system. This factor includes the difficulty of handling the system, and also the difficulty of repairing of inspecting the system when required to ensure its reliability at its best. For the design criteria, the sub factors are divided into three, which is the complexity, size and also its compatibility. Complexity and compatibility are sharing the same weightage which is 0.3 while the size factor is the a little bit in concern in the selection which is 0.4. This is due to the further consequences of choosing bigger system in which requires bigger area thus inducing higher cost. While the complexity and compatibility of the design is more referred to the installation procedures and also the connection between the systems to the other system in the gas district cooling plant.

47

4.4.1

Heat Recovery System Objective Tree and Decision Matrix

Heat Recovery System 1

Quality of service

Cost

0.5

0.4

Operation (OPEX)

0.6

Design

Capital (CAPEX)

Output

Maintenance 1

0.4

48

0.1

Sizing 0.4

0.6

Table 6: Weighted decision matrix for Heat Recovery System Primary Design criteria Criterion

Weight Unit factor

Cost

0.24

Exp

Concept 1 Concept 2 Concept 3 Concept 4 Concept 5 Not Selected Horizontal HRSG Not Selected Vertical HRSG OTSG (Zulfaqqar) (Adli) (Razin) (Faez) (Choong) Mag Score Rate Mag Score Rate Mag Score Rate Mag Score Rate Mag Score Rate Norm. Norm. Norm. Med 6 1.68 Norm. Norm. Norm. Med 7 1.68 Low 8 1.92

0.16

USD

Norm. Norm. Norm. 5.8M

8

1.28

Norm. Norm. Norm. 5.8M 8

1.28

Low

9

1.44

0.5

Tn/hr Norm. Norm. Norm. High (40)

8

4

Norm. Norm. Norm. High (40)

8

4

Med (32)

7

3.5

Exp

Norm. Norm. Norm. Hard

5

0.2

Norm. Norm. Norm. Easy

9

0.36

Easy

9

0.36

Area

Norm. Norm. Norm. Large 5

0.3

Norm. Norm. Norm. Med

8

0.48

Small 9

0.54

Quality of service

Operation (OPEX) (0.6) Capital (CAPEX) (0.4) Output (1)

Maintenance 0.04 Design Sizing

0.06 Total

7.0

7.22

49

7.0

7.8

7.76

4.4.2

Justification (Heat Recovery System) The heat recovery system is important in the gas district cooling system. The function

of this system is to recover the exhaust waste heat. Hence, it is important to choose the suitable candidate in order to implement this system in our gas district cooling plant. In order to determine the best heat recovery system, several criteria were listed in the objective tree. There are three criteria listed in the objective tree diagram for choosing the best heat recovery system, which are cost, quality of service and design. The highest weightage in the objective tree diagram is given to the quality of service which is 0.5. As we need to maximize as much as possible output for the system. Cost is given second highest weightage in the objective tree diagram after quality of service which is 0.4. Cost also need to be taken into serious consideration as the initial expenses (CAPEX) and annual operational and maintenance cost (OPEX) cannot be too expensive or beyond the budget limit. Operational cost (OPEX) is set to 0.6 because this will be the cost client need to bear in order to run and maintain the equipment throughout the year of usage. As higher cost will lead to higher expenditure in order to keep the equipment running in good condition. While 0.4 weightage is given to initial expenses (CAPEX). Even the weightage allocation is slightly lower than (OPEX) the initial expenses should be low as possible. Lastly, design also is one of the criteria listed in objective tree in choosing the best component. The weightage is given 0.1 which is the lowest compare to the other criteria. Under this criterion there is complexity which is given 0.4 weightage and sizing 0.6. As the complexity of the heat recovery system is almost the same more weightage is allocate to the sizing category. Sizing refer to the area size of the plant will be build and constructed, bigger area will promote to higher expense in constructing it. Remaining area are able to use for other important equipment or usage.

50

4.5.1

Refrigeration System Objective Tree and Decision Matrix

Refrigeration system 1

Cost

Performance 0.3

Operation (OPEX)

0.5

Capital (CAPEX) 0.6

Environmental Effect

CO2 Emission

Output Capacity

Efficiency 0.4

0.2

0.4

1 0.6

51

Table 7: Weighted decision matrix for Refrigeration System Primary Criterion

Design Criterion

Weight factor

Unit

Concept 1 – Absorption Chiller (Zulfaqqar) Mag. Score Rate 104K 7 1.26

Concept 2 – Vapor Compression Chiller (Adli) Mag. Score Rate 73K 9 1.62

Concept 3 – Vapor Compression Chiller (Razin) Mag. Score Rate 73K 9 1.62

Concept 4 – Absorption Chiller (Faez) Mag. Score Rate 104K 7 1.26

Concept 5 – Absorption Chiller (Choong) Mag. Score Rate 104K 7 1.26

Cost (0.3)

Operation (OPEX)

0.18

USD $/yr

0.12

USD $

571K

6

0.72

540K

7

0.84

540K

7

0.84

571K

6

0.72

571K

6

0.72

0.20

Exp

mid

5

1

high

7

1.4

high

7

1.4

mid

5

1

mid

5

1

(0.4) Output Capacity

0.30

RT

2500

9

2.7

325

4

1.2

325

4

1.2

2500

9

2.7

2500

9

2.7

(0.6) CO2 Emission

0.20

kg/G J

20

8

1.6

30

7

1.4

30

7

1.4

20

8

1.6

20

8

1.6

(0.6) Capital (CAPEX)

Performance (0.5)

Environment Effect (0.2)

(0.4) Efficiency

(1) Total

7.28

6.46

52

6.46

7.28

7.28

4.5.2

Justification (Refrigeration System)

Another subsystem that played an important factor in Gas District Cooling system is the Refrigeration system. Refrigeration system is the system where the production of the chilled water for the usage of consumer occurs. The aim for the Refrigeration system need to achieve is to have a system that is economically feasible (for both initial cost and operating cost), to have an excellent performance throughout its useful life, and also to be as environmental friendly as possible. The evaluation will be done by considering several criteria that are relevant to the above aims. The criteria will be given weightage and will be rated using the 10-point scoring system. By the end, the concept which gains the highest total rating will be the winning concept for this particular subsystem. For this particular subsystem, three primary criteria that are most relevant were identified. The criteria are; cost, performance and environmental effect. Similar to any engineering projects, cost played a pivotal role in a project to determine whether it is feasible or not. Investors will mostly be looking at the cost criteria to decide whether it is worth or not to invest into a particular project. However, despite of its importance, cost criterion was assigned with the second highest weightage (0.30) as it is less crucial in comparison to the performance criterion, at least only for this subsystem. Like any other subsystems, the capital expenditure (CAPEX) and operational expenditure (OPEX) were taken into consideration with OPEX has been given with a higher weightage (0.6) compared to CAPEX (0.4) due to its long term importance. Meanwhile, the second primary criterion which is the performance has been assigned with the highest weightage (0.5). The reason for this is because the performance of the refrigeration system is very important as it will determine the production output of the chilled water distribution. If there is any performance drop for this subsystem, it will heavily affect the chilled water production, which is the main product for a GDC plant. Under the performance criterion, there are two design criterions considered. Both of them are efficiency, and output capacity. The output capacity has been given the weightage of 0.6, which is higher than the efficiency (0.4) since the output capacity of chilled water is the utmost priority for the refrigeration subsystem, particularly for a GDC plant.

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Finally, the last primary criterion to be evaluated is the environmental effect which takes up the weightage of 0.2. Environmental concerns are still one of the important part to be considered in this subsystem and that is the main reason why does the environment effect was taken as one of the factors in consideration. However, despite of its importance, it does not outweigh the other two primary criterions – cost and performance. The only design criterion set under the environmental effect is the CO2 emission from the refrigeration system. Highest score will be given to the system which adopting the refrigeration system that has the lowest CO2 emission. In this subsystem, concepts that are Absorption Chiller as the choice for the Refrigeration System has the highest overall score (7.28) followed by the Vapor Compression Chiller (6.46). In terms of Cost, the Absorption chiller has been given the score of 7 for the OPEX because the cost to run the Absorption chiller in long term is considerably low. However, the Vapor Compression Chiller has a much lower operational cost and has been given a higher score (9). For the CAPEX, Absorption chiller had scored 6, which is slightly lower than the Vapor Compression chiller (7) because the absorption chiller system is a bit expensive as far as the first cost is concerned for the system. In term of performance, the Absorption chiller had been given the score of 5 in terms of overall efficiency for being slightly less efficient compared to the Vapor Compression Chiller overall. However, in terms of the output capacity, the absorption chiller is far more superior because it is capable to produce about 8 times more chilled water output than the Vapor compression chiller. Due to that reason, the absorption chiller had been given the score of 9. Finally, in terms of the environmental effect, the absorption chiller did slightly better than the Vapor Compression chiller as the amount of the CO2 emitted by the absorption chiller is 20kg/GJ which is 10kg/GJ less than the Vapor Compression Chiller and is also generally low by industry standard. Due to this, the absorption chiller has been given the score of 8.

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4.6.1

Heat Rejection System Objective Tree and Decision Matrix

Heat Rejection System 1

Cost

Performance 0.5

Design 0.3

0.2 Flowrate

Operation (OPEX)

0.6

Capital (CAPEX)

1

Complexity

Adaptability 0.6

0.4

55

0.4

Table 8: Weighted decision matrix for Heat Rejection System Primary Criterion

Design Criterion

Weight factor

Unit

Exp

Concept 1 – Induced Draft Cross Flow Cooling Tower (Zulfaqqar) Mag. Score Rate med. 6 1.8

Concept 2 – Induced Draft Cross Flow Cooling Tower (Adli) Mag. Score Rate med. 6 1.8

Concept 3 – Forced Draft Counter Flow Cooling Tower (Razin) Mag. Score Rate high 3 0.9

Concept 4 – Induced Draft Cross Flow Cooling Tower (Faez) Mag. Score Rate med. 6 1.8

Cost (0.5)

Operation (OPEX)

0.30

Mag. low

Score 8

Rate 2.4

0.20

Exp

med.

6

1.2

med.

6

1.2

med.

6

1.2

med.

6

1.2

high

3

0.6

(0.4) Flowrate

0.20

m3/h r

480

6

1.2

480

6

1.2

768

8

1.6

480

6

1.2

36.5 K

3

0.6

(1) Complexity

0.18

Exp

med.

6

1.08

med.

6

1.08

high

4

0.72

med.

6

1.08

low

8

1.44

(0.6) Adaptability

0.12

Exp

high

8

0.96

high

8

0.96

low

3

0.36

high

8

0.96

low

3

0.36

(0.6) Capital (CAPEX)

Performance (0.2) Design (0.3)

Concept 5 – Natural Draft Cooling Tower (Choong)

(0.4) Total

6.24

6.24

56

4.78

6.24

5.4

4.6.2

Justification (Heat Rejection System)

One of the important subsystems that exist in the Gas District Cooling system is the heat rejection system. The main role of the Heat Rejection System is to reject waste heat from the overall system of the Gas District Cooling plant. This waste heat may come from the auxiliary boilers, gas turbines and several other components that require cooling. The primary criterions that are being taken into consideration for the selection of the best Heat Rejection System are; cost, performance, and also design. All of these criterions were given their own respective weightage according to their level of importance towards the overall subsystem and also to the whole main system. There are also design criterions, placed under all primary criteria and will also be given their own respective weightage according to their level of importance. All of the criterion will be given scores and 10-point scoring system will be utilized where 0 is the lowest score given, indicating the worst and 10 is the highest, indicating the best. The first primary criterion considered for this subsystem is Cost which carries the weightage of 0.5. Cost has been given the highest weightage compared to the rest of the criterion is because of its importance in affecting the feasibility of this project in both short term and long term. Investors will be using cost as their main reference to see whether it is worth enough for them to invest to this project for both short and long term. Under the Cost criterion, there are two design criterions being set which is the capital expenditure (CAPEX) and also the operational expenditure (OPEX). OPEX for this subsystem has been assigned with the weightage of 0.6 as compared to CAPEX’s 0.4. The main reason for this is because the main concern of cost for this particular subsystem is the long term cost. The Heat Rejection System will be used for quite a long time and it is particularly important to make sure that the cost to maintain it to be as minimal as possible to ensure a high profitability. Next, the second primary criterion considered for this subsystem is the performance. The subsystem’s performance in delivering an optimum flowrate of cooled condensate (to cool the system) has been considered as well. However, the performance is the least concern for this subsystem because it is not as important as the other criterion. Hence, due to this, the performance criterion was given with the least weightage which is 0.2. Under the Flowrate, the only design criterion considered is the flowrate (in m3/hr). As mentioned earlier, this flowrate refers to the flowrate of cooled condensate produced from this subsystem.

57

On top of that, another vital primary criterion considered for this system is the design. This criterion has been given the second highest weightage (0.3) due to its importance in affecting the cost criterion as well as the performance criterion. Under Design, there are another two criterions considered which are the system complexity and also the system adaptability. System complexity will affect heavily on the cost, especially the OPEX because if the Heat Rejection system is too complex, the maintenance work will be a bit complex, hence causing the operating cost to soar. Meanwhile, the system adaptability refers to the capability of the system to adapt to various kinds of environmental conditions and at the same time maintaining its optimum performance. Under this criterion, system complexity has been given the weightage of 0.6 and the system adaptability has been given the weightage of 0.4. In this subsystem, concepts that are utilizing Induced Draft Cross Flow Cooling Tower as the choice for the Heat Rejection System has the highest overall score (6.36) followed by the Natural Draft Cooling Tower (5.1) and finally the Induced Draft Counter Flow Cooling Tower (4.72). In terms of Cost, the Induced Draft Cross Flow Cooling Tower has been given the score of 6 for the OPEX because the operational cost of the Induced Draft Cross Flow Cooling Tower is comparatively lower than the Forced Draft Counter Flow Cooling Tower due to its simpler design and a bit higher than the Natural Draft Cooling Tower since the Induced Draft Cross Flow Cooling Tower uses some electricity to power up the fan to suck out all the air from the chamber. For the CAPEX, Induced Draft Cross Flow Cooling Tower had also scored 6, which is the same as the Forced Draft Counter Flow Cooling Tower as the capital cost for both is comparatively the same and also much less than the CAPEX of the Natural Draft Cooling Tower. In term of performance, the Induced Draft Cooling Tower had been given the score of 6 as well as it is able to handle the near-optimum flowrate which is 480 m3/hr. However, the Forced Draft Counter Flow Cooling Tower had performed better as it is able to handle 768 m3/hr. Meanwhile the Natural Draft Cooling Tower is able to handle about 36500 m3/hr which is too high for a Gas District Cooling plant. Finally, in terms of design, the Induced Draft Cross Flow Cooling Tower had scored 6 out of 10 for the system complexity, as its system is moderately complex compared to Natural Draft Cooling Tower but a little bit simpler than the Forced Draft Counter Flow Cooling Tower. As far as the system adaptability goes, the Induced Draft Cross Flow Cooling Tower scored the highest point among the rest as it

is

very

capable

to

adapt

to

changes

58

in

working

environment/parameters.

5.

SELECTED CONCEPT

5.1

Winning Concept

The finalized rating for the evaluation concepts are presented in the table below: Table 9: Concept Selection Subsystem

Concept

Fuel Supply & PreTreatment System

Concept 1 (Zulfaqqar) Concept 2 (Adli) Concept 3 (Razin) Concept 4 (Faez) Concept 5 (Choong)

Heat CoCoRefrigeration Combustion Generation Recovery Cycle System System System System


Total

7.74

6.48

9.79

7

7.28

6.36

44.65

6.54

6.80

10.36

7.22

6.46

6.36

43.74

7.74

6.48

9.79

7

6.46

4.72

42.19

7.74

6.80

11.37

7.80

7.28

6.36

47.35

7.74

6.80

11.37

7.76

7.28

5.10

46.05

Based on the table and values calculated above, it can be seen that Concept 4 has the highest rating in total by using the weighted decision matrix. The criteria chosen are based on the aspects required for the operation of the gas district cooling system. The scores obtained are given by the evaluation all indicators in each criterion for every alternative available in the subsystem. In this project, the cost has been the major concern for evaluating the alternatives in the subsystem. This factor is to ensure that the project proposal is capable in minimizing cost required and at the same time maximize the efficiency of the system for the usage of the desired customers or buildings. However, Health, Safety and Environment (HSE) in the industry standards needs to be taken seriously into account to avoid any bad occurrences of any catastrophic event. Based on the weightage scores calculated above, the highest score is in the Concept 4 with the score of 47.35. The chosen concept has scored all six subsystems listed which are the fuel supply and pre-treatment system, co-combustion system, co-generation system, Heart recovery system (HRS), refrigeration cycle system, and heat rejection system. Unfortunately, the total score might be unfair as some concepts do not require HRS system due to the usage of steam turbine in their concepts. However, taking into account of the average score for HRS 59

system is 7, the maximum score that can be compensated is 44.65, which is still lower that the highest score calculated earlier. Concept 4 uses drying of biomass system before entering the indirect co-firing system. The reason behind the selection of this concept is basically to maximize the heat produced and at the same time to reduce time taken to burn the biomass materials due to the presence of humidity in the materials. The selection of indirect co-firing is basically to produce fuel gas in which will be using by the gas turbine. This includes the process of gasification of the organic materials in the biomass itself. In the selection of co-generation system, gas turbine is still one of the best turbines available so far in the market compare to the other turbines. This is due to the high efficiency produced by the gas turbine to generate electricity, smaller in size and also capable in producing high power output for large usage from the customers or buildings. The excess heat produced by the gas turbine can be channelled back to the vertical HRS system in order to produced useful steam to be channelled to the refrigeration system. The selection of vertical-based system is basically to use the density differences of hot and cold air so that the proper steam can be produced. On the other side, the selection of absorption chiller and also induced-draft cross flow cooling tower is basically due to its efficiency, availability of its replacement parts and also the capability of producing cooled water in a short time with the mixture of refrigerant. The induced-draft cooling tower is selected due to presence of hot air in which will naturally goes up to the atmosphere. This process also will reduce the recirculation in which the discharged air enters back into the intake due to low entry and high exits of air velocities. The overall concept sketch for the selected concept is shown:

60

Winning concept’s selection matrix (Faez’s)

Subsystem

Alternatives 1

2

3

4



Baling of fuels


Drying of biomass


Direct Co-firing

Indirect Co-Firing

Parallel Co-Firing

Gas turbines


Vertical HRSG



Steam turbines

Horizontal HRSG



Absorption Chiller






61

5

Stirling engines


5.2

Winning concept’s sketch (Faez’s)

62

5.3

Subsystems for winning concept

Fuel Supply & Pre-Treatment System: Drying of Biomass

Co-Combustion System: Indirect Co-firing

Co-Generation System: Gas Turbines

63

Heat Recovery System: Vertical Heat Recovery Steam Generator (HRSG)

Refrigeration Cycle System: Absorption Chiller

Heat Rejection System: Induced Draft Cross Flow Cooling Tower

64

6.

DETAILED SELECTED CONCEPT’S WORKING PRINCIPLE

6.1

Overall system’s working principle The new system working principle is based on following subsystem which is: 1- Fuel supply and pre-treatment – Drying of biomass 2- Co Combustion system – Indirect co firing 3- Co-generation system – Gas turbines 4- Heat recovery system – Vertical HRSG 5- Refrigeration cycle system – Absorption Chiller 6- Heat rejection system – Induced draft cross flow cooling tower.

Initially,the process starts with drying the biomass material. Due to the moisture and water content in the material, it is recommended to reduce it by applying various drying methods which can improve the efficiency of combustion system. After drying process completed, gasification process will take place. In this process the biomass solid is converted into the combustible gases. The output of this process is synthesis gas (syngas) which can be used to produce heat energy by combusting it. The gas then is used to power up gas turbines. Gas turbines will generate electricity and the excess exhaust heat will be recovered using heat recovery steam generator. HRSG will mainly absorb heat from the hot exhaust and produce steam. The steam then enter absorption chiller. Function of absorption chiller is to reject heat and create low temperature condition for steam by circulate it with mixture of liquid refrigerant water and absorbent with high pressure. Low temperature steam then is supplied to the consumer. Lastly, induced draft cross flow cooling tower is used to remove excess heat from the refrigeration system to outside environment.

65

Selected concept’s process flow

Air

Electricity

Gas Turbine

Compress or

Combustion Chamber Fuel Gas Indirect Co-firing System (Gasification) Dry Biomas

Generator

Chilled Water

Exhaust Heat Vertical HRSG

Steam

Steam Absorption Chiller

Steam Water

Drying of Biomass

Induced Draft Cross Flow Cooling Tower

66

Returned Chilled Water

6.2

Subsystem’s working principle 6.2.1

Working Principles (Drying of Biomass)

Biomass fuels mainly contain a portion of water in the contents which termed as moisture content. It is recommended to reduce the moisture content by applying various drying methods which can further improve the efficiency of the combustion system. Besides utilization of fuel with low moisture content can also lowers the investment cost due to more complex technology and process control that mainly affect fuel with high moisturization [3]. Drying of biomass fuels can be seen as economical way of saving on total fuel costs due to its simple process. Basically, the wood logs are piled outdoors with temperature ranging from 35oC above during the summer which naturally reduced the moisture content by 50 to 30 wt% (w.b.) from convection [3]. However, the piling of wood outdoor is only accomplished in the initial stage as the humidity or uncertain weather conditions may affect the biological degradation of wood due to micro-organisms. Afterwards, the biomass fuels are passed through to a continuous drying technologies which may include belt dryers, drum dryers, tube bundle dryers and superheated steam dryers. Drum dryers in the form of rotating drum is most commonly used drying technologies in biomass sector [13]. Rotary dryers has several variations for its design but the most-widely used in industry is the directly heated single-pass rotary dryer. Usually, the biomass material (e.g. wood chip) are filled into a rotating drum which are fed with hot gas that later react with each other. While rotating, the solids in the dryer are lifted that causes reaction with the hot gas flowing in the system while enhancing the heat and mass transfer. Normally, the hot gas can be in the form of flue gas or heated incoming air from a burner or steam heater. Inside the rotating drum, the biomass and hot air flow co-currently which leads to the hottest gases to come in contact with the wettest material [13]. Fine particles which are contained in the exhaust gases leaving the dryer are screened through a cyclone or multicyclone. Indirectly heated rotary dryer operates based on heat conduction where heat is transferred from steam or hot air which passes through the outer wall of the dryer or even inner central shaft of the drum [13]. This design is mainly applied where the hot flue gases or air may contaminate the material within the dryer thus reducing the system performance.

67

Inlet gas coming through the rotary dryers may include temperature ranging from 450o 2,000oF (232o - 1,093oC). Outlet temperature from rotary dryers have ranges from 160o 230oF (71o - 110oC) and in most cases the outlet temperatures are higher than 104oC to avoid condensation of acids and resins [13].

Figure 6: Rotary dryers operation flow for biomass drying

68

6.2.2

Working Principles (Indirect Co-firing)

Indirect co-firing system as known as gasification is a process that converts solid biomass into combustible gases. It is a thermochemical process involving heating the solid biomass in an oxygen-starved environment, partial oxidation, or indirect heating in the absence of oxygen to produce fuel gas called synthesis gas (syngas). Syngas produced can used to produce heat energy by combusting it. The heating value of syngas is within the range of 10 to 50% that of natural gas, depending on the carbon and hydrogen content of the biomass and the properties of gasifier [21]. A schematic diagram of a typical gasifier is shown in Figure 7. The gasification process follows several steps and the first step is pyrolysis. Pyrolysis is a step where thermal decomposition of solid biomass takes place and vaporizes the volatile components of the biomass at around 1000°F. The volatile vapours are mainly hydrogen, carbon monoxide, carbon dioxide, methane, hydrocarbon gases, tar and water vapour. Since biomass feedstock tend to have more volatile components 70 to 86% on a dry basis, pyrolysis plays vital role in gasification of biomass [21].

Figure 7: Schematic Diagram of Gasifier Pyrolysis is followed by further gasification process that converts the leftover tars and char into carbon monoxide by using provision of addition heat such as steam or partial combustion. Some of the tars and hydrocarbons in the vapours are thermally cracked to give smaller molecules, with higher temperatures resulting in fewer remaining tars and hydrocarbon. The char is converted into gas by various reactions between carbon dioxide and 69

steam through steam gasification to generate carbon monoxide and hydrogen. For the production of hydrogen, higher temperatures and pressures are prefer, while carbon monoxide production is prefers higher temperatures and carbon dioxide production is prefers higher pressures [21]. The gases formed from these processes are further react with the reverse water-gas shift reaction in order to change the concentration of carbon monoxide, steam, carbon dioxide and hydrogen within the gasifier. In the end, mixture of the gases is produced from the gasification process and can be used to produce heat energy to generate steam, drive gas turbine and so on [21].

70

6.2.3

Working Principles (Gas Turbine)

Co-generation system or know as combined heat and power (CHP) system is basically a system that produces electricity and heat at the same time. For the same power output, cogeneration system uses less fuel than traditional separate heat and power production, thus making it useful for distribution of heat and electricity demand at the time. There are two types of co-generation system, a topping cycle and also a bottoming cycle. Topping cycle is mainly for the generation of the electricity or mechanical energy first by using a fuel and then the remaining portion of the waste heat is then used in order to produce useful thermal energy. The bottoming cycle produces heat first for manufacturing process by using fuel combustion process. The remaining portion is then use for generation of electricity. Generally, bottoming cycle is used for process-based industries, such as glass and steel. There are various types of co-generation system available, however most of the popular alternatives is the gas turbine and also steam turbine. Gas turbine operates similar to jet engines, with additional heat recovery system in order to capture the heat from the exhaust of the turbine. Gas turbines are highly reliable and also has a wide range of power output (500kW to 250MW). The working principal of the basic gas turbine is shown below.

Figure 8: Working principle of basic gas turbine 71

6.2.4

Working principles (Heat Recovery Steam Generator)

Heat recovery steam generator (HRSG) is a heat exchanger designed to recover the exhaust waste heat from power generation plant prime movers, such as gas turbines or large reciprocating engines, thus improving overall energy efficiencies. HRSGs can be used to generate steam for district heating or factory processes, or to drive a steam turbine to generate more electricity. There are several types of HRSG, but the basic construction techniques are largely similar, comprising banks of tubes mounted in the exhaust path. Exhaust gases at temperatures of 430º–650ºC heat these tubes, through which water is circulated. HRSGs mainly absorb heat from the hot exhaust in the flue gases by convection heat transfer, but, in certain sections, heat is transferred by both radiation and convection. The water is typically held at high pressure to temperatures of around 200ºC, boiling to produce the steam.

HRSG design and construction HRSGs typically comprise three sections: 1) Low pressure (LP) 2) Reheat/intermediate pressure (IP) 3) High pressure (HP) This a triple pressure system, which maximizes plant thermal efficiency. Each section has a steam drum and an evaporator section where water is converted to steam. The steam then passes through superheaters to raise the temperature and pressure past the saturation point. Diverter valves regulate inlet flows, allowing the gas turbine to continue to operate when there is no steam demand, or if the HRSG needs to be taken offline.

Component in HRSG Evaporator This is where the heat from the gas turbine exhaust turns the water in the tubes into steam. The evaporator is so important that it defines the overall HRSG configuration. Since the inlet and outlet temperatures are both close to the saturation temperature for the system pressure, the amount of heat that may be removed from the flue gas is limited. 72

Superheater This dries the saturated steam from the steam drum perhaps only heated a little above saturation point, but sometimes to a much higher temperature for extra energy storage. The superheater is usually positioned in the hot gas stream before the evaporator. The type used depends on the evaporator type.

Economizer This preheats the feedwater, and it replaces steam removed via superheater or steam outlet, and also because of water loss through blowdown. The economizer is conventionally fitted in the path of the colder gas downstream of the evaporator. The type of economizer also depends on the evaporator type, with configurations being typically similar to those of superheaters.

Steam drum The drum stores the steam generated in the water tubes and acts as a phase-separator for the steam/water mixture.

Figure 9: Components of HRSG

73

6.2.5

Working Principle (Absorption Chiller)

In the last section, the chosen unit for the Refrigeration System is the Induced Absorption Chiller. For this section, the overall working principle of the Absorption Chiller will be explained.

Figure 10: Absorption Chiller Similar to the compressor in an electric vapor compression cycle, the absorption system uses its "thermal" compressor (consisting of the generator, absorber, pump and heat exchanger) to boil water vapor (refrigerant) out of a lithium bromide/water solution and compress the refrigerant vapor to a higher pressure. As the pressure of the refrigerant increase, its condensing temperature also does too. In this high temperature and pressure, the refrigerant vapour condenses into liquid. Since the temperature of refrigerant condensation is higher than the ambient temperature, the heat flows out from the condenser and released to the outside environment [7]. Then, the high pressure liquid flows through the throttling valve in which at this stage, its pressure will be reduce and by reducing the fluid’s pressure, this will also cause the boiling point of the fluid to drop. The reduced pressure fluid will then be passing through the evaporator where it will be boiled at reduced temperature and pressure. Since the boiling temperature is now lower than the conditioned air temperature, the heat will move from the conditioned air stream to the evaporator hence causing it to boil [7].

74

Next, the vapour produced will pass through the absorber where it will return to liquid state and then being pulled into the lithium bromide solution (absorption process). The diluted lithium bromide solution will be pumped back to the generator. Since Lithium bromide (absorbent agent) would not boil, the water is easily separated by applying a little bit of heat. The resultant water vapour will pass through the condenser, absorbent solution returns to the absorber and the cycle repeats [7]. Below is the diagram which describes pictorially the process inside the absorption chiller.

Figure 11: Absorption Chiller process

75

6.2.6

Working Principle (Induced Draft Cross Flow Cooling Tower)

In the last section, the chosen unit for Heat Rejection System is the Induced Draft Cross Flow Cooling Tower. For this section, the overall working principle of the Induced Draft Cross Flow Cooling Tower will be explained. Induced Draft Cross Flow Cooling Tower falls into the category of mechanical drafttype cooling tower in which the air is being moved using fans. In Induced Draft Cross Flow Cooling Tower, the water flows vertically through the fill while the air flows horizontally, across the flow of the falling water.

Figure 12: Example of fill which being used in the cooling tower Due to this, the air does not have to pass through the distribution system, allowing the use of gravity flow hot water distribution basins mounted at the top of the unit above the fill. These basins are universally applied on all crossflow towers [20]. Below is the example of the Induced Draft Cross Flow Cooling Tower;

Figure 13: Induced Draft Cross Flow Cooling Tower

76

Typically, the fan setup for the Induced Draft Cross Flow Cooling Tower will be at the top of the structure which draws air upwards against the downward flow of water passing around the wooden decking or packing.

Figure 14: Fan being setup on top of the cooling tower

Since the airflow is counter to the water flow, the coolest water at the bottom is in contact with the driest air while the warmest water at the top is in contact with the moist air, resulting in increased heat transfer efficiency [12].

77

6.3

Peer evaluation of the selected concept 6.3.1

Zul’s evaluation Muhammad Zulfaqqar Kasim

Fuel Supply & Pre-

Drying of biomass system reduces the humidity in raw

Treatment Statement

biomass material which reduces the required heat to

Drying of Biomass

combust. Hence, lower time will be needed to achieve perfect combustion process. It also lowers the need of fuel supply in co-combustion system.


Gasification process in the indirect co-firing system enables

Indirect Co-Firing

the production of fuel that is suitable for use in a gas turbine. The produced fuel namely syngas, has high power to heat ratio and more efficient than the direct combustion process of the solid biomass since it can be combusted at higher temperature. Conversion process of solid biomass to syngas produces

less

combustion

of

waste the

emissions solid

compared

biomass

making

to

direct

it

more

environmental friendly.

Co-Generation System

Gas turbines generally produce high power output and also

Gas Turbine

have higher efficiency and lower start up duration compared to steam turbine. Additionally, the exhaust heat from the turbine can be recovered using heat recovery system together to produce useful thermal energy.


Vertical HRSG generally has high steam production output

Vertical Heat Recovery

depending on the amount of exhaust heat recovered. Besides

Steam Generator (HRSG) that, vertical HRSG takes up less space which can be practical in reducing the usage of space in a plant. Simpler design of vertical HRSG could also mean less maintenance cost.

78

Refrigeration Cycle

Useful steam generated from the heat recovery system is

System

used in absorption chiller to produce chilled water.

Absorption Chiller

Comparing to other components of refrigeration cycle system, absorption chiller produces less CO2 emission. This is due to the process of the absorption chiller which used steam instead of fuel to generate chilled water.


Induced draft cross flow cooling tower takes up less space

Induced Draft Cross

and it is suitable for moderate-size plant. It also has a lower

Flow Cooling Tower

operational and capital costs compared to other types of cooling tower. Besides that, it has simpler design and highly adaptable to different environment. It also capable in reducing the recirculation effect in which will reduce the efficiency of the heat rejection process.

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6.3.2

Adli’s evaluation M. Amir Adli Nazarudin

Fuel Supply & Pre-Treatment System Drying of Biomass

• Reduction in total fuel costs by lowering the moisture content in biomass fuels. • Improvement in combustion efficiency and ash emission. • Integrating natural heating process and dryer which save in operating cost.

Co-combustion System Indirect Co-Firing

• Availability of fuel resource (e.g. woods) which could replace dependability on fossil fuels. • Producing low calorific fuel gas that could power the gas turbines. • No considerable impact on the boiler performance e.g. stability, availability and capacity.

Co-generation (CHP) System Gas Turbines

• Capable of producing large power output rated at >150 kW and great efficiency of > 30%. • High initial investment for installation and commissioning but relatively low operating or maintenance costs (major overhaul every 3-4 years). • Suitable for large industrial or commercial applications which require considerable amount of power.

Heat Recovery System Vertical Heat Recovery Steam Generators

• Vertical design requires less floor space in the power plant. • Has smaller boiler volume and less probability of steam blockage in economizers during start-up.

Refrigeration Cycle System Absorption Chiller

• Saving in operating costs by avoiding peak electric demand charges and rates. • Eliminate the use of CFC and HCFC refrigerants. • Very high efficiency at 0.60 COP and 5.86 kW/ton for single effect absorption.

Heat Rejection System Induced-Draft Cross Flow Cooling Tower

• Equipped with axial fans to facilitate the flow of air into the unit. • Used in smaller capacities, air flow horizontally while the water fall downward.

80

6.3.2

Razin’s evaluation

RAZIN AKMAL B RUSLAN Fuel supply & pre treatment system This system help to remove the moisture Drying of biomass and water content in the biomass material. By removing the mositure content it will improve the efficiency of the combustion system. Moisture will delay the combustion process and more energy needed to fully burnt the biomass. As dry biomass combustion more quicker and less energy neeeded. Co-combustion system Syngas is produce from the gasification of Indirect co-firing indirect co-firing. This output can be use to produce heat enerygy by combusting it. The advantage of the system that it has low emission of contaminant to environment. Co-generation system Gas turbine is choosen because this system Gas turbines is already establish and been used by many GDC plant. The benefits of gas turbine compare to steam turbine is the output is higher and also more efficient. In term of maintenance cost, the cost of maintenance gas turbines more cheaper. So it is more favourable. Heat recovery system Vertical HRSG have higher output compare Vertical Heat recovery steam generator to other system. In term of maintenance , it is easily repaired and the sizing area not consuming large space. Refrigeration cycle system Eventhough the capital cost and operational Absorption chiller cost of absorption chiller is high. The output capacity of the system is very high and it is enviromentally friendly. Heat rejection system Has simpler design. Consume medium space Induced draft cross flow cooling tower to built thus decrease construction cost. The capital and operational cost also lower compare to other type heat rejection system. Have average performanc and can be consider suitable for the plant system.

81

6.3.4

Faez’s evaluation Ku Muhammad Faez Ku Ariffin

Fuel Supply & Pre-

Drying of biomass system helps to reduce the humidity level

Treatment Statement

in biomass which eventually reduces the required heat to

-Drying of Biomass

combust. Thus, it will require lower time to achieve perfect combustion process. It also lowers the fuel supply in cocombustion system.


Gasification process in the indirect co-firing system enables

-Indirect Co-Firing

the production of fuel to be use in the gas turbine, which is known as syngas. In addition, syngas has high ratio of power to heat and has more efficient than direct combustion of the solid biomass because it can be combusted at higher temperature. Conversion process of solid biomass to syngas has lesser byproduct of contaminants compared to direct combustion of the solid biomass thus it has low emission of contaminants to environment and makes it better than direct combustion in term of environmental friendly.


Gas turbine has wide range of power output and also higher

-Gas Turbine

efficiency and lower start up duration compared to steam turbine since it is using air to drive the turbine. Besides, the exhaust heat from the turbine could be captured and recovered using heat recovery system together to produce useful thermal energy.


Vertical HRSG has high output of steam produced,

-Vertical Heat Recovery

depending the amount of exhaust heat enters. Besides that,

Steam Generator (HRSG) vertical HRSG has a medium size which is practical in reduces the whole system capacity. It also has simple maintenance compared to other types of HRSG and thus the cost of maintenance can be minimized.

Refrigeration Cycle

Useful steam produce from the heat recovery system is used

System

to power up absorption chiller and generate chilled water.

-Absorption Chiller

Comparing to other components of refrigeration cycle 82

system, absorption chiller is more environmental friendly in term of CO2 emission. This is due to the process of the absorption chiller is which using steam instead of fuel to generate chilled water. Heat Rejection System

Induced draft cross flow cooling tower has medium size and

-Induced Draft Cross

it is suitable for moderate-size plant, and also lower

Flow Cooling Tower

operational and capital costs compared to other types of cooling tower. In addition, its design is simpler and has high adaptability for different environment. It also capable in reducing the recirculation effect in which will reduce the efficiency of the heat rejection process.

83

6.3.5

Choong’s evaluation Choong Weng Hong

Fuel Supply & Pre-

Applying drying of biomass helps to reduce the moisture

Treatment Statement

content in biomass which eventually reduces the required

Drying of Biomass

heat to combust. With this pre-treatment, the efficiency of co-combustion system could be improved. It also lower the investment cost in fuel supply in co combustion system.


Syngas produced from indirect co-firing, which also known

Indirect Co-Firing

as gasification, can be directly used in generating steam or gas turbine or engines with heat recovery. Besides that, syngas has high ratio of power to heat and is potentially more efficient than direct combustion of the solid biomass because it can be combusted at higher temperature. Conversion of solid biomass to syngas using gasification has lesser byproduct of contaminants such as flying ashes compared to direct combustion of the solid biomass. Thus, gasification has low emission of contaminants to environment and this makes it better than direct combustion in term of environmental friendly.


Gas turbine has higher efficiency and lower start up duration

Gas Turbine

compared to steam turbine since it is using air to drive the turbine. It also has a wide range of power output. Moreover, the heat exhaust from the turbine could be captured and recovered using heat recovery system. Thus, the system efficiency is improved.


Vertical HRSG has high output of steam depending on the

Vertical Heat Recovery

exhaust heat from co-generation system. Besides that,

Steam Generator (HRSG) vertical HRSG has a medium size which reduces the whole system capacity. It also has simple maintenance compared to horizontal HRSG and thus lower the cost of maintenance. Refrigeration Cycle

Steam produce from the heat recovery system is used to

System

power up absorption chiller and generate chilled water. By

Absorption Chiller

comparing to others components of refrigeration cycle 84

system in morphology chart, absorption chiller is more environmental friendly in term of CO2 emission. This is because absorption chiller is using steam instead of fuel to generate chilled water. Heat Rejection System

Induced draft cross flow cooling tower has medium size and

Induced Draft Cross Flow it is suitable for not very large plant such as biomass-based Cooling Tower

GDC plant. It also has lower costs in operational and capital compared to other types of cooling tower. Moreover, its design is not complex and has high adaptability. Thus, it is suitable for biomass-based GDC plant.

85

7.

Governing Equation

7.1

Gasification

If the syngas is used for direct burning, the gasification efficiency is defined as:

In which:

ƞ𝑡ℎ =

�𝐻𝑔 × ṁ𝑔 � + (ṁ𝑔 × 𝜌𝑔 × 𝐶𝑝 × 𝛥𝑇) × 100% 𝐻𝑔 × 𝑀𝑠

Ƞth = gasification efficiency (%) Hg = heating value of the gas (kJ/m3) ṁg = volume flow of gas (m3/s) ρg = density of the gas (kg/m3) Cp = specific heat of the gas (kJ/kg.ºC) 𝛥T = temperature difference between the gas at the burner inlet and the fuel entering the gasifier (ºC) 7.2

Closed-Cycle Gas Turbine

Data which refer to the operation of the gas turbine are useful to calculate the power output and total efficiency of the closed gas turbine (utilized in co-generation plant). Compressor pressure ratio, γ Inlet temperature at each compressor side, oC Inlet temperature turbine, oC Lowest pressure in cycle, bar Isentropic efficiency of compressor, ηc Isentropic efficiency of turbine, ηT Pressure loss in boiler, % Pressure loss in intercooler, regenerator, % Pressure loss after cooler, % Effectiveness of regenerator, % Generator efficiency, ηg Mechanical efficiency, ηm Mass flow rate of gases in the cycle, 𝑚̇ *Combustion efficiency, ηcomb

86

The temperature increase in the compressor is calculated by the following equation: 𝐶𝑝 −1 � 𝐶𝑝

𝑇1 � �𝛾 Δ𝑇𝑐 = 𝑇2 − 𝑇1 = 𝜂𝑐

�

where cp is the specific heat ratio of the flue gases based on temperature, oC. The temperature increase in the turbine is given from the relation:

Δ𝑇𝑇 = 𝑇6 − 𝑇7 = 𝜂𝑇 × 𝑇6 �1 −

𝛾𝑇

1

𝐶𝑝 −1 � � � 𝐶𝑝

where γT is the turbine pressure ratio in terms of P6 / P7 and cp is the specific heat ratio of the flue gases based on temperature, oC. The power output from the turbine is calculated from the equation as follows: 𝑃𝑒𝑙 = (𝑃𝑇 × 𝜂𝑚 − 𝑃𝐶 )𝜂𝑔

𝑃𝑒𝑙 = �𝑚̇𝑐𝑝𝑇 Δ𝑇𝑇 𝜂𝑚 − 2𝑚̇𝑐𝑝𝑐 Δ𝑇𝑐 �𝜂𝑔 87

The total efficiency of the closed-cycle gas turbine operation is calculated as: 𝜂𝑡𝑜𝑡𝑎𝑙 =

𝑃𝑢𝑠𝑒𝑓𝑢𝑙 𝑃𝑒𝑙 = 1 𝑃𝑓𝑢𝑒𝑙 𝑚̇𝑐𝑝 (𝑇6 − 𝑇5 ) 𝜂

𝑐𝑜𝑚𝑏

where T5 is calculated based on heat exchanger efficiency, ηHE as follows: 𝜂𝐻𝐸 = 7.3

𝑇5 − 𝑇4 𝑇7 − 𝑇4

Absorption Chiller

Cooling capacity of the chiller load:

where;

𝑄𝑐𝑜𝑜𝑙𝑖𝑛𝑔 = 𝑚̇𝐶𝐻𝑊 × 𝐶𝑝 × (𝑇𝐶𝐻𝑊𝑅 − 𝑇𝐶𝐻𝑊𝑆 )

𝑚̇𝐶𝐻𝑊 is the flow rate of the chilled water

TCHWR is the temperature of the chilled water entering the chiller TCHWS is the temperature of the chiller water leaving the chiller Cp is the specific heat of water The heat delivered to the chiller by steam condensation is calculated from (the quantity can also be estimated from electrical power consumption in the steam boiler):

where;

𝑄ℎ𝑒𝑎𝑡 = 𝑚̇𝑠𝑡𝑒𝑎𝑛 × (ℎ𝑠𝑡𝑒𝑎𝑚 − ℎ𝑐𝑜𝑛𝑑𝑒𝑛𝑠𝑎𝑡𝑒 )

𝑚̇𝑠𝑡𝑒𝑎𝑚 is the flow rate of the steam supply

hstean is the enthalpy of the steam supply (based on temperature) hcondensate is the enthalpy of the condensate (based on temperature

88

8.

CONCLUSION It has been a challenge to produce a cooling system that is excellent in terms of its

maintainability, cost efficiency, and energy efficiency. The existing individual cooling system is neither that efficient in terms of energy efficiency nor in terms of cost efficiency. Meanwhile, the current GDC system that utilizes natural gas is becoming too costly to run due to ever increasing price of petroleum based fuel. To tackle this issue, several objectives were set for this design project. Firstly, to produce a Biomass-powered GDC design that has a better or comparable output compared to conventional GDC. Secondly, to design a cost-efficient Biomass-powered GDC plant throughout its service in terms of maintenance cost and also in terms of fuel cost. Lastly to produce a cleaner Biomass-powered GDC by utilizing renewable alternative source of fuel. The design project starts by selecting a datum to be the system and also performance reference for the Biomass-GDC plant design. Next, the original system of the selected datum was dissected (undergo decomposition) both physically and functionally to identify thoroughly the subsystems in the referred datum, and also according to the requirements set by the project question (A Biomass system to be included in the GDC system). After having all the information of the basic system, a morphology chart was produced, in which all the alternatives/means to obtain the desired output were listed down in a table. After that, several concepts were generated from the alternatives given and justifications were made for each and every concepts generated. Each and every member of the team will be having their own concepts generated. Later, all of these concepts were evaluated. However, the evaluation was done through the breakdown of each concept’s subsystems. Objective trees for each subsystem were created and from there, the weightage for every primary and design criteria were assigned according to their importance. Then, after having all of the criterions sorted out, it was then being evaluated using Weighted Decision Matrix (WDM). In this matrix, scores and rating will be given to every concept’s individual subsystems. Later, the scores/ratings for all the concept’s subsystems will be totalled up and the concept that yielded the highest sum will be chosen as the main concept for the project. In the case for this project, the concept chosen is Faez’s concept where the subsystems for his concepts are; drying of Biomass method for Fuel Supply & Pre-Treatment system, Indirect co-firing for co-combustion system, Gas 89

turbines for Co-Generation system, Vertical Heat Recovery Steam Generator (HRSG) for Heat Recovery system, Absorption chiller for Refrigeration Cycle System, and finally Induced Draft Cross Flow Cooling Tower for the Heat Rejection System. The entire overall and the chosen subsystems’ working principles, advantages and strength of the selected concepts were also discussed in the previous part of the reports. Each and every members of the group had also given their own feedback and comments regarding the chosen concept. Finally, several related governing equations for subsystems were identified and had also been included in the report as the preparation for the next stage of the project. All in all, the current progress of the project is generally on track in achieving all the objectives set for the project as the concept selected for this project is generally able to produce output that is comparable to the normal GDC plant, a relatively cost efficient plant in terms of fuel costs and maintenance and able to utilize biomass as the alternative fuel.

90

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94

MSD I - Final Group Report (Biomass-Powered Gas Disctrict Cooling Plant)

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