Industrial Training Report On Indraprastha Power Generation Co. Ltd & Pragati Power Co. Ltd.
Submitted By : SANU SAURABH PRATIK 1021640044 IIMT COLLEGE OF ENGG.
Acknowledgement I express my sincere gratitude to the management of “Indraprastha Power generation Co. Ltd & Pragati Power Co. Ltd” for providing me with the opportunity to undergo training in this esteemed organization. I take the prerogative to express my gratitude Mr. Stainder Sharma (A.M., TG) for his valuable suggestion and guidance through my training period. I also take the opportunity to thanks Mr. Nitin Kumar (A.M. TG), Mr. Harish Kumar (Manager, Boiler), Mr.Taneja (A.M. Boiler for diligent guidance without which the project would not have been success. I special thanks to Swati Upadhyay (Assistant manager HR) for sharing their experience and provide their support in technical matters. I also acknowledge the entire staff of IPGCL & PPCL for making brief stay in the power plant a memorable.
Preface With day to day advantage of new technology the older machinery are being replaced by new machinery. Now it has not been the work of semi skilled persons. It has opened a new horizon for degree holder engineers. But to do the job properly a suitable training is needed. The knowledge of entire system is must for an engineer to do the trouble shooting in the quickest possible way so that the production does not get effected. So for engineering the industrial training is playing a vital role in developing the practical knowledge. The industrial training is not merely an academic requirement but a professional necessity too. With the increasing demand and utilization of electricity and mechanical and electrical engineer should be well versed or at least must be familiar with the generation of electricity, at the same time must be capable for fault detection. It is thus the responsibility of a mechanical engineer to deal with the sophistication and make the maximum possible utilization.
CONTENTS S.NO 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Title of Heading About the company Introduction of Rajghat Power House Overview of thermal power plant Steam Rankine Cycle Steam Turbine Turbo-Generator Arrangement Bearings Valves The steam & water circuits Deareator Boiler Condenser Feed Water Pump Coal handling Plant Ash handling Plant Economizer Turbo Generator Water Treatment Plant Gas Turbine Power Station (GTPS) Principle of a gas Turbine power Station Brayton Cycle Air Compressor Combustion Chamber Gas Turbine Pragati Power Station Silent Features of PPCL Brief History Fuel Raw Water Emission Control Funding
Page No. 06 09 11 12 14 16 19 20 21 22 26 27 31 38 42 46 51 52 54 62 62 63 64 64 64 65 66 67 67 67 68 68
33 34 35 36 37 38 39 40 41 42 43
Load Factor Mechanical Equipment Generators Stator Rotor Bearing Auxiliary System Appendix-A Appendix-B Appendix-C Landmarks
69 69 74 77 78 78 79 82 84 85 86
About the company Beholding the grimness of power situation in Delhi and failure of all previous attempts in restoring the quality of service to the citizens Delhi Electricity Board Regulatory Commission (DERC) was constituted in May 1999 whose prime responsibility was to look into the entire gamut of existing activity and search for various ways of power sector reforms. This was followed with a Tripartite Agreement which was signed by the government of Delhi, DVB employees to ensure the cooperation of stakeholders in this reform process. The tripartite agreement sent off very positive vibes to the people in general as well as to the investor community about the sincere and hassle-free objectives of power reforms. The Government of India on July 1, 2002, implemented the reforms by unbundling DVB into six companies, one holding company, one generation company (GENCO), one transmission company (TRANSCO) and three distribution companies (DISCOMS). The government handed over the management of the business of electricity distributions to there private companies since July 1, 2002 with 51% equity with the private sector. It was thus that IPGCL (GENCO) came into existence with the aim of meeting the power demands of a city which is the capital of one of the most populated countries of the world and whose resources fall much below its demand and since then its contribution to the power sector has been beyond the expectations as is evident from the
current power situation in the city. The following facts may summarize the success story of a never before fundamental reform: 330 MW capacity Pragati Power Station was commissioned in the year 2002-03 and performing excellently. Achieved 100.4% PLF during the month of Jan.,’05 and 88.27% PLF (Deemed PLF 95%) during the year 2004-05, Pragati Power Corporation Ltd. paid dividends of Rs.17.5 Cr., for FY 2003-04 & Rs.14 Cr. for FY 2004-05 as well as 2005-06. The performance of Indraprastha Gas Turbine Power Station which was 47.24% in 2001-02 increased to 70.76% (deemed PLF 75.35%) in 2005-06. This is the best performance of the station in a year since its commissioning in 1985-86. The station also achieved highest ever generation in a day, 5.743 MU (84.86% PLF) on 26.12.05 and highest ever generation in a month, 166.227 MU (79.23% PLF) in October, 2005. The forced outages of the station have also reduced from 17.75 % to 5.2 %. The overall performance of GENCO increased from 45.90% during the year 2001-02 to 64.35% in 200506.
IPGCL (Indraprastha Power generation Co. Ltd) & PPCL (Pragati Power Co. Ltd.) are the companies which produces electricity in Delhi. Under IPGCL & PPCL, 4 power stations are in operation to supply electricity continuously. Power Stations Associated with IPGCL are: 1.) Rajghat Power Plant. 2.) Gas Turbine Power Station , I.P Estate. And Those with PPCL are: 1.) Pragati Power Co. Ltd (PPCL -1), I.P Estate. 2.) Pragati Power Co. Ltd (PPCL -2 ) , Bawana.
Rajghat Power House Two Units of 67.5 MW were installed in 1989-90 at Rajghat Power House as Replacement of old Units and the present generation capacity of this Station is 135 MW. Further, the station has acquired the following certifications:
ISO-9001:2000 for Quality Management ISO-14001:2004 for Environment Management.
OHSAS-18001:2007 for Occupational Health & Safety Management
Rajghat Power House Specifications
1. Location:
Rajghat
2. Type: thermal power plant
Coal
3. Installed Capacity: 135 MW
2 x 67.5 MW =
based
4. Land Detail a. Plant area: b. Ash dump area:
40 acres 24 acres
5. Cooling Water a. Source:
River Yamuna
b. Cooling Method: cycle with cooling tower 6. Fuel: Coal a. Type: b. Linked coal mines: c. Gross calorific value: kcal/kg d. Ash content: e. Sulphur content: f. Requirement i. With design coal: 2000MT/day ii. With actual coal: 2400MT/day g. Stockyard a. Area: b. Capacity: 7. Oil a. Type: b. Nearest service outlet: Shakurbasti oil depot
Closed
Bituminous Piparwar 3180-4280 35-42.2 % 0.5 %
72000 sq. mt. 20000MT
LSHS\LDO Mathura-
Overview of a Typical Thermal Power Plant
Power plants generate electrical power by using fuels like coal, oil or natural gas. A simple power plant consists of a boiler, turbine, condenser and a pump. Fuel, burned in the boiler and superheater, heats the water to generate steam. The steam is then heated to a superheated state in the superheater. This steam is used to rotate the turbine which powers the generator. Electrical energy is generated when the generator windings rotate in a strong magnetic field. After the steam leaves the turbine it is cooled to its liquid state in the condenser. The liquid is pressurized by the pump prior to going back to the boiler. Thus the main inputs required by a plant are: Coal: Should have high calorific value and low ash content Water: De-mineralized water for steam generation
Air In this chapter first steam and its properties are described which are essential to the understanding of the underlying principle of the thermal plant, the Rankine cycle which is presented next. Steam Steam power is fundamental to what is by far the largest sector of the electricity-generating industry and without it the face of contemporary society would be dramatically different from its present one. We would be forced to rely on hydro-electric power plant, windmills, batteries, solar cells and fuel cells, all of which are capable of producing only a fraction of the electricity we use. Steam is produced by boiling of water and it is achieved at atmospheric pressure at 100 degree Celsius. Let us consider a quantity of water that is contained in an open vessel. Here, the air that blankets the surface exerts a pressure on the surface of the fluid and, as the temperature of the water is raised, enough energy is eventually gained to overcome the blanketing effect of that pressure and the water starts to change its state into that of a vapour (steam). If the pressure of the air blanket on top of the water were to be increased, more energy would have to be introduced to the water to enable it to break free. In other words, the temperature must be raised further to make it boil. To illustrate this point, if the pressure is increased by 10% above its normal atmospheric value, the temperature of the water must be raised to just above 102 °C before boiling occurs.
The information relating to steam at any combination of temperature, pressure and other factors may be found in steam tables, which are nowadays available in software as well as in the more traditional paper form. These tables were originally published in 1915 by Hugh Longbourne Callendar (1863-1930), a British physicist. Because of advances in knowledge and measurement technology, and as a result of changing units of measurement, many different variants of steam tables are today in existence, but they all enable one to look up, for any pressure, the saturation temperature, the heat per unit mass of fluid, the specific volume etc. Steam becomes superheated when its temperature is raised above the saturation temperature corresponding to its pressure. This is achieved by collecting it from the vessel in which the boiling is occurring, leading it away from the liquid through a pipe, and then adding more heat to it. This process adds further energy to the fluid, which improves the efficiency of the conversion of heat to electricity. As stated earlier, heat added once the water has started to boil does not cause any further detectable change in temperature. Instead it changes the state of the fluid. Once the steam has formed, heat added to it contributes to the total heat of the vapour. This is the sensible heat plus the latent heat plus the heat used in increasing the temperature of each kilogram of the fluid through the number of degrees of superheat to which it has been raised. In a power plant, a major objective is the conversion of energy locked up in the input fuel into either usable heat or electricity. In the interests of
economics and the environment it is important to obtain the highest possible level of efficiency in this conversion process. Rankine Cycle: The Working Principle The Carnot cycle postulates a cylinder with perfectly insulating walls and a head which can be switched at will from being a conductor to being an insulator. Even with modifications to enable it to operate in a world where such things are not obtainable, it would have probably remained a scientific concept with no practical application, had not a Scottish professor of engineering, William Rankine, proposed a modification to it at the beginning of the twentieth century. The concepts that Rankine developed form the basis of all thermal power plants in use today. Even today’s combined-cycle power plants use his cycle for one of the two phases of their operation.
In the system shown in figure, water is heated in feed heaters (A to B) using steam extracted from the turbine. Within the boiler itself, heat is used to further pre-warm the water (in the economiser) before it enters the evaporative stages (C) where it boils. At D superheat is added until the conditions at E are reached at the turbine inlet. The steam expands in the turbine to the conditions at point F, after which it is condensed and returned to the feed heater. The energy in the steam leaving the boiler is converted to mechanical energy in the turbine, which then spins the generator to produce electricity. The diagram shows that the energy delivered to the turbine is maximised if point E is at the highest possible value and F is at the lowest possible value.
THERMAL EFFICIENCY
Steam Turbine (Prime Mover )
A steam turbine at Rajghat Power station
Raising steam Steam is mostly raised from fossil fuel sources, mostly coal but also oil and gas, in a combustion chamber. Recently these fuels have been supplemented by limited amounts of renewable biofuels and agricultural waste. The chemical process of burning the fuel releases heat by the chemical transformation (oxidation) of the fuel. This can never be perfect. There will be losses due to impurities in the fuel, incomplete combustion and heat and percentage of the available energy in the fuel.
Working Principles High pressure steam is fed to the turbine and passes along the machine axis through multiple rows of alternately fixed and moving blades. From the steam inlet port of the turbine towards the exhaust point, the blades and the turbine cavity are progressively larger to allow for the expansion of the steam. The stationary blades act as nozzles in which the steam expands and emerges at an increased speed but lower pressure. (Bernoulli's conservation of energy principle Kinetic energy increases as pressure energy falls). As the steam impacts on the moving blades it imparts some of its kinetic energy to the moving blades. There are two basic steam turbine types, impulse turbines and reaction turbines, whose blades are designed control the speed, direction and pressure of the steam as is passes through the turbine.
Impulse Turbines The steam jets are directed at the turbine's bucket shaped rotor blades where the pressure exerted by the jets causes the rotor to rotate and the velocity of the steam to reduce as it imparts its kinetic energy to the blades. The blades in turn change the direction of flow of the steam however its pressure remains constant as it passes through the rotor blades since the cross section of the chamber between the blades is constant. Impulse turbines are therefore also known as constant pressure turbines. The next series of fixed blades reverses the direction of the steam before it passes to the second row of moving blades.
Reaction Turbines The rotor blades of the reaction turbine are shaped more like aerofoils, arranged such that the cross section of the chambers formed between the fixed blades diminishes from the inlet side towards the exhaust side of the blades. The chambers between the rotor blades essentially form nozzles so that as the steam progresses through the chambers its velocity increases while at the same time its pressure decreases, just as in the nozzles formed by the fixed blades. Thus the pressure decreases in both the fixed and moving blades. As the steam emerges in a jet from between the rotor blades, it creates a reactive force on the blades which in turn creates the turning moment on the turbine rotor, just as in Hero's steam engine. (Newton's Third Law - For every action there is an equal and opposite reaction). The turbine employed at the station comprises of 47 stages one of which is impulse and the rest are reaction stages.
Turbine-Generator arrangement The plant employs a 2-pole synchronous generator with a synchronous speed of 3000 rpm. The output frequency is determined by the relation
where N is the rotor speed in RPM f is the output frequency of generator
P is the number of poles of generator The generator is air cooled and the bearings are cooled by oil which is supplied by various oil pumps EOP, JOP, BOP etc. The detailed description of the generator unit is provided in Appendix-C. The following figure shows the arrangement of turbine and generator set.
Overall turbine and generator arrangement
Bearings Steam turbines are provided with journal bearings and thrust bearings. Journal bearings are at each end of each rotor to support the weight of the rotor. One thrust
bearing is provided for the entire steam turbine to maintain the axial position of the rotor. Journal Bearings. The journal bearings are constructed of two halves that enclose the shaft. The inside of the bearing adjacent to the shaft is lined with Babbitt metal. Babbitt is an alloy of tin, copper, and antimony that has ant seizing qualities and a natural oiliness. The journal bearings are oil-pressure lubricated. Oil flow is controlled to limit oil temperature rise to a set value. Thrust Bearings. The thrust bearing consists of Babbitt metal lined, stationary shoes that run against the rotor thrust runner. Shoes on both sides of the runner prevent movement in either axial direction. The thrust bearing compartment is oil-pressure flooded with the oil introduced near the shaft and flowing outward by the centrifugal action of the runner. Oil flow is controlled to limit oil temperature rise to a set value. Valves Major control valves associated with the steam turbine and their operations are as follows: Main Steam Stop (Throttle) Valves: The steam from the steam generator flows to the main steam stop or throttling valves. The primary function of the stop valves is to provide backup protection for the steam turbine during turbine generator trips in the event the main steam control valves do not close. The energy in the main
steam and steam generator can quickly cause the turbine to reach destructive overspeed on loss of the generator load. The main steam stop valves close from full open to full closed in 0.15 to 0.5 s. The stop valves are also closed on unit normal shutdown after the control valves have closed. A secondary function of the stop valves is to provide steam throttling control during startup. The stop valves have internal bypass valves that allow throttling control of the steam from initial turbine roll to loads of 15% to 25%. During this startup time, the main steam control valves are wide open and the bypass valves are used to control the steam flow. Main Steam Control (Governor) Valves: The steam flows from the stop valves to the main steam control or governor valves. The primary function of the control valves is to regulate the steam flow to the turbine and thus control the power output of the steam turbine generator. The control valves also serve as the primary shutoff of the steam to the turbine on unit normal shutdowns and trips.
Steam & Water Circuits Steam Generation and use The steam generation occurs in banks of tubes that are exposed to the radiant heat of combustion. The steam leaves the drum and enters a bank of tubes where more
heat is taken from the gases and added to the steam, superheating it before it is fed to the turbine. The superheater comprises a single bank of tubes but in many cases multiple stages of superheater tubes are suspended in the gas stream, each abstracting additional heat from the exhaust gases. In boilers (rather than HRSGs), some of these tube banks are exposed to the radiant heat of combustion and are therefore referred to as the radiant superheater. Others, the convection stages, are shielded from the radiant energy but extract heat from the hot gases of combustion.
Fig: Schematic of a boiler
After the flue gases have left the superheater they pass over a third set of tubes (called the economizer), where almost all of their remaining heat is extracted to prewarm the water before it enters the drum. Finally the last of the heat in the gases is used to warm the air that is to be used in the process of burning the fuel. The major moving items of machinery shown in the diagram are the feed pump, which delivers water to the system, and the fan which provides the air needed for combustion of the fuel (in most plants each of these is duplicated). In a combined-cycle plant the place of the combustion-air fan and the fuel firing system is taken by the gas turbine exhaust. Feed water-condensate cycle Inside the plant, the steam and water system forms a closed loop, with the water leaving the condenser being fed back to the feed pumps for reuse in the boiler. However, certain other items of plant now become involved, because the water leaving the condenser is cold and contains entrained air which must be removed. Air becomes entrained in the water system at start-up (when the various vessels are initially empty), and it will appear during normal operation when it leaks in at those parts of the cycle which operate below atmospheric pressure, such as the condenser, extraction pumps and low pressure feed heaters. Leakage can occur in these areas at flanges and at the sealing glands of the rotating shafts of pumps. Air entrainment is aided by two facts: one is that cold water can hold greater amounts of
oxygen (and other dissolved gases) than can warm water; and the other is that the low-pressure parts of the cycle must necessarily correspond with the low temperature phases.
Steam and Water circuit
The Deareator The Deareator removes dissolved gases by vigorously boiling the water and agitating it, a process referred to as 'stripping'. The water entering at the top is mixed with steam which is rising upwards. The steam, taken directly from the boiler or from an extraction point on the turbine, heats a stack of metal trays and as the water cascades down past these it mixes with the steam and becomes agitated, releasing the entrained gases. The steam pressurizes the Deareator and its contents so that the dissolved gases are vented to the atmosphere. Minimizing corrosion requires the feed-water oxygen concentration to be maintained below 0.005 ppm or less and although the Deareator provides an effective method of removing the bulk of entrained gases it cannot reduce the concentration below about 0.007 ppm. For this reason, scavenging chemicals are added to remove the last traces of oxygen.
Principle of a Deareator
Boiler Steam generator or a boiler is a closed pressure vessel used for generation of steam under pressure. A boiler is usually made of steel in which the chemical energy of fuel is converted by combustion in to heat and this heat energy of products of combustion is transferred to water so as to produce steam. When steam is used in power generation, it is generated at high pressure and in large quantities due to high
efficiency requirements. The design of such boiler is quite intricate and it depends upon the type of fuel used and its capacity. In a boiler, the working fluid i.e. water receives heat due to combustion of fuel and is converted into steam at constant pressure. Its efficiency is around 90%.
A boiler is a device for generating steam, which consistsof two principal parts: the furnace, which provides heat, usually by burning a fuel, and the boiler proper, a device in which the heat changes water into steam. The steam or hot fluid is then recirculated out of the boiler for use in various processes in heating.
WATER TUBE BOILER Here in rajghat power house water tube boiler is used for generating the steam. In these boilers water is inside the tubes and hot gases are outside the tubes. They consist of drums and tubes. The boiler receives the feed water, which consists of varying proportion of recovered condensed water (return water) and fresh water, which has been purified in varying degrees (make up water). The make-up water is usually natural water either in its raw state, or treated by some process before use. Feed-water composition therefore depends on the quality of the make-up water and the amount of condensate returned to the boiler. The steam, which escapes from the boiler, frequently contains liquid droplets and gases. The water remaining in liquid form at the bottom of the boiler picks up all the foreign matter from the water that was converted to steam. The impurities must be blown down
by the discharge of some of the water from the boiler to the drains. The permissible percentage of blown down at a plant is strictly limited by running costs and initial outlay. The tendency is to reduce this percentage to a very small figure.
Boiler Operation: The boiler is a rectangular furnace about 50 ft on a side and 130 ft tall. Its walls are made of a web of high pressure steel pressure tubes about 2.3 inches in diameter. Pulverized coal is air blown into the furnace from fuel nozzle at the four corners and it rapidly burns, forming a large fire ball at the centre. The thermal radiation of the fire ball heats the water that circulates through the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four times the throughput and is typically driven by pumps. As the water in the boiler circulates it absorbs heat and changes into steam at 700˚F (370˚C) and 3200 psi (22.1 Mpa). It is separated from the water inside a drum at the top of the furnace. The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace. Here the steam is superheated to 1000˚F (540˚C) to prepare it for the turbine.
Proper treatment of boiler feed water is an important part of operating and maintaining a boiler system. As steam is produced, dissolved solids become concentrated and form deposits inside the boiler. This leads to poor heat transfer and reduces the efficiency of the boiler.
Condenser A condenser is a device or unit used to condense a substance from its gaseous to its liquid state, typically by cooling it. In so doing, the latent heat is given up by the substance, and will transfer to the condenser coolant. Condensers are typically heat exchangers which have various designs and come in many sizes ranging from rather small (hand-held) to very large industrial-scale units used in plant processes. For example, a refrigerator uses a condenser to get rid of heat extracted from the interior of the unit to the outside air. Condensers are used in air conditioning, industrial chemical processes such as distillation, steam power plants and other heat-exchange
The function of the condenser is to condense exhaust steam from the steam turbine by rejecting the heat of vaporisation to the cooling water passing through the condenser.
The
temperature
of
the
condensate
determines the pressure in the steam/condensate side of the condenser. This pressure is called the turbine backpressure and is usually a vacuum. Decreasing the condensate temperature will result in a lowering of the turbine backpressure. Note: Within limits, decreasing the turbine backpressure will increase the thermal efficiency of the turbine. Condenser and cooling system The condensers and cooling systems involved in condensing the exhaust steam from a steam turbine and transferring the waste heat away from the power station.
Types of Cooling Systems The type of cooling system used is therefore heavily influenced by the location of the plant and on the availability of water suitable for cooling purposes. The selection process is also influenced by the cooling system's environmental impacts. Open cycle cooling systems may be used for plants sited beside large water bodies such as the sea, lakes or large rivers that have the ability to dissipate the waste heat from the steam cycle. In the open system, water pumped from intakes on one side of the power plant passes through the condensers and is discharged at a point remote from the intake (to prevent recycling of the warm water discharge).
Open systems typically have high flow rates and relatively low temperature rises to limit the rise in temperature in the receiving waters. A typical 350 MW unit would have a flow of some 15000 to 20000 L/s.
Open
Cycle
with
Helper
Cooling
Tower
In this system, cooling towers are installed on the discharge from open systems in order to remove part of the waste heat, so that the load on the receiving waters is contained within pre set limits. Systems with helper cooling towers are common in Germany and France where cooling supplies are drawn from the large rivers. The helper towers are used in the warmer summer periods to limit the temperature of the discharged cooling water, usually to less than 30 Celsius.
Closed Cycle Wet Cooling Systems In closed cycle wet cooling systems, the waste energy that is rejected by the turbine is transferred to the cooling water system via the condenser. The waste heat in the cooling water is then discharged to the atmosphere by the cooling tower. In the cooling tower, heat is removed from the falling water and transferred to the rising air by the evaporative cooling process. The falling water is broken up into droplets or films by the extended surfaces of the tower 'fill'. This 'fill' in the later Queensland towers is manufactured from plastic. Some of the warm water, typically 1 to 1.5% of the cooling water flow, is transferred to the rising air, and this is visible in the plume of water vapour above towers in times of high humidity. The evaporation rates of the Queensland 350 MW cooling systems are typically 1.8 liters of water per
kWh
of
power
generated.
Closed Cycle Dry Cooling Systems Dry cooling systems are used where there is insufficient water, or where the water is too expensive to be used in an evaporative system. Dry cooling systems are the least used systems as they have a much higher capital cost, higher operating temperatures, and lower efficiency than wet cooling systems. In the dry cooling system, heat transfer is by air to finned tubes. The minimum temperature that can be theoretically provided is that of the dry air, which can be regularly over 30º C and up to 40º C on typical summer afternoons in Queensland. Compare this to wet cooling towers, which cool towards the wet bulb temperature, which is typically 20º C on summer afternoons. The steam condensing pressures and temperatures of a dry cooled unit are significantly higher than a wet cooled unit, due to the low transfer
rates of dry cooling and operation at the dry bulb temperature. There are two basic types of dry cooling systems: The direct dry cooling system. The indirect dry cooling system.
Environmental
Effects
of
Cooling
Systems:
All the heat transferred from the exhaust steam to the cooling system eventually finds its way into the earth's atmosphere. In the once-through cooling water system, heat is removed from the steam turbine and transferred to the source body of water. The heat is then gradually transferred to the atmosphere by evaporation, convection and radiation. However, this waste heat transfer process may negatively affect the body of water buy increasing the temperature of the water. In a recirculating cooling system, the cooling water carries waste heat removed from the steam turbine exhaust to the cooling tower, which rejects the heat directly to the atmosphere. Because of this direct path to the atmosphere, surrounding water bodies typically do not suffer adverse thermal effects. Some water is discharged from the cooling water system to maintain the concentration of chemicals in the cooling water below licensed limits. This water is often discharged to surrounding watercourses.
Feed Water Pump The hydraulic machines which convert the mechanical energy into the hydraulic energy are called as PUMP. The hydraulic energy is in the form of pressure energy. The pumps are classified in two parts: 1. RECIPROCATING PUMPS 2. CENTRIFUGAL PUMPS The feed water is also of centrifugal type pumps. The main functions of these type pumps are to feed the water coming out from the condenser to the boiler at the desired pressure. It is either motor or turbine driven. It consumes about 2-2.5% of the power output.
Feed water heaters A feed water heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feed water reduces the irreversibility involved in steam generation and therefore improves the thermodynamic efficiency of the system.[4] This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feed water is introduced back into the steam cycle.
In a steam power plant (usually modeled as a modified Rankine cycle), feed water heaters allow the feedwater to be brought up to the saturation temperature very gradually. This minimizes the inevitable irreversibilities associated with heat transfer to the working fluid (water).
Cycle discussion and explanation
It should be noted that the energy used to heat the feed water is usually derived from steam extracted between the stages of the steam turbine. Therefore, the steam that would be used to perform expansion work in the turbine (and therefore generate power) is not utilized for that purpose. The percentage of the total cycle steam mass flow used for the feed water heater is termed the extraction fraction and must be carefully optimized for maximum power plant thermal efficiency since increasing this fraction causes a decrease in turbine power output. Feed water heaters can also be open and closed heat exchangers. An open feed water heater is merely a direct-contact heat exchanger in which extracted steam is allowed to mix with the feed water. This kind of heater will normally require a feed pump at both the feed inlet and outlet since the pressure in the heater is between the boiler pressure and the condenser pressure. A deaerator is a special case of the open feed water heater which is specifically designed to remove non-condensable gases from the feed water. Closed feed water heaters are typically shell and tube heat exchangers where the feed water passes throughout the tubes and is heated by turbine extraction steam. These do not require separate pumps before and after the heater to boost the feed water to the pressure of the extracted steam as with an open heater. However, the extracted steam (which is most likely almost fully condensed after heating the feed water) must then be throttled to the condenser pressure, an isenthalpic
process that results in some entropy gain with a slight penalty on overall cycle efficiency. Many power plants incorporate a number of feed water heaters and may use both open and closed components. Feed water heaters are used in both fossil- and nuclear-fueled power plants. Smaller versions have also been installed on steam locomotives, portable engines and stationary engines. An economiser serves a similar purpose to a feed water heater, but is technically different. Instead of using actual cycle steam for heating, it uses the lowest-temperature flue gas from the furnace (and therefore does not apply to nuclear plants) to heat the water before it enters the boiler proper. This allows for the heat transfer between the furnace and the feed water to occur across a smaller average temperature gradient (for the steam generator as a whole). System efficiency is therefore further increased when viewed with respect to actual energy content of the fuel.
Coal Handling Plant Coal handing plant is the one most important part of the boiler plant. The handling problem of coal in the boiler plant is major problem because for the generation of boiler there are only two raw materials required. One is water and the second is coal. To handle the large amount
of handle in a very small and continuing time, we required a plant which is suit according to our need. In the coal handling plant coal from the coal wagons is unloaded in coal handling plant and this coal is send to the raw coal bunkers with the help of belt conveyers.
Coal Mill The coal is conveying by the help of coal conveyers. The large amount or large sized storage container situated at the top of the main plant building. The main part of the coal mill is pulverization. Coal Pulverizing Raw coal is fed through a central coal inlet at the top of the pulveriser and falls by gravity to the rotating grinding table, mixing with classifier rejects returned for
re-grinding. Centrifugal action forces the coal outward to the grinding ring where it is pulverized between the ring and three grinding rollers. Grinding load, transmitted from the tension rods through the loading frame to the roller assemblies, holds the rollers in contact with the grinding ring. The rollers adjust vertically as the depth of the coal load increases or decreases. A nozzle ring on the outside perimeter of the grinding ring feeds primary air to the pulverizer. Pyrites and tramp metal fall through the nozzle ring openings to be scraped into a rejects hopper. A stream of low-velocity air carries the particles of pulverized coal upward where they enter the classifier inlet vanes. Fine particles travel to the burners in the primary air stream, but the larger, heavier particles are returned to the grinding zone for further pulverization. Most efficient way to utilizing coal for steam generation is to burn it in the pulverized form. Pulverized coal fire is a method where the crushed coal generally reduced to a fineness such that 70 – 80% passes through a 200 mesh sieve is carried forward by air through pipes directly to burners or storage bus from where it is passed to burners and discharge into combustion chamber. The mixture of coal and air ignites and burns in suspension condition for pulverizing the coal equipments and system would be required with highly availability.
The major equipments in a pulverizing plant are: PULVERIZER FEEDER
PULVERIZER COAL FIRING SYSTEM There are basically two system of pulverized coal firing in use: 1. In direct firing system 2. Direct firing system
RAW COAL FEEDER Feeders can be divided in two types: 1. Volumetric feeder 2. Gravimetric feeder BOWL MILL Bowl mill is provide to crush the coal from sized clinkers to powdered from for better ignition of the coal inside the furnace. Coal is transported to the bowl mills by coal feeder. The coal is pulverized in the bowl mill where it is ground to a powder form of the order of 200 meshes. The mill consists of a round metallic table on which coal particles fall. This table is rotated with the help of a motor. These are three large rollers, which are spaced 120˚ apart. When there is no coal, these rollers do not rotate but when coal is fed to the table it packs up between roller and the table and this force the roller to rotate. Coal is crushed by the crushing action between rollers and the rotating table.
ASH HANDLING PLANT Ash handling system is always designed to handle bottom ash from steam generating units and fly ash from
ESP, economizer, air peheater and stack hopper for disposal to ash disposal area and storing to fly ash storage silo. A steam generating unit [for Rajghat power house] of 67.5 MW set would require about 60.2 tonnes of coal per hour at MCR with worst coal and the ash handling system is designed for the same. Ash collected in bottom ash hopper in a shift of 8 hours will be emptied through clinker grinder and jet pump. The fly ash collected at various fly ash hoppers will be extracted sequentially by creating vaccum in fly ash lines. Alternatively provision has been made to collect 100% dry fly ash of both the units in storage silos for commercial use. BOTTOM ASH REMOVAL SYSTEM The bottom ash removal system of each unit consists of a water impounded single ‘V’ type ash hopper with the following major accessories. 1. Seal trough to allow the boiler expands downward while maintaining a gas seal. 2. Poke hole 3. Sluice hole 4. Sluice gate 5. Sluice gate enclosure fitted with access door 6. Normal water level overflow weir. FLY ASH REMOVAL SYSTEM Two types of fly ash removal system has been envisaged out of which one type will be working for wet disposal system and alternatively other type will be working for dry disposal system. A. fly ash disposal system B. fly ash dry disposal system ELECTROSTATIC PRECIPITATOR
The principal components of an electrostatic precipitator (ESP) are two sets of electrodes insulated from each other. The first set is composed of rows of electrically grounded vertical parallel plates called the collection electrodes, between which the dust-laden gas flows. The second set of electrodes consists of wires called discharge or emitting electrodes that are centrally located between each pair of parallel plates. The wires carry a unidirectional negatively charged high-voltage (between 20-100KV) current from an external DC source. The applied high voltage generates a unidirectional, non uniform electrical field whose magnitude is greatest near the discharge electrodes. When that voltage is high enough, a blue luminous glow called a corona, is produced around them. Electrical forces in the corona accelerate the free electrons present in the gas so that they ionize the gas molecules, thus forming more electrons and positive gas ions. The new electrons create again more free electrons and ions which results in a chain reaction.
The positive ions travel to the negatively charged wire electrodes. The electrons follow the electrical field towards the grounded electrodes. But their velocity decreases as they move away from the corona region around the wire electrodes towards the grounded plates. Gas molecules capture the low velocity electrons and become negative ions. As these ions move to the collecting electrodes, they collide with fly ash particles in the gas stream and give them negative charge and the strength of the electric field. When the particles collect on the grounded plates, they lose their charge on the ground. The electrical resistivity of the particles however, causes only partial discharging and the retained charge tends to hold the particles to the plates. High resistivity causes retention of most of the charge, which increases the forces holding the particles to the plate and makes removal more difficult. This can be rectified either by operating at high gas temperature or by super imposing during operation under high-resistivity conditions.
Collected particulates matter must be removed from the collecting plates on a regular schedule to ensure efficient collector operation. Removal is usually accomplished by a mechanical hammer scarping system. The vibration knocks the particulate matter off the collect in plates and into a hopper at the bottom of the precipitator.
BOILER DRAUGHT Draught means the force needed to draw. With regard to the boilers the requirements is to provide an adequate supply of air to the furnace grate to maintain the proper combustion of fuel, to the resulting gases from the system and to discharge these flue gases from the chimney to the surroundings. It is of two types: 1. NATURAL OR CHIMNEY DRAUGHT 2. ARTIFICIAL DRAUGHT Most boilers now depend on mechanical draught equipment rather than natural draught. This is because natural draught is subjected to outside air conditions and temperature of flue gases leaving the furnace, as well as the chimney height. All these factors make proper draught hard to attain and therefore make mechanical draught much more economical. There are three types of mechanical draught: I.
INDUCED DRAUGHT
II.
FORCED DRAUGHT
III.
BALANCED DRAUGHT
Economiser An economizer is a heat transfer device used for heating the feed water with the help of hot flue gases before leaving the chimney. It helps in improving the efficiency of the power plants. Economizer is consisting of large number of vertical tubes, made of cast iron, joined with horizontal pipes. The cold feed water is pumped into horizontal pipe through a stop valve. The hot flue gases from boiler pass over the vertical tubes and these gases transfer the heat to cold water rising in these tubes. Finally the hot feed water is supplied to the boiler from stop valve. At the other end of pipe, a safety valve is mounted to guard by the system against the increased pressure. A blow-off-cock is mounted at the end of horizontal pipe to remove any mud or sediments of feed water. Any soot formation on the tubes will effect greatly the coefficient of thermal conductivity, consequently the rate of heat transfer is reduced. This reduced the efficiency of the economizer. In to remove the deposits of the soot from vertical pipes each pipe is provide with a scrapper. In boiler, economizer are heat exchange devices that heat fluids, usually water up to bur=t not normally beyond the boiling point of that fluid. Economizers are so named because they can make use of the enthalpy in fluid stream that are hot but not hot enough to b used in a boiler, thereby recovering more useful enthalpy ang=d improving the boiler’s efficiency.
They are a device fitted to the boiler which saves energy by using the exhaust gases from the boiler to preheat the cold water used the fill the feed water.
Turbo Generator The turbine generator consists of a series of steam turbines interconnected to each other and a generator on a common shaft. There is a high pressure turbine at one end, followed by an intermediate pressure turbine, two low pressure turbines and the generator. As the steam moves through the system and loses pressure and temperature energy it expands in volume, requiring increasing diameter and longer blades at each succeeding stage to extract the remaining energy. The entire rotating mass may be over 200 tons and 100 ft (30 m) long. It is so heavy that it must be kept turning slowly even when shutdown (at 3 rpm) so that the shaft will not bow even slightly and become unbalanced. This is so important that it is one of four functions of blackout emergency power batteries on site. There are emergency lighting, communication, station alarms and turbo generator lube oil. Super heated steam from the boiler is delivered through 14-16 inch (350-400 mm) diameter piping to the high pressure turbine where it falls in pressure to 600 psi (4 MPa) and to 600˚F (315˚C) through the stage. It exits via 24-26 inch (600-650 mm) diameter cold reheat lines and passes back into the boiler where the steam is reheated in special reheat pendant tubes back to 1000˚F (540˚C). The hot reheat steam is conducted to the intermediate pressure turbine where it falls in both temperature and pressure and exits
directly to the long bladed low pressure turbine and finally exits to the condenser. The generator 30 ft (9 m) long and 12 ft (3.7 m) diameter, contains a stationary stator and a spinning rotor, each containing miles of heavy copper conductor- no permanent magnets here. In operation it generates up to 21000 amps at 24000 volts AC (504 MW) as it spins at either 3000 or 3600 rpm, synchronized to the power grid. The rotor spins in a sealed chamber cooled with hydrogen gas, selected because it has the highest known heat transfer coefficient of any gas and for its low viscosity which reduces wind age losses. This system requires special handling during startup, with air in the chamber first displaced by carbon dioxide before filling with hydrogen does not mix with oxygen in the air.
TURBO GENERATOR
The power grid frequency is 60 Hz across north America and 50 Hz in Europe, Oceania, Asia and some parts of Africa. The electricity flows to a distribution yard where transformer step the voltage up to 115,230,500 or 765 KV AC as needed for transmission to its destination. The turbine shaft usually rotates at 3000rpm. This speed is determined by the frequency of the electrical system used in this country and is the speed at which a 2 pole generator must be driven to generate alternating current at a frequency of 50 cycles/sec. when as much as energy as possible have been extracted from the steam it is exhausted directly to the condenser. This runs the length of the low pressure part of the turbine and may be beneath on either side of it. The condenser consist of a large vessel containing 20000 tubes each about 25 mm in diameter cold water from the river, estuary, sea or cooling tower is circulated through these tubes and as the steam from the turbine passes round them it is rapidly condensed in to water condensate. Because water has a much smaller comparative volume than steam, a vaccum is created in the condenser. This allows the steam to reduce down to pressure below that of the normal atmosphere and more energy can be utilized.
Water Treatment Plant In the power plant, the objective of water treatment plant is to produce boiler feed water so that there shall be
a. No scale formation causing resistance to passage of heat and burning of tube, b. No corrosion and c. No priming or foaming problems. This will ensure that the steam generated shall be clean and the boiler plant will provide trouble free uninterrupted service. This chapter details the system for production of such water in a power plant. As the types of boiler are not alike their working pressure and operating conditions vary and so do the types and methods of water treatment. Water treatment plants used in thermal power plants are designed to process the raw water to water with vary low in dissolved solids known as “demineralized water”. No doubt, this plant has to be engineered very carefully keeping in view the type of raw water to the thermal plant, its treatment costs and overall economics. Actually, the type of demineralization process chosen for a power station depends on three main factors: 1. The quality of the raw water 2. The degree of deionization i.e. treated water quality 3. Selectivity of resins.
The fig. shows a schematic diagram of water treatment process which is generally made up of two sections:
Pretreatment section Demineralization section
Pre-Treatment Plant: Pre-treatment plant removes the suspended solids such as clay, slit, organic, and inorganic matter, plants and other microscopic organism. The turbidity may be taken as of two types of suspended solids in water. Firstly, the separable solids and secondly, the non-separable solids (colloids). The coarse components such as sand, silt etc. can be removed from water by the simple sedimentation. Finer particles however, will not settle in any reasonable time and must be flocculated to produce the large particles which are settling able. Long term ability to remain suspended in water basically a function of both size and specific gravity. The settling rate of the colloidal and finely divided suspended matter is so slow that removing them from water by plain sedimentation is tanks having ordinary dimensions are impossible. Settling velocity of finely divided and colloidal particles under gravity also is so small that ordinary sedimentation is not possible. It is necessary, therefore, to use procedure which agglomerates the small particles in to larger aggregates, which have practical settling velocities. The term “coagulation” and “flocculation” have been used indiscriminately to describe process of turbidity removal. “Coagulation” means to bring together the suspended particles. The process describes the effect produced by the addition of a chemical ALg (
SP^)g to a colloidal dispersion resulting in particle destabilization by a reduction of force tending to keep particles apart. Rapid mixing is important at this stage to obtain uniform dispersion of the chemical and to increase opportunity for particles to particle contact. This operation is done by flash mixer in the clariflocculator. Second stage of formation of settle able particles from destabilized colloidal sized particles is termed a “flocculation”. Here coagulated particles grow in size by attaching to each other. In contrast to coagulation where thr primary force is electrostatic or inter-ionic. “Flocculation” occurs by chemical bridging. Flocculation is obtained by gentle and prolonged mixing which converts the submicroscopic coagulated particle in to discete, visible and suspended particles. At this stage particles are large enough to settle rapidly under the influence of gravity and may be removed. If pretreatment of the water is not done efficiently then consequences are as follows: SiOg may escape with water which will increase the anion loading. Organic matter may escape which may cause organic fouling in the anion exchanger beds. In the pre-treatment plant chlorine addition provision is normally made to combat organic contamination. Cation loading may unnecessary increase due to addition of Ca(OH)g in excess of calculated amount for raising the pH of water for maximum floe formation and also AKOrDg may precipitate out. If less than calculated amount of Ca(OH), is added ,proper pH flocculation will not be obtained and
silica escape to demineralization section will occur, thereby increasing load on anion bed.
Demineralisation: This filter water is now used for demineralising purpose and is fed to cation exchanger bed, but enroute being first dechlorinated, which is either done by passing through activated carbon filter or injecting along the flow of water, an equivalent amount of sodium sulphite through some stroke pumps. The residual chlorine which is maintained in clarification plant to remove organic matter from raw water is now detrimental to cation resin and must be eliminated before its entry to this bed. Normally, the typical scheme of demineralization upto the mark against average surface water is three bed systems with a provision of removing gaseous carbon dioxide from water before feeding to anion exchanger. Now, let us see, what happens actually in each bed when water is passed from one to another. Resins, which are built on synthetic matrix of a styrene divinely benzene copolymer, are manufactured in such a way that these have the ability to exchange one ion for another, hold it temporarily in chemical combination and give it to a strong electrolytic solution. Suitable treatment is given to them in such a way that a particular resin absorbs only a particular group of ions. Resins when absorbing and releasing cationic portion of dissolved salts,
is called cation exchanger resin and when removing anionic portion is called anion exchanger resin. The present trend is of employing strongly acidic exchanger resin and strongly basic anion exchanger resin in a DM plant of modern thermal power plant. We may see that the chemically active group in a cationic resin Sox-H (normally represented by RH) and in an anionic resin the active group is either tertiary amine or quaternary ammonium group (normally the resin is represented by ROH). The reaction of exchange may be further represented as below: CATION RESIN: RH
+
Na
R Na
K
K
Ca
Ca
Mg
Mg
+
H2SO4
HCl
HNO3
ANION RESIN: ROH
+
HCl HNO3
H2SO4
RSO4 +
H2O
Cl NO3
Recharging the exhausted form of resins i.e. regeneration employing 5% of acid / alkali as below:
CATION RESIN:
RK
+
H Cl
RH
+ NaCl
K K Cl2 Ca Ca Cl2 Mg Cl2
ANION RESIN: R SO4 + Cl NO3
NaOH
ROH +
Na2SO4 NaCl Na NO3
As seen above the water from the ex-cation contains carbonic acid also sufficiently, which is very weak acid difficult to be removed by strongly basic anion resin and causing hindrance to remove silicate ions from the bed. It is therefore a usual practice to remove carbonic acid before it is led to anion exchanger bed. The ex-cation water is trickled in fine streams from top of a tall tower packed with ranching rings and compressed air is passed from the bottom. Carbonic acid break into CO^ and water mechanically (Henry’s law) with the carbon dioxide escaping in to the atmosphere. The water is accumulated in suitable storage tank below the tower, called degassed water dump, from where the same is led to anion exchanger bed, using acid resistant pump. The ex-anion water is fed to the mixed bed exchanger containing both cationic resin and anionic resin. This bed not only takes care of sodium slip from cation but also silica slip from anion exchanger very effectively. The final
output from the mixed bed is extra- ordinarily pure water having less than 0.2 /mho conductivity, H 7.0 and silica contest less than 0.02 ppm. Any deviation from the above quality means that the resins in mixed bed are exhausted and need regeneration, regeneration of mixed bed first calls for suitable back washing and settling, so that the two types of resins are separated from each other. Lighter anion resin rises to the top and the heavier cation resin settles to the bottom. Both the resins are then regenerated separately with alkali and acid, rinsed to the desired value and air mixed, to mix the resin again thoroughly. It is then put to final rinsing till the desired quality is obtained. It may be mentioned here that there are two types of strongly basic anion exchanger. Type ll resins are slightly less basic than Type l, but have higher regeneration efficiency than Type l. again as Type ll resins are unable to remove silica effectively, Type l resins also have to be used for the purpose. As such, the general condition so far prevailing in India is to employ Type ll resin in anion exchanger’s bed and Type l resin in mixed bed. It is also a general convention to regenerate the above two resins under through fare system i.e. the caustic soda entering in to mixed bed for regeneration, of Type l anion resin, is utilized to regenerate Type ll resin in cation exchanger bed. The concept of utilizing the above resin and mode of regeneration is now a days being switched over from the economy to a more higher cost so as to have more stringent quqlity control of the final demineralized water.
Gas Turbine Power Station Six Gas Turbine Units of 30 MW each were commissioned in 1985-86 to cater to the power demand in peak hours. Initially this Station worked as peaking power station but due to growing power demand, it was converted into combined cycle gas turbine station with commissioning of Waste Heat Recovery Units in 1995-96. The total capacity of this Station is 270 MW. The gas supply has been tied up with GAIL through HBJ Pipeline. The APM gas allocation is not sufficient for full generation from the power station. Subsequently, with the availability of Regassified LNG, an agreement was made with GAIL for supply of R-LNG so that maximum generation could be achieved.
Principle of a Gas Turbine Plant Air is compressed(squeezed) to high pressure by a fan-like device called the compressor.Then fuel and compressed air are mixed in a combustion chamber and ignited.Hot gases are given off, which spin the turbine wheels. Most of the turbine’s power runs the compressor. Part of it drives the generator/machinery.
Gas turbines burn fuels such as oil, nature gas and pulverized(powdered) coal.Instead of using the heat to
produce steam, as in steam turbines, gas turbines use the hot gases directly to turn the turbine blades. Gas turbines have three main parts: i)
Air compressor
ii)
Combustion chamber
iii) Turbine
Brayton Cycle The Brayton cycle is a thermodynamic cycle that describes the workings of the gas turbine engine, basis of the jet engine and others. It is named after George Brayton (1830–1892), the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber in 1791. It is also sometimes known as the Joule cycle.
Air compressor: The air compressor and turbine are mounted at either end on a common horizontal axle (shaft), with the combustion chamber between them. Gas turbines are not self starting. A starting motor initially drives the compressor till the first combustion of fuel takes place, later, part of the turbine’s power runs the compressor. The air compressor sucks in air and compresses it, thereby increasing its pressure.
Combustion chamber: In the combustion chamber, the compressed air combines with fuel and the resulting mixture is burnt. The greater the pressure of air, the better the fuel air mixture burns. Modern gas turbines usually use liquid fuel, but they may also use gaseous fuel, natural gas or gas produced artificially by gasification of a solid fuel.
Turbine: The burning gases expand rapidly and rush into the turbine, where they cause the turbine wheels to rotate. Hot gases move through a multistage gas turbine. Like in steam turbine, the gas turbine also has fixed (stationary) and moving (rotor) blades. The stationary blades guide the moving gases to the rotor blades and adjust its velocity. The shaft of the turbine is coupled to a generator or machinery to drive it.
Layout Of a Gas Turbine Power Plant
Pragati Power Station To bridge the gap between demand and supply and to have reliable supply to the Capital City, a 330 MW combined cycle Gas Turbine Power Project was set up on fast track basis. This plant consists of 2 x 104 MW Frame 9-E Gas Turbine Units commissioned in 2002 – 03 and 1 x 122 MW STG Unit commissioned in 2003 – 04. Gas supply has been tied up with GAIL through HBJ Pipeline. The station is performing satisfactorily meeting the targets set by DERC and CEA.
Salient Features i.
ii.
Due to paucity of water this plant was designed to operate on treated sewage water which is being supplied from Sen Nursing Home & Delhi Gate STPs. Emission of oxides of nitrogen (Nox) has been limited to 35 PPM, lowest in the country, for which special technology is used by installing Dry Low Nox Combustors.
With the commissioning of Pragati Power Station, total capacity of IPGCL & PPCL is 994.5MW and all our efforts are made to maximize the generation.
Brief History A contract was signed with M/s BHEL for installation of 330MW gas based power plant in the vicinity of 220V, I.P. Extension, Switchyard on 05.05.2003. The station is comprised of 2x104MW gas turbines of GT Frame-9E and 1x122MW steam turbine. The Waste Heat emanating from gas turbines is being utilized to generate 122MW power through steam turbine. The hot gases of 560o centigrade with a mass flow of approx. 14000 metric ton per hour is passed through 02 Nos. waste heat recovery boilers of generate steam. The environmental friendly quality power generation through this station is pumped to 220kV Sub Station of Delhi Transco Limited and the entire power is being utilized by citizen of Delhi.
Fuel The primary fuel for gas turbine is natural gas being supplied by M/s GAIL through HBJ pipe line. The gas is received at GAIL Terminal installed in the vicinity of the power station. M/s GAIL is committed to supply 1.75 MCMD of gas on daily basis. The caloric value of natural gas being received for power generation is in the band of 8200-8500 kilocalories. The secondary fuel for gas turbine id HSD/Naptha, which is to be used only in case no gas supply is available. Demineralized water is injected to control Nox. While machine is operated on Liquid fuel i.e. HSD/Naptha.
Raw
Water
Raw water requirement is met through Sewage treated water being drawn from Sen Nursing Home and Delhi Gate Sewage Treatment Plant. The demineralized water
requirement for steam generation is met up through sewage treated water by treating this through RODM (reverse osmosis de-mineralised) process. The production of cooling water requirement for condenser and other equipment is also met through STW after processing through Lime softening system. The plant effluent is discharged to river Yamuna after naturalizing and thus the effluent discharge is better than sewage water. In fact cleaner water is being discharged to Yamuna River, making the project more eco-friendly.
Emission
Control
In order to make control on flue gas emission specifically Nox. & CO2 a special emphasises being given. To control Nox & CO2, State of art, Dry Low Nox. (DLN) Burners have been installed on gas turbine while on natural gas. While the machine is to run on HSD/Naptha water injection arrangement has been provided to control the Nox. & CO2. at present the value of Nox. & CO2 is in order on 1718 PPM and 4.22% respectively on base load while O 2 is 15%. The allowable limit of Nox. approved by DPCC (Delhi Pollution Control Committee) is 35 PPM, however, there is no cap on CO2 emission. This is the first plant in India with a facility to control Nox. Emission and is an eco-friendly power station. Also a thick belt of plantation has been grown on periphery of the power plant and small slim bs inside the power plant to make it environment friendly.
Funding The total value of installation the power plant is approx.
Rs. 1077.30 crore, which is met by drawing loan from Power Finance Corporation Ltd. and equity of 30% from Delhi Govt.
Load
Factor
The plant is now fully stabilized and average plant load factor is 90+ during the month of August and September 2003. All efforts are made to achieve higher plant load factor.
Mechanical Equipment Heat recovery steam generator A heat recovery steam generator or HRSG is an energy recovery heat exchanger that recovers heat from a hot gas stream. It produces steam that can be used in a process or used to drive a steam turbine. This combination produces electricity more efficiently than either the gas turbine or steam turbine alone. The HRSG is also an important component in cogeneration plants. Cogeneration plants typically have a higher overall efficiency in comparison to a combined cycle plant. This is due to the loss of energy associated with the steam turbine.
The HRSG at PPCL
Evaporator Section The most important component would, of course, be the Evaporator Section. So an evaporator section may consist of one or more coils. In these coils, the effluent (water), passing through the tubes is heated to the saturation point for the pressure it is flowing. Superheater Section The Superheater Section of the HRSG is used to dry the Saturated vapour being separated in the steam drum. In some units it may only be heated to little above the saturation point where in other units it may be superheated to a significant temperature for additional energy storage. The Superheater Section is normally located in the hotter gas stream, in front of the evaporator. Economizer Section The Economizer Section, sometimes called a preheater or preheat coil, is used to preheat the feed water being introduced to the system to replace the steam (vapour) being removed from the system via the superheater or steam outlet and the water loss through blow down. It is normally located in the colder gas downstream of the evaporator. Since the evaporator 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 due to the approach to the evaporator, whereas the economizer inlet temperature is low, allowing the flue gas temperature to be taken lower. .
Block diagram of a power plant which utilizes the HRSG . The steam turbine-driven generators have auxiliary systems enabling them to work satisfactorily and safely. The steam turbine generator being rotating equipment generally has a heavy, large diameter shaft. The shaft therefore requires not only supports but also has to be kept in position while running. To minimize the frictional resistance to the rotation, the shaft has a number of bearings. The bearing shells, in which the shaft rotates, are lined with a low friction material like Babbitt metal. Oil lubrication is provided to further reduce the friction between shaft and bearing surface and to limit the heat generated. Condenser The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted
to condensate (water) by flowing over the tubes. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum. For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 C where the vapour pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum. Thus leaks of non-condensable air into the closed loop must be prevented. Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning. The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a river, lake or ocean.
A typical water cooled condenser
Deaerator A steam generating boiler requires that the boiler feed water should be devoid of air and other dissolved gases, particularly corrosive ones, in order to avoid corrosion of the metal. Generally, power stations use a Deareator to provide for the removal of air and other dissolved gases from the boiler feed water. A Deareator typically includes a vertical, domed deaeration section mounted on top of a horizontal cylindrical vessel which serves as the deaerated boiler feed water storage tank. Practical considerations demand that in a steam boiler/steam turbine/generator unit the circulating steam, condensate, and feed water should be devoid of dissolved gases, particularly corrosive ones, and dissolved or suspended solids. The gases will give rise to corrosion of the metal in contact thereby thinning them and causing rupture. The solids will deposit on the heating surfaces giving rise to localised heating and tube ruptures due to overheating. Under some conditions it may give rise to stress corrosion cracking. Cooling Towers: Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wetbulb air temperature or rely solely on air to cool the working fluid to near the dry-bulb air temperature. Common applications include cooling the circulating
water used in oil refineries, chemical plants, power stations and building cooling. The towers vary in size from small roof-top units to very large hyperboloid structures (as in Image 1) that can be up to 200 metres tall and 100 metres in diameter, or rectangular structures (as in Image 2) that can be over 40 metres tall and 80 metres long. Smaller towers are normally factory-built, while larger ones are constructed on site.
Cooling Towers Electrical Side: GENERATORS: The class of generator under consideration is steam turbine-driven generators, commonly called turbo generators. These machines are generally used in nuclear and fossil fuelled power plants, co-generation plants, and combustion turbine units. They range from relatively
small machines of a few Megawatts (MW) to very large generators with ratings up to 1900 MW. The generators particular to this category are of the two- and four-pole design employing round-rotors, with rotational operating speeds of 3600 and 1800 rpm in North America, parts of Japan, and Asia (3000 and 1500 rpm in Europe, Africa, Australia, Asia, and South America). At PPCL 3000 rpm, 50 Hz generators are used of capacities 122 MW. As the system load demands more active power from the generator, more steam (or fuel in a combustion turbine) needs to be admitted to the turbine to increase power output. Hence more energy is transmitted to the generator from the turbine, in the form of a torque. This torque is mechanical in nature, but electromagnetically coupled to the power system through the generator. The higher the power output, the higher the torque between turbine and generator. The power output of the generator generally follows the load demand from the system. Therefore the voltages and currents in the generator are continually changing based on the load demand. The generator design must be able to cope with large and fast load changes, which show up inside the machine as changes in mechanical forces and temperatures. The design must therefore incorporate electrical current-carrying materials (i.e., copper), magnetic flux-carrying materials (i.e., highly permeable steels), insulating materials (i.e., organic), structural members (i.e., steel and organic), and cooling media (i.e., gases and liquids), all working together under the operating conditions of a turbo generator.
An open Electric Generator at Power Plant Since the turbo generator is a synchronous machine, it operates at one very specific speed to produce a constant system frequency of 50 Hz, depending on the frequency of the grid to which it is connected. As a synchronous machine, a turbine generator employs a steady magnetic flux passing radially across an air gap that exists between the rotor and the stator. (The term “air gap” is commonly used for air- and gas-cooled machines). For the machines in this discussion, this means a magnetic flux distribution of two or four poles on the rotor. This flux pattern rotates with the rotor, as it spins at its synchronous speed. The rotating magnetic field moves past a three-phase symmetrically distributed winding installed in the stator core, generating an alternating voltage in the stator winding. The voltage waveform created in each of the three phases of the stator winding is very nearly sinusoidal. The output of the stator winding is the three-phase power, delivered to the power system at the voltage generated in the stator winding.
In addition to the normal flux distribution in the main body of the generator, there are stray fluxes at the extreme ends of the generator that create fringing flux patterns and induce stray losses in the generator. The stray fluxes must be accounted for in the overall design. Generators are made up of two basic members, the stator and the rotor, but the stator and rotor are each constructed from numerous parts themselves. Rotors are the high-speed rotating member of the two, and they undergo severe dynamic mechanical loading as well as the electromagnetic and thermal loads. The most critical component in the generator is the retaining rings, mounted on the rotor. These components are very carefully designed for high-stress operation. The stator is stationary, as the term suggests, but it also sees significant dynamic forces in terms of vibration and torsional loads, as well as the electromagnetic, thermal, and high-voltage loading. The most critical component of the stator is arguably the stator winding because it is a very high cost item and it must be designed to handle all of the harsh effects described above. Most stator problems occur with the winding. STATOR The stator winding is made up of insulated copper conductor bars that are distributed around the inside diameter of the stator core, commonly called the stator bore, in equally spaced slots in the core to ensure symmetrical flux linkage with the field produced by the rotor. Each slot contains two conductor bars, one on top
of the other. These are generally referred to as top and bottom bars. Top bars are the ones nearest the slot opening (just under the wedge) and the bottom bars are the ones at the slot bottom. The core area between slots is generally called a core tooth. ROTOR The rotor winding is installed in the slots machined in the forging main body and is distributed symmetrically around the rotor between the poles. The winding itself is made up of many turns of copper to form the entire series connected winding. All of the turns associated with a single slot are generally called a coil. The coils are wound into the winding slots in the forging, concentrically in corresponding positions on opposite sides of a pole. The series connection essentially creates a single multiturn coil overall, that develops the total ampere-turns of the rotor (which is the total current flowing in the rotor winding times the total number of turns). There are numerous copper-winding designs employed in generator rotors, but all rotor windings function basically in the same way. They are configured differently for different methods of heat removal during operation. BEARINGS All turbo generators require bearings to rotate freely with minimal friction and vibration. The main rotor body must be supported by a bearing at each end of the generator for this purpose. In some cases where the rotor shaft is very long at the excitation end of the machine to accommodate the slip/collector rings, a “steady” bearing
is installed outboard of the slip-collector rings. This ensures that the excitation end of the rotor shaft does not create a wobble that transmits through the shaft and stimulates excessive vibration in the overall generator rotor or the turbo generator line. There are generally two common types of bearings employed in large generators, journal” and “tilting pad” bearings. Journal bearings are the most common. Both require lubricating and jacking oil systems. Jacking oil pumps and Lube oil pumps are used for this purpose.
AUXILIARY SYSTEMS All large generators require auxiliary systems to handle such things as lubricating oil for the rotor bearings, hydrogen cooling apparatus, hydrogen sealing oil, demineralized water for stator winding cooling, and excitation systems for field-current application. Not all generators require all these systems and the requirement depends on the size and nature of the machine. For instance, air cooled turbo generators do not require hydrogen for cooling and therefore no sealing oil as well. On the other hand, large generators with high outputs, generally above 400 MVA, have water-cooled stator windings, hydrogen for cooling the stator core and rotor, seal oil to contain the hydrogen cooling gas under high pressure, lubricating oil for the bearings, and of course, an excitation system for field current. There are five major auxiliary systems that may be used in a generator. They are given as follows:
1. Lubricating Oil System 2. Hydrogen Cooling System 3. Seal Oil System 4. Stator Cooling Water System 5. Excitation System PROTECTION: The protection system of any modern electric power grid is the most crucial function in the system. Protection is a system because it comprises discrete devices (relays, communication means, etc.) and an algorithm that establishes a coordinated method of operation among the protective devices. This is termed coordination. The key function of any protective system is to minimize the possibility of physical damage to equipment due to a fault anywhere in the system or from abnormal operation of the equipment (over speed, under voltage, etc.). Protective systems are inherently different from other systems in a power plant. Electric power generators are most often the most critical electrical apparatus in any power plant. Protection systems can be divided into systems monitoring current, voltage (at the machine’s main terminals and excitation system), windings, and/or cooling media temperature and pressure, and systems monitoring internal activity, such as partial discharge, decomposition of organic insulation materials, water content, hydrogen impurities, and flux probes. Protective functions acting on the current, voltage, temperature, and pressure parameters are commonly referred to as primary
protection. The others are referred to as secondary protection or monitoring devices. Secondary functions tend to be monitored real time, or on demand. For instance, hydrogen purity is monitored on-line real time, while water content (for water leaks) is not. Temperature detectors (RTDs or thermocouples) on bearings (and sometimes in on windings) may be monitored on-line real time, or they may not. Furthermore these functions may more often than not result in an alarm, rather than directly trip the unit (e.g., core monitors). To the primary protective functions monitoring currents, voltages, temperatures and pressures, there can be added the mechanical protective function of vibration. Typically it will alarm, but it can also be set to trip the unit. Protections function can also be divided into shortcircuit protection functions. The short-circuit protection comprises impedance, distance, and current differential protection.
APPENDIX A Design\Rated Parameters (RPH )
1. Generation: max. 2. Load: max. 3. Boiler steam pressure: 4. Boiler steam temperature: 5. Opacity: mg/Nm 6. Unburnt carbon in fly ash: 7. Unburnt carbon in bottom ash: 8. Feed water temperature after HPH: C 9. Steam temp. at throttle valve before ESV: 10. Steam pressure ESV (kg/cm2): kg/cm2 11. Vaccum: 12. Exhaust hood temp.: C 13. Circulating water rise of temp.: 14. Fuel oil pressure (LSHS): 15. Generator stator temp.: 16. Steam flow before ESV: 17. Steam consumption per MW: 18. Turbine heat rate: kcal/kWh 19. DM water conductivity: mho/cm 20. DM water silica: 21. Clarifier water outlet turbidity: 22. Feed water conductivity: mho/cm 23. Feed water silica: 24. Boiler water conductivity: mho/cm 25. Boiler water silica: 26. Moisture in turbine oil (at filter point):
1.62 (MU) 67.5 (MU) 95 kg/cm2 540 deg C 150 < 1.0 % < 3.5 % 236.85 deg 535 deg C 86.49 695 mm 44.25 deg 8 deg C 7 kg/cm2 100 deg C 257.5 T/hr 3.81 T/hr 2232 <
1.0
< 20 ppb 10 N.T.U 6 m 0.02 ppm 30-70 < 1 ppm 100 ppm
27. Auxiliary consumption: day (both units) 28. Make-up water consumption: (both units) 29. Clarifier water inlet conductivity: m mho/cm
11.2 % per 624 kl/day 600-1700
APPENDIX B Details of Fans and Pumps used in the plant (RPH) Fans Equipment ID Fan FD Fan B.F.P C.E.P PA Fan
Type Radial Double Suc. Radial Double Suc. Radial Double Suc. Centrifugal Radial Single Suc.
Capacity 81 m3/sec
Make BHEL
57 m3/sec
BHEL
318.4 T/hr
BHEL
283.2 T/hr 18 m3/sec
KSB BHEL
Drives Equipment ID Fan FD Fan PA Fan Bowl Mills B.F.P C.E.P
Type Squirrel I.M. Squirrel I.M. Squirrel I.M. Squirrel I.M. Squirrel I.M. Squirrel I.M.
Capacity (KW) cage 400
Make BHEL
cage 400
BHEL
cage 190
BHEL
cage 260
BHEL
cage 2000
BHEL
cage 250
BHEL
APPENDIX C Turbine Specifications (RPH)
Make: Capacity: Exhaust Temperature: C Critical speed: Governing: Efficiency: Actual heat consumption: kg/KWh
BHEL 67.5 MW 44.25 deg 1800 RPM Hydraulic 95 % 3.85
Generator Specifications
Make: TARI Type: Rated Capacity: MW/ 84.375 MVA Power factor: Frequency: Stator: 4639 A Rotor: (max.), 601 A Rotor S.C. ratio: Type of Cooling:
BHELTurbo 673.5 0.8 lag 50 Hz 10.5 KV, 303 0.56 Air
V
LANDMARKS 1905 -First Diesel Power Station established in Delhi. 1911 -Steam Generating Station set up in Delhi. 1932 -Management of Central Power House handed over to NDMC. 1939 -DCEPA Ltd. established. 1947 -DESTC taken over by DCEPA Ltd. 1951 -Delhi State Electricity Board formed. 1955 -Purchase of Power From Nangal. 1958 -Delhi Electric Supply Undertaking came into existence. 1959 -Certain NDMC area of electric supply taken over by DESU. 1962 -U.J.V.E. Supply Co. taken over by DESU. 1963 -MES&T Corp. Taken over by DESU. 1963 -Unit # 1 of I.P. Station commissioned (33.6 MW). 1966 15 MW set installed at RPH. 1967 -One Unit of 62.5 MW commissioned under I.P. Station extension project 1967 -First 220KV S/Stn. Set up at I.P. Station. 1967 -Pool operation of DESU & Bhakra System at 220KV S/Station set up at Narela. 1968 -All the three units of 62.5MW commissioned at I.P. Station Extension project put on commercial use. 1971 -Fifth unit of 55/60 MW commissioned at I.P. Station and 220 KV S/Stn. Set up at Narela. 1986 -Six units of 30MW each at GTPS commissioned for commercial use. 1989 -Replacement units of 2X67.5MW at RPH commissioned for commercial use.
1995 -Three WHRUs of 34 MW each at GTPS commissioned for commercial use. 24.02.1997 -Delhi Vidyut Board came into existence. 10.06.2000 -Foundation stone for 330 MW CCGT Pragati Power Project laid. 09.01.2001 -PPCL was incorporated. 30.06.2002 -Delhi Vidyut Board split in 6 companies namely : (1) BSES Rajdhani Power Ltd. (2) North Delhi Power Ltd. (3) BSES Yamuna Power Ltd. (4) Delhi Transco Ltd. (5) Indraprastha Power Generation Co. Ltd. (6) Delhi Power Co.Ltd. 01.07.2002 -Indraprastha Power Generation Co. Ltd. And Pragati Power Generation started working independently under Govt. of NCT Delhi. 15.05.2003 -Pragati Power Project (330 MW) fully commissioned for commercial
CONCLUSION During our visit to power plant station from June 11,2012 to July 24,2012. The modernization of world as we see today would not become possible if electrical power do not come into picture. Today each area of Science & technology is highly affected by the use of electrical energy. Electrical energy is the only reliable form of Energy which is easily converted into any form of energy whether it is Mechanical, Chemical, Light, and Sound etc. The electrical energy has been used not only in industrial areas but also in residential and commercial application as well. The reason behind the popularity of this form of energy is because it can be easily transferred to one place to another with efficiency. So at the outset I would like to conclude that there is no doubt without the development of this form of energy, we would never achieved the faster pace of growth rate as today the world is growing and this has become possible only due to the development of power system.
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