PRAGATI POWER CORPORATION LIMITED
INTERNSHIP REPORT
By Aman Sati (2k12/ME/029) Akshay Malik (2k12/ME/024) Amaya Kak (2k12/ME/030)
CERTIFICATE This is to certify that Akshay Malik , student of B-Tech Branch Mechanical, Batch 2012-2016 of Delhi Technological University successfully completed his industrial training at Pragati Power Corporation Limited (PPCL) Power Plant Pragati-1,New Delhi for four weeks from 9th June to 4th July. He has completed the whole training as per the training report submitted by him.
ACKNOWLEDGEMENT
With profound respect and gratitude, I take the opportunity to convey my thanks to complete the training at PRAGATI POWER CORPORATION LIMITED.
I extend my thanks to Mr. V.P. SINGH for providing me this opportunity to be a part of this esteemed organization.
I would also like to offer my sincere thanks to the technical staff of PPCL for their co-operation and guidance that helped me a lot during the course of my training. I have learnt a lot working under them and I will always be indebted of them for this value addition in me.
INTRODUCTION Pragati Power Corporation Ltd. (PPCL) The Company Pragati Power Corporation Limited is an undertaking of Government of NCT of Delhi. It was incorporated on 9th January,2001 to undertake power generation activities for supplying power to Delhi. It is one of the leading Undertakings of GNCTD, generating profits since inception and paying dividends regularly. It is presently having capital base of 2,019 crores and asset base of 3,319 crores. The projected asset base and revenue income of Company in the near future are 6,000 crores and 5,000 crores respectively. The first project undertaken by the company was 330 MW gas based CCGT which was fully commissioned in the year 2003-04. The station is presently operating at above 85% availability.PPCL is presently setting up a 1500 MW Gas Based CCGT plant at Bawana in North-West Delhi to augment the power generation at Load-Centre. Project is expected to fully commission by July 2011. PPCL is also proposing to put up a 750 MW Gas Based CCGT at Bamnauli in South-West Delhi. The project is expected to be commissioned in the year 2013-14.
Pragati – I (330 MW):
To have reliable supply to the Capital City, a 330 MW combined cycle Gas Turbine Power Project was set up by PPCL on fast track basis. The plant consists of 2 x 104 MW GE Frame 9-E Gas Turbine Units commissioned in 2002 – 03 and 1 x 122 MW STG Unit commissioned in 2003 – 04. The station is using APM, PMT and R-LNG Gas, supplied by GAIL through HBJ Pipeline. The station is performing well and has achieved availability of more than 85%. The power generation from the station is pumped to the adjacent 220kV Sub Station of Delhi Transco Limited and the entire power is supplied to the discoms of Delhi i.e. NDPL, NDMC, BRPL & BYPL. The Special features of the plant are as under:
Due to paucity of water in the capital city, the plant is operating on treated sewage water supplied from Sen Nursing Home & Delhi Gate STPs. The STP water is further treated in RO-DM Plant.
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 (DLN) Combustors. This is the first plant in India with a facility to control Nox. Emission. The plant effluent is discharged to river Yamuna after neutralizing and thus the effluent discharge is better than river water, making the project eco-friendly.
Combine Cycle Power Plant: In electric power generation a combined cycle is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy, which in turn usually drives electrical generators. The principle is that after completing its cycle (in the first engine), the working fluid of the first heat engine is still low enough in its Entropy that a second subsequent heat engine may extract energy from the waste heat (energy) of the working fluid of the first engine. By combining these multiple streams of work upon a single mechanical shaft turning an electric generator, the overall net efficiency of the system may be increased by 50 – 60 percent. That is, from an overall efficiency of say 34% (in a single cycle) to possibly an overall efficiency of 51% (in a mechanical combination of two (2) cycles) in net Carnot thermodynamic efficiency. This can be done because heat engines are only able to use a portion of the energy their fuel generates (usually less than 50%). In an ordinary (non combined cycle) heat engine the remaining heat (e.g., hot exhaust fumes) from combustion is generally wasted.
Fig: T-S diagram of combine cycle Combining two or more thermodynamic cycles results in improved overall efficiency, reducing fuel costs. In stationary power plants, a widely used combination is a gas turbine (operating by the Brayton cycle) burning natural gas or synthesis gas from coal, whose hot exhaust powers a steam power plant (operating by the Rankine cycle). This is called a Combined Cycle Gas Turbine (CCGT) plant, and can achieve a thermal efficiency of around 60%, in contrast to a single cycle steam power plant which is limited to efficiencies of around 35-42%. Many new gas power plants in North America and Europe are of this type. Such an arrangement is also used for marine propulsion, and is called a combined gas and steam (COGAS) plant. Multiple stage turbine or steam cycles are also common.
Fig: Block diagram of combine cycle power plant
Gas Turbine:
A gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. (Gas turbine may also refer to just the turbine element.) Energy is added to the gas stream in the combustor, where air is m i x e d w i t h f u e l a n d i g n i t e d . C o m b u s t i o n i n c r e a s e s t h e t e m p e r a t u r e , velocity and volume of the gas flow. This is directed through a nozzle over the turbine's blades, spinning the turbine and powering the compressor. Energy is extracted in the form of shaft power, compressed air and t h r u s t , i n a n y c o m b i n a t i o n , a n d u s e d t o p o w e r a i r c r a f t , t r a i n s , s h i p s , generators, and even tanks. Gas turbines are described thermodynamically by the Brayton cycle, in which air is compressed isentropically, combustion occurs at constant pressure, and expansion over the turbine occurs isentropically back to the starting pressure.
The term Brayton cycle has more recently been given to the gas turbine engine. This also has three components:
1. a gas compressor 2. a burner (or combustion chamber) 3. an expansion turbine Ideal Brayton cycle: 1. isentropic process - ambient air is drawn into the compressor, where it is pressurized. 2. isobaric process - the compressed air then runs through a combustion chamber, where fuel is burned, heating that air—a constant-pressure process, since the chamber is open to flow in and out. 3. isentropic process - the heated, pressurized air then gives up its energy, expanding through a turbine (or series of turbines). Some of the work extracted by the turbine is used to drive the compressor. 4. isobaric process - heat rejection (in the atmosphere). Actual Brayton cycle: 1. 2. 3. 4.
adiabatic process - compression. isobaric process - heat addition. adiabatic process - expansion. isobaric process - heat rejection.
Gas Turbines essentially consist of following sections: Primary Section consists of:Air Intake system having 784 pairs of cylindrical and conical cartridge filters Compressor Section having 18 stages of the rotor and starter Blading: Combustor (Combustion Chamber) consists of 18 combustors cross fire tubes, fuel nozzles, spark plug igniters and flame detectors. Turbine Section having 3 stages Exhaust system
Air Intake system:
The effects of inlet air filtration are both positive and negative. The negative side of filtration is that whatever is placed in the path of air coming into the gas turbine causes a pressure loss, resulting in reduced performance or efficiency of the machine. However, inlet filtration will help sustain the gas turbine’s performance above an acceptable level and minimize the occurrence of the degradation effects discussed above. Turbine inlet filtration becomes a trade-off. Cleaner air with reduced particle or moisture content controls wear and fouling at reduced efficiency. Unfiltered or less-filtered air at lower pressure loss gives better efficiency initially, but the “dirty” air can result in temporarily or permanently damaged machinery internal parts. Thus, it is clear that filtration is needed. The challenge is to keep pressure loss to a minimum while removing a satisfactory amount of particles and moisture. Effective filtration can require several filter stages to remove different materials from the air, or to remove more particles, different phases (solid, liquid), or smaller particles. Filters to remove rain and snow, mist, smoke or dust, and finer particles all require variations in filter design. The most common approach to meet these varied needs is the use of multiple stage filtration systems, usually with two or three stages, each stage with a different purpose and design.
Compressor Compressor used in gas turbine is Axial –Flow type High Performance Made Possible by Advanced Aerodynamics, Coatings, and Small Blade Tip Clearances Even Small Amounts of Deposits on Compressor Blades May Cause Large Performance Losses As air flows into the compressor, energy is transferred from its rotating blades to the air. Pressure and temperature of the air increase. Most compressors operate in the range of 75% to 85% efficiency.
Combustion Chamber The purpose of the combustor is to increase the energy stored in the compressor exhaust by raising its temperature. Combustion air, with the help of swirler vanes, flows in around the fuel nozzle and mixes with the fuel. This air is called primary air and represents approximately 25 percent of total air ingested by the engine. The fuel-air mixture by weight is roughly 15 parts of air to 1 part of fuel. The remaining 75 percent of the air is used to form an air blanket around the burning gases and to lower the temperature.
Turbine Section The three-stage turbine section is the area in which the energy in the hot pressurized gas produced by compressor and combustion sections is converted into mechanical energy. The first stage of turbine rotor blade consists of blades. Air cooling arrangements are provided for turbine 1st and 2nd stage.
Gas Turbine Accessory Systems Starting System To get compressor initially rotated, starting motor provide 6 rpm Then excitation to crank till 700 rpm Once at 400-420 rpm, fuel injected and spark ignited 1 min. warm up time Accelerating mode around 3000 rpm at FSNL Power Transmission System Reduction gears used to transfer torque With split shaft, turbines can run @ different speeds
Exhaust System Simple Cycle Stack Transition to HRSG
Auxiliary components of gas turbine There are main three auxiliary components of gas turbine are: Gas turbine starter Inlet air filter Fin- fan air cooler.
Gas turbine starter The gas turbine requires a starting mechanism to spin the main shaft initially, and once the turbine reaches its rated speed this mechanism detaches automatically. This starting process normally uses an electric motor to spin the main turbine shaft. The motor is bolted to the outside of the engine and uses a shaft and gears to connect to the main shaft. The electric motor spins the main shaft until there is enough air blowing through the compressor and the combustion chamber to light the turbine. Fuel starts flowing and an igniter similar to a spark plug ignites the fuel. Then fuel flow is increased to spin the engine up to its operating speed.
Fan air coolers Gas turbines operate with a constant volume of air flow, but the power they generate is determined by the mass flow of air. As a result, the denser the air is when it flows through the turbine, the greater that the output power will be. Warm air is less dense than cold air, and therefore gives a lower power output. In addition, warm air is harder to compress than cold air, thus requiring greater work from the compressor, leaving less net available shaft energy.
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 (cogeneration) or used to drive a steam turbine (combined cycle). HRSGs consist of four major components: the economizer, evaporator, superheater and water preheater. The different components are put together to meet the operating requirements of the unit. See the attached illustration of a Modular HRSG General Arrangement. Modular HRSGs can be categorized by a number of ways such as direction of exhaust gases flow or number of pressure levels. Based on the flow of exhaust gases, HRSGs are categorized into vertical and horizontal types. In horizontal type HRSGs, exhaust gas flows horizontally over vertical tubes whereas in vertical type HRSGs, exhaust gas flow vertically over horizontal tubes. Based on pressure levels, HRSGs can be categorized into single pressure and multi pressure. Single pressure HRSGs have only one steam drum and steam is generated at single pressure level whereas multi pressure HRSGs employ two (double pressure) or three (triple pressure) steam drums. As such triple pressure HRSGs consist of three sections: an LP (low pressure) section, a reheat/IP (intermediate pressure) section, and an HP (high pressure) section. Each section has a steam drum and an evaporator section where water is converted to steam. This steam then passes through superheaters to raise the temperature beyond the one at the saturation point.
Steam Turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical work. The available heat energy of the steam first is converted into kinetic energy by the expansion of the steam in suitably shaped passage, or nozzle, form which it issues as a jet, at a proper angle, against curved blades mounted on a revolving disk or cylinder and by the reaction of the jet itself as it leaves the curved passage. The pressure on the blades, causing rotary motion, is solely due to the change of momentum of the steam jet during its passage through these blades. The steam energy is converted mechanical work by expansion through the turbine. The expansion takes place through a series of fixed blades (nozzles) and moving blades each row of fixed blades and moving blades is called a stage. The moving blades rotate on the central turbine rotor and the fixed blades are concentrically arranged within the circular turbine casing which is substantially designed to withstand the steam pressure. On large output turbines the duty too large for one turbine and a number of turbine casing/rotor units are combined to achieve the duty. These are generally arranged on a common centre line (tandem mounted) but parallel systems can be used called cross compound systems.
Working Cycle The steam turbine works on rankine cycle, the Rankine cycle is a thermodynamic cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses steam as the working fluid. A Rankine cycle describes a model of the operation of steam heat engines most commonly found in power generation plants. Common heat sources for power plants using the Rankine cycle are coal, natural gas, oil, and nuclear.
Process 1-2: The working fluid is pumped from low to high pressure, as the fluid is a liquid at this stage the pump requires little input energy. Process 2-3: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapour. Process 3-4: The dry saturated vapour expands through a turbine, generating power. This decreases the temperature and pressure of the vapour, and some condensation may occur. Process 4-1: The wet vapour then enters a condenser where it is cooled at a constant pressure and temperature to become a saturated liquid. The pressure and temperature of the condenser is fixed by the temperature of the cooling coils as the fluid is undergoing a phase-change.
Constructional Features: The steam turbine at P.P.C.L has a tandem compound shaft arrangement with H.P and L.P section. 1) H.P turbine: The H.P turbine is of single flow, double shell construction with horizontally split casings allowance is made for thermal movement of the inner casing within the outer casing. The main steam enters the inner casing from top and bottom. 2) L.P turbine: The casing of the double flow L.P turbine is of three shell design. The shells are of horizontally split welded construction. The inner casing which carries the first rows of stationary blades is supported on the outer casing so as to allow for thermal expansion.
3) Blading:
The entire turbine is provided with reaction blading. The moving blades of H.P turbine and the initial rows of L.P turbine with inverted T roots and integral shrouding are machined from solid rectangular bar.
4) Bearings:
The H.P rotor is supported on two bearings a combined journal and thrust bearing at its front and a journal bearing close to the coupling with L.P motor. The L.P rotor has a journal bearing at its end. The combined journal and thrust bearing takes up residual thrust from both directions.
5) Shaft gland and interstage sealing:
The shaft gland seals the steam inside the cylinders against atmosphere and the interstage seals restrict leakage at blade tip.
6) Valves: Steam enters the turbine from the HRSG into a series of valves. These valves are controlled by the governor with regulates the amount of steam passing through the turbine in order to maintain the constant speed required to generate power at 50 cycles per second.
7) Turbine governing system: The turbine has an electro-hydraulic governing system backed up with a hydraulic governing system. An electric system measures and controls speed, output and operate the control valves hydraulically in conjunction with an electro-hydraulic converter.
8) Turbine monitoring system: In addition to the measuring instruments and instruments indicating pressures, temperatures, valves positions and speed, the monitoring system also includes measuring instruments and indicators for the following values: Differential expansion between the shafting and turbine casing. Bearing pedestal vibrations, measured at all turbine bearings. Relative shaft vibrations measured at all bearings.
Technical specification: H.P turbine
: Single flow with 28 reaction stages.
L.P turbine
: Double flow with 8 reaction stages.
Main stop and control valves L.P stop and control valves
:2 :2
Speed:Rated Speed
: 50.0/s
Max. Speed no time limitation : 51.5/s Min speed no time limitation
: 47.5/s
Power Station Station Station Capacity (MW) Units (MW)
Year of Commissioning Gas Water Sources
Beneficiary Areas
Pragati-I Power Station 330 2 X 104 (GTs) + 1 X 122 (STG) 2002 -03 By GAIL Treated water from Sen Nursing Home and Delhi Gate STPs NDMC, South Delhi
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 100C where the vapour pressureof 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 uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a river.
Cooling Tower A cooling tower is a heat rejection device, which extracts waste heat to the atmosphere though the cooling of a water stream to a lower temperature. The type of heat rejection in a cooling tower is termed "evaporative" in that it allows a small portion of the water being cooled to evaporate into a moving air stream to provide significant cooling to the rest of that water stream. The heat from the water stream transferred to the air stream raises the air's temperature and its relative humidity to 100%, and this air is discharged to the atmosphere. Evaporative heat rejection devices such as cooling towers are commonly used to provide significantly lower water temperatures than achievable with "air cooled" or "dry" heat rejection devices, like the radiator in a car, thereby achieving more cost-effective and energy efficient operation of systems in need of cooling. Think of the times you've seen something hot be rapidly cooled by putting water on it, which evaporates, cooling rapidly, such as an overheated car radiator. The cooling potential of a wet surface is much better than a dry one.
Water Treatment Plant Requirement of Water A) COOLING PURPOSE FOR GT’S, STG LUBE OIL, GENRATOR, EXCITER AND OTHER AUXILLARIES, CONDENSER B) FOR STEAM GENERATION
REQUIRMENT OF WATER TREATMENT FOR MAKING DE-MINERALISED AND SOFT WATER AS PER REQUIRED PARMETER OF WATER FOR THE PLANT WE ARE USING UPTO 19 MLD TREATED SEWAGE RAW WATER FROM DG STP & SNH STP DUE TO NON AVIALABLITY OF RAW WATER FROM OTHER SOURES i.e. YAMUNA RIVER,CANAL OR GROUND WATER.
Analysis Parameter of the Raw water from STP:Raw Water Quality:Parameters
Value
Parameters
Value
pH
6.8 to 8.5
FRC
Nil
COND
1300 to 1800
PHOSPHATE
0.1
ALKALINITY
260 to 400
SILICA
25 to 30
TOTAL HARDNESS
260 to 340
TURBIDITY
<15 NTU
CALCIUM
140 to 230
COD
<150
CHLORIDE
160 to 230
Organic matter
<150
IRON
0.2
BOD
AERATOR Raw water form DG & SNH
RESERVOIR -A 16000m3
RESERVOIR – B 16000m3
SUMP
RAW WATER PUMP - A 675m3
RAW WATER PUMP – B 675 m3
Lime removes the temporary hardness NaOH removes both temporary as well as permanent hardness Clarified Water Quality:-
Parameters
Value
Parameter
Value
pH
9.8 to 10.2
CHLORIDE
180 to 250
COND
IRON
0.2
ALKALINITY
1300 to 1800 280 to 400
FRC
1
TOTAL HARDNESS
160 to 250
PHOSPHATE
0.1
CALCIUM
80 to 150
SILICA
25 to 30
COD
100 to 120
TURBIDITY
<30 NTU
ORGANIC MATTER 100 to 120
BOD
