15-10-2012, 03:18 PM
PRACTICAL TRAINING REPORT ON PANIPAT THERMAL POWER PLANT
PRACTICAL TRAINING.pdf (Size: 1.24 MB / Downloads: 461)
ORGANISATION: AN INTRODUCTION
Thermal Power Stations require a number of equipments performing a number of complex processes with the ultimate aim to convert chemical energy of coal or oil to electrical energy. This involves the generation of steam in the boiler by burning coal and/or oil. The steam in turn drives the turbine. The generator coupled with the turbine produces electricity which is stepped up with the help of transformers and is fed into grid station through transmission lines.
INTRODUCTION OF P.T.P.S.:
Haryana Power Sector comprises four wholly State-owned Corporations viz. HPGCL, HVPNL, UHBVNL and DHBVNL which after unbundling of the HSEB in 1998 are responsible for power generation, transmission, distribution and trading in the State. The State power sector was restructured on August 14, 1998. The Haryana State Electricity Board (HSEB) was recognized initially into two State-owned Corporations namely Haryana Vidyut Prasaran Nigam Ltd. (HVPN) and Haryana Power Generation Corporation Ltd. (HPGCL). HPGCL was made responsible for operation and maintenance of State‘s own power generating stations. HVPNL was entrusted the power transmission and distribution functions. The demand of Haryana is increasing exponentially @ more than 14 % per year on account of industrialization and more consumption on agriculture sector and also because of being part of National Capital Region.
Panipat Thermal Power Station (PTPS) has a total installed generation capacity of 1367.8 MW comprising of four Units of 110 MW each( unit1 unrated to 117.8 MW during R&M) , two Units of 210 MW each and two Units of 250 MW each. As all the balance of plant facilities viz. Coal Handling Plant, Ash Handling Plant, Cooling towers, C.W. System are separate for 4x110 MW Unit 1 to 4 and are completely independent from Units 5 to 8. Keeping this in view and in order to improve the performance of the Plant and to have a better control, a need was felt to bifurcate PTPS into two Thermal Power Station i.e. PTPS-1, comprising of 4x110MW Units 1 to 4 and PTPS-2 comprising of 210MW /250MW Units 5 to 8.In this regard the Board of Directors in its 54th meeting held on 29.03.07, approved the proposal of bifurcation of Panipat Thermal Power Station.
WATER:
The raw water required for the thermal power station has been taken from WESTERN
YAMUNA CANAL through a channel. This water is lifted by RAW WATER PUMPS and is fed
into CLARIFIERS to remove the turbidity of the water. The clean water is stored in CLEAR
WELLS, from there it is sent to WATER TREATMENT PLANTS, COOLING WATER
SYSTEMS and SERVICE WATER SYSTEMS.
The water in the WATER TREATMENT PLANT is FILTERED and DEMINERALISED. The
filtered water is sent to PLANT and COLONY through plant and colony potable pumps. The
DEMINERALISED WATER (D.M water) is stored in bulk storage tanks for use in boiler and
turbine. The cooling water for condensation of steam is circulated with the help of
CONDENSATE WATER (C.W) PUMPS through COOLING TOWERS. The hot water from the
outlet of the condenser is sprayed in the cooling towers to reduce its temperature. Some part of it
is used in cooling various auxiliaries in plant through BEARING COOLING WATER PUMPS.
COAL:
The coal reaches the Power Station in RAILWAY WAGONS. The daily consumption of coal in
STAGE-I&II is about 3000 M Tonnes & for Stage-III, it is about 2500 M Tonnes. The
unloading of coal from railway wagons is done mechanically by tilting the wagon by WAGGON
TIPPLER. The coal is then sent to COAL CRUSHER by conveyor belts. The crushed coal
(about 20 mm) is sent either to coal mill bunkers or storage yard. The coal is also transported to
coal bunkers from storage yard through conveyor belts when the coal wagons are not
available. The crushed coal stock for 15 days to 1 month is kept in coal stock yard. The coal
from the mill bunkers goes to coal mills through RAW COAL FEEDERS where it is further
pulverized to powder form & is then transported to the furnace of the boiler with the help of
PRESURED AIR from PRIMARY AIR (P.A.) FANS. In PTPS direct pressurized pulverized
fuel firing system has been used.
GENERAL WORKING OF THERAM POWEER STATION
Coal is conveyed from an external stack and ground to a very fine powder by large metal spheres
in the pulverized fuel mill. There it is mixed with preheated air driven by the forced draught fan.
The hot air-fuel mixture is forced at high pressure into the boiler where it rapidly ignites. Water
of a high purity flows vertically up the tube-lined walls of the boiler, where it turns into steam,
and is passed to the boiler drum, where steam is separated from any remaining water. The steam
passes through a manifold in the roof of the drum into the pendant super heater where its
temperature and pressure increase rapidly to around 200 bar and 540°C, sufficient to make the
tube walls glow a dull red. The steam is piped to the high pressure turbine, the first of a threestage
turbine process. A steam governor valve allows for both manual control of the turbine and
automatic set-point following. The steam is exhausted from the high pressure turbine, and
reduced in both pressure and temperature, is returned to the boiler re heater. The reheated steam
is then passed to the intermediate pressure turbine, and from there passed directly to the low
pressure turbine set. The exiting steam, now a little above its boiling point, is brought into
thermal contact with cold water (pumped in from the cooling tower) in the condenser, where it
condenses rapidly back into water, creating near vacuum-like conditions inside the condenser
chest. The condensed water is then passed by a feed pump through a deaerator, and prewar med,
first in a feed heater powered by steam drawn from the high pressure set, and then in the
economizer, before being returned to the boiler drum. The cooling water from the condenser is
sprayed inside a cooling tower, creating a highly visible plume of water vapor, before being
pumped back to the condenser in cooling water cycle. The three turbine sets are sometimes
coupled on the same shaft as the three-phase electrical generator which generates an intermediate
level voltage (typically 20-25 kV). This is stepped up by the unit transformed to a voltage more
suitable for transmission (typically 250-500 kV) and is sent out onto the three-phase transmission
system. Exhaust gas from the boiler is drawn by the induced draft fan through an electrostatic
precipitator and is then vented through the chimney stack.
Fuel Firing System and Igniter System
From the pulverized coal bin, coal is blown by hot air through the furnace coal burners at an
angle which imparts a swirling motion to the powdered coal to enhance mixing of the coal
powder with the incoming preheated combustion air and thus to enhance the combustion. The
thermal radiation of the fireball heats the water that circulates through the boiler tubes near the
boiler perimeter. To provide sufficient combustion temperature in the furnace before igniting the
powdered coal, the furnace temperature is raised by first burning some light fuel oil or processed
natural gas (by using auxiliary burners and igniters provide for that purpose).
Air Path
External fans are provided to give sufficient air for combustion. The forced draft fan takes air
from the atmosphere and, first warming it in the air pre heater for better combustion, injects it via
the air nozzles on the furnace wall. The induced draft fan assists the FD fan by drawing out
combustible gases from the furnace, maintaining a slightly negative pressure in the furnace to
avoid backfiring through any opening. At the furnace outlet, and before the furnace gases are
handled by the ID fan, fine dust carried by the outlet gases is removed to avoid atmospheric
pollution. This is an environmental limitation prescribed by law, and additionally minimizes
erosion of the ID fan.
AIR & FLUE GAS CYCLE:
For the proper combustion to take place in the boiler right amount of Oxygen or air is needed in
the boiler. The air is provided to the furnace in two ways- PRIMARY AIR & SECONDARY
AIR. Primary air is provided by P.A. fans and enters the boiler along with powdered coal from
the mills. While the secondary air is pumped through FORCED DRAFT FANS better known as
F.D Fans which are also two in numbers A&B. The outlet of F.D fans combine and are again
divided into two which goes to Steam coiled Air pre heaters (S.C.A.P.H) A&B where its
temperature is raised by utilizing the heat of waste steam. Then it goes to Air Pre heater-A&B
where secondary air is heated further utilizing the heat of flue gases. The temperature of air is
raised to improve the efficiency of the unit & for proper combustion in the furnace. Then this air
is fed to the furnace. From the combustion chamber the flue gases travel to the upper portion of
the boiler and give a portion of heat to the PLATIUM SUPER HEATER. Further up it comes in
contact with the REHEATER and heats the steam which is inside the tubes of reheated. Then it
travels horizontally and comes in contact with FINAL SUPER HEATER. After imparting the
heat to the steam in super heater flue gases go downward to the ECONOMIZER to heat the cold
water pumped by the BOILER FEED PUMPS (B.F.P.). These all are enclosed in the furnace.
After leaving the furnace the flue gases go to the Air Heaters where more heat of the flue gases is
extracted to heat primary and secondary air.
Boiler Furnace and Steam Drum:
Once water inside the boiler or steam generator, the process of adding the latent heat of
vaporization or enthalpy is underway. The boiler transfers energy to the water by the chemical
reaction of burning some type of fuel. The water enters the boiler through a section in the
convection pass called the economizer. From the economizer it passes to the steam drum. Once
the water enters the steam drum it goes down the down comers to the lower inlet water wall
headers. From the inlet headers the water rises through the water walls and is eventually turned
into steam due to the heat being generated by the burners located on the front and rear water
walls (typically). As the water is turned into steam/vapor in the water walls, the steam/vapor
once again enters the steam drum. The steam/vapor is passed through a series of steam and water
separators and then dryers inside the steam drum. The steam separators and dryers remove the
water droplets from the steam and the cycle through the water walls is repeated. This process is
known as natural circulation. The boiler furnace auxiliary equipment includes coal feed nozzles
and igniter guns, soot blowers, water lancing and observation ports (in the furnace walls) for
observation of the furnace interior. Furnace explosions due to any accumulation of combustible
gases after a trip out are avoided by flushing out such gases from the combustion zone before
igniting the coal. The steam drum (as well as the super heater coils and headers) have air vents
and drains needed for initial startup. The steam drum has an internal device that removes
moisture from the wet steam entering the drum from the steam generating tubes. The dry steam
then flows into the super heater coils.