REPORT ON BASIC OPERATION OF VINDHYACHAL SUPER THERMAL POWER STATION
BASED ON SUMMER TRAINING UNDERTAKEN IN
NATIONAL THERMAL POWER CORPORATION LIMITED VINDHYACHAL
DURATION:
MAY29TH to JUNE 25TH, 2010
Acknowledgement
At the outset I would like to convey my regards towards training department of NTPC, Vindhyachal for giving me such a great opportunity to observe and learn operation of this Superthermal Plant.
My heartfelt thanks goes toMr. ANIL SHRIVASTAVA, DGM (EMD), NTPC VINDHYACHAL who led the entire team of VSTPS for proper functioning of each department in a modernized and techno-commercial atmosphere to make the project touch such peaking performance. I also express my gratitude towardsMr. S.D.P. PANDEY (Senior Engineer, FES), without his assistance I would not be here. He has provided me the best moral support which I was in need for.
I would give my special thanks to Mr SANJAY SHARMA (HR-EDC), for giving his very kind permission to undergo the training programme under the able guidance of NTPC engineers. I would like to appreciate Mr Pankaj Kumar (Sr. Engineer., EMD DEPT), Mr .Vikas Gupta (Engineer, EMD.) & Mr. Ajit Singh( Engineer, EMD) under whose able guidance I completed the training. All these people were of immense importance regarding the knowledge and supports for the well furnished equipments.
At last I would like to convey my appreciation to all the members of the Electrical and Maintenance Dept. and members of various stages whose valuable guidance and suggestions helped me accomplishing this report.
INTRODUCTION
NTPC (National thermal power corporation) is India’s largest power generation company. It was set up in the year 1975 to accelerate power development in India. It has an installed capacity of 37,104 MW and planned to grow up to 75000 MW till year 2017.There are 15 coals based and 7 gas based plant in India located across the country. NTPC is the sixth largest thermal power generator in the world and the second most efficient utility in terms of capacity utilization based on data of 1998.
NTPC HEADQUARTERS:
Sl no / Headquarter / City1 / NCRHQ / Noida
2 / ER-1,HQ / Patna
3 / ER-2,HQ / Bhubaneshwar
4 / NER / Lucknow
5 / SR,HQ / Hyderabad
6 / WR,HQ / Mumbai
NTPC PLANTS:
Coal based:
Sl no / City / State / Capacity(MW)
1 / Singrauli / U.P. / 2000
2 / Korba / Chattisgarh / 2100
3 / Ramagundam / Andhra Pradesh / 2600
4 / Farakka / W.B. / 1600
5 / Vindhyachal / M.P. / 3260
6 / Rihand / U.P. / 2000
7 / Kahalgaon / Bihar / 2340
8 / NCTPP,Dadri / U.P. / 1330
9 / Talcher,Kaniha / Orissa / 3000
10 / Unchahar / U.P. / 1050
11 / Talcher Thermal / Orissa / 2460
12 / Simhadri / Andhra Pradesh / 1000
13 / Tanda / U.P. / 440
14 / Badarpur / Delhi / 705
15 / Sipat-II / Chattisgarh / 1000
Total / 24885
Gas based:
Sl no / City / State / Capacity(MW)1 / Anta / Rajasthan / 413.2
2 / Kawas / Gujarat / 645.4
3 / Dadri / UP / 817.5
4 / Jhanor / Gujarat / 648.6
5 / Rajiv Gandhi / Kerala / 350.7
6 / Faridabad / Haryana / 430
Total / 3955
Hydel based:
The company has also stepped up its hydel projects implementation. Currently the company is mainly interested in Northeast India wherein the ministry of power in India has projected a hydel power feasibility of 3000 MW.
There are few run of the river hydro projects are under construction on tributary of Ganga. In which three are being made by NTPC limited. These are:
- Lohariang Pala Hydro Power project(600 MW)
- TapovanVishnugad Hydro power project
- LataTapovan Hydro Power Project
As a public sector company, it was incorporated in the year 1975 to accelerate power development in the country as a wholly owned enterprise of the Government of India. At present, Government of India holds 89.5% of the total equity shares of the company and the balance 10.5% is owned by FIIs, Domestic Banks, public and others. Within a span of 31 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.
NTPC-VINDHYACHAL SUPER THERMAL POWER PROJECT is one of the most prestigious flagships of NTPC striving ahead to bridge the country generation gap especially in the western region. It is the largest power station in India. Vindhyachal super thermal power station was conceived as a pit head coal based super thermal plantfor which land was acquired during stage I of the project. The total land area acquired is 5378 acres of land.
The station is located in Singrauli district in Madhya Pradesh in the north western side of the country. , having a latitude and longitude of 24⁰6’ N and 82⁰40’ E respectively.
It has secured ISO 14001 and ISO 9002 certificate in the field of environment and power generation but also in various other fields. On November 2009,it made glorious achievement by ensuring production up to 3260 MW. By next few months, it adds 1000 MW more to its capacity (i.e. 4260 MW). A proposal has also been made to add another 500 MW in Stage V for which field study is going on.
IMPORTANT DATA
Address- P.O. Vindhyanagar 486 885, SIdhi, Madhyapradesh
Approved Capacity- 3260 MW
Stages:-
Stage1—6×210 =1260 MW
Stage2---2×500=1000 MW
Stage3---2×500=1000MW
Stage4---2×500=1000MW (Under construction)
Stage5---1×500=1000MW (Proposed)
Coal source- Nigahi Hills
Water source- Discharge canal of Singrauli (Shaktinagar) Super Thermal Power Station
Beneficiary States- Madhya Pradesh, Chattisgarh, Maharashtra, Gujarat, Goa, DamanDiu and Dadar Nagar Haveli.
Units Commissioned
Stage1
Unit 1- 210 MW October 1987
Unit 2- 210 MW July 1988
Unit 3- 210 MW February 1989
Unit 4- 210 MW December 1989
Unit 5- 210 MW March 1990`
Unit 6- 210 MW February 1991
Stage2
Unit 7- 500 MW March 1999
Unit 8-500 MW February 2000
Stage3
Unit 9- 500 MW July 2006
Unit 10- 500 MW March 2007
PRODUCTION OF ELECTRICITY:
given b
chimney
Coal to Electricity
The means and steps involved in the production of electricity in a coal-fired power station are described below.
The coal, brought to the station by train or other means, travels from the coal handling plant by conveyer belt to the coal bunkers, from where it is fed to the pulverizing mills which grinds it as fine as face powder. The finely powdered coal mixed with pre-heated air is then blown into the boiler by fan called Primary Air Fan, with additional amount of air called secondary air supplied by Forced Draft Fan. As the coal has been grounded so finely the resultant ash is also a fine powder. Some of this ash binds together to form lumps which fall into the ash pits at the bottom of the furnace. The water quenched ash from the bottom of the furnace is conveyed to pits for subsequent disposal or sale. Most of ash, still in fine particles form is carried out of the boiler to the precipitators as dust, where it is trapped by electrodes charged with high voltage electricity. The dust is th en conveyed by water to disposal areas or to bunkers for sale while the cleaned flue gases pass on through ID Fan to be discharged up the chimney.
Meanwhile the heat released from the coal has been absorbed by the many kilometres of tubing which line the boiler walls. Inside the tubes is the boiler feed water which is transformed by the heat into the steam at high pressure and temperature. The steam super-heated in further tubes (Super Heater) passes to the turbine where it is discharged through the nozzles on the turbine blades. Just the energy of the wind turns the sail of the wind-mill, so the energy of the steam, striking the blades, makes the turbine rotate.
Coupled to the end of the turbine is the rotor of the generator – a large cylindrical magnet, so that when the turbine rotates the rotor turns with it. The rotor is housed inside the stator having heavy coils of copper bars in which electricity is produced through the movement of the magnetic field created by the rotor. The electricity passes from the stator winding to the step-up transformer which increases its voltage so that it can be transmitted efficiently over the power lines of the grid.
The steam which has given up its heat energy is changed back into water in the condenser so that it is ready for re-use. The condenser contains many kilometres of tubing through which the colder is constantly pumped. The steam passing around the tubes looses the heat and is rapidly changed back to water. But the two lots of water (i.e. boiler feed water & cooling water) must never mix. The cooling water is drawn from the river, but the boiler feed water must be absolutely pure, so as not to damage the boiler tubes. Chemistry at the power station is largely the chemistry of water.
To condense the large quantities of steam, huge and continuous volume of cooling water is essential. In most of the power stations the same water is to be used over and over again. So the heat which the water extracts from the steam in the condenser is removed by pumping the water out to the cooling towers and then the cooled water is recirculated again through the condenser.
Steps Involved In Power Generation In VSTPS
The conversion of coal into electricity consists of various intermediate stages. This are described below –
1.Coal handling Plant-
CHP is the first stage of any Thermal Power Plant .The coal from the mines is brought to the plant by use of Coal wagons. . Merry-Go-Round rail system of transport is adopted for transportation of coal from the mines to plant site. NTPC has its own MGR system which results in an annual profit of 45 crores. Coals are unloaded by track hoppers. As the coal from mines contain particles of different sizes, so water is sprinkled on the coal so as to stop flow of coal with air and to stop the loss. Coal in the track hopper is then send to crusher house for crushing it to size no less than 20mm. Crushed coal is sent to bunkers through conveyer belt system. Afterwards according to requirement coals are taken into mills through gravimetric feeder to pulverize it to a size of 200 mesh. Primary air mixed with pulverized coal is fed to the centre of boiler burning zone. Pre heated secondary air enters boiler, surrounds the pulverized coal and helps in combustion.
Capacity of each crusher / 600MT/HourMaximum coal inlet size / 200mm
Maximum coal outlet size / 20mm
Motor Rating / 375KW
Motor Speed / 740 Rpm
Capacity of conveyer belt / 1200 T/Hour
Belt Speed / 2.6 m/s
Belt width / 1.4 m
Belt Type / Nylon-Nylon Caracus
2.Air Draft System:
Primary air system:
-Ambient air is drawn into the primary air ducting by two 50% duty, motor driven axial reaction fans.
-Air discharging from each fan is divided into two parts, one passes first through a air pre-heater then through a gate into the P.A bus duct. The second goes to the cold air duct. The mix of both is used to carry the pulverized coal to the boiler.
-
Secondary air system:
-Ambient air is drawn into the secondary air system by two 50% duty, motor driven axial reaction forced draft fans with variable pitch control.
-Air discharging from each fan passes first through a air preheater then through a isolating damper into the secondary air bust duct.
-The cross over duct extends around to each side of the boiler furnace to form two secondary air to burner ducts.
-At the sides of the furnace, the ducts split to supply air to two corners. Then split again to supply air to each of nineteen burner/air nozzle elevations in the burner box
-
Primary and Secondary air System in the Boiler:
Air Preheater:
Air preheater is heat transfer surface where temperature of air is raised by flue gas. It gives:
-Improved boiler efficiency
- Improved combustion
- Hot primary air for drying coal
Induced draft system:
It sucks flue gas from boiler and releases it to atmosphere through chimney. The flue gas contains fly ash particles, deposited in ESP hoppers and SOx, NOx etc. The flue gas path is shown below
Electrostatic Precipitator (ESP):
It is a device which captures the dust particles from the flue gas thereby reducing the chimney emission.Precipitators function by electrostatically charging the dust particles in the gas stream. The charged particles are then attracted to and deposited on plates or other collection devices. When enough dust has accumulated, the collectors are shaken to dislodge the dust, causing it to fall with the force of gravity to hoppers below. The dust is then removed by a conveyor system for disposal or recycling.
Theory of Precipitation:
Here six activities typically takes place.
Ionization - Charging of particles.
Migration - Transporting the charged particles to the collecting surfaces.
Collection - Precipitation of the charged particles onto the collecting surfaces.
Charge Dissipation - Neutralizing the charged particles on the collecting surfaces.
Particle Dislodging - Removing the particles from the collecting surface to the hopper by rapping mechanism.
Particle Removal - Conveying the particles from the hopper to a disposal point governed by fly ash disposal system.
Major Fans in Boiler Draft System:
•PA Fans
•FD Fans
•ID Fans
PRIMARY AIR FAN: It serves two main purposes:
a)Transportation of coal from mill to furnace
b)Coal moisture removal
•NO OF FANS PER BOILER : TWO
•TYPE : RADIAL
•INDUCTION MOTOR RATING : 1480 KW
•SPEED : 1480 RPM
•CONTROL: INLET VANE CONTROL
FORCED DRAFT FAN: It provides air for combustion.
•NO : TWO
•TYPE : AXIAL REACTION
•MOTOR RATING : 800 KW
•SPEED :1480 RPM
•CONTROL: BLADE PITCH CONTROL
INDUCED DRAFT FAN: It maintains furnace draft.
•NO OF FANS PER BOILER : TWO
•TYPE : AXIAL IMPULSE
•MOTOR RATING : 1300 KW
•SPEED : 740 RPM
•CONTROL: INLET VANE CONTROL
Steam cycle:-
The demineralised water, which is used to produce steam, passes through various intermediate stages. The DM water passes through a series of water heaters namely LP heaters, Gland Steam Cooler(GSC),HP heaters and afterwards passes through Deaerator, Boiler feed pump, economizer and then goes to boiler drum.In LP heater and HP heater ,heat is transferred from steam (coming from turbine) to water which increases the temperature of the water. The direct mixing of steam with water is not allowed. In Deaerator, steam comes in direct contact of water. Deaerator is used to remove the air of feed water to prevent corrosion of boiler tubes and turbine blades. The presence of air also reduces the efficiency of cycle. The boiler feed pump is used to pump water to boiler drum through economizer. Boiler Economizer are feed-water heaters in which the heat from waste gases is recovered to raise the temperature of feed-water supplied to the boiler. In the midst of HPH and Economizer, a three element feed flow regulating system has been incorporated which regulates the steam flow from the boiler, the feed water flow to the boiler and the water level in the boiler drum.
The boiler drum serves two purposes:-
1. Separating steam from mixture of water and steam
2. It houses all the equipments for purification of steam.
In VSTPS the boiler used is water tube boiler. Here the heat source is outside the tubes and the water to be heated is inside. Most high-pressure and large boilers are of this type. In the water-tube boiler, gases flow over water-filled tubes. These water-filled tubes are in turn connected to boiler drums.
In stage I natural circulation takes place. Natural circulation is the ability of water to circulate continuously, with gravity and changes in temperature being the only driving force known as "thermal head“.
The down comer contain relatively cold water, whereas the riser tube contain steam water mixture ,whose density is comparatively less .this density difference is the driving force ,for the mixture. (thermo-siphon principle).Circulation takes place at such a high rate that the driving force and frictional resistance in water wall are balanced. Natural circulation is limited to boiler with drum operating pressure around 175 Kg/cm2.However, when the pressure in the water-tube boiler is increased, the difference between the densities of the water and saturated steam falls, consequently less circulation occurs. To keep the same level of steam output at higher design pressures, the distance between the Bottom ring header and the steam drum must be increased, or some means of forced circulation must be introduced. Beyond 180 Kg/cm2 of pressure, circulation is to be assisted with mechanical pumps, to overcome frictional losses. This is known as forced circulation which is employed in stage II and stage III.
The water coming from boiler drum on its passage through down comer and riser tube is converted into a mixture of water and steam and goes back to boiler drum. The steam from boiler drum passes through a series of super heaters like LTSH (Low temperature Super Heater), Platen super heater, convective super heater. Super heater heats the high-pressure steam from its saturation temperature to a higher specified temperature. The steam at super heater outlet gains a temperature of 5400C. It is then passed to HPT (High Pressure turbine) and the temperature of the steam goes down. The steam is sent back to reheater to gain back the temperature. The reheated steam is sent to IPT (Intermediate Pressure Turbine), then from IPT to LPT(Low pressure turbine). The HP, IP, LP turbines and the rotor of the turbo generator are connected on the same shaft. As the high pressurized steam drives the turbine blades, so rotor of the generator also rotates. The steam after losing its pressure begins to condense in condenser by exchanging heat with circulating cooling water. The condensate is then move to hot well. Then from hot well the condensate is pumped by CEP (condensate extraction pump) to LP heater. The cycle continues which is termed as steam cycle.