4. Water Packaging
Source of RawWater : Damodar River
Water Requirement:
To provide make-up water to the water/steam cycle.
For cooling of the steam for re-use as condensate.
For general domestic use.
RESERVOIR AERATOR
DM PLANT
BOILER MAKE-UP
CW MAKE-UP DMF
POTABLE WATER
GRAVITY FILTERCLARIFLOCCULATOR
5. Water Packaging : De-Mineralization Plant
Activated
Carbon Filter
Strong Acidic
Cation
Exchanger
Degasser
Tower
Strong Basic
Anion Exchanger
Mixed
Bed
Ultra Filtration
SKID
DM Water
Storage Tank
7. Coal Mill (Pulverizer)
▪ Supplies pulverized coal as per
steam generation requirement
▪ Facilitates combustion by pre-
combustion drying up.
▪ Separates incombustibles.
DSTPS has 10 Bowl Mills for each
boiler
Name : 803XRP
8. Boiler
▪ Steam is generated from DM water by heat addition to DM water at
constant pressure & temperature.
Boiler Description at DSTPS, Andal
▪ Top supported, fusion welded
▪ Vertical water-tube boiler
▪ Controlled Circulation
▪ 4-corner tilting tangential firing
9. Boiler Mountings
▪ Pressure Gauges
– For measuring pressures at various points
▪ Valves
– For safety, and to maintain unidirectional flow
▪ Water Level Indicator
– For optimum running of boiler
▪ LRSB (Long Retractable Soot Blower)
– For cleaning soot from boiler’s inner surfaces
▪ Tapping and Manholes
– Maintenance Purpose
10. Boiler Accessories
▪ Air Preheater
– Air is pre-heated by flue gases to ensure complete combustion of even low-grade fuel,
like Lignite.
▪ Economizer
– Feed-water is heated by the outgoing flue gases before entering boiler drum.
▪ Superheaters
– Steam is heated to higher temperature to ensure dryness fraction remains above 0.8
▪ Reheaters
– Steam is reheated between HPT and IPT, and again between IPT and LPT
12. Generator and Exciter
▪ Generates electrical power by the interaction of the
rotating magnetic fields of the stator and rotor
kW: 500000 Speed: 3000 RPM
kVA: 588000 Frequency: 50 Hz
P.F.: 0.85 Lag Coolant: H2 and H2O
Made at BHEL, Haridwar
▪ Brushless excitation system
13. Auxiliaries
▪ Regenerators
– HP Heaters (3 nos)
– LP Heaters (3 nos)
▪ Boiler Feed Pump
– Pressurizes feed water from De-aerator before
entering into boiler
– Turbine Driven Boiler Feed Pump
▪ works with steam extracted from IP turbine
exhaust.
– Motor Driven Boiler Feed Pump
▪ works with a motor. HP Heater
14. Condenser
▪ A shell and tube type surface
heat exchanger.
▪ Cooling water flows twice
through the tubes.
▪ Steam condenses by giving
up heat and is collected at the
hot well below.
▪ Maintained at 45˚C and little
below atmospheric pressure.
15. Cooling Towers
▪ The heated cooling water
after passing through the
condenser, is brought to the
cooling towers.
▪ Heat is given out in the
atmostphere.
▪ The water is recirculated back
as cooling water.
16. Ash Handling Plant
▪ Ash is categorised into :
– Bottom Ash
▪ collected at the bottom of the boiler
– Fly Ash
▪ collected at the Electro-Static Precipitator
▪ It is transported in the form of slurry
▪ Ash is either given away to cement
factories, or is stored in Ash dykes.
17. Control and Automation
▪ Highly Automated by use of PLC
controllers
▪ Control Rooms :
– Boiler Control Room
– CHP Control Room
– Switchyard Control Room
18. Conclusion
▪ The practical experience I have gathered during the overview training
of this thermal power plant in two weeks will be very useful as a
stepping stone in building bright professional career in future life.
▪ It gave me large spectrum to utilize the theoretical knowledge and to
put it into practice.
▪ The trouble shooting activities in operation and decision making in
case of crisis made me more confident to work in the industrial
atmosphere.
Editor's Notes
Good Afternoon, esteemed professor and my beloved friends. Thank you for this opportunity to talk about Durgapur Steel Thermal Power Station or DSTPS, based on my two week vocational training..
DSTPS is a 2x500 MW power station, one of the eight power stations under Damodar Valley Corporation, situated at Andal. It is a pioneer in technological advancement of Thermal Power Generation, currently running at 35 % of its maximum capacity.
Thermal Power Generation involves 3 stages of energy transformations. Chemical Energy stored in fuel is converted to heat energy, that is further converted to rotational energy of the turbine, which in turn produces electrical energy.
A power plant has 3 major raw materials. Water is used for steam generation, cooling and other domestic purposes after conditioning. The fuels, coal and oil, participate in combustion with the help of air, to produce the necessary heat, and then is carried out of the chimney as flue gas.
For every 1MW produced, water is consumed at 4 m3/hr. DSPTS requires 4000 m3/hr at its maximum capacity. This water is pumped from the Damodar River 13 kms away and is used for various purposes like water-steam cycle, cooling cycles, drinking etc. The water is first stored in a reservoir for sedimentation, following which it undergoes aeration to remove dissolved organic gases and fouling, chlorination to kill germs, and clarification to reduce turbidity by adding alum solution. The only impurities at this point are the dissolved ions and colloidal silica, which are removed at DM Plant. The clarified water itself is used for cooling water and domestic purposes.
DM Plant, or the de-mineralization plant has several stages. The ACF removes excess chlorine and organic matters to prevent fouling of the resins in SAC. SAC exchanges all the cations with H+ ion, while SBA exchanges all anions with hydroxide. The mixed bed takes care of any leftover ions. After this stage, only colloidal silica remains in the water, which is removed by passing pressurized water through a membrane. The DM Water is then stored in tanks and supplied as required.
The next major raw material, Coal, arrives in rail wagons, which are emptied by track hoppers and wagon tipplers. Coal is sized to less than 20 mm, and then stored or sent to the bunkers using conveyor belts. These are fed to the coal burners of the boiler after pulverizing as per requirement.
Coal received from the bunker via a gravimetric feeder enters the mill through the central feed tube into the rotating bowl. The coal particles move out due to centrifugal action and gets crushed under the rollers and is carried upwards by the air, through the classifier. Coal dust of 175 mesh size is allowed to discharge, while the rest falls back in the inner cone. The air, called primary air, is preheated by the flue gas to get rid of any moisture.
The boiler, called the mother plant, is a hanging type, vertical, water-tube boiler, with 4-corner tangential firing. That is, fuel is fired from 4 corners of the boiler, tangential to the fireball. Water from BFP passes through the economizer to the boiler drum, from where, it circulates through the water walls, divisional panels, and finally superheater before moving out to the HP Turbine. There is also Hot Reheat and Cold Reheat panels for reheating.
Both primary air and secondary air are heated by the outgoing flue gases, which increases the thermal efficiency of the plant. The feedwater is also heated by the flue gases in the economizer. Superheaters are placed nearest to the heat source within the boiler to increase work output. The reheaters heat steam once between HP and IP turbine, ie, hot reheat, and again between IP and LP turbines, called cold reheat.
There are three turbines, one high pressure turbine with 17 stages, another intermediate pressure turbine which is a double flow turbine with 12 stages in each flow. The third, Low pressure turbine, is also a double flow turbine with 6 stages per flow.
The turbine-generator along with various auxiliaries are stationed at 17 m height. The primary coolant used in the exciter is hydrogen gas, which is further cooled by water. The generator uses a brushless excitation system.
The first HP heater is the de-aerator itself, for which steam is extracted from IP turbine’s 12th stage. For the next 2 HP heaters, steam is extracted from IP Turbine’s 7th stage and from cold reheater’s exit. The LP heaters extract steam from the LP turbine’s 5th, 3rd and 2nd stages. There are two boiler feed pumps, one that is driven by a turbine of its own, and one driven by electricity, ie, motor. The motor-driven pump comes to play during startup of the plant when there is no steam available.
Condenser is basically a heat exchanger. There are numerous tubes. Cooling water is made to flow once through the bottom tubes and then again back through the upper tubes. The exhaust steam enters through the top, exchanges heat, changes phase and settles as condensate in the bottom, called the hotwell. In case of a leakage, the leaking tube is sealed in both ends.
The cooling water from various equipments are are collected and the heat is rejected to the atmosphere. The hot water is sprayed from the top, The venturi shaped cooling towers create a natural draft for air, that absorbs the heat and water vapours and takes them along. Clarified water is added to make-up for the lost water.
The residue from the boiler, ie, ash must be cleaned periodically and effectively for proper functioning of the power station. The ash deposited at the bottom of the boiler is collected by two PLC-operated bottom ash hoppers that are emptied every 4 hours. The ash is carried away in the form of slurry after grinding. Fly ash is collected by electrostatic precipitation and is collected using vacuum pumps in dry mode, or as slurry in wet mode. These are given away to local cement factories, stored in ash ponds.
DSTPS flaunts a highly automated Power Generation System consisting of various sensors, automatic control mechanisms, PLC controllers, etc. All activities are constantly monitored by Scada systems in control rooms, supervised by technical personnel.
In conclusion, the vocational training was an enlightening experience. Connecting the gap between college books and control room screens. I’ve seen and known a lot of things about the working of a full-fledged power station, the various cycles, and auxiliary systems to keep it running smoothly.