KTPS

CONTENT

Acknowledgement

Kolaghat Thermal Power Plant

Introduction

Power Plant Layouts

Main and Auxiliary Equipment Mechanical Equipment Electrical Equipment

Water Chemistry

Conclusion

AcknowledgementWithout effort of many people in any work can’t be accomplished. The achievement of dreams for accomplishment would be acknowledged the effort of the person behind it.

I express my gratitude to Mr. Ram Chandra Lakshman, Senior Manager(Electrical) and Mr. Uttam Kumar Paul, A.M.(PS) for allowing me to carry a project on Kolaghat Thermal Power Station.

Lastly, I would like to thanks the supervisors, senior engineers, workers, and other members of this power station. They are very friendly and helpful to me. They share their experience and guide me well.Once again, I thanks to all the staff of the power plant for their help in my vocational training.

Kolaghat Thermal Power Station

Kolaghat Thermal Power Station is a major thermal power station in West Bengal. It is located at Mecheda, approx. 55 km from Kolkata in the Purba Medinipur district. The power plant is operated by West Bengal Power Development Corporation Limited.

The power plant has six units of 210 MW each for a total capacity of 1260 MW. The units were commissioned in two stages during the period of 1984 to 1995.

INTRODUCTION

A Thermal Power Plant converts the heat energy of coal into electrical energy. Coal is burnt in a boiler which converts water into steam. The expansion of steam in turbine produces mechanical power which drives the alternator coupled to the turbine. Thermal Power Plants contribute maximum to the generation of Power for any country. Thermal Power Plants constitute 75.43% of the total installed captive and non-captive power generation in India. In thermal generating stations coal, oil, natural gas etc. are employed as primary sources of energy.

GENERAL LAYOUT OF THERMAL POWER STATION

Main & Auxiliary Equipment1. Mechanical Equipment2. Electrical Equipment

Mechanical Equipment:

Coal Handling Plant: The function of coal handling plant is automatic feeding of coal to the boiler furnace. A thermal power plant burns enormous amounts of coal. A 210MW plant may require around 2000 tons of coal daily. At the receiving location stock yard or send to coal bunkers. To make sure to generate electricity when we want to, we’ve to make sure that coal is in the right place at the right time. Typically, 15 days’ stock is maintained at site. The stock yard stocks these & helps in times of lean supply from the mines or when transportation isn’t available.

Coal Conveyor: It is used to move coal around efficiently. Coal arriving by train can be stocked for later use or taken straight to the coal bunkers. CHP control room with remote control system helps to ensure that the conveyor take the coal to the right bunkers.

Stack & Reclaim: Machines are used to put coal out to the stockpile & reclaim coal from stockpile. Water is sprayed on coal to stop them from getting burnt when in storage yard due to internal heat up & sun heat. Coal when powdered is heated & being lifted by hot air that is sent into mills. This goes & burns inside the furnace producing ash & converting the water in the pipe lines into steam. Boiler: A boiler or steam generator is a closed vessel in which water under pressure, is converted into steam. It is one of the major components of a thermal power plant & always designed to absorb maximum amount of heat released in the process of combustion.Boilers are of two types-

I. Fire tube boiler,II. Water tube boiler.

Inside the boiler there in enough steel tubing to stretch the 500 km & they are joined together by about 20,000 joints.

Technical Data:

Max. Continuous Evaporation: 700ton/hr Outlet Temperature: 5400c Outlet Pressure: 136kg/cm3

Water Handling Capacity:

The water holding capacity of differential sections are given below: forced Flow Section (Economizer): 16.90 tonsBoiler Drum NWL: 126.76 tonesBoiler Drum Full: 14886 tons

Turbine: A steam turbine converts heat energy of steam into mechanical energy and drives the generator. It uses the principle that steam when issuing from a small opening attains a high velocity. This velocity attained during expansion depends on the initial and final heat content of the steam. This difference between and final heat content represents the heat energy converted into kinetic energy. These are of two types: -

I. Impulse turbineII. Reaction turbine

Technical Data:

Rated output of turbine: 210 MWRated speed: 3000 rpmRated pressure of steam before emergency stop valve: 130 kg/cm3 absRated live steam temperature: 5350cSteam flow: 670 ton/hr.

High Pressure Turbine: High pressure steam at 5400c, 170 ksc pressure passes through HPT. The exhaust steam from this section returned to the boiler to reheating before being used in next section of the turbine set. The blades in the high pressure turbine are the smallest of the all the turbine blades, this is because the incoming steam has very high energy & occupies a low volume. The blades are fixed to a shaft & as the steam hits the blades it causes the shaft to rotate.

Intermediate Pressure Turbine: On leaving the boiler reheater, steam enters the IPT at 5400c & 40 ksc pressure. From here the steam goes straight to the next section of the turbine set. The steam has expanded & has less energy, when it enters this section, so here turbine blades are bigger than those in the HPT. The blades are fixed to a shaft & as the steam hits to the blades it causes the shaft to rotate.

Low Pressure Turbine: From the IPT, the steam continues its expansion in the 3 LPT. The steam entering to the turbine at 3000c & 6 ksc pressure. To get the most work out of the steam, exhaust pressure is kept very low, just 50 mile-bar above a complete vacuum. The tip speed of the largest blades with the shaft spinning at 3000 rpm is 2000 kmph.

Super heater: Super heater is a component of a steam-generating unit in which steam, after it has left the boiler drum, is heated above its saturation temperature. The amount of superheat added to the steam is influenced by the location, arrangement, and amount of super heater surface installed, as well as the rating of the boiler. The super heater may consist of one or more stages of tube banks arranged to effectively transfer heat from the products of combustion. Super heaters are classified as convection, radiant or combination of these.

Reheater: Some of the heat of superheated steam is used to rotate the turbine where it loses some of its energy. Reheater is also steam boiler component in which heat is added to this intermediate-pressure steam, which has given up some of its energy in expansion through the high-pressure turbine. The steam after reheating is used to rotate the second steam turbine where the heat is converted to mechanical energy. This mechanical energy is used to run the alternator, which is coupled to turbine, there by generating electrical energy.

Economiser:Flue gases coming out of the boiler carry lot of heat. An economiser extracts a part of this heat from flue gases and uses it for heating feed water. This use of economiser results in saving coal consumption and higher boiler efficiency.

Air Pre Heater:After flue gases leave economiser, some further heat can be extracted from them and used to heat incoming heat. Cooling of flue gases by 200c increases the plant efficiency by 1%.Air preheaters may be of three types:

I. Plate typeII. Tubular type

III. Regenerative type

Cyclotron Separator: The Filter 1 Cyclotron combines a long tapered cone, a high velocity inlet, and a large internal helix to easily separate from the air stream all moderate size particles, such as saw dust chips and particles from metal grinding. The Cyclotron fans are positioned on the clean air side of the cyclone and are direct drive for low maintenance. In addition, the fans have backward inclined blower wheels for high efficiency and low noise operation. Optional Safety After Filters ensure that even the smallest particles are captured. Standard filter material for the after-filters is 16-ounce seared, felted polyester, designed to hold large dust particles to the outer edges, thus forming a filter cake which heightens filtering efficiency and facilitates easy removal.

Condenser: Steam after rotating steam turbine comes to condenser. Condenser refers here to the shell and tube heat exchanger (or surface condenser) installed at the outlet of every steam turbine in Thermal power stations of utility companies generally. These condensers are heat exchangers which convert steam from its gaseous to its liquid state, also known as phase transition. In so doing, the latent heat of steam is given out inside the condenser. Where water is in short supply an air cooled condenser is often used. An air cooled condenser is however significantly more expensive and cannot achieve as low a steam turbine backpressure (and therefore less efficient) as a surface condenser. The purpose is to condense the outlet (or exhaust) steam from steam turbine to obtain maximum efficiency and also to get the condensed steam in the form of pure water, otherwise known as condensate, back to steam generator or (boiler) as boiler feed water.

Technical Data

Flow: 300 ton/hrPressure: 4.5 to 6.5 kg/cm3

Temperature: 2500c

Cooling Towers:A condenser needs huge quantity of water to condense the steam. Typically, a 1260MW plant needs about 1000MGallon of water. Most plants use a closed cooling system where warm water coming from condenser is cooled and reused. Cooling tower is a steel or concrete hyperbolic structure having a reservoir at the base for storage of cooled waterHeight of the cooling tower may be 150 m or so and diameter at the base is 150 m.

Technical Data

No. of water pumps: 4Capacity: 4000 m3/hrNo. of cooling water makeup pumps: 5Capacity: 2000 m3/hr

ID Fan: Induced Draught Fan sucks the gases out of the furnace and throw them into the stack by creating sufficient negative pressure in the furnace (5-10 mmwc) in the balanced draft units and is Located in between the ESP and Chimney in the flue gas path. Radial Fans -double suction-backward curved vane with inlet guide vane(IGV)control and VFD control is use in all boilers. It handles large volume hot dust/ash laden flue gas (temp up to 1500C) from furnace and all leakages occurring in the system till the inlet of the fan. Overcome the pressure drop inside the furnace, Super heater, Re -heater, Economiser, gas ducting & ESP and Consumes max. power in all boiler auxiliaries as it handles the large volume and heavy pressure drop of the flue gas.

FD Fan:Forced Draught Fan supplies secondary air to the furnace through APH to assist in combustion & supplies total air flow to the furnace except where an independent atmospheric P.A fan is used. It provides air for sealing requirement and excess air requirement in the furnace. It is axial fan-reaction type with blade pitch control is use in the Pulverized fired boiler (210 MW).

PA Fan: Primary Air Fan supplies high pressure primary air through APH needed to dry & transport coal directly from the coal mills to the furnace. Primary air for mills is divided into cold & hot primary air. It is axial fan-double stage-reaction type with blade pitch control is use in the Pulverized fired boiler (210 MW).

Low Pressure Feed Heaters:Feed water from condensate extraction pumps passes through low pressure heaters. Steam is used to the feed water. After the last feed heater, the feed water is at around 1600c.

High Pressure Feed Heaters:With the similar purpose to the low pressure feed heaters, the high pressure feed heaters are the last stage of feed water heating before the feed water enters the boiler system at the economizer. Feed water leaving these heaters is at 2500c.

Deaerator:From the low pressure feed heaters, the water passes through the deaerator before going to the high pressure feed heaters. One of the feed water heaters is a contact type open heater, known as deaerator, others being closed heaters. It is used for the purpose of deaerating the feed water. The presence of dissolved gases like O2, CO2. In water makes the water corrosive, as they react with the metal to form ion oxide. These gases are removed in the deaerator. To neutralize the effect of the residual dissolved O2 & CO2 in water, sodium or hydrazine is injected in suitable calculated doses in the feed water at the section of the BFP.

Boiler Feed Pump: The boiler feed pump pumps water into the boiler, overcoming the boiler pressure of 160 bar to achieve it. The pump is driven by a steam turbine or an electric motor. It runs at 7000rpm.

Electrical Equipment:

Transformers: It is a device that transfers electric energy from one alternating-current circuit to one or

more other circuits, either increasing (stepping up) or reducing (stepping down) the voltage. Uses for transformers include reducing the line voltage to operate low-voltage devices (doorbells or toy electric trains) and raising the voltage from electric generators so that electric power can be transmitted over long distances. Transformers act through electromagnetic induction; current in the primary coil induces current in the secondary coil. The secondary voltage is calculated by multiplying the primary voltage by the ratio of the number of turns in the secondary coil to that in the primary.

Generator: An alternator is an electromechanical device that converts mechanical energy to alternating current electrical energy. Most alternators use a rotating magnetic field. Different geometries - such as a linear alternator for use with Stirling engines - are also occasionally used. In principle, any AC generator can be called an alternator, but usually the word refers to small rotating machines driven by automotive and other internal combustion engines.

Technical Data: Max continuous MVA rating: 247 MVAMax continuous MW rating: 210 MWRated terminal voltage: 15.75 KVRated stator current: 9050 ampRated power factor: 0.85 lagRated speed: 3000 rpmRated frequency: 50 HzExcitation voltage: 500 VExcitation current: 2600 ampEfficiency: 98.4%No. of terminal brought out: 9Phase connection: Double starDirection of rotation when viewed from slip ring end: antilock wisePermissible temperature rating: 1050c for stator windings, 1150c for rotor winCooling Medium: HydrogenExcitation System: Static

Rotor:The shaft that runs through the turbine is coupled to the rotor, which is a large electromagnetic inside a cylinder of copper windings called the stator. The rotor weighs 100 tonnes & rotates at 3000 rpm.Stator:As the electromagnet rotates inside the copper windings, a magnetic field is created which induces a 3 phase alternating electric current in the stator windings. Together the stator & rotor is known as generator. The stator weighs 300 tonnes. Electricity is generated at over 80 times the voltage in our homes. This is stepped up to about 4,00,000 volts and then transmitted.

Electrostatic Precipitator: Each boiler has 4 passes with 7 fields each contains high voltage electrodes. Theses attract the dust & ash from the flue gasses. At regular intervals the electrodes are rapped with motor driven hammers & the PFA falls into hoppers below. This is one of the way to clean up the flue gases or smoke sent up the chimney. Technical Data:

Rapper- Collected Electrode rappingVibrator- Discharging Electrode Rapping

Exciters: Excitation system is required to provide the necessary field current to the rotor winding of a synchronous machine. Availability of excitation at all times important. Larger the load currents, lower the speed and lagging power factor which require more excitation.Types:

I. DC Excitation System II. AC Excitation System

III. Static Excitation System Exciters

Bus-Bar: Bus bar is a main bar or conductor carrying an electric current to which many connections are to be made. Usually two buses are provided in a system one is called the “Main” bus and other “Auxiliary” or transfer bus. There are many shapes of bus bar available like round tubes, round solid bars or square tube. Material used for bus bar is aluminium because it has high corrosion resistance than copper and lower cost. Bus bar of 5 to 6 meter in length Bus- Bars.

Circuit Breaker: A circuit breaker is a mechanical device used to open and close contact under normal and abnormal conditions. Relay is use as a sensor with circuit breaker for automatic operation. Circuit breaker carry normal current without over- heating or damage.

Function of circuit breaker: - To carry full load current continuously To open and close the circuit under no load

To break the circuit under short-circuit condition Circuit Breakers.

Isolator: Isolator are devices they are auto-operated or manually in off load condition, mainly for maintenance purpose of a faulty line. Circuit breakers trip during fault or heavy current flow in the transmission line. Isolator physically isolates line and it ensures the service man his personal safety unlike CB as it is not much transparent in its condition. Isolators are always opened in no load condition (after opening of CB) because it lacks the mechanism of operating in high voltage.

Batteries: All power plant and sub-stations DC supply for protection and control purpose. DC supply is provided from Storage batteries. Lead acid batteries mostly used in power stations because their higher cell voltage and lower cost Batteries.

Water ChemistryWater: Rupnarayan river is the main source of water. This water absorbs different types of gases from atmosphere like Nitrogen, Oxygen and to a lesser extent Carbon-dioxide. Apart from this, the water travels to various places & catches organic matter, suspended solids etc. Types:

I. Cooling WaterII. Boiler water

III. Process waterIV. Consumptive water.

Water Treatment in Power Plant:

Pre-treatment of raw water Filter water for softening & DM plant Ultra-pure/ demineralised water for boiler makeup/ steam generation Cooling water system Monitoring of steam/ water parameters& HP/LP Dosing system

Demineralization (DM) Water Treatment Plants

The function of demineralization plant is to remove dissolved salt by ion exchange method (chemical method) and there by producing pure feed water for boiler. The salts which make the water hard are generally-chloride, carbonates, bi-carbonates, silicates & phosphates of sodium, potassium, iron, calcium and magnesium.

In D M plant there are three types of resin used for boiler feed water treatment process: -

1. Cation exchange resin

2. Anion exchange resin

3. Mixed Bed resin

Resins are chemical substances (usually polymers of high molecular weight) used to react with salts & eliminates them by chemical process.

As the name suggests, the cation exchange resin, exchanges the cation & anion exchange resin, exchanges anions with the salts dissolved in hard-water.

1.Cation Exchange Resin

NaCl + RSO3H = RSO3 - Na + + HCl. Thus H2SO4, H2CO3 are also produced. We have removed Na

+ but the water has become acidic.

2. Anion Exchange Resin

HCl + R4NOH = R4NCl + H2O. This way we have eliminated Cl - and thus acidity of the water. Similar reaction for H2SO4 also.

3. Mixed Bed Resins

These mixed bed resins are used in Demineralization plant of boiler feed water treatment, to remove the ions (especially Na + and SO3 2- ) which may further present in the water after foregoing process of purification.

ConclusionIn vocational period at Kolaghat Thermal Power Station, we achieved a sound knowledge about industry apart from general procedure. There are many things to learn. We get to know industrial culture, its working procedure and its management procedure. It’ll very helpful for us in our working life. It us one of the renounced power plant.

Once again I want to express my cordial thanks to all the employees and workers of the KTPS for their support assistance and valuable feedback. It is impossible for me to do it successfully without their help.