introduction to ntpc (3) (1)

7/29/2019 Introduction to Ntpc (3) (1)

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Type Public

Founded 1975

Headquarters Delhi, India

Key people R S Sharma, Chairman &

Managing director

Industry Product Electricity generation


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National Thermal Power Corporation is the largestpowergeneration company in India. Forbes Global

2000 for 2008 ranked it 411th in the world. It is anIndian public sector companylisted on the Bombay

Stock Exchange although at present the

Government of India holds 89.5% of its equity.

NTPC was established as a public sector power utilityby Government of India on November 7, 1975.

The reason NTPC was created was to bridge thehuge electricity supply-demand gap and the State

Electricity Boards were not able to cope up with the

situation.


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Installed Capacity 720 MW

Derated Capacity 705 MW

Location New Delhi

Coal Source Jharia Coal Fields Water Source Agra Canal

Transfer of BTPS Ownership of BTPS was

To NTPC transferred to NTPC with

effect from 01.06.2006

through GOIs Gazette

Notification


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The thermal (steam) power plant uses a

dual (vapour + liquid) phase cycle. It is a

closed cycle to enable the working fluid

(water) to be used again and again. Thecycle used is RANKINE CYCLE" modified

to include super heating of steam,

regenerative feed water heating andreheating of steam.


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The Coal is transported up to the raw coalbunkers with the help of belt conveyors. Coal istransported to Bowl Mills by Coal feeders The coalis pulverized in the Bowl Mill, where it is ground toa powder form. The mill consists of a round

metallic table on which coal particles fall. Thistable is rotated with the help of a motor. There arethree large steel rollers which are spaced 120"apart. Coal is crushed by the crushing action

between the rollers and rotating table. Thiscrushed coal is taken away to the furnace throughcoal pipes with the help of hot and cold air mixturefrom P.A. Fan.


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Water from the boiler feed pump passes through

economizer and reaches the boiler drum. Water from the

drum passes through down comers and goes to bottom ring

header. Water from the bottom ring header is divided to all

the four sides of the furnace. Due to heat and- the density

difference the water rises up in the water wall tubes . "Water

is partly converted to steam 'as it rises up in the furnace. Thissteam and water mixture is again taken to the boiler drum

where the steam is separated from water. Water follows the

same path while the steam is sent to superheaters for

superheating. The superheaters are located inside the

furnace and the steam is superheated (540"C) and finally it

goes to turbine.


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From the boiler, a steam pipe conveys steam tothe turbine through a stop valve and throughcontrol valves that automatically regulate thesupply of steam to the turbine where it passes

through a ring of stationary blades fixed to thecylinder wall. These act as nozzles and direct thesteam into a second ring of moving bladesmounted on a disc which rotates the blades and

its passage of some heat energy is changed intomechanichal energy. The turbine shaft usuallyrotates at 3,000 revolutions per minute


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BOILER -A boiler is a closed vesselin which water or other fluid isheated. The heated or vaporizedfluid exits the boiler for use invarious processes or heatingapplications. Construction of boilers

is mainly of steel, stainless steel,and wrought iron. In live steammodels, copper or brass is oftenused. Historically copper was oftenused for fireboxes (particularly forsteam locomotives), because of its

better thermal conductivity. Theprice of copper now makes thisimpractical.


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MAIN BOILER: AT 100% LOAD Evaporation 700t/hr Feed water temperature 247C

Feed water leaving economizer 276C

STEAM TEMPERATURE:

Drum 341C Super heater outlet 540C Reheat inlet 332C Reheat outlet 540C

STEAM PRESSURE: Drum design 158.20 kg/cm2

Drum operating 149.70 kg/cm2 Super heater outlet 137.00 kg/cm2 Reheat inlet 26.35 kg/cm2

Reheat outlet 24.50 kg/cm2


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FUEL:1. COAL DESIGN WORST

Fixed carbon 38% 25% Volatile matter 26% 25%

Moisture 8% 9%

2. OIL

Calorific value of fuel oil 10,000 kcal/kg

Sulphur content 4.5% W/W

Moisture content 1.1% W/W

Flash point 66C


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The primary function of oil and coal burning systemsthe process of steam generation is to provide controlledefficient conversation of the chemical energy of the fuelinto heat energy which is then transferred to the heatabsorbing surfaces of the steam generator. Thecombustion elements of a fuel consist of carbon,

hydrogen and usually a small amount of sulphur. Whencombustion is properly completed the exhaust gaseswill contain, carbon dioxide, water vapour, sulphurdioxide and a large volume of Nitrogen, Combustion isbrought about by combining carbon and hydrogen orhydrocarbons with the oxygen in air. When carbon

burns completely, it results in the formation of a gasknown as carbon dioxide. When carbon burnsincompletely it forms carbon monoxide.


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1. TIME

2. TEMPERATURE

3. TURBULENCE

4. DESIGN OF BOILER

5. FUEL USED


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INTRODUCTION:

Furnace is primary part of boiler

where the chemical energy of fuel is converted to

thermal energy by combustion. Furnace is

designed for efficient and complete combustion.

Major factors that assist for efficient combustion

are amount of fuel inside the furnace and

turbulence, which causes rapid mixing betweenfuel and air. In modern boilers, water-cooled

furnaces are used.


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1. FIRED DRY BOTTOM FURNACE

2. SLAG TYPE FURNACE

3. OIL FIRED BOILER FURNACE


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1. I.D FANS

2. F.D FANS

3. PRIMARY AIR FANS


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The induced Draft Fans are generally of AxialImpulse

Type. Impeller nominal diameter is of the order of 2500mm.

The fan consists of the following sub-assemblies

Suction Chamber

Inlet Vane Control

Impeller

Outlet Guide Vane Assembly

The outlet guides are fixed in between the case of thediffuser and the casing. These guide vanes serve todirect the flow axially and to stabilize the draft-flowcaused in the impeller. These outlet blades are

removable type from outside. During operation of the fanitself these blades can be replaced one by one.Periodically the outlet blades can be removed one at atime to find out the extent of wear on the blade. Ifexcessive wear is noticed the blade can be replaced bya new blade.


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The fan, normally of the same type as ID Fan,consists of the following components:

*Silencer

* Inlet bend

* Fan housing

* Impeller with blades and setting mechanism

* Guide wheel casing with guide vanes and diffuser.

The centrifugal and setting forces of the bladesare taken up by the blade bearings. The bladeshafts are placed in combined radial and axialantifriction bearings which are sealed off to theoutside. The angle of-incidence of the blades maybe adjusted during operation. The characteristicpressure volume curves of the fan may be changedin a large range without essentially modifying theefficiency. The fan can then be easily adapted to

changing operating conditions.The rotor is accommodated in cylindrical roller

bearings and an inclined ball bearing at the driveside adsorbs the axial thrust. Lubrication andcooling these bearings is assured by a combined oillevel and circulating lubrication system.


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P.A. ran if flange mounted design, single stagesuction, NDFV type, backward curved bladedradial fan operating on the principle of energytransformation due to centrifugal forces. Some

amount of the velocity energy is converted topressure energy in the spiral casing. The fan isdriven at a constant speed and the flow iscontrolled by varying the angle of the inlet vanecontrol. The Special feature of the fan is that isprovided with inlet guide vane control with apositive and precise link mechanism.


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A pulverizer is a mechanicaldevice for the grinding of

many different types of

materials. For example, they

are used to pulverize coal for

combustion in the steam-

generating furnaces of fossil

fuel power plants.


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1.BALL AND TUBE MILLS

2.RING AND BALL MILLS

3.MPS MILL

4.BOWL MILL


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Advantage of pulverized coal

Efficient utilization of cheap and low grade coal

Flexibility to meet fluctuating load

Elevation of bending loser


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WATER CIRCULATION SYSTEM:Water must flow through the heat absorption

surface of the boiler in order that it beevaporated into steam. In drum type units(natural and controlled circulation) the wateris circulated from the drum through thegenerating circuits and then back to the drumwhere the steam is separated and directed tothe super heater. The water leaves the drumthrough the down comers at a temperatureslightly below the saturation temperature. Theflow through the furnace wall is at saturationtemperature. Heat absorbed in water wall is

latent heat of vaporization creating a mixtureof steam and water. The ratio of the weight ofthe water to the weight of the steam in themixture leaving the heat absorption surface


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1. NATURAL CIRCULATING SYSTEM

2. CONTROLLED CIRCULATING SYSTEM

3. COMBINES CIRCULATING SYSTEM


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Water delivered to steam generator fromfeed heater is at a temperature wellbelow the saturation value correspondingto that pressure. Entering first theeconomizer it is heated to about 30-40Cbelow saturation temperature. Fromeconomizer the water enters the drum

and thus joins the circulation system.Water entering the drum flows throughthe down comer and enters ring heaterat the bottom. In the water walls a part ofthe water is converted to steam and themixture flows back to the drum. In thedrum, the steam is separated, and sent

to super heater for super heating andthen sent to the high pressure turbine.Remaining water mixes with theincoming water from the economizer andthe cycle is repeated.


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Beyond 80 kg/cm of pressure,circulation is to be assisted with

mechanical pumps to overcome the

frictional losses. To regulate the flowthrough various tubes, orifice plates are

used. This system is applicable in the

high sub-critical regions (200 kg/cm).


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Beyond the critical pressure,phase transformation isabsent, and hence oncethrough system is adopted.However, it has been found

that even at super criticalpressure, it is advantageous torecirculate the water throughthe furnace tubes andsimplifies the start up

procedure. A typical operatingpressure for such a system is260 kg/cm.


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The ash produced inthe boiler istransported to ashdump area by meansof sluicing typehydraulic ash handlingsystem, whichconsists of Bottomash system, Ash water

system and Ash slurrysystem.


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In the bottom ash system the ash discharged fromthe furnace bottom is collected in two watercompounded scraper through installed belowbottom ash hoppers. The ash is continuouslytransported by means of the scraper chain

conveyor onto the respective clinker grinders whichreduce the lump sizes to the required fineness. Thecrushed ash from the bottom ash hopper fromwhere the ash slurry is further transported tooperation, the bottom ash can be dischargeddirectly into the sluice channel through thebifurcating chute bypass the grinder. The position ofthe flap gate in the bifurcating chute bypasses thegrinder.


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High pressure water required for bottom ash hopperquenching nozzles, bottom ash hopper spraying,clinker grinder sealing scraper bars, cleaning nozzles,bottom ash hopper seal through flushing, economizerhopper flushing nozzles and sluicing trench jetting

nozzles is tapped from the high pressure water ringmainly provided in the plant area. Low pressure water required for bottom ash hopper

seal through make up, scraper conveyor make up,flushing apparatus jetting nozzles for all fly ash

hoppers excepting economizer hoppers, is trappedfrom low pressure water rings mainly provided in theplant area.


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Bottom ash and fly ashslurry of the system issluiced upto ash pumpalong the channel with theacid of high pressure waterjets located at suitable

intervals along the channel.Slurry pump suction lineconsisting of reducingelbow with drain valve,reducer and butterfly valve

and portion of slurry pumpdelivery line consisting ofbutterfly valve, pipe & fittinghas also been provided.

introduction to ntpc (3) (1)

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