Viral Traning Report

Vocat ional Training Report for Combined Cycle Power Plant

A STUDY REPORT ON COMBINED CYCLE POWER PLANT AT HAZIRA, SURAT

Submitted by: VIRAL J. PATEL Department Of Mechanical Engineering. Govt. engineering college, valsad, Gujarat.

ACKNOWLEDGEMENT


We find it most difficult part of the entire project to record

our gratefulness to various persons to extended us more than the

necessary quantum of co-operation & help in this project. The words that

follow are merely the formal expression of are deep sense of

indebtedness that is better treasured in thoughts that said in words.

It is pleasure giving verbal expressions to our

feeling of deepest gratitude towards Mr.Anil Matoo (Head HR dept.) ,

Mr.Nishith Dayal, SVP (Maintenance) & Mr. Sandip Sinha,VP

(Purchase) and our project guide also who guided and encouraged us

during the entire training period .

We would also like to express our gratitude to Mr.

Ramesh Reddi, Mr. Moreshwar Wanjari, Mr. Shailendra sah,, Mr.

S.Boothalingam,

Mr. Sandip Goel, Mr. Nilesh Varasada, Mr. Amlan De Sarkar,Mr. D.

Patel of mechanical department also Mr. Gulshan Rana,HR Department

for their unreserved co-operation, constant guidance and constructive

criticism.

We are very thankful to Essar Group for giving us

this golden opportunity to complete our training from a renowned industry.

CONTENT


1. About Essar

2. Essar Combined Cycle power plant

3. Simple and Combined Cycle

4. Gas Turbine and auxiliaries

5. Heat Recovery Steam Generation

6. Steam turbine and auxiliaries

7. Water Treatment Plant Soften Plant DM Plant

ESSAR POWER

Powering Ahead…


COMPANY OVERVIEW:

The Essar group is one of India’s largest corporate

houses. Its interests span the manufacturing and service sectors in both

the old and new economies; in steel, telecom, shipping, oil, power and

construction.

Its massive investments over the past decade have created compelling

tangible and intangible assets that have now begun to release value.

ESSAR POWER:

substantially, giving us one of the lowest costs of production in India.

The government has notified Essar Power as an infrastructure company,

giving us the advantage of lower interest charges.

Essar power is a significant force on India’s private

power generating landscape. It set up India’s first new generation

independent power plant at Hazira, Gujarat, after the government open

the power generation to private participation in the early 1990’s. It has

consistently set new standards of excellence in the Indian power sector

and meets the highest operating benchmarks. It supplies around 7% of

the Gujarat state’s power needs.

. Being India's first multi-fuel plant, it can operate simultaneously

on naphtha and gas, which will be a major advantage once LNG


becomes freely available. By switching over to LNG, our variable costs

have fallen

Essar Power Limited has an immaculate track record of

safety. The Company has been consistently winning safety awards from

various institutions. This award has been

conferred on Essar Power Limited for maintaining excellent record in

safety and successfully

maintaining the incident rate far lower than that of national standards of

U.K. and also striving for the continuous improvement in Health and

Safety standards. Earlier it had received this award in the year 1998 and

1999.

Key value drivers:

- 515MW plant, which is India’s first independent power plant and first

multi fuel plant.

- World-class plant design and construction, equipment from General

Electric, Siemens and Honeywell.

- Highly automated, with India’s lowest manpower to megawatt ratio.

- One of the few companies to receive the ‘Sword of Honour’ from the

British safety council.


- One of India’s best technical teams, capable of setting up varied

power plants and of acting as operation and maintenance contractors.

- Planning projects totaling over 3000MW of new capacity.

SIMPLE CYCLE The gas turbine operating itself is called as simple cycle. The simple cycle is a constant flow cycle with a constant addition of heat energy .It is commonly referred to as the Brayton cycle, after George Brayton .This cycle is plotted on temperature entropy co-ordinates .The constant pressure line diverge with increasing temperature and entropy. This divergent of constant pressure line makes the simple cycle gas turbine possible.

The term Brayton cycle has more recently been given to

the gas turbine engine .This also has three components:

A gas compressor

A burner(combustion chamber)

An expansion turbine

Air is compressed from state 1(atmospheric pressure) to

state2 in an axial flow compressor, while heat is added between states 2

and 3 in a combustor .Work is then derived from expansion of hot

combustion gases from states 3 and 4.Since the expansion from states 3


to 4 yield more work than that required to compress the air from state 1to

2, useful work is produced to drive a load such as generator. The

efficiency of simple cycle is 32%.

COMBINED CYCLE:


The electricity generated in combined cycle by using

both gas turbine generator and steam turbine generator. Gas turbine

works on Brayton Cycle and Heat Recovery Steam Generator (HRSG)

works on Rankine cycle.

A simple Rankine cycle is consist of 4 components the

boiler (steam generators ),a turbine, a condenser and a boiler feed pump

.The simple cycle is shown on T-S diagram .Note that this boiler has a

super heater thus the steam temperature at the entrance of the turbine is

above the saturation temperature.

The first process in Rankine cycle 3-4 is the increase in

pressure of the condensate from the condenser using boiler feed pump.

The second Rankine cycle process represented by line 4-1 is addition of

heat to water entering the boiler, the conversion of water from liquid to

steam and superheating of steam .This process is assumed to occur at

constant pressure. The steam is then expanded and cool as it passes

through the the turbine as represented by line 1-2.The last process in

Rankine cycle is condensation of steam that exhausts from the turbine,

represented by line 2-3.

The heat required to make the Rankine cycle work is

determined by the area under the curve 4’-1 and the heat lost from cycle


Air

GasGasTurbineTurbineCompressorCompressor

Fuel

CombustionSystem

Exhaust

Alternator

Boiler

SteamSteamTurbineTurbine

Alternator

Condenser

Cooling Water

Boiler FeedPump(s)

CondensateExtractionPump(s)

DeareatorTo otherBoilers

From OtherBoilers

is under the curve 3’-2.The area between the curve represents the heat

which is converted into useful mechanical work.

The efficiency of this cycle is about 50%.

ESSAR COMBINED CYCLE POWER PLANT

Name of the Company : Essar power ltd


Type of the Plant : Combined cycle power plant

Capacity : 515MW

Configuration of the Plant : 3 Gas turbine generator of 110MW=330MW 1 Steam Turbine Generator of 185MW

Types of Fuels used : NGL/Naphtha/Natural Gas /HSD Location of the Plant : Hazira, 27 Km from Surat, 7Km from Surat airport

Date of Commissioning : GT#1 : 14.08.1985 GT#2 : 15.08.1985 GT#3 : 13.11.1997 STG : 26.04.1997


Water Source : Wariv pump house at Tapi river (15Km from surat)

GAS TURBINE


MS-9000 gas turbine includes the compressor, combustion chamber,

turbine, the turbine casing exhaust frame, exhaust diffusers etc.

Model : PG9171E

Shaft : 1

Speed : 3000rpm

Maximum firing

Temperature : 1123.8deg C

Exhaust temperature : 550deg C

Flow : 412.9Kg/s

Technology features:

High reliability

High efficiency - Simple cycle 32% and Combined cycle 50%

Multi-fuel capability

Modular design

Low-installed cost

High application flexibility

On-site maintenance capability

Built to operate in remote & hostile environments

Emergency start features

The major constructional features are:


17 stage axial compressor

Variable inlet guide vanes for optimum efficiency

Pressure lubricated 3-bearing system

Combustion system consisting of 14 nos. reverse flow chambers

3-stage turbine , air cooled first and second stage nozzles an

buckets

Factory packaged and tested accessory base for easy installation

Starting through motor

ACCESSORY COMPARTMENT:

Most of the mechanical and electrical auxiliary

equipment necessary for starting and operating the gas turbine is

contained within the accessory compartment.

There are many systems involved in operation of

turbine. Several of these systems have accessory devices, mechanisms,

located in the accessory section. These may include the starting, fuel,

lubrication, hydraulic, cooling water and atomizing air system. Several

major components of the accessories compartment include the starting

means, the torque converter and the accessory drive gear.

ACCESSORY EQUIPMENT


BASE MOUNTED AUXILIARIES – All turbine auxiliaries are base –

mounted to save installation costs and facilitate factory reliability tests of

the complete system

AUXILIARIES OIL PUMPS– A variety of oil pumps and drives and

available to meet individual requirements.

STARTING DEVICE– Before the gas turbine can be fired and brought

to operating speed it must be first be rotated or cranked by the

accessory equipment. This is accomplished by an AC induction motor.

GAUGE PANELS – Instrument grouped in centralized location for operator convenience.

TORQUE CONVERTER-The starting motor drives the torque

converter through a flexible coupling. It provides the cranking torque and

speed required by the turbine or starter. It is coupled to the accessories

gear. This same equipment continuous to rotate the turbine rotor at slow

speed for cool down purpose. Provides torque multiplication for starting

function.

ACC.GEAR BOX –The accessory drive gear is the gearing assembly

coupled directly through a flexible coupling to the turbine rotor. Its main

function is to drive each gas turbine accessory at its proper speed and to


connect the turbine to its starting device. Provides auxiliary drives for

main lube oil pump, main atomizing air compressor, main hydraulic

supply pump, the liquid fuel pump and the water pump.

Driven Accessory:

Torque Converter : 3000rpm

Atomizing Air Compressor : 6600rpm

Hydraulic Supply Pump : 1425rpm

Lube Oil Pump : 1425rpm

OIL COOLERS AND FILTERS – All lubricant pumped from lube oil

reservoir to the bearing header flows through Dual lube fluid heat

exchanger to remove excess heat.

Two (Dual) filters are used with a transfer valve

installed between the filters to direct oil flow through either filter and into

the lube oil header. Only one filter will be in service at a time.

FUEL FLOW DIVIDER – The flow divider equally distributes input

fuel flow to the 14 combustion nozzles. It consists of 14 gear pump

element in a circular arrangement having a common inlet with a single

timing gear. As the fuel enters the flow divider each pair of gear

elements distributes one-fourteenth of the fuel flow into each of the fuel

lines going to the fuel nozzle.


COMPRESSOR

The axial flow compressor consists of

compressor rotor and the enclosing casing. The compressor casing

includes the inlet guide vanes, the 17 stages of rotor and stator blading

and the exit guide vanes.

In the compressor, air is compressed in stages

by a series of alternate rotating (rotor) and stationary (stator) airfoil

shaped blades. The rotor blades supply the force needed to compress

the air and the stator blades guides the air. Compressed air exit through


compressor exit casing. Air is extracted from the diff. stages of

compressor is used for sealing and pulsation control.

o Manufacturer : General Electric Company

o Type : Multi-Stage, Axial Flow

o Compressor : 11:1o Operating Speed : 3000rpm

o Inlet Guide Vane : Variable-Modulating Type

The main components of compressor are explained below:

ROTOR: The compressor rotor is an assembly of 17 individual wheels,

two stub shafts and compressor rotor blades. Each wheel and the wheel

portion of each stub shaft have slots broached around its periphery, the

rotor blades are inserted into theses slots.

STATOR: The stator casing composed of four sections

Inlet casing Forward compressor casing After compressor casing Compressor discharge casing

INLET CASING:


The inlet casing is located at the forward end of the gas

turbine. Its prime function is to uniformly direct air into compressor .It also

supports the no. 1 bearing housing.

FORWARD CASING:

The forward compressor casing contains the first

4compressor stator stages. It also transfers the structural loads from the

adjoining casing to the forward support.

AFTER CASING:

The after compressor casing contains the fifth through

tenth compressor stages. Extraction ports in the casing permit removal

of fifth and eleventh stage compressor

air. This air is used for cooling and sealing function and also used for

pulsation control.

DISCHARGE CASING:

The compressor discharge casing is the final portion of

the compressor section. The function of the compressor discharge

casing is to contain the final seven compressor stages to form both the


inner and outer valves of the compressor diffuser, and to join the

compressor and turbine stators.

COMBUSTION SYSTEM

The combustion system is of the reverse flow type with

14th combustion chamber arranged around the periphery of the


compressor discharge casing. This system also includes fuel nozzles,

spark plug ignition system, flame detectors and crossfire tubes.

High pressure air from compressor discharge is

directed into the combustion chamber liner, around the transient pieces.

This air enters the combustion zone for proper fuel combustion through

metering holes and to cool the combustion liner through slots. Fuel

supply is through nozzle.

Combustion chambers are numbered counter

clockwise when viewed looking downstream and starting from the top of

the machine.

COMBUSTION WRAPPER:

The combustion wrapper is a fabricated casing that

encloses the combustion area and provides a support surface for the

combustion chamber assembly. The plenum is formed in which the

compressor discharge air flow is directed to the combustion Chamber.

COMBUSTION CHAMBER:

Discharge air from the compressor flows upstream

along the outside of the combustion liner towards the liner cap. This air

enters the combustion chamber through the fuel nozzle, swirl tip,

metering holes in both cap and liner and combustion holes in the forward

half of the liner. Additional air is mixed with the combustion in a dilution


zone through metering house. Along the length of the combustion liner

and liner cap are openings to provide a film of air for cooling the walls of

liner and cap.

NOZZLES:

Each combustion chamber consists of a fuel nozzle.

Gaseous fuel is


admitted directly into each chamber through metering holes located in

the outer valve of the gas swirl tip. The liquid fuel is atomized with air

and then spread in the combustion zone. The action of the swirl tips

imparts a swirl to the combustion air for proper combustion.

CROSSFIRE TUBES:

All combustion chambers are interconnected with the

help of crossfire tubes. These tubes propagate flame from the fired

chambers to the unfired chambers.

SPARK PLUG:

Two high voltage retractable electrodes spark plug are

installed in adjacent combustion chamber for initiating the combustion.

FLAME DETECTORS:

During the starting sequence it is essential that an

indication of the presence or absence of flame be transmitted to the

control system. For this reason, flame monitoring system is used

consisting of two sensors which are installed on two adjacent

combustion chambers.


TURBINE SECTION

In the three stage turbine section the energy in the form of high

temperature pressurized gas, produced by the compressor and

combustion sections, is converted into mechanical energy.

TURBINE ROTOR:

This assembly is consists of two wheel shafts; the first,

second and third stage turbine wheels with buckets; and two turbine

spacer. The journal for the no.2 bearing is a part of the forward wheel

shaft similarly after wheel shaft includes the no.3 bearing journal. The

turbine rotor assembly is arranged so that the buckets can be replaced

without unstacking the wheels, spacers and wheel shaft assemblies.

BUCKETS:

The turbine buckets increases in size from the first to the

third stage. Because of the pressure reduction from energy conversion in

each stages, and increased annulus area is required to accommodate

the gas flow; thus necessitating increasing the size of the buckets.


STATOR:

The MS-9000 gas turbine stator structure internally

supports the turbine nozzles, shrouds, no.3 bearing and turbine exhaust

diffuser.

NOZZLE:

There are three stages of stationary nozzles which

direct the high velocity flow of the expanded hot combustion gas against

the turbine bucket causing the turbine rotor to rotate. Because of the

high pressure drop across these nozzles, there are seals at both the

inside and the outside diameter to prevent loss of system energy by

leakage.

There are mainly three stages of nozzles; first stage nozzles,

second stage nozzles and third stage nozzles. Since theses nozzles

operate in the hot combustion gas flow they are subjected to thermal

stress hence needed to be cooled.

SHROUDS:

The turbine bucket tips run against annular curved

segments called turbine shrouds. It provides a cylindrical surface for

minimizing bucket tip clearance leakage. It acts as a high thermal

resistance between the hot gases and the comparatively cool shell.

EXHAUST FRAME ASSEMBLY:


Exhaust frame assembly consist of the exhaust frame and

exhaust diffuser. The exhaust frame is bolted to the after flange of the

turbine shell. The exhaust diffuser, located at the extreme after end of the

gas turbine, bolts to, and is supported by, the exhaust frame.

GAS TURBINE AUXILIARY SYSTEMS

FILTERS:

Filters are the primary component of gas turbine. The purpose

of filter is to filter out the dust particle at the size of 2 micron. These

particles if allowed in may cause severe

erosion of compressor and turbine blades. There are three banks of

filters and there are in all 1280 filters. The types of filter used are cartridge

cylindrical filter. SEA fine dust holding capacity is 5525gm.

PULSATION:

These filters are self cleaning filters. These filters are self

cleaned by reverse pulse of high pressure air through filters. This reverse

cleaning process is called as pulsation. The pulse frequency is one pulse

per minute. At a time 4 filters get the pulsation. The air used for pulsation

is bled off from the 11th stage of compressor.

MEEFOG SYSTEM:


The efficient temperature is 15deg.C. But specially in

summer it goes beyond 15deg C and ultimately the efficiency drops. To

low down the temperature of atmospheric air water at pressure 7Kg/cm2

is sprinkled on the filtered air. This system is called as the MEEFOG

system.

INLET DUCT SCREEN:

Inlet screens are provided immediately upstream of the

initial filters to prevent the entry of leaves, twigs papers and other similar

objects. These screens must be kept free from any excess accumulation

of such debris to ensure free air flow.


TURBINE STARTING SYSTEM:

The starting motor is used for rotating or cranking turbine

before it can be fired and started. Typically, the Gas turbine becomes

self sustaining at 60 % speed after which the starting motor is

withdrawn. The starting system consists of an induction motor and

torque converter coupled to accessory gear. A motor driven torque

adjustor drive forms an integral part of the torque converter system

which provides means for adjusting torque output within specified

ranges.

TURBINE /GEN. LUBRICATING OIL SYSTEM:

The lubricating oil is used for main turbine bearings,

generator bearings, accessory gears and the Lube oil circuit also feeds

the Hydraulic oil & Trip oil circuits. It is also used as hydraulic fluid in

starting means torque converter.

System components:

1. Main lube oil pump (Shaft driven from acc. gear)

2. Auxiliary lube oil pump (AC motor driven submerged centrifugal

pump)

3. Emergency lube oil pump (DC motor driven sub merged

centrifugal pump)

4. Lube oil reservoir in Accessory Base approx. 10 KL capacity.


The Aux. lube oil pump provides oil during gas turbine startup

and when main pump cannot supply adequate pressure for safe

operation.. The Aux. Oil pump cuts off at the Gas turbine speed of

95%. During full speed operation the shaft driven main oil pump is

capable of delivering oil for all the above functions . Emergency

lube oil pump supplies lube oil during emergency conditions e.g. Loss of

AC power & avoids damage to the bearings.

TURBINE TRIP OIL & HYDRAULIC SYSTEM:

The gas turbine protection system is designed to provide

for a safe shutdown of gas turbine . The protections are strictly for

abnormal and emergency operating condition requiring immediate

shutdown of the Turbine. The Hydraulic oil is the high pressure oil

required to operate the fuel valves & the IGV’s as per the command

from the Speedtronic mark V.

The Trip oil is the primary interface between the turbine

control and protection system circuits (SPEEDTRONIC control system)

and the Fuel valves on the turbine which admit or shut off fuel. In the

event of a trip initiation , the trip oil drains out causing the

Hydraulic oil circuit to be depressurized . This results in the fuel

valves to close.

ATOMISING AIR SYSTEM:


Liquid fuels require to be broken into particles by high-

pressure atomizing air, which increases surface area, and hence

complete and proper combustion is achieved. Air for this purpose is

taken from last stage of the compressor, and the pressure is

increased before delivery to the nozzle.

System components:

1. Main atomizing air compressor.

2. Booster air compressor.

3. Atomizing air heat exchanger.

During turbine start up, atomizing air is supplied by motor

driven booster compressor, because accessory gear driven main

compressor does not deliver sufficient pressure at low turbine speed.

Booster compressor shutdown at 95% turbine speed during startups.

For maintaining a uniform inlet temperature to the atomizing air

compressor, air taken from the atomizing air extraction is passed

through air-to-water heat exchanger.

COOLING AND SEALING AIR SYSTEM:

The air drawn from the compressor fifth stage is

used for feeding air to the cooing and sealing air system . This

system provides necessary air flow to the parts of the rotor and stator for


1. Cooling of Internal turbine parts subjected to high temperature like

shrouds in the stator.

2. Sealing of Turbine exhaust side & Compressor inlet side bearings.

TURBINE VENTILATING SYSTEM:

Ventilating system is provided in turbine, accessory and

load compartment for ventilating hot air & for removing the fuel oil

fumes from the turbine / accessory compartment which can be a

safety hazard. The vent fans, driven by an AC motor pulls air into

accessory compartment and after circulating, exhaust the heated air out

through vertical stack. In turbine compartment-cooling air is brought in

through six ventilating louvers and heated air is exhausted through vent

fans located on turbine compartment roof. Cooling air for load

compartment is brought in through two ventilation openings and heated

air is exhausted through vent fan.

COMPRESSOR WATER WASH SYSTEM:

Gas turbines can experience a loss of performance

during operation as a result of deposits of atmospheric components

such as dirt, insects, dust and hydrocarbon film on compressor parts

which occur with the ingestion of air. Most of these can be removed by

inlet air filtration however, the dry components that pass through the

filters as well as wet contaminants ,have to be removed periodically


by washing with a water and detergent solution followed by a water

rinse. Water wash may be performed both on - line as well as off - line.

GAS FUEL SYSTEM:

Gas fuel system is designed to deliver gas fuel to

turbine combustion chamber at the proper pressure and flow rates to

meet all of the starting, accelerating and loading of gas turbine. Gas

comes through the scrubbers where it loses the condensates and

passes through the filters where the dust is removed.

The filtered gas is delivered to the gas turbine

where a stop ratio valve maintains the pressure of the gas at

desired value . The gas quantity fed into the gas turbine is

controlled by a control valve which is controlled by Speedtronic Mk

V . Gas is supplied to each combustion chamber from a ring which

equally divides the gas in to 14 parts and is supplied to the can through

individual lines.

LIQUID FUEL SYSTEM:

OFF-BASE fuel system consists of fuel tanks,

forwarding pumps and fuel selection skid. The pumps provide the fuel at

required pressure to the fuel selection skid where it gets filtered

through Off-base filters and after metering it goes to On-base filters

in accessory compartment.


ON-base liquid fuel system consists of hydraulically

operated stop valve, filters, gear driven screw pump, and flow divider.

Fuel after filtration , is supplied equally to 14 nozzles of combustion

chambers by flow divider at required pressure and flow rate,

provided by shaft driven screw pump . In the event of turbine tripping

hydraulic oil gets drained and stop valve closes. Since NGL and

NAPTHA have very low lubricating property lube oil is added to through

lubricity injection module where Hitec is added to the fuel with the help

of pumps at the required rate. Lubricator pump provides forced

lubrication to the bearings of the main fuel oil pump .

LIQUID FUEL SYSTEM (HSD):

HSD is used as the start up liquid fuel. After the Gas

Turbine starts generating power, the fuel is changed over to Naphtha.

To remove entrapped naphtha from combustion system during gas

turbine startup and shut down & also in the event of a trip, HSD is used

as the draining medium and procedure is called as Naphtha draining.

After draining has been accomplished fuel is

pumped back to the storage tank by an AC driven pump. This system is

known as waste fuel drainage system.

GAS TURBINE AUXILIARY COOLING WATER SYSTEM:

The cooling water system is a closed system

designed for cooling the Turbine and generator lube oil, the atomizing air


and Turbine supports. It consists of both on -base and Off-base

mounted components. The On-base components include

1. Lube fluid heat exchangers in Accessory base.

2. Turbine support legs.

3. Four Nos. Heat exchangers of generator hydrogen cooling system.

4. Flow regulation valves orifices.

The off base system comprises cooling towers & ACW circulation

pumps.

TURBINE SUPPORTS:

The gas turbine is mounted to its base by vertical

supports at three locations; the forward supports at the lower half vertical

flange of the forward compressor casing and the after two on either side

of the turbine exhaust frame. The outer surface of each after support leg

is a water jacket. Cooling water is circulating through the jackets is to

minimize thermal expansion of the support legs and assist in maintaining

alignment between the turbine and the generator.

The support legs maintain the axial and vertical

position of the turbine, while a gib key coupled with the turbine support

legs maintains its lateral position.

BEARINGS:


The MS-9000 GT unit contains three main journal bearing

used to support the gas turbine rotor.

No 1bearing: It is located in the center of the inlet casing assembly

and contains three bearings active thrust bearing, inactive thrust

bearing and journal bearing.

No. 2 bearing: It is located in the center of the inner cylinder of the

compressor discharge casing.

No. 3 bearing: It is located at the after end of the turbine shaft in the

center of the exhaust frame assembly.

HEAT RECOVERY STEAM GENERATION

INTRODUCTION:

In the simple cycle the temperature of the exhausted

gas leaving a gas turbine can be high as 1100degF.High temperature

gas represents a source of heat energy .Some of which are recovered if

there is any alternative to do so .By recovering the waste heat the output

and efficiency of power plant can be increased .

The function of HRSG is to recovery the waste

heat available in exhaust gases and transfers it to the water and steam.

The heat recovered is used to generate steam at high pressure and

temperature .Additional power in a steam turbine driven generator is


generated from the steam .HRSG provides the critical link between the

gas turbine and Rankine cycle in the combined cycle plant.

OPERATION:

The condensate from gland steam condenser passes

through condenser preheated (CPH) and then to deaerator. In deaerator

the excess gases are removed .In feed water tank (FWT) the steam is

taken from LP mean steam header which is called as pegging .To

increase the temperature to the saturation temperature(118degC) at a

pressure of 1.2bar which increases the rate of oxygen release. Then this

DM water in pump through three individual LP and HP feed water

system.

HIGH PRESSURE WATER / STEAM FLOW PATH

After passing through the feed water regulating

valve the water flows through high pressure low

temperature(HPLT)economizer ,then the water flows through the high

pressure intermediate temperature( HPIT ) economizer and passes

through high pressure high temperature(HPHT) economizer.

After leaving HPHT economizer, the water enters HP

steam drum through feed water inlet nozzle and continuous to the HP

evaporator .Natural circulation is maintained

in the HP evaporator by means of two down comers which feed the

water to the lower evaporator headers. The steam is generated and


flows upward in the evaporator tubes .The saturated water steam

mixture is conducted from the upper HP evaporator to the HP drum

through 24 risers .The saturated steam separated from the saturated

water steam mixture by the drum internals and then exit through two

saturated steam outlets.

The saturated steam leaving the drum passes through

the HPLT S/H .The

steam then flows through HPIP S/H, then through the desuperheater

where small portion of water is tapped from the FWT and used as spray

water for HP S/H desuperheater to minimize the temperature and then

pass through HPHT S/H .The steam leaving the HPHT S/H is combined

into the HP outlet steam header.

As there are three gas turbines connected to three

HRSG, three HPHT S/H outlets are connected to main HP steam header

LOW PRESSURE WATER /STEAM FLOW PATH

The water from FWT is pumped through three LP FWP

and passes through the feed regulating value. The LP feed water enters

the HRSG at the LP economizer. The water flow through LP economizer

enter the LP steam drum through the feed water inlet nozzle and

continuous on the LP evaporator. Natural circulation is maintained by

means of two down comers. Steam is generated and flows upward in the

evaporator tubes. The saturated water steam mixture is conducted to the

LP steam drum through 14 risers. The saturated steam separated and


exit through two saturated steam output. The saturated steam outlet

direct the LP saturated steam to the single stage LP S/H and combines

with the LP steam outlet header.

As there are three HRSG, three LP S/H outlets are

connected to the LP common header.

GAS SIDE FLOW PATH

The exhaust passes through the diverter damper and

then will pass by the pressure section in the following order.

HPHT S/H --- HPIT S/H --- HPLT S/H --- HP

EVAPORATOR---HPHT ECONOMISER --- HPIT ECONOMISER --- LP

S/H --- LP EVAPORATOR --- HPLT ECONOMISER --- LP

ECONOMISER --- CONDENSATE HEATER .

The exhaust gas will leave condensate heater and exit the

HRSG through the main exhaust stack.


HP AND LP BYPASS SYSTEM

The HP and LP steam bypass is a primary safety device for

HRSG against over pressurization. In the event of steam turbine trip , the

entire steam production of HRSG is diverted through the condenser by

means of HP and LP bypass valve. The steam dumped to the condenser

is mixed with the desuper rating water spray to avoid high temperature in

condenser.

The bypass steam also allows steam generator to gradually

buildup the pressure and temperature of HP and LP during start up.

This system enables hot restarting of unit and warming up

steam line.


DRUM

The main function of drum is to reduce the moisture content of

saturated steam leaving the drum by mechanical means.

The feed water is fed to the drum through the feed water

nozzle. The water then enters the down comers and the steam water

mixture enters through risers. The steam water mixture is collected in the

internal compartment the saturated steam travels through turbo

separators which is also called as centrifugal separators as it works on

the principle of centrifugal action. When the steam water mixture enters

the turbo separators due to the spinning action, the centrifugal force act

on the steam water mixture. The saturated steam at high velocities there

by loses most of its entrained water and enters the corrugated plate

driers. The drier directs the steam and forces any remaining entrained

water against the corrugated plates since the velocity is relatively low,

this water can not be picked up again and runs down the corrugated

plates and returns to the lower part of drum.

HP operating pressure : 84.5Kg/cm2

HP operating temperature : 298.3degC

LP operating pressure : 6Kg/cm2

LP operating temperature : 164.4degC

COTINUOUS BLOW DOWN LINE (CBD):


CBD line controls the concentration of the soluble solids in

the boiler water because it constantly removes a small portion of solids

and their by maintains relatively constant concentration in the boiler

water.

INTERMITTENT BLOW OFF LINE (IBD):

IBD should always be used to free a boiler of sediment ,

when the boiler is being shut down .The should be blow down at least

once every 24 hour or more often during commissioning if the water is of

inferior quality or the amount of make is large .

SAFETY VALVE:

It serves to protect pressure vessels from overpressure on

S/H outlet .They serve the additional purpose of protecting the S/H from

over heating in the event of sudden interruption in the steam

consumption.

WATER LEVEL INDICATOR:

The main function of the water level indicator is to indicate

the water level inside the drum, which should be at normal set value.

CHEMICAL DOSING:


Trisodium phosphate is used for maintaining the pH of

the water inside the drum .The pH is maintained at 9.5.


STEAM TURBINE AND GENERATOR

Steam turbine coverts heat energy of steam to mechanical

energy .Steam turbine consists of two section High pressure and Low

pressure. HP steam is supplied from common main steam header from all

three HRSG the LP steam is supplied from the common LP main

steam header through one stop and control valve. LP steam enters after

last stage of HP turbine where it mixes with HP steam which has already

done its work. Then finally it enters the LP turbine through crossover pipe.

Type : Impulse Turbine

Rating : 186.1MW

Speed : 3000rpm

HP steam flow : 526.56T/hr

LP steam f low : 606.3T/hr

HP Throttle Temperature : 520deg C

HP Throttle Pressure : 76Kg/cm2

LP Throttle Temperature : 205degC


LP Throttle Pressure : 5.1Kg/cm2

HP turbine stages : 11

LP turbine stages : 16

Generator uses hydrogen as cooling medium .There

are 4 Nos. of water cooled heat exchanger for cooling hydrogen. The hot

water is then cooled in Induced draught cooling tower (IDCT) for further

recirculation.

Generator parameter

Type : Hydrogen cooled

Voltage : 240540 KVA

Ampere : 9258 A

Output : 15 KV

CONDENSER SYSTEM

The condenser helps in converting the exhaust system into

water thus allow recycling of DM water .The condensate system consist of

condensate system and extraction system.

Condensation of LP exhaust steam from by pass system

and all the drain are connected to the condenser. Condenser is of surface


type and condensation of steam takes place at the surface of the tubes

which are cooled by cooling water flowing inside them. This cooling water

gets heated up due to the heat transfer. This hot water is then sent to the

IDCT for cooling process with the help of 18 induced draught fans.

STEAM TURBINE AUXILIARY SYSTEMS

GENERATOR COOLING SYSTEM:

The generator is cooled by hydrogen due its higher heat

transfer coefficient the hydrogen is then cooled by the cooling water

system. A 30 psi of Hydrogen pressure is maintained within the

generator and the gas is circulated within the generator housing with

the help of fans fixed on the rotor .The gas absorbs heat from the

generator windings . To maintain the purity of hydrogen continuous

scavenging is done. Hydrogen is sealed in the turbine with the help of

the seal oil which is derived from lube oil at little higher pressure than

the H2 pressure. In the event of loss of seal oil pressure or very low

purity of the hydrogen automatic emergency purging of hydrogen takes

place. The Hydrogen, in such cases is purged with the help of CO2

which is supplied from the CO2 skid.

COOLING WATER SYSTEM:

To cool the lube oil, Generator and the Auxiliaries, cooling

water system is provided which consists of 4 x 33% AC motor driven


pumps and 4 X 33 % IDCT fans .Duplex filters are provided to filter

dirt out of the cooling water . The cooling water chemistry is

maintained by means of chemical treatment.

FIRE PROTECTION:

Fire protection is provided for Load & Turbine & compressor

Compartment. In the event of detection of fire, solenoid valve of CO2

tank gets operated.

The CO2 fire protection system extinguishes fire by reducing the

O2 content of the air in the compartment from an atmospheric normal of

21% to less than 15 %, an insufficient concentration to support

combustion. To reduce O2 content, a quantity of Co2 equal to or greater

than 34% of compartment volume is discharged into the compartment in

one minute, and recognizing the reflash potential of combustibles

exposed to high temperature metal it provides an extended discharge to

maintain an extinguishing concentration for a prolonged period to

minimize the likelihood of a reflash condition.



WATER TREATMENT PLANT

FUNTIONS:

To minimize the amount of corrosion products such as oxides of iron,

copper and nickel .These oxides invariably plate out on heat transfer

surface which must be periodically remove.

To minimize the hardness causing impurities such as magnesium,

Calcium, silicon .This impurity causes hard adherent scale formation

which results in tube failure.

To remove organic impurities, suspended solids, floating impurities

from raw water.

WATER TREATMENT PROCEDURE:

Raw water:

Raw water source for ESSAR PLANT is from warior pump

house situated on Tapi river located 15 Km from Hazira.

If there is any discontinuity in raw water inlet from warior,

then there is another substitute where in the raw water intakes from

water sump located at ESSAR Steel plant.

The raw water is stored in the raw water sump. The water

level in the sump is indicated with the help of 10 steps which are counted

from top. If the water level reaches 1.5 the intake of water stops and if

the level reaches the step 6 the water intake is started. By any reason


the water level reaches the 9th step then there is difficulty in suction

hence the plant trips.

CLARIFLOCULATER:

Dosing:

Alum is added as a coagulant, which helps in coagulating the

suspended particle from the raw water.

Amount of alum added =2.5Kg\hr

Chlorine act as anti bacterial chemical .Polyelectrolyte is

added as a catalyst which increases the rate of reaction..

The water is brought up in the mixing chamber, where it

mixes properly for the increase in the rate of reaction.

Then the water from mixing chamber is divided into two

Clarifloculator which consist of two circular concentric tanks. In central

tank there is a moving body which moves at the rate of 30min\rev.

In the clarifloculator, the raw water undergoes

sedimentation, coagulation, flocculation, chlorination.Then it is

accumulated in water storage tank

Type of clariflocculator : vertical centrifugal

Capacity : 1200m3\hr


SOFTEN WATER PLANT:

The water from clarified water storage tank is pump

with the help of clarified water pump to the soften plant .In soften plant

the water is sampled and accordingly the sodium sulphite is added which

is then pass through pressurized sand filter (PSF).PSF is the tank

containing layer of sand and is also pressurized.

The water from PSF is divided into two, 95% is sending

to soften tank which is completely filled with resin and 5% is stored in the

filter water tank.

The 95% water coming out from soften plant is sent to

induced cooling tower (IDCT) fore bay and gas turbine cooling tower

(GTCT).

R-Na +CaCO3 R-Ca +NaCO3

R-Na +MgSO4- R-Mg+NaSO4


WATER TREATMENT PLANT


DEMINERALISING PLANT

The 5% water from PSF which is stored in filter water tank

is allowed to pass through the activated carbon filter (ACF) and then it is

used for two purposes.

-Drinking

-DM water

NEED OF DM PLANT:

The DM water is used in STG, GTG and in condenser for cooling and

make up purpose .this water should be mineral free or else these

mineral

react with metal pipe lines and cause the damage.

The DM water is also used in generator usually to cool the hydrogen

gas used for cooling purpose.

DM PLANT PROCESS

The water from ACF is treated in DM plant as follows:

1. SAC (Strong Acid Cation):

When water is pass through SAC the cations are removed

from the water as follows:

R-H++ CaCO3 R-Ca + HCO3

R-H+ + CaCl R-Ca + HCL


R-H+ + MgSO4 R-Mg + H2SO4

R-H+ + NaCL R-Na + HCL

R-H+ + CaSO4 R-Ca + H2SO4

2. DEGASSER:

In degasser the water is allowed to fall from particular

height and the gas is blown just below that of water fall by a degasser

pump as a result all the gases especially CO2 removed from the water.

HCO3-+ O2 CO2 + H2O

3. SBA(Strong Based Anion):

When the gas is passed through all the

anion are removed as follows-

R-OH-+ HCL R-CL + H2O

R-OH- + H2SO4 R-SO4 + H2O


4. MIXED BED:

When the cations and anions which are not being

removed in SAC and SBA are removed by passing through mixed bed

which contain SAC as well as SBA resin.

REGENERATION:

After some time, the ability of SAC and SBA resin to

exchange cations and anions gets exhausted and so regeneration is a

necessary process.


The regenerate HCl is used in case of SAC and caustic

soda is used in case of SBA .In MB both HCl and caustic soda is used.

The reactions are given below.

SCA:

R-Ca + HCl R-H + CaCl

R-Mg + HCL R-H + MgCl

R-Na + HCl R-H + NaCl

SBA:

R-Cl + NaOH R-OH + NaCl

R-SO4 + NaOH R-OH + NaSO4



I had an extremely memorable experience here with personas like

Mr. Jay Patel (EPoL.), Mr. Gaurav Punj (EPoL.), Mr. Vivek Makode

(BPoL.), Mr. Mithul Patel (BPoL.) and last but surely not the least

Mr. Ramesh Reddy (HOD, mechanical department).

I am also very grateful to the Essar family for lending out such

supporting hands to the young engineers like us.

The working conditions here are such that it will take the best out

of you, no matter what.

I am sincerely in debt to the other heads of various departments for

being so cooperative and understanding and also the back bone of

this organization- the technicians; they were of great support and

took a great interest in us.

I pay all of you sincere thanks.

Viral Traning Report

Documents

essar power limited

power generation

indias private power

essar group

indian power sector

lng vocational training

gujarat states power

combined content1