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Vocational Training Report for Combined
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
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
- 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
Vocational Training Report for Combined
From OtherBoilers
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:
Vocational Training Report for Combined
From OtherBoilers
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
Vocational Training Report for Combined
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
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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
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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
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• 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
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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.
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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.
Vocational Training Report for Combined
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.
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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.
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
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.
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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.
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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.
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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:
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
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.
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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
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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
Vocational Training Report for Combined
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.
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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
Vocational Training Report for Combined
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
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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
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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.
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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.
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• 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
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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
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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
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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:
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
Vocational Training Report for Combined
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
Vocational Training Report for Combined
• 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
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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
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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
Vocational Training Report for Combined
WATER TREATMENT PLANT
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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
Vocational Training Report for Combined
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.
Vocational Training Report for Combined
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
Vocational Training Report for Combined
Vocational Training Report for Combined
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.