Korangi CCPP Internship Report

Internship Report
Summer 2014
Karachi Electric - Korangi Combined Cycle Power Plant
Submitted by: Syed Zaire Hasan Rizvi
Date: 24/07/2014

1 | P a g e
Internship Report – Korangi Combined Cycle Power Plant
Awcknoledgements
I would like to acknowledge Mr. Mohammad Shumail & Mr. Ghulam Sarwar for taking out time
and guiding us throughout this period of 4 weeks, making sure everything was explained
thoroughly and also for providing us with the literature. A special thank you to Mr. Naushad Alam
for having us at the Korangi Combine Cycle Power Plant and allowing us supervised access to the
entire plant and also to the staff of every department for giving an overview of the respective
operations.

2 | P a g e
Abstract
The Korangi Combined Cycle Power Plant produces 220MW of power, operating on 4 gas turbines
and one steam turbine. This report contains the basic operation and construction of the plant
which includes the LM6000 Gas turbine, Steam Turbine, Reserve Osmosis Plant, Air Intake House,
Lubrication Systems of the Turbine and Generator, Heat Recovery Steam Generator and the
Natural Gas compressors.

3 | P a g e
Table of Contents
Awcknoledgements .......................................................................................................................................................................... 1
Abstract ............................................................................................................................................................................................ 2
Korangi Combine Cycle Power Plant Introduction............................................................................................................................ 4
Gas Turbine Basics, Construction & Operation................................................................................................................................. 5
Introduction................................................................................................................................................................................. 5
Components of the gas turbine (LM 6000) .................................................................................................................................. 5
Working principle of the Gas Turbine .......................................................................................................................................... 6
Component Breakdown............................................................................................................................................................... 7
NOx Control ............................................................................................................................................................................... 11
SPRINT System ........................................................................................................................................................................... 11
Water Wash system................................................................................................................................................................... 11
Ventilation and Combustion Air System......................................................................................................................................... 12
Introduction............................................................................................................................................................................... 12
Filter house ................................................................................................................................................................................ 13
Turbine Lube Oil System ................................................................................................................................................................. 14
System Overview: ...................................................................................................................................................................... 14
Turbine Supply Lube Oil System Operation Overview: .............................................................................................................. 14
Turbine Scavenge Oil System Operation Overview:................................................................................................................... 14
Components of the Turbine Lube Oil System: ........................................................................................................................... 15
50Hz Generator Lube Oil System.................................................................................................................................................... 16
System Overview ....................................................................................................................................................................... 16
Component Description:............................................................................................................................................................ 16
Heat Recovery Steam Generator (HRSG)........................................................................................................................................ 17
Introduction:.............................................................................................................................................................................. 17
Fundamental parts of HRSG:...................................................................................................................................................... 17
HRSG Modules ........................................................................................................................................................................... 18
Types of HRSG............................................................................................................................................................................ 18
Forced Circulation HRSG Operation:.......................................................................................................................................... 19
Steam Turbine................................................................................................................................................................................. 21
Overview:................................................................................................................................................................................... 21
Operation Overview:.................................................................................................................................................................. 21
Reverse Osmosis (RO) Plant............................................................................................................................................................ 22
Introduction:.............................................................................................................................................................................. 22
Sea Water Reverse Osmosis System:......................................................................................................................................... 23
Permeate Water RO System: ..................................................................................................................................................... 24
Fuel Gas Compressors..................................................................................................................................................................... 25
Table of Figures............................................................................................................................................................................... 27

4 | P a g e
Korangi Combine Cycle Power Plant Introduction
K-Electric is the only vertically-integrated power utility in Pakistan. It produces electricity from
its own generation units with an installed capacity of 2341 MW. It also has power purchase
agreements for 1021 MW from various IPPs (Independent Power Producers), WAPDA, KANUPP
(Karachi Nuclear Power Plant) and through imports.
K-Electric has currently 5 running power plants which light up the largest city of Pakistan. These
plants are:
1. Bin Qasim Power Station 1 (Capacity: 1260 MW)
2. Bin Qasim Power Station 2 (Capacity: 560 MW)
3. Korangi Thermal Power Station (Capacity: 125 MW) – Decommissioned
4. Korangi Combined Cycle Power Plant (Capacity: 220 MW)
5. SITE Gas Turbine Power Station (Capacity: 88 MW)
6. Korangi Gas Turbine Power Station (Capacity: 88 MW)
The Korangi Combined Cycle Power Plant has 4 General Electric LM6000 Aeroderative gas
turbines (which were used on a boeing 747) producing approx. 42MWs of power each.
Currently Gas turbines 1 & 2 are operating on an open cycle whereas Gas Turbines 3 & 4 are
operating on a combined cycle. A steam turbine is provided with superheated steam from the
Heat Recovery Steam Generator installed behind GT 3 & 4. The ST works on the closed cycle
producing up to 25MWs of energy.
The CCPP has its very own water purification plant called the Reverse Osmosis Plant which
takes in sea water and purifies it so it can be safely used in various location at the CCPP.
Figure 2: CCPP Overview
Figure 1: the 4 LM6000 GTs + HRSG Unit

5 | P a g e
Gas Turbine Basics, Construction & Operation
Introduction
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an
upstream rotating compressor couple to a downstream turbine and a combustion chamber in
between.
At the Korangi Combined Cycle power plant we have 4 gas turbines. Two of which operate on an
open cycle (Exhaust is released into the air) and the other two operate on a closed cycle (Exhaust
gasses pass through the HRSG, generating steam to power the steam turbine – Combine Cycle).
Components of the gas turbine (LM 6000)
1. Compressor
a. Low pressure compressor (5 Stages)
b. High pressure compressor (14 Stages)
2. Combustion Chamber
3. Turbine
a. High pressure turbine (2 Stages)
b. Low pressure turbine (5 Stages)
Figure 3: Cross-section of the LM6000 Gas Turbine
LPC (S stage)
HPC (14 Stage)
HPT (2 Stage)
LPC (5 Stages)

6 | P a g e
Working principle of the Gas Turbine
This cycle is recognized as the Brayton Cycle. This cycle occurs in all internal combustion engines.
Figure 4: Open cycle gas tubine
Figure 5: T-S Diagram representation of an ideal Brayton Cycle Figure 6: P-v Diagram Representation of an ideal Brayton Cycle
A brief summary of the Brayton steps are as follows:
1. Compression occurs between the intake and the outlet of the compressor (represented
by line 1-2). Pressure and temperature of the air increases.
2. Combustion occurs in the combustion chamber where fuel is mixed with the compressed
air and ignited. The addition of heat due to combustion causes a sharp increase in volume
(Represented by line 2-3).
3. Expansion occurs as hot gasses accelerate from the combustion chamber. The gasses at
constant pressure and increased volume enter the turbine and expand through it
(Represented by line 3-4).
4. Exhaust occurs at the engine exhaust stack with a large drop in volume at a constant
pressure (Represented by line 4-1).
Compression Combustion Expansion Exhaust

7 | P a g e
Component Breakdown
Convergent and Divergent Ducts:
Compressors in gas turbine engines use convergent and divergent ducts to generate the high
pressures necessary to (a) provide a “wall of pressure, “preventing expanding hot gas from exiting
through the engine inlet, as well as, through the exhaust; and (b) provide the proper ratio of air-
to-fuel for efficient combustion and cooling of the combustion chamber.
The principle of the continuity equation, 𝐴1 𝑉1 = 𝐴2 𝑉2, is used here.
Inlet Guide Vanes:
Inlet Guide Vanes direct, or align, airflow into the first rotating blade section where velocity is
increased by the addition of energy. The following stator vane section is divergent, providing an
increase in static pressure and a decrease in air velocity.
Compressors:
All turbine engines have a compressor to increase the pressure of the incoming air before it
enters the combustor. Compressor performance has a large influence on total engine
performance. Compressors (flows) are of two main types: Axial and Centrifugal.
- Axial Compressor flow: It is given this name because the flow through the compressor
travels parallel to the axis of rotation.
- Centrifugal Compressor flow: The flow through this compressor is turned perpendicular
to the axis of rotation.
The compressor has two stages, Low pressure compressor and high pressure compressor. The
LM6000 LPC is a 5 stage, axial-flow compressor with a 5 stage fixed stator. The compression ratio
of this stage is 1:2.5 (Actually being roughly 1:2.1). The HPC is a 14 stage, axial-flow compressor
with variable stators in stages 0-5. The compression ratio for this stage is 1:12, making the overall
compressor ratio of 1:30.
*Compressor Stalling:
If air moves from its general direction of motion, also called the angle of attack, a stall can occur.
Consequently, low pressure on the upper surface disappears on the stator blade. Turbulence on
the backside of stator blade forms a wall that leads to the stall. In case of a stall, front stages
supply too much air for the rear stages to handle, resulting in choking.
Causes of stall
1. Not completely smooth and even blades
2. Defects on blade surface
3. Too high angle of attack.

8 | P a g e
4. Decrease in engine speed leads to decrease in compression ratio, therefore the volume of air
in rear of the compressor will be greater. This excess volume causes choking action in rear of the
compressor. Consequently, air velocity in front of the compressor is decreased with an increased
tendency to stall.
Combustors:
In the combustor section of the gas turbine, the fuel is combined with high pressure air and
burned. The resulting high temperature exhaust gas is used to turn the turbine and produce
thrust when passed through a nozzle.
There are three main types of combustors:
- Annular Combustor
- Tubular Combustor
- Can-Annular Combustor
On the LM6000 installed here at CCPP we have singular annular combustor. Key feature is the
rolled-ring inner and outer liners; the low smoke emission, swirl-cup dome design and the short
burning length. This short burning length reduces liner cooling air consumption which improves
the exit temperature pattern factor and profile.
Flame Stabilizing and General Flow Patterns:
The temperature of the flame in the center of the combustor is approx. 3200⁰F at its tip when the engine
is operating at full load. Metals used in the combustion chamber are not capable of withstanding
temperatures in this range; therefore the design provides airflow passages between the inner
and outer walls of the camber for cooling and flame shaping. Approximately 82% of the airflow
into the combustion chamber is used for cooling purposes and the remaining 18% is used for fuel
combustion.
Turbine:
The turbine of the gas engines are located downstream of the combustor to extract energy from
the hot flow and turn the compressor. Work is done on the turbine by the hot exhaust flow from
the combustor. Since the turbine extracts energy from the flow, the pressure decreases across
the turbine. The pressure gradient helps keep the boundary layer flow attached to the surface of
the turbine blades.
Since the turbine blades exist in a much more hostile environment as compared to the
compressor blades, they must be made of special materials that can withstand such heat or they
must be actively cooled. In active cooling, the nozzles and the blades are hollow and cooled by
air which is bled off the compressor. The cooling air flows through the blade and out through the
small holes on the surface to keep the surface cool.

9 | P a g e
Like the compressor, the turbine is divided into two stages, high pressure turbine and low
pressure turbine. The HPT is a two-stage design which drives the HPC by extracting energy from
the hot-gas path steam. The LPT is a 5 stage assembly which drives the LPC and the load device
(in this case the 50Hz generator).
Turbine Shafts:
The standard gas turbine shaft arrangements are as follows:
1. Single shaft:
Figure 7: Single Shaft
The traditional Single Shaft assembly consists of the axial flow compressor, turbine and power
turbine (all mechanically linked). This is a favored configuration for electrical generation because
this provides additional speed stability of the electrical current during large load fluctuations.
2. Twin shaft:
Figure 8: Twin Shaft
In the standard two shaft arrangement the compressor and the turbine are only connected and
an unconnected power turbine and output shaft that will rotate independently. This
configuration is preferred for variable speed drive packages such as pumps and compressors.

10 | P a g e
3. Concentric Shaft (used by the LM6000):
Figure 9: Concentric Shaft
This is essentially a two shaft configuration with the gas generator core designed with two spools,
a low pressure shaft and a high pressure shaft. This engine configuration allows the load to be
driven from either the exhaust end or the compressor intake end. Here at Korangi CCPP, the load
(Generators) are attached to the exhaust end on the Low pressure shaft.
4. Concentric Shaft:
Figure 10: Concentric Shaft with Power Turbine
This is essentially a two shaft arrangement with a gas generator originally designed for
propulsion. An independently rotating power turbine is added to the gas path as the
power/torque producer.
*Critical Speed: The critical speed is the theoretical angular velocity that excites the natural
frequency of a rotating object, such as a shaft, propeller, leadscrew, or gear. As the speed of
rotation approaches the object's natural frequency, the object begins to resonate, which
dramatically increases system vibration. The resulting resonance occurs regardless of orientation.
When the rotational speed is equal to the numerical value of the natural vibration, then that
speed is referred to as critical speed.

11 | P a g e
NOx Control
Oxides of nitrogen result from thermal fixation of molecular nitrogen and oxygen in the
combustion air. Its rate of formation is extremely sensitive to local flame temperature and, to a
lesser extent, to local oxygen concentrations. Maximum thermal NOx production occurs at a
slightly lean fuel-to-air ratio due to the excess availability of oxygen for reaction within the hot
flame zone. Control of the local flame fuel-to-air ration is critical in achieving reductions in
thermal NOx.
Reduction of NOx emissions are accomplished by:
1. Injection of water of steam at fuel nozzle in order to reduce combustion temperatures.
2. Specially designed Dry Low Emissions (DLE) combustors and fuel systems.
SPRINT System
The SPRay INTercooling (SPRINT) is s technological advancement developed by GE to enhance
the output pf the gas turbine. SPRINT increases the output by 9% at ISO and by more than 20%
on 90F days. Basically as ambient temperature rises, the effectiveness of the system increases.
The mist injection process starts once the turbine reaches full load operation.
At the gas turbines installed here at the CCPP, only the LPC sprint manifold in installed which
consists of a single row of 23 nozzles locates the inlet of the LPC. This cooling system lowers the
HPS inlet temperature which in turn lowers the HPC compressor discharge temperature and also
leads in the increase of compressor pressure ratio.
Air is extracted from the 8th stage of the HPC which is then atomized to produce mist which is
used in the SPRINT system. To prevent corrosion, the mist droplets are of less than 20 microns.
Water Wash system
The water wash system provides a mechanism for cleaning engine compressor blades to increase
efficiency and improve engine power output versus the fuel burnt. Water wash is either done
online (while the turbine is running) or offline (while the turbine is not running) to remove
contaminants such as:
 Dirt or soil
 Sand
 Coal dust
 Insects
 Salt (corrosion)
 Oil
 Turbine exhaust gas

12 | P a g e
Ventilation and Combustion Air System
Introduction
The ventilation and combustion air systems can be divided into three sub-systems:
1. Gas turbine Enclosure Ventilation air system: This provides the gas turbine enclosure with
sufficient ventilation air to cool the gas turbine exterior and the inside of the enclosure.
The air flows through the filter house from where it flows down the ductwork into the gas
turbine enclosure. From here it is discharged back into the atmosphere via the exhaust
fans. This maintains the gas turbine enclosure under a negative pressure.
2. The generator enclosure ventilation air system: From the filter house the air is drawn into
one of the generator cooling fans and is discharged into the generator enclosure. On the
driven end, the air flows along the rotor shaft and is then discharged into the generator
exhaust and back into the atmosphere. Most of the air flows along the rotor shaft but a
portion of incoming air flows across the exciter and then is discharged into the generator
air-cooling system.
3. Gas turbine combustion air system: The combustion air system provides around
230,000scfm to operate the gas turbine at all required levels. Air enter the filter house,
passes through all the filters (discussed later) and into the inlet volute.
Figure 11: Air Intake House

13 | P a g e
Filter house
Air enters the filter house and flows through various filtrations and cooling equipment. The air
flows down the ducts to the combustion air inlet volute and to the two enclosures for cooling.
 Guard Filter: Used in areas where there is a large concentration of airborne contaminates.
It is a disposable filter utilized to catch a majority of the airborne contaminates which
prolong the life of the more expensive barrier filters.
 Barrier Filters: They are made of a composite type material and filter the incoming
ventilation air to remove any solid contamination.
 Chiller Coils: They cool the combustion air to approx. 48⁰F to 50⁰F to increase the power
output of the turbine. These chiller coils can also be used for anti-icing in the winters (Not
applicable here at CCPP). Cooling the air is a very integral part since cooling it increases
the mass flow of the air and therefore resulting in a healthy combustion and greater
power output.
 Drift Eliminator: It separates moisture from the combustion air. It is made of polyurathene
and is in the shape of an ‘S’ so when the air enters at the bottom it has two sharp curves
before passing out. This change in direction of the air flow causes any moisture to drop
out.
 FOD Screen: This is the last chance filtration with the screen rated at 1200 microns and is
supported by a stainless steel mesh. If any filter before isn’t working properly, the FOD
screen catches those foreign objects instead. Basically it is installed to increase
protection.

14 | P a g e
Turbine Lube Oil System
System Overview:
The LM6000 gas turbine uses synthetic lube oil to conduct many crucial operations. These
operations include:
- Lubricate and cool turbine bearing and gearboxes
- Provide oil to the variable geometry control system
- Lubricate the over-running clutch for the hydraulic starter motor
The gas turbine has a total of 8 bearings (6 roller bearings and 2 ball bearings). The turbine uses
anti-friction bearings which help supporting the load on the shaft, reduce friction created by
thrust and turning and hold the shaft in alignment.
The roller bearings take radial loads whereas the ball bearings take both radial and axial loads.
Each rotating system uses one ball bearing.
Figure 12: Bearing positions on GT
The turbine lube oil system has two distinct sub-systems 1) A pressurized supply system and 2) A
separate scavenge system. Where both of these filters have their own filtration.
Turbine Supply Lube Oil System Operation Overview:
The pump for the turbine lube oil is mounted on the right side of the accessory gearbox. The
supply comes from a 150 Gallon stainless steel turbine lube oil reservoir mounted on the auxiliary
skid. From here the supply element passes through the duplex supply oil filters (which are rated
at 6 microns). The two way selector valves allow either filter to be online where the other can
remain offline as a backup or due to maintenance. The lube oil is then further piped to the turbine
supply header to lubricate the bearings, gearbox and hydraulic starter clutch.
Turbine Scavenge Oil System Operation Overview:
The oil that is supplied to the gearbox and bearing sumps is recovered by one of the six scavenge
elements of the oil pump. The scavenged oil passes over magnetic chip detectors, these chips
can be produced due to wear and tear of the bearings installed. The oil from all six elements also
passes over a common chip detector. After this comes the pressure relief valve (PRV) through

15 | P a g e
which the oil passes into the scavenge filters (rated at 6 microns) but if excess pressure is
detected by the PRV it lifts allowing the excess oil to return directly to the reservoir to avoid damages
to the line and other components. The oil then flows through the shell and tube type heat exchangers
after which it returns to the reservoir. There is temperature control valve (TCV) installed at the cooler
discharge which bypasses oil around the coolers when oil temperature is below the set-point.
Components of the Turbine Lube Oil System:
1) Reservoir: A stainless steel, 150 gallon tank located on the auxiliary skid. It contains
heaters to keep the lube oil temperature at least 90⁰F
2) Lube Oil Supply and Scavenge Pump: As mentioned earlier, it as one supply element and
six scavenge elements. The pumps here are positive displacement types
3) Scavenge Oil Filters: These are located on the auxiliary skid. The filters are rated at 6
microns and each element is designed for 100% flow and pressure.
4) Supply lube Oil Filters: These are located on the auxiliary skid. The filters are rated at 6
microns and each element is designed for 100% flow and pressure.
5) Temperature Control Valve: This is a fully automatic 3-way fluid temperature controller
for mixing applications. Temperature is sensed at the outlet valve (port A) and port B
remains fully open until temperature reached approx. 100⁰F. As the oil continues to rise,
port B starts to close off and Port C starts to open, mixing the hot and cold oils. These
valves continually modulate, maintaining a nominal oil temperature of 110⁰F. These
valves operate on the principal of thermal expansion. The wax element inside, after
getting energized, drives the plunger outwards hence regulating the valves.
6) Lube oil coolers: In the turbine lube oil system we have the shell and tube type heat
exchanger. It consists of a bundle of tubes enclosed in a shell. The cooling liquid flows
through the tubes and the liquid to be cooled enters the shell at one end which then
passes by the tubes and is discharged through the other end.
7) Air/Oil Separator: Located at the roof of the enclosure, the air/oil separator is a two-stage
design which a heat exchanger between the stages. It is installed to remove most of the
oil mist created due to heating of the oil in the reservoir.

16 | P a g e
50Hz Generator Lube Oil System
System Overview
The Generator Lube Oil System (GLOS) uses mineral lube oil to lubricate, cool and clean the
gearbox and generator bearings. In addition, the mineral oil is used to lift the generator rotor
shaft for easier Break-away. GLOS as two distinct subsystems 1) Pressurized supply system 2)
Jacking oil system. Each of these subsystem has its own filters
The supply system has three pumps, one DC motor driven pump and two AC motor driven pumps.
A single AC motor driven pump provides lubricating oil during operations. If the header pressure
drops to 12psi (pump failure) the secondary AC motor comes online to provide oil to the system
and maintain the header pressure at 12psi. If the pressure continues to drop, the DC motor driven
pump comes online. In an event of a complete electrical or mechanical failure, the four 20gal
rundown tanks feed oil to the bearing on both the generator and gearbox for a safe system
shutdown.
The jacking oil pump is used during startup and provides high-pressure oil to the rotor shaft to
life the shaft up so it breaks away easily.
Component Description:
A/C Motor driven pump relief valve: on the discharge side of the motor driven lube oil pumps
the relief valves are installed to protect the system from over pressurization. In the case of over
pressurization the oil is directed back into the reservoir tank.
Pressure Control Valve: It controls the lube oil header pressure by returning excess pressure back
to the lube oil reservoir.
Generator Lube Oil Coolers: The shell and tube type coolers are installed to cool down the oil
after it returns from the generator. The oil flows through the tubes where the water flows are
over the tubes resulting in an exchange of heat.
Temperature Control Valve: Just like the one installed in the turbine lube oil system, the
temperature control valve here regulated lube oil return temperature by bypassing some of the
hot oil around the lube oil cooler and mixing it with the cooled oil from the oil cooler.
Generator Lube Oil Filters: There are two filters installed, one working at one time where the
other one acts as a backup. They are rated at 6 microns and each element can handle 100% flow
and pressure. Each filter had three elements.
Lube Oil Rundown Tanks: The four rundown tanks are located on the generator with one on each
end. These tanks provide an emergency source of lube oil to the bearings in case of pump failure
for safe shutdown.

17 | P a g e
Heat Recovery Steam Generator (HRSG)
Introduction:
As the natural gas is burned in the single annular combustor of the LM6000 gas turbine, it is a
well-known fact that the exhaust temperatures would be high and letting the exhaust gas into
the environment would be a waste of energy. The HRSG is installed here at the CCPP which
utilizes the high exhaust temperatures to convert water from the RO to superheated steam which
powers the 25MW steam turbine.
The steam turbine has two different stages, LP turbine and HP turbine. So the steam generated
at the HRSG is for both the LP and HP turbines, the only difference is the pressure that is
maintained.
Fundamental parts of HRSG:
Four basic HRSG components are:
1. Evaporators (Gas to wet steam heat exchanger)
a. HP Evaporator and LP Evaporator
2. Economizers (Gas to water heat exchanger)
a. HP economizer 1 & 2 and LP Economizer
3. Superheaters (Gas to dry steam heat exchanger)
a. HP Superheater and LP Superheater
4. Preheater (gas to water heat exchanger)
a. Condensate Preheater
Figure 13: Serrated Finned Tubes

18 | P a g e
HRSG Modules
Types of HRSG
There are three main types:
1. Natural Circulation HRSGs
2. Forced Circulation HRSGs
3. Once Through HRSGs
The one used at Korangi CCPP is the Forced Circulation HRSG where the exhaust gas glows
vertically and the water/steam flows horizontally and uses serrated fins on its tubing to maximize
heat transfer (See Figure 13 on previous page).
8
• Preheater
7
• HP Economizer 1
6
• LP Economizer
5
• LP Evaporator
4
• HP Economizer 2
3
• LP Superheater
2
• HP Evaporator
!
• HP Superheater

19 | P a g e
Forced Circulation HRSG Operation:
Feedwater from the RO Plant enters the HRSG from the top where it first goes through the
Economizer where the water is preheated and directed to the respective steam drums (LP and
HP steam have different drums and different HRSG components). Since the steam is less dense
as compared to water, it rises and the water accumulates at the bottom. The water at the bottom
of the tank is pumped to the evaporator where saturated steam is made and then returned again
to the steam drum. The superheated steam is pumped to the superheated, located at the very
bottom since high temp. are required, where dry superheated steam is produced and pumped
on to the steam turbine. The HP drum is maintained at a pressure of 54 bar and the LP turbine is
maintained at a pressure of 8 bar.
The LP drum and HP drum are dozed with LP phosphate and HP phosphate respectively and also
with ammonia and oxygen. This maintains the pH levels at approx. 9.5 and eliminates the
possibility of corrosion in the steam turbine.
Figure 14: Schematic of Forced Circulation HRSG

20 | P a g e
Figure 15: Detailed Schematic of the HRSG Heating Unit
Pre-Heater
HP and LP
Economizer
LP Evaporator
HP Economizer 2
LP Superheater
HP Evaporator
HP Superheater Exhaust Intake
ExhaustGasFlowDirection

21 | P a g e
Steam Turbine
Overview:
 Max load: 25MW
 RPMs: 4500
 Stages: 9 Overall; 6HP & 3LP.
Operation Overview:
The steam turbine operates on the rankine cycle where superheated steam is generated and
pumped into the steam turbine which rotates and drives the load, the generator. The two
different stages of the steam turbine requires different steam pressure and depending upon the
load a valve controls the amount of steam that enters the HP and LP turbine. The valve reduces
the steam that enters the HP turbine to about 10-12 Bar. After expanding through the turbine
the steam pressure drops to about 2-3 Bar and this is where LP steam is enters. Since the steam
turbine operates on a closed cycle, the exhaust steam is condensed and pumped back to the
HRSG to be superheated and used again in the steam turbine.

22 | P a g e
Reverse Osmosis (RO) Plant
Introduction:
The reverse osmosis plant here at the Korangi Combined Cycle Power Plant is used to treat sea
water by passing it through semi-permeable membrane under high pressure. The final product
(Permeate Water) is used for various applications such as for cooling and in the HRSG for steam
generation.
Osmosis is phenomena that occurs naturally in which a solution that is less concentrated will
migrate to a solution with high concentration through a semi-permeable membrane. Where as
in reverse osmosis an external force is applied to the high concentration solution which passes
through a semi-permeable membrane that allows the passage of water molecules but not the
majority of the salts ect. To achieve this, the force applied should generate pressure more than
the ‘Osmotic Pressure’ to initiate the reverse osmosis phenomena.
There are two stage systems common to the RO plant, single and double stage systems. Single
stage is fairly simple, the feed water enters as one stream and exists the RO as permeate water
from one side and condensate from the other. In the double stage the concentrate of the first
stage becomes feed water for the second stage. By increasing the stages the recovery from the
system increases.
Also used are the single and double pass system. The single pass system is the same as the single
stage system. Where as in the double pass system the permeate of the first pass becomes the
feed water to the second pass which produces a higher quality permeate water.
Chemical Dosing:
Five different types of chemical dosing are done in the feed water in order to minimize the
fouling, scaling, chemical attacks and biological growth. Two dosing are done before the
Multimedia Filters and three are done after the multimedia filters.
 Coagulant/Ferric Chloride Injection System: This promotes the clumping of particular
matter in water, forming a larger size and thus promoting settling of particulates and
clarification of the water.
 Flocculants: An electrolyte added to a colloidal suspension to cause the particles to
aggregate and settle out as the result of reduction in repulsion between particles.
 Sodium Meta-Bisulfate Injection System: This is used to remove the presence of chlorine.
 Caustic Injection System: Sodium Hydroxide is injected in the system to increase the pH
of the water to approx. 6.4 for the intermediate tank.
 Anti-Scalant Injection System: Anti Scalant is used to stop and remove the formation of
scaling in RO membranes.

23 | P a g e
Sea Water Reverse Osmosis System:
This system mainly consist of:
 Cartridge filters
 HP Multistage pump
 Booster Pump
 ERD System
 18 Membrane modules
After passing through the Bernoulli filters and getting the first and second chemical dozing, the
water enters the main RO system where it passes through the 7 Multi Media Filters (MMF). A
MMF contains eight layers of media consisting of stones, white gravel, purple garnet, white sand,
brown sand, pink garnet, purple garnet and anthracite coal. The feed water enters from the top,
passes through the media and is collected at the bottom. After passing through the MMF, the
water enters the cartridge filters (having 82 propylene filters rated at 5 Microns). Two lines are
extracted from the cartridge filter housing where one line supplies water to high pressure pump
inlet and the other one is going to ERD (energy recovery deceive) inlet. Each module contains 7
members and at the inlet of the membranes the pressure is about 52 bar which is increased by
the help of a high pressure multistage pump. In the RO membranes water is divided into two
streams, ones is permeate and the other one is concentrated water (waste product). The
permeate is transferred to the Intermediate tank where it has a conductivity of 400-500µs/cm
(compared to 55,000µs/cm at the start). The concentrated water goes to the EDR inlet where
high pressure concentrated water runs a turbine and transfers it pressure to the Low pressure
Sea water which comes in the EDR from the cartridge filters. The high pressure water leaving the
EDR passes through a booster pump which raises the pressure to 54 bar from where it is supplied
to the inlet of the RO membranes.
Figure 16: Sea Water RO Modules

24 | P a g e
Permeate Water RO System:
After the SWRO the permeate water is stored in an intermediate tank from where it is supplied
to PWRO system by the PRWO supply pumps. After passing through the 3 microns rated filters
water enters the booster pumps which raise the pressure of the water and feed it into the 12
PWRO modules (containing 4 membranes each) yielding in the permeate water having a
conductivity of approx. 10µs/cm. The permeate water from the PWRO enters the EDI machine
which removes the ionic impurities by the electro deionization method. The final product water
has a conductivity of 0.075 µs/cm and is then stored in demin tank and 3 KPTS tanks as a backup.
From here the water is supplied in two streams. The first stream supplies water to GT-1 and GT-
2 operational tanks, Skids and serge tank for evaporator chillers and the Second stream supplies
water to closed cooling first filling and hot well of steam turbine.

25 | P a g e
Fuel Gas Compressors
Introduction
4 FGC’s are currently installed at CCPP. The basic purpose of FGC installation is to meet the gas
pressure requirement of 46 bars for the gas turbine fuel requirement.
Stage # 1:
Gas comes from Gas yard into separator in which separates the moisture and condensate
present in the gas. Condensate is settling down in the separator and gas moves in the suction
bottle of the first stage compressor.
First stage contains 2 cylinders having 3 suction and 3 discharge valves at each. Gas enters at
2.2 bar and discharge at 7.9 bar at 1100C temperature and accumulate in discharge bottle of
first stage. Pressure safety valve is placed between discharge bottle and inter cooler which sets
at 17.2 bar.
After discharge bottle gas is passed through water cooler which lowers the temperature and
specific volume of the gas. Water cooler is the shell and tube type heat exchanger having
compressed gas in tube side and water at shell side.
Stage # 2:
After the inter-cooler Compressed gas is entered in the inter stage separator of 2nd stage where
gas and condensate separates. Gas is then enter in the 2nd stage cylinders where it compressed
down to the pressure of 18.4 bar, after compression temperature of gas is 124 0C. After
compression gas comes in discharge bottle from where it follows into the heat exchanger,
having compressed gas on tube side and cooling water on shell side.
A pressure safety valve is placed between discharge bottle and inter cooler which sets at 29
bar.
Stage# 3:
From the inter-cooler of second stage, gas is forwarded to the suction bottle of 3rd stage cylinder
where it further compressed to 46 bar and temperature of gas at this stage is 124 0C. 3rd stage
cylinder has 4 suction and 4 discharge valves.
Compressed gas is then transferred to the heat exchanger having gas on shell side and water on
tube side. From heat exchanger compressed gas is transferred to discharge separator which
separates the gas and moisture from where it supplied into the discharge header followed by a
non returning valve and shut off valve.

26 | P a g e
A pressure safety valve is placed between discharge bottle and intercooler of 3rd stage. Which
sets at 52 bar. Blow down valve is also placed before inter cooler, used to depressurize the
system.
A line from 3rd stage intercooler is also provided followed by the two Pressure Control Valves for
Fuel Gas recycling purpose. Recycle systems connects the outlet of 3rd stage cooler to inlet
separator before PCV.

27 | P a g e
Table of Figures
Figure 2: CCPP Overview...............................................................................................................................4
Figure 1: the 4 LM6000 GTs + HRSG Unit......................................................................................................4
Figure 3: Cross-section of the LM6000 Gas Turbine.....................................................................................5
Figure 4: Open cycle gas tubine....................................................................................................................6
Figure 5: T-S Diagram representation of an ideal Brayton Cycle Figure 6: P-v Diagram Representation
of an ideal Brayton Cycle ..............................................................................................................................6
Figure 7: Single Shaft.....................................................................................................................................9
Figure 8: Twin Shaft ......................................................................................................................................9
Figure 9: Concentric Shaft...........................................................................................................................10
Figure 10: Concentric Shaft with Power Turbine........................................................................................10
Figure 11: Air Intake House.........................................................................................................................12
Figure 12: Bearing positions on GT.............................................................................................................14
Figure 13: Serrated Finned Tubes...............................................................................................................17
Figure 14: Schematic of Forced Circulation HRSG ......................................................................................19
Figure 15: Detailed Schematic of the HRSG Heating Unit...........................................................................20
Figure 16: Sea Water RO Modules..............................................................................................................23

Korangi CCPP Internship Report

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Korangi CCPP Internship Report

Similar to Korangi CCPP Internship Report (20)

Korangi CCPP Internship Report