Internship Report on 747

Internship Report On Power Generation At 747 MW Combined Cycle Power Plant GENCO-II Thermal Power Station Guddu

By Syed Ashraf Ali Shah Rizvi ROLL NO:- 14ME112 MUET JAMSHORO Submitted To D.M Training Center GENCO-II Thermal Power Station Guddu

Acknowledgement

First of all I thanks the almighty Allah and also those who supported me to complete this report successfully.

I want to thanks the Dy. Plant Manager of 747 MW CCPP, Mr. Zulfiqar Ali Gopang to give me chance to complete my internship at 747MW CCPP, TPS Guddu. I would also like to thanks Mr. Gulzar Shaikh (Head Of Training Center) for his kind cooperation during internship period. I thanks my mentor Syed Qaim Ali Shah (Operator), Combined Cycle Power Plant, TPS Guddu. He provided me the practical knowledge of the power plant, without his guidance and help I could not completed my internship. I also like to thanks other Engineers and staff of 747MW CCPP, TPS Guddu for their cooperation with me.

1

Executive Summary

Internship provides students the opportunity to test their interests in a particular zone and also provides students high level of practical knowledge. Mehran University Jamshoro has added this internship program for the graduating students to introduce them to the professional life.

I got an opportunity to complete my internship at 747MW CCPP, TPS Guddu which is the major power station of WAPDA in Pakistan. My internship started on 09th June, 2016 and ended on 27th June, 2016 (18 Days). There I worked and visited different units of 747 MW CCPP.I got practical knowledge about power plants and observed the operating system of power plants. There I also got the knowledge of days to days problems appearing in the Power Plant facing by Engineers.

I were assigned to the 747MW combined cycle power plant, but I was lucky because during this internship period I got a chance to visit 600MW CCPP, other auxiliary components of power plant. I gathered practical experience about different major components of power plant such as Generator, compressor, combustion chamber, gas turbine, steam turbine, operation and control unit, cooling system of the plant. Inside the report I described about my experiences at 747MW CCPP, TPS Guddu.

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Training Schedule

Below Table contains my training schedule at GENCO-II, TPS Guddu. My internship started on 09th June, 2016 and ended on 27th June, 2016.I visited 747MW combined cycle power plant (CCPP), 600MW combined cycle power plant (CCPP).

Training Schedule Day

Thursday

Start/End

B

time

r

8am-1pm

09/06/16

Friday

8am-1pm

10/06/16

Saturday

__

11/06/16 Sunday

__

12/06/16 Monday

8am-1pm

13/06/16

Tuesday

8am-1pm

15/06/16

e 1 Syed Qaim Ali Shah (operator) p a m 747MW (CCPP) - k 2 p 1m Zakaullah Bhatti (operator) t p 747MW (CCPP) mi - m 2 p e 1m Syed Qaim Ali Shah (operator) p 747MW (CCPP) m 1- Syed Qaim Ali Shah (operator) 2p p 747MW (CCPP) m m 1- Syed Qaim Ali Shah (operator) p2 pm 747MW (CCPP) -m 2 p m 1 Syed Qaim Ali Shah (operator) p 747MW (CCPP) m 2 p m

14/06/16

Wednesday

Mentor

8am-1pm

1 Syed Qaim Ali Shah (operator) p 747MW (CCPP) m 2 p m 3

Location

Total hours

747 MW Control Room (Gas Turbine)

5

747 MW Control Room (Gas Turbine)

5

OFF

-

OFF

-

Gas Turbine

5

Of 747MW CCPP (sight) Gas

5

Turbine Of 747MW CCPP (sight) Auxiliaries of Gas Turbine (sight)

5

Day

Thursday

Start/End

B

time

r

8am-1pm

16/06/16 Friday

8am-1pm

17/06/16

Saturday

__

18/06/16 Sunday

__

19/06/16 Monday

8am-1pm

20/06/16

Tuesday

8am-1pm

21/06/16

Wednesday

8am-1pm

22/06/16

Thursday 23/06/16

8am-1pm

Mentor

Total hours

1 eSyed Qaim Ali Shah (operator) p a m 747MW (CCPP) - k 2 1 Syed Qaim Ali Shah (operator) p p t m 747MW (CCPP) m - i 2 m p me 1 Syed Qaim Ali Shah (operator) p m 747MW (CCPP) 1- Syed Qaim Ali Shah (operator) p2 747MW (CCPP) p m 1-m Syed Qaim Ali Shah (operator) p2 747MW (CCPP) m p -m 2 p 1m Syed Qaim Ali Shah (operator) p m 747MW (CCPP) 2 p m

1 p m 2 1p pm m 2 p m

Location

Mehboob Malik (Attendant) 747MW (CCPP)

Mehboob Malik (Attendant) 747MW (CCPP)

Air Inlet

5

Filters (sight) Lube Oil Pumps Or Sealing Pumps (sight)

5

OFF

-

OFF

-

Generator and DC source for excitation

5

Cooling System of Hydrogen & Cooling system of water which cools Hydrogen.

5

747 MW Control Room (Boiler)

5

Boiler HRSG and Feed Pumps of (LP, IP and Hp) Turbines (sight)

5

Day

Friday

Start/End

B

time

r

8am-1pm

24/06/16

Friday

2pm-7pm

24/06/16

Sat & Sun 25~26/06/16 Monday 27/06/16

__ 8am-2pm

Mentor

e 1 Agha Shah Mohammad p a m (Operator) - 747MW k (CCPP) 2 p 1 Agha Shah Mohammad mt p (Operator) mi - 747MW (CCPP) 2 m p e m 1 p m 1p2 m p -m 2 p m

Location

Total hours

747 MW Control Room (Steam Turbine)

5

5

Syed Qaim Ali Shah (operator)

Steam Turbine, Condensate Pump, vacuum pump, Condenser, Hot well, Gland steam condenser, Startup Boiler. OFF

747MW (CCPP) Syed Qaim Ali Shah (operator)

600MW

6

747MW (CCPP)

Combined Cycle Power Plant

-

Table of Contents

Acknowledgment ....................................................................................................................... 1 Executive Summary ................................................................................................................. 2 Training Schedule.......................................................................................................................3 Table of Contents.........................................................................................................................4 Chapter 1: Introduction............................................................................................................5 1.1 Objective of my internship............................................................................................5 1.2 Introduction to 747MW CCPP, TPS Guddu................................................................5

Chapter 2: Combined Cycle Power Plant 2.1 Introduction to Combined Cycle Power Plant 2. 2 Turbine Unit 2.2.1 Gas Turbine Unit 2.2.2 Steam Turbine Unit

2.3 Plant Starting Conditions 2.4 Significant Components of Combined Cycle Power Plant 2.4.1 Generator (as a MOTOR) 2.4.2 Torque Converter 2.4.3 Auxiliary Gear Box 2.4.4 Exciter 2.4.5 Compressor 2.4.6 Combustion Chamber 2.4.7 Exhaust System

2.5 Plant Shut Down Procedure

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Chapter 1: Introduction 1.1 Objective of Our Internship The main purpose of the internship is to merge my academic knowledge with practical knowledge of power station. I took this program to fulfill my academic requirement. I chose a power plant for this industrial training for a close observation of a power plant and application of my academic knowledge in practical field. In my internship, I have focused on generation system of 747MW CCPP, TPS Guddu. My main target was to get a complete overview of 747MW Combined Cycle Power Plant.

1.2 Introduction to 747MW CCPP, TPS Guddu 747MW CCPP is the major power plant of WAPDA in Pakistan. The installed generation capacity of 747MW CCPP, TPS Guddu

is 747 MW. This plant has been playing an

important role in the generation of power from 2014~2015.

Geographical position of the power station is very suitable for power generation. • 747MW CCPP, is situated near the Sui gas field. Good quality and pressure of Methane gas is available at the power plant from the Sui Southern Gas Transmission and Distribution Company.

• 747MW CCPP, is situated on the bank of the Indus River. This river also makes the transportation of large equipments easier for this power plant.

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Chapter 2: Combined Cycle Power Plant 2.1 Introduction to Combined Cycle Power Plant It is a power generating system where a gas turbine produces electricity and the exhaust of this gas turbine is used to run steam turbine and produce electricity. Here two types of turbines run at the same time by using one common fuel supplying system. So this is called combined cycle. It is a popular system for producing electricity because of higher efficiency and cost effectiveness. Figure below shows two gas turbine units (GT1 and GT2) and one steam turbine unit (ST1) of combined cycle power plant. The present capacity of combined cycle power plant of 747MW CCPP, TPS Guddu is shown in table below. The 747MW CCPP, TPS Guddu consists of three units. These are as follows. 

Two gas turbines units,



One steam turbine unit. Power generation capacity of combined cycle power plant of 747MW. Plant description Maximum capacity Present capacity Gas turbine unit-1

241 MW

225 MW

Gas turbine unit-2

241 MW

225 MW

Steam turbine unit

265 MW

232 MW

Total combined cycle power

747 MW

682 MW

plant

2 . 2 Turbine Units There are two gas turbine units and a steam turbine unit installed at the combined cycle power plant. 2.2.1 Gas Turbine Unit In the gas turbine unit there is a gas turbine. The gas turbine gives the mechanical energy. A continuous combustion process produces hot gas. The hot gas drives the gas turbine. The mechanical energy of turbine is used to generate electrical energy. The size of the gas turbine unit is much smaller than the steam turbine unit. Because gas turbine unit does not need any kind of boiler like steam turbine unit. Gas turbine unit startup

time is much faster compared to the steam turbine unit. The maintenance cost of gas turbine unit is low comparing to the steam turbine unit because gas turbine unit design is much simpler.

Combined cycle power plant design view. There are three most important components of gas turbine unit. These are as follows. 

Generator,



Turbine,



Compressor.

They are placed on the same axis with coupling among these. Fluid coupling technique is used in all coupling sections. Fluid coupling is a technology where the turbine rotates a fluid (mainly oil) and this rotating fluid rotates the generator. The compressor of gas turbine unit takes air from air filter which is attached to the compressor. The air filter can filter out dust particles in air. T h e s a m e g e n e r a t o r 1 s t used as a motor to rotate the common shaft at the beginning when the plant starts. A digital tachometer is used as speed sensor. When the machine starts at a crank speed up to 23% rpm then it waits for purging (purge time 10~20sec). (Purging is the process to clean the combustion chamber and turbine because there is the presence of hot flue gasses in it). Then the rpm returns to 13%

and gas is allowed to flow in the combustion chamber and combustion starts. When the combustion starts, the speed of the common shaft starts to increase. Air-fuel controller is used to control the combustion, which usually controls the flow of fuel. Then generator which is used as a motor (during startup) is automatically converted into generator when the crank speed appears at 90% rpm and then emf is induced from the generator.

There is a lube oil pump used to supply oil at different bearing. The oil creates force at different bearings at the beginning, when the common shaft starts to rotate. Due to centrifugal force after starting rotation the common shaft goes to center. AC and DC both types of pumps are installed in gas turbine unit. Normally AC pump is used for starting bearing lubrication. After a certain rotational speed in gas engine, fuel is injected to combustion chamber. Spark injection is needed to start combustion. The output of combustion is hot flue gases. The hot gas drives the turbine. Due to increased kinetic energy of turbine, compressor’s rotor shaft speed also increases. As a result compression of air is also increased. As a consequence combustion also increases gradually.

Impulse reaction turbine is used in gas engine unit. When the gas hits the blades of turbine then the turbine rotates and gives mechanical energy. The gas turbine is a composition of 3 stages turbine. Single stage consists of fixed blades and moving blades. Fixed blades are used to increase the velocity of flue gasses When the hot flue gases comes from combustion chamber to fixed blades the velocity of hot flue gases increases and then hit the moving blade which rotates and rotates the shaft. In this way velocity of flue gases decreases then 2nd stage's fixed blades are used to again increase the velocity of hot flue gases and again it strikes the moving blades and rotates the turbine in this way 3rd stage also plays the same role and then exit from the Diffuser.

The excitation of rotor starts when rotating speed of turbine reaches to 2200 rpm. It is important for the rotor protection to start the excitation at optimum speed of turbine. If we excite the rotor at low rpm, the inductive reactance will be low and it will act like a short circuit and will damage the rotor windings. When the generator speed becomes 3000 rpm, it will provide 50 Hz frequency(standard frequency of Pakistan 50 Hz). The process by which

the generated power is sent to national power grid is called synchronizing. When the rotating speed of generator rises to 2900 rpm the synchronizing process also starts either manually or automatically. During my internship period I have seen a synchronizing process, which was for a gas turbine unit. 0.5% voltage variation between grid and supply is allowed according to national load dispatch center. An auto synchronizer is used to perform this task easily.

2.2.2 Steam Turbine Unit Steam turbine unit in combined cycle power plant is designed so that the waste flue gases from gas turbine unit can be used. In 747MW CCPP, we use three turbines on one shaft (HP, IP and LP turbines). The exhaust gas temperature from the gas turbine is at about 615~616˚ C. This heat energy carries the exhaust gas which is used to generate steam at a certain pressure. This steam turbine is capable of generating maximum of 265MW. No external boiler furnace chamber is used to produce steam. The heated gas comes into the boiler directly from the gas turbine when the plant is in combined cycle mode or directly goes to the atmosphere through the vent when the plant is in open cycle mode. A motor driven gate is used to change the direction of exhaust gas of gas turbine. There is a de-mineralized water storage tank beside the boiler on the ground. This water is used to make steam in the boiler. A boiler feed pump is used to supply the water into boiler. In 747MW CCPP, Boiler there are three drums (IP, LP and HP drums) which converts water into steam through different circuits which is used to run the Turbine. There are two types of evaporators in the steam turbine unit. These are low pressure and high pressure evaporators. Water converts into steam and the steam goes to the steam turbine through a pipe. There is a distance between boiler drum and steam turbine. Before traveling to turbine the steam comes from steam separator through super heater which makes wet steam to dry steam. Finally the steam turbine rotates due to the activity of high pressured steam. The used steam comes from turbine and it is converted into water by condensation because of high cost of de-mineralization and then we will recycle it for making it again workable to run the steam turbine.

2.3 Plant Starting Conditions To start the combined cycle power plant some pre-conditions must be satisfied. These are as follows.  Power supplies should be at certain level: The auxiliary power supply is essential to run the unit. The auxiliary powers are taken from the 500 V bus bar. Different pumps need auxiliary power. The feed pumps needs each of 367 KW power. To run the combined cycle power plant AC and DC auxiliary powers should be prepared before plant starts.  Steam turbine barring gear should be engaged: Steam turbine barring gear rotates the turbine rotor at low rpm when the plant turns off generating power. So in any emergency to shut down the plant, the barring gear can be made active manually or automatically.  Valve position should be correct for starting: After starting the plant fuel should be supplied through the governor in efficient manner. All valves positions either open or close can be accessed manually. The governor valve, lubricant oil valves, water and gas pressure control valves should be on correct position to run the lube oil system, water circulation system properly.  Trips and instrument air pressure should be right: Waste heat recovery unit needs to be run after starting the gas turbine unit. There are trip circuits to control the flow of air compressor unit. All the waste heat recovery unit trips must be well to operate successfully.  Damper should be closed: Damper is used to control the flow of heated gas from gas turbine to steam turbine unit. The damper is needed to be open only when the combined cycle (gas turbine and steam turbine) runs. After the starting of gas turbine unit, the damper is open to run the steam turbine unit.

2.4 Significant Components of Combined Cycle Power Plant The design of gas power plant is much simpler than steam power plant. Here all equipments are in interlock system. So it is important for gas power plant operation to operate its all equipments properly. The important parts of combined cycle power plant are as follows.  Generator (as a Motor)  Turning Gear  Auxiliary gear box,  Exciter,  Compressor,  Combustion chamber,  Exhaust system

2.4.1 Generator (as a MOTOR): The main purpose of motor is to rotate the shaft until the combustion engine starts. In gas engine power plant combustion engine does not operate at the zero rpm of the shaft. At 90% rpm shaft gets its own self driven speed. At that time this motor works as a generator automatically.

2.4.2 Torque Converter: The weight of shaft is near about 150 tons. When the plant stops, the inertia of this shaft is too high. At that time if we want to rotate the shaft a heavy stress falls on the shaft. As the result the coupling point of shaft can be damaged. In order to solve this problem, we use torque converter which rotates the shaft continuously at 5~6 rpm to overcome above problem.

2.4.3 Auxiliary Gear Box In the power system exciter, compressor, turbine all are operated on a common shaft.

Friction can be created at the bearings. So we need to supply lubricating oil at high pressure on those bearings. This lubricating oil helps to shift the primary position of the shaft. Inside the bearing, the shaft lays down when the rotor does not rotate. After starting rotation, the rpm of shaft increases. Lubricating oil helps to rotate the shaft without friction. Auxiliary gearbox supplies this lubricating oil in all bearing points. For this there are two lube oil pumps: ac lube oil pump and dc lube oil pump. Normally ac lube oil pump operates and dc lube oil pump is for back up. Lead acid battery is used to operate this dc lube oil pump. The plant will not operate if both these pumps do not work.

2.4.4 Exciter Direct current is required to energize the magnetic field of the generator and this direct current source comes from an external source which is called exciter. This is important for AC power generating system. This exciter can be of 2 types- brush or brush less. Brush less exciter method is used to transfer the DC excitation to the generator fields

2.4.5 Compressor For the combustion of fuel we need fresh air. This air is collected by filters and these filters are stored at the high elevation because the air of higher elevation contains fewer particles. These air filters remove dust particles. D u s t particles of air are dangerous for the blades of turbine, which decreases the life time of the turbine. Then this fresh air heats up and passes to the compressor. The compressor is used for providing air in an efficient manner to the combustion chamber. Compressor supplies air at high pressure. The axial flow compressor is used in the gas engine of combined cycle power plant. The compressor contains 18 stages of rotor blades, The engine can compress approximately 14kg of air per second. At the compressor ends the temperature rises of the air is about 405° C. In this axial flow compressor, each stage increases the pressure of air from the previous stage.

2.4.6 Combustion Chamber Air comes from the compressor during the time when the shaft rotates at 13% rpm. There are eighteen combustors. There is a governor to control the supply of air and fuel. Air and fuel comes to the combustion chamber through governor. There are 2 spark plugs which creates

sparks as the result air blast with gas and created high temperature and pressure. Then this burnt gas supplies for the turbine. On combustion time the temperature of the combustion chamber is near about 1350º C. So supply of air over this combustion chamber reduces the temperature of the chamber. The temperature of this air is near about 415º C. If we want to produce more power then we need to supply more fuel to create more combustion.

2.4.7 Exhaust System The temperature of exhaust gas from gas turbine is about 616ºC to 620º C. This burnt gas of gas turbine is used to run the steam turbine unit. The exhaust gas from gas turbine is passed to the boiler of steam turbine unit through a horizontal axis pipe. When the steam turbine unit is not used to produce electrical power, the burnt gas from gas turbine unit is used to leave into the atmosphere through a vertical pipe. This vertical pipe is connected to a chimney.

2.5 Plant Shut Down Procedure In the case of any emergency, where we need to shut down the combined cycle plant, we need to consider barring system, lubricating oil system, waste heat recovery unit, synchronization with national power grid. For manually shut down the plant, first we need to cut off the power supply from national grid. Next the main fuel supply should be gradually turned off using the governor control. Then, the turbine rpm will start to decrease from 3000 rpm towards 0 rpm. Afterwards, the barring sequences should start when the plant is shut downed. After shutting down the power generation, only lubricating oil system has to keep active. When the turbine reaches 20 rpm rotation speed than the barring gear has to be engaged with the turbine shaft. Next the turbine shaft has to rotate next 48 hours with 20 rpm. After 48 hours, the turbine shaft needs to be rotated with 1 rpm for the next 24 hours. If the barring sequence fails then the turbine shaft may be damaged.