INTERNSHIP REPORT

RAJIV GANDHI COMBINED CYCLE POWER PLANT-NTPC

LTD.Guided by

Mr. M.S DINESH KURUP

Sr.MANAGER (MTP)

RGCCPP-KAYAMKULAM

By

SREESANKAR.J

M.E THERMAL ENGINEERING

S.N.S COLLEGE OF TECHNOLOGY

COIMBATORE-35

ABOUT NTPC LIMITED

NTPC Limited (formerly known as National Thermal Power Corporation Limited) is a Central Public Sector Undertaking (CPSU) under the Ministry of Power, Government of India, engaged in the business of generation of electricity and allied activities. It is a company incorporated under the Companies Act 1956 and a "Government Company" within the meaning of the act.

The headquarters of the company is situated at New Delhi. NTPC's core business is generation and sale of electricity to state-owned power distribution companies and State Electricity Boards in India. The company also undertakes consultancy and turnkey project contracts that comprise of engineering, project management, construction management and operation and management of power plants. The company has also ventured into oil and gas exploration and coal mining activities.

It is the largest power company in India with an electric power generating capacity of 42,964 MW. Although the company has approx. 18% of the total national capacity it contributes to over 27% of total power generation due to its focus on operating its power plants at higher efficiency levels (approx. 83% against the national PLF rate of 78%).

It was founded by Government of India in 1975, which held 75% of its equity shares on 31 March 2013 (after divestment of its stake in 2004, 2010 and 2013).In May 2010, NTPC was conferred MAHARATANA status by the

Union Government of India. It is listed in Forbes Global 2000 for

2014 at 424th rank in the world.

ABOUT RAJIV GANDHI COMBINED CYCLE POWERPLANT, KAYAMKULAM

The Rajiv Gandhi Combined Cycle Power Plant (also known as Rajiv Gandhi CCPP Kayamkulam or NTPC Kayamkulam) is a combined cycle power plant located at Choolatheruvu in Alappuzha district, Kerala, India.

The power plant is owned by NTPC Limited. The power plant is fueled by imported and indigenous naphtha. Source of the cooling water is Achankovil River. Total installed capacity of the plant is 350MW.

The plant is a combined cycle power plant comprising of two Gas Turbines and one Steam Turbine of capacities 115MW (2), and 120MW respectively. Unite 1 was commissioned on 1998 November, Unite 1 on February 1999 & Unite 3 on October 1999.

HSD (High Speed Diesel), Naphtha are used as fuels.

THERMODYNAMIC CYCLES CARNOT CYCLE

RANKINE CYCLE

BRAYTON CYCLE

A. CARNOT CYCLE

The Carnot cycle is a theoretical thermodynamic cycle proposed by Nicolas Léonard Sadi Carnot in 1824 and expanded by others in the 1830s and 1840s.

It can be shown that it is the most efficient cycle for converting a given amount of thermal energy into work, or conversely, creating a temperature difference (e.g. refrigeration) by doing a given amount of work.

Every single thermodynamic system exists in a particular state. When a system is taken through a series of different states and finally returned to its initial state, a thermodynamic cycle is said to have occurred. In the process of going through this cycle, the system may perform work on its surroundings, thereby acting as a heat engine.

A system undergoing a Carnot cycle is called a Carnot heat engine, although such a "perfect" engine is only a theoretical limit and cannot be built in practice.

B. RANKINE CYCLE

The Rankine cycle is a model that is used to predict the performance of steam engines. The Rankine cycle is an idealized thermodynamic cycle of a heat engine that converts heat into mechanical work. The heat is supplied externally to a closed loop, which usually uses water as the working fluid. The Rankine cycle, in the form of steam engines, generates about 90% of all electric power used throughout the world, including virtually all biomass, coal, solar thermal and nuclear power plants. It is named after William John Macquorn Rankine, a Scottish polymath and Glasgow University professor.

C. BRAYTON CYCLE The Brayton cycle is a thermodynamic cycle that describes the

workings of a constant pressure heat engine. Gas turbine engines and air breathing jet engines use the Brayton Cycle. Although the Brayton cycle is usually run as anopen system (and indeed must be run as such if internal combustion is used), it is conventionally assumed for the purposes of thermodynamic analysis that the exhaust gases are reused in the intake, enabling analysis as a closed system.

The engine cycle is named after George Brayton (1830–1892), the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber in 1791.[1] It is also sometimes known as the Joule cycle. The Ericsson cycle is similar to the Brayton cycle but uses external heat and incorporates the use of a regenerator. There are two types of Brayton cycles, open to the atmosphere and using internal combustion chamber or closed and using a heat exchanger.

COMBINED CYCLE In electric power generation a combined cycle is an assembly

of heat engines that work in tandem from the same source of heat, converting it into mechanical energy, which in turn usually drives electrical generators.

The principle is that after completing its cycle (in the first engine), the working fluid of the first heat engine is still low enough in its entropy that a second subsequent heat engine may extract energy from the waste heat (energy) of the working fluid of the first engine.

By combining these multiple streams of work upon a single mechanical shaft turning an electric generator, the overall net efficiency of the system may be increased by 50 – 60 percent.

That is, from an overall efficiency of say 34% (in a single cycle) to possibly an overall efficiency of 51% (in a mechanical combination of two (2) cycles) in net Carnot thermodynamic efficiency. This can be done because heat engines are only able to use a portion of the energy their fuel generates (usually less than 50%). In an ordinary (non combined cycle) heat engine the remaining heat (e.g., hot exhaust fumes) from combustion is generally wasted.

Combining two or more thermodynamic cycles results in improved overall efficiency, reducing fuel costs. In stationary power plants, a widely used combination is a gas turbine (operating by the Brayton cycle) burning natural gas or synthesis gas from coal, whose hot exhaust powers a steam power plant (operating by the Rankine cycle).

This is called a Combined Cycle Gas Turbine (CCGT) plant, and can achieve a thermal efficiency of around 60%, in contrast to a single cycle steam power plant which is limited to efficiencies of around 35-42%. Many new gas power plants in North America and Europe are of this type. Such an arrangement is also used for marine propulsion, and is called a combined gas and steam (COGAS) plant. Multiple stage turbine or steam cycles are also common.

Combined Cycle consists of

A.Topping cycleB.Bottoming cycle

DIFFERENT SYSTEMS IN THE PLANT

o Condensate Systemo Feed Water System

High Pressure Feed Water System Low Pressure Feed Water System

o Condensate Recirculation Systemo Cooling water Systemo Cooling Tower Systemo Steam Circuit

High Pressure Circuit Low Pressure Circuit

o Fuel Oil System HSD (High Speed Diesel) Naphtha

o Seal Steam Systemo Turbine Oil System (Steam Turbine/Lub Oil

System)

CONDENSATE SYSTEM • The steam after condensing in the condenser known as

condensate, is extracted out of the condenser hot well by condensate pump and taken to the deaerator through ejectors, gland steam cooler and series of LP heaters

• Condensate Extraction Pump : To pump out the condensate to D/A through ejectors, GSC and LPH

• Gland Steam Condenser: To increase the temperature of condensate.

Condensate polishing unit: To remove cat-ion and an-ion from the condensate.

FEED WATER SYSTEM Feed water system serves three purposes in the power plant. They provide efficiency gains in the steam cycle by increasing the

initial water temperature to the boiler, so there is less sensible heat addition which must occur in the boiler,

They provide efficiency gains by reducing the heat rejected in the condenser, and they reduce thermal effect in the boiler.

Steam is extracted from selected stages in the turbine to shell and tube heat exchangers or to open feed water heaters where the steam and feed water are in direct contact.

HP FEED WATER SYSTEM Located downstream of boiler feed pump. Typically, the tube side design pressure is at least 100 KG/CM2, and the steam source is high pressure turbine.

LP FEED WATER SYSTEMLocated (with regard to the feed water flow) between condensate pump and either boiler feed pump. It normally extracts steam from the low pressure turbine.CONDENSATE RECIRCULATION SYSTEM

o Condensate Pumps

o The function of these pumps is to pumps out the condensate to the deaerator thru' ejectors, gland steam cooler, and L.P. heaters. These pumps have FIVE stages and since the suction is at a negative pressure, special arrangements have been made for providing sealing.

o The pressure build up in 5 stages as suction is at negative pressure.

o Recirculation

o It is done when the de aerator level controller trips in order to prevent cavitations.

o Boiler Feed Pump

o To give the required pressure to the feed water before entering into boiler

o Horizontal barrel type multi stage pump.

COOLING WATER SYSTEM

Cooling water system is the system that handles various cooling needs of the power plant.Cooling water is used in condenser to remove heat from the steam.The cooled water from the condenser is send to the Cooling tower system for further cooing purpose.Cooling water system for turbine designed to accommodate the heat dissipation requirement of the turbine and the generator lubrication system, generator cooling system.CW system is a closed loop system which gets CW from cooling water module. It pumps CW to GT and generators which receives heat from GT and generators components.DMCWS [DEMINERALISED COOLING WATER SYSTEM]

DMCWS supplies cooling water to equipment when ever its necessary.DMCWS supplies CW to HPBFP (High Pressure Boiler Feed Pump), LPBFP (Low Pressure Boiler Feed Pump), CPHRCP etc.DMCWS consists of a closed loop circuit that consists of a DMCWS over head tank which is an expansion tank (Constant level of water is maintained always)Two plate type heat exchangers, and ACWS (Auxiliary Cooling Water System) which is used to cool down the water coming from DMCWS.ACWS gets the cold water from the CW sump.

COOLING TOWER SYSTEMRemove heat from the water discharged from the condenser so that the water can be discharged to the river or re circulated and reused.

Air can be circulated in the cooling towers through natural draft and mechanical draft.

At RGCCPP there are induced draft type cooling towers.

STEAM CIRCUIT High Pressure Circuit Low pressure Circuit

Steam circuit is the circuit that involves all steam handling in the plant.The hot exhaust from the gas turbine is passed to the HRSG with a temperature of 521oC, 50.45 KG, 166.65T/Hr.

HIGH PRESSURE CIRCUITHigh pressure circuit handles the high temperature high pressure process that leads to the HPT (High Pressure Turbine) in the steam cycle.The circuit includes HP Drum, HPBP (High Pressure Boiler Pump), HP Turbine.

LOW PRESSURE CIRCUITLow pressure circuit handles the low temperature high pressure process that leads to the LPT (Low Pressure Turbine) in the steam cycle.The circuit includes LP Drum, LPBP (Low Pressure Boiler Pump), LP Turbine.

GAS TURBINE Gas turbine model series: MS 9001 Shaft Relation: Counter Close Wise Turbine Shaft Speed: 3000RPM Control: SPEEDTRONIC MARK V Solid state electronic control

system. Air In: 28oC Fuel: Natural Gas, Naphtha, HSD. Power turbine Stages: 3

Functional Description

The MS9001 is a Simple cycle, single-shaft gas turbine with 14 combustion, reverse flow combustion system. The Ms9001 gas turbine assembly consists of 6 major sections:

Air Inlet Compressor Combustion System Turbine Exhaust Support Systemo Compressor Section Rotor Stator Inlet casing Forward compressor casing After compressor casing Compression Discharge Casingo Combustion System Combustion Wrapper Combustion Chambers(no.14) Spark Plugs Ultraviolet flame Detectors Fuel Nozzle Cross Fire Tubeso Turbine Section Turbine Rotor Turbine Casing Exhaust Frame Exhaust Diffusers Nozzle

GAS TURBINE FLAME DETECTION SYSTEM

The Honeywell flame mounting system describes are designed to detect the ultraviolet radiations emitted by a hydrocarbon flame and provide either a logic signal [System YG 150Aol] a relay contact closure to indicate flame in a gas turbine.

AUXILIARY UNITE FOR A GAS TURBINE The auxiliary unite of this type are specially designed for compact

turbo alienate unites with: To drive the “Turbo axillaries” at appropriate speed. To drive the turbine through its starting device in the starting

process. They are equipped with integral oil pumps The gear is of single helical type. Casing Gearing Lub oil pumps

STARTING SYSTEMTiming power is supplied by the starting system during gas turbine starting and stopping.

ELECTRIC STARTING MOTORThe prime motor is a 4 pole, 6600VAC, 50Hz, 1750HP motor. The motor operates in the single speed to produce the necessary horse power to start of the gas turbine.

LUBRICATION OIL SYSTEMLubrication of the gas turbine and generator is fulfilled by a common force-feed lubrication systemSystem consists of:

TankPumpsCoolersProtection devices

Hydrocarbon based lubrication oil (recommended for the gas turbine)FUEL SPECIFICATION OF BHEL/GE

Firing temperature: 1600oF [870oC] or HigherFuel Used: HSD (High Speed Diesel)

Naphtha: A highly volatile fuel with a boiling range between gasoline and light distillate. The low flas point and high volatility require special safety considering its very low viscosity may result in poor lubricity.

HSD is used in the starting stage of the turbine and when it reaches 2000 RPM the fuel switches to Naphtha.

PURGING AIR SYSTEMPurging is the process of removing unburned fuel and air before the turbine starts.In the starting stage of the GT there is a 15 second purging stage that is been automatically performed by the control system.In the stage some amount of HSD is supplied in to the combustion chamber and burned and is purged out.

HYDRAULIC SUPPLY SYSTEMHydraulic fluid of a high pressure is provided by the hydraulic supply system to operate control of the GT.High Pressure Hydraulic oil controlling the GT start/stop and control valve assembly fuel oil by pass valve assembly and variable Inlet Guide vanes (IGV) mechanism.Major system compounds include:

Main hydraulic supply pumpAuxiliary supply pumpSystem filterTransfer valvesThe accumulator manifold assembly

TRIP OIL SYSTEM

It is the primary protection interface between the gas turbine control panel and the component as the turbine which shut off.

SEAL STEAM SYSTEMSeal steam system is a system that seals the HPT & LPT preventing the turbine from leaking the steam during work done.The shaft and turbine consists of a annular grooves that reduce the pressure so as to prevent the wastage.LPT sealing system will prevent air coming in, as the pressure inside the turbine is low as compared to atmosphere. The steam collected from leak steam is used for GSC (Gland Steam Condenser)

FIRE PROTECTION SYSTEMThe CO2 fire protection system for the gas turbine unites extinguishing the fire by reducing the oxygen.To reduce the oxygen content, a quantity of Co2 greater than 34% a compared by volume is discharged in to the combustion chamber, when exposed to high temperature.

OVER SPEED PROTECTION SYSTEMUnder normal operation the speed of the shaft is under the control of speed loop or temperature loop.The over speed protection system consists of a primary electronic system.The primary electronic over speed protection system senses the turbine speed, speed detection software and associated circuits.Mechanical over speed protection system is a backup for electronic over speed protection system failure.

OVER TEMPERATURE PROTECTION SYSTEMThe over temperature protection system protects the GT from possible damage caused by over firing. It is a backup system which operates only after failure of the speed and temperature over ride loops.

Control of turbine is done mainly by start up speed acceleration, synchronization and temperature controlsTemperature, speed, vibration, flame and compressor operation limits over temperature and over speed systems are provided as independent backup system for temperature control and speed control systems.Vibration detections and protection is activated by abnormal turning vibration amplitude.Flame Diction and protection system is activated if flame is not established during start up or if it is lost during operation.

WORKING OF THE PLANTCombined cycle power generation combines 2 cycles for operation, namely the gas turbine cycle and the vapor power (or steam turbine) cycle.In a gas turbine power plant, the turbine starts with HSD (High Speed Diesel) and when it reaches 2000 RPM the fuel switches to Naphtha and compressed air undergo combustion.The resultant high pressure gas drives the gas turbine which in turn produces electricity.Although it is clean and fast in starting up, the gas turbine power plant suffers from low thermo efficiency of about 25 to 30%.Much of the energy is wasted in the form of gas turbine exhaust.The combined cycle power generation makes use of the merits of the high temperature (1100 to 1650°C) gas turbine cycle and the lower temperature (540 to 650°C) steam turbine cycle.The hot exhaust gas from the gas turbine, instead of being released as waste, is captured and channeled to the steam turbine where steam is heated by the exhaust to drive the turbine.A combined cycle power plant consists of two main parts: the gas turbine plant and the steam turbine plant.In the gas turbine plant, atmospheric air enters through the compressor and into the combustor (or combustion chamber) where fuel (usually natural gas) is added.

Combustion takes place and the hot gas drives the turbine, which in turn drives the generator and produces electricity.The hot flue gas from the gas turbine enters a heat exchanger, sometimes known as Heat Recovery Boiler or Heat Recovery Steam Generator [HRSG], where it is used to heat up the steam.The superheated steam is then used to drive the steam turbine which in turn drives the generator to produce electricity.The exit steam from the steam turbine goes through a condenser and then back to the heat exchanger where the cycle repeats itself.

ELECTRICAL SYSTEMThe power production in RGCCPP-Kayamkulam by two 115MW Gas Turbines and one 120MW Steam Turbine unite is supplied to the customers through two buses of 220KV.Power evacuation lines are to 4 places: Edappon Kundara Pallom 1 Pallom 2Produced current 115MW current is stepped up to 220KV by using a step up transformer and is uploaded to the 220KV Bus.A Unite Auxiliary Transmission (UAT) line of 1.66KV bus is also available for the plant use.A Bus coupler is used to separate the two lines of GTPP. This keeps two plants isolated.The plant also consists of a Black Start Diesel Generator (BSDG). In case of any plant black out.

BACK CHARGINGBack charging is the process of taking required amount of power back from the main power line when the plant is not running.