industrial training ntpc

7/31/2019 Industrial Training Ntpc

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INDUSTRIAL

TRAINING

AT

REPORT

Submitted by,

SOHAN RAM CHOUDHARY

08M268

MECHANICAL ENGINEERING


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Introduction to NTPC Ltd.NTPC, the largest power Company in India, was setup in 1975 to accelerate power

development in the country. It is among the worlds largest and most efficient power

generation companies. In Forbes list of Worlds 2000 Largest Companies for the year

2009, NTPC occupies 317th

place.

NTPC has installed capacity of 31,704 MW. It has 15 coal based power stations

(24,825 MW), 7 gas based power stations (3,955 MW) and 5 power stations in Joint

Ventures (2,864MW). The company has power generating facilities in all major regions

of the country. It plans to be a 75,000 MW company by 2017.

NTPC has gone beyond the thermal power generation. It has diversified into hydro

power, coal mining, power equipment manufacturing, oil & gas exploration, power

trading & distribution. NTPC is now in the entire power value chain and is poised to

become an Integrated Power Major.

NTPC's share on 31 Mar 2008 in the total installed capacity of the country was19.1% and it contributed 28.50% of the total power generation of the country during

2007-08. NTPC has set new benchmarks for the power industry both in the area of power

plant construction and operation.

With its experience and expertise in the power sector, NTPC is extending

consultancy services to various organizations in the power business. It provides

consultancy in the area of power plant constructions and power generation to companies

in India and abroad.

Recognizing its excellent performance and vast potential, Government of the Indiahas identified NTPC as one of the jewels of Public Sector 'Navratnas'- a potential global

giant. Inspired by its glorious past and vibrant present, NTPC is well on its way to realize

its vision of being "A world class integrated power major, powering India's growth, with

increasing global presence".

THE TRAINING:

I was given the opportunity to broaden my field of knowledge by having an exposure in

such an industry. The industrial training commenced in 1 June, 2010 to 30 June, 2010. Iwas given the following machines to visit during my 4 weeks of training period:

1. Gas Turbine

2. Steam Turbine

3. Combustion Chamber

4. Cooling Tower


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FLOW CHART OF NTPC KAWAS PLANT:


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SALIENT FEATURES OF PROJECT01) Gas Turbine : 106 MW, 3 Stage Impulse Type

02) GT Compressor : 17 Stages Axial Flow Compressor

03) Combustion Chambers : Cannular type with 2 Igniters and

14 Combustor baskets

04) Air filter type and Particle Size : Self cleaning inlet air filter, for

removing 5 micron particle size and

above and Handling air flow 380

kg/sec.

05) Bypass Stack : Vertical circular 5.93 m. dia & 55 m.

high

06) Waste Heat Recovery Boiler : Double drum, non-firing, assisted

(WHRB) Circulation Type heat recovery boiler

07) WHRB Steam Parameters : Press Flow Temperature

(Kg/cm) (Ton/hr) (Deg. C.)

HP Steam 71.3 174 520LP Steam 7.1 40 192

08) Steam Turbine : 116 MW, impulse, tandem

Compound, Double exhaust, condensing

type, with HP Turbine 13 stage horizontal

single flow LP Turbine 5 stage horizontal

double flow

09) Condenser : Two Pass Surface Condenser, each

Having 9200 no. Stainless Steel Tubes

10) Generator rated output : 134 MVA for GT & 145 MVA for ST

Rated Terminal voltage : 11.5 KV with Blushless Excitation

Rated speed : 3000 RPM

Type of cooling : Air-Cooled

11) Black start facility : 2.5 MW Diesel Generator Set

12) Cooling Tower type : Two Natural Draft Cooling Tower

(One for each module)

Cooling water (Design flow) : 24000 m/hr

Range of cooling : 10 C

Dimensions : 106.3 meters height & Base diameter of

92 m.13) Cooling water pumps/ : 5 (one common standby)/11910 m/hr &

Design parameters 22.4 MWC

14) Pre-treatment Plant : 2 Clariflocculators each rated for

1500 m/hr

15) DM Water Plant : Two streams of 55 m/hr


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COMBINED CYCLE POWER PLANT:Combine cycle power plant integrates two power conversion cycle-Brayton cycle (Gas turbine)

and Rankine cycle (Steam turbine) with the principal objective of increasing overall plant

efficiency.

BRAYTON CYCLEGas turbine plants operate on this cycle in which air is compressed (process 1-2, in P-V diagram

of figure-1B). This compressed air is heated in the combustor by burning fuel, where plant of

compressed air is used for combustion (process 2-3) and the flue gases produced are allowed to

expand in the turbine (process 3-4), which is coupled with the generator. In modern gas turbines

the temp. of the exhaust gases is in the range of 500 C to 550 C.

RANKINE CYCLE:The conversion of heat energy to mechanical energy with the aid of steam is based on

this thermodynamic cycle. In its simplest form the cycle works as follows:

The initial stage of working fluid is water (point 3 of figure 2), which at a certain

temperature is pressurized by a pump (process 3-4) and fed to the boiler

In the boiler the pressurized water is heated at constant pressure (process 4-5-6-1)

Superheated steam (generated at point-1) is expanded in the turbine (process1-2), which

is coupled with generator. Modern steam power plants have steam temperature in the

range of 500C to 550 C at the inlet of the turbine.


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COMBINING TWO CYCLES TO IMPROVE EFFICIENCYWe have seen in the above two cycles that exhaust is at temperature of 500-550 C and inRankine cycle heat is required to generate steam at the temperature of 500-550 C. Thereforegas turbine exhaust heat can be recovered using a waste heat recovery boiler to run a steam

turbine on Rankine cycle.

If efficiency of gas turbine cycle (when natural gas is used as fuel) is 31% and the efficiency of

Rankine cycle is 35%, then over all efficiency comes to 49%. Conventional fossil fuel fired

boiler of the steam power plant is replaced with a heat recovery steam generator (HRSG).Exhaust gas from the gas turbine is led to the HRSG where heat in exhaust gas is utilized to

produce steam at desired parameters as required by the steam turbine.

Evolution of gas turbines and combined cycle plants

Early History

Gas Turbines or Combustion turbines (an expression which has become popular in past

few years) were first developed in the late 18th century. Patents for modern versions of

combustion turbines were awarded in late nineteenth century to Franze Stolze and

Charles Curtis, however all early versions of gas turbines were impractical because the

power necessary to drive compressors outweighed the power generated by turbine. This

is because of the fact that the turbine inlet temperature (TIT) required to deliver positive

output and a certain minimum acceptable efficiency was above the allowable

temperatures that could be faced by materials available in those days. For example in

1904 two French engineers, Armengaud and Lemale built a unit, which did little more

than turn itself over. The reasonmaximum temperature that could be used was about

500 degree C and the compressor efficiency was abysmally low at 60 %.3.1.2Gas turbine performanceeffect of tit and compression ratio

A Gas Turbine in its simplest form works on Joule Brayton Cycle, which consists of

following:

Compression (1-2): A rotating compressor acts as a fan to drive the working fluid into

the heating system. The fluid is pressurized adiabatically, thus its temperature increases.


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Compressors are of the dynamic type, in which each stage increases the fluid velocity,

and then lets it diffuse to gain pressure.

Combustion (2-3): The fluid is heated by internal combustion, in a continuous process-

taking place at constant pressure. A steady supply of fuel mixes with air at high velocity

from the compressor and burns as it flows through a flame zone. Combustion occurs in a

very small volume, partly because it takes place at high pressure.

Expansion (3-4): The working fluid at high pressure is then released to the turbine,

which converts the fluid's energy into useful work as the temperature of the working fluid

decreases. Part of this work is returned to the compressor. The remainder is used for the

application intended: Generation of electricity, pumping, and turbojet propulsion.

The use of a compressible gas such as air as working fluid permits the absorption and

release of considerable amounts of energy. Such energy is basically the kinetic energy of

its molecules, which is proportional to its temperature. Ideal gas turbine cycles are based

on the Joule or Brayton cycles, i.e., compression and expansion at constant entropy, and

heat addition and release at constant pressure.

In an ideal cycle, efficiency varies with the temperature ratio of the working fluid in the

compression process, which is related to its pressure ratio. The inlet temperature in the

turbine section is generally limited by turbine technology, materials strength, corrosion

and other considerations. The increment of temperature also depends on the initial

Figure-1: Joule Brayton Cycle

1

23

C

T

Fuel

4Exhaust

Figure 2: PV and TS Diagram of Joule BraytonCycle.


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temperature of the working fluid. Some effects must be considered which diminish

efficiency in real operating cycles, such as inefficiency in compression and expansion,

loss of pressure during heat addition and rejection, variation of working fluid specific

heat with temperature, incomplete combustion, etc.

Gas Turbine Design Advancements:In gas turbine design the firing temperature, compression ratio, mass flow, and

centrifugal stresses are the factors limiting both unit size and efficiency. For example,

each 55C (100F) increase in firing temperature gives a 10 - 13 percent output increase

and a 2 - 4 percent efficiency increase. The most critical areas in the gas turbine

determining the engine efficiency and life are the hot gas path, i.e., the combustion

chambers and the turbine first stage stationary nozzles and rotating buckets. The

development process takes time, however, because each change of material

may require years oflaboratory and field tests to ensure its suitability in terms of creepstrength, yield limit, fatigue strength, oxidation resistance, corrosion resistance, thermal

cycling effects, etc.

The above figure shows how overall (net) efficiency of simple and combined-cycle

power plants has improved since 1950. The efficiency of simple cycle gas turbine plants

has doubled, and with the advent of combined-cycle plants, efficiency has tripled in the

past fifty years. Turbine nozzles and buckets are cast from nickel super alloys and arecoated under vacuum with special metals to resist the hot corrosion that occurs. The high

temperatures encountered in the first stage of the turbine are of great importance,

particularly if contaminants such as sodium, vanadium and potassium are present. Only a

few parts per million of these contaminants can cause hot corrosion of uncoated

components at the high firing temperature encountered. With proper coating of nozzles

and buckets and treatment of fuels to minimize the contaminants, manufacturers claim

the hot-gas-path components should last 30,000 to 40,000 hours of operation before

Increase in Efficiency over the years.


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replacement, particularly the hot-gas-path parts, that give rise to the relatively high

maintenance cost for gas turbines (typical O&M annual costs 5 percent of the capital

cost).

GAS TURBINE PLANT:

Introduction:

The gas turbine is a common form of heat engine working with a series of processes

consisting of compression of air taken from atmosphere, increase of working medium

temperature by constant pressure ignition of fuel in combustion chamber, expansion of SI

and IC engines in working medium and combustion, but it is like steam turbine in itsaspect of the steady flow of the working medium. It was in 1939, Brown Beaver

developed the first industrial duty gas turbine. The out put being 4000 KW with open

cycle efficiency of 18%. The development in the science of aerodynamics and metallurgy

significantly contributed to increased compression and expansion efficiency in the recent

years.

At Kawas, the GE-Alsthom make Gas Turbine (Model 9E) has an operating

efficiency of 31% and 49% in open cycle and combined cycle mode respectively when

natural gas is used as fuel. Today gas turbine unit sizes with output above 250 MW at

ISO conditions have been designed and developed. Thus the advances in metallurgical

technology have brought with a good competitive edge over conventional steam cycle

power plant.

Kawas Gas Turbine Plant:The modern gas turbine plants are commonly available in package form with few

functional sub assemblies.


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The 9E model GEC-Alsthom package consists of

Control compartment

Accessory compartment

Turbine compartment

Inlet exhaust system

Load package Generator excitation compartment

CO2 fire protection unit

Each station component is a factory assembled pretested assembly & is housed in all

weather & acoustic proof enclosure. Advantages of gas turbine plant

Some of the advantages are quite obvious, such as fast operation, minimum site investment.

Low installation cost owing to standardization, factory assembly and test. This makes the

installation of the station easy and keeps the cost per installed kilowatt low because the

package power station is quickly ready to be put in operation.

Site implementation includes one simple and robust structure to get unit alignment.

Transport: Package concept makes easier shipping, handling, because of its robustness.

Low standby cost: fast start up and shut down reduce conventional stand by cost.

The power requirements to keep the plant in standby condition are significantly lower than

those for other types of prime movers.

Maximum application flexibility: The package plant may be operated either in parallel with

existing plants or as a completely isolated station. These units have been used, widely for

base, peaking and even emergency service. The station can be equipped with remote control

for starting, synchronizing & loading.Control reliability: the microcomputer based control, with an integrated temperature system

(ITS) provides accurate control, quick protection and complete sequential start up & shut

down & operation. Maintenance Cost is comparatively low.

GAS TURBINE EQUIPMENT DATA SUMMARYCOMPRESSOR SECTION

Number of compressor stages Seventeen (17)

Compressor type Axial flow, heavy duty

Casing split Horizontal flange

Inlet guide vanes Modulated

TURBINE SECTION

Number of turbine stages Three (3)

Casing splits Horizontal

Nozzles Fixed area

COMBUSTION SECTION

Type Fourteen (14) multiple combustors, reverse flow design


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Fuel nozzles One (1) per combustion chamber i.e. (one for gas & one forliquid)

Spark plugs Two-(2) electrode type, spring-injected self-retracting.

Flame detectors Four (4),ultra-violet type

BEARING ASSEMBLIES

Quantity Three (3)

Lubrication Pressure lubrication

No.1 bearing assembly (Located in inletcasing assembly)

Active and inactive thrust and journal, all contained in oneassembly

Journal Elliptical

Active thrust Tilting pad, self-equalizing

Inactive thrust Tapered land

No.2 bearing assembly (Located in the

compressor discharge casing)

Elliptical journal

No.3 bearing assembly (Located in theexhaust frame)

Journal, tilting pad

STARTING SYSTEM

Starting device Electrical starting motor 1 MW drive

Torque converter Hydraulic with adjustor drive

Fuel pump Accessory gear-driven, Continuous out put screw type pump

Gas stop ratio & control valve Electro hydraulic servo-control

LUBRICATION SYSTEM

Lubricant Petroleum base

MOT capacity- 3,300 gallons (aprox.) i.e.12,540 litres (aprox.)

Main tube pump Shaft driven.

Emergency lube pump D.C. motor driven vertical submerged, centrifugal type

(88QE)

Auxiliary lube pump A.C. motor driven, vertical submerged, centrifugal (88QA)

Heat exchanger (s)Type Oil heat to fresh water

Quantity Two in parallel

Filter (s)

Type Full flow with transfer valve

Quantity Two (Duplex)

Cartridge type Five-micron filtration pleated paper.

HYDRAULIC SUPPLY SYSTEM

Main hydraulic supply pump Accessory gear-driven, variable positive displacement, axial

piston

Auxiliary hydraulic supply pump Driven by electric motor (88HQ), with accumulators- 2 nos.

COOLING WATER SYSTEM

Pumps Two water pumps located on lube oil tank inside theaccessory compartment.

Water cooling modules 15 nos. fans and finned tube radiators

CONTROL SYSTEM

SPEEDTRONIC MARK IV control system


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Gas Fuel SystemThe gas fuel system is designed to deliver gas fuel to the turbine combustion chamber at the

proper pressure and flow rates to meet all of the starting, acceleration and loading requirements of gasturbine operation. A schematic diagram of the gas fuel system is given in figure. The major components

of a gas fuel system are the gas stop/ratio and gas control valves located on the accessory base.Associated with the two gas valves are the necessary inlet piping strainer, fuel vent valve, control servovalves, pressure gauges and the distribution piping to the 14 combustion fuel nozzles. The fuel gas stop

ratio valve and the gas control valve, two independent valves, are located inside the gas fuel panel, of

the accessory base. The gas fuel flows through the gas stoop ratio valve and then into the gas controlvalve on its way to the gas manifold and individual combustion chambers. The position of each valve is

servo controlled by electrical signals from the gas turbine SPEEDTRONIC control system. Both the gas

stop ratio valve and gas control valve are actuated by single acting, hydraulic cylinders

The following major components comprise the gas fuel system:

Strainer

Fuel gas supply pressure alarm switch

Gas stop ratio valve VSR

Gas control valve VGC

Stop ratio LVDTS 96GC-1, 2

Stop ratio valve-control servo valve 90SR

Gas control valve- control servo valve 65 GC

Gas fuel dump valves VH5 and VH12

Gas fuel vent solenoid valve 20 VG-1 and 2

Pressure gauges

Lines to the 14 combustion chambers

Liquid Fuel System:The liquid fuel system pumps and distributes fuel as supplied from the off base forwarding

system, to the fourteen fuel nozzles of the combustion system. The fuel system filters the fuel and device

the fuel flow in to 14 equal parts for distribution to the combustion chamber at the required pressure andflow rates. Controlling the position of the fuel pump bypass valve VC3 regulates the amount of fuel

input to the turbine combustion system by varying the amount of bypassed fuel. The fuel system shownin the schematic diagram is comprised of the following major components plus several other control

devices, switches and gauge.

Temporary fuel oil strainer SFI

Fuel oil stop valve VSI. Liquid fuel pumps PFI.

Fuel pump discharge relief valve VR-4

Fuel bypass valve VC-3

High-pressure fuel strainer Fuel line check valve

Fuel nozzle assemblies

False start drain valve VA17-1 andVA17-2 (in bottom of combustion wrapper and exhaust frame)Control device also associated with the fuel system include the liquid fuel pressure switches 63 FL-2,

Servo valve 65 FP that controls the fuel bypass valve, fuel clutch solenoid 20 CF, and permissive limit

switches 33 FL-1 an2 and trip relay valve VH4 in the fuel oil stop trip control circuit.


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Atomizing Air SystemAtomizing air system provides sufficient pressure in the air atomizing chamber of the fuel nozzle

body to maintain the ratio of atomizing air pressure to compressor discharge pressure at approximately

1.2 or greater over the full operating range of the turbine. Since the output of the main atomizing air

compressor, driven by the accessory gear, is low at turbine firing speed, during starting, atomizing aircompressor provides a similar pressure ratio during the firing and warm up period of the starting cycle

and during a portion of the accelerating cycle. Continuous blow down to atmosphere is also provided toclear the main gas turbine compressor of accumulated dirt. Major system components include: the mainatomizing air compressor, starting air compressor, atomizing air heat exchanger and an air filter.

WASTE HEAT RECOVERY BOILER: (WHRB)The exhaust hot gases of the GT come to the Waste Heat Recovery Boiler (WHRB) if we do not

bypass them through bypass stack.

The WHRB produces superheated steam at Low & High pressures. The steam generator

comprises of an economizer, an evaporator with drum and a super heater section for both LP & HPsystems. Boiler used here in KGPP is waste heat recovery type which is generally denoted WHRB.

Waste heat recovery boiler general details:

The WHRB includes the following:

1. Water heater2. L.P economizer3. H.P economizer4. L.P evaporator5. H.P evaporator6. L.P super heater7. Two H.P super heater8. L.P & H.P drum

9. L.P & H.P circulating pumps10.Diverter damper11.Weather protection damper12.Bypass stack13.Chimney

Make : COCKERILL mechanical industries

Qty. installed : 4

Type : dual drum, assisted circulation, vertical

Unfired, dual pressure boilerTotal heating surface : H.P=655504sq.m

L.P=19938sq.m

Final temp of steam : H.P=520deg.C

L.P=109deg.COverall length : 15440mm

Design press : H.P=83bar

L.P=7.6bar


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STEAM TURBINE:Rankine Cycle :

Process 1-2 : Water from the condenser at low pressure is pumped into the boiler at highpressure.this process is reversible adiabatic.

Process 2-3: Water is converted into the steam at constant pressure by addition of heat inthe boiler.

Process 3-4 : Reversible adiabatic expansion of the steam in the steam turbine.

Process 4-1 : Constant pressure heat rejection in the condenser to convert condensate intowater.

The steam leaving the boiler may be dry and saturated, wet or superheated. The

corresponding T-S

Diagram are 1-2-3-4-1; 1-2-3-4-1; 1-2-3-4-1.


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Steam TurbineST operates at 3000 rpm. The steam is provided to ST through the two WHRBS

which are mounted at the exhaust of both the GT of each module. The single casing machine

is equipped with two admissions to take HP & LP steam from HP & LP drums. The axial

exhaust of ST is directly connected to the horizontally arranged 2 pass surface condenser.

Steam Bypass System

To increase operation and start-up flexibility of the plant, a steam bypass system is

integrated, which automatically goes into operation, if any of the following operation cases

occur:

a. ST start-up or shutdown,

b. Turbine trip

The steam bypass system is designed to handle the whole steam production at full

pressure under all ambient conditions. It consists of an isolating and a steam pressure

reducing valves with integrated water injection and the associated measurement, control

and protective devices. Injection water for desuperheating of the steam is taken from the

main condensate line.

Cooling Water System

A natural draught wet cooling tower system transposes the waste heat of the water steam

cycle to the atmosphere. Two 100% main cooling water pumps supply the cold water from the

cold-water basin to the main condensers and the intercoolers of the CCW system. The condenser

tubes in clean conditions.

Losses in the system are made up by clarified raw water. The cooling water quality is

controlled by the cooling water sampling water sampling and dosing station, where chemicals

can be dosed.

Closed Cooling Water System

A separate closed cooling water system for each unit ensures the cooling of the lube

oil system, the HP feed water pumps, the LP boiler preheated circulating pumps, the generator

air coolers, the sampling system, etc.

The heat is dissipated to the main cooling water system via 100% capacity water-to-

water heat exchanger.


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Losses in the system are made up by DM water from the DM water system. To achieve

a defined quality of the water, and inhibitor dosing station is connected to CCW system.

COOLING TOWER:

Cooling Towers have one function:

Remove heat from the water discharged from the condenser so that the water

can be discharged to the river or re circulated and reused.

Some power plants, usually located on lakes or rivers, use cooling towers as a method of

cooling the circulating water (the third non-radioactive cycle) that has been heated in the

condenser. During colder months and fish non-spawning periods, the discharge from the

condenser may be directed to the river. Recirculation of the water back to the inlet to the

condenser occurs during certain fish sensitive times of the year (e.g. spring, summer, and fall)so that only a limited amount of water from the plant condenser may be discharged to the

lake or river. It is important to note that the heat transferred in a condenser may heat the

circulating water as much as 40 degrees Fahrenheit (F). In some cases, power plants may

have restrictions that prevent discharging water to the river at more than 90 degrees F. In

other cases, they may have limits of no more than 5 degrees F difference between intake and

discharge (averaged over a 24 hour period). When Cooling Towers are used, plant efficiency

usually drops. One reason is that the Cooling Tower pumps (and fans, if used) consume a lot

of power.

Major Components

Cooling Tower (Supply) Basin

Water is supplied from the discharge of the Circulating Water System to a Distribution Basin,

from which the Cooling Tower Pumps take suction.

Cooling Tower Pumps

These large pumps supply water at over 100,000 gallons per minute to one or more Cooling

Towers. Each pump is usually over 15 feet deep. The motor assembly may be 8 to 10 feet

high. The total electrical demand of all the Cooling Tower pumps may be as much as 5% of

the electrical output of the station.

Cooling Towers

There are 2 types of towers - mechanical draft and natural draft

Natural Draft Cooling Tower

The green flow paths show how the warm water leaves the plant proper, is pumped to the

natural draft cooling tower and is distributed. The cooled water, including makeup from the

lake to account for evaporation losses to the atmosphere, is returned to the condenser.


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PLANT AT A GLANCE:

GAS TURBINE DESIGN EFFICIENCY

Heat Rate

(Kcal/Kwh)

Efficiency (%)

Open Cycle

Gas 2695 31.8

Liquid fuel 2730 31.4Combined Cycle

Gas 1741 49.23

Liquid fuel 1776 48.26

CONCLUSION

After analyzing the NTPC 656.2 MW combined cycle power plant, we can describe that this

power plant is very efficient one as compare to other power plant is very efficient. One as

compare to other power plants in its series. Also we would like to add up that it is very

compact in size, less pollute in nature, easily controlled and decent power plant that we had

ever seen

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