IN-PLANT TRAINING PROJECT REPORT
ON
Submitted by
Banpreet Singh Sodhi 2. Char Charan an kum kumar ar 3. Shri Shrika kant nt Sing Singh h 4. Satish 5. Ashi Ashish sh Gadka Gadkari ri 1.
NATIONAL POWER TRAINING I NSTITUTE NAGPUR
THE TWO STAGES IN KTPS:-
Stage 1: Unit1-115 MW Unit 2-115 MW Unit 3-115 MW Unit 4-115 MW Stage 2: Unit 5-210MW Unit 6-210MW Unit7-210MW
KTPS UNIT DETAILS: U. No.
Inst.Capacity in MW
Derated Capacity
Present capacity:1 capacity:1080MW 080MW Date of Commi.
Make Boiler
T.G.
1
120
115
03.06.1974
ABL
Zamech
2
120
115
24.03.1975
ABL
Zamech
3
120
115
03.03.1976
ABL
Zamech
4
120
115
22.07.1976
ABL
Zamech
5
200
200
15.07.1978
Russian
6
210
210
30.03.1982
7
210
210
13.01.1983
CE Through BHEL --do— --do--
Russian Russian
SCENARIO OF POWER INDUSTRY IN INDIA Indian electricity act: The first supply undertaking in the country was sponsored by a company in the year 1896 which constructed a small generating station at Surat in Gujarat. The electricity legislation was first made in India in 1887 based on English framework, which was modified time-to-time. Then after independence this act was reinforced by the provisions of Indian (supply) Act 19 48. Recently government has enacted Electricity Act, 2003, which replaces all above acts.
Growth of Power Industry: The growth of installed capacity since independence till year 2003 is shown in fig. below.
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In 1947 when India became independent the installed capacity was merely 1364 MW. Out of these 63% was contributed by private companies and balance 37% by govt. undertakings. About 78% power was generated from oil.
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After 1955 the electricity boards were performed by State Governments and most of the small private powers generating companies were merged into these boards.
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The real growth of power industry started from 1960 o nwards and jumped up exponentially from 1970 onwards. This is because o f the large scale industrialization taking place in process industries and textile sector.
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The major break through in the power industry was achieved in 1975 with the formation of National Thermal Power Corporation (NTPC) and National Hydro Electric Power Corporation (NHPC), the Central Government PSUs.
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The remarkable rise of installed capacity took place after 1990 due to opening of utility power generation sector to private companies. Similarly thrust was given to install captive power plants by power intensive industries (cement, steel, textile etc.). the licensing policy was further liberalized.
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The present installed capacity is about 108000 MW, inclusive of generation by all sectors.
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The share of NTPC is almost 22000MW.
SECTOR WISE BREAK-UP Figure below shows the break-up of installed capacity sector-wise. As shown in the figure, the majority of power generation in India i.e. 67% is contributed by coal, fired thermal power stations. The hydro power stations contribute only 21% against the potential of 84000MW. The nuclear power generation, which is at present 3%, may rise to about 8% by the year 2010.
Highlights of Power position Peak load demand
:120000 MW
Present Power Generation
:105000 MW
Peak Power Deficit
:15%
Average Plant Load Factor on all India basis :64%
Resources Potential in India for Power Generation Coal reserves
:84000 Million Tons
Lignite
:5000 Million Tons
Crude oil
:84000 MW
Hydro
:728 Million Tons
Natural gas
:686 Billion Tons
Uranium
:6700 Tons
Thorium
:363000 Tons
Solar + Wind
:20000 MW
Biomass
:6000 MW
BOILER AND ITS AUXILLIARIES 1. Principles of steam generation. 2. Boiler drum. 3. Water wall tubes. 4. Super heaters. 5. Reheaters. 6. Economizers.
7. Electro-static precipitators. 8. Coal mill (bowl type). 9. Air pre heaters.
10.
ID fan.
11.
FD fan.
12. Chimney.
13.
PA fan.
14. Wind box. 15. Soot blowers.
PRINCIPLES OF STEAM GENERATION. Steam generation is the process of converting water into steam, a vapor exhibiting the properties of a gas by application of heat. Heating water at any pressure eventually will cause it to boil and steam will be released. For effecting steam generation, it is essential to transfer heat from a source to the water. Heat in boilers is transferred by all of the following modes during combustion: 1. Conduction 2. Convection 3. Radiation
A boiler, which provides steam of large quantity, must have sufficient heating surface. The heating surfaces are in the form of round tubes. Through these tubes placed in heating zones, water or steam will be circulated to receive sensible heat, latent heat and superheat. A boiler will have number of circuits of heating surfaces such as economizer, water walls, boiler bank, super-heater and re-heater for efficiently transferring the heat of combustion to the water and steam. They may absorb heat either by radiation, convection or both.
BOILER DURM AND ITS INTERNALS. In the erection of a power boiler, the lifting of the boiler drum is the first mile stone activity. Functions of the boiler: (a). Separation of saturated steam from the steam-water mixture produced by the evaporating tubes. (b). Mixing feed water from economizer and water separated from steam-water mixture, and re-circulate through the evaporating tubes. (c). Carrying out blow down for reduction of boiler water salt concentration. (d). Treatment of boiler water by chemicals. As the quantity of water contained in the drum below the water level is relatively small compared to the total steam output, the function of water storage in the drum is not significant. The boiler drum is generally made of carbon steel; located at the top of the boiler. The higher elevation at which the drum is located provides the necessary head for circulation and facilitates the natural circulation in the evaporating tubes of the boiler. INTERNALS:- Inside the boiler drum a number of fittings are installed to carryout various functions. Following components together are termed as drum internals. •
Feed header
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Anti vortex spider or vortex inhibitors
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Steam separators
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Steam dryers or scrubbers
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C.B.D. line
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E.B.D. line
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Chemical dozing line
WATER WALL TUBES Evaporator tubes, called as the water walls running from bottom ring header to riser tubes, line the furnace walls from inside. The water walls absorb the heat from fire ball by radiation due to which temperature of flue gases is restricted below ash fusion temperature to prohibit the melting of fly ash. Also the temperature of furnace walls is brought down to evaporation temperature by water cooling effect and so the refractory thickness is reduced drastically.
SUPER HEATERS The steam separated and given out by the boiler drum is only in dry saturated condition. For many applications, especially for running a turbine, on efficiency aspects the steam must be in superheated condition. To meet this requirement the boilers are provided with separate tube circuits in the flue gas path. These heat transfer areas are termed as super heaters. When the saturated steam from the drum is circulated through the tubes of super heaters the steam temperature increases.
REHEATERS. Re haters are provided only in boilers supplying steam to large capacity steam turbines (capacity more than 100Mwe). Like super heaters, re heaters are also heating surfaces in the flue gas path meant for heating the steam. The difference is, in re heaters the steam brought back at low pressure from the turbine is heated to a higher temperature before returning back to the turbine. This is required for improving cycle efficiency.
ECONOMISER. Economizers are provided in the boilers to improve the efficiency of the boiler by extracting the heat from flue gases and add it as either sensible heat alone or sensible heat and latent heat to feed water before the water enters the evaporating surface of the boiler.
ADVANTAGES:- Provision of economizer in a boiler brings in two major advantages . 1. As the economizer recovers the heat in the flue gas that leaves the boiler and transfer to working fluid there will be savings in fuel consumption. 2. As the feed water is preheated in the economizer and enters the
boiler tubes at an elevated temperature (near to saturation temperature) the heat transfer area required for the evaporation surface required will be reduced considerably. As such the size of boiler will also be reduced.
ELECTRO STATIC PRECIPITATOR
WORKING PRINCIPLE:- The principles upon which an electrostatic precipitator operates are that the dust laden gases pass into a chamber where the individual particles of dust are given an electric charge by absorption of free ions from a high voltage DC ionising field. Electric forces cause a stream of ions to pass from the discharge electrodes to the collecting electrodes and the particles of dust entrained in the gas are deflected out of the gas stream into the collected surfaces where they are retained either by electrical or molecular attraction. They are removed by an intermittent blow usually referred as rapping. This causes the dust particles to drop into dust hoppers situated below the collecting electrodes.
DESCRIPTION:- The electrostatic precipitator essentially consist of two sets of electrodes, one in form of thin wires called discharge or emitting electrodes and other set called collecting electrodes in form of pipes or plates. The emitting electrodes are placed in centre of pipes or midway between two plates and are connected usually to negative polarity of high voltage DC source of order 25-100 kV. The collecting electrodes are connected to the positive of source and grounded.
COAL MILL. Coal mill (bowl type) is a vertical spindle medium mill. In a bowl mill the coal is pulverized between a disc called bowl rotated by the drive assembly and rollers kept above the disc loaded by springs or pneumatic or hydraulic loading devices. The coal mill works under pressure, to prevent the entry of dust laden air to the gear box a sealing arrangement is provided. The mill has three grinding roll assemblies called roller journal assemblies.
ADVANTGES: low power consumption Reliability, Min. maintenance Ability to handle wide range of coals.
AIR HEATERS Air heater is an important boiler auxiliary, which primarily preheats the combustion air for rapid and efficient combustion in the furnace. The air heater recovers the waste heat from the outgoing flue gas of a boiler and transfers the same to the combustion air. In an utility boiler the flue gas leaves the economizer at a temperature of around 380degree C. as every 55 degree drop in the flue gas temperature improves the boiler efficiency by about 2.5%, having an air heater in the downstream of economizer the boiler efficiency is considerably improved. Further the air heater may also be used for heating the air to dry the coal in the pulverizing plant .
INDUCED DRAFT FAN Induced draft fans evacuate combustion products from the boiler furnace by creating the negative pressure to establish a slight suction in the furnace (usually 5-10 mm). these fans must have enough capacity to accommodate any infiltration caused by the negative pressure in the equipment downstream of the furnace and by any seal leakage in air heaters. As ID fans are now typically located downstream of any particulate removal system they are relatively clean service fan. Since ID fans have to compensate for heavy pressure drop of flue gas across boiler contour, the power requirement is very high and it is the boiler auxiliary, which consumes maximum ower. As such high efficiency fans are demanded for this application. The airfoil radial fans, which have efficiencies of more than 88% and can, have capacities greater than 1.6 lakh m3 /min. the airfoil blade shape minimizes turbulence and noise. The blades and centre plates
may also be fitted with wear plates and replaceable nose section for greater wear life.
FORCED DRAFT FAN Forced draft fans supply air necessary for fuel combustion and must be sized to handle the stoichiometric air plus the excess needed for proper burning of the specific fuel. In addition, they provide air to make up for air heater leakage and for some sealing air requirements. FD fans supply the total airflow except when an atmospheric suction primary air fan is used. FD fans operate in the cleanest environment associated with a boiler and are generally the quietist and most efficient fans in the power plant. They are particularly well suited for high speed operation. radial aerofoil or variable pitch axial fans are preferred for FD service.
PRIMARY AIR FAN These are the large high pressure fans which supply the air needed to dry and transport coal either directly from the coal mills to the furnace or to the intermediate bunker. These fans may be located before or after the milling equipment. The most common applications are cold primary air fans, hot primary air fans and pulverizer exhauster fans.
CHIMNEY Though in natural circulation boilers, the Chimney creates the draught in the boiler, in large boilers where mechanized draught system is adopted the function of a Chimney is largely limited to discharge flue gases to the atmosphere at such height and velocity that the concentration of pollutants is kept within acceptable limits at ground level. The pollutants exiting from the chimney must first clear the area of turbulent air created by the wind around the chimney top. To ensure this height of the chimney is sufficiently high above the boiler house or near by buildings and the gases are emitted with sufficient upward velocity. Generally the height of the chimney is decided based on the concentration of pollutants in the flue gas, emission standards, wind velocity, location of the plant etc.
WIND BOX The wind box assembly is installed at each corner of the furnace in a tangentially fired system. The wind box is vertically divided into number of compartments which are provided with coal nozzles, air nozzles and fuel oil nozzles alternately.
SOOT BLOWERS Soot blowers are the devices, which admit the blowing medium over the heating surfaces. Soot blowers are made according to the surface they have to clean. The soot blowers for water walls are called wall blowers or deslaggers. Long retracts and half retracts are used for super heaters, reheaters and economizers. Rotary air heaters are provided swivel blowers. The exact mechanism of a blower depends on the manufacturer.
BOILER CONSTRUCTION
HISTORY OF BOILERS:
Boiler means any closed vessel exceeding 22.75 liters in capacity used for steam generation under pressure. The first Boiler was developed in 1725 & it’s working pressure was 6 to 10 kg/cm2 and was called Wagon Boiler.
TYPES OF BOILERS: There are two types of Boilers : 1) Fire tube boilers (Carnish & Lauchashire blrs.) developed in the year 1844 2) Water tube boilers developed in the year 1873. Water tube Boilers are used in Thermal Bower stations. These are sub divided according to water circulation
1) Natural circulation :
Drum to down comers to ring main header to water wall tubes & back to drum. Due to difference in density of water and steam this type of circulation takes place. 2) Forced circulation :
As operating pressure of the boiler approaches to the critical pressure, additional pumps are required to install in down comers, because at this pressure there is no appreciable density difference between water and steam to have a natural circulation of water.
According to working pressure the Boiler, Boilers are classified as: 1) Drum type sub critical pressure boiler: When working pressure of the boiler is between 130 kg/cm2 and 180 kg/cm2, the boiler is called as, “Drum type sub critical pressure boiler”.
2) Critical pressure Boilers : When boiler working pressure is 221.2 kg/cm2, it is termed as, “Critical pressure Boilers”. 3) Super critical or drum less once through boilers: When boiler working pressure is 240 kg/cm2, it is called as, “Super critical”. All modern Boilers are top slung from steel structures. From the beams a series of slings take up the boiler loads. Approximately suspended weight of one 210 MW boiler is 3640 metric tones. Height of Boiler is about 64 meters and Boiler drum is at a height of 52 meters from the ground.
Boiler design consideration : Following factors are taken into consideration for designing the modern boiler. 1) Lowest capital cost, ease of construction, simplicity, safety, good working condition, ease of maintenance. 2) Efficient operation, effective baffling for heat transfer, well insulated casings, ability to deliver pure steam with effective drum internals to generate steam of fuall capacity. 3) Availability of auxiliaries.
Period of constructions : In India the Boiler is being constructed in three years i.e. 36 months.
References: •
NPTI manual
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Encarta
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Wikipedia search
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www.mahagenco.com
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