2. INTRODUCTION TO NTPC
Power Development
Although electric power generation in India on a commercial basis is almost a century old, substantial power
development efforts began only after independence. At the launch of the First Five-Year plan in 1951, power
generation was recognized as a major input for the country's economic development and was accorded high
priority. Power sector outlays have been among the highest in successive Five-Year Plans ever since. The first two
Plans focused on hydro power (as component of multi-purpose projects). Subsequent plans emphasized on rapid
installations of thermal power stations. As a result of Plan efforts, India's installed power generation capacity grew
to 16,664 MW in 1974. However, assessment of the planned growth since 1951 indicated that with the uneven
distribution of resources, power development with only States as spatial units, would result in large inter-state
imbalances. This, and the need for quicker and greater capacity addition, led the Government of India to assume a
leading role in large scale power generation as a matter of policy and, through an amendment of the Electricity
(Supply) Act, National Thermal Power Corporation Ltd. (NTPC) and National Hydroelectric Power Corporation Ltd.
(NHPC) were set up in the central sector to supplement the efforts of the States.
Consequently, total installed capacity of power utilities has increased from 1,362 MW in 1947 to 104918 MW in
March 2002. Electricity generation, which was only about 4.1 billion units in 1947, has risen to 515 billion units in
2001-02.
3. National Thermal Power Corporation Limited (NTPC) is the largest thermal power generating company of India. It was
incorporated in the year 1975 with the objective of planning, promoting and organizing an integrated development of
thermal power in the country. NTPC is a public sector company wholly owned by Govt. of India. Today NTPC has power
generating capacity in all the four major power regions of the country.
4. OPERATION
BADARPUR THERMAL POWER PLANT:
Approved Capacity: 705 MW
Installed Capacity: 705MW
Location: New Delhi
Coal Source: Jharia Coal Fields
Water Source: Agra Canal
Beneficiary States: Delhi
Unit Sizes:
3X95 MW
2X210 MW
Unit Commissioned:
Unit 95 MW - 1973-74
Unit II- 95 MW 1974-75
Unit III- 95 MW 1974-75
Unit IV - 210 MW 1978-79
Unit V - 210 MW - 1981-82
The Management of the Centrally owned Badarpur Thermal Power Station was handed over to NTPC on April 15, 1978.
5. Widescreen Pictures
Pictures can also be presented more dramatically in widescreen.
COAL TO ELECTRICITY
Basic Power Plant Cycle
The thermal (steam) power plant uses a dual (vapour + liquid) phase cycle. It is a closed cycle to enable the working fluid
(water) to be used again and again. The cycle used is "Rankine Cycle" modified to include super heating of steam,
regenerative feed water heating and reheating of steam.
On large turbines, it becomes economical to increase the cycle efficiency by using reheat, which is a way of partially
overcoming temperature limitations. By returning partially expanded steam, to a reheat, the average temperature at which
heat is added, is increased and, by expanding this reheated steam to the remaining stages of the turbine, the exhaust
wetness is considerably less than it would otherwise be conversely, if the maximum tolerable wetness is allowed, the initial
pressure of the steam can be appreciably increased.
Bleed Steam Extraction. For regenerative system, nos. of non-regulated extractions is taken from HP, IP turbine.
Regenerative heating of the boiler feed water is widely used in modern power plants; the effect being to increase the
average temperature at which heat is added to the cycle, thus improving the cycle efficiency.
6. BOILER MAINTENANCE DEPARTMENT
MAIN BOILER – BOILER FUNDAMENTALS
BOILERS
A boiler is an enclosed vessel that provides a means for combustion heat to be transferred into water until it becomes
heated water or steam. The hot water or steam under pressure is then usable for transferring the heat to a process.
Water is a useful and cheap medium for transferring heat to a process. When water is boiled into steam its volume
increases about 1,600 times, producing a force that is almost as explosive as gunpowder. This causes the boiler to be
extremely dangerous equipment that must be treated with utmost care. The process of heating a liquid until it reaches
its gaseous state is called evaporation. Heat is transferred from one body to another by means of (1) radiation, which is
the transfer of heat from a hot body to a cold body through a conveying medium without physical contact, (2)
convection, the transfer of heat by a conveying medium, such as air or water and (3) conduction, transfer of heat by
actual physical contact, molecule to molecule. The heating surface is any part of the boiler metal that has hot gases of
combustion on one side and water on the other. Any part of the boiler metal that actually contributes to making steam is
heating surface. The amount of heating surface a boiler is expressed in square meters. The larger the heating surface
a boiler has, the more efficient it becomes. The quantity of the steam produced is indicated in tons of water evaporated
to steam per hour.
7. Water tube or "water in tube" boilers in which the conditions are reversed with the water passing through the tubes and
the hot gasses passing outside the tubes (see figure 1.3). These boilers can be of single- or multiple-drum type. These boilers
can be built to any steam capacities and pressures, and have higher efficiencies than fire tube boilers.
8. Boiler structural:
The boiler structural is divided into two parts.
•Supporting Structure.
•Galleries and stair ways.
Supporting Structures:
Boilers supporting structure consists of a systematic arrangement of columns stiffened with horizontal beams and vertical
diagonal bracings and comprise of low carbon steel material. It is composed of 18 main columns and 12 auxiliary
columns. The main columns support the main boiler components viz. drum, water wall membranes, panels,
superheaters, reheaters, economisers, air preheater, burners and galleries at various levels. The auxiliary columns,
supports the boiler platforms and other ducts coming in that region. The total weight of supporting structures is about 970
M.T.
Galleries and stairways:
Galleries and stairways around the combustion and heat recovery areas are provided for proper approach to the boiler.
Stairways on both the side of Boiler are provided. All the floors are covered with floor gratings of required depth for
walkway and are tig welded to the structure. The total weight of Galleries and stairway are 900 M.T.
9. Boiler Drum:
The function of steam drum is to separate the water from the steam generated in the furnace walls and to reduce the
dissolved solid contents of the steam to below the prescribed limit of 1 ppm. The drum is located on the upper front of
boiler.
Economiser:
The purpose of economiser is to preheat the boiler feed water before it is introduced into the steam drum by recovering
heat from the flue gases leaving the boiler. The economiser is located in the boiler rear gas pass below the rear horizontal
superheater. The economiser is continuous unfinned loop type and water flows in upward direction and gas in the
downward direction.
Super Heater:
There are three stages of superheater besides the side walls and extended sidewalls. The first stage consists of horizontal
superheater of convection mixed flow type with upper and lower banks located above economiser assembly in the rear
pass. The upper bank terminates into hanger tubes, which are connected to outlet header of the first stage superheter. The
second stage superheater consists of pendant platen which is of radiant parallel flow type. The third stage supherheater
pendant spaced is of convection parallel flow type.
The outlet temperature and pressure of the steam coming out from the superheater is 540°C and 157 Kg/Cm2
respectively
for H.P. units.
10. Reheater:
The function of reheater is to reheat the steam coming out from high pressure turbine to a temperature of 540°C.
The reheater is composed of two sections.
•The front pendant section.
•Rear pendant section.
The rear pendant section is located above the furnace arc and the rear water wall and front pendant section is
located between the rear water hanger tubes and the superheater platen section.
Burners:
There are total twenty four pulverised coal burners for corner fired C.E. type boilers and twelve oil burners provided
each in between two pulverised fuel burner.
The pulverised coal burners are arranged in such a way that six mills supply the coal the burners at 4 corners, of the
furnace. All the nozzles of the burners are interlinked and can be tilted as a single unit from +30° to -30°C.
The oil burners are fed with heavy fuel oil till boiler load reaches to about 25%.
11. Plant Auxiliary Maintenance Department
Water Treatment Plant
Water treatment process which is generally made up of two sections:
Pretreatment section
Demineralisation section
Internal Treatment
This final D.M effluent is then either led to hot well of the condenser directly as make up to boilers, or being
stored in D.M. Water storage tanks first and then pumped for make up purpose to boiler feed.
As the D.M. Water has a good affinity to absorb carbon dioxide and oxygen, and both are extremely harmful to
metal surfaces for their destruction like corrosion, these have to be removed before it is fed to boiler. This is
being done in deaerator. Still the residual oxygen which is remaining in the water is neutralized by a suitable
doze of hydrazine, at the point after deaerator. To have further minimum corrosion, the pH of feed water is to be
maintained at around 9.0 for which purpose ammonia in suitable doze is added to this make up water at a point
along with hydrazine as stated above.
12. TURBINE COMPONENTS
The Turbine
The 210 MW turbine installed in our power stations is predominantly of condensing-tandom -compound, three
cylinder,- horizontal, disc and diaphragm, reheat type with nozzle governing and regenerative system of feed water
heating and is coupled directly with A. C. Generator
The various main components of the turbine are described in the following sections.
Turbine Casings
High Pressure Casing: The high pressure casing is made of creep resisting Chromium Molybdenum -vanadium (Cr-
Mo-V) steel casting. The top and bottom halves of the casing are secured together at the flange joint by heat tightened
studs to ensure an effective seal against steam leakage. Four steam chests, two on top and two on sides are welded to
the nozzle boxes, which in turn are welded to the casing at the middle bearing end. The steam chests accommodate four
control valves to regulate the flow of steam to the turbine according to the load requirement. Nozzle boxes and steam
chests are also made of creep resisting Cr-Mo-V steel castings.
13. Intermediate Pressure Casing: The intermediate pressure casing of the turbine is made of two parts. The front part is
made of creep resisting Chromium-Molybdenum-Vanadium steel castings and the exhaust part is of steel fabricated
structure. The two parts are connected by a vertical joint. Each part consists of two helves having a horizontal joint. The
horizontal joint is secured with the help of studs and nuts. These nuts and studs are made of creep resisting Cr-Mo-V steel
forgings. The control valves of I.P Turbine are mounted on the casing itself. In the intermediate pressure turbine the nozzle
boxes are cast integral with the casing, the first stage nozzle segment o IPT is a welded construction like other diaphragms
and in mounted directly in the casing. Next two diaphragms are also housed incasing while other 8 diaphragms are housed
in three liners which in turn are mounted in casing. From the intermediate pressure turbine, steam is carried through cross-
over pipes to the double flow low pressure cylinder. Each cross over pipe is provided with a compensator for taking care of
thermal expansion and to ensure that no heavy thrust or turning moments are thrown on to the flanged connections at the
intermediate pressure cylinder exhaust and the low pressure cylinder inlet.
Low Pressure Casing: The L.P. casing consists of three parts i.e. one middle part and two exhaust parts. The three
parts are fabricated from weldable mild steel the exhaust casings are bolted to the middle casings by a vertical flange. The
casings are divided in the horizontal plane through the turbine centre line. The lower half of the L.P. casing has an integral
bearing pedestal.
14. MAINTENANCE AND PLANNING DIVISION
Not withstanding the ruggedness that is in the machine, a little care at periodic intervals will ensure a trouble
free service and prevent breakdowns, also avoid loss of maintenance and shut down. It is always worthwhile a
log book for each motor, where in various reading are entered daily and details of any major and minor overhaul
listed maintenance schedules could be broadly divided into seven categories:
•Routine maintenance.
•Periodic maintenance.
•Capital maintenance.
•Breakdown maintenance.
•Preventive maintenance.
•Opportunity maintenance.
•Predictive maintenance.
15. Training Work
On site demonstration of removal of waste log of wood from the Water Treatment Plant under the
supervision of Head of WTP department, Mr. Pratap Singh.
Demonstration of the working of steam nozzle illustrating the flow of stream under the supervision
of Head of Boiler Maintenance Department, Mr. Gyanendra Singh
Annual Maintenance of NTPC plant conducted by the Maintenance and Planning Division Dept.
under the supervision of Head MPD, Mr. Mahindra Singh demonstrating the maintenance of
Condenser walls and Turbine Blades maintained under the Turbine Maintenance Department.
