Principles of Energy Conversion

Thermal Power Plant Visit

Report

Submitted By

1. Krishna Walse (B12121)

2. Mohit Bhatia (B12109)

3. Nikhil Kayathwal (B12106)

4. Abhishek Badwan (B12132)

Introduction

Guru Gobind Singh Super Thermal Power Station is situated near village Ghanauli

on Ropar-Kiratpur Sahib National highway NH-21. It is about 12 km from Ropar

and 55 km from Chandigarh. The plant has an installed capacity of 1260 MW. The

first unit was commissioned in September, 1984. During March 1985, the second

unit was commissioned and in later years four more units were added.

The station received the Incentive award for reducing fuel oil consumption in 1999.

The station also received the Shield and excellent performance by Prime minister

of India during 1986-87 for achieving 70.08% PLF against then 53.2%. The plant

has its source of water supply from Nangal Hydel Channel. The coal used mainly

comes from mines in Bihar, West Bengal and Madhya Pradesh from more than 50

sources called collieries.

Salient Features of the Power Plant

1. Location Ropar, about 50 km from Chandigarh on Chandigarh Nangal highway no.21 near Ghanauli village railway station

2. No. of Houses 06

3. No. of Units 06

4. Total Generation Capacity 210*6 = 1260 MW

5. Source of Water Supply From Nangal hydel channel

6. Fuel used Coal from coal fields of Bihar, West Bengal and Madhya Pradesh more than 50 sources called collieries. Distances of these sources is between 1417 km & 1560 km.

7. Turbine 210 MW 3 cylinder mix flow tandem coupled 3000 rpm BHEL make.

8. Generator 247 MVA, 15.75 kV, 9050 A at .82 lag, 50 Hz, double star two pole

9. Commissioning Unit 1 = 26/09/84 Unit 2 = 29/03/85 Unit 3 = 31/03/88 Unit 4 = 29/01/89 Unit 5 = 29/03/92 Unit 6 = 30/03/93

10. Cost of Project Stage 1 Rs 380 Crores Stage 2 Rs 438 Crores Stage 3 Rs 599 Crores

11. Total Energy Contribution Anually

6942 MUs

12. Cost per Unit Rs 1.84

Main Systems in Power Plant

1. Cooling Tower

2. Transmission Line

3. Transformer

4. Electric Generator

5. Steam Turbine

6. Condensate Pump

7. Surface Condenser

8. Deaerator

9. Feed water Heater

9. Coal Pulverizer

10. Super heater

11. Economizer

12. Air preheater

13. Precipitator

Cooling Tower

A cooling tower is a heat rejection device which extracts waste heat to

the atmosphere through the cooling of a water stream to a lower temperature.

Cooling towers may either use the evaporation of water to remove process heat

and cool the working fluid to near the wet-bulb air temperature or, in the case

of closed circuit dry cooling towers, rely solely on air to cool the working fluid to

near the dry-bulb air temperature.

Following are the types of cooling tower.

1. Natural Draft

Utilizes buoyancy via a tall chimney. Warm, moist air naturally rises due to the

density differential compared to the dry, cooler outside air. Warm moist air is less

dense than drier air at the same pressure. This moist air buoyancy produces an

upwards current of air through the tower.

2. Mechanical Draft

Uses power-driven fan motors to force or draw air through the tower.

3. Induced Draft

A mechanical draft tower with a fan at the discharge (at the top) which pulls air up

through the tower. The fan induces hot moist air out the discharge. This produces

low entering and high exiting air velocities, reducing the possibility of

recirculation in which discharged air flows back into the air intake. This fan/fin

arrangement is also known as draw-through.

4. Forced Draft

A mechanical draft tower with a blower type fan at the intake. The fan forces air into the tower, creating high entering and low exiting air velocities. The low exiting velocity is much more susceptible to recirculation. With the fan on the air intake, the fan is more susceptible to complications due to freezing conditions. Another disadvantage is that a forced draft design typically requires more motor horsepower than an equivalent induced draft design. The benefit of the forced draft design is its ability to work with high static pressure. Such setups can be installed in more-confined spaces and even in some indoor situations. This fan/fill geometry is also known as blow-through.

5. Fan Assisted Natural Draft

A hybrid type that appears like a natural draft setup, though airflow is assisted by a fan.

Structural Stability

Being very large structures, cooling towers are susceptible to wind damage, and several spectacular failures have occurred in the past. At Ferry bridge power station on 1 November 1965, the station was the site of a major structural failure, when three of the cooling towers collapsed owing to vibrations in 85 mph (137 km/h) winds. Although the structures had been built to withstand higher wind speeds, the shape of the cooling towers caused westerly winds to be funneled into the towers themselves, creating a vortex. Three out of the original eight cooling towers were destroyed, and the remaining five were severely damaged. The towers were later rebuilt and all eight cooling towers were strengthened to tolerate adverse weather conditions. Building codes were changed to include improved structural support, and wind tunnel tests were introduced to check tower structures and configuration.

Transmission Lines

Electric-power transmission is the bulk transfer of electrical energy, from

generating power plants to electrical substations located near demand centers.

This is distinct from the local wiring between high-voltage substations and

customers, which is typically referred to as electric power distribution.

Transmission lines, when interconnected with each other, become transmission

networks. The combined transmission and distribution network is known as the

"power grid" in the United States, or just "the grid". In the United Kingdom, the

network is known as the "National Grid".

Overhead Transmission

High-voltage overhead conductors are not covered by insulation. The conductor

material is nearly always an aluminum alloy, made into several strands and

possibly reinforced with steel strands. Copper was sometimes used for overhead

transmission, but aluminum is lighter, yields only marginally reduced performance

and costs much less. Overhead conductors are a commodity supplied by several

companies worldwide. Improved conductor material and shapes are regularly used

to allow increased capacity and modernize transmission circuits.

High Voltage Direct Current

High-voltage direct current (HVDC) is used to transmit large amounts of power

over long distances or for interconnections between asynchronous grids. When

electrical energy is to be transmitted over very long distances, the power lost in AC

transmission becomes appreciable and it is less expensive to use direct

current instead of alternating current. For a very long transmission line, these lower

losses (and reduced construction cost of a DC line) can offset the additional cost

of the required converter stations at each end.

Transformer

A transformer is an electrical device that transfers energy between two or more

circuits through electromagnetic induction.

A varying current in the transformer's primary winding creates a varying magnetic

flux in the core and a varying magnetic field impinging on the secondary winding.

This varying magnetic field at the secondary induces a varying electromotive

force (emf) or voltage in the secondary winding. Making use of Faraday's Law in

conjunction with high magnetic permeability core properties, transformers can thus

be designed to efficiently change AC voltages from one voltage level to another

within power networks.

Energy Losses

Real transformer energy losses are dominated by winding resistance joule and

core losses. Transformers' efficiency tends to improve with increasing transformer

capacity. The efficiency of typical distribution transformers is between about 98

and 99 percent.

Cooling

To place the cooling problem in perspective, the accepted rule of thumb is that the

life expectancy of insulation in all electric machines including all transformers is

halved for about every 7 C to 10 C increase in operating temperature, this life

expectancy halving rule holding more narrowly when the increase is between

about 7 C to 8 C in the case of transformer winding cellulose insulation.

Transformers are generally cooled using fans.

Electric Generator

In electricity generation, a generator is a device that converts mechanical

energy to electrical energy for use in an external circuit. The source of mechanical

energy may vary widely from a hand crank to an internal combustion engine.

Generators provide nearly all of the power for electric power grids. The reverse

conversion of electrical energy into mechanical energy is done by an electric

motor, and motors and generators have many similarities. Many motors can be

mechanically driven to generate electricity and frequently make acceptable

generators.

Armature

The power-producing component of an electrical machine. In a generator,

alternator, or dynamo the armature windings generate the electric current. The

armature can be on either the rotor or the stator.

Field

The magnetic field component of an electrical machine. The magnetic field of the

dynamo or alternator can be provided by either electromagnets or permanent

magnets mounted on either the rotor or the stator.

Principle

The operating principle of electromagnetic generators was discovered in the years

of 18311832 by Michael Faraday. The principle, later called Faraday's law, is that

an electromotive force is generated in an electrical conductor which encircles a

varying magnetic flux.

Steam Turbine

A steam turbine is a device that extracts thermal energy from

pressurized steam and uses it to do mechanical work on a rotating output shaft. Its

modern manifestation was invented by Sir Charles Parsons in 1884. Because the

turbine generates rotary motion, it is particularly suited to be used to drive

an electrical generator about 90% of all electricity generation in the United States

(1996) is by use of steam turbines. The steam turbine is a form of heat engine that

derives much of its improvement in thermodynamic efficiency from the use of

multiple stages in the expansion of the steam, which results in a closer approach

to the ideal reversible expansion process.

Principle of Operation and Design

An ideal steam turbine is considered to be an isentropic process, or constant

entropy process, in which the entropy of the steam entering the turbine is equal to

the entropy of the steam leaving the turbine. No steam turbine is truly isentropic,

however, with typical isentropic efficiencies ranging from 2090% based on the

application of the turbine. The interior of a turbine comprises several sets of blades

or buckets. One set of stationary blades is connected to the casing and one set of

rotating blades is connected to the shaft. The sets intermesh with certain minimum

clearances, with the size and configuration of sets varying to efficiently exploit the

expansion of steam at each stage.

Condensate Pump

A condensate pump is a specific type of pump used to pump

the condensate (water) produced in an HVAC (heating or

cooling),refrigeration, condensing boiler furnace or steam system.

Construction and Operation

Condensate pumps as used in hydronic systems are usually electrically

powered centrifugal pumps. As used in homes and individual heat exchangers,

they are often small and rated at a fraction of a horsepower, but in commercial

applications they range in size up to many horsepower and the electric motor is

usually separated from the pump body by some form of mechanical coupling.

Large industrial pumps may also serve as the feed water pump for returning the

condensate under pressure to a boiler.

Steam Condensate

In industrial steam systems the condensate pump is used to collect and return

condensate from remote areas of the plant. The steam produced in the boiler can

heat equipment and processes a considerable distance away. Once steam is used

it turns to hot water or condensate. This pump and possibly many more around the

plant returns this hot water back to a make-up tank closer to the boiler, where it

can be reclaimed, chemically treated, and reused, in the boiler, consequently it can

sometimes be referred to as a condensate return pump.

Condenser

A condenser is a commonly used term for a water-cooled shell and tube heat

exchanger installed on the exhaust steam from a steam turbine in thermal power

stations. These condensers are heat exchangers which convert steam from its

gaseous to its liquid state at a pressure below atmospheric pressure. Where

cooling water is in short supply, an air-cooled condenser is often used. An air-

cooled condenser is however, significantly more expensive and cannot achieve as

low a steam turbine exhaust pressure (and temperature) as a water-cooled surface

condenser.

Requirement

The steam turbine itself is a device to convert the heat in steam to

mechanical power. The difference between the heat of steam per unit mass at the

inlet to the turbine and the heat of steam per unit mass at the outlet from the turbine

represents the heat which is converted to mechanical power. Therefore, the more

the conversion of heat per pound or kilogram of steam to mechanical power in the

turbine, the better is its efficiency. By condensing the exhaust steam of a turbine

at a pressure below atmospheric pressure, the steam pressure drop between the

inlet and exhaust of the turbine is increased, which increases the amount of heat

available for conversion to mechanical power. Most of the heat liberated due

to condensation of the exhaust steam is carried away by the cooling medium

(water or air) used by the surface condenser.

Deaerator

A deaerator is a device that is widely used for the removal of oxygen and other

dissolved gases from the feed water to steam-generating boilers. In particular,

dissolved oxygen in boiler feed waters will cause serious corrosion damage in

steam systems by attaching to the walls of metal piping and other metallic

equipment and forming oxides (rust). Dissolved carbon dioxide combines with

water to form carbonic acid that causes further corrosion. Most deaerators are

designed to remove oxygen down to levels of 7 ppb by weight (0.005 cm/L) or

less as well as essentially eliminating carbon dioxide.

Tray Type Deaerator

Boiler feed water enters the vertical deaeration section above the

perforated trays and flows downward through the perforations. Low-pressure

deaeration steam enters below the perforated trays and flows upward through the

perforations. Some designs use various types of packed bed, rather than

perforated trays, to provide good contact and mixing between the steam and the

boiler feed water.

Spray Type Deaerator

The boiler feed water is sprayed into section where it is preheated by the rising

steam from the sparger. The purpose of the feed water spray nozzle and the

preheat section is to heat the boiler feed water to its saturation temperature to

facilitate stripping out the dissolved gases in the following deaeration section.

Feed Water Heater

A feed water heater is a power plant component used to pre-heat water delivered

to a steam generating boiler. Preheating the feed water reduces the irreversibilities

involved in steam generation and therefore improves the thermodynamic

efficiency of the system. This reduces plant operating costs and also helps to

avoid thermal shock to the boiler metal when the feed water is introduced back into

the steam cycle. In a steam power plant (usually modeled as a modified Rankine

cycle), feed water heaters allow the feed water to be brought up to the saturation

temperature very gradually. This minimizes the inevitable irreversibilities

associated with heat transfer to the working fluid (water). See the article on

the Second Law of Thermodynamics for a further discussion of such

irreversibilities.

Types

Feed water heaters can also be "open" or "closed" heat exchangers. An open heat

exchanger is one in which extracted steam is allowed to mix with the feed water.

This kind of heater will normally require a feed pump at both the feed inlet and

outlet since the pressure in the heater is between the boiler pressure and

the condenser pressure. A deaerator is a special case of the open feed water

heater which is specifically designed to remove non-condensable gases from the

feed water.

Coal Pulverizer

A pulverizer or grinder is a mechanical device for the grinding of many different

types of materials. For example, a pulverizer mill is used to pulverize

coal for combustion in the steam-generating furnaces of fossil fuel power plants.

Types

1. Ball and Tube Mill

A ball mill is a pulverizer that consists of a horizontal rotating cylinder, up to three

diameters in length, containing a charge of tumbling or cascading steel balls,

pebbles, or rods. A tube mill is a revolving cylinder of up to five diameters in length

used for fine pulverization of ore, rock, and other such materials; the material,

mixed with water, is fed into the chamber from one end, and passes out the other

end as a slurry.

2. Ring and Ball Mill

This type of mill consists of two types of rings separated by a series of large balls,

like a thrust bearing. The lower ring rotates, while the upper ring presses down on

the balls via a set of spring and adjuster assemblies, or pressurised rams. The

material to be pulverized is introduced into the center or side of the pulverizer

(depending on the design). As the lower ring rotates, the balls to orbit between the

upper and lower rings, and balls roll over the bed of coal on the lower ring. The

pulverized material is carried out of the mill by the flow of air moving through it.

The size of the pulverized particles released from the grinding section of the mill is

determined by a classifier separator. If the coal is fine enough to be picked up by

the air, it is carried through the classifier. Coarser particles return to be further

pulverized.

3. Vertical Spindle Roller Mill

Raw coal is gravity-fed through a central feed pipe to the grinding table where it

flows outwardly by centrifugal action and is ground between the rollers and table.

Hot primary air for drying and coal transport enters the wind box plenum

underneath the grinding table and flows upward through a swirl ring having multiple

sloped nozzles surrounding the grinding table. The air mixes with and dries coal in

the grinding zone and carries pulverized coal particles upward into a classifier.

Super Heater

A super heater is a device used to convert saturated steam or wet steam into dry

steam used in steam engines or in processes, such as steam reforming. There are

three types of super heaters namely: radiant, convection, and separately fired. A

super heater can vary in size from a few tens of feet to several hundred feet (a few

metres to some hundred metres).

Steam Engines

In a steam engine, the super heater re-heats the steam generated by the boiler,

increasing its thermal energy and decreasing the likelihood that it

will condense inside the engine. Super heaters increase the thermal efficiency of

the steam engine, and have been widely adopted. Steam which has been

superheated is logically known as superheated steam; non-superheated steam is

called saturated steam or wet steam. Super heaters were applied to steam

locomotives in quantity from the early 20th century, to most steam vehicles, and to

stationary steam engines. This equipment is still used in conjunction with steam

turbines in electrical power generating stations throughout the world.

Economizer

Economizers (US and Oxford spelling), or economizers (UK), are mechanical

devices intended to reduce energy consumption, or to perform useful function such

as preheating a fluid. The term economizer is used for other purposes as

well. Boiler, power plant, heating, ventilating, and air conditioning (HVAC) uses are

discussed in this article. In simple terms, an economizer is a heat exchanger.

Use in Power Plants

Modern-day boilers, such as those in coal-fired power stations, are still fitted with

economizers which are descendants of Green's original design. In this context they

are often referred to as feed water heaters and heat the condensate from turbines before it is pumped to the boilers. Economizers are commonly used

as part of a heat recovery steam generator in a combined cycle power plant. In an

HRSG, water passes through an economizer, then a boiler and then a super heater. The economizer also prevents flooding of the boiler with liquid water that

is too cold to be boiled given the flow rates and design of the boiler.

Refrigeration

Another use of the term occurs in industrial refrigeration, specifically vapor-

compression refrigeration. Normally, the economizer concept is applied when a

particular design or feature on the refrigeration cycle, allows a reduction either in

the amount of energy used from the power grid; in the size of the components

(basically the gas compressors nominal capacity) used to produce refrigeration, or both.

Air Preheater

An air preheater (APH) is a general term used to describe any device designed to

heat air before another process (for example, combustion in a boiler) with the

primary objective of increasing the thermal efficiency of the process. They may be

used alone or to replace a recuperative heat system or to replace a steam coil.

The purpose of the air preheater is to recover the heat from the boiler flue

gas which increases the thermal efficiency of the boiler by reducing the useful heat

lost in the flue gas. As a consequence, the flue gases are also conveyed to the flue

gas stack (or chimney) at a lower temperature, allowing simplified design of the

conveyance system and the flue gas stack. It also allows control over the

temperature of gases leaving the stack (to meet emissions regulations, for

example).

Tubular Type

Tubular preheaters consist of straight tube bundles which pass through the outlet

ducting of the boiler and open at each end outside of the ducting. Inside the

ducting, the hot furnace gases pass around the preheater tubes, transferring heat

from the exhaust gas to the air inside the preheater. Ambient air is forced by a fan

through ducting at one end of the preheater tubes and at other end the heated air

from inside of the tubes emerges into another set of ducting, which carries it to the

boiler furnace for combustion.

Electrostatic Precipitator

An electrostatic precipitator (ESP) is a highly efficient filtration device that removes

fine particles, like dust and smoke, from a flowing gas using the force of an induced

electrostatic charge minimally impeding the flow of gases through the unit. In

contrast to wet scrubbers which apply energy directly to the flowing fluid medium,

an ESP applies energy only to the particulate matter being collected and therefore

is very efficient in its consumption of energy (in the form of electricity).

Plate Precipitator

The most basic precipitator contains a row of thin vertical wires, and followed by a

stack of large flat metal plates oriented vertically, with the plates typically spaced

about 1 cm to 18 cm apart, depending on the application. The air or gas stream

flows horizontally through the spaces between the wires, and then passes through

the stack of plates. A negative voltage of several thousand volts is applied between

wire and plate. If the applied voltage is high enough, an electric corona

discharge ionizes the gas around the electrodes. Negative ions flow to the plates

and charge the gas-flow particles. The ionized particles, following the negative

electric field created by the power supply, move to the grounded plates. Particles

build up on the collection plates and form a layer. The layer does not collapse,

thanks to electrostatic pressure (due to layer resistivity, electric field, and current

flowing in the collected layer).