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If the FAN is located at the bottom of the TOWER and AIR is blown by the fan up through the descending water it is called as forced DRAFT cooling towers.

If the fan is located at the top of the tower and airs enters through the louvers located on the tower’s side and drawn up and discharge through the fan casing, it is called as induced draft.

If the fan is located at the bottom of the tower and air is blown by the fan up through the descending water it is called as forced draft cooling towers.

If the fan is located at the top of the tower and airs enters through the louvers located on the tower’s side and drawn up and discharge through the fan casing, it is called as induced draft.

1. STEEL CHIMNEY
2. SITE CONSTRUCTED chimney
3. PLASTIC chimney

There are two TYPES of LOADS acting on the chimney namely:

• Its own weight which is considered to as a single VERTICAL force acting through the centroid, and
• The Wind pressure, which is considered as the horizontal force acting on the centroid of vertical projected AREA.

There are two types of loads acting on the chimney namely:

The MAIN purpose of chimney is to emit the flue gases at a considerable height to avoid nuisance to the surrounding PEOPLE.

The main purpose of chimney is to emit the flue gases at a considerable height to avoid nuisance to the surrounding people.

1. Mechanical Dust COLLECTOR:

• GRAVITATIONAL separators
• Bag house dust collector

There are three types of bag house dust collector:

• Open pressure type
• Closed pressure type
• Closed suction type

2. CYCLONE. Separators
3. Electrostatic Precipitator (ESP)

1. Mechanical Dust collector:

There are three types of bag house dust collector:

2. Cyclone. Separators
3. Electrostatic Precipitator (ESP)

• To REMOVE the ashes from the furnace ash HOPPER.
• To TRANSPORT the ashes from furnace ash hopper to a storage.
• To DISPOSE the ashes from the storage.

1. Mechanical handling SYSTEM
2. HYDRAULIC system
3. PNEUMATIC system
4. STEAM JET system

1. The layout is simple and economical
2. It GIVES direct CONTROL of combustion
3. Coal transportation system is simple
4. MAINTENANCE COST is less

• UNIT (or) DIRECT SYSTEM.
• BIN (or) CENTRAL system.

The pulveriser is USED to pulverise the coal in order to increase the SURFACE EXPOSURE. Pulverised coal enables rapid combustion.

The different types of PULVERISING mills are:

1. Ball mill
2. Hammer mill
3. Ball and race mill.

The pulveriser is used to pulverise the coal in order to increase the surface exposure. Pulverised coal enables rapid combustion.

The different types of pulverising mills are:

Over feed STOCKERS:

• Travelling GRATE stockers
• SPREAD stockers

Under feed stockers:

• Single RETORT stocker
• Multi retort stocker

Over feed stockers:

Under feed stockers:

The stocker FIRING method is USED for firing SOLID coal where as PULVERIZED firing method is used for firing pulverized coal.

The stocker firing method is used for firing solid coal where as pulverized firing method is used for firing pulverized coal.

In the induced draught system, when the furnace is opened for FIRING, the COLD airs enters the furnace and dilate the combustion. In the forced draught system, when the furnace is opened for firing, the HIGH pressure air will try to blow out suddenly and furnace MAY stop.

Hence the furnace cannot be opened for firing (q) inspection in both, systems. Balanced draught, which is a combination of induced and forced draught, is used to OVERCOME the above stated difficulties.

In the induced draught system, when the furnace is opened for firing, the cold airs enters the furnace and dilate the combustion. In the forced draught system, when the furnace is opened for firing, the high pressure air will try to blow out suddenly and furnace may stop.

Hence the furnace cannot be opened for firing (q) inspection in both, systems. Balanced draught, which is a combination of induced and forced draught, is used to overcome the above stated difficulties.

In an induced DRAUGHT SYSTEM, a BLOWER (induced draft fan) is placed near (or) at the base of the chimney. The fan SUCKS the flue gas from the furnace creating a partial vacuum inside the furnace. Thus atmospheric AIR is induced to flow through the furnace to aid the combustion of fuel. The flue gases drawn by the fan passes through chimney, to the atmosphere.

In an induced draught system, a blower (induced draft fan) is placed near (or) at the base of the chimney. The fan sucks the flue gas from the furnace creating a partial vacuum inside the furnace. Thus atmospheric air is induced to flow through the furnace to aid the combustion of fuel. The flue gases drawn by the fan passes through chimney, to the atmosphere.

• Since the fan handles COLD air, the fan size and the power required are less.
• No NEED of WATER cooled BEARINGS because the air being HANDLED is cold air,
• Pressure throughout the system is above atmospheric pressure so the air leakage into the furnace is reduced.

In this SYSTEM, the blower (forced DRAFT fan) is located at the BASE of the boiler near the grate. AIR is forced to the furnace by forced fan and the flue GASES are forced to chimney through economizer and air preheater.

In this system, the blower (forced draft fan) is located at the base of the boiler near the grate. Air is forced to the furnace by forced fan and the flue gases are forced to chimney through economizer and air preheater.

In modem power PLANTS, the draught should be flexible to meet the FLUCTUATING loads and it should be independent of atmospheric conditions. To achieve this, the aid of draft fans becomes MUST and by EMPLOYING the draft fans, the height of the CHIMNEY would be reduced.

In modem power plants, the draught should be flexible to meet the fluctuating loads and it should be independent of atmospheric conditions. To achieve this, the aid of draft fans becomes must and by employing the draft fans, the height of the chimney would be reduced.

The tall chimney creates the NATURAL draught by the temperature difference between hot gases in the chimney and cold atmospheric air OUTSIDE the chimney.

The ADVANTAGES are:

• No external power is required.
• Air pollution is less since gases are discharged at high level.
• No maintenance COST.
• Capital cost is less than artificial draught.

The tall chimney creates the natural draught by the temperature difference between hot gases in the chimney and cold atmospheric air outside the chimney.

The advantages are:

DRAUGHT is CLASSIFIED as:

1. Natural draught
2. ARTIFICIAL draught

The artificial draught is further classified as:

• STEAM jet draught
• Mechanical draught
• Induced draught
• Forced draught

Draught is classified as:

The artificial draught is further classified as:

Draught is DEFINED as a SMALL PRESSURE difference required between the fuel bed (furnace) and outside air to maintain constant flow of air and to discharge the gases through CHIMNEY to the atmosphere. Draught can be obtained by chimney, fan, steam jet (or) air jet (or) COMBINATION of these.

Draught is defined as a small pressure difference required between the fuel bed (furnace) and outside air to maintain constant flow of air and to discharge the gases through chimney to the atmosphere. Draught can be obtained by chimney, fan, steam jet (or) air jet (or) combination of these.

In screw conveyor, an endless helicoids screw is fitted to the shaft. On one end of the shaft, the DRIVING mechanism is fitted and the other end of the shaft is supported on a BALL bearing. While the screw is rotating, the coal is TRANSFERRED` from one end to the other end.

Bucket conveyors are USED as vertical lifts. The coal is LOADED at the bottom and unloaded at the top in the bucket conveyors.

In screw conveyor, an endless helicoids screw is fitted to the shaft. On one end of the shaft, the driving mechanism is fitted and the other end of the shaft is supported on a ball bearing. While the screw is rotating, the coal is transferred` from one end to the other end.

Bucket conveyors are used as vertical lifts. The coal is loaded at the bottom and unloaded at the top in the bucket conveyors.

BELT conveyors are mostly used for transporting coal over long DISTANCE with large QUANTITY. An endless belt is made to run over a pair of end drums and pulleys and supported by series of ROLLER at regular INTERVALS.

Belt conveyors are mostly used for transporting coal over long distance with large quantity. An endless belt is made to run over a pair of end drums and pulleys and supported by series of roller at regular intervals.

1. Belt CONVEYORS
2. Screw conveyors
3. Bucket ELEVATORS
4. Grab bucket elevators
5. SKIP hoists
6. FLIGHT conveyors.

The COAL transfer starts by carrying of coal from unloading point to the storage site.

The coal transfer starts by carrying of coal from unloading point to the storage site.

The coal from coal nines cannot be directly fed into the FURNACE. PROPER preparation of coal should be done before feeding the coal to the furnace. In the coal preparation, the coal passes through the different equipments like

1. Crushers
2. SIZERS
3. Dryers and MAGNETIC SEPARATORS.

The coal from coal nines cannot be directly fed into the furnace. Proper preparation of coal should be done before feeding the coal to the furnace. In the coal preparation, the coal passes through the different equipments like

In order to handle large QUANTITY of coal inside the plant, some mechanical HANDLING systems are PROVIDED f6r smooth, easy and better controlled OPERATION. The IMPLANT coal handling is divided, into following categories.

• Coal unloading
• Coal preparation
• Coal transfer
• Coal storage

In order to handle large quantity of coal inside the plant, some mechanical handling systems are provided f6r smooth, easy and better controlled operation. The implant coal handling is divided, into following categories.

Out plant handling includes the handling of coal mine to the THERMAL power plant. These handlings are outside the plant in the following WAYS.

• TRANSPORTATION by sea (or) river
• Transportation by rail
• Transportation by road
• Transportation of coal by PIPELINE.

Out plant handling includes the handling of coal mine to the thermal power plant. These handlings are outside the plant in the following ways.

• Out PLANT HANDLING.
• In plant handling.

• Any type of fuel solid, liquid (or) gaseous fuel (or) domestic and INDUSTRIAL waste can be used in FBC system. Any type of combustible matter can be burned by adjusting the factors as size, air velocity and rate of feed.
• High heat TRANSFER rate is possible to the surfaces immersed in the bed, because solid mixing is extremely possible.
• High combustion EFFICIENCY.
• The solid fuel need not be pulverized in fluidized bed BOILERS.

When the HIGH velocity gas is passed through a packed BED of finely divided SOLID particles, the particles become suspended in the gas stream and the packed bed becomes a fluidized bed. When the gas velocity is very high, the fluidized bed become turbulent and rapid mixing of particles OCCURS. Ultimately, the, behaviour of mixture solid particles and gas become a fluid. Burning of a FUEL in such a state is known as Fluidized Bed Combustion. The boiler plant using this fluidized bed combustion is known as fluidized bed boilers.

When the high velocity gas is passed through a packed bed of finely divided solid particles, the particles become suspended in the gas stream and the packed bed becomes a fluidized bed. When the gas velocity is very high, the fluidized bed become turbulent and rapid mixing of particles occurs. Ultimately, the, behaviour of mixture solid particles and gas become a fluid. Burning of a fuel in such a state is known as Fluidized Bed Combustion. The boiler plant using this fluidized bed combustion is known as fluidized bed boilers.

The waste heat boilers use the waste heat in gases coming out of diesel engines and gas turbines at high temperature (or) use the waste as a FUEL in the incineration.

Some boilers use the INDUSTRIAL DIRTY gases for POWER GENERATION.

The waste heat boilers use the waste heat in gases coming out of diesel engines and gas turbines at high temperature (or) use the waste as a fuel in the incineration.

Some boilers use the industrial dirty gases for power generation.

• MUNICIPAL WASTE.
• INDUSTRIAL waste.
• PAPER waste.
• RUBBER waste.

Waste heat is the heat which is not at all used and EXHAUSTED out as a waste product. Waste heat is normally AVAILABLE from the INDUSTRY in the form of process steam and WATER at high temperature.

Also, the waste heat is discharged with the exhaust GASES in so many industries. This heat can be recovered for useful purpose. This process is known as waste heat recovery.

Waste heat is the heat which is not at all used and exhausted out as a waste product. Waste heat is normally available from the industry in the form of process steam and water at high temperature.

Also, the waste heat is discharged with the exhaust gases in so many industries. This heat can be recovered for useful purpose. This process is known as waste heat recovery.

• Direct CONTACT HEATER
• DRAIN pump method
• All drains to hot well
• CASCADE system

• HEAT supplied to BOILER becomes reduced.
• Thermal efficiency is increased since the AVERAGE temperature of heat addition to the CYCLE is increased.
• DUE to bleeding in the turbine, erosion of turbine due to moisture is reduced.

Regeneration MEANS heating the feed water by steam TAKEN from the turbine. The steam is EXHAUSTED (bled) from the turbine at several locations before EXHAUST and is supplied to regenerative (feed water heater) to heat the feed water.

Regeneration means heating the feed water by steam taken from the turbine. The steam is exhausted (bled) from the turbine at several locations before exhaust and is supplied to regenerative (feed water heater) to heat the feed water.

Assume I kg of steam is expanded in the TURBINE. Before complete amount of steam is expanded, some amount of steam (m kg) is extracted ‘EXTRACTING the steam in the turbine before exhaust is CALLED bleeding. This bled steam is used to HEAT the feed WATER.

Assume I kg of steam is expanded in the turbine. Before complete amount of steam is expanded, some amount of steam (m kg) is extracted ‘Extracting the steam in the turbine before exhaust is called bleeding. This bled steam is used to heat the feed water.

• GAS Reheating.
• LIVE stream reheating.
• Combined gas live STEAM REHEATER.

• Due to reheating, NETWORK done increases.
• Heat supply increases.
• Thermal EFFICIENCY increases.
• Due to reheating, the turbine exit dryness fraction increases so MOISTURE decreases so blade EROSION becomes minimum so LIFE of the turbine will be increased.

If the dryness fraction of steam LEAVING the TURBINE is less than 0.88, then, corrosion and erosion of turbine blades occur. To avoid this SITUATION, reheat is USED.

In the reheat cycle, the EXPANSION of steam takes place in one (or) more turbines. Steam is expanded in the HP turbine first, and then it is reheated. The reheated steam is again expanded in. the LP turbine.

If the dryness fraction of steam leaving the turbine is less than 0.88, then, corrosion and erosion of turbine blades occur. To avoid this situation, reheat is used.

In the reheat cycle, the expansion of steam takes place in one (or) more turbines. Steam is expanded in the HP turbine first, and then it is reheated. The reheated steam is again expanded in. the LP turbine.

The major disadvantage in La Mont boiler is the deposition of salt and sediment on the inner SURFACE of the water tubes. It reduces the heat transfer and ultimately the steam generating capacity.

In Loeffler boiler, this problem is SOLVED by PREVENTING water from flowing through the boiler tubes. The steam is generated OUTSIDE the tubes.

The major disadvantage in La Mont boiler is the deposition of salt and sediment on the inner surface of the water tubes. It reduces the heat transfer and ultimately the steam generating capacity.

In Loeffler boiler, this problem is solved by preventing water from flowing through the boiler tubes. The steam is generated outside the tubes.

BENSON boiler is the high pressure, vertical fire tube boiler. This boiler has no DRUM and is ~designed to operate at critical pressure of 225 bars. Benson boiler has no drum.

So the TOTAL weight of the Benson boiler is reduced by 20%, when COMPARED to other boilers. The ERECTION of Benson boiler is easier and quicker.

Benson boiler is the high pressure, vertical fire tube boiler. This boiler has no drum and is ~designed to operate at critical pressure of 225 bars. Benson boiler has no drum.

So the total weight of the Benson boiler is reduced by 20%, when compared to other boilers. The erection of Benson boiler is easier and quicker.

La Mont BOILER is a forced circulation high pressure water tube boiler.

The major disadvantage is the FORMATION of BUBBLES, salt and sediment on the inner surfaces of the heating surfaces. This reduces the heat flow and STEAM GENERATION.

La Mont boiler is a forced circulation high pressure water tube boiler.

The major disadvantage is the formation of bubbles, salt and sediment on the inner surfaces of the heating surfaces. This reduces the heat flow and steam generation.

• LA MONT BOILER
• BENSON boiler
• Loeffler boiler
• Velox boiler.

• The AMOUNT of scale formation is less, SINCE the velocity of water through PIPES are more.
• All parts of the system are heated uniformly, so there is no danger of OVERHEATING.

The high-pressure BOILERS are used to increase the efficiency of the PLANT and to reduce the COST of electricity production.

The high-pressure boilers are used to increase the efficiency of the plant and to reduce the cost of electricity production.

In the COMBINED cycle, the exhaust GAS from the diesel engine is expanded in the turbine, which is coupled with compressor which supplies pressurized air to the diesel engine. This increases diesel engine output. This ARRANGEMENT is known as turbo charging.

In the combined cycle, the exhaust gas from the diesel engine is expanded in the turbine, which is coupled with compressor which supplies pressurized air to the diesel engine. This increases diesel engine output. This arrangement is known as turbo charging.

• Combined CYCLE of gas TURBINE and steam POWER PLANT.
• Combined cycle of gas turbine and diesel power plant.

Since the power required COMPRESSING the AIR is LESS in isothermal process it is required to maintain the, temperature of air constant as far as possible. Hence the air leaving the L.P. compressor is cooled by INTERCOOLER and then PASSED to the H.P compressor.

Since the power required compressing the air is less in isothermal process it is required to maintain the, temperature of air constant as far as possible. Hence the air leaving the L.P. compressor is cooled by intercooler and then passed to the H.P compressor.

The LUBRICATION system consists of oil PUMPS, oil tanks, filters, coolers and CONNECTING pipes. The purpose of the lubrication is to REDUCE the friction of moving PARTS and also pipes to reduce the wear and tear of moving parts.

The lubrication system consists of oil pumps, oil tanks, filters, coolers and connecting pipes. The purpose of the lubrication is to reduce the friction of moving parts and also pipes to reduce the wear and tear of moving parts.

The function of cooling system is to remove heat from the engine CYLINDER to KEEP the temperature of the cylinder in low RANGE and extend engine life.

The function of cooling system is to remove heat from the engine cylinder to keep the temperature of the cylinder in low range and extend engine life.