Cochran boiler • It is a multi-tubular vertical fire tube boiler having a number of horizontal fire tubes. it is the modification of a simple vertical boiler where the heating surface has been increased by means of a number of fire tubes. It consists of Shell • grate • Fire box • Flue pipe • Fire tubes • Combustion chamber • Chimney • Man-hole •
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Cochran boiler• It is a multi-tubular vertical fire tube boiler having a number of
horizontal fire tubes. it is the modification of a simple verticalboiler where the heating surface has been increased by means ofa number of fire tubes.
It consists of
Shell• grate• Fire box• Flue pipe• Fire tubes• Combustion chamber• Chimney• Man-hole•
• It is a multi-tubular vertical fire tube boiler having a number ofhorizontal fire tubes. it is the modification of a simple verticalboiler where the heating surface has been increased by means ofa number of fire tubes.
It consists of
Shell• grate• Fire box• Flue pipe• Fire tubes• Combustion chamber• Chimney• Man-hole•
• ShellIt is hemispherical on the top, where space is provided for steam.
GrateIt is placed at the bottom of the furnace where coal is burnt.
Fire box (furnace )It is also dome-shaped like the shell so that the gases can be deflectedback till they are passed out through the flue pipe to the combustionchamber.
Flue pipe:It is a short passage connecting the fire box with the combustion chamber.
Fire tubes:A number of horizontal fire tubes are provided, thereby the heatingsurface is increased.
Cochran boiler
• ShellIt is hemispherical on the top, where space is provided for steam.
GrateIt is placed at the bottom of the furnace where coal is burnt.
Fire box (furnace )It is also dome-shaped like the shell so that the gases can be deflectedback till they are passed out through the flue pipe to the combustionchamber.
Flue pipe:It is a short passage connecting the fire box with the combustion chamber.
Fire tubes:A number of horizontal fire tubes are provided, thereby the heatingsurface is increased.
Cochran boiler• Combustion chamber:
It is lined with fire bricks on the side of the shell to preventoverheating of the boiler. Hot gases enter the fire tubes from theflue pipe through the combustion chamber.
Chimney:It is provided for the exit of the flue gases to the atmosphere fromthe smoke box.
Manhole:It is provided for inspection and repair of the interior of the boilershell.
Normal size of a Cochran boiler:Shell diameter – 2.75 meters:Height of the shell – 6 meters.
• Combustion chamber:It is lined with fire bricks on the side of the shell to preventoverheating of the boiler. Hot gases enter the fire tubes from theflue pipe through the combustion chamber.
Chimney:It is provided for the exit of the flue gases to the atmosphere fromthe smoke box.
Manhole:It is provided for inspection and repair of the interior of the boilershell.
Normal size of a Cochran boiler:Shell diameter – 2.75 meters:Height of the shell – 6 meters.
Cochran boiler• Working of the Cochran boiler:• Coal is fed into the grate through the fire hole and burnt. Ash
formed during burning is collected in the ashpit provided just belowthe grate and then it is removed manually.
The hot gases from the grate pass through the flue pipe to thecombustion chamber. The hot gases from the combustion chamberflow through the horizontal fire tubes and transfer the heat to thewater by convection.
The flue gases coming out of fire tubes pass through the smoke boxand are exhausted to the atmosphere through the chimney.Smoke box is provided with a door for cleaning the fire tubes andsmoke box.
• Working of the Cochran boiler:• Coal is fed into the grate through the fire hole and burnt. Ash
formed during burning is collected in the ashpit provided just belowthe grate and then it is removed manually.
The hot gases from the grate pass through the flue pipe to thecombustion chamber. The hot gases from the combustion chamberflow through the horizontal fire tubes and transfer the heat to thewater by convection.
The flue gases coming out of fire tubes pass through the smoke boxand are exhausted to the atmosphere through the chimney.Smoke box is provided with a door for cleaning the fire tubes andsmoke box.
Cochran boiler• The following mountings are fitted to the boiler:
Pressure gauge: this indicates the pressure of the steam inside the boiler.
Water gauge: this indicates the water level in the boiler. The water level in theboiler should not fall below a particular level, otherwise the boiler will be overheated and the tubes may burn out.
Safety valve: the function of the safety valve is to prevent an increase of steampressure in the boiler above its normal working pressure.
Steam stop valve: it regulates the flow of steam supply to requirements.
Blow-off cock: it is located at the bottom of the boiler. When the blow-off cock isopened during the running of the boiler, the high pressure steam pushes (drains)out the impurities like mud, sand, etc., in the water collected at the bottom.
Fusible plug: it protects the fire tubes from burning when the water level in theboiler falls abnormally low.
• The following mountings are fitted to the boiler:
Pressure gauge: this indicates the pressure of the steam inside the boiler.
Water gauge: this indicates the water level in the boiler. The water level in theboiler should not fall below a particular level, otherwise the boiler will be overheated and the tubes may burn out.
Safety valve: the function of the safety valve is to prevent an increase of steampressure in the boiler above its normal working pressure.
Steam stop valve: it regulates the flow of steam supply to requirements.
Blow-off cock: it is located at the bottom of the boiler. When the blow-off cock isopened during the running of the boiler, the high pressure steam pushes (drains)out the impurities like mud, sand, etc., in the water collected at the bottom.
Fusible plug: it protects the fire tubes from burning when the water level in theboiler falls abnormally low.
Cochran boiler• Salient features of Cochran boiler:• The dome shape of the furnace causes the hot
gases to deflect back and pass through the flue.The un-burnt fuel if any will also be deflectedback.
• Spherical shape of the top of the shell and thefire box gives higher area by volume ratio.
• It occupies comparatively less floor area and isvery compact.
• It is well suited for small capacity requirements.
• Salient features of Cochran boiler:• The dome shape of the furnace causes the hot
gases to deflect back and pass through the flue.The un-burnt fuel if any will also be deflectedback.
• Spherical shape of the top of the shell and thefire box gives higher area by volume ratio.
• It occupies comparatively less floor area and isvery compact.
• It is well suited for small capacity requirements.
la Mont boiler
• A forced circulation boiler was first introduced byLa-Mont in the year 1925 which is used in Europeand America. This is a modern high pressureboiler (water tube type steam boilers) working onforced circulation system.
Working principle of La Mont BoilerThe image shows the flow circuit of La MontBoiler.
• A forced circulation boiler was first introduced byLa-Mont in the year 1925 which is used in Europeand America. This is a modern high pressureboiler (water tube type steam boilers) working onforced circulation system.
Working principle of La Mont BoilerThe image shows the flow circuit of La MontBoiler.
la Mont boiler• Steam separator drum
The la Mont boilerconsists of a steamseparator drum which isplaced wholly outsidethe boiler setting .
• The drum receives amixture of steam andwater from theevaporator tubes andfeed water from theeconomizer.
• The steam is separatedfrom water in the drum.
• Steam separator drumThe la Mont boilerconsists of a steamseparator drum which isplaced wholly outsidethe boiler setting .
• The drum receives amixture of steam andwater from theevaporator tubes andfeed water from theeconomizer.
• The steam is separatedfrom water in the drum.
la Mont boiler• Circulating pump
The water from the drumis then drawn to thecirculating (centrifugal)pump through the down-comer.
• The pump circulates water(“forced circulation”)equal to 8 to 10 times theweight of steamevaporated.
• This prevents the tubesfrom being overheated.
• Circulating pumpThe water from the drumis then drawn to thecirculating (centrifugal)pump through the down-comer.
• The pump circulates water(“forced circulation”)equal to 8 to 10 times theweight of steamevaporated.
• This prevents the tubesfrom being overheated.
la Mont boiler
• Distributing headerThe circulating pumpdelivers the feedwater to thedistributing headerwith orifices at apressure above thedrum pressure.
• Distributing headerThe circulating pumpdelivers the feedwater to thedistributing headerwith orifices at apressure above thedrum pressure.
la Mont boiler• Evaporator
The header distributeswater through orificesinto the evaporatortubes acting in parallel.
• Orifice in the headercontrols the flow ofwater to theevaporator tubes.
• Here part of the wateris evaporated and amixture of steam andwater from these tubesenters the drum.
• EvaporatorThe header distributeswater through orificesinto the evaporatortubes acting in parallel.
• Orifice in the headercontrols the flow ofwater to theevaporator tubes.
• Here part of the wateris evaporated and amixture of steam andwater from these tubesenters the drum.
la Mont boiler• Convection super heater
• The steam produced in theboiler is nearly saturated.
• This steam as such shouldnot be used in the steamturbine.
• The presence of moisturein it will cause corrosion ofturbine blades, etc. to raisethe temperature of steamand thereby to increase theturbine efficiency, superheater is used.
• Convection super heater
• The steam produced in theboiler is nearly saturated.
• This steam as such shouldnot be used in the steamturbine.
• The presence of moisturein it will cause corrosion ofturbine blades, etc. to raisethe temperature of steamand thereby to increase theturbine efficiency, superheater is used.
la Mont boiler• Steam outlet
Superheated steam fromthe super heater passesout to the steam turbinethrough the steam outlet.
EconomizerThe quantity ofsuperheated steam thusdelivered to turbine iscontinuously made up inthe form of feed water.
• Feed water supplied by thefeed pump is heated in theeconomizer on its way tothe steam separator drum.
• Steam outletSuperheated steam fromthe super heater passesout to the steam turbinethrough the steam outlet.
EconomizerThe quantity ofsuperheated steam thusdelivered to turbine iscontinuously made up inthe form of feed water.
• Feed water supplied by thefeed pump is heated in theeconomizer on its way tothe steam separator drum.
la Mont boiler•
The economizer is a deviceused to preheat the feed waterusing the hot gases leaving theboiler.
• Before the gases are let off tothe atmosphere, they aremade to flow in a definitepassage in the economizer sothat some of the heat in thehot gases, which otherwisegets wasted, can be used topreheat the feed water.
• The preheated water requiresonly a small amount of heat tobe supplied in theboiler, resulting in some savingof the fuel burnt.
•
The economizer is a deviceused to preheat the feed waterusing the hot gases leaving theboiler.
• Before the gases are let off tothe atmosphere, they aremade to flow in a definitepassage in the economizer sothat some of the heat in thehot gases, which otherwisegets wasted, can be used topreheat the feed water.
• The preheated water requiresonly a small amount of heat tobe supplied in theboiler, resulting in some savingof the fuel burnt.
la Mont boilerAir pre heaterSince the heat of the exit gasescannot be fully extractedthrough the economizer, theair pre heater is employed torecover some of the heatescaping in these gases.
These exit gases preheat theair from the blower in the airpre heater.
The preheated air is suppliedto the furnace for combustion.
CapacityThe capacity of la-mont boileris about 50 Tonnes/hr ofsuperheated steam at apressure of 170 kgf/sq.cm. andat a temperature of 500’C..
Air pre heaterSince the heat of the exit gasescannot be fully extractedthrough the economizer, theair pre heater is employed torecover some of the heatescaping in these gases.
These exit gases preheat theair from the blower in the airpre heater.
The preheated air is suppliedto the furnace for combustion.
CapacityThe capacity of la-mont boileris about 50 Tonnes/hr ofsuperheated steam at apressure of 170 kgf/sq.cm. andat a temperature of 500’C..
Loeffler Boiler• Salient features of Loeffler Boiler
The novel feature of the Loeffler Boiler is to evaporate water solelyby means of superheated steam. The furnace heat is supplied onlyto economiser and superheater. In other words, steam is used as aheat absorbing medium.
The major difficulty experienced in La-Mont boiler is deposition ofsalt and sediment on the inner surfaces of water tubes.
• The deposition reduces the heat transfer, ultimately, the generatingcapacity. This difficulty was solved in Loeffler boiler by preventingthe flow of water into the boiler tubes.
• Feed water is evaporated in the drum using part of the superheatedsteam coming out from the water-heater.
• Thus only the dry saturated steam passes through the tubes. Poorfeed water can, therefore, be used without any difficulty in theboiler, which is great advantage of this boiler.
• Salient features of Loeffler BoilerThe novel feature of the Loeffler Boiler is to evaporate water solelyby means of superheated steam. The furnace heat is supplied onlyto economiser and superheater. In other words, steam is used as aheat absorbing medium.
The major difficulty experienced in La-Mont boiler is deposition ofsalt and sediment on the inner surfaces of water tubes.
• The deposition reduces the heat transfer, ultimately, the generatingcapacity. This difficulty was solved in Loeffler boiler by preventingthe flow of water into the boiler tubes.
• Feed water is evaporated in the drum using part of the superheatedsteam coming out from the water-heater.
• Thus only the dry saturated steam passes through the tubes. Poorfeed water can, therefore, be used without any difficulty in theboiler, which is great advantage of this boiler.
Loeffler Boiler• Economiser
The feed water from thefeed tank is supplied to theeconomiser by feed pump.
• In the economiser the feedwater is made to flowthrough a number of tubessurrounding which the hotgases leaving the furnacepass over.
• There is a heat exchangefrom the hot gases to thefeed water, which ispreheated in theeconomiser.
• EconomiserThe feed water from thefeed tank is supplied to theeconomiser by feed pump.
• In the economiser the feedwater is made to flowthrough a number of tubessurrounding which the hotgases leaving the furnacepass over.
• There is a heat exchangefrom the hot gases to thefeed water, which ispreheated in theeconomiser.
Loeffler Boiler• Evaporated Drum
• It is housed away from thefurnace.
• It contains a mixture ofsteam and water.
• The feed water from theeconomiser tubes enters theevaporator drum into whichis also passed two-thirds ofthe superheated steamgenerated by the boiler.
• The superheated steam givesits superheat to the water inthe drum and evaporates itto saturated steam.
• Evaporated Drum
• It is housed away from thefurnace.
• It contains a mixture ofsteam and water.
• The feed water from theeconomiser tubes enters theevaporator drum into whichis also passed two-thirds ofthe superheated steamgenerated by the boiler.
• The superheated steam givesits superheat to the water inthe drum and evaporates itto saturated steam.
Loeffler Boiler• Mixing Nozzles
The nozzles distribute andmix the superheatedsteam throughout thewater in the evaporatordrum.
Steam circulating pumpA steam circulating pumpforces this saturatedsteam from theevaporator drum to theradiant super heaterthrough the tube of thefurnace wall.
• Mixing NozzlesThe nozzles distribute andmix the superheatedsteam throughout thewater in the evaporatordrum.
Steam circulating pumpA steam circulating pumpforces this saturatedsteam from theevaporator drum to theradiant super heaterthrough the tube of thefurnace wall.
Loeffler Boiler• Radiant super heater
The radiant super heater isplaced in the furnace.
• The hot gases in thefurnace are used forsuperheating thesaturated steam from thedrum.
• The radiant super heaterreceives heat from theburning fuel throughradiation process.
• Radiant super heaterThe radiant super heater isplaced in the furnace.
• The hot gases in thefurnace are used forsuperheating thesaturated steam from thedrum.
• The radiant super heaterreceives heat from theburning fuel throughradiation process.
Loeffler Boiler• Convection super heater
Steam from the radiantsuper heater enters theconvection super heaterwhere it is finally heated tothe desired temperature of500’C.
• The convection superheater receives heat fromthe flue gases entirely byconvective heat transfer.
• Both radiant and convectionsuper heater are arrangedin series in the path of theflue gases.
• Convection super heaterSteam from the radiantsuper heater enters theconvection super heaterwhere it is finally heated tothe desired temperature of500’C.
• The convection superheater receives heat fromthe flue gases entirely byconvective heat transfer.
• Both radiant and convectionsuper heater are arrangedin series in the path of theflue gases.
Loeffler Boiler• Steam outlet
About one-third of thesuperheated steam from theconvection super heater passesto the steam turbine while theremaining two-thirds is passedon to evaporator drum toevaporated the feed water tosaturated steam.
CapacityCapacity of the Loeffler boiler isabout 100 Tonnes/Hr ofsuperheated steam generated ata pressure of 140 kgf/sq.cm andat a temperature of 500’C.
• Steam outletAbout one-third of thesuperheated steam from theconvection super heater passesto the steam turbine while theremaining two-thirds is passedon to evaporator drum toevaporated the feed water tosaturated steam.
CapacityCapacity of the Loeffler boiler isabout 100 Tonnes/Hr ofsuperheated steam generated ata pressure of 140 kgf/sq.cm andat a temperature of 500’C.
Babcock and Wilcox boiler
Babcock and Wilcox boiler• Babcock and Wilcox boiler: Babcock and Wilcox
is a water-tube boiler is an example of horizontalinclined tube boiler it also a High Pressure Boiler.
• Construction: Babcock and Wilcox boiler withlongitudinal drum. It consists of a drumconnected to a series of front end and rear endheader by short riser tubes.
• To these headers are connected a series ofinclined water tubes of solid drawn mild steel.The angle of inclination of the water tubes to thehorizontal is about 15° or more.
• Babcock and Wilcox boiler: Babcock and Wilcoxis a water-tube boiler is an example of horizontalinclined tube boiler it also a High Pressure Boiler.
• Construction: Babcock and Wilcox boiler withlongitudinal drum. It consists of a drumconnected to a series of front end and rear endheader by short riser tubes.
• To these headers are connected a series ofinclined water tubes of solid drawn mild steel.The angle of inclination of the water tubes to thehorizontal is about 15° or more.
Babcock and Wilcox boiler• Working: The fire door the fuel is supplied to grate where it
is burnt.• The hot gases are forced to move upwards between the
tubes by baffle plates provided.• The water from the drum flows through the inclined tubes
via down take header and goes back into the shell in theform of water and steam via uptake header.
• The steam gets collected in the steam space of the drum.The steam then enters through the anti priming pipe andflows in the super heater tubes where it is further heatedand is finally taken out through the main stop valve andsupplied to the Steam turbine or Steam engine whenneeded.
• Working: The fire door the fuel is supplied to grate where itis burnt.
• The hot gases are forced to move upwards between thetubes by baffle plates provided.
• The water from the drum flows through the inclined tubesvia down take header and goes back into the shell in theform of water and steam via uptake header.
• The steam gets collected in the steam space of the drum.The steam then enters through the anti priming pipe andflows in the super heater tubes where it is further heatedand is finally taken out through the main stop valve andsupplied to the Steam turbine or Steam engine whenneeded.
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