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Combustion is a surface process, and results from heating of the solid material. Coal is pulverized so as to give a greater surface to volume ratio, and thus burn more readily.
Indeed powdered materials will sometimes combust explosively, such as explosions in flour mills.
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Is there any relation between HGI and grade of coal?
YES, there is a relation between HGI and coal quality. HGI is the parameter to indicate the hardness or grindability of the coal when it is used in pulverized coal for boiler
How is coal refined?
Coal refining is nowhere near as complex as oil refining. Coal is washed with a water or chemical bath to remove some impurities. As much as 30 percent of the sulfur can be removed by washing. At the power plant, coal is pulverized to a heavy powder just before being burned. From http://www.ucsusa.org/clean_energy/coalvswind/brief_coal.html
Disadvantages and advantages of pulverized coal?
Advantages of Pulverized Coal Firing:The main advantage of pulverized firing system lies in the fact that by breaking a given mass of coal into smaller pieces exposes more surface area for combustion.Greater surface area of coal per unit mass of the coal allows faster combustion as more coal surface is exposed to heat and oxygen. This reduces the excess air required to ensure complete combustion and the required fan power alsoWide variety and low grade coal can be burnt more easily when the coal is pulverizedPulverized coal gives faster response to load changes as the rate of combustion can be controlled easily and immediately. Automatic control applied to pulverized coal fired boilers is effective in maintaining an almost constant steam pressure under wide load variationsThis system is free from clinker and slagging troublesThis system works successfully with or in combination with the gas and oilIt is possible to use highly pre-heated secondary air (350oC) which helps in rapid flame propagationThe pulverized system can be repaired easily without cooling the system as the pulverizing equipment is located outside the furnaceLarge amount of heat release is possible in this system compared to stoke firing systemThe banking losses are low compared to stoke firing systemThe boiler can be started from cold very rapidly and efficiently. This is highly important when grid stability is of the important concernThe external heating surface is free from corrosion and fouling as smokeless combustion is possibleThere are no moving parts in the furnace or boiler subjected to high temperature. Therefore the life of the pulverized fuel firing system is more and operation is trouble-lessPractically no ash handling problem in this type of firing systemThe furnace volume required is considerably less as the use of the burners which produce turbulence in the furnace makes it possible to complete combustion with minimum travelDisadvantages of Pulverized Coal firing:The capital cost of the pulverized coal firing system is considerably high as it requires many additional auxiliary equipment. Its operation cost is also high compared to stoke firing systemThe system produces fly ash (fine dust) which requires special and costly fly-ash removal equipments as electrostatic precipitatorsThe flame temperatures are high and the conventional types of refractory lined furnaces are not inadequate. It is always necessary to provide water cooled walls for the safety of the furnace. The maintenance cost is also high as working temperature is high which causes rapid deterioration of the refractory surface of the furnaceThe possibility of the explosion is more as coal burn like gasThe storage of powdered coal requires special attention and high protection from the fire hazards
What are the three requirements of combustion?
When coal is burned in the boiler of a power plant, it is not just set alight like the coal in a domestic fireplace. It has to burn fast¾ for power is the energy converted per second, and it has to burn completely¾for efficiency is a measure of how much energy is usefully harnessed rather than lost. The efficient combustion of coal needs the "three T's"¾temperature high enough to ignite the fuel, turbulence vigorous enough for the fuel constituents to be exposed to the oxygen of the air, and time long enough to assure complete combustion. The three requirements are best met by pulverized coal, which is forced into the furnace by an air stream under high pressure and is ignited as it enters through a nozzle. Pulverized coal was introduced in the early 1920's and represented a major advance over the previous stoker firing.
Is pulverizing sugar a chemical or a physical change?
It is a physical change. The sugar is still sugar after it is pulverized.
What type of coal can be used in pulverized combustion?
Bituminous and subbituminous coals are user to make the pulverized coal for coal burners. This is coal containing the compound bitumen. It is a soft coal. They are graded according to their carbon content. They can be processed into coke before being pulverized.
What is the unit of Hardgrove Grindability Index?
It has no units because we are determining the degree of pulverized coal.
Is there any relation between HGI and grade of coal?
YES, there is a relation between HGI and coal quality. HGI is the parameter to indicate the hardness or grindability of the coal when it is used in pulverized coal for boiler
What has the author H Heywood written?
H. Heywood has written: 'Researches on the production of pulverized coal'
What moves coal over land?
Coal is transported by;Rail (large pieces and small pellets)Truck (large pieces and small pellets)Slurry pipelines ( pulverized coal in water)
What has the author K M Sprouse written?
K. M. Sprouse has written: 'Theory of pulverized coal conversion in entrained flows ..' -- subject(s): Combustion, Coal liquefaction, Coal gasification
What do you call a high speed rotating device that removes moisture from pulverized coal or other solids?
It is a vibratory centrifuge
What has the author Ali Mahmoud Zghoul written?
Ali Mahmoud Zghoul has written: 'Evolution of sulfur and nitrogen species during pulverized coal combustion' -- subject- s -: Coal, Combustion
Is there a sentence with the word pulverized in it?
Gravel is pulverized rock.Crushing force pulverized the granite.
What has the author D Pershing written?
D. Pershing has written: 'Bench-scale studies to identify process parameters controlling reburning with pulverized coal' -- subject(s): Combustion, Coal, Environmental aspects, Technological innovations
How is coal refined?
Coal refining is nowhere near as complex as oil refining. Coal is washed with a water or chemical bath to remove some impurities. As much as 30 percent of the sulfur can be removed by washing. At the power plant, coal is pulverized to a heavy powder just before being burned. From http://www.ucsusa.org/clean_energy/coalvswind/brief_coal.html
Disadvantages and advantages of pulverized coal?
Advantages of Pulverized Coal Firing:The main advantage of pulverized firing system lies in the fact that by breaking a given mass of coal into smaller pieces exposes more surface area for combustion.Greater surface area of coal per unit mass of the coal allows faster combustion as more coal surface is exposed to heat and oxygen. This reduces the excess air required to ensure complete combustion and the required fan power alsoWide variety and low grade coal can be burnt more easily when the coal is pulverizedPulverized coal gives faster response to load changes as the rate of combustion can be controlled easily and immediately. Automatic control applied to pulverized coal fired boilers is effective in maintaining an almost constant steam pressure under wide load variationsThis system is free from clinker and slagging troublesThis system works successfully with or in combination with the gas and oilIt is possible to use highly pre-heated secondary air (350oC) which helps in rapid flame propagationThe pulverized system can be repaired easily without cooling the system as the pulverizing equipment is located outside the furnaceLarge amount of heat release is possible in this system compared to stoke firing systemThe banking losses are low compared to stoke firing systemThe boiler can be started from cold very rapidly and efficiently. This is highly important when grid stability is of the important concernThe external heating surface is free from corrosion and fouling as smokeless combustion is possibleThere are no moving parts in the furnace or boiler subjected to high temperature. Therefore the life of the pulverized fuel firing system is more and operation is trouble-lessPractically no ash handling problem in this type of firing systemThe furnace volume required is considerably less as the use of the burners which produce turbulence in the furnace makes it possible to complete combustion with minimum travelDisadvantages of Pulverized Coal firing:The capital cost of the pulverized coal firing system is considerably high as it requires many additional auxiliary equipment. Its operation cost is also high compared to stoke firing systemThe system produces fly ash (fine dust) which requires special and costly fly-ash removal equipments as electrostatic precipitatorsThe flame temperatures are high and the conventional types of refractory lined furnaces are not inadequate. It is always necessary to provide water cooled walls for the safety of the furnace. The maintenance cost is also high as working temperature is high which causes rapid deterioration of the refractory surface of the furnaceThe possibility of the explosion is more as coal burn like gasThe storage of powdered coal requires special attention and high protection from the fire hazards
