The excess air required for the combustion of pulverised coal is of the order of about __________ percent. (A) 5 (B) 15 (C) 30 (D) 45

The excess air required for the combustion of pulverised coal is of the order of about __________ percent.
(A) 5
(B) 15
(C) 30
(D) 45
by

1 Answer

Answer :

(B) 15
by

Related questions

Black smoke coming out of the chimney of a furnace is an indication of the use of __________ in the furnace. (A) Low amount of excess combustion air (B) Large quantity of excess combustion air(C) Hydrocarbon fuel(D) Pulverised coal as fuel

Description : Black smoke coming out of the chimney of a furnace is an indication of the use of __________ in the furnace. (A) Low amount of excess combustion air (B) Large quantity of excess combustion air (C) Hydrocarbon fuel (D) Pulverised coal as fuel

Last Answer : (A) Low amount of excess combustion air

Combustion of pulverised coal as compared to that of lump coal (A) Develops a non-luminous flame (B) Develops a low temperature flame (C) Can be done with less excess air (D) Provides a lower rate of heat release

Description : Combustion of pulverised coal as compared to that of lump coal (A) Develops a non-luminous flame (B) Develops a low temperature flame (C) Can be done with less excess air (D) Provides a lower rate of heat release

Last Answer : (C) Can be done with less excess ai

Which of the following would require maximum amount of % excess air for complete combustion? (A) Coke oven gas (B) Furnace oil (C) Pulverised coal (D) Lump coal (fixed on chain grate)

Description : Which of the following would require maximum amount of % excess air for complete combustion? (A) Coke oven gas (B) Furnace oil (C) Pulverised coal (D) Lump coal (fixed on chain grate)

Last Answer : (D) Lump coal (fixed on chain grate)

Combustion of pulverised coal compared to the lumpy coal (A) Provides better control of furnace temperature (B) Facilitates combustion with lower excess air (C) Provides higher thermal efficiency & flame temperature (D) All (A), (B) & (C)

Description : Combustion of pulverised coal compared to the lumpy coal (A) Provides better control of furnace temperature (B) Facilitates combustion with lower excess air (C) Provides higher thermal efficiency & flame temperature (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)

The function of an economiser in a boiler is to preheat the (A) Feedwater (B) Combustion air (C) Pulverised coal (D) Furnace oil

Description : The function of an economiser in a boiler is to preheat the (A) Feedwater (B) Combustion air (C) Pulverised coal (D) Furnace oil

Last Answer : (A) Feedwater

In case of pulverised coal fired steam boiler, the secondary air serves the main purpose of (A) Transportation of coal (B) Drying of coal (C) Combustion of coal by supplying it around the burner (D) Preheating the primary air

Description : In case of pulverised coal fired steam boiler, the secondary air serves the main purpose of (A) Transportation of coal (B) Drying of coal (C) Combustion of coal by supplying it around the burner (D) Preheating the primary air

Last Answer : (C) Combustion of coal by supplying it around the burner

The function of secondary combustion air is to (A) Pneumatically convey the pulverised coal (B) Completely burn the volatile matter (C) Burn the lumpy coal (D) None of these

Description : The function of secondary combustion air is to (A) Pneumatically convey the pulverised coal (B) Completely burn the volatile matter (C) Burn the lumpy coal (D) None of these

Last Answer : (B) Completely burn the volatile matter

Temperature of preheated air used for the transportation of pulverised coal through pipes to the burner of a boiler furnace is restricted to a maximum limit of about 300° C to avoid the (A) Requirement of large volume combustion chamber (B) Risk of explosion (C) Chances of clinker formation (D) Incomplete combustion of coal

Description : Temperature of preheated air used for the transportation of pulverised coal through pipes to the burner of a boiler furnace is restricted to a maximum limit of about 300° C to avoid the (A) ... chamber (B) Risk of explosion (C) Chances of clinker formation (D) Incomplete combustion of coal

Last Answer : (B) Risk of explosion

Emission of dense white smoke out of the chimney of a thermal power plant is an indication of the use of (A) Less air for combustion (B) Correct amount of air for combustion (C) Too much air for combustion (D) Pulverised coal in boilers

Description : Emission of dense white smoke out of the chimney of a thermal power plant is an indication of the use of (A) Less air for combustion (B) Correct amount of air for combustion (C) Too much air for combustion (D) Pulverised coal in boilers

Last Answer : (C) Too much air for combustion

The main function of primary air in pulverised coal fired burner is to (A) Burn CO to CO2 (B) Dry and transport the coal (C) Have proper combustion by supplying it around the burner (D) Preheat the tertiary air used for complete combustion of CO to CO2

Description : The main function of primary air in pulverised coal fired burner is to (A) Burn CO to CO2 (B) Dry and transport the coal (C) Have proper combustion by supplying it around the burner (D) Preheat the tertiary air used for complete combustion of CO to CO2

Last Answer : (B) Dry and transport the coal

In case of pulverised coal fired steam boiler, the secondary air serves the main purpose of (A) Transportation of coal (B) Drying of coal (C) Combustion of coal by supplying it around the burner (D) Preheating the primary air

Description : In case of pulverised coal fired steam boiler, the secondary air serves the main purpose of (A) Transportation of coal (B) Drying of coal (C) Combustion of coal by supplying it around the burner (D) Preheating the primary air

Last Answer : (C) Combustion of coal by supplying it around the burner

Pick out the wrong statement. (A) Pulverised fuel can be completely burnt with less percentage of excess air compared to lump coal (B) Low grade coal can be used, but generally high volatile matter coals are more suitable for making pulverised fuel (C) Regulation of furnace temperature and atmosphere (oxidising or reducing) is easily possible with pulverised fuel firing (D) None of these

Description : Pick out the wrong statement. (A) Pulverised fuel can be completely burnt with less percentage of excess air compared to lump coal (B) Low grade coal can be used, but generally high volatile ... and atmosphere (oxidising or reducing) is easily possible with pulverised fuel firing (D) None of these

Last Answer : (D) None of these

Overall thermal efficiency of a lumpy coal fired suitably designed heating furnace, if operated & maintained properly may be about __________ percent. (A) 10-15 (B) 25-30 (C) 45-50 (D) 65-70

Description : Overall thermal efficiency of a lumpy coal fired suitably designed heating furnace, if operated & maintained properly may be about __________ percent. (A) 10-15 (B) 25-30 (C) 45-50 (D) 65-70

Last Answer : (B) 25-30

Use of pulverised coal in boilers provides (A) Higher calorific value (B) Better combustion (C) Smokeless burning (D) Less erosion on furnace wall

Description : Use of pulverised coal in boilers provides (A) Higher calorific value (B) Better combustion (C) Smokeless burning (D) Less erosion on furnace wall

Last Answer : (B) Better combustion

Use of pulverised coal in boiler furnace provides (A) High calorific value (B) Better combustion (C) Smokeless burning (D) Less erosion on furnace walls

Description : Use of pulverised coal in boiler furnace provides (A) High calorific value (B) Better combustion (C) Smokeless burning (D) Less erosion on furnace walls

Last Answer : (B) Better combustion

The advantage of firing pulverised coal in the furnace lies in the fact, that it (A) Permits the use of high ash content coal (B) Permits the use of low fusion point ash coal(C) Accelerates the burning rate and economises on fuel combustion(D) All (A), (B) and (C)

Description : The advantage of firing pulverised coal in the furnace lies in the fact, that it (A) Permits the use of high ash content coal (B) Permits the use of low fusion point ash coal (C) Accelerates the burning rate and economises on fuel combustion (D) All (A), (B) and (C)

Last Answer : (C) Accelerates the burning rate and economises on fuel combustion

Coal is pulverised before burning in large capacity boiler furnaces mainly to (A) Ensure its complete combustion (B) Facilitate easy ash removal (C) Enhance its calorific value (D) Provide trouble free operation

Description : Coal is pulverised before burning in large capacity boiler furnaces mainly to (A) Ensure its complete combustion (B) Facilitate easy ash removal (C) Enhance its calorific value (D) Provide trouble free operation

Last Answer : (A) Ensure its complete combustion

Oxygen content in a flue gas was found to be 4%. It implies that excess air used for combustion was around __________ percent. (A) 4 (B) 96 (C) 20 (D) 40

Description : Oxygen content in a flue gas was found to be 4%. It implies that excess air used for combustion was around __________ percent. (A) 4 (B) 96 (C) 20 (D) 40

Last Answer : (C) 20

Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of __________ mm. (A) 0.007 (B) 0.30 (C) 50 (D) 0.014

Description : Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of __________ mm. (A) 0.007 (B) 0.30 (C) 50 (D) 0.014

Last Answer : (B) 0.30

Ash content in the middling coal (a byproduct of coal washeries) in India ranges between __________ percent. (A) 15 to 25 (B) 35 to 45 (C) 55 to 75 (D) 75

Description : Ash content in the middling coal (a byproduct of coal washeries) in India ranges between __________ percent. (A) 15 to 25 (B) 35 to 45 (C) 55 to 75 (D) 75

Last Answer : (B) 35 to 45

Amount of coal lost in ash particle, which is carried through the boiler system, depends upon the (A) Physical nature, ash content and fineness of the coal (B) Amount of excess air supplied and load on the boiler (C) Type of burner and combustion chamber (D) All (A), (B) and (C)

Description : Amount of coal lost in ash particle, which is carried through the boiler system, depends upon the (A) Physical nature, ash content and fineness of the coal (B) Amount of excess air supplied and load on the boiler (C) Type of burner and combustion chamber (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Pick out the wrong statement. (A) High concentration of oxygen in flue gas means high stack loss (B) Gaseous fuels require the least % excess air for complete combustion (C) The ratio of fixed carbon to volatile matter percentage in coal is called its 'fuel ratio' (D) Calorific value of natural gas is more than that of LPG

Description : Pick out the wrong statement. (A) High concentration of oxygen in flue gas means high stack loss (B) Gaseous fuels require the least % excess air for complete combustion (C) The ratio of fixed carbon to ... coal is called its 'fuel ratio' (D) Calorific value of natural gas is more than that of LPG

Last Answer : (D) Calorific value of natural gas is more than that of LPG

Pick out the wrong statement. (A) Strongly caking coal should not be used in the Lurgi gasifier (B) Acetylene gas cannot be used for illumination purpose (C) Water gas is called blue gas because of the color of the flame, when it is burnt (D) Gaseous fuels require less percentage of excess air for combustion as compared to liquid fuels

Description : Pick out the wrong statement. (A) Strongly caking coal should not be used in the Lurgi gasifier (B) Acetylene gas cannot be used for illumination purpose (C) Water gas is called blue gas ... is burnt (D) Gaseous fuels require less percentage of excess air for combustion as compared to liquid fuels

Last Answer : (B) Acetylene gas cannot be used for illumination purpose

In practical operation of any furnace, zero oxygen percentage or theoretical CO2 percentage in flue gas is rarely achieved, because of (A) Use of non-preheated combustion air (B) Use of pulverised solid fuels (C) Imperfect mixing of fuel & air and infiltration of air (D) Use of excessive positive draft in the furnace

Description : In practical operation of any furnace, zero oxygen percentage or theoretical CO2 percentage in flue gas is rarely achieved, because of (A) Use of non-preheated combustion air (B) Use of pulverised solid ... of fuel & air and infiltration of air (D) Use of excessive positive draft in the furnace

Last Answer : (C) Imperfect mixing of fuel & air and infiltration of air

A travelling grate stoker is meant for the efficient burning of __________ coal. (A) Caking (B) Pulverised (C) Non-caking (D) High ash

Description : A travelling grate stoker is meant for the efficient burning of __________ coal. (A) Caking (B) Pulverised (C) Non-caking (D) High ash

Last Answer : (C) Non-caking

Bulk density of pulverised coal may be about __________ kg/m3 . (A) 100 (B) 500 (C) 1000 (D) 1500

Description : Bulk density of pulverised coal may be about __________ kg/m3 . (A) 100 (B) 500 (C) 1000 (D) 1500

Last Answer : (B) 500

Limestone powder is injected during pulverised coal burning in boilers to __________ the flue gases. (A) Reduce SO2 content in (B) Catalytically convert SO2 to SO3 in (C) Increase the dew point of (D) None of these

Description : Limestone powder is injected during pulverised coal burning in boilers to __________ the flue gases. (A) Reduce SO2 content in (B) Catalytically convert SO2 to SO3 in (C) Increase the dew point of (D) None of these

Last Answer : (A) Reduce SO2 content in

Function of secondary air in pulverised coal firing is to (A) Transport the coal to the burner (B) Dry the coal (C) Ensure efficient burning of coal around the burner (D) Reduce primary air requirement

Description : Function of secondary air in pulverised coal firing is to (A) Transport the coal to the burner (B) Dry the coal (C) Ensure efficient burning of coal around the burner (D) Reduce primary air requirement

Last Answer : (C) Ensure efficient burning of coal around the burner

Combustion of pulverised fuel (A) Requires larger combustion chamber than rich gaseous fuel (B) In a metallurgical furnace does not contaminate the product in the furnace by ash from fuel (C) Suppresses the discharge of fine dust and grit into atmosphere (D) All (A), (B) and (C)

Description : Combustion of pulverised fuel (A) Requires larger combustion chamber than rich gaseous fuel (B) In a metallurgical furnace does not contaminate the product in the furnace by ash from fuel (C) Suppresses the discharge of fine dust and grit into atmosphere (D) All (A), (B) and (C)

Last Answer : (A) Requires larger combustion chamber than rich gaseous fuel

As the C/H ratio of the fuel increases, the amount of CO2 formed on combustion __________ for the same percentage of excess air. (A) Decreases (B) Increases (C) Remain same (D) May increase or decrease depending on the type of fuel

Description : As the C/H ratio of the fuel increases, the amount of CO2 formed on combustion __________ for the same percentage of excess air. (A) Decreases (B) Increases (C) Remain same (D) May increase or decrease depending on the type of fuel

Last Answer : (B) Increases

Acid rains are produced by (a) excess NO2 and SO2 from burning fossil fuels (b) excess production of NH3 by industry and coal gas (c) excess release of carbon monoxide by incomplete combustion (d) excess formation of CO2 by combustion and animal respiration.

Description : Acid rains are produced by (a) excess NO2 and SO2 from burning fossil fuels (b) excess production of NH3 by industry and coal  gas (c) excess release of carbon monoxide by incomplete  combustion (d) excess formation of CO2 by combustion and  animal respiration.

Last Answer : (a) excess NO2 and SO2 from burning fossil fuels

Acid rains are produced by (a) excess NO2 and SO2 from burning fossil fuels (b) excess production of NH3 by industry and coal gas (c) excess release of carbon monoxide by incomplete combustion (d) excess formation of CO2 by combustion and animal respiration.

Description : Acid rains are produced by (a) excess NO2 and SO2 from burning fossil fuels (b) excess production of NH3 by industry and coal gas (c) excess release of carbon monoxide by incomplete combustion (d) excess formation of CO2 by combustion and animal respiration.

Last Answer : (a) excess NO2 and SO2 from burning fossil fuels

Furnace oil consumption in a furnace for a given duty employing preheated combination air (at 300°) may be reduced by about __________ percent as compared to the use of atmospheric combustion air. (A) 5 (B) 10 (C) 20 (D) 35

Description : Furnace oil consumption in a furnace for a given duty employing preheated combination air (at 300°) may be reduced by about __________ percent as compared to the use of atmospheric combustion air. (A) 5 (B) 10 (C) 20 (D) 35

Last Answer : (C) 20

A sample of natural gas containing 80% methane (CH4 ) and rest nitrogen (N2 ) is burnt with 20% excess air. With 80% of the combustibles producing CO2 and the remainder going to CO, the Orsat analysis in volume percent is (A) CO2 : 6.26, CO : 1.56, O2 : 3.91, H2O :15.66, N2 : 72.60 (B) CO2 : 7.42, CO : 1.86, O2 : 4.64, N2 :86.02 (C) CO2 : 6.39, CO : 1.60, O2 : 3.99, H2O:25.96, N2 :72.06 (D) CO2 : 7.60, CO : 1.90, O2 : 4.75, N2 : 85.74

Description : A sample of natural gas containing 80% methane (CH4 ) and rest nitrogen (N2 ) is burnt with 20% excess air. With 80% of the combustibles producing CO2 and the remainder going to CO, the Orsat analysis in volume percent is (A) CO2 : 6 ... 96, N2 :72.06 (D) CO2 : 7.60, CO : 1.90, O2 : 4.75, N2 : 85.74

Last Answer : (B) CO2 : 7.42, CO : 1.86, O2 : 4.64, N2 :86.02

For every 10% increase in the excess air; the fuel consumption increases by __________ percent. (A) 0.1 (B) 0.2 (C) 0.5 (D) 1.0

Description : For every 10% increase in the excess air; the fuel consumption increases by __________ percent. (A) 0.1 (B) 0.2 (C) 0.5 (D) 1.0

Last Answer : (A) 0.1

Coal is finally pulverised to 200 mesh size for burning in boilers by a (A) Hammer crusher(B) Ball mill(C) Roll crusher(D) Gyratory crusher

Description : Coal is finally pulverised to 200 mesh size for burning in boilers by a (A) Hammer crusher (B) Ball mill (C) Roll crusher (D) Gyratory crusher

Last Answer : (B) Ball mill

Sphericity of pulverised coal is (A) 1 (B) < 1 (C) > 1 (D) ∞

Description : Sphericity of pulverised coal is (A) 1 (B) < 1 (C) > 1 (D) ∞

Last Answer : (B) < 1

Which of the following is the most important deterrents to an extended use of pulverised coal in boiler firing? (A) Ash disposal problem (B) Excessive fly ash discharge from the stack (C) Higher power consumption in its transportation (D) Erosion of induced draft fan blades

Description : Which of the following is the most important deterrents to an extended use of pulverised coal in boiler firing? (A) Ash disposal problem (B) Excessive fly ash discharge from the stack (C) Higher power consumption in its transportation (D) Erosion of induced draft fan blades

Last Answer : (A) Ash disposal problem

The advantages of firing pulverised coal in the furnace lies in the fact that, it (A) Permits the use of high ash content coal (B) Permits the use of low fusion point ash coal (C) Accelerates the burning rate and economises on fuel consumption (D) All (A), (B) and (C)

Description : The advantages of firing pulverised coal in the furnace lies in the fact that, it (A) Permits the use of high ash content coal (B) Permits the use of low fusion point ash coal (C) Accelerates the burning rate and economises on fuel consumption (D) All (A), (B) and (C)

Last Answer : (C) Accelerates the burning rate and economises on fuel consumption

Fuel used in B.F. stove is (A) Pulverised coal (B) Furnace oil (C) Blast furnace gas/mixed gas (D) Coke oven gas

Description : Fuel used in B.F. stove is (A) Pulverised coal (B) Furnace oil (C) Blast furnace gas/mixed gas (D) Coke oven gas

Last Answer : (C) Blast furnace gas/mixed gas

Junker's calorimeter is used to determine the calorific value of (A) Pulverised coal (B) Gaseous fuels (C) Fuel oil (D) None of these

Description : Junker's calorimeter is used to determine the calorific value of (A) Pulverised coal (B) Gaseous fuels (C) Fuel oil (D) None of these

Last Answer : (B) Gaseous fuels

Which of the following fuels is generally not used in thermal power plant boiler firing? (A) Furnace oil, light diesel oil and tar/PCM (B) Pulverised coking coal (C) Coal middling from washeries (D) B.F. gas, coke oven gas and L.D. converter gas

Description : Which of the following fuels is generally not used in thermal power plant boiler firing? (A) Furnace oil, light diesel oil and tar/PCM (B) Pulverised coking coal (C) Coal middling from washeries (D) B.F. gas, coke oven gas and L.D. converter gas

Last Answer : (B) Pulverised coking coal

Grindability index of a coal is 100. It implies that the (A) Coal can be pulverised with great difficulty (B) Coal can't be pulverised (C) Coal can be easily pulverised (D) Power consumption in grinding the coal will be very high

Description : Grindability index of a coal is 100. It implies that the (A) Coal can be pulverised with great difficulty (B) Coal can't be pulverised (C) Coal can be easily pulverised (D) Power consumption in grinding the coal will be very high

Last Answer : (C) Coal can be easily pulverised

Which of the following is the most important deterrents to an extended use of pulverised coal in boiler firing? (A) Ash disposal problem (B) Excessive fly-ash discharge from the stack (C) High power consumption in its transportation (D) Erosion of induced draft fan blades

Description : Which of the following is the most important deterrents to an extended use of pulverised coal in boiler firing? (A) Ash disposal problem (B) Excessive fly-ash discharge from the stack (C) High power consumption in its transportation (D) Erosion of induced draft fan blades

Last Answer : (A) Ash disposal problem

Which of the following will be unsuitable for dust cleaning from flue gas at 400°C from a pulverised coal fired boiler? (A) Multicyclones (B) Bag filter (C) Wet scrubber (D) Hydrocyclones

Description : Which of the following will be unsuitable for dust cleaning from flue gas at 400°C from a pulverised coal fired boiler? (A) Multicyclones (B) Bag filter (C) Wet scrubber (D) Hydrocyclones

Last Answer : (B) Bag filter

Pulverised coal used in boiler firing need not have (A) Less moisture content (B) High fusion point of its ash (C) High bulk density (D) Lower ash conten

Description : Pulverised coal used in boiler firing need not have (A) Less moisture content (B) High fusion point of its ash (C) High bulk density (D) Lower ash conten

Last Answer : (B) High fusion point of its ash

Which of the following fuels is the best for burning on chain grate stoker? (A) Non-caking coal (B) Caking coal (C) Coking coal (D) Pulverised coal

Description : Which of the following fuels is the best for burning on chain grate stoker? (A) Non-caking coal (B) Caking coal (C) Coking coal (D) Pulverised coal

Last Answer : (A) Non-caking coal

Pick out the wrong statement. (A) Theoretical flame temperature is the temperature attained by the products of combustion, when the fuel is burned without loss or gain of heat (B) Burning the fuel with theoretically required amount of pure oxygen results in attainment of maximum adiabatic flame temperature (C) Burning the fuel with excess pure oxygen results in maximum theoretical flame temperature (D) Adiabatic flame temperatures of actual combustions are always less than the maximum values

Description : Pick out the wrong statement. (A) Theoretical flame temperature is the temperature attained by the products of combustion, when the fuel is burned without loss or gain of heat (B) ... flame temperature (D) Adiabatic flame temperatures of actual combustions are always less than the maximum values

Last Answer : (C) Burning the fuel with excess pure oxygen results in maximum theoretical flame temperature

High relative humidity decreases the evaporative process and as the temperature is increased, the relative humidity decreases. The comfort range for human body is the ambient temperature of 22 to 27°C with relative humidity ranging from __________ percent. (A) 5 to 10 (B) 15 to 25 (C) 45 to 50 (D) 75 to 80

Description : High relative humidity decreases the evaporative process and as the temperature is increased, the relative humidity decreases. The comfort range for human body is the ambient temperature of 22 to 27°C with relative humidity ranging from __________ ... to 10 (B) 15 to 25 (C) 45 to 50 (D) 75 to 80

Last Answer : (C) 45 to 50

Quantity of coke produced from metallurgical coal may be around __________ percent. (A) 30 (B) 50 (C) 75 (D) 95

Description : Quantity of coke produced from metallurgical coal may be around __________ percent. (A) 30 (B) 50 (C) 75 (D) 95

Last Answer : (C) 75