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

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
by

1 Answer

Answer :

(C) Can be done with less excess ai
by

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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)

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

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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)

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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

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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

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

A coal having high ratio of volatile matter to fixed carbon as compared to a coal having low ratio of volatile matter to fixed carbon (A) Is less liable to spontaneous combustion on storage (B) Is more difficult to ignite and produces a shorter flame (C) Requires smaller combustion space and less secondary air (D) None of these

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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

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

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Last Answer : (B) Better combustion

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Coke oven gas is a better fuel than blast furnace gas, because of its higher (A) Calorific value, cleanliness and relatively low distribution cost (due to its low specific gravity) (B) Adiabatic flame temperature (C) Heat release rate (thus requiring smaller combustion chamber) (D) All (A), (B) and (C)

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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

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A fuel with high heat release rate will (A) Require smaller combustion chamber (B) Have high calorific value (C) Have high adiabatic flame temperature (D) None of these

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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)

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

During combustion of a gaseous fuel, the presence of a non-luminous flame is an indication of the (A) Incomplete combustion (B) Complete combustion (C) High oxygen in flue gas (D) None of these

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Last Answer : (B) Complete combustion

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

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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

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To avoid fire by spontaneous combustion of coal due to its low temperature oxidation, it should be stored in (A) Shallow and small piles (B) Fine sizes without the presence of any lump (C) Closed space without any ventilation facility (D) Large heaps with small surface to volume ratio

Description : To avoid fire by spontaneous combustion of coal due to its low temperature oxidation, it should be stored in (A) Shallow and small piles (B) Fine sizes without the presence of any lump (C) Closed space without any ventilation facility (D) Large heaps with small surface to volume ratio

Last Answer : (A) Shallow and small piles

Cannel coal (A) Is non-coking (B) Has a high volatile matter content and burns with a luminous smoky flame (C) Is a non-banded coal which can be ignited easily with a match stick or candle flame, hence is so named (D) All (A), (B) and (C

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

Use of excess of combustion air in the combustion of fuels results in (A) Heat losses (B) Long flame (C) Condensation of water vapour from the fuel gas (D) None of these

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Last Answer : (A) Heat losses

Short/intense flame is produced during combustion of gaseous fuel by using (A) High amount/current of combustion air(B) Low amount/current of combustion air(C) Preheated secondary air(D) Very little excess air

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Last Answer : (A) High amount/current of combustion air

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

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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

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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

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Last Answer : (B) Completely burn the volatile matter

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

Oxygen enrichment of combustion air does not result in increase of the (A) Flame temperature (B) Oxygen in the flue gas (C) Stack loss (D) Heat transfer rate in the furnace

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Last Answer : (B) Oxygen in the flue gas

Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature? (A) Calorific value of the fuel (B) Flame temperature achieved (C) Speed of combustion of fuel (D) Heat transfer rate to the stock in the furnace

Description : Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature? (A) Calorific value of the fuel (B) Flame temperature achieved (C) Speed of combustion of fuel (D) Heat transfer rate to the stock in the furnace

Last Answer : (A) Calorific value of the fuel

Actual flame temperature is always lower than the adiabatic flame temperature, because there is (A) No possibility of obtaining complete combustion at high temperature (B) Always loss of heat from the flame (C) Both (A) and (B) (D) Neither (A) nor (B)

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Last Answer : (C) Both (A) and (B)

A sooty flame can be made non-luminous by (A) Admitting more gas (B) Shutting gas supply (C) Admitting more air (D) Shutting air supply

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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

High excess air in combustion of fuels results in (A) Increased fuel consumption (B) Incomplete combustion (C) Smoky flame (D) None of these

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Last Answer : (A) Increased fuel consumption

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

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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

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

Size of the combustion chamber of a furnace depends upon the (A) Heat release rate of the fuel (B) Preheat temperature of fuel & air (C) Method of mixing the fuel & air (D) All (A), (B) and (C)

Description : Size of the combustion chamber of a furnace depends upon the (A) Heat release rate of the fuel (B) Preheat temperature of fuel & air (C) Method of mixing the fuel & air (D) All (A), (B) and (C)

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

If the specific heat of gaseous products of combustion of a fuel is high, the abiabatic flame temperature will be (A) Low (B) High (C) Very high, if the fuel is of low calorific value (D) None of these

Description : If the specific heat of gaseous products of combustion of a fuel is high, the abiabatic flame temperature will be (A) Low (B) High (C) Very high, if the fuel is of low calorific value (D) None of these

Last Answer : (A) Low(A) Low

Preheating of combustion air is done to (A) Increase the adiabatic flame temperature (B) Increase the calorific value of the fuel (C) Complete the combustion of fuel (D) Reduce its requirement for effecting the complete combustion

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Last Answer : (A) Increase the adiabatic flame temperature

Presence of nitrogen in combustion air does not reduce the (A) Amount of heat liberated (B) Flame temperature (C) Flue gas temperature (D) Any of the above

Description : Presence of nitrogen in combustion air does not reduce the (A) Amount of heat liberated (B) Flame temperature (C) Flue gas temperature (D) Any of the above

Last Answer : (A) Amount of heat liberated

In high temperature carbonisation of coal compared to low temperature carbonisation (A) Yield of ammonia is less (B) Aromatic content of tar is low (C) H2 content in the coke oven gas is more (D) Calorific value of the coke oven gas is lower

Description : In high temperature carbonisation of coal compared to low temperature carbonisation (A) Yield of ammonia is less (B) Aromatic content of tar is low (C) H2 content in the coke oven gas is more (D) Calorific value of the coke oven gas is lower

Last Answer : (C) H2 content in the coke oven gas is more

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

The maximum adiabatic flame temperature in air as compared to that in pure oxygen is (A) Much lower (B) Much higher (C) Same (D) Either lower or higher, depends on the type of fuel

Description : The maximum adiabatic flame temperature in air as compared to that in pure oxygen is (A) Much lower (B) Much higher (C) Same (D) Either lower or higher, depends on the type of fuel

Last Answer : (A) Much lower

The hottest part of the flame lies in its _________zone. (A) Non-luminous (B) Luminous (C) Yellow (D) Unburnt gases

Description : The hottest part of the flame lies in its _________zone. (A) Non-luminous (B) Luminous (C) Yellow (D) Unburnt gases

Last Answer : (A) Non-luminous

Stack heat losses can be minimised by (A) Controlling the excess air (B) Oxygen enrichment of combustion air (C) Using low c.v. fuels (D) Maintaining proper draft in the furnace

Description : Stack heat losses can be minimised by (A) Controlling the excess air (B) Oxygen enrichment of combustion air (C) Using low c.v. fuels (D) Maintaining proper draft in the furnace

Last Answer : (A) Controlling the excess air

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

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

Too much of excess air in combustion results in high (A) Fuel consumption for the same heat load (B) Stack gas temperature (C) Percentage of oxygen in flue gases (D) All (A), (B) and (C)

Description : Too much of excess air in combustion results in high (A) Fuel consumption for the same heat load (B) Stack gas temperature (C) Percentage of oxygen in flue gases (D) All (A), (B) and (C)

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

The main drawback of supplying more excess air in the combustion of fuel is the (A) Excessive power requirement of air blower (B) Enhanced sensible heat loss in the flue gas (C) Intermittent and uncontrolled combustion of the fuel (D) High exit flue gas temperature from the furnace

Description : The main drawback of supplying more excess air in the combustion of fuel is the (A) Excessive power requirement of air blower (B) Enhanced sensible heat loss in the flue gas (C) Intermittent and uncontrolled combustion of the fuel (D) High exit flue gas temperature from the furnace

Last Answer : (B) Enhanced sensible heat loss in the flue gas

What happens to a nichrome wire in a non-luminous flame?

Description : What happens to a nichrome wire in a non-luminous flame?

Last Answer : The color of wire is unchanged.

The hottest part of the gas flame is known as – (1) blue zone (2) non-luminous zone (3) luminous zone (4) dark zone

Description : The hottest part of the gas flame is known as – (1) blue zone (2) non-luminous zone (3) luminous zone (4) dark zone

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