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

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
by

1 Answer

Answer :

(C) Imperfect mixing of fuel & air and infiltration of air
by

Related questions

Fuel economy in an industrial furnace operation cannot be achieved by the use of (A) Stoichiometric combustion air (B) Non-preheated combustion air (C) Combustion air not enriched with oxygen (D) Recuperators

Description : Fuel economy in an industrial furnace operation cannot be achieved by the use of (A) Stoichiometric combustion air (B) Non-preheated combustion air (C) Combustion air not enriched with oxygen (D) Recuperators

Last Answer : (A) Stoichiometric combustion air

In a furnace operation, which is not preheated? (A) Solid fuels (B) Hydrocarbon containing fuel gases (e.g. coke oven gas, refinery gas etc.) (C) Both (A) and (B) (D) Neither (A) nor (B)

Description : In a furnace operation, which is not preheated? (A) Solid fuels (B) Hydrocarbon containing fuel gases (e.g. coke oven gas, refinery gas etc.) (C) Both (A) and (B) (D) Neither (A) nor (B)

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

Out of the following fuels used in a furnace exhausting flue gas at a temperature of 600°C, the percentage stack loss will be maximum in case ofcomplete combustion of(A) Furnace oil with air(B) Furnace oil with oxygen(C) Blast furnace gas with air(D) Blast furnace gas with oxygen

Description : Out of the following fuels used in a furnace exhausting flue gas at a temperature of 600°C, the percentage stack loss will be maximum in case ofcomplete combustion of (A) Furnace oil with air (B) Furnace oil with oxygen (C) Blast furnace gas with air (D) Blast furnace gas with oxygen

Last Answer : (C) Blast furnace gas with air

Higher furnace temperature cannot be achieved by use of a lean fuel gas in the furnace by (A) Increasing the draft in the furnace (B) Preheating the fuel gas (C) Oxygen enrichment of combustion air (D) Preheating the combustion air

Description : Higher furnace temperature cannot be achieved by use of a lean fuel gas in the furnace by (A) Increasing the draft in the furnace (B) Preheating the fuel gas (C) Oxygen enrichment of combustion air (D) Preheating the combustion air

Last Answer : (A) Increasing the draft in the furnace

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

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

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

Higher efficiency in the combustion of solid fuel cannot be achieved by (A) Proper fuel preparation (B) Keeping the flue gas exhaust temperature very high (C) Adopting efficient-fuel firing technique & equipment (D) Supplying correct quantity of combustion air

Description : Higher efficiency in the combustion of solid fuel cannot be achieved by (A) Proper fuel preparation (B) Keeping the flue gas exhaust temperature very high (C) Adopting efficient-fuel firing technique & equipment (D) Supplying correct quantity of combustion air

Last Answer : (B) Keeping the flue gas exhaust temperature very high

Volumetric composition of flue gas analysed with the Orsat apparatus is : CO2 = 12%, O2 = 8%, CO = nil, N2 = 80%. This flue gas composition indicates that (A) Pure oxygen has been used for combustion (B) Nitrogen percentage in the fuel is very high (C) Excess air has been used for combustion (D) Hydrogen is not present in the fuel

Description : Volumetric composition of flue gas analysed with the Orsat apparatus is : CO2 = 12%, O2 = 8%, CO = nil, N2 = 80%. This flue gas composition indicates that (A) Pure oxygen has been used for combustion ... very high (C) Excess air has been used for combustion (D) Hydrogen is not present in the fuel

Last Answer : (C) Excess air has been used for combustion

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

Which of the following accentuates clinkering troubles on furnace grate burning coal? (A) Low reactivity of carbonised residue containing high proportion of iron & sulphur (B) Low forced draft & fuel bed temperature (C) Thick firebed and preheated primary air (D) All (A), (B) and (C)

Description : Which of the following accentuates clinkering troubles on furnace grate burning coal? (A) Low reactivity of carbonised residue containing high proportion of iron & sulphur (B) Low forced draft & fuel bed temperature (C) Thick firebed and preheated primary air (D) All (A), (B) and (C)

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

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

Combustion of fuel in a furnace with oxygen enriched air results in higher (A) Flue gas volume (B) Flame temperature (C) Fuel consumption (D) Stack loss

Description : Combustion of fuel in a furnace with oxygen enriched air results in higher (A) Flue gas volume (B) Flame temperature (C) Fuel consumption (D) Stack loss

Last Answer : (B) Flame temperature

A carbonaceous fuel (containing no H2 or hydrocarbons) is burnt and the resulting flue gas contains 21% CO2 . It means that (A) 21% excess air has been used for combustion (B) 21% excess oxygen has been used for combustion (C) Complete combustion of fuel has taken place (D) No excess air has been used for combustion

Description : A carbonaceous fuel (containing no H2 or hydrocarbons) is burnt and the resulting flue gas contains 21% CO2 . It means that (A) 21% excess air has been used for combustion (B) 21% excess oxygen has ... (C) Complete combustion of fuel has taken place (D) No excess air has been used for combustion

Last Answer : (C) Complete combustion of fuel has taken place

Fuel economy in furnaces can be achieved by (A) Using oxygen enriched combustion air (B) Preheating the combustion air (C) Reducing the heat loss through furnace openings & doors (D) All (A), (B) and (C

Description : Fuel economy in furnaces can be achieved by (A) Using oxygen enriched combustion air (B) Preheating the combustion air (C) Reducing the heat loss through furnace openings & doors (D) All (A), (B) and (C

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

White flue gas (resembling steam) coming out of the chimney of a thermal power plant indicates that the fuel used in the boiler furnace is (A) Tar (B) Coke oven gas (C) Pitch (D) Pulverised coke

Description : White flue gas (resembling steam) coming out of the chimney of a thermal power plant indicates that the fuel used in the boiler furnace is (A) Tar (B) Coke oven gas (C) Pitch (D) Pulverised coke

Last Answer : (B) Coke oven gas

Incomplete combustion of fuel in the furnace is judged by high __________ of the flue gases. (A) CO content (B) Dew point (C) CO2 content (D) O2 content

Description : Incomplete combustion of fuel in the furnace is judged by high __________ of the flue gases. (A) CO content (B) Dew point (C) CO2 content (D) O2 content

Last Answer : (A) CO content

Which of the following advantages is not associated with the use of preheated air for combustion of a fuel in the furnace? (A) Increase in calorific value of the fuel (B) Increase in flame temperature (C) Reduction in scale losses (D) Saving in fuel consumption

Description : Which of the following advantages is not associated with the use of preheated air for combustion of a fuel in the furnace? (A) Increase in calorific value of the fuel (B) Increase in flame temperature (C) Reduction in scale losses (D) Saving in fuel consumption

Last Answer : (A) Increase in calorific value of the fuel

Use of preheated air for combustion of fuel in the furnace, increases the (A) Scale losses of the furnace stock (B) Calorific value of the fuel (C) Flame temperature (D) None of these

Description : Use of preheated air for combustion of fuel in the furnace, increases the (A) Scale losses of the furnace stock (B) Calorific value of the fuel (C) Flame temperature (D) None of these

Last Answer : (C) Flame temperature

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)

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

Flue gas obtained on complete combustion of pure acetylene (a hydrocarbon fuel) will contain (A) CO (B) CO2 (C) H2O (D) Both (B) & (C)

Description : Flue gas obtained on complete combustion of pure acetylene (a hydrocarbon fuel) will contain (A) CO (B) CO2 (C) H2O (D) Both (B) & (C)

Last Answer : (D) Both (B) & (C)

Heat transfer rate to the charge/stock in a furnace does not depend upon the (A) Type of fuels viz. solid, liquid or gaseous (B) Flue gas temperature (C) Emissivity of refractory walls (D) Initial temperature of the charged stock

Description : Heat transfer rate to the charge/stock in a furnace does not depend upon the (A) Type of fuels viz. solid, liquid or gaseous (B) Flue gas temperature (C) Emissivity of refractory walls (D) Initial temperature of the charged stock

Last Answer : (A) Type of fuels viz. solid, liquid or gaseous

Oxygen percentage in the flue gas coming out of a gaseous fuel fired furnace should be ideally about __________ percent. (A) < 2 (B) < 5 (C) < 8 (D) < 10

Description : Oxygen percentage in the flue gas coming out of a gaseous fuel fired furnace should be ideally about __________ percent. (A) < 2 (B) < 5 (C) < 8 (D) < 10

Last Answer : (A) < 2

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

Description : 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

Last Answer : (B) Oxygen in the flue gas

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)

Smoke is produced due to (A) Insufficient supply of combustion air and insufficient time for combustion (B) Poor quality of fuel and improper mixing of fuel & combustion air (C) Poor design & overloading of furnace (D) All (A), (B) and (C)

Description : Smoke is produced due to (A) Insufficient supply of combustion air and insufficient time for combustion (B) Poor quality of fuel and improper mixing of fuel & combustion air (C) Poor design & overloading of furnace (D) All (A), (B) and (C)

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

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

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

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

Description : 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

Last Answer : (B) Complete combustion

Efficiency of the combustion of a fuel is judged by the __________ the flue gas. (A) % of CO2 in (B) % of O2 in (C) Temperature of (D) Colour of

Description : Efficiency of the combustion of a fuel is judged by the __________ the flue gas. (A) % of CO2 in (B) % of O2 in (C) Temperature of (D) Colour of

Last Answer : (B) % of O2 in

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

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)

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)

Which of the following accentuates clinkering trouble on furnace grate burning coal? (A) Low reactivity of carbonised residue containing high proportions of iron & sulphur (B) Low forced draught and fuel bed temperature (C) Thick fire bed and preheated primary air (D) All (A), (B) and (C)

Description : Which of the following accentuates clinkering trouble on furnace grate burning coal? (A) Low reactivity of carbonised residue containing high proportions of iron & sulphur (B) Low forced draught and fuel bed temperature (C) Thick fire bed and preheated primary air (D) All (A), (B) and (C)

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

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

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

Combustion of furnace oil in a furnace (soaking pit) with preheated combustion air at 400°C results in saving of about __________ percentfurnace oil as compared to its combustion with atmospheric air, if the fluegas outlet temperature from the soaking pit is 1200°C.(A) 5(B) 60(C) 20(D) 40

Description : Combustion of furnace oil in a furnace (soaking pit) with preheated combustion air at 400°C results in saving of about __________ percentfurnace oil as compared to its combustion with atmospheric air, if the flue gas outlet temperature from the soaking pit is 1200°C. (A) 5 (B) 60 (C) 20 (D) 40

Last Answer : (C) 20

Temperature of a furnace fired with low calorific value fuel gas (i.e. lean gas) can be increased by (A) Preheating the combustion air (B) Oxygen enrichment of combustion air (C) Preheating the fuel gas (D) All (A), (B) & (C)

Description : Temperature of a furnace fired with low calorific value fuel gas (i.e. lean gas) can be increased by (A) Preheating the combustion air (B) Oxygen enrichment of combustion air (C) Preheating the fuel gas (D) All (A), (B) & (C)

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

The main advantage of forced draft over natural draft is that (A) Combustion of fuel is complete (B) Smaller height chimney can be used (C) Furnace control is easier (D) All (A), (B) & (C)

Description : The main advantage of forced draft over natural draft is that (A) Combustion of fuel is complete (B) Smaller height chimney can be used (C) Furnace control is easier (D) All (A), (B) & (C)

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

Ingress of cold air in the furnaces through cracks, charging doors, openings etc(A) Reduces the flue gas temperature and makes the furnace atmosphereoxidising(B) Increases the load on the induced draft fan(C) Reduces the furnace draught(D) All (A), (B) and (C)

Description : Ingress of cold air in the furnaces through cracks, charging doors, openings etc (A) Reduces the flue gas temperature and makes the furnace atmosphere oxidising (B) Increases the load on the induced draft fan (C) Reduces the furnace draught (D) All (A), (B) and (C)

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

Which among the following has the highest flue gas loss on combustion due to Hydrogen in the fuel? a) natural gas b) furnace oil c) coal d) light diesel oil

Description : Which among the following has the highest flue gas loss on combustion due to Hydrogen in the fuel? a) natural gas b) furnace oil c) coal d) light diesel oil

Last Answer : a) natural gas

Oxygen trim control strategy __ a. continuously measures the oxygen content in the flue gas b. adjusts the combustion air flow c. Continually tuning the air-fuel mixture. d. All of above

Description : Oxygen trim control strategy __ a. continuously measures the oxygen content in the flue gas b. adjusts the combustion air flow c. Continually tuning the air-fuel mixture. d. All of above

Last Answer : d. All of above

Advantages of fluidised bed combustion are (A) Reduced NOx formation in flue gas (B) Lower furnace operating temperature (C) High heat transfer rate (D) All (A), (B) & (C)

Description : Advantages of fluidised bed combustion are (A) Reduced NOx formation in flue gas (B) Lower furnace operating temperature (C) High heat transfer rate (D) All (A), (B) & (C)

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

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

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

The maximum percentage of CO2 in a flue gas (from a carbonaceous fuel) can be(A) 21(B) 77(C) 79(D) 29

Description : The maximum percentage of CO2 in a flue gas (from a carbonaceous fuel) can be (A) 21 (B) 77 (C) 79 (D) 29

Last Answer : (A) 21

Advantages of use of preheated combustion air are (A) Saving in fuel consumption (B) Reduction in scale losses (C) Increase in flame temperature (D) All (A), (B) and (C)

Description : Advantages of use of preheated combustion air are (A) Saving in fuel consumption (B) Reduction in scale losses (C) Increase in flame temperature (D) All (A), (B) and (C)

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

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

Description : 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

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