If oxygen content in the flue gas rises too high, fuel is being wasted by (A) Incomplete combustion (B) Dry gas/stack gas loss (C) Moisture loss (D) None of these

If oxygen content in the flue gas rises too high, fuel is being wasted by
(A) Incomplete combustion
(B) Dry gas/stack gas loss
(C) Moisture loss
(D) None of these
by

1 Answer

Answer :

(B) Dry gas/stack gas loss
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Fuel combustion is never cent per cent efficient due to (A) Incomplete combustion (B) Dry gas/stack gas loss (C) Moisture loss (D) All (A), (B) and (C)

Description : Fuel combustion is never cent per cent efficient due to (A) Incomplete combustion (B) Dry gas/stack gas loss (C) Moisture loss (D) All (A), (B) and (C)

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

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)

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

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

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Which of the following accounts for maximum energy loss in a boiler? (A) Flue gases (B) Ash content in the fuel (C) Incomplete combustion (D) Unburnt carbon in flue gases

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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

Incomplete combustion of a fuel is characterised by the high __________ in the flue gas. (A) Smoke (B) Temperature (C) Oxygen (D) Carbon monoxide

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Last Answer : (D) Carbon monoxide

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

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

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

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Last Answer : (C) Blast furnace gas with air

When incomplete combustion loss is high, the flue gas analysis shows large amount of (A) CO2 (B) CO (C) O2 (D) C

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Last Answer : (B) CO

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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

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Last Answer : d. All of above

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

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

The biggest loss in the boiler is a) Moisture in fuel b) Dry flue gases c) Steam formation d) Unburnt carbon

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Last Answer : b) Dry flue gases

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

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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

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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

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High sulphur content in a fuel __________ of the flue gases. (A) Decreases the dew point (B) Increases the dew point (C) Reduces the combustion efficiency by limiting the permissible temperature reduction (D) Both (B) and (C)

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The engine produces dark black smoke due to a) Burning of oil b) Due of incomplete combustion c) Due to moisture in fuel d) None of these Ans. b

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Moisture loss is determined by the (A) Humidity of combustion air (B) Moisture content of fuel (C) Both (A) and (B) (D) The water formed by combustion reaction

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

measures oxygen and temperature of the flue gas. a) Fuel efficiency monitor. b) Combustion analyzer. c) Contact thermometer. d) Infrared thermometer.

Description : measures oxygen and temperature of the flue gas. a) Fuel efficiency monitor. b) Combustion analyzer. c) Contact thermometer. d) Infrared thermometer.

Last Answer : Combustion analyzer

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

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

__________ the exhaust gas is an indication of the incomplete combustion of fuel. (A) Low temperature of (B) High temperature of (C) High % of CO in (D) High % of CO2in

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Last Answer : (C) High % of CO in

Acid dew point temperature (ADT) of a flue gas produced by the combustion of a fuel containing 1% sulphur may be about __________ °C. (A) 80 (B) 130 (C) 180 (D) 250

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Last Answer : (B) 130

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

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Last Answer : (B) % of O2 in

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)

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

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

Last Answer : (A) Increased fuel consumption

A liquid/gaseous fuel containing hydrocarbons and high amount of sulphur is burnt with 40% excess air. The flue gas still contains large amount of carbon monoxide. This may be due to the (A) Presence of large quantity of hydrogen in the fuel (B) Low calorific value of the fuel (C) High sulphur content in the fuel (D) Lack of thorough mixing of fuel with air

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Economizer is provided to utilize the flue gas heat for ___ a) preheating the boiler feed water b) preheating the stock c) preheating the combustion air d) preheating fuel

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Flow rate of high velocity flue gas discharged through a stack to the atmosphere can be most conveniently measured by a (A) Pitot tube (B) Manometer (C) Rotameter (D) None of these

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_______ is highly poisonous gas produced as a result of incomplete combustion. a) oxygen b)carbon dioxide c)carbon mono oxide d)soot

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

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

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Last Answer : (A) < 2

Why is water not suitable for putting out a petrol fire? (1) The oxygen content of water is isolated by petrol and thus it helps in burning (2) Petrol is too inflammable to be extinguished by water (3) The heat required for combustion of petrol is very low (4) Water, being heavy, slips below petrol which thus remains in contact with air and burns

Description : Why is water not suitable for putting out a petrol fire? (1) The oxygen content of water is isolated by petrol and thus it helps in burning (2) Petrol is too inflammable to be extinguished by ... very low (4) Water, being heavy, slips below petrol which thus remains in contact with air and burns

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Description : Why is water not suitable for putting out a petrol fire? (1) The oxygen content of water is isolated by petrol and thus it helps in burning (2) Petrol is too inflammable to be extinguished by ... very low (4) Water, being heavy, slips below petrol which thus remains in contact with air and burns

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Last Answer : Water, being heavy, slips below petrol which thus remains in contact with air and burns

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)

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Pick out the wrong statement. (A) A slight haze at the top of chimney indicates good combustion in the furnace (B) A bag filter incurs very small pressure drop and is very efficient for removal of submicronic dust particles from flue gases at very high temperature (C) Electrostatic precipitator is the most efficient dust collection equipment for removal of submicronic dust particles present in flue gas (D) None of these

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Last Answer : (B) A bag filter incurs very small pressure drop and is very efficient for removal of submicronic dust particles from flue gases at very high temperature

Which of the following gases is produced due to incomplete combustion of fuel? (1) Carbon Dioxide (2) Carbon Monoxide (3) Methane (4) Ethane

Description : Which of the following gases is produced due to incomplete combustion of fuel? (1) Carbon Dioxide (2) Carbon Monoxide (3) Methane (4) Ethane

Last Answer : (2) Carbon Monoxide Explanation: Carbon monoxide (CO) is an odorless, colorless gas formed by the incomplete com bustion of fuels. It is produced from the partial oxidation of carbon-containing com pounds; it forms when there is not enough oxygen to produce carbon dioxide.

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

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

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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Ostwald charts are meant for (A) Computing the excess/deficiency of combustion air (B) Calculation of flue gas temperature (C) Computation of flue gas analysis (D) None of these

Description : Ostwald charts are meant for (A) Computing the excess/deficiency of combustion air (B) Calculation of flue gas temperature (C) Computation of flue gas analysis (D) None of these

Last Answer : (A) Computing the excess/deficiency of combustion air

Orsat apparatus is meant for (A) Gravimetric analysis of flue gas (B) Finding out combustion efficiency (C) Direct determination of nitrogen in flue gas by absorbing it in ammoniacal cuprous chloride (D) None of these

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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

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With increase in moisture content of coal, its (A) Calorific value increases sometimes (B) Bulk density always decreases (C) Clinkering tendency during combustion increases (D) None of these

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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

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