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

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
by

1 Answer

Answer :

(B) Oxygen in the flue gas
by

Related questions

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

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

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

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)

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

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

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)

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

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Last Answer : (B) Enhanced sensible heat loss 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

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Last Answer : (A) Calorific value of the fuel

To reduce the stack loss, heat recovery from flue gas can be done by (A) Preheating of cold stock (B) Preheating of combustion air (C) Steam generation in waste heat boilers (D) All (A), (B) and (C)

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

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

Description : 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

Last Answer : (B) Dry gas/stack gas loss

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

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

Air filtration in a furnace (A) Reduces its thermal efficiency (B) Is indicated by flame sting out (C) Increases the flue gas temperature (D) None of these

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Last Answer : (A) Reduces its thermal efficiency

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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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

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

In a furnace, the heat taken by the charge/stock and the heat lost to the furnace structure & flue gases depends on the (A) Rate of firing and emissivity of flame (B) Thermal conductivity of the charge & structural materials of furnace (C) Nature of process; whether batch, continuous or intermittent (D) All (A), (B) and (C)

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

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

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

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 : a) natural gas

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

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

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

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

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Last Answer : (C) Flame temperature

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)

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

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

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

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

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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

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

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

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. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Description : . The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C ... from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Last Answer : (A) 165.4

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

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

Last Answer : (D) Carbon monoxide

Major sources of noise in furnace operation arises from air inspirators, combustion, side wall vibrations and fluctuation in the process heat load. A 50% increase in fuel firing rate may increase the furnace noise level by about __________ decibels. (A) 3 (B) 30(C) 7 (D) 70

Description : Major sources of noise in furnace operation arises from air inspirators, combustion, side wall vibrations and fluctuation in the process heat load. A 50% increase in fuel firing rate may increase the furnace noise level by about __________ decibels. (A) 3 (B) 30 (C) 7 (D) 70

Last Answer : (A) 3

For the case of a fuel gas undergoing combustion with air, if the air/fuel ratio is increased, the adiabatic flame temperature will (A) Increase (B) Decrease (C) Increase or decrease depending on the fuel type (D) Not change

Description : For the case of a fuel gas undergoing combustion with air, if the air/fuel ratio is increased, the adiabatic flame temperature will (A) Increase (B) Decrease (C) Increase or decrease depending on the fuel type (D) Not change

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Deficiency of combustion air during combustion of a gaseous fuel (A) Lengthens the flame (B) Causes heat loss of fuel by its partial combustion (C) Both (A) & (B) (D) Shortens the flame

Description : Deficiency of combustion air during combustion of a gaseous fuel (A) Lengthens the flame (B) Causes heat loss of fuel by its partial combustion (C) Both (A) & (B) (D) Shortens the flame

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

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)

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)

Description : 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)

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

The heat recoverable from flue gases of furnaces depends on the (A) Thermal efficiency of furnace (B) Quantity of flue gases (C) Flue gas temperature drop through the furnace (D) All (A), (B) and (C)

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

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

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.

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Theoretical flame temperature of a fuel is that temperature which is attained, when the fuel is completely burnt 'using theoretical amount of air in (A) Air (B) Oxygen (C) Either (A) or (B) (D) Either (A) or (B) without gain or loss of heat

Description : Theoretical flame temperature of a fuel is that temperature which is attained, when the fuel is completely burnt 'using theoretical amount of air in (A) Air (B) Oxygen (C) Either (A) or (B) (D) Either (A) or (B) without gain or loss of heat

Last Answer : (D) Either (A) or (B) without gain or loss of heat

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

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

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

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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Last Answer : (A) Require smaller combustion chamber

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

Description : 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

Last Answer : (A) Pitot tube

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)

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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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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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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