Description : 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
Last Answer : (A) Heat losses
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
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)
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
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
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
Description : A coal having high amount of volatile matter (A) Would require smaller combustion chamber (B) Produces very little of tar and gas on carbonisation (C) Ignites easily and burns with long smoky flame (D) All (A), (B) and (C)
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
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
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
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)
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
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
Last Answer : (B) Decrease
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
Description : During combustion of gaseous fuels, deficiency of air (A) Lengthens the flame (B) Tends to shorten the flame (C) Does not affect the flame length (D) Increases the flame temperature
Last Answer : (A) Lengthens the flame
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
Description : With increase in calorific value of fuels, their adiabatic flame temperatures (A) Increase (B) Decrease (C) Remain unchanged (D) May increase or decrease; depends on the quantity of products of combustion
Last Answer : (D) May increase or decrease; depends on the quantity of products of combustion
Description : Lignite is (A) A high rank coal (B) A coking coal (C) Can be used for gasification and steam generation (D) A black banded coal which burns with a non-smoky yellowish flame
Last Answer : (C) Can be used for gasification and steam generation
Description : 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
Last Answer : (D) All (A), (B) and (C
Description : . A coal having high volatile matter content will (A) Give less yield of tar and gas on carbonisation (B) Burn with a small non-smoky flame (C) Have a very high calorific value (D) None of these
Last Answer : (D) None of these
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
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)
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
Description : Preheating of a gaseous fuel results in increased (A) Flame length (B) Flame temperature (C) Quantity of flue gas
Description : Bituminous coal (A) Ignites less easily than anthracite (B) Is generally coking (C) Burns with smoky yellow flame (D) Both (B) and (C)
Last Answer : (D) Both (B) and (C)
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
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
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
Description : __________ 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
Last Answer : (C) High % of CO in
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)
Description : 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
Last Answer : (A) Increase the adiabatic flame temperature
Description : Preheating of __________ the flame temperature. (A) The gaseous fuel before combustion decreases (B) Combustion air decreases (C) Either the fuel or the air or both, increases (D) Either the fuel or the air does not affect
Last Answer : (C) Either the fuel or the air or both, increases
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
Description : Supply of excess air for complete combustion of fuel is necessitated to facilitate (A) Its thorough mixing with air (B) Attainment of chemical equilibrium (C) Attainment of high temperature (D) None of these
Last Answer : (A) Its thorough mixing with air
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
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
Description : 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
Last Answer : (A) Require smaller combustion chamber
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
Description : 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
Last Answer : (A) Flue gases
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)
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
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
Description : The optimum percentage of excess air for combustion depends upon the__________ of the fuel. (A) Type (solid, liquid or gaseous) (B) Calorific value (C) Sulphur content (D) Ignition temperature
Last Answer : (A) Type (solid, liquid or gaseous)
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
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
Description : 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 ... release rate (thus requiring smaller combustion chamber) (D) All (A), (B) and (C)
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.
Description : 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
Last Answer : ans b