Furnace Technology MCQs : This section focuses on the "Furnace Technology". These Multiple Choice Questions (MCQs) should be practiced to improve the Furnace Technology skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
Question 1
__________ atmosphere is maintained inside an iron blast furnace.
A. Oxidising
B. Reducing
C. Inert
D. Decarburising
Question 2
__________ is an indirectly heated furnace.
A. Open hearth furnace
B. Muffle furnace
C. Soaking pit
D. Reheating furnace
Question 3
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
Question 4
An example of a periodic furnace is the
A. blast furnace stoves
B. blast furnace
C. coke oven heating chamber
D. rotary kilns
Question 5
An example of shaft furnace is the
A. L.D. converter
B. glass melting tank
C. blast furnace
D. soaking pit
Question 6
Calcination of limestone to produce lime is done in a __________ kiln.
A. tunnel
B. rotary
C. vertical shaft
D. both (b) and (c)
Question 7
Cement Kiln is a
A. rotary Kiln
B. tunnel Kiln
C. natural draft furnace
D. batch furnace
Question 8
Ceramic coating material for furnace refractory, which increases its emissivity and thus the radiation heat transfer rate in the furnace, comprises of
A. graphite powder
B. thoria
C. zircon powder
D. beryllium
Question 9
Ceramic recuperators (made of SiC) is economical, only when used for preheating combustion air above __________ °C.
A. 250
B. 650
C. 850
D. 1000
Question 10
Ceramic recuperators compared to metallic recuperators for the same duty
A. are lighter.
B. occupy more space.
C. are less costly.
D. have higher pressure differential between flue gas & air side.
Question 11
Coke ovens in steel plant are heated by
A. electricity
B. blast furnace gas/mixed gas
C. coke oven gas
D. both (b) and (c)
Question 12
Example of an indirectly heated furnace is
A. hood annealing furnace
B. muffle furnace
C. both (a) and (b)
D. neither (a) nor (b)
Question 13
Fuel used in B.F. stove is
A. pulverised coal
B. furnace oil
C. blast furnace gas/mixed gas
D. coke oven gas
Question 14
Heat transfer rate to the stock/charge in the furnace does not depend upon the
A. emissivity of the refactory walls.
B. size of the furance.
C. use of waste heat recovery equipments.
D. thickness of the stock.
Question 15
Higher furnace temperature can not 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.
Question 16
In a furnace employing forced draught as compared to induced draught,
A. air is sucked in, so air leaks are more and hence the furnace efficiency is reduced.
B. the fan operates hot and hence blades are liable to corrosion and erosion.
C. positive pressure exists in the furnace.
D. none of these
Question 17
In a muffle furnace, the muffle
A. retards the heat transfer.
B. assists in temperature equalisation in the charge.
C. permits the use of controlled atmosphere for the protection of stock.
D. all (a), (b) and (c).
Question 18
In order to maintain a reducing atmosphere in a furnace, it should have
A. no O2 in flue gas
B. CO in flue gas
C. high excess air
D. none of these
Question 19
In producer gas making furnace, steam is added along with air to mainly control the
A. fusion of coal ash & clinker formation.
B. C. V. of producer gas.
C. temperature of producer gas.
D. tar content in producer gas.
Question 20
In reverberatory furnace, charge is heated mainly by
A. conduction.
B. natural convection.
C. radiation of heat from the roof of the combustion chamber.
D. none of these.
Question 21
Large tonnage of refractory bricks are dried in a
A. shaft furnace
B. rotary hearth furnace
C. tunnel kiln
D. muffle furnace
Question 22
Low stack loss indicates the
A. use of sub-stoichiometric air for combustion.
B. efficient use of fuel.
C. inefficient use of fuel.
D. oxygen enrichment of combustion air.
Question 23
Maximum heat transfer in high temperature furnaces is by
A. conduction
B. convection
C. radiation
D. either (a), (b) or (c); depends on the type of furnace
Question 24
Means for giving direction to the circulation of gases in furnaces are
A. fans.
B. arrangement of heating stock in the furnaces.
C. location of outlet ports and heating & combustion devices.
D. all (a), (b) and (c).
Question 25
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.
Question 26
Pulverised fuel fired furnaces employ __________ fuel firing.
A. horizontal
B. vertical
C. tangential
D. all (a), (b) and (c)
Question 27
Regenerators are installed in
A. coke ovens
B. open hearth furnace
C. both (a) & (b)
D. neither (a) nor (b)
Question 28
Soaking pits are meant for heating steel
A. ingots
B. coils
C. sheets
D. slabs
Question 29
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).
Question 30
The amount of combustible escaping uncon-sumed from the furnace, depends upon the
A. air supplied and furnace temperature.
B. burner design (thoroughness of mixing versus stratification).
C. air preheat and the flow of gases in the furnace (mixing by induction, by acceleration or by change of direction).
D. all (a), (b) and (c).
Question 31
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).
Question 32
The purpose of controlling the furnace atmosphere is to prevent surface attack by
A. oxidation/scaling
B. decarburising
C. sulphur penetration
D. either of the above
Question 33
The reason for excessive clinker formation in gas producers is the
A. use of coal/coke containing a high % of fines and ash.
B. use of fuel having too low an ash fusion temperature.
C. development of hot spots in the fuel bed and an abnormally high rate of gasification.
D. all (a), (b) and (c).
Question 34
The thermal efficiency of a steel slab reheating furnace (walking beam type) may be about __________ percent.
A. 15
B. 40
C. 70
D. 85
Question 35
The thermal efficiency of an air/fuel gas preheating recuperator may be as high as __________ percent.
A. 50
B. 65
C. 85
D. 99
Question 36
Thermal efficiency of a limestone calcination rotary kiln may be around __________ percent.
A. 20
B. 40
C. 65
D. 80
Question 37
Thermal efficiency of blast furnace stoves used for heating blast (air) may be about __________ percent.
A. 20
B. 40
C. 60
D. 80
Question 38
Thickness of stock does not affect the fuel economy of furnaces, if the material to be heated is of
A. low emissivity
B. high thermal conductivity
C. both (a) and (b)
D. neither (a) nor (b)
Question 39
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).
Question 40
Tunnel kilns are usually used for
A. roasting of pyrites.
B. drying/tempering of refractories.
C. reheating of slabs.
D. melting of glass.
Question 41
Which furnace employs preheating, heating and soaking zones ?
A. Soaking pit
B. Reheating furnace
C. Open hearth furnace
D. Cupola
Question 42
Which is a continuous furnace ?
A. Coke ovens
B. Annealing furnace
C. Glass tank furnace
D. None of these
Question 43
Which is not a hearth furnace ?
A. Glass tank furnace
B. Open hearth furnace
C. Cupola
D. Reheating furnace
Question 44
Which is the most thermally efficient furnace ?
A. Reheating furnace
B. Reverberatory furnace
C. Rotary kilns
D. Boiler furnace
Question 45
Which of the following is a heat treatment furnace ?
A. Muffle furnace
B. Annealing furnace
C. Reheating furnace
D. Rotary kiln
Question 46
Which of the following is a natural draft furnace ?
A. Blast furnace stoves
B. Power plant boilers
C. Sintering furnace
D. None of these
Question 47
Which of the following is not a directly fired furnace ?
A. By-product coke oven
B. Calcination kiln
C. Sintering furnace
D. Open hearth furnace
Question 48
Which of the following is not an additive for flue gases from furnace to reduce its dew-point?
A. Ammonia
B. Fine dolomite
C. Alkaline powders
D. None of these
Question 49
Which of the following is the most suitable for preheating combustion air above 650°C ?
A. Regenerator
B. Metallic recuperator
C. Ceramic recuperator
D. None of these
Question 50
Overfire burning in a furnace is a phenomenon characterised by
A. Supply of excess fuel
B. Supply of excess air
C. Burning carbon monoxide and other incombustible in upper zone of furnace by supplying more air
D. None of these
Question 51
Which of the following variables does not affect the furnace capacity?
A. Size of the furnace
B. Gas velocity in furnace
C. Ratio of wall surface to surface of stock
D. None of these
Question 52
Reducing atmosphere is maintained in a
A. Calcination kiln
B. Blast furnace
C. Soaking pit
D. L.D. converter
Question 53
Main gas valve in a gaseous fuel burner is a __________ valve.
A. Gate
B. Butterfly
C. Globe
D. None of these
Question 54
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 of the above
Question 55
Which furnace employs an I.D. fan for the removal of flue gases from the furnace?
A. Coke oven
B. Blast furnace stoves
C. Beehive coke oven
D. High pressure boiler
Question 56
The function of an economiser in a boiler is to preheat the
A. Feedwater
B. Combustion air
C. Pulverised coal
D. Furnace oil
Question 57
Which of the following is a heat treatment furnace?
A. Muffle furnace
B. Annealing furnace
C. Reheating furnace
D. Rotary kiln
Question 58
The electric furnace in which heat is produced by a combination of induced current and skin effect is called __________ furnace.
A. Arc
B. Resistance
C. Low frequency induction
D. High frequency induction
Question 59
An electric furnace producing heat by means of an electric arc struck between each of three electrodes and the charge is called __________ furnace.
A. Resistance
B. Arc
C. Low frequency induction
D. None of these
Question 60
Calcination of limestone to produce lime is done in a __________ kiln.
A. Tunnel
B. Rotary
C. Vertical shaft
D. Both B and C
Question 61
Pot furnace which is either regenerative or recupterative, is used in the manufacture of
A. Glass
B. Stainless steel
C. Potteries
D. Refractory bricks
Question 62
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 of the above
Question 63
The heating capacity of muffle furnace depends on the
A. Surface area & emissivity of the stock
B. Properties of the muffle wall (temperature, area, emissivity)
C. Both A & B
D. Neither A nor B
Question 64
Fuel economy in an industrial furnace operation can not be achieved by the use of
A. Stoichiometric combustion air
B. Non-preheated combustion air
C. Combustion air not enriched with oxygen
D. Recupterators
Question 65
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
Question 66
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 of the above
Question 67
Forced recirculation of furnace gases is practised
A. To increase heat transfer by convection
B. To ensure uniform temperature
C. In furnaces, operating below 750°C
D. All of the above
Question 68
The amount of combustible escaping uncon-sumed from the furnace, depends upon the
A. Air supplied and furnace temperature
B. Burner design (thoroughness of mixing versus stratification)
C. Air preheat and the flow of gases in the furnace (mixing by induction, by acceleration or by change of direction)
D. All of the above
Question 69
Which is the most thermally efficient furnace?
A. Reheating furnace
B. Reverberatory furnace
C. Rotary kilns
D. Boiler furnace
Question 70
In a heating process, a heat flow diagram in which the quantities of heat in the various items of a heat balance are represented by the width of a band is called the
A. Ostwald chart
B. Cox chart
C. Sankey diagram
D. None of these
Question 71
An improved and fuel efficient version of the pusher type reheating furnace is the __________ furnace.
A. Walking beam
B. Shaft
C. Tunnel
D. Rotary hearth
Question 72
Which of the following variables affects the furnace capacity?
A. Temperature of flue gas
B. Thermal conductivity of stock
C. Thickness of heating stock
D. All of the above
Question 73
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
Question 74
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
Question 75
If the flame is produced under the hearth and then sweeps up into the heating chamber, this is called a/an __________ furnace.
A. Sidefired
B. Underfired
C. Covered
D. Recirculating
Question 76
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
Question 77
Hearth furnaces are not used for
A. Roasting
B. Melting
C. Reheating
D. None of these
Question 78
The heating capacity of continuous reheating furnace depends upon the
A. Hearth area and furnace temperature
B. Emissivity of the stock
C. Ratio of wall surface to stock surface
D. All of the above
Question 79
Means for giving direction to the circulation of gases in furnaces are
A. Fans
B. Arrangement of heating stock in the furnaces
C. Location of outlet ports and heating & combustion devices
D. All of the above
Question 80
If fuel and air are mixed ahead of the burner, it is called a/an __________ burner.
A. Premix
B. Outside mixing type
C. Rotary
D. Diffusion
Question 81
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 of complete combustion of
A. Furnace oil with air
B. Furnace oil with oxygen
C. Blast furnace gas with air
D. Blast furnace gas with oxygen
Question 82
Protective gas used in the annealing furnace for steel coil comprises of
A. 95% N₂ + 5% H₂
B. 5% H₂ + 9% N₂
C. 100% CO
D. 100 %H₂
Question 83
__________ furnace is not an electric furnace.
A. Arc
B. Induction
C. Pot
D. Resistance
Question 84
In reverberatory furnace, charge is heated mainly by
A. Conduction
B. Natural convection
C. Radiation of heat from the roof of the combustion chamber
D. None of these
Question 85
Scaling of furnace stock is reduced by __________ in flue gas.
A. CO
B. H₂
C. High CO/CO₂
D. All of the above
Question 86
Which is a regenerative furnace?
A. Coke oven heating chamber
B. Open hearth furnace
C. Both A and B
D. Neither A nor B
Question 87
Dampers are located
A. Before the I.D fan
B. After the I.D. fan
C. Near the top of the chimney
D. Anywhere after the I.D. fan
Question 88
Decarburisation of steel
A. Is the removal of carbon from iron carbide (Fe₃C)
B. Affects its crystalline structure
C. Is favoured by CO₂
D. All of the above
Question 89
An example of indirectly heated furnace is the
A. Soaking pit
B. Muffle furnace
C. Reheating furnace
D. None of these
Question 90
The resistance furnace produces heat by the
A. Electric arc struck between electrodes and the charge
B. Flow of current through a heating element
C. Combination of induced current and skin effect
D. None of these
Question 91
Which of the following is not a continuous waste heat recovery equipment from the flue gases going out of furnace?
A. Economiser
B. Regenerator
C. Ceramic recuperator
D. Waste heat boiler
Question 92
Flue gas outlet temperature from the chimney of any furnace should be ideally about __________ °C.
A. 50
B. 100
C. 150
D. 250
Question 93
In order to maintain a reducing atmosphere in a furnace, it should have
A. No O₂ in flue gas
B. CO in flue gas
C. High excess air
D. None of these
Question 94
In order to maintain an oxidising atmosphere in a furnace, it should have
A. More of excess air
B. Less of excess air
C. More of CO in flue gas
D. More of CO₂ in flue gas
Question 95
Which of the following furnaces will have maximum thermal efficiency?
A. Soaking pits
B. Walking beam reheating furnace
C. Boiler furnace
D. Rotary kilns
Question 96
Blast furnace stoves are meant for heating
A. Air
B. Blast furnace gas
C. Steam
D. None of these
Question 97
Higher furnace temperature can not 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
Question 98
Neutral atmosphere is maintained in a/an __________ furnace.
A. Cold rolled steel coil annealing
B. Open hearth
C. Soaking pit
D. Walking beam reheating
Question 99
The method of Lobo and Evans is concerned with the calculation of the
A. Heat absorption in radiant section of a furnace
B. Heat transfer by forced convection in a reboiler
C. Heat transfer in vacuum condensers
D. Mass transfer co-efficient
Question 100
Pulverised fuel fired furnaces employ __________ fuel firing.
A. Horizontal
B. Vertical
C. Tangential
D. All of the above
Question 101
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
Question 102
Reverberatory furnace is used for
A. Roasting/reduction of ores
B. Annealing steel coil
C. Heating air
D. Steel melting
Question 103
Which of the following is the most important deterrants 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
Question 104
Circulation of gases in furnace is caused by the
A. Change in volume during a change of temperature
B. Difference in density between hot and cold gases
C. Furnace pressure in conjunction with draft in flues
D. All of the above
Question 105
Metallic recuperators are not used for waste heat recovery, if the hot flue gas temperature is above __________ °C, because corrosion prevails at higher temperatures.
A. 350
B. 750
C. 1050
D. 1250
Question 106
Rate of heat release in a furnace, which is the measure of heat intensity is defined as
A. Kcal/hr/m³ combustion space
B. Kcal/m³ combustion space
C. Kcal/hr
D. None of these
Question 107
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 of the above
Question 108
In salt bath furnace, heat is transferred to the charge mainly by
A. Conduction
B. Convection
C. Radiation
D. None of these
Question 109
Which of the following is a batch furnace?
A. Cupola
B. Reheating furnace
C. Glass tank furnace
D. None of these
Question 110
Which of the following is a rotary furnace?
A. Lime kiln
B. Soaking pit
C. Stoves
D. Annealing furnace
Question 111
Which furnace employs natural draft?
A. Coke oven
B. Boiler
C. Rotary kilns
D. L.D. converter
Question 112
Heat balance of furnace provides means of determining the
A. Thermal efficiency of the process
B. Sources of heat losses
C. Scope of reduction of heat losses
D. All of the above
Question 113
Waste heat from the outgoing flue gases in a thermal power plant is recovered by a/an
A. Economiser
B. Steam superheater
C. Air preheater
D. All of the above
Question 114
In producer gas making furnace, steam is added along with air to mainly control the
A. Fusion of coal ash & clinker formation
B. C. V. of producer gas
C. Temperature of producer gas
D. Tar content in producer gas
Question 115
Maximum thermal efficiency of boiler may be about __________ percent.
A. 10
B. 25
C. 65
D. 90
Question 116
Overall thermal efficiency of a lumpy coal fired suitably designed heating furnace, if operated & maintained properly may be about __________ percent.
A. 10-15
B. 25-30
C. 45-50
D. 65-70
Question 117
Thermal efficiency of an open hearth furnace may be about __________ percent.
A. 5
B. 20
C. 50
D. 80
Question 118
Furnace pressure is normally controlled by regulating the
A. Air pressure
B. Fuel gas pressure
C. Speed of I.D. fan
D. Damper
Question 119
Which of the following is a directly fired intermittant furnace?
A. Walking beam reheating furnace
B. Reverberatory furnace
C. Tower furnace
D. Tunnel kiln
Question 120
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 of the above
Question 121
Specific heating capacity of a furnace is expressed as
A. Weight heated/hr
B. Weight heated/furnace volume
C. Weight heated/hr/furnace volume
D. None of these
Question 122
Design of waste heat boiler for recovery of waste heat from furnace gases depends upon the
A. Quantity & temperature of waste gas
B. Dust concentration & nature of dust in waste gas
C. Corrosive nature of the waste gas
D. All of the above
Question 123
The rate of scaling of furnace stock depends upon the
A. Temperature
B. Time
C. Nature of atmosphere
D. All of the above
Question 124
Which of the following is a natural draft furnace?
A. Blast furnace stoves
B. Power plant boilers
C. Sintering furnace
D. None of these
Question 125
Which furnace employs preheating, heating and soaking zones?
A. Soaking pit
B. Reheating furnace
C. Open hearth furnace
D. Cupola
Question 126
Thickness of stock does not affect the fuel economy of furnaces, if the material to be heated is of
A. Low emissivity
B. High thermal conductivity
C. Both A and B
D. Neither A nor B
Question 127
Which is not accomplished in an underfired furnace?
A. Increase in heating capacity/m² of floor space
B. Elimination of cold spot at the bottom of the charge
C. Reduction in the temperature of furnace gases
D. Portection of the periphery of the charge from excessive radiation
Question 128
Which is a continuous furnace?
A. Coke ovens
B. Annealing furnace
C. Glass tank furnace
D. None of these
Question 129
Which is not a hearth furnace?
A. Glass tank furnace
B. Open hearth furnace
C. Cupola
D. Reheating furnace
Question 130
Which one shows the diagramatic heat balance in a furnace?
A. Sankey diagram
B. Cox chart
C. Ostwald chart
D. None of these
Question 131
Maximum heat transfer in high temperature furnaces is by
A. Conduction
B. Convection
C. Radiation
D. Either A, B or C; depends on the type of furnace
Question 132
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 of the above
Question 133
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
Question 134
Operation of blast furnace stove is based on the principles of a __________ furnace.
A. Regenerative
B. Recuperative
C. Both A and B
D. Neither A nor B
Question 135
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
Question 136
The main function of a muffle in the muffle furnace is to
A. Protect the charge from the effects of the products of combustion
B. Smooth out temperature inequalities on the combustion side of the muffle wall
C. Both A & B
D. Neither A nor B
Question 137
Which of the following is a periodic furnace?
A. Tunnel kiln
B. Rotary kiln
C. Soaking pit
D. Reheating furnace
Question 138
Low stack loss indicates the
A. Use of sub-stoichiometric air for combustion
B. Efficient use of fuel
C. Inefficient use of fuel
D. Oxygen enrichment of combustion air
Question 139
In furnaces operating at very high temperature (say) 1250°C, e.g. soaking pit), the maximum heat transfer takes place by
A. Conduction
B. Convection
C. Radiation
D. Can not be predicted
Question 140
The reason for excessive clinker formation in gas producers is the
A. Use of coal/coke containing a high % of fines and ash
B. Use of fuel having too low an ash fusion temperature
C. Development of hot spots in the fuel bed and an abnormally high rate of gasification
D. All of the above
Question 141
In a muffle furnace, the muffle
A. Retards the heat transfer
B. Assists in temperature equalisation in the charge
C. Permits the use of controlled atmosphere for the protection of stock
D. All of the above
Question 142
Example of an indirectly heated furnace is
A. Hood annealing furnace
B. Muffle furnace
C. Both A and B
D. Neither A nor B
Question 143
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 of the above
Question 144
Tunnel kilns are usually used for
A. Roasting of pyrites
B. Drying/tempering of refractories
C. Reheating of slabs
D. Melting of glass
Question 145
Which of the following is not a directly fired furnace?
A. By-product coke oven
B. Calcination kiln
C. Sintering furnace
D. Open hearth furnace
Question 146
Test specimen for determination of refractoriness under load (RUL) of a refractory is heated in a
A. Furnace employing neutral atmosphere
B. Carbon resistance furnace
C. Reducing atmosphere
D. Furnace employing negative pressure
Question 147
Thermal efficiency of furnaces can be improved by
A. Waste heat recovery from flue gas
B. Minimising heat losses from furnace walls
C. Maintaining proper draught
D. All of the above
Question 148
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 of the above
Question 149
Which of the following accentuates clinker-ing 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 of the above
Question 150
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
Question 151
Which one is not an induced draught furnace?
A. Blast furnace stove
B. Sintering furnace
C. High pressure boiler
D. None of these
Question 152
In which of the following furnaces, the gases are sucked through the stock bed from below?
A. Soaking pit
B. Sintering machine
C. Beehive oven
D. None of these
Question 153
A refractory wall separating the stock and the source of heat is provided in a
A. Updraft kiln
B. Muffle furnace
C. Continuous furnace
D. None of these
Question 154
Pick out the wrong statement.
A. Addition of methane to the furnace atmosphere reduces decarburising by hydrogen
B. Nitrogen in presence of steam decar-burises high carbon steel, whereas hydrocarbon gases carburise the surface of steel at annealing temperatures
C. Active nitrogen (formed by cracking ammonia at the metal surface) cause nitride formation with increase in surface hardness
D. None of these
Question 155
While the fuel fired furnace can be used upto a maximum temperature of about 1700°C, the electric furnace can be used upto a temperature of about __________ °C.
A. 2000
B. 3000
C. 4500
D. 6000
Question 156
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 intermittant
D. All of the above
Question 157
Very high pressure boilers are usually __________ boilers.
A. Fire tube
B. Water tube
C. Waste heat
D. Natural circulation
Question 158
Recuperator is
A. Not used for fuel gas preheating
B. An intermittant waste heat recovery equipment
C. A continuous waste heat recovery equipment
D. Heavier than regenerator meant for the same duty
Question 159
Ceramic recuperators compared to metallic recuperators for the same duty
A. Are lighter
B. Occupy more space
C. Are less costly
D. Have higher pressure differential between flue gas & air side
Question 160
Regenerators compared to the recuperators for the same duty
A. Occupy more space
B. Are less costly
C. Are of smaller size
D. All of the above
Question 161
Regenerators as compared to recuperators for the same duty
A. Store smaller quantity of waste heat
B. Are lighter & compact
C. Involve higher initial cost
D. All of the above
Question 162
Regenerators are installed in
A. Coke ovens
B. Open hearth furnace
C. Both A & B
D. Neither A nor B
Question 163
Use of pulverised coal in boilers provides
A. Higher calorific value
B. Better combustion
C. Smokeless burning
D. Less erosion on furnace wall
Question 164
Artificial draught produced by a fan in the furnace can be controlled by the
A. Speed of the fan
B. Damper
C. Variation in the pitch of fan blades
D. All of the above
Question 165
Heat transfer rate to the stock/charge in the furnace does not depend upon the
A. Emissivity of the refactory walls
B. Size of the furance
C. Use of waste heat recovery equipments
D. Thickness of the stock
Question 166
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
Question 167
In low or standard frequency induction furnace, heat is produced by the
A. Combination of induced current and skin effect
B. Induction and resistance
C. Current flow through a heating element
D. None of these
Question 168
Combustion of furnace oil in a furnace (soaking pit) with preheated combustion air at 400°C results in saving of about __________ percent furnace 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
Question 169
Rotary kilns are used in the
A. Calcination of limestone & dolomite
B. Cement manufacture
C. Both A and B
D. Neither A nor B
Question 170
Regenerators are normally provided in the
A. Glass melting furnace
B. Open hearth furnace
C. By product coke ovens
D. All of the above
Question 171
In a furnace employing forced draught as compared to induced draught,
A. Air is sucked in, so air leaks are more and hence the furnace efficiency is reduced
B. The fan operates hot and hence blades are liable to corrosion and erosion
C. Positive pressure exists in the furnace
D. None of these
Question 172
Coke ovens in steel plant are heated by
A. Electricity
B. Blast furnace gas/mixed gas
C. Coke oven gas
D. Both B and C
Question 173
Which of the following is not a recuperative furnace?
A. Soaking pit
B. Reheating furnace
C. Steamboiler
D. Coke oven
Question 174
Regenerators are used for waste heat recovery in
A. By-product coke ovens
B. Beehive coke oven
C. Blast furnace stoves
D. Soaking pits
Question 175
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 of the above
Question 176
Shaft furnaces are used for
A. Smelting
B. Calcining
C. Roasting
D. All of the above
Question 177
Reheating furnace (pusher type) is used for heating
A. Ingots
B. Slabs
C. Steel coils
D. Steel sheets
Question 178
In which of the waste heat recovery equipment, the flow of flue gas and air is alternately reversed after a fixed interval of time?
A. Recuperator
B. Regenerator
C. Waste heat boiler
D. None of these
Question 179
Turndown ratio of a burner gives an idea of the __________ in the furnace.
A. Range of fuel firing rates
B. Volume of the combustion chamber
C. Maximum heat input rate only
D. Minimum heat input rate only
Question 180
Furnace aerodynamics is related to the __________ in the furnace.
A. Movement of gases
B. Measurement of flue gas volume
C. Temperature control
D. Pressure adjustment
Question 181
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
Question 182
Turn down ratio of a burner
A. Should be as low as possible i.e., 1 : 2
B. Should be 1:1 for a batch type furnace.
C. Is the ratio of maximum to minimum permissible heat input rates
D. Is normally much more for a continuous furnace as compared to a batch furnace
Question 183
Heat transfer takes place through a liquid medium surrounding the submerged material under heating, in case of a/an
A. Blast furnace
B. Steam boiler
C. Salt bath furnace
D. Annealing furnace
Question 184
Unit of furnace loading is
A. Ton stock/hr/m² hearth area
B. Ton stock/hr
C. Ton stock/m² hearth area
D. Both B and C