Heat transfer Flashcards
Air is best heated with steam in a heat exchanger of
double pipe type with fin on air side.
Black liquor generated during paper manufacture is concentrated in a
multiple effect evaporator
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively
C/E
Reynold’s analogy states that
Nst α f
With increase in temperature, the thermal conductivity of non-metallic amorphous solids
increases
Fourier’s law applies to the heat transfer by
conduction
In the equation Q = UAΔt; Δt is
logarithmic mean temperature difference
With increase in porosity, the thermal conductivity of a solid substance
decreases
For an ideal black body
absorptivity = 1
For every 10% increase in the excess air; the fuel consumption increases by __________ percent.
0.1
Main component of sewage gas produced during anaerobic decomposition of organic waste (by suitable bacteria) during sewage disposal is
CH4
A fuel containing carbon and carbon monoxide (but containing no hydrogen or its compounds) is burnt in pure oxygen at constant pressure. Its gross calorific value as compared to net calorific value will be
Same
Initial pressure of oxygen introduced into the ‘bomb’ of the bomb calorimeter for determination of calorific value of coal/fuel oil may be around __________ atm.
25-30
Pure carbon is completely burnt in oxygen. The flue gas analysis is 70%CO2, 20%CO and 10%O2. The percent excess oxygen used is
0
__________ of the coal is the basis for Seylor’s coal classification.
Ultimate analysis
Main constituents of benzol are
benzene, toluene & xylene.
“Overfire burning” in a furnace is a phenomenon characterized by the
burning of carbon monoxide and other incombustibles in upper zone of furnace by supplying more air.
The calorific value of ‘LPG’ (50% propane + 50% butane) is about __________ kcal/Nm3.
25, 000
petrographic constituents of coal is non-coking
Fussain
__________ has the widest inflammability limit (explosion limit) of all the gases.
Acetylene
In flue gas analysis by Orsat’s apparatus, carbon dioxide is absorbed by
potassium hydroxide.
Caking index of the coal blend used for the manufacture of metallurgical coke should be around
21
Proximate analysis of coal determines its __________ content.
moisture, volatile matter, ash & fixed carbon.
Presence of free moisture in coal is most disadvantageous during
its pulverization (as it requires more power).
The heat of combustion of a fuel
is always negative.
Abrasion index of blast furnace coke should be around __________ percent.
80
The calorific value of producer gas is around __________ kcal/Nm3
1300
The calorific value of L.D. converter gas is about __________ Kcal/Nm3
1800
Higher fuel combustion efficiency can not be achieved by
reducing Sulphur content in the fuel.
Which of the following is the maximum coal producing state in India ?
Jharkhand
Height of coke oven is limited (say maximum up to 7 metres) mainly by the
problem of uniform heating along its height.
Bunsen burner is an example of a/an __________ burner.
inside mixing/premix type
The reaction, C + CO2 2CO, taking place during coal gasification is called the __________ reaction.
Boudouard
The cooling medium used in dry quenching of coke is
nitrogen
Gobar gas is produced by the __________ of ‘gobar’ (cow dung).
fermentation
Shatter index of the coke is a measure of its
strength
When the coal is heated in absence of air, it is called its
carbonization
A carbonaceous fuel (containing no H2 or hydrocarbons) is burnt and the resulting flue gas contains 21% CO2. It means that
complete combustion of fuel has taken place.
Fusion point of coal ash generally varies from 1000 to 1700° C. Ash having fusion point less than __________ °C is liable to form clinker.
1100
Light oil whose major component is benzol, is obtained by the distillation of crude tar in the temperature range of __________ °C.
80-170
Pick the odd man out.
Wood
Which of the following has the highest heat of combustion?
C2H6
Calorific value of wood gas is about __________ kcal/Nm3.
3300
Which adsorbant is used for removing sulphur compounds (S Q, H2S, RSH etc.) removal from coke oven gas in by-products recovery plant ?
Bog iron (i.e., moist ferric hydroxide)
Temperature of coke oven gas just before entering into saturator (for recovery of NH3) is about __________ °C.
65
A sample of natural gas containing 80% methane (CH4) and rest nitrogen (N2) is burnt with 20% excess air. With 80% of the combustibles producing CO2 and the reminder going to CO, the Orsat analysis in volume percent is
CO2 : 7.42, CO : 1.86, O2 : 4.64, N2:86.02
During combustion of a gaseous fuel, the presence of a non-luminous flame is an indication of the
complete combustion
Calorific value of coke even gas produced by low temperature carbonization of coal is about __________ Kcal/Nm3.
6500
By-products recovery process from coal carbonization is termed as direct, indirect and semi direct process depending upon the method of recovery of
ammonia
Naphthalene is removed from coke oven gas by
scrubbing with wash oil (a petroleum product).
Hardgrove grindability index of four coal samples are given below. Which of them is the easiest to grind ?
100
For every 10% increase in the excess air; the fuel consumption increases by __________ percent.
0.1
Main component of sewage gas produced during anaerobic decomposition of organic waste (by suitable bacteria) during sewage disposal is
CH4
Softening temperature of coal ash is a measure of the __________ of coal.
clinkering tendency
A fuel containing carbon and carbon monoxide (but containing no hydrogen or its compounds) is burnt in pure oxygen at constant pressure. Its gross calorific value as compared to net calorific value will be
same
Presence of phosphorous in metallurgical coal
Badly affects the quality of steel.
Initial pressure of oxygen introduced into the ‘bomb’ of the bomb calorimeter for determination of calorific value of coal/fuel oil may be around __________ atm.
25-30
Pure carbon is completely burnt in oxygen. The flue gas analysis is 70%CO2, 20%CO and 10%O2. The percent excess oxygen used is
0
__________ of the coal is the basis for Seylor’s coal classification.
Ultimate analysis
If the specific heat of gaseous products of combustion of a fuel is high, the abiabatic flame temperature will be
low
The calorific value of ‘LPG’ (50% propane + 50% butane) is about __________ kcal/Nm3.
25, 000
Which of the following petrographic constituents of coal is non-coking ?
Fussain
__________ has the widest inflammability limit (explosion limit) of all the gases.
Acetylene
In flue gas analysis by Orsat’s apparatus, carbon dioxide is absorbed by
potassium hydroxide.
Caking index of the coal blend used for the manufacture of metallurgical coke should be around
21
Proximate analysis of coal determines its __________ content.
moisture, volatile matter, ash & fixed carbon.
Abrasion index of blast furnace coke should be around __________ percent.
80
Tar yield in the low temperature and high temperature carbonization of dry coal may be respectively __________ percent.
10 & 3
Cannel coal and boghead coal are the examples of
sapropelic coals
Higher fuel combustion efficiency can not be achieved by
reducing Sulphur content in the fuel.
Height of coke oven is limited (say maximum upto 7 metres) mainly by the
problem of uniform heating along its height.
Bunsen burner is an example of a/an __________ burner.
inside mixing/premix type
When steam is passed over coal resulting in the endothermic reaction represent by, C + H2O = CO + H2, it is called the __________ of coal.
gasification
Dry air requirement for burning 1 Nm3 of CO to CO2 may be around __________ Nm3.
2.4
Coal is heated in absence of air for 7 minutes at a temperature of about __________ °C, during its volatile matter determination for proximate analysis.
950
The calorific value of a gas of composition CO2 = 20%, H2 = 50%, CH4 = 30%, is y. If the composition of gas is changed to H2 = 50%, CH4 = 30%, CO2 = 10%, N2 = 10%, then the calorifice value will be
y
For which pair of the fuel gases, calorific value (C.V.) of one fuel is almost double that of the other on volume basis (i.e., kcal/Nm3 ), while the C.V. is same on weight basis (i.e., kcal/kg) ?
Propane and acetylene
If CO2 is not fully absorbed by the KOH solution meant for its absorption in the orsat apparatus, it will appear as
SO2
By-products are __________ recovered in ‘Beehive ovens’.
not at all
The sequence of absorption in flue gas analysis by Orsat’s apparatus is respectively
CO2, O2, CO
Which of the following is the most important deterrents to an extended use of pulverised coal in boiler firing ?
Ash disposal problem
Calorific value of both the solid & liquid fuels can be determined by using __________ calorimeter.
Bomb
Which of the following fertilisers is produced in the by-products recovery (from coke oven gas) plant attached to an integrated steel plant ?
Ammonium sulphate
Coals used for the generation of producer gas should have
high volatile matter content.
A coal having higher volatile matter content will necessarily have lower
ignition temperature.
Of the total tar present in raw coke oven gas, the tar recovered in primary cooler is about __________ percent.
25
Purity of coke means that, it is high in carbon and low in
volatiles
Out of the following, which is the most important parameter for the blast furnace grade coke ?
CSR & CRI
The gasification reaction represented by, C + H2O = CO + H2, is
endothermic
Insitu theory and drift theory are related to the
origin of coal.
Which of the following will generate maximum volume of product of complete combustion (Nm3/Nm3 of fuel) ?
Natural gas
Which of the following will be unsuitable for dust cleaning from flue gas at 400°C from a pulverized coal fired boiler ?
Bag filter
