Fuel and Combustion Flashcards
Higher efficiency in the combustion of solid fuel can not be achieved by
keeping the flue gas exhaust temperature very high.
A coal containing very high percentage of durain is called______coal
splint
During combustion of gaseous fuels, deficiency of air
lengthens the flame.
Gross and net calorific value of a fuel will be the same
if its hydrogen/hydrogen compound content is zero.
Which is not used as a binder in coal briquetting
Line
Size of blast furnace grade coke is______mm.
25-80
Presence of______in a dry gaseous fuel does not contribute to its calorific value.
Oxygen
The internal energy of the combustion products is______compared to that of reactants.
less
Junker’s calorimeter is used to determine the calorific value of
gaseous fuels
Combustion reaction of fuels is a/an______reaction.
exothermic
Improper storage condition results in the weathering of coal and spontaneous combustion, which increases its
friability & oxygen content.
Which constituents of coal is the most important in the production of coke?
Carbon
High temperature in gasification of coal favours
low production of CO2. / high production of CO.
Stack heat losses can be minimised by
controlling the excess air.
Laboratory gas is obtained by the cracking of
kerosene
Ratio of primary air to secondary air increases with increase in the rank of coal, because the
ratio of fixed carbon to volatile matter increases.
Carbon Content by weight in air dried wood may be about______percent.
50%
Natural draught produced by a chimney depends upon the
density of the chimney gases/ height of the chimney.
Gross & net calorific value is the same for
L.D. converter gas
Combustion of pulverised coal as compared to that of lump coal
can be done with less excess air.
‘Wobbe index’ is a characteristic o
gaseous fuels
Presence of free moisture in coal during its high temperature carbonisation
protects the volatile products from pyrolysis (cracking) in the presence of hot coke and hot oven walls.
Gray King Assay and Swelling Index of a coal is a measure of its
swelling characteristics.
Explosion limit of blast furnace gas is 37 to 71% gas in gas-air mixture. It means that the blast furnace gas will explode when burnt in a confined space, if its concentration in the gas-air mixture is______ percent.
in between 37 & 71%
Coke oven gas consists mainly of
H2, & CH4
Fuel gases containing hydrocarbons (ie.g. coke oven gas) are not preheated before burning, mainly because
the hydrocarbons crack thereby choking and fouling the heat transfer surface by carbon soot.
Which is the most reactive (as regards the formation of CO + H2 from C + H2O)
Low temperature coke
Calorific value of coal middling generated in coal washers during washing of coal may be around ______ Kcal/kg.
4000 Kcal/kg
Flue gas discharge velocity through chimney of a big thermal power plant may be around ______ m/sec.
10
Which of the following is used for making the explosive ‘TNT’?
Toluene
Adiabatic flame temperature of a fuel is dependent on the initial temperature of
Air and Fuel
Which gaseous fuels has the lowest calorific value ?
Blast furnace gas
Which is not a by-product recovered in a high temperature coal carbonization plant ?
Ethylene
Pensky-Marten apparatus is used for those oils, whose flash points are ______ °F.
> 120
In high temperature carbonization of coal compared to low temperature carbonization
H2 content in the coke oven gas is more.
When incomplete combustion loss is high, the flue gas analysis shows large amount of
CO
The temperature at which plastic layer formation takes place during carbonization of coal varies from ______ °C
350 to 450
Yield of coke oven gas in low temperature carbonization of coal is about______Nm3 /ton of dry coal.
160
Temperature of preheated air used for the transportation of pulverized coal through pipes to the burner of a boiler furnace is restricted to a maximum limit of about 300° C to avoid the
risk of explosion.
Blast furnace coke is made from coal by
→high temperature carbonization.
Yield of blast furnace gas is about______Nm3 /ton of pig iron.
adsorption on bog iron bed.
In Lurgi coal gasifier,
→larger quantity of coal can be processed.
Mineral matter content (M) and ash content (A) in coal are approximately related as
M = 1.1A
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
Degree of carbonization of coal during coke making can be roughly judged by the ______ of the coke produced.
volatile matter
Ammonia content in raw coke oven gas is about______gm/Nm3.
15
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
Quantity of coke oven gas produced by high temperature carbonization of one ton of dry coal may be around______Nm3 .
300
Coking coals are invariably
bituminous coals
‘Fuel’ can be defined as a substance which produces heat by
→combustion / nuclear fission / nuclear fusion.
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
Deficiency of combustion air during combustion of a gaseous fuel
lengthens the flame / causes heat loss of fuel by its partial combustion.
64-132) rank coal (ASTM) means a coal with 64%
fixed carbon and having a heat value of 13, 200 BTU/1b.
The sequence of absorption in flue gas analysis by Orsat’s apparatus is respectively
CO2, O2, CO
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
Function of secondary air in pulverised coal firing is to
ensure efficient burning of coal
Calorific value of gobar gas (containing CH4 = 60% , H2 = 10% ; CO2 = 30%) may be about ______ Kcal/Nm3.
5400