Fuels and Combustion Quiz 6

1 / 50

Preheating of coal charge for the coke ovens reduces the ___________?

Time of carbonisation

All A., B. and C.

Fuel consumption in coking

Yield of gas and tar

2 / 50

One kg of carbon for theoretically complete combustion requires _______ kg of air?

11.5

0.5

3 / 50

Oxygen required for theoretically complete combustion of 1 Nm3 methane is _______ Nm3?

4 / 50

Naphthalene is used for making__________?

Insecticides (e.g. moth balls)

Drug intermediates e.g. ?-naphthol

Unsaturated polyesters

All A., B. and C.

5 / 50

Pick out the wrong statement ?

Coals are divided in four species according to their carbon content in Seylor?s classification

Carbonisation time in a by-product coke oven is about 16 hours

Gross and net calorific value of a fuel is the same, if it does not contain hydrogen or hydrocarbons

Carburetted water gas is also called blue gas

6 / 50

Pick out the wrong statement ?

None of these

Pulverised fuel can be completely burnt with less percentage of excess air compared to lump coal

Regulation of furnace temperature and atmosphere (oxidising or reducing) is easily possible with pulverised fuel firing

Low grade coal can be used, but generally high volatile matter coals are more suitable for making pulverised fuel

7 / 50

Pick out the wrong statement ?

Gaseous fuels require the least % excess air for complete combustion

Calorific value of natural gas is more than that of LPG

The ratio of fixed carbon to volatile matter percentage in coal is called its ?fuel ratio?

High concentration of oxygen in flue gas means high stack loss

8 / 50

Net calorific value is the gross calorific value less the ________ heat of water in the product of combustion when cooled to 15?C ?

Latent

Sensible and latent

None of these

Sensible

9 / 50

Pick out the correct statement ?

Oxygen content decreases from lignite to bituminous coal as the coalification increases

With increase in oxygen content, moisture holding capacity of coal increases and the caking power decreases

All A., B. and C.

The less the oxygen content, better is the coal, as it reduces the calorific value

10 / 50

Preheating of a gaseous fuel results in increased______?

Flame temperature

Flame length

Ignition temperature

Quantity of flue gas

11 / 50

Pick out the wrong statement ?

Percentage of ash in coke produced from medium coking coal is more than that in coal

The calorific value (kcal/Nm3) of coke oven gas reduces on removal of hydrogen from it by cryogenic method

Coal based fertiliser plants in India at Talcher (Orissa) and Ramagundam (A.P) employ Kopper-Totzek process of coal gasification

Ash is normally removed as ?fly-ash? in Kopper-Totzek process of coal gasification

12 / 50

Presence of force moisture in coal is most disadvantageous during its ___________?

Washing

Transportation and handling

Pulverisation

Storage

13 / 50

Nitrogen in coal__________?

Is present upto 1-2%

Comes from protein in parent vegetable matter

All A., B. and C.

Is recovered as ammonia during its carbonisation

14 / 50

Presence of free moisture in coal is most disadvantageous during__________?

Combustion of fire slacks on the grates

Handling (e.g. when emptying wagons)

Its pulverisation (as it requires more power)

None of these

15 / 50

Of the total tar present in raw coke oven gas, the tar recovered in primary cooler is about ________ percent?

16 / 50

Pick out the wrong statement ?

The minimum temperature, at which a petroleum oil vapor catches fire and continues to burn, is called its flash point

LPG is also used as fuel for automobiles & small furnaces and for cutting & welding of metals

Each ton of petroleum oil on distillation produces about 30-50 Nm3 of gas

Maximum yield of naphthalene is obtained on distillation of crude oil

17 / 50

Preheating of combustion air is done to _____?

Increase the calorific value of the fuel

Complete the combustion of fuel

Increase the adiabatic flame temperature

Reduce its requirement for effecting the complete combustion

18 / 50

Octane number of 2, 2, 4 ? trimethyl pentane is ___________?

100

More than 100

In between 0 and 100

19 / 50

Preheating of _______ the flame temperature?

The gaseous fuel before combustion decreases

Combustion air decreases

Either the fuel or the air or both, increases

Either the fuel or the air does not affect

20 / 50

Naphthalene recovered from coke oven gas is used_____?

As moth balls (insecticides)

As moisture proof coating on fibres

For making electrodes

As a fuel in furnaces

21 / 50

Presence of phosphorous in metallurgical coal___________?

Is not undesirable

Reduces its calorific value

Badly affects the quality of steel

Increases its caking power

22 / 50

Out of the following, which is the most important parameter for the blast furnace grade coke ?

Moisture content

Volatile matter content

CSR & CRI

Ash content

23 / 50

Orsat apparatus___________?

Gives flue gas analysis on dry basis

Determines N2 in flue gas indirectly

All A., B. & C.

Can?t determine CO in flue gas, if it is < 0.2%

24 / 50

Pick out the wrong statement ?

Reactivity of coke is inversely proportional to its absolute density

Abrasion index of the coke is a measure of its hardness

Cokes of high reactivity are obtained from strongly coking coals

Cokes of high reactivity are obtained from weakly coking coals

25 / 50

Presence of _______ in a dry gaseous fuel does not contribute to its calorific value?

Carbon

Sulphur

Oxygen

Hydrogen

26 / 50

Prime coking coal is always blended with medium or non- coking coal before carbonisation___________?

Because, it alone produces unreactive coke

Neither A. nor B.

Both A. and B.

To check against its excessive swelling during heating, which may exert high pressure and damage coke oven walls

27 / 50

Pick out the wrong statement ?

Theoretical flame temperature is the temperature attained by the products of combustion, when the fuel is burned without loss or gain of heat

Burning the fuel with theoretically required amount of pure oxygen results in attainment of maximum adiabatic flame temperature

Adiabatic flame temperatures of actual combustions are always less than the maximum values

Burning the fuel with excess pure oxygen results in maximum theoretical flame temperature

28 / 50

Natural draft created by the chimney depends upon _______?

Its height

Temperature of the flue gas

Neither A. nor B.

Both A. & B.

29 / 50

Natural draught produced by a chimney depends upon the _______?

Neither A. nor B.

Height of the chimney

Both A. and B.

Density of the chimney gases

30 / 50

Presence of nitrogen in combustion air does not reduce the ______?

Any of the above

Flame temperature

Amount of heat liberated

Flue gas temperature

31 / 50

Orsat apparatus is meant for _____?

Gravimetric analysis of flue gas

Finding out combustion efficiency

None of these

Direct determination of nitrogen in flue gas by absorbing it in ammoniacal cuprous chloride

32 / 50

Percentage of nitrogen in blast furnace gas may be around___________?

33 / 50

Pick the odd man out?

Briquettes

Oil gas

Wood

Pitch creosote mixture

34 / 50

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

Increases the loss of fine coal dust from the ovens when charging

Reduces the coking time

None of these

35 / 50

Percentage of methane in coke oven gas may be around _______?

36 / 50

Nitrogen present in the flue gas is determined in the Orsat apparatus by absorbing it in_______?

KOH

Ammoniacal cuprous chloride

None of these

Pyrogallol solution

37 / 50

Oxygen content in a flue gas was found to be 4%. It implies that excess air used for combustion was around _______ percent?

38 / 50

Producer gas comprises mainly of _________?

CO & H2

CO2 & N2

CO2 & H2

CO & N2

39 / 50

Percentage of carbon monoxide in blast furnace gas may be around ______ ?

40 / 50

Pick out the wrong statement ?

Specific heat of coal decreases with increases in the volatile matter and decrease in the C/H ratio of coal

Refractive index and reflectance of coal increases with the increasing rank of coal

Angle of repose of coal increases with its increasing size

Specific gravity of coal increases with its increasing maturity

41 / 50

Pitch creosote mixture (PCM) as compared to furnace oil is a better fuel, because its _____?

Emissivity factor is higher

Flue gas has lower dew point thereby facilitating more waste heat recovery

Sulphur content is lower

All A., B. and C.

42 / 50

Narrow coke ovens as compared to wider coke ovens__________?

Produce smaller coke

Produce stronger coke

Require less time of carbonisation

All A., B. and C.

43 / 50

Pensky-Marten apparatus is used for those oils, whose flash points are ______ ?F?

< 90

90-110

< 120

> 120

44 / 50

Producer gas containing least amount of tar is produced by the__________?

High pressure gasification of coal (e.g. in Lurgi gasifier)

Atmospheric pressure gasification of coal (e.g., in Kopper-Totzek gasifier)

Partial combustion of large size (< 50 mm) coke

Partial combustion of coal

45 / 50

Oxygen percentage (by weight) in atmospheric air is__________?

46 / 50

Number of macrocomponents present in coal according to Stopes are _____?

Six

Four

Five

Two

47 / 50

Out of the following fuels, the difference between the net and gross calorific value is maximum in case of__________?

Blast furnace gas

Bituminous coal

Pitch

Fuel oil

48 / 50

Percentage of hydrogen in coke oven gas may be around _____?

49 / 50

Out of the following fuels, the difference between gross and net calorific value will be minimum in case of_____?

Natural gas

Coke oven gas

Water gas

Blast furnace gas

50 / 50

Power alcohol as compared to straight run gasoline has lower _________?

Viscosity

Calorific value

Octane number

Specific gravity

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