Fuels and Combustion

181.Gross and net calorific value of a fuel will be the same

1. If its ash content is zero
2. If its carbon content is very low
3. If its hydrogen/hydrogen compound content is zero
4. Under no circumstances

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182.Gross calorific value will be equal to the net calorific value for

1. H₂
2. C2H₂
3. CO
4. C2H6

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183.Gross heating value of coal is _________ the net heating value.

1. Higher than
2. Lower than
3. Same as
4. None of these

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184.Hard coke is manufactured from

1. Lignite
2. Bituminous coal
3. Semi-anthracite
4. Anthracite

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185.Hard pitch is used for making

1. Pulverised fuel
2. Perfumes
3. Insecticides
4. Plastics

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186.Hardgrove Grindability index of four coal samples are given below. Which of them is the easiest to grind?

1. 50
2. 70
3. 85
4. 100

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187.Heat penetration rate in narrow coke ovens in high temperature carbonisation of coal is around _________ cm/hr.

1. 2.5
2. 0.5
3. 10
4. 20

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188.Height of coke oven is limited (say maximum upto 7 metres) mainly by the

1. Problem of uniform heating along its height
2. Structural strength of silica bricks
3. Problem in door cleaning
4. Buckling of ram of pusher car at the time of coke pushing

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189.High amount of sulphur and phosphorous in coke causes

1. Decrease in its calorific value
2. Increase in its strength
3. Brittleness of steel made by using it
4. None of these

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190.High ash coals

1. Are soft & friable (poor strength and size stability)
2. Require longer time of carbonisation as ash offers resistance to heat transfer
3. Produce larger quantity of coke oven gas
4. None of these

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