Fuels and Combustion

21.A coal having high amount of volatile matter

1. Would require smaller combustion chamber
2. Produces very little of tar and gas on carbonisation
3. Ignites easily and burns with long smoky flame
4. All (A), (B) and (C)

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22.A coal having high ratio of volatile matter to fixed carbon as compared to a coal having low ratio of volatile matter to fixed carbon

1. Is less liable to spontaneous combustion on storage
2. Is more difficult to ignite and produces a shorter flame
3. Requires smaller combustion space and less secondary air
4. None of these

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23.A coal having high volatile matter content will

1. Give less yield of tar and gas on carbonisation
2. Burn with a small non-smoky flame
3. Have a very high calorific value
4. None of these

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24.A coal having higher volatile matter content will necessarily have lower

1. Ash fusion temperature
2. Calorific value
3. Ignition temperature
4. Caking index

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25.A coal having higher volatile matter content, has lower

1. Smoking tendency on burning
2. Coke oven gas yield on carbonisation
3. Chance of catching fire during storage in open space
4. Ignition temperature

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26.A coal that softens and fuses on heating is

1. Classified
2. Carbonised
3. Caking
4. Non-caking

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27.A coal with high _________ content, would ignite most easily.

1. Fixed carbon
2. Volatile matter
3. Ash
4. Oxygen

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28.A coal with high ash content

1. Has higher calorific value
2. Is harder and stronger
3. Is not subjected to washing
4. Has low quantity of mineral matter

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29.A coal with high ash content is undesirable, as

1. It is abrasive to the coal pulveriser (i.e. ball mill) and the combustion chamber
2. The ash in molten condition gets absorbed in the pores of the refractory lining of the furnace and causes its spalling due to different co-efficient of expansion/contraction of the refractory and the ash
3. The ash retains the sulphur & phosphorus and thus affects the quality of products in metallurgical furnace apart from increasing the slag volume. Besides, it may fuse and stick to the boiler tubes thereby reducing the heat transfer
4. All (A), (B) and (C)

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30.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

1. More
2. Less
3. Same
4. Data insufficient; can't be predicted

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