Question 31 : Which of the following is not a by-product recovered in a high temperature coal carbonisation plant ?
1. Napthalene
2. Benzol
3. Pitch-cresosote mixture (PCM)
4. Ethylene
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Question 32 : Flue gas discharge velocity through chimney of a big thermal power plant may be around __________ m/sec.
1. 0.5
2. 10
3. 50
4. 500
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Question 33 : Which of the following is used for making the explosive 'TNT' ?
1. Toluene
2. Benzol
3. Pyridine
4. Cerosote
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Question 34 : Which of the following gaseous fuels has the lowest calorific value ?
1. Refinery gas
2. Gobar gas
3. Blast furnace gas
4. Converter gas
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Question 35 : Calorific value of coal middling generated in coal washeries during washing of coal may be around __________ Kcal/kg.
1. 1000
2. 4000
3. 6000
4. 8000
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Question 36 : 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.
1. in between 37 & 71%
2. < 37%
3. none of these
4. >71%
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Question 37 : A coal with high ash content is undesirable, as
1. 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.
2. it is abrasive to the coal pulveriser (ie.g. ball mill) and the combustion chamber.
3. all of three
4. the ash retains the sulphur & phosphorus and thus affects the quality of products in metallurgical furnace apart from increasing the slag volume.
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Question 38 : Gray King Assay and Swelling Index of a coal is a measure of its
1. swelling characteristics.
2. agglutinating properties.
3. abradability
4. resistance to impact breakage.
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Question 39 : Wobbe index' is a characteristic of
1. liquid fuels
2. gaseous fuels
3. solid fuels
4. fat coals
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Question 40 : Combustion of pulverised coal as compared to that of lump coal
1. develops a non-luminous flame.
2. develops a low temperature flame.
3. can be done with less excess air.
4. provides a lower rate of heat release
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