Fuels and Combustion

131.Correct viscosity of furnace oil at the burner tip for proper atomisation is about 25 centistokes. To reduce the viscosity of high viscosity furnace oil (250 centistokes) to the correct atomisation viscosity (i.e. 25 cst), it should be preheated to about __________°C.

1. 70
2. 85
3. 105
4. 145

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132.Critical Air Blast (CAB) value of coke is a direct measure of its

1. Reactivity
2. Hardness
3. Strength
4. None of these

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133.Deficiency of combustion air during combustion of a gaseous fuel

1. Lengthens the flame
2. Causes heat loss of fuel by its partial combustion
3. Both (A) & (B)
4. Shortens the flame

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134.Degree of carbonisation of coal during coke making can be roughly judged by the _________ of the coke produced.

1. Colour
2. Moisture content
3. Ash content
4. Volatile matter

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135.Desirable "Micum Index" values of metallurgical coke are

1. M40 > 78% and M10 < 10%
2. M40 > 4% and M10 < 80%
3. M40 > 10% and M10 < 78%
4. M40 > 98% and M10 < 2%

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136.Dry air required to burn 1 kg of carbon completely may be around _________ kg.

1. 11
2. 2
3. 20
4. 38

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137.Dry air requirement for burning 1 Nm³ of CO to CO₂ may be around _________ Nm³.

1. 2.4
2. 1.75
3. 0.87
4. 11.4

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138.During coal carbonisation process, the conversion of semi-coke to coke is accompanied by an increase in the _________ of the mass.

1. Density
2. Porosity
3. Electrical resistivity
4. None of these

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139.During coking of coal, the ash content (percentage)

1. Increases
2. Decreases
3. Remain constant
4. None of these

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140.During combustion of a gaseous fuel, the presence of a non-luminous flame is an indication of the

1. Incomplete combustion
2. Complete combustion
3. High oxygen in flue gas
4. None of these

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