Fuels and Combustion

321.Softening temperature of coal ash is a measure of the _________ of coal.

  1. Caking tendency
  2. Coking tendency
  3. Clinkering tendency
  4. Size stability

Correct answer: (C)
Clinkering tendency

322.Sometimes water is sprayed during coal charging in the coke oven, which helps in

  1. Prevention of clinker formation in the oven
  2. Controlling the dust nuisance while charging the coal
  3. Reducing the cracking of hydrocarbons in the gas and increasing the percentage of CO & H2 in the gas (due to the endothermic reaction represented by C + H2O = CO + H2)
  4. All (A), (B) and (C)

Correct answer: (D)
All (A), (B) and (C)

323.Spontaneous combustion of coal on storage results due to

  1. Inadequate ventilation
  2. Low temperature oxidation
  3. Storage in large heaps with small surface to volume ratio
  4. All (A), (B) and (C)

Correct answer: (D)
All (A), (B) and (C)

324.Stack (chimney) height in a big thermal power plant is dictated by the

  1. Pollution control aspect
  2. Draught to be created
  3. Limitation of constructional facilities
  4. None of these

Correct answer: (B)
Draught to be created

325.Stack heat losses can be minimised by

  1. Controlling the excess air
  2. Oxygen enrichment of combustion air
  3. Using low c.v. fuels
  4. Maintaining proper draft in the furnace

Correct answer: (A)
Controlling the excess air

326.Steam is intermittently admitted into the fuel bed during the production of producer gas to

  1. Convert CO to CO2
  2. Increase the combustion rate
  3. Increase the gas production rate
  4. Minimise the chances of clinker formation

Correct answer: (D)
Minimise the chances of clinker formation

327.Stoichiometric combustion of 12 kg of carbon requires _________ of oxygen.

  1. 1kg mole
  2. 22.4 Nm3
  3. 32 kg
  4. All (A), (B) and (C)

Correct answer: (D)
All (A), (B) and (C)

328.Sulphur in metallurgical coal

  1. Contributes to its heating value
  2. Affects the quality of steel produced as cracks develop on the surface while rolling the steel
  3. Both (A) and (B)
  4. Neither (A) nor (B)

Correct answer: (C)
Both (A) and (B)

329.Supply of excess air for complete combustion of fuel is necessitated to facilitate

  1. Its thorough mixing with air
  2. Attainment of chemical equilibrium
  3. Attainment of high temperature
  4. None of these

Correct answer: (A)
Its thorough mixing with air

330.Tar is a better fuel than furnace oil, because of its

  1. Higher calorific value
  2. Lower sulphur content
  3. Higher emissivity (0.8-0.9) resulting in higher radiation heat transfer rate
  4. Both (A) and (B)

Correct answer: (A)
Both (A) and (B)

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