All Free Chemical Engineering MCQs with Answers

• A. Reduces its sulphur and ash content
• B. Controls its ash fusibility and increases its calorific value
• C. Improves its coking properties
• D. All A., B. and C.

Explanation: Coal washing removes mineral matter, thereby lowering ash and some sulphur, raising calorific value, and improving coking behaviour.

• A. Origin of coal
• B. Origin of petroleum oil
• C. Coalification
• D. Variation of coal quality with depth

Explanation: In-situ theory proposes that coal formed where the original plant material grew, whereas drift theory proposes transport and deposition…

• A. Colour
• B. Volatile matter
• C. Ash content
• D. Moisture content

Explanation: Carbonisation drives off volatile constituents, so the volatile-matter content of coke is a practical indication of how far carbonisation…

• A. Incomplete combustion
• B. Dry gas/stack gas loss
• C. Moisture loss
• D. All A., B. and C.

Explanation: Combustion loses energy through unburned fuel, heat carried away in dry stack gas, and the heating or vaporisation of moisture.

• A. Volatile matter
• B. Fixed carbon
• C. Ash
• D. Oxygen

Explanation: Volatile matter contains easily vaporised combustible compounds, so coal rich in it ignites readily at a lower temperature.

• A. Blast furnace gas
• B. Natural gas
• C. Producer gas
• D. Water gas

Explanation: Natural gas is mainly methane, whose combustion requires about 9.5 Nm³ of air per Nm³ of gas.

• A. Has poor strength and abrasion resistance
• B. Produces more slag when used in the blast furnace
• C. Is desirable in producer gas manufacture
• D. None of these

Explanation: Ash is carried into the blast furnace with coke and combines with flux to form slag, so high-ash coke increases slag production.

• A. Caking power
• B. Calorific value
• C. Oxygen content
• D. Hydrogen content

Explanation: Low-temperature oxidation consumes combustible constituents and lowers caking power, hydrogen content and calorific value.

• A. Contains more than 90% durain
• B. Contains more than 90% fussain
• C. Is non-coking
• D. Contains mainly vitrain & clarain and is generally coking

Explanation: Bright coal is composed mainly of the bright bands vitrain and clarain, and it is generally suitable for coking.

• A. 1 to 2
• B. 5 to 15
• C. 3 to 4
• D. 20 to 40

Explanation: When coal is stored on an unpaved or soft floor, the lower layer becomes pressed into the ground and is lost as carpet loss.

• A. Have high adiabatic flame temperature
• B. Have high calorific value
• C. Require smaller combustion chamber
• D. None of these

Explanation: A high heat-release rate allows the required heat duty to be obtained in a smaller furnace volume, so the combustion chamber can be…

• A. Yield of ammonia present in coke oven gas
• B. Free carbon content in tar
• C. Yield percentage of coke
• D. Difference in gross & net calorific value of the coke oven gas

Explanation: Low-temperature carbonisation produces coke-oven gas with a lower hydrogen proportion than high-temperature carbonisation, so less water…

• A. 5
• B. 25
• C. 55
• D. 80

Explanation: Blast-furnace gas contains a large amount of nitrogen brought in with the air blast, commonly around 50 to 60% by volume.

• A. Decreases
• B. Increases
• C. Remain constant
• D. None of these

Explanation: Coking drives off volatile matter while the mineral ash remains with the coke.

• A. 6
• B. 12
• C. 18
• D. 24

Explanation: Ash is conserved during coking, but volatile matter is removed, so its percentage rises.

• A. Coke oven gas
• B. Water gas
• C. Producer gas
• D. Blast furnace gas

Explanation: Coke-oven gas contains a relatively high proportion of hydrogen and methane, giving it the greatest calorific value among these gases.

• A. Is less liable to spontaneous combustion on storage
• B. None of these
• C. Requires smaller combustion space and less secondary air
• D. Is more difficult to ignite and produces a shorter flame

Explanation: A high volatile-matter-to-fixed-carbon ratio makes coal easier to ignite and gives a longer flame, while also increasing its tendency to…

• A. Fixed
• B. Moving
• C. Entrained
• D. Fluidised

Explanation: The Koppers-Totzek gasifier pulverises coal and carries it with oxygen and steam through the reaction zone.

• A. 230 V AC
• B. 60 KV AC
• C. 230 V DC
• D. 60 KV DC

Explanation: Electrostatic precipitators use a high-voltage direct-current field to create corona ionisation and charge tar or dust particles.

• A. Aromatic compounds
• B. Aliphatic compounds
• C. Paraffins
• D. Olefins

Explanation: High-temperature carbonisation produces coal tar rich in benzene, toluene, phenols, naphthalene and other aromatic substances.