Free Plant Design and Economics MCQs with Answers

• A. Air supplied and furnace temperature
• B. All A., B. and C.
• C. Air preheat and the flow of gases in the furnace (mixing by induction, by acceleration or by
• D. change of direction)
• E. Burner design (thoroughness of mixing versus stratification)

Explanation: Unburned combustible losses depend on the available air and furnace temperature, burner mixing quality, air preheat, and gas-flow patterns…

• A. Temperature
• B. Time
• C. Nature of atmosphere
• D. All A., B. and C.

Explanation: Scaling is accelerated by higher temperature, longer exposure time, and an oxidising or otherwise favourable furnace atmosphere.

• A. Use of coal/coke containing a high % of fines and ash
• B. All A., B. and C.
• C. Development of hot spots in the fuel bed and an abnormally high rate of gasification
• D. Use of fuel having too low an ash fusion temperature

Explanation: Clinker forms when ash softens and fuses, especially with low ash-fusion fuel, hot spots, excessive local gasification, or high fines and…

• A. Physical nature, ash content and fineness of the coal
• B. Amount of excess air supplied and load on the boiler
• C. Type of burner and combustion chamber
• D. All A., B. and C.

Explanation: Unburnt coal carried with fly ash depends on coal fineness, ash content, and physical properties, as well as excess air, boiler load…

• A. Weight heated/hr
• B. Weight heated/furnace volume
• C. Weight heated/hr/furnace volume
• D. None of these

Explanation: Specific heating capacity measures furnace throughput relative to furnace size, so its unit is weight heated per hour per unit furnace…

• A. Ton stock/hr/m2 hearth area
• B. Ton stock/hr
• C. Ton stock/m2 hearth area
• D. Both B. and C.

Explanation: Furnace loading is a rate of production normalised by hearth area, expressed as tons of stock heated per hour per square metre of hearth.

• A. 20
• B. 40
• C. 65
• D. 80

Explanation: A limestone-calcination rotary kiln typically has a thermal efficiency of roughly 40%, although the exact value varies with kiln design…

• A. 10
• B. 25
• C. 65
• D. 90

Explanation: Modern well-designed boilers can transfer roughly 80 to 90% of the fuel heat to the steam, so about 90% is a reasonable maximum.

• A. Saving in fuel consumption
• B. Reduction in scale losses
• C. Increase in flame temperature
• D. All A., B. and C.

Explanation: Preheating combustion air recovers heat that would otherwise leave with the flue gas, thereby reducing fuel consumption, limiting scale…

• A. 20
• B. 40
• C. 60
• D. 80

Explanation: Blast-furnace stoves are regenerative heat exchangers and commonly achieve thermal efficiencies of about 80%.

• A. Potteries
• B. Stainless steel
• C. Glass
• D. Refractory bricks

Explanation: A pot furnace with regenerative or recuperative heating is a furnace used for melting glass, where the charge is held in refractory pots.

• A. Slabs
• B. Coils
• C. Sheets
• D. Ingots

Explanation: Soaking pits heat steel ingots uniformly throughout their cross-section before rolling.

• A. Both A. and B.
• B. Cement manufacture
• C. Calcination of limestone & dolomite
• D. Neither A. nor B.

Explanation: Rotary kilns provide continuous high-temperature processing and are used both to calcine limestone or dolomite and to manufacture cement…

• A. Same
• B. Less
• C. More
• D. Either more or less; depends on the flue gas density

Explanation: For the same mass flow and draught pressure, forced-draught equipment handles cooler, denser air and therefore a smaller volume.

• A. Hardening makes the steel more brittle
• B. High alloy steels contain more than 50% alloying element
• C. Both B. and C.
• D. 18/8 stainless steel is a magnetic steel

Explanation: High-alloy steels do not require more than 50% alloying elements, and 18/8 stainless steel is normally a non-magnetic austenitic steel.

• A. All A., B. and C.
• B. Causing metal embrittlement
• C. Attacking the grain boundaries; particularly severe on low carbon and nickel bearing steels at
• D. high temperature
• E. Accelerating the rate of scaling

Explanation: Sulphur dioxide in hot furnace gases promotes scaling, can cause embrittlement, and may attack grain boundaries in susceptible steels at…

• A. 1 to10
• B. 1 to 8
• C. 1 to 15
• D. 0 to 10

Explanation: The Mohs hardness scale is numbered from 1 for talc to 10 for diamond. Therefore, the stated range is 1 to 10, not 0 to 10.

• A. Cork
• B. Glass
• C. Rubber
• D. Graphite

Explanation: Rubber is an elastomer, so it undergoes both elastic recovery and viscous deformation, giving it viscoelastic behaviour.

• A. Aqua regia
• B. Ferrous sulphate
• C. Hydrochloric acid (10%)
• D. None of these

Explanation: Aluminium is attacked by aqua regia and hydrochloric acid, while ferrous sulphate solution can also promote corrosion through chemical…

• A. Babbitt metal
• B. Monel
• C. Inconel
• D. Chlorinet - 2 alloy

Explanation: Monel, Inconel and Chlorimet-2 are nickel-containing corrosion-resistant alloys.