Free Plant Design and Economics MCQs with Answers

• A. Gypsum
• B. Quartz
• C. Feldspar
• D. Fluorite

Explanation: On the Mohs scale, talc has hardness 1 and gypsum has hardness 2, making gypsum the next softest listed mineral.

• A. Mica flakes
• B. Rubber
• C. Glass
• D. None of these

Explanation: Natural rubber is mainly cis-1,4-polyisoprene, a hydrocarbon polymer composed largely of carbon and hydrogen.

• A. Surgical instruments
• B. Chemical equipments
• C. Powerful magnets
• D. Boiler tubes

Explanation: Alnico contains aluminium, nickel, and cobalt and is designed to retain strong magnetism, so it is used for powerful permanent magnets.

• A. Hydrochloric acid (concentrated)
• B. Benzoic & boric acids
• C. Phosphoric acid (95%) & sulphuric acid (95%)
• D. Acetic acid

Explanation: High-silicon cast iron resists many strong acids, including concentrated sulphuric and hydrochloric acids, but concentrated hydrochloric…

• A. Keep the pipe in proper orientation
• B. Account for contraction/expansion of pipe due to temperature changes of the surroundings
• C. Make the pipe joint leak-proof
• D. Account for the pressure variation side the pipeline

Explanation: Disc compensators absorb thermal expansion and contraction in long, large-diameter pipelines.

• A. All A., B. and C.
• B. Combine with salts (e.g. chlorides sulphates etc.) & bases (e.g. lime, magnesia etc.) forming
• C. fusible aluminates silicates etc
• D. Shrink during firing
• E. Are not resistant to the action of basic slags

Explanation: Fireclay is an alumino-silicate acidic refractory, so basic slags and alkaline salts can form low-melting compounds with it.

• A. Roof of open hearth furnace
• B. By-product coke ovens
• C. Dome of blast furnace stoves
• D. Beehive coke ovens

Explanation: Silica bricks are used in by-product coke ovens, open-hearth furnace roofs and commonly in stove domes because they withstand high…

• A. Greater strength
• B. Low heat capacity
• C. Low thermal conductivity
• D. High insulating properties

Explanation: Lower porosity means fewer voids and a denser brick, which generally gives greater mechanical strength.

• A. Fireclay
• B. Silicon carbide
• C. Corundum
• D. Siliceous fireclay

Explanation: Silicon carbide is preferred for high-temperature ceramic recuperators because it has high thermal conductivity, excellent thermal-shock…

• A. Corundum
• B. Carborundum
• C. Beryllia
• D. Thoria

Explanation: Beryllia has a very low neutron absorption cross-section while remaining effective in moderating fast neutrons, so it is used as a…

• A. All A., B. and C.
• B. Higher moulding pressure
• C. Finer grog size
• D. Higher firing temperature

Explanation: Permeability is reduced by densifying the brick and reducing pore size, achieved through higher moulding pressure, finer grog and higher…

• A. Slag attack
• B. Thermal spalling
• C. Fusion under load
• D. CO attack

Explanation: Repeated heating and cooling produces expansion and contraction stresses, which can crack and detach refractory pieces through thermal…

• A. Crushing strength
• B. Both A. and B.
• C. Resistance to slag attack
• D. Neither A. nor B.

Explanation: Zircon improves the chemical stability of silica refractories against slags, especially by reducing penetration and reaction with the…

• A. Silicon carbide bricks
• B. Porous fireclay bricks
• C. Semi-silica bricks
• D. Dead burnt magnesite ramming mass

Explanation: A basic open-hearth furnace requires a basic refractory bottom to resist basic slags, so dead-burnt magnesite is used as a ramming mass.

• A. 1350
• B. 1715
• C. 2570
• D. 2800

Explanation: Pure silica melts at approximately 1715°C, although its crystal transformations occur at much lower temperatures.

• A. Beryllia
• B. Alumina
• C. Thoria
• D. Zirconia

Explanation: Thoria (ThO₂) has an exceptionally high melting point of about 3300°C, higher than alumina, beryllia, and zirconia.

• A. Making sheaths for thermocouple
• B. Lining high temperature ceramic kilns
• C. Furnaces subjected to fluctuating temperature
• D. High frequency induction furnaces in the form of inductors

Explanation: Zirconia withstands very high temperatures and is used for thermocouple sheaths and kiln linings, but its poor thermal-shock resistance…

• A. None of these
• B. Iron oxide
• C. Lime slag
• D. Molten steel

Explanation: Dolomite bricks are basic refractories containing calcium and magnesium oxides, and they resist contact with molten steel in steelmaking…

• A. Low co-efficient of thermal expansion
• B. Poor thermal spalling resistance
• C. Tendency to expand unduly high during firing
• D. Very high cost

Explanation: Fireclay refractories generally have a low coefficient of thermal expansion, giving them comparatively good resistance to thermal shock.

• A. Resistance to CO attack
• B. Resistance to slag penetration
• C. RUL
• D. Permanent linear change

Explanation: The spray test evaluates how readily slag penetrates and attacks a refractory surface.