Free Plant Design and Economics MCQs with Answers

• A. Al2O3
• B. CaO
• C. SiO2
• D. All A., B. & C.

Explanation: Al2O3, CaO, and SiO2 act as impurities in magnesite and lower its effective refractoriness by forming lower-melting compounds with MgO.

• A. Both A. and B.
• B. Better spalling resistance
• C. Less fusion point
• D. Neither A. not B.

Explanation: Semi-silica bricks contain less silica than silica bricks, giving them a lower fusion point, while their lower quartz content improves…

• A. Preheating
• B. Burning
• C. Cooling
• D. All the above

Explanation: The burning zone of a limestone rotary kiln experiences the highest temperature and severe chemical attack, so chrome-magnesite is used…

• A. High thermal conductivity
• B. Low porosity
• C. Non-wetting characteristics
• D. High density

Explanation: Carbon blocks do not readily wet with molten iron or slag, so their non-wetting surface prevents molten material from adhering and forming…

• A. 60 and 40
• B. 20 and 80
• C. 50 and 50
• D. 80 and 20

Explanation: Most cermets contain a ceramic phase as the major component, commonly about 80%, bonded with roughly 20% metal.

• A. Coke oven regenerator
• B. Bottom hearth of reheating furnace
• C. Hearth of soaking pits
• D. Burning zone of limestone rotary kilns

Explanation: Chrome-magnesite bricks are suitable for highly basic, high-temperature zones such as soaking-pit hearths, reheating-furnace hearths, and…

• A. Zirconia
• B. Magnesia
• C. Silicon carbide
• D. None of these

Explanation: Zirconia and magnesia are single-oxide refractories because they are based primarily on ZrO2 and MgO.

• A. Dome of blast furnace stoves
• B. Electric arc furnace roof
• C. Glass melting furnaces
• D. All A., B. and C.

Explanation: High-alumina refractories withstand high temperatures and chemical attack, making them suitable for blast-furnace-stove domes…

• A. Tridymite
• B. Cristobalite
• C. Quartz
• D. None of these

Explanation: Tridymite is the stable silica modification approximately from 870°C to 1470°C.

• A. Hearth of the blast furnace
• B. Nuclear reactors, missiles & space crafts
• C. Insulation of high temperature furnaces
• D. Roof of electric furnaces

Explanation: Cermets combine ceramic hardness and high-temperature resistance with metallic toughness, making them suitable for severe aerospace and…

• A. Low co-efficient of expansion
• B. High RUL (1600°C) and refractoriness (> 2000°C)
• C. All A., B. and C.
• D. High spalling resistance

Explanation: Zircon refractories have low thermal expansion, high refractoriness above 2000°C, a high refractoriness-under-load value near 1600°C, and…

• A. Are bonded with lime and clay
• B. (Free from silica) have better thermal fatigue resistance than silica and magnesite refractories.
• C. Are resistant to basic slag
• D. All A., B. and C.

Explanation: Chromite refractories are relatively neutral, tolerate basic slags, and their silica-free composition gives better thermal-fatigue…

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

Explanation: Zircon nozzles are used in continuous steel casting because zircon resists molten-steel attack, erosion and thermal shock.

• A. Both A. & B.
• B. Fireclay bricks
• C. Silica bricks
• D. Neither A. nor B.

Explanation: Silica bricks undergo marked expansion on heating, especially because of the quartz-to-cristobalite and tridymite transformations.

• A. Television sets
• B. Transformers
• C. Magnetic switches
• D. Thermal insulation

Explanation: Ferromagnetic ceramics, commonly ferrites, are used in transformer cores, magnetic switches and television components.

• A. Dehydrate the dried refractory
• B. All A., B. and C.
• C. Form ceramic bonds necessary for development of high crushing strength in the finished
• D. product
• E. Develop stable mineral forms in them

Explanation: Firing removes chemically bound water, develops stable mineral phases and produces the ceramic bonds responsible for the brick's high…

• A. crack when subjected to sudden change of temperature
• B. Cannot be used in the dome of hot blast stoves
• C. Have lower thermal conductivity than fireclay bricks
• D. All A., B. and C.

Explanation: Silica refractories have poor resistance to sudden temperature changes because their phase transformations and low thermal-shock tolerance…

• A. Silica
• B. Fireclay
• C. Magnesite
• D. Corundum

Explanation: Fireclay bricks have relatively low linear thermal expansion up to about 1000 °C, approximately 0.5%.

• A. Softening
• B. Resistance to compressive loads
• C. Fracture due to uneven expansion at high temperature
• D. Resistance to chemical action of gases and molten fluxes

Explanation: Spalling is the breaking or flaking of a refractory surface caused mainly by uneven thermal expansion, thermal shock, or temperature…

• A. 85% alumina
• B. Carbon
• C. Fireclay
• D. Corundum

Explanation: Bauxite calcining kilns require a highly alumina-rich lining because of their high temperature and severe abrasion.