Free Plant Design and Economics MCQs with Answers

• A. Beehive oven
• B. Zinc roaster
• C. Coke oven walls
• D. Lead blast furnace

Explanation: Fireclay bricks are suitable for several furnace linings, but coke ovens require silica-brick walls because silica refractories withstand…

• A. Depends on the nature of slag & refractory
• B. Decreases at higher temperature
• C. Decreases, if defective joints & cracks exist in the refractory
• D. All A., B. and C.

Explanation: Slag corrosion depends on chemical compatibility between the slag and refractory, and higher temperature generally accelerates attack.

• A. Tar dolomite bricks
• B. Mullite bricks
• C. Fireclay bricks
• D. High alumina bricks

Explanation: Fireclay, mullite and high-alumina bricks are alumino-silicate refractories.

• A. Fusion point
• B. Specific gravity
• C. RUL
• D. None of these

Explanation: Specific gravity indicates the extent of conversion of silica minerals during firing; properly fired silica brick generally has the…

• A. Fireclay bricks
• B. Tar bonded dolomite bricks
• C. Mullite bricks
• D. Magnesite bricks

Explanation: Tar-bonded dolomite bricks can deteriorate through moisture-related hydration of free lime and magnesia, so temperature and humidity must…

• A. Rotary kilns
• B. None of these
• C. Sun
• D. Tunnel kilns

Explanation: Refractory green shapes are dried under controlled conditions in tunnel kilns or tunnel driers before firing, which prevents rapid…

• A. Silicon carbide
• B. Alumina
• C. Zirconia
• D. Graphite

Explanation: Silicon carbide is electrically conductive and retains strength at high temperature, making it suitable for resistance-heating bars and…

• A. Direct bonded basic
• B. Fireclay
• C. Silica
• D. Magnesite

Explanation: Fireclay bricks are fired at approximately 1250–1400°C, lower than the usual firing temperatures for silica and basic magnesia…

• A. Silicon carbide
• B. Chromite
• C. Magnesite
• D. Graphite

Explanation: Magnesite is a basic refractory because its principal component is magnesium oxide, MgO.

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

Explanation: Quartz is the stable silica modification at lower temperatures, up to about 870°C under the simplified refractory classification used…

• A. Increases
• B. Remains unchanged
• C. Decreases linearly
• D. Decreases

Explanation: Alumina has a very high melting point and increases the high-temperature stability of firebricks.

• A. 1380
• B. 1520
• C. 1710
• D. 1915

Explanation: Seger cone 32 corresponds approximately to 1710°C, placing it among the high-temperature silica-brick refractoriness grades.

• A. Fireclay
• B. Carborundum
• C. Chromite
• D. Graphite

Explanation: Graphite conducts electricity well because it has mobile electrons in its layered structure.

• A. All A., B. and C.
• B. Is crushed firebrick
• C. Is a non-plastic material
• D. Contains both alumina and silica

Explanation: Grog is calcined and crushed refractory material, commonly crushed firebrick; it is non-plastic and mainly contains alumina and silica.

• A. 800-1000
• B. 1600-1800
• C. 1000-1200
• D. 2400-2600

Explanation: Magnesite bricks are fired at about 1600–1800°C to develop a stable, dense magnesia structure and achieve high refractoriness.

• A. Muffle furnace
• B. Zinc smelting furnace
• C. All A., B. and C.
• D. Ceramic recuperators

Explanation: Silicon carbide refractories resist high temperatures, thermal shock, and chemical attack, so they are used in muffle furnaces…

• A. Rod
• B. Ball
• C. Tube
• D. Pug

Explanation: A pug mill mixes plastic or moist refractory batches uniformly with water and also kneads the mass.

• A. Both A. and B.
• B. Spalling resistance reduces
• C. Resistance to slag attack increases
• D. Neither A. nor B.

Explanation: Greater density improves resistance to slag penetration and attack, but it reduces the ability of silica refractories to accommodate…

• A. MgAl2O3
• B. MgAl2O4
• C. MgSO4
• D. MgAl2O3.2H2O

Explanation: Spinel is the compound magnesium aluminate, formed by combining MgO and Al2O3, so its formula is MgAl2O4.

• A. 35-40
• B. > 94
• C. 80-85
• D. 55-60

Explanation: Ordinary firebrick is usually made from fireclay and contains about 55–60% SiO2, with alumina making up much of the remainder.