This set of Engineering Materials and Metallurgy Quiz focuses on “Cements, Metallurgical Coke and Synthetic Resins”.
1. What is the maximum permissible amount of ash on carbonization after coal is washed?
Explanation: As coal contains foreign substances, they need to be washed to rid them of this impurity. This is done either in gravity or floatation type machine. This coal, after washing and draining, must not exhibit ash content of more than 6% on carbonization.
2. What is the solid residue that remains after heating of coal in the absence of air?
Explanation: Coke is an important element used in iron-making and metallurgical applications. It is the solid and cellular residue that remains after bituminous coal is heated in the absence of air. This is done at a temperature above which thermal decomposition occurs.
3. What is the level of fineness to be achieved in crushed coal?
Explanation: The coal, after being washed, is blended to form a uniform configuration. This allows even low-grade coal to be used in operations. The blended mix is crushed to achieve a fine quality of 70-80% below a 3 mm mesh.
4. For how long must coke be burnt?
a) 2-3 hours
b) 6-8 hours
c) 18-24 hours
d) 30-36 hours
Explanation: Coal is subjected to destructive distillation at a temperature of 1150-1200oC.This forms hard and porous coke which has high carbon content. The burning of this coke lasts for 18-24 hours but is about 25% longer for foundry coke.
5. What is the appearance of oven coke?
c) Dark grey to light silver
d) Matte black
Explanation: Oven coke made either in by-product or beehive ovens may appear as a dull dark grey to light silver grey in color and are lustrous. They are hard and may appear with a few cracks and fractures.
6. Which of the following factors are not used to evaluate the quality of coke?
a) Size and shape
d) Electrical resistivity
Explanation: High-quality foundry coke typically contains a reduced amount of volatile matter, ash, and sulfur. This quality is generally determined by evaluating the physical, chemical, and thermal properties of coke.
7. Which of the following is not an advantage of coke over coal?
c) Low smoke
Explanation: Coke is a porous material that burns rapidly. It produces little to no smoke and contains zero water content. Coal, however, is a naturally occurring substance that is purer than coke.
8. What is the temperature at which low-temperature coke is prepared?
Explanation: Low-temperature coke is primarily used for the production of gas. It is produced at a temperature ranging between 450 and 700oC. It may also be used for making fuel briquettes.
9. What is high-temperature coke used for?
b) Production of gas
c) Fuel briquettes
Explanation: High-temperature coke is produced by operation at around 1000oC. It is otherwise known as metallurgical coke. This coke finds application in iron making processes and melting of ferrous and non-ferrous metals and alloys.
10. ________ is produced due to a chemical reaction between two or more substances.
a) Synthetic resin
b) Metallurgical coke
Explanation: Synthetic resins are defined as those man-made products formed as a result of a chemical reaction of two or more substances. This is usually carried out in the presence of heat or a catalyst. These resins include synthetic rubbers and silicones.
11. Neoprene was originally known as ________
a) Phenol formaldehyde
d) Polyvinyl halides
Explanation: Polychloroprene was the first synthetic elastomer discovered in 1931. It originated in Nieuwland and has since been known as Neoprene. This led to the discovery of several types of synthetic polymers.
12. Which of the following is not an application of synthetic resins?
c) Thermal insulation
d) Ion exchange
Explanation: Synthetic resin is a polymer formed artificially by chemical reaction. It is used in textiles, paints, and plastics. Some special synthetic resins are used as ion exchange media.
13. What is Portland cement primarily composed of?
Explanation: Portland cement is a common binder used for civil construction purposes. It mainly consists of calcium oxide (over 42%) with carbon dioxide (over 35%), followed by small quantities of Fe2O3, MgO, Al2O3, and over 15% of SiO2.
14. At what temperature is limestone heated to make Portland cement?
Explanation: Portland cement is manufactured by heating limestone and other raw materials at 1450oC in a kiln. This process is known as calcination. Here, calcium carbonate (limestone) releases carbon dioxide, which in turn becomes calcium oxide CaO.
15. The hardening process of Portland cement is known as _______
Explanation: Portland cement hardens and sets by capturing water. This involves intricate chemical reactions which may take up to 24 hours. This process, known as hydration, also causes bonding.
16. After burning of raw materials, Portland cement involves blending with ______
a) 3% baryte
b) 3% anhydrite
c) 3% hanksite
d) 3% gypsum
Explanation: Raw materials are ground to 200 mesh and burnt in a cement kiln. After burning, the resultant, called clinker, is ground to 325 mesh and blended with 3% gypsum. It is then stored in a cement silo, ready for use.
17. Which of the following cement are not used as a cement replacement?
a) Siliceous fly ash
b) Calcareous fly ash
c) Silica fume
d) Slag cement
Explanation: Siliceous fly ash, calcareous fly ash, and slag cement are common cement generally used as replacements of cement. Silica fume, on the other hand, is generally used as a property enhancer.
18. What is the specific gravity of Portland cement?
Explanation: Specific gravity is defined as the ratio of the density of a material to the density of reference material. Portland cement has a higher specific gravity compared to other common cement. The specific gravities of Portland cement, slag cement, calcareous fly ash, and silica fume are 3.15, 2.94, 2.65, and 2.22 in that order.
19. White Portland cement is obtained due to sintering at _______
Explanation: White Portland cement is similar to ordinary and grey Portland cement in most aspects. This differs from other types of Portland cement due to their white appearance, which is a result of low Fe2O3 content. As opposed to the normal operating at 1450oC, white Portland cement requires sintering at 1600oC.
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