This set of Chemical Industry Multiple Choice Questions & Answers (MCQs) focuses on “Inorganic Chemical – Cement and Lime”.
1. Which type of cement is used for brick mortar composition?
a) Portland cement
b) High alumina
c) Hydraulic lime
d) Pozzolana
View Answer
Explanation: Hydraulic lime is used only for brick mortar composition, low price and strength. Pozzolana cement is mixture of volcanic ash, burnt clay or shale in 2-4 parts with hydrated lime.
2. Which type of cement is manufactured by fusing limestone and bauxite?
a) Regular type portland cement
b) High alumina
c) Magnesium oxychloride
d) Portland cement
View Answer
Explanation: High alumina cement is manufactured by fusing limestone’s and bauxite; rapid rate of high strength development to high values but with high heat rate liberation; superior resistance to sea and sulphate waters.
3. Which unit operation mentioned below is not involved in cement rock beneficiation?
a) Grinding
b) Flotation
c) Thickening
d) Compression
View Answer
Explanation: The unit operations which are involved in cement beneficiation are grinding, classification, flotation, thickening etc. Rock is wet-ground, fed to a hydro separator where the overflow goes directly to the final thickener.
4. Why cement beneficiation is done?
a) To remove silica and iron content
b) To remove silica and aluminum content
c) To remove silica and sulfur content
d) To remove silica and magnesium content
View Answer
Explanation: Much of the locally available limestone has too high a silica and iron content for direct use in cement manufacture. These undesirable constituents can be removed by ore dressing or beneficiation methods which are based on fluid mechanics and adsorption.
5. Why dry grinding process is preferred in the Portland cement production?
a) Savings in heat
b) High pressure
c) High grade
d) Low pressure
View Answer
Explanation: Dry grinding process is predominant than wet grinding process because of savings in heat (less water to evaporate) and accurate control is possible. The sequence may include rough crushing.
6. Which lime has this criteria- Calcium>90%CaO?
a) Slaked lime
b) Hydraulic lime
c) Quicklime
d) Only lime
View Answer
Explanation: Quicklime: high calcium(>90% CaO); low magnesium (5-25% MgO), dolomitic (25-40% MgO). Hydraulic lime and slaked lime contain Ca(OH)2 and MgO-Mg(OH)2 in varying percentage.
7. Which raw material is used in the hydrated lime process?
a) Quicklime
b) Limestone
c) Coal
d) Gypsum
View Answer
Explanation: Pure quicklime is used as raw material in hydrated lime process. Quicklime lump, crushed to 2 cm or less, is added along with water or steam to a vertical cylindrical pug mill containing 18-24 extended horizontal arms.
8. CaO(s) + H2O -> Ca(OH)2 -where this chemical reaction occur?
a) Calcination limestone
b) Portland cement production
c) Cement rock beneficiation
d) Hydrated lime
View Answer
Explanation: In hydrated lime process, quicklime reacts with water and the product from this complete reaction is light, dry slaked lime which is classified by screen or air separators to remove any overburned lime that did not hydrated.
9. Which one mentioned below is not a raw material used in the Portland cement production?
a) Clay
b) Limestone
c) Gypsum
d) Quicklime
View Answer
Explanation: Quantitative requirements of Portland cement production are- clay-0.1 to 0.3 ton, limestone 1.2to1.3 tone, gypsum- 0.03 to 0.05, coal-0.25 to 0.40 and water is 3 tons required.
10. What is “x” in the following flow chart?
a) Rotary kiln
b) Pulverizer
c) Waste- heat boiler
d) Rake classifier
View Answer
Explanation: In Portland cement production, dry powdered feed or wet slurry is fed to the direct-fired counter-current rotary kiln. The residence time is 1-3 hours and the feed mixture is decarbonated and fused to form the cement compounds.
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