This set of Iron Making Multiple Choice Questions & Answers (MCQs) focuses on “Chemical Characteristics of Coal for Coke Making”.
1. The chemical characterization of coals for coke making is done by __________
a) Proximate analysis and ultimate analysis
b) Proximate analysis
c) Ultimate analysis
d) Thermal analysis
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Explanation: Chemical characterization of coals for coke making is done by proximate analysis and ultimate analysis. The ultimate analysis indicates the chemical composition of coal. Hydrogen, carbon, nitrogen, oxygen, phosphorus and sulphur contents are determined.
2. An ash decides the ____________
a) Physical characteristics of coke
b) Chemical characteristics of coke
c) Thermal characteristics of coke
d) Plastic characteristics of coke
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Explanation: An ash decides the physical characteristics of coke. Ash has a major impact on the performance of blast furnace. The use of high ash coke increases the coke rate and also the slag volume in the blast furnaces.
3. Every 1% increase in coke ash increases the coke rate by ____________
a) 23–25 kg/thm
b) 20-25 kg/thm
c) 25-30 kg/thm
d) 15-25 kg/thm
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Explanation: Every 1% increase in coke ash increases the coke rate by 23–25 kg/thm under the Indian conditions. In India coke with 18–22% ash made from a coal blend with 14–18% ash is normally used.
4. Every 1% increase in the ash content of coke typically ____________
a) Decreases the productivity by around 3%
b) Increases the productivity by around 3%
c) Decreases the productivity by around 10%
d) Increases the productivity by around 10%
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Explanation: Every 1% increase in the ash content of coke typically decreases the productivity by around 3%. This is the reason why the coke rate is higher and the productivity is lower in Indian blast furnaces even when working efficiently.
5. The actual carbon that is available in coke to carry out reduction of iron oxide to hot metal in a blast furnace is termed as _____________
a) Effective carbon
b) Core coal
c) Charcoal
d) Effective coke
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Explanation: The actual carbon that is available in coke to carry out reduction of iron oxide to hot metal in a blast furnace is termed as ‘effective carbon’. The amount of ‘effective carbon’ decides the quality of the coke.
6. Sulphur is present in coal as _____________
a) Organic and inorganic sulphur
b) Organic sulphur
c) Inorganic sulphur
d) Metallic sulpur
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Explanation: Sulphur is present in coal as both organic and inorganic (pyritic) sulphur. In Indian coals total sulphur contents is 0.5–0.6%. 70% of the sulphur is present in inorganic form and 30% in organic form.
7. External desulphurisation of blast furnace hot metal is done to bring down the sulphur levels to _______________
a) About 0.030%.
b) About 0.040%.
c) About 0.050%.
d) About 0.060%.
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Explanation: External desulphurisation of blast furnace hot metal is done to bring down the sulphur levels to about 0.030% maximum. It is done prior to the use of hot metal in blast furnace steelmaking.
8. Alkalis are present in coal in the form of ______________
a) Sodium and potassium oxides (Na2O and K2O)
b) Potassium oxides (K2O)
c) Sodium oxides (Na2O)
d) Calcium oxide (CaO)
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Explanation: Alkalis are present in coal in the form of sodium and potassium oxides (Na2O and K2O) to the extent of 0.20–0.35%.
9. Half of the total alkali input comes from the _______________
a) Coke ash
b) Dolomite
c) Iron ore
d) Limestone
View Answer
Explanation: Half of the total alkali input comes from the coke ash. Remaining is from fluxes like limestone and dolomite. The alkali content in any coal is a chief parameter used for its selection in coke making.
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