This set of Iron Making Multiple Choice Questions & Answers (MCQs) focuses on “Kinetics of Gasification of Carbon by CO2”.
1. Which step is the rate controlling step in gasification?
a) Chemical reaction
b) Physical reaction
c) Inward diffusion of CO2 through the pores
d) Outward diffusion of CO through the pores
View Answer
Explanation: The chemical reaction is much slower compared with the other steps; hence it is the principal rate controlling step. Large activation energy is required to carry out the chemical reaction.
2. Blast furnace coke has carbon percentage of __________
a) 80-90%
b) 90-95%
c) 70-80%
d) 65-75%
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Explanation: Blast furnace coke has a carbon percentage of 80-90%. Blast furnace coke is rich in carbon. Rest 10-20% is ash, which consists of various inorganic oxides. The gasification reaction is also of significant interest in the carbothermic reduction of some other metals as well as in several chemical industries.
3. Rate of the gasification reaction increases with the increase in temperature.
a) True
b) False
View Answer
Explanation: This happens because of the large activation energy. An increase in temperature provides the required activation energy for gasification and hence the rate of reaction increases. That is why the direct reduction in a blast furnace takes place only in the bosh and lower stack regions.
4. The degree of gasification of carbon (Fc) is given as Fc = mass loss of carbon in the sample / total mass of carbon in the sample.
a) True
b) False
View Answer
Explanation: The gasification reaction is of significant interest in the carbothermic reduction of some other metals as well as in several chemical industries. Due to this reason the physical chemists, chemical or metallurgical engineers study the kinetics of the reaction keenly since the early 1920s.
5. The reactivity (Rc) is define as Rc=dFc/dt.
a) True
b) False
View Answer
Explanation: The term Reactivity is commonly used to denote the speed of the gasification reaction. Higher the reactivity of the sample, the faster is the gasification. There has been a linear relationship between Fc and t up to Fc=0.3-0.4. Rc remains constant in this region.
6. There are 5 kinetic steps involved in the gasification of a piece of carbon.
a) True
b) False
View Answer
Explanation: 5 steps involved are as follows:
i. Transfer of CO2 to the solid interface
ii. Diffusion of gases into solid through the pores
iii. Chemical reaction
iv. Diffusion of CO outwards
v. Transfer of CO across the boundary to the bulk
7. The rate increases with an increase in pore surface area (S).
a) True
b) False
View Answer
Explanation: Since the chemical reaction is the rate controlling step, the reaction occurs internally. Therefore, the rate increases with an increase in pore surface area (S). It so happens that S varies from 0.1 m2/g–1 to 103 m2/g–1, depending on the nature of carbon.
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