This set of Biomass Energy Multiple Choice Questions & Answers (MCQs) focuses on “Biomass Gasification – 1”.
1. What is unique about the gasification agent entering in a fluidized gasifier?
a) Enters from bottom at a relatively fast rate as compared to a fixed bed gasifier
b) Enters from bottom at a relatively slow rate as compared to a fixed bed gasifier
c) Enters from top at a relatively fast rate as compared to a fixed bed gasifier
d) Enters from top at a relatively slow rate as compared to a fixed bed gasifier
View Answer
Explanation: In a fluidized gasifier, the gasification agent enters the bed from the bottom at a relatively faster rate and exits from the top. This type of gasification features a uniform temperature distribution in the bed zone.
2. What ensures consistency of temperature in fluidized gasifier?
a) Gasification agent
b) Air-fluidized bed material
c) Biomass
d) Air non-permeable bed material
View Answer
Explanation: Fluidized gasifier features a uniform temperature distribution in the bed zone. This is achieved using an air-fluidized bed material. Biomass and gasification agent do not contribute towards the temperature consistency.
3. What are the three types of fluidized gasifiers used?
a) Single fluidized bed, dual fluidized bed and bubbling fluidized bed
b) Straight fluidized bed, dual fluidized bed and bubbling fluidized bed
c) Circulating fluidized bed, dual fluidized bed and bubbling fluidized bed
d) Single fluidized bed, dual fluidized bed and straight fluidized bed
View Answer
Explanation: Circulating fluidized bed, dual fluidized bed and bubbling fluidized bed are the three main types of fluidized gasifiers used. They are mainly used to achieve a uniform temperature distribution.
4. How is the temperature maintained in a bubbling fluidized bed?
a) Biomass
b) Gasification agent
c) A constant ratio of biomass and gasification agent
d) Manipulating the ratio of biomass and gasification agent
View Answer
Explanation: A bubbling fluidized bed gasifier applies inlet from the bottom and moves the bed of fine-grained materials. The temperature is maintained by manipulating the ratio of biomass and gasification agent.
5. What is the temperature range in a bubbling fluidized bed?
a) Between 700 and 900 degree Celsius
b) Less than 500 degree Celsius
c) Above 1000 degree Celsius
d) Between 100 and 200 degree Celsius
View Answer
Explanation: The temperature range in a bubbling fluidized bed gasifier is between 700 and 900 degree Celsius. This distribution is achieved by manipulating the ratio of biomass and gasification agent.
6. What is the biomass decomposed to in a bubbly fluidized bed?
a) Producer gas
b) Char and gas products with a low tar percentage
c) Char and gas products with a high tar percentage
d) Char with a low tar percentage
View Answer
Explanation: The biomass is decomposed to char and other gaseous products with a low percentage of tar. Since this is a gasifier, one of the products has to be a gas. So, the option without gaseous products is incorrect.
7. What are the two main units in a circulating fluidized bed?
a) Bubbling fluidized bed and dual fluidized bed
b) Bubbling fluidized bed and gasifier unit
c) Circulating unit and gasifier unit
d) Circulating unit and dual fluidized bed
View Answer
Explanation: The two main units in a circulating fluidized bed are circulating unit and gasifier unit. Bubbling fluidized bed and dual fluidized bed are types of fluidized gasifier. They are not a part of circulating fluidized bed gasifier.
8. Where can the ash and hot gas be separated in a circulating fluidized bed gasifier?
a) Gasifier unit
b) Circulation unit
c) Tornado separator
d) Cyclone separator
View Answer
Explanation: Ash and hot gas can be separated in the cyclone separator. The bed material and the char is circulated between the reaction chamber and the cyclone separator where the separation takes place.
9. The two separate fluidized beds in a dual fluidized bed gasifier are used for pyrolysis and combustion process.
a) True
b) False
View Answer
Explanation: A dual fluidized bed gasifier consists of two separated fluidized beds. One of the beds is used for pyrolysis and the other is used for combustion. Generally, the first bed is used for pyrolysis.
10. Which of the following best indicates the process in a dual fluidized bed gasifier?
a) Combustion reactor → pyrolysis reactor
b) Pyrolysis reactor → combustion reactor
c) Evaporation reactor → condensation reactor
d) Combustion reactor → condensation reactor
View Answer
Explanation: The first bed in a dual fluidized bed gasifier is used for pyrolysis. The second bed is used for combustion. The second reactor provides heat by burning char provided from the first reactor.
11. What are the two types of entrained flow gasifiers?
a) Bubbling fluidized gasifier and dual fluidized gasifier
b) Bubbling fluidized gasifier and top-fed gasifier
c) Top-fed gasifier and side-fed gasifier
d) Side-fed gasifier and dual fluidized gasifier
View Answer
Explanation: The two main types of entrained flow gasifiers are top-fed gasifier and side-fed gasifier. Bubbling fluidized bed and dual fluidized bed gasifiers are fluidized bed gasifiers and not entrained flow gasifiers.
12. Which of the following gasifiers is suitable for integrated gasification combined cycle (IGCC)?
a) Fluidized gasifier
b) Fixed bed gasifier
c) Downdraft gasifier
d) Entrain flow gasifier
View Answer
Explanation: Entrail flow gasifiers are suitable for IGCC. They are applied in large-scale gasification and are widely used for coal, biomass and refinery residues. Downdraft is a type of fixed bed gasifier which is not suitable for IGCC.
13. Which of the following is a problem due to tar formation in gasifiers?
a) Equipment blockages
b) High system efficiency
c) Improved quality of gas
d) Reduction in maintenance
View Answer
Explanation: Tar formation in a gasifier leads to equipment blockage, lower system efficiency and increased maintenance. The most important problem is that it contaminates the gas and reduces its quality.
14. Which of the following is a component of tar?
a) Sodium
b) Benzene
c) Chlorine
d) Nickel
View Answer
Explanation: Tar is generally composed of carbon compounds like benzene, naphthalene, single-ring aromatic hydrocarbons, toluene, etc. It does not contain of non-carbon materials like sodium, chlorine and nickel.
15. Tar is removed by choosing the appropriate catalyst.
a) True
b) False
View Answer
Explanation: Tar is removed by choosing the appropriate catalyst. Other methods include setting the appropriate operation parameter and downstream removal after gasification – mechanical method and thermal cracking.
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