Biomass Gasification Processes

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Questions and Answers

Which of the following best describes the primary advantage of gasification over direct combustion of biomass?

Gasification increases fuel heating value by removing non-combustible components. (correct)
Gasification requires a higher oxygen supply, leading to more complete oxidation.
Gasification operates at significantly higher temperatures, maximizing energy output.
Gasification produces only CO2 and water vapor, eliminating other emissions.

Which of the following is a characteristic difference between syngas produced by gasification and biogas produced by anaerobic digestion?

Biogas has a higher heating value and is primarily composed of CO and H2.
Syngas has a lower heating value and is mainly composed of CO and H2. (correct)
Biogas contains no CO2, making it burn cleaner than syngas.
Syngas has a higher heating value and is mainly composed of CO2 and CH4.

Which of the following is the correct order of zones in a typical down draft gasifier?

Drying, Pyrolysis, Reduction, Oxidation
Pyrolysis, Drying, Oxidation, Reduction
Oxidation, Reduction, Drying, Pyrolysis
Drying, Pyrolysis, Oxidation, Reduction (correct)

How does the equivalence ratio affect the gasification process, and what happens when it falls outside the ideal range?

Effective gasification occurs with an equivalence ratio of 0.2 to 0.4; less than 0.2 leads to pyrolysis dominance, while greater than 0.4 leads to combustion dominance. (B) Signup and view all the answers

Why are up draft gasifiers considered less suitable for highly volatile feedstocks compared to down draft gasifiers?

Up draft gasifiers draw gas through unburned fuel, resulting in high tar and water vapor content. (B) Signup and view all the answers

Compared to fixed bed gasifiers, what is a major advantage of fluidized bed gasifiers regarding fuel flexibility?

Fluidized bed gasifiers can effectively process biomass with high moisture content. (D) Signup and view all the answers

What is the main operational difference between bubbling fluidized bed gasifiers and circulating fluidized bed gasifiers?

Circulating fluidized bed gasifiers recirculate unburned fuel back into the gasifier. (B) Signup and view all the answers

How do the reaction pathways of hydrogen and sulfur differ between gasification and combustion?

Hydrogen turns into H2O in combustion, while sulfur becomes H2S in gasification. (B) Signup and view all the answers

Which type of gasifier is known for its rapid response to changes in gas production, despite producing poor quality gas?

Cross draft gasifier (B) Signup and view all the answers

During gasification, what chemical process primarily occurs in the reduction zone of a gasifier?

Reduction of CO2 to form carbon monoxide (B) Signup and view all the answers

In the context of gasification reactions, what distinguishes heterogeneous reactions from homogeneous reactions?

Heterogeneous reactions involve reactants in different phases, whereas homogeneous reactions involve reactants in the same phase. (C) Signup and view all the answers

What is the primary purpose of the water gas shift reaction in a gasifier?

To adjust the ratio of hydrogen to carbon monoxide in the product gas (D) Signup and view all the answers

Which factor primarily determines the design of a gasifier?

The feedstock's characteristics (e.g., moisture content, particle size, composition) (C) Signup and view all the answers

Why will fuels with high oxygen-to-carbon ratios have smaller heating values?

High oxygen content dilutes the fuel, reducing the proportion of combustible elements. (C) Signup and view all the answers

Which of the following is a disadvantage associated with cross draft gasifiers?

High exit temperature of the gas and low CO2 reduction (A) Signup and view all the answers

What is the primary purpose of the annular jacket in a down draft gasifier?

To efficiently transfer heat from the exit gas to the incoming solid material, enhancing drying. (B) Signup and view all the answers

What is common challenge in operating fluidized bed gasifiers related to gas-solid interactions?

Managing the complex flow and mixing of gas and solid phases (A) Signup and view all the answers

In an up draft gasifier, why is the gas produced likely to contain tar and water vapor?

The gas moves from a high-temperature zone to a low-temperature zone, carrying tar and moisture. (B) Signup and view all the answers

What is the primary reason gasification did not remain the primary method for energy production after the shift to petroleum?

Petroleum was easier to store and transport compared to gasified fuels. (B) Signup and view all the answers

How does gasification contribute to reducing pollution compared to direct combustion of biomass?

Gasification produces less SOx and NOx emissions and allows valuable chemical production. (B) Signup and view all the answers

Flashcards

Gasification

Thermochemical conversion of biomass into energy products.

Biochemical Conversion

A method to produce biogas from biomass.