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Sat 515:Energy Conversion Technology Ii Question Paper
Sat 515:Energy Conversion Technology Ii
Course:Master Of Science In Renewable Energy
Institution: Kenyatta University question papers
Exam Year:2008
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KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2007/2008
SECOND SEMESTER EXAMINATION FOR THE DEGREE OF MASTER OF
SCIENCE (RENEWABLE ENERGY)
SAT 515: ENERGY CONVERSION TECHNOLOGY II
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DATE: Friday 13th June, 2008 TIME: 9.00 a.m. – 12.00 Noon
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INSTRUCTIONS:
There are FIVE questions in this paper. Answer ANY THREE questions.
Question 1
Suitable biomass materials can be converted to useful gaseous fuel by thermal
gasification technology.
(a) Describe in details the chemical and physical transformations that take place
during biomass gasification process, showing all the principle reactions taking
place at each process stage.
(15 marks)
(b) Discuss in details, pointing out the scientific principles, THREE important
parameters/factors that must be controlled for optimum performance of the
gasification technology.
(10 marks)
Question 2
Organic materials can be decomposed through anaerobic digestion technology, under
appropriate conditions, to produce methane (CH ) , which can be used to power IC
4
engines, generate electric power and in various household energy applications.
(a)
Describe, in details, the anaerobic digestion process that take place in methane
production.
(9 marks)
(b)
Clearly describe, giving scientific principles, how each of the following
factors influence the production of biogas in the anaerobic digestion process.
Indicate the optimum of each.
(i)
Temperature
(ii)
pH
(iii)
Substrate loading rate
(iv)
C N ratio of the substrate.
Question 3
Name the three commonly used biomass-gasifier designs and describe the operation
of each. Give the advantages and disadvantages of each design. Using a suitable
illustration/drawing, show the operation and the reaction zones for each design.
(25 marks)
Question 4
Pyrolysis technology can be used for biomass “liquefaction”, gasification, and
“carbonization”, i.e., to convert the primary solid biomass to a liquid fuel (boi-oil),
gaseous fuel, or high-grade solid fuel (charcoal).
(a)
Name and discuss the relevant modes of pyrolysis, clearly elaborating the
conditions under which such fuels can be generated from biomass through
pyrolysis. Show the product distribution under each mode.
(10 marks)
(b)
Describe in details the sequential chemical and physical transformations that
take during the wood carbonization process using the kiln technology;
indicating the temperature variations, and the products at each stage.
(10 marks)
(c)
Discuss the main factors that influence charcoal yields.
(5 marks)
Question 5
The product gases from biomass gasification processes, both thermochemical and
biochemical, contains some impurities with various negative effects.
(a)
Tar is the key impurity in the product gas from biomass thermal gasification
process. Explain, clearly and in details, why tar is a problem in application of
producer gas, and how to minimize it.
Name other impurities in producer gas, and explain their negative effect.
(12 marks)
(b)
(i)
Name the principal impurities in biogas and explain their negative
effects which necessitates their removal.
(3 marks)
(ii)
Discuss in details the techniques that can be used to remove the
impurities.
(10 marks)
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