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Woodfuel Combustion Technology Question Paper
Woodfuel Combustion Technology
Course:Master Of Science In Energy Technology
Institution: Kenyatta University question papers
Exam Year:2008
KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2007/2008
SECOND SEMESTER EXAMINATION FOR THE DEGREE OF MASTER OF SCIENCE (RENEWABLE ENERGY)
SAT 513: WOODFUEL COMBUSTION TECHNOLOGY
DATE: MONDAY, 16TH JUNE 2008 TIME: 9.00 A.M. – 12.00 NOON
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INSTRUCTIONS: 1) There are FIVE questions in this paper
2) Answer any THREE questions. All questions carry
equal marks.
3) State all assumptions made and define all symbols used.
QUESTION 1
After designing a woodfuel combustion/end-use device (i.e., stove), it is important to test it before finally producing it for marketing or personal end-use.
a) Explain the reason (i.e., main purposes) for stove testing and name the three basic
tests that can be carried out. (3 marks)
b) (i) One of the three tests is meant for efficiency testing in a laboratory. This is the
key technique for stove testing.
Name this test and describe it in details, step-by-step, how it is carried out.
(10 marks)
(ii) Name the equipment needed/required for testing and show how you
would analyse data collected above [(b(i)]. (5 marks)
c) Explain how each of the other two tests is carried out and explain the use/purpose
of each test. (7 marks)
QUESTION 2
The necessary fundamentals of biomass/woodfuel combustion include certain chemical and physical properties of the fuels.
(a) (i) Name the three categories of biomass chemical characteristics (broad chemical
properties), and show the specific characteristics that each determines.
(3 marks)
(ii) Define each of the specific characteristics named under a(i) above
and explain how each undergoes combustion during the combustion
of the primary woodfuel. (6 marks)
(b) Explain, in details, how each of the broad chemical properties influences the
biomass combustion process and the importance of their knowledge in designing
combustion devices – stoves. (9 marks)
(c) Name the physical properties of concern in the combustion of woodfuel and
design of the end-use device (stove).
Explain the influence of each on the combustion process and design of the
end-use device. (7 marks)
QUESTION 3
Conversion of woodfuels, physical and/or chemical, but the final product biofuel still
in solid form as per this subject; is important for several reasons.
(a) Outline and clearly explain what may necessitate conversion of woodfuels.(5 marks)
(b) Name the two relevant physical conversion processes. Define and explain each
of the processes. Give examples of the relevant primary biomass used in each of
the physical conversion process. (5 marks)
(c) Carbonization is the only relevant thermochemical conversion process in this
subject.
(i) Describe in details the carbonization process, elaborating all the chemical
and physical transformations that take place, temperature variations, and
the products at each process-stage. Show the final products distribution.(12 marks)
(ii) What are the suitable operating conditions and why is charcoal
preferred more than firewood? (3 marks)
QUESTION 4
A woodfuel-stove design has to achieve certain objectives for it to be successful.
(a) (i) Name the two broad objectives and indicate the meaning of each. (2 marks)
(ii) Show and clearly explain the specific objectives under each broad
objective. (6 marks)
(b) Clearly define each of the two broad objectives and show the approaches to
achieving each. Discuss approaches in details. (13 marks)
(c) A woodfuel combustion system consists of two key parts and a number of others.
Name the two key parts and explain the role of each. Show the other parts of the
system. (4 marks)
QUESTION FIVE
(a) Describe in details, stage-by stage, the woodfuel combustion process. Show
all chemical reactions and/or process equation, and temperature at each stage.
(18 marks)
(b) When designing a woodfuel stove, the main theme/objective is to maximize heat
tapping from the fire-bed and minimize heat loss from the combustion chamber.
Explain how this can be achieved. (4 marks)
(c) Define the term calorific value of a fuel and explain the determining factors.
(3 marks)
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