Final Project - Elam

64 Pages·2014·19.09 MB·English

UNIVERSITY OF NAIROBI

DEPARTMENT OF ENVIRONMENTAL AND BIOSYSTEMS ENGINEERING

FEB 540: DESIGN PROJECT
FINAL PROJECT REPORT
DESIGN OF A SIMPLE BIOGAS COMPRESSOR

PREESENTED BY:
BABU ELAM OCHIENG’
F21/0020/2008

SUPERVISOR: J. O. AGULLO

SUBMITTED TO: Eng. MUTULI DANIEL

Submitted in partial fulfillment of the requirements of the degree of Bachelor of Science in
Environmental and Biosystems Engineering of University of Nairobi
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
DECLARATION

I declare that this project is my work and has not been presented for a degree in any other
university.

Signed: Date: .
BABU O. E.
(F21/0020/2008)

This project has been submitted for examination with my approval as university supervisor.
Signed: Date: .
J.O. AGULLO
(SUPERVISOR)

ii
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
DEDICATION
I dedicate this project to my family, especially my parents for their unconditional love, continued
financial support and moral guidance. May God bless you abundantly.

iii
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
ACKNOWLEDGEMENTS
My sincere gratitude goes to my supervisor, Mr. J.O. Agullo for his assistance, excellent
supervision, direction, guidance, support and invaluable recommendations up to the completion
of the project. Special gratitude also goes to the Effluent Treatment Plant team at Kenya
Breweries Limited for their cooperation and assistance in data collection especially Mr. Andrew
Ayany for his assistance in explaining the data and helping in one way or another in my fact
finding mission.
I gratefully acknowledge the entire staff of Environmental and Biosystems Engineering
Department for successfully coordinating our undergraduate degree program. Thanks to my
classmates for the role played in the period, their criticism and knowledge shared throughout the
process without which it would be difficult to achieve this.
Lastly I am indebted to my family and friends for their support throughout. May God bless you
all abundantly.

iv
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
ABSTRACT
The design of a simple biogas compressor was done to envision the problem of storage through
compression and transportation of biogas and its use as an alternative source of fuel. This will
help reduce major dependence on imported fuels such as petrol and diesel. A lot of biogas is
being produced and many digesters set up all over the country but no mode of compression for
convenient use of the gas is done. Most biogas digesters and producers do not compress the gas
but use it as it is directed through a pipeline for use in households, generation of electricity and
heating purposes. Compressors may be employed and these can be powered but can an off grid
compressor be designed to help in the rural setup with high capacity of biomass and also in small
scale producers that may not require electricity (motor powered) compressors.
Having this in mind a simple design was done by looking at the properties of biogas and its
compressibility with references to work that has already been done elsewhere. Choice of the
compressor was also done by looking at different types of compressors and selecting the most
appropriate compressor which was taken to be the reciprocating compressor. The compressor
was to compress biogas to pressures of about 11bar which meant that 1m3 of biogas could be
reduced to a volume of about 0.17m3. The final design was simple as it took mechanisms of the
tire pump (reciprocating) and powered by cycling mechanism. A simple coded program was also
developed using visual basic to help in the analysis in different scenarios and sizing of the
compressor.
From the design it was learnt that there is a lot of potential in biogas compression ant this would
help reduce the energy problems experienced in the country and also help in self sustainability in
energy production. It therefore means that we as a nation need to embrace simple technologies to
help in our way to greater heights not only in the energy sector but also in self development.

v
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
The simple biogas compressor can therefore be applied to help in the storage of biogas and hence
energy storage. When well implemented the technology can greatly act as a source of
employment to many Kenyans in both rural and urban area setups and also would be a stepping
stone to more development to the achievement of vision 2030.

vi
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
Table of Contents
1. INTRODUCTION ............................................................................................................................... 1
1.1. Background Information ............................................................................................................. 1
1.2. Problem Statement………………………………………………………………………………………………………………..3
1.3. Problem Justification………………………………………………………………………………………………………………4
1.4. Objectives………………………………………………………………………………………………………………………………4
1.4.1. Overall Objective……………………………………………………………………………………………………………4
1.4.2. Specific Objectives………………………………………………………………………………………………….………4
1.5. Statement of Scope………………………………………………………………………………………………………….......5
2. LITERATURE REVIEW ....................................................................................................................... 6
3. THEORITICAL FRAMEWORK…………………………………………………………………………………………….…….10
3.1. Types of compressors…………………………………………………………………………………………………….…….10
3.1.1. Positive displacement compressors ……………………………..……………………………………………..11
3.1.2. Dynamic compressors ……………………………………………………………………………………………….…12
3.2. Gas Laws………………………………………………………………………………………………………………………………12
3.3. Polytropic processes…………………………………………………………………………………………………………….13
3.4. 1st Law of Thermodynamics……………………………………………………………………………………………..…..13
3.5. 2nd Law of Thermodynamics…………………………………………………………………………………………………14
3.6. Theory of Compressors…………………………………………………………………………………………………………14
3.6.1. Work of compression on steady flow……………………………………………………………………………18
3.7. Biogas…………………………………………………………………………………………………………………………………..19
4. METHODOLOGY……………………………………………………………………………………………………………………22
4.1. Study area…………………………………………………………………………………………………………………………...22
4.2. Pertinent factors ……………………………………….………………………………………………………………………..22
4.3. Choosing the compressor…………………………………………………………………………………………………….23
4.4. Scrubbing of Hydrogen sulphide…………………………………………………………………………………………..23
4.5. Assessment of properties of Biogas……………………………………………………………………………………..23
4.6. Design and sizing of the compressor…………………………………………………………………………………….26
4.7. Rod load calculations……………………………………………………………………………………………………………27
4.8. Transmission………………………………………………………………………………………………………………………..28
4.9. Selection of materials…………………………………………………………………………………………………………..29
5. RESULTS AND DISCUSSION..………………………………………………………………………………………………….30
6. CONCLUSION AND RECOMMENDATIONS……………………………………………………………………………..36
7. REFERENCES.………………………………………………………………………………………………………………………..37
8. APPENDICES…………..…………………………………………………………………………………………………………….38
Appendix 1: Operating range of compressors…………………………………………………………………………..38
Appendix 2: Calculations…………………………………………………………………………………………………………..38
Appendix 3: L.P.G. cylinder standards……………………………………………………………………………………….45
Appendix 4: Cylinder material choice………………………………………………………………………………………..47
Appendix 5: Reciprocating Cylinder Volumetric efficiency…………………………………………………………48
Appendix 6: AutoCAD drawings………………………………………………………………………………………………..49
Appendix 7: Visual Basic code……………………………………………………………………………………………………52

vii
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
LIST OF FIGURES
Figure 2.1: Maruti-800car tested on enriched biogas compressed in CNG cylinder……………8
Figure 3.1: Types of compressors………………………………………………………………10
Figure 3.2: Reciprocating compressor………………………………………………………….15
Figure 3.3: Compressor schematic layout……………………………………………………...15
Figure 3.4: Ideal compression cycles…………………………………………………………..16
Figure 3.5: PV diagram of compression with no restriction…………………………………...17
Figure 3.6: PV diagram with clearance volume………………………………………………..18
Figure 3.7: Steady flow process………………………………………………………………..19
Figure 3.8: H S scrubbing setup……………………………………………………………….21
2
Figure 4.1: Foot pump, cycle and air compressor……………………………………………...23
Figure 4.2: Compression cycle…………………………………………………………………24
Figure 4.3: Offset slider crank mechanism……………………………………………………..28
Figure 4.4: System process……………………………………………………………………..33
Figure 4.5: Final Compressor design…………………………………………………………..33
Figure 4.6: System supply scheme……………..……………………………………………….34
Figure 4.7: Visual Basic 6 program user interface……………………………………………..35
Figure 8.1: Operating range of reciprocating compressors…………………………………….38
Figure 8.2: Typical observed volumetric efficiency……………………………………………48
Figure 8.3: AutoCAD drawings of compressor views................................................................49
Figure 8.4: Parts and Assembly of compressor….......................................................................50
Figure 8.5: Cylinder details……………………………………………………………………51

viii
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
LIST OF TABLES
Table 2.1: Total upgraded biogas consumption for buses in Stockholm city……………………8
Table 3.1: Composition of Biogas……………………………………………………………….20
Table 8.1: LPG cylinder draw off rates………………………………………………………….45
Table 8.2: Design Ratings of Typical Applications……………………………………………...45
Table 8.3: Capacity of LPG containers…………………………………………………………..46
Table 8.4: Rankings for top five compressor cylinder material possibilities……………………47

ix
DESIGN OF A SIMPLE BIOGAS COMPRESSOR
F21/0020/2008 UoN
1. INTRODUCTION
1.1.Background Information
Gaseous fuels such as natural gas and biogas are being explored as alternatives to petrol and
diesel. This is as a result of costs implied in petrol and diesel such as importation and also the
emission rates. Biogas is a clean burning energy that is taking ground in recent times. It is
generally methane collected from decomposing organic matter. There are a lot of inspirations for
the use of biogas ranging from political (Kyoto protocol, EU and national legislations),
environmental (reduction of organic and biological pollution), veterinary (treatment of animal
by-products not intended for human consumption), energy (replacement of fossils to local
resources), recovery (production of new products from wastes), agricultural (waste treatment,
fertilizers) and social aspects (labor market and regional development). Biogas is produced when
organic matter is digested and decomposed by anaerobic bacteria and mostly composed of
methane and carbon dioxide. It is also known as landfill gas and gobar gas in India which has
numerous biogas plants in the rural areas.
Biogas has been around since there has been biomass and other waste decaying, decomposing
and digested by bacteria. It is thought that it was first discovered in a swamp but the true
potential of this gas wasn't realized until the 1890's when the gas was used for lighting in
England. In 1630 Von Helmont found that flammable gases could evolve from decaying organic
matter and in 1667 Shirley notes his findings on biogas then known as marsh gas. Biogas history
can be summarized as below
1808 – Sir Humphrey Davy found that methane was present in the gas that is formed by the
Anaerobic Digestion of manure.

1