ABSTRACT
Increased
public awareness posed by global warming has led to greater concern over the
impact of anthropogenic emissions from incinerators. This lead to the
development of alternative air pollution control systems such as wet scrubber systems, gravity separators,
centrifugal collectors, fabric filters and electrostatic precipitators (ESP).
This thesis is aimed at designing, construction and testing of a relatively
simple, efficient and practical unit suitable for incinerator exhaust gas
cleaning. A low energy orifice wet scrubber was constructed and tested with an
existing small scale domestic waste incinerator. The inlet and outlet
temperatures of the scrubber were recorded with pyrometers and the chimney
outlet measured with infra-red thermometer. Smoke samples were passed through
filter papers separately at the scrubber inlet and outlet to capture the smoke
particles. The particles were observed under microscope at the KNUST Physics
laboratory and the results analyzed. The smoke emissions from the incinerator
exhaust during the testing of the incinerator were compared to the Ringelmann
smoke chart and the smoke density before and after the filter installation
determined. The scrubber was able to reduce the smoke density from 21.34 % to
17 %. The test result on particle distribution showed that the scrubber could
not collect particle matter (PM) less than 5 μm and particle collection
efficiency for PM greater than 30 μm was more than 80 percent. Mean particle
size diameter at scrubber inlet and outlet were 73.4 μm and 23.8 μm
respectively.
CHAPTER ONE
GENERAL INTRODUCTION
1.1 Background of
the project
Incineration process allows complete oxidation of solid
wastes, liquids or gases at elevated temperatures. Several communities have
adopted diverse ways of waste disposal, for instance burial, disposing in
landfill location and hasty disposal in gutters and bushes. These waste dumping
systems have been established to be unsafe and not hygienic.
Disposing municipal solid waste (MSW) has become a serious
problem in present societies, though, some measures have been adopted to avoid,
recycle, reuse and reduce these wastes. Improved and environmentally accepted
options for waste disposal include incineration with air pollution control
(Quina et al, 2011).
Nevertheless, Ghana, like many other countries is diverting
from the precarious and unsafe ways of waste disposal to hygienic waste
incineration with energy recuperation which is intended at reducing volumes of
waste with little pollution and producing energy as well. A number of
incinerators have been constructed in Ghana for domestic waste treatment but all
are without air pollution control devices. For instance, the Ghana Education
Trust Fund in 2007 to 2008 constructed incinerators in all Girls Senior High
Schools in Ghana purposely for sanitary towels disposal but all were without
air pollution control devices.
In order to attain the required
standards of emission for current incinerators, the use of different air
pollution control equipment is important. Such values cannot be achieved by
small-scale incinerators which have no particulate control equipment. According
to the World Health Organisation, appropriate design and proper incinerator
operation should attain necessary temperature, residence time and other
conditions to eliminate pathogens and reduce emissions.
Incineration has the aim of taking care of and disposing of
waste as well as reducing incinerator emissions and hazards. Small-scale
incineration is viewed as an intermediary way of disposal for health-care and
domestic waste and hence the need for incinerator flue gas treatment.
1.2 Statement of
the Problem
The use of small-scale incinerators appears to be very
extensive nowadays and it is preferred to the unhygienic ways of disposing
waste in unsecured pits, landfills and uncontrolled burning. The main problems related
with uncontrolled burning are the huge volume of gaseous emissions which may
cause environmental health risks and the harmful smoke and air pollution
residues that remain after incineration.
Incinerator operators are usually exposed to various risk
levels of toxins irrespective of their use of standard protective clothing.
People living around incinerators are also exposed to some level of emissions.
Any method of disposing waste which creates more toxins than the waste put in
it is considered an unwise and unsustainable disposal method (GAIA, 2008).
Incinerators in general cannot meet the requisite emission standards without
the use of emission controls (Bateman, 2004).
High black smoke emission levels are produced by small scale
domestic and medical incinerators found in Ghana. There is therefore the need
to design and construct air pollution control devices for incinerators to clean
exhaust flue gas of small scale incinerators. This will guarantee the use of
small scale incinerators as sustainable, environment and operator friendly and
hygienic.
1.3 Objectives of
the thesis
The main objective of the thesis is to design an air
pollution control device suitable for exhaust gas cleaning of small scale
incinerators in Ghana for the reduction of black smoke emissions. The specific
objectives are:
To rehabilitate the existing small scale incinerator at the
KNUST mechanical engineering workshop for use as a case study.
To design and
construct at the
KNUST mechanical engineering
workshop, a relatively simple, efficient, and a small air pollution
control device suitable for gas cleaning of small-scale incinerators
To test the air pollution control device to ascertain its
performance with regard to black smoke emission reduction.
1.4 Significance
of the thesis
The purpose of this thesis is to design, construct and test a
filter system suitable for flue gas cleaning of small-scale incinerators in
order to reduce black smoke emissions. The thesis also seeks to sensitize
people about the need for best practices for incinerator design and
construction as well as the inclusion of air pollution control devices in
locally manufactured small-scale incinerators to lower emissions to acceptable
standards.
1.5 Methodology
Incineration and air pollution control methods would be
reviewed. The areas of interest includes the understanding of the various types
of air pollution control devices commonly used with regard to small scale
incinerators with emphasis on their design and collection efficiencies. The
KNUST library, KNUST Journals, books and the internet as well as field surveys
would be used.
The proposed scrubber would be constructed at KNUST
mechanical engineering workshop. The Ringelmann smoke chart would be used to
analyze the flue gas from the stack and the smoke density of the flue gas
without scrubbing determined and compared to that with scrubbing.
Flue gas samples at inlet and outlet of the scrubber would be
analyzed under a microscope at the KNUST Physics department to determine
particle size distribution and the particle collection efficiency.
1.6 Limitation of
the study
The study was limited to black smoke emission of small scale
domestic incineration. Although scrubbers could remove some gaseous pollutants,
their effectiveness with respect to this scrubber was not studied. Factors such
as liquid droplets, atomization analysis were not considered in the study.
1.7 Assumption
It was assumed during the testing that the domestic waste
used during incineration without scrubbing and that with scrubbing were of the
same composition.
1.8 Thesis
Organization
The thesis is organized into five chapters. The first chapter
is an introduction to the thesis topic. The chapter includes the background of
the project, the problem statement, the aims and objectives as well as the
significance of the project and the limitations of the project.
Chapter two gives a literature review on incinerators and
pollution control devices. This chapter discusses waste classification, the
common types of incinerators, incinerator emissions and their control, emission
limits as well as various air pollution control devices. Some designed air pollution
control systems are also discussed.
The third chapter contains
information on the methodology the thesis has used to come up with the proposed
scrubber. It includes the design criteria, design requirements, materials
selection for construction of the proposed air pollution control device.
The fourth chapter gives the results and discussions
regarding the testing of the air pollution control device.
The fifth chapter gives the conclusion and recommendation of
the project.
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Item Type: Ghanaian Topic | Size: 76 pages | Chapters: 1-5
Format: MS Word | Delivery: Within 30Mins.
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