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.

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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