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Utilization of a Small-Scale Energy Solution Based on Municipal Solid Waste in Ethiopia

초록/요약

Electricity is a basic requirement for the sustainable economic development of a country. However, Ethiopian electrification is limited to 29% in rural and 85% in urban areas. Despite of on-going projects of power plants, transmission lines, and substation expansion works, the power demand is still high and growing rapidly even the current electric energy supply cannot satisfy the local demand. This being so, rural and some urban areas are challenged with a power issue. Connectivity for the growing industries and other infrastructures are also additional power issues that the country cannot provide. So, the country requires more power plants in order to satisfy the growing demand and sustain economic development. Actually, majority of the country’s renewable energy source is from hydroelectric power. And those power plants cannot provide the required power with their maximum capacity throughout the year, rather it causes a brownout during dry season. This is a drawback of hydro. Therefore, the country requires more renewable energy from wind, solar, geothermal, biomass and of course from waste-to-energy in order to fill the energy gap that cannot be resolved by hydro alone. By considering this, this study focuses on analyzing and designing an alternative small-scale power plant that can be generated from municipal solid waste. Municipal solid waste is a collection of used materials or garbage that is discarded by the public. The physical composition of solid waste is mostly made of plastics, papers, textiles, organic, inorganic and other materials. Currently, solid waste collection and disposal are causing problems for the society. Millions tons of solid waste from every household, commercial sector, hospitals, and industries waste (hazardous waste) are generated every day. Urban waste management agencies confronted with great challenges within disposing solid wastes generated in an effective, efficient and environmentally safe manner. To address these challenges, utilizing municipal solid waste for energy recovery purposes and development of a small-scale power plant seems to be the best solution to tackle waste management and electric power generation issues. Thus, the study collects secondary data from published and unpublished documents, which deal with physical and elemental composition of waste, moisture content, and calorific value of the solid waste that is available in Ethiopia. After collecting the required information, analyzing and interpreting the conditions of solid waste based on standards has been done. Finally, the best probable energy recovery technology from solid waste is suggested which is renewable waste-to-energy power plant. To estimate the energy recovery potential, the study conducts a detailed analysis of identifying the solid waste generation rate and its characterization by selecting three cities, Addis Ababa Surroundings, Mekelle, and Dire Dawa. Addis Ababa, the capital city of Ethiopia has high population density compared to the other two towns. Addis Ababa as an economic hub of the country generates the majority of the waste of the country. Dire Dawa and Mekelle also have a significant number of populations and a huge potential for energy recovery options form solid waste. Based on the gathered information, waste characterization and generation rate are studied for its suitability for energy. Their ultimate and proximate analysis indicates the elemental composition, moisture content and the calorific value of waste. After the analysis, the waste-to-energy plant potential is analyzed using Aspen PLUS software. The plant technology based on the current technology in Korea, is selected in considering green gas emission rate and efficiency of energy production. Thus, Plasma Enhanced Integrated Gasification Combined Cycle (PE-IGCC) power plant ultimately selected and its performance is analyzed using Aspen PLUS. The technology uses a method of hybrid plasma gasification that can provide electric power using a combination of steam turbine and syngas engine generator. The plant efficiency is calculated as 37.17% and 80% of electricity is generated from gas engine generator. The remaining 20% is generated from a steam turbine. Finally, the study analyzes and design a PE-IGCC power plant with an estimation of 5MW for Addis Ababa and 1.5 MW for Dire Dawa and Mekelle. The proposed solution can replace partial diesel generators at Kality ICS power plant with a syngas engine for the case of Addis Ababa. This will enhance renewable energy and reduce the cost of diesel. For the remaining two cities, Mekelle and Dire Dawa, the proposed solution can operate as a standalone power source and also considered as a small-scale waste to energy power plant for rural electrification purpose. In conclusion, the economic cost and financial feasibility analysis of the plant also included in this study.

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목차

1 Introduction ...................................................................................................................................... - 1 -
1.1 Background .............................................................................................................................. - 1 -
1.2 Problem Statement ................................................................................................................... - 7 -
1.3 Objective and expected outcomes ............................................................................................ - 8 -
1.4 Significance of the Study ......................................................................................................... - 9 -
1.5 Thesis organization .................................................................................................................. - 9 -
2 Literature Review ............................................................................................................................. - 9 -
2.1 Introduction .............................................................................................................................. - 9 -
2.2 Municipal Solid Waste in Ethiopia ........................................................................................ - 15 -
2.3 Trends of Solid Waste Collection and Disposal in Ethiopia .................................................. - 17 -
2.4 Municipal Solid Waste in Addis Ababa and Surrounding Towns ......................................... - 23 -
2.4.1 Challenges Associated with the Disposal Site in Addis Ababa Surroundings ............... - 24 -
2.5 Municipal Solid Waste in Dire Dawa City ............................................................................ - 25 -
2.5.1 Challenges Associated with the Disposal Site in Dire Dawa City ................................. - 26 -
2.6 Municipal Solid Waste in Mekelle City ................................................................................. - 26 -
2.6.1 Challenges Associated with the Disposal Site in Mekelle City ..................................... - 27 -
2.7 The Physical, Chemical and Biological property of MSW .................................................... - 28 -
2.7.1 Specific density .............................................................................................................. - 28 -
2.7.2 Particle size and size distribution ................................................................................... - 28 -
2.7.3 Permeability or hydraulic conductivity .......................................................................... - 29 -
2.7.4 Elemental Constituents and Characteristics of Solid Waste .......................................... - 29 -
2.8 Energy Content of MSW in Ethiopia ..................................................................................... - 31 -
2.9 Heating Value Calculation ..................................................................................................... - 33 -
2.10 Waste to Energy Conversion Technologies ........................................................................... - 35 -
2.10.1 Incineration .................................................................................................................... - 37 -
2.10.2 Conventional Gasification .............................................................................................. - 39 -
2.10.3 Pyrolysis ......................................................................................................................... - 43 -
2.10.4 Plasma arc gasification ................................................................................................... - 44 -
2.11 Advanced Waste-to-Energy Gasification Technologies ........................................................ - 46 -
2.11.1 Integrated Plasma Gasification Combine Cycle (IPGCC) ............................................. - 46 -
2.11.2 Plasma Enhanced Integrated Gasification Combine Cycle (PE-IGCC) ......................... - 46 -
2.12 Global trends of WtE plant and its technology ...................................................................... - 48 -
2.12.1 Plasma Gasification Technology ................................................................................... - 52 -
3 Methodology .................................................................................................................................. - 56 -
3.1 General Methodology ............................................................................................................ - 56 -
3.2 Aspen PLUS Software ........................................................................................................... - 56 -
3.3 Plant Model Sequence of Operation ...................................................................................... - 59 -
3.4 PE-IGCC Plant Components and Operation Description ...................................................... - 61 -
4 Results and Discussion .................................................................................................................. - 63 -
4.1 MSW Characterization and ASPEN Result ........................................................................... - 63 -
4.2 Syngas Energy calculation ..................................................................................................... - 66 -
4.3 Net Electric Power Result of PE-IGCC Power Plant ............................................................. - 68 -
4.4 Discussion .............................................................................................................................. - 69 -
5 Financial analysis and Cost Estimation ......................................................................................... - 72 -
5.1.1 Result of financial analysis ............................................................................................ - 73 -
6 Conclusion and Recommendation ................................................................................................. - 77 -
6.1 Conclusion ............................................................................................................................. - 77 -
6.2 Recommendations .................................................................................................................. - 79 -
7 Project Implementation Framework ............................................................................................... - 83 -
i. Tentative schedule for project implementation .......................................................................... - 83 -
ii. Strategic implementation of the required platform .................................................................... - 86 -
References .............................................................................................................................................- 92 -
Annex I- Financial Statement for 5MW & 1.5MW plants ................................................................... - 102 -
Annex II- Aspen Simulation Result- 5MW PE-IGCC Plant ................................................................ 109
Annex –III Aspen Simulation Result 1.5MW PE-IGCC Plant ................................................................. 115

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