Techno-economic analysis of electricity and heat production by co-gasification of coal, biomass and waste tyre in South Africa.

Abstract South Africa has large deposit of coal that supports about 95% of electric power generation in the country. The fuel is fast depleting, though the current reserve may serve for the next century. However, the emissions from the coal projects huge threat to the environment. Similarly, the country has abundant solid wastes that can be co-gasified with coal to H 2 enriched syngas for clean energy production. A 5 MW combined heat and power plant was studied using different coal-to-solid waste ratios of 1:1, 3:2, and 4:1 and economy of the plant was evaluated with feedstock costing (WFC) and without feedstock costing (WOFC). The lower heating value of the fuels, determined from a model equation was applied to estimate the annual feedstock requirement and the feed rate. Net Present Value (NPV), Internal Rate of Return (IRR), and Payback Period (PBP) were used to evaluate the viability of the power generation at the 10th, 11th, 17th and 18th year business periods. The predicted optimum period of the plant is the 10th year. The use of Coal + Pine saw-dust (PSD) blend of blend ratio 1:1, is the most attractive feedstock for the energy generation. A higher profit of about 13.82%, and 23.56% were estimated for the use of Coal + PSD as compared to the use of 100% Matla coal at WFC and WOFC, thus; enabling a savings of about 1, 868.81 t feedstock per annum. The use of Coal + PSD blend of blend ratio 1:1 reduces the CO, CO 2 , SO 2 , and NO X emissions by 3.4%, 23.28%, 22.9%, and 0.55%, respectively. Graphical abstract Image 1 Highlights • Co-gasification of different South African feed stocks was evaluated in a 5 MW CHP plant. • Feedstocks evaluated are coal, waste tyre and biomass (corn cob, pine saw-dust & sugarcane bagasse). • Evaluation target were; Profitability: annual feedstock savings, investment cost savings, and emissions reduction. • Coal-to-PSD of 1:1 ratio, gave the highest annual profit of 13.82% and 23.56% at WFC and WOFC, respectively, and ZAR6,416,301.77 investment cost was saved. • CO, CO 2 , SO 2 , and NO X emission reductions of 3.4%, 23.28%, 22.9% and 0.85% resulted from Coal + PSD of blend raio1:1. [ABSTRACT FROM AUTHOR]