Process Modelling of Biogas Utilization System for the Landfill in Astana

Abstract

This thesis provides estimates of energy potential of biogas produced from a landfill in Astana in the form of electricity, as well as the economic assessment of the proposed power plant design. The goals were accomplished by first assuring a sufficient amount of landfill gas production rate. Then, a field work was carried to determine the precise biogas content. Theoretical calculations were done using the empirical equations recommended by the US Environmental Protection Agency (EPA). The energy model was simulated on ASPEN Plus. To reduce the concentration of corrosive hydrogen sulfide (H2S) in the gas, a model of a water scrubbing system was simulated in this work. Further, to obtain a maximum rate of power production, the upgraded biogas was utilized in a combined cycle gas turbine (CCGT) unit. By adding the Rankine cycle to the Brayton cycle to build up the combined system, the efficiency of the system increased from 35% to 49%, with 5 MWh power output. After obtaining the results of the energy model, the economic viability of the project was evaluated. The analysis showed that with right investment terms, the project is highly profitable. With equity payback period of 2 years, the NPV of the project was above 6.5 billion KZT, and annual life cycle savings around 1 billion KZT.