Thermo-economic Analysis of a Retrofit Small Scale Municipal Solid Waste Power Plant

Abstract

This paper evaluates the thermo-economics of a retrofit small scale municipal solid waste (MSW)-fueled power plant in Port Harcourt, Rivers State, Nigeria. The design parameters for the combustion chamber which utilizes mass combustion in stoker crate furnace is operated at steam saturation pressure of 38.2bar, with fuel consumption rate of 41.3tonnes/hr (11.88kg/s) and was selected for the amount of MSW generated in Port Harcourt metropolis. The data used to assess the availability of the fuel (MSW) were obtained from waste dumpsites controlled by Rivers State Waste Management Agency (RIWAMA). MATLAB Software modeling was used for the thermodynamic analysis to appropriately retrofit a steam turbine to the selected combustor and the result show that the optimal performance of the proposed MSW plant gives a net power output of 5.23MW. The result further shows that heat in the steam entering the turbine is equivalent to 0.71MWh per tonnes of waste. Therefore, at 17.3% thermal efficiency of the proposed MSW plant, 0.13 MWh of electricity will be produced per tonnes of waste combusted. However, it is estimated that the plant may consume 15% of the electricity, which implies that 0.11MWh/tonne will be exported to the grid. Thus, as the plant is expected to process 340770.3tonnes/yr of MSW, the net electricity output of the proposed plant is estimated at 37.48GWh per year. The economic evaluations have shown that the Net present worth of the plant is $6395107.07 with a payback period of 7years for a 20years life cycle. This work thus indicates huge potentials in generating electrical energy and wealth from MSW in Port Harcourt and beyond with the use of cheap and readily available fuel from municipal solid waste.