Techno-economic assessment for the production of 400 tpd of sulphuric acid using waste sulphur gases from coal combustion and pyrolysis gases

Abstract

This study focused on the techno-economic assessment of sulphur gas removal from coal combustion, pyrolysis and gasification in the flue gas stream in order to reduce harmful emissions from the coal industry which causes adverse effects to the environment. A potential of valorisation of the SO2 to valuable, sulphuric acid (H2SO4) is therefore analysed. The design of a 400 tpd H2SO4 production process utilizing sulphur from coal combustion and pyrolysis flue gases is proposed. Experiments conducted indicated a 2.12%.wt by mass of coal is the sulphur content in the flue gases. The modified Claus Process, Amine Process and the Contact Process were selected as the best processes for optimum H2SO4 production. Based on the mass balances, the calculated gas flow rate from the power station boilers which utilize an average of 6000 tpd of coal was 146.33 t/hr. Economic analysis showed that the production cost of a tonne of H2SO4 is USD 32.47 and the profit margin was USD 57.53, the return on investment (ROI) was 44%, with a payback period of 2.28 years and the breakeven point was 60 tpd indicating the viability of utilizing the recovered sulphur to produce H2SO4 both technically and economically.