Optimisation of process parameters of wet scrubbing of biogas from night soil and vegetable waste using historical and Taguchi design

Abstract

A floating-drum biogas plant has been constructed with night soil and vegetable waste from the student's home as feed. To upgrade the quality of the biogas, wet scrubber unit has been designed for removing carbon dioxide (CO2) and hydrogen sulphide (H2S) and for enriching the methane (CH4) percentage by using water as an absorbent along with plastic balls. Historical design is employed to optimise the process parameters of wet scrubber like gas pressure, water flow rate (WFR) and gas flow rate (GFR) to obtain optimum methane percentage after scrubbing. Taguchi design is employed to identify the influence of parameters and their intensity on methane yield. With the optimised process parameters of 7.8 bar of gas pressure, 11.8 lpm of WFR and 5.9 lpm of GFR, the biogas was scrubbed. After upgradation, the biogas methane percentage has been increased from 44.15% to 91.89% and calorific value has been increased from 18,983 kJ/m³ to 30,525 kJ/m³.