Optimization of pressurized water scrubbing for biomethane production / Ng Jia Ying

Faculty of Chemical and Process Engineering Technology

Final Year Report (Bachelor of Chemical Engineering Technology) -- Universiti Malaysia Pahang Al-Sultan Abdullah - 2025

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Biomethane is a form of renewable source of energy produced from the upgrading of biogas by removal of carbon dioxide, nitrogen, hydrogen sulfide and other harmful component. Pressurized water scrubbing (PWS) is one of the most convenient method of biogas upgrading by using water as a medium to absorb the contaminants from the biogas. The objective of this research was to use Aspen Plus software to optimize the pressurized water scrubbing (PWS) for biomethane production by identifying the optimum operating conditions so that biomethane purity of ≥ 95% (v/v) and minimum methane loss can be achieved. The procedure were generally divided into three phases which are simulation model validation , sensitivity analysis on process equipment and system optimization. The separation of carbon dioxide from biogas became favorable at high pressure and low temperature. Flash vessel was added to the system to recover up to 98.84% of dissolved methane in water up back to the scrubbing system. Under optimal conditions, the maximum yield of biomethane purity was 91.45% (v/v) followed by methane losses of 1.95% and CO2 removal efficiency of 99.9%, where the absorber was operating at 40 bar pressure, 5℃ water temperature, 20 L/min water flowrate and 8 kg/hr biogas flowrate. The purity of biomethane was limited at 91.45% due to the presence of high nitrogen composition in biogas, and nitrogen was highly insoluble in water due to its molecular structure. In conclusion, the optimization of PWS system itself using Aspen Plus software was considered successful as there was an increases in biomethane purity, however the nitrogen content in biogas acts as a limitation that hindered the biomethane from achieving high purity.