Continuous Water Absorption - Regeneration using Microbubble Technology for CO2 Removal in Biogas Upgrading System

In this work, a system for upgrading biogas to biomethane was developed consisting of a continuous water absorption - regeneration using microbubble technology. The biogas upgrading system was tested using a 30% CO2-N-2 simulated biogas. Microbubbles in the water absorbent were generated using a 0.5-inch venturi ejector before introducing into a gas separation unit. Various flow rates of the simulated biogas between 2 and 10 L/min were tested, at a constant water flow rate of 15 L/min, operating at pressure of 7 bar and their CO2 removal efficiency was monitored. The bubble bottle was initially tested the absorbent regeneration by distributing air into CO2 rich liquid to make CO2 desorption. The regeneration unit was designed to create a counter current between air and used water with air flow rates of 5-30 L/min. The optimum absorption conditions were found to be a liquid/gas ratio of 7.5 achieved with a simulated biogas flow rate of 2 L/min and 15 L/min water. An optimum air flow rate of 30 L/min in the regeneration unit produced a CO2 removal efficiency from the simulated biomethane of over 90%.