A Novel Simple Dipping-Nebulizing Water Absorption for Biogas Purification

Biogas impurities CO₂ and H₂S decrease the quality of biogas, which leads to a reduced caloric value and corrosive behavior, respectively. A vertical/columnar wet scrubber has been widely employed for biogas purification in which the absorption of impurities strongly depends on the contact time and surface area between the biogas and water. The drawback of this method lies in the stability of CH4 production due to the influence of the bioreactor conditions and the fluctuating condition of the surrounding environment. In this work, we present a novel design of simple water absorption columns embedded with an ultrasonic nebulizer for biogas purification. In this designed system, CO₂ and H₂S become dissolved in the water, as the CH₄ characterized by water low solubility is released on the surface of the water by using an ultrasonic diffuser/nebulizer. We optimized the water absorption performance by varying the water pH in the range 6.0–7.3. The results indicate that water pH affects biogas purification in the designed system. The optimum pH condition was 6.78, which yielded CH4 enrichment of 11%, O₂ increase of 29%, CO2 reduction of 32%, and H₂S reduction of 99.8%. To evaluate the biogas purification process in the upscaled system, a model and SIMULINK-based simulation were developed to predict the biogas purification process.