Optimization of a chemical scrubbing process based on a Fe-EDTA-carbonate based solvent for the simultaneous removal of CO2 and H2S from biogas

Abstract

The potential of a novel Fe/EDTA/carbonate-based scrubbing process for the simultaneous removal of H2S and CO2 from biogas was studied by evaluating the influence of Fe/EDTA molarity (M), carbonate concentration (IC), biogas (B), air (A) and liquid (L) flow rates on biogas upgrading performance using a Taguchi L16(45) experimental design. The ANOVA demonstrated that molarity of the Fe/EDTA solution was a significant factor influencing H2S concentration (0.035 % at 0.00 M to 0.000 % at 0.05 M). IC impacted on the concentrations of CO2 (13.1 and 4.5 % at 4000 and 10,000 mg L−1, respectively), N2 and CH4 (85.9 and 94.5 % at 4000 and 10,000 mgIC L−1, respectively). The biogas flow rate affected the concentrations of CO2 (2.5 to 13.8% at 10 and 40 mL min−1, respectively), O2, N2 and CH4 (95.9 to 85.4% at 10 and 40 mL min−1, respectively). Likewise, the recycling liquid flow rate affected CO2 (8.3 and 5.9 % at 5 and 30 mL min−1, respectively), O2, N2 and CH4 (90.5 and 93.3 % at 5 and 40 mL min−1, respectively) concentrations. Finally, the air flow rate impacted on CO2 (10.8 and 6.7 % at 800 and 1000 mL min−1, respectively), H2S, N2 and CH4 (87.9 and 92.2 % at 800 and 1000 mL min−1, respectively) concentrations. Process optimization provided the optimal conditions for each control factor. Continuous biogas upgrading operation at M2-IC1-B2-A4-L4 (0.05 M, 10,000 mgIC L−1, 10 mL min−1, 1000 mL min−1 and 30 mL min−1, respectively) provided CH4, CO2, O2, N2 and H2S concentration in the upgrading biogas of 97.4, 1.4, 0.29, 0.97 and 0%, respectively, which complied with biomethane regulations.