Biochar Fixed-Bed Adsorber for Hydrogen Sulfide Removal from Biogas Before Combined Heat and Power Use

Abstract

Hydrogen sulfide (H₂S) present in biogas is a major concern for combined heat and power (CHP) applications due to its corrosive nature, toxicity, and adverse effects on engine performance and equipment durability. This study investigates the performance of a biochar fixed-bed adsorber for the removal of hydrogen sulfide from biogas prior to its utilization in CHP systems. The research focuses on evaluating adsorption efficiency, breakthrough behavior, and operational parameters influencing sulfur removal under continuous flow conditions. Experimental analyses were conducted to examine the effects of biochar particle size, bed height, inlet H₂S concentration, gas flow rate, moisture content, temperature, and contact time on adsorption capacity and removal performance. Results demonstrated that biochar possesses significant adsorption affinity toward hydrogen sulfide due to its porous structure, large surface area, and active surface functional groups. Optimized operating conditions substantially improved H₂S removal efficiency and prolonged breakthrough time within the fixed-bed system. Kinetic and adsorption equilibrium analyses revealed that both physical adsorption and surface chemical interactions contribute to sulfur capture mechanisms in the biochar medium. The fixed-bed adsorber maintained stable operation with effective contaminant removal and reduced pressure drop during continuous biogas treatment. Comparative assessment with conventional desulfurization materials indicated that biochar offers advantages such as lower cost, renewable feedstock utilization, reduced environmental impact, and potential for adsorbent regeneration. Furthermore, the removal of hydrogen sulfide significantly improved biogas quality and enhanced the operational reliability of CHP systems. The findings highlight the potential of biochar-based fixed-bed adsorption technology as an efficient and sustainable solution for biogas purification and renewable energy utilization applications.