Methanol Production from Biogas-derived Syngas

¹ College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
² Beijing Advanced Innovation Centre for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, China
³ Chemical Engineering Department, KU Leuven, Leuven, Belgium
⁴ School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, China

^* Corresponding author: yangmiaobuct@163.com
^* Corresponding author: dengyimin1807@163.com

Abstract

"Green" hydrogen must gradually replace fossil fuel-based H₂. The anaerobic digestion (AD) of sewage sludge or agro-industrial waste yields a CH₄/CO₂ biogas and a NH₄⁺ digestate. Three ways to produce H₂ can be applied: (1) the Dry Reforming of CH₄, and CO₂, DRM (from biogas); (2) the Catalytic CH4 Decomposition, CDM (from biogas after CO₂ capture) and (3) the Catalytic Ammonia Decomposition (CDA, from digestate). DRM produces the ideal syngas at 700 °C and for a 50-50vol% CH₄/CO₂ biogas. CDM with a selected catalyst produced 95% H₂. The ammonia-rich digestate was stripped and NH₃ was catalytically decomposed into H₂ and N₂ at 650 °C. Considering the well known difficulties of storing H₂, a conversion of syngas to methanol was studied for a wastewater treatment plant (WWTP) with A.D. of 300,000 person equivalent (PE) is examined; and simulated using Aspen Plus®. This AD process generates a daily feed rate of 4,485 m³ CH₄, 2,415 m³ CO₂ and 320 kg NH₃, resulting in a CH₃OH production of 183 kg/hr. The additional CDA H₂ flow (631 m³/day) is not needed in the methanol production and can be co)fired in the Combined Heat and Power (CHP) normally associated with AD. CDA will produce more H₂ if NH₃-richer manure would be digested.