Removal of sulfur contaminants from biogas to enable direct catalytic methanation

Abstract

In the near future, renewable energy sources will replace fossil energy. To allow full carbon utilization of renewable biomass, we have demonstrated a possible integration between a biogas reactor, an electrolysis unit, and a catalytic methanation reactor. Stringent removal of all sulfur contaminants in raw biogas is required to enable this integration. We demonstrate how existing bulk sulfur removal solutions, like a biotrickling filter loaded with Acidithiobacillus thiooxidans and impregnated activated carbon, are unable to meet this requirement. Only the main sulfur contaminant hydrogen sulfide (H 2 S) can effectively be removed. Contaminants carbon disulfide (CS 2), dimethyl sulfide (DMS), and carbonyl sulfide (COS) will leak through the carbon filter, long before hydrogen sulfide can be detected. Utilization of surplus oxygen from the combined system is proven problem free and allows sulfur removal without introducing contaminants. Provided that a recommended sulfur guard is included, the proposed design is ready for full-scale implementation.

Container-Sized CO2 to Methane: Design, Construction and Catalytic Tests Using Raw Biogas to Biomethane

“…The backup carbon filter could not remove all the bulk sulfur from the biogas to ppb levels required by the Ni catalyst. A potential future improvement could be a sacrificial ZnO adsorbent before the active Ni catalyst, which can reduce the sulfur level to ppb in case of such unforeseen conditions [35,36]. Still, it was surprising to see that the catalyst was active and showing more than 90% CO 2 conversion at all the time.…”

Focus on Materials for Sulfur-Resistant Catalysts in the Reforming of Biofuels

“…In fuels derived from natural sources, the concentration of sulfur species can be included within a very wide range. For example, the sulfur level in biodiesel is present as trace, and in amounts lower than 10 mg/Kg [47,48], while the sulfur level in biogas-mainly present as H 2 S-is 1500 ppm v on average [49,50].…”

Catalytic methanation of CO2 in biogas: experimental results from a reactor at full scale

“…Included from earlier work. 23 Reaction Chemistry & Engineering Paper point at 280°C (the desired reactor temperature 23 ). The specific dimensions of the two reactor tubes is proprietary information of Haldor Topsøe A/S.…”

“…This double pass strategy ensures a methane content/Wobbe index within the specifications of natural gas. 23 Actual gas composition is measured by a gas chromatograph (Micro GC 490, Agilent Technologies, United States) equipped with two channels (MS5A and PPQ columns) and a thermal conductivity detector allowing analysis of hydrogen, nitrogen, methane, carbon monoxide and carbon dioxide. Using automatic sampling, the GC performs online analysis, but some delay is expected due to machine processing time and the physical distance the sample has to travel to the GC.…”