Abstract
A new process for removing sulfur from gas using electricity is presented. The process combines electrochemical production of active oxidizing species with an oxidative scrubber for desulfurization. Reactions for the electrochemical cell and the scrubbing tower are presented and a scrubbing set-up with a continuous electrolyte recirculation is validated on synthetic biogas. The test shows that a gas flow of 200 L/h with 1330 ppm H 2 S can be cleaned down to non-detectable levels of sulfur in a single step, at a current efficiency of 29%. This is a very high removal percentage for a high concentration of H 2 S. Solid sulfur can be removed from the system after the experiments. The sulfur has traces of NaClO and no other products were detected. A simple model based on estimated gas side mass transfer coefficients were used to estimate a scrubber height of only a few centimeters. The experiments supports the model. This technology allows for a robust implementation of sulfur free applications in a future green fuel and green chemistry like Power-to-X (PtX) and carbon capture and utilization (CCU). Sulfur compounds are poison for most heterogeneous catalysts, thus for carbon utilization, the carbon gas source has to be desulfurized .
Highlights
The renewable energy sector is booming and especially the biogas industry is growing [1]
The Scanning electron microscopy (SEM) used for analyzing the sulfur content was a Hitachi tabletop SEM TM3000 equipped with energy dispersive x-ray spectroscopy (EDS)
The effect of current, gas flow and the current efficiency was investigated in the sections below to give a better understanding of the process
Summary
The renewable energy sector is booming and especially the biogas industry is growing [1]. For biogas plants with first generation upgrading facilities, this is a fundamental issue, as the maximum allowed oxygen content can be as low as 100 ppm for biomethane [21]. Another drawback of the biolog ical cleaning process is the slow response time when it comes to fluc tuating H2S levels. An electro-assisted scrubbing process operating at moderately low pH values would be preferred for biogas applications. The aim is to develop a cheap, stable and robust process that selectively removes H2S down to the very low ppm level, while leaving the CO2 in the biogas. This reaction for removal of H2S in a synthetic biogas is tested in this paper
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