Warm Plasma Application in Tar Conversion and Syngas Valorization: The Fate of Hydrogen Sulfide

Mateusz Wnukowski,Wojciech Moroń

doi:10.3390/en14217383

Mateusz Wnukowski, Wojciech Moroń

Open Access

https://doi.org/10.3390/en14217383

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Abstract

Warm plasma techniques are considered a promising method of tar removal in biomass-derived syngas. The fate of another problematic syngas impurity—hydrogen sulfide—is studied in this work. It is revealed that processing simulated syngas with a microwave plasma results in hydrogen sulfide conversion. For different gas flow rates (20–40 NLPM) and hydrogen sulfide concentrations ranging from 250 ppm to 750 ppm, the conversion rate varies from ca. 26% to 45%. The main sulfur-containing products are carbon disulfide (ca. 30% of total sulfur) and carbonyl sulfide (ca. 8% of total sulfur). Besides them, significantly smaller quantities of sulfates and benzothiophene are also detected. The main components of syngas have a tremendous impact on the fate of hydrogen sulfide. While the presence of carbon monoxide, methane, carbon dioxide, and tar surrogate (toluene) leads to the formation of carbonyl sulfide, carbon disulfide, sulfur dioxide, and benzothiophene, respectively, the abundance of hydrogen results in the recreation of hydrogen sulfide. Consequently, the presence of hydrogen in the simulated syngas is the main factor that determines the low conversion rate of hydrogen sulfide. Conversion of hydrogen sulfide into various sulfur compounds might be problematic in the context of syngas purification and the application of the right technique for sulfur removal.

Highlights

With the consequent and accelerating departure from fossil fuels, biomass gasification might be considered a promising alternative [1]
The gases included nitrogen, hydrogen, carbon monoxide, carbon dioxide, methane, and a 10% mixture of hydrogen sulfide in nitrogen. Their flow rate was controlled with mass flow controllers (MFCs) (Aalborg XFM47 for nitrogen and β-ERG 1000 for hydrogen sulfide) or rotameters
The transformation of hydrogen sulfide during microwave plasma treatment of simulated syngas is evaluated in this work

Summary

Introduction

With the consequent and accelerating departure from fossil fuels, biomass gasification might be considered a promising alternative [1]. This is due to biomass neutrality in carbon dioxide emissions, and due to gasification flexibility. The common feature of these compounds is their ease of condensation at low temperatures. They create a hazard of technical problems, e.g., malfunction of machines used for energy production and the fouling of pipelines as well as filters [1,4]. A firm, proven, and effective technique of reducing the tar content in the process gas is essential for the wide commercialization of biomass gasification

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