Progress toward Biomass and Coal-Derived Syngas Warm Cleanup: Proof-of-Concept Process Demonstration of Multicontaminant Removal for Biomass Application

Abstract

Systems comprising multiple sorbent and catalytic beds have been developed for the warm cleanup of coal- and biomass-derived syngas. Tailored specifically for biomass application, the process described here consists of six primary unit operations: (1) a Na2CO3 bed for HCl removal, (2) two regenerable ZnO beds in parallel for bulk H2S removal, (3) a ZnO bed for H2S polishing, (4) a NiCu/SBA-16 sorbent for trace metal (e.g., AsH3) removal, (5) a steam reforming catalyst bed for tars and light hydrocarbon reformation and NH3 decomposition, and (6) a Cu-based LT-WGS catalyst bed. Simulated biomass-derived syngas containing possible inorganic contaminants (H2S, AsH3, HCl, and NH3) and hydrocarbons (methane, ethylene, benzene, and naphthalene) was used to demonstrate process effectiveness. The efficiency of the process was demonstrated for a period of 175 h, during which time no signs of deactivation were observed. However, postrun analysis revealed that small levels of sulfur slipped through the sorbent bed train to the two downstream catalytic beds. Future improvements will be made to the trace metal polishing sorbent to ensure complete inorganic contaminant removal (to low parts per billion level) prior to the catalytic steps. However, dual regenerating ZnO beds were effective for continuous removal for the vast majority of the sulfur present in the feed gas. The process was effective for complete AsH3 and HCl removal. The steam reforming catalyst completely reformed all the hydrocarbons present in the feed (methane, ethylene, benzene, and naphthalene) to additional syngas. However, postrun evaluation, under kinetically controlled conditions, indicates some deactivation of the steam reforming catalyst occurred. Spent catalyst characterization suggests this can be attributed, in part, to coke formation, likely due to the presence of benzene and/or naphthalene in the feed. Future adaptation of this technology may require dual, regenerable steam reformers. The process and materials described in this report hold promise for the warm cleanup of a variety of contaminant species within warm syngas.

Online Characterization of Syngas Particulates Using Aerosol Mass Spectrometry in Entrained-Flow Biomass Gasification

“…For the end-user, tars probably pose the greatest problem from biomass gasification (Torres et al 2007). From a syngas catalytic upgrading perspective, tars can plug catalytic beds or poison the catalyst by physical deactivation or by adsorbing on active sites, where they are known to form carbon deposits and graphitic sheets, i.e., coking (Yung et al 2009;Howard et al 2013). In addition, particulate matter commonly causes corrosion and erosion on downstream process equipment such as e.g.…”

Arsine adsorption in copper-exchanged zeolite under low temperature and micro-oxygen conditions

“…Although numerous materials have been reported as adsorbents for the effective removal of AsH 3 , high operating temperatures are typically required. [12][13][14][15][16][17][18] For instance, Poulston et al have reported that Pd can be used to modify Al 2 O 3 for the adsorption of AsH 3 from simulated ue gas at temperatures between 204 C and 288 C. 19 Jiang et al found that activated carbon modied with sulfonated cobalt phthalocyanine (CoPcS) and Cu(NO 3 ) 2 was able to adsorb AsH 3 efficiently, and the AsH 3 adsorption capacity was 35.7 mg g À1 adsorbent at 60 C and a 4% oxygen content. 20 However, some shortcomings with the present activated carbons have been identied including their thermal instability.…”

Steam reforming of hydrocarbons from biomass-derived syngas over MgAl2O4-supported transition metals and bimetallic IrNi catalysts

“…The product gas from a biomass gasifier is mainly composed of H 2 , CO, CO 2 , CH 4 , H 2 O, and small quantities of higher hydrocarbon gases such as ethane, organic compounds broadly classified as tars, and inorganic impurities, such as H 2 S, HCl, NH 3 , and alkali metals [2]. Many of these inorganic constituents must be removed to part per billion levels because they strongly interact with downstream watergas-shift and/or synthesis catalysts [3]. Tars are notorious for condensing and subsequently polymerizing on downstream equipment such as compressor and gas turbine surfaces [4].…”

“…H 2 S) and catalyst coking are generally the two main reasons for the deterioration of the catalyst performance during steam reforming of biomassderived syngas. In a previous report we demonstrated proof-of-concept for a warm syngas cleanup process that is efficient for removing the inorganic constituents (to ppb level) from the biomass-derived syngas prior to the steam reforming unit [3]. Upon sulfur removal catalyst deactivation due to coking can still be problematic.…”