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Title: Warm Cleanup of Coal-Derived Syngas: Multicontaminant Removal Process Demonstration

Abstract

Warm cleanup of coal- or biomass-derived syngas requires sorbent and catalytic beds to protect downstream processes and catalysts from fouling. Sulfur is particularly harmful because even parts-per-million amounts are sufficient to poison downstream synthesis catalysts. Zinc oxide (ZnO) is a conventional sorbent for sulfur removal; however, its operational performance using real gasifier-derived syngas and in an integrated warm cleanup process is not well reported. In this paper, we report the optimal temperature for bulk desulfurization to be 450oC, while removal of sulfur to parts-per-billion levels requires a lower temperature of approximately 350oC. Under these conditions, we found that sulfur in the form of both hydrogen sulfide and carbonyl sulfide could be absorbed equally well using ZnO. For long-term operation, sorbent regeneration is desirable to minimize process costs. Over the course of five sulfidation and regeneration cycles, a ZnO bed lost about a third of its initial sulfur capacity, however sorbent capacity stabilized. Here, we also demonstrate, at the bench-scale, a process and materials used for warm cleanup of coal-derived syngas using five operations: 1) Na2CO3 for HCl removal, 2) regenerable ZnO beds for bulk sulfur removal, 3) a second ZnO bed for trace sulfur removal, 4) a Ni-Cu/C sorbent formore » multi-contaminant inorganic removal, and 5) a Ir-Ni/MgAl2O4 catalyst employed for ammonia decomposition and tar and light hydrocarbon steam reforming. Syngas cleanup was demonstrated through successful long-term performance of a poison-sensitive, Cu-based, water-gas-shift catalyst placed downstream of the cleanup process train. The tar reformer is an important and necessary operation with this particular gasification system; its inclusion was the difference between deactivating the water-gas catalyst with carbon deposition and successful 100-hour testing using 1 LPM of coal-derived syngas.« less

Authors:
; ; ; ; ; ; ORCiD logo
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1347855
Report Number(s):
PNNL-SA-120510
Journal ID: ISSN 0887-0624; BM0101010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Energy and Fuels; Journal Volume: 31; Journal Issue: 3
Country of Publication:
United States
Language:
English

Citation Formats

Spies, Kurt A., Rainbolt, James E., Li, Xiaohong S., Braunberger, Beau, Li, Liyu, King, David L., and Dagle, Robert A.. Warm Cleanup of Coal-Derived Syngas: Multicontaminant Removal Process Demonstration. United States: N. p., 2017. Web. doi:10.1021/acs.energyfuels.6b02568.
Spies, Kurt A., Rainbolt, James E., Li, Xiaohong S., Braunberger, Beau, Li, Liyu, King, David L., & Dagle, Robert A.. Warm Cleanup of Coal-Derived Syngas: Multicontaminant Removal Process Demonstration. United States. doi:10.1021/acs.energyfuels.6b02568.
Spies, Kurt A., Rainbolt, James E., Li, Xiaohong S., Braunberger, Beau, Li, Liyu, King, David L., and Dagle, Robert A.. Wed . "Warm Cleanup of Coal-Derived Syngas: Multicontaminant Removal Process Demonstration". United States. doi:10.1021/acs.energyfuels.6b02568.
@article{osti_1347855,
title = {Warm Cleanup of Coal-Derived Syngas: Multicontaminant Removal Process Demonstration},
author = {Spies, Kurt A. and Rainbolt, James E. and Li, Xiaohong S. and Braunberger, Beau and Li, Liyu and King, David L. and Dagle, Robert A.},
abstractNote = {Warm cleanup of coal- or biomass-derived syngas requires sorbent and catalytic beds to protect downstream processes and catalysts from fouling. Sulfur is particularly harmful because even parts-per-million amounts are sufficient to poison downstream synthesis catalysts. Zinc oxide (ZnO) is a conventional sorbent for sulfur removal; however, its operational performance using real gasifier-derived syngas and in an integrated warm cleanup process is not well reported. In this paper, we report the optimal temperature for bulk desulfurization to be 450oC, while removal of sulfur to parts-per-billion levels requires a lower temperature of approximately 350oC. Under these conditions, we found that sulfur in the form of both hydrogen sulfide and carbonyl sulfide could be absorbed equally well using ZnO. For long-term operation, sorbent regeneration is desirable to minimize process costs. Over the course of five sulfidation and regeneration cycles, a ZnO bed lost about a third of its initial sulfur capacity, however sorbent capacity stabilized. Here, we also demonstrate, at the bench-scale, a process and materials used for warm cleanup of coal-derived syngas using five operations: 1) Na2CO3 for HCl removal, 2) regenerable ZnO beds for bulk sulfur removal, 3) a second ZnO bed for trace sulfur removal, 4) a Ni-Cu/C sorbent for multi-contaminant inorganic removal, and 5) a Ir-Ni/MgAl2O4 catalyst employed for ammonia decomposition and tar and light hydrocarbon steam reforming. Syngas cleanup was demonstrated through successful long-term performance of a poison-sensitive, Cu-based, water-gas-shift catalyst placed downstream of the cleanup process train. The tar reformer is an important and necessary operation with this particular gasification system; its inclusion was the difference between deactivating the water-gas catalyst with carbon deposition and successful 100-hour testing using 1 LPM of coal-derived syngas.},
doi = {10.1021/acs.energyfuels.6b02568},
journal = {Energy and Fuels},
number = 3,
volume = 31,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2017},
month = {Wed Feb 15 00:00:00 EST 2017}
}
  • Systems comprising of multiple sorbent and catalytic beds have been developed for the warm syngas cleanup of coal- and biomass-derived syngas. Tailored specifically for biomass application the process described here consists of six primary unit operations: 1) Na2CO3 bed for HCl removal, 2) two regenerable ZnO beds for bulk H2S removal, 3) ZnO bed for H2S polishing, 4) NiCu/SBA-16 sorbent for trace metal (e.g. AsH3) removal, 5) steam reforming catalyst bed for tars and light hydrocarbons reformation and NH3 decomposition, and a 6) Cu-based LT-WGS catalyst bed. Simulated biomass-derived syngas containing a multitude of inorganic contaminants (H2S, AsH3, HCl, andmore » NH3) and hydrocarbon additives (methane, ethylene, benzene, and naphthalene) was used to demonstrate process effectiveness. The efficiency of the process was demonstrated for a period of 175 hours, during which no signs of deactivation were observed. Post-run analysis revealed small levels of sulfur slipped through the sorbent bed train to the two downstream catalytic beds. Future improvements could be made to the trace metal polishing sorbent to ensure complete inorganic contaminant removal (to low ppb 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, post-run evaluation, under kinetically-controlled conditions, indicates deactivation of the steam reforming catalyst. Spent material characterization suggests this is 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 a warm cleanup of a variety of contaminant species within warm syngas.« less
  • This project met the objective to further the development of an integrated multi-contaminant removal process in which H2S, NH3, HCl and heavy metals including Hg, As, Se and Cd present in the coal-derived syngas can be removed to specified levels in a single/integrated process step. The process supports the mission and goals of the Department of Energy's Gasification Technologies Program, namely to enhance the performance of gasification systems, thus enabling U.S. industry to improve the competitiveness of gasification-based processes. The gasification program will reduce equipment costs, improve process environmental performance, and increase process reliability and flexibility. Two sulfur conversion conceptsmore » were tested in the laboratory under this project, i.e., the solventbased, high-pressure University of California Sulfur Recovery Process High Pressure (UCSRP-HP) and the catalytic-based, direct oxidation (DO) section of the CrystaSulf-DO process. Each process required a polishing unit to meet the ultra-clean sulfur content goals of <50 ppbv (parts per billion by volume) as may be necessary for fuel cells or chemical production applications. UCSRP-HP was also tested for the removal of trace, non-sulfur contaminants, including ammonia, hydrogen chloride, and heavy metals. A bench-scale unit was commissioned and limited testing was performed with simulated syngas. Aspen-Plus®-based computer simulation models were prepared and the economics of the UCSRP-HP and CrystaSulf-DO processes were evaluated for a nominal 500 MWe, coal-based, IGCC power plant with carbon capture. This report covers the progress on the UCSRP-HP technology development and the CrystaSulf-DO technology.« less
  • The U.S. Department of Energy is currently working on coupling coal gasification and high temperature fuel cell to produce electrical power in a highly efficient manner while being emissions free. Many investigations have already investigated the effects of major coal syngas species such as CO and H2S. However coal contains many trace species and the effect of these species on solid oxide fuel cell anode is not presently known.Warm gas cleanup systems are planned to be used with these advanced power generation systems for the removal of major constituents such as H2S and HCl but the operational parameters of suchmore » systems is not well defined at this point in time. This paper focuses on the effect of anticipated warm gas cleanup conditions has on trace specie partitioning between the vapor and condensed phase and the effects the trace vapor species have on the SOFC anode. Results show that Be, Cr, K, Na, V, and Z trace species will form condensed phases and should not effect SOFC anode performance since it is anticipated that the warm gas cleanup systems will have a high removal efficiency of particulate matter. Also the results show that Sb, As, Cd, Hg, Pb, P, and Se trace species form vapor phases and the Sb, As, and P vapor phase species show the ability to form secondary Ni phases in the SOFC anode.« less
  • One of the key obstacles for the introduction of commercial gasification technology for the production of power with Integrated Gasification Combined Cycle (IGCC) plants or the production of value added chemicals, transportation fuels, and hydrogen has been the cost of these systems. This situation is particularly challenging because the United States has ample coal resources available as raw materials and effective use of these raw materials could help us meet our energy and transportation fuel needs while significantly reducing our need to import oil. One component of the cost of these systems that faces strong challenges for continuous improvement ismore » removing the undesirable components present in the syngas. The need to limit the increase in cost of electricity to < 35% for new coal-based power plants which include CO{sub 2} capture and sequestration addresses both the growing social concern for global climate change resulting from the emission of greenhouse gas and in particular CO{sub 2} and the need to control cost increases to power production necessary to meet this social objective. Similar improvements to technologies for trace contaminants are getting similar pressure to reduce environmental emissions and reduce production costs for the syngas to enable production of chemicals from coal that is cost competitive with oil and natural gas. RTI, with DOE/NETL support, has been developing sorbent technologies that enable capture of trace contaminants and CO{sub 2} at temperatures above 400 °F that achieve better capture performance, lower costs and higher thermal efficiency. This report describes the specific work of sorbent development for mercury (Hg), arsenic (As), selenium (Se), cadmium (Cd), and phosphorous (P) and CO{sub 2} removal. Because the typical concentrations of Hg, As, Se, Cd, and P are less than 10 ppmv, the focus has been on single-use sorbents with sufficient capacity to ensure replacement costs are cost effective. The research in this report describes the development efforts which expand this sorbent development effort to include Se, Cd, and P as well as Hg and As. Additional research has focused on improving removal performance with the goal of achieving effluent concentrations that are suitable for chemical production applications. By contrast, sorbent development for CO{sub 2} capture has focused on regenerable sorbents that capture the CO{sub 2} byproduct at higher CO{sub 2} pressures. Previous research on CO{sub 2} sorbents has demonstrated that the most challenging aspect of developing CO{sub 2} sorbents is regeneration. The research documented in this report investigates options to improve regeneration of the CO{sub 2} capture sorbents. This research includes effort on addressing existing regeneration limitations for sorbents previously developed and new approaches that focus initially on the regeneration performance of the sorbent.« less
  • The syngas redox (SGR) process to produce hydrogen from coal derived syngas is described. The process involves reduction of a metal oxide to metallic form with syngas and subsequent regeneration with steam to generate hydrogen in a cyclic operation. Metal oxides of Ni, Cu, Cd, Co, Mn, Sn, and Fe were evaluated for this process based upon thermodynamic equilibrium limitations. It was found that Fe{sub 2}O{sub 3} provided the best conversion of syngas to combustion products CO{sub 2} and H{sub 2}O along with a high conversion of steam to hydrogen. Other oxides provide high conversion of syngas but were foundmore » lacking in producing hydrogen from steam. Composite particles with Fe{sub 2}O{sub 3} as the key ingredient were developed that undergo multiple redox cycles without loss of activity. Analysis of process economics with respect to particle recyclability showed that the particles should undergo at least a 100 redox cycles without diminishing its activity. Process modifications to address carbon formation on reaction of syngas with iron oxide are discussed. Detailed process simulation showed that the SGR process is capable of converting 74% of the coal energy into hydrogen energy (higher heating value (HHV) basis) while delivering a pure CO{sub 2} stream without the need for costly separation technology. 38 refs., 17 figs., 5 tabs.« less