The Syngas Processing Key Technology area focuses on the development of high-efficiency processes to remove contaminants present in raw syngas (these include hydrogen sulfide, ammonia, hydrogen chloride, and carbonyl sulfide, as well as various forms of trace metals, including arsenic, mercury, selenium, and cadmium) to extremely low levels demanded by stringent regulatory limits on air emissions, and to prevent the harmful effects of these contaminants on downstream equipment components and processes. Although conventional technologies exist to perform syngas cleanup, they rely on chemical or physical absorption processes operated at low temperature, which causes a significant efficiency penalty. Syngas Processing Key Technology development aims at highly efficient, advanced processes that operate at moderate to high temperatures that will provide multi-contaminant control to meet the highest environmental standards and performance demands of gas turbines for electricity generation, and of downstream processes for fuels and chemicals synthesis.
Also, Syngas Processing research is pursuing various technologies for efficient separation/recovery of hydrogen and carbon dioxide (CO2) from syngas, which support carbon capture and storage initiatives in other programs and which improve performance of all the downstream processes for syngas utilization including power generation, fuels synthesis, chemicals synthesis, and CO2 utilization.
Warm Syngas Cleanup
Research Triangle Institute (RTI) recently completed a successful demonstration of their High Temperature Desulfurization Process, which is a so-called warm syngas cleanup technology operating at relatively high syngas temperatures for removing hydrogen sulfide and carbonyl sulfide. In this demonstration, they cleaned a 50 MWe slipstream of coal-derived syngas down to a total sulfur level of less than one part per million. For further information, see Recently Completed Projects below.
Also, RTI researched integration of their warm syngas cleanup technology in concert with other technologies, specifically Aerojet Rocketdyne's PWR Advanced Gasifier Pilot Plant Definition. See Recently Completed Projects below for more information.
TDA Research Inc. has developed a warm gas multi-contaminant removal system to be used after the bulk warm gas sulfur removal such as that developed by RTI. Their high-capacity, low-cost sorbent targets removal of anhydrous ammonia (NH3), mercury (Hg), and trace contaminants from coal- and coal/biomass-derived syngas.
Hydrogen Recovery Membranes
Hydrogen is often the desired product of the gasification process, given its importance as primary feedstock for fuels synthesis, fertilizer and chemicals synthesis, or power generation in 90% CO2 capture scenarios. In this case, inexpensive post-gasification separation of hydrogen from CO2 following (or along with) the shifting of gas composition is needed. For effective integration with advanced gasification technologies, and to realize the full advantages of high-temperature gas cleaning technologies, hydrogen and CO2 separation must be accomplished at high process temperatures. High temperature operation also offers the possibility of enhancing the water-gas-shift process through integration with advanced membranes operating at similar temperatures. Technologies that are capable of producing both hydrogen and CO2 at high pressure can avoid significant recompression costs that would further enhance plant economics, particularly in the case of carbon storage which requires very high compression of the CO2.
The hydrogen transport membrane, which uses metal or metal alloy materials with surface exchange catalysts to separate hydrogen from CO2, is being aggressively developed. Several projects have developed hydrogen membranes that have achieved fluxes and hydrogen purity high enough to encourage continued development of this cutting edge technology. These technologies operate at higher process temperatures designed to integrate at increased efficiency with advanced warm syngas cleanup technologies. This also offers the possibility of enhancing water gas shift through integration with advanced membranes, since both processes operate at similar temperatures.
The primary technical challenges for membrane-based technologies include optimization of the composition and microstructure of membrane materials, development of thin defect-free membrane films for enhancing flux, development of robust seals, ability to accommodate contaminants in the syngas, and operation at high-permeate pressures.
Praxair recently completed a project developing hydrogen transport membrane technology for separation of CO2 and hydrogen in coal-derived syngas for IGCC applications; see Recently Completed Projects below. Worcester Polytechnic Institute completed a project developing an integrated, cost-effective hydrogen production and separation process that employs palladium and palladium-alloy membranes.
High Hydrogen, Low Methane Syngas from Low-Rank Coals for Coal-to-Liquids Production
Research is being done to investigate catalytic pyrolysis and gasification of coal, using low-cost catalysts such as red mud and widely available minerals. The research targets reduction/minimization of methane production and increasing hydrogen yield even at the milder conditions typical of catalytic gasification, reducing water gas shift requirements, and reducing downstream gas cleanup requirements, thereby facilitating increased use of abundant low-rank coal for power generation and fuels synthesis.
Advanced Reactor Design for Integrated WGS/Pre-combustion CO2 Capture
Researchers are developing a method to produce high-hydrogen syngas utilizing a warm gas CO2 scrubber integrated with a water-gas shift catalyst, enabling economic capture of greater than 90% of the carbon emissions. Also, they are assessing the technical and economic feasibility for using this technology in IGCC and coal to chemicals plants using low-rank coal and woody biomass as feedstocks.
Enhanced Coal Syngas for Carbon Capture
Praxair is conducting research focused on integrating its oxygen transport membrane syngas converter for CO2 capture.
National Carbon Capture Center
The National Carbon Capture Center (NCCC) at the Power Systems Development Facility (PSDF) in Wilsonville, AL is developing technologies under realistic conditions that will reduce the cost of advanced coal-fueled power plants with CO2 capture. This technology development includes the design, procurement, construction, installation, and operation of a flexible facility for the testing of processes for pre-combustion CO2 capture, post-combustion CO2 capture and oxy-combustion.
Active syngas processing projects hosted by NCCC, supported by DOE
As part of the support for the Syngas Processing key technology, studies are being conducted to provide unbiased comparisons of competing technologies, determine the best way to integrate process technology steps, and predict the economic and environmental impacts of successful development.
Recently Completed Projects
Other key technologies within Gasification Systems include the following: