The Reactor Engineering Design key technology area addresses control of chemical reactions in increasingly modular and intrinsically efficient reactors, allowing for smaller reactors and streamlined processes, with a focus on conversion of coal into syngas. Clean syngas enables highly efficient and low carbon footprint power generation, and is ideal for fuels or chemicals production, or combinations thereof (i.e. polygeneration). Improved performance of reactors for gasification, syngas upgrading and cleanup, and conversion of syngas into fuels or power will enable low-cost and highly energy-efficient systems with excellent environmental performance. Fields of investigation under Reactor Engineering Design currently include:
Current reactor design (including coal gasification reactors) is based on a long legacy of industrial use, characterized by simplistic geometries, limited control over reactants inside, and incremental advancements with surprisingly little significant change over time. However, advances in technology have resulted in tools that should allow development of more sophisticated reactor concepts that will allow much more precision and control in these reacting systems, and which can be developed more quickly and inexpensively.
The Gasification Systems Program will pursue development in promising areas of advanced gasification technologies to lower costs and increase efficiency of modular coal syngas production and syngas conversion to value-added products. The Program also plans to leverage ongoing technological advances to make rapid advances in reactor engineering and design. Notably, these include exponentially increasing computing power at lower costs, expected to allow increasingly realistic computer models to simulate coal-particle behavior during coal conversion processes, and breakthroughs in advanced manufacturing to significantly drop the capital costs for small-scale reactors and modular plants.
Staged Opposed Multi Burner (OMB) for Modular Gasifier/Burner—A University of Kentucky team is making innovative burner modifications of their pilot-size staged-opposed multi-burner entrained flow gasifier (utilizing coal slurry as a feed for high temperature gasification) and testing to evaluate improvements in performance. Although OMB gasification is commercialized at full scale, the University of Kentucky OMB pilot gasifier is a one ton-per-day unit (a small fraction of the commercial unit size), so that it can serve as a test bed for small-scale modularization of an entrained flow gasifier with standardized burners, enabling investigation of modular gasifier performance and optimization.
Small Scale Engineered High Flexibility Gasifier—Southern Research Institute is developing a novel, cost-effective, radically engineered modular gasifier having applications to 1-5-MW energy-conversion systems, such as combined heat and power (CHP). The gasifier is pressurized, oxygen-blown, and uses a simple small-scale modular design. This approach targets flexibility to optimize fuel throughput and thermal efficiency, to manipulate coal conversion, and to produce syngas of a desired composition, while producing negligible tar. The potential is for reduction of cost of coal conversion via an optimized, factory-built modular system to allow scale-up via modular expansion and deployment at remote sites.
Chemical looping gasification
The Ohio State University is conducting research utilizing chemical looping to separately produce hydrogen and CO2 from gasification of carbonaceous feedstocks including coal. The technology involves use of an iron-based oxygen carrier, which is circulated through a series of moving beds where it reacts with the feedstock, producing CO2 and hydrogen in separate reactors. The carrier is regenerated by oxidizing in a separate fluidized bed combustor. Through innovative use of reactor design engineering and carrier manipulation, this concept keeps reaction products segregated, eliminating the need for gas separations operations (air separation to produce oxygen, hydrogen separation). Two current projects involve pilot scale demonstration/testing and process economics evaluation of this technology.
Modular syngas cleanup, separations and conversion
Syngas cleanup processes 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. Highly efficient, advanced processes that operate at moderate to high temperatures, referred to as warm syngas cleanup, 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, modular gasification systems need 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
Advanced Syngas Cleanup for Radically Engineered Modular Systems (REMS)—development of modular designs for the cleanup of warm syngas with reduced costs, emissions, and improved thermal efficiency, enabling 1-5-MW REMS-based plants to be cost competitive with large state-of-the-art commercial plants using abundant domestic coal reserves.
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.
Warm Gas Multi-Contaminant Removal System—TDA Research Inc. is developing 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.
Separation/recovery of hydrogen and carbon dioxide from syngas
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, has been under development in several projects. These 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.
Application of Chemical Looping with Spouting Fluidized Bed for Hydrogen-Rich Syngas Production from Catalytic Coal Gasification
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.
Integrated Water-Gas-Shift (WGS) / Pre-Combustion Carbon Capture Process
Enhanced Coal Syngas Reforming
Praxair has been conducting research focused on integrating its oxygen transport membrane into a syngas reformer, thereby improving syngas reformation from separate steps of steam reforming, autothermal reforming, and air separation into a “solid state” combined reforming approach, increasing efficiency of the reforming reaction steps.
OTM-Enhanced Coal Syngas for Carbon Capture Power Systems and Fuel Synthesis Applications
Process and Reaction Intensification, Onsite NETL Research
NETL’s R&IC is focused on developing new reactors and reaction pathways that enable process intensification and/or reduce the overall cost of small-scale energy conversion. The initial focus is to investigate new reactors and reactions such that a techno-economic analysis can be performed to determine the benefit of the technology and provide R&D guidance on technology goals. Later, the focus will shift to determining realistic goals and refining the pathway to achieve those technology specific goals. The technological areas under investigation are as follows:
In addition to work being done by R&IC, TDA Research is working to determine the kinetic benefits of small coal particles in order to reduce the cost of smaller-scale coal gasification units. Smaller-scale coal gasification has commercial potential for on-site/on-demand power generation or as part of modular fuels and chemicals production facilities. This project supports this need.
Virtual Reactor Optimization, Onsite NETL Research
NETL’s R&IC is focused on the creation and validation of advanced computational toolsets for design and optimization of novel reactor systems. These toolsets will be based on the use of multiphase computational fluid dynamics to predict reactor performance, and the simulation-based optimization that use these predictions to meet optimal performance criteria. In this work, certain elements pertain to reactor design:
National Carbon Capture Center
Transport Reactor Integrated Gasification (TRIG™), originally developed by Kellogg, Brown, and Root (KBR) based on the company's fluidized catalytic cracking technology, has been enhanced through extensive testing by Southern Company at the Power Systems Development Facility in cooperation with NETL. Testing corroborated that the gasifier effectively handles low-rank coals (e.g., Powder River Basin lignite), which account for half of the worldwide coal reserves but are often considered uneconomic as energy sources due to high moisture and ash contents.
Some projects hosted by the NCCC:
NETL continues preparing and maintaining baseline studies to provide unbiased comparisons of competing energy conversion system technologies, determining the best way to integrate process technology steps, and predicting the economic and environmental impacts of successful development.
Recently Completed Projects:
Other key technologies within Gasification Systems include the following: