DOE Selects Projects to Address Challenges of Large-Scale Hydrogen Production from Coal, Coal-Biomass
September 4, 2008 // Published as a news service by IHS
The ability of hydrogen to fuel transportation, power generation and industrial processes with only water as a byproduct makes it an efficient and clean fuel to meet growing U.S. energy demands while assuring energy security, said DOE.
The National Academies affirmed in a 2004 report that hydrogen could fundamentally transform U.S. energy systems, but coal must be a significant component for making very large amounts of the gas.
To address the challenges of large-scale production of hydrogen from coal, the Hydrogen Fuel Initiative was launched in 2003, announcing a $1.2B commitment to a hydrogen economy that minimizes U.S. dependence on foreign oil and reduces greenhouse gas emissions.
The selected projects fall under the DOE Office of Fossil Energy Hydrogen and Clean Fuels Program, which supports R&D in technologies that can deliver affordable hydrogen produced from coal or coal/biomass mixtures with near-zero environmental emissions.
The DOE OFfice of Fossil Energy National Energy Technology Laboratory (NETL) will manage the projects, focusing on the alternate hydrogen production pathway.
This approach utilizes processes to convert synthesis gas (syngas) - the hydrogen and carbon monoxide portion of a cleaned gas mixture - to high-quality hydrocarbon liquid fuels or substitute natural gas (SNG). These products can be reformed to provide hydrogen near the point of use or used directly in commercial internal combustion engines in the interim until a hydrogen infrastructure is established.
Research will be conducted specifically on the production of liquid hydrocarbon fuels from coal/biomass mixtures in the coal-biomass-to liquids (CBTL) process. This process, when combined with carbon capture and sequestration or carbon reuse, is compatible with three overarching principles, said DOE. The CBTL system:
- Uses domestic feed stocks.
- Has a greenhouse gas footprint better than conventional petroleum fuels.
- Is projected to be economical at a world oil price significantly below existing levels of over $100 per barrel.
Since the entrained-flow (EF) oxygen-blown gasification process operating at high temperatures and pressures offer highest efficiency and cost effectiveness, the EF process was chosen as the CBTL gasifier. The projects, selected under three areas of interest, are described below.
Area 1: Feeding Coal/Biomass Mixtures Across a Pressure Gradient
This area focuses on the development of optimal methods to pretreat and feed biomass into a high-temperature, high-pressure coal gasifier.
- General Electric (GE) Global Research (Niskayuna, N.Y.) - GE Global Research, with the support of GE Energy and Idaho National Laboratory (INL), proposes to demonstrate the use of the GE Posimetric pump technology as a dry method of feeding coal/biomass mixtures to pressurized, EF gasifiers.
The technical objective is to demonstrate the ability of the Posimetric solids pump to handle mixtures of coal and biomass that encompass the relevant range of coal rank (bituminous, sub-bituminous and lignite) and biomass type (wood, corn stover and switchgrass) at biomass loadings up to at least 50% by weight. (DOE share: $624,959; recipient share: $487,285; duration: 24 months)
- Southern Research Institute (Birmingham, Ala.) - A primary challenge related to biomass utilization in large-scale commercial CBTL is the ability to reliably feed a variety of biomass feedstocks to the gasifier as biomass-coal mixtures. Southern Research Institute and its partner, Tk Energi A/S of Denmark, have identified an approach to feeding coal/biomass blends that utilizes a proven, existing biomass feed system to demonstrate feeding coal/biomass mixtures at high operating pressures similar to those encountered in EF gasifiers.
The overall objective of this project is to design and demonstrate a biomass pretreatment system and a coal/biomass co-feed system for the high-pressure, commercial EF gasifiers to be utilized in future large-scale CBTL facilities. (DOE share: $1,053,894; recipient share: $571,435; duration: 24 months)
Area 2: Characterization of the Products from Gasifying Coal/Biomass Mixtures
It is anticipated that the EF oxy-gasification of various coal/biomass combinations will produce different raw syngas compositions. To aid the R&D on CBTL syngas clean-up systems, a database of raw syngas compositions from the EF gasification of various coal/biomass combinations is needed, said DOE.
- GE Global Research - GE Global Research plans to undertake five major steps to achieve their technical objectives for this project. They will conduct initial experiments using a bench-scale gasifier to characterize the product streams and optimize the product analysis methods and procedures based on the bench-scale results.
Next they will characterize the co-gasification products in an EF reactor and then they will identify the clean-up requirements for mixtures containing three types of coal (bituminous, sub-bituminous and lignite) and three types of biomass (corn stover, wood sawdust and switchgrass).
Finally, they will evaluate the applicability of the observed trends to a wider range of coal-biomass fuels by comparing the experimental results of this program with the predictions of a fundamentals-based kinetic model, which was developed by GE under a separate program. (DOE share: $838,913; recipient share: $209,728; duration: 24 months)
Area 3: Optimization of the Fischer-Tropsch (FT) and Water-Gas-Shift (WGS) Processes
It is anticipated that ash, sulfur, species, trace toxic metals, halides and nitrogen poison species will be lower in syngas from coal/biomass EF gasification than from coal alone as a feed to the EF gasifier. Sodium and potassium compounds, such as potassium chloride and sodium chloride, are syngas contaminants of concern that may be increased in concentration in the EF gasification of coal/biomass mixtures with hot gas or warm gas clean-up systems. This activity attempts to quantify the effects on WGS and FT catalysts from poison that may result from EF gasification of coal/biomass mixtures.
- Research Triangle Institute (RTI) International (Research Triangle Park, N.C.) - The objective of this project is to quantify the effects on WGS and FT catalysts from syngas contaminants generated during EF gasification of coal/biomass mixtures. The specific contaminant effects that will be quantified are changes in catalyst activity and selectivity; changes in the catalyst's physical/chemical properties; catalyst changes resulting from simultaneous interaction with multiple contaminants; and the effect of contaminant concentration on catalyst changes.
This research project will investigate the effects of a select group of contaminants present in syngas derived from gasification of a coal/biomass mixture in an EF gasifier, including hydrogen sulfide, ammonia, sodium chloride, potassium chloride, arsine, hydrogen selenide and mercury. RTI International will partner with SŸd-Chemie Inc. (SCI) in this effort. (DOE share: $980,236; recipient share: $245,064; duration: 24 months)
- Tda Research Inc. (Wheat Ridge, Colo.) - The primary objective of this project is to investigate the effects of coal and biomass contaminants on the performance (activity and selectivity) and life of the WGS and FT catalysts used to convert syngas to liquid fuels. The scientists will investigate the impact of a list of potential contaminants on commercially available and generic (prepared based on scientific and patent literature) WGS and FT catalysts. Tda will undertake this study with the Center for Applied Energy Research (CAER) at the University of Kentucky. (DOE share: $898,266; recipient share: $224,631; duration: 36 months)
- University of Kentucky Research Foundation (Lexington, Ky.) - Interest in the conversion of biomass-derived syngas, as well as syngas derived from coal and biomass mixtures, to Fischer-Tropsch synthesis products has increased, said DOE. Conventional catalysts based on iron and cobalt may not be suitable for these purposes without further development.
Ash, sulfur compounds, traces of metals, halide compounds and nitrogen-containing chemicals will likely be lower in concentration in syngas derived from mixtures of coal and biomass (using EF oxygen-blown gasifier gasification) than solely from coal; however, other compounds may actually be increased. Of particular concern are compounds containing alkali chemicals like the chlorides of sodium and potassium.
Researchers at the University of Kentucky Center for Applied Research will carry out experiments to ascertain the impact of these higher sodium and potassium alkali levels on not only the performance of WGS and FT processes, but also on the catalyst structure-function properties. (DOE share: $1,135,746; recipient share: $285,850; duration: 36 months)
Source: U.S. Department of Energy (DOE) Office of Fossil Energy.