Carbon Mitigation Initiative

Eighth Year Report 2009
Carbon Capture: Future Plans

Gasification of Low-Rank Coals

Tom Kreutz of the Williams Group will take the lead in pursuing two new activities relating to the gasification of low-rank coals. The first is a study of coal/CO2 slurries for both coal pressurization prior to gasification and long-distance transport of coal. This concept might offer strategic benefits if CO2 is readily available—e.g., if CCS is pursued routinely for coal energy systems. Coal transport via such slurries will be investigated as an alternative to rail transport. Such slurries might represent a low-cost approach for realizing high gasification pressures. This strategy might facilitate gasification of low-rank coals, for which water-slurry feeding is uneconomic.

The second project will be an extension of the dry-feed gasification model to include: use of low-rank coals via heat-integrated fluidized bed drying, novel water-gas shift strategies (developed at ECN by visiting colleague Michiel Carbo) and implications for the choice of partial water quench vs. syngas cooler designs for the gasifier, detailed modeling of acid gas removal via physical solvents, and integrating the optimization methodology of Emanuele Martelli for the bottoming (steam) cycle.

Systems Analyses for Synthetic Fuels

During the past year several commercial synthetic fuel projects have been announced that will make gasoline via methanol production from coal followed by MTG (methanol to gasoline) synthesis. A related near-commercial set of technologies is the MTO (methanol to olefins) process coupled to the MOGD (Mobil's olefin to gasoline and diesel) process. In an effort led by Larson and Williams, the Williams group will carry out detailed techno-economic analyses of coal-based MTG and MTO/MOGD technologies and make comparisons to F-T liquids systems. As in the case of previous analyses, they will examine systems without and with CCS, systems that maximize hydrocarbon yield and that provide considerable co-product power, systems that co-process biomass with coal, and systems that use only biomass.

Catalytic hydrogasification, originally developed by Exxon in the 1970s and currently promoted by Great-Point Energy, gasifies coal at a relatively low temperature (700 C) in a fluidized bed in the absence of O2; it is especially well suited for use with low-rank coals and biomass. Kreutz will take the lead in carrying out a detailed techno-economic comparison of converting coal and biomass to substitute natural gas (SNG) via catalytic hydrogasification and traditional syngas methanation, without and with CCS and considering both systems that maximize SNG yield and systems that provide considerable co-product power.

Integrated Supply/Demand Approaches for Realizing Zero GHG Emissions for LDVs

Deep reductions in GHG emissions for light-duty vehicles (LDVs) can be realized by shifting to advanced end-use technologies and by using ultra-low GHG emitting energy supplies in LDVs based on these advanced end-use technologies. Williams will take the lead in carrying out a detailed techno-economic systems analysis of alternative combinations of advanced end-use and supply technologies and compare the different combinations with respect to both GHG emissions and costs to consumers. For advanced end-use technologies, attention will be focused on alternative LDV options that John Heywood's group at MIT has recently analyzed in depth. Alternative supply options considered will include zero net GHG-emitting FTL fuels derived from CBTL with CCS polygeneration systems as well as negative GHG emitting power from biomass power plants with CCS—supply systems that the Williams Group has already modeled.

Collaboration with Politecnico di Milano

In 2009, the collaboration between Politecnico di Milano and the Williams Group will continue to focus on the two topics studied during 2008. The new model for the optimization of heat recovery will be improved as part of Emanuele Martelli's PhD thesis. As for CO2 separation via phase change, new configurations will be analyzed, possibly considering the integration of low-temperature CO2 and sulfur separation, as well as applications other than IGCCs.

Energy in China

Eric Larson of the Williams Group will lead an activity aimed at: (i) completing the research carried out in 2007 at Tsinghua University by Cathy Kunkel on CBTL systems based on both crop residues and mixed prairie grasses grown on grasslands in China and (ii) preparing papers on same for submission to peer-reviewed journals.

Williams and Larson will also collaborate with Li Zheng and colleagues at Tsinghua University to analyze prospects for CCS early action in China—focussing on low-cost CO2 sources at coal gasification plants that make chemicals and synthetic fuels. This effort will bring together and extend prior work at Princeton (by Kyle Meng with Williams and Michael Celia in 2005 focussing on CCS opportunities near plants that make ammonia from coal in China) and at Tsinghua (including a recent optimization analysis of CO2 source sink matching).

Backing Out Coal Power with Low-C Power via Economic Dispatch Competition

Major findings of the Williams Group's research for this year are that coal/biomass polygeneration with CCS and wind/CAES power systems would be very competitive in economic dispatch, thereby offering market-based options for displacing carbon-intensive existing coal power with low carbon power. Kreutz will lead an analytical effort in collaboration with Williams to estimate the extent to which these technologies might displace existing coal power on electric grids as a function of GHG emissions prices, oil prices, and other parameters by modeling economic dispatch for the PJM ISO or alternative grid for which good data are available.

Self-Consistent Comparison of Alternative Energy Technologies

The spreadsheet model developed by the Williams Group to help the authors of the NRC's America's Energy Future study has proved to be a powerful tool for comparing alternative energy supply technologies on a self-consistent basis. Over the next two years, Kreutz will lead an effort to expand this spreadsheet model to include both the new systems we intend to analyze as discussed above and other high-profile technologies such as nuclear power and renewable energy that were researched by other groups involved in the NRC study. The group hopes to gain a better understanding of how all these energy technologies interrelate and compete in a future with rising GHG emission prices and uncertain oil and feedstock prices.

Improving Energy Storage Technologies

In the year ahead, the Arnold Group will be continuing work on assessment and optimization of energy storage technologies by integrating their existing knowledge with the other work groups in CMI. On the technology front, the group will continue studies in lithium-based battery systems and carbon based supercapacitor systems. Ultimately, they seek to provide small-scale prototype examples of fully integrated storage with renewable energy generation such as solar cells or wind based power.

Alternative Fuels Combustion

The Law Group will continue collaborating with Ford on the simulation of engine processes. The emphasis will be predicting engine knock, which is a primary factor limiting the improvement of combustion efficiency, especially with the development of high-compression engines. The reduced reaction mechanisms for n-heptane and iso-octane will be extended to the more complex and realistic primary reference fuels (PRF) and integrated to the engine simulation codes developed at Ford. Collaboration with the simulation group at the Sandia National Laboratory will also be initiated for HCCI (homogeneous charge compression ignition) engines, again using the highly efficient reaction mechanisms that Law and colleagues have developed. The Sandia group under the direction of Dr. Jackie Chen is world renowned in performing high-fidelity direct numerical simulations (DNS) of combustion processes in engines.

Finally, a comprehensive experimental and modeling research program on the combustion of biofuels has been initiated and will form the major thrust of the group's current program. In addition to studying the combustion chemistry of ethanol, the group will also initiate research on the higher alcohols such as propanol and butanol, as well as their blends with conventional gasoline fuels.

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