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Advances in co-gasification of coal and biomass are resulting in more interest in poly-generation facilities that can produce hydrogen rich syngas for producing chemicals, fuels and energy, with much lower carbon emissions. When biomass is blended with hydrocarbon feedstocks like coal (biomass cofiring) and when the carbon dioxide (CO₂) produced during the gasification process is captured using pre-combustion CO₂ capture technologies, it is possible to emit less CO₂ into the atmosphere than it took to grow the biomass material, resulting in net negative or low CO₂ emissions. Here, we present the first carbon capture pilot plant data for CO₂ removal from coal and biomass derived syngas using physical solvent absorption. The physical solvent (DEPG at 35.0 L·h^-1 and 10.5 °C) was tested in a packed absorption column under pre-combustion CO₂ capture conditions using the biomass derived syngas mixtures (3.54 MPa at 3.4 std. m³·h^-1 and 53.1 °C) to assess any changes in the absorption process resulting from co-gasification. Overall, the CO₂ absorption performance of the solvent did not appear to be impacted by the varying feedstock compositions as indicated by average CO₂ removal efficiency of 97.3 % with a standard deviation of 1.6 % across all trials. Despite minor accumulation of organic gas species in the solvent and gas streams exiting the absorber, there did not appear to be any strong correlations between CO₂ capture performance and coal type or biomass type or mixture concentration. Further, these results indicate traditional physical solvent absorption processes can be used with minimal impact from novel gasification feedstock mixtures including coal, wood and corn stover mixtures, but longer term testing is recommended to fully assess the impact of accumulating inorganic and organic species from biomass feedstock.

A 2nd Phase Front End Engineering Design study of a gasification plant concept to co-produce electric power and hydrogen with net-negative CO2 emissions is being completed under the U.S. Department of Energy’s (DOE’s) 21st Century Power Plants initiative, whose goal is to advance innovative power plant concepts that are capable of flexible, net-zero carbon emission operations while producing cost-effective hydrogen to support economy-wide decarbonization goals. The proposed standalone plant would be constructed in Nebraska, USA. The specified design feedstock is a hybrid blend of Powder River Basin (PRB) subbituminous coal from Wyoming and local Nebraska biomass (corn stover), 50% each by weight (dry basis). Other potential feedstocks, including woody biomass (eastern red cedar) and waste plastic (auto shredder residue) were evaluated as alternates. The process block comprises a high-pressure, oxygen-blown fluidized bed gasifier coupled with water-gas shift, Selexol process for acid gas (H2S and CO2) removal, and pressure-swing adsorption (PSA) to yield 8,500 kg/h of high-purity hydrogen. Off-gas from the PSA unit is used in a gas turbine combined cycle plant (the power block) to supply 50 MWe net electric power to the grid. Overall thermal efficiency of the plant is 50% (HHV) with net atmospheric CO2 removal at a rate of 32 t/h. Design activities necessary to provide input to the current front-end engineering design (FEED) study, including, site selection, gasifier technology selection, investment case preparation, and the development of the Environmental Information Volume (EIV) for the host site, have been completed. These, as well as the current FEED activities, are described in this presentation.

One promising process that is a candidate for meeting the goals of the US Department of Energy’s 21st Century Power Plant initiative is to gasify a mixture of coal and biomass to yield a syngas, which can have CO2 removed and then be used to produce hydrogen as well as an off-gas that can be used to flexibly produce power. This concept would overall be carbon net-negative and readily meet the 21st Century Power Plant initiative targets of smaller scale MW generation, high ramp rates and turndown, feedstock flexibility, and high efficiency—at a reasonable cost. Moreover, adding the large-scale production of “ultra-green” hydrogen yields a system tailored for the coming hydrogen economy, providing long-term energy storage and an attractive co-product for sale. The objective of the work being led by the Electric Power Research Institute, Inc. (EPRI), with support by Bechtel Corporation (Bechtel), Gas Technology Institute (GTI), Hamilton Mauer International, Inc. (HMI), Nebraska Public Power District (NPPD), NexantECA, Inc. (Nexant), and Wärtsilä, is to perform a front-end design and engineering (FEED) study on an oxygen-blown gasification system coupled with water-gas shift, pre-combustion CO2 capture, and pressure-swing adsorption working off a coal/biomass mix to yield high-purity hydrogen and a fuel off-gas that can generate power. Several designs are being considered that will be capable of producing 50 MW net from a flexible generator, over 8500 kg/hr of hydrogen, and net-negative CO2 emissions, at an efficiency of 50% net HHV. The plant would be hosted at an NPPD site, where opportunities for enhanced oil recovery and sequestration have been investigated and the need for low-carbon power and hydrogen is imminent. The principal biomass to be used is corn stover—prevalent in Nebraska where the plant will be located—mixed with Powder River Basin (PRB) coal, necessitating a gasifier that can use this feedstock and be flexible to allow other types. Waste plastics will also be reviewed for use. Two oxygen-blown gasifiers have been identified as candidates that have done testing with biomass including corn stover: the GTI gasifier—a high-pressure, fluidized-bed type—and HMI’s, a lower pressure moving-bed type. Both have relative advantages that were investigated in the Phase I design study, with a resultant down select of one system for which the FEED will be performed in Phase II. The technical tasks for the project are: • Design Development: Completion of design activities necessary to provide inputs for the FEED study. Multiple design cases will be assessed with the selection of the optimal one for the FEED. • Investment Case Preparation: Development of the draft investment case for the proposed process with business cases performed for the proposed host site and two other locations. • Host Site Selection: Evaluation of the two potential host sites within NPPD’s portfolio to select the preferred candidate based on technical, economic, and environmental considerations. • Environmental Information Volume (EIV) Development: Completion of the EIV for the host site. • FEED Study: Completion of a FEED study based on the design selected in Phase I. A Greenhouse Gas Life Cycle Analysis will also be performed for the process. • Update Investment Case: Finalization of the investment case based on findings from the FEED. The advantages of the proposed project are significant. Having an engaged U.S. power utility willing to provide a host site that will produce energy from coal plus a deep and experienced team is critical; the process meets all the goals of DOE’s 21st Century Power Plant initiative at an estimated total plant cost of ~$880M and a production cost of hydrogen of ~$2/kg-H2 while producing net-negative carbon power. If developed, this process has real commercial potential in the United States—supported by EPRI’s initial review of the considerable interest from selected U.S. utilities—and elsewhere around the globe. The process has fewer environmental hurdles compared to other concepts, lowering regulatory and protest risks—providing a pathway to preserving the viability of a critical indigenous energy source by transforming its use to match a changing world. This presentation outlines the motivation for the effort, summarizes project plans, work completed to date, results of the Phase I effort and, and detailed work scope for the remainder of the project in the Phase II FEED effort.

With the current move towards a net-zero carbon economy, “green” hydrogen production from gasification of inexpensive carbonaceous feed stocks such as coal wastes and biomass will have an increasing role to play. Combined use of the underutilized feedstocks such as coal fines, biomass and plastics portion of the municipal solid wastes (MSW), in distributed modular gasification (DMG) based processes integrated with hydrogen production and carbon capture, will enable a net-zero or even net-negative carbon footprint. However, such modular gasification processes will require the hydrogen separation processes to operate with high efficiency and at lower operating pressures than are typically used in traditional hydrogen production processes. TDA Research, Inc. is developing a highly efficient modular hydrogen separation process that can efficiently separate the carbon from the hydrogen in the synthesis gas generated by the gasification of coal fines, plastic wastes from MSW and biomass to produce high purity >99.9% “green” hydrogen that has negative carbon emissions. TDA’s proposed process uses next generation adsorbents to remove carbon dioxide (which can be sent for storage or utilization) and carbon monoxide to produce the high purity hydrogen in a single stage modular pressure swing adsorption (PSA) process. In the Phase I project we completed the laboratory scale proof-of-concept demonstration of the modular hydrogen separation process and completed a preliminary process design and techno-economic feasibility and life cycle analysis to show the merits of the proposed technology. The new process was able to achieve a carbon capture efficiency of >97.5+% (>99.9% CO2 capture efficiency) while producing > 99.9% H2. The new next-generation sorbents proposed here were able to achieve a very high capacity for CO2 of > 20% wt. CO2 and a CO capacity of > 1.5% wt. CO. The new sorbents not only have a very high selectivity for CO2/H2 and CO/H2 but also CO2/N2 and CO/N2. This allows us to explore other options such as using 93% O2 from Vacuum assisted Pressure Swing Adsorption (VPSA) Air Separation Units (ASUs) to produce high purity H2 with carbon capture in the single stage process, further reducing the cost of H2 produced from the DMG processes. We carried out more than 100 adsorption/desorption cycles demonstrating stable working capacity establishing cyclic steady state. We used adsorption modeling to optimize the PSA cycle sequence to recover high purity sequestration ready CO2 and CO rich tail gas separately at a high recovery >75%. Based on these results, we completed an engineering design and estimated the levelized cost of hydrogen (LCOH) to be between $4.17 and $4.48 and the breakeven selling price for CO2 to be $65-85/tonne on a $2018 basis. The increase in the Levelized cost of Hydrogen (LCOH) is estimated to be 28.5% lower than the two-stage process (separate acid gas removal step to capture CO2 followed by a H2 PSA process to produce high purity H2) employed in the DOE study for the coal/biomass co-gasification hydrogen production plants with carbon capture. Our preliminary LCA (Life Cycle Assessment) study confirms that when using biomass as a co-gasification feedstock we achieve a negative carbon footprint, this results in the hydrogen produced from these waste streams to be “green”. In the Phase II project, TDA we will build a sub-scale prototype unit to demonstrate our sorbent-based multi-bed high efficiency H2 PSA process that produces > 99.9% hydrogen from syngas derived from biomass, coal and plastic wastes while providing sequestration ready high purity CO2. With the successful completion of Phase II R&D effort, the technology will be ready for a pilot-scale demonstration and the technology readiness will be raised from TRL 3 to TRL 5.

Previous research has provided strong evidence that CO₂ and H₂O gasification reactions can provide non-negligible contributions to the consumption rates of pulverized coal (pc) char during combustion, particularly in oxy-fuel environments. Fully quantifying the contribution of these gasification reactions has proven to be difficult, due to the dearth of knowledge of gasification rates at the elevated particle temperatures associated with typical pc char combustion processes, as well as the complex interaction of oxidation and gasification reactions. Gasification reactions tend to become more important at higher char particle temperatures (because of their high activation energy) and they tend to reduce pc oxidation due to their endothermicity (i.e. cooling effect). The work reported here attempts to quantify the influence of the gasification reaction of CO₂ in a rigorous manner by combining experimental measurements of the particle temperatures and consumption rates of size-classified pc char particles in tailored oxy-fuel environments with simulations from a detailed reacting porous particle model. The results demonstrate that a specific gasification reaction rate relative to the oxidation rate (within an accuracy of approximately +/- 20% of the pre-exponential value), is consistent with the experimentally measured char particle temperatures and burnout rates in oxy-fuel combustion environments. Conversely, the results also show, in agreement with past calculations, that it is extremely difficult to construct a set of kinetics that does not substantially overpredict particle temperature increase in strongly oxygen-enriched N2 environments. This latter result is believed to result from deficiencies in standard oxidation mechanisms that fail to account for falloff in char oxidation rates at high temperatures.

The proposed project includes construction and operation of a power plant consisting of coal gasification facilities and engine generators which would produce electrical power and heat. The recovered heat and a portion of the carbon dioxide emissions from the engines would support an onsite greenhouse and other heat and power customers. The proposed project site is located on the Marathon North Pole Terminal property in North Pole, Alaska. Two gasifiers would convert the coal into syngas, which would be fed through a gas cleanup train and then combusted in six reciprocating engines driving electric generators. Heat recovery on the engine cooling loops and exhaust trains would provide heat to a glycol/water circulation system for use in the greenhouse, in the Marathon facilities and for other customers. Natural gas would fuel two additional engine generators and would also be available to supplement the syngas-fired engines.

This study explored the feasibility of utilizing lowly-reactive coal gasification fly ash (CGFA) for stabilizing road aggregate bases. Three types of aggregate stabilizers including the ordinary Portland cement (OPC)-CGFA, hydrated lime (CH)-CGFA and alkali-activated CH-CGFA were evaluated based on the performances of compacted base specimens. It was found that the OPC-CGFA stabilized bases showed better mechanical and durability properties while the CH-CGFA samples had low water stability and freeze-thaw durability due to the dissolution of unreacted CH. However, the reaction degree of CGFA associated with the performances of CH-CGFA stabilization could be considerably enhanced by the alkali-activation. The sustainability and economic feasibility analyses showed the use of CGFA could significantly reduce the CO₂ emissions and costs, highlighting the synergy between the recycling of CGFA and the construction of sustainable road bases. Here, a framework of selecting CGFA-based stabilizers for road bases was proposed considering the performance ratings of the material properties.

Coal is a globally abundant resource that historically has been used for power generation via combustion. As the power industry replaces coal with cleaner methods of generation, energy-rich coal could be used in other chemical and fuel applications. This study presents a coal utilization option in which coal combustion is replaced with a carbon-free nuclear power plant and the coal is upgraded to valuable products for a variety of markets. Coal is prepared for conversion first by the pyrolysis process, which will optimize solid, liquid, and gaseous products based on the market size and potential product value, maximizing the monetary value of coal. This process is designed using bituminous coal from the Appalachian region as a basis to provide a pathway to preserve or transition coal-related jobs and create new jobs associated with the clean energy transition. Process modeling in the AspenOne Suite will be used to determine each component’s sensitivities, costs, inputs, and outputs. Dispatch modeling in the FORCE toolset will optimize the entire system and calculate the NPV for the refinery lifetime. Advanced and light-water reactors are considerations to supply the heat, steam, and electricity to the process. This paper focuses on the technical and market analysis used to determine the optimal processes and product pathways for the carbon refinery. Product pathways are on activated carbon, formic acid synthesis, and methanol synthesis for further upgrading to marketable chemical and polymer products.

Coal is a globally abundant resource that historically has been used for power generation via combustion. As the power industry replaces coal with cleaner methods of generation, energy rich coal could be used in other chemical and fuel applications. This study presents a coal utilization option in which coal combustion is replaced with a carbon-free nuclear power plant and the coal is upgraded to valuable products for a variety of markets. Coal is prepared for conversion first by the pyrolysis process, which will optimize solid, liquid, and gaseous products based on the market size and potential product value, maximizing the monetary value of coal. This process is designed using bituminous coal from the Appalachian region as a basis to provide a pathway to preserve or transition coal-related jobs and create new jobs associated with the clean energy transition. Process modeling will be used to determine each component’s sensitivities, costs, inputs, and outputs Advanced and light-water reactors are considerations to supply the heat, steam, and electricity to the process. This paper focuses on the technical and market analysis used to determine the optimal processes and product pathways for the carbon refinery. Product pathways are on activated carbon, formic acid synthesis, and methanol synthesis for further upgrading to marketable chemical and polymer products.

Coal is a globally abundant resource that historically has been used for power generation via combustion. As the power industry replaces coal with cleaner methods of generation, energy-rich coal could be used in other chemical and fuel applications. This study presents a coal utilization option in which coal combustion is replaced with a carbon-free nuclear power plant and the coal is upgraded to valuable products for a variety of markets. Coal is prepared for conversion first by the pyrolysis process, which will optimize solid, liquid, and gaseous products based on the market size and potential product value, maximizing the monetary value of coal. This process is designed using bituminous coal from the Appalachian region as a basis to provide a pathway to preserve or transition coal-related jobs and create new jobs associated with the clean energy transition. Process modeling in the AspenOne Suite will be used to determine each component’s sensitivities, costs, inputs, and outputs. Dispatch modeling in the FORCE toolset will optimize the entire system and calculate the NPV for the refinery lifetime. Advanced and light-water reactors are considerations to supply the heat, steam, and electricity to the process. This paper focuses on the technical and market analysis used to determine the optimal processes and product pathways for the carbon refinery. Product pathways are on activated carbon, formic acid synthesis, and methanol synthesis for further upgrading to marketable chemical and polymer products.