The U.S. Department of Energy’s National Energy Technology Laboratory has developed a software platform titled Carbonaceous Chemistry for Computational Modeling (C3M) that can be used to seamlessly connect the reaction kinetics typically found in the gasification process to various computational fluid dynamic (CFD) packages, including MFIX, ANSYS-FLUENT, and BARRACUDA, for advanced gasifier simulation. In this study, a pilot-scale transport gasifier was simulated by employing the C3M platform to incorporate various kinetics into the CFD simulation. It was found that appropriate chemical kinetics for gasification reactions are key to the numerical prediction of syngas composition and the kinetics from Niksa Energy Associate’s PC Coal Lab yielded reasonable agreement to the experimental data. Using the C3M platform, different chemistry kinetics for coal devolatilizationgenerated by METC Gasifier Advanced Simulation (MGAS), Niksa Energy Associate’s PC Coal Lab (PCCL), Chemical Percolation Model for Coal Devolatilization (CPD), and Advanced Fuel Research’s Functional-Group, Depolymerization, Vaporization, Cross-linking (FG-DVC)were evaluated for the transport gasifier simulation. Results showed that the effect of devolatilization kinetics on the transport gasifier simulation is considered to be secondary comparing to the char gasification reactions because of the relatively long residence time of coal particles in the system.

We explore the relationship between mechanical, transport, and critical state characteristics of coal−biomass mixtures by evaluating mixture composition, stress, strength, rhelogy, and permeability of coal−biomass mixtures. We report measurements of strength and permeability evolution for uniformly graded (passing no. 200 mesh) granular mixtures of coal− biomass in the proportions (a) 100% sub-bituminous coal, (b) 75−25% sub-bituminous coal−biomass, and (c) 100% biomass. We observe response at confining stresses in the range 5 and 25 MPa and at strain rates of ∼10 −4 /s. The pure biomass is the most compliant and weakest of the three mixtures, and the coal is the stiffest and strongest. The samples stiffen with compaction as confining stress increases. Results show strain hardening for all sample mixtures resulting from grain breakage. Work hardening behavior is characterized using a CAP model. In all samples, permeability reduces with an increase in axial strain and yields permeabilities in the range 10 −14 −10 −16 m 2 (10−0.1 mD). We define the evolution of permeability as a function of changes in both porosity and grain breakage and link this to a model representing the harmonic mean of the particle diameters, as they evolve. This characterization works well and the harmonic mean of the particle size distribution is the best predictor of permeability evolution. These measurements are important in characterizing feed characteristics of dry-fed coal−biomass mixtures to prevent gas-flow back and to maintain feed rates into pressurized gasifiers.

We describe measurements of permeability on coal-biomass mixtures, which are a potential feedstock to gasifiers to reduce net carbon emissions. Permeability is measured under anticipated dry feed stress conditions to determine the potential for fugitive gas emission from the gasifier into the feed hopper. Cylindrical samples of coal-biomass blends are housed within a triaxial apparatus capable of applying mean and deviatoric stresses and of concurrently measuring gas permeability. We measure the evolution of strain, porosity and permeability under mean stresses of 3.5, 7 and 14 MPa. Permeability is measured by pulse transmission testing using N 2 and He as the saturant and assuming the validity of Darcy's law. Porosity is measured by pressure pulse with He as saturant and assuming an ideal gas. Experiments are conducted on a range of coals and biomass blends at mixtures of 100 percent coal through 100 percent biomass. Measured permeabilities are in the range 10 -13 to 10 -16 m 2 with the 100 percent biomass blends showing lower permeabilities than the coal biomass and 100 percent coal blends. Permeabilities change in loading and unloading and exhibit hysteresis. We fit the data to connect permeability with porosity using relations for porous media where permeability changes proportionally to the cube of the change in porosity. This model performs adequately since there is little size reduction in the granular mass due to the applied isotropic loading.

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The authors would like to thank CWI (CH2M-WG Idaho) personnel for sampling the Fluidized Bed Steam Reformer (FBSR) feedstock supersacks of coal. The authors would like to thank Ronnie Rutherford of the Savannah River National Laboratory (SRNL) Analytic R&D Programs and Materials Characterization for performing the coal heat treatments and sieve analyses and Whitney Riley and David Best of the Process Science Analytic Laboratory (PSAL) for the analyses of the coal ash. The authors would also like to thank Tommy B. Edwards of the Environmental & Chemical Process Technology (E&CPT) for the statistical analysis of the coal particle size data.The coal feedstock analyses were supported by the Department of Energy -Environmental Management (DOE-EM) Operation Support Team (OST). The OST serves the interests of EM-1 and EM-20/21, and performs an advisory role to EM-1 and EM-20/21. Specifically, EM-1 requested that the OST work with the Idaho site whenever possible to provide assistance regarding technical issues that are in the knowledge base of the team members. Work was performed under Contract No.