Molecular Simulation of Carbon Dioxide Adsorption for Carbon Capture and Storage.

Molecular Simulation;Coal;Carbon Dioxide;Adsorption;Civil and Environmental Engineering;Physics;Engineering;Science;Applied Physics and Environmental Engineering

Tenney, Craig M.Wright, Steven J. ;

University of Michigan

关键词: Molecular Simulation;    Coal;    Carbon Dioxide;    Adsorption;    Civil and Environmental Engineering;    Physics;    Engineering;    Science;    Applied Physics and Environmental Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/62442/ctenney_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Capture of CO2 from fossil fuel power plants and sequestration in unmineable coal seamsare achievable methods for reducing atmospheric emissions of this greenhouse gas. Toaid the development of effective CO2capture and sequestration technologies, a series ofmolecular simulation studies were conducted to study the adsorption of CO2 and relatedspecies onto heterogeneous, solid adsorbents.To investigate the influence of surface heterogeneity upon adsorption behavior in activatedcarbons and coal, isotherms were generated via grand canonical Monte Carlo (GCMC)simulation for CO2 adsorption in slit-shaped pores with several variations of chemical andstructural heterogeneity. Adsorption generally increased with increasing oxygen contentand the presence of holes or furrows, which acted as preferred binding sites.To investigate the potential use of the flexible metal organic framework (MOF)Cu(BF4)2(bpy)2 (bpy=bipyridine) for CO2capture, pure- and mixed-gas adsorption wassimulated at conditions representative of power plant process streams. This MOF was chosenbecause it displays a novel behavior in which the crystal structure reversibly transitionsfrom an empty, zero porosity state to a saturated, expanded state at the ;;gate pressure”.Estimates of CO2 capacity above the gate pressure from GCMC simulations using a rigidMOF model showed good agreement with experiment. The CO2 adsorption capacity andestimated heats of adsorption are comparable to common physi-adsorbents under similarconditions. Mixed-gas simulations predicted CO2/N2and CO2/H2selectivities higher thantypical microporous materials.To more closely investigate this gating effect, hybrid Monte-Carlo/molecular-dynamics(MCMD) was used to simulate adsorption using a flexible MOF model. Simulation cell volumesremained relatively constant at low gas pressures before increasing at higher pressure.Mixed-gas simulations predicted CO2/N2 selectivities comparable to other microporousadsorbents.To study the molecular processes relevant to storage of CO2 in unmineable coal seamswith enhanced methane recovery, a representative bituminous coal was simulated usingMD and a hybrid Gibbs-ensemble-Monte-Carlo/MD method. Simulation predicted a bulkdensity of 1.24 g/ml for the dry coal, which compares favorably with the experimental valueof 1.3 g/ml. Consistent with known coal properties, simulation models showed stacking ofmacromolecular graphitic regions and preferential adsorption of CO2 relative to methane.