(515g) CO2 Utilization Via Chemical Looping Dry Reforming: Process Modeling and Systems Analysis

Authors: 
Mantripragada, H. C., University of Pittsburgh
Veser, G., University of Pittsburgh
CO2 capture and storage or sequestration (CCS) is one of the key climate change mitigation technologies. In CCS, CO2 is captured from flue gases of power plants or industrial sources, and the high-purity CO2 is compressed and stored in deep geologic formations. However, this process is associated with high energy consumption and cost. Utilizing the captured CO2 instead for conversion into valuable chemicals and fuels could not only (partially) close the anthropogenic carbon cycle, but also be a cost-effective alternative to make CCS technology commercially viable. Among CO2 utilization routes, dry reforming of methane to syngas is promising since it couples CO2 utilization to fuels production, one of the few markets with a scale to absorb the huge amounts of CO2 emitted from power generation. We have previously proposed “chemical looping dry reforming” (CLDR) as a promising process alternative to conventional dry reforming [1-2], and later extended this approach towards an alternate process configuration that directly produces fully separated syngas streams, i.e. separate effluent streams of H2 and CO [3-4]. Like all “looping” processes, CLDR is based on the use of spatially or temporally separated reactors for fuel conversion with an oxide carrier followed by re-oxidation of the carrier with an oxidant (here: CO2). In the present paper, we analyze the feasibility of CLDR by combining the dry reforming reaction with power generation using waste heat recovery.

In our study, the overall system is designed to produce a desired flow rate and composition of the syngas (i.e. the CO/H2 ratio) from natural gas, while maximizing the yield and minimizing the overall energy consumption. The CO2 feed is assumed to come from a CO2 capture at a power plant or other industrial process. Building on our previous fixed-bed experimental results, reactor-level mass and energy balance calculations are performed to calculate the effect of operating conditions such as flow rates, solids conversion and temperature on the final product composition, selectivity and yields. The systems-level model includes thermodynamic calculations of individual process components such as blowers, compressors, and heat recovery equipment, as well as steam turbines. Using sensitivity analysis on parameters such as selectivity and fuel conversion, we identify the carbon carrier properties required to improve process performance, and compare results to a conventional CO2 dry reforming process as well as to conventional H2 production pathways from CH4 using autothermal reforming or steam methane reforming. Preliminary cost assessments will also be conducted to evaluate the comparative economic feasibility of the CLDR process.

[1] M. Najera, R. Solunke, T. Gardner, and G. Veser, “Carbon capture and utilization via chemical looping dry reforming”, Chem. Eng. Res. & Des. 89 (2011) 1533-1543

[2] S. Bhavsar, M. Najera, and G. Veser, “Chemical Looping Dry Reforming as Novel, Intensified Process for CO2 Activation”, Chem. Eng. Technol. 35 (2012) 1281–1290.

[3] A. More, S. Bhavsar, and G. Veser. “CO2 Activation Via Chemical Looping Dry Reforming Of Methane”, Energy Technology 4 (2016) 1147–1157.

[4] A. More, Ch. Hansen, and G. Veser, "Production of inherently separated syngas streams via chemical looping methane cracking", Catal. Today 298 (2017) 21-32.