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Particulate Formation from a Copper Oxide-Based Oxygen Carrier in Chemical Looping Combustion for CO2 Capture
Citation:
He, F., W. P. Linak, S. Deng, AND F. Li. Particulate Formation from a Copper Oxide-Based Oxygen Carrier in Chemical Looping Combustion for CO2 Capture . ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 51(4):2482-2490, (2017).
Impact/Purpose:
Chemical looping combustion (CLC) processes represent an alternative, potentially efficient strategy for power generation from fossil fuels with in situ CO2 capture. CLC typically uses mixed metal oxide-based oxygen carrier particles to oxidize carbonaceous fuels into concentrated CO2. This is accomplished by circulating the oxygen carrier particles between a fuel oxidizing fluidized bed and a reducing fluidized bed where the reduced carrier is combusted with air to release heat for power generation. This research examined the effect of repeated redox reactions on particle emissions for one promising CuO supported by Al2O3 oxygen carrier using an experimental fluidized bed combustor. Based on measurements made in a small fluidized bed combustor, we calculate Cu attrition losses of 5 kg/h for a CuO-Al2O3 oxygen carrier with 2500 hours residence in a 1000 MWth power plant without recovery. These results suggest that CuO-Al2O3-based oxygen carriers are good candidates for CLC applications, causing relatively low additional particle emissions, and may be of interest to CLC research groups, governmental and industrial energy generation technology developers, and environmental regulators interested in the potential emissions from advanced fossil fuel power conversion technologies designed for CO2 capture.
Description:
Attrition behavior and particle loss of a copper oxide-based oxygen carrier from a methane chemical looping combustion (CLC) process was investigated in a fluidized bed reactor. The aerodynamic diameters of most elutriated particulates, after passing through a horizontal settling duct, range between 2 and 5 μm. A notable number of submicron particulates are also identified. Oxygen carrier attrition was observed to lead to increased CuO loss resulting from the chemical looping reactions, i.e., Cu is enriched in small particles generated primarily from fragmentation in the size range of 10-75 μm. Cyclic reduction and oxidation reactions in CLC have been determined to weaken the oxygen carrier particles, resulting in increased particulate emission rates when compared to oxygen carriers without redox reactions. The generation rate for particulates < 10 μm was found to decrease with progressive cycles over as-prepared oxygen carrier particles and then reach a steady state. The surface of the oxygen carrier is also found to be coarsened due to a Kirkendall effect, which also explains the enrichment of Cu on particle surfaces and in small particles. As a result, it is important to collect and reprocess small particles generated from chemical looping processes to reduce oxygen carrier loss.
URLs/Downloads:
http://pubs.acs.org/doi/pdfplus/10.1021/acs.est.6b04043
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