Evaluation of the Effects of Molybdenum on Sulfur Deposition in Iron-Based Oxygen Carriers for Coal Direct Chemical Looping Processes
Loading...
Date
2017-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
The Ohio State University
Abstract
Increasing demand of energy and global warming creates a challenging balancing case for fossil fuel based power generation plants. While mature carbon capture technology is already developed, the technology is often burdened with significant economic penalties. Coal direct chemical looping (CDCL) is an oxy-combustion process at The Ohio State University that successfully utilizes a counter-current moving bed and iron-based metal oxide oxygen carriers to capture carbon dioxide (CO2) without incurring heavy costs. However, iron-based metal oxides in CDCL processes are susceptible to the formation of iron-sulfide (Fe-S) bonds, due to the presence of sulfur from coal. Sulfur deposition is known to decrease the reactivity of oxygen carriers and reduce metal carrier performance. In this study, molybdenum was investigated for its characteristics that preferentially enhance the adsorption of sulfur when compared with iron oxide. The goal of this study was to explore the kinetics of sulfur deposition with varying mixed metal-oxide concentrations. Thermogravimetric (TGA) experiments were studied at temperatures of 700ºC, 800ºC, and 900ºC with incremental iron-molybdenum ratios of binary powder mixtures. A 1:20 mixed volumetric ratio of hydrogen to 500-ppm hydrogen sulfide gases
was utilized to reduce the binary mixture while encouraging sulfur deposition. X-Ray Powder Diffraction (XRD) was employed to qualitatively analyze the formation of both molybdenum-sulfide and iron-sulfide bonds. Experiments were conducted to assess the
ability for molybdenum to selectively inhibit sulfur deposition on iron in the binary mixture. Although further testing is necessary to scale up the experiment, molybdenum has shown promise in slowing the formation of iron-sulfide bonds in CDCL processes. Enhancement of environmentally friendly combustion processes may allow for a lessened impact of fossil fuels, and ultimately a more efficient utilization of coal-derived energy.
Description
Graduation with Honors Research Distinction
Keywords
Chemical looping, Materials Science, Sustainability, Sulfur Poisoning