Doctor of Philosophy, The Ohio State University, 2022, Chemical Engineering

Chemical looping uses a metal oxide oxygen carrier to provide the necessary oxygen for the partial or complete combustion of fuel. Chemical looping systems can be configured to produce sequestration ready CO2, high purity syngas, high purity hydrogen, or any combination of the three. The uniqueness of the moving bed reducer reactor pioneered at The Ohio State University (OSU) is the basis of the systems presented here. The work presented in this dissertation aims to determine process improvements and applications for which chemical looping provides an efficient alternative to traditional processing methods for the reduction in emissions and potential cost savings. The use of biomass fuel in a moving bed reducer chemical looping system was investigated on a bench scale reactor system, known as Biomass-to-Syngas (BTS). Tars, which are known to cause operational issues, were measured at the outlet of the system. A reduction in these tars from traditional gasification of the order of 1g/m3 to a concentration of 0.3g/m3 was observed, due to the unique catalytic cracking ability of the Iron-Titanium Composite Metal Oxide (ITCMO) used in this study.1,2 This reduction in present tars shows just one area where the use of a chemical looping system increases the quality of syngas produced from biomass fuels. Additional improvements to the BTS process were investigated, to reduce the amount of steam input and determine reactor length characteristics. Experimental trials found that the reducer reactor length was a critical factor, as a continued increase in reactor length results in a decrease in syngas purity. This decrease is attributed to water-gas-shift (WGS) occurring in the lower portion of the reducer, increasing the amount of CO2 undesirably. The amount of steam injected to the system, typically done to tune the H2:CO ratio and to increase gasification kinetics, was studied to determine process efficiency. It was found that for a hardwood biomass, only 5% steam (fed b (open full item for complete abstract)

Committee: Andrew Tong (Advisor); Jeffery Chalmers (Committee Member); Joel Paulson (Committee Member); Harpreet Singh (Committee Member) Subjects: Chemical Engineering; Energy; Engineering

Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering

In this work, new CO2-selective membranes were synthesized and their applications for fuel cell fuel processing and synthesis gas purification were investigated. In order to enhance CO2transport across membranes, the synthesized membranes contained both mobile and fixed site carriers in crosslinked poly(vinyl alcohol). The effects of crosslinking, membrane composition, feed pressure, water content, and temperature on transport properties were investigated. The membranes have shown a high permeability and a good CO2/H2 selectivity and maintained their separation performance up to 170°C. One type of these membranes showed a permeability of 8000 Barrers and a CO2/H2selectivity of 290 at 110°C. The applications of the synthesized membranes were demonstrated in a CO2-removal experiment, in which the CO2 concentration in retentate was decreased from 17% to < 10 ppm. With such membranes, there are several options to reduce the CO concentration of synthesis gas. One option is to develop a water gas shift (WGS) membrane reactor, in which both WGS reaction and CO2-removal take place. Another option is to use a proposed process consisting of a CO2-removal membrane followed by a conventional WGS reactor. In the membrane reactor, a CO concentration of less than 10 ppm and a H 2concentration of greater than 50% (on dry basis) were achieved at various flow rates of a simulated autothermal reformate. In the proposed CO2-removal/WGS process, with more than 99.5% CO2 removed from the synthesis gas, the CO concentration was decreased from 1.2% to less than 10 ppm (dry), which is the requirement for fuel cells. The WGS reactor had a gas hourly space velocity of 7650 h-1 at 150°C and the H2 concentration in the outlet was more than 54.7% (dry). The applications of the synthesized CO2-selective membranes for high-pressure synthesis gas purification were also studied. We studied the synthesized membranes at feed pressures > 200 psia and temperatures ranging from 100-150 °C. The effects of (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor) Subjects: