THE EXPERIMENTAL AND THEORETICAL INVESTIGATION OF THE HYDROGEN SULFIDE SPLITTING CYCLE FOR HYDROGEN PRODUCTION
Date
2015-05-28
Authors
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Journal ISSN
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ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
In Dr. Hui Wang’s research group at the University of Saskatchewan, an H2S splitting cycle was earlier developed as a novel method to convert H2S, a significant waste product in the oil and gas industry, to hydrogen, which is desired in the same industry for hydrotreating processes. In this research, it was realized that hydrogen could also be produced from variety of sulfur-containing feedstock as long as it could be converted into SO2 to feed the Bunsen reaction followed by hydroiodic acid decomposition to form hydrogen. Therefore, an exergy analysis was performed on various chemical reaction routes, or open-cycles, to make use of sulfur-containing compounds, which exist in different industry sectors as byproducts or waste products, for hydrogen production. The exergy analysis tells which route makes hydrogen production fromvsulfur-containing feedstock more energy-efficient.
The sulfur-iodine (S-I) water-splitting cycle inspired the development of the H2S splitting cycle. Similarly, this cycle, along with its alternative open-loop cycles, consists of three or four reaction sections. This research has experimentally focused on the Bunsen reaction, the centre section for the original H2S splitting cycle as well as the open-loop cycles. An iodine-toluene solution was used to render the Bunsen reaction to occur at ambient temperature so as to avoid the side reactions and I2 vapour deposition which usually occur at higher temperatures. For the multiphase reaction system when organic solution is used, however, the improvement ofvcross-phase mass transfer becomes crucial. Glass-made, Low Flow Corning® Advanced-FlowTM Reactor (LF-AFR) was chosen for this study due to its excellent resistance to acid-caused corrosion and capability to improve the mixing efficiency of multiphase fluids. With this reactor, the overall mass transfer coefficients were calculated for binary systems (SO2-water and SO2-toluene). The effects of operating conditions such as gas and liquid flow rates, the water to toluene ratio, and the temperature in the ambient range (22-70 oC) on the absorption rates of SO2 and the I2 reaction rate were studied at the University of Saskatchewan. It was understood that the mass transfer coefficients are highly dependent on the gas and liquid flow rates in the LF-AFR. Gas phase composition also played a big role where the KLa values tended to be smaller for the systems with the highest gas phase resistance. The mass transfer study implied that the gas absorption in liquid was completed in the contacting fluidic module where the gas-liquid mixture was initially mixed. Later, all experiments at higher flow rates of fluids were conducted in the next commercially available size of Corning® Advanced-FlowTM Reactor products (G1-AFR) at the Corning Reactor Technology Center. The results revealed the seamless scaling-up capability of Corning reactors from the LF-AFR to the G1-AFR when the flow rates were increased twenty times.
Based on the experimental results for the Bunsen reaction in this thesis and the results for other sections studied earlier by this group, a hydrogen production plant with the H2S splitting cycle technology was designed in a typical size of the hydrogen plant of a heavy oil upgrader followed by an economic analysis.
Description
Keywords
H2S splitting cycle, Bunsen reaction, mass transfer study, Corning Advanced-Flow Reactors, Hydrogen Prodction
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Chemical and Biological Engineering
Program
Chemical Engineering