ABSTRACT
The objective of this project is to develop a process for the separation of hydrogen from coal gasification based syngas components for end uses such as clean energy production. The research is expected to provide significant impetus to Illinois coal in finding a place in the FutureGen vision as well as tapping emerging markets for high purity hydrogen. SIU has developed a process that is capable of separating hydrogen from synthesis gas. The process is flexible such that it can be used within the gasifier to separate hydrogen or as a separate unit process, depending on the requirements of the process design. The basic idea of the research is to design and apply solids to be used in a fixed bed reactor that will increase the hydrogen yield as well as capture greenhouse gases in its matrix through reaction. The end product envisioned in this process is pure hydrogen. The spent solids would then be regenerated thermoneutrally while releasing sequestration ready carbon dioxide. The project involves the validation of this process along with the evaluation of the process parameters to maximize the hydrogen content in the product stream. The effect of sulfur (present as H2S) in the product stream on the process efficiency was also evaluated. Most importantly, the solids were designed such that they have the maximum selectivity to the beneficial reactions while maintaining their structure and activity through the reaction-regeneration cycles.
Iron (created by reduction of hematite with syngas) was selected as the Boudouard catalyst and CaO was selected as the carbon dioxide removal material. Thermogravimetric and Temperature Programmed Reduction Analysis were utilized to evaluate the reaction rate parameters, and capacity for CO2. Specially synthesized CaO (wherein the surface properties were modified) was found to provide better capacity and reaction rates as compared to commercially available CaO. In addition, these specially synthesized CaO showed lower deactivation over multiple cycles. Experiments were also performed with different compositions of syngas to identify the optimal conditions for pure H2 production. Finally, simultaneous coal gasification and hydrogen enrichment experiments were conducted. It was found that for a Fe2O3: Coal ratio of 22:1, and Fe2O3: CaO ratio of 1:3, no COx was released, while for a Fe2O3: Coal ratio of 44:1, no H2S was released.
This 2005 report was prepared by Dr Tomasz Wiltowski and Southern Illinois University at Carbondale with support in part by grants made possible by the Illinois Department of Commerce and Economic Opportunity through the Office of Coal Development and the Illinois Clean Coal Institute.