Syngas production and hydrogen separation technologies are very mature, and also extremely important for energy and chemical industries. Furthermore, these processes are the most expensive elements for many applications such as hydrogen production from renewable sources. Enhancing or intensifying these very mature technologies is very challenging, but would have tremendous impact on the performance and economics of many processes. Traditional Integrated Gasification Combined Cycle (IGCC) for syngas production need to include a carbon capture process in order to regulate their carbon dioxide emission as more and more countries and regions have implemented carbon tax policy. Integration of this process with Pd membrane has long been considered a key component to make it more feasible. With these two technologies combined together, we can produce high purity hydrogen while capturing carbon dioxide and toxic gases from the syngas product. Besides, although manufacturing the membrane reactor is expensive, after considering the carbon tax factor, it actually is more economically preferable compare with the traditional Pressure Swing Adsorption (PSA) process. Most research on Pd membrane technology has been conducted at lab scale; nonetheless, the contribution of a palladium membrane technology to economic and societal development requires its commercialization, diffusion and utilization. To generate enough incentives for commercialization, it is necessary to demonstrate the scalability and robustness of the membranes in industrial settings. Consequently, a multitube membrane module suitable for IGCC system was designed and manufactured and sent to National Carbon Capture Center (NCCC) for testing. This work developed a Computational Fluid Dynamics (CFD) model for the module and validated the model utilizing the pilot-scale experimental data generated under industrial conditions. The model was then up-scaled and used to determine the intrinsic phenomena of palladium membrane scale up. This study reveals the technical/engineering requirements for the effective design of large-scale multitube membrane modules. Mass transfer limitations and concentration polarization effects were studied quantitatively with the developed model. Methods for diminishing the concentration polarization effect were proposed and tested through the simulations such as i) increasing convective forces and ii) designing baffles to create gas recirculation. For scaled-up membrane modules, mass transfer limitation is an important parameter to consider as large modules showed severe concentration polarization effects. IGCC systems produce H2 from coal combustion; other ways of H2 production include steam-reforming processes, using natural gas or bio-ethanol as the reactant. The product contains a mixture of H2, CH4, CO, CO2 and steam. Thus, steam-reforming processes are often followed by a Pressure Swing Adsorption (PSA) unit in order to obtain pure hydrogen. Palladium membrane, on the other hand, can be integrated with steam-reforming processes and achieve the simultaneous production and purification of H2 in a single unit by reaching process intensification. Higher H2 production rate can be reached by process intensification as one of the products H2 is constantly being removed. Temperature control is a very important topic in steam reforming processes, as the reaction is overall highly endothermic; although implementing an in-unit membrane improves H2 production rate, it also makes the temperature control more difficult as the reaction equilibrium is altered by the removal of one of the products H2. Hereby, an experimental study of catalytic membrane reactor (CMR) was carried out along with both isothermal and non-isothermal CFD simulations that are validated by the experimental data in order to visualize the temperature distribution inside the reactor and understand the influence of the operating conditions including temperature, pressure and the sweep gas flow patter on the permeate side.
| Identifer | oai:union.ndltd.org:wpi.edu/oai:digitalcommons.wpi.edu:etd-dissertations-1544 |
| Date | 26 April 2018 |
| Creators | Ma, Rui |
| Contributors | Anthony G. Dixon, Advisor, Nikolaos K. Kazantzis, Committee Member, Micheal T. Timko, Committee Member, John M. Sullivan, Committee Member |
| Publisher | Digital WPI |
| Source Sets | Worcester Polytechnic Institute |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Doctoral Dissertations (All Dissertations, All Years) |
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