A novel Chemical Switching Reforming (CSR) reactor for pure hydrogen production with integrated CO2 capture

The Chemical Switching Reforming (CSR) concept enables pure hydrogen production with integrated CO2 capture from a single reactor. Methane is fed to the reactor where it is reformed to carbon monoxide and hydrogen over a Ni-based catalyst. Hydrogen is then extracted via perm-selective membranes, thereby achieving high hydrogen purity as well as a high degree of methane and carbon monoxide conversion. Heat for the endothermic reforming reaction is supplied in a separate air stage where the catalyst acts as an oxygen carrier and reacts with oxygen from air to produce heat. During the project, valuable information has been gained both on the experimental and simulation fronts. Experimentally, a new combined thermogravimetric analysis (TGA) and mass spectroscopy (MS) approach was used to assess the catalytic activity of the oxygen carrier material. This approach is able to deliver results on the simultaneous effect of heterogeneous and catalytic reaction, just as would be the case in the real system. A sudden activation of catalytic activity was observed when the oxygen carrier becomes sufficiently reduced. A cold-flow fluidized bed unit with flat vertical membranes has also been successfully constructed and operated. Gas extraction through the flat membranes had a large impact on the fluidization behaviour of the bed. A digital image analysis (DIA) technique was used to fully characterize the bubble dynamics (size, number, velocity and shape) under different gas extraction conditions and revealed both the extraction rate and the extraction location as highly influential parameters. Large extraction rates resulted in the formation of stagnant zones at the membranes that can result in operational and performance challenges for the real reactor. On the other hand, moving the extraction location more towards the centre of the bed resulted in more uniform bubble rise behaviour that will have a positive impact on reactor performance. These findings were successfully reproduced in a simulation campaign with an improved wall friction model to capture the formation of stagnant zones. This validated modelling approach was then used to conduct reactive simulations to test the degree to which the conclusions drawn in the cold-flow experiments are representative of the real reactive process. Simulations revealed a very similar impact of gas extraction in the cold-flow and reactive cases, thus confirming that cold-flow experiments give a good indication of hydrodynamic behaviour in the real reactor. Key conclusions from the cold-flow experiments were also confirmed by the reactive simulations. For example, moving the extraction location more towards the centre of the reactor resulted in better reactor performance with a lower membrane surface area. The full CSR process has also been successfully simulated to reveal good hydrogen recovery through the membranes (70-80%) and a low degree of CO2/N2 mixing. Furthermore, results showed that the hydrogen recovery varies along the CSR cycle and that alternative feed strategies may be necessary to ensure steady performance. An efficient feed strategy was devised where the residual fuel gases from the reforming stage of the CSR operation are fed to the reduction stage in order to use all residual fuel to provide heat for the endothermic reforming reaction. The project has also further improved the promising Lagrangian dense discrete phase modelling (DDPM) approach for fluidized bed reactor modelling. Validation against experimental results and simulations carried out with the conventional two fluid model (TFM) approach was successfully completed. The DDPM can resolve flows on much coarser grids than the TFM, but is still limited by computational capacity when simulating large-scale reactors. The project showed that the filtered TFM approach is the most suitable for completing large-scale reactor simulations within reasonable timeframes. To date, the project has successfully completed demonstration of the CSR concept without the inclusion of membranes. Even without membranes, this concept presents an interesting concept for efficient hydrogen production with inherent CO2 capture. Membranes are currently being tested for inclusion in the existing CSR reactor. Demonstration of the membrane CSR concept will be completed during 2017 by the PhD student employed by the project. Techno-economic assessments of the membrane-assisted CSR concept show that the CSR concept will be able to produce hydrogen with inherent CO2 capture at a similar cost as the conventional steam-methane reforming (SMR) pathway. This cost is almost 20% lower than conventional SMR with CO2 capture. Successful experimental demonstration of the CSR concept will therefore give good grounds for further scale-up of this concept.

This project will demonstrate the technical and economic feasibility of a novel reactor concept, Chemical Switching Reforming (CSR), for pure hydrogen production from natural gas reforming with integrated CO2 capture. The CSR concept aims to combine the a dvantages of the excellent heat transfer and gas-solid mixing characteristics of fluidized beds with the controlled removal capability of membrane reactors, using a novel switching concept to achieve an inherently safe, high throughput and cost effective reactor operation. Environmentally friendly, pure hydrogen production is therefore achieved in a single reactor, while other methods, such as auto-thermal reforming, would require the inclusion of additional process constituents to achieve this outcome. Two existing experimental units will be upgraded with membrane bundles for use in this project. These units will be employed to prove the technical feasibility of CSR, gain operating experience with this novel reactor concept and provide experimental data for validating reactive multiphase flow models to be further developed in this project. These validated models will be used to project reactor performance to larger scales for the purpose of accelerating process scale-up and eventual commercialization in future projects. A simulated pilot scale CSR reactor will form the basis for an economic evaluation of the CSR concept within this project. Four work packages are included. All tasks are related to the proof of feasibility of the novel reactor concept. In WP1, a PhD candidate from NTNU will demonstrate the technical feasibility of CSR by cold experiments at SINTEF and hot reactor experiments at TU/e. In WP2, a postdoc researcher at SINTEF leads development of reactive multiphase flow models to be valida ted against experimental results from WP1. In WP3, the postdoc researcher will use these models to conduct an economic evaluation of the CSR concept. The entire project will be managed by SINTEF through WP4.