Zhongxiang Chen

Novel circulating fast fluidized-bed membrane reformer for efficient production of hydrogen from steam reforming of methane

The coupling of steam reforming and oxidative reforming of methane for the efficient production of hydrogen is investigated over Ni/Al2O3 catalyst in a novel circulating fast fluidized-bed membrane reformer (CFFBMR) using a rigorous mathematical model. The removal of product hydrogen using palladium hydrogen membranes “breaks” the thermodynamic equilibrium barrier exists among the reversible reactions. Oxygen can be introduced into the adiabatic CFFBMR for oxidative reforming by direct oxygen (or air) feed and through dense perovskite oxygen membranes. The simulations show that high productivity of hydrogen can be obtained in the CFFBMR. The combination of these two different processes does not only enhance the hydrogen productivity but also save the energy due to the exothermicity of the oxidative reforming. Based on the preliminary investigations, four parameters (number of hydrogen membranes, number of oxygen membranes, direct oxygen feed rate and steam-to-carbon feed ratio) are carefully chosen as main variables for the process optimization. The optimized result shows that the hydrogen productivity (moles of hydrogen produced per hour per m3 of reactor) in the novel CFFBMR is about 8.2 times higher than that in typical industrial fixed-bed steam reformers.

Simulation for steam reforming of natural gas with oxygen input in a novel membrane reformer

The performance of a novel circulating fast fluidized bed membrane reformer (CFFBMR) is investigated using a reliable mathematical model. The removal of product hydrogen using hydrogenpermselective membranes ‘‘breaks’’ the thermodynamic equilibrium in the reversible system and makes it possible to operate the process at lower temperatures. The oxidative reforming of a part of the feed methane by oxygen input into the reformer using direct feed or through oxygen-permeable membranes supplies the heat needed for the highly endothermic steam reforming of methane. The combination of the exothermic oxidative reforming and endothermic steam reforming not only produces high yield hydrogen but also makes it possible to operate the CFFBMR under autothermal conditions. The novel configuration is a highly efficient hydrogen producer with minimum energy consumption. The simulation results show that the hydrogen productivity (moles of hydrogen produced per hour per m 3 of reactor) of the CFFBMR is about 8 times that in an industrial fixed bed and 112 times that in a bubbling fluidized bed membrane reformer. D 2003 Published by Elsevier Science B.V.

Efficient Production and Economics of Clean-Fuel Hydrogen∗

This paper briefly discusses the following main issues: 1. The future of the hydrogen economy. 2. Thermo-chemistry of hydrogen production for different techniques of autothermal operation for different feedstocks. 3. Improvement of the hydrogen yield and minimization of reformer size by contining fast fluidization with hydrogen and oxygen membranes and with in-situ CO 2 sequestration. 4. Efficient production of hydrogen using a novel membrane-circulating fluidized-bed autothermal reformer. 5. Preliminary investigation of the economics of hydrogen production using these novel technologies. 6. Novel gasification process for the direct production of hydrogen from biomass. It is shown that a hydrogen economy is not a myth as some people advocate, and that with well-directed research it will represent a bright future for humanity to utilize a clean, everlasting fuel that is also free of deadly conflicts for the control of energy sources. It is also shown that efficient autothermal production of hydrogen using novel reformer configurations and a wide range of feedstock is a very promising route for achieving a successful hydrogen economy. A novel process for the production of hydrogen from different renewable biomass sources is presented and discussed. The process combines the principles of pyrolysis with the simultaneous use of catalysts, membranes and in-situ CO2 sequestration to produce pure hydrogen directly from the unit.

Practical Implications of Bifurcation and Chaos in Chemical and Biological Reaction Engineering

This paper concentrates on the practical implications of bifurcation and chaos on novel approaches for the production of the clean fuels: hydrogen and ethanol, and the simulation of the acetylcholine neurocycle in the brain. One problem from the field of chemical reaction engineering and two from the field of biological reaction engineering, the three problems have one thing in common: the practical implications of bifurcation and chaos. The novel approach for hydrogen production is based on a novel circulating fluidized bed catalytic membrane reformer configuration achieving, simultaneously, both autothermicity and breaking the thermodynamic barriers using different techniques (membranes and/or CO2 sequestration). The static bifurcation characteristics of the autothermic process and their implications on design and operation for maximum hydrogen yield and productivity are addressed. Experimental set-up for this novel process is being developed at University of British Columbia (UBC).The novel approach for the ethanol production does not use a novel configuration, however it uses a classical configuration but with a novel mode of operation. A CSTR fermenter is used exploiting bifurcation and chaos theories to maximize ethanol yield and productivity. The sequence of research work consisted of: developing a reliable and relatively simple model to describe the fermentation process, verification of the model against experimental results, using the model in an extensive bifurcation and chaos analysis investigation to identify the regions of bifurcation and chaos and their characteristics. This is followed by using these results to guide an experimental investigation of bifurcation and chaos and their implications on improving ethanol yield and productivity.This paper also introduces our preliminary efforts to investigate the bifurcation and chaotic behavior of acetylcholine neurocycle in the brain using diffusion-reaction models in order to gain some insight into their possible connection to Alzheimer and Parkinson Diseases (AD/PD).