MODELLING STUDIES ON METHANOL STEAM REFORMING FOR HYDROGEN PRODUCTION

Abstract

Hydrogen is a potential alternative fuel which is easily available, environment friendly clean fuel, and act as an energy carrier which has highest specific energy content of all conventional fuels. There are many fuels available for the production of hydrogen but methanol is considered as renewable resources which can be produced by non conventional as well as conventional energy resources. There are many methods available for hydrogen production; laboratory scale, reforming and non reforming processes. Steam reforming of methanol (SRM) over Cu-based catalysts with different support and promoters has good potential to obtain high yield of hydrogen. Methanol steam reforming possesses a complex reaction system and several undesired reaction paths, as a result some undesired product such as CO, CO2 and CH4 are also formed in substantial amount with the product stream. Purification of hydrogen is necessary and important before its subsequent use in fuel cell. PROX and WGS reactor are used with the reformer to reduce the concentration of CO in the feed. The removal of hydrogen from the reactor by using H2 selective membrane which enhances the H2 yield with high purity and suppresses the CH4 production. Several modifications are required in the reforming process to produce H2 rich gas in comparison to conventional reforming process. One dimensional, isothermal, steady state mathematical models have been developed for fixed bed and membrane reactor. Two reactor configurations are considered for simulation; fixed bed reactor (FBR) and membrane reactor MR (H2 selective Pd/Pd-Ag membrane reactor with one reaction tube). Langmuir-Hinshelwood (L-H) kinetic expressions are taken for the mathematical model. Mass balance is done on all the gaseous components present for two reactor configurations FBR and MR for getting model equations. These model equations for fixed bed and membrane reactors are solved simultaneously using ode45 toolbox in MATLAB. The performance of membrane reactor has been analysed and compared with fixed bed reactor in terms of conversion, molar flow rates, and product yield at S/M ratio 2, temperature 593 K and pressure 1 atm. Hydrogen yield is increases to 2.76 using H2 selective membrane in a reactor. Comparison of hydrogen yield, molar flow rates and conversion are also analysed on different steam to methanol ratio for both FBR and MR. The studies shows that the by increasing S/M ration hydrogen yield is increasing in a significant amount. By using MR, a better hydrogen yield with high purity and lower CO concentration is obtained as compared to FBR