SIMULATION STUDIES OF AUTOTHERMAL REACTOR SYSTEM FOR H-2 PRODUCTION FROM METHANOL STEAM REFORMING

Steam reforming of methanol is a principal route for the production of hydrogen. Owing to the high endothermicity of this reaction, attentio n must be directed at energy-saving measures to improve production eco nomics. However, the novel concept involving the coupling of the oxida tion of the methanol (a strongly exothermic step) to the steam reformi ng reaction is an intuitively attractive operation for energy minimisa tion. This paper reports the results of a mathematical investigation o n the performance of a class of adiabatic dual-bed catalytic reactor s ystems with cylindrical and spherical geometries that may be used to p romote internal heat exchange for the coupled reaction network. Analys is shows that, while the coaxial cylindrical system and the dual-bed s ingle tubular reactor generally need optimal water-to-methanol feed ra tios of about 3-4, the spherical arrangement always requires a ratio l ess than 1 for equivalent or even better performance. The spherical re actor system in which the oxidation catalyst was placed in the inner s phere with steam reforming in the annular space showed the most promis ing performance in terms of reactor efficiency (about 80%) and H-2 pro duction (125 m(3) gas (m(3) reactor)(-1) s(-1)) while the coaxial reac tors exhibited the poorest efficiency (less than 10%) for a H-2 produc tion rate of 19.5 m(3) gas (m(3) reactor)(-1) s(-1). Thus the spherica l reactor with an inner oxidation catalyst bed is the most attractive configuration for this autothermal process in terms of product maximiz ation, feed and energy minimization.