Scaling Relations for Autothermal Operation of Catalytic Reactors

Abstract

Autothermal operation (AO) has several advantages for carrying out highly exothermic catalytic partial oxidation (CPO) and/or oxidative dehydrogenation (ODH) reactions compared to traditional cooled multitubular reactors. In steady-state autothermal operation (AO), there is no heat addition to the reactor or intentional heat removal by cooling through reactor walls; the heat of reaction is removed mainly by convective flow of the cold feed. The existence of an ignited high temperature (and conversion) state at the lowest possible feed temperature and/or space time is essential. This work examines the impact of various design and operating variables on the feasibility and economic scale-up of shallow packed-bed catalytic reactors for autothermal operation. Specifically, we present scaling relations that can be used to examine the impact of effective bed thermal conductivity, bed length, particle size, catalyst activity, reaction kinetics, and operating pressure on the extinction (blow-out) flow rate or feed temperature for large scale autothermal CPO and ODH reactors operated close to the adiabatic limit. The scale-up relations derived for a single-step CPO/ODH reaction are verified by numerical simulations. They are also validated using the highly complex oxidative coupling of methane (OCM) as an example.