Heat effects in a membrane reactor for the water gas shift reaction

M.E. ADROVER; E. LÓPEZ; D. BORIO; M. PEDERNERA

Natural Gas Conversion VIII

ELSEVIER SCIENCE BV

Año: 2007; p. 183 - 188

Most of the hydrogen is produced industrially by steam reforming of hydrocarbons (mainly natural gas) or alcohols (e.g., for fuel cell applications). The process gas stream coming from the steam reformer is composed by H2, CO, CO2, H2O and small amounts of unconverted reactants (CH4). The CO concentration of the gas leaving the reformer must be reduced up to a specified level, with two main goals: 1) increase the H2 production rate and 2) purify the process stream. To these ends, the Water Gas Shift Reaction (WGSR) is widely used: The reaction is moderately exothermic and strongly controlled by the chemical equilibrium, which is favored at low temperatures. In small scale processes, such as the fuel processing for fuel cells (e.g., PEM cells) normally the WGSR is carried out at an intermediate temperature level, requiring large reactor volumes to reach the necessarily high CO conversions.An attractive alternative to increase the CO conversion is the membrane reactor (MR). The main idea of this design is the selective permeation of reaction products (e.g., H2) to shift the equilibrium towards products and consequently decrease the CO outlet concentration, or reduce the amount of catalyst for a desired conversion level. The purpose of the present work, where the performance of the MR is simulated and compared with that of the conventional fixed bed reactor (CR). To compare both types of reactors, two extreme operating conditions are selected: isothermal and adiabatic operations.