Modeling and analysis of ceramic-carbonate dual-phase membrane reactor for carbon dioxide reforming with methane

摘要

A new high temperature tube-shell membrane reactor (MR) design for separation and utilization of CO_2 from the flue gas and for simultaneous production of syngas through carbon dioxide reforming of methane (CRM) is reported. The MR is based on a dual-phase CO_2 permeation membrane consisting of mixed-conducting oxide and molten carbonate phases. High temperature CO_2-containing flue gas and CH_4 are respectively fed into the shell and tube sides of the reactor packed with a reforming catalyst. Under performance conditions, CO_2 permeates selectively through the membrane from the shell side to the tube side and reacts with CH_4 to produce syngas. Additionally, the heat from the flue gas can transfer directly through the membrane to provide energy for the endothermic CRM reaction. An isothermal steady-state model was developed to simulate and analyze CRM in the MR in this work. The effect of the design and operational parameters, such as inlet CH_4 flow rate, shell side CO_2 partial pressure and the flue gas composition, i.e., containing O_2 or not, as well as the membrane thickness on the reactor performance with respect to the CH_4 conversion and the CO_2 permeation flux were investigated and discussed. The results show that the MR has a high efficiency in separating and utilizing CO_2 from the flue gas. For a CH_4 space velocity of 3265.31 h~(-1), with a membrane thickness of 0.075 mm and the shell side CO_2 partial pressure of 1 atm, a CH_4 conversion of 48.06% and an average CO_2 permeation flux of 1.52 mL(STP) cm~(-2) min~(-1) through the membrane tube at 800 ℃ are obtained. Further improvement of the MR performance can be achieved by involving O_2 in the permeation process.