Polymer electrolyte membrane fuel cell grade hydrogen production by methanol steam reforming: A comparative multiple reactor modeling study

摘要

Analysis of a fuel processor based on methanol steam reforming has been carried out to produce fuel cell grade H_2. Six reactor configurations namely FBR1 (fixed bed reactor), MR1 (H_2 selective membrane reactor with one reaction tube), MR2 (H_2 selective membrane reactor with two reaction tubes), FBR2 (FBR1 + preferential CO oxidation (PROX) reactor), MR3 (MR1 + PROX), and MR4 (MR2 + PROX) are evaluated by simulation to identify the suitable processing scheme. The yield of H_2 is significantly affected by H_2 selective membrane, residence time, temperature, and pressure conditions at complete methanol conversion. The enhancement in residence time in MR2 by using two identical reaction tubes provides H_2 yield of 2.96 with 91.25 mol% recovery at steam/methanol ratio of 1.5, pressure of 2 bar and 560 K temperature. The exit retentate gases from MR2 are further treated in PROX reactor of MR4 to reduce CO concentration to 4.1 ppm to ensure the safe discharge to the environment. The risk of carbon deposition on reforming catalyst is highly reduced in MR4, and MR4 reactor configuration generates 7.4 NLmin~(-1) of CO free H_2 from 0.12 mol min~(-1) of methanol which can provide 470 W PEMFC feedstock requirement. Hence, process scheme in MR4 provides a compact and innovative fuel cell grade H_2 generating unit.