Hydrogen Production From Two-step Steam Methane Reforming In A Fluidized Bed Reactor

摘要

Based on the chemical looping (CL) concept, two-step steam methane reforming (SMR) system with a reduction/oxidation (redox) reaction of iron oxides to produce pure hydrogen is proposed. This system consists of fuel reactor (FR) and steam reactor (SR). The feasibility of producing pure hydrogen without any purifying steps in SR and the synthetic gas (syngas, CO + H_2) to the Fisher-Tropsch reaction in FR was evaluated. The effect of reaction temperature on the redox reactivity of iron oxides was determined in thermo-gravimetric analyzer (TGA) and the effects of gas velocity and reactant concentration on the reactivity at the isothermal condition in a fluidized bed reactor were determined. The conversion range of the optimum reaction (FeO → Fe_3O_4) in the two-step SMR system is found to be from 0 to 0.5 based on the iron oxides. In this condition, hydrogen (H_2) with CO-free and synthetic gas (syngas) having the H_2/(2CO + 3CO_2) molar ratio of 0.65 can be obtained in SR and FR, respectively. The solid inventory ratio of FR to SR to compensate the difference of reaction rates in the redox system of FeO/Fe_3O_4 is determined to be 2.9.