No abstract

Decreasing the reduction temperature of an oxygen carrier is the key to reduce energy consumption further and avoid the operational difficulties of chemical looping air separation (CLAS). The copper manganese composite oxygen carrier with zirconia as an inert binder, which has a relatively low temperature of oxygen uncoupling, was developed. In the packed-bed reactor, effects of several important operating parameters, viz., the feed gas rate, temperature, and inlet oxygen concentration, on the separation reactivity were discussed. At higher reaction temperatures, the reduction reactivity increases but the oxidation reactivity decreases. In comparison to a copper oxygen carrier, the equilibrium oxygen concentration of the copper manganese oxygen carrier is greatly enhanced. High gas flow rates can accelerate the separation reaction. In the reduction step, a lower oxygen concentration leads to a higher reduction reactivity. In the oxidation step, the higher oxidation reactivity requires higher oxygen concentrations. The oxygen uncoupling kinetics was determined by the lnln kinetic method. The separation activation energy was determined at 162.95 kJ mol–1, and the most likely mechanism function is the unreacted shrinking core model (R 2). The main compositions in fresh and oxidized composite oxygen carriers are Cu x Mn3–x O4 and ZrO2. After reduction, the active phase compositions are transformed into Cu x Mn2–x O2. The inert phase of ZrO2 is stable during the redox reaction. The repeated separation capability of the composite oxygen carrier over 20 consecutive redox cycles is high.

This work proposes a chemical looping method to achieve the coproduction of N2 and H2. The system include a fuel reactor, a H2 generator and a N2 generator. Thermodynamics analysis is carried out to evaluate the feasibility of this method. In the fuel reactor, when the reaction temperature is 1000°C, 1.067kmol Fe and 0.851kmol FeO can be transported to the H2 generator and 2.991kmol syngas is produced. In the H2 generator, when the reaction temperature is 500°C, 0.223kmol Fe, 0.485kmol FeO and 0.425kmol Fe3O4 can be transported to the N2 generator and 1.250kmol H2 is produced. In the N2 generator, when the reaction temperature is 600°C, 1kmol Fe2O3 can be transported to the fuel reactor and 1.484kmol N2 is produced.