Sulfur Tolerance and Rate of Oxygen Release of Combined Mn–Si Oxygen Carriers in Chemical-Looping with Oxygen Uncoupling (CLOU)

Abstract

Sulfur tolerance and rate of oxygen release of combined Mn–Si oxygen carriers for chemical-looping with oxygen uncoupling (CLOU) is investigated. The oxygen carriers were produced by spray-drying and calcined at 1150 °C. The resistance toward sulfur and the rates of oxygen release were evaluated in a laboratory-scale fluidized-bed reactor. It was found that the combined Mn–Si oxygen carrier is tolerant to SO2, at least up to a partial pressure of 5000 vppm. The rates of oxygen release were determined in the temperature range of 975 to 1100 °C using devolatilized wood char as fuel while fluidizing with N2, to maintain a low oxygen partial pressure surrounding the particles. The Arrhenius parameters ko and Eapp for the release of oxygen were estimated for the investigated materials assuming a zero-order reaction with respect to oxygen. The rates of oxygen release were relatively high, particularly at above 1050 °C. From the obtained reaction rates, the solids inventory required for combustion of coal was determined to be as low as 40 kg/MWth in the fuel reactor at 1100 °C. The results indicated that combined Mn–Si oxygen carriers could be interesting materials for the CLOU process by virtue of their resistance to sulfur deactivation and high rate of oxygen release.