Evaluation of a new DCFB reactor system for chemical looping combustion of gaseous fuels

A 120 kW(th) chemical looping combustion pilot plant, has been used to evaluate the performance of up to 10 different oxygen carrier materials within more than 1000 h of operation. It was one of the largest pilot plants, featuring a scale up ready design and auto thermal operation. Initially the plant was designed for nickel based oxygen carriers. During the evaluation of other materials, limitations of the reactor design caused by different design demands of the oxygen carriers have been identified. A new reactor system has been installed incorporating design adaptations to improve the reactor flexibility and performance. The new air reactor is narrower and allows higher gas velocities and high solid circulation rates, even at lower fuel loads. The upper loop seal, connecting the air reactor with the fuel reactor has been optimized to reduce a gas leakage between the reactors, identified in the old reactor system. The new fuel reactor consists of two sections, a lower part with a larger cross section and a narrower upper part. This allows larger specific inventories in the reactor and good gas/solid contact over the full reactor height. The new reactor system has been evaluated during a benchmark campaign, using a manganese based oxygen carrier which has also been used in the old unit. The results are reported in this work. The new design meets the design criteria, high solids circulation is possible, higher specific inventories can be operated and the gas leakage via the upper loop seal has been reduced significantly.