Operating experience with chemical looping combustion in a 120 kW dual circulating fluidized bed (DCFB) unit

摘要

This study presents first operating experience with a 120 kW chemical looping pilot rig. The dual circulating fluidized bed reactor system and its auxiliary units are discussed. Two different oxygen carriers, i.e. ilmenite, which is a natural iron titanium ore, and a designed Ni-based particle, are tested in the CLC unit. The pilot rig is fueled with H sub(2), CO and CH sub(4) respectively at a fuel power of 65-145 kW. High solids circulation, very low solids residence time and low solids inventory are observed during operation. Owing to the scalability of the design concept, these characteristics should be quite similar to those of commercial CLC power plants. Ilmenite shows a high potential for the combustion of H sub(2)-rich gases (e.g. from coal gasification with steam). The H sub(2) conversion is quite high but there is still a high potential for further improvement. The Ni-based oxygen carrier achieves the thermodynamic maximum H sub(2) and CO conversion and also very high CH sub(4) conversion. A variation of the air/fuel ratio and the reaction temperature indicates that the Ni/NiO ratio of the particle has an influence on the performance of the chemical looping combustor. Generally, low solids conversion in air and fuel reactors is observed in almost any conditions. Despite a very low H sub(2)O/CH sub(4) molar ratio, no carbon formation is observed.