Chemical-Looping Coal Combustion – Results from the ACCLAIM project
Conference contribution, 2014
This work concerns the first 22 months of the 30-month ACCLAIM project. The project has involved both experimental activities in CLC pilots of 1.5 kW, 10 kW and 100 kW, as well as laboratory investigations and studies in a cold-flow model. Furthermore, investigations have been made using modelling with different approaches and with different aims.
The main result of the pilot operation is that several low-cost materials should be able to improve gas conversion significantly as compared to previously tested ilmenite. Promising low cost materials include iron and manganese ores. Two manganese ores were evaluated by operation in a 10 kW CLC reactor system. These materials are called Sinfin, and Mangagran. Both materials performed well with respect to gas conversion, and oxygen demand was clearly lower as compared to ilmenite. The production rate of fines suggested an expected lifetime of around 300 h for one of the manganese materials, Sinfin, which is a distinct improvement as compared to the Buriturama ore previously tested in the 10 kW unit.
Further, the fate of fuel contaminants like sulphur and nitrogen has been investigated. Models to describe fluidization and to predict conversion have been developed and are validated against operational data. Mathematical modelling and cold-flow modelling show possible ways of increasing process performance by modification of process or reactor design.
A 100 kW CLC unit was operated with a mixture of ilmenite and a Brazilian manganese ore called Buritirama, which had been tested in a previous project and had been found to be much more reactive than ilmenite, although concerns had been raised regarding the attrition resistance. The mixture of ilmenite and Buritirama gave significant improvements in gas conversion in comparison to ilmenite.