Evaluation of so2 sorbent utilization in fluidized beds

A bench-scale fluidized-bed reactor was used to evaluate more than forty limestone and dolomite samples from twenty-five deposits and quarries in Nova Scotia, New Brunswick, and Alberta for their ability to capture SO2 emitted during the fluidized-bed combustion of coal. Nineteen of the samples were also evaluated by thermogravimetric analysis; a comparison of the two methods is given. The detrimental effect of coal ash on the sulphation capacities of two limestones was studied. Sulphation appears to decrease with increasing iron oxide content in the ash. Various methods of improving the limestone utilization in fluidized beds were investigated. Finely ground and pelletized limestone improved the sulphation capacity as much as five times that of the coarse limestone. Similar improvements were observed by hydrating partially sulphated bed material, and also by grinding and pelletizing used bed material. The parameters of the sulphation curve equation derived from the FBR tests are incorporated with the operating data for large-scale fluidized-bed units in the Argonne National Laboratory model to predict the performance of the sorbents in those units. The model prediction compares very well with actual data from a pilot-scale fluidized-bed and the Summerside fluidized-bed combustor.