COMPARISON OF SO2 CAPTURE CAPACITIES OF LIMESTONES AND DOLOMITES UNDER PRESSURE

The sulfur capture capacities of 11 limestones and six dolomites were determined by means of a pressurized thermogravimetric analyser. The d eterminations were made under conditions relevant to pressurized fluid ized bed combustion. The actual experiments were performed at two diff erent temperatures (850 and 950 degrees C) and at a pressure of 1.5 MP a. Additionally, some experiments were performed at atmospheric pressu re for comparison. The particle size of the samples was screened to 20 0-400 mu m. By using a thin (1 mm) sample layer diluted with an inert material (quartz sand), the external mass transfer and the interpartic le diffusion problems were excluded. For each experiment the conversio n versus time curve was determined. The results showed great variation s between different sorbent qualities. Conversions between 7 and 83% w ere measured. The sulfur absorption capacity order was approximately t he same under both atmospheric and pressurized conditions. Higher temp erature resulted in considerably higher conversion. The temperature ef fect differed between the absorbents and was clearly more pronounced f or the dolomites than for the limestones. This resulted in one absorbe nt being more efficient at 850 degrees C, while the other absorbent wa s more efficient at 950 degrees C.