UTILIZATION OF HIGHLY IMPROVED FLY ASH FOR SO_2 CAPTURE

概要

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A fly ash of low calcium content (1.67 wt% CaO) was ground (to particle sizes ofunder 5 μm) and treated with slaked lime (Ca(OH)2) to produce an improved sorbent for high-temperature dry sorbent injection. Four samples were treated at 350 K for 8 hours with different Ca(OH)2 concentrations (6.6–28.6 wt%). The specific pore surface area and pore volume were extensively characterized before and after treatment. Sulfation tests were performed by exposing the treated samples to a 0.31 vol% SO2 containing atmosphere at 1123 K in a thermo-gravimetric analyzer (TGA). The TGA experimental conditions were carefully controlled to closely simulate those encountered in an atmospheric fluidized bed combustor (AFBC).The treated fly ash sorbents showed higher SO2 sorptivity compared to untreated sorbents. The sorption capacity was found to increase as the Ca(OH)2 concentration increased in the range of interest. Up to 92% CaO conversion could be achieved when the 28.6% Ca(OH)2 fly ash sorbent was sulfated for 1 hour. Treatment of fly ash with Ca(OH)2 enhanced the specific surface area (by about 5 to 8 times), which was principally responsible for the high SO2 capture.
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