Insight into High Temperature Gas-Phase Arsenic Capture by a CaO–Ca12Al14O33 Synthetic Sorbent
Concerns about arsenic emission issues are growing as the arsenic discharged from coal-fired power plants seriously endangers the ecological environment and public health. The gas-phase arsenic capture by a CaO–Ca12Al14O33 synthetic sorbent at 1000–1200 °C in the simulated flue gas was conducted, with the influence of the addition ratio of Ca12Al14O33, temperature, retention time, and acid gases NO/SO2 considered in the study. The results indicated that the synthetic sorbent containing 15 wt % Ca12Al14O33 (Ca85Al15) exhibited much better arsenic adsorption performance than CaO, which was ascribed to the greatly strengthened sintering resistance of CaO particles by adding Ca12Al14O33, enabling arsenic adsorption and chemical reactions. Both the increasing temperature and retention time facilitated arsenic adsorption by Ca85Al15, and the hypertoxic arsenic vapor (As3+) was converted into arsenate (Ca3(AsO4)2) with less toxicity. In the presence of NO, the arsenic capture was gradually suppressed with increasing retention time. On the other hand, SO2 could slightly facilitate the capture of arsenic at 1000–1100 °C for 10 min; nevertheless, due to the formation of Ca4Al6O12SO4, the promotion effect was inhibited at a higher temperature and a longer retention time. In general, the study provided a basis for developing highly efficient solid sorbents toward controlling arsenic vapor emission derived from coal combustion, and the appropriate conditions for arsenic capture were at 1000–1100 °C.
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