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.

The enrichment characteristics of trace elements (Cr, Mn, Co, Ni, Cd, Pb, Hg, As, Se) were investigated under air and O2/CO2 atmosphere during fluidized bed coal combustion. Results showed that Co, Ni, Cd, Pb, Hg, As, Se were more volatile than Cr and Mn. The increase of temperature promoted Mn, Co, Ni, Cd and Pb to migration from bottom ash to fly ash, and contributed Hg, As and Se to vapor phase. Cr, Mn, Co, Cd, Se tended to decrease in bottom ash and increase in fly ash during oxy combustion, while 21%O2/79%CO2 atmosphere led to the emission of gaseous As and the enrichment of Ni, Pb in both bottom ash and fly ash. With the increase in O2 concentration, the relative enrichment of all the trace elements except As increased, suggesting that their volatility were inhibited. Adding limestone and mixture of limestone and kaolinite had an inhibiting effect on volatilization of trace elements (especially Mn, Cd, Pb, Hg, As, Se) and the inhibiting behavior was strengthened under the oxy atmosphere.

No abstract

Coal-red power plants are the main sources of atmospheric Pb. The mineral composition of coal is an important factor of the trace element distribution. The Pb volatilization characteristics of the anthracite, lignite and bitumite were examined in the horizontal tube furnace. SiO 2 , Al 2 O 3 , CaO and Fe 2 O 3 were chosen as the mineral compositions and PbO was chosen as Pb source to investigate the e ect of minerals on Pb volatilization during coal combustion. The results indicated that the occurrence modes of Pb and mineral composition were major factors in Pb volatilization and the coal containing more silicon and aluminum had the lower Pb volatilization rate. The intrinsic minerals in coal immobilized the released Pb through both physisorption and chemisorption. The combustion and thermogravimetric investigation showed that the Pb capture e ciency of the four minerals ranked as SiO 2 >Al 2 O 3 >CaO>Fe 2 O 3 . The formation of the non-volatile materials such as PbSiO 3 , Ca 2 PbO 4 and PbFe 12 O 19 accounted for the capture mechanisms of SiO 2 , CaO and Fe 2 O 3 , while Al 2 O 3 stabilized Pb via the physisorption. The synergy of SiO 2 and Al 2 O 3 exhibited the most superior capture e ciency on Pb, which provided references to the preparation of oriented Pb removal adsorbent.