Co-capture of PbCl2 and CdCl2 vapors in a high-temperature furnace by green-produced calcium carbonate/montmorillonite composite sorbent

Abstract

Injecting sorbent into the furnace is a promising technology for heavy metal emission control, and the development of high-performance in-furnace sorbents is of great importance. In this work, the thermal interaction behavior of calcium carbonate/montmorillonite (CM) composite sorbents at high temperatures and the adsorption of heavy metal chloride vapors were investigated. The adsorption performance of the green-produced calcium carbonate/montmorillonite composite sorbent for PbCl2 and CdCl2 vapors was investigated in a self-designed gas-solid two-phase rapid adsorption experimental system. The composite sorbent exhibited better adsorption performance for heavy metal chloride vapors than the single mineral sorbent. When the doping mass ratio of calcium carbonate was 30%, it exhibited superior heavy metal chloride vapor adsorption capacity at 700 ℃ and 800 ℃. The increase of adsorption temperature was beneficial to improved stability of heavy metal elements in the adsorption products. The addition of O2 promoted the adsorption of Pb and Cd by the sorbent, while the presence of CO2, SO2 and NO inhibited the adsorption of Pb and Cd. The characterization results indicated that the calcia-silica-alumina component of the CM composite sorbent underwent a series of thermal interactions at high temperatures. The presence of calcium changed the mineral evolution of the silica-alumina component, produced more active components, and promoted the high-temperature melting of the sorbent. In addition, the excellent pore properties of the CM composite at high temperatures facilitated the rapid diffusion of heavy metal chloride vapor, which also promoted the adsorption of heavy metals.