The migration and volatilization of toxic elements during briquette pyrolysis procedure

Briquetting technique can be an excellent energy saving utilization of pulverized coal, and the thermal chemical treatment of briquette has attracted the extensive attention of researchers due to its efficiency and applicability. To reveal the migration and volatilization characteristic of toxic trace elements (As, Se and Cd) during pyrolysis procedure of briquette, this paper studied the effects of mineral composition, pyrolysis parameters and occurrence state on element migration by multidisciplinary methods. Results show that the migration of toxic elements from solid phase to tar and gas phase are accelerated by increasing the pyrolysis temperature. Except for temperature, both the occurrence states and lower boiling point jointly determine release of element Se, while release behavior of As and Cd is mainly attributed to the occurrence states. At the pyrolysis temperature interval of 500–800 °C, the volatilization ability of toxic elements following the trend of Se > Cd > As. The element oxides SiO2 have a strong affinity to elements Cd and As with high correlation index, which play a key role on Cd and As elements absorption during heat treatment to prevent emission. Due to the easily vaporized characteristics of Se, some other suitable measures should be explored to reduce environmental pollution.