Distribution Rule of Gaseous Phase Salts During Melting of Fly Ash from MSW Incineration Plant

The secondary fly ash problem in the application process of fly ash of municipal solid waste incineration (shorter form: fly ash) melting treatment technology has become a constraint. It is beneficial to the development of harmless and resource utilization technology of secondary fly ash by mastering the distribution law of salt in the gas phase product of fly ash melting, and it can be used as a reference for the design of tail gas purification equipment and operation. The fly ash released from one municipal solid wastes incineration plant in Jiangsu Province was adopted. The fly ash melting experiments were performed in a self-designed high-temperature pilot-scale plasma arc furnace system. The weight subtraction method, X-ray fluorescence spectroscopy, atomic absorption spectrometry and electrochemical process were used to analyze melting fly ash and slag during melting and to abtain gaseous phase migration rate of Na, K, Ca, Mg and Fe. The thermodynamic model was used to simulate the distribution rules of gaseous phase salts at 1000~1600 ℃, with 0~50% auxiliary material, at different atmosphere (without gas, nitrogen or air) and 0~12% water content of fly ash. The simulation results showed that NaCl, (NaCl)2, KCl, (KCl)2, CaCl2, KCaCl3, KMgCl3, FeCl2 etc. were main compositions of gaseous phase salts during fly ash melting. These compositions distribution was greatly effected by melting temperature and was little effected by melting atmosphere, auxiliary material amount and water content of fly ash. At atmosphere, there were new product Na2SO4 in gaseous phase salts. The simulation values and the experimental values of gaseous phase migration ratio of Na and K fitted well, and the simulation values were largely smaller than the experimental ones of Ca, Mg and Fe. It is suggested that the distribution law of gaseous product salt should be used to develop the technology of salt separation or chloride salt utilization, so as to realize the comprehensive utilization of secondary fly ash, change the current situation that the secondary fly ash is mainly landfill, and thoroughly realize the harmless and resource utilization of fly ash. © 2021, Editorial Department of Advanced Engineering Sciences. All right reserved.