Release rule of gaseous phase pollutants during melting of fly ash from MSW incineration plant

The fly ash released from one municipal solid wastes (MSWs) incineration plant was adopted to to analyze the influences of different melting temperatures and sand additive amounts on the compositions and amounts of pollutants in flue gas during the melting process. The fly ash melting experiments were performed in a self-designed high-temperature tube-furnace with temperature controlled and the pollutants collected by a self-design exhaust gas collection system. The weight subtraction method, X-ray fluorescence spectroscopy, atomic absorption spectrometry and electrochemical process were used to analyze volatile matters and gaseous pollutants during melting. The thermodynamic model was used to simulate the production of volatile matters and gaseous pollutants under different melting temperatures and sand additive amounts. The results show that during fly ash melting at 1 000-1 600 ℃ (experiment temperature 1 450 ℃ and 1 550 ℃) and 10%-30% sand (weight ratio of SiO₂ to fly ash), the main pollutants in melting flue gas are the melting fly ash, HCl, H₂S, SO₂, etc. With the increase of the temperature and sand additive amount, the volatile matter (gas yield) increases, and the effect of the temperature is greater than that of the sand. The simulation values and the experimental values fit well, and the simulation values are slightly larger than the experimental ones. The main compositions of melting fly ash are sodium, potassium and chloride salts, and include some volatile Pb and Zn. The main compositions of slag are silicate, aluminate or aluminosilicate, as well as a little sulfide and chloride. The heavy metal leaching contents of slag melted at 1 450 ℃ with 15% sand are below the national inspection line.