Chlorine evolution characteristics during lab-scale combustion of MSW pyrolysis char obtained from 200 t/d pyrolysis demonstration plant.

Pyrolysis is an effective method for treating municipal solid waste (MSW). Chlorine in MSW causes the production of dioxins, chlorine gas (Cl2), hydrogen chloride (HCl) and some other chlorine-containing compounds, and these chlorine-containing compounds are also very harmful to the environment and human health. This study investigates chlorine evolution during the combustion of chlorine-rich MSW pyrolysis char obtained from a 200 t/d MSW pyrolysis demonstration (DEMO) project under industrial conditions. The speciation and distribution of chlorine within the MSW pyrolysis char were meticulously examined via X-ray fluorescence (XRF) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses. The results indicate that the pyrolytic char contains 9.28 % chlorine, with 12.83 % as organic chlorine (organic-Cl) and 87.17 % as inorganic chlorine (inorganic-Cl). After combustion, the ash retains 5.65 % chlorine, all in the form of inorganic-Cl. During combustion, organic-Cl is released as HCl gas. Meanwhile, inorganic-Cl is converted to Cl2 or evaporates as alkali metal chlorides. These chlorides later react with metal oxides to form HCl gas. Thermogravimetry-fourier transform infrared spectroscopy-mass spectrometry (TG-FTIR-MS) analysis indicates that organic-Cl dissociates as C-Cl and releases HCl between 220-320 °C and Cl2 between 400 °C -550 °C. The microporous structure of MSW pyrolysis char significantly affects its combustion behavior. It facilitates the diffusion of chlorine-containing gases. Increasing pyrolysis temperature and time can reduce the chlorine content of MSW pyrolysis char. These findings provide valuable insights for MSW pyrolysis char reuse.