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.