Low-temperature microwave co-pyrolysis of medical waste and walnut shells: effective regulation of organic chlorine to inorganic chlorine conversion in pyrolyzed char

To regulate the migration and transformation of chlorine in the pyrolysis process of medical waste, this study utilized microwave pyrolysis technology for co-pyrolyzing medical gloves (MG) with walnut shells (WS). Furthermore, we innovatively combined microwave thermogravimetry to explore the migration and transformation mechanisms of chlorine under varying temperatures and mix ratios. Under microwave pyrolysis alone, the chlorine in MG mainly existed in the form of HCl and organic chlorine in oil. When WS was added, the chlorine element in HCl migrated to the char, while the organic chlorine in the char was converted to inorganic chlorine. Under optimal microwave co-pyrolysis conditions, the chlorine content in pyrolysis oil decreased to ∼5 %, while chlorine fixation by pyrolysis char reached 65.63 mg/g, a 35.45 mg/g increase compared to MG pyrolysis alone. Through the characterization of pyrolysis char, it was found that the metal oxides in WS could absorb HCl and immobilize it in the form of metal chlorides in the char, thus effectively reducing the generation of HCl. This study successfully achieved efficient fixation of chlorine while improving the quality of pyrolysis oil and gas, which provides a new idea for the thermal treatment and resource recycling of PVC-containing medical waste.