Thermogravimetric characteristics and different kinetic models for medical waste composition containing polyvinyl chloride-transfusion tube

DENG Na(邓娜), WANG Wei-wei(王维维), CUI Wen-qian(崔文谦), ZHANG Yu-feng(张于峰), MA Hong-ting(马洪亭)

(School of Environmental Engineering, Tianjin University, Tianjin 300072, China)

Abstract:Thermogravimetric study of medical transfusion tube (MTT) waste containing polyvinyl chloride (PVC) was carried out using the thermogravimetric analyser (TGA) with N₂, at different heating rates of 5, 10, 20, 30, 50 °C/min. The purpose is to obtain pyrolysis characteristics and kinetic parameters of medical waste. The experimental results indicate that the pyrolysis behavior of the MTT sample is in agreement with its main ingredient of PVC, appearing two stair stepping stages. The influence of the additives in MTT on pyrolysis behavior was also revealed, which could improve MTT pyrolysis at lower temperature in the first stage, and cause obvious unsmoothness and asymmetry of the second DTG peak. Four n-order kinetic models of Coats-Redfern, Ozawa, Kissinger and Freeman-carroll were used to get the kinetic parameters. Furthermore, a novel “two-step four-reaction model” was established to simulate the whole continuous process. The different methods and the kinetic parameters thus obtained were discussed and compared with each other in literatures. The reasons of deviation among kinetic values were tried to be elucidated. The new established model could more satisfactorily describe the pyrolysis process of MTT, being more mechanistic and conveniently serving for the engineering.

Key words:medical waste; polyvinyl chloride (PVC); medical transfusion tube (MTT); pyrolysis characteristics; model