Study On the Pyrolysis Characteristics of Biomass Compositions In Medical Wastes

Study on the Pyrolysis Characteristics of Biomass Compositions in Medical Wastes

DENG Na*, Wang Weiwei, ZHANG Yu-feng, MA Hong-ting

（School of Environmental Science & Engineering, Tianjin Uninversity, Tianjin 300072, China)

Abstract: To obtain pyrolysis characteristics of biomass compositions in medical wastes, thermogravimetric study of cotton swabs, toilet paper, gauze, absorbent cotton was carried out using the thermogravimetric analyser (TGA) with N₂. The heat change in pyrolysis process was analyzed and the properties of pyrolysis residues are reported. The overall mathematics model with two-step and four-reaction was established to simulate the pyrolysis processes. The results show that:(1) The decomposition processes of toilet paper, gauze and absorbent cotton appear one obvious stage in 260~420℃, whose pyrolysis mechanisms are in agreement with cellulose, their main ingredient. The pyrolysis of cotton swabs occurs at lower temperature than other three samples, with the weight loss at the temperature range of 207~417℃. A shoulder peak is observed on the left of the main DTG (differential thermogravimetric) peak of cotton swabs corresponding to semi-cellulose decomposition. (2) Due to the influence of the solvent used during the papermaking process, the maximum rate of weight loss of toilet paper takes place at 371℃ lower than 383℃ of the other three ones. (3) All the biomass medical wastes present endothermic pyrolysis reaction.  The peak temperatures of DTA (differential thermal analysis) are a little higher than that of DTG for the delay of heat transfer. (4) All of the pyrolysis residues of the samples are black fluffy carbon-like solid matter, which could reflect the traits of original material. (5)The established model could satisfactorily describe the weight loss and differential process of the above four biomass samples.

Keywords: medical waste; biomass; pyrolysis characteristics; kinetic model