Pyrolysis Characteristics And Kinetic Model Studies Of Medical Solid Wastes

Pyrolysis technology is regarded as a most potential thermochemistry treatment technology for medical wastes. The hinge of its technologic development and design consists in the through knowledge on pyrolysis characteristics of medical wastes. In this dissertation,organic medical wastes compositions are divided into 7 kinds by main component characteristics,and 18 typical compositions are selected from above kinds of wastes for the serial experimental and modeling study on pyrolysis characteristics. The main work and results are as follows:1. Experimental and modeling study on pyrolysis characteristics of monocomponent medical waste:(1) Proximate analysis, ultimate analysis and LHV of the most of medical waste compositions are obtained by experiment to provide basis datum for pyrolysis characteristics study.(2) Non-isothermal kinetic tests are carried out using a thermogravimetric analyzer (TGA) with N₂ for thermal degradation of monocomponent medical waste. According to TG/DTG curves, taking account of sample information of main component, proximate analysis, and ultimate analysis, in detail, mechanism analyzing of pyrolysis reaction reasonably explain and describe weight loss behavior of all samples; according to DTA curves, the study reports heat change in pyrolysis process; the properties of pyrolysis residues of waste samples are also given in the dissertation. The results reveals that pyrolysis behaviors are complicated, and evidently differ from heterogeneity of waste materials; by reason of difference in characteristic impurity and treating process for medical wastes aiming to special purpose for medical service, even in homogeneous waste sample, the pyrolysis characteristics vary from each other too.(3)Three conventional methods: Coats-Redfern,Ozawa and Kissinger are used to determine the kinetics parameters on thermal degradation all medical wastes. The results are discussed and compared with a view of pyrolysis mechanism.(4) A unitive mechanism is put forward on pyrolysis for single medical waste composition, and the corresponding model could satisfactorily describe thermal degradation process of all samples. The effect of the original waste compositions and all their product with different pyrolysis time or temperature in process could be estimated based on the model, which could effectively direct and optimize designwork of pyrolysis reactor.2. Experimental and modeling study on pyrolysis characteristics of mixed-medical waste compositions:(1) Typical binary compositions chosen from each kind of medical wastes are pyrolyzed in the TGA, the result shows:â‘ Significant or weak reactions are observed between chloric tube for transfusion and other samples;â‘¡In thermal degradation process of mixtures containing catheter and other components, the DTG peak temperature representing CaCO3 decomposition in catheter sample is obviously lower than that of catheter monocomponent; While, the shape of the DTG peak keeps unchanged.â‘¢No evident reaction occurs between the other mix-samples, it is considered that their co-pyrolysis characteristics be chalinear superposition of monocomponent pyrolysis characteristics.(2) Pyrolysis experiment is carried out in the TGA when tube for transfusion is blended with gauze at different ratio. Based on reaction mechanism, pyrolysis behavior of mixtures is roundly analyzed. Hereinto, author puts forward an intro-reaction model on pyrolysis of bicomponent medical wastes, which accords with the tube for transfusion/gauze experimental process nicely; vice versa, also validates the experimental reaction mechanism. In addition, laboratory-made batch fixed-bed apparatus was used to pyrolysis crude medical wastes at 700℃. Emission, residue and fuel compositions detection reveal that pyrolysis technology could significantly convert waste to energy product with least pollution.