Steam Sterilizing Treatment Process For Medical Waste And Heat Mass Transfer Models In Moist Sterilization

Medical waste treatment is a new field in environmental engineering. More and more attentions have been paid to medical waste steam treatment technology for its low investment and treatment cost, and the researches on this technology become very important both in theory and practice.Two correlated parts were studied in this paper. The first part was about steam sterilizing process for medical waste. Based on theoretical analysis and experimental verification, various interrelations of factors such as air remnant, chamber temperature and sterilizing time were investigated. The experiments showed that the more air remained, the lower temperature reached in chamber, and air remnant extended heat transfer time and impaired sterilizing performance. It was found that the liquid waste needed less sterilizing time than solid waste. The relationships among the killing rate of bacillus stearothermophilus, thermal death time and temperature were formulated and the relations between air remnant, pressure and temperature in sterilizing chamber were also developed in this part.How to determine sterilizing time is quite critical in medical waste sterilization. It includes thermal death time and heat transport time. The former depends on bacteria: the later involves heat mass transfer.The second part was about heat mass transfer models in moist sterilization process,from which the heat transport time could be theoretically calculated. Medical wastes were divided into dense media and porous media. One dimensional heat and mass transfer models were established from one piece of waste from each media respectively. The calculation results demonstrated that dense material needed less heat penetrating time.The parameters involved in the heat mass transfer models in porous media were estimated. By adopting desorption apparatus, multivariable optimization method, and comparing calculated moisture evaporation amount with measured ones, the relations between moisture diffusion coefficient and moisture content were determined. The relations among moisture diffusion coefficient, moisture content and temperature were then derived. Sorption method and optimal approach were used to measure and calculate moisture increase values and temperature, by which the relational expressions among thermal diffusion coefficient, moisture content and temperature were obtained.In the end, the heat and mass transfer models in porous media were numerically...