Study On The Melting Characteristics Of Medical Glass And Medical Waste Slag

Medical wastes include infectious, toxic and radioactive wastes and belong to hazardous wastes, such as chemical wastes, infectious wastes and contaminated sharps and so on. Incineration has been identified as the best disposal option for medical wastes because it is harmless and realizes a large reduction in volume as well as resources recovery. The compositions and characteristics of medical wastes and medical waste slag are important parameters for improving incinerator design, operation and control. Generally, large amounts of medical glass bottles present in medical wastes have rather low fusion temperatures and couldn't participate in combustion. Therefore medical glass composes the principal component of medical waste slag and influences the melting characteristics of slag badly. When medical wastes are incinerated in a rotary kiln incinerator, medical glass is heated and melted. Molten glass may adhere to the inner wall, leading to slagging. In other cases, the molten glass probably tumbles and rolls, bonding to other slag particles;finally large slag agglomerates are formed, blocking the exit of rotary kiln. Therefore, the melting characteristics of medical glass and medical waste slag are important for optimizing medical waste incineration and preventing slagging of rotary kiln incinerators.The composition and fusion temperatures of medical glass, collected from a medical waste disposal center, were analyzed and compared with medical waste slag, biomass ash and coal ash. The contribution of glass components to fusion temperatures of medical glass was investigated by comparing different glass samples.Softening temperature was increased with a rise of SiO2 and CaO content, whereas it was declined sharply while B2O3 and Na2O content increased. The fusibility of blended glass was researched by adjusting the proportion of several medical glasses. Using coal ash slagging indices, the slagging propensity was assessed for medical glass.The effects of glass components on the melting characteristics of medical glass have been researched by the SiO2 replacement method. The experimental results showed that different components played quite different influences on fusion temperatures;that of Na20 was the most marked. The softening temperature and flow temperature decreased 19.8℃and 34.0℃respectively with every 1% rise of Na2O content. Predictive functions of four characteristic melting temperatures have been obtained by simplifying the multi-variant Taylor series. And predictive functions were verified by testing glass samples.The calculated results revealed that predictive values of fusion temperatures tallied well with experimental values.In order to investigate the effects of medical waste slag on incinerator operation, medical waste slag samples were collected from a medical waste disposal center to analyze their chemical components, microscope structure, mineralogy and fusion temperatures.The effects of chemical components (SiO2, Al2O3, B2O3, Fe2O3,CaO, CaSO4, Na2O and NaCl) on the melting characteristics of medical waste slag were analyzed by substituting analytical reagents for chemical components.Rotary kiln incineration has several advantages when used to dispose of hazardous wastes, for example being adapted for various feeds and simple operation. So an experimental platform of rotary kiln incinerator have been designed and established to investigate the pyrolysis and incineration disposal for hazardous wastes.This experimental platform was composed of hazardous waste feeding system, incineration system (rotary kiln incinerator,secondary combustion chamber and heat recovery equipment) and flue gas treatment system (quench tower and double bags filter).