Grinding Process Of The Waste Tires Rubber Powder In The Fluidized-bed Jet Mill & Optimal Designing Of The Cryogenic System

Grinding is an important but challenging method to achieving waste tire recycling. The crumb rubber of the mechanical grinding of tires at ambient temperature is coarse. At the same time, this method produces considerable quantities of heat, which will cause spontaneous combustion. The main disadvantage of the cryogenic grinding which uses liquid nitrogen as the heat sink is the high cost. So, it is uncompetitive economically. In order to obtain fine product under ambient temperature and reduce the cost of the cryogenic grinding, the following work has been done:(1)A new equipment fluidized-bed jet-mill was used to grind waste tire powder which was produced by the ambient mechanical grinding. The effect of the operating parameters such as inlet pressure, feed load, grinding temperature on the grinding was studied. The results showed that the volume moment diameter d(4,3) of the ground particles decreased as the inlet pressure increased, the feed load decreased, the grinding temperature decreased.(2)The effect of the operating parameters such as inlet pressure, feed rate, classifier rotation speed on the continuous grinding product at ambient temperature was studied. The results showed that the ambient temperature continuous grinding product d(4,3) decreased as the inlet pressure increased. The product d(4,3) decreased firstly as the feed rate then increased. The product d(4,3) decreased as the classifier rotation speed increased. The minimum d(4,3) of the ambient temperature continuous grinding product was 109.7μm, which was obtained when the feed rate was 15.4g/min, the inlet pressure was 0.6MPa and the classifier rotation speed was 1800rpm. The corresponding hold up was 366.5g. While, when the grinding temperature was between -75℃ and -85℃, the feed rate was 19.2g/min, the inlet pressure was 0.6MPa and the classifier rotation speed was 2400rpm, the cryogenic continuous grinding product d(4,3) was 65.3 μm and the corresponding hold up was 184.8g. According to the SEM photograph, the ambient jet grinding product was smooth, which was different from the ambient mechanical grinding product. While, the cryogenic grinding product was irregular with sharp corners.(3)The population balance model was solved by the first Kapur function to obtain the selection and breakage functions of the grinding of the waste tire rubber particles in the fluidized-bed jet mill. The results showed that the inlet pressure, the feed load, the grinding temperature had effect on the selection and breakage functions. The breakage mechanism for rubber particles in the mill could be discussed by these functions. A cubic polynomial for the Kapur functions was proposed to effectively simulate the product size distributions under various conditions.(4)A process of LNG cold energy utilization of waste tire rubber particles was proposed and simulated. Exergy analysis theory was adopted to improve the process. Based on the LNG thermodynamic curve and energy level match principle, a section and integration process was processed. The power consumption and the exergy loss of the system was reduced.