Research on cryogenic grinding of plastics with air turbine refrigeration system

Abstract

Cryogenic grinding has been the development in the field of ultrafine grinding of plastics, especially the ones with low softening temperature. The common refrigeration methods are difficult to apply in engineering production, as liquid nitrogen effects in high operation costs. Freon, lithium bromide, and ammonia show dissatisfactory refrigeration effect and need complex system. The authors chose a kind of typical thermoplastic elastomer, EVA (ethylene vinyl acetate), as their subject for research. Based on thorough study of material properties and grinding mechanism of EVA, the authors accomplished experiments to grind EVA into fine powders, effectively enhancing the fine grinding efficiency of particles at low costs, and creating a new way of recycling renewable plastics on a large scale with high quality and low energy consumption. An engineering approach to analyse the core processes of refrigeration and grinding is introduced with the energy conservation law to guide the improvement of equipment performance during the process. The key issues of the grinding process and effects are discussed in detail.