Garbage sorting technology is a crucial theoretical foundation for garbage classification. Sorting technology contains reasonable and effective advanced technical thinking. After a large number of experimental results and operational use, it can explore more suitable garbage treatment equipment for China's market. So continuously improving and perfecting the technical level of garbage sorting and treatment equipment is more beneficial to the advancement of garbage sorting technology in China and to change the harmony between our living environment and society. This is a long-term livelihood plan that benefits the country and the people, and it is more necessary to receive support and promotion from all sectors of society. Below, we will briefly introduce the screening and wind separation techniques in garbage sorting technology.

1. Screening: Screening is based on the different particle sizes of solid waste, using a sieve to pass fine particles smaller than the sieve hole through the screen surface, while coarse particles larger than the sieve hole remain on the screen surface, completing the separation process of coarse and fine materials. Screening includes two stages: material stratification and fine particle sieving. Material stratification is the condition for completing separation, while fine particle sieving is the purpose of separation. Screening can mainly separate useful substances such as paper, plastic, glass, etc. from garbage. The advantage of this method is that nearly 90% of the substances in household waste are easily sieved, so collisions can increase the likelihood of substances passing through the sieve holes, resulting in improved sorting efficiency; The disadvantage is that the composition of household waste is complex and irregular, which can easily lead to significant fluctuations in sorting efficiency.

At present, the screening equipment mainly used in the garbage treatment industry includes three types: tension relaxation screen, drum screen, and disc screen. The relaxation screen achieves particle size classification and self-cleaning function through the relaxation motion of the flexible mesh surface, and is mainly used for the separation of small particle components in household waste with high moisture content. The drum screen can be classified into single section single-stage, single section multi-stage, and double section multi-stage structures according to particle size classification and processing capacity. The equipment has strong universality and the efficiency of the drum screen is high, suitable for separating materials of different sizes, but the screen surface needs to be replaced. Disk screens are commonly used for initial and pre screening of household waste. They can adapt to the separation of materials of different sizes by adjusting the distance between the disk shafts, and have self-cleaning ability without the need for additional cleaning devices. However, there may be entanglement issues with long rope materials during the screening process.

2. Gravity sorting and wind sorting: Gravity sorting is the process of separating products with different densities based on the density differences between different substances in solid waste. The particle group in the moving medium is subjected to the effects of gravity, medium dynamics, and mechanical forces, resulting in structural looseness and migration stratification. The principle of wind sorting is consistent with that of gravity sorting. The implementation method is to use gas as the sorting medium. Under the action of gas flow, lighter materials are blown upwards towards a farther horizontal distance, while heavy materials can only be thrown out at a closer distance in the horizontal direction due to inertia. In this way, solid waste particles can be separated according to density and particle size; Wind powered sorting is suitable for the separation of heavy materials and plastics, but it consumes a lot of energy, especially in the final processing of plastic sorting, where it exhibits a lower sorting rate. This is because the airflow inside the sorting machine is complex, and the fluctuation of plastic purity during final processing is large. In this case, the narrow wind speed range only exists, which can only maintain the sorting efficiency at around 80%. Wind sorting equipment is mainly used for automatic sorting of lightweight materials (paper, plastic film, etc.) in urban household waste. According to the layout of the main space, it is divided into horizontal air separators and vertical air separators. The horizontal air separator has a simple structure and easy maintenance, but its accuracy is not high, and it is often used in conjunction with crushers and drum screens. Vertical air sorting machines can be divided into various forms such as bottom blowing, top suction, and a combination of drum suction, which have the characteristics of small footprint, flexible layout, and high sorting accuracy.