Faced with increasingly severe waste treatment problems, screening and air separation technologies have become an indispensable part of waste sorting. These technologies not only improve the efficiency of waste treatment but also support resource recycling, thereby promoting environmental sustainability.

1. Screening Technology

Screening technology is a method of separation based on differences in material particle size. It separates materials of different particle sizes using sieves, achieving the separation of coarse and fine materials. This process includes two stages: material stratification and fine particle screening. Material stratification is a prerequisite for separation, while fine particle screening is the purpose of separation. Screening technology can effectively separate recyclable materials such as paper, plastic, and glass from waste.

Advantages: Nearly 90% of the materials in municipal solid waste are easily screenable, which increases the likelihood of them passing through the sieve openings, thus improving sorting efficiency.

Disadvantages: Due to the complex and irregular composition of municipal solid waste, sorting efficiency may fluctuate significantly.

In the waste treatment industry, commonly used screening equipment includes tension screens, drum screens, and disc screens. These devices each have their own characteristics and are suitable for waste treatment in different scenarios.

** **Tension Screen:** Suitable for separating small-particle components of municipal solid waste with high moisture content. It achieves particle size classification and self-cleaning through the tension and relaxation motion of a flexible mesh surface.

**Drum Screen:** High efficiency, suitable for separating materials of different sizes, but requires regular screen replacement.

**Disc Screen:** Suitable for primary and pre-screening of municipal solid waste. It has self-cleaning capabilities and requires no additional cleaning equipment, but may experience entanglement issues with long rope-like materials.

2. Gravity Separation and Air Separation

Gravity separation and air separation operate on the same principle, utilizing the density differences between different substances. Gravity separation achieves separation through the loosening and stratification of particle groups in the moving medium, while air separation uses gas as the medium, separating lightweight and heavy materials under the action of gas flow.

Air separation: Suitable for separating heavy materials and plastics, but it consumes a lot of energy, especially in the final processing of plastics where the separation rate is low. This is because the airflow inside the separator is complex, and the purity of the plastic fluctuates greatly, resulting in a separation efficiency of only about 80%.

Air separation equipment plays an important role in the automatic separation of lightweight materials (such as paper and plastic film) in municipal solid waste. Based on the layout of the main space, air separation equipment can be divided into horizontal and vertical types.

Horizontal air separator: Simple structure and easy maintenance, but low precision; often used in conjunction with crushers and drum screens.

Vertical air separator: Small footprint, flexible layout, high separation precision, suitable for more refined separation needs.

Conclusion

Screening and air separation technologies play an important role in waste treatment. They not only improve the efficiency of waste treatment but also promote resource recycling and reduce environmental pollution. With continuous technological advancements and innovations, these technologies will play an even greater role in the field of waste treatment, contributing to the construction of a greener and more sustainable urban environment.