Garbage sorting and impurity removal technology and equipment
Release time：2026 / 01 / 09 16:53:18 Author：Guoxin Machinery
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The sorting and impurity removal of construction waste can be divided into two methods: manual and mechanical sorting. Mechanical sorting efficiently separates impurities in construction waste based on their physical characteristics such as size, magnetism, and specific gravity, mainly including screening, air separation, magnetic separation, hydraulic flotation, etc; Manual sorting mainly targets impurities that are difficult to separate by general mechanical means such as non-magnetic metals, glass, ceramics, etc. In the process of treating construction waste, due to the diverse types of impurities it contains, the impurity removal process often involves the use of multiple sorting methods.
1) Wind selection
Wind sorting is a commonly used method of gravity sorting, which uses air as the sorting medium to sort solid waste according to specific gravity and particle size under the action of airflow. It can be divided into two types according to the direction of airflow: suction type and blowing type. The principle of suction type air separation is similar to that of dust collectors. In the process of conveying or screening construction waste, suction ports are set up to use negative pressure to separate lightweight materials, fine particles, etc., and then collect impurities through cyclone dust collectors, bags, etc. The basic principle of blower wind selection is that the airflow can carry lighter materials upwards or horizontally to farther places, while heavy materials settle due to the inability of the rising airflow to support them, or are thrown out of the horizontal direction at a closer distance due to inertia. The light materials carried away by the airflow are further separated from the airflow. According to the different target separation materials, the wind speed at the suction and exhaust ports is generally controlled between 15-50m/s.
2) Magnetic Separation
The magnetic materials in construction waste are almost entirely steel bars in concrete building structures. After the demolition of buildings, exposed waste steel bars, larger volume steel plates, steel beams, anchor bolts, etc. can be manually sorted after gas cutting treatment. Waste steel bars wrapped and mixed in concrete blocks need to be crushed and sorted through magnetic separation. The magnetic separation process for construction waste is generally arranged after each level of crushing process, and the most common magnetic separation process is the combination of a cross belt magnetic separator and a permanent magnet drum magnetic separator.
3) Hydraulic flotation
The lightweight materials such as waste plastics, waste wood, waste paper, and aerated concrete mixed in construction waste have a lower specific gravity than water, and their floatability in water is utilized to separate them from concrete, bricks, and other materials. Different from the flotation process in the mineral processing industry, the flotation of construction waste does not require the addition of flotation reagents to change its floatability. Separation can be achieved through the difference in natural floatability. Construction waste is fed from the middle of the flotation equipment, and non floatable heavy materials sink onto the conveying device at the bottom of the flotation equipment and are transported out to one side by the conveying device. During the conveying process, water is also drained; Light impurities float on the water surface and are scraped out from the other side of the flotation equipment by the upper blade device. The characteristics of construction waste flotation are high processing capacity, high sorting efficiency, and good impurity removal effect. However, due to the presence of a certain amount of soil in construction waste, a water circulation system is required to regularly remove sediment from the water. To avoid rapid accumulation of sediment, the content of waste soil in the construction waste raw materials entering the flotation process should not be too high, and the particle size should be moderate. Therefore, primary crushing and pre screening of waste soil should be carried out before flotation. At the same time, flotation should be combined with manual sorting, air separation, magnetic separation and other impurity removal processes, and should not bear excessive impurity removal loads.
4) Micro powder removal
During the crushing, screening, strengthening, and shaping processes of recycled construction waste aggregates, a certain amount of micro powder is generated. When recycled aggregates are used to prepare concrete or mortar, excessive micro powder content can affect the strength and durability of recycled concrete. The standard for recycled aggregate in our country defines it as fine particles with a particle size less than 75 μ m, and has strict limits on the content of micro powder in recycled aggregate. In the mechanism sand industry, wet sand washing machines are commonly used in China to remove micro powders, which require a water circulation system. There are problems such as high investment, large land occupation, high treatment costs, and secondary pollution. To solve the above problems, dry equipment such as pneumatic classifiers and vibrating air screens have emerged and become the development trend of micro powder removal technology equipment. The pneumatic classifier can effectively remove micro powder from recycled fine aggregates, utilizing the principle of combining reselection and pneumatic classification. The material falls due to gravity and is subjected to a wind force during the falling process, causing the separation of aggregate and fine powder. The wind force drives small particles through the sieve, and particles larger than 75 μ m are intercepted. The fine powder is collected by the subsequent dust removal system along with the air; At the end of gravity descent, there is a secondary wind force acting on the material, causing small particles to form a vortex in the volute cavity for secondary separation, resulting in more thorough removal of micro powder.
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