What aspects should we pay attention to in heavy medium coal selection?

In heavy medium coal selection, it is necessary to control the particle size and impurities of the washed raw coal. It is necessary to control the feed particle size within the range required by the heavy medium cyclone and set up a manual impurity and iron remover to remove impurities.

Heavy medium coal selection should maintain a uniform and stable coal feeding rate of the cyclone, not exceeding its processing capacity. The frequent fluctuations in coal feeding not only affect the sorting efficiency of the cyclone, making product quality unstable, but also affect subsequent processes. If the feeding amount of the medium sieve and magnetic separator is unstable, it will bring great trouble to the process debugging and management of the medium sieve and magnetic separator, and increase the consumption of the medium. When an online ash analyzer is installed on a clean coal belt conveyor, unstable coal washing volume can cause frequent changes in coal seam thickness on the clean coal belt, affecting the measurement accuracy of the ash analyzer.

The measure is to input raw coal through electronic belt scales and other measuring devices, always measure online, and control the washing amount within a stable range. When there is a large amount of gangue or lump coal, the washing amount is appropriately controlled (reduced) according to the measuring device.

The fluctuation of the density of the circulating suspension in heavy medium coal preparation not only affects the stability of product quality and the separation efficiency of the cyclone, but also causes fluctuations in the feeding properties of subsequent operation steps. Therefore, it is necessary to control the stability of the density of the circulating suspension, so that it fluctuates within the density range.

Excessive belt media not only increases coal processing costs, but also affects the ash content of clean coal. For the process of using X-ray online ash analyzer for online control, the increase in iron content in clean coal will also affect the measurement accuracy of the ash analyzer. Generally, it is required that the medium of coal does not exceed LKG/ton. In order to minimize the medium of the product as much as possible, heavy medium coal selection should grasp the following points:

(1) Strengthen the daily maintenance of dielectric screens, select screen plates with high aperture ratio, good wear resistance, and no magnetic permeability, regularly inspect and replace damaged screen plates in a timely manner to improve dielectric efficiency and reduce the occurrence of accidents such as running out and blockage.

(2) The coal feeding capacity of the desizing sieve should be less than its larger processing capacity. According to relevant data, when using a pre selected dredging process with a mesh size of 0.5 millimeters, the processing capacity per unit area is generally 4 to 6 tons per hectare.

(3) Try to improve the dielectric efficiency of the curved screen as much as possible, ensuring that the curved screen removes more than 85% of suspended solids in the feed in advance to reduce the load on the dielectric screen. It is required that the feed of the curved screen be evenly fed into the screen surface at a certain pressure along the tangent line. At the same time, high-pressure water can be used to rinse the screen surface once during each shift to prevent blockage of the screen holes and prevent a large amount of medium from entering the intermediate screen when the material on the curved screen enters, causing abnormal diversion and unstable suspension density and liquid level in the mixing drum.

(4) The water spray rate, water pressure, and water concentration of the sieve have a significant impact on the release of intermediates in the product. The final removal of the medium is mainly achieved through water spraying, and sufficient water and pressure can roll the product deep, which is beneficial for the separation of the medium from the surface of the product. According to relevant information, for non desliming processes, pressurized water spraying is generally required.