With the increasingly fierce competition in the powder industry, more and more customers want to achieve more refined materials, and the powder industry is constantly developing in the direction of nanopowder, so the previous single processing method is no longer applicable. , Then the preparation of nanopowder has become a puzzle for the enterprise. The preparation of powder is nothing more than grinding to disperse the fineness. There are two types of wet grinding and dry grinding. The representative of dry grinding is the ball mill. In wet grinding, bead mill is popular.
The factory generally uses physical and mechanical grinding methods to make the powder materials reach nanometer fineness. Dry grinding technology is the earliest technology, it was first applied to the grinding and decomposition of materials.
As the earliest grinding technology, it has advantages in the field of material grinding. Its advantage is that the production cycle is short, the later processing is relatively simple, and the cost is lower. Of course, dry grinding also has obvious disadvantages, for example, the powder is easy to stick together during the grinding process. It is difficult to obtain smaller grades of powder (the powder is difficult to grind very fine), and the temperature of the powder is likely to rise during the grinding process, which may cause the produced powder to fail to meet the requirements.
But, if a dry mill is used to grind the powder, the temperature of the powder will rise sharply due to the introduction of a large amount of energy. Or how to avoid explosion protection when the powder particles are refined? These problems are difficult to control for the mill. Because of these factors, wet grinding technology came into being. It can be said that wet grinding solves the problems that dry grinding cannot solve.
The advantage of wet grinding technology is that smaller particles (including nano-scale particles) can be obtained. But at the same time, this method also has some shortcomings. The production cycle of grinding materials using wet grinding technology is longer, and post-processing is more complicated than dry grinding. And the cost is more expensive.
Dry grinding means that the water content of the material does not exceed 4% during the grinding operation, while wet grinding is to suspend the raw material in the carrier liquid stream for grinding, and appropriate additives such as dispersants are added to help the grinding process. When the moisture content of the material exceeds 50% in the wet grinding machine, the problem of dust flying can be overcome. In food processing, the ground material is often used as a preparatory operation for leaching to make the components easy to dissolve, so it is quite suitable for wet grinding. However, wet operation generally consumes more energy than dry operation, and the equipment wears more seriously.
Mechanical dry grinding is difficult to obtain sub-micron powders, and the cost of chemical powder production is high. Therefore, wet grinding has become an important method for preparing ultrafine powders.
Now if the fineness of the product is not high, and the grinding requirements are not strict, you can choose a dry grinder, which is more cost-effective and faster. Most chemical companies choose wet grinding, so wet grinding machines are used. Wet grinding machines are mainly divided into vertical grinding machines and horizontal grinding machines.
The vertical grinder is an earlier product with lower cost, but it has insufficient sealing and due to the influence of gravity, resulting in insufficient dispersion of the ground raw materials, so it has basically been replaced by a horizontal grinder. Horizontal grinders are the mainstream grinders in the market now. They have good sealing properties, solvents and raw materials are not volatile, and the influence of gravity is low, and dust is not generated, which is more conducive to the safety and efficiency of production. Since all grinding machines use different grinding methods, they are also subdivided into many types such as basket grinders, mass grinders, and ultra-fine grinders. Each classification of grinders is mainly tailored to different production materials and processing processes, and there is no accurate and unified standard.
All in all, it is difficult to obtain sub-micron powders by mechanical dry grinding, and the cost of chemical powdering is high. Therefore, wet grinding has become an important method for preparing ultrafine powders. From the practical application point of view, there is no absolute difference between the advantages and disadvantages of the two. Appropriate treatment methods should be selected according to the actual product characteristics and economic benefits.