In the field of powder processing, high-end products generally refer to powders that have extremely strict standards for the fineness, particle size distribution, purity (low pollution), particle morphology, chemical activity or physical properties of the finished powder. For example:
- Ultrafine powder: D97 ≤ 10μm or even lower (such as 5μm, 3μm);
- Narrow particle size distribution: The proportion of specific particle size ranges is extremely high, and the content of coarse particles and ultrafine powder needs to be strictly controlled.
- High purity/low pollution: The content of metal ions (especially iron) is extremely low, and there is no contamination from foreign impurities such as grinding media wear.
- Specific physical property requirements: such as high whiteness required for titanium dioxide and kaolin, integrity of specific crystal structure, high specific surface area and good dispersibility, etc.
- High value-added applications: covering high-end coatings, inks, pharmaceuticals, food, cosmetics, electronic materials, advanced ceramics, catalysts and other fields.
So, how effective is the Raymond mill in grinding high-end products? The conclusion is that Raymond mills are generally not very suitable for grinding "high-end products" with strict requirements. Their limitations are mainly reflected in the following aspects:
There is a clear upper limit to the fineness
The theoretical upper limit of fineness for standard Raymond mills is usually around D97=325 mesh (approximately 45μm). Even after optimization and with a closed-circuit system, some models can only achieve a maximum of D97=400 mesh (approximately 38μm). To achieve ultra-fine grinding (such as D97<30μm or finer), not only is the difficulty extremely high, but it is also accompanied by problems such as soaring energy consumption and sharp reduction in output, which has exceeded the optimal working range of its design.
Difficult to achieve a narrow particle size distribution
Raymond mills mainly rely on air separation and classification to achieve finished product sorting. Compared with jet mills, vertical mills or dedicated ultrafine classifiers, their classification accuracy (powder selection efficiency) is relatively low. A small amount of coarse particles and ultrafine powder are prone to remain in the finished product, and the particle size distribution is relatively wide, making it difficult to meet the strict requirements of high-end applications for particle size distribution.
The risk of metal pollution is relatively high
The grinding core of the Raymond mill is the direct crushing effect between the grinding roller and the grinding ring. Even if wear-resistant materials are used, the wear during the grinding of hard materials cannot be avoided. Metal impurities produced by wear (mainly iron) can mix into the finished powder. For high-purity products with extremely low iron content or those sensitive to metal ions (such as pharmaceuticals, electronic materials, high-end ceramic glazes, titanium dioxide, etc.), this kind of contamination can be regarded as a fatal defect.
Affects the morphology and activity of particles
The crushing method of the Raymond mill mainly relies on extrusion and shearing. This approach is prone to destroying the original mineral crystal form, generating a large number of irregular and sharp-edged particles, and may even increase internal defects within the particles. For high-end products that require maintaining the original crystal form, sphericity or specific surface activity (such as some catalysts and fillers), the Raymond mill is not an ideal choice.
Risk of temperature rise
When pursuing high-fineness grinding or processing heat-sensitive materials, the heat generated in the grinding area can cause a significant increase in material temperature, which may lead to problems such as material denaturation, oxidation, and accelerated agglomeration, thereby affecting their physical and chemical properties.
Comprehensive evaluation
For mid-to-low-end powder demands (such as within 325 mesh, in fields like building materials and fillers where purity and particle size distribution requirements are not extremely strict), Raymond mills remain a mature and economical solution due to their advantages of simple structure, stable operation, convenient maintenance, and relatively low investment and operating costs.
However, for the genuine demands of "high-end products" (ultra-fine, narrow distribution, high purity, low iron, specific morphology/activity), the shortcomings of Raymond mills in key aspects such as fineness limit, metal contamination risk, classification accuracy and particle morphology control are very prominent, and it is difficult to meet the production requirements.
