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(1) The hard material with larger or medium grain size is crushed and impacted, and the teeth have different shapes on the pulverizing tool;
(2) The smaller size of the hard material is crushed, impacted, milled, and the surface of the pulverizing tool has no teeth and is smooth;
(3) Powdered or muddy materials are ground, impacted, crushed;
(4) Materials with weak abrasiveness are impacted, struck, and ground, and sharp teeth are provided on the pulverizing tool;
(5) The abrasive material is mainly crushed, and the surface of the crushing tool is smooth;
(6) The tough material is sheared or quickly struck;
(7) Multi-component materials can be crushed by selection under impact, or multiple force fields can be combined.
2 Requirements for selecting the material of the crushing machine In addition to the airflow crushing, most of the dry crushing will rely on the high-speed rotating rotor, and the particles between the rotor and the fixed stator will be crushed by the shearing force frequently, or the rotating parts and the fixing parts Frequent grinding between the parts, so that the parts in direct contact with the material are seriously worn, so that insoluble impurities and metal particles are easily generated during the pulverization process.
According to GMP, pharmaceutical equipment has corrosion resistance requirements for materials that are in direct contact with materials. Generally, austenitic stainless steel is used for this material, and the hardness of austenitic stainless steel surface is relatively low for multimetals. When austenitic stainless steel is used as the material of the pulverizer, metal particles are easily generated. However, an important way to reduce wear particles is to increase the hardness of the material of the pulverizer. The lower the carbon content in the material, the lower the hardness, and the high carbon material is very easy to rust. Therefore, the choice of the material of the pulverizing machine in the pulverizing equipment should pay attention to the contradiction between the corrosion resistance and the hardness of the material.
To deal with the above contradictions, it is necessary to analyze the main points of the contradiction. The wear resistance of the crushing machine is the main body, and the corrosion resistance must be ensured under the premise of ensuring wear resistance. For dry pulverizing equipment, the dry matter of the material generally does not precipitate chloride ions, that is, the probability of intergranular corrosion in the material is extremely low, that is, the material of the pulverizing machine must be similar to the lower hardness. 316L ultra low carbon stainless steel. Therefore, the author suggests that the material of the crushing machine can be selected from three aspects:
(1) High alloy nickel-chromium steel [2];
(2) Austenitic stainless steel is specially treated, such as stainless steel hardening treatment like medical surgical equipment. It is reported that domestic pharmaceutical machinery manufacturers have successfully applied this example;
(3) Hard ceramics.
3 Other principles to be considered 3.1 Bearings and seals at the rotor. In addition to selecting high-precision bearings, the bearings should be sealed multiple times. While ensuring that the lubricant in the bearing does not leak, it is also necessary to ensure that the material powder does not penetrate into the bearing (that is, no dust is allowed to remain). These two points are necessary to prevent cross-contamination.
3.2 Dust removal, generally a large amount of dust will escape from the powder outlet, so most of the crushing equipment (especially the classification and combination equipment) have dust removal devices. When selecting dust removal, the dust removal material should be required. The dust removal material should be determined according to the product variety and safety level.
3.3 Washability, in addition to the direct contact with the material, there is no cleaning blind zone, pay attention to the following points:
(1) For equipment that is manually cleaned, the part in direct contact with the material shall be completely disassembled;
(2) For equipment with CIP or WIP, the cleaning problem at the bearing should be considered. In the PHARMAPLEX bearing system of the Japanese Hosokawa Micron company, the treatment method is that any particles eroded from the bearing seal can be taken out through a cleaning passage to ensure that the product chamber is not contaminated [4].
3.4 In terms of online particle size analysis, this is a consideration for selecting advanced crushing equipment. Features of the online particle size analysis system:
(1) Control product quality and adjust grading during production;
(2) Continuous quality control at large measurement frequency, stable product quality, automatic recording of all parameters, no manual sampling, offline operation.
How to choose the crushing equipment
1 The nature of the plant material is determined by the method of applying force and then the type of crushing equipment. Before selecting the crushing equipment, the method of crushing and applying force should be clarified. People can take corresponding force according to the material properties, particle size and requirements of crushed products [1] ], and then ask for the type of crushing equipment.