one. introduction
In the pulverization of industrial materials, special materials are often unable to be pulverized at normal temperatures. The cryogenic low-temperature pulverizer system is used in various materials that cannot be pulverized at normal temperature, and is widely used in various chemical, petrochemical, machinery, shipbuilding, automotive, electronics, clothing, coatings, printing, engineering plastics, rubber, thermoplastic materials. The food industry (chili powder, pepper, etc.), Chinese and Western medicines and other products are superfinely pulverized and then heated.
two. principle
The principle of pulverization: by using the cold source liquid nitrogen to exchange heat with the material, the material is cooled to an embrittled state; the embrittled material is subjected to numerous crushing, shearing and rubbing in the pulverizing chamber through the pulverizing mechanism to finally become fine granules. The fineness of the pulverized material can reach the micron level (600~2000 mesh). The cold option can be selected according to the performance of the material. If the liquid nitrogen is used as the refrigerant, the minimum cooling temperature can reach 196 degrees below zero. The cooling rate is very fast, and it is the preferred coolant for some materials that need rapid cooling and low embrittlement temperature. .
Third, the process
The low-temperature pulverizer system uses liquid nitrogen as a cold source. After the pulverized material is cooled and chilled at a low temperature, it enters the mechanical pulverizer cavity and rotates through the impeller at high speed. Material and blades, toothed disc, material and material Under the combined effects of repeated impact, collision, shearing, friction, etc., the pulverization effect is achieved: the pulverized material is classified by an air flow sieve classifier and collected and heated; the material that does not meet the fineness requirement is returned to the silo to continue crushing, and the air is cooled. Most of the return bins are recycled.
The material pulverization heating system process is shown in the figure:
1. The pulverizer uses a pre-cooling silo to pre-cool the material, and the pre-cooling silo is equipped with a precision liquid gas gasification device to forcibly cool the material during the liquid gas gasification process.
2. The material that has reached the cooling and embrittlement is sent to the pulverizer chamber by a screw feeder.
3. The independent rolling pair ensures that the machine operates normally in a low temperature environment. The refrigerant refilling compensation compensates for the heat generated by the material during the pulverization process. The injection amount of the refrigerant is regulated by the low temperature valve, and the high pressure airflow generated when the material is pulverized is The flow of the refrigerant lost pressure expansion is discharged into the machine cavity through the swirling window of the static classifier of the pulverizer. After the material is crushed, the required fineness is achieved, and the airflow enters the discharge system, and the coarse material hits.
The blade hitting the stationary classifier bounces back to the pulverizer chamber to achieve a coarse step grading effect.
4. The material is sent to the external classifier through the induced draft fan to adjust the speed of the classifier impeller, which can achieve the fineness we need. The use of the external classifier reduces the time for the material to return to temperature during the screening, reduces labor, shortens the production cycle, and reduces the use of the site. The crushed material can be directly packaged and transported.
5. After grading, the coarse material is fed into the feeding mechanism through the pipeline and enters the pulverizer to be re-pulverized. The fine material enters the cyclone separation.
The cyclone separator separates the material from the air and the material is deposited by rotation on the bottom of the cyclone.
6. The gas mixture containing the rare material particles flowing out from above the cyclone re-enters the second cyclone separation, and finally separates the air flow with a certain cold source through the pipeline to the crusher main machine feed.
Air inlet.
7, using the inclined angle discharge system to discharge, the inclined spiral discharge system to ensure that the air of the cyclone will not
The discharge port flows out.
8. Add a section of cylindrical spiral heating pipe (4 sections) to the material discharge system to heat the material.
four. AI regulator selection and introduction
In the control system, the AI ​​regulator warms the discharge by controlling the heating belt above the circular heating tube, so that the final material temperature meets the actual use requirements. The specific model of the instrument is: AI-526AGL0 (4 units).
Fives. AI regulator debugging
The PID control parameters of the instrument can be set by self-tuning. Under normal circumstances, the self-tuning can achieve a more accurate control effect. If the parameters are set so that the control effect is not ideal, the PID parameters can be fine-tuned to correct the control process. Overshoot, oscillation and other phenomena.
six. to sum up
The pulverizing system overcomes the problem that the special material cannot be pulverized at normal temperature, and reduces the disadvantage of the traditional chilling machine by the cooling reflow, the discharge air compensation, the grading in the system, etc., and is an advanced pulverizing machine at home and abroad, filling up the gap. The blank of such technology at home and abroad is an indispensable tool for the crushing process of materials. At the same time, the control of the AI ​​regulator ensures that the temperature of the final material can meet the requirements of actual use.
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