What are the temperature control and dehumidification techniques for drying and cooling in pet food production line DE?

Freshly produced aquatic feed pellets from the pellet mill reach temperatures as high as 80-110℃, with a moisture content exceeding 20%. Improper drying and cooling processes can lead to mold growth and damage to heat-sensitive nutrients. A Shandong aquatic feed factory suffered a direct economic loss of 50,000 yuan due to a 60% loss of Vitamin C in a batch of bass feed caused by improper drying temperature control. The core techniques for the drying and cooling process are "gradient temperature control and precise dehumidification."

Drying operations require a "segmented temperature control" technique to avoid nutrient loss and uneven drying caused by a single temperature. Rotary drum dryers typically consist of three heating zones: the feeding zone is controlled at 70-80℃ to quickly evaporate surface moisture; the middle zone is raised to 80-90℃ to thoroughly remove internal moisture; and the discharge zone is lowered to 60-70℃ to prevent over-drying and dust generation. Drying time needs to be adjusted according to pellet size: 25-30 minutes for shrimp feed (2-3mm) and 15-20 minutes for fish feed (3-5mm). During operation, a moisture meter should be installed at the dryer outlet to monitor the feed moisture content in real time, ensuring the final moisture content is controlled at 12%-13%. This moisture content guarantees storage stability and prevents pellet brittleness and breakage.

The key to cooling operation is "airflow matching and temperature difference control." When using a counter-flow cooler, the airflow speed needs to be adjusted according to the pellet temperature and moisture content. For hot, wet pellets just entering the cooler, the airflow speed should be controlled at 3-4 m/s to quickly remove surface heat. When the pellet temperature drops below 40℃, the airflow speed should be reduced to 1-2 m/s to slowly remove residual moisture. The cooling time is usually controlled at 15-20 minutes, ultimately bringing the pellet temperature close to room temperature (temperature difference not exceeding 5℃) to prevent excessively high pellet temperatures from causing "sweating" and rehydration after packaging. During operation, the cooler filter screen should be cleaned regularly, every 4 hours, to prevent dust from clogging the filter and reducing cooling efficiency. Simultaneously, the fan operation status should be checked to ensure stable airflow. If insufficient airflow is detected, the dust accumulated on the fan impeller should be cleaned promptly.

The drying and cooling of special feeds requires customized techniques. For aquatic feeds with added probiotics, the drying temperature must be controlled below 50℃ to avoid killing the probiotics. In this case, the drying time should be extended to 35-40 minutes, using a low-temperature, slow drying method. For floating aquatic feeds, the air velocity should be appropriately increased to 4-5 m/s during the cooling process to ensure uniform removal of moisture from the pellets and maintain buoyancy stability. In addition, the dried and cooled pellets need to be screened to remove broken particles and dust. The broken particle content should be controlled below 5% to ensure the uniformity of the feed pellets. The screened broken particles can be returned to the mixing stage for reuse, reducing raw material waste.

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