Counter-flow cooler

Counter-flow cooler is the most widely used in feed processing plants. It is composed of Impeller Feeder (closed air action), top cover, outlet pipe, cone shaped feeder, shell, upper and lower material level device, discharge mechanism, frame and outlet hopper, etc.

In the process of cooling, the particles enter the cooler through the feeder (air breaker) and evenly scatter in the cooler through the rhomboidal disperser. The cooler is equipped with upper and lower material level device. At the beginning, the particle material gradually accumulates. When the particle material touches the upper material level device, the discharging mechanism begins to discharge the material. The discharging mechanism will stop working when the particle material drops to the lower level. The discharge time can also be controlled by installing a feed level indicator and a time relay. Fan is always working, particles from the top down gradually discharged, cold air from the bottom up through the material layer, the particles for cooling. Material and air flow in the opposite direction, so called counter-flow cooler. Because this kind of working mode is that the cold air contacts with the colder particles, while the high-temperature particles contact with the hotter air, avoiding the sudden cooling phenomenon caused by the direct contact between the cold air and the hot material, thus preventing the possibility of cracks on the surface of particles. This kind of cooler has large air inlet area, easy to adjust air volume and cooling time, and good cooling effect. But this cooler is not suitable for cooling powders.

The discharge mechanism of counter-flow cooler has two forms: push and pull type (also known as reciprocating mobile type) discharge mechanism and swing type discharge machine.

Push and pull type discharge machine is composed of partition frame, movable frame and fixed frame. The movable frame is driven by eccentric connecting rod mechanism and reciprocates on the track for discharging. When discharging stops, the movable frame must stop at a certain position (controlled by the travel switch), or the phenomenon of material leakage will occur. The discharge flow can be adjusted by adjusting the front and rear positions of the fixed frame.

Swing discharge mechanism consists of frame, rotary shaft with upper and lower baffles, bearing with seat, connecting rod, linkage, oil cylinder and hydraulic pump station (or cylinder). The rotation angle of the shaft is controlled by the limit switch to change the discharge rate. Normally, the discharge mechanism is always in the position of non-discharge. When the production is finished, the material in the machine can be emptied by manual switch.

The matching quality of cooling air network will have great influence on the cooling effect. If the matching of the air network is not reasonable, the cooling effect can`t be guaranteed.

The air network system is composed of muffler, fan, air pipe, disc valve, cyclone separator (also called Centrifugal Dust Collector or cyclone), airlock discharger and counter-flow cooler. When designing the air network system, the following rules shall be followed:

1. Shorten the length of the entire wind system as long as possible, reduce the number of corners, avoid the loss of the wind due to the loss of pressure, and the cooling effects.

2. Shorten the length of the pipe as much as possible to prevent the dust from affecting the ventilation area.

3. In order to prevent condensed water, the air pipe should be covered with thermal insulation materials.

4. Reasonable selection of duct diameter, so that the wind speed in the duct up to 12~16m/s. If the wind is too low, the dust is easily tied to the wall of the air duct, and the condensate is easy to produce.

5. The wind pipe should be equipped with air conditioning, so that the wind can be adjusted by different circumstances.

6. Centrifugal filter should be installed in front of the fan. Dust removal is carried out by using negative pressure to ensure that the fan blade is not adhered by damp dust, which will affect the work of the fan.

7. Because fan noise is bigger, had better match with silencer in fan exit.