Countercurrent cooler

Appointment

The purpose of the countercurrent fuel pellet cooler is to ensure effective cooling of the pellets after the pelletizing process, after the press granulator. This is necessary to reduce their temperature and humidity, which in turn improves the quality of the granules, acquires the necessary hardness and thereby prolongs their shelf life.

Characteristic

A cooler is used to cool the wood pellets before packaging and storage. Due to the friction that occurs in the matrix during the granulation process, additional heat is generated in the granules. The heat must be removed before sieving and storing the granules.

During the cooling process, the moisture content of the granules (pellets) decreases due to the evaporation of water, and physico-chemical changes occur in them. As a result, the granules acquire the necessary hardness, humidity and temperature.

The cooler consists of a cooling chamber, a pellet unloading device that is simultaneously a frame, an airlock with a drive, an unloading funnel and supports. Countercurrent pellet cooler with aspiration system. Complete with a cyclone precipitator, a sluice gate and a vibrating pellet sifter.

The residence time in the cooler and the diameter of the wood pellets are crucial for determining the size of the cooler.

• Integrated unloading system with hydraulic, pneumatic or electric position sensors.
• Cooling chamber for pellets and other products in the form of granules with a square cross section.
• 3 level sensors mounted on the cooler door.
• Electronic temperature sensor 4...20 mA, for temperature control (signal processing is carried out using local control).
• Sprinkler system (standard for wood pellets).
• Rotating valve on the lid of the cooler with direct drive.

The principle of operation

1. Hot pellets transported by a conveyor from under the granulator press enter the cooling chamber through the sluice gate.
2. The pellets are cooled by air passing through the pellet layer, coming from below through the nozzle of the discharge funnel and then through the gaps between the unloading elements. At any point in the granule layer, the temperature difference between the granules and the air is minimal, which prevents temperature shock, allows uniform cooling of the granules and minimizes their destruction (marriage).
3. The filling of the cooling chamber is regulated by level sensors. When the upper sensor is triggered, the unloading mechanism turns on, when the lower sensor is triggered, it turns off.
4. The unloading device is unique, it is designed in such a way that during its operation, the destruction of granules does not occur due to their jamming between the edges of the moving parts of the unloading mechanism. An emergency level sensor (optional) can be installed on the cooling chamber to prevent the product from backing up the loading airlock.
5. When this sensor is triggered, the supply of pellets stops. For visual observation of the filling of the cooling chamber with granules, an observation window is mounted on its side front wall. The window can be equipped with a limit switch (optional), which prevents the window from opening when the cooler is running and prohibits its activation when the window is open.
6. From the cooling chamber, the granules are fed through an unloading funnel to a vibrating screen, where the conditioned granules are separated from the crumbs. The unloading device may be able to smoothly adjust the output speed, which ensures the most efficient operation of the pellet cooler.

Thus, a continuous heat exchange process between the two streams takes place in the countercurrent cooler, which ensures efficient and stable cooling.

Advantages

• The possibility of supplying cooling air from the outside.
• High energy efficiency due to the use of a unique patented unloading system, in which there are no reciprocating movements.
• Minimal destruction of granules during unloading for the same reason.
• The ability to smoothly change the speed of unloading pellets.
• The possibility of continuous unloading of granules synchronized in performance with the granulator.
• The rubber blades of the loading sluice gate ensure minimal damage to hot, flimsy pellets and minimal chance of jamming the sluice.
• Mechanical rotary level sensors that, unlike any other sensors, do not have false alarms.