The aroma of the spices will be open through the grinding process and a problem is that a mill not only produces powder but also heat. The result is the loss of a large part of the aroma during the grinding process.
In most cases it is sufficient to delete only the energy of the grinding process. That means the product has the same temperature at the entry and the outlet of the grinding plant. More cooling energy is expensive without advantages and creates some additional problems like condensation.
Some Spice Products are necessary to grind in a frozen status, if they are fatty like nutmegs, mace or coriander with high fat content. With a grinding process using extreme cold, cryogenic grinding, the product is pre-cooled in a stirrer bunker (batch) or in a cooling screw (continuous).
If freezing is not necessary, only to save the aroma, cooling with L-CO2 is sufficient to delete the grinding heat. The optimal temperature is a function of the product property and the adjustment of the temperature can be done with the quantity of gas. A temperature sensor behind the milling chamber controls it and with a chosen set value, a valve regulates the quantity of gas.
A cooling with L-N2 and a nozzle is also possible, but not directly into the grinding chamber.
An advantage of a closed system is the missing contact with the air of the room which supports hygiene. The gas displaces the Oxygen in the plant, reducing the danger of fire and dust explosions making it sufficient for meeting ATEX regulation.
Advantages of the cool grinding plant in contrast to a conventional Grinding plant:
• reduced loss of aroma
• no air humidity
• better hygiene, no dirt or germ in the plant
• small expenditure for cleaning (Filter external)
• through circeled air pipe low consumption of gas
• compact grinding plant, lower plant costs
• no oxigen in the plant, no dangerous of fire or dust explosions (ATEX)
Advantages of L-CO2-Grinding in contrast to deep temperature L-N2 plant:
• no precooling of the plant
• no precooling of the product
• no closed defrosting of the product
• no special materials of the plant construction
• no isolation of the plant
For each product with the required fineness and output an optimal combination of milling parameters are available, special fineness diagrams can be used for finding these parameters. For complementing the mill into a complete grinding plant, the following characteristics are important:
Characteristics for Plant Engineering:
• Required product output
• Product fineness
• Processing mode (continuous or batch)
• Plant design
• Available room size
• Safety regulations in the customer’s country