Cryogenic grinding is a process used to grind materials at low temperatures using liquid nitrogen. This technique is used to produce fine, uniform particle sizes and is commonly used in the food, pharmaceutical, and chemical industries. The following are the general steps involved in cryogenic grinding:
The first step in cryogenic grinding is to prepare the material to be ground. This involves selecting the appropriate material and preparing it by drying, milling, or grinding to a specific particle size.
The material is then cooled to a temperature below its brittle point, typically around -196°C (-320°F). This is achieved by using liquid nitrogen, which is sprayed onto the material as it is fed into the grinding machine.
The cooled material is then ground to the desired particle size using a grinding machine such as a hammer mill, pin mill, or a jet mill. The grinding machine is designed to reduce the temperature of the material during the grinding process to prevent melting or sticking.
The ground material is then sieved to remove any large particles or lumps. This ensures that the powder is fine and uniform in size.
Finally, the powder is packaged into small bags or containers for distribution.
The machinery used in cryogenic grinding can vary depending on the specific process and the scale of production. A grinding machine such as a hammer mill or a pin mill may be used for grinding. Cryogenic cooling is typically achieved using a liquid nitrogen cooling system, which includes a storage tank, a vaporizer, and a delivery system to supply liquid nitrogen to the grinding machine. Other equipment that may be used includes sieving machines for sieving the powder and packaging machines for packaging the final products.