Shock freezing of bulk materials
Temperature-sensitive bulk materials, bulk materials that are prone to sticking at high temperatures or change their properties positively at low temperatures can be cooled and / or embrittled using cryogenic liquid nitrogen or carbon dioxide. With this method, very low material temperatures can be achieved.
Liquid nitrogen has a boiling point of -196 °C at an ambient pressure of 1 bar. In a product cooler (in most cases a paddle screw cooler), the bulk material comes into direct contact with liquid nitrogen. Due to the very good heat transfer from solid bulk material to liquid nitrogen, it is possible to achieve large temperature differences with a short cooling distance.
The goals of the cryogenic shock freezing of bulk materials are:
- Fast cooling even to very low temperatures
- Bulk materials that are prone to sticking remain free-flowing and doseable
- Positive change of cell structure
- Prevention of thermal damage
The Messer Group operates a highly specialized test facility, which offers the opportunity to profit from process developments and to estimate cooling costs. Qualified cooling tests can be carried out using liquid nitrogen. All grinding parameters, such as throughput, electricity and nitrogen requirements as well as the particle size distribution are measured, evaluated and made available to the customer.
Cooling tests can also be realized at the customer’s site. Granulate coolers, nitrogen control valves and temperature control can be provided.