This cryogenic technology, which must be adapted to the respective requirements and material properties, is based on the different coefficients of linear expansion and the embrittlement potential of the materials in question. For example, rubber shrinks 7.5 times more than iron when cooled with liquid nitrogen (-196°C). The composite material can then be separated by means of impact stress.
Diagram: Influence of temperature on linear expansion of metals and plastics
The goals of the cryogenic composite separation are:
- a high degree of separation of the composites, because a pure an individual material fraction has a higher market value
- high throughput for low production costs
- avoidance of thermal damage to the ground products
- prevention of dust explosions and fires during grinding
Messer operates a highly specialized test facility, which offers the opportunity to benefit from process developments, estimate production costs or produce sample batches. Separation tests can be carried out here using liquid nitrogen or other industrial gases. All relevant parameters, such as the degree of separation, electricity and gas requirements as well as throughput are measured, evaluated and made available to the customer.
Even existing mills at the customer’s site can be optimized. Granulate coolers, nitrogen control valves and temperature control can be provided for carrying out tests on these plants on site.