Snow jets
The CO 2 -Schneestrahlen as the dry ice blasting a jet of compressed air method , in which carbon dioxide is used as the blasting agent. With regard to the mechanisms of action, CO 2 snow blasting is very similar to dry ice blasting. A major difference, however, lies in the way the abrasive is fed. Since a continuous supply of blasting media is used, CO 2 snow blasting is not a so-called batch process - such as dry ice blasting, the process of which must be supplied with dry ice.
The blasting agent (liquid carbon dioxide ) is supplied continuously from riser cylinders or CO 2 low-pressure tanks. An essential feature of CO 2 snow blasting is the use of the liquid phase of carbon dioxide; solid particles as blasting media are generated directly in the process. If the CO 2 is already in solid form before the blasting process, it is called dry ice blasting. The liquid carbon dioxide is fed to a compressed air jet and expanded to form a snow / gas mixture.
A distinction is made between two process variants, the so-called two-substance ring nozzle and the jet nozzle with agglomeration chamber. With the two-substance ring nozzle, the liquid carbon dioxide is expanded to ambient pressure at the nozzle outlet. The resulting CO 2 snow particles are bundled and accelerated by a jacket jet of supersonic compressed air . Due to the low kinetic energy of the particles, this process variant is not very abrasive and is therefore mainly used for cleaning finely structured, highly sensitive components. In the second CO 2 snow jet principle, the liquid carbon dioxide is added to the compressed air flow in a relaxation space, the so-called agglomeration chamber. Compared to the two-substance ring nozzle, larger snow particles are created, which are accelerated by the compressed air in a subsequent nozzle, leading to a significantly higher level of abrasiveness.
The main advantages of CO 2 snow blasting are that it can be automated thanks to the continuous supply of blasting media. Due to the lower kinetic energy of the carbon dioxide particles, CO 2 snow blasting is a significantly less abrasive process than dry ice blasting. Areas of application are currently the cleaning of finely structured, highly sensitive components and, when using nitrogen instead of compressed air as an acceleration medium, use under clean room conditions .