Carbon Dioxide Pellet Blasting

 

This section was developed using information and original text from the Zebra Mussel (Dreissena polymorpha) Control Handbook for Facility Operators.

 

Carbon dioxide pellet blasting (or "thermal shock" blasting) is similar to sand blasting except that carbon dioxide pellets are used instead of sand. Carbon dioxide pellet blasting is preferred over conventional sandblasting because sand removes only the zebra mussel's outer shell, exposing the soft inner tissues which absorb the pressure. Unlike sandblasting, this method removes more organic material and is less likely to damage the surface. The rate of removal is approximately 1/4 to 1/2 m/ min, and the results are suitable for the application of a coating.

 

The surface that needs to be cleaned must first be dewatered. Liquid carbon dioxide is maintained in an insulated pressurized tank. As the liquid is piped into a pelletizer, it forms dry ice pellets. These are then piped into a pressurized air stream and directed out of the blast nozzle. The temperature of 84C and the strong force of the pressurized air stream and pellets cause embrittlement of the zebra mussel shell, inner tissue, byssal threads, and biofilm, making removal easy. The pellets fragment upon impact and rapidly expand to a gaseous stage, assisting in the cleaning of porous or riveted surfaces. This method has been used extensively to remove organics from aircraft, producing no deterioration of surfaces. In confined areas where the removal of sand is a problem, no additional material must be removed, since carbon dioxide pellets readily vaporize.

 

Claudi and Mackie (1994) recommend the prompt cleaning of any dewatered surface due to the stench of dead mussels. If the mussels are allowed to die and putrefy, the resulting smell would result in a very poor work environment.

 

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Management and Control Options

Reactive Control Methods