Paint deposition
As paint separation technologies are referred to which the significant solvent and paint mist amounts incurred during painting, be kept under control and disposed of.
Overspray
In spray applications, overspray is the proportion of the paint used that does not get onto the workpiece, but escapes into the environment in the form of paint mist . In order to protect the environment, this must be separated, disposed of or recycled in a controlled manner.
Classic wet washing
The standard technology for collecting and treating the overspray is the Venturi scrubber . When it is used, the overspray is separated from the air flow with the aid of atomized water.
In the spray booths , the evaporating solvents and the paint mist are transported to the separation system by filtered and conditioned air. Air flows through the cabin from top to bottom, striving for a flow that is as laminar as possible .
Large-scale paint shops are often equipped with gas scrubbers . These are located below the cabin. Their task is to bring the air laden with paint mist droplets into interaction with the wash water as intensively as possible. In order to absorb the spray mist as completely as possible, the spray mist is strongly accelerated by constriction in the suction devices (Venturi principle) in order to then be absorbed into the aqueous phase at a high relative speed .
The resulting paint sludge is then separated from the washing water. The washing water is treated and made available again for the washing process. If the washing water is untreated, odors can occur due to putrefaction processes. The paint sludge is then disposed of or processed. In most cases, the cabin air used to transport the spray mist is no longer used, but released again to the outside. To save energy, a recirculation mode is aimed for in modern painting systems. So z. B. in the field of plastic painting only circulated air.
new technologies
In the meantime, two other technologies have been adapted to the painting process in order to efficiently solve the problem of paint separation.
Dry separation
With dry separation, the overspray is bound with the help of stone dust and then reused.
The overspray is separated from the air with the help of rigid body filters. Stone powder is used as a separating agent so that the filter does not stick together due to the paint overspray, but rather a long service life can be guaranteed.
The stone meal is first applied to the filter as a basic protection, the paint particles attach to the stone meal. When a certain pressure loss is exceeded, the rock powder coating is cleaned off the filter again by means of a pressure surge from the clean gas side. A new layer of stone meal is brought to the filter until the stone meal is concentrated with a fixed amount of varnish. The stone meal is then replaced.
The saturated stone meal can be used thermally in the cement industry or incinerated in coal-fired power plants.
Electrostatic separation
In the case of electrostatic separation, the particles contained in the overspray are electrostatically separated in a wet electrostatic precipitator on the surfaces provided. The particles are removed from the surfaces with a separating agent, which is usually a mixture of water and other additives, and conveyed into a storage container, where they agglomerate and can be removed from the liquid cycle in a subsequent step using a decanter or centrifuge .
literature
- VDI 3455: 2013-08 Emission Reduction; Systems for series painting of automobile bodies (emission control; high-volume car body painting plants). Beuth Verlag, Berlin. ( Summary and table of contents online )
Individual evidence
- ↑ VDI 3455: 2013-08 emission reduction; Systems for series painting of automobile bodies (emission control; high-volume car body painting plants). Beuth Verlag, Berlin, p. 75.
- ↑ see: Paint sludge discharge device
- ↑ VDI 3456: 2018-05 emission reduction; Refinishing and finishing of vehicles (emission control; refinishing and finishing of vehicles). Beuth Verlag, Berlin, p. 60.
- ↑ VDI 3455: 2013-08 emission reduction; Systems for series painting of automobile bodies (emission control; high-volume car body painting plants). Beuth Verlag, Berlin, p. 80.