Circulation of process water from acid degreasing, polishing, copper plating and de-chroming of impression cylinders.

Sulfuric acid, chromic acid, copper, sodium carbonate, trisodium phosphate, silver nitrate, sodium hydroxide solution and sodium silicate.

No matter whether identity papers, postage stamps, currency notes or food packaging must be printed. Gravure printing with engraved impression cylinders is an important method to obtain high-quality printed products in the world of today.

in the production of these impression cylinders, different purge and rinse waters, most of which are acidic and contain heavy metals, are obtained. It is forbidden to dispose of these effluents without proper treatment. The quality of the purge/rinse water in the production of impression cylinders is very important. The water must have very poor conductivity to ensure that the surface of the impression cylinders is of the required quality. The continuous circulation of the rinse/purge water by the VACUDEST® method provides water as required.

Before the water, which has very low pH, enters the VACUDEST® vacuum distillation unit, it must be neutralized. This also improves the quality of the distillate because acids cannot be entrained. The addition of lime-milk or flocculant such as is known from conventional treatment methods is not necessary.

If hydrochloric acid is used in the preparation of the impression cylinders, it may be necessary to select materials of sufficient resistance for the VACUDEST® treatment. If polishing or the removal of spent copper coats produces a lot of particles and copper chips, the particulate should be eliminated by a band filter before distillation.

The practical experience of continuous operation show that the distillation of the purge/rinse water can provide water of constant high quality and 100 % circulation of the rinse/purge water is possible. The VACUDEST® system clearly reduces the cost of fresh water and also the treatment cost of the purge/rinse water.