Electroflotation halves volume of residual substances in steel and metal processing

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Source: EnviroChemie GmbH

A well known manufacturer of forging equipment and large presses, as well as a manufacturer of articulated crankshafts, both located in Germany, have commissioned the construction of E-Flo Dr. Baer electroflotation plants developed by Envirochemie. These plants are particularly well suited to cleaning process water which is heavily contaminated with surfactants and oil, partly recirculate it, and discharge it in compliance with the law.

In contrast to the well-known dissolved-air flotation (DAF), which uses very fine air bubbles to produce the flotation effect, the electroflotation technology recently introduced by Envirochemie works with micro-fine hydrogen and oxygen gas bubbles. The micro gas bubbles are generated by applying a low voltage to specially coated electrodes that have reversible polarity. The gas bubbles, which are identical in size and evenly distributed throughout, create a clean phase-separated flotation layer of oil, grease and surfactant mixture. This is then drawn off from the surface with a vacuum suction device without including a significant amount of water. The resulting oil-water mixture has a water content which is approx.

50% lower than in conventional flotation technology using air introduction and mechanical removal.

High water temperatures, which are a limiting factor for dissolved-air flotation, are of benefit in the newly developed process. They improve the separability of the oil-water mixture, as well as the separation of the flotate. The system reaches its temperature limits at approx. 90 °C. Due to the lower water content, the volume of the residual substances is reduced by approx. 50% compared to traditional processes, also due to the lower consumption of chemicals. The energy required for the production of gas bubbles is just 0.1 kWh/m³. Before entering the actual flotation chamber, the process wastewater passes through a mechanical separator for undissolved free oil, grease and sludge, and then to an Envochem flocculation reactor, in which suitable splitting agents and flocculants are dosed to separate the emulsion.

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