Recirculation of rinsing water in the powder coating process

A coating plant saves a lot of Co2, transport and packaging costs with a modern fully automatic powder coating plant and a circulation of the rinsing water through a waste water treatment system.

Reku is a family-run company based in Tyrol as a wholly owned subsidiary of Reku Produktion & Entwicklung GmbH. Reku was a pure manufacturing company for stainless steel parts (60 percent) and sheet steel parts (40 percent), mainly for the pharmaceutical and food industries. Three truckloads of parts were packed, transported, coated externally, packed again and transported back every week - this is now completely eliminated: Reku Color now coats the parts itself on site in Radfeld/Tyrol.

During surface treatment prior to powder coating by degreasing or chrome-free passivation, large quantities of rinsing water are required after each process step. This rinsing water must be neutralized and treated directly on site so that heavy metals are removed and toxic substances are eliminated. The goal here is to have a reliable system that operates automatically, monitors the requirements of surface technology, and does not interfere because of poor or fluctuating water quality. Therefore, a sustainable wastewater treatment system was to be put into operation at Reku Color's new plant that would cover the requirements and reliably treat the wastewater from the new powder coating plant.

Already during the planning of the new coating plant, reference plants in Bavaria and Austria were visited and the experience of the plant operators was used to get an idea of the process steps and diversity of the processes. Even at this stage, suppliers were sought who would meet expectations: including H2O.

As already seen during the reference visits, there are also major differences here. This is where the modular treatment system from H2O in Steinen, Germany, comes into play: The Vacudest M 1.500 CC vacuum evaporator system treats the rinse water from pretreatment and the deionized water so ideally that it can be reused in the various rinses and process steps without hesitation. The distillate can be used directly in the rinses - or after-treated via an ion exchanger as DI water of the highest quality, thus saving valuable drinking water.

The contaminants separated during treatment with the Vacudest are only fractions of the total quantity (< 5 percent) and can thus be collected by the disposal company in a cost-minimized and professional manner.

In addition to the already mentioned recirculation of the rinsing water, this process offers several other advantages. The neutralized rinsing water is evaporated at approx. 86°C under vacuum. The steam is compressed to ambient pressure in the vapor compressor (vacuum pump) and heated to approx. 120°C in the process. This hot steam is then used to heat the incoming process water. Compared to atmospheric evaporation, this saves more than 95% energy. The distillate produced in this way is virtually free of heavy metals and salt and can be reused directly as rinse water in the running process.

In addition, H2O innovations were integrated into the system at Reku, which further improve the rinse water quality and keep it at a constantly high level. With the help of these modules, Reku Color can produce in a sustainable, environmentally friendly and cost-effective manner:

Clearcat (CC): The module for oily rinse water. The patented process, which has received an award from the Baden-Württemberg Ministry of the Environment, excellently separates organic impurities. Hydrocarbon concentrations in the distillate < 10 mg/l can thus be reliably achieved - the use of a maintenance- and cost-intensive residual oil separator is thus eliminated and sustainable savings made.

Activepowerclean (APC): The system for lower energy consumption. The proven APC system has now been successfully used in Vacudest since 1998. The ceramic fluidized bed continuously cleans the heat exchanger mechanically during the process. This significantly reduces the formation of deposits on the walls and drastically reduces energy and cleaning agent consumption.

E-service/remote maintenance: support from the specialists. The modern Vacutouch machine control system allows convenient remote access to the Vacudest vacuum distillation system via the Internet. This enables H2O's service experts to provide fast and competent assistance remotely. This eliminates the need for more than 40 percent of all previously required unscheduled on-site service technician visits. In this way, Reku Color reduces downtimes, increases system availability and reduces its service costs.

Ing. Markus Zott, plant manager at Reku Color, draws the following conclusion: "With the new powder coating system, we can cover everything from private customers to industrial companies and save ourselves a lot of time, transport and packaging costs. Our employees can concentrate on their actual tasks. The new wastewater treatment plant from H2O helps us to manufacture in a sustainable, clean and environmentally friendly way. The H2O service staff was very friendly and helpful and did a very good job. The Vacudest also runs very reliably without much operator effort." (OM-05/23)