Galvanotechnics

Change of a hot-dip galvanising to meterials loss minimized process technique

The aims of the project, namely „Conversion to a technical process that minimises material loss while reducing costs at the same time“, were essentially realised. The results attained can easily be transferred and converted to other hot-dip galvanising plants as entire or partial solutions for corresponding production areas.

Summary

In the surface finishing sector, which also includes hot-dip galvanising, it is almost exclusively end-of-pipe technologies that are used for environmental protection. Converting to preventative, production-integrated pollution control systems is frequently regarded in the sector as too expensive and therefore as uncompetitive.
The aim of the plan was to counter these reservations through examining and converting, as far as possible and practically feasible, all stages of the hot-dip galvanising process, while at the same time reducing costs. The aim was also to prove that correctly implemented environmental protection improves technological progress and competitiveness.An actual status analysis was carried out at the beginning of the project. The operating data obtained in the analysis was then presented to the project partners for compiling the actual status and as basic data for PC models. After carrying out research on current technology and patents, a rough concept with possible variants was compiled for the conversion. This was developed into a detailed concept with the conversion variants, which were then partly implemented.
Results:
Degreasing: In addition to optimising the degreaser (regenerating with individual components), a regenerator for sluicing oil/grease out of the degreasing solution was developed (thermal dissociation, patent application EP 1 281 791 A1). Result: unlimited bath exposure time, cost reduction approx. 6.000 EUR/a.
Drying oven: Installation of a cross-flow/counter-flow heat-recovery system and other energy saving measures. Result: Energy saving approx. 150-170 KWh (= 30-35 %).
Galvanising bath: Measures for materials saving (Zn; zinc consumption reduction) through „semi-automation of the galvanising bath“, „use of new zinc alloys“, „installation of a zinc ash treatment plant“, „use of a vibration-dross grab“ and other peripheral individual measures. Result: Zinc saving in comparison with initial situation approx. 17 % and additionally approx. 12.000 €/a an account of other effects.
General pre-treatment: Here considerable problems occurred when treating the rinsing water with the electro dialysis plant adopted from the Genthin „removal process“ project. The problem will be dealt with further during the course of the project.
The partial project „Conversion to mixed pickling baths“ was tested on a technical scale and then developed on an industrial scale until ready for implementation. Patent applications were made for some stages (Note No. DE 101 07 936 C2). It was not, however, realised on account of both the project’s short implementation time and the financial limitations created by the current economic situation. Zinc elimination from mixed pickling baths is possible using the ionic exchange process. At the same time, logistic advantages (increased plant productivity) can be utilised and internal cycles (fluxing agent production) closed. Any required final concentration in respect to zinc content can be realised in the old pickling baths. The calculated savings potential is approx. 50.000 EUR/a.

More Project Informations

Project title: Change of existing galvanization plants to meterials loss minimized process technique at simultaneous costs reduction: Change of a hot-dip galvanising (TV 16)

Project number: 01RK9740/1

Project period: 1998 - 2002

Project region: Germany (Lower Saxony)

Project contact:

Herr Külker
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Source: German National Library of Science and Technology Hannover (TIB)