Hot-dip Galvanizing

Reduction of zinc consumption in the hot-dip galvanizing process

The internal and continuous processing of the flux solution keeps the iron content in the flux bath at a constantly low level, which drastically reduces the generation of the disruptive residual products iron-zinc and zinc ash. As a result, raw materials such as zinc and natural gas can be used much more efficiently.

Summary

Initial situation
The galvanizing company Sulz GmbH hot galvanizes prefabricated steel parts. To this end, the parts are chemically treated in a series of processes and then immersed in a bath of liquid zinc. This is followed by a flux bath which enables a better coating of the steel surface with the liquid zinc.
Until now, the residual products of iron-zinc and zinc ash created in the galvanizing bath have had to undergo external reprocessing, as a result of which the zinc was lost to the company.
The galvanizing bath was heated with natural gas to temperatures of around 450°C to keep it in a permanent liquid state.

The aim of the project was to reduce specific natural gas and zinc requirements, to eliminate the use of dangerous chemicals, eliminate the need to transport hazardous substances, improve the galvanizing quality and extend the capacity of the plant while at the same time lowering operating costs.
 

Technical solution and findings

  • The iron content in the flux bath is to be maintained at a continuous level of less than 5g per litre of flux solution using the company's Fluxomat processing system and the flux solution Hegaflux Ferrokil, which is based on a permanganate mix.
  • The flux solution is continuously pumped from flux bath to settling tank and back. The Hegaflux Ferrokill is added to the flux solution in the settling tank to settle the iron content as slurry. As a result, less iron is carried to the galvanizing bath, and the amount of iron-zinc created is reduced by around 20%.
  • The parts to be galvanized are dried before they are immersed in the galvanizing bath to ensure that the flux solution reacts less with the liquid zinc. This reduces the amount of zinc ash created to about 50%, and less energy is required to vaporise the moisture.
  • The galvanizing bath is heated by a heat recovery system integrated into the galvanizing furnace.
  • Zinc consumption in the new system has been reduced by about a quarter. 66kg of zinc are used per tonne of material.
  • It was possible to reduce specific energy consumption to around 60%.
  • In addition, production stops and the transportation of hazardous substances (CO2 emissions) have been eliminated and the chemicals H2O2 and NH3 are no longer used.

Conclusions
In addition to significant environmental benefits, the new process also results in economic savings in the field of energy and resources and in an improved product quality.

Source: Final report

Project Participants

Implementing Institutions

Verzinkerei Sulz GmbH

Technological Providers

Dipl.-Ing. Herwig GmbH

More Project Information

Project title: Reduzierung des Zinkeinsatzes beim Feuerverzinken durch Kombination eines neuen Fluxmittels mit einer innovativen Flussmittelaufbereitungsanlage

Project number: 20133

Project period: 2008 - 2010

Project region: Germany (Baden-Württemberg)

Project contact:

Frau Puder
This email address is being protected from spambots. You need JavaScript enabled to view it.
+49 (340) 2103 3067
+49 (340) 2104 3067

View Publication

Source: Environmental library of the Federal Environment Agency (UBA)