Citation: Pöpperlová, J.; Ottweiler, S.;
Vossberg, A.; Krupp, U. Feasibility
Study on Automation of Zinc Ash
Skimming Process in Batch
Galvanising. Automation 2023, 4, 1–10.
https://doi.org/10.3390/
automation4010001
Academic Editor: Qingsong Xu
Received: 13 November 2022
Revised: 18 December 2022
Accepted: 25 December 2022
Published: 28 December 2022
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
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Attribution (CC BY) license (https://
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4.0/).
Article
Feasibility Study on Automation of Zinc Ash Skimming Process
in Batch Galvanising
Jana Pöpperlová
1,
* , Stephan Ottweiler
1
, Andreas Vossberg
2
and Ulrich Krupp
1
1
Steel Institute (Institut für Eisenhüttenkunde) (IEHK), RWTH Aachen, Intzestrasse 1, 52072 Aachen, Germany
2
German Social Accident Insurance Institution for the Woodworking and Metalworking
Industries (Berufsgenossenschaft Holz und Metall) (BGHM), Seligmannallee 4, 30173 Hannover, Germany
* Correspondence: jana.poepperlova@iehk.rwth-aachen.de
Abstract:
The aim of the presented feasibility study was to systematically investigate the automation
of the skimming (i.e., removal) of zinc ash from the surface of the zinc bath in order to minimise the
risks for workers due to mechanical hazards (risk of falling into the zinc kettle) and chemical hazards
(inhalation exposure to zinc vapours) by eliminating this activity. As part of the feasibility study,
automatic separation and skimming systems from various applications, such as removal systems
of slags and metal foam, were identified. For this purpose, their technical feasibility and suitability
were considered. Two automated techniques, a mechanical and a gas-based skimming system, were
selected for the subsequent laboratory-based evaluation. In the scope of the practical feasibility study,
the selected skimming techniques were designed, constructed, and evaluated based on near-process
prototype tests on a laboratory scale. The focus was on the efficiency of the skimming systems,
related to the removal of zinc ash from the free surface of the molten zinc (general efficiency), as
well as to the zinc ash removal with a simulated attachment system of the samples to be galvanised
(task-related efficiency). The desired complete removal of zinc ash from the zinc bath surface was
demonstrated with two automated methods: a pulse wave method of the mechanical skimming
system and a gas-based skimming system in general, operating independently from the attachment
system. Additionally, as part of the process-related simulation of the complete batch galvanising
process, a fully automated combination of the zinc ash skimming and extraction system was achieved
on a laboratory scale.
Keywords:
zinc ash skimming; zinc ash extraction; mechanical skimming; gas-based skimming;
batch galvanising
1. Introduction
During the batch galvanising process, reaction products are formed on the surface of
the molten zinc, and if they are deposited on the galvanised surfaces, they degrade the
quality of the components. These reaction products floating on the molten zinc are called
zinc ash. The zinc ash is formed by the evaporation (boiling off) of the flux from the surface
of the galvanised components after immersing them in the zinc bath. In order to prevent
the zinc ash from depositing on the surface of the component and thus to ensure the optical
quality of the galvanising in particular, the zinc ash is currently removed manually. That
means the zinc ash is skimmed off the surface of the molten zinc, away from the immersed
components and towards the front of the kettle before the galvanised products are extracted
from the zinc bath. Throughout this process step, the workers manually skimming the zinc
ash are exposed to mechanical and chemical hazards. The mechanical hazard includes the
risk of workers falling into the molten zinc, and the chemical hazard describes the risk due
to inhalation of the toxic substances evaporating from the molten zinc.
The Permanent senate commission for the investigation of health hazards of chemical
compounds in the work area of the German research foundation (DFG) specifies a maximum
Automation 2023, 4, 1–10. https://doi.org/10.3390/automation4010001 https://www.mdpi.com/journal/automation
