Hazardous Waste Treatment

Simulation of material flows in copper foil manufacturing

An analysis of the material flows in the neutralising facility for sludge and wastewater containing copper and sulphuric acid made a monetary assessment of the copper content possible and showed potential for optimisation.

Summary

Gould Electronics GmbH of Eichstetten, Germany, produces copper foil for the manufacture of circuit boards in a complex process.

One of the sub processes is neutralisation. In this process, sludge and wastewater containing copper and sulphuric acid from the production process are neutralised by the addition of caustic soda, and dry sludge and wastewater with a high copper content is produced in an overlapping system of settling basins. The dry sludge can be sold on the basis of its high copper content.

A complex model was developed as a means of achieving greater transparency in the largely ignored sub process, whereby a steady circulation amount for the initial transient phase in the system is calculated independently and evaluation options for each of the components in the wastewater or sludge offered. In addition, the parameters used by the model allow a speedy analysis of the various scenarios. The company was provided with an Excel-based import tool for this purpose.

The simulation showed that 99.6% of the total copper content is in fact concentrated into the dry sludge, and that the actual value of the copper-bearing dry sludge is around EUR 300,000, whereby the monetary value within the neutralisation process of the copper before treatment and the cost of additives such as the neutralising caustic soda and thermal energy in the form of natural gas for the drying process play an important role.

The model enables the company to optimise the value of the copper flows resulting from neutralisation. It can examine, for example, whether it is possible to reduce the copper content of each of the initial sludges during production, thus eliminating the elaborate treatment of the valuable copper later during neutralisation, and what cost savings this would bring.

The process still offers considerable potential, particularly in the field of transparency and costing. It is therefore recommended that further simulations of the production process be carried out.

Source: Final report

More Project Information

Project period: 2003 - 2004

Project region: Germany (Baden-Württemberg)

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Source:  Landesanstalt für Umwelt Baden-Württemberg