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04.18.2012

Befesa Zinc Freiberg GmbH produces Waelz Oxide through recycling of zinc containing wastes

Befesa Zinc Freiberg GmbH is a company of Befesa Medioambiente S.A. Its business focuses on recycling of zinc containing wastes through thermal volatilization in waelz furnaces. The company produces a zinc concentrate which is used as feed material in zinc production.

Befesa Zinc Freiberg is based in Freiberg, Germany, in the Federal Land of Saxony, not far away from the regional capital.

Zinc is used on a large scale in corrosion prevention of steel, e.g. in galvanised steel construction or galvanised auto bodies. These components are scraped after their operational life span and come as scrap with the adherent zinc back to steel plants. In the steel plants the scrap is melted down in order to produce new steel. The zinc of the corrosion prevention is evaporated during the melting down process and removed as so-called steel dust in the off-gas cleaning systems of the steel plants. This dust is mainly hazardous waste. Befesa Zinc Freiberg offers recycling of these wastes to the steel plants. As mentioned above, it produces a zinc concentrate from this steel dust, which is reconverted into metallic zinc by zinc producers. This zinc, in turn, is used in corrosion prevention. In this way, the cycle of zinc closes. Befesa Zinc Freiberg makes a significant contribution in sustainable management of the natural resources of zinc through recycling of hazardous wastes of the steel plants and the return of zinc to the cycle of use.

The delivered zinc containing wastes, which have a zinc content of 20 to 35 %, are blended with a reducing agent in the pelletizing unit and continuously fed into a waelz furnace. In this furnace the zinc is evaporated and thus separated from the other elements of the wastes. The zinc leaves the furnace in counter flow to the remaining feeding and is deposited as so-called waelz oxide in the off-gas cleaning system of the processing plant. This oxide contains, in comparison to the wastes, 60 to 65 % zinc. Besides zinc also chlorides are evaporated in the thermal process, which accumulate in the waelz oxide as well. With the chloride compounds contained in the waelz oxide is hard to sell. That’s the reason why at Befesa Zinc Freiberg the chlorides are leached out in a second step of the process. This is done in a three steps, which use a counter flow, and whereby we obtain clean water in an evaporative crystallisation. The marketable end product is a zinc concentrate (Waelz Oxide) with a zinc content of, approximately, 65 to 68 % and a chlorine content lower than 0.1 %. This product is sold to zinc producers worldwide, who produce metallic zinc from it.

Befesa Zinc Freiberg operates two waelz furnaces, one with a length of 43 m and one with a length of 50 m, and a diameter of 3.6 m, at the site of Freiberg. Both furnaces have a throughput capacity of 220,000 t of zinc containing wastes altogether. About 60,000 t of zinc concentrate are recovered out of these wastes. 40,000 t of zinc can be returned to the cycle of raw materials with these 60,000 t and don’t have to be produced under exploitation of natural resources.

With a capacity of 220,000 t, Befesa Zinc Freiberg operates one of the biggest recycling plants of this kind in Europe.

The plant has 88 employees in Freiberg and achieved a turnover of approximately M€ 50 in 2011.

Diagram of the cycle of zinc.

Diagram of the cycle of zinc.

Diagram of flow sheet.

Diagram of flow sheet.

View of Befesa Zinc Freiberg.

View of Befesa Zinc Freiberg.

View of Befesa Zinc Freiberg facilities.

View of Befesa Zinc Freiberg facilities.

A waelz furnace of Befesa Zinc Freiberg.

A waelz furnace of Befesa Zinc Freiberg.

Interior of a waelz furnace of Befesa Zinc Freiberg.

Interior of a waelz furnace of Befesa Zinc Freiberg.