| With a nearly 100 years experience, Steuler Anlagenbau GmbH, Germany, develops, plans and builds plants world-wide for surface finishing, wire refinement, water and waste water treatment, regeneration, absorption, catalytic and flue gas cleaning applications. With 1,700 employees and subsidiaries in P.R China, Brazil, Spain, Austria, the company is one of the world�s largest suppliers for the wire chemical treatment industry.
The company provides a wide range of pickling systems, such as tunnel pickling lines that are suitable for the fully automatic pickling of large quantities. For in-line process, Steuler offers multi-wire pickling lines particularly suitable for the galvanizing process and steel-cord, using HCl or H2SO4 as pickling medium. When using HCl, it is important to generate a high-wire turbulence and to run a closed system. The use of an optimised air-jet system is very important to keep the drag-out as low as possible, an effective working cascade rinsing is to be mentioned as well. The use of an electrolytic pickling (bipolar action) is necessary when using H2SO4. The benefits of bipolar electrolytic pickling, compared with chemical pickling, are as follows:
- A reduction of the pickling time by 50 to 75%;
- Better surface quality
- Low concentrated acid is required for electrolytes, therefore the danger of corrosion of the material to be pickled is very small;
- Faster decomposition of scale resp. oxides by polarisation potential;
- With bipolar method, no mechanical contacts are made with the wire as the cleaning electrolyte acts as the contact.
Steuler�s systems work with a current density ranging from 20 to 120A/dm2. Throughout this pickling operation, the iron content of H2SO4 will increase by approximately 0.24 to 0.28g/A per hour. For a reduction of the pickling solution, the company offers various systems, such as:
- Cascade pickling: reduction of fresh acid consumption, continuous feeding of fresh acid automatically controlled for stable iron content;
- Acid recovering system: H2SO4 (98%) no recovery appr. 10 to 20kg/t; H2SO4 (98%) with recovery appr. 2.0 to 5kg/t.
In order to achieve a high-quality wire, some applications require an additional alkaline pickling stage. The feature of such a system is that no pickling residues remain on the wire surface. Furthermore, this system can be used as the cleaning stage prior to the furnace.
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