Service Life Extension of the Alkaline Degreasing Bath Fluid in the Steel Galvanizing Line at Arcelor

oleh Karel Klofac, Khalid Farooq, Tom Wood, Eric Ingels

Penerbit - Arcelor-Mittal Steel, Pall Corporation

Kategori - Novel Am

Surface preparation of steel prior to galvanization is accomplished by passing the sheet through a series of baths to degrease and clean the metal surface. The first of these baths contains an alkaline solution with pH in the range of 13-14 to remove oils from the metal surface. Maintaining the alkaline sprays with oil levels below 5 g/L is required to achieve clean surfaces for proper adhesion of the zinc based galvanizing material to the metal surface. It is a common practice in the industry to drain a large portion of the alkaline solution periodically and drain the full bath once a month. Typical methods employed to remove the oily and solid contaminants from the degreasing baths include the use of settling tanks to decant the emulsified oils, coalescer type oil separator, and coarse bag or magnetic type filtration to remove particulate. This paper discusses an alternate method, based on 50-nanometer, ceramic membrane cross-flow system, which has been successfully utilized at Arcelor Mittal Steel Belgium site at Genk (former Sikel) and several other steel mills in Europe. The system at Genk, which has the capacity of generating 2 m 3 /hr (9 GPM) of clean permeate was commissioned in 2002 and has been operating successfully since. The utilization of the ceramic membrane cross-flow system has resulted in significant cost savings as a result of reduced alkaline solution and water usage and the need to treat the waste.

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