INVESTIGATION OF THE CORROSION PROBLEM IN THE PIPELINE OF ENRICHED ALUMINA RECYCLE TO ALUMINIUM CELL

Document Type : Research Paper

Authors

1 Professor, Mining and Met. Eng. Department, Faculty of Eng. Assiut University, Assiut, Egypt

2 Professor, Mechanical Eng. Department, Assiut University, Assiut, Egypt

3 M.Sc student, Engineer,Aluminium Company of Egypt

Abstract

In this work, the failure of pipeline used for recycling the enriched alumina to self-baked (Soderberg) cells is investigated; the study includes also the deterioration of pipeline that recycling the enriched alumina to pre-baked cells and that recycling fresh alumina. Systematic measurements for the loss in the pipeline –wall thickness with the time are carried out. The gaseous emissions from the cells and the characteristics of enriched alumina are analyzed. Based on the analyses and visual inspections, a corrosive- wear sequence was identified, for the failure of pipeline of Soderberg system. The scales formed on the pipe inner wall are easily destroyed by the alumina impact due to the weak adherence of such scales. This resulted in the exposure of the fresh steel surface to the highly corrosive environment that prevails inside the pipeline, which accelerates the corrosion of the metal. For the pipeline recycling enriched alumina of pre-baked system, hard and dense layers were formed, which were strictly adherent to substrate. The loss in the pipeline wall thickness of the fresh and pre-baked alumina pipelines is negligible compared to Soderberg enriched line (0.5 versus 5.0 mm/year); however, the operating conditions of the particles impact (velocity, particle size, flux) were close to each other in value. Therefore, the failure mode of pipeline in the Soderberg system is an erosioncorrosion process.

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JES. Journal of Engineering Sciences
Volume 36, No 4
July and August 2008
Pages 963-975

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