Case study of magnetically-stirred casting furnaces at New Zealand aluminium smelters limited

Abstract

New Zealand Aluminium Smelters Limited (NZAS) manufactures the highest purity primary aluminium ingot, high quality extrusion billet and rolling slab products. In 2011, NZAS installed Zmag’s MagStir™ into a 50T casting furnace. MagStir utilises Zmag Permanent Magnetic Circuit, the world’s first, proprietary permanent magnet-based technology for contactless stirring in the bath. Agitation of casting furnaces during alloying to achieve elemental dissolution and temperature control is the key part of furnace preparation and when performed in an efficient manner, it can give significant savings in fuel and alloying costs and increased throughput. In 2016, NZAS added MagStir to two more casting furnaces and achieved significant improvements in temperature control during all phases of furnace preparation. This paper is a case study on the benefits of stirring in general, specific benefits observed using Zmag’s MagStir at NZAS as well as lessons learned in the operation of the systems over 5 years.