Furnace dust utilisation using the pneumatic injection: a methodology

Abstract

The issue of generating dust waste is present in steel and foundry plants around the world, as all melting furnaces generate tonnes of dust every year. This dust is obviously considered to be a waste material; however, the dust itself still contains certain chemical elements (mostly iron and zinc) which can be utilised by being returned to the furnace during the melting process. This means increasing their content in the liquid metal bath or in the dust that is finally sucked out from the furnace that can then be used as a raw material in the zinc metallurgy industry. There are several methods to achieve this, and one of them is pneumatic powder injection with the use of a pneumatic dust feeder and injection lance to introduce the dust directly under the surface of liquid metal. The paper presents both a theoretical approach as well as industrial applications as the result of the authors’ work in this field of the pneumatic conveying technique. Both the benefits and limitations of dust reuse are presented. The same method can be used to re-introduce cupola dust into the cupola and electric arc furnace together with some carburiser or ferroalloy additions. The results show the crucial influence of the process’s pneumatic and dimensional parameters that are needed to achieve proper jet penetration inside the liquid metal volume. The authors’ own theoretical formula for the so-called critical jet radius describing its potential to penetrate the liquid alloy is shown here, too. This complex approach has proven to be a huge potential of the pneumatic powder injection technique as a tool to utilise dust wastes in melting furnaces in steel and foundry plants.