(491c) Flash -Reactor Process for the Recovery of Dusts Containing Zn

The development of processing routes for the treatment of metal and metal oxide contained residues, particulary dusts and slag, becomes a major environmental issue. Economical recycling of waste materials and the creation of saleable products are more and more important since dumping of these substances is complicated and expensive. The dusts from the iron and steel industry with high contents of heavy metals contain also zinc, which is an interesting commodity. The high contents of zinc of the dusts are a consequence of processing automobile scrap in the steel industry. The isolation of zinc from the dusts and its utilisation is important due to economical and ecological reasons. A very promising process for zinc recovery is the so called flash -reactor process. The Chair of Thermal Processing Technology at the University of Leoben designed and erected a pilot plant in cooperation with Tribovent Process Development GmbH, voestalpine Group and the Chair of Non-ferrous Metallurgy. The main components of the plant are the dosing system for the dust, the burner unit and a reaction chamber situated below the burner unit (Fig. 1). The dust is inserted through the dosing system into the burner unit and is mixed with oxygen. The oxygen is inserted through a ring line around the burner unit. The dust/oxygen mixture is directly fed to a fuel gas/oxygen flame between the burner unit and the reaction chamber, where the dust is immediately slagged. This slagging process produces a flue gas, which contains gaseous zinc. Due to the reducing process conditions afterburning of the flue gas required. In that way the gaseous zinc is oxidized to solid zinc oxide. The deslagging takes place at the lower end of the burning chamber. The goal of this process route is on the one hand to convert the dust into a slag bath and on the other hand to remove zinc in form of a ZnO-dust concentrate. Aim of the pilot plant is the optimization of the process concerning dust feeding and dispersing, operation temperature and pressure as well as atmosphere and furthermore precipitation of the ZnO-dust and flue gas cleaning with focus on high product yield and quality and to minimize energy and costs. Fig. 1: The principle construction of a flash -reactor plant [2] [1] Antrekowitsch, Jürgen; et al.: Use of the Flash Reactor Principle in Processing Residues from Steel Metallurgy. Leoben: University of Leoben, Department Metallurgy, Non-ferrous Metallurgy, 2005. [2] Edlinger, Alfred: RecoDust ? Verfahren ? Pyrometallurgische Raffination von Stahlwerksrückständen. Duisburg: 2nd Meeting of the IISI-Project on By-Product Management, 18-20. Juni 2007.