Proceedings of the 2 nd World Congress on Mechanical, Chemical, and Material Engineering (MCM'16) Budapest, Hungary – August 22 – 23, 2016 Paper No. MMME 129 DOI: 10.11159/mmme16.129 MMME 129-1 Influence of the Moisture Content on the Flowability of Blast Furnace Dust Christof Lanzerstorfer Process Engineering and Production/University of Applied Sciences Upper Austria Stelzhamerstraße 23, Wels, Austria c.lanzerstorfer@fh-wels.at Abstract - In this paper the influence of the moisture content on the flow characteristics of blast furnace dust is investigated. The flowability of granular material is essential for the design and operation of dust separators, transport equipment and storage silos. Two blast furnace dust samples from different blast furnaces were investigated. The moisture content was adapted for measurement with the shear tester by adding water to the dried blast furnace dust samples. The measurement showed a significant decrease in flowability at higher moisture content of the dust samples. The bulk density of the dust samples was lower at higher values of the moisture content. For the finer blast furnace dust the wall friction angles increased with the moisture content, while for the coarser blast furnace dust a decrease in the wall friction angles was observed for low moisture content. At higher moisture content the wall friction angle increased with the water content. Keywords: Blast furnace, dust, moisture content, flowability 1. Introduction Iron and steel are still the most important commercial metals. The annual production in Germany of steel and pig iron in 2014 was 42.9 Mio t and 27.9 Mio. t, respectively [1]. The blast furnace (BF) serves to produce pig iron from iron ore. The shaft of the BF is filled continuously from the top with layers of iron-bearing materials (iron ore, sinter, pellets, etc.) and coke. In order to reduce the iron oxides by carbon monoxide, heated air is fed into the BF in a counter-current flow. The reaction of oxygen with the coke to carbon monoxide also supplies the required heat for the process. The reduction gas leaves the BF as top gas. This dust containing gas can be used as a fuel after removal of the dust because of its heating value. The separation of the dust is performed in two stages. First, the coarse dust is collected in a dry dust separator (a dust catcher or a cyclone). In a second separation step the remaining fine dust is collected, usually by a venturi scrubber or an annular gap scrubber. In some BFs an electrostatic precipitator or a fabric filter is installed as a second de-dusting stage. The dust collected in the first-stage dust separator consists mainly of iron oxides (15%-40% Fe) and coke particles (25%-40% C) which are fine enough to be carried by the discharged gas [2]. Minor constituents are calcium oxide, aluminium oxide and silica [2-4]. The mass median diameter of dust catcher dust is typically in the range of 100 – 200 μm. Therefore, the BF dust is usually recycled to the sinter plant [5,6] to recover the valuable components. The average amount of dust separated in the first-stage dust catcher of European BFs is 18 kg dust per ton of hot metal produced [2]. The dust has to be discharged from the dust separator, transported and stored. For smooth operation of these processes the flow properties of the material are crucial. The flowability of fine granular material depends on several properties: grain size, grain size distribution and grain shape [7,8]. The moisture content of the material also has a significant influence on the flow properties. Increasing moisture content leads to reduced flowability because of the increasing influence of the liquid bridges between the particles and the resulting capillary forces [9,10]. At high moisture content, when the pores between the particles are filled with water, the particles form a suspension in water and the cohesive forces decrease [9,11,12]. However, this effect cannot be observed with all materials [13]. The flow properties of dust catcher dust have been investigated in a recent study [14]. The flowability of the dry dust catcher dusts has been reported to be very good. In this study the influence of the moisture content on the flowability of BF dust was investigated. Measurements with BF dusts from two different blast furnaces were performed. The flowability at increased water content is important because the dust is often wetted to avoid dust generation during handling and storage of the material.