A Case Study on Accretion Formation in Rotary Kiln of DRI Process
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ORIGINAL ARTICLE
A Case Study on Accretion Formation in Rotary Kiln of DRI Process V. Shankar Rao1 • S. N. Gurugubelli1
Received: 5 September 2020 / Accepted: 24 October 2020 The Indian Institute of Metals - IIM 2020
Keywords Direct reduced iron Coal Iron ore Rotatory kiln Accretion
High-silica and high-alumina in iron ore along with high ash content in coal are attributed for the accretion build-up in kiln. These form low melting complex compounds such as iron-magnesium silicate. To reduce the accretion formation in DRI process, a more elaborate understanding is needed. In this context, we have reported a case study of 100 tons per day (tpd) rotary kiln (Fig. 1). The size of the kiln is 42 m length and 3 m outer diameter (2.6 m internal diameter), and inclination of 2.5, resting on three support stations. The longitudinal positioning of the kiln on its riding rings is controlled by hydraulic systems. Lifetime of the kiln operation is 29 days.
1 Introduction
2 Experimental Procedure
In coal-based DRI plants rotary kiln is used for the reduction of iron ore. Accretion rings formations inside the kiln adversely affect the performance of plant in terms of low production and inferior quality, which frequently lead to shut down. About 70% of the coal-based DRI rotatory kiln shut down is due to the accretion formation [1]. Literature on the coal-based rotary kiln DRI process is not sparse but not many have focussed on the accretion formation [1, 2]. A comprehensive study on the accretion formation in DRI kiln during sponge iron production has been published by Shrives and Shrives [1]. Rao outlined the accretion formation in an experimental rotary kiln [2].
In the present investigation, sampling and analyses were done as per following standards. Iron ore–IS:1405:1982, IS:1493-1(1981); DRI–IS:15774(2007); sulphur– IS:15403(2003); coal–IS:1350-1(1984). Analyses were carried out in duplicate to ensure accuracy in results. For microstructure analysis, specimens were prepared by mounting in epoxy resin and polishing on silicon carbide (SiC) paper down to 2000 grit, followed by ultrasonic cleaning.
Abstract In coal-based DRI process, accretion formation inside the rotary kiln is a genuine complex problem. Accretion formation in a rotary kiln of 100 tpd DRI plant has been investigated. The nature of accretion formation with respect to the charge burden and operational parameter have been discussed. High ash content in the coal and excess use of dolomite lead to accretion formation. Two different types of accretion are revealed; the major one is due to agglomeration of DRI by-products while another one is sintered product of DRI.
& V. Shankar Rao [email protected] 1
Metallurgical Engineering, JNTUK—University College of Engineering, Vizianagaram 535003, India
3 Raw Materials and Kiln Operation The temperature and process control in the kiln was carried out by air injection tubes spaced evenly along the kiln length. At the kiln discharge end, a central burner was used with light diesel oil (LDO) for hea
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