Features of operation of the central trough of a blast furnance smelting vanadium pig iron

Abstract

During a class-two overhaul of blast furnace No. 2 in May-June of 1998, the Chusovoi Metallurgical Plant installed a central trough designed by the company Techservice (in Slovakia) and began using new trough refractories. The plant initially used refractories supplied by the company that made the trough. The main layer of the trough lining was composed of refractory SPK, while the working layer was made of refractory BASAPAMIX 1300.The plant later changed to a trough refractory made by the company Plibur in Pervoural'sk in accordance with a technology developed by the Austrian firm PLIBRIKO. According to the specifications, this refractory contains 57-60% A1203, 9-11% SiO 2, 15-16% SiC, and .3-1.7% Fe203. The refractory has a bulk density of 2.56 tons/m 3, porosity of 31.0%, shrinkage of 0.62%, and ultimate compressive strength of 10.9 N/mm 2.Use of the new trough and new refractories has increased the period between repairs from 2 days to 1 month and improved the performance indices of the blast furnace (Table 1). Between scheduled repairs, the damaged sections of the lining are repaired by guniting after the pig iron has been drained from the trough.However, despite the satisfactory condition of the tamped lining overall, there have been some problems with the operation of the central trough during the smelting of vanadium pig iron. The problems have arisen mainly in connection with the rapid incrustation of the sides of the trough and the formation of thick layers of mechanically strong masses of material in the bottom part. This material contains up to 25% titanium (in terms of TiO2) and up to 3.0% vanadium (in terms of V205). The thickness of the slag crusts reaches 200-500 mm.Detailed studies made it possible to determine the composition and features of formation of the crusts formed after repeated tappings of the smelting products.The material of the crusts is an inhomogeneous mass composed mainly of a slag melt that contains cavities (pores), inclusions of metal and coke, and carbon-bearing deposits (Fig. 1). We should particularly mention the presence of large amounts of material in the form of pebbles (bean-shaped granules) having sizes ranging from several millimeters to 6-7 cm or more (Fig. 2). The crusts are very hard -they can be cut only by a diamond circular saw.All of the crust samples that were studied consisted of three structural elements -a small "bobbin" consisting mainly of carbides, granules of metal, and a slag component that cements the granules together (Table 2). It was determined that despite the scatter of the data, all of the components have a high concentration of titanium. This is especially true of the carbide "bobbins," which have a titanium content of up to 42%. Even the metal inclusions have a titanium content 10 times greater than that of the pig iron (2.7 to 0.25%). The inclusions also have higher concentrations of the other elements, but to a much lesser extent. For example, the inclusions contain roughly twice as much chromium, manganese, and sulfur and 1.4 times more van...