DOI 10.1007/s11015-017-0434-8 Metallurgist, Vol. 60, Nos. 11–12, March, 2017 (Russian Original Nos. 11–12, Nov.–Dec., 2016)

IMPROVING THE JUNCTION BETWEEN THE HOT-BLAST MAIN AND THE BUSTLE PIPE OF A BLAST FURNACE V. G. Druzhkov and M. Yu. Shirshov

UDC 669.162.22-52

Alternatives of hot-blast supply to the bustle pipe and the geometry of the tuyere stocks as one of the causes of nonuniform hot-blast distribution are discussed. Rational junctions between the hot-blast main and the bustle pipe and rational combinations of designs of junctions between the bustle pipe and the hot-bustle main and the blowpipe that minimize the nonuniformity of the hot-blast distribution are proposed. Keywords: blast furnace, hot-blast supply, bustle pipe, hot-blast main, uniform hot-blast distribution, tuyere stock geometry, junction.

The hot-blast distribution among the tuyeres in the hearth of a blast furnace (BF) is known to be considerably nonuniform. This problem has been given little attention [1, 2]. Possible causes of nonuniform hot-blast distribution are the following [1–4]: 1) straight-line (at a right angle) supply of hot-blast air to the bustle pipe, because of which the wind rate in the inlet sectors and their opposites are usually higher than elsewhere; 2) the geometry of the tuyere stocks; 3) penetration of refractory fragments of damaged combustion chambers of the stoves and/or damaged hot-blast mains into the tuyeres; 4) different gas permeability of materials above the tuyeres because of the nonuniform circumferential distribution of the burden; 5) distortions of the burden surface profile; 6) reduced open cross-section of tuyeres because of slagging; 7) inadequate mixing of hot and cold airs controlled with the mixing valve; and 8) furnace profile distortion because of excessive erosion of the lining (in sectors above iron tapholes and slag notches) and formation of excessive wall accretion and salamander. There are other causes such as the turbulence of the hot-blast air at the junction with the backdraft stack [4]. The improved uniformity of hot-blast distribution among the tuyeres was attributed to the following [1]: hot-blast air is introduced into the bustle pipe not horizontally, but at some angle, which reduces the probability that hot blast and refractory fragments penetrate directly into the tuyeres in this sector. The main task for blast-furnace operators in Russia and all over the world is still to improve the perimetrical uniformity of a BF to better utilize the thermal and chemical energy of the hearth gas by reducing the nonuniformity of the distribution of hot-blast air among the tuyeres [1, 2, 5] and materials over the furnace top [6]. A radical method to accomplish this task is to introduce an automatic blast distribution system (ABDS) of new generation [4, 7, 8]. An analysis showed that improving the design of the junction between the hot-blast main and the bustle pipe [9] may appear effective. Alternatives of hot-blast supply to the bustle pipe and combinations of junctions between the bustle pipe and the hot-blast main and the blowpipe are discussed. Magnitogorsk State Technical University, Magnitogorst, Russia; e-mail: [email protected], [email protected]. Translated from Metallurg, No. 12, pp. 39–42, December, 2016. Original article submitted June 22, 2015. 0026-0894/17/1112-1239 ©2017 Springer Science+Business Media New York

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Fig. 1. Supply of hot-blast air to the bustle pipe (a, b) and the geometry of tuyere stocks (c, d, e).

Fig. 2. Unidirectional supply of hot-blast air to the bustle pipe: a) straight-line supply of hot blast; b–d) tuyere stocks of typical design; e) Gipromez tuyere stock; ƒ) Paul Wurth tuyere stock [10].

Figure 1 shows alternative hot-blast mains connected at different angles to the bustle pipe and the geometry of tuyere stocks. The Ferrous Metallurgy Department of the Nosov Magnitogorsk State Technical University has developed rational alternative junctions between the hot-blast main and the bustle pipe (Figs. 2 and 3). In Figs. 2b, d–ƒ, the bustle pipe and the 1240

Fig. 3. Unidirectional (from above) supply of hot-blast air to the bustle pipe with two connecting pipes: a) straight-line supply of hot blast; b) tuyere stocks of typical design; c) Gipromez tuyere stock; d) Paul Wurth tuyere stock [10].

hot-blast main are in the same plane. In Fig. 2c, the hot-blast air enters the bustle pipe at some angle. However, in designing new and modifying existing BFs, it is reasonable to combine alternatives c, d, and ƒ to reduce the probability that hot-blast air flow is straight along the tuyere. Another alternative is to supply hot-blast air from above (Fig. 3). Alternatives c and d are the most acceptable. The geometry of the tuyere stock in case b is such that hot-blast air moves straight along the tuyere. The above alternatives are by no means all possible combinations of junctions between the bustle pipe and the hotblast main and the blowpipe. It should be noted that the hot-blast main is connected to the bustle pipe between tuyeres. However, the greater the working volume of the furnace, the shorter the distance between the tuyeres and the greater the diameters of the hot-blast main and the bustle pipe. Therefore, it is clear that the probability that a part of the hot-blast air flow is straight along the tuyere increases with increase in the working volume of the furnace (Figs. 2 and 3). It is possible to make the distribution of hot blast among tuyeres more uniform by tangentially supplying hot-blast air to the bustle pipe (Fig. 4). Tangential supply of hot-blast air increases its velocity in the bustle pipe by weakening the impact of hot-blast air on its wall. As a result, the static pressure and the wind rate in the inlet sectors and their opposites decrease, which affects the gas counterflow and the descent of the burden in the hearth. Moreover, such hot-blast supply slows down the damage of the lining near the hot-blast inlet. All this improves the performance and capacity of BFs and reduces the coke rate. Conclusions. In designing new and modifying existing blast furnaces, attention should be paid to the way the hotblast air is supplied to the bustle pipe. 1241

Fig. 4. Tangential hot-blast supply: 1) bustle pipe; 2) blast furnace; 3) tuyere stocks; 4) hot-blast main.

The distribution of hot-blast air among tuyeres can be made more uniform using: 1) rational junction between the hot-blast main and the bustle pipe and combination of designs of junctions between the bustle pipe and the hot-blast main and the blowpipe; 2) tangential hot-blast supply to the bustle pipe.

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