RU2197534C1 - Method of steel making in open-hearth furnace and open-hearth furnace for realization of this method - Google Patents

Abstract

FIELD: nonferrous metallurgy; facilitating steel making processes. SUBSTANCE: proposed method includes charging metal burden , heating and melting this burden , final melting at heating; in the course of melting, inert gas or neutral gas is delivered through several multi-nozzle blowing units located in porous refractory layer of furnace hearth forming single system of hidden bottom blowing of bath. Jet is formed on side of one end walls of furnace and combustion products are discharged on opposite side. Direction of jet and discharge of combustion products are regularly changed and differential delivery of gas is effected through said blowing units at maximum delivery through one of them which is nearest to jet. Maximum delivery of gas embraces zone of furnace hearth located on side of its front wall. Open-hearth furnace has body, front, rear and end walls, hearth with refractory porous layer and multi-nozzle blowing units arranged along longitudinal axis of hearth, gas supply units and combustion products discharge units which are mounted in end walls of furnace; one multi-nozzle blowing unit is shifted relative to longitudinal axis of furnace hearth towards front wall. EFFECT: enhanced efficiency due to improved mixing. 3 cl, 9 dwg

Description

 The invention relates to ferrous metallurgy, and more specifically to processes of steel smelting in an open-hearth furnace, as well as to designs of open-hearth furnaces.

 The significant beneficial effect of mixing the open-hearth bath of a furnace on the course of the smelting process is known.

. Von Josse Bachmayer und Walter Hirtenlehner. Vortrag gehalten beim Kurzseminar in Kladno, TSCHECHIEN am. 30 Juni. 1993 г.).The two most effective systems for hidden bottom flushing of a bath with an inert or neutral gas are known, the use of which can significantly intensify the melting process in an electric furnace: the TLS system and the VVS system (see, for example, NEUESTE ERFAHRUNGEN MIT BEDECKTEM -

. Von Josse Bachmayer und Walter Hirtenlehner. Vortrag gehalten beim Kurzseminar in Kladno, TSCHECHIEN am. 30 Juni. 1993).

 It is known that of these two systems of hidden bottom purging, the VVS system is most widely used. It is this system that has spread to open hearth furnaces.

 A known method of smelting in an open-hearth furnace, which describes a method of hidden bottom-flushing baths using the VVS system, as well as the design of the furnace for implementing this method (see, for example, RF patent 2164244, C 21 C 5/04, published March 20, 2001, ., bull. 8).

 A known method of steel smelting in an open-hearth furnace, which includes filling the metal charge, heating and melting it, adjusting the liquid metal to the required characteristics and purging it with a neutral gas or inert gas by means of multi-nozzle blowing devices located in the porous refractory layer of the hearth. Liquid metal is purged through several devices located along the hearth of the furnace and forming a single system of bottom purging of the bath in zones.

 The open source also describes an open-hearth furnace for steelmaking with hidden bottom blowing, containing a body, front and rear walls, with a refractory porous layer and multi-nozzle blowing devices placed along the longitudinal axis of the hearth.

 The known method of steelmaking in an open-hearth furnace, as well as the design of the open-hearth furnace, according to the essential features, are closest to the proposed ones, therefore they are taken as a prototype.

 A significant disadvantage of the known method and device is their low efficiency in solving the problem of mixing the bath. The noted drawback is due to the fact that conditions are not created for the movement of steel along the hearth of the furnace, as a result, the mixing of steel is localized only in areas covered by the action of purge devices, without noticeable movement of metal between the zones.

 The proposed method of steel smelting in an open-hearth furnace, as well as the design of the furnace are also based on the use of devices of the VVS system, but are free from this drawback. They ensured the movement of the bath metal along the furnace, thereby significantly improving the process of mixing steel and, on this basis, increased the efficiency of the melting process.

 The noted technical result is achieved due to the fact that in the method of steel smelting in an open-hearth furnace, including filling the metal charge, heating and melting it, and lapping with heating of the furnace bath during the torch smelting process, an inert or neutral gas is supplied through several multi-nozzle blowing devices located in porous refractory layer of the hearth of the furnace and forming a single system of hidden bottom purge baths. In this case, a torch is formed on the side of one of the end walls of the furnace, and the discharge of combustion products is on the other side. The direction of the formation of the torch and the removal of combustion products are periodically interchanged, and the gas is supplied through the indicated purge devices with the highest flow through one of the purge devices closest to the torch.

 The greatest gas supply covers the hearth zone of the furnace, located on the side of its front wall.

 The open-hearth furnace for steelmaking contains a body, front, rear and end walls, underneath with a refractory porous layer and multi-nozzle blowing devices of hidden bottom blowing, means for supplying gas and removal of combustion products located along the longitudinal axis of the hearth.

 Means for supplying gas and exhausting combustion products are made in the end walls of the furnace, and one extreme in the row multi-nozzle purge device is offset relative to the longitudinal axis of the furnace hearth to its front wall.

 These signs are significant and interconnected causal relationship with the formation of a set of essential features sufficient to achieve a technical result.

The best embodiment of the invention
The present invention is illustrated by a specific embodiment, which, however, is not the only possible, but clearly demonstrates the possibility of achieving this set of features of a given technical result.

The method and device are illustrated by drawings, where
- in FIG. 1-8 in the plan are shown under the furnace with various options for the arrangement of devices for hidden bottom blowing relative to the hearth of the furnace and with different intensities of the supply of inert or neutral gas through these devices;
- in FIG. 9 shows the percentage movement of the bath metal along the furnace, depending on the arrangement of devices and the differentiated gas supply through them, shown in FIG. 1-8.

The proposed method is as follows. On the hearth of the furnace 1, along its longitudinal axis 2, multi-nozzle blowing devices are placed (hidden bottom blowing devices), for example, VVS systems, the action of which covers zones 3 of the furnace bottom; the front wall of the furnace 4; back wall of the furnace 5; torch 6; flue gases 7. An inert or neutral gas with different intensities q _{i is} supplied through the devices of hidden bottom purging.

 The method is implemented as follows.

In the open-hearth furnace several devices of multi-nozzle blowing devices (devices of hidden bottom blowing), for example, the VVS system, are installed, when inert or neutral gas is supplied through the gas, they cover zone 3 of the furnace bath located above the said devices (Fig. 1). The devices are placed along the longitudinal axis 2 of the furnace and the gas supply through them is carried out differentially (unequally). Basically, the specified differentiation in the gas supply through the devices is reduced to its increased supply through at least one of the end devices, i.e. q ₂ > q ₁ in all FIGS. 1-8.

 Since during the operation of the open-hearth furnace, the action of the torch 6 and the exhaust gas 7 change between themselves by periodic switching, also periodically the greatest gas supply is carried out through the device closest to the torch. Thus, each time the flare is switched, the device closest to the flare becomes the end device through which the greatest gas supply is carried out.

 Moreover, the end devices are biased towards the front wall 4 of the furnace, thereby covering the zone 3 of the hearth 1 of the furnace located on the side of the front wall 4 of the furnace with the highest gas supply. The latter is ensured by placing the extreme in a row of devices with an offset relative to the longitudinal axis 2 of the hearth of the furnace to its front wall 4 (Fig. 8).

 The effectiveness of the proposed technical solution was evaluated by two methods.

 Firstly, by computer simulation, the percentage of displacement of the metal located in the zone of action 3 of the extreme device with the highest gas supply was established by volume of the furnace. In the calculations, the real parameters of the 130-ton open-hearth furnace and the devices of the hidden bottom purge of the VVS system were taken.

Secondly, on a cold model of a 130-ton open-hearth furnace made of plexiglass at a scale of 1:15 and equipped with a system of hidden bottom blowing. As the working gas, air was used, the supply of which through the devices of hidden bottom purging was carried out using a gas distribution station. On the model, the air flow rate varied within 0.5 ... 3.5 nl / min, which was 20 times less than with computer simulation. The model was divided across the partition into two equal halves, one of which was filled with cold (t = 18-21 ^o С) and the other with hot (t = 55-58 ^o С) water. The water temperature was measured by three thermometers with a division value of 0.1 ^o C. The measurements were carried out simultaneously along the edges of the model and in the center (after removing the partition), in the upper and lower layers of water. As a criterion of efficiency, we took the time during which the averaging of water temperature over the entire volume of the bath occurs.

 The results obtained by both methods of evaluating the effectiveness made it possible to determine the best embodiments of the invention: the variants in FIG. 6 and 8 of the arrangement of hidden bottom-flush devices, for example, the VVS system and the implementation of differential gas supply through these devices with the highest supply through one of the end devices, and each time the torch is switched, the specified end device is the device closest to it.

 At the same time, by realizing the greatest gas supply through the end devices located on the side of the front wall of the furnace (option in Fig. 8), blowing primarily covers the hearth zone of the furnace near its front wall. Moreover, due to the "flipping" of the torch and the organization of the greatest supply of inert / neutral gas through the end devices located on the side of the working torch, reinforce the one noted in FIG. 9 (6 and 8) the effect of metal mixing due to the formation of the “wave” phenomenon, i.e. vibrational movement of metal along the volume of the furnace bath.

 Example 1

Hidden bottom flushing devices are located along the longitudinal axis of the furnace hearth (Fig. 1). The same inert / neutral gas is supplied through these devices with a flow rate of q ₁ = 40 nl / min. 60 minutes after the start of the purge, 2.3% of the metal located above the extreme (from the side of the torch) purge device spreads over the entire volume of the furnace bath (Fig. 9, 1).

 Example 2

Hidden bottom flushing devices are located (FIG. 2) similarly to FIG. 1. Carry out a differential gas supply through devices with the highest supply through both end devices: provide q ₂ = 70 nl / min, q ₁ = 10 nl / min (Fig. 2). 60 minutes after the start of purging, 4% of the metal located above the extreme (from the side of the torch) purge device spreads over the entire volume of the furnace bath (Fig. 9, 2).

 Example 3

Hidden bottom flushing devices are located with a shift of the extreme ones asymmetrically relative to the longitudinal axis of the furnace hearth: one of them is offset to the front wall 4 of the furnace, the other to the rear wall 5 of the furnace (Fig. 3). The same gas supply through all devices is carried out in an amount of q ₁ = 40 nl / min. 60 minutes after the start of purging, 2.5% of the metal located above the extreme (from the side of the flare) purge device spreads throughout the entire volume of the furnace bath (Fig. 9, 3).

 Example 4

Hidden bottom flushing devices are located similarly to FIG. 3. Carry out a differential gas supply through devices with the highest supply through both end devices: provide q ₂ = 70 nl / min, q ₁ = 40 nl / min. 60 minutes after the start of purging, 12% of the metal located above the extreme (from the side of the torch) purge device spreads over the entire volume of the furnace bath (Fig. 9, 4).

 Example 5

Hidden bottom flushing devices are located similarly to FIG. 3 and 4. Differential gas supply through the devices with the highest supply through the extreme device opposite the torch is carried out, q ₂ = 70 nl / min, q ₁ = 10 nl / min. 60 minutes after the start of the purge, 9% of the metal located above the extreme (opposite the torch) purge device spreads over the entire volume of the furnace bath (Fig. 9, 5).

 Thus, the adoption, as the last device, through which the largest amount of gas is supplied, on the side opposite the torch, reduces the efficiency of metal mixing by 3% (compare examples 4 and 5).

 Example 6

Hidden bottom flushing devices are located similarly to FIG. 3-5. Differential gas supply through the devices with the highest supply through the end device, offset to the front wall of the furnace and located on the side of the torch. Provide q ₂ = 70 nl / min, q ₁ = 10 nl / min. 60 minutes after the start of the purge, 15% of the metal located above the extreme (from the side of the torch) purge device spreads over the entire volume of the furnace bath (Fig. 9, 6).

 Example 7

 We analyzed a gas purge analogous to Example 6, but with all devices located along the longitudinal axis of the furnace. 60 minutes after the start of the purge, 12% of the metal located above the extreme (from the side of the torch) purge device spreads over the entire volume of the furnace bath (Fig. 9, 7).

 Thus, the shift of the extreme purge device towards the front 4 of the furnace wall allows (see 6 and 7 in Fig. 9) to increase the degree of mixing of the metal by 3%.

 Example 8

 The favorable effect of the displacement of the end device, through which the largest amount of gas is supplied to the furnace bath towards the front wall of the furnace, was taken into account (see Example 6). We also took into account that in the open-hearth furnace the torch is periodically switched over. Therefore, they moved both extreme purge devices to the front 4 wall of the furnace (Fig. 8). A differential gas supply was carried out with the highest supply through the end device located on the side of the torch. 60 minutes after the start of purging, 15% of the metal located above the extreme purge device (from the side of the torch) spreads over the entire volume of the furnace bath (Fig. 9, 8).

 Thus, the application of this proposal enhances the effect of mixing the metal in the bathtub of the open-hearth furnace, due to the effect of hidden bottom purging, as they organize the movement of metal along the bathtub of the furnace. An increase in the degree of mixing of the metal of the open-hearth furnace bath improves the course of the smelting process.

Claims (3)

 1. A method of steel smelting in an open-hearth furnace, including filling a metal charge, heating and melting it, and lapping with heating of a furnace bath in a torch smelting process, while in the process of smelting an inert or neutral gas is supplied through several multi-nozzle purge devices located in a porous refractory layer the hearth of the furnace and forming a single system of hidden bottom purge baths, characterized in that the torch is formed on the side of one of the end walls of the furnace, and the exhaust of the combustion products on the side of the other, and this direction of the formation of the torch and the removal of combustion products are periodically interchanged, and the gas supply is carried out through these purge devices with the highest flow through one of the devices closest to the torch.  2. The method according to p. 1, characterized in that the greatest gas supply cover the hearth zone of the furnace, located on the side of its front wall.  3. An open-hearth furnace for steelmaking, comprising a body, front, rear and end walls, underneath with a refractory porous layer and multi-nozzle blowing devices of hidden bottom blowing, means for supplying gas and removal of products of combustion, characterized in that the means for supplying are arranged along the longitudinal axis of the hearth gas and exhaust of combustion products are made in the end walls of the furnace, and one extreme in the row multi-nozzle purge device is offset relative to the longitudinal axis of the furnace hearth to its front wall.

Images