AU2014334965B2

AU2014334965B2 - Wall lining for a metallurgical furnace

Info

Publication number: AU2014334965B2
Application number: AU2014334965A
Authority: AU
Inventors: Nikolai Mikhailovich BARSUKOV; Konstantin Valerievich BULATOV; Ilfat Ildusovich ISKHAKOV; Sergei Aleksandrovich LEPIN; Dmitry Yurievich SKOPIN; Sergei Aleksandrovich YAKORNOV
Original assignee: Obschestvo S Ogranichennoi Otvetstvennostyu Mednogorsky Medno Serny Komb
Current assignee: OBSCHESTVO S OGRANICHENNOI OTVETSTVENNOSTYU "MEDNOGORSKY MEDNO-SERNY KOMBINAT"
Priority date: 2013-10-15
Filing date: 2014-12-10
Publication date: 2018-02-22
Anticipated expiration: 2034-12-10
Also published as: RU2013146135A; CL2016000889A1; EA029948B1; WO2015057113A2; AU2014334965A1; WO2015057113A3; EA201600267A1; RU2555697C2

Abstract

The invention relates to metallurgy and can be used in other technical fields in which a reduction in the rate of erosion of a lining is required. A cooling element is disposed in a tuyere region inside a metallurgical furnace. This element is in contact with a lining which contains elements made from a thermally conductive material and is adjacent to the cooling element. The lining is comprised, across its entire width and height, of layers of materials with different thermal conductivities. The lining is in contact with the melt or with the gaseous atmosphere of the furnace. The thermally conductive material is an alloy of copper, nickel and iron. The alloy is selected such that the melting point thereof is not lower than the melting point of copper. The lining provides an increase in the working life of the refractory wall of a furnace in the melt bubbling regions and in the gaseous atmosphere of the furnace.

Description

TECHNICAL FIELD

The invention relates to metallurgy, specifically to linings for metallurgical furnaces, positioned in melt zones, in zones for bubbling melts by gaseous media where the most refractory loads and the maximum lining erosion rates present, and can be also used in other furnaces where refractory is subjected to a high heat action in regions comprising a melt, or where a lining is subjected to a high-speed flow of exhaust gases, exactly, the lining of the invention can be used in metallurgy, chemical industry and power engineering.

BACKGROUND

In a lining in a bath of a melting furnace metal plates may be introduced into the masonry at a depth being 0.2 to 0.25 as large as a refractory length to reduce a thermal resistance of the lining. The plates may be in contact with a furnace shell. Such a technique of lining provides for operation of the refractory at a low level of a melt heat action to the refractory and cannot be used in furnaces where a melt movement speed is high.

An apparatus may be used for cooling a wall of a metallurgical shaft furnace. When a refractory - for example, a fire-proof concrete - contacts solid products, members having transverse ribs cooled by a heat-transfer medium (for example, water) and assembled into one packet are placed under a pressure into the concrete from an inner side of a shell. This provides for operation of the lining in a zone of exhaust gases and does not ensure operation of cooling means in a melt zone. This especially relates to furnaces where the types of melts are explosive with respect to a heat-transfer medium (a matte, a matte-slag emulsion, metals). Such an apparatus cannot be used in furnaces where a refractory heating rate is highly intensive.

The majority of metallurgical furnaces have an outer shell a refractory lining is adjacent to. Voids between the shell and the lining are filled with a special filler or materials having a high heat conductivity. To reduce a refractory temperature, pressurized water-cooled members (water blocks) may be placed in a slag bath of an ore-thermal furnace. The members are placed in the slag belt of the furnace through a row of refractory bricks down to a depth of from 230 to 460 mm. In destruction of a member, the contact of the heat-transfer medium (the pressurized water) typically does not result in explosions, but wetting and bleeding of the masonry result in emergencies of furnaces.

To prevent a heat-transfer medium from leakages out of a cooled member into a lining, a cooling loop of the member can be placed from the outside of a furnace. The present design makes it possible to reduce a fault rate in operation of the furnace, but does not exclude a probability of the emergency at presence of the melt leakages out of the metallurgical furnace.

In some furnaces a highly thermally conductive material introduced into a refractory lining. However, this does not achieve a fire side, while action of a non- stationary heat flow results in overheating of an outer layer. Because of this, thermal stresses and cleavage occur in a protective refractory. Further, local introduction of the highly thermally conductive material into the refractory lining results in irregularity of a temperature field in the refractory lining, said irregularity also causing thermal stresses and destruction (cleavage) to occur in the protective refractory layer. The cooling means can provide a heat sink from the highly thermally conductive material, but introduction of the water cooling means into the furnace can always create a risk of the emergency. The prototype provides for creation of the outer cooling loop on the furnace, which significantly complicates the design and increases the costs for creation thereof but does not exclude burning the cooling jacket through because of leakages of the melt being aggressive with respect to the heat-transfer medium, and does not exclude the emergency risk. Cooling a lining of a furnace roof may not exclude the melt to leak out, and present embodiments are suitable for cooling a lining in case if the melt cannot enter the furnace zone. Local cooling of the lining by introduction of copper rods thereto, said rods being cooled from the outside, causes occurrence of a temperature gradient from a rod end to a fire side of the refractory up to 17 C/mm which results in occurrence of thermal stresses and cleavage in the refractory at the moments of non- stationary heat actions. Thus, such an arrangement does not provide for explosion prevention in cooling, does not exclude the thermal stresses and cleavage to occur in the refractory, while a crust (scull) has a harmful influence upon a cooling mode because a heat transfer coefficient drops. The total thermal resistance is influenced not only by a thickness and heat conductivity of a layer, but also by an outer thermal resistance of the layer, as determined by external heat exchange conditions - the Bio criterion (Bi) - and particularly by a melt-to-wall heat transfer coefficient ai. Under conditions when ai > 250 kcal/m2-°C, the external heat exchange becomes a dominant factor, and operation of the wall under said conditions is determined by the criterion Bi while the temperature adjustment is impossible without periodical occurrence of a scull layer.

SUMMARY

Some embodiments of the present invention provide a wall lining for a metallurgical furnace, said lining operating in a zone where it is in contact with a melt or a high- speed gas flow and increasing a service life of a furnace wall.

Some embodiments of the present invention provide a wall lining for a metallurgical furnace, including a refractory lining, a thermally conductive filler which comprises members made of a thermally conductive material and is adjacent to a cooled member, wherein the refractory lining is in contact with the melt or a gas atmosphere of the furnace, while an inner side of a lining wall comprises members made of a highly thermally conductive material; in accordance with the invention, the wall lining is embodied layer by layer below and above an axis of tuyeres throughout a thickness and a height with materials having different heat conductivities, the thickness of the thermally conductive material layer and the refractory layer being determined by corresponding inner-to-outer thermal resistance ratios of Bi = (1.67-3 16.81)10 for the thermally conductive material and Bi = 1.67-7.5 for the refractory.

The cooled member is mounted in the tuyere zone within the metallurgical surface. A copper, nickel, and iron-based alloy is used as the thermally conductive material.

At the same time, the alloy is selected such that its melting temperature is not lower than that of the copper.

Some embodiments of the present invention provide that the metallurgical furnace refractory lining is capable of operating within the tuyere zone of the furnace where the melt is bubbled by oxygen gas, or in a region where the movement of exhaust gases is intensive.

DETAILED DESCRIPTION A fire side 6 of a refractory and thermally conductive ribs (Fig. 1) is subjected to a high temperature of a melt or a gas phase of a furnace. A shell of the furnace 1 has a cooled member 3 mounted within the metallurgical furnace in a zone of a maximum heat action directly near said shell. A thermally conductive material 2 fills voids between the shell, the cooled member, and the refractory. A number of cooled members mounted in the furnace can be various. The cooled members are made of a highly thermally conductive material which is an alloy, wherein the alloy is selected such that its melting temperature is not lower than that of copper. The number of the cooled members is determined by structural aspects, conditions under which the refractory lining of the metallurgical furnace operates, in other words, by dimensions of a maximum refractory bum-back zone, that is, the zone where the maximum heat and mass exchange takes place. The members are cooled by a cooling system that provides explosion safety conditions when a heat- transfer medium contacts a melt being explosive-dangerous with respect to water or contacts a gaseous atmosphere 7 of the furnace 1 (water is prevented from contact with the explosive melt in destruction of a member wall).

An outer surface of the cooled member 3 (Fig. 1) is in close contact with a thermally conductive material 4 by means of clamps 8. An outer surface of the refractory 5 is in contact with the thermally conductive material 4, which provides for removal of heat from the refractory 5 - from a maximum temperature zone to the cooled member 3, thereby to provide for reduction in a fire side temperature down to a value below a scull melting temperature, which results in formation of scull on a surface 6 of the refractory and material. The formed scull protects the refractory and material against wear. When outer heat exchange conditions are intensified in an unplanned way, a mode is possible when a scull layer will be molten and reduction in a protective lining layer will take place, but a rate of said reduction is well below than a refractory bum-back rate without cooling, which increases a service life of the metallurgical furnace.

Selection of a thickness for lining layers is determined by conditions for the criterion Bi: Bi = (δ/λ):(1/αι), where: δ is a layer thickness; λ is a layer thermal conductivity; oti is a coefficient of heat transfer from the melt.

The ratio of the inner thermal resistance δ/λ to the outer thermal resistance 1/ai is determined by a material thickness, a material heat conductivity, and external heat exchange conditions ai. A maximum value of Bi for a material layer corresponds to a maximum thickness 5.0 mm for the thermally conductive layer while a minimum thickness is 2.0 mm. The thermally conductive material layer 5.0 mm thick is designed for placement thereof in a zone for bubbling the melt by a gas, while the thermally conductive material layer 2.0 mm thick is designed for placement thereof in a gas, slag and matte-slag space of the furnace. The maximum value of Bi for a refractory material corresponds to a minimum thickness of the refractory at its maximum thermal conductivity λ = 6.98 W/m-°C.

The refractory bricks are preliminary compressed by the thermally conductive material prior to placement of the lining into the metallurgy furnace. There is the test of fixture of the thermally conductive material to the cooled member. The cooled members are first mounted into the metallurgical furnace.

Said members extend within the furnace and behind the shell thereof (Fig. 1). The step of lining the wall begins with placement of a layer of the thermally conductive material 4 followed by placement of a layer of the refractory brick 5 and then - by placement of a layer of the thermally conductive material 4 again. After that, the layer of the material 4 is fixed (Fig. 1) on the cooled member 3. Next, the lining operations are repeated. Gaps between the shell, the member, and the refractory are filled with a thermally conductive filler, paste or mastic. The gap filling is tested by a probe. The cooled members are coupled to an explosive safety cooling system after mounting the lining.

The lining was tested in the Noranda-type melting furnace and the horizontal converter for reprocessing copper mattes. The lining (Fig. 1) was placed in the tuyere zone of the furnace where the melt is bubbled by an oxygen-reached gas. The cooled members were placed within the furnace below and above the axis of tuyeres and in the gas space of the furnace - in a zone where a high-speed, high-temperature gas flow moves. After knocking the refractory masonry out through the side surface of the furnace, 12 cooled members were mounted within the furnace near its shell. Ribs made of the thermally conductive material 4 (Fig. 1) were preliminary compressed on the refractory 5 and the cooled member 3. The step of lining was begun after mounting the cooled members, as shown in Fig. 1. Gaps between the shell, the cooled member and the ribs were poured with the thermally conductive mastic. The cooled members were coupled under conditions of rarefaction to the explosive safety cooling system after mounting the wall. The service life of the wall was doubled despite the use of the oxygen-reached gas which was absent in the prior art solutions. 6 cooled members were mounted in the tuyere zone of the horizontal converter for reprocessing copper mattes (2 members were mounted below the axis of tuyeres and 4 members - above it). The wall lining for the horizontal converter is similar to that for the Noranda-type melting furnace. The refractory brick thickness before the cooled members in the Noranda-type melting furnace and the horizontal converter was 520 mm. The cooled members are coupled to an explosive safety system after completion of the lining.

Throughout this specification, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in Australia.

Claims

1. A wall lining for a metallurgical furnace, including a refractory lining, a thermally conductive filler which comprises members made of a thermally conductive material and is adjacent to a cooled member, wherein the refractory lining is in contact with a melt or a gaseous atmosphere of the furnace, while an inner side of a lining wall comprises members of a highly thermally conductive material, said wall lining being characterized in that it is embodied layer by layer below and above an axis of tuyeres throughout a thickness and a height with materials having different heat conductivities, the thickness of the thermally conductive material layer and the refractory layer being determined by corresponding inner- 3 to-outer thermal resistance ratios of Bi=(l.67-16.81)10’ for the thermally conductive material layer and Bi = 1.67-7.5 for the refractory.

2. The lining according to claim 1, characterized in that the cooled member is mounted in a tuyere zone within the metallurgical furnace.

3. The lining according to claim 1 or claim 2, characterized in that a copper, nickel, and iron-based alloy is used as the thermally conductive material.

4. The lining according to claim 3, characterized in that the alloy is selected such that its melting temperature is not lower than that of the copper.