CA1188095A - Smelting furnace - Google Patents

Abstract

Smelting furnace Abstract A smelting furnace, the refractory sole (3) of which is contained in a metallic casing (5) having expansion joints (6, 7, 7'), comprises means (18, 19) for cooling the expansion joints, these means enabling to solidify actually any liquid phase that might tend to infiltrate into the joints.

Description

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BACKGROUND OF THE INVENTION

The present invention relates to a smelting furnace comprising in combination:
- a sole made of refractory material contained in a metallic casing having a plurality of expansion joint~, - elastic return means external of the metallic casing presslng inwardly against metallic casing so that the casing will follow contractions of the sole, - a hollow butt strap abuttin~ the exterior side of each expansion joint, and - means for introducing cooling fluid through each hollow butt strap so as to cool each expansion joint.

The aim of the expansion joints is to avoid de-struction of the metallic casing by phenominons of swel1ing, expansion and contraction of the refractory material, while -the aim of the elastic return means is to allow the function-i.ng of the expansion joints.

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v~s Such a furnace is described in Belgian Paten-t n 411 323. In this known furnace a sheet is inserted where the joints are provided, between the sole and the metallic casing so as to avoid that refractory material of the sole penetrates into the opening of -the ~oints. No measure is taken, however, to ~void -tha-t liquid phase, that infiltrates into the refractory sole and reaches a ~oint, flows through this joint. This known furnace is thus notsuited -to carry out metallurgical reactions producing a liquid phase, the melting point of which is markedly lower than the reaction temperature, since under these conditions the li~uid phase has a strong tendency to infiltrate deeply into the sole. Such a situation occurs, for instance, when lead bearing ores or concentrates are smelted to yield a slag phase and a lead bullion phase :
the meltin~ point of the slaq requires an operating temp-erature of some 1,200C, while the melting point of the lead bullion is about 330C.

DISC:~OSURE OF THE INVENTION

The aim of the present invention is to provide a urnace as defined before, avoiding the drawback of the known ~urnace.

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Therefore, the furnace according to the invention comprises means to cool the expansion joints. These means enable to solidify actually all liquid metal that might tend to infiltrate through the joints.

5 Other details and characteristics of the invention will appear from the description of an embodiment of the Eurnace according to the invention, given hereafter as a non-restrictive e~ample and with reference to the enclosed drawings.

Fi~ure 1 represents part of a vertical section through a furnace arcording to the invention.
Figure 2 represents an enlarged and more detailed view of an expan-sion joint of the furnace of figure l.
Figure 3 represents a smaller scale development of the casing of the furnace of figure 1.

The same refer~nce notations indicate identical elements in the different figures.

The furnace represented on the figures is a rectangular electric furnace with immerged elec~rodes that can be used to smelt lead bearing ores or concentrates. In that furnace the liquid bath 1, heated by electrodes 2, is contained by means of the refractory lining of sole 3 and of side ~alls 4. The refractory lining of the sole is enclosed in a casing 5, comprising a longitudinal expansion ~oint 6 and two transversal expansion ~oints 7 and 7' (see figure 3).
Casing S is composed of several sections ~a, 8b, 8c, ~d, ~e and 8f, made of steel sheet, each of these sections bein~ free to move individually; they form togetller bottom ~ and side walls l~. Rottom 9 of casing 5 rests on a set of beams 11 and 12. The expansions and contractions of the sole are controlled by means of beams 13 and tie-rods 14, through springs 15.

~8~9~i As shown on figure 2, the junction between two adjacent sections, e.g. sections 8a and 8b, is realized by a metallic strap lh placed between the re~ractory sole 3 and the edges of these sections that are situated along opening 17 between them. In this way the e~pansion joints 6, 7 and 7' are rea]i~ed. The width of opening l7, that may be ~ero when the furnace is cold, increases hTith the temperature of the furnace. It is obvious that strap l~ should be wide enough, e.g. 20 cm, to remain always in contact with each of both adjacent sections, in ~he case of fig. 2, sections 8a and 8b.
A hollow butt-strap 18, cooled by circulation of a cooling fluid l9 such as water, is applied on joints 6, 7 and 7'. Butt-strap 18 is applied against joints 6, 7 and 7' by tightening bolts 2], bor~P by one side of an angle-iron 20, the other side of which is welded by its free end to one of the two adjacent sections. As shol~ on figure 3, the butt straps 18 are composed of several rectilinear sections 22 which can be easily removed and replaced independently from each other, thanks to the system of fi~ation by tightening bolts, repre-sented on figure 2.

The cooled butt-strap l~ creates in the refractory material of sole 3 near strap 16 a cold zone in which all liquid metal l, that might have inflltrated into sole 3 until this zone, actually solidifies.

25 5O1e 3 is made of bricks of a conventional material 23 with low thermal conductivity, such as magnesia, the thermal conductivity of ~hich is ranging about 3 ~/mC. The entire sole may be of such material. It is particularly advantageous, ho~ever, to make the sole parts, which are close to the butt-s~raps 18, in a refractory material, the thermal conductivity of which is higher than lO l~/mC, T~ith a view to enlarge the cold zone created by the butt-straps.
~ricks 24, that co~e into contact with straps 16, are thus preferably silicon carbide bricks, the conductivity of which is ranging about 20 T~/mC, or graphite bricks, the conductivity of t~ich is ranging about 80 W/mC.

Straps 16 may be made of steel, but are preferably made of a self-lubricating metallic material such as graphitic cast iron. ~utt-strap 1~ may be a steel section but its upper side that is turned ~owards casing 5 is advantageously covered by a strap 25 in a self-lubrica-ting metallic material such as graphitic cast iron~

It should be understood that the invention is by no means restricted to the above described embodiment and that it can be modified in many ways ~thout leaving ehe scope of the present patent application.
lo sO, for instance, the number and disposition o~ the joints may be modified in function of the geometry of the furnace and the bricks placed near the silicon carbide or graphite bricks 24 may be also silicon carbide or graphite bricks.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A smelting furnace comprising in combination (a) a sole made of refractory material, (b) a metallic casing surrounding said sole, said metallic casing including a plurality of expansion joints, (c) elastic return means external of said metallic casing, which return means presses inwardly against said metallic casing so that said metallic casing will follow contractions of sole, (d) a hollow butt strap abutting the exterior side of each expansion joint, and (e) means for introducing cooling fluid through each hollow butt strap so as to cool each expansion joint.

2. The furnace according to claim 1 wherein the butt straps are in sections (22) adapted to be removed and replaced individually.

3. The furnace according to claim 2 wherein each butt-strap is held in place by tightening bolts (21) passing through one of the sides of an angle-iron (20) the other side of which is fixed by its free end to the metallic casing.

4. The furnace according to claim 2 wherein the portions of the sole that are in contact with the expansion joints are made of a material having a thermal conductivity higher than 10 W/m°C.

5. The furnace according to claim 2 wherein the inner sides of the expansion joints are covered by silicon carbide or graphite bricks.

6. The furnace according to claim 2 wherein the portion of the butt-strap that is in contact with the expansion joint is made of a self-lubricating metallic material.

7. The furnace according to claim 6 wherein the self-lubricating material is graphitic cast iron.

8. The furnace according to claim 2 wherein the joint parts (16) that are in contact with the refractory material of the sole, are made of a self-lubricating metallic material.

9. The furnace according to claim 8 wherein the self-lubricating material is graphitic cast iron.