The invention relates to reheating furnaces with movable beams intended to heat steel products, for example made of carbon steel or stainless steel, in particular slabs, blooms, blanks or billets, to a temperature suitable for their rolling at hot.

State of the prior art

The oven allows products to be heated to high temperatures, around 1150 ° C for carbon steel. Heating of the furnace is commonly done by burners operating in a slight excess of air, which results in the presence of oxygen in the furnace. Significant oxidation of the products in the oven results from the combination of high temperature and the presence of oxygen.

Steel reheating furnaces operate continuously and have significant production capacities, ranging for example from 120 t / h to 650 t / h. The weight loss of products resulting from oxidation is commonly of the order of 0.6%. When it comes off the products, scale falls on the oven floor where it accumulates.

By the term scale, the present description designates not only the scale itself resulting from the oxidation of the products, but more generally any solid polluting residue.

Scaling can be done during periodic shutdowns of the oven. This solution is not satisfactory, because it leads to a significant loss of production due to the time required for cooling the furnace, the manual removal of the scale, and then raising the temperature of the furnace. The furnace can be equipped with scrub doors from which an operator will tackle, that is to say scrape and mechanically remove, the scale using a tool, of the rake type. This solution is not satisfactory either, because access to the scale located in the center of the oven is not easy. In addition, the opening of these scrub doors causes air to enter the furnace, which has the effect of increasing the oxidation of the products present inside.

We know the furnace with movable spars equipped with fixed spars, and movable spars. The spars feature cooled andirons and keels. The mobile beams allow the transport of the products in the oven by following a rectangular cycle comprising a first phase of ascent which makes it possible to lift the products from the fixed beams. This is followed by a second phase of horizontal transport and then a third phase of placing the products on the fixed spars. The products are thus moved one step on the fixed spars before the fourth phase of returning the movable spars to their initial position. The total duration of a rectangular cycle is approximately 55 seconds.

To limit the black marks caused by the shadow of the andirons on the products, the side members can be offset transversely towards the exit of the furnace, also called the discharge zone.

Where the andirons are offset, at the entrance to the oven in the product deposit area and towards the oven outlet where the temperature of the products is higher, more scale forms, which must be removed periodically.

The Applicant has improved the operation of a furnace as presented and filed patent application EP2516950 for a reheating furnace with movable beams which ensures, in a simple and efficient manner, the automatic removal of part of the scale, or other polluting residue, avoiding the aforementioned drawbacks. To this end, it has been proposed that in the areas of the oven where scale is mainly produced, or other polluting residue, in particular towards the entrance and exit of the oven, the hearth is thicker than in the rest of the oven, that inclined surfaces are installed in this thicker zone of the floor, with a slope of the walls sufficient to avoid sloping, so as to collect scale and residues and lead them to evacuation ducts which open into tanks water, and that the water tanks are fixed on the translation frame allowing the continuous evacuation of a part of the scale coming from the evacuation ducts, while maintaining the tightness of the oven. The increase in the thickness of the sole allows in fact an implantation of hoppers formed by the inclined surfaces having a significant slope while having a large opening flush with the sole in order to cover the maximum possible surface. This characteristic helps to evacuate scale or other residue.

The Applicant has continued to work on the possibilities of improving such furnaces with movable beams.

Indeed, the solution according to the prior art is not entirely satisfactory, because the scale falls mainly on the sole between the passages for the movable keel, outside the hoppers described above, and this scale is not evacuated. Also, the evacuat
ion of this majority portion of scale can be achieved only during periodic shutdowns of the oven, over a period of between six and twelve months.

Disclosure of the invention

One aim of the invention is in particular to remedy all or part of the aforementioned drawbacks.

According to a first aspect of the invention, there is proposed a furnace with refractory spars comprising movable spars comprising movable andirons supported by movable keels, and fixed spars comprising fixed andirons supported by fixed keels, and means of drives arranged to move a lifting frame and a translation frame according to a rectangular movement cycle having two vertical positions, respectively upper and lower, and an intermediate vertical position according to which the mobile andirons are at the same height as the fixed andirons, the Movable andirons projecting above the fixed andirons in the upper position, the movable andirons being at a lower level than the fixed andirons in the lower position.

According to the invention, the oven further comprises:

- a plurality of fixed refractory spars extending longitudinally,

- a plurality of movable refractory spars extending longitudinally.

The movable refractory spars are arranged transversely between the fixed refractory spars and separated on each side of the fixed refractory spars by a space, the movable keels are fixed to the movable refractory spars, and the movable refractory spars are fixed to the translation frame and arranged substantially at the same height as the fixed refractory side members in the intermediate position.

The furnace further comprises a plurality of longitudinal water tanks arranged in line with the separation spaces and fixed on the fixed refractory spars delimiting a separation space, and a plurality of skirts fixed on the mobile refractory spars delimiting said separation space and plunging in the water tanks.

Fixed refractory spars and movable refractory spars may extend all or part of the length of the furnace.

Advantageously, the fixed refractory spars and the movable refractory spars have an inclined and rounded profile on the upper part, the inclined profile being able to present a slope forming with the horizontal an angle greater than the slope angle of the scale.

In one possibility, the fixed refractory spars and the movable refractory spars are made of low-cement concrete, based on tabular alumina and spinel.

The oven may further include scrapers attached to the plurality of skirts. The profile of the scrapers can be adapted to promote crushing and scale removal. The squeegees can have, for example, a spade-shaped profile.

The water trough can be fitted with flush flushes arranged to flush water, and scale, from the discharge to the charge.

According to one embodiment, the furnace may include refractory spars over only part of the length of the furnace.

At least one water tank may have a rectangular shape, at least one transverse section of the water tank providing a connection between two longitudinal sections of the water tank arranged on either side of a refractory spar.

According to one embodiment, the furnace comprises water tanks equipped with two flushes of water at their end located on the charging side, allowing the evacuation of the scale, and of a part of the water, in a transverse tank. towards a central evacuation.

According to a second aspect of the invention, there is provided a method for continuously crushing and removing the scale in a furnace with refractory spars comprising movable spars comprising movable andirons supported by movable keels, and fixed spars comprising fixed andirons supported by fixed pins, and drive means arranged to move a lifting frame and a translation frame according to a rectangular displacement cycle having two vertical positions, upper and lower respectively, and an intermediate vertical position according to which movable andirons are at the same height as fixed andirons, with movable andirons projecting above the fixed andirons in the upper position, with the movable andirons at a lower level than the fixed andirons in the lower position.

The furnace used in the process for continuously grinding and removing the scale comprises a plurality of fixed refractory spars extending longitudinally, a plurality of movable refractory spars extending longitudinally, the mobile refractory spars being arranged transversely between the fixed and separate refractory spars on each side of the refractory spars fixed by a separation space, the movable keels being fixed to the movable refractory spars, and the movable refractory spars being fixed to the translation frame and arranged substantially at the same height as the fixed refractory spars in the intermediate position, the furnace comprising furthermore a plurality of water tanks arranged in line with the separation spaces and fixed on one of the refractory spars, and a plurality of skirts, fixed on the other refractory spar delimiting said separation space, immersed in the water tanks , the scale being crushed by the side members as it passes through the separation spaces and being continuously discharged by the plurality of water tanks.

Description of figures

Other advantages and features of the invention will become apparent on reading the detailed description of implementations and embodiments which are in no way limiting, with regard to the accompanying drawings in which:

[Fig.l] is a schematic longitudinal sectional view of a reheating furnace with movable beams according to the prior art, with part broken away in the central part,

[Fig.2] is a schematic top view of the interior of the oven shown in Figure 1, [Fig.3] is a schematic longitudinal sectional view of a reheating oven according to a first embodiment of the invention, with part torn off in central part,

[Fig.4] is a top view of the interior of the oven shown in Figure 3,

[Fig.5] presents on its left part a half-section according to the section BB of Figures 3 and 4, and has on its right part a half-section according to the section A- A of Figures 1 and 2, [Fig.6 ] shows three vertical positions of a mobile refractory spar relative to fixed refractory spars according to the invention of the furnace shown in Figure 3, [Fig.7] is a schematic longitudinal sectional view of a reheating furnace according to a second embodiment of the invention, with part cut away in the central part, [Fig.8] is a top view of the interior of the oven shown in Figure 7,

[Fig. 9] is a detail view on a larger scale of the oven shown in Fig. 7, with the right side part cut away,

[Fig.10] is a top view of the interior of an oven according to a third embodiment of the invention,

[Fig.l 1] is a detail view of a water tank shown in top view on the left part of the drawing and in cross section on the right part of the drawing, according to a first embodiment of the invention,

[Fig.12] is a detail view of a water tank shown in top view on the left part of the drawing and in cross section on the right side of the drawing, according to a second embodiment of the invention.

Description of embodiments

Since the embodiments described below are in no way limiting, it is in particular possible to consider variants of the invention comprising only a selection of characteristics described, subsequently isolated from the other characteristics described, if this selection of characteristics is sufficient. to confer a technical advantage or to differentiate the invention from the state of the prior art. This selection comprises at least one characteristic, preferably functional without structural details, or with only part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art. .

In the figures, an element appearing in several figures retains the same reference.

Description of the prior art

In Figure 1 is schematically shown in side view a heating furnace F with movable beams 10 according to the prior art. The two end parts of the furnace, the charging side and the charging side are shown, the central part being torn off. As shown by the arrow in FIG. 1 which illustrates the direction of movement of the products, the loading side is located to the right of the figure and the unloading side to the left. This is the case for all the figures which represent an oven in side view.

A translation frame 3 rests on upper rollers 33 for translating a lifting frame 2 which itself rests on ramps 1 having an inclined plane, through the lower rollers 22.

A drive means (not shown) according to a horizontal reciprocating movement, parallel to the longitudinal direction of the furnace, is provided for the translation frame 3; another similar drive means (not shown) is provided for the lifting frame 2. These drive means are for example hydraulic cylinders. The combination of the back and forth movements, and the vertical up and down movement due to the ramps 1, results in a rectangular cycle of movement.

The movable side members 10 have which The mobile 10Q and 10C mobile andirons, the andirons being supported by the mobile pins which are fixed below the translation frame 3.

The movable keels 10Q pass through the fixed sole 6.

Fixed spars 11 (Figure 2), comprising fixed keels 11Q mounted on the sole 6 and fixed andirons 1 IC, the fixed andirons being carried by the fixed keels, are interposed between the movable spars 10.

The fixed hearth 6 has, on the laboratory side of the furnace, a part lined with refractory materials forming a fixed refractory hearth 6R.

When the sole passes through the movable keels 10Q, the seal between the sole 6 and the oven mechanics is obtained by longitudinal water tanks 4 (figure 1) integral with the translation frame 3, crossed by the movable keels 10Q , and skirts 7 integral with the sole 6 and immersed in the water of the water tanks 4.

Oblong openings OB (FIG. 2), also called buttonholes, are provided in the sole 6 for the passage and the longitudinal relative movement of the movable pins 10Q. When it comes off the products, a small amount of scale falls into the existing oblong OB openings in the sole 6 at the passage of the movable pins 10Q and in the bottom of the water tanks 4.

A plurality of scrapers 5 (FIG. 5) is fixed to the base of the skirts 7, over the length of the latter, and is thus immersed in the water tanks 4. The scrapers 5 allow the transport of the scale to the hoppers. recovery (not shown), placed at the end of the water tanks 4, by the relative movement between the water tanks 4 and the scrapers 5, obtained by the combination of the fixed position of the scrapers 5 and the rectangular displacement of the water tanks water 4.

More precisely, in the high position, with each advance of the water tanks 4 fixed on the mobile translation frame 3, the scrapers 5 fixed on the fixed skirts which open into the water tanks 4 push the quantity of scale located in the bottom water tanks 4 with a step of translation from the furnace outlet to the furnace inlet, that is to say from the discharge towards the charging, to the ends of the water tanks 4.

The evacuation of the scale recovered under the installation is ensured via evacuation pipes. The evacuation pipes open into, or are connected to, evacuation circuits provided with valve 20 (figure 1) with membrane, acting as a flush 20, allowing at each opening the evacuation of a quantity of scale and water which falls, through a transverse chute 21, into a wagon on wheels 23.

Description of the invention

In Figure 3 is schematically shown a first embodiment of an FF oven according to the invention. The two end parts of the furnace, the charging side and the charging side are shown, the central part being torn off.

As in the prior art, the FF oven comprises the translation frame 3 which rests on the upper translation rollers 33 of the lifting frame 2 which itself rests on the ramps 1 having an inclined plane, via the rollers. lower 22.

The drive means for the lifting and translation frames (not shown) are as in the prior art.

The movable spars 10 are also formed by movable keels 12Q and movable andirons 10C. The movable keels 12Q according to the invention are shorter than the movable keels 10Q according to the prior art. They are supported by a new type of LRM mobile refractory spar.

The LRM mobile refractory spar is placed and fixed on the translation frame 3 over the entire length of the furnace. According to another possibility, the LRM mobile refractory spar is placed on the translation frame over only part, or more, of the length of the furnace.

The movable keels 12Q pass through, and are fixed on, the LRM movable refractory spar comprising refractory materials which rest on a metal structure.

At each end of the furnace, a clearance J (FIG. 4) is provided at the level of each mobile spar, so that the longitudinal movement of the mobile spar is possible.

New type LRF fixed refractory spars are available.

The LRF fixed refractory spars have fixed pins 13Q and fixed andirons 1 IC, the fixed andirons 1 IC being carried by the fixed pins 13Q. The LRF fixed refractory spars are interposed between the LRM mobile refractory spars.

The refractory materials of which the LRM mobile refractory spars and the LRF fixed refractory spars are made are refractory concretes with high working temperature and high resistance to abrasion and impact. They can be, for example, concretes with a low cement content, based on tabular alumina and spinel. For example, concrete can contain 92% A1203 and 5% MgO.

Refractory materials can be heavy concrete which has a particularly high density. After drying, this density is for example 3000 kg / m3 (which can even go up to 6000 km / m3) against 2000 to 2300 km / m3 for traditional concrete (for comparison the density of lightweight concrete is between 300 and 2000 kg / m3).

More precisely, the fixed LRF and mobile LRM refractory spars comprise a metallic lower part, on the side opposite the laboratory of the furnace, on which the refractory material rests. This metal lower part is connected to the translation frame for the mobile refractory spars and to the fixed sole for the fixed refractory spars. The fixed and movable keels pass through the refractory material and are fixed to the metal lower parts.

As illustrated in FIG. 5 in its left part, the transverse juxtaposition of the LRM mobile refractory spars and of the LRF fixed refractory spars according to the invention forms a functional equivalent of the refractory hearth 6R of the furnace according to the prior art shown in FIG. right part of figure 5.

A space E is left between the LRM mobile refractory spars and the LRF fixed refractory spars, over the entire height of the refractory. This space E has the function, in a first upper part of conical shape, to guide the scale towards an evacuation passage located in its lower part. We thus have a scale evacuation space on each side of the LRF fixed refractory spars and the LRM mobile refractory spars, all along the furnace, or along the length equipped with LRM and LRF refractory spars according to the invention.

The up and down and front-to-rear translational movements of the mobile refractory spars relative to the fixed refractory spars allow the scale to be crushed and

facilitate the passage of scale without blocking an amalgam, or even pieces, of refractory lining.

The distance between the side members in the lower part of the space E is sufficient for the passage of the scale after grinding. In its lower part, it is for example between 50 and 100 mm.

It is understood that the scale which previously remained on the fixed refractory hearth 6R can now fall through the evacuation passages E.

In addition, the LRF fixed and mobile LRM refractory spars according to the invention have, transversely, an inclined and rounded profile on the upper part on which the pins are positioned. The inclined profile is determined with an angle greater than the slope angle, facilitating the crushing and evacuation of the scale in the passage E provided for this purpose between the fixed refractory spars and the LRM mobile refractory spars. The angle of the inclined profile is for example greater than 45 °.

The seal between the sole, formed by the fixed and mobile refractory side members, and the oven mechanics consisting of the lifting frame and the translation frame, is obtained by longitudinal water tanks 40 (figures 3 and 5) integral with the side members fixed refractories and metal skirts 70 integral with the mobile refractory spars and plunging into the water tanks 40.

The water tanks 40 are fixed on each side of the LRF fixed refractory spars.

The skirts 70 are fixed on each side of the LRM mobile refractory spars.

Furthermore, the profile of the skirts 70 makes it possible to avoid the direct radiation of the environment of the laboratory of the furnace on the surface of the water contained in the water tanks 40 in order to minimize heat losses through the openings and the consumption of water. 'water.

The water tanks 40 are no longer crossed by the mobile keels 10Q.

The length of the movable pins is reduced compared to that according to the prior art, of the order of one meter and fifty centimeters.

As can be seen in FIG. 6, the mobile refractory spars can have three vertical positions with respect to the fixed refractory spars, respectively low (to the left of the figure), intermediate (in the center of the figure), and high (to the right of the figure). the figure).

In addition, the keel passage according to the prior art was surrounded by fibrous fibers which when torn off led to oxidation. This is no longer the case with the solution according to the invention in which the 12Q keel is embedded in the refractory of the LRM mobile refractory spar. Bottom keel lining solutions had been sought, for example by means of stainless steel sheets, but the latter heated, deformed and did not hold.

According to the example shown in this embodiment, the mobile skirts 70 are equipped with a plurality of scrapers 50 fixed to the metal skirts 70. The scrapers 50 plunge into the water tanks 40 and allow the transport of the scale towards recovery hoppers (not shown), placed at the end of the tanks, by the relative movement between the water tanks and the scrapers obtained by the association tion of the rectangular displacement of the scrapers 50 and of the fixed position of the water tanks 40.

More precisely, the translation frame 3 being in the high position, at each advance of the LRM mobile side members, the metal scrapers 50 push the quantity of scale found in the bottom of the water tanks 40 between two scrapers with a translation step towards the end of the water tanks 40.

The scrapers help to crush the scale, which facilitates its discharge into the water tank 40. The scrapers thus have a profile suitable for promoting the crushing and discharge of the scale, for example in the form of a spade.

The end of the water tank 40 is equipped with a diaphragm valve 20 (Figure 3), acting as a flush 20, which discharges the scale through the chutes 21 in the wagons on wheels 23, l 'evacuation in the direction of the exit of the oven towards the entrance of the oven.

According to a first variant of this first embodiment, described only for its differences with the first embodiment, the skirts 70 are not equipped with squeegees.

The scale can be driven from the water tanks 40 onto which it falls by a device external to the oven, for example by hoses of the fire hose type.

According to a second variant of this first embodiment, the water tanks 40 can be provided with nozzles (80) for spraying water (FIG. 3), arranged at the level of the discharge, which push the scale towards the end of the tank. water 40 located on the side of the charging station.

The water tanks 40 can be provided with water injection 80, for example spray nozzles, which, under pressure, drives the scale towards the flushes 20.

According to this variant, it is possible not to equip the skirts 70 with squeegees.

Of course, the skirts 70 can still be equipped with scrapers to improve the crushing of the scale.

According to a third variant of this first embodiment, described only for its differences with the first embodiment and possibly combinable with the first variant, two or three intermediate discharge points for the scale can be provided.

For this purpose, it is proposed to have at each of these discharge points a transverse tank provided with conduits receiving the scale coming from the water tanks 40. On each side of the transverse tank, the tank is equipped with flushing toilets. which push the scale towards the center of the transverse tank, equipped with other conduits equipped with diaphragm valves.

Each of the transverse bins can advantageously be placed between two wheels 33.

This second variant is particularly advantageous in the context of a very long oven.

The water tanks can also be attached to the LRM mobile refractory spars. In this case, it is necessary to take into account the wave effect at the end of the water tank generated by the movement of the side members.

In Figures 7 to 9 is schematically shown a second embodiment of an FFF oven according to the invention.

The FFF oven is only described for its differences from the first embodiment, and could use the characteristics of one or more of the variants of the first embodiment.

As can be seen in FIG. 7, on the side of the charging, the oven has a longitudinal part P2 similar to that described according to the prior art, from the charging to a longitudinal position from which a part begins. PI similar to that as described with reference to the first embodiment of the invention.

Note that, to limit the black marks caused by the shadow of the andirons on the products, the refractory spars can also be offset transversely towards the exit of the furnace, as can be seen in Figure 8.

In this embodiment, the furnace comprising LRF refractory longitudinal members, LRM over only part of its length, at least one water tank 40 has a rectangular or U-shaped shape, at least one transverse section 41 of the water tank ensuring a connection between two longitudinal sections 42 of the water tank arranged on either side of a fixed refractory spar.

Figure 11 illustrates an exemplary embodiment of a water tank 40 according to the invention, in the case shown in Figures 3 and 4 where the water tank runs the entire length of the oven, with a top view of the water tank on the left part of the figure and a cross-sectional view thereof on the right part of the figure. The rectangular water tank comprises two longitudinal parts 42 arranged on either side of a fixed refractory spar, not shown, and two transverse connections 41 between these longitudinal parts arranged on either side of the refractory spar, at each end of the longitudinal parts. To seal the oven, skirts 70, not shown, dive into the water tank along the longitudinal parts 42 and s transverse links 41, thus ensuring continuity of the joint

hydraulic. It is also noted that the water tank is provided with two flushes 20, located on the transverse link 41 located on the side of the charging of the oven, one for each longitudinal part of the water tank, and spray nozzles. water 80 represented by arrows.

FIG. 12 illustrates another exemplary embodiment of a water tank 40 according to the invention, in the case represented in FIGS. 7 and 8 where the refractory longitudinal members according to the invention are only on a part of the furnace, in this case when discharging, with a top view of the water tank on the left part of the figure and a cross-sectional view thereof on the right part of the figure. The rectangular water tank also comprises two longitudinal parts 42 arranged on either side of a fixed refractory spar, not shown, and two transverse links 41 between these longitudinal parts arranged on either side of the refractory spar. , at each end of the longitudinal parts. Note that in this exemplary embodiment, the water tank is provided with a flush 20 disposed on each longitudinal part of the water tank, and water spray nozzles 80 represented by arrows.

FIG. 10 illustrates a variant of the exemplary embodiment shown in FIG. 8 in which the transverse offset of the side members to limit the black marks caused by the shadow of the andirons on the products is carried out on the PI part of the oven, in this example about mid-length thereof.

Of course, the invention is not limited to the examples which have just been described and numerous modifications can be made to these examples without departing from the scope of the invention. In addition, the different characteristics, shapes, variants and embodiments of the invention can be associated with each other in various combinations as long as they are not incompatible or exclusive of each other.

Claims
1. Furnace with movable spars comprising a plurality of fixed refractory spars (LRF) extending longitudinally and a plurality of refractory movable spars (LRM) extending longitudinally, the movable refractory spars being arranged transversely between the fixed refractory spars and separated from each other. each side of the refractory spars fixed by a space (E), drive means arranged to move a lifting frame (2) and a translation frame (3), supporting the mobile refractory spars (LRM), according to a cycle of rectangular displacement having two vertical positions, upper and lower respectively, and an intermediate vertical position according to which the movable side members are at the same height as the fixed side members, the movable side members projecting above the fixed side members in the upper position, the side members movable at a lower level than the fixed side members in the lower position , the furnace further comprising a plurality of longitudinal water tanks (40) arranged in line with the separation spaces (E) and fixed to one of the refractory spars (LRF, LRM) delimiting a separation space (E), and a plurality of skirts (70) fixed to the other refractory spar (LRF, LRM) delimiting said separation space (E) and plunging into the water tanks (40),

characterized in that the fixed refractory spars (LRF) and the fixed mobile refractory spars (LRM) have an inclined and rounded profile on the upper part, the inclined profile having a slope forming with the horizontal an angle greater than the angle of scaling of scale.

2. Furnace according to the preceding claim, wherein the fixed refractory spars (LRF) and the movable fixed refractory spars (LRM) extend over all or part of the length of the furnace.

3. Furnace according to any one of the preceding claims, in which the fixed refractory spars (LRF) and the movable refractory spars (LRM) are made of low-cement concrete, based on tabular alumina and spinel.

4. Furnace according to any one of the preceding claims, further comprising scrapers (50), the profile of which is adapted to promote the crushing and evacuation of the scale, fixed on the plurality of skirts (70).

5. Oven according to the preceding claim, wherein the scrapers have a suitable spade-shaped profile.

6. Oven according to any one of the preceding claims, in which the water tank (40) is provided with water spray nozzles (80) and toilet flushes (20) arranged to expel the water and the water. scale of the water tank.

7. Furnace according to any one of the preceding claims, comprising refractory spars (LRF, LRM) over only part of the length of the furnace, characterized in that at least one water tank (40) has a rectangular shape or U-shaped, at least one transverse connection (41) of the water tank providing a connection between two longitudinal sections (42) of the water tank arranged on either side of a refractory spar.

8. A method of continuously grinding and removing scale in a movable spar furnace comprising a plurality of fixed refractory spars (LRF) extending longitudinally and a plurality of movable refractory spars (LRM) extending longitudinally, the longitudinal members. Mobile refractory spars being arranged transversely between the fixed refractory spars and separated on each side of the fixed refractory spars by a space (E), drive means arranged to move a lifting frame (2) and a translation frame (3) , supporting the mobile refractory spars (LRM), according to a rectangular displacement cycle having two vertical positions, respectively upper and lower, and an intermediate vertical position according to which the mobile spars are at the same height as the fixed spars, the mobile spars forming protrusion above the fixed side members in the upper position, the movable side members being at a level below the fixed side members in the lower position, the furnace further comprising a plurality of longitudinal water tanks (40) arranged in line with the separation spaces (E) and fixed to one of the refractory side members (LRF, LRM ) delimiting a separation space (E), and a plurality of skirts (70) fixed to the other refractory spar (LRF, LRM) delimiting said separation space (E) and plunging into the water tanks (40),

characterized in that the fixed refractory spars (LRF) and the fixed movable refractory spars (LRM) having an inclined and rounded profile on the upper part, the inclined profile having a slope forming with the horizontal an angle greater than the angle of sloping the scale, the scale being crushed by the side members as it passes through the separation spaces (E) and being continuously discharged by the plurality of water tanks.

9. Method according to the preceding claim, further comprising a step of crushing and removing the scale by scrapers (50) with an adapted profile attached to the plurality of skirts (70).