FR2807151A1 - REFRACTORY LINING FOR FURNACES CONTAINING FUSED METAL - Google Patents

Abstract

A refractory lining for a furnace containing molten metal, having a face plated to the inside of the steel plate wall of the furnace and a face in contact with the molten metal, comprises a first assembly of an insulating layer (1), a highly insulating layer (2) and a metal side and a second assembly of one or more dense layers (5) non-wettable by the molten metal. Between these two assemblies it incorporates at least one insulating or non-insulating refractory layer (3) strengthened by a reinforcing medium. By preference the reinforcing medium is a metallic or non-metallic lattice or reinforcing fibres. An Independent claim is included for a furnace incorporating such a refractory lining.

Description

I The present invention relates to a refractory lining for ovens

containing liquid metal.

  The current lining of this type of oven, plated on the internal face of the external sheet of the oven and in contact with the molten metal is successively composed of: - one or more insulating layers of refractory materials on the side of

prison.

  - optionally semi-insulating or insulating safety layers ensuring non-wettability by the molten metal of the insulating layers

previous.

  - dense layers not wettable by molten metal.

  However, such a lining has certain drawbacks or defects, namely: - insufficient strength and longevity due to cracking of the layers

dense.

- Limited oven performance.

- Heat loss.

  - The invention overcomes the drawbacks with a refractory lining for furnaces containing molten metal, said lining having a face pressed inside the sheet metal wall of the furnace and a face in contact with the molten metal, lining of the type comprising, on the sheet side, a first set of insulating (1) and very insulating (2) layers and on the metal side, a second set of one or more dense layers (5) not wettable by molten metal, characterized in that , between the two assemblies, it comprises at least one refractory layer (3)

  insulating or semi-insulating reinforced by a reinforcement means.

  - The lining according to the invention may also comprise between the layer

  army and the set of dense layers, a very insulating layer.

  - The invention also relates to an oven isolated by such a lining and

  possibly combined with the action of thermo plungers.

  The invention will be better understood using the description below made in

  reference to the following appended figures: - Figure 1: sketch showing in cross section a lining of the prior art. - Figure 2: sketch showing in cross section a packing according to the invention. In order to better understand the effectiveness of a packing according to the invention, its

  performances are compared to those of a lining of the prior art.

  We first refer to Figure 1.

  The lining of the prior art cited as an example comprises: - Two or more successive insulating layers (a) (b), the layer (a) of which is pressed against the outer sheet (t) of the furnace

  - An insulating safety layer (c).

  - Two successive layers (d) (e) of which the last layer (e) in contact

  liquid metal, is healthy (not cracked).

  Their characteristics are shown by way of example in the following table. Ref. Quality layer A [Wlm.K] Thickness [m] T [C] a Insulation 0. 08 0.030 63.82 b Very insulating 0.1 0.050 197.84 c Insulating 0.1 0.050 376. 83 d Insulating 0.1 0.070 555.22 e Dense not wettable by 1.94 0.100 711. 58 metal and healthy. Total thickness 0.300 [m] We now refer to FIG. 2 corresponding to a nonlimiting example of the invention and which successively comprises: - two or more insulating (1) and very insulating (2) layers including the layer (1 ) on the side of the outer sheet (6) of the oven (similar to

layers (a) and (b) above).

  - an insulating or semi-insulating reinforced layer (3), the insulating material of which is reinforced by any reinforcing means, for example chosen from the set [mesh (metallic or non-metallic), reinforcing fibers (metallic or non-metallic)]. This reinforced layer (3) removes the insulating layer (c) from the previous case. Indeed, surprisingly, in addition to its role of mechanical reinforcement, it increases the thermal insulation and provides a safety function guaranteeing the non-wettability of the refractory by the molten metal. Its coefficient 2 of thermal conductivity can be chosen in the interval [0.35 2.5] with a preferential value close to 1, for example included

between 1 and 1.1 W / m.K.

  - an optional highly insulating layer (4) replacing the insulating layer (d) of the previous case. - a dense layer (5) not wettable by the metal corresponding to the

layer (e) of the previous case.

  The characteristics of layers (1) to (5) are given by way of nonlimiting example in the following table: Ref. layer Quality A [W / m.K] Thickness Tq [OC] T [C] (ri) [m] with layer with layer

(5) healthy. (5) cracked.

  1 Insulating 0.021 0.015 63.22 73.63 2 Very insulating 0.08 0.050 314.57 393. 37 3 Army and not 1.06 0.080 534 673.14 wettable 4 Very insulating 0.035 0.015 581.05 706.93 Dense and not 1.94 0.100 711.86 706.93 wettable Total thickness 0.260 [m] Temperatures are temperatures averages verified experimentally. The last two columns indicate the temperatures of the layers respectively in the case where the dense layer is healthy and in the case where it is

1 s cracked.

  In the case where this dense layer (5) is cracked, a temperature of about 70 to 75 of the layer 1 and the outer sheet is acceptable and the oven

  can continue to operate without requiring intervention.

  The reinforced layer (3) plays its role and can last longer without loss

huge isolation and energy.

  A lining of the type of the invention makes it possible to construct, for a total thickness less than or equal, walls of highly insulating ovens, while offering great operating safety, an increased service life, a significant energy saving. The energy saving can be further increased by combining the action of the lining according to the invention with the use of immersion heaters immersed in the

liquid metal.

  Throughout the description and the claims, the qualifiers

  "semi-insulating" and "very insulating" can be attributed to layers whose coefficient of thermal conductivity (A,) is:

  - approximately [1 2.5] W / m.K for a semi-insulating layer.

  - approximately [0.35] W / m.K for an insulating layer.

  - approximately <0.35 W / m.K for a very insulating layer.

Claims (8)

  1. Refractory lining for furnaces containing molten metal, said lining having a face pressed inside the sheet metal wall of the furnace and a face in contact with the molten metal, lining of the type comprising, sheet side, a first set of insulating layers (1) and very insulating (2) and on the metal side, a second set of one or more dense layers (5) not wettable by molten metal, characterized in that, between the two sets, includes at least one insulating refractory layer (3)   or semi-insulating reinforced by a reinforcement means.   2. Packing according to claim 1 characterized in that the means   reinforcement is chosen from the set (mesh, reinforcing fibers).   3. Packing according to one of claims 1 to 2 characterized in   that it further comprises, between the reinforced layer (3) and the assembly of   dense layers, a very insulating layer (4).   4. Packing according to one of claims 1 to 3 characterized in   that the coefficient A of the reinforced layer (3) is included in   the interval [0.35 W / m.K 2.5 W / m.K].   5. Packing according to claim 4 characterized in that the   coefficient 2 is preferably between 1 and 1.1 W / m.K.   6. Packing according to one of claims 4 to 5 characterized in that   that the coefficient A of the highly insulating layer (4) is <0.35 W / m.K.   7. Industrial oven for melting metal, characterized in that its wall is internally insulated by a coating according to one of the claims 1 to 6.   8. Oven according to claim 7 characterized in that the   packing is combined with the action of immersion heaters.