EP0627605A1 - Intern envelope for furnaces, in particular metallurgical furnaces - Google Patents

Abstract

The invention relates to a furnace or a metallurgical vessel with a refractory lining (1) within the furnace or vessel shell (2). An inner shell (3) surrounding the refractory lining (1) is arranged at a distance from the jacket (2). This arrangement ensures that the pressure on the furnace casing (2) is reduced by the expansion of the refractory lining (1) during operation of the furnace and thus the stresses in the refractory lining (1) and in the casing (2) are limited to values, which are within the permissible stress values of the materials. <IMAGE>

Description

The invention relates to a furnace or a metallurgical vessel with a refractory lining within the furnace or vessel wall.

Furnaces or metallurgical vessels essentially consist of a circular steel jacket and a fire-resistant lining, which protects the jacket against excessive heating. The furnace or vessel jacket is formed from cylindrical and conical, possibly also spherical and toroidal steel sections. The fireproof lining is a masonry of trapezoidal stones or a homogeneous layer applied as an informal mass and solidified by subsequent firing. The refractory lining has a greater thickness than the surrounding furnace or vessel jacket.

During the operation of a furnace or metallurgical vessel, the refractory lining is considerably hotter than the steel jacket and therefore has a tendency to expand more than the jacket. The temperature gradient from inside to outside can be over 1000 ° C.

Since the expansion of the refractory lining is limited by the casing, a radially directed pressure is created in the contact surface (peripheral joint) of the refractory lining towards the casing. This pressure creates a tensile stress in the jacket on the one hand, and a reaction stress in the refractory lining on the other hand.

The magnitude of these tensile and compressive stresses depends on the thickness, the temperature, the elastic and thermal properties of both the refractory lining and the materials of the furnace or vessel shell. If the compressive stress in the refractory lining becomes too high, breakouts on the inner wall thereof will result. If the tensile stress in the jacket becomes too high, it deforms plastically and permanently. The coat can even tear.

The object of the invention is to limit the stresses in the refractory lining as well as in the furnace or vessel shell on the one hand to permissible values and on the other hand to reduce the thickness of the furnace or vessel shell in a furnace or metallurgical vessel, without exceeding the permissible voltage values.

The object is achieved according to the invention in the manner as specified in the claims.

The stresses in the jacket of the metallurgical furnace or vessel and in the refractory lining can be limited according to the invention by initially leaving a gap between the lining and the jacket when the refractory lining is introduced. When heated, ie when the furnace or vessel is heated, this gap closes due to thermal expansion of the refractory lining until the refractory lining is firmly against the jacket. Only then will compressive stress build up in the refractory lining and tensile stress in the jacket.

However, before the fire-resistant lining lies against the jacket, its cohesion, e.g. as a stone bandage, not secured. There is therefore a risk that shear forces cause dislocations and cracks in the refractory lining, which can severely damage it and put further operation of the furnace or vessel into question.

The task was therefore to ensure the cohesion of the refractory lining as long as it is not yet in contact with the furnace or vessel jacket.

According to the invention, this is done in such a way that a relatively thin, circumferentially closed inner shell is attached inside the furnace or vessel, on the inner wall of which the refractory lining is applied in a pressure-resistant manner during delivery. There is initially a radial distance between the inner shell and the furnace or vessel shell.

The inner shell is expediently dimensioned in such a way that a gap is produced between the inner shell and the jacket, which gap is defined in accordance with the physical conditions.

When starting up, ie while the furnace or vessel is heating up, the refractory lining and with it the inner shell expands until it lies against the jacket. During this process, the refractory lining is kept from the outside at all times, its circumference remains circular and the balance of forces is always maintained for each element (stone) of the lining.

If the fireproof lining clings to the jacket after placing the inner shell, i.e. after the circumferential gap has closed, the compression stress then occurring in the refractory lining and the tensile stress occurring in the jacket are significantly lower than in furnaces or metallurgical vessels which do not have the inner shell according to the invention.

Often attempts are made to reduce the heat flow between the refractory lining and the jacket by introducing substances with high thermal resistance, e.g. Mineral fiber mats to reduce. Because of the low density and correspondingly low compressive strength of these insulating materials, there is a risk that the refractory lining, especially at the beginning of the thermal expansion process, as mentioned above, will lose its cohesion as a ring.

According to the feature of a subclaim, the protection of the furnace or vessel jacket against excessive heating can be achieved by introducing highly heat-insulating materials between the inner shell and the oven or vessel jacket without the fireproof lining being endangered at any time.

In some cases, additional cooling of the furnace or vessel jacket is desirable. According to the invention, effective cooling can be achieved in that according to the features of subclaims on the outer surface of the inner shell according to the invention, strips or the like at short intervals. be placed on the inside wall of the jacket when the oven or vessel is heating up. This allows the heat transfer area to be kept small. By a cooling medium can be conducted through the channels formed between the strips.

Fig.1

ausschnittsweise den Bereich des Gestelles eines Hochofens und den Verlauf des zugehörigen Ausmauerungsdruckes im Betriebszustand,

Fig.2

einen Längsschnitt durch einen Teil eines Ofens vor dem Anheizen,

Fig.3

einen Querschnitt durch ein Segment eines Ofens vor dem Anheizen,

Fig.4

einen Längsschnitt durch einen Teil des Ofens mit einer wärmedämmenden Schicht,

Fig.5

einen Schnitt durch ein Segment eines Ofens mit aufgesetzten Leisten,

Fig.6

einen Längsschnitt durch einen Teil des Ofens mit aufgesetzten Ringen oder Wendeln und

Fig.7

ausschnittsweise den Gestellbereich eines Hochofens mit einer begrenzten Innenschale.

Embodiments of the invention are explained below with reference to the schematic drawings. Show it:

Fig. 1

sections of the area of the frame of a blast furnace and the course of the associated brick pressure in the operating state,

Fig. 2

a longitudinal section through part of a furnace before heating,

Fig. 3

a cross section through a segment of a furnace before heating,

Fig. 4

a longitudinal section through part of the furnace with a heat-insulating layer,

Fig. 5

a section through a segment of an oven with attached strips,

Fig. 6

a longitudinal section through part of the furnace with rings or coils and

Fig. 7

sections of the frame area of a blast furnace with a limited inner shell.

The longitudinal section of the casing of a metallurgical furnace (2) in the area of the so-called frame (10) of a blast furnace can be seen from FIG. The course of the associated lining pressure is on the side in shape a horizontally hatched area (9). Not only is the thickness of the lining (1) large in the frame, but also the resulting lining pressure (9) is high. In the area of the frame base (10), the lining forms a disc with a very high lining pressure (9), which also decreases due to the decreasing temperature and ends in a point.
Fig.2 shows the refractory lining (1), the inner shell (3) according to the invention and the jacket (2). There is a gap (4) between the inner shell (3) and the jacket (2) of the furnace or vessel, which gap decreases during the heating up due to the expansion of the lining (1).

3 shows a cross section through a segment of a metallurgical furnace with the lining (1), the inner shell (3) and the jacket (2) before heating. The forces (11, 12) which act on an element (stone) of the lining (1) and are in equilibrium are shown as arrows.

4 shows in a longitudinal section through part of a metallurgical furnace that a heat-insulating layer (5) is arranged in the gap between the inner shell (3) and the jacket (2) and fills this gap before it is heated.

5 shows in a cross section through a wall segment of a furnace that strips (6) are placed on the inner shell (3) according to the invention. Channels (8) are thus formed between the strips (6) and the walls of the inner shell (3) and jacket (2). formed through which a gaseous or liquid cooling medium can be passed.

6 shows in a longitudinal section through the wall of a metallurgical furnace the arrangement of rings or coils (7) which are arranged between the inner shell (3) and the jacket (2). A cooling channel (8) is also formed here.

Fig. 7 shows in longitudinal section the frame area of a blast furnace (1, 10) in the state before heating with an inner shell (3) limited to a small area. High pressures would occur in this area without the presence of the inner shell (3). The inner shell (3) absorbs the pressure of the hot lining (1) on the casing (2) and prevents permanent deformation in this endangered area of the furnace.

Claims (5)

Furnace or metallurgical vessel with a refractory lining inside the furnace or vessel wall,
characterized by a thin-walled inner shell (3) which surrounds the refractory lining (1) on the outside, a space (4) being present between the inner shell (3) and the furnace or vessel shell (2) before the furnace or vessel is heated. Furnace or metallurgical vessel according to claim 1,
characterized,
that between the inner shell (3) and the furnace or vessel jacket (2) a heat-insulating layer (5) is attached. Furnace or metallurgical vessel according to claim 1,
characterized,
that internals such as strips (6), rings or coils (7) are arranged on the outer surface of the inner shell (3) at intervals. Furnace or metallurgical vessel according to claim 3,
characterized,
that the channels (8) formed between the inner shell (3) and internals (6, 7) are provided for the flow of a cooling medium. Furnace or metallurgical vessel according to claim 1,
characterized,
that the attachment of an inner shell (3) is limited to only a portion of the lining (1).

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