GB1590271A

GB1590271A - Refractory bricks and refractory linings

Info

Publication number: GB1590271A
Application number: GB35340/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-08-23
Filing date: 1977-08-23
Publication date: 1981-05-28
Also published as: ZA765036B; DE2738001A1

Description

(54) REFRACTORY BRICKS AND REFRACTORY LININGS (71) I, HANS WALTER GOLDBERGER GROSS, a South African citizen, of 249 Ocean View Drive, Seapoint, Cape Town, Cape Province, Republic of South Africa, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement This invention relates to refractory bricks and to brickwork constructed from such bricks.

When installing the refractory linings in industrial furnaces, particularly in metallurgical ones where operating temperatures in excess of 1400"C are reached, attention must be paid to the fact that refractory materials expand considerably during the transition from ambient to operating temperature.

This thermal expansion of the refractory linings occurs when the furnaces are heated up to operating temperature. At this temperature the brickwork must be tight and without open joints.

Customarily, the thermal expansion of the refractory linings is compensated for by providing an appropriate amount of 'give' in the framework of the furnaces (e.g.

adjustable screw bolt connections or compressible springs) to absorb the pressure which occurs during expansion; by arranging expansion joints in the brickwork and filling the joints with combustible material (carton etc) which burns out when the temperature rises and expansion takes place; and/or by arranging expansion joints between the brickwork and supporting structure and filling the joints with compressible material.

The state of the art is discribed more fully in Austrian Patent 331171.

The present invention aims to provide refractory linings including bricks with a certain controlled compressibility and thus to entirely or partly replace the methods described above.

The present invention thus provides a refractory lining for a furnace, the lining including a refractory brick which has an integral compressible layer on at least one face of a relatively incompressible block of the brick, said layer being being in face-to-face engagement with a surface of an adjacent refractory brick to be crushed upon thermal expansion of bricks of the lining when the furnace is heated.

Generally speaking the compressibility of the compressible layer is caused by reducing the surface of contact of the respective brick, whereby the compression force brought to bear on each point of contact between the two bricks in face-to-face engagement is increased in inverse proportion to the area of the reduced contact surface.

The compressible layer may thus be formed by a pattern of crushable raised formations provided on at least one face of the relatively incompressible block of the brick, the relatively incompressible block being such that it will not be significantly compressed by the pressure arising during normal use of the brick in a furnace.

These raised formations may be ribs separated by depressions, and may have been formed during the pressing of the brick before firing thereof.

The compressible layer may alternatively be formed by a crushable cavity-containing layer provided on said at least one face of the relatively incompressible block of the brick. The crushable cavity-containing layer may be a result of mechanically eroding the brick to form cavities therein, for example by sand blasting, punching or cutting after firing of the brick.

The refractory brick may have a single compressible layer with a height which is from 0,5 to 1,3 percent of the greatest distance that the brick extends away, from the layer. Alternatively, the refractory brick may include two compressible layers and the total height of the compressible layers may be from 0,5 to 1,3 percent of the distance between the layers.

The invention also extends to an industrial furnace having a refractory lining comprising a plurality of bricks having integral compressible layers for compensating for thermal expansion of the bricks, when heated, the compressible layers being provided on faces of relatively incompressible blocks of the bricks.

When the industrial furnace is used the or each compressible layer is partially crushed by thermal expansion of the bricks to form a tight joint between adjacent bricks.

The invention extends to the construction of a complete or partial new lining in the manner described as well as to the repair of such lining when damaged in the course of utilization.

For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is an elevational view of a refractory brick; Figure 2 illustrates, to an enlarged scale, portions of two refractory bricks of the form shown in Figure 1 arranged side-by-side; Figures 3 and 4 illustrate further rib patterns for refractory bricks Figures 5 to 7 illustrate possible rib profiles; and Figure 8 illustrates a further form of refractory brick in accordance with the present invention.

Refractory bricks are manufactured by means of a moulding process involving the application of very high pressures to raw refractory material in moulds. The material is thus highly compressed when the "green" bricks emerge from the mould.

After firing, the bricks are hard and dense.

The brick 10 illustrated in Figure 1 includes a block 11 which bears a pattern of zig-zag raised ribs 12 on one side face 13 thereof. When two such bricks are placed side-by-side, as shown in Figure 2, they abut at the crests 15 of the ribs. When the furnace brickwork is heated, the bricks undergo thermal expansion and the ribs come under pressure, which tends to crush and flatten them. Compression of the ribs enables the expansion of the bricks to be accommodated and, at the same time, a tight joint comes into existance between the side faces 13 of the blocks.

Where both sides of each brick are ribbed, the height 'Z' of the crests 15 of the ribs above the side faces 13 of the block 11 is chosen as half the estimated expansion of the brick in the direction normal to the side faces. Where only one side face of the brick is ribbed, the height 'Z' of the ribs 12 is equal to the anticipated expansion.

In Figure 2 the height 'Z' can be approximately 1 mm for a brick which is 100 mm between its major side faces 13, this being the direction in which expansion must be allowed for.

It will be understood that the portion of the brick between the side face 13 of the block 11 and the crests 15 of the ribs 12 constitutes a compressible layer.

Alternative rib patterns are shown in Figures 3 and 4 i.e. a straight line pattern in Figure 3 and a wafer pattern of intersecting ribs in Figure 4. Figures 5 to 7 illustrate possible rib profiles. Thus ribs of triangular section are illustrated in Figure 5, semi-circular cross-section in Figure 6 and rectangular cross-section in Figure 7.

It will be understood that the profiles of the ribs and their pattern must be chosen such that they do not interlock when placed side-by-side. If the patterns interlock neatly then expansion of the brick cannot be accommodated by compression of the ribs.

The pattern of ribs can be provided, during the moulding procedure, by providing a complementary pattern of ribs and depressions on the appropriate mould surfaces.

Referring now to Figure 8, this illustrates, to a greatly enlarged scale, a portion 16 of the side face of a refractory brick before sand blasting (the left hand portion) and a portion 17 of the brick after sand blasting. Sand blasting thus produces a layer (between the lines X and Y) which will compress when forced under pressure against a smoother surface, such as that represented by the un-blasted surface of the refractory brick.

In other words, peaks 18 on the blasted surface tend to flatten and fill the depressions 19 which are left when refractory material has been removed, the actual amount being dependent on the granular sizing of the material. By way of example, the treatment of the surface should proceed until approximately 40 to 60% of the material between the lines X and Y has been removed. This generally means that the distance between the lines X and Y is approximately 0,5mm.

WHAT I CLAIM IS 1. A refractory lining for a furnace, the lining including a refractory brick which has an integral compressible layer on at least one face of a relatively incompressible block of the brick, said layer being in faceto-face engagement with a surface of an adjacent refractory brick to be crushed upon thermal expansion of bricks of the lining when the furnace is heated.

2. A refractory lining according to claim 1, wherein the compressible layer is formed by a pattern of crushable raised formations provided on said at least one face of the relatively incompressible block of the brick.

3. A refractory lining according to claim 2, wherein the raised formations are ribs separated by depressions.

4. A refractory lining according to claim 2 or 3, wherein the crushable raised formations have been formed during pressing of the brick before firing thereof.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. a plurality of bricks having integral compressible layers for compensating for thermal expansion of the bricks, when heated, the compressible layers being provided on faces of relatively incompressible blocks of the bricks. When the industrial furnace is used the or each compressible layer is partially crushed by thermal expansion of the bricks to form a tight joint between adjacent bricks. The invention extends to the construction of a complete or partial new lining in the manner described as well as to the repair of such lining when damaged in the course of utilization. For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is an elevational view of a refractory brick; Figure 2 illustrates, to an enlarged scale, portions of two refractory bricks of the form shown in Figure 1 arranged side-by-side; Figures 3 and 4 illustrate further rib patterns for refractory bricks Figures 5 to 7 illustrate possible rib profiles; and Figure 8 illustrates a further form of refractory brick in accordance with the present invention. Refractory bricks are manufactured by means of a moulding process involving the application of very high pressures to raw refractory material in moulds. The material is thus highly compressed when the "green" bricks emerge from the mould. After firing, the bricks are hard and dense. The brick 10 illustrated in Figure 1 includes a block 11 which bears a pattern of zig-zag raised ribs 12 on one side face 13 thereof. When two such bricks are placed side-by-side, as shown in Figure 2, they abut at the crests 15 of the ribs. When the furnace brickwork is heated, the bricks undergo thermal expansion and the ribs come under pressure, which tends to crush and flatten them. Compression of the ribs enables the expansion of the bricks to be accommodated and, at the same time, a tight joint comes into existance between the side faces 13 of the blocks. Where both sides of each brick are ribbed, the height 'Z' of the crests 15 of the ribs above the side faces 13 of the block 11 is chosen as half the estimated expansion of the brick in the direction normal to the side faces. Where only one side face of the brick is ribbed, the height 'Z' of the ribs 12 is equal to the anticipated expansion. In Figure 2 the height 'Z' can be approximately 1 mm for a brick which is 100 mm between its major side faces 13, this being the direction in which expansion must be allowed for. It will be understood that the portion of the brick between the side face 13 of the block 11 and the crests 15 of the ribs 12 constitutes a compressible layer. Alternative rib patterns are shown in Figures 3 and 4 i.e. a straight line pattern in Figure 3 and a wafer pattern of intersecting ribs in Figure 4. Figures 5 to 7 illustrate possible rib profiles. Thus ribs of triangular section are illustrated in Figure 5, semi-circular cross-section in Figure 6 and rectangular cross-section in Figure 7. It will be understood that the profiles of the ribs and their pattern must be chosen such that they do not interlock when placed side-by-side. If the patterns interlock neatly then expansion of the brick cannot be accommodated by compression of the ribs. The pattern of ribs can be provided, during the moulding procedure, by providing a complementary pattern of ribs and depressions on the appropriate mould surfaces. Referring now to Figure 8, this illustrates, to a greatly enlarged scale, a portion 16 of the side face of a refractory brick before sand blasting (the left hand portion) and a portion 17 of the brick after sand blasting. Sand blasting thus produces a layer (between the lines X and Y) which will compress when forced under pressure against a smoother surface, such as that represented by the un-blasted surface of the refractory brick. In other words, peaks 18 on the blasted surface tend to flatten and fill the depressions 19 which are left when refractory material has been removed, the actual amount being dependent on the granular sizing of the material. By way of example, the treatment of the surface should proceed until approximately 40 to 60% of the material between the lines X and Y has been removed. This generally means that the distance between the lines X and Y is approximately 0,5mm. WHAT I CLAIM IS

1. A refractory lining for a furnace, the lining including a refractory brick which has an integral compressible layer on at least one face of a relatively incompressible block of the brick, said layer being in faceto-face engagement with a surface of an adjacent refractory brick to be crushed upon thermal expansion of bricks of the lining when the furnace is heated.

5. A refractory lining according to claim

1, wherein the compressible layer is formed by a crushable cavity-containing layer provided on said at least one face of the relatively incompressible block of the brick.

6. A refractory lining according to claim 5, wherein said crushable cavity-containing layer is a result of mechanically eroding the brick to form cavities therein.

7. A refractory lining according to any preceding claim, wherein the brick with the compressible layer has a single compressible layer with a height which is from 0,5 to 1-3 percent of the greatest distance that the brick extends away from the layer.

8. A refractory lining according to any one claims 1 to 6, wherein the brick with the compressible layer has compressible layers on opposite faces, the total height of the compressible layers being from 0,5 to 1,3 percent of the distance between the layers.

9. An industrial furnace having a refractory lining according to any preceding claim for compensating for thermal expansion of the bricks of the lining, when heated.

10. An industrial furnace according to claim 9, having the or each compressible layer at least partially crushed by thermal expansion of the bricks.

11. A refractory lining according to claim 1, wherein the brick is substantially as herein described with reference to the accompanying drawing.