GB2340226A - Refractory brick comprising condition measuring device - Google Patents

Description

2340226 1 REFRACTORY BRICK The present invention relates to refractory

bricks.

Steel making furnaces are commonly lined with refractory bricks. These are constructed of ceramic materials which are able to withstand the extremely high temperatures involved in handling liquid steel.

However, even refractory materials tend to degrade over extended periods and therefore it is necessary to reline the furnace with fresh refractories. This is a major operation, and involves a complete shutdown of the furnace for a significant period of time whilst the remnants of the original refractories are removed and fresh refractories provided. As a result, it is highly desirable to postpone relining operations until the existing refractories are indeed excessively worn. However, the operation cannot be delayed excessively as this would risk complete failure of the refractory lining with potentially disastrous results.

It would therefore be highly desirable to provide an active monitoring of the refractory lining. This would allow the relining operation to be timed precisely to that point when the existing lining could no longer be relied upon, subject to any prudent safety margins. The cost penalties of premature relining would thus be avoided, without risking lining failure. However, such monitoring has not hitherto been possible for the simple reason that all available sensors have been constructed such that their immediate destruction by (for example) melting would be inevitable in the context of a steel furnace. Once the sensor had melted, this would provide an escape hole in the furnace.

2 The present invention therefore provides a refractory brick for lining a metallurgical device, comprising a means for non-destructively measuring at least one of the length of the brick, heat flux through the brick, and the stress state of the brick, the means being adjacent or within the brick, and means for relaying the output of the measuring means to the units based from the brick, the measuring means being constructed of a ceramic material and/or metals with a melting point greater than that of iron.

The apparently conflicting demands of the measuring means, ie that it be made of a refractory material and yet be capable of measuring length (etc) of the brick can be satisfied if it principally includes a light transmissive element or other such sensor arranged longitudinally within the brick. Suitable light transmissive elements are optical fibres, silica rods, sapphire rods, etc. These are all essentially of suitable refractory materials and are likely to withstand the environment for at least as long as the refractory brick. Thus, the length of the device can be measured by suitably known methods of measuring light transmission paths. As the brick degrades, the length of the light transmission path will reduce and this information can be relayed back.

The silica and alumina rods can typically be between 5 and 25mm in diameter. Alternatively a bundle of optical fibres can be used. length would of course correspond to the length of the brick.

The relaying means will preferably operate via cabling or via electromagnetic transmission. Suitable transmission wavelengths are those in the infrared, optical or microwave regions.

Thus, the present invention allows monitoring of the state of refractory bricks within the furnace. Sensors need not of course be included in every brick, as the cost could then be prohibitive. It should be sufficient in practice for them to be included within a reasonable number of bricks 3 spaced about the periphery of the furnace.

The bricks (or other bricks between them) could of course include sensors for other parameters such as stress, heat flux and temperature. This data could complement the length data to provide valuable operating information.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying figures, in which; Figure 1 is a vertical section through a steel teeming ladle incorporating a refractory brick according to the present invention; Figure 2 is an enlarged version of part of Figure 1; Figures 3 and 4 are side and end views respectively of a single refractory brick according to a first embodiment; Figures 5 and 6 are side and end views respectively of a single refractory brick according to a second embodiment; and Figures 7 and 8 show an alternative version based on a refractory rod, figure 7 being a longitudinal section and figure 8 being an end view.

The device illustrated in the Figures is a piece of refractory that contains sensors which can measure temperature and stress related effects. The sensors are made from refractory material that can withstand furnace operating temperatures. The refractory surrounding the sensor is of a similar composition to the lining in which the sensor is to be used.

The device, once built into a lining of a metallurgical device, will be able to measure any or ail of the following: lining wear, lining deformation, 4 stress development, heat flux and temperature distribution.

The sensing device comprises three main components:

The sensor 10. One or more is embedded in the refractory 12 either singly or in clusters. A sensor is a polycrystalline, vitreous or single crystal ceramic in the form of a rod or fibre. Materials such as fused silica, sintered alumina, sapphire and optical fibres can be used. Composite sensors can also be fabricated incorporating various ceramic materials or ceramic materials and carbon. The sensor protrudes from the cold face of the ref ractory.

The transmitter/receiver 14 is attached to the sensor where it protrudes from the cold face of the refractory. It sends electromagnetic radiation such as infrared, microwave or optical signals into the sensor and receives them from the sensor when the modified signal has been reflected out. In certain applications it is necessary to water or air cool the transmitter/receiver to protect its circuitry.

The processor 16 is situated outside the metallurgical device and is connected to the transmitter/receiver by means of electrical cables or optical fibres 18. The processor generates the signal that is sent down the sensor and processes and interprets the modified signal when it is received back from the transmitter/receiver.

Various techniques are available to embed the sensor in the refractory. Examples are:

(a) Cutting a brick into sections, hollowing out the relevant parts and installing the sensor and transmitter/receiver. Grooves etc. are filled with an appropriate air setting, phosphate or resin bonded mortar before the brick is re-assembled and mortared together. This technique is particularly appropriate for blast furnace carbon where a similar technique is used to manufacture composite blocks that can be handled as one unit.

(b) Co-pressing the sensor in the brick. After pressing, the end of the sensor is exposed by machining away surrounding material before curing and/or firing. The transmitter/receiver is subsequently fitted. This technique is appropriate to resin bonded or phosphate bonded bricks.

(c) Preforming a refractory rod in which sensors are embedded, and then drilling or otherwise forming a hole in the furnace lining, and inserting the rod into the hole. The rod would need to be about 25mm in diameter.

When used to make measurements in refractory castables the sensor can be installed as the refractory is cast, or can be installed in a precast block which is subsequently installed.

Flat sensors can be incorporated in the joints between refractories. As these are non-metallic, they act in place of a mortar and resist penetration by metal and slag.

Figures 3 and 4 show side and end views respectively of a first embodiment. In this embodiment, a brick 102 includes a centrally located fused silica rod 104. This is inserted by drilling through the centre of the brick 102, inserting the rod 104, and sealing the gap with a conventional refractory mortar 106.

A control circuit 108 includes a light pulse generator and a timer, arranged to send a light pulse along the interior of the fused silica rod 104 for reflection off its end face. The travel time is then used to compute the 6 length of the brick. As the brick is worn away and degraded, so is the fused silica rod wire 4. As a result, its length slowly decreases and this is detected by the circuitry 108 and transmitted to processing means as described above.

Figures 5 and 6 show side and end sections similar to those of Figures 3 and 4. In this case, the fused silica rod 114 is not embedded within the refractory brick 112 but is affixed to an edge surface thereof. The control circuitry 118 is once again adapted to send suitable signals along the rod 114. Only a light connection need be made between the two using known adhesives, as the fused silica rod 114 will become embedded within the refractory mortar on construction of the refractory lining.

Figures 7 and 8 illustrate an alternative sensor element for use in the invention. It corresponds to suggestion (c) above. Instead of employing a standard shape refractory brick as described above, an elongate cylinder 120 of refractory material is employed. Grooves 122 are formed on the sides of the cylinder 120, in this case four equally spaced grooves. The number and distribution of grooves will of course be determined by the number and nature of sensors intended for use. A housing 124 for transmitters and/or receivers is provided at one end of the cylinder 120.

This assembly is inserted as described above, ie by drilling a hole in the side of the furnace wall and inserting the cylinder 120.

It will be appreciated that many variations can be made to the abovedescribed embodiments, without departing from the scope of the present Application. All such variations are intended to be encompassed herewithin.

Claims (9)

1. 7 CLAIMS

   A refractory brick for lining a metallurgical device, comprising a means for non-destructively measuring at least one of the length of the brick, heat flux through the brick, and the stress state of the brick, the means being adjacent or within the brick, and means for relaying the output of the measuring means to the units based from the brick, the measuring means being constructed of a ceramic material and/or metals with a melting point greater than that of iron.
2. 2. A refractory brick according to claim 1 in which the measuring means includes a light transmissive element arranged longitudinally within the brick.
3. 3. A refractory brick according to claim 2 in which the light transmissive elements comprises at least one of an optical fibre, silica rod, and/or sapphire rod.
4. 4. A refractory brick according to claim 2 in which the light transmissive element is one of a silica or alumina rod and between 5 and 25mm in diameter.
5. 5. A refractory brick in which the light transmissive element comprises a bundle of optical fibres.
6. 6. A refractory brick according to any preceding claim in which the relaying means operates via at least one of cabling or electromagnetic transmission.
7. 7. A refractory brick according to claim 6 in which the relaying means operates via electromagnetic transmission at a wavelength in at least one of the infrared, optical or microwave regions.
8. 8 8. A refractory brick according to any preceding claim including sensors for at least one of stress, heat flux and/or temperature.
9. 9. A refractory brick substantially as herein described with reference to and/or as illustrated in the accompanying drawings.