GB1578058A - Refractory articles - Google Patents

Description

(54) REFRACTORY ARTICLES (71) We, DIDIER-WERKE A.G., a Company organised under the laws of the Federal Republic of Germany, of Lessingstrasse 16, 62 Wiesbaden, West Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to refractory articles especially in the form of a refractory building element or moulded component with inserts for heat dissipation from hot places.

Generally the mechanical and chemical resistance of refractory material decreases with increasing thermal load. Therefore in many cases it is possible to reduce the wear of a material by cooling. This method is applied, for instance, to blast furnaces by cooling with water or steam, to Siemens-Martin furnaces by cooling with air or water, and to those parts of sliding gates of metallurgical vessels which are subject to wear, by cooling of the refractory sliding plates with air.

Water cooling or cooling by evaporating water is very efficient because heat transfer between the flowing water or the condensing steam and the cooling tube is very good and because, due to the high specific heat of water, much heat can be dissipated with a relatively small quantity of water.

The efficiency of air cooling is much lower because the heat transfer is 50 -- 100 times lower than for water and, since the specific heat of air is low, large quantities of air are required to dissipate significant quantities of heat.

The use of cooling water in steel making plants, however, is limited because it is dangerous to take cooling water or steam close to liquid metal.

In the event of a breakdown or a fault it must be feared that large quantities of water could get into contact with liquid metal and this could result in an explosion. Therefore water cooling is generally limited to parts of refractory linings which are exposed to high temperature only or at the most are in contact with liquid slag, such as for example the cooling boxes in arc furnaces or staves in the walls of blast furnaces. Also in these cases the cooling system is divided into small units with separate water supplies so that faulty cooling elements can be shut off quickly.

Refractory components which are continuously in contact with a large quantity of liquid meta] either are cooled by air cooling or one uses layers of refractory material of high thermal conductivity which are intended to dissipate heat from endangered places. For example cermet inserts in sliding plates or layers of graphite in the bottom of blast furnaces are known. The thermal conductivity of such materials is around 20 - 80 kcal/mhr K so that firstly relatively large cross sections are required to dissipate the required quantities of heat and secondly heat dissipation at the cool end of the cooling layer in the bottom of a blast furnace to the cooled outer casing is a problem.

The problem which the present invention aims to solve is to provide an arrangement for the cooling of surfaces of refractory building elements or moulded components which are subject to wear by contact with liquid metal which approaches the effectiveness of water cooling whilst the highest possible safety is maintained.

According to the present invention a refractory article, e.g. in the form of a building element or a moulded component having at least one surface which is adapted in use to be exposed to a heat source, this surface being referred to herein as the hotter surface has at least one heat pipe located within the article and has one end extending out through a surface of the article, which surface is adapted in use to be remote from the heat source, this surface being referred to herein as the cooler surface, the other end of the heat pipe being arranged to abstract heat from the article, the or each heat pipe operating on the capillary principle. The end of the heat pipe which extends to or through the cooler surface of the article is preferably provided with cooling means.

Heat pipes used may be more or less efficient and have a larger or smaller surface areas.

However, for moulded components the use of one single pipe of suitable efficiency can be sufficient. The thermal conductivity of heat pipes is about a thousand times higher than than of copper and thus with a relatively small cross section they can dissipate large quantities of heat over considerable distances.

Nevertheless the distruction a heat pipe is most unlikely to result in an explosion effecting the manufacturing process because the quantity of coolant involved is so small.

For efficient use of heat pipes in refractory building elements or moulded components the heat absorbing end of the or each heat pipe, looking through the article towards the hotter surface of the article, should terminate just before the lowest boundary for wear of the refractory material whilst the cooled ends of the pipes protrude out of the material. The lowest boundary for wear is the plane through which wear will not penetrate during the intended service life of the component. In this way the accumulation of heat which in many cases frequently occurs at the cold end of the refractory material is removed and heat dissipation is assured. Furthermore those heat pipes which were not affected by the process of wear can possibly be recovered for re-use from the remaining refractory material.

According to the invention the heat pipes can be moulded into hydraulically or chemically set material or they can be cemented into moulded channels in ceramically set refractory material.

In the bottom of blast furnaces for example heat pipes which are replacing layers of graphite can be placed between the two uppermost layers of carbon. In special cases thermally endangered places in the foundation of the furnace can also be cooled by means of heat pipes.

For refractory building elements or moulded components with ducts for molten metals, as for example the discharge nozzles or the areas of the sliding plates below the discharge nozzles which are subject to wear, it may be an advantage to cool the walls of the discharge nozzle by means of heat pipes to reduce wear of the refractory material. For this purpose the heat absorbing ends of the heat pipes are taken from the outside to the region of the discharge nozzle in the individual refractory part which is subject to wear or to the moulded component.

When a number of heat pipes protrude from the cold side of a refractory building element or a moulded component it may be an advantage to cool the cold ends by a common cooling system.

The invention also provides for manufacture of refractory building elements or moulded components together with heat pipes and cooling systems as a pre-fabricated building unit whereby installation is much facilitated.

The invention may be put into practice in various ways and certain specific embodiments will be described by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 shows a section of a heat pipe of circular cross section; Figure 2 shows a perspective view of a refractory slab with an embedded air cooled heat pipe; Figure 3 shows a section of a refractory building element with a water cooled heat pipe; Figure 4 shows a plan view of water cooled heat pipes installed in the sliding plate of a sliding gate and Figure 5 shows a refractory lining with water cooled heat pipes in the region of an advancing area of wear.

Figure 1 shows the design of a heat pipe 1, which in principle is an elongate pressure vessel, closed at the ends, with a number of internal longitudinal capillaries 2 and which contains a liquid, preferably water in an amount insufficient te fill the pipe. During operation one end of the pipe is exposed to a thermal load and the other end is cooled.

Thus water at the hot end is evaporated whilst steam flows to the cold end of the pipe where it condenses and then, in the form of its condensate, again flows by capillary action to the heated end of the pipe. The resulting natural steam-water-circulation can dissipate considerable quantities of heat.

In detail, the heat pipes which are available with various cross sections are evacuated, for example, to 0.02 bar and filled with 5 to 20 g H20 per metre length. At 100"C this produces a vapour pressure of one atmosphere in the pipe. The working temperature of the pipe is between 100 C and 2000C whilst the temperature gradient from the hot end to the cold end of the pipe is only a few degrees Kelvin. If necessary an arrangement for controlling the pressure can be provided at the cold end of the pipe According to the simple application of Figure 2 a heat pipe 3 of rectangular cross section is used with its heat absorbing end 4 embedded in one end of a refractory slab 5, the hot working face of which is at the other end of the slab. The end 4 is thus located just before the lowest boundary for wear 6 of the slab, looking along the slab 5 from the cooler end to the hotter end. The free end of pipe 3 has cooling fins 7 which can be air cooled~by forced ventilation if the cooling by free convection of the ambient atmosphere is not sufficient. Such a building unit consisting of slab 5 and heat pipe 3 can for example be used for refractory linings which until now incorporated a material of high thermal conductivity between the bricks and the metallic jacket of the vessel.

According to Figure 3 the heat pipe 10 which is again placed just before the lowest boundary of wear 8 of a refractory building element 9 is water cooled. For this purpose the folded flattened cooling end 11 is surrounded by a connector 12 for a supply of cooling water through pipe 13 which connects to cooling box 14 which has a connection 15 for discharge of cooling water.

Figure 4 shows a sliding plate 16 for a sliding gate, which is liable to suffer the most wear in use, has embedded in it heat pipes 17, 18 for dissipation of heat from the region of the discharge passage or aperture 19 which forms the outlet duct for liquid metal. The plate 16 and the heat pipes 17, 18 as well as the common arrangement 20 for cooling the cold ends of the heat pipes are arranged as interchangeable pre-fabricated units resting in the frame 21 which has recesses 22 for the free ends of the heat pipes. The two cooling water connections 23 and 24 have flexible connecting hoses 25 and 26 which can follow the movement of the plate during opening and closing of the sliding shutter.With due regard to the working temperature of heat pipes 17 and 18 a temperature between 100" and 200"C in the region of duct 19 is obtainable so that considerable cooling of the sliding plate is possible without any risk i.e.

without the fear of cooling water mishaps.

Placing the heat absorbing ends of the pipes more or less close to the aperture 19, and even the possibility of clamp-like fitting of the pipe ends to the aperture, results in more or less intense cooling of the wall of the aperture.

Figure 5 shows heat pipes 28 provided in a refractory lining to counteract advancing areas of wear. An example of such uneven wear occurs in electric furnaces in the wall opposite to the electrodes, and takes the shape of shallow troughs 30 extending into the lining from the hot side 31 of the lining. By aimed heat dissipation from hot spots on parts of the lining which are subjected to above average thermal load, by means of the heat pipes 28 inserted through the furnace jacket 32, wear of the lining can be levelled out as indicated by the dotted line 33. The cooler ends of the heat pipes are surrounded by a cooling box 34 with a cooling water supply 35 and a cooling water discharge.

WHAT WE CLAIM IS:- 1. A refractory article having at least one surface which is adapted in use to be exposed to a heat source, this surface being referred to herein as the hotter surface and having at least one heat pipe located within the article and having one end extending out to or through a surface of the article, which surface is adapted in use to be remote from the heat source, this surface being referred to herein as the cooler surface, the other end of the heat pipe being located within the refractory article and being arranged to abstract heat from the article, the or each heat pipe operating on the capillary principle.

2. A refractory article as claimed in claim 1 in the form of a refractory building element or a refractory moulded component.

3. A refractory article as claimed in claim 1 or claim 2 in which the or each heat pipe is metallic.

4. A refractory article as claimed in any one of claims 1 to 3 in which the end of the heat pipe which extends to or through the cooler surface of the article is provided with cooling means.

5. A refractory article as claimed in one of claims 1 to 4 in which the heat absorbing end of the or each heat pipe looking through the article towards the hotter surface, is located just outwardly of the plane of maximum wear for which the article is designed whilst the other end of the heat pipe protrudes out of the material.

6. A refractory article as claimed in any one of claims 1 to 5 in which the or each heat pipe is moulded into hydraulically or chemically set refractory material.

7. A refractory article as claimed in any one of claims 1 to 5 in which the or each heat pipe is cemented into moulded channels in ceramically set refractory material.

8. A refractory article as claimed in any one of claims 1 to 7 in which the cool ends of some or all of the heat pipes are served by a common cooling system.

9. A refractory article as claimed in any one of claims 1 to 8 in the form of a prefabricated unit of refractory material and heat pipes with a cooling system provided at the cold ends of the heat pipes.

10. A refractory article as claimed in claim 1 in a form defining a duct for molten metals characterised in that the heat absorbing end of the or each heat pipe is located in the region of the duct ;1. A refractory article as claimed in claim 10 in the form of a fixed or sliding plate for a sliding gate for a metallurgical vessel, the duct being the outlet passage passing through the plate.

12. A structure composed of co-operating refractory articles arranged to provide an interior surface, which in use will be exposed to a heat source, and a cooler exterior surface, heat pipes being located in the joints between individual refractory articles, each heat pipe having one end located near the interior surface so as to be adapted to extract heat from the interior surface of the structure and the other end extending out to or beyond the exterior surface, the heat pipes operating on the capillary principle.

13. A structure as claimed in claim 12 in which the cool end of each heat pipe is provided with cooling means.

14. A structure as claimed in claim 13 in which the cool end of some or all the heat pipes are served by a common cooling system.

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

Claims (1)

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

   boundary of wear 8 of a refractory building element 9 is water cooled. For this purpose the folded flattened cooling end 11 is surrounded by a connector 12 for a supply of cooling water through pipe 13 which connects to cooling box 14 which has a connection 15 for discharge of cooling water.

   Figure 4 shows a sliding plate 16 for a sliding gate, which is liable to suffer the most wear in use, has embedded in it heat pipes 17, 18 for dissipation of heat from the region of the discharge passage or aperture 19 which forms the outlet duct for liquid metal. The plate 16 and the heat pipes 17, 18 as well as the common arrangement 20 for cooling the cold ends of the heat pipes are arranged as interchangeable pre-fabricated units resting in the frame 21 which has recesses 22 for the free ends of the heat pipes. The two cooling water connections 23 and 24 have flexible connecting hoses 25 and 26 which can follow the movement of the plate during opening and closing of the sliding shutter.With due regard to the working temperature of heat pipes 17 and 18 a temperature between 100" and 200"C in the region of duct 19 is obtainable so that considerable cooling of the sliding plate is possible without any risk i.e.

   without the fear of cooling water mishaps.

   Placing the heat absorbing ends of the pipes more or less close to the aperture 19, and even the possibility of clamp-like fitting of the pipe ends to the aperture, results in more or less intense cooling of the wall of the aperture.

   Figure 5 shows heat pipes 28 provided in a refractory lining to counteract advancing areas of wear. An example of such uneven wear occurs in electric furnaces in the wall opposite to the electrodes, and takes the shape of shallow troughs 30 extending into the lining from the hot side 31 of the lining. By aimed heat dissipation from hot spots on parts of the lining which are subjected to above average thermal load, by means of the heat pipes 28 inserted through the furnace jacket 32, wear of the lining can be levelled out as indicated by the dotted line 33. The cooler ends of the heat pipes are surrounded by a cooling box 34 with a cooling water supply 35 and a cooling water discharge.

   WHAT WE CLAIM IS:-

   1. A refractory article having at least one surface which is adapted in use to be exposed to a heat source, this surface being referred to herein as the hotter surface and having at least one heat pipe located within the article and having one end extending out to or through a surface of the article, which surface is adapted in use to be remote from the heat source, this surface being referred to herein as the cooler surface, the other end of the heat pipe being located within the refractory article and being arranged to abstract heat from the article, the or each heat pipe operating on the capillary principle.

   2. A refractory article as claimed in claim 1 in the form of a refractory building element or a refractory moulded component.

   3. A refractory article as claimed in claim 1 or claim 2 in which the or each heat pipe is metallic.

   4. A refractory article as claimed in any one of claims 1 to 3 in which the end of the heat pipe which extends to or through the cooler surface of the article is provided with cooling means.

   5. A refractory article as claimed in one of claims 1 to 4 in which the heat absorbing end of the or each heat pipe looking through the article towards the hotter surface, is located just outwardly of the plane of maximum wear for which the article is designed whilst the other end of the heat pipe protrudes out of the material.

   6. A refractory article as claimed in any one of claims 1 to 5 in which the or each heat pipe is moulded into hydraulically or chemically set refractory material.

   7. A refractory article as claimed in any one of claims 1 to 5 in which the or each heat pipe is cemented into moulded channels in ceramically set refractory material.

   8. A refractory article as claimed in any one of claims 1 to 7 in which the cool ends of some or all of the heat pipes are served by a common cooling system.

   9. A refractory article as claimed in any one of claims 1 to 8 in the form of a prefabricated unit of refractory material and heat pipes with a cooling system provided at the cold ends of the heat pipes.

   10. A refractory article as claimed in claim 1 in a form defining a duct for molten metals characterised in that the heat absorbing end of the or each heat pipe is located in the region of the duct ;1. A refractory article as claimed in claim 10 in the form of a fixed or sliding plate for a sliding gate for a metallurgical vessel, the duct being the outlet passage passing through the plate.

   12. A structure composed of co-operating refractory articles arranged to provide an interior surface, which in use will be exposed to a heat source, and a cooler exterior surface, heat pipes being located in the joints between individual refractory articles, each heat pipe having one end located near the interior surface so as to be adapted to extract heat from the interior surface of the structure and the other end extending out to or beyond the exterior surface, the heat pipes operating on the capillary principle.

   13. A structure as claimed in claim 12 in which the cool end of each heat pipe is provided with cooling means.

   14. A structure as claimed in claim 13 in which the cool end of some or all the heat pipes are served by a common cooling system.

   15. A refractory article as claimed in claim

   1 substantially as specifically described herein with reference to Figure 1 or Figure 1 and Figure 2, or Figure 3 or Figure 3 and Figure 2.

   16. A refractory article as claimed in claim 1 substantially as specifically described herein with reference to Figure 4 or Figure 4 and Figure 2.

   17. An assembly incorporating one or more refractory articles as claimed in any one of claims 1 to 15.

   18. An assembly as claimed in claim 17 substantially as specifically described with reference to Figure 5.