Heating – Heating or heat retaining work chamber structure – Masonry with metallic casing or support
Patent
1996-11-14
1998-07-28
Bennett, Henry A.
Heating
Heating or heat retaining work chamber structure
Masonry with metallic casing or support
110336, 110338, 110340, F27D 112
Patent
active
057855170
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
The present application comprises the U.S. national stage application of international application PCT/AU95/00074 designating the United States and having an international filing date of Feb. 16, 1995, which application, in turn, claims the priority of Australian application PM 3930, filed Feb. 16, 1994.
BACKGROUND OF THE INVENTION
The present invention relates to refractory wall linings used in furnaces. In particular, the present invention relates to cooling arrangements for refractory wall linings.
Furnaces operating at high temperatures are used in a number of different processes, including the smelting of metals. Most furnaces are constructed from an outer shell made of a metallic material, which is usually steel. The outer shell is lined with a layer of refractory bricks to insulate the outer shell from the extreme temperatures in the interior of the furnace and also to prevent the very hot materials contained in the furnace from contacting the outer shell. Refractory linings should have a long life in order to minimise the considerable down time associated with relining a furnace.
Refractory linings are generally made from materials that are fairly unreactive with the contents of the furnace. However, erosion and destruction of refractory linings does occur and it has been found that the rate of erosion and destruction of the lining increases as the temperature of the hot face of the lining (that is, the face of the lining exposed to the interior of the furnace) increases. Therefore, numerous attempts have been made to decrease the temperature of the hot face of the lining in order to increase the life of the refractory lining.
One construction proposed for use in decreasing the temperature of the hot face involves the installation of a water-cooling circuit in the refractory lining. As water flows through the cooling circuit, it extracts heat from the refractory lining and acts to decrease the temperature of the hot face of the lining. Although such constructions operate to satisfactorily reduce the temperature of the lining, they involve the use of cooling water circuits within the lining. Any leakage of water from the cooling circuit has the potential to seep into the furnace and cause explosions and hydration of the refractory. This is obviously an extremely hazardous situation and it is now believed that internal water-cooling of refractory linings should be avoided.
Another approach that has been adopted by industry involves the placement of solid cooling members of high thermal conductivity through the wall of a furnace and into a lining. The outer portion of the solid cooling members remain outside the refractory lining. The portions of the cooling members located external to the furnace are cooled by a water cooling circuit. Accordingly, if leaks develop in the water-cooling circuit, water cannot come into contact with the hot contents of the furnace, which eliminates hydration and reduces the danger of explosion. The solid cooling members are generally spaced about half a meter apart from each other. This leads to large temperature gradients in the refractory lining. Areas of high temperature in the lining wear much more quickly than areas of relatively lower temperature and wear of the lining is very uneven. Furthermore, the large temperature gradients in the lining set up large thermal stresses in the refractory lining.
United Kingdom Patent No. 1,585,155 describes an arc-furnace that is provided with a composite lining that includes an exposed inner layer of refractory material facing the furnace interior. An outer layer of refractory material that backs onto the inner layer is provided, with this outer layer of refractory material being in thermal contact with the inner layer. The outer layer is made of a material that has a higher thermal conductivity than the inner layer. The outer layer may be in contact with the furnace casing, which dissipates heat to the surroundings or, more usually, to a forced air or water-cooling medium. The composit
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Elliott Barry John
Gray Neil Boon
Harris Jonathan Alan
Leggett Anthony Regnar
Bennett Henry A.
The University of Melbourne
Wilson Gregory
WMC Resources Ltd.
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