Lining for use in blast furnaces

Abstract

A lining for use in a blast furnace preferably for use in furnaces burning bio fuels, e.g. straw or wood chips or wood shavings and the like as well as ovens in power stations where fuel having a biological origin is used includes an interior surface which is in contact with slag particles. The interior surface is clad by elements (3, 4, 12) made by a ceramic or semi-ceramic material and an insulation of a cement based foam material is arranged in one or more layers (17). The foam material is advantageously placed between the interior surface and an exterior load carrying construction which for example can be a steel pillar arranged exterior of the blast furnace. With a lining for blast furnace as describes above the risk of a collapse in the insulating material is avoided at the same time it is avoided that the interior wall deteriorates due to the chemical composition of the slag particles which are present in the bio fuelled oven.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a lining for use in blast furnaces as used in power stations and the like having an interior surface which can come into contact with slag particles as well as an insulating layer consisting of an inorganic insulation material which surrounds the blast furnace lining.

[0002] The invention also relates to a lining for use in blast furnaces for power stations and the like, especially blast furnaces using fuels of biological origin.

[0003] Within the meaning of this application the term lining for use in blast furnaces shall be construed as meaning that the lining is arranged in the area of the furnace where the mineral part of the fuel in the shape of furnace slag particles falls towards the bottom of the oven.

[0004] In power stations the bottom of the oven will normally consist of a water filled bath. The slag particles are removed by a slag removing device, which will continuously remove the instantly cooled particles which have fallen into the water.

[0005] Until now linings in blast furnaces using fuels having biological origin have been made as traditional linings of the type used in coal fired blast furnaces in coal fired power stations. These constructions typically consist of steel with special additives which makes it resistant to the harsh environment inside the furnace. The interior steel cladding has having an exterior insulation, for example a mineral glass wool.

[0006] The use of insulation is effected in order to bring down the temperature on the outside of the furnace, the side which is turned towards the surroundings where people can come into contact with the construction. The surface temperature of the side of the construction which people can come into contact with is usually set to be a maximum of 65° C. warm. This is the safety value which has been chosen in order for people working in the vicinity of blast furnaces and the like not to get burnt, if they accidentally should touch the surface of the oven.

[0007] In EP-A-672880 a lining for a blast furnace is disclosed. The lining comprises three distinct layers. An innermost layer consisting of ceramic tiles, an intermediate layer comprising insulating bricks and an outer layer in the shape of a cladding.

[0008] From U.S. Pat. No. 3,887,173 is another blast furnace construction known. This construction is completely uninsulated, but has burnt bricks containing a high allumina type cement as its surface facing the slag particles inside the blast furnace.

[0009] In U.S. Pat. No. 5,485,986 a metal furnace is disclosed made up from a mould of steel, wherein is cast a thermal insulating layer made from a hardening stone forming agent, based mainly on silica and alumina with an added foaming agent containing hydrogen peroxide as blowing agent. The interior wall which is to come into contact with the molten metals is made from a heat treated refractory concrete. The furnace is closed with access lids made from the insulating inorganic foam insulating material cast in steel moulds.

[0010] The slag particles resulting from the burning of coal are characteristic in that they are acidic. Therefore certain types of steel have been developed which have been modified in order to endure the influence from acidic slag particles at the high temperatures which arise in blast furnaces, typically in the order of 350° C.-400° C.

[0011] Fuels having a biological origin, so-called bio fuels, for example straw or wood chips or wood shavings, are characteristic in that when these materials are burnt, the slag particles have a very high alkalinity. There apparently does not exist steel types which will remain stable under the influence of slag particles from bio fuels at the temperatures which are present in the section of the blast furnace where the slag particles come. This lack of durability against the slag particles with a high alkaline content is a problem which causes a need to often replace and renovate the lining in ovens which use bio fuels. In order to replace and renovate the interior of the oven, it is necessary to shut the active oven down. This is a very time-consuming and costly exercise. In order to avoid damaging the oven during the shutting down process it has to be cooled down slowly and controlled in order to minimise temperature related stresses in the construction. Likewise once the interior has been renovated the oven must be heated slowly and controlled again until reaching operating temperature by when production can be resumed.

[0012] Customarily, the blast furnace wall will consist as described above of a interior steel lining having an insulation outside the steel layer. Typically, the insulation is a mineral or glass wool, which consists of minuscule inorganic fibres kept together by a carbolic acid. However, at high temperatures the carbolic acid will disintegrate and evaporate and minuscule vibrations will cause the fibre structure without the binder to collapse which will cause the fibres to be rattled loose and gather in cavities. This leaves uninsulated cavities in the blast furnace wall. The insulating characteristics of this part of the wall will be greatly reduced in relation to the theoretic insulation at which the wall was designed had the insulation material, for example the mineral or glass wool, had its fibres in the theoretically manufactured arrangement. This lack of insulation is obviously a problem in itself in that the control of the oven will be very difficult and the oven itself will be exposed to temperature gradients which it was not designed for. Furthermore, the surface of the oven facing areas where people will have access to it will reach temperatures above the 65° C., which is the safe level without getting burnt.

[0013] Furthermore, a greater problem exists in that when the insulation is torn down for replacement or the blast furnace is removed, the fibres will be free in the environment. This type of respirable fibres has often been under suspicion for being a direct or indirect factor in causing cancer.

[0014] It is therefore the object of the present invention to device a lining for a blast furnace of the type mentioned above wherein the above mentioned problems have been alleviated by using an insulation which will not collapse during the normal use of the blast furnace and which will not cause dust or respirable fibres to be set loose in the environment.

[0015] Furthermore, the interior surface of the lining is resistant against slag particles with a high alkalinity and will in itself be able to withstand alkalinic slag particles at the temperatures which are occurring in blast furnaces of this type.

[0016] The above object is achieved by the present invention by providing a lining comprising an insulation which comprises one or more layers of a cement based foam.

[0017] In a further advantageous embodiment of the invention the lining is distinguished in that the interior surface is made from a ceramic or semi-ceramic material and that an insulation in the form of one or more layers of a cement based foam is provided.

[0018] In an advantageous embodiment the foam is placed between the interior surface of the blast furnace and the load carrying construction, which is arranged around the blast furnace.

[0019] The invention hereby provides a novel insulation of the type which does not collapse and which is easy to place and which will not let respirable fibres loose in the environment.

[0020] Furthermore, there is provided an interior surface in the blast furnace of a ceramic or semi-ceramic material which will be able to resist the influence of alkalinic slag particles and temperatures, which are occurring in blast furnaces of this type which are fed by bio fuels, set temperatures being at least 350° C. to 400° C. and up to about 1100° C. to 1200° C.

[0021] In order to provide an interior ceramic or semi-ceramic interior surface, a concrete like material can advantageously be used. For production of the material, a cement which can endure high temperatures, for example an aluminous cement is used and preferable a compact binder is used. The compact binder can be achieved by an intimate composition of particles from an aluminous cement with ultra fine inorganic particles, for example from an amorphous silica, for example the kind of silicium which is used in the production process of silicone metals.

[0022] Furthermore, the provision of one or more layers of a thermally insulation inorganic cement based foam as insulation will provide lower design temperatures for the load carrying construction, which will be surrounding the blast furnace. By achieving a lower design temperature the possibility of using alternative materials for making the load carrying construction becomes present, for example the use of traditional reinforced concrete. This is a economically more attractive solution to form a load carrying construction in traditional reinforced concrete than the ones used today where the internal steel cladding is used as the load carrying construction.

[0023] One example of the insulation foam which in an economic way gives technically and environmental advantages is the use of a foam called Cemskum, sold by Cemsystems I/S. The foam can be foamed in situ between the interior surface and the exterior load carrying construction.

[0024] By placing a layer of an inorganic foam, as for example Cemskum, the risk of disintegration and thereby lessening of the insulating capability is avoided. Furthermore, for environmental reasons it is advantageous to be able to avoid working with the mineral and glass wool products constructed by using respirable fibres which have been under suspicion as being a factor in causing cancer.

[0025] By having the interior lining made from a ceramic or semi-ceramic material which can resist high temperatures and can resist the influence of alkaline slag particles at the temperatures which are present in the blast furnace, an improved durability of the blast furnace as a hole is achieved. When the durability of the blast furnace is improved the economy of running the blast furnace as explained above is also improved by not having to shut down the oven in order to repair or replace parts of the interior of the blast furnace. By using a construction according to the present invention more non-planned stops of the oven can be greatly reduced.

[0026] The interior ceramic or semi-ceramic surface can advantageously be made from a concrete like material where there during the manufacturing process is used a cement which can endure high temperatures, for example an aluminous cement.

[0027] In further advantageous embodiments used especially compact binders are used, which are achieved by an intimate composition of particles of a aluminous cement with ultra fine inorganic particles, for example from an amorphous silicium, for example a silica which is manufactured by producing a silicone metal. These materials can be used when manufacturing prefabricated elements at room temperature. It is also possible to produce them at room temperature in situ. Furthermore, elements of this type can easily be mounted or replaced when needed.

DESCRIPTION OF THE DRAWING

[0028] The invention will now be explained with reference to the attached drawing where

[0029] FIG. 1 shows a wall in a blast furnace according to the invention seen from the inside,

[0030] FIG. 2 shows an end wall in the blast furnace shown in FIG. 1,

[0031] FIG. 3 shows the other end wall of the blast furnace,

[0032] FIG. 4 shows the principle in the construction of an element having an interior surface and

[0033] FIG. 5 shows the principle in the construction of another element for an interior surface.

[0034] In the figures one embodiment of the invention for a lining for a blast furnace has been shown having a thermally insulating intermediate layer arranged in a power station which can be fed with bio fuels. Praxis had shown that the traditional construction of a lining in a blast furnace with an interior surface of steel has shown itself not to be able to withstand the influences from strong alkalinic slag particles and has made it necessary to replace the steel construction in the blast furnace three times in an average year.

[0035] FIG. 1 illustrates a first wall 1, respectively a second wall 2, in the blast furnace interior seen from the inside. It is illustrated that there is used premanufactured elements 3,4 of which four are equipped with recesses 5 for arrangement of nozzles 6 (see FIG. 2) for injection of cooling water which will cause disintegration and instant cooling of larger slag particles.

[0036] The premanufactured elements 3,4 are mounted on fixtures (not shown) which are fastened to the exterior load carrying steel or reinforced concrete construction.

[0037] FIG. 2 illustrates one end wall 7 and cuts through the walls 1,2. FIG. 3 shows the other end wall 8 and a cut through the walls 1,2.

[0038] In FIGS. 2 and 3 the construction is illustrated in which is used an interior lining of premanufactured elements 3,4 and an intermediate insulating layer 9 where this is geometrically possible and technically necessary which is above, a water bath 10 equipped with means 11 for removing slag particles from the bottom of said water bath 10.

[0039] The principle of the construction of a plain element 3 is illustrated in FIG. 4. This element is intended for being built in at the interior surface of the blast furnace. A position for the element 3 is illustrated in FIG. 2.

[0040] The principle of making a more complicated interior lining element 12 is illustrated in FIG. 5. This element 12 is intended for being mounted on the interior surface of the blast furnace. A position for the element 12 is illustrated in FIG. 2. The interior ceramic or semi-ceramic surface is equipped with an arrangement of 30 mm thick pre-manufactured plate elements 3,4,12 which are equipped with cylindrical welding bushings 13 with a perforation 14, which facilitates that the plate elements 3,4,12 can be welded on to load bearing elements (not shown) which also have the additional function as being distance keepers. The distance keepers maintain the distance between the surrounding load carrying support construction, for example a steel construction or a reinforced concrete construction and inwards towards the interior of the blast furnace.

[0041] The cylindrical welding bushings 13 are welded on to a net 15 of stainless steel rods 16 which constitute the primary reinforcement in the elements 3,4,12. The elements are made of a steel fibre reinforced abrasion resistant and high temperature stabile material 17 which is cast at room temperature and also hardened at room temperature.

[0042] In one advantageous embodiment the material 17 consists of ⅓ by weight of pulverised bauxite with a grain size in the interval from 1 mm-3 mm, ⅓ part by weight of ground bauxite with a grain size in the interval from 0 mm-1 mm and ⅓ part by weight of Cemsystems' binder AL6310. In order to achieve a liquid flowable casing mass when vibrated there is added a water content equal to about 20% by weight of the amount of binder. The high temperature stable and stainless steel fibres have been added in an amount of 3% by weight of the binder and in one example is of the type sold by the name Densit Stahl Faser, 1.4841 with dimensions diameter 0.40 mm, length 12.5 mm. Casting of the elements is done by vibrating the casting material in steel moulds. Immediately after casting the material in the steel moulds a curing compound has been applied to all free surfaces. The newly cast material with the applied curing compound has then been left for hardening in the steel mould. The following day the elements has been demoulded and the element has thereafter been left for hardening until mounting.

[0043] The thermal insulation used in the example is manufactured in situ by Cemskum which is described in a brochure for Cemskum, type RC2-0TS/I40-TAR5. Before placing the foam material the premanufactured elements have been mounted as described above on the load carrying steel construction or reinforced concrete construction. After the premanufactured elements have been correctly placed and welded on to the load carrying construction the foam material is mixed and by a standard pump pumped into the space between the premanufactured elements and the outer load carrying construction. Pumping of the material can take place by a relatively simple pump means.

Claims

1. A lining for use in blast furnaces as used in power stations and the like having an interior surface which can come into contact with slag as well as an insulating layer consisting of an inorganic insulating material which surrounds the blast furnace, characterized in that the insulation comprises one or more layers of a cement based foam and that the interior lining is made from a ceramic or semi-ceramic material.

2. A lining for use in blast furnaces for power stations and the like, especially blast furnaces using fuel of a biological origin, characterized in that the interior surface is made from a ceramic or semi-ceramic material and that an insulation in the form of one or more layers of a cement based foam is provided surrounding the ceramic or semi-ceramic surface.

3. Lining according to claim 1 or 2, characterized in that the foam is placed between the interior surface and the load carrying structure which is arranged outside the blast furnace.

4. Lining according to claim 1, 2 or 3, characterized in that the foam is foamed in situ in a space between the interior surface and the load carrying structure.

5. Lining according to any of the preceding claims, characterized in that the interior surface is made from a concrete like material comprising a high temperature resistance cement, preferably an aluminous cement, as well as a binder of ultra fine particles, preferably of an amorphous silica in order to obtain a compact binding in the material.

6. Lining according to any of the preceding claims, characterized in that the load carrying construction is made from reinforced concrete.

7. Lining according to any of the preceding claims, characterized in that the interior surface is resistant to the influence of alkaline slag particles at temperatures in the range of at least 350° C. and 400° C. and preferably up to the range of 1100° C. to 1200° C.

8. Lining according to any of the preceding claims, characterized in that the interior surface is made from premanufactured elements.

9. Lining according to claim 8, characterized in that the premanufactured elements contain a reinforcement netting and that there are openings for the reception of means for attaching the elements to the load carrying construction.

10. Lining according to claim 1 or 3-10, characterized in that the interior surface is of metal, preferably steel.