Patent Application
20160176762
The invention relates to a refractory commixture according to ISO/R 836, DIN 51060, in the form of a dry, mineral mixture, and use of the commixture for the production of non-molded or molded refractory products, which are resistant, to a great extent, to the attack of fayalitic slags (iron silicate slags) and sulfates, and are resistant to non-ferrous metal melts, particularly to copper melt. The invention furthermore relates to a brick composed of a commixture according to the invention.
Fayalitic slags are formed, for example, in the production of copper from copper pyrite (CuFeS2). Copper pyrite is roasted, resulting in the formation of what is called copper matte, which contains copper sulfide (Cu2S) and iron compounds, for example FeS and Fe2O3. The copper matte is processed further to produce crude copper, wherein molten copper matte is treated in a converter, with a supply of air and the addition of SiO2, for example in the form of quartz. In this connection, a fayalitic slag is formed, which mainly contains the mineral fayalite (2FeO.SiO2) and crude copper oxide (Cu2O).
At present, converters for the production of crude copper, for example a Pierce-Smith converter, are mainly lined, on the fire side, with fired magnesia chromite products (e.g. DE 14 71 231 A1). However, in this connection, these refractory products are only insufficiently resistant to attack by sulfates, which result from oxidation of the sulfides, for example in the form of magnesium sulfate. Magnesia chromite bricks furthermore have only limited or insufficient high-temperature anti-wetting properties, and they demonstrate insufficient penetration resistance to hot non-ferrous metal melts, particularly copper melts.
Magnesia chromite bricks are also used in melting units for the production of other non-ferrous metals (non-ferrous metals such as Ni, Pb, Sn, Zn), and there they result in similar problems.
It is the task of the invention to create a refractory mineral commixture for refractory products, and refractory products produced from it, which have good anti-wetting properties against non-ferrous metal melts, particularly against copper melt, when used in a refractory lining, produce improved penetration resistance to fayalitic slags, and guarantee better resistance to sulfate attack at usage temperatures than the refractory products used in this refractory sector until now.
This task of the invention is accomplished by means of a refractory commixture that is mainly formed, for example by more than 90 wt.-%, from a dry substance mixture composed of olivine raw material, magnesia meal (MgO meal), silicon carbide meal (SiC meal), and a dry, fine-particle silica.
Furthermore, a dry commixture according to the invention can contain up to 10, particularly up to 5 wt.-% anti-oxidants usually used for refractory products, and/or other additives and/or admixtures, wherein, however, the amount ratio of the components olivine, MgO, SiC, and SiO2 is supposed to be kept the same.
The naturally occurring olivine raw material, which is available on the market, is used, according to the invention, as what is called a coarse-grain granulate in the field, and is supposed to have 100 wt.-% if at all possible, but at least 70 wt.-% of the mineral forsterite, according to the invention. The remainder can be the mineral fayalite and/or other known contaminants of the raw material, such as enstatite and/or monticellite and/or merwinite. It lies within the scope of the invention to use a synthetically produced, pure forsterite material by itself or in combination with a natural olivine raw material. To the extent that olivine raw material is mentioned within the scope of the invention, this also relates to the synthetic forsterite material.
The grain size of the olivine raw material granulate that is used lies in the medium-grain and coarse-grain range, for example between 0.1 and 6, particularly between 1 and 6 mm, wherein the granulate has a Gaussian grain size distribution, for example. The olivine raw material is used in amounts of 30 to 60 wt.-%, particularly of 40 to 50 wt.-%, in the commixture mixture according to the invention.
Magnesia is used in fine-particle form, in the form of a meal or powder having grain sized, for example, of 100 wt.-%≦1 mm. For example, melt magnesia and/or sintered magnesia and/or synthetic dead-burned or caustic magnesia. (The terms “meal” and “powder” are understood, within the scope of the invention, as being the same terms having the same meaning, and are known in the field. They are generally understood to mean dry, loose bulk material composed of solid particles<1 mm, particle size.)
The MgO content of the magnesia should preferably amount to>90 wt.-%, particularly>95 wt.-%. The remainder is usual contaminants such as silicates and/or iron oxide.
The MgO meals also have a Gaussian grain size distribution, for example.
The MgO meal is used, in the dry commixture mixture, in amounts of 35 to 50, particularly of 40 to 45 wt.-%.
Silicon carbide (SiC) is available on the market as a synthetic product having a high degree of purity, and in different grain sizes and grain size distributions, and is used, according to the invention, in powder form or in meal form, for example with grain sizes of 100 wt.-%≦1 mm, for example. The grain size distribution preferably corresponds to a Gaussian grain distribution.
The SiC powder is used, for example, at a purity of>90 wt.-%, particularly>94 wt.-% of SiC. The amount used in the dry commixture mixture amounts to from 5 to 20, particularly from 10 to 15 wt.-%.
The fine-grain, dry silica is a silica that reacts with the MgO of the magnesia meal in an aqueous milieu, forming magnesium silicate hydrate phases, and forms magnesium silicate hydrate gel and/or magnesium silicate hydrate crystallites and/or magnesium silicate hydrate crystals, for example. The SiO2 content of the fine-particle dry silica preferably lies above 90 wt.-%, particularly above 94 wt.-%. The commixture according to the invention contains no liquid silicas containing water, such as silica sol or silica gel or sodium silicate or the like in the mixture, according to the invention. It has surprisingly been shown that dry fine-particle silica forms MSH phases more quickly when water enters the commixture according to the invention, with the MgO of the magnesia, and hardens more quickly and yields higher cold pressure strengths. It has not yet been clarified why this is so.
The silica should be selected to be so fine-particle that a reaction between the MgO of the magnesia particles and particles of the silica occurs in a fresh commixture mass that is formed by adding water to a dry commixture according to the invention and mixing, and that magnesium silicate hydrate phases—also referred to as MSH phases hereinafter—form, for example as gel and/or crystallites and/or crystals, which phases bring about solidification of the mass that contains water, in the manner of hydraulic binding. Preferably, for this purpose the commixture is composed in such a manner that in the aqueous milieu, in other words after addition of water to the commixture according to the invention, a pH above 7, particularly above 10 occurs.
Accordingly, crystalline quartz meals having a fineness of the quartz particles of below 500, particularly below 200 Ξm, for example, are suitable for the reaction to form MSH phases.
Furthermore, the following are particularly well suited for the invention as dry, fine-article silicas:
Silica Dust
Pyrogenic Silica
Precipitated Silica
Within the scope of the invention, at least one of the aforementioned silicas is used. It is practical if the silicas are selected with reference to their ability to react with the MgO of the magnesia meal, and if it is ensured that the silica reacts with the MgO as completely as possible during hardening.
The fine-particle, dry silica is used in the dry commixture mixture at 0.1 to 10, particularly at 0.5 to 5 wt.-%.
According to the invention, preferably only water is mixed into the dry commixtures according to the invention as described above, calculated to 100 wt.-%, to produce refractory products according to the invention.
Preferably, the following dry commixtures are therefore compiled, in wt.-%:
Additional Refractory
Admixture for Refractory
Binder for refractory
Preferably, the silica is at least one of the above amorphous silicas.
The amounts of the reaction partners MgO and SiO2 in commixtures according to the invention are selected in such a manner that when water is added at 1 to 10, particularly at 2.5 to 6 wt.-%, with reference to the dry substance of the commixture, during a time period between 6 and 120, particularly between 8 and 12 hours, in a temperature range from 50 to 200, particularly from 100 to 150° C., cold pressure strengths from 40 to 160, particularly from 60 to 150 MPa can be guaranteed.
Preferably, it is provided, according to the invention, that the MgO of the magnesia meal that is capable of reaction is present, in terms of amount, predominating over the fine-particle silica that is capable of reaction. From this, the result is to be achieved that after water is added, MgO-rich MSH phases are formed, which can form forsterite (2 MgO.SiO2), which increases the forsterite proportion of the olivine raw material, under the effect of high temperatures up to 1350° C., for example.
According to the invention, predominant mass ratios of MgO to SiO2 of up to 500 are practical. In particular, the ratio lies between 1.2 and 100, preferably between 1.34 and 50, very particularly preferably between 1.34 and 35.
Refractory products according to the invention are produced from dry commixtures according to the invention, after water is added, wherein a mixture with amounts of water, with reference to the mass of the dry commixture, amounts to 1 to 10 wt.-%, preferably 2.5 to 6.0 wt.-%.
What are called fresh masses that contain water are pressed, according to the invention, to produce molded brick blanks, with water contents between 1 and 5, particularly between 1.5 and 3 wt.-%, for example, using usual pressing methods. The molded bricks are allowed to harden and dry in a temperature range between 15 and 200, preferably between 50 and 200, particularly between 100 and 150° C., according to the invention, wherein MSH phases are formed. After hardening, the bricks have relatively high strength values and can be handled, so that a refractory lining can be built from them. According to the invention, the bricks have cold pressure strength values between 40 and 100, particularly between 60 and 80 MPa, for example.
It lies within the scope of the invention to ceramically fire the molded bricks that have been hardened or solidified and dried by means of the formation of MSH phases, so that sintered products, for example composed of forsterite, are preferably formed from the MSH phases, and sinter bridges composed of forsterite, for example, form between the olivine grains or olivine particles and/or MgO meal particles and/or SiO2 particles. Ceramic firing is preferably carried out in the temperature range from 400 to 1400, particularly from 600 to 1200° C., and during a time period of 1 to 24, particularly of 4 to 12 hours, wherein it is advantageous to perform the firing in a reducing atmosphere.
It is sufficient for pressing bricks and forming MSH phases to add 1 to 5, particularly 1.5 to 3 wt.-% water to a commixture according to the invention. It lies within the scope of the invention to add known flow agents to the batch containing water, in order to increase the ductility of the batch. Such flow agents are known to a person skilled in the art. They are generally added in amounts of 0.01 to 2, particularly of 0.1 to 1.5 wt.-%.
According to the invention, ductile casting masses or ramming masses are produced from the dry commixtures according to the invention, using higher water contents, for example of 4 to 10 wt.-%, particularly of 4 to 6 wt.-%, and from these masses, refractory, monolithically preformed finished parts are produced by means of shaping in molds. In this connection, solidification by means of the formation of MSH phases takes place, for example, at room temperature, and drying takes place with a correspondingly elevated temperature treatment. The strength development of the molded mass corresponds to that of the molded and tempered bricks. In general, however, the strength values actually lie higher. Within the scope of the present invention, the term “tempering” is supposed to mean temperature treatment of the water-containing batch, in the temperature range indicated, including drying.
It is practical if a product according to the invention is produced in that a homogeneous batch having a predetermined plastic or ductile or flow-capable processability is produced from a commixture having at least the dry substances of olivine raw material, magnesia, SiC, and silica, and water, using suitable mixers. This ductile or flow-capable mass of the batch can be used on site for lining melt converters. As has already been described, however, monolithically molded finished parts or pressed bricks can also be produced from the batch; the latter can be used in unfired or ceramically fired form to line melt converters, for example.
The invention therefore relates to a dry commixture composed exclusively or, for example, mainly of, i.e., for example, by over 90 wt.-% of olivine granulate, particularly over 95 wt.-%, MgO meal and SiC meal, and a fine-particle, dry SiO2 component, particularly in the form of microsilica. The remainder, in each instance, can be, for example, at least one other refractory raw material granulate such as magnesia chromite, magnesium spinels, spinels, chromium oxide, zirconium oxide, silicon nitride, zirconium and/or at least one refractory additive such as magnesia chromite, magnesium spinels, spinels, chromium oxide, zirconium oxide, silicon nitride, zirconium and/or at least one admixture such as liquefiers and/or binding regulators.
For example, within the scope of the invention, pressed or non-pressed molded bodies are produced from a commixture batch containing water as indicated above, by means of pressing, and the molded bodies are brought to residual moisture values of preferably between 0.1 and 2 wt.-%, or, according to a further embodiment of the invention, the molded bodies are additionally fired ceramically in a ceramic firing kiln, at temperatures between preferably 400 and 1400, particularly between 600 and 1200° C., in an oxidizing atmosphere, particularly, however, in a reducing atmosphere, for a time period preferably between 1 and 24, particularly between 4 and 12 hours. In this connection, the firing conditions are selected, according to the invention, in such a manner that the components olivine raw material and SiC do not react with one another, if at all possible, or react only to a small proportion during firing, so that these components are available in situ in the melting unit, for example in the converter, during attack of a melt and/or slag, in order to guarantee refractoriness, according to the invention, particularly by means of an anti-wetting effect and chemical resistance to melt and slag components.
Using the non-fired and fired molded bodies according to the invention, it is possible to create linings of non-ferrous metal melt converters that are superior to the previous linings, with regard to infiltration resistance and corrosion resistance to non-ferrous metal melts and non-metallic melts (liquid slags) of non-ferrous metal smelting. In particular, the superiority of the refractory products according to the invention shows itself in copper melt converters, for example in a Pierce-Smith converter (PS converter).
The non-fired, pressed, dried molded bodies according to the invention have the following properties, for example:
Raw density: 2.65 to 2.80 kg/m3
Cold pressure strength: 40 to 100, particularly 60 to 80 MPa.
The fired molded bodies according to the invention have the following properties, for example:
Raw density: 2.55 to 2.75 kg/m3,
Cold pressure strength: 30 to 80, particularly 40 to 70 MPa.
The finished parts according to the invention have the following properties, for example:
Raw density: 2.55 to 2.75 kg/m3
Cold pressure strength: 40 to 180, particularly 50 to 150 MPa.
The products according to the invention are specifically suitable for use in PS converters for copper production, but they can also be used, with the advantages described, in other applications in which fayalitic slags and runny non-ferrous metal melts occur, as is the case in practically the entire non-ferrous metal industry, with advantages as compared with the usual refractory products.
The concept according to the invention is based on the fact that based on olivine coarse grain as well as SiC and MgO fine grain or meal grain, equilibrium in the brick occurs, between the reaction substances from the brick and the slag, only at melting process temperatures above 1000° C., for example between 1200 and 1350° C. At these temperatures, SiC is still fully effective, in spite of oxidizing melting process conditions, with regard to the anti-wetting effect. MgO reacts with the oxidation product of the SiC that occurs, namely the SiO2, to form further forsterite. MgO is selected, according to the invention, in stoichiometric excess to SiO2 that is available for reaction, in order to prevent the formation of enstatite, which is not refractory. These reactions in situ during the melting process seal the brick directly on the fire side, and prevent penetration by the very runny metal melt, for example copper melt. The SiC furthermore acts as a slag brake. In contact with the omnipresent fayalite slags, the excess MgO furthermore reacts, together with the forsterite, to form olivine mixed crystals. The temperature of the solid is thereby increased, i.e. the reaction product of slag/brick solidifies, i.e. it leads to stiffening of the slag, and the corrosion reaction is stopped or at least greatly reduced.
According to the invention, the pressed molded bodies, which have a water content between 1 and 5, particularly between 1.5 and 3, are therefore allowed to harden, wherein the MSH phases form, which bring about the hardening. The hardening time is temperature-dependent. It is practical if the pressed molded bodies are allowed to harden and dry in the temperature range between 50 and 200, particularly between 100 and 150° C., for 6 to 120, particularly for 24 to 96 hours, until they reach a residual moisture between 0.1 and 4.5, particularly between 0.1 and 2.5 wt.-% water content, in a suitable drying unit. In this connection, cold pressure strengths between 40 and 100, particularly between 60 and 80 MPa are achieved.
The non-pressed fresh masses produced according to the invention, which are cast into molds or vibrated, if necessary, for monolithic finished components, have water contents between 4 and 10, particularly between 4 and 6 wt.-%. They are introduced into molds and vibrated, if necessary. They are allowed to harden in air between 15 and 35° C., for example, and to dry in the temperature range indicated above for the pressed molded bodies, down to residual moisture values as for the pressed molded bodies. In this connection, cold pressure strengths between 40 and 180, particularly between 50 and 150 MPa are achieved.
According to a further embodiment of the invention, at least one known water-containing binder for refractory products, from the following group: lignin sulfonate, magnesium sulfate, and ethyl silicate, is used in place of water or preferably in combination with it, in an amount calculated relative to the dry substance of a commixture of 2 to 5 wt.-%, for example, for pressed products, and of 4 to 10 wt.-%, for example, for finished components and casting masses. In this connection, the water proportion of these binders contributes to the MSH phase formation described above.
Furthermore, within the scope of the further embodiment of the invention, a known binder for refractory products, from the group of pitch and/or tar and the known synthetic resins such as phenolic formaldehyde resins can be used in place of water, in amounts of 2 to 5 wt.-%, for example, calculated as above, in each instance. The additional forsterite only forms in situ at higher temperatures, because of the presence of MgO and SiO2 in the commixture.
The invention therefore creates the following new refractory commixtures and their use.
The invention essentially relates to a commixture composed of mineral, refractory materials for the lining of units used for non-ferrous metal melts, preferably for the lining of copper melt converters, containing more than 90 wt.-%, particularly more than 95 wt.-% of a mixture of the following components, or very preferably consisting of the following components:
It lies within the scope of the invention to combine this commixture according to the invention with at least one characteristic of the following characteristics:
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 010 854.3 | Jun 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/058851 | 4/30/2014 | WO | 00 |
