DE971010C - Process for the manufacture of basic refractory products - Google Patents

Description

Process for making basic refractory products The invention relates to a method for producing basic refractory products, in particular at low temperature, by converting selected starting materials.

In an older proposal, which the use of preformed or natural, low-melting silicates for binding granular materials, which essentially consists of firstly lime, magnesia and silica and secondly magnesia, Alumina or silica, it was particularly emphasized that a reaction between the fine parts of the refractory material and the non-refractory silicate the melting of the latter and the formation of a substantial amount of liquid, necessary to shrink the mass and to firmly bond the refractory particles must be carefully avoided. This is achieved by using either refractory Components without fine parts are used or the non-refractory component is added in granular form.

Surprisingly, it has now been found that with the union and Solidification of such refractory material the tendency of fine particles to be faster to react as coarse particles, can be exploited if the is not refractory Component is formed in place in the granular particles.

It is already known to combine magnesia or lime with various natural, partially at lower temperatures to implement melting silicates, and it Refractory masses have already been produced in some of these reactions. White too those skilled in the art that it may be useful in the manufacture of refractory compositions Use coarse-grained parts with finely ground parts.

In contrast, the invention is based on the fundamental knowledge that for the production of basic refractory products the grain sizes (surfaces), Quantities and composition of the reactants regulated in a certain way must be so that the implementation takes place in two defined and separate stages. The process of making basic refractory products from relatively coarse-grained raw material such as dolomite, magnesia or lime, and a finely divided one siliceous binder by molding and firing according to the invention characterized in that calcareous substances, possibly magnesia, im essential but not contain clay, or substances containing magnesia, which may be Clay, but essentially contains no lime, with finely ground silicic acid Substances mixed and fired to form a non-refractory second component which, when using lime, consists essentially of calcium or calcium-magnesium silicate or when using magnesia from a magnesium or magnesium aluminum silicate exists, with such grain sizes being selected in the overall mixture that the surface of the free and bound silica at least 42% of the total surface of the non-volatile constituents, and that in the overall composition the mixture when using lime the ratio of lime to silicic acid at least as high as in calcium orthosilicate and the amount of magnesia when using magnesia at least sufficient to react with all of the silica to form magnesium orthosilicate and to react with all of the clay as magnesium aluminate.

When the mixture is then heated, the reaction takes place in two separate ways Stages instead; First, a melt of the non-refractory silicate is in place and place formed which then envelops the refractory grains, and afterwards Heating takes place in a second stage, a reaction between the liquid (melt) and excess basic oxide take place in the grains, d. i.e., the liquid will essentially eliminated by conversion into the corresponding refractory silicate, and the grains are combined and solidified into a highly refractory mass.

In this way, through a suitable choice of grain size, the course of the reaction, the properties of the composite mass or its shape, the temperature, at that begins to set or harden, the composition and amount of the formed Liquid, the viscosity of the liquid, the temperature range at which the plastic state of the composite mass persists, and even the density and other physical properties of the final product over a wide range can be regulated at will.

In order to explain the method according to the invention in more detail, first set out the basic principles as fully as possible.

i. When silica and a basic oxide with which they are in the solid state can react, mixed and heated, so depends the speed of the in The initial stages of the reaction depend on the size of the surfaces in contact the respondent from. Therefore, fine particles react much faster as coarse particles.

2. If two reactants that are in contact are heated, so are their contact surfaces are the same, and before liquid formation they become accordingly react in proportion to the weights, correspond to the same surfaces; In the solid state, however, this tendency can be outweighed by the higher heat of formation a special connection of the two reactants, which thereby preferentially is formed.

3. When two oxides are mixed and considered potential reactants are heated, they usually form liquid at the lowest possible temperature, and this can be the melting point of the lowest-melting eutectic in binary Be a system. However, if a connection has already been established, the temperature the melting point of some other eutectic when liquid begins to form be. For example, lime and silica are relatively lower for a long time Heated temperatures, there is a great tendency to form highly refractory Dicalcium silicate; since there are several compounds and eutectics in this system the formation of the eutectic liquid depends on which oxide is in excess and in what quantity it is present.

q .. The course of the reaction between two oxides can depend on the speed depend on the heating. Slow and delayed heating below the melting point any eutectic present in the system maintains the formation of a compound to promote, whereas with very rapid heating the eutectic already melts, before the formation of the compound can proceed to any significant degree. In this case is the amount of liquid present at any given temperature usually much larger than slow heating.

5. If the formation of liquid from two oxides has taken place, it begins to react with the remaining solids or to dissolve as much of them as can be absorbed at this temperature, and the course of the reaction or absorption is largely determined by the relative surface area of solids. If, for example, coarse lime is mixed with a small part of silica which has been ground so finely that its surface greatly outweighs that of the lime; so the reaction proceeds in the direction of the formation of a more silicic acid-containing liquid as long as the surface of the silica predominates; If the silica has almost disappeared and the surface of the lime itself predominates, the course of the reaction is reversed and the liquid becomes more basic until no more solid can be absorbed at the temperature in question. In general, depending on the prevailing conditions, any of the following processes can take place: a) Complete melting, b) Increase in the amount of liquid without complete melting, c) Dissolution of one solid and simultaneous precipitation of another whose solubility limit has been reached, d) Complete solidification, e) Steps b) and c) or b), c) and d) in more or less rapid succession. 6. With three or more reactants, the course of the reaction is similar except that selectivity is more likely to play a role. When lime, magnesia and silica are the reactants, the lime and silica prefer to react in both the initial and final stages and the selectivity is of two different types. If fine silica is reacted with coarse dolomite, the eutectic melting at 1321 ° C (with 61.5% silica, 30.5 % lime and 8.0% magnesia) is formed first, even if this is also the case Includes selective extraction of lime from the lime-magnesia complex. If this eutectic ultimately reacts with a large excess of dolomite, then all of the magnesia appears as periclas together with tricalcium silicate and free lime, whereby the bound magnesia is released in this process. With three reactants, the early precipitation of a relatively refractory intermediate or end product occurs more frequently than when two reactants are present.

7. Finds the reaction between granular solids in one Temperature instead of having little or no liquid formed at any one time the product is not set strongly, neither hot nor after cooling down.

B. When there is considerable liquid in a mass of granular materials is formed, the cooled mass has a strong bond and is well solidified. The useful range was 6 to 30% of the refractory to be bonded determined.

9. When heating granular materials of the type described here is the normal course of reactions as determined by periodic examination of the heated The mass is determined with a prick or other sharp instrument, the following: a) Development of a sticky and plastic state, mainly from the finer components of the mass, at the beginning of the liquid formation, b) Increasing stickiness with increasing liquid formation, c) Decreasing stickiness and increasing hardness as soon as the liquid has the coarser refractory grains reacts and is itself converted into fire-resistant compounds, which in the case of the relevant Temperature are fixed, d) Final formation of a highly refractory mass, the is hard and solid even at 160o to 1700 ° C and no longer contains any liquid. This strength is usually retained. when the mass is at room temperature is cooled. In the case of dicalcium silicate formation, dust formation and decay can occur enter after cooling unless a stabilizing agent such as boric acid is added is used to prevent the inversion from beta to gamma form. to. Although the Significance of the relative surface areas of the reacting oxides can be seen from the above is still a practical method of calculation for the application of the invention these areas are required.

The determination of the realtiven surface of the reactants lies based on their sieve analysis. Any sieve division can be used. As an illustration the division according to Tyler is chosen, who uses the principle of square openings is based on twice the area of the next smaller size. It is believed, that is the average diameter of the particles that pass through a given sieve have fallen and are held back to one on the next lower of the series Third of the difference between the two mesh sizes is greater than the diameter the smaller opening. Although this relationship changes a little with every sieve analysis, it is a sufficiently precise approximation. This method is also satisfactory, regardless of whether all of the Tyler series screens are used or every second one is left out. The relative surface area of very fine fractions is so great that, disregarding any major refinement, it suffices to denote Take mean diameter of all material that passes through a Tyler sieve with zoo meshes (mesh size 0.05 mm) falls.

The following table lists the most common particle sizes used in refractory materials and the corresponding linear dimensions of the actual Tyler openings. From these, the average diameter for particles which passed through a sieve and were retained on the next in line was calculated, using the above assumptions. In the last column the relative surface areas per unit weight of particles of the given size are given, these surface areas being inversely proportional to the respective diameters, a relationship which is rigidly valid for particles of any given shape. For the sake of simplicity, the particle size which passes through a sieve with sieve openings of 9.42 mm and is retained on a sieve with sieve openings of 6.72 mm has been taken as a unit. Estimated ter through- relative sectional area Meshes in Particulate Pro Tyler mm size particle weight uniformity knife mm (9.42mm 9.423 -g, 42mm + 3) 7.0 1 00 3 6.72 - 3 + 4 4.93 1'42 4 4.76 -4 + 6 3.48 2, o1 6 3.36 - 6 + 8 2.47 2.83 8 2.38 - 8 + io 1.885 4.02 i0 2.00 -10 + 14 1.33 5.72 14 141 -14 + 2.0 o, 895 8; 26 20 o, 84 - 2o + 28o, 67 11.33 28 0.59 - 28 +35 0437 1599 35 0.50 -35 + 48 0.342 22.65 48 0.29 - 48 + 65 0236 32.15 65 0.21 -65 +100 o, 168 4530 ioo 0.49 - iooMaschen 0.45 154.92 -100+ 150 O, iig 64.03 150 0.105 -150-f- 200o, o83g 9o, 61 200-0.074 -2oo meshes 0.0249 308.25 The minus sign means that the particles have passed through the relevant sieve, the plus sign that the particles have been retained by the relevant sieve.

Because of the many practical uses of the described Method and the need to clearly distinguish between that for carrying out the invention To distinguish between the procedure required and such procedures, with which a satisfactory setting is not achieved, it is desirable to use a to give a considerable number of examples.

Three very typical cases are listed first, in which as a result Disregarding the teachings of the invention, little or no liquid in place and Place formed and unification and solidification of the refractory material not was achieved. The following are examples of the many within the scope of the invention allowable variations.

To further emphasize the differences in the procedures, are illustrated in the three examples in which the principles of the invention are not applied and the same raw materials for the first nine examples of successful methods and the same weight ratios applied, however, take those taking place Reactions due to variations in grain size and consequently in relative surface areas a different course.

The selected raw materials are hard-burned dolomite (the so-called double fired dolomite) and quartzite. Both materials are available cheaply in a purity of 950 /, on upwards, and for the sake of simplicity all will Impurities ignored and the dolomite with 58.2% CaO and 41.8% M90 and the quartzite assumed to be 100 ° / a Si 02. Both materials are on about 9.42 mm maximum size available shredded and are in a ratio of g2.6 parts by weight Dolomite and 7.4 parts by weight quartzite to be used. Are they fully implemented, so in each case they form about 28.1% tricalcium silicate and leave 33.2% free lime and 38.7% free magnesia as periclas. Example i For use dolomite and silica are used as repair material in an open hearth furnace crushed on passage through a sieve with a mesh size of 9.42111111, then carefully mixed and placed in the desired place in the hot oven. There the two materials have almost identical sieve analyzes, the amount of dolomite is each given sieve fraction on average 12.5 times the amount of silica (92.6 / 7.4), and their surfaces have the same proportions. When the reaction occurs there are traces of low-melting liquid around every silica particle, big or small, educated; because of the large amount of fine dolomite immediately available almost instantly, however, it is converted into refractory silicates with it instead, and at no time is there an appreciable amount of fluid. Because the coarse nature of the respondents the equilibrium (if any) reached only after a long period of heating, after which particles of tricalcium silicate (which will likely include some orthosilicate) throughout the mass are, however, no noticeable shrinkage has taken place and no general Setting result. Because the teachings of the inventive method are not applied the objectives were not achieved.

Example 2 In this case the silica is left in the coarse 1 state and the dolomite is finely comminuted. This only worsens the situation, since more fine dolomite than before is now available for immediate conversion with any liquid that has formed. The result is even worse than in example i. 1 Example 3 Both reactants are now comminuted to pass through 100 meshes and slowly heated to 1650 ° C., the highest temperature of the 1 open hearth oven, and held for one hour. As in example i, the surfaces of the two components are again proportional to their respective weights. Since there is a large excess of lime to combine with the silica, these oxides react selectively in preference to magnesia and silica, as explained above, and a silicate with a high lime-silica ratio tends to be formed. For reasons that are not entirely clear, the formation of the orthosilicate actually begins first, and this even at a temperature well below the melting point of any of the possible binary or ternary eutectics. In contact with excess lime at 1650 ° C, however, the silica ultimately reacts to form tricalcium silicate, all of the magnesia and a large part of the lime still remaining free, as already explained, and since there was no appreciable amount of liquid at any time, the mass is as a whole soft and easily crumbling. Obviously the results are similar if any other: direct comminution ”of both reactants is used. Example 4 In this case the dolomite is first crushed to about 3 meshes, a suitable size for repairing steel furnace walls, and the -8 mesh material is removed by sieving and ground to a 100-mesh pass, as is the case with silica Case is. The lime-magnesia-silica eutectic is used as a binding agent, which melts at 1321 ° C and contains 30.5, 8, o and 645% of the three oxides. It is then necessary to calculate the required surfaces of the dolomite and silica. Since the use of dolomite involves an excess of magnesia over the eutectic composition, only the lime and silica need be considered as initial reactants. Their proportions by weight are 30.5 and 61.5, and ideally these should also be their relative surface areas. Since, according to the table above, -100 mesh silica has a surface area of 155 units per unit weight, the total surface area is 1147 units, and 1147 units are required for the lime or 976 units for the dolomite. The following table shows how the surface area of the coarse dolomite is calculated from its sieve analysis Weight area total Mesh percentage factor area units -3 + 4 51 442 72.42 -4 + 6 26 2.01 52.26 -6 + 8 23 2.83 65 0 9 Total ...... ioo 189.77 Per unit ..... 1 i, go Each unit of coarse dolomite thus has i, g units of area, while each dolomite unit crushed to 100 meshes has 155 units. A simple algebraic calculation shows that to obtain 976 units of area, 87.37 parts of coarse dolomite and 5.23 parts of fine dolomite are required. These provide 166 or 81o surface units.

The above calculation has been given in detail as an explanation of the method used; however, since the 5.23 parts of fine dolomite account for 83% of the required surface area of the dolomite, it is evident that no detailed calculation of the surface area of the very coarse material is necessary. In fact, when the coarse fraction is completely disregarded and 6.3 parts of fine dolomite are used to provide the 976 surface units, the results are quite satisfactory. This method is acceptable when, as here, the coarse particles are on average about 10 times the average diameter of the particles in the fine fraction and the target is a highly silicate liquid.

When the mixture of coarse and fine dolomite and fine silica is exposed to increasing temperature as in a laboratory test or on the Walls of an open hearth furnace, the formation of liquid occurs easily as the beginning of melting can be observed at almost exactly 1321 ° C, the melting point of the eutectic whose composition was the goal. The liquid formed (7.4 / 0.6i5 Weight percent or roughly 12 weight percent) quickly envelops all larger particles, and as the temperature rises, a series of reactions occurs, until the paste-like one The mass becomes hard and firm, even at the highest oven temperatures. This State remains after cooling. Example 5 In this case is a finer one Dolomite crushed to pass through 6 meshes at a temperature to tie that is as low as possible. Because the average particle size is about half the size of that of the previous example, you can just use the fraction remove from -16 meshes, and grind them just like the silica to a size which falls through zoo meshes. The relative grain sizes and surfaces are then essentially the same as before and the reactions are more similar Way. The setting can be done by firing at 1350'C, but one thing is a bit higher temperature desirable when carrying out the reactions to completion are.

A mixture of this kind can be used for mending as in example 4 will. However, there are noticeable differences between the two cases. From the from a practical point of view, it is desirable that little dust is generated when Refractories can be thrown into an oven because the dust can be in some Cases with the furnace gases are discharged as in an open hearth or yourself place in the middle of an oven instead of on the walls where it is needed, like in an electric furnace. The coarser material therefore has a practical one Advantage. On the other hand, very coarse materials do not bind as quickly or too such a dense mass, as is the case with such materials, the one considerable amount of fines contain. Thus, the second Material type can be chosen for this purpose.

Furthermore, the coarser materials take a considerably longer time Time to fully react and excrete all fluids, and become consequently remain longer in a plastic or paste-like state. These Cases show how the degree of setting, the temperature range at which the plastic State remains, and the density of the end product by changing the grain sizes the reacting materials can be determined. Example 6 This is the case Similar to that of Example 5 except that the average particle diameter is the coarse fraction again reduced by 5o0 /, d. H. to about i, oi6 mm. While such a case is technically unusual, the same procedure as that previously described, can be used when the fine fraction is ground in such a way that that the same ratios of average diameter and total surface area the coarse and fine fraction are maintained. Example 7 This example is a modification of Example 6 and, for economic reasons, should be the same as there extremely fine grinding required. In this case there is no Grinding beyond 100 stitches is necessary, but the contact between the finer fractions, which are said to be the initial reactants, by mixing these materials and shaping them into spheres. The parts then react in the desired order. The deformation to balls is not recommended when bricks are to be produced, but it is satisfactory in the manufacture of composite repair materials for furnaces. example 8 There is another possible method of applying the conditions of Example 6, which can often turn out to be the most economical. Instead of Grinding of the silica and part of the dolomite to a high degree of fineness to mix with the coarse dolomite, the fine dolomite is omitted and the Silica left sufficiently coarse to achieve the desired surface area between to produce this component and the entire dolomite.

Since, as in Example 4, the generation of the eutectic melting at 1321 ° C is desired, the required surfaces are silica and dolomite again 1i47 and 976. The relative weights are 7.4 and 92.6; if thus the total dolomite is taken into account, the average required is Particle diameter of the silica is 0.069 mm, which is a little smaller than the size of particles falling through 15o meshes and being retained on zoo meshes .. It is also more than the production of a small grain size of this kind satisfactory and much lighter, about the right proportions of -65 + ioo and -ioo meshes. In this case the calculation shows that the ratios 16.5 and 83.5% result in the desired surface. This modification which the Reaction of the silica with the surface portion only of the dolomite present instead of using specially ground and extremely fine dolomite as more or less thus does not require a very fine grinding of the Silica. On average is. the silica, however, is much finer than that Dolomite, the ratio is around 15: 1. Example 9 When using a Mixture of dolomite and silica can be used instead of sifting out the coarser parts and to subject the fine parts to further comminution (as in Example 4), the grinding method can sometimes be changed to get the desired proportion is present on fine particles. For example, dolomite can be found in a jaw crusher or vibratory crusher reduced to 3 or 4 meshes in a tube or ball mill from. small diameter are introduced, preferably with the desired proportion on fine silica, and there without the addition of a heavy grinding agent be ground until the particles are eroded by gradual attrition and any desired proportion of fine material is formed. By simply stopping the mill, if a sieve analysis of the product, the desired proportion of fines shows a self-setting mixture of coarse and fine material is obtained. In a continuous process, the amount used is only controlled so that the desired percentage of fines is obtained in the product, which easily as calculated above. It is immaterial whether the silica is of any greater fineness is than the fine dolomite, provided that, first, the ratio of the particle size the coarse and fine fractions of dolomite are sufficiently large that they are almost react independently, or secondly, the total surface area of both the coarse and the coarse of the fine dolomite fractions the desired ratio to the surface area of the silica having. Example 10 In Examples 4 through 9, the aim in each case was that Formation of about 12% of the lime-magnesia-silica eutectic which melts at 1321 ° C, and this result was achieved in essentially all cases. Using however, of the same raw materials in exactly the same proportions, it is good possible by regulating the grain size of the constituents a different proportion of a other low-melting material that acts as a binder. For example, it may be desirable to use a larger amount of liquid from a lower amount of liquid To generate viscosity. The lime-magnesia-silica phase equilibrium diagram shows that in this system a eutectic melting at 1359 ° C with the composition 29.7% Ca0.20.3% M90, 50.0% SiO2 is present. Because of his lower in silicate it has a considerably lower viscosity than that Eutectic melting at 1321 ° C, and when it is made of 7, q.0 /, silica and dolomite is formed, it apparently produced 14.80 /, liquid compared to 120 /, at the previous cases. These proportions are both within what is most desirable Area. If the same calculation method is used as in example q., the proportion of dolomite from -ioo meshes only increases until its surface (strictly speaking including the surface of the coarser dolomite) the desired Has relationship to the surface area of the silica. As practical in this case there is no selective force as between lime and magnesia, it is correct taking the entire surface of the dolomite instead of that of the lime alone, and Since the silica makes up 50% of the total weight, the same areas are required. After heating there will undoubtedly be some of the eutectic melting at 1321 ° C formed first, but as soon as the temperature rises sufficiently, this happens quickly to the eutectic melting at 1359 ° C because of the additional fine lime and magnesia, and effective binding then takes place. example ii This example was chosen to define an approximate limit of the area in which this method works satisfactorily in binding granular dolomites with silica can be used. However, this limit does not lie in the reaction method Formation of fluid in place is justified, but rather arises from it the fact expressed in previous applications that the low-melting point The component itself should be essentially completely liquid at 150 ° C, to effect a satisfactory bond for the refractory grains of the dolomite. In the present case this requires a silica content of about 42 0 / in the low melting point. Such a bond can be formed in place be by adding 7. ¢ parts of silica from -ioo mesh with 92.6 parts of dolomite a Such a grain size can be used that the surface 58 / q.2 of 1147 or 1584 Units is. While the reaction of these components easily in the desired As it takes place, experiments have shown that the bond does not develop as strongly is like with low-melting constituents of higher silica content, and this case is therefore viewed as a borderline case. The method is down to 42 0 /, silica applicable but not below. This limit is of course the same like that of the surface of the silica, based on the total surface of all particles in the full mix.

Example 12 It remains in the series of dolomite-silica combinations Another very important case to be considered, which is the extreme limit after the represents another direction. This extreme is the use of 7.4% finer, Free silica with coarse, hard-burned dolomite of any commercial grain size with little or no fine fraction in it. In fact, good binding is guaranteed, if about 5 to 15%, fine silica is used and fine dolomite is essentially does not exist. This surprising result is made by studying the lime-magnesia-silica equilibrium diagram explained. This shows the fact that when converting fine silica from large Surface with coarse dolomite of small surface (i.e. when implementing a large proportion of silica with a relatively small proportion of dolomite) a little of the eutectic melting at 1321 ° C is formed. With everyone about this lying temperature begins the solution of the remaining solids, and base and Acids react at any particular time in relation to the instantaneous values their surfaces. As a result of the predominant surface of the fine silica the melt increasingly contains silicic acid with increasing temperature until the silica has been largely absorbed, as explained in Principle 5 above. Then the course the reaction is reversed, and since the silicic acid-containing melt contains the coarse dolomite particles enveloped, it continues to react with them until its composition increases Amount of liquid through the low-melting areas in which the 1321 and 1359C melting eutectic lies, and finally in the area in which the Fire resistance increases rapidly towards the final equilibrium, has gone. If 7, q.0 /, silica is used, the end products are exactly the same as before.

This gives rise to the principle - one of general use - that - even if you start from pure silica or highly refractory silicates - a continuous series of melts of decreasing acidity are formed, when the grain sizes are controlled so that the direction of liquid formation after the disappearance of the silica or the silicates as such over an area low-melting compositions or eutectics is conducted. At one or several points in this series, the conditions are most favorable for development of liquids that are effective binders for basic, refractory materials represent.

Although this particular principle usually does not require anything else as a rough estimate of the surface area of the reactants, is its application not in all cases the procedures described in the previous examples superior, because when using a relatively large amount of coarse basic refractory material and a small amount of a fine, acidic reactant The result is usually a product of high porosity, which for some purposes is less is useful as a denser material that is of a wider range of grain sizes is derived.

Example 13 In all of the above examples was one of the raw materials a hard-burned dolomite, as usual more open when mending Hearth ovens and electric steel ovens is used. The method of tying through Reaction and fluid formation in place is also in the same way applicable to mixtures containing raw dolomite, which in the pure state 30.40 /, Contains lime, 21.90 /, magnesia and 48.70 / 0 carbon dioxide. If you use the example 14 specified calculation method, it can be seen that one for the formation of the same at 1321 ° C melting eutectic and the same end product to 7.4 parts of fine silica 92.6 / o, 513 or 18o, 6 parts of raw dolomite must be used, of which 170.4 Parts -3 +8 meshes can be and io, 2 parts to the fineness of the silica of -ioo meshes would have to be ground. In other words, you just take into account the non-volatile oxides present. The raw dolomite and silica were after Heating to 400 ° C and cooling to room temperature strongly bound. The product was undesirably porous, but the coarse particles were so perfect glazed that if the mass was kept under water for 48 hours, in spite of that Due to their high content of free lime, an almost negligible extinction occurred.

It can be seen that, if desired, one can make a large amount of a mixture of 7.4 parts of fine silica and 10.2 parts of fine crude dolomite which can be maintained indefinitely without change and this mixture mixed with coarser hard burned dolomite as required can use. At times, other proportions may be cheap. Example 14 In some steelworks, raw dolomite, from which the fine particles have been removed, is largely used as a repair material for open hearth furnaces, but it does not bind itself at the point in question and therefore gives the walls only temporary protection as it is carried away by the slag and must be replaced at the end of each heating. Much greater stability can be achieved if the same principle as in Example 12 is used and about 5 to 10% fine silica is incorporated into this dolomite. In order to reduce segregation and dust generation, it may be desirable firstly to apply the mixture wet, with or without temporary bonding in order to bring about the coating of the coarse particles by the fines, or secondly to deform the silica into spheres. If the latter route is followed, it is preferable to use a mixture of 7.4 parts of fine silica and 10.2 parts of fine crude dolomite to form the eutectic, which melts at 1321 ° C, on the spot before reacting with the coarse dolomite as in Example 13. Example 15 In all of the above examples, free silica was used as the silicic acid-containing material. However, it is often easier or more economical to use other raw materials. For example, two waste products are available in the province of Ouebec, neither of which, as such, has the most desirable composition for use as a low melting ingredient, but which, finely ground and mixed together in appropriate proportions, are excellent starting materials for the formation of low melting eutectics on site . These materials and their approximate composition are as follows: C.0 I Mg0 I Si0, I A1.03 I F e O I P20, f L.0.1 A. Phosphorus furnace slag ................ 47.4 0.5 44.1 4.0 0.2 1.2 0.0 S. Asbestos waste (mainly serpentine) ... i, o 38, o 38, o 1.5 8, o - 13.5 Mixture of 55 ° / o A and 45 ° / o B (calculated on a dead burned basis) ................ 28.7 18.8 44.7 3.1 4.0 0.7 - A low-melting composition is obtained as the reaction product of 55 parts of slag (mainly calcium metasilicate) and 45 parts of asbestos waste on the spot, which, based on its main components alone, 31.1% lime, 20.4% magnesia and 48.5% ° / o contains silica, that is to say proportions very close to those of the eutectic of 1359C, which has a composition of 29.7; 2o, 3 and 50.0%. The presence of the insignificant oxides brings about the fusion at a slightly lower temperature, but they are not present in sufficient quantity to noticeably affect the composition of the end product, for example if 5.5 parts of slag and 4.5 parts of asbestos waste are components of - 100 meshes are mixed with parts of relatively coarse burnt dolomite. Excellent bonding results when these ingredients are burned together. Raw dolomite can also be used as a refractory granular material.

Instead of asbestos waste, other magnesium silicates, such as Ollvin, Talc, forsterite and enstatite can be used. When used with calcium metasilicate Suitable low-melting compositions are produced in approximately equal parts.

Example 16 If it is desired instead to prepare the eutectic of 1321 ° C on-site using the same raw materials, it is necessary to add some fine silica as well .; As the calculation shows, the use of 58 parts of slag, 20 parts of asbestos waste and 22 parts of silica yields a product which contains the three main components in the proportions 30.5 % lime, 8.7% magnesia and 60.8% / o contains silica, which for all practical purposes is close enough to the composition of the eutectic with 31.5, 8, o and 61.504 . The total mixture can then consist of 5.8 parts of slag, 2.0 parts of asbestos waste and 2.2 parts of silica, all ground to 100 meshes or finer, plus parts of relatively coarse burnt dolomite. The bond produced by the firing is as good as that of Example 15.

The same eutectic is produced equally well on the spot by using 40 parts of slag, 42 parts of silica and 18 parts of dolomite, all as fine particles which, when reacted, produce liquid containing the three main oxides in a ratio of 30.40 /, lime, 8 , o0 /, magnesia and 61.60 /, silica. This in turn shows how easy it is to bring suitable raw materials into such a proportion that a truly eutectic composition is produced. Example 17 Good results are also obtained when the fine dolomite of the previous example is omitted and the same proportions of fine slag and silica are used. These two components then start to react with each other and with the coarse dolomite at 132 ° C or below and continue the reaction until they have absorbed enough lime and magnesia to again reach the eutectic composition. As in Examples 12 and 14, the on-site eutectic formation succeeds because the composition of the initial reactants is directed through a range of low melting point compositions by reacting with the surface portions of the refractory granular particles themselves. Example 18 On-site liquid formation equals well in a binary system such as the lime and silica system, although such cases are usually of little economic interest. Coarse quick lime mixed with fine silica and enough fine lime to produce a liquid with the eutectic composition of 1438 ° C with 36% lime and 640% silica after heating, for example, turns into the binding agent for the coarse lime . Exemplary reaction and on-site liquid formation are at least of equal interest in the magnesia-alumina-silica field, where it is possible to utilize the described method of binding granular magnesia. For example, a pulp material for the permanent floors of open hearth steel furnaces can be made by combining a mixture of 48 parts fine serpentine and 52 parts spherical clay of the following composition with granular magnesia: Ca 0 I Mg 0 I Si 0a I Al, 0, I Fe 0 I Alk. I LOI A. Serpentine ............................ 1.0 41.5 415 0.5 1.2 - 14.3 B. Ball clay (mainly aluminum silicate) 0.5 0.2 62.9 28.1 1.0 2.0 5.3 Mixture of 42% A and 58% B (calculated on a dead burned basis) ............... o.8 19.3 59.3 18.1 1.2 1.3 - In this mixture the magnesia, silica and alumina are present in the ratios 2o, o, 61.3 and 18.7 compared to 20.3, 61.4 and 18.3 for the eutectic of 1347 ° C, i.e. perhaps in the most favorable composition in the system. If the crude constituents cannot easily be balanced with the desired percentage of silica, a little free silica can be added or a less silica earth can be used. Dead-burned brucite grains are available as coarse material (about - 10 + 2o meshes), which are obtained from rock near Wakefield (Quebec); 80 parts of the same are combined with 20 parts of the plastic serpentine-clay mixture and tamped into a furnace floor. If desired, a small amount of sodium silicate or some other chemical binder can also be added, but this is not absolutely necessary with a good binding clay. After drying, considerable strength is developed, and upon firing, the eutectic of 1347 ° C is first formed in place, and this then reacts with the magnesia of the grains to form a highly refractory mixture of periclas, forsterite and magnesium aluminate - 1e5 spinel. Example 20 There is another desirable eutectic in the magnesia-alumina-silica system which melts at 1362 ° C and contains 25, ai and 54%, respectively, of these three oxides. It can be formed on the spot in a similar way to the eutectic of 1347 ° C of Example ig, by mixing approximately equal parts of fine olivine and kaolin with granular seawater magnesia or other material of similar composition, which is to a suitable (always proportionate coarse) grain size is crushed, united. However, if the eutectic of 1347 ° C is formed and this then reacts with magnesia, a considerable proportion of the eutectic of 1362 ° C is always formed; thus the latter is seldom the primary goal.

From a study of the magnesia-alumina-silica phase equilibrium diagram it can be seen that desired low-melting liquids in place and Place by the reaction aiideier coal materials than that in the examples ig and 2o specified can be formed. Forsterite, enstatite or talc can be used in place of the magnesia-containing serpentine of the example ig and calcined clays or Brick gravel can be used in place of the spherical clay containing clay. Essentially equal proportions of each type of silicate bring the useful low-melting points Compositions, and final corrections or adjustments can be made possibly by adding magnesia, silica or materials containing alum be made in appropriate quantities.

It is found that in Examples 15 to 20 the starting materials for the non-refractory silicate must be so fine that they are practically independent react with each other from the coarse mass.

Example 21 For orientation purposes, a series of laboratory tests were carried out with 100 mesh silica and "directly crushed" dead-burned dolomite, in which the proportions of dolomite and silica were kept constant in uninterrupted tests, but a coarse dolomite fraction was omitted; the surface was thus gradually increased. The following results were obtained: - Attempt no. 1 I 2! 3 4! 5 Dolomite ........ -3/8 "-3 stitches -4 stitches -8 stitches -2o stitches (g, 42 mm) Relative surface 840 /,) dolomite. . 736 953 1300 2156 408o 16% silica 248o 248o 248o 248o 2480 ° / o silica Start of reaction (= Total surface) ... 77.1 72.2 65.6 53.5 37.8 Observations very good very good pretty good mediocre holds together, when burning bond, bond bond, bond, however light to 1400 ° C and rough glaze, less rough, mediocre, not as good as crumbling Cool to very porous glaze as No. i, glaze, No. 3, however Room temperature porous relatively better than No. 5 very porous Observations very good very good very good pretty good crumbling, when burning bond, bond, bond, bond, but less than at 1500 ° C and rough glaze rough glaze medium light glaze at 1400 ° C, Can cool on until solid glaze particles can be used Abraded at room temperature will As the lime-magnesia-silica phase equilibrium diagram shows, the first two products were excellent because the initial compositions crossed a low melting point. No. 3 and No. 4 were satisfactory because they were close to the eutectic compositions at 1321 and 1359 ° C, respectively, and the fifth was unsuccessful because there was so much fine dolomite that too little liquid was formed and a temperature of 1650 ° C is required for complete melting of the initial reactants. Example 22 In another series of laboratory tests, seven blends were made. In each of these, 7.40 /, silica of - 100 mesh with combinations of calcined dolomite of - 3 -E- 8 mesh and - 100 mesh were used, with the proportions of the latter two ingredients ranging from o to 92.6 and 92 .6 to o ° / o lay. The test conditions and the results obtained are given in the table below: Attempt no. 1 I 2 I 3 I 4 (5 I 6 I 7 % -3 + 8 stitches Dolomite ............ 0.0 67.5 76.9 86.3 87i7 90.35 92.6 ° / o -ioo meshes Dolomite ............ 92.6 25, i 15.7 6.3 5.43 2.25 0.0 ° / o -ioo meshes Silica ......... 7.4 7.4 7.4 7.4 7.4 7.4 7.4 Attempt no. 1 I 2 I 3 I 4 I 5 I 6 I 7 Relative surface -3 + 8 stitches- Dolomite .......... 0 130 148 166 167 173 178 -ioo meshes- Dolomite ........... 14350 389o 2433 976 842 349 0 -ioo meshes- Silica ........ 1147 1147 1147 1147 1147 1147 1147 % Silica at Start of reaction (=% of the total surface) ......... 7.4 22.2 3o.8 50.1 53.2 68.7 86.6 Observations with soft as well as low bad bad good good best Firing at 1400 ° C dry bond sufficient bond bond bond bond and chilling on neter clay bond of all Room temperature The results in the first three experiments were very poor because the proportions and grain sizes were such that any low-melting liquid precipitated out essentially as quickly as it was formed by reaction with fine dolomite, which has a much larger surface area than silica. All of these attempts illustrate the poor results obtained if the teachings of the invention are not followed. Trials # 4 and # 5 were both successful in that the silica in the non-refractory silicates formed first ranged from 50.1 to 53.2%, and consequently these non-fire-resistant silicates became sufficiently below 1400 ° C Temperature completely melted. No. 6 and No. 7 were bound at least as well, although the temperatures of the completely liquid state of the primary silicates were around 165o and 170 ° C, because after liquid initially formed at 1321 ° C, both remaining solids (silica and Dolomite) continued in solution until the silica supply was exhausted (at a temperature of 1400 ° C the melt would contain about 62.5% silica), whereupon the dolomite absorption due to the low-melting composition ranges of the eutectics of 1321 and 1359 ° C up to one Silica content of about 48 /, continued and complete solidification occurred at 1400 ° C. At a temperature of 1500 ° C, which was used in a parallel experiment, no liquid excretion occurred until the silica content was reduced to about 420/1. These cases therefore correspond to Example 12. It should be noted that Run No. 7 was described as having the best bond of all, but the end product was very porous because of the small amount of fines. Trials # 4 and # 5 had the best density. Clear evidence has been obtained of the selective action of silica with lime in preference to magnesia; had the latter reacted to the full extent in which it was present, much less of the eutectic fluid would have formed, and the bond at 1400 ° C. would have been less satisfactory.

The above examples of the conditions required to be satisfactory Binding of grains of refractory material lead or not lead, as well as the Discussion of the included principles will show the expert how that the desired results can best be achieved. The limits of the invention need but not to be more precisely determined.

The segregated or granular particles of refractory material are usually those that are in technical practice in manufacturing of bricks, mending steel furnaces, etc., their size range differs from a product that passes essentially completely through an 8 mesh sieve falls to a product in which the largest particles are 19.05 to 25.4o mm in size are, extends. On the coarser side, there is no special limit beyond to which the method is not applicable; on the finer side is the practical one Limit the use of granular materials, at least 50% of which are on one 2o-mesh sieve are retained.

These granular materials must be one of several reactive ones Contain alkaline earths, with lime and magnesia being the main ones. Of these, lime is the more basic and thus the reactive oxide when it is alone is used or as in dolomite and dead-burned Quebec dolomite at least io 0/0 (weight percent) lime and at least 6% more lime is present than for binding with all of the silica as calcium orthosilicate is required. The whole Magnesia is then essentially in the form of an inert periclase. If a noticeable If the amount of lime is present, clay is troublesome in that it is low-melting Forms compounds that are not separated out by reacting with more lime.

Most technical magnesites contain more than 8o% magnesia, there is little clay and less than 5 weight percent lime, and magnesia is then the reactive basic oxide. Through implementation with the Silica and alumina that may be present in the non-refractory material converts it converts these into refractory magnesium orthosilicate and magnesium aluminate and must therefore are present in the final blend in a weight ratio that is substantially at least corresponds to x.34 times that of silica and 0.4 times that of alumina. Would a smaller amount of magnesia (or, in the same way, a larger amount of silica) used, some of the magnesia at final equilibrium would be considered non-refractory Magnesium aluminum silicate cordierite (2 Mg 0 - 2A12 03 - 5 Si 02) and not as the refractory orthosilicate forsterite (2 Mg 0 - Si 02) occur. Is that magnesia reactive oxide, 10 per cent or more of free magnesia is required in the grains.

The manufacture of a non-refractory silicate by choosing appropriate Starting material in reactive form has already been discussed. A suitable reactive Shape can be created by finely grinding and mixing the initial reactants, to create a large area of contact between them, either between the solid components themselves or between the initial liquid and the finer ones Particles, such as in the case of fine silica in contact with only coarse, hard-burned dolomite. It can also be created without extremely fine grinding, by keeping the contact between the constituents of the starting material for the not refractory silicates by deformation in balls or briquettes or in any other way is improved so that the reaction between these components is almost independent of other solids present, whether coarse or fine, takes place.

The term "non-refractory silicates" refers to eutectics and especially ternary eutectics and also includes some low-melting compounds, like diopside (Ca 0 - Mg 0 - 7'S'02) and Akerrnanite (2 Ca 0 - MgO - 2 Si 02), but not on monticellite (Ca 0 'Mg 0 - S' 02), the silica content of which is too low is to be effective. The most useful eutectics are those that are in the field Melting 130o to 1400 ° C, however, as the phase equilibrium diagrams show, considerable areas of the composition are present in which a high proportion Liquid is formed at low temperatures, and the method according to the invention includes all such ternary domains in which essentially all of them are not refractory silicate is melted at 1500'C, as well as the corresponding binary Areas in which substantial amounts of liquid are formed at 1550 ° C. In In terms of silica content, the range includes composition of the non-refractory silicates of the process according to the invention all those in which the starting material as a group, based on dead burned or lossless Base, at least 420 /, contains silica. In other words, the total surface area all non-volatile oxides in the particles of the total mixture of granular particles and the siliceous material is no greater than 2.4 times the surface area the free and bound silica in the mixture. The granular material to be bound often contains a little bound silica. Usually she's in the rough granular particles are not present in sufficient quantity to remove the surface of the free and bound silica noticeably affect, however, it can, as in the case of the calcareous Ouebec magnesite, even most of the silica in the final mix supply, and it is then important to use them in the calculation of the composition of the To include the end product.

The starting material for the non-refractory silicates includes actual parts of the complete mixes that are produced by reaction in the not refractory silicates enter. When surface and grain size are controlled in this way, that the melting of the fines is almost independent of the coarse refractory material is brought about, these fine fractions form essentially the whole Starting material; However, if the surfaces of the granular refractory material even the low-melting silicates through reaction with silica or as a fine fraction imported silicates are supposed to form, so do the grains to this extent as well represent true starting material and are to be understood as such here. However, it is evident that even in the latter case the granular refractory material in great excess is present, and only those parts of it which are a constituent of the non-refractory silicates with at least 42% silica are actual Starting material for these silicates.

The process of the invention encompasses those granular mixtures refractory materials and the raw material for non-refractory silicates, which after complete reaction the essential excretion of the low-melting point Result in liquids. If the composition of the reaction participants is given, so is the calculation of the minimum proportion of granular refractory required Material is relatively simple, but in common practice that is used Proportion much greater than this minimum. For example, it can be used during manufacture of bricks with 1o to 2o0 /, lime may be desirable, lime and silica just with it To compensate for dicalcium silicate, whereas when using dolomite as a repair material only enough silica is used to bind the mass well since the introduction a lot of silica in basic steel furnaces is not practical. The silica forms then tricalcium silicate with some of the lime, and all of the magnesia and the Most of the lime remains free. With excess magnesia but no lime all of the silica reacts to form forsterite (2 Mg 0 - Si 02) and all of the alumina to spinel (M g0 - A1203), with a lot of magnesia usually remaining as periclas.

A number of practical uses have been identified in the examples given this binding method. Some of the most useful uses lie in the manufacture of bricks, mending materials and ramming mixes for Furnace bottoms. However, the method of the invention is not specific to some technical Phrases restricted, just to the application a method in which by choosing the grain size - which in turn by the required Surface is determined - the binding of basic refractory granular materials is produced in two different stages, the first stage being the Starting materials of a low-melting silicate implemented on the spot in order to produce it in liquid form, and in the second stage this low-melting point Silicate itself essentially by reaction with the granular particles to be bound is eliminated. These granular particles can, as explained above, in some Cases themselves represent one or more of the constituents of the non-refractory silicate, however, they still essentially remain in their original physical state State and become when it reacts with the liquid formed in place have, themselves strongly bonded with each other.

Claims (5)

PATENT CLAIMS: i. Process for the production of basic, refractory Products made from relatively coarse-grained raw materials such as dolomite, magnesia or Lime, and a finely divided silica-containing binder by molding and firing, characterized in that calcareous substances, possibly magnesia, im essential but not contain clay, or substances containing magnesia, which may be Clay, but essentially contains no lime, with finely ground silicic acid Substances mixed and fired to form a non-refractory second component which, when using lime, consists essentially of calcium or calcium-magnesium silicate or when using magnesia from a magnesium or magnesium aluminum silicate exists, with such grain sizes being selected in the overall mixture that the surface of free and bound silica at least 420 /, the total surface of the non-volatile constituents, and that in the overall composition of the Mixture when using lime the ratio of lime to silica at least as high as in calcium orthosilicate and the amount of magnesia when using magnesia at least sufficient to react with all of the silica to form magnesium orthosilicate and to react with all of the alumina as magnesium aluminate. 2. Procedure according to Claim i, characterized in that the alkaline earth in the starting material for the non-refractory component is introduced in such amounts that an excess about what is theoretically necessary for the formation of the corresponding orthosilicate Amount is available, i.e. 6 per cent for lime and 10 per cent for magnesia. 3. Procedure according to claim i and 2, characterized in that the composition of the starting material for the non-refractory component is set so that this substantially is liquid at 1500 ° C. 4. The method according to claim i to 3, characterized in that that the raw materials are moistened to avoid segregation and dust generation and be mixed. 5. The method according to claim i to 4, characterized in that the starting materials for the non-refractory component are mixed and crumbled. Considered publications: German Patent Specifications No. 849 82o, 824 773; British Patent Nos. 193 576, 211944; Austrian Patent No. 174 340; Searle "Refractory Materials" 1950, p. 233, para. 2; Reports of the "German Ceramic Society", 1930, p. 47fl., "About the production and use of dolomite stones".