MXPA00001824A - WET MILLING OF Mg(OH)2 - Google Patents

Abstract

A method for producing a stabilized magnesium hydroxide slurry involving wet milling a starting magnesium hydroxide slurry. Also disclosed is a stabilized magnesium hydroxide slurry produced by the method and magnesia-based products produced from the wet milled magnesium hydroxide slurry. Washed magnesium hydroxide slurry is either (a) fed directly to a wet mill (1) at a controlled rate for particle size reduction, or (b) introduced to a disk filter (2) to increase percent solids to greater than about 60%. If the disk filter (2) is used, the discharge is directed to a pug mill (3). Flow is recycled within the pug mill (3) through high-shear mixer (4). The pug mill discharge is collected in purge tank (5). A pump (6) is used to withdraw slurry from surge tank (5) and feed wet mill (1) at a controlled rate which rate dictates residence time in wet mill (1). This rate can be altered to control particles size reduction. The milled slurry is collected in storage tank (7).

Description

MOLDING IN WET MUD OF MAGNESIUM HYDROXIDE This application claims priority to the provisional patent applications of E.U.A. Nos. 60 / 056,094 and 60/071, 748, the entire contents of which is incorporated herein by reference.

FIELD OF THE INVENTION The present invention relates to a method for producing a stabilized sludge of magnesium hydroxide which involves wet grinding a starting sludge of magnesium hydroxide. The present invention also relates to a stabilized sludge of magnesium hydroxide produced by the wet milling method, to dry products of magnesia hydroxide and magnesia based, using the wet milled magnesium hydroxide sludge of the invention. This invention is particularly useful for the production of particulate magnesium hydroxide suitable for use as a flame retardant additive.

BACKGROUND OF THE INVENTION Magnesium hydroxide, Mg (OH) 2, is useful in various chemical processes, including, but not limited to, the following: pH adjustment; precipitation of heavy metal contaminants; Smearing and neutralization of acid vapors, such as those associated with flue gases or process exhaust gases; and the production of specialty magnesium components, such as Mg (OH) 2 in the form of particles, magnesia of chemical grade, MgO of high reactivity of various activities, periclase, etc. It is desirable to obtain a stabilized magnesium hydroxide slurry that can be used for the uses described above. It is also desirable to develop economic routes to achieve such magnesium hydroxide sludge. It is particularly desirable to obtain a magnesium hydroxide in the form of particles with an average particle size between about 0.5 and 5 μm, and surface area, measured by gas absorption methods, of 4-25 m2 / g. Magnesium hydroxide is used in the form of particles for example, as a flame retardant additive, due to its ability to decompose endothermally with the release of water and its environmentally attractive nature. It is also particularly desirable to develop economic routes to achieve such magnesium hydroxide in the form of particles. The prior art methods of producing magnesium hydroxide in the form of particles include: (i) adding lime to seawater. This produces magnesium hydroxide with a BET surface area that is usually greater than 15 m2 / g and is often more than 30 m2 / g. The BET surface area is generally in the range of 10-40 m2 / g and the particle size (D50) is generally in the range of 2-10 microns. This process results, in general, in magnesium hydroxide particles having a surface area that is too high to be used in a number of magnesium hydroxide products. (ii) adding a base, such as ammonium hydroxide, sodium or calcium, to a magnesium salt solution. This usually produces magnesium hydroxide with a high BET surface area (> 25 m2 / g). Under special conditions, magnesium hydroxide powders with a particle size (D50) of 0.5-1.5 microns can be obtained. These powders have a BET surface area in the range of 3-10 m2 / g and flame retardant additives are effective. However, such powders are relatively expensive to produce, since the washing of the precipitate is required to remove the coproduct (ammonium, sodium or calcium salt). (iii) hydration of magnesium oxide produced by pyrolysis or calcination. The hydration of magnesium oxide produced by pyrolysis of a magnesium salt solution, for example, magnesium chloride, has been the favored procedure although this method is relatively expensive to carry out. The hydration of magnesium oxide, produced by pyrolysis of magnesium chloride, typically provides a magnesium hydroxide powder having a BET surface area of < 12 m2 / g and a mean particle size (D8) of 0.8-1.3 microns.

The hydration of magnesium oxide produced by calcination of magnesium hydroxide or magnesium carbonate is potentially attractive since there is no by-product to be eliminated. The degree of calcination that is used determines the surface area of the magnesium hydroxide powder. Slight calcination gives magnesium oxide with a BET surface area of at least 25 m2 / g (often> 50 m2 / g). Such magnesium oxide is easily hydrated, but gives a powder of magnesium hydroxide with a similarly high BET surface area. The hard calcination gives a magnesium oxide with a large particle size (D50) and a reduced BET surface size (often <1 m2 / g). This magnesium oxide is extremely difficult to hydrate, unless a catalyst, such as magnesium chloride, is used. When a catalyst is used, the product usually comprises particles of relatively large particle size (D50) and high BET surface area. Representative of the prior art processes for the production of magnesium hydroxide are the methods set forth in the U.S.A. No. 3,739,058; patent of E.U.A. No. 3,508,869; patent of E.U.A. No. 2,940,831; and patent of E.U.A. No. 3,080,215. A commercial process of magnesium hydroxide, as set forth in those patents, will produce a particulate material having a size range of about 0.5 to 15 microns, with an average particle size of about 5-6 microns, with more small 20% of the material that approximately 3 microns and 20% larger than approximately 9 microns. As long as the magnesium hydroxide achievements are stable enough, they represent an effective and convenient way by which magnesium hydroxide can be supplied. For example, stabilized magnesium hydroxide sludge has many advantages over other forms of magnesium hydroxide, including the ability to be handled, transferred and stored easily and capable of being reliably dosed to chemical processes as desired. Magnesium hydroxide sludge can typically be derived from three basic sources: seawater, brackish well water and magnesite ore. In a preferred process, the magnesium hydroxide sludge is produced from the chemical reaction of dolina (CaO-MgO) and well water from brackish water. Well water from wells comprises mainly calcium chloride, but also includes magnesium chloride. The chemical reaction of dolina and brackish well water produces a slurry of magnesium hydroxide in a solution containing chloride. The sludge is further treated to increase the solids content, typically to between about 30% and 60%. Unless stated otherwise, all percentages in this application are percentages by weight on an MgO basis. Richmond et al., U.S. Patent. No. 5,514,357, discloses a method for producing a stabilized magnesium hydroxide sludge produced by conventional methods, such as from brackish well water consisting of physically deflocculating the magnesium hydroxide solids in a starting mud and optionally adding a cationic polymer and a thickening agent. Richmond et al., U.S. Patent. No. 5,762,901, discloses a method for producing a stabilized magnesium hydroxide sludge consisting of physically deflocculating the magnesium hydroxide solids in a starting sludge and controlling the chloride ion content in the slurry. Witkowski et al., Patent of E.U.A. No. 5,487,879, discloses a process for producing a stabilized magnesium hydroxide sludge from burned natural magnesite which involves hydrating under pressure a mixture containing burned natural magnesite and water in the presence of chloride ions and cationic polymer. Although the above procedures achieve a stabilized magnesium hydroxide sludge, there remains a need to further control the production of stabilized magnesium hydroxide sludge in order to control the characteristics of the desired products of Mg (OH) 2 and MgO and, in particular, of Mg (OH) 2 in the form of particles. The present inven allows the production of Mg (OH) 2 and MgO products that could not be produced easily and economically with convenal methods. These products include those that require submicron particle sizes of Mg (OH) 2 and MgO, specified (for example high) surface area of Mg (OH) 2 and MgO, and specified (for example very high) Mg (OH) density ) 2 and MgO.

BRIEF DESCRIPTION OF THE INVENTION It is therefore an object of the present invention to provide a method for producing a stabilized magnesium hydroxide sludge having specified properties according to the needs of the characteristics of the final sludge and / or the final product of Mg (OH) 2 / MgO. The present invention is thus directed to a method for producing a stabilized sludge of magnesium hydroxide, the stabilized sludge of magnesium hydroxide being produced by the method and the magnesium-based products using the stabilized magnesium hydroxide sludge of the invention. According to the method of the present invention, a wet-milled magnesium hydroxide sludge, produced by conventional methods such as brackish well water, having a desired solids content, i.e., generally between about 30-80% of solids, by weight (MgO base), and viscosity of approximately 50-1000 cps; average particle size varying from about 0.5-7 μm; particle size range of about < 0.1-30 μm, and specific surface area of approximately 5-25 m2 / g, is subjected to milling in number to produce a stabilized magnesium hydroxide slurry having specified characteristics such as Mg (OH) 2 sludge viscosity, as well as average particle size, particle size range and surface area of Mg (OH) 2 solids.

Wet milling, which can be carried out by a variety of processes and equipment, refers to a process in which the solid particles of magnesium hydroxide in the slurry are milled using energy developed by the particle-to-particle interactions, the interactions of media to particles, the interactions of particle to chamber of milling and the forces of cutting effect. The method of the present invention advantageously produces a stabilized sludge of magnesium hydroxide having specified characteristics that can be further processed by converting various magnesia-based products. The stabilized magnesium hydroxide sludge of the invention is characterized, in particular, by its controlled viscosity of Mg (OH) 2 mud, as well as by the controlled average particle size, the range of particle sizes controlled and the area of controlled surface (which is directly controlled based on the degree of particle size reduction) of the Mg (OH) solids. The stabilized magnesium hydroxide slurry of the invention has the advantages mentioned above as well as other advantages that will be apparent to those skilled in the art from the following more detailed description, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic showing the method for preparing a stabilized magnesium hydroxide sludge involving wet moles in a magnesium hydroxide starting sludge of the present invention. The means, the speed of the mill and the consumption can be controlled to provide a desirable product. Figure 2 is a graph showing the viscosity with respect to particle size for (a) unground magnesium hydroxide slurry and (b) the wet milled magnesium hydroxide slurry of example 1, showing the grinding to various particle sizes. Figures 3 and 4 are tables showing the percentage of cumulative mass with respect to the refiner for the wet milled muds of magnesium hydroxide of example 9. In the following description, similar parts are designated by like reference numerals through all the figures DETAILED DESCRIPTION OF THE INVENTION All patents, patent applications and bibliographies cited in this description are hereby incorporated by reference in their entirety.

As an additional aid to understand the invention, without being limited thereto, it is believed that the wet milling process of the invention, that is, where the magnesium hydroxide sludge is wet milled, progresses with respect to the conventional processes for making Mg (OH) 2 sludge. This method of the invention allows a faster, less complicated processing of Mg (OH) 2 mud. The process of the invention also progresses with respect to conventional processes for making Mg (OH) 2 and MgO products and, in particular, for making Mg (OH) 2 in the form of particles. The process of the invention allows the faster, less complicated production of Mg (OH) 2 in the form of particles. The method of the present invention for producing a stabilized magnesium hydroxide sludge using wet milling comprises passing a magnesium hydroxide sludge through a wet milling apparatus only once. The speed (dwell time) is controlled, the type of media and quality are selected and the speed of circulation of the media is controlled. All these variables have an impact on the degree of grinding of the Mg (OH) 2 particles in the stabilized magnesium hydroxide sludge. By controlling the process parameters of the wet milling process, a stabilized magnesium hydroxide slurry having specified characteristics such as a specified viscosity of Mg (OH) mud, specified average particle size, range of particle sizes can be produced. specified, distribution of specified particle sizes and a specified surface area of Mg (OH) 2 solids. The method of the invention thus allows the production of a stabilized sludge of magnesium hydroxide, as well as the products of Mg (OH) 2 and MgO, which has specified characteristics. Referring to Figure 1, the method of the invention is described below: 1. The washed mud of magnesium hydroxide or a) is fed directly to a wet mill 1 at a controlled rate for its reduction in particle size , or b) is inserted into a disk filter 2 to increase the percentage of sounds to more than about 60%. 2.- If the disc filter 2 is used, the discharge is directed to a putty 3 mill. 3.- The flow is recirculated inside the putty mill 3 through a Silverson mixer (East Longmeadow, MA). cutting effect, the cationic polymer is injected at the levels stated in the US patents Nos. 5,514,357 and 5,762,901, based on the chloride concentration of the solution. The discharge of the mastic mill is collected in a swell tank 5. 4. A pump 6 is used to extract the mud from the tan of swell 5 and the wet mill 1 is fed at a controlled speed that establishes the residence time in the wet mill 1. this speed can be altered to control the reduction in particle size. 5.- The media time (zirconium oxide, glass, steel, zirconium silicate, etc.), medium size (1 mm, 1.5 mm 2 mm, etc.), number of media (50%, 60%, 70%, etc. of the milling chamber filled) and the reduction speed of the mill media (600 RPM, 800 RPM, 1000 RPM, etc.) also determine the degree of particle size reduction and surface area increase, the ways Simpler to control the particle size is the consumption control and the control of the speed of recycling. 6.- The ground mud is collected in a storage tank 6. The ground mud is suitable as a stabilized sludge and to dry to Mg (OH) 2, in the form of particles calcined to MgO or calcined and concreted for the periclase solution . The different final applications require the control of particle size at varying levels. For example, stabilized sludge generally requires an average particle size of about 1-4.5 μm, dry Mg (OH) 2 (particulate) generally requires an average particle size of about 0.5-1 μm, 1.5-2.0 μm, where not ground to 5-8 μm, the high activity MgO generally requires an average particle size of about 0.7-1.0 Om or unground, the periclase compression enhancement of about <1 μm - 4 μm and BSG periclase enhancement of about < 1.5 μm.

The stabilized magnesium hydroxide sludge of the present invention comprises average particle sizes of Mg (OH) 2 solids not readily achieved by conventional methods, for example: 1) A slurry of magnesium hydroxide containing Mg (OH) 2 with average particle size of Mg (OH) 2 solids greater than 3 microns and less than 10 microns known from dolina, and brackish well water can be very easily milled to achieve a stabilized magnesium hydroxide sludge contains Mg (OH) 2 with an average particle size of less than 0.5-6 microns or as desired. The conditions of wet milling can be successfully altered to produce any desired average particle size that is smaller than the average starting particle size. 2) The reduction of the average particle size beyond 2 microns may result in excessively high viscosity. However, control of other variables such as surface area, chloride ion content and percentage of solids or the use of additives such as cationic polymer can counteract any negative effects. 3) Mg (OH) 2 can be successfully and economically produced in the form of particles with an average particle size of less than 1 miera by wet milling the magnesium hydroxide sludge and then by drying in addition to the flame retardant additives. , Mg (OH) 2 is used in the form of particles, for example, in plastics and rubber compounds, and as a filler, for example, in coatings of wire and cable, etc. 4) Wet milling of a stabilized magnesium hydroxide sludge to decrease the particle size of the Mg (OH) 2 particles before calcination to create MgO has multiple benefits, a benefit realized is that the approximate volumetric density of the Calcined powder can be increased or reduced depending on the required particle size distribution. Increasing the approximate volumetric density allows the addition of more product to trucks or rail cars, thus reducing shipping costs on a "per ton" basis. 5) The stabilized magnesium hydroxide sludge of the invention can be used to prepare slightly burned MgO (i.e., Chemical Grade Magnesia) - There are requests in which customers want magnesia of submicron particle size. This product is commonly produced by jet milling the MgO powder, which is energy intensive and very expensive. Wet grinding of Mg (OH) 2 sludge prior to calcination to the submicron size makes it possible to produce chemical grade submicron magnesia directly from a calcination furnace. 6) In the production of periclase (MgO burned very strongly), it is first calcined in magnesium hydroxide sludge of the invention to form MgO powder similar to that described above. Second, the MgO powder is compressed to form an almond-shaped agglomerator (raw agglomerates). These agglomerates are then fed to a higher feed furnace for a final heat treatment and production of high density MgO. It has been found that wet grinding of Mg (OH) 2 sludge before calcination to less than 4 microns improves the compression characteristics of the powder. The benefits include: a) greatly increasing the breaking strength of the raw agglomerate, b) the density of the crude agglomerate is higher, c) the costs to produce raw agglomerates are lower due to the higher production of agglomerated flights during the compression (less rupture), and d) the MgO powder can be calcined to a lesser degree, reducing operating costs, while still producing high quality raw agglomerates. 7) A significant increase in the specific volumetric gravity (GEV) of the baked agglomerates (periclase) is observed after high temperature heat treatment when the particulate mud is wet milled 1.5 microns. The GEV is one of the most important properties desired for the periclase used in refractory bricks. An increase in GEV results in a minimization of the brick failure. The voids during the heat treatment are thus eliminated by concretion. It is easier to eliminate smaller voids. Wet milling results in smaller voids between the particles in the compressed agglomerates. 8) Operations in rotary kilns that produce MgO from Mg (OH) 2 mud can be improved, using the wet grinding of a starting mud. You can get control of product size and enhanced GEV. In terms of heat treatment the rotary kiln produces MgO burned more intensely than the kiln and lighter than burned in the higher feed kilns. This can reduce operating costs. 9) The production of the stabilized sludge using wet milling requires only one step through the multi-step equipment with conventional methods, such as the use of a Gaulin or a Silverson. Both the Gaulin and the Silverson defroculate by means of cutting effect. By wet grinding, the Mg (OH) 2 particles are deflocculated and fractionated into smaller particle sizes. 10) The experimental data show that the freezing and thawing of the sludge of the invention have acceptable stability properties. It is a fact that the properties of the starting furnace of Mg (OH) 2 establish a large degree of the final properties of the products of Mg (OH) 2 and MgO produced therefrom. Wet milling is a tool that enables enhanced "on-demand processing" of the starting mud beyond conventional methods. Wet milling can make significant progress in product quality possible while at the same time reducing operating costs. The present invention will be further illustrated with the following non-limiting examples. The examples are illustrative and do not limit the claimed invention to the materials, conditions, process parameters and more particulars cited herein.

EXAMPLE 1 A starting magnesium hydroxide sludge "(98 HP)" was taken from a raw feed surge tank, indicated in Table 1 (below) for chemistry, particle size, specific surface area, percentage of solids and viscosity. This slurry contained 500 ppm Betz 1195 (cationic coagulant) and was deflocculated with a disc filter clays mill and a high-shear Silverson mixer before storage in the tank and wet milling. The typical process sequence in the stabilized production of magnesium hydroxide is similar to that set forth in the U.S. Patents. Nos. 5,514,357 and 5,762,901 and in the patent applications of E.U.A. Nos. 08 / 853,412 and 08 / 968,135, the entire contents of which are incorporated herein by reference. Alternatively, in this experiment, one step was completed with an LV-40 model, EMCO Zinger Mill (Epworth Mfg. Co. South Haven, Ml). The mill chamber was charged to 70% capacity (86,183) with zirconium oxide grinding media. The flow through the mill was controlled at 0.883-1.073 liters per second (l / s). A total of 62,458 liters of stabilized sludge was produced.

Several differences in the properties of the stabilized sludge from this experiment were noted with respect to the stabilized sludge prepared according to conventional procedures: 1) the apparent specific surface area increased after wet milling; and 2) the reduction of the particle size with wet grinding was 2 μm larger than with the conventional methods (the average particle size decreased by at least 2 microns with respect to 1 miera or less, the break was determined). the particles by sedimentation monitored by X-rays (Micromeritics Co., GA), where the sample is dispersed in liquid, the X-ray beams are radiated through the liquid, and as the particles settle, a measure of the particles settle so quickly). Similarities were also observed: 1) 7-day drain = 94.7%. The percentage of drainage is an adequate measure to assess the stability of a mud. This is determined based on the performance capability of a sample after a given period of sedimentation. As an example, a bottle with lid, with a high density polyethylene sample with a diameter of 13.34 cm in height by 5.08 cm in diameter, previously filled, obtained from Colé Parmer, with mud at its capacity, is filled, after a given period. of storage not stirred at room temperature, the lid is removed, a glass stirring rod is inserted at the bottom of the bottle and the end is rotated slowly one turn around the inner periphery of the bottle. The bottle is then weighed, inverted 180 ° C for a period of 15 seconds, reweighed and the percentage of drainage is calculated as follows:% drainage = (bottle weight filled-weight bottle left) x100 (bottle weight filled- bottle weight) The remaining solids are then probed in the bottle with a stir bar to determine if they are soft, sticky (eg, bubble gum) or hard. A sludge is considered to have "long-term stability" if it has a drainage percentage of at least 90% after 7 days at least 85% after 14 days and at least 80% after 28 days. It has also been surprisingly discovered that the Mg (OH) 2 stabilized sludge prepared according to the invention (as shown in Example 1) can be frozen and then thawed, while retaining its stability. This was demonstrated by taking a sample of frozen sludge, allowing thawing and determining stability as before. The 7-day drain results showed that the stability was 88% -92%, without sticky sedimentation. This is in contrast to the characteristics of conventional sludge that loses stability when frozen and thawed.

EXAMPLE 2 Referring to Table 2, different grades of Mg (OH) 2 sludge, produced from a doline / wellbore water reaction, were wet milled at the particle size ranges indicated therein as compared to muds not ground. Samples 3, 4, 7 and 8 were wet milled. In all cases, wet grinding to a finer degree resulted in more sticky material (higher compaction). The compaction test involves forming a cylindrical pellet with a die and a press. 5.5 grams of Mg (OH) 2 powder (MgO powder) are placed in a die with a diameter of 2.54 cm. A pellet is then formed at 175 kg / cm2 of load on a press. The pellet is removed from the die. The breaking strength is then determined with a load applied to the flat face of the pellet. A higher compaction value indicates that the flow properties of the powder are lower or alternatively, that the compaction properties are improved.

EXAMPLE 3 Referring to table 3, table 3 shows results of stabilized sludge production. The objective of the particle size was 3-4 μm, which was 1.5-2 μm less than the starting particle size of the sludge. The viscosity was improved with respect to the unground mud. The unground sludge was prepared using disc filter, addition of cationic coagulant and Silverson. The results indicate that the +100 mesh and +325 mesh particles (ie, 145 μm and 4 μm, respectively) were essentially removed.

EXAMPLE 4 Referring to Table 4, Table 4 shows results comparing the conventional procedure (ie, use of a Gaulin) for the production of stabilized sludge with the wet milling method. The results indicate the superior reduction of coarse agglomerates (of +100 mesh and +325 mesh), with wet grinding. Referring to table 5, table 5 shows additional results for particle size and distribution for stabilized sludge produced by means of wet milling. A 270 mesh (55 μm) sieve was added in this evaluation.

EXAMPLE 5 Referring to tables 6 and 7, tables 6 and 7 show results of an experiment to produce chemical grade MgO of high submicron reactivity from a wet milled Mg (OH) 2 sludge. The starting mud had an average particle size of 6.69 μm. The mud was milled at 1.00 μm. The mud was then burned with a vertical multi-hearth furnace (Herreshoff). The resulting MgO had a surface area of about 45 m2 / g and an average particle size of less than 1 μm. Typical results with the unground product provide the average particle size in excess of 3 μm in the same activity (surface area = 45 m2 / g).

EXAMPLE 6 Referring to tables 8 and 9, tables 8 and 9 show results of an experiment to enhance the compression characteristics of the MgO powder by wet milling the starting Mg (OH) 2 before calcination at 1.56 μm. The results were compared with unground Mg (OH) 2. Both starting sludges were calcined identically calcined, as indicated by the activity test and the surface area. The wet milled sample showed enhanced compaction resistance, 7.634 kg / cm2 with respect to 1.828 kg / cm2 for the unground sample.

EXAMPLE 7 Referring to table 10, table 10 shows that wet milling breaks the particles. This conclusion is derived based on the fact that the particle size is reduced and the surface area is increased.

EXAMPLE 8 Referring to Tables 11 and 12, Tables 11 and 12 show another example of MgO production of high submicron reactivity wet milling of Mg (OH) 2 sludge prior to calcination. A non-milled mud was used as a comparison. Tables 11 and 12 also show a significant improvement in the compression characteristics of the MgO produced from the wet milled mud, which is evidenced in the higher compaction values of MgO with respect to the unground. This is in contrast to the existing production of the Mg (OH) 2 sludge, in which, only defocusing occurs, ie the apparent particle size decreases, but the surface area does not change.

EXAMPLE 9 Tables 13 and 14 and Figures 3 and 4 show, respectively, particle size analysis of submicron wet milled Mg (OH) 2 ..}. Although the present invention has been fully described through the examples with reference to the accompanying drawings, it should be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications deviate from the scope of the present invention, they should be construed as included therein.

TABLE 1 Analysis of sludge 98HP milled from tank 100 to tank 210 B Sedimentation test * Particles of magnesium hydroxide starting mud before wet milling. The starting mud contained 50 ppm of Betz 1195 and was desclofuló with a clay mill with disk filter and Silverson mixing of high cutting effect.

TABLE 2 Dry hydroxide compaction ^ 1 TABLE 3 Results of FloMq production cycles wet milled (98 HP) CO TABLE 4 Comparisons of Quran for FloMaq wet milled and treated with Gaulin fifteen TABLE 5 Screening analysis for FloMaq 98HP wet milled or TABLE 6 Sludge 98 Lib wet milled MqO lightly burned, produced from a wet milled mud J Properties of the mud before and after wet grinding TABLE 7 Calcined MgO results (calcined after grinding) l t TABLE 8 Warm wet milled mud MgO powder MgO powder Sample Result of the activity test Resistance to compaction 97LB unground 21.4 seconds 1,828 kg / cm2 97LB wet grind 21.4 seconds 4,640 kg / cm³ at 1.56 μm OJ J Conclusion: Compression is greatly enhanced with wet grinding TABLE 9 Sample Surface area of calcined MgO * Particle size of calcined MgO * 97LB unground 19.6 m2 / g 3.32 μm 97LB wet milled 19.8 m2 / g 0.51 μm to 1.56μm Conclusion: The smaller particle size of Mg (OH) 2 results in smaller particle size of the MgO at the same level of calcination. This is the reason why the resistance to compaction increased. J 4 ^. * Calcinated after being ground TABLE 10 Properties of wet milled mud Average particle size% < 2μm surface area Mud 98HP (unground) 5.22 microns 26.4% 12.0 m2 / g (Wet grinding) 0.79 microns 67.4% 19.0 m2 / g Mud 97LB (unground) 6.74 μm 10.0% 14.5 m2 / g Wet grinding 1.56 μm 54.6% 21.6 m2 / g OJ L? Conclusion: The particles in the wet mill can be broken. The test is the increase experienced with the surface area.

TABLE 11 Liqhtbutn 98 HP sludge calcination - unground with respect to wet milling J n Conclusion: Submicron MgO with relatively high surface area can be produced by grinding at the starting Mg (OH) 2 humerus to submicron levels. The compaction values are also substantially realized.

TABLE 12 BSG Periclase Enhancement Typical mud (unground) with respect to wet milled mud OJ ^ 1 All samples of wet milled mud had average diameters of less than 1.5 μm.

TABLE 13 98HP 8a 6REF SV-4 Sample identification: 98HP 8a 6REP SV-4 Unit number: 1 Sample type: Hydroxide Start 13:50:57 Type of liquid: Sedisperse a-11 Report 14:28:15 Total cycle time: 0:37:06 Density of the sample: 2.3800 g / cm3 Density of liquid: 0.7450 g / cm3 Temp. of analysis: Type of cycle: High speed Liquid viscosity: 05.0 Degrees 1.1208 cp Starting diameter 100.00 μm No. of Reynolds: 0.53 Final diameter: 0.18 μm Full scale mass% 100 TABLE 14 98HP SV-4 3GPH 1 PASS Sedigraph 5100 02.08 Unit number: 1 Sample number in the directory: 98-DRX-2/4 Start 11: 42: 23 Sample number in the directory: 98HP Sv- 8GPH Report 12: 35:16 1 PASS Total cycle time: 0:52:44 Density of the sample: Type of sample: Hydroxide 2.3800 g / cm3 Type of liquid: Sedisperse a-11 Liquid density: 0.7450 g / cm3 Temp. of analysis: Type of cycle: High speed Liquid viscosity: 05.0 Degrees 1.1204 cp Starting diameter 100.00 μm Reynolds number: 0.53 Final diameter: 0.18 μm Full scale mass% 100 Vise. 220 CPS

Claims (25)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for preparing a stabilized magnesium hydroxide sludge, comprising wet milling a magnesium hydroxide slurry, characterized in that said wet milling reduces the average particle size of said magnesium hydroxide slurry.

2. The method according to claim 1, further characterized in that the parameters are controlled to control the properties of said stabilized magnesium hydroxide sludge.

3. The method according to claim 2, further characterized in that said properties include an average particle size of the magnesium hydroxide solids in said magnesium hydroxide slurry.

4. The method according to claim 1, further characterized in that said wet grinding reduces the average particle size of the Mg (OH) 2 solids in said magnesium hydroxide starting slurry to less than about 4 microns.

5. A stabilized sludge of magnesium hydroxide, further characterized in that said stabilized magnesium hydroxide slurry is prepared by wet grinding a magnesium hydroxide sludge, because said wet milling reduces the average particle size of said sludge. magnesium hydroxide.

6. The stabilized magnesium hydroxide slurry according to claim 5, further characterized in that said stabilized magnesium hydroxide slurry has an average particle size of less than about 4 microns.

7. A method for preparing a dry Mg (OH) 2 powder, comprising: wet mole a magnesium hydroxide starting mud, further characterized in that said wet grinding reduces the average particle size of said hydroxide slurry of magnesium; and drying said wet milled magnesium hydroxide slurry to form said dry Mg (OH) 2 powder, wherein said dried Mg (OH) 2 powder has an average particle size of less than about 2 microns.

8. A method for preparing a dry MgO powder, comprising: wet mole a magnesium hydroxide starting mud, further characterized in that said wet grinding reduces the average particle size of said magnesium hydroxide slurry; drying said wet milled magnesium hydroxide slurry to form said dry powder of Mg (OH) 2; and calcining said dry Mg (OH) 2 powder to form said dry MgO powder, wherein said dried MgO powder has an average particle size of less than about 3 microns.

9. The method according to claim 8, further characterized in that said wet milling of said starting magnesium hydroxide sludge results in an increase in the approximate volumetric density of said dry MgO powder.

10. The method according to claim 8, further characterized in that said dry MgO powder is used to produce slightly burned MgO.

11. The method according to claim 8, further characterized in that said dry MgO powder is used to produce very intensely burned MgO.

12. The method according to claim 11, further characterized in that said MgO is made very intensely burned by compressing MgO powder forming agglomerates and heat treated to produce periclase.

13. The method according to claim 12, further characterized in that said wet milling of said starting magnesium hydroxide sludge results in an increase in the volumetric specific gravity of said periclase.

14. The method according to claim 12, further characterized in that said wet grinding said magnesium hydroxide starting sludge results in an increase in the rupture resistance of said periclase.

15. A method for producing a stabilized sludge of magnesium hydroxide, comprising: defloclulating a starting sludge of magnesium hydroxide; and wet grinding said deflocculated magnesium hydroxide slurry, wherein said wet milling reduces the average particle size of said magnesium hydroxide slurry.

16. The method according to claim 15, further characterized in that said stabilized magnesium hydroxide sludge comprises Mg (OH) 2 particles having an average particle size of less than about 12.0 and 15.0 m2 / g.

17. The method according to claim 15, further characterized in that said stabilized magnesium hydroxide slurry having an average particle size of less than about 4 microns.

18. The method according to claim 15, further characterized in that said stabilized magnesium hydroxide slurry has a solids content between about 50% and about 65%.

19. The method according to claim 15, further characterized in that said stabilized magnesium hydroxide sludge comprises between about 25% and 45% of Mg (OH) 2 particles of less than 2 microns in size.

20. The method according to claim 15, further characterized in that said stabilized magnesium hydroxide sludge comprises between about 15% and 35% of Mg (OH) 2 particles of less than 1 miter in size.

21. - The method according to claim 15, further characterized in that said stabilized magnesium hydroxide sludge comprises Mg (OH) 2 particles having an average size of between about 2.5 and 5 microns.

22. A stabilized sludge of magnesium hydroxide prepared according to the method of claim 16, further characterized in that said stabilized magnesium hydroxide slurry is able to maintain its stability upon being frozen and thawed.

23. The method according to claim 1, further characterized in that said magnesium hydroxide starting sludge comprises Mg (OH) 2 particles having an average particle size between about 4 microns and 8 microns.

24. A method for controlling the particle size of a magnesium hydroxide sludge, which comprises controlling the wet milling of a magnesium hydroxide particle slurry, further characterized in that said wet milling reduces the average particle size of the slurry. said slurry of magnesium hydroxide.

25. A method for preparing a dry powder of Mg (OH) 2l comprising: wet milling a starting mud of magnesium hydroxide, further characterized in that said wet milling reduces the average particle size of said hydroxide slurry. magnesium, and drying said magnesium hydroxide slurry wet-milled to form a dry powder of Mg (OH) 2. SUMMARY SHEET OF THE INVENTION A method for producing a stabilized magnesium hydroxide sludge which involves wet grinding a magnesium hydroxide starting sludge; a stabilized magnesium hydroxide sludge produced by the magnesia-based method and products produced from the wet-milled magnesium hydroxide sludge is also exposed; the washed magnesium hydroxide sludge is either directly fed to a wet mill at a controlled rate for size reduction, or it is introduced to a disk filter to increase the percentage of solids to more than about 60%; if the disc filter is used, the discharge is directed to a putty mill; the flow is recirculated inside the mill of putties by means of a mixer of high cutting effect; the discharge of the putty mill is collected in a swell tank, a pump is used to extract the mud from the swell tank and it is fed to the wet mill at a controlled speed, a speed that establishes the time of stay in the wet mill; you can alter this speed to control the reduction in particle size; the ground mud is collected in the storage tank.