Active magnesium oxide and preparation method thereof

Abstract

The invention discloses an active magnesium oxide and a preparation method thereof, and relates to the technical field of magnesium oxide preparation. The method comprises the following steps: calcining and dissociating the first magnesium ore, strengthening leaching and carbonization separation to obtain calcium carbonate and active low-calcium magnesium-rich liquid; calcining and dissociating the second magnesium ore and mechanically grinding to obtain fine material, or directly mechanically grinding the second magnesium ore to obtain fine material; pumping the active low-calcium magnesium-rich liquid into a hydration activation tank, stirring and then conveying the fine material to the hydration activation tank, the active low-calcium magnesium-rich liquid and the fine material undergo hydration reaction and form a composite magnesium salt; drying and breaking up the composite magnesium salt and conveying it to a calcining furnace, calcining, cooling and spiral discharging to obtain active magnesium oxide. The magnesium oxide prepared by the method has moderate density, rich active sites, good dispersibility, excellent adsorption, hydration and ionization properties, and has significant effects and cost advantages as an alkaline precipitant, which is conducive to the market promotion and application of high-activity magnesium oxide products in the fields of environmental protection and metallurgy.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium oxide preparation, and in particular to active magnesium oxide and a preparation method thereof. Background Art

[0002] Active magnesium oxide is a key raw material for the preparation of high-precision inorganic materials, electronic components, high-quality glass and efficient adsorbents for harmful gases. It can also be used as a vulcanization accelerator in the rubber industry, an environmentally friendly agent for heavy metal wastewater treatment, and an efficient alkaline precipitant in the metallurgical field. The diverse application potential of active magnesium oxide is deeply affected by its activity value. The key indicators for characterizing its activity include iodine absorption value, citric acid value and hydration degree, each of which independently reflects its unique physical and chemical properties.

[0003] Specifically, the iodine absorption value is directly related to the specific surface area of ​​magnesium oxide particles, which characterizes its adsorption capacity. The higher the iodine absorption value, the stronger the adsorption efficiency of magnesium oxide. The citric acid value reveals the reaction efficiency of magnesium oxide with acidic media. The lower the citric acid value, the faster the reaction rate. The degree of hydration measures the activity of magnesium oxide with water and is a quantitative measure of the affinity of magnesium oxide with water. The higher the degree of hydration, the higher the hydration activity, which can promote the generation of hydroxide ions. However, the active magnesium oxide currently sold on the market often focuses on the optimization of a single active indicator. For example, the rubber industry prefers products with high iodine absorption values. The environmental protection and metallurgical fields are in urgent need of composite products that comprehensively optimize the adsorption, hydration and ionization properties, that is, simultaneously pursuing a balance between high iodine absorption value, low citric acid value and high hydration degree to achieve excellent application results.

[0004] At present, the production technology of active magnesium oxide is dominated by the carbon ammonium method, carbonization method and light calcination method. These processes are all based on the intermediate of light composite magnesium salt, and are finally formed after the calcination step. However, the existing technical system still faces challenges in practical application: the carbon ammonium method has a cumbersome process and the chlorine content of the product is relatively high. Although the low-temperature calcination process retains the activity, it sacrifices the purity of the product; the light calcination method has suitable product purity and density, but the activity is insufficient, and it is difficult to meet the application scenarios with high activity requirements; in contrast, the carbonization method is known for its high output quality. Through a refined process flow, magnesium oxide with high hydration and purity can be obtained, which is particularly suitable for use as an alkaline precipitant. However, the low bulk density characteristics of the magnesium oxide product obtained by the carbonization method invisibly increase the production cost and logistics and transportation burden.

[0005] Therefore, providing a method for preparing magnesium oxide with high activity and high bulk density has become a technical problem to be solved urgently by those skilled in the art. Summary of the invention

[0006] The invention discloses an active magnesium oxide and a preparation method thereof, so as to solve the technical problem that the preparation method of active magnesium oxide in the related art is difficult to take into account both the activity and the bulk density of magnesium oxide.

[0007] In order to solve the above problems, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a method for preparing active magnesium oxide.

[0009] The method for preparing active magnesium oxide of the present invention comprises the following steps:

[0010] S100: calcining and dissociating the first magnesium ore, strengthening leaching and carbonizing and separating the ore to obtain calcium carbonate and active low-calcium magnesium-rich liquid;

[0011] S200: calcining and dissociating the second magnesium ore and mechanically grinding the second magnesium ore to obtain a fine material, or directly mechanically grinding the second magnesium ore to obtain a fine material;

[0012] S300: pumping the active low-calcium magnesium-rich liquid into the hydration activation tank, starting the stirring, and then conveying the fine material to the hydration activation tank, the active low-calcium magnesium-rich liquid and the fine material undergo hydration reaction to form a composite magnesium salt;

[0013] S400: The composite magnesium salt is dried and broken up and then transported to a calcining furnace, where it is calcined, cooled and spirally discharged to obtain active magnesium oxide.

[0014] According to an optional embodiment, in step S300, the mass ratio of the fine material to the active low-calcium and magnesium-rich liquid is 1:0.6-5.

[0015] According to an optional embodiment, in step S300, the temperature for the hydration reaction between the fine material and the active low-calcium magnesium-rich solution is 40-70° C. and the time is 0.5-24 hours.

[0016] According to an optional embodiment, in step S100, obtaining calcium carbonate and active low-calcium magnesium-rich solution comprises the following steps:

[0017] S110, calcining the first magnesium ore in a high temperature furnace to dissociate it into calcined white;

[0018] S120, leaching the calcined white and digestion water intensified, and then filtering to remove slag, to obtain digestion liquid;

[0019] S130, pumping the digestion liquid into an enhanced gas-liquid reactor and adding an activator, and introducing carbon dioxide to carbonize the digestion liquid;

[0020] S140, separating the carbonized liquid into calcium carbonate and active low-calcium and magnesium-rich liquid through solid-liquid separation.

[0021] According to an optional embodiment, in step S130, the activator is one or more of oxalic acid, sodium phosphate, and magnesium polycarboxylate, and the mass ratio of oxalic acid, sodium phosphate, and magnesium polycarboxylate is: 1-15:0-8:0-1;

[0022] The dosage of the activator is 0.05% to 5.0% of the mass of magnesium oxide in the digestive solution, and the activator is prepared as a solution with a mass concentration of 10% and added to the digestive solution.

[0023] According to an optional embodiment, the activator is oxalic acid, sodium phosphate and magnesium polycarboxylate, and the mass ratio of oxalic acid, sodium phosphate and magnesium polycarboxylate is 6~12:5:1, and the dosage of the activator is 0.5%~2.0% of the mass of magnesium oxide in the digestive juice.

[0024] According to an optional embodiment, in step S110, the first magnesium ore is one of dolomite, magnesite, and by-product magnesium salt, and the calcination dissociation temperature is 800-1200° C., and the calcination time is 0.1-240 min.

[0025] In step S120, the solid-liquid ratio of the enhanced leaching is 1g:15-50ml, the temperature is 30-90°C,

[0026] In step S130, the carbonization endpoint pH is 7.5-10.0.

[0027] According to an optional embodiment, in step S200, the second magnesium ore is one or more of magnesite, hydromagnesite, brucite, magnesium carbonate, and magnesium hydroxide, and the calcination dissociation temperature of the second magnesium ore is 600-900° C., and the time is 0.1-240 min.

[0028] Or the second magnesium ore is light-burned magnesium oxide, and the light-burned magnesium oxide is directly mechanically finely ground to obtain fine material;

[0029] The particle size of the fine material is 1-45 μm.

[0030] According to an optional embodiment, in step S400, the drying temperature is 120-250° C.; the calcination temperature is 500-800° C., and the residence time is 0.1-120 min.

[0031] A second aspect of the present invention provides an activated magnesium oxide.

[0032] The active magnesium oxide prepared by the method for preparing active magnesium oxide according to any one of the technical solutions of the present invention has a bulk density greater than 0.5 g / cm 3 , with a specific surface area higher than 50m 2 / g, hydration degree higher than 80%, citric acid value lower than 15s, and iodine absorption value higher than 80mg / g.

[0033] The technical solution adopted by the present invention can achieve the following beneficial effects:

[0034] The preparation method of active magnesium oxide of the present invention uses the first magnesium ore and the second magnesium ore as raw materials, couples the light calcination method and the carbonization method, uses the magnesium bicarbonate solution, an intermediate product of the magnesium oxide production process of the carbonization method, as a hydrate, rapidly hydrates the light calcined powder into magnesium hydroxide, and generates multiple chemical reactions in the exothermic process to form magnesium carbonate, basic magnesium carbonate and a composite magnesium salt of magnesium hydroxide, and the bulk density of the magnesium oxide precursor material formed by hydration at a low liquid-solid ratio is significantly increased. The magnesium oxide precursor can be used to obtain a bulk density greater than 0.5 g / cm 3 , with a specific surface area higher than 50m 2 / g, hydration degree higher than 80%, citric acid value lower than 15s, and iodine absorption value higher than 80mg / g of magnesium oxide material, which solves the problem of difficulty in taking into account both the activity and bulk density of magnesium oxide in related technologies.

[0035] In addition, the preferred technical solution of the present invention also has the following beneficial effects:

[0036] The preparation method of active magnesium oxide of the present invention, the activator (one or more of oxalic acid, sodium phosphate, and magnesium polycarboxylate) added during the carbonization process can also accelerate the hydration process of magnesium oxide, make the crystals of the hydration product thinner, and enhance the dispersibility, thereby improving the hydration efficiency and increasing the reaction activity, while improving the dispersibility of the magnesium oxide precursor product, reducing the product size, and significantly increasing the roughness of the product surface, guiding the generation of hollow spherical magnesium oxide precursor materials. In addition, during the calcination process of the composite magnesium salt, the combination product of oxalic acid and sodium phosphate with magnesium will decompose into magnesium oxide, carbon dioxide and water, which increases the active sites on the surface of the powder without affecting the quality of the product, and improves the reaction activity of the magnesium oxide product.

[0037] The high-activity magnesium oxide prepared by the preparation method of the active magnesium oxide of the present invention has moderate density, rich active sites, good dispersibility, excellent iodine absorption activity, citric acid reaction activity and hydration degree, and has excellent adsorption, hydration and ionization properties. It has significant effects and cost advantages as an alkaline precipitant, which is conducive to the market promotion and application of high-activity magnesium oxide products in the fields of environmental protection and metallurgy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 It is a process flow chart for preparing active magnesium oxide according to an embodiment of the present application. DETAILED DESCRIPTION

[0040] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0041] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0042] Figure 1 The process flow chart of preparing highly active magnesium oxide in this application is shown. Figure 1 As shown, the preparation method of active magnesium oxide comprises the following steps:

[0043] S100: Calcine carbonate and active low-calcium magnesium-rich solution are obtained by calcining and dissociating the first magnesium ore, strengthening leaching and carbonizing and separating the first magnesium ore. Preferably, the calcium ion concentration in the active low-calcium magnesium-rich solution is lower than 1 mmol / L, and the magnesium ion concentration is higher than 0.15 mol / L.

[0044] S200: calcining and dissociating the second magnesium ore and mechanically grinding the second magnesium ore to obtain fine material, or directly mechanically grinding the second magnesium ore to obtain fine material.

[0045] S300: Pump the active low-calcium magnesium-rich liquid into the hydration activation tank, start stirring, and then transport the fine material to the hydration activation tank. The active low-calcium magnesium-rich liquid reacts with the fine material to form a composite magnesium salt.

[0046] S400: The composite magnesium salt is dried and broken up and then transported to a calcining furnace, where it is calcined, cooled and spirally discharged to obtain active magnesium oxide.

[0047] In some embodiments, in steps S100 and S200, the first magnesium ore and the second magnesium ore are calcined and dissociated in a high-temperature furnace. The high-temperature furnace may be a roller kiln, a suspension kiln, a rotary kiln, a boiling kiln or a ring kiln. Exemplarily, the high-temperature furnace is indirectly heated by gas calcination, and the carbon dioxide flue gas generated by gas oxidation and material decomposition can be recycled to the carbonization process of step S100 through plate heat exchange and purification compression, and the waste heat generated by the heat exchange of carbon dioxide flue gas can be supplied to the drying system of step S400, thereby achieving full utilization of heat.

[0048] In some embodiments, in step S100, obtaining calcium carbonate and active low-calcium magnesium-rich solution comprises the following steps:

[0049] S110, calcining the first magnesium ore in a high temperature furnace to dissociate it into calcined white.

[0050] Exemplarily, the first magnesium ore is one of dolomite, magnesite, and by-product magnesium salt. By-product magnesium salt is an inorganic salt solid such as magnesium carbonate and magnesium hydroxide produced by an industrial production enterprise. Exemplarily, the size of the first magnesium ore is less than 50 mm, the calcination dissociation temperature is 800-1200° C., and the calcination time is 0.1-240 min.

[0051] S120, the calcined white and the digestion water are subjected to enhanced leaching and then micro-filtered to remove the residue to obtain the digestion solution.

[0052] Exemplarily, the solid-liquid ratio of the enhanced leaching is 1 g: 15-50 ml, and the temperature is 30-90°C.

[0053] S130, pumping the digestion liquid into the enhanced gas-liquid reactor and adding an activator, and introducing carbon dioxide to carbonize to obtain a carbonized liquid.

[0054] Exemplarily, the carbonization endpoint pH is 7.5-10.0.

[0055] Exemplarily, the carbonization process is a one-stage carbonization process or a multi-stage carbonization process.

[0056] Exemplarily, the activator is one or more of oxalic acid, sodium phosphate, and magnesium polycarboxylate. The mass ratio of oxalic acid, sodium phosphate, and magnesium polycarboxylate is: 1~15:0~8:0~1. The dosage of the activator is 0.05%~5.0% of the mass of magnesium oxide in the digestive solution. The activator is prepared as a solution with a mass concentration of 10% and added to the digestive solution. Preferably, the activator is oxalic acid, sodium phosphate, and magnesium polycarboxylate, and the mass ratio of oxalic acid, sodium phosphate, and magnesium polycarboxylate is: 6~12:5:1, and the dosage of the activator is 0.5%~2.0% of the mass of magnesium oxide in the digestive solution.

[0057] S140, separating the carbonized liquid into calcium carbonate and active low-calcium and magnesium-rich liquid through solid-liquid separation.

[0058] The main reaction equation involved in step S100 is as follows:

[0059] The first magnesium ore is calcined and dissociated: MgCO3+CaCO3=MgO+CaO+2CO2↑.

[0060] Calcined white enhanced leaching: MgO+CaO+2H2O=Mg(OH)2+Ca(OH)2.

[0061] Carbonization separation of digestive fluid: Mg(OH)2+Ca(OH)2+3CO2=Mg(HCO3)2+CaCO3↓+H2O.

[0062] In some embodiments, in step S200, the second magnesium ore is one or more of magnesite, hydromagnesite, brucite, magnesium carbonate, and magnesium hydroxide, the calcination and dissociation temperature of the second magnesium ore is 600-900°C, the time is 0.1-240min, and the second magnesium ore is calcined and dissociated and then mechanically finely ground to obtain calcined fine material. Exemplarily, the relevant indicators of the calcined fine material are preferably a particle size ≤45μm, a purity ≥95%, and a citric acid value ≤30s.

[0063] Alternatively, the second magnesium ore is light-burned magnesium oxide, and the light-burned magnesium oxide does not need to be calcined and dissociated, and the light-burned magnesium oxide is directly mechanically finely ground to obtain fine material. Exemplarily, the obtained fine material has a particle size of 1 to 45 μm.

[0064] Exemplarily, the mechanical fine grinding equipment preferably adopts a vertical mill, a jet mill or a Raymond mill.

[0065] The main reaction equation involved in step S200 is as follows:

[0066] MgCO3=MgO+CO2↑ and / or Mg(OH)2=MgO+H2O.

[0067] In some embodiments, in step S300, the mass ratio of the fine material to the active low calcium magnesium-rich solution is 1: 0.6-5. The temperature for the hydration reaction of the fine material and the active low calcium magnesium-rich solution is 40-70° C., and the time is 0.5-24 hours.

[0068] The products of the hydration reaction between the fine material and the active low-calcium magnesium-rich liquid are mainly composite magnesium salts containing magnesium carbonate, basic magnesium carbonate and magnesium hydroxide. The main reaction equations during the hydration reaction are as follows:

[0069] Fine material hydration: MgO+H2O=Mg(OH)2.

[0070] Synergistic Activation:

[0071] 2Mg(HCO3)2+3Mg(OH)2=4MgCO3·Mg(OH)2·4H2O;

[0072] Mg(HCO3)2+Mg(OH)2=2MgCO3+2H2O.

[0073] From the above reaction process, it can be seen that the hydration product of the fine material directly participates in the decomposition reaction of magnesium bicarbonate, promotes the formation of magnesium carbonate and basic magnesium carbonate, and is beneficial to improving the activity of the calcined material obtained from magnesium carbonate and basic magnesium carbonate.

[0074] In some embodiments, in step S400, the composite magnesium salt is flash dried at a flash drying temperature of 120-250° C., preferably 120-180° C. The low-temperature calcining furnace used for the composite magnesium salt is a rotary kiln, a suspension kiln or a boiling kiln, the calcining temperature is 500-800° C., and the residence time is 0.1-120 min.

[0075] The main reaction equations during calcination are as follows:

[0076] 4MgCO3·Mg(OH)2·4H2O=5MgO+5H2O+4CO2↑;

[0077] MgCO3=MgO+CO2↑;

[0078] Mg(OH)2=MgO+H2O.

[0079] For the sake of clarity, the active magnesium oxide and the preparation method thereof provided by the present application are described in detail below through specific examples.

[0080] Example 1

[0081] The method for preparing active magnesium oxide in this embodiment comprises the following steps:

[0082] S100: calcining dolomite with a particle size of 30-50 mm in a roller kiln at 1100°C for 3 hours to obtain calcined white;

[0083] The calcined white is conveyed to the digestion tank by a belt, and digestion water is added at a solid-liquid ratio of 1g:20ml at 60°C, and a mixed solution is obtained after leaching for 60 minutes. The mixed solution is filtered through a drum microfilter to remove large particles of impurities that cannot be digested, and then a digestion solution is obtained;

[0084] The digestion liquid is cooled to 30°C by a water-cooling jacket and then pumped into an enhanced gas-liquid reactor, carbon dioxide is introduced to carry out a carbonization reaction until the end point pH is 7.6, and a diaphragm filter press is used to separate the carbonized liquid into solid and liquid to obtain calcium carbonate and active low-calcium magnesium-rich liquid;

[0085] The active low-calcium magnesium-rich liquid is pumped into the next-stage enhanced gas-liquid reactor, an activator is added and carbon dioxide is introduced to carbonize to a pH of 8.0. A diaphragm filter press is used to separate the carbonized liquid into solid-liquid separation to obtain magnesium-rich slag and active low-calcium magnesium-rich liquid. The magnesium-rich slag returns to the digestion section, and the active low-calcium magnesium-rich liquid enters the cache stirring tank.

[0086] In this embodiment, the mass of the activator added to the enhanced gas-liquid reactor is 0.05% of the total mass of magnesium oxide in the digestive liquid. The activator is a 10% solution prepared by mixing oxalic acid, sodium phosphate and magnesium polycarboxylate in a mass ratio of 12:5:1.

[0087] S200: In a fluidized bed kiln at 700°C, calcining magnesia for 45 minutes to obtain calcined magnesium oxide powder, and then grinding the calcined magnesium oxide powder mechanically with a Raymond mill to obtain fine material with a particle size of less than 45 μm.

[0088] S300: Pump the active low calcium magnesium-rich liquid into the hydration activation tank, and transport the fine material to the hydration activation tank under stirring. The active low calcium magnesium-rich liquid and the fine material undergo hydration reaction and form a composite magnesium salt. The hydration reaction time is 8 hours, and the hydration reaction temperature is 60°C. In the specific implementation, the fine material is transported from the buffer bin at the bottom of the Raymond mill to the hydration activation tank 10 cm from the top through a belt. The mass ratio of the fine material to the active low calcium magnesium-rich liquid is 1:1.5.

[0089] S400: The composite magnesium salt is conveyed to the inside of the flash dryer through a spiral feeder, falls to the rotating blade and is instantly broken into fine particles, and quickly forms dry powder under hot air drying at 220°C, and is then conveyed to the calcining furnace under negative pressure. In specific implementation, the induced draft fan is connected after the bag filter, the dry powder is collected by the bag and shaken off by pulses and air hammers, and enters the spiral feed port of the calcining furnace through the discharge valve. The dried composite magnesium salt is calcined in a rotary calcining furnace at a temperature of 650°C for 40 minutes, and the composite magnesium salt gradually releases water and carbon dioxide to obtain a highly active magnesium oxide product.

[0090] Example 2

[0091] The method for preparing active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 0.5% of the total mass of magnesium oxide in the digestive liquid.

[0092] Example 3

[0093] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2.0% of the total mass of magnesium oxide in the digestive liquid.

[0094] Example 4

[0095] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 5.0% of the total mass of magnesium oxide in the digestion liquid.

[0096] Comparative Example 1

[0097] The preparation method of active magnesium oxide in this comparative example is different from that in Example 1 in that no activator is added to the enhanced gas-liquid reactor.

[0098] The activity indexes of the highly active magnesium oxide obtained in Examples 1 to 4 and Comparative Example 1 were tested, and the test results are shown in Table 1 below.

[0099] The bulk density is determined by the method of "Determination of bulk density in inorganic chemical products" GB / T 23771-2009.

[0100] The specific surface area is determined by the determination method of “Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method” GB / T 19587-2004.

[0101] The iodine absorption value and citric acid value are determined using the determination method of "Industrial Active Light Magnesium Oxide" HG / T 3928-2012.

[0102] The hydration degree is determined by the method of "Chemical Activity of Light-burned Magnesium Oxide" YB / T 4019-2006.

[0103] Table 1 Activity test results of magnesium oxide obtained in Examples 1 to 4 and Comparative Example 1

[0104]

[0105] It can be seen from Table 1 above that the bulk density of the activated magnesium oxide prepared in Examples 1 to 4 is greater than 0.5 g / cm 3 , with a specific surface area higher than 50m 2 / g, hydration degree higher than 80%, citric acid value lower than 15s, iodine absorption value higher than 80mg / g. And it can be seen from Table 1 that adding an appropriate amount of activator can also help to increase the specific surface area, iodine absorption value and hydration degree of magnesium oxide, and also help to reduce the citric acid value of magnesium oxide. In addition, it can be seen from Table 1 that the addition of activator slightly reduces the bulk density of magnesium oxide, but it can still be maintained at 0.5g / cm 3 above.

[0106] Example 5

[0107] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the calcination temperature in step S400 is 500°C.

[0108] Example 6

[0109] The method for preparing active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the calcination temperature in step S400 is 600°C.

[0110] Example 7

[0111] The method for preparing active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the calcination temperature in step S400 is 700°C.

[0112] Example 8

[0113] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the calcination temperature in step S400 is 800°C.

[0114] The activity indexes of the highly active magnesium oxide prepared in Examples 3 and 5 to 8 were tested, and the test results are shown in Table 2. The detection method is the same as above.

[0115] Table 2 Activity test results of magnesium oxide obtained in Example 3 and Example 5 to 8

[0116]

[0117] It can be seen from Table 2 that the bulk density of the activated magnesium oxide prepared in Examples 3 and 5 to 8 is greater than 0.5 g / cm 3 , with a specific surface area higher than 50m 2 / g, hydration degree is higher than 80%, citric acid value is lower than 15s, and iodine absorption value is higher than 80mg / g. And it can be seen from Table 2 that the increase of calcination temperature helps to increase the bulk density of magnesium oxide. In addition, it can be seen from Table 2 that the increase of calcination temperature will affect the activity of magnesium oxide, specifically, it can reduce the specific surface area and iodine absorption value of magnesium oxide. At about 600℃, the citric acid value is the lowest, and at about 650℃, the hydration degree is the highest.

[0118] Example 9

[0119] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the mass ratio of the fine material to the active low-calcium magnesium-rich liquid in step S300 is 1:0.6.

[0120] Example 10

[0121] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the mass ratio of the fine material to the active low-calcium magnesium-rich liquid in step S300 is 1:2.

[0122] Embodiment 11

[0123] The preparation method of active magnesium oxide in this embodiment is different from that in Example 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the mass ratio of the fine material to the active low-calcium magnesium-rich liquid in step S300 is 1:3.5.

[0124] Example 12

[0125] The method for preparing active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the mass ratio of the fine material to the active low-calcium magnesium-rich liquid in step S300 is 1:5.

[0126] Comparative Example 2

[0127] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the mass ratio of the fine material to the active low-calcium magnesium-rich liquid in step S300 is 1:0.3.

[0128] Comparative Example 3

[0129] The preparation method of active magnesium oxide in this embodiment is different from that in Embodiment 1 in that the mass of the activator added to the enhanced gas-liquid reactor is 2% of the total mass of magnesium oxide in the digestion liquid, and the mass ratio of the fine material to the active low-calcium magnesium-rich liquid in step S300 is 1:6.

[0130] The activity indexes of the highly active magnesium oxide prepared in Example 3, Examples 9 to 12, and Comparative Examples 2 and 3 were tested, and the test results are shown in Table 3. The testing method is the same as above.

[0131] Table 3 Activity test results of magnesium oxide obtained in Examples 3, 9-12, Comparative Examples 2 and 3

[0132]

[0133] It can be seen from Table 3 that the bulk density of the activated magnesium oxide obtained in Examples 3 and 9 to 12 is greater than 0.5 g / cm 3 , with a specific surface area higher than 65m 2 / g, hydration degree higher than 80%, citric acid value lower than 15s, iodine absorption value higher than 80mg / g. And it can be seen from Table 3 that a higher solid-liquid ratio helps to increase the bulk density of magnesium oxide and reduce the citric acid value. In addition, it can be seen from Table 3 that an increase in the solid-liquid ratio will cause a decrease in the specific surface area of ​​magnesium oxide, a decrease in the iodine absorption value and a decrease in the hydration degree. Comprehensively considering that the solid-liquid ratio is 1:0.6~5, the activity of magnesium oxide can be maintained at a specific surface area higher than 50m 2 / g, hydration degree higher than 80%, citric acid value lower than 15s, and iodine absorption value higher than 80mg / g.

[0134] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0135] In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in a reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0136] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing active magnesium oxide, characterized in that: The steps include: S100: calcining and dissociating the first magnesium ore, strengthening leaching and carbonizing and separating the ore to obtain calcium carbonate and active low-calcium magnesium-rich liquid; S200: calcining and dissociating the second magnesium ore and mechanically grinding the second magnesium ore to obtain a fine material, or directly mechanically grinding the second magnesium ore to obtain a fine material; S300: pumping the active low-calcium magnesium-rich liquid into the hydration activation tank, starting the stirring, and then conveying the fine material to the hydration activation tank, the active low-calcium magnesium-rich liquid and the fine material undergo hydration reaction to form a composite magnesium salt, and the mass ratio of the fine material to the active low-calcium magnesium-rich liquid is 1:0.6-5; S400: The composite magnesium salt is dried and broken up and then transported to a calcining furnace, where it is calcined, cooled and spirally discharged to obtain active magnesium oxide.

2. The method for preparing activated magnesium oxide according to claim 1, characterized in that: In step S300, the temperature of the hydration reaction between the fine material and the active low-calcium magnesium-rich solution is 40-70° C. and the time is 0.5-24 hours.

3. The method for preparing active magnesium oxide according to claim 1, characterized in that: In step S100, obtaining calcium carbonate and active low-calcium magnesium-rich solution comprises the following steps: S110, calcining the first magnesium ore in a high temperature furnace to dissociate it into calcined white; S120, leaching the calcined white and the digestion water intensified, and then filtering the residues to obtain the digestion solution; S130, pumping the digestion liquid into an enhanced gas-liquid reactor and adding an activator, and introducing carbon dioxide to carbonize the digestion liquid; S140, separating the carbonized liquid into calcium carbonate and active low-calcium and magnesium-rich liquid through solid-liquid separation.

4. The method for preparing active magnesium oxide according to claim 3, characterized in that: In step S130, the activator is one or more of oxalic acid, sodium phosphate, and magnesium polycarboxylate, and the mass ratio of oxalic acid, sodium phosphate, and magnesium polycarboxylate is: 1-15:0-8:0-1; The dosage of the activator is 0.05% to 5.0% of the mass of magnesium oxide in the digestive solution, and the activator is prepared as a solution with a mass concentration of 10% and added to the digestive solution.

5. The method for preparing active magnesium oxide according to claim 4, characterized in that: The activator is oxalic acid, sodium phosphate and magnesium polycarboxylate, and the mass ratio of oxalic acid, sodium phosphate and magnesium polycarboxylate is 6-12:5:1, and the dosage of the activator is 0.5%-2.0% of the mass of magnesium oxide in the digestive fluid.

6. The method for preparing active magnesium oxide according to claim 3, characterized in that: In step S110, the first magnesium ore is one of dolomite, magnesite, and by-product magnesium salt, and the calcination dissociation temperature is 800-1200° C., and the calcination time is 0.1-240 min. In step S120, the solid-liquid ratio of the enhanced leaching is 1g:15-50ml, the temperature is 30-90°C, In step S130, the carbonization endpoint pH is 7.5-10.

0.

7. The method for preparing active magnesium oxide according to claim 1, characterized in that: In step S200, the second magnesium ore is one or more of magnesite, hydromagnesite, brucite, magnesium carbonate, and magnesium hydroxide, and the calcination dissociation temperature of the second magnesium ore is 600-900° C., and the time is 0.1-240 min. Or the second magnesium ore is light-burned magnesium oxide, and the light-burned magnesium oxide is directly mechanically finely ground to obtain fine material; The particle size of the fine material is 1-45 μm.

8. The method for preparing active magnesium oxide according to claim 1, characterized in that: In step S400, the drying temperature is 120-250°C; the calcination temperature is 500-800°C, and the residence time is 0.1-120 min.

9. An activated magnesium oxide prepared by the method for preparing activated magnesium oxide according to any one of claims 1 to 8, characterized in that: The bulk density of the active magnesium oxide is greater than 0.5 g / cm 3 , with a specific surface area higher than 50m 2 / g, hydration degree higher than 80%, citric acid value lower than 15s, and iodine absorption value higher than 80mg / g.

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