CN114735729A - Method for preparing magnesium carbonate with large apparent specific volume - Google Patents
Method for preparing magnesium carbonate with large apparent specific volume Download PDFInfo
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- CN114735729A CN114735729A CN202210605938.0A CN202210605938A CN114735729A CN 114735729 A CN114735729 A CN 114735729A CN 202210605938 A CN202210605938 A CN 202210605938A CN 114735729 A CN114735729 A CN 114735729A
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- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 title claims abstract description 66
- 239000001095 magnesium carbonate Substances 0.000 title claims abstract description 66
- 229910000021 magnesium carbonate Inorganic materials 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 287
- 238000005406 washing Methods 0.000 claims abstract description 111
- 238000001035 drying Methods 0.000 claims abstract description 78
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 61
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 61
- 238000006703 hydration reaction Methods 0.000 claims abstract description 23
- 238000001914 filtration Methods 0.000 claims abstract description 22
- 239000000460 chlorine Substances 0.000 claims abstract description 21
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 21
- 230000036571 hydration Effects 0.000 claims abstract description 20
- 238000004537 pulping Methods 0.000 claims description 110
- 239000000463 material Substances 0.000 claims description 89
- 238000002386 leaching Methods 0.000 claims description 80
- 238000003756 stirring Methods 0.000 claims description 70
- 239000012065 filter cake Substances 0.000 claims description 49
- 238000003825 pressing Methods 0.000 claims description 48
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims description 45
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 claims description 45
- 235000012538 ammonium bicarbonate Nutrition 0.000 claims description 45
- 239000001099 ammonium carbonate Substances 0.000 claims description 45
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 44
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 32
- 239000000347 magnesium hydroxide Substances 0.000 claims description 32
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 32
- 239000002002 slurry Substances 0.000 claims description 32
- 239000000395 magnesium oxide Substances 0.000 claims description 29
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 29
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 29
- 229910052742 iron Inorganic materials 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 16
- 239000012535 impurity Substances 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 13
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 9
- 239000000292 calcium oxide Substances 0.000 claims description 9
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- 239000000126 substance Substances 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 238000000926 separation method Methods 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 5
- 238000005534 hematocrit Methods 0.000 claims 1
- 229930000044 secondary metabolite Natural products 0.000 claims 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 abstract description 14
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical class [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 abstract description 2
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 123
- 235000014380 magnesium carbonate Nutrition 0.000 description 52
- 229910021529 ammonia Inorganic materials 0.000 description 45
- 238000011084 recovery Methods 0.000 description 40
- 239000000706 filtrate Substances 0.000 description 36
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 30
- 238000004064 recycling Methods 0.000 description 25
- 238000010009 beating Methods 0.000 description 24
- 229910002092 carbon dioxide Inorganic materials 0.000 description 17
- 239000001569 carbon dioxide Substances 0.000 description 15
- 239000000047 product Substances 0.000 description 14
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 13
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 13
- 229910001424 calcium ion Inorganic materials 0.000 description 13
- 229910001425 magnesium ion Inorganic materials 0.000 description 13
- 239000002253 acid Substances 0.000 description 9
- 239000002994 raw material Substances 0.000 description 7
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 239000000428 dust Substances 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000011085 pressure filtration Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000003139 buffering effect Effects 0.000 description 3
- 229910000019 calcium carbonate Inorganic materials 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 230000000887 hydrating effect Effects 0.000 description 3
- 238000004806 packaging method and process Methods 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- QWDJLDTYWNBUKE-UHFFFAOYSA-L magnesium bicarbonate Chemical compound [Mg+2].OC([O-])=O.OC([O-])=O QWDJLDTYWNBUKE-UHFFFAOYSA-L 0.000 description 2
- 229910000022 magnesium bicarbonate Inorganic materials 0.000 description 2
- 239000002370 magnesium bicarbonate Substances 0.000 description 2
- 235000014824 magnesium bicarbonate Nutrition 0.000 description 2
- 159000000003 magnesium salts Chemical class 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 241001131796 Botaurus stellaris Species 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000834 fixative Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 235000013312 flour Nutrition 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000000976 ink Substances 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 229940127554 medical product Drugs 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 239000006072 paste Substances 0.000 description 1
- 150000004686 pentahydrates Chemical class 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 230000009967 tasteless effect Effects 0.000 description 1
- 239000000606 toothpaste Substances 0.000 description 1
- 229940034610 toothpaste Drugs 0.000 description 1
- 150000004684 trihydrates Chemical class 0.000 description 1
- 239000003643 water by type Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/24—Magnesium carbonates
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses a method for preparing magnesium carbonate with large apparent specific volume, belonging to the field of magnesium metal compounds. The method consists of the following steps: hydration step, synthesis step, water washing and filtering step and drying step. The invention has the beneficial effects that: the prepared magnesium carbonate has a specific volume of 12.5-16.7mL/g, a chlorine content of not more than 0.05wt% and a water content of 1.01-1.35 wt%.
Description
Technical Field
The invention relates to the field of magnesium metal compounds, in particular to a method for preparing magnesium carbonate with large apparent specific volume.
Background
Magnesium carbonate is an inorganic substance with the chemical formula MgCO3Molecular weight 84.31, relative density 3.037. Decomposed at 350 deg.C and lost carbon dioxide at 900 deg.C. Slightly soluble in cold water and slowly soluble in acid. Its trihydrate is colorless needle crystal, its melting point is 165 deg.C, and its relative density is 1.850. The pentahydrate is white monoclinic crystal, has a relative density of 1.73, and is decomposed by heating in air. The anhydrous substance can be obtained by introducing carbon dioxide into magnesium salt water solution while adding sodium carbonate to obtain hydrate, and drying the hydrate at below 50 deg.C.
The magnesium carbonate is white tasteless powder, has two common forms of amorphous powder and monoclinic crystal, has the characteristics of no combustion and light texture, and can be used for a heat-insulating and high-temperature-resistant fireproof heat-insulating material. Asbestos-grade magnesium carbonate is an excellent insulating material, and is used in the departments of shipbuilding, boiler manufacturing and the like, and can also be used for manufacturing daily chemicals such as high-grade glass products, magnesium salts, pigments, paints, fire-retardant coatings, printing ink, ceramics, cosmetics, toothpaste and the like, medical products and the like. The food-grade magnesium carbonate can be used as flour additive, and can also be used as desiccant, color fixative, carrier, anticaking agent, etc.
The existing magnesium carbonate synthesis method mainly comprises the following four modes:
1. from magnesite (MgCO)3) Mixing with coke, and calcining to obtain magnesium oxide. Adding water to form a paste, and adding CO2Introducing magnesium bicarbonate, filtering, and heating the filtrate to obtain basic carbonate precipitate.
2. Heating dolomite (MgCO) with small fire3·CaCO3) The magnesium carbonate is decomposed and crushed, and then the magnesium oxide is dissolved into magnesium hydrogen carbonate under the action of water and carbon dioxide under the pressure of 0.508-0.609MPa, and at this time, the calcium carbonate is left, and the calcium carbonate is obtained by filtering and heating.
3. Dissolving equal amount of crystalline magnesium sulfate and crystalline sodium carbonate in 10 times of water respectively, heating to 60-80 deg.C, mixing thoroughly, generating CO2Precipitation occurs simultaneously with the gas. Filtering to obtain precipitate, mixing with hot water of 70-80 deg.C, and filtering. The washing process is repeated, and the precipitate is dried at 50-60 deg.C after being washed thoroughly.
4. The bittern-soda process includes diluting bittern with water, adding soda solution, filtering, washing, crushing, drying, crushing, wind selection, packing and other steps to obtain light magnesium carbonate.
The inventor finds that the apparent specific volume of the existing magnesium carbonate product is usually in the range of 5-6.67mL/g, and the related index of the apparent specific volume cannot be effectively improved; furthermore, the conventional magnesium carbonate product is not ideal in specific volume index, so that the application scene of the conventional magnesium carbonate product is single, the application requirements of the fine industrial field and the high-end field on magnesium carbonate cannot be met, the product adaptability is not ideal, and the bottleneck for restricting the further development of magnesium carbonate is formed; meanwhile, the existing magnesium carbonate product has the problems of high impurity content, complex post-treatment, high impurity removal energy consumption and high impurity removal equipment and labor cost.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the method for preparing the magnesium carbonate with the large apparent specific volume, which can effectively improve the apparent specific volume of the magnesium carbonate, reduce the impurity content of the magnesium carbonate product, improve the product quality, widen the application scene of the magnesium carbonate and enhance the product adaptability.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a process for preparing magnesium carbonate of large apparent specific volume, said process consisting of the steps of: hydration, synthesis, water washing and filtering and drying;
further, the hydration step is operated in such a way that magnesium oxide raw powder in a predetermined part is mixed with water to prepare magnesium oxide slurry; generating magnesium hydroxide through hydration reaction to prepare magnesium hydroxide slurry with the solid content of 20-22 wt%;
the specification of the magnesium oxide raw powder is that the content of magnesium oxide is more than or equal to 97wt%, the content of calcium oxide is less than or equal to 0.05wt%, the content of acid insoluble substances is less than or equal to 0.05wt%, the content of iron is less than or equal to 0.001wt%, and the content of chlorine radical is less than or equal to 0.7 wt%.
Further, the operation of the synthesis step consists of the following steps: adding water for the first time, adding water for the second time and adding water for the third time;
the method for adding water for one time comprises the steps of mixing magnesium hydroxide slurry with primary water in a predetermined volume part, and heating to 25-30 ℃; adding ammonium bicarbonate in a predetermined amount, and stirring for 10-20min to obtain a primary composition;
wherein the volume part ratio of the magnesium hydroxide slurry to the primary water is 6: 9-10;
the weight ratio of the ammonium bicarbonate to the primary water is 1.6: 9-10;
the secondary water adding method comprises the steps of heating the primary composition under the stirring state of 200-250rpm, increasing the stirring speed to 300-400rpm when the temperature is increased to 40-42 ℃, and continuing stirring for 2-3 min; then at 0.3-0.5m3At the water adding speed of/min, adding a predetermined part of secondary water; secondary water additionAfter the completion, the stirring speed is reduced to 200-250rpm to prepare a secondary composite;
wherein the volume part ratio of the secondary water to the primary water is 10-12: 9-10;
the third water adding method comprises heating the secondary composition under the stirring state of 200-250rpm, increasing the stirring speed to 300-400rpm when the temperature is increased to 50-55 ℃, and continuing stirring for 3-5 min; then at 0.3-0.5m3Adding water for a predetermined part of tertiary water at a water adding speed of/min; after the third water addition is finished, the stirring speed is reduced to 250rpm at 200-;
wherein the volume part ratio of the tertiary water to the secondary water is 5-6: 10-12.
Further, the operation of the water washing and filtering step comprises the following steps: primary pulping and water washing, secondary pulping and water washing and leaching;
the primary pulping and washing method comprises the steps of carrying out filter pressing on the synthetic pulp to obtain a synthetic pulp filter cake; mixing the synthetic pulp filter cake with primary pulping water, stirring and pulping for 1-2h to prepare a primary pulping water-washing material;
the volume part ratio of the synthetic pulp to the primary pulping water is 3: 5-7;
the secondary pulping and washing method comprises the steps of carrying out filter pressing on a primary pulping and washing material to prepare a filter cake of the primary pulping and washing material; mixing the filter cake of the primary pulping and water washing material with a predetermined part of secondary pulping water, stirring and pulping for 1-2h to prepare a secondary pulping and water washing material;
the volume part ratio of the primary beating water to the secondary beating water is 1: 1-2;
the leaching method comprises the steps of carrying out filter pressing on the secondary pulping and washing material to prepare a secondary pulping and washing material filter cake; firstly, leaching a secondary pulping and water-washing material filter cake by adopting a preset part of primary leaching water; then leaching the secondary pulping water-washing material filter cake by adopting a predetermined part of secondary leaching water; after leaching, carrying out filter pressing on the leached filter cake of the secondary pulping and water washing material to prepare a leached filter cake;
the volume part ratio of the primary leaching water, the secondary leaching water and the primary beating water is 0.5-1:0.5-1: 1.
The drying step is carried out by drying the leaching filter cake until the water content is not more than 1.5wt%, and then the magnesium carbonate with large apparent specific volume is prepared.
Preferably, in the hydration step, the hydration reaction is carried out by heating to 90-95 ℃ and keeping the temperature for 2-3h under the stirring condition of 200-300rpm to prepare the magnesium hydroxide slurry.
Further, the operation of the drying step comprises the following steps: primary drying and secondary drying;
the primary drying method comprises the steps of carrying out primary drying on the leaching filter cake until the moisture content is not more than 5wt%, and preparing a primary drying material; performing cyclone separation on the primary dried material to remove impurities, and performing secondary drying;
the secondary drying method comprises the steps of carrying out secondary drying on the primary dried material subjected to cyclone separation until the moisture content is not more than 1.5wt% to obtain a secondary dried material; after cyclone separation and impurity removal are carried out on the secondary dried material, the magnesium carbonate with large apparent specific volume is prepared.
Preferably, the primary drying method is that the drying vacuum degree is 0.08-0.095MPa, and the drying temperature is 120-150 ℃;
the secondary drying method comprises the steps of drying the mixture at the vacuum degree of 0.08-0.095MPa and the drying temperature of 150-180 ℃.
The method for preparing the magnesium carbonate with large apparent specific volume further comprises the following steps: and (4) ammonia recovery.
The ammonia recovery step comprises the following steps that in the reaction process of the synthesis step, ammonia gas generated in the synthesis tank is pumped into the ammonia gas recovery barrel through a fan, and the ammonia gas is condensed and absorbed by water contained in the ammonia gas recovery barrel; when the concentration of free ammonia in the ammonia gas recovery barrel is more than 1mol/L, transferring the materials in the ammonia gas recovery barrel into an ammonia filtrate recovery tank for later use.
In the step of water washing and filtering, filtrate generated by pressure filtration is completely recycled to an ammonia filtrate recycling tank for later use.
Introducing carbon dioxide in a predetermined part into the material in the ammonia filtrate recovery tank to regenerate ammonium bicarbonate; after the carbon dioxide is introduced, adding ammonium bicarbonate with a predetermined part, uniformly stirring at 100-300rpm, and adjusting the concentration of the ammonium bicarbonate to be 2mol/L to prepare an ammonium bicarbonate solution. And the ammonium bicarbonate solution is recycled to the synthesis step and is transferred into a synthesis tank as a raw material to react with the magnesium hydroxide slurry.
The content of ammonium bicarbonate is more than or equal to 95wt%, the content of calcium oxide is less than or equal to 0.02wt%, the content of iron is less than or equal to 0.001wt%, the content of chloride is less than or equal to 0.01wt%, the content of sulfate radical is less than or equal to 0.01wt%, and the ammonium bicarbonate is clear and transparent after being dissolved in acid and has no impurities and no suspended matters after being dissolved in water.
The specification of the water contained in the ammonia gas recovery barrel is that the magnesium ion content is less than or equal to 5mg/L, the calcium ion content is less than or equal to 20mg/L, the iron content is less than or equal to 0.5mg/L, the chlorine root content is less than or equal to 20mg/L, and the sulfate radical content is less than or equal to 250 mg/L.
The weight ratio of the carbon dioxide to the magnesium oxide raw powder in the hydration step is 1: 1.6-2.0.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method for preparing the magnesium carbonate with the large apparent specific volume effectively improves the apparent specific volume of a magnesium carbonate product to 12.5-16.7mL/g, greatly improves the performance of the magnesium carbonate compared with the prior art with the apparent specific volume of 5.1-6.7mL/g, further optimizes the performance of the magnesium carbonate, effectively expands the application scene and the application field of the magnesium carbonate, and effectively enhances the adaptability of the magnesium carbonate product.
(2) According to the method for preparing the magnesium carbonate with the large apparent specific volume, the chlorine radical of the magnesium carbonate product is not more than 0.05wt%, the impurity content of the magnesium carbonate is further reduced, the purity of the magnesium carbonate is improved, the complexity of impurity removal post-treatment is effectively simplified, the impurity removal energy consumption is reduced, the related equipment and labor cost are reduced, and the economic benefit is remarkable.
(3) According to the method for preparing the magnesium carbonate with the large specific volume, the moisture content in the magnesium carbonate product is 1.01-1.35wt%, the application requirements of more scenes are met while the quality of the magnesium carbonate is further improved, and the product adaptability is enhanced.
(4) According to the method for preparing the magnesium carbonate with the large apparent specific volume, the ammonia gas or the filtrate containing the free ammonia which is the circulating medium generated in the production process of the magnesium carbonate is recycled, the regeneration of the ammonium bicarbonate is realized in the ammonia recycling step, the consumption of the ammonium bicarbonate which is used as the raw material for producing the magnesium carbonate is greatly reduced, the effective recycling and the cyclic utilization of the magnesium carbonate are realized, the utilization rate of the raw material is greatly improved, the consumption of the raw material is reduced, the production cost of enterprises is reduced, and the economic benefit is remarkable.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present invention, specific embodiments of the present invention will now be described.
Example 1
A method for preparing magnesium carbonate with large apparent specific volume comprises the following steps:
1. hydration step
Putting magnesium oxide raw powder in a predetermined part into a hydration tank, and then putting water in a predetermined part to prepare magnesium oxide slurry; heating to 90 ℃ under the stirring condition of 200rpm, preserving the heat for 2h, completely hydrating the magnesium oxide into magnesium hydroxide to prepare magnesium hydroxide slurry, and finishing the hydration step.
The solid content of the magnesium hydroxide slurry is 20 wt%.
The specification of the magnesium oxide raw powder is that the content of magnesium oxide is more than or equal to 97wt%, the content of calcium oxide is less than or equal to 0.05wt%, the content of acid insoluble substances is less than or equal to 0.05wt%, the content of iron is less than or equal to 0.001wt%, and the content of chlorine radical is less than or equal to 0.7 wt%.
The specification of the water is that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L, and the content of sulfate radicals is less than or equal to 250 mg/L.
2. Synthesis procedure
1) One water adding step
Adding magnesium hydroxide slurry and primary water in predetermined volume parts into a synthesis tank, and adjusting the temperature of the magnesium hydroxide slurry in the synthesis tank to 25 ℃; adding ammonium bicarbonate in a predetermined amount, and stirring at 200rpm for 10min to obtain a primary composition.
Wherein the magnesium hydroxide slurry: the volume part ratio of the primary water is 6:9.
The ammonium bicarbonate: the weight ratio of the primary water is 1.6:9.
2) Secondary water adding step
Under the stirring state of 200rpm, the synthesis tank starts to heat up; when the temperature of the materials in the synthesis tank reaches 40 DEG CWhen the stirring speed is increased to 300rpm, the stirring is continued for 2 min; then at 0.3m3At a water adding speed of/min, adding a predetermined part of secondary water; after the secondary water addition was completed, the stirring speed was reduced to 200rpm to prepare a secondary composition.
Wherein the volume part ratio of the secondary water to the primary water is 10: 9.
3) Three water adding steps
Under the stirring state of 200rpm, the temperature of the synthesis tank is continuously increased; when the temperature of the materials in the synthesis tank reaches 50 ℃, the stirring speed is increased to 300rpm, and the stirring is continued for 3 min; then at 0.3m3Adding water for a predetermined part of tertiary water at a water adding speed of/min; after the water is added for three times, the stirring speed is reduced to 200rpm, and the temperature of the synthesis tank is continuously increased; when the temperature of the materials in the synthesis tank reaches 60 ℃, preserving the heat for 0.5h, completing the synthesis step and preparing the synthetic pulp; and finally, placing the synthetic pulp into a buffer tank for later use.
Wherein the volume part ratio of the tertiary water to the secondary water is 5: 10.
In the synthesis process, ammonia gas generated in the synthesis tank is pumped into an ammonia gas recovery barrel through a fan, and the ammonia recovery step is carried out.
In the synthesis step, the specifications of the primary water, the secondary water and the tertiary water are that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L and the content of sulfate radicals is less than or equal to 250 mg/L.
3. Water washing and filtering step
1) One-time pulping and water washing
Putting the synthetic pulp in the buffer tank into a No. 1 filter press, and performing filter pressing treatment to obtain a synthetic pulp filter cake; and (3) placing the synthetic pulp filter cake into a No. 1 pulping tank, adding a predetermined part of primary pulping water, stirring and pulping for 1h under the stirring condition of 400rpm, and finishing primary pulping and washing to obtain a primary pulping and washing material.
Meanwhile, in the primary pulping and washing step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for later use, and the ammonia recycling step is waited to be carried out.
The volume part ratio of the synthetic pulp to the primary beating water is 3: 5.
In the step of primary pulping and washing, the filter pressing treatment is carried out under the conditions that the feeding pressure is 0.5MPa and the pressing pressure is 0.8 MPa.
2) Secondary beating and water washing
Putting the primary pulping and water washing material into a No. 2 filter press, and performing filter pressing treatment to obtain a primary pulping and water washing material filter cake; and (3) putting the filter cake of the primary pulping water-washing material into a No. 2 pulping tank, adding a predetermined part of secondary pulping water, stirring and pulping for 1h under the stirring condition of 400rpm, and finishing secondary pulping water-washing to obtain a secondary pulping water-washing material.
Meanwhile, in the secondary pulping and washing step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for later use, and the step of recycling ammonia is waited for.
The volume portion ratio of the primary beating water to the secondary beating water is 1:1.
In the secondary pulping and washing step, the filter pressing treatment is carried out under the feeding pressure of 0.5MPa and the pressing pressure of 0.8 MPa.
3) Leaching with water
Putting the secondary pulping and washing material into a No. 3 filter press, and performing filter pressing treatment to obtain a filter cake of the secondary pulping and washing material; then leaching the secondary pulping and washing material filter cake by adopting a preset part of primary leaching water in a left-in and right-out filter press water inlet and outlet mode, and leaching the secondary pulping and washing material filter cake by adopting a preset part of secondary leaching water in a right-in and left-out filter press water inlet and outlet mode; and (4) carrying out filter pressing after leaching is finished to obtain a leaching filter cake.
Specifically, a water inlet valve on the left side of a filter washing water pipeline is opened, a water discharge valve on the right side of the filter washing water pipeline is opened, leaching is carried out by adopting primary leaching water, and after leaching is finished, the valves are closed; and then opening a right water inlet valve at the side of the filter washing water pipe, opening a left water discharge valve at the side of the filter washing water pipe, and leaching by adopting secondary leaching water until leaching is finished.
Meanwhile, in the leaching step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for standby, and the ammonia recycling step is waited to be carried out.
The primary eluting water: secondary leaching water: the volume part ratio of the primary beating water is 0.5:0.5: 1.
In the leaching step, the filter pressing treatment is carried out under the pressing pressure of 0.8 MPa.
In the step of water washing and filtering, the specifications of the primary beating water, the secondary beating water, the primary leaching water and the secondary leaching water are that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L, and the content of sulfate radicals is less than or equal to 250 mg/L.
4. Drying step
1) One-time drying
Putting the leaching filter cake prepared in the leaching step into a No. 1 flash dryer, and carrying out primary drying until the water content is not more than 5wt% to prepare a primary dried material; after the primary drying is finished, the primary drying material is discharged to the buffering storage bin after fine dust is separated through the No. 1 cyclone separator.
The primary drying is carried out, the vacuum degree is 0.08MPa, and the drying temperature is as follows: 120 deg.C.
2) Secondary drying
Transferring the material prepared by primary drying from the buffer storage bin into a No. 2 flash dryer, and performing secondary drying until the moisture content is not more than 1.5wt% to prepare a secondary dried material; after the secondary drying is finished, the secondary dried material is discharged to a packaging machine after fine dust is separated by a No. 2 cyclone separator, and the magnesium carbonate with large specific volume is prepared.
And (3) secondary drying, wherein the vacuum degree is 0.08MPa, and the drying temperature is as follows: at 150 ℃.
Through detection, the apparent specific volume of the magnesium carbonate is 16.7mL/g, the chlorine content is 0.047wt%, and the water content is 1.35 wt%.
5. Ammonia recovery step
In the reaction process of the synthesis step, ammonia gas generated in the synthesis tank is pumped into an ammonia gas recovery barrel through a fan, and the ammonia gas is condensed and absorbed by water contained in the ammonia gas recovery barrel; when the concentration of free ammonia in the ammonia gas recovery barrel is more than 1mol/L, transferring the materials in the ammonia gas recovery barrel into an ammonia filtrate recovery tank for later use.
In the step of water washing and filtering, filtrate generated by pressure filtration is completely recycled to an ammonia filtrate recycling tank for later use.
Introducing carbon dioxide in a preset part into the material in the ammonia filtrate recovery tank to regenerate ammonium bicarbonate; after the carbon dioxide is introduced, adding ammonium bicarbonate in a predetermined part, uniformly stirring at 100rpm, and adjusting the concentration of the ammonium bicarbonate to be 2mol/L to prepare an ammonium bicarbonate solution. And recycling the ammonium bicarbonate solution to the synthesis step, and transferring the ammonium bicarbonate solution serving as a raw material into a synthesis tank to react with the magnesium hydroxide slurry.
The content of ammonium bicarbonate is more than or equal to 95wt%, the content of calcium oxide is less than or equal to 0.02wt%, the content of iron is less than or equal to 0.001wt%, the content of chloride is less than or equal to 0.01wt%, the content of sulfate radical is less than or equal to 0.01wt%, and the ammonium bicarbonate is clear and transparent after being dissolved in acid and has no impurities and no suspended matters after being dissolved in water.
The specification of the water contained in the ammonia gas recovery barrel is that the magnesium ion content is less than or equal to 5mg/L, the calcium ion content is less than or equal to 20mg/L, the iron content is less than or equal to 0.5mg/L, the chlorine root content is less than or equal to 20mg/L, and the sulfate radical content is less than or equal to 250 mg/L.
The weight ratio of the carbon dioxide to the magnesium oxide raw powder in the hydration step is 1: 1.6.
Example 2
A method for preparing magnesium carbonate with large apparent specific volume comprises the following steps:
1. hydration step
Putting magnesium oxide raw powder in a predetermined part into a hydration tank, and then putting water in a predetermined part to prepare magnesium oxide slurry; heating to 92 ℃ under the condition of stirring at 250rpm, preserving the heat for 2.5h, completely hydrating the magnesium oxide into magnesium hydroxide to prepare magnesium hydroxide slurry, and finishing the hydration step.
The solid content of the magnesium hydroxide slurry is 21 wt%.
The specification of the magnesium oxide raw powder is that the content of magnesium oxide is more than or equal to 97wt%, the content of calcium oxide is less than or equal to 0.05wt%, the content of acid insoluble substances is less than or equal to 0.05wt%, the content of iron is less than or equal to 0.001wt%, and the content of chlorine radicals is less than or equal to 0.7 wt%.
The specification of the water is that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L, and the content of sulfate radicals is less than or equal to 250 mg/L.
2. Synthesis procedure
1) One water adding step
Adding magnesium hydroxide slurry and primary water in predetermined volume parts into a synthesis tank, and adjusting the temperature of the magnesium hydroxide slurry in the synthesis tank to 28 ℃; adding ammonium bicarbonate in a predetermined amount, and stirring at 220rpm for 15min to obtain a primary composition.
Wherein the magnesium hydroxide slurry: the volume part ratio of the primary water is 6: 9.5.
The ammonium bicarbonate: the weight ratio of the primary water is 1.6: 9.5.
2) Secondary water adding step
Under the stirring state of 220rpm, the synthesis tank starts to heat up; when the temperature of the materials in the synthesis tank reaches 41 ℃, the stirring speed is increased to 350rpm, and the stirring is continued for 2.5 min; then at 0.4m3At the water adding speed of/min, adding a predetermined part of secondary water; after the secondary water addition was complete, the stirring speed was reduced to 230 rpm.
Wherein the volume part ratio of the secondary water to the primary water is 11: 9.5.
3) Three water adding steps
Under the stirring state of 220rpm, the synthesis tank is continuously heated; when the temperature of the materials in the synthesis tank reaches 52 ℃, the stirring speed is increased to 350rpm, and the stirring is continued for 4 min; then at 0.4m3Adding water for a predetermined part of tertiary water at a water adding speed of/min; after the water is added for three times, the stirring speed is reduced to 220rpm, and the temperature of the synthesis tank is continuously increased; when the temperature of the materials in the synthesis tank reaches 60 ℃, preserving the heat for 0.75h, completing the synthesis step and preparing the synthetic pulp; and finally, placing the synthetic pulp into a buffer tank for later use.
Wherein the volume part ratio of the tertiary water to the secondary water is 5.5: 11.
In the synthesis step, ammonia gas generated in the synthesis tank is pumped into an ammonia gas recovery barrel through a fan to be subjected to the ammonia recovery step.
In the synthesis step, the specifications of the primary water, the secondary water and the tertiary water are that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L and the content of sulfate radicals is less than or equal to 250 mg/L.
3. Washing and filtering step
1) One-time pulping and water washing
Putting the synthetic pulp in the buffer tank into a No. 1 filter press, and performing filter pressing treatment to obtain a synthetic pulp filter cake; and (3) placing the synthetic pulp filter cake into a No. 1 pulping tank, adding a predetermined part of primary pulping water, stirring and pulping for 1.5h under the stirring condition of 450rpm, and completing primary pulping water washing to obtain a primary pulping water washing material.
Meanwhile, in the primary pulping and washing step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for later use, and the ammonia recycling step is waited to be carried out.
The volume part ratio of the synthetic pulp to the primary beating water is 3: 6.
In the primary pulping and water washing step, the filter pressing treatment is carried out under the feeding pressure of 0.55MPa and the pressing pressure of 0.9 MPa.
2) Secondary beating and water washing
Putting the primary pulping and water washing material into a No. 2 filter press, and performing filter pressing treatment to obtain a primary pulping and water washing material filter cake; and (3) putting the filter cake of the primary pulping water-washing material into a No. 2 pulping tank, adding a predetermined part of secondary pulping water, stirring and pulping for 1.5 hours under the stirring condition of 450rpm, and finishing secondary pulping water-washing to obtain a secondary pulping water-washing material.
Meanwhile, in the secondary pulping and washing step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for later use, and the step of recycling ammonia is waited for.
The volume part ratio of the primary beating water to the secondary beating water is 1: 1.5.
In the secondary pulping and water washing step, the filter pressing treatment is carried out under the feeding pressure of 0.55MPa and the pressing pressure of 0.9 MPa.
3) Leaching with water
Putting the secondary pulping and washing material into a No. 3 filter press, and performing filter pressing treatment to obtain a filter cake of the secondary pulping and washing material; then leaching the secondary pulping washing material filter cake by adopting a preset part of primary leaching water in a left-in and right-out filter press water inlet and outlet mode, and leaching the secondary pulping washing material filter cake by adopting a preset part of secondary leaching water in a right-in and left-out filter press water inlet and outlet mode; and (4) carrying out filter pressing after leaching is finished to obtain a leaching filter cake.
Specifically, a water inlet valve on the left side of a filter washing water pipeline is opened, a water discharge valve on the right side of the filter washing water pipeline is opened, leaching is carried out by adopting primary leaching water, and after leaching is finished, the valves are closed; and then opening a right water inlet valve at the side of the filter washing water pipe, opening a left water discharge valve at the side of the filter washing water pipe, and leaching by adopting secondary leaching water until leaching is finished.
Meanwhile, in the leaching step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for standby, and the ammonia recycling step is waited to be carried out.
The primary eluting water: secondary leaching water: the volume part ratio of the primary beating water is 0.6:0.8: 1.
In the leaching step, the filter pressing treatment is carried out under the pressing pressure of 0.8 MPa.
In the step of water washing and filtering, the specifications of the primary beating water, the secondary beating water, the primary leaching water and the secondary leaching water are that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L, and the content of sulfate radicals is less than or equal to 250 mg/L.
4. Drying step
1) One-time drying
Putting the filter cake prepared in the leaching step into a No. 1 flash dryer, and carrying out primary drying until the water content is not more than 5wt% to prepare a primary dried material; after the primary drying is finished, the primary drying material is discharged to the buffering storage bin after fine dust is separated through the No. 1 cyclone separator.
The primary drying is carried out, the vacuum degree is 0.09MPa, and the drying temperature is as follows: at 140 ℃.
2) Secondary drying
Transferring the material prepared by primary drying from the buffer storage bin into a No. 2 flash dryer, and performing secondary drying until the moisture content is not more than 1.5wt% to prepare a secondary dried material; after the secondary drying is finished, the secondary dried material is discharged to a packaging machine after fine dust is separated by a No. 2 cyclone separator, and the magnesium carbonate with large specific volume is prepared.
And (3) secondary drying, wherein the vacuum degree is 0.09MPa, and the drying temperature is as follows: 160 ℃.
Through detection, the apparent specific volume of the magnesium carbonate is 14.2mL/g, the chlorine content is 0.050wt%, and the water content is 1.19 wt%.
5. Ammonia recovery step
In the reaction process of the synthesis step, ammonia gas generated in the synthesis tank is pumped into an ammonia gas recovery barrel through a fan, and is condensed and absorbed by water contained in the ammonia gas recovery barrel; when the concentration of free ammonia in the ammonia gas recovery barrel is more than 1mol/L, transferring the materials in the ammonia gas recovery barrel into an ammonia filtrate recovery tank for later use.
In the step of water washing and filtering, filtrate generated by pressure filtration is completely recycled to an ammonia filtrate recycling tank for later use.
Introducing carbon dioxide in a preset part into the material in the ammonia filtrate recovery tank to regenerate ammonium bicarbonate; after the carbon dioxide is introduced, adding ammonium bicarbonate in a predetermined part, uniformly stirring at 200rpm, and adjusting the concentration of the ammonium bicarbonate to be 2mol/L to prepare an ammonium bicarbonate solution. And the ammonium bicarbonate solution is recycled to the synthesis step and is transferred into a synthesis tank as a raw material to react with the magnesium hydroxide slurry.
The specification of the ammonium bicarbonate is that the content of the ammonium bicarbonate is more than or equal to 95wt%, the content of calcium oxide is less than or equal to 0.02wt%, the content of iron is less than or equal to 0.001wt%, the content of chloride is less than or equal to 0.01wt%, the content of sulfate radical is less than or equal to 0.01wt%, and the ammonium bicarbonate is clear and transparent after being dissolved in acid, and has no impurities and no suspended matters after being dissolved in water.
The specification of the water contained in the ammonia gas recovery barrel is that the magnesium ion content is less than or equal to 5mg/L, the calcium ion content is less than or equal to 20mg/L, the iron content is less than or equal to 0.5mg/L, the chlorine root content is less than or equal to 20mg/L, and the sulfate radical content is less than or equal to 250 mg/L.
The weight ratio of the carbon dioxide to the magnesium oxide raw powder in the hydration step is 1: 1.8.
Example 3
A method for preparing magnesium carbonate with large apparent specific volume comprises the following steps:
1. hydration step
Putting magnesium oxide raw powder in a predetermined part into a hydration tank, and then putting water in a predetermined part to prepare magnesium oxide slurry; heating to 95 ℃ under the stirring condition of 300rpm, preserving the heat for 3h, completely hydrating the magnesium oxide into magnesium hydroxide to prepare magnesium hydroxide slurry, and finishing the hydration step.
The solid content of the magnesium hydroxide slurry is 22 wt%.
The specification of the magnesium oxide raw powder is that the content of magnesium oxide is more than or equal to 97wt%, the content of calcium oxide is less than or equal to 0.05wt%, the content of acid insoluble substances is less than or equal to 0.05wt%, the content of iron is less than or equal to 0.001wt%, and the content of chlorine radical is less than or equal to 0.7 wt%.
The specification of the water is that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L, and the content of sulfate radicals is less than or equal to 250 mg/L.
2. Synthesis procedure
1) One water adding step
Adding magnesium hydroxide slurry and primary water in predetermined volume parts into a synthesis tank, and adjusting the temperature of the magnesium hydroxide slurry in the synthesis tank to 30 ℃; adding ammonium bicarbonate solution in predetermined amount, and stirring at 250rpm for 20min to obtain primary composition.
Wherein the magnesium hydroxide slurry: the volume part ratio of the primary water is 6: 10.
The ammonium bicarbonate solution is prepared by an ammonia recovery step.
The weight ratio of the ammonium bicarbonate to the primary water contained in the ammonium bicarbonate solution is 1.6: 10.
2) Secondary water adding step
Under the stirring state of 250rpm, the synthesis tank starts to heat up; when the temperature of the materials in the synthesis tank reaches 42 ℃, the stirring speed is increased to 400rpm, and the stirring is continued for 3 min; then at 0.5m3At the water adding speed of/min, adding a predetermined part of secondary water; after the secondary water addition was complete, the stirring speed was reduced to 250rpm to produce a secondary composition.
Wherein the volume part ratio of the secondary water to the primary water is 12: 10.
3) Three water adding steps
Under the stirring state of 250rpm, the temperature of the synthesis tank is continuously increased; when the temperature of the materials in the synthesis tank reaches 55 ℃, the stirring speed is increased to 400rpm, and the stirring is continued for 5 min; then at 0.5m3At a water addition rate of/min, adding predetermined portionsA number of tertiary waters; after the third time of water addition is finished, the stirring speed is reduced to 250rpm, and the temperature of the synthesis tank is continuously increased; when the temperature of the materials in the synthesis tank reaches 60 ℃, preserving the heat for 1h to finish the synthesis step and prepare the synthetic pulp; and finally, placing the synthetic pulp into a buffer tank for later use.
Wherein the volume part ratio of the tertiary water to the secondary water is 6: 12.
In the synthesis step, ammonia gas generated in the synthesis tank is pumped into an ammonia gas recovery barrel through a fan to be subjected to the ammonia recovery step.
In the synthesis step, the specifications of the primary water, the secondary water and the tertiary water are that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L, and the content of sulfate radicals is less than or equal to 250 mg/L.
3. Water washing and filtering step
1) One-time pulping and water washing
Placing the synthetic pulp in the buffer tank into a No. 1 filter press for filter pressing treatment to obtain a synthetic pulp filter cake; and (3) placing the synthetic pulp filter cake into a No. 1 pulping tank, adding a predetermined part of primary pulping water, stirring and pulping for 2 hours under the stirring condition of 500rpm, and completing primary pulping and washing to obtain a primary pulping and washing material.
Meanwhile, in the primary pulping and washing step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for later use, and the ammonia recycling step is waited to be carried out.
The volume part ratio of the synthetic pulp to the primary beating water is 3: 7.
In the step of primary pulping and washing, the filter pressing treatment is carried out under the conditions that the feeding pressure is 0.6MPa and the pressing pressure is 1.0 MPa.
2) Secondary beating and water washing
Putting the primary pulping and water washing material into a No. 2 filter press, and performing filter pressing treatment to obtain a primary pulping and water washing material filter cake; and (3) putting the filter cake of the primary pulping water-washing material into a No. 2 pulping tank, adding a predetermined part of secondary pulping water, stirring and pulping for 2 hours under the stirring condition of 500rpm, and finishing secondary pulping water-washing to obtain a secondary pulping water-washing material.
Meanwhile, in the secondary pulping and washing step, filtrate generated by filter pressing treatment is recycled to an ammonia filtrate recycling tank for standby, and the ammonia recycling step is waited to be carried out.
The volume part ratio of the primary beating water to the secondary beating water is 1:2.
In the secondary pulping and washing step, the filter pressing treatment is carried out under the feeding pressure of 0.6MPa and the pressing pressure of 1.0 MPa.
3) Leaching with water
Putting the secondary pulping and washing material into a No. 3 filter press, and performing filter pressing treatment to obtain a filter cake of the secondary pulping and washing material; then leaching the secondary pulping and washing material filter cake by adopting a preset part of primary leaching water in a left-in and right-out filter press water inlet and outlet mode, and leaching the secondary pulping and washing material filter cake by adopting a preset part of secondary leaching water in a right-in and left-out filter press water inlet and outlet mode; and (4) carrying out filter pressing after leaching is finished to obtain a leaching filter cake.
Specifically, a water inlet valve on the left side of a filter washing water pipeline is opened, a water discharge valve on the right side of the filter washing water pipeline is opened, leaching is carried out by adopting primary leaching water, and after leaching is finished, the valves are closed; and then opening a right water inlet valve at the side of the filter washing water pipe, opening a left water discharge valve at the side of the filter washing water pipe, and leaching by adopting secondary leaching water until leaching is finished.
Meanwhile, in the leaching step, filtrate generated by filter pressing treatment is recycled into an ammonia filtrate recycling tank for standby, and the ammonia recycling step is waited to be carried out.
The primary eluting water: secondary leaching water: the volume part ratio of the primary beating water is 1:1: 1.
In the leaching step, the filter pressing treatment is carried out under the pressing pressure of 0.8 MPa.
In the step of water washing and filtering, the specifications of the primary beating water, the secondary beating water, the primary leaching water and the secondary leaching water are that the content of magnesium ions is less than or equal to 5mg/L, the content of calcium ions is less than or equal to 20mg/L, the content of iron is less than or equal to 0.5mg/L, the content of chlorine radicals is less than or equal to 20mg/L, and the content of sulfate radicals is less than or equal to 250 mg/L.
4. Drying step
1) One-time drying
Putting the filter cake prepared in the leaching step into a No. 1 flash dryer, and drying for the first time until the water content is not more than 5wt% to prepare a first-time dried material; after the primary drying is completed, the primary dried material is discharged to the buffering storage bin after fine dust is separated by the 1# cyclone separator.
The primary drying is carried out, the vacuum degree is 0.095MPa, and the drying temperature is as follows: at 150 ℃.
2) Secondary drying
Transferring the material prepared by primary drying from the buffer storage bin into a No. 2 flash dryer, and performing secondary drying until the moisture content is not more than 1.5wt% to prepare a secondary dried material; after the secondary drying is finished, the secondary dried material is discharged to a packaging machine after fine dust is separated by a No. 2 cyclone separator, and the magnesium carbonate with large specific volume is prepared.
And (3) secondary drying, wherein the vacuum degree is 0.095MPa, and the drying temperature is as follows: 180 ℃ is carried out.
Through detection, the apparent specific volume of the magnesium carbonate is 12.5mL/g, the chlorine content is 0.049wt%, and the water content is 1.01 wt%.
5. Ammonia recovery step
In the reaction process of the synthesis step, ammonia gas generated in the synthesis tank is pumped into an ammonia gas recovery barrel through a fan, and is condensed and absorbed by water contained in the ammonia gas recovery barrel; when the concentration of free ammonia in the ammonia gas recovery barrel is more than 1mol/L, transferring the materials in the ammonia gas recovery barrel into an ammonia filtrate recovery tank for later use.
In the step of water washing and filtering, filtrate generated by pressure filtration is completely recycled to an ammonia filtrate recycling tank for later use.
Introducing carbon dioxide in a preset part into the material in the ammonia filtrate recovery tank to regenerate ammonium bicarbonate; after the carbon dioxide is introduced, adding ammonium bicarbonate in a predetermined part, uniformly stirring at 300rpm, and adjusting the concentration of the ammonium bicarbonate to be 2mol/L to prepare an ammonium bicarbonate solution. And the ammonium bicarbonate solution is recycled to the synthesis step and is transferred into a synthesis tank as a raw material to react with the magnesium hydroxide slurry.
The specification of the ammonium bicarbonate is that the content of the ammonium bicarbonate is more than or equal to 95wt%, the content of calcium oxide is less than or equal to 0.02wt%, the content of iron is less than or equal to 0.001wt%, the content of chloride is less than or equal to 0.01wt%, the content of sulfate radical is less than or equal to 0.01wt%, and the ammonium bicarbonate is clear and transparent after being dissolved in acid, and has no impurities and no suspended matters after being dissolved in water.
The specification of the water contained in the ammonia gas recovery barrel is that the magnesium ion content is less than or equal to 5mg/L, the calcium ion content is less than or equal to 20mg/L, the iron content is less than or equal to 0.5mg/L, the chlorine root content is less than or equal to 20mg/L, and the sulfate radical content is less than or equal to 250 mg/L.
The weight ratio of the carbon dioxide to the magnesium oxide raw powder in the hydration step is 1: 2.0.
Comparative example 1
The technical scheme of the embodiment 1 is adopted, and the difference is as follows: in the synthesis step, a one-time water adding reaction process is adopted, and all parts of water are added at one time. The other steps remain unchanged.
The magnesium carbonate prepared in comparative example 1 had a specific volume of 5.1mL/g, a chloride content of 0.051wt%, and a water content of 1.36 wt%.
Comparative example 2
The technical scheme of the embodiment 1 is adopted, and the difference is as follows: in the step of water washing and filtering, only one time of pulping and water washing is adopted, and the process of filter pressing is carried out. The other steps remain unchanged.
The magnesium carbonate prepared in comparative example 2 had a specific volume of 16.5mL/g, a chlorine content of 0.22wt%, and a moisture content of 1.35 wt%.
Comparative example 3
The technical scheme of the embodiment 1 is adopted, and the difference is as follows: in the drying step, only one drying process is adopted. The other steps remain unchanged. Wherein the drying temperature is 120-150 ℃.
The magnesium carbonate prepared in comparative example 3 had a specific volume of 16.6mL/g, a chlorine content of 0.050wt%, and a moisture content of 4.9 wt%.
All percentages used in the present invention are mass percentages unless otherwise indicated.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A method for preparing magnesium carbonate with large apparent specific volume is characterized by comprising the following steps: hydration, synthesis, water washing and filtering and drying;
the hydration step is operated in such a way that magnesium oxide raw powder in a preset part is mixed with water to prepare magnesium oxide slurry; generating magnesium hydroxide through hydration reaction to prepare magnesium hydroxide slurry with the solid content of 20-22 wt%;
the operation of the synthesis step consists of the following steps: adding water for the first time, adding water for the second time and adding water for the third time;
the method for adding water for one time comprises the steps of mixing magnesium hydroxide slurry with primary water in a predetermined volume part, and heating to 25-30 ℃; adding ammonium bicarbonate in a predetermined amount, and stirring for 10-20min to obtain a primary composition;
the secondary water adding method comprises the steps of heating the primary composition under the stirring state of 200-250rpm, increasing the stirring speed to 300-400rpm when the temperature is increased to 40-42 ℃, and continuing stirring for 2-3 min; then at 0.3-0.5m3At the water adding speed of/min, adding a predetermined part of secondary water; after the secondary water is added, the stirring speed is reduced to 200-250rpm to prepare a secondary compound;
the third water adding method comprises heating the secondary composition under the stirring state of 200-250rpm, increasing the stirring speed to 300-400rpm when the temperature is increased to 50-55 ℃, and continuing stirring for 3-5 min; then the thickness is 0.3-0.5m3Adding water for a predetermined part of tertiary water at a water adding speed of/min; after the third water addition is finished, the stirring speed is reduced to 250rpm at 200-;
and the drying step is operated in such a way that the filter cake obtained in the water washing and filtering step is dried until the water content is not more than 1.5wt%, and the magnesium carbonate with large apparent specific volume is prepared.
2. The method for preparing magnesium carbonate with large hematocrit as claimed in claim 1, wherein the hydration step comprises heating to 90-95 ℃ and maintaining the temperature for 2-3h under the stirring condition of 200-300rpm to obtain magnesium hydroxide slurry.
3. The method for preparing magnesium carbonate with large apparent specific volume according to claim 1, wherein the water is added for one time, and the volume part ratio of the magnesium hydroxide slurry to the water is 6: 9-10;
the primary water is added, and the weight ratio of the ammonium bicarbonate to the primary water is 1.6: 9-10;
adding water for the second time, wherein the volume part ratio of the secondary water to the primary water is 10-12: 9-10;
and adding water for the third time, wherein the volume part ratio of the water for the third time to the water for the second time is 5-6: 10-12.
4. The process for preparing magnesium carbonate with large apparent specific volume according to claim 1, wherein the operation of the water washing and filtering step consists of the following steps: primary pulping and water washing, secondary pulping and water washing and leaching;
the primary pulping and washing method comprises the steps of carrying out filter pressing on the synthetic pulp to obtain a synthetic pulp filter cake; mixing the synthetic pulp filter cake with primary pulping water, stirring and pulping for 1-2h to prepare a primary pulping water-washing material;
the secondary pulping and washing method comprises the steps of carrying out filter pressing on a primary pulping and washing material to prepare a filter cake of the primary pulping and washing material; mixing the filter cake of the primary pulping and water washing material with a predetermined part of secondary pulping water, stirring and pulping for 1-2h to prepare a secondary pulping and water washing material;
the leaching method comprises the steps of carrying out filter pressing on the secondary pulping and washing material to prepare a secondary pulping and washing material filter cake; firstly, leaching a secondary pulping water-washing material filter cake by adopting a preset part of primary leaching water; then leaching the secondary pulping water-washing material filter cake by adopting a predetermined part of secondary leaching water; and after leaching, carrying out filter pressing on the leached filter cake of the secondary pulping and water washing material to prepare a leached filter cake.
5. The method for preparing the magnesium carbonate with the large apparent specific volume according to claim 4, wherein the primary pulping water is washed, and the volume part ratio of the synthetic pulp to the primary pulping water is 3: 5-7;
the secondary pulping water is washed, and the volume part ratio of the primary pulping water to the secondary pulping water is 1: 1-2;
and leaching, wherein the volume part ratio of the primary leaching water, the secondary leaching water and the primary pulping water is 0.5-1:0.5-1: 1.
6. The method for preparing magnesium carbonate with large apparent specific volume according to claim 1, wherein the drying step is comprised of the following steps: primary drying and secondary drying;
the primary drying method comprises the steps of carrying out primary drying on the leaching filter cake until the moisture content is not more than 5wt%, and preparing a primary drying material; after cyclone separation and impurity removal are carried out on the primary dried material, secondary drying is carried out;
the secondary drying method comprises the steps of carrying out secondary drying on the primary dried material subjected to cyclone separation until the moisture content is not more than 1.5wt%, and preparing a secondary dried material; after cyclone separation and impurity removal are carried out on the secondary dried material, the magnesium carbonate with large apparent specific volume is prepared.
7. The method for preparing magnesium carbonate with large apparent specific volume as claimed in claim 6, wherein the primary drying method comprises drying at a temperature of 120-150 ℃ and a vacuum degree of 0.08-0.095 MPa;
the secondary drying method comprises the steps of drying the mixture at the vacuum degree of 0.08-0.095MPa and the drying temperature of 150-180 ℃.
8. The method for preparing magnesium carbonate with large apparent specific volume according to claim 1, wherein the specification of the raw magnesium oxide powder is that the content of magnesium oxide is more than or equal to 97wt%, the content of calcium oxide is less than or equal to 0.05wt%, the content of acid-insoluble substances is less than or equal to 0.05wt%, the content of iron is less than or equal to 0.001wt%, and the content of chlorine radicals is less than or equal to 0.7 wt%.
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| GB1434608A (en) * | 1972-06-27 | 1976-05-05 | Ente Minerario Siciliano | Process for preparing magnesium oxide |
| RU2535690C2 (en) * | 2012-04-26 | 2014-12-20 | Андрей Вилорьевич Доронин | Method of obtaining magnesium oxide |
| CN104591234A (en) * | 2015-01-09 | 2015-05-06 | 中南大学 | Process for preparing light magnesium carbonate from industrial magnesium hydroxide |
| CN105883865A (en) * | 2016-04-13 | 2016-08-24 | 北京化工大学 | Environment-friendly preparation process of high-purity and superfine anhydrous magnesium carbonate |
| CN108751235A (en) * | 2018-08-09 | 2018-11-06 | 苏州市泽镁新材料科技有限公司 | A kind of preparation method of nanoscale high purity light magnesium carbonate |
| CN109553120A (en) * | 2019-01-25 | 2019-04-02 | 广西银亿新材料有限公司 | A kind of method that carbon ammonia method prepares translucent basic magnesium carbonate |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1434608A (en) * | 1972-06-27 | 1976-05-05 | Ente Minerario Siciliano | Process for preparing magnesium oxide |
| RU2535690C2 (en) * | 2012-04-26 | 2014-12-20 | Андрей Вилорьевич Доронин | Method of obtaining magnesium oxide |
| CN104591234A (en) * | 2015-01-09 | 2015-05-06 | 中南大学 | Process for preparing light magnesium carbonate from industrial magnesium hydroxide |
| CN105883865A (en) * | 2016-04-13 | 2016-08-24 | 北京化工大学 | Environment-friendly preparation process of high-purity and superfine anhydrous magnesium carbonate |
| CN108751235A (en) * | 2018-08-09 | 2018-11-06 | 苏州市泽镁新材料科技有限公司 | A kind of preparation method of nanoscale high purity light magnesium carbonate |
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