CN1830787A - Method of preparing high purity magnesium oxide by closed pyrolysis magnesium chloride hydrate - Google Patents
Method of preparing high purity magnesium oxide by closed pyrolysis magnesium chloride hydrate Download PDFInfo
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- CN1830787A CN1830787A CN 200610071248 CN200610071248A CN1830787A CN 1830787 A CN1830787 A CN 1830787A CN 200610071248 CN200610071248 CN 200610071248 CN 200610071248 A CN200610071248 A CN 200610071248A CN 1830787 A CN1830787 A CN 1830787A
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- hydrochloric acid
- pyrolysis
- magnesium oxide
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- magnesium chloride
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 59
- 239000000395 magnesium oxide Substances 0.000 title claims abstract description 48
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 238000000197 pyrolysis Methods 0.000 title claims description 50
- 238000000034 method Methods 0.000 title claims description 48
- DHRRIBDTHFBPNG-UHFFFAOYSA-L magnesium dichloride hexahydrate Chemical compound O.O.O.O.O.O.[Mg+2].[Cl-].[Cl-] DHRRIBDTHFBPNG-UHFFFAOYSA-L 0.000 title description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 98
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims abstract description 72
- 229910001629 magnesium chloride Inorganic materials 0.000 claims abstract description 36
- 239000007789 gas Substances 0.000 claims description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 19
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 16
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 16
- 238000003860 storage Methods 0.000 claims description 15
- 239000002253 acid Substances 0.000 claims description 10
- 238000010521 absorption reaction Methods 0.000 claims description 9
- 230000036571 hydration Effects 0.000 abstract description 32
- 238000006703 hydration reaction Methods 0.000 abstract description 32
- 239000012535 impurity Substances 0.000 abstract description 27
- 238000005406 washing Methods 0.000 abstract description 13
- 238000004519 manufacturing process Methods 0.000 abstract description 11
- 238000001914 filtration Methods 0.000 abstract description 4
- 238000001354 calcination Methods 0.000 abstract 1
- 235000012245 magnesium oxide Nutrition 0.000 description 45
- 239000000047 product Substances 0.000 description 24
- 239000000428 dust Substances 0.000 description 21
- 238000000354 decomposition reaction Methods 0.000 description 20
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 16
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 15
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 14
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 13
- 235000011941 Tilia x europaea Nutrition 0.000 description 13
- 239000004571 lime Substances 0.000 description 13
- 239000013535 sea water Substances 0.000 description 11
- 239000011777 magnesium Substances 0.000 description 10
- 239000012267 brine Substances 0.000 description 9
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 9
- 239000001103 potassium chloride Substances 0.000 description 8
- 235000011164 potassium chloride Nutrition 0.000 description 8
- 229910021529 ammonia Inorganic materials 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000007788 liquid Substances 0.000 description 7
- 239000008267 milk Substances 0.000 description 7
- 210000004080 milk Anatomy 0.000 description 7
- 235000013336 milk Nutrition 0.000 description 7
- 238000000926 separation method Methods 0.000 description 7
- 239000011780 sodium chloride Substances 0.000 description 7
- 241001131796 Botaurus stellaris Species 0.000 description 6
- 239000011575 calcium Substances 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- 239000006071 cream Substances 0.000 description 5
- 239000001095 magnesium carbonate Substances 0.000 description 5
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 5
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 5
- 235000014380 magnesium carbonate Nutrition 0.000 description 4
- 238000005507 spraying Methods 0.000 description 4
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000005243 fluidization Methods 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000011819 refractory material Substances 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 235000013373 food additive Nutrition 0.000 description 1
- 239000002778 food additive Substances 0.000 description 1
- DKAGJZJALZXOOV-UHFFFAOYSA-N hydrate;hydrochloride Chemical compound O.Cl DKAGJZJALZXOOV-UHFFFAOYSA-N 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000012047 saturated solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
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- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
A process for preparing high-purity magnesium oxide from the hydrated magnesium chloride by sealed thermo-decomposing includes such steps as thermo-decomposing in sealed condition, removing impurities by hydration, filtering, washing and calcining. Absorbing its tail gas can obtain hydrochloric acid.
Description
Technical Field
The invention relates to hydrated magnesium chloride (MgCl) obtained by dehydrating solution refined from bischofite or seawater brine in a salt lake2·2H2O or MgCl2·4H2O) is taken as a raw material, and the technology for preparing high-purity magnesium oxide through thermal decomposition in a closed pyrolysis furnace belongs to the technical field of inorganic chemical industry.
Background
Magnesium oxide is a widely used source in industryMaterials, to the extent and form of their processing, are given different uses: such as light magnesium oxide, used as a rubber filler, a food additive, a water treatment agent, a catalyst carrier, magnesium cement production, magnesium refractory production, etc.; dead burned and electrofused magnesia is a high-grade refractory material with excellent performance, and is largely used in the industries of chemical industry, metallurgy, ceramics and the like. Natural magnesium oxide exists as a periclase mineral, but has no industrial value because of its very small content. The magnesium oxide for industrial use is mainly from magnesite (MgCO)3) Dolomite (CaCO)3·MgCO3) Seawater, brine, etc. At present, the following methods are mainly used for preparing high-purity magnesium oxide:
1. preparation from natural magnesite
The natural magnesite is subjected to flotation and hot separation processes to produce high-quality magnesium oxide with the MgO content of more than 98 percent, and mature production experience is obtained at home and abroad, but the high-purity magnesium oxide with the MgO content of more than 99 percent is difficult to obtain from the magnesite.
2. Extracting from seawater (bittern)
Reaction of sea water or bittern with alkali to produce Mg (OH)2And (4) precipitating, and filtering, washing and roasting the precipitate to obtain the high-purity magnesium oxide.
① lime milk method
Sea water or brine with Ca (OH)2Action to form Mg (OH)2Simple in terms of reaction, but need to be preparedMeets the requirements of Mg (OH)2The process is not so easy. If seawater or bittern directly reacts with lime cream, fine colloidal precipitate is generated, the settling speed is slow, the carried impurities (lime cream and various impurities in seawater or bittern) are more, in order to remove calcium, reduce boron and purify, water is needed to be used for multiple times of washing, a large amount of water is consumed, and in order to solve the problem of Ca content in the lime cream, the lime cream and various impurities in seawater or bittern are not needed to be washed, and the problem of Ca content in the lime cream2+In Japan, a rehydration method was developed, namely in Mg (OH)2After precipitation, washing, drying, light burning, washing with seawater to reduce Ca again2+After the content is reduced, the magnesium oxide is lightly burned, and the ultrahigh-purity magnesium oxide with the purity of more than 99 percent can be prepared by the process. To solve the problem of precipitation of Mg (OH) by lime milk method2The problems of difficult sedimentation, filtration, washing and the like are solved, and a seed crystal method is adopted at home and abroad.The research institute of Luoyang refractory material utilizes calcium chloride solution generated by brine and lime milk to achieve the purpose of controlling certain pH value, so that the precipitate is easy to filter and wash. The main disadvantage of the lime milk method is that the process is complex, mainly the operation of calcium removal and boron reduction, and the total production cost is still higher although the raw material cost is lower.
② Ammonia process
By reacting ammonia or aqueous ammonia with brine to produce Mg (OH)2The process of (2) is referred to as the ammonia process. Since ammonium hydroxide is a weak base, in Mg2+The ammonia method is suitable for brine with higher concentration. The reaction of ammonia or ammonia water with bittern features the generation of Mg (OH)2The crystallization degree is higher, the sedimentation speed is fast, the filtration and the washing are easy, and the filtered mother liquor can be reused. Is obviously superior to the lime milk method in technical and technological aspects. The main disadvantage is the higher cost than the lime milk process. If the technology and the process such as ammonia recovery or production by-products are adopted, the production cost can be reduced. The major countries of high purity magnesium oxide, such as the United states, Japan, and England, use seawater as raw material, Mg2+The concentration is low, so the lime milk method is adopted to produce high-purity magnesium oxide without the ammonia method.
3. Thermal method for producing high-purity magnesium oxide
The pyrolysis method for producing high-purity magnesium oxide is basically characterized in that the chlorine radical of the magnesium chloride is removed by pyrolysis. The treatment method can be divided into spraying method and fluidization method according to different treatment devices and means.
① spraying method
The method is also called Aman method, is the first method for industrially producing high-purity magnesium oxide by a thermal decomposition method in the world, is invented by Ruthner division company of Andritz company of Austria, and is adopted by all countries in the world. The main process flow is as follows: and (3) further concentrating the brine after potassium extraction to a certain concentration, directly spraying the brine into an Aman reaction furnace for pyrolysis, wherein crude magnesium oxide produced after pyrolysis contains undecomposed chlorides such as magnesium chloride, calcium chloride and potassium chloride, and the like, and can be washed out by multiple stages with water, and the crude magnesium oxide is completely hydrated to form magnesium hydroxide. The filtered filter cake is roasted at 800-1000 deg.c to obtain magnesia with content over 99% and hydrochloric acid as by-product of about 20%. The spray roasting reactor has large equipment volume and low production strength, thus leading to the problems of large investment scale, complex process control and the like.
② liquid state method
In the CN1080618A patent: the method comprises the steps of taking a composite fluidized bed (spouted and current-carrying) as a pyrolysis reactor, directly decomposing a bischofite saturated solution into MgO and HCl at the temperature of 700-800 ℃, collecting MgO powder by a material collecting system consisting of a cyclone separator, a settling chamber and a cloth bag material collector, condensing and circularly spraying and absorbing HCl in a product gas phase by adopting a multi-stage absorption method to obtain a byproduct industrial dilute hydrochloric acid. The content of the obtained MgO product can reach 95 percent, the decomposition rate is 99.4 percent, and the concentration of the obtained industrial dilute hydrochloric acid is 18 to 22 percent (wt). As the method carries out pyrolysis under fluidization, a large amount of hot air is needed as a pyrolysis medium like an Aman method, the pyrolysis temperature is high, the concentration of HCl in tail gas is low, the tail gas treatment capacity is large, and the treated tail gas can only obtain 18-22% (wt) hydrochloric acid.
Disclosure of Invention
The invention aims to provide a novel method for producing high-purity magnesium oxide, which comprises the specific process of dehydrating solution refined from bischofite or seawater brine in a salt lake to obtain hydrated magnesium chloride (MgCl)2·2H2O or MgCl2·4H2O) is taken as a raw material, the hydrated magnesium chloride is added into a closed pyrolysis furnace (2) through a feeder (1) for pyrolysis at the pyrolysis temperature of 400-600 ℃ for 0.5-3.5 hours, and the hydrated magnesium chloride is decomposed into MgO, HCl and H in the pyrolysis furnace2O, the reaction equation is:
the decomposition products are mainly MgO and a small amount of MgCl which is not decomposed2Water-soluble impurities such as KCl, NaCl and the like, in order to remove the impurities in the water-soluble impurities, the decomposition products are put into a hydration tank (3), and hydration impurity removal treatment is carried out in the hydration tank (3), namelyDissolving KCl, NaCl and other water soluble impurities in water, reacting MgO with water to hydrate into Mg (OH)2The reaction equation is:
the product after hydration and impurity removal treatment is sent into a filter (4) for solid-liquid separation and washing, and then is sent into a roasting furnace (5) for roasting for 1.5 to 3.5 hours at the temperature of 500 ℃ and 650 ℃ to obtain high-purity magnesium oxide, wherein the content of the magnesium oxide is more than 99 percent, and the reaction equation is as follows:
hydrogen chloride gas and water vapor generated in the decomposition process of hydrated magnesium chloride in a pyrolysis furnace enter a cyclone dust collector (6) to removedust in impurity bands, the dust obtained by the cyclone dust collector (6) is discharged into a hopper (7), and then the dust is conveyed into a hydration tank (3) to be hydrated and subjected to impurity removal treatment; the dedusted gas enters a condenser (8), and part of water HCl and H2O is hydrochloric acid with the concentration of 30-36 percent and is introduced into an acid storage tank (9), uncondensed gas is introduced into a hydrochloric acid absorption tower (11) through a fan (10) and is absorbed into hydrochloric acid and is introduced into the acid storage tank (9), and the gas reaching the emission standard is discharged in an emptying mode.
Compared with Aman method and fluidization method, the method has the advantages of low decomposition temperature, convenient tail gas treatment, simple process flow compared with lime method, easy obtainment of high-purity magnesium oxide product, no need of other raw materials except the raw materials, high concentration of the obtained hydrochloric acid, high magnesium oxide content in the high-purity magnesium oxide product obtained by the method of the invention more than 99%, stable process and the like.
Drawings
The invention will be further explained with reference to the drawings
The attached drawing is a process flow chart of the invention, and in the figure, 1, a feeder 2, a closed pyrolysis furnace 3, a hydration tank 4, a filter 5, a roasting furnace 6, a cyclone dust collector 7, a hopper 8, a condenser 9, an acid storage tank 10, a fan 11 and a hydrochloric acid absorption tower
Detailed Description
Example 1: 500g of hydrated magnesium chloride (content: MgCl)269.54％、H228.24 percent of O, 0.28 percent of MgO0.28 percent and the balance of KCl, NaCl and the like are added into a closed pyrolysis furnace (2) through a feeder (1) for pyrolysis at the pyrolysis temperature of 600 ℃ for 0.5 hour to obtain 140g of a decomposition product, the decomposition rate of hydrated magnesium chloride is 99.2 percent, the pyrolysis product is put into a hydration tank (3) for hydration impurity removal treatment, the product after the hydration impurity removal treatment is sent into a filter (4) for solid-liquid separation and washing, then is sent into a roasting furnace (5) for roasting for 1.5 hours at 700 ℃ to obtain 133g of high-purity magnesium oxide with the magnesium oxide content of 99.16 percent, hydrogen chloride gas and water vapor generated in the decomposition process of the hydrated magnesium chloride in the pyrolysis furnace enter a cyclone dust collector (6), dust obtained by the cyclone dust separator (6) is discharged into a hopper (7) and is sent into the hydration tank (3) for hydration impurity removal treatment, the dedusted gas enters a condenser (8), part of water vapor and hydrogen chloride gas become concentrated hydrochloric acid, the concentrated hydrochloric acid is introduced into a storage tank (9), uncondensed gas is introduced into a hydrochloric acid absorption tower (11) by a fan (10) to be absorbed into hydrochloric acid, the hydrochloric acid is introduced into an acid storage tank (9), the concentration of the hydrochloric acid is 30-36%, and the gas reaching the emission standard is discharged and discharged.
Example 2: 500g of hydrated magnesium chloride (content: MgCl)273.79％、H2O22.07%, MgO2.15% and the balance KCl, NaCl, etc.) are added into a closed pyrolysis furnace (2) through a feeder (1) for pyrolysis, the pyrolysis temperature is 400 ℃, the pyrolysis time is 3.5 hours, 170g of decomposition product is obtained, the decomposition rate of hydrated magnesium chloride is 87%, the pyrolysis product is put into a hydration tank (3) for hydration impurity removal treatment, the product after the hydration impurity removal treatment is sent into a filter (4) for solid-liquid separation and washing, then the product is sent into a roasting furnace (5), roasting is carried out for 3.5 hours at 500 ℃ to obtain 120g of high-purity magnesium oxide, the content of the magnesium oxide is 99.21%, hydrogen chloride gas and water vapor generated in the decomposition process of the hydrated magnesium chloride in the pyrolysis furnace enter a cyclone dust collector (6), and dust obtained by the cyclone dust collector (6) is discharged into a hopper (7)) And is sent toCarrying out hydration impurity removal treatment in a hydration tank (3), introducing the dedusted gas into a condenser (8), introducing part of steam and hydrogen chloride gas into a storage tank (9), introducing the uncondensed gas into a hydrochloric acid absorption tower (11) by a fan (10) to absorb the uncondensed gas into hydrochloric acid, introducing the hydrochloric acid into an acid storage tank (9), wherein the concentration of hydrochloric acid is 30-36%, and discharging the gas reaching the emission standard.
Example 3: 500g of hydrated magnesium chloride (content: MgCl)273.79％、H2O22.07%, MgO2.15% and the balance KCl, NaCl, etc., are added into a closed pyrolysis furnace (2) through a feeder (1) for pyrolysis, the pyrolysis temperature is 500 ℃, the pyrolysis time is 75 minutes, 154g of decomposition product is obtained, the decomposition rate of hydrated magnesium chloride is 96.4%, the pyrolysis product is put into a hydration tank (3) for hydration impurity removal treatment, the product after the hydration impurity removal treatment is sent into a filter (4) for solid-liquid separation and washing, then is sent into a roasting furnace (5), roasting is carried out for 2.5 hours at 500℃ to obtain 141g of high-purity magnesium oxide and 99.18% of magnesium oxide, hydrogen chloride gas and water vapor generated in the decomposition process of the hydrated magnesium chloride in the pyrolysis furnace enter a cyclone dust collector (6), dust obtained by the cyclone separator (6) is discharged into a hopper (7) and is sent into the hydration tank (3) for hydration impurity removal treatment, the dedusted gas enters a condenser (8), part of water vapor and hydrogen chloride gas become concentrated hydrochloric acid, the concentrated hydrochloric acid is introduced into a storage tank (9), uncondensed gas is introduced into a hydrochloric acid absorption tower (11) by a fan (10) to be absorbed into hydrochloric acid, the hydrochloric acid is introduced into an acid storage tank (9), the concentration of the hydrochloric acid is 30-36%, and the gas reaching the emission standard is discharged and discharged.
Example 4: 500g of hydrated magnesium chloride (content: MgCl)273.79％、H2O22.07 percent, MgO2.15 percent and the balance of KCl, NaCl and the like) is added into a closed pyrolysis furnace (2) through a feeder (1) for pyrolysis, the pyrolysis temperature is 550 ℃, the pyrolysis time is 2 hours, a decomposition product 148g is obtained, the decomposition rate of hydrated magnesium chloride is 99.5 percent, the pyrolysis product is put into a hydration tank (3) for hydration impurity removal treatment, the product after the hydration impurity removal treatment is sent into a filter (4) for solid-liquid separation and washing, then is sent into a roasting furnace (5) and is heated at 550 DEG CThen, roasting for 2 hours to obtain 141g of high-purity magnesium oxide with the magnesium oxide content of 99.2 percent, and introducing hydrogen chloride gas and water vapor generated in the decomposition process of hydrated magnesium chloride in a pyrolysis furnaceAnd (2) putting the dust obtained by the cyclone separator (6) into a cyclone dust collector (6), discharging the dust into a hopper (7), conveying the dust into a hydration tank (3) for hydration and impurity removal, feeding the dedusted gas into a condenser (8), introducing a part of water vapor and hydrogen chloride gas into concentrated hydrochloric acid into a storage tank (9), introducing the uncondensed gas into a hydrochloric acid absorption tower (11) by a fan (10), absorbing the uncondensed gas into hydrochloric acid, introducing the hydrochloric acid into an acid storage tank (9), wherein the concentration of the hydrochloric acid is 30-36%, and discharging the gas reaching the emission standard.
Example 5: 500g of hydrated magnesium chloride (content: MgCl)256.13％、H241.83 percent of O and the balance of KCl, NaCl and the like) is added into a closed pyrolysis furnace (2) through a feeder (1) for pyrolysis, the pyrolysis temperature is 400 ℃, the pyrolysis time is 1.5 hours, 118g of a decomposition product is obtained, the decomposition rate of hydrated magnesium chloride is 99.1 percent, the pyrolysis product is put into a hydration tank (3) for hydration and impurity removal treatment, the product after the hydration and impurity removal treatment is sent into a filter (4) for solid-liquid separation and washing, then the product is sent into a roasting furnace (5) for roasting for 2 hours at 650 ℃ to obtain 111g of high-purity magnesium oxide and 99.21 percent of magnesium oxide, hydrogen chloride gas and water vapor generated in the decomposition process of the hydrated magnesium chloride in the pyrolysis furnace enter a cyclone dust collector (6), dust obtained by the cyclone dust collector (6) is discharged into a hopper (7) and is sent into the hydration tank (3) for hydration and impurity removal treatment, and the gas after dust removal enters a condenser (8), part of water vapor and hydrogen chloride gas become concentrated hydrochloric acid, the concentrated hydrochloric acid is introduced into a storage tank (9), uncondensed gas is introduced into a hydrochloric acid absorption tower (11) through a fan (10) to be absorbed into hydrochloric acid, the hydrochloric acid is introduced into an acid storage tank (9), the concentration of the hydrochloric acid is 30-36%, and the gas reaching the emission standard is discharged and discharged.
Claims (1)
1. A method for preparing high-purity magnesium oxide by closed pyrolysis of hydrated magnesium chloride is characterized in that the hydrated magnesium chloride is added into a closed pyrolysis furnace (2) through a feeder (1) for pyrolysis at the pyrolysis temperature of 400-, the dedusted gas enters a condenser (8), part of water vapor and hydrogen chloride gas become concentrated hydrochloric acid, the concentrated hydrochloric acid is introduced into an acid storage tank (9), uncondensed gas is introduced into a hydrochloric acid absorption tower (11) by a fan (10), the hydrochloric acid is obtained by collecting the tower, the hydrochloric acid is introduced into the acid storage tank (9), and the gas reaching the emission standard is discharged and discharged.
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| CNB2006100712482A CN100417596C (en) | 2006-03-21 | 2006-03-21 | Method of preparing high purity magnesium oxide by closed pyrolysis magnesium chloride hydrate |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100453463C (en) * | 2006-12-21 | 2009-01-21 | 青海中信国安科技发展有限公司 | Process and apparatus for preparing magnesium oxide and hydrogen chloride mixed gas by two-stage dynamic calcining of magnesium chloride |
| CN102030347A (en) * | 2010-11-05 | 2011-04-27 | 中国科学院青海盐湖研究所 | Method for preparing high-purity magnesium oxide by pyrolysis of magnesium chloride |
| CN102303878A (en) * | 2011-07-29 | 2012-01-04 | 中国科学院青海盐湖研究所 | Method for preparing silicon steel grade magnesium oxide with pyrolyzed magnesium oxide |
| CN104773744A (en) * | 2014-01-15 | 2015-07-15 | 中国科学院过程工程研究所 | Method for preparing high purity magnesium oxide from old brine |
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| CN1080618A (en) * | 1992-07-03 | 1994-01-12 | 中国科学院上海硅酸盐研究所 | A kind of Technology for preparing high-purity magnesium oxide |
| CN1281499C (en) * | 2004-06-04 | 2006-10-25 | 天津科技大学 | Process for producing high purity magnesia |
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