CN1174921C - High-purity mangesium oxide or magnesium carbonate preparing process in circular medium - Google Patents

High-purity mangesium oxide or magnesium carbonate preparing process in circular medium Download PDF

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CN1174921C
CN1174921C CNB011003731A CN01100373A CN1174921C CN 1174921 C CN1174921 C CN 1174921C CN B011003731 A CNB011003731 A CN B011003731A CN 01100373 A CN01100373 A CN 01100373A CN 1174921 C CN1174921 C CN 1174921C
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magnesium
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magnesium oxide
circulating medium
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CN1362371A (en
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兴 沈
沈兴
周花蕾
刘志权
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Abstract

The present invention relates to a method for preparing high-purity magnesium oxide or magnesium carbonate in circulating media, which comprises: (1), ammonia gas is absorbed by pure water until a total ammonia concentration achieves 5 to 16 mol/l; (2), carbon dioxide is led in until carbonization degree is from 0.40 to 0.60; (3), magnesium chloride or magnesium sulfate or magnesium nitrate is added according to a molar ratio of 1: 2: 4 of Mg<2+>, CO2 and NH3; (4), high-purity magnesium carbonate is obtained by thermal decomposition at 80 to 390 DEG C, or, the high-purity magnesium oxide is obtained by the thermal decomposition at 390 to 600 DEG C. The high-purity magnesium oxide which comprises more than or equal to 98% of MgO can be prepared from industrial magnesium chloride, magnesium sulfate and magnesium nitrate, and low-boron low-calcium ultra-high purity light magnesium oxide which comprises more than or equal to 98% of MgO can be prepared from Tsinghai salt lake magnesium chloride.

Description

Method for preparing high-purity magnesium oxide or magnesium carbonate in circulating medium
The invention relates to a method for preparing high-purity magnesium oxide or magnesium carbonate in a circulating medium.
Magnesium oxide is a product of inorganic substances with great yield and wide application. It can be roughly divided into two categories of chemical magnesium oxide and metallurgical magnesite. Chemical magnesium oxide is widely used in the sectors of ceramics, rubber, plastics, paper, paints, dyes, medicine, magnetic materials, building materials, composite materials, and the like. The light magnesia is metallurgical magnesia after pelletizing, high temperature calcining or electric melting and crushing, and is mainly used for metallurgical furnace lining and refractory brick making. Magnesium carbonate is generally an intermediate product in the process of producing magnesium oxide, and is also an independent chemical product, and is mainly used for fire prevention, heat preservation and insulating materials. With the improvement of product quality in recent years, the quality of magnesium oxide used as a raw material is required to be higher and higher in various industries.
The metallurgical magnesite is mainly from two main channels of a magnesite calcining method and a method for extracting magnesite from seawater, seawater brine, well salt brine or salt lake brine. The purity of magnesium oxide produced by the direct ore calcination process is difficult to increase due to the limitation of the impurities in the ore.
The large-stone bridge magnesite occupying 1/3 of the total storage capacity in the world has been a base for metallurgical magnesite for a long time, but the grade is still 95-97% of MgO. China has a long coastline, namely seawater magnesium chloride MgCl2·6H2O, also called seawater bischofite, is abundant in resource. In addition, 47 hundred million tons of magnesium chloride are stored in the Qinghai Chevrolet salt lake in China. Original salt lake carnallite KCL MgCL2·6H2O, a byproduct of bischofite MgCL of salt lake after extracting potash fertilizer2·6H2O, the quantity is huge and the impurity is very little, the expansion project of 100 ten thousand tons of potash fertilizers produced every year is started, the self-designed freezing crystallization method of China is adopted, which means that 270 ten thousand tons of bischofite as a byproduct is produced every year, if not, the utilization and consumption are adopted in timeIf the salt lake is put back, the structure of the salt lake resource is damaged, and the postnatal troubles and problems are left for the offspring. However, the seawater and brine high-purity magnesium oxide industry in China has not been developed so far, and the high-purity magnesium oxide containing more than or equal to 98 percent of MgO used in the metallurgical industry and other industries still mainly depends on import at present.
As is well known, the methods for producing high purity magnesium oxide from seawater or brine include, in summary, the slurry method, the ammonia method, the ammonium carbonate method, the carbonization method, the soda method, and the pyrolysis method (i.e., the Aman method). The process adopted by each country depends on local resources according to local conditions.
The method for preparing the magnesium oxide with high purity by preparing the ammonium magnesium carbonate double salt and then thermally decomposing is still only in the research and exploration stage abroad until no industrialized production process exists at present. The synthesis method and properties of the magnesium double salt are studied late and reported little, and its crystal structure is recorded by JCPDS card late in 1979 (J. APPL. Crystal.12.611 (1979)). At the following stage: ger 1,073.462(1960), Ger (east)87, 772(1972), Czech 161, 555(1975), Revue de Chimiemine' rale, t.22, (1985) p.692 and the like, although ammonium magnesium carbonate tetrahydrate double salts are prepared in succession, it has also been reported that high purity magnesium oxide or magnesium carbonate can be obtained by thermally decomposing the double salts. However, these patents and studies relate to the synthesis principle adopted, the ammonium salt raw material for compounding, the process, and the like, and the synthesis principle is summarized, and magnesium chloride is taken as the magnesium salt raw material as an example, and can be expressed as the main reaction formula:
the ammonium salt raw material for compounding in the process is finished solid ammonium carbonate or ammonium carbonate aqueous solution. The synthesis principle is based on the complex reaction of two kinds of single salt in water solution to produce double salt.
The method has themain problems that (1) ammonium carbonate is adopted as an ammonium salt raw material, so that the cost is high, and impurities are easy to introduce. (2) The double salt method process has low utilization rate of equipment, 6.26 tons of double salt is needed to be produced for producing 1 ton of magnesium oxide, and the problem of recycling the gas released by the thermal decomposition of the double salt is not mentioned.
The invention aims to provide a method for preparing high-purity magnesium oxide or magnesium carbonate in a circulating medium. The method is a method for preparing high-purity light magnesium oxide at the early stage, namely ammonium carbonate magnesium complex salt, which is suitable for chemical engineering and metallurgical magnesite, by taking bischofite as a main raw material in view of the market and resource characteristics of China. The method has low cost, low energy consumption, high utilization rate of raw materials, and high product purity.
In order to achieve the purpose, the invention adopts the following technical scheme: the method for preparing high-purity magnesium oxide or magnesium carbonate in circulating medium includes preparing high-purity magnesium oxide and high-purity magnesium carbonate.
1. The method for preparing the high-purity magnesium oxide comprises the following steps:
(1) absorbing ammonia gas with industrial gas cylinder or gas purity equivalent to the gas cylinder by pure water at normal pressure and room temperature of-40 ℃ until the total ammonia concentration is 5-16 mol/L ammonia water;
(2) then introducing carbon dioxide gas cylinder gas or carbon dioxide with the purity equivalent to the gas cylinder gas to carbonized ammonia water with the carbonization degree of 0.40-0.60, wherein the carbonization degree is the molar ratio of the total carbon dioxide concentration to the total ammonia concentration; if the degree of carbonization is outside this range, no single-phase double salts are obtained and mixtures containing other magnesium salts may occur.
(3) Then removing impurities from one or more of industrial-grade magnesium chloride, magnesium sulfate and magnesium nitrate according to Mg2+∶CO2∶NH3Slowly adding into the carbonized ammonia water under normal pressure and room temperature-60 ℃ to obtain tetrahydrate ammonium magnesium carbonate double salt precipitate;
(4) finally, after washing and filtering the tetrahydrate magnesium ammonium carbonate double salt, the dry material is thermally decomposed at the temperature of 390-600 ℃ to obtain the high-purity magnesium oxide.
2. And (3) washing and filtering the tetrahydrate ammonium magnesium carbonate double salt in the step (4), and decomposing the dry material at the low temperature of 80-390 ℃ to prepare the high-purity magnesium carbonate.
In the method of the invention, in the step 1- (4), the filtered dry material is firstly subjected to low-temperature thermal decomposition at 80-390 ℃ to prepare anhydrous magnesium carbonate, and then is subjected to thermal decomposition. Anhydrous magnesium carbonate as intermediate product and Mg2CO3More than or equal to 98 percent of high-purity magnesium carbonate. The method is divided into two steps of low-temperature decomposition and thermal decomposition, and pure carbon dioxide can be obtained in the second thermal decomposition, so that the method is favorable for recycling.
In the method of the invention, in the steps 1- (4) and 2- (4), the filtered filtrate is evaporated and crystallized to obtain ammonium chloride, ammonium sulfate, ammonium nitrate or a mixture thereof and pure water. Wherein ammonium chloride, or ammonium sulfate or ammonium nitrate or their mixture can be used as chemical raw material and cheap fertilizer. Pure water recovery can be utilized in step (1) of the process.
In the method of the invention, in the steps 1- (4) and 2- (4), the gas released by thermal decomposition is a mixed gas of ammonia gas, carbon dioxide gas and water vapor, and the carbon dioxide is absorbed by an absorption tower and then used as a process circulating medium in the step (2).
In the method, in the step (3), the solution obtained after the impurities of the industrial-grade magnesium chloride, magnesium sulfate and magnesium nitrate is a magnesium solution obtained by removing impurities in advance through a primary recrystallization method or removing impurities through primary hydrogen sulfide introduction and active magnesium oxide addition, wherein the primary hydrogen sulfide introduction and active magnesium oxide addition impurity removal process comprises introducing hydrogen sulfide into a crude magnesium solution until saturation, adding active magnesium oxide powder containing 2-5 times of boron by weight, fully stirring, boiling and filtering to obtain a pure magnesium solution.
In the process of the present invention, in said step (1), the total ammonia concentration of the aqueous ammonia is preferably 8 to 12 mol/liter. Can be increased to 16 mol/L in a closed container, and the larger the concentration is, the more the yield is.
In the method of the present invention, in the step (2), the carbonization degree of the carbonized aqueous ammonia is preferably 0.50.
In the method of the present invention, the thermal decomposition temperature of the dry material in the step 1- (4) is preferably 500-550 ℃.
In the method of the present invention, in the steps 1- (4) and 2- (4), the temperature of the low-temperature thermal decomposition of the filtered dry material is preferably 200 ℃ to 250 ℃.
The main reaction of the ammonium carbonate magnesium complex salt method provided by the invention is shown as follows by taking bischofite as an example:
formula (1)
Formula (2)
Formula (3)
In the above formula (1), gaseous ammonia and carbon dioxide are now (first) made into carbonized ammonia water with a carbonization degree of about 0.50 in water as the ammonium salt raw material, and the main component in the carbonized ammonia water is ammonium carbamate NH2COONH4Instead of ammonium carbonate, which is fundamentally different from the prior art double salt process. The synthesis principle is as follows: at a carbonization degree of about 0.50 (i.e., CO)2/NH3The molar ratio is equal to 0.5 and only at this degree of carbonization does the complete reaction of formula (1) above) occur in aqueous ammonium carbamate solution, which, when a solution of magnesium salts is added, promotes the hydrolysis of ammonium carbamate and the formation of double salts.
The double salt obtained by precipitation at a temperature between room temperature and 60 ℃ is actually a salt of a defined composition MgCO3·(NH4)2CO3·4H2Orthogonal crystals of O. Such crystal precipitates are coarse particles similar to magnesium carbonate but less soluble than magnesium carbonate in the same solution. If a small amount of magnesium ammonium carbonatetetrahydrate is added into the carbonized ammonia water solution before the preparation of the precipitate to be used as a seed crystal, the magnesium chloride solution is controlled from small to large, the whole adding process is controlled to be at a slower speed, and moderate stirring intensity is controlled, so that crystal precipitate with excellent clarification and filterability is obtained. Therefore, compared with the prior methods for producing magnesium oxide or magnesium carbonate by adopting the method for preparing high-purity magnesium oxide or magnesium carbonate in circulating mediumThe process has the following remarkable advantages:
(1) the magnesium ammonium carbonate tetrahydrate double salt is a crystal with definite composition, and when the crystal is formed and precipitated, impurity ions, especially Ca which is difficult to remove by sulfide precipitation method are removed2+、Na+、K+And CL-、SO4 2-、NO3 -、(B(OH)4)-1The plasma remains in solution;
(2) the crystallized and precipitated particles are large, and impurity ions attached to and clamped between the precipitated particles are easy to wash away by water;
(3) carrying out two-step thermal decomposition on tetrahydrate magnesium ammonium carbonate complex salt, wherein ammonium carbonate is decomposed into ammonia and carbon dioxide while dehydrating in the first step (formula 2), the decomposition temperature range is 80-390 ℃, and the product is anhydrous magnesium carbonate; the second step (formula 3) is the decomposition of magnesium carbonate to magnesium oxide and evolution of carbon dioxide, starting at a decomposition temperature of 390 ℃. If the decomposition is controlled at 400-600 ℃, the light magnesium oxide with the apparent specific volume of 7-5 ml/g can be prepared. But the thermal decomposition temperature is lower and the industrial production energy consumption is lower in general;
(4) the water vapor, ammonia gas and carbon dioxide gas released by thermal decomposition are pure gases, and are cooled and absorbed by water to be used as circulating media for process precipitation, so that raw materials are saved, and the high purity of the product is ensured;
(5) the by-products of the process, ammonium chloride, ammonium sulfate or ammonium nitrate, can be used as chemical raw materials and cheap fertilizers, and have a wider outlet compared with the by-product of the slurry method, namely calcium chloride. The distilled water collected in the evaporation crystallization process can be used as pure water for batching and washing precipitation in the process.
The invention will be further explained with reference to the drawings.
FIG. 1 is a process flow diagram of the process of the present invention
As shown in FIG. 1, the reactor is used in a weak acid and weak base corrosion resistant reaction vessel which is externally provided with a circulating cooling water jacket, internally provided with a thermometer and a stirring paddleAbsorbing ammonia gas from industrial liquid ammonia gas cylinder or gas cylinder with purity by using a certain amount of pure water, controlling the liquid temperature to be below 40 ℃ below zero to the ammonia water concentration of 5-16 mol/L, and taking 8-10 mol/L as the most appropriate concentration range in a normal pressure and non-closed container. Changing the carbon dioxide introduced into the industrial carbon dioxide gas cylinder or the carbon dioxide equivalent to the purity of the cylinder gas to the carbonization degree (CO)2/NH3Molar ratio) equal to 0.40-0.60, preferably 0.50. If ammonia can be introduced into the closed reactor to a concentration of 16 mol/l or even higher, but carbon dioxide still needs to be introduced to a degree of carbonization of 0.50, the volumetric throughput can be increased.
MgCl industrial grade seawater magnesium chloride2·6H2O, magnesium sulfate MgSO4·7H2O, magnesium nitrate Mg (NO)3)2·6H2O, MgCl in Qinghai salt lake2·6H2Magnesium salt such as O is dissolved in pure water to a nearly saturated solution at room temperature. Impurity removal is carried out by adopting a recrystallization method or a hydrogen sulfide-active magnesium oxide method. The latter is to introduce hydrogen sulfide into the solution to saturation, then add active magnesium oxide powder containing 2-5 times of boron in the solution, fully stir, boil and filter to obtain purified magnesium solution.
According to Mg2+∶CO2∶NH3Adding slowly into the ammonia carbide water solution while stirring at room temperature-60 deg.C under the condition of controlling the solution temperature to 1: 2: 4, and optimally mixing in the molar ratio of (0.95-0.98) to 2: 4 to obtain the magnesium ammonium carbonate tetrahydrate double salt precipitate.
In an evaporation crystallizer with a circulating water cooling cover, filtrate is evaporated and crystallized into byproducts such as ammonium chloride, ammonium sulfate, ammonium nitrate and the like, and distilled water is collected to be pure water which can be used for supplementing a water absorption process and washing a precipitated filter cake.
The filter cake is pulped and washed by pure water with the volume of 3 times, and then filtered and dried to obtain pure tetrahydrate of ammonium magnesium carbonate double salt. Part of the filtrate is returned to the magnesium salt dissolving process, and the surplus is discharged.
The magnesium ammonium carbonate tetrahydrate is decomposed at the temperature of 80-390 ℃, preferably at the temperature of 200-3More than or equal to 98 percent of anhydrous magnesium carbonate. Ammonia, carbon dioxide and water vapor released by decomposition return to water absorptionAnd (5) collecting.
The magnesium carbonate is continuously heated to 390-550 ℃, and the best control is 500-550 to carry out high-temperature thermal decomposition, so that the light magnesium oxide with the apparent specific volume of 7-5 ml/g is prepared. The carbon dioxide gas released by decomposition is returned to the carbonization step as the raw material gas.
When industrial-grade seawater magnesium chloride, magnesium sulfate, magnesium nitrate and other solids or brine thereof are used as magnesium salt raw materials, the impurities are removed through primary recrystallization or primary hydrogen sulfide-active magnesium oxide, and primary precipitation and thermal decomposition are carried out, so that the magnesium salt containing MgO and B is not less than 98 percent2O3Less than or equal to 0.008 percent and less than or equal to 0.30 percent of CaO. Under the same process conditions, when the magnesium chloride in Qinghai salt lake of China is used as the raw material of magnesium salt, the magnesium salt lake with MgO content more than or equal to 99% and B content can be prepared2O3Less than or equal to 0.005 percent ofThe CaO is less than or equal to 0.05 percent, and the industrial ultra-high pure light magnesium oxide has no boron and low calcium.
Ammonia, carbon dioxide and water vapor released by low-temperature thermal decomposition in the process are absorbed by water to form dilute carbonized ammonia water, and the dilute carbonized ammonia water can be recycled in the continuous production process. Only the ammonia needed for generating the byproduct ammonium chloride and the ammonia lost in the process absorption need to be supplemented into the dilute carbonized ammonia water until the total ammonia concentration of the solution is 8-10 mol/L. After the carbonization procedure continues to absorb the carbon dioxide released by high-temperature thermal decomposition, the carbon dioxide can also be recycled, and the carbonized ammonia water which is only needed to be supplemented and introduced into the carbon dioxide gas cylinder to make up the carbon dioxide lost in the carbonization procedure until the solution carbonization degree is about 0.50 is taken as a circulating medium, so that the carbonized ammonia water can be used for precipitation in the next process. The whole process is carried out repeatedly in a circulating medium, the main raw materials are industrial ammonia, carbon dioxide and magnesium salts, the main products are high-purity magnesium carbonate and magnesium oxide, the byproducts are ammonium chloride, ammonium sulfate or ammonium nitrate and the like, and a small amount of dilute water of ammonium carbonate fertilizer containing trace magnesium elements, which is harmless to soil, is discharged.
To more clearly illustrate the feasibility and process features of the present technology, the following examples are given:
the following identical apparatus was used for the tests: the water (ammonia) absorption-carbonization-precipitation processes are all carried out in a reaction vessel equipped with a circulating cooling water jacket, a thermometer and a stirring paddle. The filtration is water pump filtration. The thermal decomposition is carried out in a tubular electric furnace, the inner furnace tube is a stainlesssteel tube with one end closed and the other end provided with an air duct. The gas released by thermal decomposition enters a self-made absorption tower through a conduit, is absorbed by pure water and then is poured into the reactor above for use. The precipitated filtrate is crystallized in an evaporative crystallizer provided with a circulating cooling water cover, and the collected distilled water is used as pure water in the process.
The ammonium salt raw material is common liquid ammonia gas cylinder gas and carbon dioxide gas cylinder gas sold in the market.
The magnesium salt raw materials are commercial industrial grade seawater bischofite, magnesium sulfate, magnesium nitrate, bischofite produced in salt lake in Qinghai potash fertilizer factory, and the like.
Example 1
Is prepared from seawater bischofite through one-step purifying process by hydrogen sulfide-active magnesium oxide
1200 ml of pure water is filled in the reactor, the temperature is controlled to be less than 40 ℃ by water cooling, ammonia gas is introduced under normal pressure until the concentration of ammonia water is 8.168 mol/L, and the volume of liquid V in the solution is equal to about 1500 ml. Two carbon compounds are introduced until the degree of carbonization is 0.52. The bischofite is put in a silica gel drier for a plurality of days in advance, the dosage is 591.6g by theoretical calculation, but considering that the seawater bischofite contains about 5 percent of impurities, 622 g of bischofite is weighed and dissolved in 600 ml of pure water to prepare room temperature nearly saturated liquid, and the room temperature nearly saturated liquid is filtered. Introducing hydrogen sulfide into the filtrate until the filtrate is saturated, adding 1.5 g of active magnesium oxide powder, fully stirring, boiling and filtering. The filtrate was slowly added tothe carbonized ammonia water prepared above to precipitate. Clear and filter overnight. The filtrate is evaporated and crystallized to obtain ammonium chloride, and distilled water is collected to be used as pure water. The filter cake was washed by beating with pure water in an amount of 3 times by volume and dried by suction filtration to obtain 724.1 g of magnesium ammonium carbonate tetrahydrate containing about 5% of adsorbed water. Placing the material in a stainless steel tube, keeping the temperature at 200 ℃ for 2 hours to obtain anhydrous229 g of magnesium carbonate. Then the temperature is kept at 500 ℃ for 2 hours to obtain 109 g of magnesium oxide, and the gas released by low-temperature and high-temperature thermal decomposition is absorbed by an absorption tower and used as a process circulating medium. Warp productsAnd (3) analysis: containing 98.5% of MgO and B2O30.0080% and CaO 0.28%, the specific volume is 6.5 ml/g.
Example 2
Is prepared from industrial magnesium sulfate through one-step recrystallization purification.
Under the same temperature and pressure conditions as in example 1, ammonia was introduced into 1200 ml of pure water to 7.826 mol/l, and the volume of liquid V was about 1.47 l. Carbon dioxide is introduced until the degree of carbonization reaches 0.46. The industrial magnesium sulfate is purified once by adopting a conventional recrystallization method, namely crude magnesium salt → room temperature saturated dissolution → filtration → evaporative concentration → cooling to room temperature crystallization → filtering the crystal and placing the crystal in a silica gel drier for a plurality of days → recrystallizing the magnesium sulfate. The amount is 694.2g theoretically, but considering that the purity of 98% can be achieved by one-time recrystallization, 708 g of material is weighed and dissolved in 700 ml of purewater to prepare nearly saturated liquid. Controlling the temperature of the liquid to be less than 60 ℃, and adding the magnesium solution into carbonized ammonia water for precipitation. Clear and filter overnight. Evaporating and crystallizing the filtrate to obtain ammonium sulfate, and collecting distilled water for pure water. The filter cake is pulped and washed by pure water with the volume ratio of 3 times and then is filtered and dried. The dry material is kept at 600 ℃ for 2 hours to obtain 104 g of magnesium oxide. The gas released by thermal decomposition is absorbed by the absorption tower and used as a process circulating medium. Product analysis: containing 98.8% of MgO and B2O30.0072% and 0.15% of CaO, the specific volume is 5.5 ml/g.
Example 3
Magnesium nitrate is used as magnesium salt raw material.
Under the same process conditions of temperature and pressure as in example 1, ammonia gas was introduced into 1200 ml of pure water to an ammonia concentration of 10.52 mol/l, and the liquid V was about 1.6 l. Carbon dioxide is introduced until the degree of carbonization reaches 0.48.
Magnesium nitrate in China is generally prepared by dissolving magnesium oxide or magnesium carbonate serving as a raw material by nitric acid, filtering, concentrating and crystallizing, and the purity of the magnesium nitrate reaches over 98 percent, so that impurities do not need to be removed. The amount is 1057.4g calculated by theory, 1100 g of magnesium nitrate is weighed and dissolved in 900 ml of pure water to prepare nearly saturated liquid. About 0.1 g of magnesium ammonium carbonate tetrahydrate is first weighed and added to the carbonated ammonia water as seed crystal, and then the magnesium solution is slowly added for precipitation. Clear overnight and filter. FiltrateEvaporating and crystallizing to obtain ammonium nitrate, and collecting distilled water for use as pure water. The filter cake is beaten and washed by pure water with the volume of 3 times of the filter cake, and is dried by suction filtration. The dried material was kept at 550 ℃ for 2 hours to obtain 155 g of magnesium oxide. The gas released by thermal decomposition is absorbed by absorption tower and used as circulating medium for technological precipitation. Product analysis: MgO 99.5%, B2O30.0043% and 0.12% CaO, as a specific volume of 6.0 ml/g.
Example 4
Is prepared from bischofite in Qinghai salt lake through one-step purifying by hydrogen sulfide-active magnesium oxide.
The process conditions of temperature and pressure are the same as those of the example 1, 1400 ml of absorption liquid in the absorption tower is taken,the ammonia gas introduced into the liquid ammonia bottle was supplemented to a total ammonia concentration of 9.480 moles/liter, at which time the liquid V was about 1.55 liters. Introducing a carbon dioxide gas cylinder until the carbonization degree is 0.55. The amount of bischofite used was 709.4g theoretically, but considering that there were about 2-3% impurities in salt lake magnesite, 730 g of bischofite dried in a silica gel dryer was weighed and dissolved in 700 ml of pure water to prepare a nearly saturated solution at room temperature, and the solution was filtered. Introducing hydrogen sulfide into the filtrate until the filtrate is saturated, adding 1 g of active magnesium oxide powder, fully stirring, boiling and filtering. The filtrate was slowly added to the carbonized ammonia water prepared above to precipitate. Clear and filter overnight. The filtrate was evaporated to crystallize ammonium chloride, and distilled water was collected for pure water. The filter cake is beaten and washed by pure water with the volume ratio of 3 times, and is dried by suction filtration to obtain 860 g of tetrahydratemagnesium ammonium carbonate. Keeping the temperature of the mixture in a tubular electric furnace at 250 ℃ for 2 hours to obtain 280 g of anhydrous magnesium carbonate. Then keeping the temperature of 450 ℃ for 4 hours to prepare 133 g of magnesium oxide. The gas released by thermal decomposition is absorbed by the absorption tower and used as a circulating medium for process precipitation. Product analysis: MgO 99.5%, B2O3The specific volume is 7.0 ml/g, and the technological yield of magnesium is about 95%.
Example 5
High-purity magnesium carbonate is prepared from bischofite in Qinghai salt lake by one-step hydrogen sulfide-active magnesium oxide purification method.
The absorption liquid 14 in the absorption tower is taken under the same temperature and pressure process conditions as those in example 100 ml of ammonia gas was additionally fed to a total ammonia concentration of 9.490 mol/l, at which time the liquid V was about 1.55 l. Introducing carbon dioxide gas until the carbonization degree is 0.56. The amount of bischofite is 710.5 g theoretically, and with impurities taken into consideration, 731 g of dried bischofite is weighed and dissolved in 700 ml of pure water to prepare a room temperature nearly saturated solution, and then the solution is filtered. Hydrogen sulfide is introduced into the filtrate until saturation, 1 g of active magnesium oxide powder is added, and the mixture is stirred, boiled and filtered. The filtrate was added to the above carbonized ammonia water to perform precipitation. Clear and filter overnight. The filtrate was evaporated to crystallize ammonium chloride, and distilled water was collected for pure water. The filter cake is beaten and washed by pure water with the volume ratio of 3 times, and is dried by suction filtration to obtain 860 g of tetrahydrate magnesium ammonium carbonate. Keeping the temperature of the mixture in a tubular electric furnace at 250 ℃ for 2 hours to obtain 280 g of anhydrous magnesium carbonate. Product analysis: containing MgCO3=99.3%
In conclusion, the method has the advantages of low cost, low energy consumption, high utilization rate of raw materials and high product purity.

Claims (14)

1. A method for preparing high-purity magnesium oxide in a circulating medium is characterized in that: the method comprises the following steps:
(1) absorbing ammonia gas with industrial gas cylinder or gas purity equivalent to the gas cylinder by pure water at normal pressure and room temperature of-40 ℃ until the total ammonia concentration is 5-16 mol/L ammonia water;
(2) then introducing carbon dioxide gas or carbon dioxide gas with the purity equivalent to that of the gas cylinder gas to carbonized ammonia water with the carbonization degree of 0.40-0.60, wherein the carbonization degree is the molar ratio of the total carbon dioxide concentration to the total ammonia concentration;
(3) then removing impurities from one or more of industrial-grade magnesium chloride, magnesium sulfate and magnesium nitrate according to Mg2+∶CO2∶NH3Slowly adding into the carbonized ammonia water under normal pressure and room temperature-60 ℃ to obtain tetrahydrate ammonium magnesium carbonate double salt precipitate;
(4) finally, after washing and filtering the tetrahydrate magnesium ammonium carbonate double salt, the dry material is thermally decomposed at the temperature of 390-600 ℃ to obtain the high-purity magnesium oxide.
2. The process of claim 1 for producing high purity magnesium oxide in a circulating medium, wherein: in the step (4), the filtered dry material is subjected to low-temperature thermal decomposition at 80-390 ℃ to prepare anhydrous magnesium carbonate, and then is subjected to thermal decomposition.
3. The process of claim 1 for producing high purity magnesium oxide in a circulating medium, wherein: in the step (4), the filtered filtrate is evaporated and crystallized to obtain ammonium chloride, ammonium sulfate, ammonium nitrate or a mixture thereof and pure water.
4. The process of claim 1 for producing high purity magnesium oxide in a circulating medium, wherein: and (4) in the step (2), the gas released by thermal decomposition is a mixed gas of ammonia gas, carbon dioxide and water vapor, and is absorbed by an absorption tower and then used as a process circulating medium in the step (2).
5. The method for preparing high-purity magnesium oxide in the circulating medium according to claim 4, wherein: in the step (3), the solution obtained after the impurities of the industrial-grade magnesium chloride, magnesium sulfate and magnesium nitrate is a magnesium solution obtained after the impurities are removed by a primary recrystallization method in advance or after the impurities are removed by introducing hydrogen sulfide once and adding active magnesium oxide once, the process of introducing hydrogen sulfide once and adding active magnesium oxide for removing the impurities is that hydrogen sulfide is introduced into the crude magnesium solution until the crude magnesium solution is saturated, active magnesium oxide powder containing 2-5 times of boron in weight is added, and the pure magnesium solution is obtained through full stirring, boiling and filtering.
6. The method for preparing high-purity magnesium oxide in the circulating medium according to claim 5, wherein: in the step (1), the total ammonia concentration of the ammonia water is 8-10 mol/L.
7. A method for producing high-purity magnesium oxide in a circulating medium according to claim 1 or 2, characterized in that: in the step (4), the dry materials are subjected to thermal decomposition at the temperature of 500-550 ℃.
8. The method for preparing high-purity magnesium oxide in the circulating medium according to claim 2, wherein: in the step (4), the filtered dry material is decomposed at low temperature of 200-250 ℃.
9. A method for producing high-purity magnesium oxide in a circulating medium according to claim 2 or 8, characterized in that: in the step (4), the gas released by low-temperature thermal decomposition is a mixed gas of ammonia gas, carbon dioxide and water vapor, and the carbon dioxide released by thermal decomposition is absorbed by an absorption tower and then used as a process circulating medium in the step (2).
10. A method for preparing high-purity magnesium carbonate in a circulating medium is characterized in that: the method comprises the following steps:
(1) absorbing ammonia gas with industrial gas cylinder or gas purity equivalent to the gas cylinder by pure water at normal pressure and room temperature of-40 ℃ until the total ammonia concentration is 5-16 mol/L ammonia water;
(2) then introducing carbon dioxide gas or carbon dioxide gas with the purity equivalent to that of the gas cylinder gas to carbonized ammonia water with the carbonization degree of 0.40-0.60, wherein thecarbonization degree is the molar ratio of the total carbon dioxide concentration to the total ammonia concentration;
(3) then removing impurities from one or more of industrial-grade magnesium chloride, magnesium sulfate and magnesium nitrate according to Mg2+∶CO2∶NH3Slowly adding into the carbonized ammonia water under normal pressure and room temperature-60 ℃ to obtain tetrahydrate ammonium magnesium carbonate double salt precipitate;
(4) and finally, washing and filtering the tetrahydrate magnesium ammonium carbonate double salt, and carrying out low-temperature thermal decomposition on the dry material at the temperature of 80-390 ℃ to obtain the high-purity magnesium carbonate.
11. The process for the preparation of magnesium carbonate of high purity in a circulating medium according to claim 10, characterized in that: in the step (4), the filtered filtrate is evaporated and crystallized to obtain ammonium chloride, ammonium sulfate, ammonium nitrate or a mixture thereof and pure water.
12. The process for the preparation of magnesium carbonate of high purity in a circulating medium according to claim 10, characterized in that: and (4) in the step (2), the gas released by thermal decomposition is a mixed gas of ammonia gas, carbon dioxide and water vapor, and is absorbed by an absorption tower and then used as a process circulating medium in the step (2).
13. The process for the preparation of magnesium carbonate of high purity in a circulating medium according to claim 12, characterized in that: in the step (3), the solution obtained after the impurities of the industrial-grade magnesium chloride, magnesium sulfate and magnesium nitrate is a magnesium solution obtained after the impurities are removed by a primary recrystallization method in advance or after the impurities are removed by introducing hydrogen sulfide once and adding active magnesium oxide once, the process of introducing hydrogen sulfide once and adding active magnesium oxide for removing the impurities is that hydrogen sulfide is introduced into the crude magnesium solution until the crude magnesium solution is saturated, active magnesium oxide powder containing 2-5 times of boron in weight is added, and the pure magnesium solution is obtained through full stirring, boiling and filtering.
14. The process for the preparation of magnesium carbonate of high purity in a circulating medium according to claim 13, characterized in that: in the step (1), the total ammonia concentration of the ammonia water is 8-10 mol/L.
CNB011003731A 2001-01-03 2001-01-03 High-purity mangesium oxide or magnesium carbonate preparing process in circular medium Expired - Fee Related CN1174921C (en)

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CN102275957B (en) * 2011-07-18 2013-05-29 南京航空航天大学 Process for producing high purity magnesium oxide with dolomite
CN103130250B (en) * 2011-11-22 2014-12-03 北京化工大学 Method for preparing active magnesium oxide
CN105060321A (en) * 2015-07-23 2015-11-18 韦海棉 Preparation process for anhydrous magnesium carbonate
WO2017041738A1 (en) * 2015-09-09 2017-03-16 有研稀土新材料股份有限公司 Recycling process of wastewater containing ammonium ion and preparation method of metal oxide
CN105271320B (en) * 2015-11-23 2017-01-04 中国科学院青海盐湖研究所 The preparation method that a kind of morphology controllable bitter earth nano is brilliant
CN109133121A (en) * 2018-08-20 2019-01-04 镇江裕太防爆电加热器有限公司 A kind of magnesium tube material production method for high temperature heater (HTH)
CN108706966A (en) * 2018-08-22 2018-10-26 连云港市隆泰镁业有限公司 A kind of preparation method and application of high-purity electrically molten magnesia
CN114314618B (en) * 2021-12-10 2023-08-22 北京石油化工学院 Magnesium carbonate double salt crystal, amorphous carbonate containing magnesium and preparation method of active magnesium oxide

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