CN1446751A - Technique for producing magnesium hydroxide and mangesia by using ammonia complete cycle method - Google Patents
Technique for producing magnesium hydroxide and mangesia by using ammonia complete cycle method Download PDFInfo
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Abstract
A process for preparing Mg(OH)2 and MgO by full circulation method includes mixing the raw material containing MgO with ammonium solution, extracting reaction while distilling in extracting-distilling tower to generate ammonia and water vapour, concentrating ammonia at middle position of tower, passing through preheater and condenser and then in booster, removing impurity from Mg liquid discharged from tower bottom, synthesizing reaction between the pure Mg liquid and the material from booster to obtain Mg(OH)2, and calcining to obtain MgO. The ammonium liquid separated from Mg(OH)2 can be cyclically used.
Description
Technical Field
The present invention relates to the production technology of magnesium hydroxide and magnesium oxide, and is especially technological process of producing magnesium hydroxide through ammonia precipitation with magnesium salt solutionand roasting to dewater to produce magnesium oxide.
Background
It is well known that magnesium oxide can be dissolved in ammonium salt solutions and therefore MgO-containing powders can be purified by extraction with ammonium chloride, ammonium sulfate and ammonium nitrate solutions to remove impurities therefrom.
Generally, after calcium oxide is mixed with ammonium salt solution, the combined ammonium in the ammonium salt can be completely converted into ammonium hydroxide only a few minutes, so that ammonia can be easily distilled out by a heating method, and the reaction can be completed by adopting distillation of a distillation tower.
The magnesium oxide has low solubility in water, which is about 200 times lower than calcium oxide at normal temperature, so the pH value is low, and when the magnesium oxide is mixed with ammonium salt solution, even if the magnesium oxide reaches equilibrium, the ammonium compound in the ammonium salt can not be completely converted into ammonium hydroxide, so the extraction method adopted in the past is to react in a kettle to prolong the extraction time and improve the conversion rate of MgO. The operation is not suitable for continuous operation, and the operation has high energy consumption according to the vapor-liquid equilibrium principle, and the evaporated ammonia gas is only suitable for preparing ammonia water.
Chinese patent CN1037690A, ammonium nitrate and magnesia are used for reaction in a reaction pot, and the concentration of the reaction extract Mg2+Mixing NH of ammonia water and magnesium liquid in the synthetic process at 1.4-3.0 mole/L4OH/Mg(NO3)2The ratio is 2 to 6 molar ratio. The synthesis process needs to add Mg (OH) for batch operation2And (4) seed crystals. The method has large solution circulation amount and high ammonia distillation energy consumption, and is difficult to solve the problems of excessive distillation residues and Mg (OH)2And (5) washing water. The operation is also discontinuous.
Spanish patent ES2020135 uses ammonium nitrate solution to react with impure MgO. This patent also uses a still for extraction. According to the method, 1 ton of MgO is produced, and the quantity of circulating ammonia is 1.5 tons. If the ammonia amount in reflux condensation of the stripping tower at the upper part of the kettle is not considered, the ammonia evaporation steam consumption can exceed 15 tons/ton MgO through simple steam-liquid balance and material balance, and if the reflux amount of the stripping tower is added, the steam consumption is higher. In addition, in the synthesis process of the method, the ammonium liquid is adopted to absorb ammonia to prepare the ammoniated ammonium liquid and the magnesium liquid, so that the process is complex, a large amount of freezing is consumed, and the circulating equivalent of the mother liquid is increased.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a novel process for preparing high-purity magnesium hydroxide and magnesium oxide, which has the advantages of full circulation of ammonia, high efficiency, low consumption and continuous operation.
The basic principle of the invention is as follows: performing extraction reaction on the ammonium salt solution and MgO in the raw material, and filtering the generated magnesium salt solution to remove impurities; the ammonia generated by the reaction is distilled, concentrated and pressurized, and is subjected to synthesis reaction with magnesium salt to obtain high-quality Mg (OH)2And then toRoasting to obtain high-quality MgO:
for simplicity and clarity of description, some abbreviations and symbols are explained in advance for their contents and their meanings: ammonium solution: the ammonium ion-rich solution, namely ammonium salt, is an extracting agent and is ammonium salt such as ammonium sulfate, ammonium nitrate, ammonium chloride and the like. In the circulating process, the synthesis product is discharged from the synthesis device and is separated to filter out Mg (OH)2Then adding or not adding the solution after washing water, and then becoming the raw material for size mixing and extraction reaction, wherein the main components of the raw material comprise magnesium salt and NH besides ammonium salt4OH；
Magnesium liquid: the solution rich in magnesium ions in the process is the raw material of the synthesis reaction, which is discharged from the bottom of the extractive distillation tower after the magnesium oxide is subjected to extraction reaction and is separated to remove impurities. The main components of the agent comprise magnesium salt, ammonium salt and NH4OH；
Diluting liquid: containing only a small amount of NH4Condensate of OH;
: free ammonia. In solution with NH4mol/L of ammonia in which OH exists;
: ammonium is incorporated. Ammonium in the solution in the presence of ammonium salt, mol/L;: total ammonia.
mol/L；: total magnesium.
mol/L；
α ratio of total ammonia to total magnesium,
mol/L。
the invention adopts a full-cycle process to carry out continuous production, and the process flow is shown as the attached figure 1: MgO-containing raw material(such as magnesite powder, brucite powder, light-burned brucite powder, etc.) is quantitatively added into a size mixing tank, and is mixed with ammonium salt solution preheated by a preheater at the upper part of the extractive distillation tower, and the mixed liquid is pumped to the lower section of the extractive distillation tower for extraction reaction and distillation. The evaporated ammonia and water vapor pass through the middle section (rectification section) of the tower to concentrate ammonia gas, pass through the upper section of the tower to exchange heat with ammonium liquid serving as a size mixing raw material, are cooled by a gas cooler, are discharged from the top of the tower to be sent to an ammonia gas supercharger, and are pressurized and then fed into a synthesis device for synthesis; the condensate in the middle section of the tower enters a weak liquor barrel outside the tower; and (3) feeding the solution discharged from the tower bottom, namely the magnesium liquid into a separation device, removing impurities, feeding the solution into a magnesium liquid barrel, pumping the solution to a synthesis device, and carrying out synthesis reaction with pressurized ammonia gas. The synthesized slurry enters a thickener for thickening, enters a separation device, separated liquid-phase ammonium liquid and liquid separated by the device enter an ammonium liquid tank, and separated solid-phase Mg (OH)2Washing in the device, wherein the washing liquid also enters into the device, and Mg (OH) is obtained after washing2Drying the magnesium hydroxide by a dehydration device and a drying device to obtain high-quality magnesium hydroxide which can be used as a finished product to be sold on the market; or the magnesium oxide can be sent to a roasting device for roasting to obtain high-quality magnesium oxide. The ammonium liquid in the ammonium liquid tank is pumped to the upper-stage preheater and becomes the extractant for the circulating process and the continuous production again.
The condensate of the dilute solution barrel is pumped to a dilute solution distillation tower for distillation, the distilled ammonia gas enters a booster 7 and also serves as a raw material for the synthesis reaction, and the residual liquid enters a storage tank for washing Mg (OH)2Or for it.
Process conditions in the circulation
Slurry mixing of ammonium solution:：2.0～5.0mol/L，Mg2+：0.5～1.5mol/L；
an extractive distillation column: temperature at the bottom of the column: 105-135 ℃,
the tower top temperature: 30-70 parts of;
discharging magnesium liquid from the bottom of the tower:：2.0～5.5mol/L，
tower with a tower bodyTop pressure: atmospheric pressure
The synthesis process comprises the steps of controlling the temperature to be 40-80 ℃ and controlling α to be 0.95-1.20;
a weak liquor distillation tower: temperature at the bottom of the column: the temperature of the mixture is 103-110 ℃,
the tower top temperature: 30-110 ℃: pressure at the top of the column: atmospheric pressure
The extractive distillation column, one of the main devices in the present invention, is basically composed of three sections: the lower part is a reactive distillation section which is a plate tower and has the structure of sieve plate type, bubble cover type or floating spraying type, and the bottom of the tower is provided with a heating device which can be indirectly heated by a reboiler and can also be directly heated by steam; the middle part is a rectifying section which is of a plate tower or a packed tower structure; the upper part is a heat exchange section which consists of an ammonium liquid preheater and a cooler and is structurally a shell-and-tube or plate heat exchanger. In order to fully utilize the heat energy, a preheating section can be added between the reactive distillation section and the rectification section, so that the whole tower is in four sections, namely the reactive distillation section, the preheating section, the rectification section and the heat exchange section are respectively arranged from bottom to top. The preheating section structure adopts a plate tower or a packed tower. The preheating of the uppermost section of the column is indirect preheating (i.e. a heat exchanger) and the preheating section is a heat exchange section in which the ammonium solution is directly contacted with ammonia and water vapor from the reactive distillation to increase the temperature of the ammonium solution. The four-section tower and the flow path are shown in the attached figure 2: ammonium liquid which is indirectly preheated by the upper section enters from the upper part of the preheating section, and after heat exchange, the ammonium liquid comes out from the lower part of the preheating section and enters a size mixing tank to be mixed with raw materials (containing MgO). The reactive distillation section at thelower part of the column is provided with a slurry adjusting feeding plate, the slurry adjusting feeding plate is fed into the feeding plate in the column by a pump, and the position of the feeding plate is preferably at the uppermost part of the section. During operation, the slurry enters the tower, the extraction reaction is started from the first tower plate, and the extraction process is completed from the bottom of the tower. The distillation is carried out in time during the reaction, and the generated ammonia is separated from the water vapor and the generated magnesium liquid; the generated ammonia is concentrated in the rectifying section, the ammonia is separated from water, and the concentrated ammonia can be directly pressurized and then used for synthesis. The device can make full use of the residual heat in the tower and preheat the ammonium liquid which participates in the extraction reaction. The invention adopts the distillation tower to simultaneously carry out extraction reaction and distillation, can separate and remove products in the reaction process in time, continuously breaks the balance of the reaction and is very beneficial to the reaction. This apparatus is much more efficient than the prior art kettle reaction, single tray distillation. It can be seen that the structure of the column is reasonable, the energy of the distillation process is fully utilized, and the steam consumption is greatly saved.
The light liquid distillation tower is a packed tower or a plate tower structure and can be continuously carried out. Another important apparatus in the cyclic process is the synthesis unit, which uses a jet or tank reactor, since the process is continuous and no seed crystals need to be added. Products with different purities and granularities can be produced according to requirements.
The material circulation amount of the invention depends on the production scale and equipment conditions, and the MgO per ton is about 10-20 m under the general condition3。
In the circulation process, the extractive distillation column can be operated under slight negative pressure, normal pressure or pressurization according to the conditions of the synthesis device and the ammonia pressurization device. The pressure at the top of the column may be from 100mmHg (0.088MPa, 660mmHg absolute pressure) to 0.4 MPa.
Compared with the prior art, the invention adopts three-section or four-section tower to carry out extraction reaction, and simultaneously high-efficiency distillation is carried out, the slurry mixing liquid enters the lower section tower, passes through the tower plate and reaches the tower bottom to complete the extraction reaction process, and the efficiency is greatly improved. Because the step is successfully realized, conditions are provided for the continuity of the whole process. The continuous production high efficiency of the invention is also incomparable with the prior art. In addition, make full use of in continuous process Converting ammonium into full-circulation extractant; the distillation and concentration of ammonia can be directly used without refrigeration, thereby saving energy.
Description of the drawings figure 1 is a process flow diagram of the present invention. Wherein 1 is a size mixing tank, 2 is an extractive distillation tower, 3, 17, 19 and 20 are material delivery pumps, 4 is a separating device, 5 is a tower heating device, 6 is a thin liquid barrel, 7 is an ammonia booster, 8 is a synthesizing device, 9 is a thin liquid distillation tower, 10 is a synthesized slurry thickener,11 is a magnesium hydroxide separating device, 12 is Mg (OH)2Washing device, 13 is Mg (OH)2DewateringDevice, 14 is Mg (OH)2Drying means, 15 being Mg (OH)2The roasting device 16 is an ammonium liquid storage tank, 18 is a magnesium liquid barrel, and 21 is a waste weak liquid storage tank after ammonia is evaporated in a weak liquid tower.
FIG. 2 is a schematic diagram of a four-stage extractive distillation column and associated process therein. Wherein Y is a preheating section, the numerals and the directions of the arrows of which are the same as those of FIG. 1.
Detailed Description
Example 1: by NH4NO3As an extracting agent, magnesia powder is used as a magnesium-containing raw material, and MgO is produced by continuous operation.
The adding amount of the slurry adjusting liquid is 150-200L/h, and the tower top is at normal pressure;
size mixing liquidMg2+≤0.5～1.5mol/L；
An extractive distillation column: the temperature of the tower bottom is 105-135 ℃, and the temperature of the tower top is 45-65 ℃;
discharging magnesium liquid from tower bottom
In the synthesis process, a kettle type reaction kettle is used, the temperature is controlled to be 40-60 ℃, and the α obtained by continuous synthesis is 0.95-1.20;
equivalent of solution circulation: MgO of 10-20 m per 1t of production3The distillation steam consumption is less than or equal to 5t/t,
the MgO content of the product is more than or equal to 98.5%, and the particle size is 30-50 μm.
Example 2 by NH4Cl is used as an extracting agent, brucite powder is used as a raw material containing MgO, and the continuous operation is carried out to produce the MgO product.
The extractive distillation tower is operated under the micro negative pressure, the vacuum degree is 80-100 mmHg (the absolute pressure is 660-680 mmHg, 0.088-0.09 Mpa), the jet reaction is adopted for synthesis, and other operation conditions are as in example 1. The steam consumption in distillation is less than 5 t/t. The purity of the product is 98.5-99%, and the granularity of the product is less than or equal to 20 mu m.
Example 3 by NH4NO3Uses light-burned brucite powder as raw material as extractant to continuously and circularly produce MgO.
The extractive distillation tower adopts four-section tower, and the extractive distillation is operated under normal pressure.
Claims (7)
1. A method for producing magnesium oxide, is to use raw materials containing magnesium oxide to get magnesium salt through extracting reaction with ammonium salt, magnesium salt reacts with ammonia to make magnesium hydroxide, and then get magnesium oxide through roasting, its characteristic is the technological process of ammonia full-cycle continuous production: mixing a magnesium oxide-containing raw material and preheated ammonium liquid in a size mixing tank (1), feeding the size mixed liquid into the lower part of an extractive distillation tower (2) for extraction reaction and distillation, feeding ammonia and water vapor into a rectifying section in the middle of the tower to concentrate the ammonia, feeding the concentrated ammonia into the upper part of the tower, discharging the concentrated ammonia out of the tower through an ammonium liquid preheater and a gas cooler to a pressurizing device (7), and pressurizing theconcentrated ammonia and feeding the ammonia into a synthesizing device (8) for synthesis reaction; the condensate after ammonia concentration in the middle of the tower enters a dilute liquid barrel (6); the magnesium liquid discharged from the tower bottom enters a separation device (4), and the magnesium liquid with impurities removed enters a synthesis device (8) to carry out synthesis reaction with ammonia; the reactant is put into a thickener (10) for thickening, solid magnesium hydroxide is obtained through a separation device (11), and then the finished product of magnesium hydroxide is obtained through washing (12), dehydration (13) and drying (14), or the finished product of magnesium oxide is obtained through further roasting (15); ammonium liquid obtained from the separation device (11) and without solid magnesium hydroxide is dehydrated with washing water and enters an ammonium liquid tank (16), and the ammonium liquid in the ammonium liquid tank is sent to a preheater of the extractive distillation tower 2 for preheating and then enters a size mixing tank (1) to become a recycled extraction raw material;
the process conditions of the circulating process are as follows:
size mixing liquid
2.0～5.0mol/L，Mg2+0.5～1.5mol/L
An extractive distillation column: temperature at the bottom of the column: 105-135 deg.C
The tower top temperature: 30-70 DEG C
Discharging magnesium liquid from the bottom of the tower:2.0～5.5mol/Lpressure at the top of the column: atmospheric pressure
The synthesis process is carried out at 40-80 deg.C and α ═ 0.95-1.20
2. The process for producing magnesium oxide according to claim 1, wherein the extractive distillation column is a three-stage column: the lower part is a reactive distillation section which is a plate tower and has the structure of a sieve plate type, a bubble cap type or a floating spraying type, and the bottom of the tower is provided with a heating device;
the middle part is a rectifying section and the structure is a plate tower or a packed tower;
the upper part is a heat exchange section which consists of an ammonium liquid preheater and an ammonia gas cooler and is structurally a shell-and-tube or plate heat exchanger.
3. The method for producing magnesium oxide according to claim 1 or 2, wherein a preheating section is provided between the extractive distillation section and the rectification section, and the structure of the preheating section is plate type or packed type, and the ammonium liquid which is indirectly preheated at the upper part of the tower is preheated again in the preheating section, and the ammonium liquid enters from the upper part of the preheating section, is directly contacted with the ammonia and the water vapor evaporated after the reaction for heat exchange, then exits from the lower part of the preheating section, and enters the size mixing tank (1) for size mixing.
4. The process for producing magnesium oxide according to claim 1 or 2, wherein said extractive distillation column has a feed plate for introducing a slurry at a lower portion thereof; located at the uppermost part of the reactive distillation section.
5. The process for producing magnesium oxide according to claim 1, wherein the condensate in the middle gas of the extractive distillation column, which is condensed and then fed into the weak liquor drum (6), is ammonia-containing weak liquor, which is fed into a weak liquor distillation column (9) to distill off ammonia and is fed into the pressure boosting device (7); the residual liquid enters a storage tank (21); the weak liquid distillation tower is a packed tower or a plate tower;
distilling a light liquid: tower bottom temperature 103-110 ℃ tower top pressure: atmospheric pressure
The temperature of the tower top is 30-60 ℃.
6. The process for producing magnesium oxide according to claim 1, wherein said synthesis unit is a jet reactor or a tank reactor.
7. The process for producing magnesium oxide according to claim 1, wherein the extractive distillation column is operated at a slight negative pressure, an atmospheric pressure or a pressurized pressure depending on the synthesis apparatus and the ammonia gas pressure-increasing apparatus, and the pressure at the top of the column is in the range of 0.088MPa to 0.4 MPa.
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| CNB021076618A CN1190365C (en) | 2002-03-22 | 2002-03-22 | Technique for producing magnesium hydroxide and mangesia by using ammonia complete cycle method |
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| CNB021076618A CN1190365C (en) | 2002-03-22 | 2002-03-22 | Technique for producing magnesium hydroxide and mangesia by using ammonia complete cycle method |
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| CN1190365C CN1190365C (en) | 2005-02-23 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102417196A (en) * | 2011-09-16 | 2012-04-18 | 沈阳化工大学 | Production method of fire retardant type magnesium hydroxide |
| CN102745724A (en) * | 2012-06-26 | 2012-10-24 | 沈阳化工大学 | Method for producing high-purity magnesium oxide by using light calcined powder as raw material |
| CN103011630A (en) * | 2012-12-26 | 2013-04-03 | 新疆蓝天镁业股份有限公司 | Method of producing high-purity magnesium hydroxide and magnesium oxide by low-grade magnesite |
| CN103241751A (en) * | 2013-04-27 | 2013-08-14 | 陕西师范大学 | Preparation method for high-purity magnesium oxide |
| CN105347703A (en) * | 2015-12-03 | 2016-02-24 | 龙岩紫云化学科技有限公司 | Calcium magnesium carbonate salt mine decomposition method |
| CN110759365A (en) * | 2018-07-25 | 2020-02-07 | 张旭 | Device for preparing magnesium hydroxide by leaching solid magnesium ore and use method |
-
2002
- 2002-03-22 CN CNB021076618A patent/CN1190365C/en not_active Expired - Lifetime
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102417196A (en) * | 2011-09-16 | 2012-04-18 | 沈阳化工大学 | Production method of fire retardant type magnesium hydroxide |
| CN102417196B (en) * | 2011-09-16 | 2014-02-12 | 沈阳化工大学 | Production method of fire retardant type magnesium hydroxide |
| CN102745724A (en) * | 2012-06-26 | 2012-10-24 | 沈阳化工大学 | Method for producing high-purity magnesium oxide by using light calcined powder as raw material |
| CN103011630A (en) * | 2012-12-26 | 2013-04-03 | 新疆蓝天镁业股份有限公司 | Method of producing high-purity magnesium hydroxide and magnesium oxide by low-grade magnesite |
| CN103011630B (en) * | 2012-12-26 | 2015-09-09 | 新疆蓝天镁业股份有限公司 | Low-grade magnesite produces high purity magnesium hydroxide and method of magnesium oxide |
| CN103241751A (en) * | 2013-04-27 | 2013-08-14 | 陕西师范大学 | Preparation method for high-purity magnesium oxide |
| CN105347703A (en) * | 2015-12-03 | 2016-02-24 | 龙岩紫云化学科技有限公司 | Calcium magnesium carbonate salt mine decomposition method |
| CN110759365A (en) * | 2018-07-25 | 2020-02-07 | 张旭 | Device for preparing magnesium hydroxide by leaching solid magnesium ore and use method |
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