CN115141941A - Comprehensive utilization method of dolomite - Google Patents
Comprehensive utilization method of dolomite Download PDFInfo
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- CN115141941A CN115141941A CN202210733938.9A CN202210733938A CN115141941A CN 115141941 A CN115141941 A CN 115141941A CN 202210733938 A CN202210733938 A CN 202210733938A CN 115141941 A CN115141941 A CN 115141941A
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- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
- C22B26/20—Obtaining alkaline earth metals or magnesium
- C22B26/22—Obtaining magnesium
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- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
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Abstract
The invention particularly relates to a comprehensive utilization method of dolomite, belonging to the technical field of magnesium metal preparation, and the method comprises the following steps: calcining dolomite to obtain calcined dolomite; digesting the calcined dolomite, and then aging to obtain a digestive liquid; mixing and carbonizing the digestive juice and carbon dioxide until the pH value of the digestive juice reaches a preset value, and then carrying out solid-liquid separation to obtain heavy magnesium water and a calcium carbonate filter cake; pyrolyzing heavy magnesium water, and then carrying out solid-liquid separation to obtain basic magnesium carbonate filter cakes; drying and roasting the basic magnesium carbonate filter cake to obtain magnesium oxide; mixing and pressing magnesium oxide and a reducing agent to obtain a briquette; carrying out vacuum reduction on the agglomerates to obtain metal magnesium and magnesium aluminate spinel; drying the calcium carbonate filter cake to obtain light calcium carbonate; the comprehensive utilization rate of dolomite resources is more than 90%, no waste residue and waste gas are discharged, light calcium carbonate and magnesia-alumina spinel are byproducts besides metal magnesium, and the problem of low utilization rate of the existing dolomite resources is solved.
Description
Technical Field
The invention belongs to the technical field of metal magnesium preparation, and particularly relates to a comprehensive utilization method of dolomite.
Background
The specific gravity of the metal magnesium is 1.74g/cm 3 Only 2/3 of aluminum, 2/5 of titanium and 1/4 of steel. The composite material has the advantages of high specific strength, high specific rigidity, good heat and electricity conducting performance, good electromagnetic shielding, damping, vibration damping, cutting processability, low processing cost, easiness in recycling and the like. As a unique strategic metal and a novel structural material in China, the material plays a greater role in the fields of traffic light weight, new energy materials, environmental protection industry, consumer electronics, ocean engineering, aerospace, military industry matching, military and civil fusion and the like. The rapid development of intercity rail transit for construction and operation in China also makes magnesium alloy castings, profiles and plates have great use.
The main methods for producing magnesium are the electrolysis method and the silicothermic method (Pidgeon method). The electrolytic method is to electrolyze magnesium chloride from brine to produce magnesium, and the Pidgeon method is to produce magnesium by reducing calcined dolomite with ferrosilicon (Si > 75%). Because of low investment cost and simple operation, the Pidgeon process becomes the main method in the prior industrial hot-process magnesium smelting process, and the magnesium metal in China is produced by the Pidgeon process, but the process has the problems of high energy consumption, low resource utilization efficiency and serious environmental pollution at present. In the traditional Pidgeon process of magnesium smelting, 11 tons of dolomite, 30 kilograms of fluorite and 1.05 tons of silicon iron are needed to be consumed for producing 1 ton of magnesium metal, and the energy consumption is 4 tons of standard coal; besides, the utilization rate of dolomite resources is extremely low, about 20 percent of magnesium oxide is utilized, a large amount of carbon dioxide and waste residues are discharged, about 15 tons of carbon dioxide are required to be discharged when 1 ton of metal magnesium is produced, and 5-6 tons of waste residues are required to be discharged when the metal magnesium is produced. The development of smelting magnesium by the Pidgeon process is restricted by high energy consumption, resource waste and high emission.
In the prior art, for example, chinese patent application CN201910354623.1 provides a magnesium smelting process capable of recycling waste gas and waste residues, comprising the steps of mixing dolomite, magnesite and reducing agent aluminum powder, pressing pellets, calcining, reducing to produce magnesium metal and solid reducing slag, reacting the solid reducing slag with a sodium carbonate solution to generate a sodium aluminate solution, and calcining released high-temperature CO 2 And introducing a sodium aluminate solution for carbon decomposition after heat recovery. The process is used for discharging CO during calcination 2 The Al in the reducing slag is recycled and extracted, but the reducing slag contains a large amount of CaO and a part of MgO, which exist in the form of dissolved slag, which indicates that the process still discharges the waste slag, and magnesite is required to be added for proportioning. The Chinese patent application CN201710320876.8 proposes a process for simultaneously preparing metal magnesium and calcium carbide by a carbothermic method, wherein calcined dolomite, magnesium oxide, quicklime, a carbonaceous reducing agent and a fluorite catalyst are mixed and proportioned, then the mixture is placed into a ball mill with a sieve for grinding and sieving, then the mixture is sent into a high-pressure pair roller ball press machine for pressing into balls, finally the balls are placed into a vacuum reactor, the vacuum reactor is vacuumized, and metal magnesium vapor and calcium carbide are produced under certain pressure and temperature. Although the process improves the utilization rate of raw materials, a large amount of carbon monoxide and carbon dioxide gas can be additionally generated, and meanwhile, magnesium oxide, quicklime, fluorite powder and the like are added for proportioning.
Therefore, the prior art has the problems of low utilization rate of dolomite resources, large carbon dioxide emission, high production energy consumption and the like.
Disclosure of Invention
The application aims to provide a comprehensive utilization method of dolomite, so as to solve the problem that the utilization rate of dolomite resources is not high at present.
The embodiment of the invention provides a comprehensive utilization method of dolomite, which comprises the following steps:
calcining dolomite to obtain calcined dolomite;
digesting the calcined dolomite, and then aging to obtain a digestive liquid;
mixing and carbonizing the digestive juice and carbon dioxide until the pH value of the digestive juice reaches a preset value, and completing carbonization to obtain heavy magnesium water and calcium carbonate;
reacting the heavy magnesium water to obtain magnesium oxide;
and carrying out vacuum reduction on the magnesium oxide to obtain metal magnesium and magnesium aluminate spinel.
Optionally, the steps of mixing and carbonizing the digestive juice and the carbon dioxide until the pH value of the digestive juice reaches a preset value and completing carbonization are carried out to obtain the heavy magnesium water and the calcium carbonate filter cake,
atomizing the digestive liquid, introducing carbon dioxide for carbonization until the pH value of the digestive liquid reaches a preset value, and then carrying out solid-liquid separation to obtain heavy magnesium water and a calcium carbonate filter cake.
Optionally, the particle size of the atomized digestive juice is 0.5-8 μm; the concentration of the carbon dioxide is 30-100%; the preset value is 7.5 +/-0.3, and the carbonization time is 2-20min.
Optionally, in the digestion process, 25-50L of water is used for each kilogram of calcined dolomite, the digestion temperature is 25-90 ℃, and the digestion time is 0.5-3h.
Optionally, the reacting the heavy magnesium water to obtain magnesium oxide specifically includes:
pyrolyzing the heavy magnesium water, and then carrying out solid-liquid separation to obtain basic magnesium carbonate filter cakes;
drying and roasting the basic magnesium carbonate filter cake to obtain magnesium oxide;
the pyrolysis temperature is 80-100 ℃, and the pyrolysis time is 1-4h.
Optionally, the roasting temperature is 500-650 ℃, and the roasting time is 1-3h.
Optionally, the temperature of the vacuum reduction is 1050-1150 ℃, the time of the vacuum reduction is 1-5h, and the vacuum degree of the vacuum reduction is 5-10Pa.
Optionally, the vacuum reduction includes mixing the magnesium oxide and a reducing agent, wherein the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the magnesium oxide to the aluminum-containing reducing agent is 2.7-3.1:1.
optionally, the aluminum-containing reducing agent includes aluminum powder made from an aluminum-based printing plate, the aluminum-based printing plate includes a 1-series alloy, and the particle size of the aluminum-containing reducing agent is 150 to 355 μm.
Optionally, the calcining temperature is 1000-1200 ℃, and the calcining time is 1-3h.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
according to the comprehensive utilization method of dolomite provided by the embodiment of the invention, the dolomite is calcined and then digested and aged to obtain a digestive liquid, and the digestive liquid is utilized to perform a series of operations such as carbonization, vacuum reduction and the like to obtain a product: the comprehensive utilization rate of the dolomite resource reaches more than 90%, the whole process has no waste residue and waste gas emission, and the problem of low utilization rate of the dolomite resource at present is solved.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a process flow diagram provided by an embodiment of the present invention;
fig. 2 is a flow chart of a method provided by an embodiment of the invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
according to an exemplary embodiment of the present invention, there is provided a comprehensive utilization method of dolomite, the method including:
s1, calcining dolomite to obtain calcined dolomite;
in some embodiments, the temperature of the calcination is from 1000 to 1200 ℃ and the time of the calcination is from 1 to 3 hours.
MgCO in dolomite 3 The decomposition temperature is 720-800 ℃ and CaCO is required 3 The decomposition temperature needs to be 900-930 ℃. In actual production, the calcination temperature is generally set to 1000 ℃ to 1200 ℃, and can be determined by experiments. If the calcination temperature is too low and the calcination time is too short, the decomposition is not completely performed; when the temperature is too high, the calcination time is too long, and MgO grains grow and gradually lose activity.
S2, digesting the calcined dolomite, and then aging to obtain a digestive liquid;
specifically, the calcined dolomite is sent into a lime slaking machine, a certain proportion of water is added, the mixture is continuously stirred and digested for a certain time, and then the mixture is aged for 12 hours to obtain a digestive juice;
in the above process, the chemical reactions that take place are specifically as follows:
(MgO+CaO)+2H 2 O＝Mg(OH) 2 +Ca(OH) 2
in some embodiments, 25-50L of water is used per kilogram of calcined dolomite during digestion, the digestion temperature is 25-90 ℃, and the digestion time is 0.5-3h.
Controlling the solid-liquid ratio of calcined dolomite to water as follows: 1kg: the reason of 25-50L is to ensure the calcined dolomite to be completely digested, so that calcium hydroxide and magnesium hydroxide are completely generated, and simultaneously, formed digestive juice is reduced to reduce the treatment amount of subsequent production.
The digestion temperature is controlled to be 25-90 ℃, energy waste is caused by overhigh temperature, and too long digestion time is caused by overlow temperature.
The aging time is controlled for 12h, the aging time is too long, the crystallinity of the magnesium hydroxide is better, the reaction activity is lower, and the carbonization is not facilitated; the aging time is too short, the magnesium hydroxide is poor in crystallization, and carbonization is not facilitated.
S3, mixing and carbonizing the digestive liquid and carbon dioxide until the pH value of the digestive liquid reaches a preset value, and then carrying out solid-liquid separation to obtain heavy magnesium water and a calcium carbonate filter cake;
in the above process, the chemical reactions that take place are specifically as follows:
Mg(OH) 2 +CO 2 +2H2O＝MgCO 3 ·3H2O
MgCO 3 ·3H 2 O+CO 2 ＝Mg(HCO 3 ) 2 +2H 2 O
Ca(OH) 2 +CO 2 ＝CaCO 3 (precipitation) + H 2 O
Specifically, the digestive juice is atomized into liquid drops of 0.5-8 microns and sent to a carbonization device, carbon dioxide is introduced for carbonization, and the carbonization end point is determined by detecting the pH value. Then a plate and frame filter is adopted to carry out solid-liquid separation to obtain heavy magnesium water and a filter cake, and the filter cake is dried in a dryer for more than 12 hours to obtain light calcium carbonate.
In some embodiments, the mixing and carbonizing of the digestive juice and the carbon dioxide are carried out until the pH value of the digestive juice reaches a preset value and the carbonization is completed, and then the solid-liquid separation is carried out to obtain the heavy magnesium water and the calcium carbonate filter cake,
atomizing the digestive liquid, introducing carbon dioxide for carbonization until the pH value of the digestive liquid reaches a preset value, and then carrying out solid-liquid separation to obtain heavy magnesium water and a calcium carbonate filter cake.
The invention adopts atomization carbonization, is easy to control, has good gas-liquid contact, uniform reaction, low energy consumption and high utilization rate of carbon dioxide, and the carbonization time is reduced to within twenty minutes from two hours of the traditional bubbling carbonization equipment.
In some embodiments, the atomized digestive juice has a particle size of 0.5-8 μm; the concentration of the carbon dioxide is 30-100%; the preset value is 7.5 +/-0.3, and the carbonization time is 2-20min.
Controlling the pH value to be 7.5 +/-0.3, controlling the pH value to be too high, incompletely carbonizing, and enabling part of magnesium carbonate to enter a calcium carbonate product; when the pH value is too low, the calcium carbonate is further carbonized into calcium bicarbonate and enters into heavy magnesium water.
The concentration of carbon dioxide is controlled to be 30% -100%, in the actual production, the concentration of the carbon dioxide of the dolomite calcination tail gas is generally 30% under the condition of concentration without being trapped, and the carbonization is faster as the concentration is higher.
In this example, the carbon dioxide is derived from dolomite calcination off-gas.
S4, pyrolyzing the heavy magnesium water, and then carrying out solid-liquid separation to obtain a basic magnesium carbonate filter cake and a decomposition liquid;
in the above process, the chemical reactions that take place are specifically as follows:
2(Mg(HCO 3 ) 2 )＝MgCO 3 ·Mg(OH) 2 ·H 2 O+3CO 2
specifically, heavy magnesium water is placed in a pyrolysis reaction kettle to be heated and continuously stirred, then a plate-and-frame filter is adopted to carry out solid-liquid separation to obtain a decomposition liquid and a filter cake, and the filter cake is dried in a dryer for more than 12 hours to obtain basic magnesium carbonate.
In some embodiments, the temperature of the pyrolysis is 80-100 ℃ and the time of the pyrolysis is 1-4h.
The pyrolysis temperature is controlled to be 80-100 ℃, and the heavy magnesium water can be decomposed within 100 ℃, so that energy waste is caused by overhigh temperature, and the pyrolysis time is too long due to overlow temperature.
In some embodiments, the decomposition liquid can enter a digestion section for digestion treatment, and the temperature of the decomposition liquid can meet digestion conditions, so that energy consumption is reduced.
S5, drying and roasting the basic magnesium carbonate filter cake to obtain magnesium oxide;
in the above process, the chemical reactions that take place are specifically as follows:
MgCO 3 ·Mg(OH) 2 ·H 2 O＝2MgO+CO 2 +2H 2 O
in some embodiments, the temperature of calcination is from 500 to 650 ℃ and the calcination time is from 1 to 3 hours.
The roasting temperature of the basic magnesium carbonate is controlled to be 500-650 ℃, and the roasting temperature can be determined through experiments. If the roasting temperature is too low and the roasting time is too short, the decomposition is not completely carried out; when the temperature is too high, the time is too long, and MgO crystal grains grow and gradually lose activity.
Specifically, the basic magnesium carbonate is placed in a roasting furnace to be roasted for 1-3h at the temperature of 500-650 ℃, and magnesium oxide is obtained.
S6, mixing and pressing the magnesium oxide and a reducing agent to obtain a briquette;
specifically, the aluminum-containing reducing agent is an aluminum-based printing plate, the aluminum-based printing plate is prepared into aluminum powder, the aluminum powder with different particle sizes is obtained after powder classification, the aluminum powder with the particle size of 150-355 mu m is selected as the reducing agent, and then the reducing agent is mixed with magnesium oxide for blending, and then the mixture is pressed into a briquette.
In some embodiments, the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the magnesium oxide to the aluminum-containing reducing agent is 2.7 to 3.1:1.
controlling the mass ratio of the magnesium oxide to the aluminum-containing reducing agent ingredient to be (2.7-3.1): the reason for 1 is to ensure that the magnesia-alumina spinel meets the requirements of SMA 66-level components in the national standard (GB/T26564-2011), the adverse effect of overlarge mass ratio value is to cause that the content of magnesia exceeds the standard, and the adverse effect of undersize is to cause that the economy is poor and the content of alumina exceeds the standard.
In some embodiments, the aluminum-containing reducing agent includes aluminum powder made of an aluminum-based printing plate including a 1-series alloy, and specifically, the 1-series alloy may be: 1060 alloy, 1050 alloy or 1050A alloy, wherein, by mass percentage, the Al content is more than or equal to 99%, and the granularity of the aluminum-containing reducing agent is 150-355 μm.
The particle size of the aluminum-containing reducing agent is controlled to be 150-355 mu m, and the excessive particle size of the aluminum-containing reducing agent can cause insufficient contact with magnesium oxide, so that the excessive particle size is not suitable for economy.
S7, carrying out vacuum reduction on the briquette to obtain metal magnesium and magnesium aluminate spinel;
specifically, the agglomerates are put into a reducing furnace for vacuum reduction (5-10 Pa) to obtain magnesium metal and magnesium aluminate spinel, wherein the reduction temperature is 1050-1150 ℃, and the reduction time is 1-5h.
In the above process, the chemical reactions that take place are specifically as follows:
4MgO+2Al＝3Mg+MgO·Al 2 O 3
in some embodiments, the temperature of the vacuum reduction is 1050-1150 ℃, the time of the vacuum reduction is 1-5h, and the vacuum degree of the vacuum reduction is 5-10Pa.
And S8, drying the calcium carbonate filter cake to obtain the light calcium carbonate.
The utilization rate of dolomite resources in the Pidgeon magnesium smelting process is extremely low, only about 20 percent of magnesium oxide is utilized, a large amount of carbon dioxide and waste residues are discharged, the reduction reaction is a solid-solid reaction, the reaction speed is low, and the reaction energy on the surface of an oxide can be increased by adding auxiliaries such as calcium fluoride and the like, so that the reaction is accelerated. The utilization rate of dolomite resources is more than 90 percent, about 6.25 tons of light calcium carbonate and about 2 tons of magnesium aluminate spinel are by-produced when 1 ton of metal magnesium is produced, and other auxiliary materials and auxiliary agents are not needed. From the thermodynamic perspective, the reduction reaction temperature is lower than that of the Pidgeon magnesium smelting process, the solid-liquid reaction is adopted, the reaction speed is high, the reduction temperature is reduced by 50-100 ℃, the reduction time is shortened by more than 50%, and no waste residue or waste gas is discharged.
The comprehensive utilization method of dolomite according to the present application will be described in detail below with reference to examples, comparative examples, and experimental data.
Example 1
The process flow chart of the invention is shown in figure 1, and the clean magnesium metallurgy for comprehensively utilizing dolomiteRefining method and process, using dolomite containing 21.45% of MgO,30.39% of CaO,0.76% of SiO 2 ，0.091％Al 2 O 3 ，0.069％Fe 2 O 3 ，46.59％CO 2 Wherein the mol ratio of CaO to MgO is 1.01, and the method comprises the following steps:
(1) Calcining dolomite at 1200 ℃ for 3h to obtain calcined dolomite;
(2) Adding water in a certain proportion into calcined dolomite for digestion, wherein the solid-to-liquid ratio is 1kg:25L, the digestion temperature is 25 ℃, the digestion time is 3h, and then the digestion solution is obtained after aging for 12 h;
(3) Atomizing the digestive juice into liquid drops of 0.5-8 microns, sending the liquid drops into a carbonization device, and simultaneously introducing carbon dioxide with the concentration of 30% for carbonization until the pH value of the digestive juice reaches 7.8. Then solid-liquid separation is carried out by adopting a plate and frame filter to obtain heavy magnesium water and filter cakes, and the filter cakes are dried for more than 12 hours in a dryer to obtain light calcium carbonate.
(4) And (3) putting the heavy magnesium water into a pyrolysis reaction kettle, heating and continuously stirring, wherein the pyrolysis temperature is 80 ℃, and the pyrolysis time is 4 hours. And then carrying out solid-liquid separation by adopting a plate and frame filter to obtain decomposition liquid and a filter cake, drying the filter cake in a dryer for more than 12 hours to obtain basic magnesium carbonate, and then placing the basic magnesium carbonate in a roasting furnace to calcine for 1 hour at 650 ℃ to obtain magnesium oxide.
(5) Preparing the aluminum-based printing plate into aluminum powder, grading the powder to obtain aluminum powder with different particle sizes, and selecting the aluminum powder with the particle size of 150 mu m;
(6) Mixing and batching magnesium oxide and aluminum powder, and then pressing the mixture into a briquette under the pressure of 100MPa, wherein the mass ratio of the magnesium oxide to the aluminum powder is 2.7:1;
(7) And (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain magnesium metal and magnesium aluminate spinel, wherein the reduction temperature is 1100 ℃, the reduction time is 2 hours, and the vacuum degree is 5-10Pa.
Example 2
The process flow diagram of the invention is shown in figure 1, a clean magnesium smelting method and process for comprehensive utilization of dolomite, adopts dolomite containing 21.45 percent of MgO,30.39 percent of CaO,0.76 percent of SiO 2 ，0.091％Al 2 O 3 ，0.069％Fe 2 O 3 ，46.59％CO 2 Wherein the mol ratio of CaO to MgO is 1.01, and the method comprises the following steps:
(1) Calcining dolomite at 1200 ℃ for 1h to obtain calcined dolomite;
(2) Adding water in a certain proportion into calcined dolomite for digestion, wherein the solid-to-liquid ratio is 1kg:30L, the digestion temperature is 60 ℃, the digestion time is 1h, and then the digestion solution is obtained after aging for 12 h;
(3) Atomizing the digestive juice into liquid drops of 0.5-8 microns, sending the liquid drops into a carbonization device, and simultaneously introducing carbon dioxide with the concentration of 50% for carbonization until the pH value of the digestive juice reaches 7.6. Then solid-liquid separation is carried out by adopting a plate and frame filter to obtain heavy magnesium water and filter cakes, and the filter cakes are dried for more than 12 hours in a dryer to obtain light calcium carbonate.
(4) And (3) putting the heavy magnesium water into a pyrolysis reaction kettle, heating and continuously stirring, wherein the pyrolysis temperature is 100 ℃, and the pyrolysis time is 2 hours. And then carrying out solid-liquid separation by adopting a plate and frame filter to obtain a decomposition liquid and a filter cake, drying the filter cake in a dryer for more than 12 hours to obtain basic magnesium carbonate, and then placing the basic magnesium carbonate in a roasting furnace to calcine for 2 hours at the temperature of 600 ℃ to obtain magnesium oxide.
(5) Preparing an aluminum-based printing plate into aluminum powder, grading the aluminum powder to obtain aluminum powder with different particle sizes, and selecting the aluminum powder with the particle size of 180 mu m;
(6) Mixing and batching magnesium oxide and aluminum powder, and then pressing the mixture into a briquette under the pressure of 122MPa, wherein the mass ratio of the magnesium oxide to the aluminum powder is 2.9:1;
(7) And (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain magnesium metal and magnesium aluminate spinel, wherein the reduction temperature is 1050 ℃, the reduction time is 5h, and the vacuum degree is 5-10Pa.
Example 3
The process flow diagram of the invention is shown in figure 1, a clean magnesium smelting method and process for comprehensive utilization of dolomite, adopts dolomite containing 20.76% of MgO,30.29% of CaO,0.96% of SiO 2 ，0.35％Al 2 O 3 ，0.56％Fe 2 O 3 ，46.24％CO 2 Wherein the mol ratio of CaO to MgO is 1.04, and the method comprises the following steps:
(1) Calcining dolomite at 1100 deg.C for 3h to obtain calcined dolomite;
(2) Adding water in a certain proportion into calcined dolomite for digestion, wherein the solid-to-liquid ratio is 1kg:50L, the digestion temperature is 90 ℃, the digestion time is 0.5h, and then the digestion solution is obtained after aging for 12 h;
(3) Atomizing the digestive juice into liquid drops of 0.5-8 microns, sending the liquid drops into a carbonization device, and simultaneously introducing carbon dioxide with the concentration of 100% for carbonization until the pH value of the digestive juice reaches 7.4. Then solid-liquid separation is carried out by adopting a plate and frame filter to obtain heavy magnesium water and filter cakes, and the filter cakes are dried for more than 12 hours in a dryer to obtain light calcium carbonate.
(4) And (3) putting the heavy magnesium water into a pyrolysis reaction kettle, heating and continuously stirring, wherein the pyrolysis temperature is 100 ℃, and the pyrolysis time is 1h. And then carrying out solid-liquid separation by adopting a plate and frame filter to obtain a decomposition liquid and a filter cake, drying the filter cake in a dryer for more than 12 hours to obtain basic magnesium carbonate, and then placing the basic magnesium carbonate in a roasting furnace to calcine for 3 hours at 550 ℃ to obtain magnesium oxide.
(5) Preparing an aluminum-based printing plate into aluminum powder, grading the aluminum powder to obtain aluminum powder with different particle sizes, and selecting the aluminum powder with the particle size of 355 mu m;
(6) Mixing and batching magnesium oxide and aluminum powder, and then pressing the mixture into a briquette under the pressure of 150MPa, wherein the mass ratio of the magnesium oxide to the aluminum powder is 3:1;
(7) And (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain magnesium metal and magnesium aluminate spinel, wherein the reduction temperature is 1150 ℃, the reduction time is 1h, and the vacuum degree is 5-10Pa.
Example 4
The process flow diagram of the present invention is shown in FIG. 1, a clean magnesium smelting process and process for the comprehensive utilization of dolomite by employing dolomite containing 20.76% MgO,30.29% CaO,0.96% SiO% 2 ，0.35％Al 2 O 3 ，0.56％Fe 2 O 3 ，46.24％CO 2 Wherein the mol ratio of CaO to MgO is 1.04, and the method comprises the following steps:
(1) Calcining dolomite at 1100 deg.C for 1h to obtain calcined dolomite;
(2) Adding water in a certain proportion into calcined dolomite for digestion, wherein the solid-to-liquid ratio is 1kg:40L, the digestion temperature is 80 ℃, the digestion time is 1h, and then the digestion solution is obtained after aging for 12 h;
(3) Atomizing the digestive juice into liquid drops of 0.5-8 microns, sending the liquid drops into a carbonization device, and simultaneously introducing carbon dioxide with the concentration of 30% for carbonization until the pH value of the digestive juice reaches 7.2. Then solid-liquid separation is carried out by adopting a plate and frame filter to obtain heavy magnesium water and filter cakes, and the filter cakes are dried for more than 12 hours in a dryer to obtain light calcium carbonate.
(4) And (3) putting the heavy magnesium water into a pyrolysis reaction kettle, heating and continuously stirring, wherein the pyrolysis temperature is 100 ℃, and the pyrolysis time is 2 hours. And then carrying out solid-liquid separation by adopting a plate and frame filter to obtain a decomposition liquid and a filter cake, drying the filter cake in a dryer for more than 12 hours to obtain basic magnesium carbonate, and then placing the basic magnesium carbonate in a roasting furnace to calcine for 2 hours at 650 ℃ to obtain magnesium oxide.
(5) Preparing an aluminum-based printing plate into aluminum powder, grading the aluminum powder to obtain aluminum powder with different particle sizes, and selecting the aluminum powder with the particle size of 150 mu m;
(6) Mixing and batching magnesium oxide and aluminum powder, and then pressing the mixture into a briquette under the pressure of 190MPa, wherein the mass ratio of the magnesium oxide to the aluminum powder is 3.1:1;
(7) And (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain magnesium metal and magnesium aluminate spinel, wherein the reduction temperature is 1150 ℃, the reduction time is 2 hours, and the vacuum degree is 5-10Pa.
Comparative example 1
Using dolomite as a raw material, ferrosilicon (75%) as a reducing agent, and a fluorite powder as an additive, using 20.76% of MgO by using dolomite, 30.29% of CaO,0.96% of SiO 2 ，0.35％Al 2 O 3 ，0.56％Fe 2 O 3 ，46.24％CO 2 Wherein the mol ratio of CaO to MgO is 1.04, and the method comprises the following steps:
the method comprises the following steps:
(1) Calcining dolomite at 1100 ℃ for 1h;
(2) Crushing ferrosilicon, then, sending the crushed small particles into a ball mill for grinding by adopting a dry ball milling method, obtaining ferrosilicon with different particle sizes after powder classification, and selecting the ferrosilicon with the particle size of 150 mu m;
(3) The calcined dolomite is ground and then mixed with the ferrosilicon and the fluorite powder, and is pressed into briquettes under the pressure of 190MPa, wherein the mass ratio of the calcined dolomite, the ferrosilicon and the fluorite is 82.1:16.5:1.4;
(4) And (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain metal magnesium and reduction slag charge, wherein the reduction temperature is 1200 ℃, the reduction time is 5h, and the vacuum degree is 5-10Pa.
Comparative example 2
Dolomite is used as a raw material, aluminum powder is used as a reducing agent, and the dolomite is subjected to calcium-magnesium separation by adopting a traditional bubbling carbonization mode to prepare magnesium oxide. 0.96% of SiO by using 20.76% of MgO as dolomite, 30.29% of CaO 2 ，0.35％Al 2 O 3 ，0.56％Fe 2 O 3 ，46.24％CO 2 Wherein the mol ratio of CaO to MgO is 1.04, and the method comprises the following steps:
(1) Calcining dolomite at 1100 deg.C for 1h to obtain calcined dolomite;
(2) Adding the calcined dolomite into a certain proportion of water for digestion, wherein the solid-to-liquid ratio is 1kg:40L, digesting at the temperature of 80 ℃ for 1h, and then aging for 12h to obtain a digestive juice;
(3) And (3) placing the digestive juice in a reaction kettle with a stirrer, and introducing 30% carbon dioxide from the bottom end for bubbling carbonization until the pH value of the digestive juice reaches 7.2. Then a plate and frame filter is adopted to carry out solid-liquid separation to obtain heavy magnesium water and a filter cake, and the filter cake is dried in a dryer for more than 12 hours to obtain light calcium carbonate.
(4) And (3) placing the heavy magnesium water in a pyrolysis reaction kettle, heating and continuously stirring, wherein the pyrolysis temperature is 100 ℃, and the pyrolysis time is 2 hours. And then carrying out solid-liquid separation by adopting a plate and frame filter to obtain a decomposition liquid and a filter cake, drying the filter cake in a dryer for more than 12 hours to obtain basic magnesium carbonate, and then placing the basic magnesium carbonate in a roasting furnace to calcine for 2 hours at 650 ℃ to obtain magnesium oxide.
(5) Preparing an aluminum-based printing plate into aluminum powder, grading the aluminum powder to obtain aluminum powder with different particle sizes, and selecting the aluminum powder with the particle size of 150 mu m;
(6) Mixing and batching magnesium oxide and aluminum powder, and then pressing the mixture into a briquette under the pressure of 190MPa, wherein the mass ratio of the magnesium oxide to the aluminum powder is 3.1:1;
(7) And (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain magnesium metal and magnesium aluminate spinel, wherein the reduction temperature is 1150 ℃, the reduction time is 2 hours, and the vacuum degree is 5-10Pa.
The light calcium carbonates produced in examples 1 to 4 and comparative example 2 were subjected to the composition analysis, and the results are shown in the following table:
| CaCO 3 ％ | MgO％ | |
| example 1 | 93.07 | 3.90 |
| Example 2 | 92.37 | 3.89 |
| Example 3 | 93.60 | 3.76 |
| Example 4 | 94.21 | 2.54 |
| Comparative example 2 | 68.72 | 13.97 |
The magnesium oxides produced in examples 1 to 4 and comparative example 2 were subjected to composition analysis, and the results are shown in the following table:
the magnesium aluminate spinel or the reducing slag produced in examples 1 to 4 and comparative examples 1 to 2 were subjected to composition analysis, and the results are shown in the following table:
| Al 2 O 3 | MgO％ | CaO％ | SiO 2 | Fe 2 O 3 | |
| example 1 | 66.85 | 29.98 | 0.84 | 1.42 | 0.25 |
| Example 2 | 65.60 | 30.78 | 1.04 | 1.28 | 0.47 |
| Example 3 | 65.22 | 30.65 | 0.84 | 1.84 | 0.67 |
| Example 4 | 64.77 | 31.13 | 0.77 | 1.44 | 0.82 |
| Comparative example 1 | 1.34 | 7.95 | 54.48 | 33.28 | 2.78 |
| Comparative example 2 | 60.27 | 30.04 | 6.70 | 1.42 | 0.77 |
One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
(1) The method provided by the embodiment of the invention solves the problems of energy, resources and environment in the dolomite magnesium smelting industry, and the process is characterized in that the magnesium metal is produced and light calcium carbonate and magnesia-alumina spinel are produced as byproducts; secondly, the atomization carbonization method is efficient and energy-saving; thirdly, the reducing agent is produced by utilizing aluminum-based printing waste plates. The method can realize no waste slag and waste gas generation in the magnesium smelting production process, and is environment-friendly, energy-saving and clean in production; meanwhile, the method is also a comprehensive utilization of the aluminum-based printing waste plate;
(2) Compared with the traditional dolomite calcium-magnesium separation process, the process provided by the embodiment of the invention adopts atomization carbonization, is easy to control, has good gas-liquid contact, uniform reaction, low energy consumption and high utilization rate of carbon dioxide, and the carbonization time is shortened to be within twenty minutes from two hours of the traditional bubbling carbonization equipment; the pH is controlled to be 7.5 +/-0.3, so that calcium and magnesium are separated more thoroughly;
(3) Compared with the existing Pidgeon process, the method provided by the embodiment of the invention has the advantages that the reduction temperature is reduced by 50-100 ℃, the reduction time is shortened by more than 50%, the energy consumption is reduced, the magnesium recovery rate is more than 85%, and no waste residue or waste gas is discharged.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A comprehensive utilization method of dolomite is characterized by comprising the following steps:
calcining dolomite to obtain calcined dolomite;
digesting the calcined dolomite, and then aging to obtain a digestive liquid;
mixing and carbonizing the digestive juice and carbon dioxide until the pH value of the digestive juice reaches a preset value, and completing carbonization to obtain heavy magnesium hydrate and calcium carbonate;
reacting the heavy magnesium water to obtain magnesium oxide;
and carrying out vacuum reduction on the magnesium oxide to obtain metal magnesium and magnesium aluminate spinel.
2. A comprehensive utilization method of dolomite according to claim 1, wherein the digestion solution and carbon dioxide are mixed and carbonized until the pH value of the digestion solution reaches a preset value, thereby obtaining heavy magnesium hydrate and calcium carbonate filter cakes,
atomizing the digestive juice, introducing carbon dioxide for carbonization until the pH value of the digestive juice reaches a preset value, and then carrying out solid-liquid separation to obtain heavy magnesium water and a calcium carbonate filter cake.
3. A comprehensive utilization method of dolomite according to claim 2, wherein the particle size of the atomized digestion liquid is 0.5-8 μm; the concentration of the carbon dioxide is 30% -100%; the preset value is 7.5 +/-0.3, and the carbonization time is 2-20min.
4. A comprehensive utilization method of dolomite according to claim 1, wherein during the digestion, 25-50L of water is used per kg of calcined dolomite, the digestion temperature is 25-90 ℃, and the digestion time is 0.5-3h.
5. The comprehensive utilization method of dolomite according to claim 1, wherein the reaction of the heavy magnesium hydrate to obtain magnesium oxide specifically comprises:
pyrolyzing the heavy magnesium water, and then carrying out solid-liquid separation to obtain basic magnesium carbonate filter cakes;
drying and roasting the basic magnesium carbonate filter cake to obtain magnesium oxide;
the pyrolysis temperature is 80-100 ℃, and the pyrolysis time is 1-4h.
6. A comprehensive utilization method of dolomite according to claim 5, wherein the roasting temperature is 500-650 ℃, and the roasting time is 1-3h.
7. A comprehensive utilization method of dolomite according to claim 1, wherein the temperature of vacuum reduction is 1050-1150 ℃, the time of vacuum reduction is 1-5h, and the vacuum degree of vacuum reduction is 5-10Pa.
8. A comprehensive utilization method of dolomite according to claim 1, wherein the vacuum reduction comprises mixing the magnesium oxide and a reducing agent, wherein the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the magnesium oxide to the aluminum-containing reducing agent is 2.7-3.1:1.
9. a comprehensive utilization method of dolomite according to claim 8, wherein said aluminum-containing reducing agent comprises aluminum powder made of an aluminum-based printing plate including a 1-series alloy, and the particle size of said aluminum-containing reducing agent is 150 to 355 μm.
10. A comprehensive utilization method of dolomite according to claim 1, wherein the calcination temperature is 1000-1200 ℃ and the calcination time is 1-3h.
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