CN115449629B - Device and method for recycling magnesium sulfate solution and reacting with lime - Google Patents

Device and method for recycling magnesium sulfate solution and reacting with lime Download PDF

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CN115449629B
CN115449629B CN202210961828.8A CN202210961828A CN115449629B CN 115449629 B CN115449629 B CN 115449629B CN 202210961828 A CN202210961828 A CN 202210961828A CN 115449629 B CN115449629 B CN 115449629B
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mixing chamber
chamber
sedimentation
slurry
mixing
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CN115449629A (en
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吴声
王嵩龄
程福祥
刘艳
常智舵
冯凯
廖春生
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China Minmetals Beijing Research Institute Of Re Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/02—Apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/46—Sulfates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/14—Magnesium hydroxide
    • C01F5/22—Magnesium hydroxide from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B11/00—Calcium sulfate cements
    • C04B11/26—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
    • C04B11/266—Chemical gypsum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Materials Engineering (AREA)
  • Environmental & Geological Engineering (AREA)
  • Mechanical Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Metallurgy (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Structural Engineering (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

The invention belongs to the technical field of metallurgical chemical industry, and relates to a device and a method for recycling magnesium sulfate solution and reacting with lime. The device comprises a first mixing chamber (1), a second mixing chamber (2), a sedimentation chamber (3), a first stirrer (4), a second stirrer (9), a mixing chamber movable partition plate (5), a mixing chamber adjustable communication port (6), a sedimentation chamber movable partition plate (7), a sedimentation chamber adjustable communication port (8) and a slurry outlet (12). The device and the method for recycling the magnesium sulfate solution and reacting with the lime can inhibit the solid-liquid direct reaction in the magnesium sulfate-lime reaction process by controlling the operation conditions, thereby improving the reaction participation rate of the magnesium sulfate, improving the respective yields of the magnesium hydroxide and the calcium sulfate, and reducing the impurity component content in each product.

Description

Device and method for recycling magnesium sulfate solution and reacting with lime
Technical Field
The invention belongs to the technical field of metallurgical chemical industry, and relates to a device and a method for recycling magnesium sulfate solution and reacting with lime.
Background
In the nonferrous metallurgy industry, in particular to a sulfuric acid roasting process for treating Baotou mixed rare earth minerals by a sulfuric acid roasting method, magnesium oxide is needed to neutralize excessive sulfuric acid in roasting ore leaching liquid, and the generated magnesium sulfate and rare earth solution enter an extraction separation process together, so that finally produced sulfuric acid rare earth extraction separation wastewater contains more magnesium sulfate. The magnesium sulfate wastewater is generally precipitated into mixed slag of magnesium hydroxide and calcium sulfate by lime, and the solution after press filtration is reused for leaching the sulfuric acid roasting ore, and the mixed slag is treated as waste slag. The process only carries out the cyclic utilization of water, and calcium and magnesium completely enter mixed waste residues, so that great waste and environmental pollution are caused.
The calcium sulfate-magnesium hydroxide mixed slag can be recycled for neutralizing the sulfuric acid roasting ore leaching liquid in theory, but if the calcium sulfate enters the acid leaching slag, the acid leaching slag amount is increased, and the treatment is difficult. In addition, because of the high content of magnesium hydroxide, the calcium sulfate-magnesium hydroxide slag is difficult to apply to the fields of cement, building materials and the like.
Calcium sulfate has a high tendency to supersaturate, which characteristic makes it prone to exist in solution, is not prone to spontaneous nucleation, and can grow into larger particles in the presence of seed crystals; magnesium hydroxide tends to precipitate finer particles. Thus, in the presence of more calcium sulfate seeds, the crystallization of the supersaturated solution of calcium sulfate can be promoted, and the two precipitates can be subjected to sedimentation or sieving separation by utilizing the difference in particle size properties of calcium sulfate and magnesium hydroxide.
Chinese patent application 201210562657.8 discloses a method for preparing magnesium hydroxide from magnesium sulfate solution, in the presence of calcium sulfate seed crystal, lime milk is added into the magnesium sulfate solution to make the generated calcium sulfate form crystal grains, and after the generated calcium sulfate and magnesium hydroxide form larger grain size difference, the purpose of separating calcium and magnesium is achieved by screening through a rotary screen.
Chinese patent application 201610318207.2 discloses a method for treating magnesium sulfate and magnesium sulfite wastewater by a lime method, which comprises the technical steps of sedimentation impurity removal, aeration oxidation, reaction crystallization separation, overflow liquid filtration, washing and drying, kettle bottom slurry washing and separation, and filtration mother liquor recycling. The purified and oxidized wastewater and lime slurry are respectively and continuously added into a reaction crystallizer, sulfate ions and calcium ions are combined to form calcium sulfate dihydrate crystals with larger particle size by controlling reaction crystallization conditions and are settled to the bottom of the reaction crystallizer, magnesium ions and hydroxide ions are combined to form magnesium hydroxide with smaller particle size, and the magnesium hydroxide continuously overflows from an overflow port of the reaction crystallizer.
The reaction process of lime and magnesium sulfate can be divided into two steps: the first step is that lime is dissolved in water to form calcium hydroxide solution; the second step is that calcium hydroxide solution and magnesium sulfate solution are respectively formed into calcium sulfate dihydrate and magnesium hydroxide in the presence of calcium sulfate seed crystal.
The solution reaction can also be regarded as that calcium hydroxide is dissolved and ionized into calcium ions and hydroxide radicals, the calcium ions react with sulfate radicals to generate calcium sulfate precipitates, and magnesium ions react with the hydroxide radicals to generate magnesium hydroxide precipitates.
In the prior art, lime or lime milk, magnesium sulfate and calcium sulfate seed crystal are directly added into the same reactor, and besides the reaction carried out by a solution phase, the possibility that calcium hydroxide solid is directly contacted with the magnesium sulfate solution and reacts on the surface of the solid exists under the condition, and the magnesium hydroxide and the calcium sulfate are easily adsorbed on the surface of the calcium hydroxide to block the continuous reaction, so that the calcium content in the product magnesium hydroxide and the magnesium content in the calcium sulfate are increased, and the subsequent application is influenced.
In the treatment process of rare earth sulfate, a small amount of rare earth chloride solution is used for washing an organic phase during extraction and separation, so that chloride ions with a certain concentration exist in a circulating solution. In the presence of chloride ions, the solution reaction can still be regarded as that calcium hydroxide is dissolved and ionized into calcium ions and hydroxide radicals, the calcium ions react with sulfate radicals to generate calcium sulfate, and the magnesium ions react with the hydroxide radicals to generate magnesium hydroxide.
Chinese patent application 201810342090.0 discloses a device and a method for recycling magnesium sulfate wastewater, wherein quicklime is added into the magnesium sulfate wastewater, an internal circulation system based on calcium ion reflux is established to achieve the effect of classifying and precipitating precipitates, and magnesium sulfate is classified and precipitated in the form of calcium sulfate and magnesium hydroxide, so that the purpose of recycling is achieved. The process adds solution such as calcium chloride to form soluble calcium solution to precipitate sulfate radical to generate magnesium chloride solution, and then uses lime to precipitate the magnesium chloride solution to generate magnesium hydroxide. The process adopts liquid/liquid reaction in the process of precipitating calcium sulfate, so that the quality of a calcium sulfate product can be ensured, but the possibility of direct solid-liquid reaction still exists in the reaction process of lime and magnesium. In addition, the process comprises a first mixing reactor, a first sedimentation tank, a first centrifugal machine, a second mixing reactor, a second sedimentation tank, a second centrifugal machine, an adjusting tank and the like, so that the solid-liquid separation amount of the internal circulation of the calcium ion reflux is large, and a certain operation difficulty exists.
Disclosure of Invention
The primary purpose of the invention is to provide a device for recycling magnesium sulfate solution and reacting lime, which can be used for inhibiting solid-liquid direct reaction in the magnesium sulfate-lime reaction process by controlling operation conditions, thereby improving the reaction participation rate of magnesium sulfate, improving the respective yields of magnesium hydroxide and calcium sulfate, and reducing the impurity component content in each product.
To achieve the object, in a basic embodiment, the invention provides a device for recycling magnesium sulfate solution and reacting with lime, the device comprises a first mixing chamber, a second mixing chamber, a sedimentation chamber, a first stirrer, a second stirrer, a movable partition plate of the mixing chamber, an adjustable communication port of the mixing chamber, a movable partition plate of the sedimentation chamber, an adjustable communication port of the sedimentation chamber and a slurry outlet,
The first mixing chamber and the second mixing chamber are separated by the movable partition board of the mixing chamber with adjustable opening, so that an adjustable communication opening of the mixing chamber with adjustable opening and closing is formed between the first mixing chamber and the second mixing chamber;
The first mixing chamber and the sedimentation chamber are separated by the sedimentation chamber movable partition plate with adjustable opening, so that an adjustable communication opening of the sedimentation chamber with adjustable opening and closing is formed between the first mixing chamber and the sedimentation chamber;
the first stirrer is arranged in the first mixing chamber and is used for stirring and mixing the slurry in the first mixing chamber;
the second stirrer is arranged in the second mixing chamber and is used for stirring and mixing the slurry in the second mixing chamber;
the slurry outlet is arranged at the top of the settling chamber, and the slurry in the settling chamber overflows from the settling chamber after exceeding the slurry outlet.
The related principle of the invention is as follows:
The invention designs a reaction device of lime-magnesium sulfate solution, which is divided into two mixing chambers and a settling chamber, wherein an adjustable communication hole of the two mixing chambers is formed between the mixing chambers by a movable plugboard, and an adjustable communication hole between the mixing chambers is formed between the settling chamber and the first mixing chamber by the movable plugboard.
A magnesium sulfate solution was added to the first mixing chamber. And adding the Mg 2+ solution above the first mixing chamber, stirring and mixing with the high-pH Ca 2+ -containing solution, reducing the pH, and gradually reducing the concentration of Mg 2+ from top to bottom. The pH value in the first mixing chamber is lower than that in the second mixing chamber but higher than that of Mg 2+ precipitate, and the main reaction in the mixing chamber is magnesium hydroxide precipitate, and the supersaturated solution of calcium sulfate is crystallized under the action of seed crystal. The first mixing chamber solution in the vicinity of the communication hole of the lower partition plate in the first mixing chamber is in a low Mg 2+ state, and this solution and a small amount of solid slurry enter the second mixing chamber through the communication hole, and the slurry in the second mixing chamber can also enter the first mixing chamber through the communication hole.
Lime powder or lime slurry is added above the second mixing chamber, the pH value of the solution is higher, the magnesium ion content in the solution is lower, the probability of the added calcium hydroxide solid directly reacting with magnesium ions can be reduced, and the main process is that calcium hydroxide is dissolved in the solution to ionize to form calcium ions. The mixing is that the proportion of solid lime is gradually reduced from top to bottom, the vicinity of the communicating hole of the lower partition board in the second mixing chamber is in a solution state mainly containing Ca 2+ ions, and the Ca 2+ solution with high pH and a small amount of solid slurry enter the first mixing chamber through the communicating hole to precipitate Mg 2+.
The calcium in the slurry entering the first mixing chamber from the second mixing chamber mainly exists in an ionic state, and at the moment, the concentration of Ca 2+ can exceed the theoretical calculation value of the saturated solubility due to the fact that the calcium sulfate has a large supersaturation degree and impurity anions exist, so that the circulation of water and the dissolution of newly added lime solids are realized. The calcium solution with high outflow alkalinity of the second mixing chamber reacts with the magnesium sulfate solution in the first mixing chamber to generate calcium sulfate precipitate and magnesium hydroxide precipitate.
The first mixing chamber is connected with the sedimentation chamber through an adjustable communication hole. In the sedimentation chamber, the rising speed of calcium sulfate crystals with higher sedimentation speed is slower, and part of calcium sulfate crystals return to the mixing chamber, so that the purpose of calcium sulfate seed crystal circulation is realized; and most of the magnesium hydroxide with slower sedimentation velocity overflows out of the reaction device and enters the subsequent sedimentation separation treatment. The size of the adjustable communication hole between the first mixing chamber and the sedimentation chamber can be adjusted, and the stirring intensity transferred from the first mixing chamber to the sedimentation chamber can be simultaneously adjusted, so that the proportion of calcium sulfate flowing back to the overflow device can be adjusted.
In summary, in the first mixing chamber, the main reaction occurs in which calcium ions and sulfate radicals in the solution form a crystalline precipitate of hydrated calcium sulfate under the action of calcium sulfate seeds:
Ca2++SO4 2-+nH2O＝CaSO4(H2O)n (1)
magnesium ions form magnesium hydroxide precipitates with hydroxide in solution:
Mg2++2OH-＝Mg(OH)2 (2)
In the second mixing chamber, the main reaction is that calcium hydroxide is dissolved in the solution and ionized into calcium ions and hydroxide ions:
Ca(OH)2＝Ca2++2OH- (3)
The two mixing chambers are connected by an adjustable communication orifice, and the mixed slurry has a certain rate of exchange. Thus, in the first mixing chamber, there is still a small amount of reaction (3) to further dissolve the calcium hydroxide which is not completely dissolved in the second mixing chamber. In the second mixing chamber, there is also reaction (2) with a small amount of reaction (1), the magnesium ions and sulfate ions which are not fully reacted in the first mixing chamber, reaction (3) still being present. The main reaction of the second mixing chamber is lime solid dissolution, but after the equilibrium steady state is reached, the calcium sulfate seed crystal gradually increases, so that the amount of calcium sulfate crystals generated by the second mixing chamber also gradually increases.
In a preferred embodiment, the invention provides a device for recycling magnesium sulfate solution and reacting with lime, wherein the adjustable communication port of the settling chamber is positioned at the bottommost part of the movable partition plate of the settling chamber.
In a preferred embodiment, the invention provides an apparatus for recycling magnesium sulfate solution for reaction with lime, wherein said apparatus further comprises an outlet baffle disposed within said settling chamber adjacent said slurry outlet, wherein said slurry within said settling chamber is at a height above the top of said outlet baffle and above said slurry outlet for overflow from said settling chamber.
A second object of the present invention is to provide a method for performing a reaction of magnesium sulfate with lime using the aforementioned apparatus, so that the solid-liquid direct reaction during the magnesium sulfate-lime reaction can be suppressed by controlling the operation conditions, thereby improving the reaction participation rate of magnesium sulfate, improving the respective yields of magnesium hydroxide and calcium sulfate, and reducing the impurity component content in each.
To achieve this object, in a basic embodiment, the present invention provides a process for reacting magnesium sulfate with lime using the aforementioned apparatus, said process comprising the steps of:
(1) Closing the movable partition plate of the mixing chamber and the movable partition plate of the sedimentation chamber, respectively adding magnesium sulfate solution and lime slurry into the first mixing chamber and the second mixing chamber, and respectively starting the first stirrer and the second stirrer to stir;
(2) After a certain time, opening the movable partition board of the mixing chamber to form an adjustable communication port of the mixing chamber with a certain opening, and continuously adding magnesium sulfate solution and lime slurry into the first mixing chamber and the second mixing chamber at a certain speed respectively;
(3) After a certain time, the movable partition plate of the sedimentation chamber is opened to form an adjustable communication port of the sedimentation chamber with a certain opening degree, so that slurry enters the sedimentation chamber from the first mixing chamber, and selective sedimentation is performed after a steady state is formed.
In a preferred embodiment, the invention provides a method for reacting magnesium sulfate with lime using the apparatus described above, wherein in step (1), magnesium sulfate solution and lime slurry are added to the first mixing chamber and the second mixing chamber, respectively, at a rate of 10 to 600 minutes, respectively, independently of each other, to fill the mixing chamber in which each is located.
In a preferred embodiment, the present invention provides a method for reacting magnesium sulfate with lime using the aforementioned apparatus, wherein in step (1), the stirring speeds of the first stirrer and the second stirrer are each independently 40 to 300rpm, respectively.
In a preferred embodiment, the present invention provides a process for reacting magnesium sulfate with lime using the apparatus described above, wherein in step (2), the period of time is from 10 to 600 minutes; the forming of a certain opening degree is that the area of the adjustable communication opening of the mixing chamber is 5-35% of the area of the movable partition plate of the mixing chamber.
In a preferred embodiment, the invention provides a method for carrying out the reaction of magnesium sulfate and lime by using the device, wherein in the step (2), continuously adding the magnesium sulfate solution and the lime slurry, wherein the adding speed is respectively independent of 1/600-1/10 of the adding volume per minute corresponding to the volume of a mixing chamber where the adding speed is respectively positioned.
In a preferred embodiment, the present invention provides a process for reacting magnesium sulfate with lime using the apparatus described above, wherein in step (3), the certain time is from 10 to 600 minutes; the forming of a certain opening degree is that the area of the adjustable communication opening of the sedimentation chamber is 5-35% of the area of the movable partition plate of the sedimentation chamber.
In a preferred embodiment, the invention provides a method for reacting magnesium sulfate with lime by using the device, wherein in the step (3), after selective sedimentation, clear liquid after sedimentation and filtration in the sedimentation chamber is returned to the second mixing chamber to dissolve lime.
The device and the method for recycling the magnesium sulfate solution and reacting with the lime have the advantages that the device and the method can inhibit the solid-liquid direct reaction in the magnesium sulfate-lime reaction process by controlling the operation conditions, thereby improving the reaction participation rate of the magnesium sulfate, improving the respective yields of the magnesium hydroxide and the calcium sulfate, and reducing the impurity component content in the magnesium hydroxide and the calcium sulfate.
The invention divides the reaction process of magnesium sulfate solution and lime milk into two stages of lime dissolution and precipitation reaction, so that the precipitation reaction stage is mainly liquid-liquid reaction, which is beneficial to reducing the impurity content in magnesium hydroxide and calcium sulfate products, and the solid-liquid separation operation in the process is reduced by the arrangement of slurry internal circulation and an outlet sedimentation chamber. The low-calcium magnesium hydroxide product obtained by the invention can be reused in the step of neutralizing residual acid in the rare earth sulfuric acid leaching solution.
Drawings
Fig. 1 is a construction diagram illustrating an apparatus for recycling magnesium sulfate solution and reacting lime according to the present invention.
Detailed Description
The following describes the embodiments of the present invention further with reference to the drawings.
An exemplary apparatus for recycling magnesium sulfate solution and reacting lime according to the present invention has a composition structure shown in fig. 1, and comprises a first mixing chamber 1, a second mixing chamber 2, a settling chamber 3, a first stirrer 4, a second stirrer 9, a mixing chamber movable partition 5, a mixing chamber adjustable communication port 6, a settling chamber movable partition 7, a settling chamber adjustable communication port 8, an outlet baffle 11, and a slurry outlet 12.
The first mixing chamber 1 and the second mixing chamber 2 are separated by a mixing chamber movable partition 5 with adjustable opening, so that a mixing chamber adjustable communication opening 6 with adjustable opening and closing is formed between the first mixing chamber 1 and the second mixing chamber 2.
The first mixing chamber 1 and the sedimentation chamber 3 are separated by a sedimentation chamber movable partition 7 with adjustable opening, so that an adjustable sedimentation chamber communicating opening 8 with adjustable opening and closing is formed between the first mixing chamber 1 and the sedimentation chamber 3. The adjustable communication port 8 of the sedimentation chamber is positioned at the bottommost part of the movable partition plate 7 of the sedimentation chamber.
A first agitator 4 is provided in the first mixing chamber 1 for agitating and mixing the slurry in the first mixing chamber 1. A second agitator 9 is provided in the second mixing chamber 2 for agitating and mixing the slurry in the second mixing chamber 2.
A slurry outlet 12 is provided at the top of the settling chamber 3, and an outlet baffle 11 is provided in the settling chamber 3, near the slurry outlet 12. The slurry in the settling chamber 3 is overflowed from the settling chamber 3 after the slurry level exceeds the top of the outlet baffle 11 and is higher than the slurry outlet 12.
An exemplary method of reacting magnesium sulfate with lime using the above-described exemplary inventive apparatus includes the steps of:
(1) The movable partition board 5 of the closed mixing chamber and the movable partition board 7 of the sedimentation chamber are respectively added with magnesium sulfate solution and lime slurry into the first mixing chamber 1 and the second mixing chamber 2, and the first stirrer 4 and the second stirrer 9 are respectively started for stirring;
(2) After a certain time, opening a movable partition plate 5 of the mixing chamber to form an adjustable communication port 6 of the mixing chamber with a certain opening, and continuously adding magnesium sulfate solution and lime slurry into the first mixing chamber 1 and the second mixing chamber 2 at a certain speed respectively;
(3) After a certain time, the movable partition 7 of the sedimentation chamber is opened to form an adjustable communication port 8 of the sedimentation chamber with a certain opening degree, so that the slurry enters the sedimentation chamber 3 from the first mixing chamber 1, and selective sedimentation is performed after a steady state is formed.
Wherein:
in the step (1), respectively adding magnesium sulfate solution and lime slurry into the first mixing chamber 1 and the second mixing chamber 2, wherein the adding speed is respectively independent and is 10-600 minutes, and the mixing chambers are filled respectively;
in the step (1), the stirring speeds of the first stirrer 4 and the second stirrer 9 are respectively 40-300rpm independently;
In the step (2), the certain time is 10-600 minutes; the forming of a certain opening degree is that the area of the adjustable communication port 6 of the mixing chamber is 5-35% of the area of the movable partition board 5 of the mixing chamber;
Continuously adding the magnesium sulfate solution and the lime slurry in the step (2), wherein the adding speed is respectively and independently 1/600-1/10 of the adding volume per minute corresponding to the volume of the mixing chamber where the adding speed is respectively positioned;
In the step (3), the certain time is 10-600 minutes; the forming of a certain opening degree is that the area of an adjustable communication port 8 of the sedimentation chamber is 5-35% of the area of a movable partition 7 of the sedimentation chamber;
In the step (3), after selective sedimentation, clear liquid after sedimentation and filtration in the sedimentation chamber 3 is returned to the second mixing chamber 2 to dissolve lime.
The application of the above-described exemplary method of the present invention is exemplified as follows.
Example 1:
A small laboratory device was produced according to FIG. 1, with an external dimension of 0.6mX0.2mX0.35 m, a 45 degree angle between the inclined plate of the settling chamber and the horizontal surface, an effective volume of a single mixing chamber of 10dm 3, and an effective volume of the settling chamber of 2.5dm 3. Initially, 6dm 3 of saturated calcium hydroxide solution was added to the second mixing chamber 2, and 6dm 3 of saturated calcium hydroxide solution and 1kg of calcium sulfate seed crystals were added to the first mixing chamber 1.
After stirring in the respective mixing chambers, a magnesium sulfate solution having a magnesium content of 28g/dm 3 and a pH of about 4 was added to the first mixing chamber 1 at a rate of 0.2dm 3/min, while lime milk having a calcium oxide content of 20wt% was added to the second mixing chamber 2 at a rate of 0.08dm 3/min. The height of the movable partition board 5 of the mixing chamber is adjusted to enable the pH value in the first mixing chamber 1 to be 10.0, the flow rate of the fine-tuning lime milk is controlled to control the pH value of the second mixing chamber 2 to be about 12, the adjustable communication port 8 of the settling chamber 3 is adjusted, and the calcium sulfate seed crystal amount in the slurry of the first mixing chamber 1 is controlled to be about 10 wt%. And (3) carrying out sedimentation separation at an overflow outlet, filtering and drying the magnesium hydroxide slurry, wherein the calcium content CaO/MgO in the obtained magnesium hydroxide is 8.2wt%, and the low-calcium magnesium hydroxide is recycled to the sulfuric acid roasting liquid to neutralize residual acid. The MgO content in the calcium sulfate is 4.8wt%, and the low-magnesium calcium sulfate can be sold as a cement raw material.
Example 2:
A pilot plant experimental device was manufactured according to FIG. 1, the external dimension was 2.5mX1 mX1.5m, the inclined plate of the settling chamber was 18.5 degrees to the horizontal ground, the effective volume of the single mixing chamber was 1.25m 3, and the effective volume of the settling chamber was 0.6m 3. Two mixing chambers were charged with saturated calcium hydroxide solution to 70% of the effective volume. The slightly acidic magnesium sulfate wastewater produced by the extraction and separation of the rare earth sulfate is subjected to sedimentation separation to obtain a calcium sulfate product after the pH value is regulated to about 4 by calcium sulfate containing magnesium hydroxide produced by the wastewater per se, and then a magnesium sulfate solution with the magnesium content of 19-22g/dm 3 is obtained and is added into the first mixing chamber 1 at the speed of 20L/min. Adding lime powder solid into the second mixing chamber 2 by using a screw feeder to perform variable frequency speed regulation, and adding clear liquid obtained by sedimentation and recovery in the sedimentation chamber 3 into the second mixing chamber 2 to perform lime slurry regulation. The adjustable communication port 8 of the sedimentation chamber 3 is adjusted to control the amount of the calcium sulfate seed crystal in the slurry in the first mixing chamber 1 to be about 12 wt%. And (3) carrying out sedimentation coarse separation on the overflow outlet, then connecting with gravity classification equipment to further separate Ca and Mg, filtering and drying magnesium hydroxide slurry, wherein the calcium content CaO/MgO=5.3wt% in the obtained magnesium hydroxide, returning calcium sulfate to neutral slightly acidic magnesium sulfate wastewater, and then carrying out filter pressing and drying to obtain a calcium sulfate product, wherein the MgO content is 0.3-0.7wt%, and the low-magnesium calcium sulfate is sold as a gypsum raw material.
Example 3:
A pilot plant test apparatus of 2.5mX1mX1.5 m was prepared as shown in FIG. 1, and a magnesium sulfate solution having a pH2 and a magnesium content of 2mol/L was continuously fed into the first mixing chamber 1, and the amount of calcium sulfate seed crystals in the slurry was controlled at 5wt% and the temperature after mixing was 70 ℃. The second mixing chamber 2 is continuously added with slaked lime powder solid and clear water, the temperature is 80 ℃, and Ca 2+ is about 1mol/L after mixing, and the pH is 13. The pH of the solution in the settling chamber 3 is 10.5, and the concentration of Mg 2+ is 0.005mol/L. And (3) carrying out sedimentation separation at an overflow outlet, filtering and drying the magnesium hydroxide slurry, wherein the calcium content CaO/MgO in the obtained magnesium hydroxide is 1.2wt%, and the low-calcium magnesium hydroxide is recycled to the sulfuric acid roasting liquid to neutralize residual acid.
Example 4:
A pilot plant test apparatus 2.5mX1m.times.1.5 m was prepared as shown in FIG. 1, and a magnesium sulfate solution having a pH8 and a magnesium content of 0.01mol/L was continuously added to the first mixing chamber 1, and the amount of slurry calcium sulfate seed crystals in the first mixing chamber 1 was controlled at 30wt% and the temperature after mixing was 20 ℃. Lime milk with a calcium oxide content of 1wt% is continuously added into the second mixing chamber 2, the temperature is 20 ℃, and Ca 2+ is about 0.01mol/L after mixing, and the pH is 9. The solution in the settling chamber 3 has pH8 and Mg 2+ concentration of 0.003mol/L. And (3) carrying out sedimentation separation at an overflow outlet, filtering and drying the magnesium hydroxide slurry, wherein the calcium content CaO/MgO in the obtained magnesium hydroxide is=2.1wt%, the MgO content in the calcium sulfate is 0.2%, the low-calcium magnesium hydroxide is recycled to neutralize residual acid, and the calcium sulfate is sold as gypsum.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. The foregoing examples or embodiments are merely illustrative of the invention, which may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the invention should be indicated by the appended claims, and any changes that are equivalent to the intent and scope of the claims are intended to be encompassed within the scope of the invention.

Claims (9)

1. A method for recycling magnesium sulfate solution and reacting with lime is characterized in that: the device used in the method comprises a first mixing chamber (1), a second mixing chamber (2), a sedimentation chamber (3), a first stirrer (4), a second stirrer (9), a movable partition plate (5) of the mixing chamber, an adjustable communication port (6) of the mixing chamber, a movable partition plate (7) of the sedimentation chamber, an adjustable communication port (8) of the sedimentation chamber and a slurry outlet (12),
The first mixing chamber (1) and the second mixing chamber (2) are separated by the movable baffle plate (5) of the mixing chamber with adjustable opening degree, so that the adjustable communication opening (6) of the mixing chamber with adjustable opening degree and opening degree is formed between the first mixing chamber (1) and the second mixing chamber (2);
The first mixing chamber (1) and the sedimentation chamber (3) are separated by the sedimentation chamber movable partition plate (7) with adjustable opening, so that an adjustable sedimentation chamber communicating opening (8) with adjustable opening and closing is formed between the first mixing chamber (1) and the sedimentation chamber (3);
the first stirrer (4) is arranged in the first mixing chamber (1) and is used for stirring and mixing the slurry in the first mixing chamber (1);
The second mixer (9) is arranged in the second mixing chamber (2) and is used for mixing the slurry in the second mixing chamber (2);
The slurry outlet (12) is arranged at the top of the sedimentation chamber (3), and the slurry in the sedimentation chamber (3) overflows from the sedimentation chamber (3) after exceeding the slurry outlet (12);
The method comprises the following steps:
(1) The movable partition board (5) of the mixing chamber and the movable partition board (7) of the sedimentation chamber are sealed, magnesium sulfate solution and lime slurry are respectively added into the first mixing chamber (1) and the second mixing chamber (2), and the first stirrer (4) and the second stirrer (9) are respectively started for stirring;
(2) After a certain time, opening the movable partition plate (5) of the mixing chamber to form an adjustable communication port (6) of the mixing chamber with a certain opening, and continuously adding magnesium sulfate solution and lime slurry into the first mixing chamber (1) and the second mixing chamber (2) at a certain speed respectively;
(3) After a certain time, the movable partition plate (7) of the sedimentation chamber is opened to form an adjustable communication port (8) of the sedimentation chamber with a certain opening degree, so that slurry enters the sedimentation chamber (3) from the first mixing chamber (1), and selective sedimentation is performed after a steady state is formed.
2. The method according to claim 1, characterized in that: the adjustable communication port (8) of the sedimentation chamber is positioned at the bottommost part of the movable partition plate (7) of the sedimentation chamber.
3. The method according to claim 1, characterized in that: the device used in the method also comprises an outlet baffle plate (11) arranged in the settling chamber (3) near the slurry outlet (12), wherein the slurry in the settling chamber (3) exceeds the top of the outlet baffle plate (11) and overflows from the settling chamber (3) after being higher than the slurry outlet (12).
4. The method according to claim 1, characterized in that: in the step (1), the magnesium sulfate solution and the lime slurry are respectively added into the first mixing chamber (1) and the second mixing chamber (2), and the adding speed is respectively independent and 10-600 minutes to fill the mixing chambers.
5. The method according to claim 1, characterized in that: in the step (1), the stirring speeds of the first stirrer (4) and the second stirrer (9) are respectively 40-300rpm independently.
6. The method according to claim 1, characterized in that: in the step (2), the certain time is 10-600 minutes; the forming of a certain opening degree is that the area of the adjustable communication opening (6) of the mixing chamber is 5-35% of the area of the movable partition plate (5) of the mixing chamber.
7. The method according to claim 1, characterized in that: in the step (2), continuously adding the magnesium sulfate solution and the lime slurry, wherein the adding speed is respectively and independently 1/600-1/10 of the adding volume per minute corresponding to the volume of the mixing chamber where the adding speed is respectively positioned.
8. The method according to claim 1, characterized in that: in the step (3), the certain time is 10-600 minutes; the forming of a certain opening degree is that the area of the adjustable communication opening (8) of the sedimentation chamber is 5-35% of the area of the movable partition plate (7) of the sedimentation chamber.
9. The method according to claim 1, characterized in that: in the step (3), after selective sedimentation, clear liquid after sedimentation and filtration in the sedimentation chamber (3) returns to the second mixing chamber (2) to dissolve lime.
CN202210961828.8A 2022-08-11 2022-08-11 Device and method for recycling magnesium sulfate solution and reacting with lime Active CN115449629B (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101817613A (en) * 2010-03-16 2010-09-01 上海金领技术有限公司 Purifier and method for performing advanced treatment on secondarily-polluted drinking water
CN201634540U (en) * 2010-03-16 2010-11-17 上海金领技术有限公司 Drinking water secondary pollution advanced treatment purifier
CN203355383U (en) * 2013-07-14 2013-12-25 上海净意环保设备有限公司 Coagulative precipitation tank
CN105858692A (en) * 2016-05-13 2016-08-17 国家海洋局天津海水淡化与综合利用研究所 Method for treating magnesium sulfate and magnesium sulfite wastewater by virtue of lime method
CN107321009A (en) * 2017-08-04 2017-11-07 南京河海环境研究院有限公司 A kind of tube settler pond
CN207286770U (en) * 2017-08-04 2018-05-01 南京河海环境研究院有限公司 A kind of tube settler pond

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101817613A (en) * 2010-03-16 2010-09-01 上海金领技术有限公司 Purifier and method for performing advanced treatment on secondarily-polluted drinking water
CN201634540U (en) * 2010-03-16 2010-11-17 上海金领技术有限公司 Drinking water secondary pollution advanced treatment purifier
CN203355383U (en) * 2013-07-14 2013-12-25 上海净意环保设备有限公司 Coagulative precipitation tank
CN105858692A (en) * 2016-05-13 2016-08-17 国家海洋局天津海水淡化与综合利用研究所 Method for treating magnesium sulfate and magnesium sulfite wastewater by virtue of lime method
CN107321009A (en) * 2017-08-04 2017-11-07 南京河海环境研究院有限公司 A kind of tube settler pond
CN207286770U (en) * 2017-08-04 2018-05-01 南京河海环境研究院有限公司 A kind of tube settler pond

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