WO2017049467A1 - Brine refining method and device based on membrane technology - Google Patents

Abstract

Provided are a brine refining method and device based on a membrane separation technology. The brine refining method comprises: adding CO₃ ^{2 -} and/or OH^- ions, serving as precipitants or a precipitant, into crude brine, enabling the CO₃ ^{2 -} and/or OH^- to have a deposition reaction with cation impurities in the crude brine to generate a deposit, and then feeding the crude brine to a ceramic membrane for filtering, and removing the impurities, so as to obtain refined brine at the permeation side of the ceramic membrane. By means of the method, calcium ions, magnesium ions, sulfate ions and other impurity ions in the crude salt can be effectively removed.

Description

Method and device for refining brine based on membrane technology Technical field

The present invention relates to brine refining technology in industrial processes, and more particularly to a brine refining method and apparatus based on membrane technology.

Background technique

In many industrial processes, it is necessary to refine the brine to remove impurity ions contained in the crude brine. Taking the chlor-alkali industry as an example, the electrolysis methods in the chlor-alkali process mainly include a diaphragm method, a mercury method, and an ion exchange membrane method. Among them, the mercury method has been gradually eliminated due to the fact that mercury is a recognized toxic substance. Nowadays, the diaphragm method and the ion exchange membrane method are widely used. The ion exchange membrane method is popular because of its low investment, low energy consumption, low operating cost and no pollution. Favored, it is used by more and more chlor-alkali plants. Ionic membrane is the core part of ionic membrane caustic soda production. Although it does not directly participate in the electrochemical reaction, it affects the physical processes such as mass transfer and conduction. The impurities such as Ca ²⁺ and Mg ²⁺ in the running medium brine are in the electrolysis process. The OH ^- reaction infiltrated from the cathode chamber forms insoluble matter on the ionic membrane, causing destruction of the physical properties of the ionic membrane, resulting in a decrease in ionic membrane current efficiency, an increase in power consumption, an increase in side reactions, and a decrease in product quality. Therefore, the quality of the brine in the tank has attracted more and more attention from enterprises. As far as the traditional flocculation and sedimentation process is concerned, the removal of calcium and magnesium insoluble matter is a major problem affecting the operation index of the trough.

CN1597519A discloses a method for removing purified calcium from magnesium and magnesium ions in crude brine. The step is: removing magnesium from the crude brine: placing the crude brine in the magnesium removal reactor, adding the PAM and the lime milk to the reactor, reacting for 0.5 hours, and preparing a primary solution; Put it into a brine clarification tank to clarify, and obtain a brine once. The remaining mud in the bottom of the bucket is washed into the mud washing tank No. 1; the calcium salt is removed once: the brine is added to the calcium removal reactor to remove The calcium reactor is added with carbonated neutralization water, and when the reaction is 0.5, a secondary solution is prepared; the secondary solution is placed in a secondary brine clarification tank for 2 to 3 hours to obtain a refined brine. However, the above method has low precision in removing impurity ions in the brine, is cumbersome to operate, and has low labor efficiency.

Summary of the invention

The object of the present invention is to provide a method for refining brine, which uses membrane separation technology to remove impurities such as Ca ²⁺ , Mg ²⁺ and the like in brine.

Technical solutions:

Brine purification method based on membrane technology, comprising the steps of: adding water to crude salt CO ₃ ^2- and / or OH ^- ions as the precipitation agent after the precipitation reaction with cationic impurities of the crude salt water to produce a precipitate, and then into a ceramic membrane Filtration was carried out to remove precipitates, and purified brine was obtained on the permeate side of the ceramic membrane.

The crude brine refers to a brine mainly containing NaCl, KCl or Na ₂ SO ₄ ; the cationic impurities are selected from Ca ²⁺ , Mg ²⁺ , Cs ⁺ or Ni ⁺ ions.

When the crude brine refers to the brine mainly containing NaCl, the crude brine is selected from the brine containing mainly NaCl, seawater or the brine obtained by dissolving the crude salt of NaCl; when the crude brine refers to the brine mainly containing KCl, the crude brine is The brine obtained after the KCl coarse salt is dissolved; when the crude brine refers to the brine mainly containing Na ₂ SO ₄ , the crude brine refers to the brine obtained by dissolving the crude salt of Na ₂ SO ₄ or the brine mainly containing Na ₂ SO ₄ .

The cation in the precipitant is the same as the cation of the main component in the crude brine.

The precipitating agent is added to one or a mixture of several of NaOH, Na ₂ CO ₃ , KOH or K ₂ CO ₃ , each of which is added in an amount greater than the amount required to completely precipitate the impurity cation.

The ceramic membrane refers to a ceramic microfiltration membrane or a ceramic ultrafiltration membrane.

The microfiltration membrane has an average pore diameter of 0.05 μm to 5 μm.

The ultrafiltration membrane has an average pore diameter of from 0.005 μm to 0.05 μm, or a molecular weight cut off of from 1,000 to 200,000 Da.

The crude brine needs to be pre-filtered prior to the addition of the precipitant.

After the precipitation reaction, the brine is filtered through a coarse filter and then sent to a ceramic membrane for filtration.

In the precipitation reaction, the residence time of the crude brine was more than 3 hours.

Before the crude brine is sent to the ceramic membrane for filtration, it is necessary to add chlorine thereto; the chlorine is added in the form of chlorine or hypochlorite.

The addition of chlorine is intermittently added every 4 to 12 hours; the amount is 50-100 mg/L, the addition time lasts for 1 to 2 hours; and the Na ₂ SO ₃ neutralization is added to the ceramic membrane supernatant. Unreacted chlorine is removed.

The turbidity of the ceramic membrane supernatant is monitored on-line, and the ceramic membrane supernatant entering the turbidity detector is diluted, so that the content of the main component in the ceramic membrane supernatant is less than 80% of its saturated solubility, and then the turbidity detection is performed. .

According to another aspect of the invention, the invention also provides a production apparatus based on the above method.

A brine refining device based on a membrane technology includes a reaction tank and a ceramic membrane module connected in series.

A dosing device in which a CO ₃ ^2- and/or OH ^- ion precipitating agent is attached to the reaction tank.

The permeate tube of the ceramic membrane module is further provided with a liquid collection tube, and the liquid collection tube is connected with the turbidity meter; and the dilution liquid tube is further disposed on the liquid collection tube.

A salt tank is also arranged in the device. The bottom of the salt tank is provided with a water inlet, and the upper portion is provided with an overflow port, and the overflow port is connected with the reaction tank.

The overflow port is connected to the reaction tank through the baffle; the filter is arranged in the baffle; the filter is hoistable.

The reaction tank is connected to the ceramic membrane module through a coarse filter.

The coarse filter is a titanium mesh filter; the titanium plate has an equivalent diameter of less than 0.5 mm.

A component communication cavity is disposed under the ceramic membrane module, and a raw material liquid flow channel of the ceramic membrane component in the ceramic membrane component is in communication with the component communication cavity, and a liquid inlet is disposed on the component communication cavity, and the liquid liquid inlet is connected with the reaction tank A mud discharge port that can be opened is respectively disposed at two ends of the component communication cavity.

The ceramic membrane element installed in the ceramic membrane module is a single tube type or a multi-channel type, and the raw material liquid flow path of the ceramic membrane element is perpendicular to the horizontal plane.

The raw material funnel further comprises a raw material funnel, the raw material funnel comprises a funnel cavity, a discharge port is arranged below the funnel cavity, a rotating shaft is arranged in the middle of the funnel cavity, and a spiral blade is arranged on the rotating shaft, A turntable is arranged above the rotating shaft, and an eccentric shaft is arranged on the turntable. The eccentric shaft is movably connected with one end of the first connecting rod; a limited position plate is arranged outside the funnel cavity, and a limited position slot is set on the limiting plate, and the limit is set. A second connecting rod is sleeved in the slot, and one end of the second connecting rod is movably connected to the other end of the first connecting rod, and an opening is formed on a side of the funnel cavity facing the limiting plate, and an outer side of the opening is arranged The plate and the baffle are connected to the other end of the second link; the radius below the funnel cavity is smaller than the upper radius; and the buck is disposed on the discharge port.

DRAWINGS

Figure 1 is a schematic view showing the structure of a ceramic membrane filtering device;

2 is a schematic structural view of a turbidity on-line detecting device for a ceramic membrane clear liquid used in Example 2;

Figure 3 is a schematic flow chart of a device for purifying brine;

Figure 4 is a schematic view showing the structure of a salt bath with a raw material funnel;

Figure 5 is a schematic structural view of a raw material funnel;

Figure 6 is a plan view of the material funnel upper turntable, the first link, the limit plate and the like in Figure 5;

Figure 7 is a structural view of a coarse filter;

Figure 8 is a plan view showing the structure of a suitable titanium mesh in a coarse filter;

Figure 9 is a plan view of another titanium mesh.

Among them, 1, the component is connected to the cavity; 2, the ceramic membrane module; 3, the material liquid inlet; 4, the mud discharge port; 5, the permeate pipe; 6, the liquid collection pipe; 7, the turbidity meter; ;9;salt tank;10, water inlet; 11, overflow port; 12, raw material funnel; 13, funnel cavity; 14, discharge port; 15, shaft; 16, spiral blade; 17, turntable; Eccentric shaft; 19, first link; 20, second link; 21, limit plate; 22, limit groove; 23, baffle; 24, opening; 25, card; 26, reaction tank; Stirring paddle; 28, baffle; 29, coarse filter; 30, filter; 31, titanium mesh; 32, recoil device; 33, titanium plate opening.

detailed description

The invention will now be further described in detail by way of specific embodiments. However, those skilled in the art will understand that the following examples are merely illustrative of the invention and should not be construed as limiting the scope of the invention. In the examples, the specific techniques or conditions are not indicated, according to the techniques or conditions described in the literature in the field (for example, refer to Xu Nanping's "Inorganic Membrane Separation Technology and Application", Chemical Industry Press, 2003) or according to Product manuals are carried out. The reagents or instruments used are not indicated by the manufacturer, and are conventional products that can be obtained commercially.

The Approximations used herein can be used to modify any number of expressions in the entire specification and claims, which can be modified to change without departing from the basic function. Therefore, a value modified by a term such as "about" is not limited to the precise value specified. In at least some cases, the approximation may correspond to the accuracy of the instrument used to measure the value. Range boundaries may be combined and/or interchanged unless otherwise stated in the context or the statement, and such ranges are determined to include and include all sub-ranges included herein. Except in the operating examples or elsewhere, all numbers or expressions indicating quantities of ingredients, reaction conditions, and the like, used in the specification and claims, should be understood in all instances as "The modification."

Values expressed in terms of ranges should be understood in a flexible manner to include not only the numerical values that are explicitly recited as the range limits, but also all individual values or sub-ranges that are within the range, as if each value and sub-range are List it. For example, a concentration range of "about 0.1% to about 5%" should be understood to include not only a concentration of about 0.1% to about 5% that is explicitly listed, but also a single concentration within a range of indications (eg, 1%, 2). %, 3%, and 4%) and subintervals (eg, 0.1% to 0.5%, 1% to 2.2%, 3.3% to 4.4%).

The "removal" in the present specification includes not only the case where the target substance is completely removed, but also the case where the part is removed (the amount of the substance is reduced). "Purification" in this specification includes the removal of any or specific impurities.

The words "including", "comprising", "comprising" or "comprising" or "comprising" as used herein are intended to encompass a non-exclusive include. For example, a process, method, article, or device that includes the listed elements is not necessarily limited to those elements, but may include other elements that are not specifically listed or are inherent in the process, method, item, or device. It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

The method provided by the present invention mainly removes and refines impurity ions contained in the crude brine. The "crude brine" described in the present invention refers to a raw material liquid to be purified, and the main component in the "saline" herein may be Refers to NaCl, KCl or Na ₂ SO ₄ ; the term "main component" or brine "mainly contained" as used in the present invention refers to the salt of the majority in salt water, and the salt is also The purified salts that are actually desired; some of the impurity ions contained in these crude brines, such as Ca ²⁺ , Mg ²⁺ , Cs ⁺ , and Ni ²⁺ ions, need to be removed.

In the present invention, when the main component in the "saline" is NaCl, the "crude brine" can be obtained by different routes, and can be a salt solution obtained by dissolving NaCl crude salt and water, or directly from the natural world. The brine. The "NaCl coarse salt" herein can be understood as a solid salt mainly containing sodium chloride obtained by evaporation and drying of sea water or brine, or a solid salt directly obtained directly from a salt well or a salt mine. In addition, the term "brine" may refer to natural brines (eg, salt lake brines, underground brines, geothermal brines or brine brines) or manually configured brines. When the main component in the "saline" is KCl, the "crude brine" may also be prepared by adding KCl solids and water-dissolving salts prepared in salt lakes and KCl salt mines. When the main component in the "saline" is Na ₂ SO ₄ , the "crude brine" may also be obtained by dissolving a solid salt in a salt ore mainly containing Na ₂ SO ₄ with water, or may be a brine mainly containing Na ₂ SO ₄ . .

Whether it is crude brine obtained by dissolving crude salt with water or brine directly produced, in addition to NaCl, KCl or Na ₂ SO ₄ as a main component, it also contains suspended particles, colloids, macromolecular impurities, organic impurities, etc. It also contains some inorganic salt impurities such as Ca ²⁺ , Mg ²⁺ , I ^- , NO ₃ ^- , Fe ³⁺ , Li ⁺ and the like.

The method provided by the present invention mainly comprises the following steps: First, CO ₃ ^2- and OH ^- ions are added to the crude brine, and after the reaction, the CO ₃ ^2- and OH ^- ions can make Ca ²⁺ and Mg ^{2+ .} It is converted into CaCO ₃ and Mg(OH) _{2 respectively} . When the crude brine also contains Cs ⁺ and Ni ⁺ ions, CO ₃ ^2- and OH ^- ions can also be converted into Cs ₂ CO ₃ and Ni(OH) _{2 .} Then, it is sent to a ceramic membrane for filtration, and CaCO ₃ , Mg(OH) ₂ , Cs ₂ CO ₃ and Ni(OH) ₂ formed by these reactions can be removed to obtain a ceramic membrane concentrate and a purified ceramic membrane supernatant.

It is known to those skilled in the art that when CO ₃ ^2- and OH ^- ions are added as a precipitant in the form of a salt, the cation of the additional precipitant needs to be the same as the cation in the crude brine to ensure that no new impurities are introduced into the brine. a cation, for example, when adding a precipitant to a crude brine containing mainly NaCl or Na ₂ SO ₄ , it is necessary to add NaOH and Na ₂ CO ₃ ; similarly, when adding a precipitant to the crude brine mainly containing KCl When refining, it is necessary to add KOH and K ₂ CO ₃ .

The concentration range of the main component in the crude brine purified in the present invention is not particularly limited, but in order to increase the efficiency of the precipitation reaction and the membrane filtration efficiency, the main component can generally be subjected to reaction and filtration purification near the solubility saturation, for example, NaCl. The concentration may be between 200 and 360 g/L, the concentration of KCl may be between 150 and 400 g/L, and the concentration of Na ₂ SO ₄ may be between 50 and 400 g/L.

The concentration range of Ca ²⁺ , Mg ²⁺ , Cs ⁺ , and Ni ⁺ ions as the impurity cation is not particularly limited and may be in the range of 0.01 to 50 g/L as long as a suitable precipitant CO ₃ ^2- is selected depending on the concentration of the impurity cation. and OH ^- ions are added in an amount, converted to cationic impurities to precipitate, CO ₃ ^2- and OH ^- ions may be added in an amount to be calculated by those skilled in the art stoichiometric balance. In order to be able to completely convert the impurity cations into a precipitate, a precipitating agent is selected from one or a mixture of NaOH, Na ₂ CO ₃ , KOH or K ₂ CO ₃ , each of which is added in an amount greater than the complete precipitation. The amount of impurity cation required, for example, the addition of NaOH, Na ₂ CO ₃ , KOH or K ₂ CO ₃ is 0.2 g/L more than the amount required to completely precipitate the impurity cation. The term "complete precipitation" as used in the present invention refers to the amount of precipitation required according to the chemical reaction equilibrium formula, and can be calculated by those skilled in the art according to the chemical reaction molar ratio, and is not understood to be that the impurity ions in the actual reaction are completely precipitation.

In the above method, the ceramic membrane used may be a ceramic microfiltration membrane or a ceramic ultrafiltration membrane, and the microfiltration membrane may be a membrane having an average pore diameter of 0.05 μm to 5 μm, and the average pore diameter of the ultrafiltration membrane used in the present invention may be 0.005 μm to 0.05 μm or a film having a molecular weight cut off of 1000 to 200,000 Da. Here, since the pore diameter of the ultrafiltration membrane is too small, it is difficult to measure the pore diameter of the membrane surface by an electron microscope or the like, so a value called a molecular weight cut off is used instead. The average pore size is used as an indicator of the pore size. Regarding the molecular weight cut off, as described in the text of the art: "The curve in which the solute molecular weight is plotted on the horizontal axis and the blocking ratio is plotted on the vertical axis, and the data is plotted as a molecular weight cutoff curve. The molecular weight of % is referred to as the molecular weight cut-off of the membrane, and the molecular weight cut off is an indicator of the membrane properties of the ultrafiltration membrane and is well known to those skilled in the art. The shape of the filter element includes a flat membrane, a tubular membrane, a multi-channel membrane, a spiral membrane, a hollow fiber membrane, and the like, and all module forms.

The porous film material constituting the ceramic film can be appropriately selected from conventionally known ceramic materials. For example, an oxide material such as alumina, zirconia, magnesia, silica, titania, cerium oxide, cerium oxide or barium titanate; cordierite, mullite, forsterite, talc, silicon may be used. a composite oxide material such as aluminous oxynitride ceramic, zircon or ferrite; a nitride material such as silicon nitride or aluminum nitride; a carbide material such as silicon carbide; and a hydroxide material such as hydroxyapatite; Elemental materials such as carbon or silicon; or two or more inorganic composite materials containing them. Natural minerals (clay, clay minerals, ceramsite, silica sand, pottery, feldspar, white sand) or blast furnace slag, fly ash, etc. can also be used. Among them, one or two or more selected from the group consisting of alumina, zirconia, titania, magnesia, and silica are preferable, and ceramic powder mainly composed of alumina, zirconia, or titania is more preferable. Here, "as a main body" as used herein means that 50% by weight or more (preferably 75 wt% or more, more preferably 80% by weight to 100% by weight) of the total of the ceramic powder is alumina or silica. For example, in a porous material, alumina is relatively inexpensive and excellent in handleability. Further, since a porous structure having a pore diameter suitable for liquid separation can be easily formed, a ceramic separation membrane having excellent liquid permeability can be easily produced. Further, among the above aluminas, α-alumina is particularly preferably used. The α-alumina has a property of being chemically stable and having a high melting point and high mechanical strength. Therefore, by using α-alumina, it is possible to manufacture a ceramic separation membrane which can be utilized in a wide range of applications such as industrial fields.

In one embodiment, a solid-liquid separation treatment may be performed as a pretreatment (pre-filtration) in order to suppress contaminants before filtration by a ceramic microfiltration/ultrafiltration membrane. The solid-liquid separation method is not particularly limited. Specific examples of the solid-liquid separation treatment include a centrifugal separation method, a press separation method, a filtration method, a floating separation method, and sedimentation. Separation method. As a centrifugal separation method, a horizontal continuous centrifugal separator (spiral decanter treatment), a separation plate type centrifugal separator, a centrifugal filter, and a Haupres type ultracentrifugal separator can be exemplified, and as a filtration method, belt filtration can be exemplified. The machine, the belt press, the screw press, the pre-coating filter, and the filter press can be exemplified as the continuous floating separation device as the floating separation method. As the sedimentation separation method, a coagulation sedimentation separator, a rapid sedimentation separator, etc. can be exemplified, but It is not particularly limited to any of the above. However, the load on the film during the treatment of the ceramic microfiltration/ultrafiltration membrane can be reduced by any one of the above or a combination thereof.

According to the above process description, the structure of the apparatus used in the present invention is as shown in FIG. 3, and mainly includes a reaction tank 26 for adding a crude brine therein, and a precipitant is added to the reaction tank 26, and an impurity cation in the crude brine. A sufficient reaction is carried out to form a precipitate and a colloid, and a stirring paddle 27 is further provided inside the reaction tank 26 for improving the uniformity and rate of the reaction; after the precipitation reaction is carried out, the brine is sent to the coarse filter 29 for pre-filtration and removal. The impurities such as large particle impurities and suspended solids contained in the brine are removed, and the produced water of the coarse filter 29 is sent to the ceramic membrane filter 2 for precision filtration, and the precipitate of the cationic impurities is removed from the ceramic membrane filter 2. , the purified brine was obtained.

In the above apparatus, the structure of the coarse filter 29 includes an outer casing, and a titanium mesh 31 is disposed inside, and the titanium mesh 31 is formed into a cylindrical shape and vertically installed in the casing. The specific structure is as shown in FIG. It is shown that the mesh number of the titanium mesh 31 can be adjusted as needed, which has better corrosion resistance. The liquid inlet of the coarse filter 29 is above the casing, and the liquid enters the casing and passes through the cylindrical titanium. The mesh 31 was filtered and the filtrate flowed out from the side of the casing. The shape of the titanium plate opening 33 on the titanium mesh may be a circle as shown in FIG. 8, or may be a triangle as shown in FIG. 9, or a square, an ellipse or the like; when the titanium plate opening 33 is a circle In the case of a shape, the diameter is preferably 1 mm or less. When the other shape is used, the equivalent diameter is preferably 1 mm or less. Further, on the permeation side of the titanium mesh 31, a recoil device 32 is preferably further provided, which is periodically provided. The backlash of the titanium mesh 31 can effectively increase the filtration speed of the coarse filter 29 and eliminate the filter cake and deposits on the surface of the titanium mesh 31.

In some cases, when a solid crude salt is used as a raw material and water is added to dissolve the salt to obtain a crude brine, a device as shown in FIG. 3 is used, mainly having a salt tank 9 stacked in the salt tank 9 There is a coarse salt, and a water inlet 10 is provided at the bottom thereof, and water is fed into the water inlet 10 through a pump, and the water flows from the bottom to the top, and reaches the overflow port 11 at the top of the salt tank 9 and overflows from the overflow. The outlet 11 flows out, and when the water flows slowly upward, the raw salt is gradually dissolved to saturation, and when it flows out from the overflow, a part of the undissolved coarse salt is carried into the subsequent equipment. After the coarse salt deposited in the salt bath is reduced, the coarse salt is poured into it. In addition, as shown in FIG. 3, it is also possible to provide a baffle 28 after the overflow port 11 and before entering the inlet of the reaction tank 26. The function of the baffle groove 28 is to deflect the raw material liquid to make the larger particles therein. The debris sinks to achieve the preliminary purification of the brine. In the baffle tank 28, a filter screen 30 can also be provided, which functions to intercept impurities such as suspended matter, and the filter screen 30 can be set to be lifted for convenient cleaning.

However, if the crude potassium chloride salt obtained by the flotation method, the carnallite method or the like is used as a raw material, since the solubility of KCl changes with temperature, the coarse salt tends to appear in the salt layer during the crystallization process. The content of MgSO ₄ in the upper part is relatively high, and in the case where the content of MgSO ₄ at the bottom of the salt layer is low, when the salt is poured into the salting tank, when the water just overflows from the top, the brine immediately after the initial flow is caused. The content of Mg ^{2+ is} higher, and the residence time of the crude brine in the reaction tank 26 is generally controlled to be about 1 hour. Then, when KOH and K ₂ CO ₃ are added to the reaction tank 26, the conventional amount can be caused. When added, the Mg ²⁺ ion is not converted into a precipitate in sufficient amount. Usually, in order to overcome this problem, it is necessary to add KOH more than 1.0 g/L more than the amount of complete precipitation, which causes the raw material. Waste, in some cases, can not completely solve the problem of concentration fluctuations. In order to overcome the problem of fluctuations in the concentration of coarse brine caused by the high content of CaCl ₂ and MgSO ₄ in the upper portion of the salt layer, the residence time of the potassium chloride crude brine in the reaction tank 26 can be controlled to be more than 3 hours. The method may be to increase the number of reaction tanks 26 to more than 3; when the crude brine has sufficient residence time, the concentration of Ca ²⁺ and Mg ²⁺ may be significantly reduced with the addition of new coarse salt. The fluctuation problem, when the amount of KOH added is controlled to be more than 0.2g/L than the completely precipitated impurities, the Mg ²⁺ reaction in the crude brine can still be ensured completely, and the raw material consumption is saved.

When the crude brine that has undergone precipitation reaction enters the ceramic membrane for filtration, the brine will also contain some organic matter. Generally, the COD in the crude brine is in the range of 200-800. These organic substances will pollute the ceramic membrane and cause membrane flux. A decrease occurs, and therefore, in some embodiments, chlorine may also be added to the crude brine entering the ceramic membrane to cause oxidative decomposition of the organic matter, thereby reducing membrane fouling. The chlorine may be added in the form of chlorine gas, hypochlorous acid or the like, and the chlorine may be added continuously in the crude brine, and the amount may be 1 to 100 mg/l in terms of available chlorine; more preferably, it is intermittently added. (The addition period may preferably be once every 4 to 12 hours, and the addition time is 1 to 2 hours each time), and the addition amount is controlled at 50 to 100 mg/l, which can produce a better effect of reducing membrane fouling than continuous addition. Moreover, the consumption of chlorine is less; in addition, the addition of Na ₂ SO _{3 to} the permeate of the ceramic membrane neutralizes unreacted chlorine. In the present invention, the determination of available chlorine is carried out by an iodometric method. The effective chlorine is oxidized with potassium iodide in an acidic solution to release a certain amount of iodine, and the iodine is titrated with a sodium thiosulfate standard solution according to the sodium thiosulfate standard. The amount of solution consumed calculates the amount of available chlorine.

The main structure of the ceramic membrane filtration device used is as shown in FIG. 1. The device may include one ceramic membrane module 2, or may have two or more ceramic membrane modules 2, and the ceramic membrane modules 2 may be connected in series. , in parallel or in a hybrid installation. In some embodiments, the ceramic membrane module 2 is mounted on the component communication chamber 1 at the bottom thereof, and when there are a plurality of ceramic membrane modules 2, in parallel with each other, the raw material liquid of the ceramic membrane element 2 is fed. The port is connected with the component connecting cavity 1 , and a liquid inlet 3 is arranged on the component connecting cavity 1 , and the liquid inlet 3 is connected with the crude brine pipe, and the function is to supply the CaCO ₃ into the ceramic membrane module 2 and The precipitated brine of Mg(OH) ₂ or the like is removed by filtration by a ceramic membrane, and a permeate outlet is provided at a side of the ceramic membrane module 2, and the ceramic membrane element mounted in the ceramic membrane module 2 may be a single tube type. It can also be multi-channel. The ceramic membrane module 2 can generally be installed vertically, ensuring that the flow path of the ceramic membrane element is perpendicular to the horizontal plane (or may be at an angle to the horizontal plane, for example, 45 to 90°), and the trapped precipitate may fall into the component communication cavity 1 In the middle, avoiding the retention in the brine, when the liquid inlet 3 is disposed at the intermediate position of the component communication cavity 1, after running for a period of time, a certain amount of mud is accumulated at the two ends of the component communication cavity 1 due to the pressure. (precipitation), because the mud is mainly located at both ends of the cavity, it will cause the process of sludge removal to be difficult. In a modified embodiment, an openable mud discharge port 4 is further provided at both ends of the component communication chamber 1, and the mud discharge port 4 can be opened to more easily remove mud. The position of the drain port 4 is not limited to the side on both end portions of the module communication chamber 1, but may be at a position on the assembly communication chamber 1 near both ends.

When using a ceramic membrane to filter brine, it is necessary to ensure that the surface of the ceramic membrane maintains the proper filtration accuracy, and the membrane layer should not be damaged to maintain the rejection of precipitates such as CaCO ₃ and Mg(OH) ₂ . In one embodiment, a liquid collecting pipe 6 is disposed on the permeate pipe 5 of the ceramic membrane element 2, and the haze meter 7 is connected to the liquid collecting pipe 6, and when the turbidity is significantly increased, it means that the ceramic membrane may be separated. The layer is damaged. Since the pressure on the side of the permeate of the ceramic membrane is high, it is preferable to depressurize the liquid to make it suitable for entering the turbidity detecting device. However, when the permeate is discharged from the membrane module, the pressure of the permeate rapidly decreases. Due to the high concentration of salts such as NaCl and KCl, crystallization tends to occur, and the crystallized material may cause inaccurate turbidity detection. Therefore, in the liquid collection tube 6 is further provided with a diluent tube 8 to reduce the concentration of the liquid. Generally, it is necessary to reduce the concentration of NaCl, KCl or Na ₂ SO ₄ in the permeate introduced into the temperature detecting device to its saturated concentration. 80% or less, it is possible to avoid the problem of inaccurate detection of the turbidity meter 7 caused by crystallization after decompression, and the concentration of sodium chloride in the ceramic membrane clear liquid can be above 300 g/L, through the inlet of the turbidity detecting device. After dilution with water, the concentration is lowered to 200 g/L, which can effectively avoid crystallization in the turbidity detection and affect the detection results.

Example 1

Using a device as shown in FIG. 3, a NaCl salt is added to the salt tank 9, and tap water is pumped from the water inlet 10 at the bottom of the salt tank 9, and the bottom of the water flows through the coarse salt layer until the top overflow port 11. The flow into the baffle groove 28, after the flow of the coarse brine in the baffle groove 28, a part of the suspended matter and the particulate impurities may settle, and a part of the filter 30 installed in the baffle groove 28 After interception, the crude brine is re-entered into the subsequent three series of reaction tanks 26, and on the reaction tank, NaOH 0.4 g/L and Na ₂ CO ₃ 1.6 g/L are added by means of on-line dosing, after the reactor is fully reacted. Ca ²⁺ and Mg ²⁺ are respectively converted into CaCO ₃ and Mg(OH) ₂ , and then enter the coarse filter 29 for pre-filtration. The obtained calcium crude salt has a calcium content of 754.2 mg/L and a magnesium content of 83.21 mg/ L, sulfate 7.6g / L, SS content 3589.33mg / L, and then sent to the ceramic membrane module 2 for filtration, can remove CaCO ₃ precipitate and Mg (OH) ₂ colloid, using an average pore diameter of 200nm alumina Ceramic membrane, 19 channels, channel inner diameter 4mm, cross-flow velocity 1m/s, operating pressure 0.4MPa, obtained ceramic membrane concentration Ceramic membrane and the purified supernatant.

Example 2

This embodiment is for explaining the turbidity detection of the ceramic membrane permeate to monitor the operation of the ceramic membrane.

The apparatus used is as shown in Fig. 2, and a permeate tube 5 is provided on the ceramic membrane module 2 for discharging the permeate. In order to prevent the damage of the ceramic membrane, the calcium and magnesium precipitates enter the permeate side, and the liquid permeate tube 5 is further provided with a liquid collecting pipe 6 for sampling a part of the permeate to be sent to the turbidimeter 7 for on-line monitoring. When the turbidity in the turbidity meter 7 is high, it is suggested that the ceramic membrane may be damaged and further analysis is required. Since the concentration of NaCl in the liquid on the permeate side is high, in some cases, it will reach 300 g/L or more. Therefore, when the permeate is discharged from the ceramic membrane module 2, the pressure is lowered, and crystallization is likely to occur, and further, As a result, the detected value of the turbidity detector does not correctly reflect the operating state of the ceramic membrane. Therefore, a diluent tube 8 is also disposed on the liquid collecting tube 6 for diluting the sampling liquid to 200 g/L of sodium chloride. Below the content, the problem of crystallization of sodium chloride can be solved.

Example 3

This example is intended to illustrate the effect of the manner in which chlorine is added to the raw material liquid to retard the flux decay and membrane fouling of the ceramic membrane.

Using a device as shown in FIG. 3, a NaCl salt is added to the salt tank 9, and tap water is pumped from the water inlet 10 at the bottom of the salt tank 9, and the bottom of the water flows through the coarse salt layer until the top overflow port 11. The flow into the baffle groove 28, after the flow of the coarse brine in the baffle groove 28, a part of the suspended matter and the particulate impurities may settle, and a part of the filter 30 installed in the baffle groove 28 After interception, the crude brine is re-entered into the subsequent three series of reaction tanks 26, and NaOH 0.6g/L and Na ₂ CO ₃ 1.9g/L are added by on-line dosing on the reaction tank, and the reaction is fully reacted. Ca ²⁺ and Mg ²⁺ are respectively converted into CaCO ₃ and Mg(OH) ₂ , and then enter the coarse filter 29 for pre-filtration. The obtained calcium crude salt has a calcium content of 836.1 mg/L and a magnesium content of 75.77 mg/ L, sulfate 8.2g / L, SS content 3769.98mg / L, COD is 460ppm, while intravenously adding sodium hypochlorite (effective free chlorine 10mg / L), and then sent to the ceramic membrane for filtration, can remove CaCO ₃ precipitation and Mg (OH) ₂ colloid, using the average pore size of the zirconium oxide ceramic film 50nm channel 19, through An inner diameter of 4mm, cross flow velocity 3m / s, the operating pressure of 0.3MPa, to give a clear solution after a ceramic film ceramic membrane concentrate and purified. The operating flux of the ceramic membrane was reduced to 400 L/m ² ·h after 313 hours of operation.

As a control, the dosage of chlorine was modified to be added once every 8 hours, the dosage time was 1.5 hours, the amount of addition was 80 mg/L, and the operation parameters of the ceramic membrane were the same when other operating parameters were the same. The amount was reduced to 400 L/m ² ·h after 622 hours of operation.

It can be seen from the operating conditions that the membrane fouling can be effectively alleviated by periodically adding chlorine.

Example 4 This example is used to illustrate the effect of increasing the residence time of the crude brine in the reaction tank.

The flow of the apparatus used in the present invention is as shown in Fig. 3. A water inlet 10 is provided at the bottom of the salt tank 9, and an overflow port 11 is provided at the upper portion of the salt tank 9, firstly poured into the salt lake 9 by the salt lake. The crude salt of KCl obtained after extraction and salting (the content of Mg ²⁺ in the upper part of the salt layer is significantly higher than that of the bottom layer), and then water is added from the water inlet 10 at the bottom of the salt tank 9, and the water overflows upward through the coarse The salt layer will gradually dissolve the coarse salt in the process until the upper overflow port 11; and the overflow port 11 is connected to the reaction tank 12 through the baffling tank 28, and the coarse salt water will carry the crude salt and particulate impurities which are not completely dissolved. Waiting to enter the reaction tank 12. At the initial stage, the calcium content in the crude brine after salting is 755.9 mg/L, the magnesium content is 692.341 mg/L, the sulfate is 7.3 g/L, and the SS content is 4738.75 mg/L. After a period of time, the salt layer of the surface layer is dissolved. Entering the reaction tank 12, the subsequent overflow of the crude brine has a calcium content of 996.1 mg/L, a magnesium content of 92.223 mg/L, a sulfate of 8.6 g/L, and an SS content of 3127.22 mg/L, which is further dissolved in the reaction tank 12. At the same time, KOH 0.7g/L and K ₂ CO ₃ 3.9g/L were continuously added to the reaction tank 12, and after the reactor was sufficiently reacted, Ca ²⁺ and Mg ²⁺ were respectively converted into CaCO ₃ and Mg ( OH) ₂ .

The ceramic membrane module 2 is a zirconia ceramic membrane having an average pore diameter of 50 nm, 19 channels, a channel inner diameter of 4 mm, a cross flow rate of 3 m/s, and an operating pressure of 0.3 MPa, to obtain a ceramic membrane concentrate and a purified ceramic membrane. Clear liquid. When two reaction tanks are used (the residence time of the crude brine is about 1.5 hours), the ion content in the ceramic membrane permeate is: magnesium ion content 383.55 mg / L, calcium ion content 89.1 mg / L, sulfate content 7.2 mg / L. When three reaction tanks are used (the residence time of the crude brine is about 3 hours), the other parameters are the same, and the ion content of the obtained ceramic membrane permeate is: magnesium ion content 19.58 mg / L, calcium ion content 17.4 mg / L The sulfate content is 7.3 mg/L. It can be seen that by increasing the reaction tank, the problem of fluctuation of ion content in the coarse brine caused by the high content of calcium and magnesium ions in the surface layer of the coarse salt can be solved.

Example 5 This example solves the problem of uneven composition of calcium and magnesium ions in the crude salt by adding a raw material funnel to the salt bath.

The raw material funnel 12 used in the present embodiment is installed in the salting tank 9 at a position as shown in FIG. 4, and is installed in the upper middle portion of the salting tank 9, and when the coarse salt is poured into the salting tank 9, it is first coarse. The salt is poured into the raw material funnel 12, and the problem that the distribution of calcium and magnesium ions in the upper and lower layers of the raw material salt is uneven, and the influence of the ions of the crude salt water is unstable and fluctuates can be solved. The specific structure of the material funnel 12 is as shown in FIG. 5 . The main structure of the material funnel 12 includes a funnel cavity 13 . Below the funnel cavity 13 is a discharge port 14 , and a rotating shaft 15 is disposed in the middle of the funnel cavity 13 . The rotating shaft 15 is provided with a spiral blade 16 on the upper side of which a turntable 17 is disposed. The turntable 17 is provided with an eccentric shaft 18, and the eccentric shaft 18 is movably connected to one end of the first connecting rod 19; outside the funnel cavity 13 The limiting plate 21 is disposed. As shown in FIG. 5, a limiting slot 22 is disposed on the limiting plate 21, and the second connecting rod 20 is sleeved in the limiting slot 22, and one end of the second connecting rod 20 and the first connecting rod The other end of the 19 is a movable connection, and an opening 24 is formed on a side of the funnel cavity 13 facing the limiting plate 21, and a baffle 23 is disposed outside the opening 24, and the baffle 23 is connected to the other end of the second link 20. .

In use, the coarse salt is first poured from the upper part of the funnel cavity 13, and the coarse salt will accumulate on the spiral blade 16 after entering the cavity. After being subjected to gravity, the coarse salt will move downward and simultaneously drive. The spiral blade 16 rotates, so that the rotating shaft 15 also rotates. Since the turntable 17 is located above the rotating shaft 15, the turntable 17 is also continuously continuous. Rotate sexually. Since the eccentric shaft 18 is disposed on the turntable 17, and the eccentric shaft 18 is movably connected to the first link 19, the rotation of the turntable 17 in turn drives the first link 19 to move, due to the movement of the first link 19 The other end is movably connected to the second link 20 that is engaged in the limiting slot 22, and then the second link 20 can be driven to reciprocate in the limiting slot 20 after the first link 19 moves around the rotating shaft 15. Movement, and because the lower portion of the second link 20 is connected to the baffle 23, and the baffle 23 is disposed outside the opening 24, the baffle 23 periodically opens the opening as the second link 20 reciprocates. 24 open or closed. Since the coarse salt flows out from the upper and lower sides of the funnel cavity 13, the outflow rate of the coarse salt is somewhat delayed, and since the opening 24 can be periodically opened and closed, the coarse salt containing more magnesium is located above. It will fall directly through the opening and fall into the bottom of the salt bath 9, avoiding the problem that the coarse salt containing more magnesium is all focused on the coarse salt.

In still other embodiments, the radius below the funnel cavity 13 is smaller than the radius above, and since the radius below is small, when the coarse salt moves below, the coarse salt moves faster in this portion and can drive the shaft. 15 rotating faster, it is possible to make the coarse salt located above from the side opening 24 more, this improvement can be more suitable for the gradient of calcium and magnesium concentration in the coarse salt, the closer to the upper coarse salt, the easier Drop directly below the opening 24. A card plate 25 can also be disposed on the discharge port 14, and the card plate 25 can be used to limit the speed of discharging. By adjusting the size of the card plate 25, the outflow speed of the coarse salt can be changed, and the rotation speed of the rotating shaft 15 can be changed. Further, the frequency of opening and closing of the upper baffle 23 is adjusted, and the speed at which the upper coarse salt falls out is adjusted.

Example 6 This example is intended to illustrate the refining of the crude salt of Na ₂ SO ₄

Using the apparatus shown in Fig. 3, a coarse salt of Na ₂ SO ₄ is added to the salt tank 9, and tap water is pumped from the water inlet 10 at the bottom of the salt tank 9, and the bottom of the water flows through the coarse salt layer until the top The overflow port 11 flows into the baffle groove 28. After the flow of the coarse brine in the baffle groove 28, a part of the suspended matter and the particulate impurities are settled, and a part of the mixture is installed in the baffle groove 28. The screen 30 intercepts, the crude brine enters the subsequent three series of reaction tanks 26, and on the reaction tank, NaOH 0.8g/L and Na ₂ CO ₃ 1.9g/L are added by means of on-line dosing, and the reactor is passed through the reactor. After sufficient reaction, Ca ²⁺ and Mg ²⁺ were respectively converted into CaCO ₃ and Mg(OH) ₂ , and then into the coarse filter 29 for pre-filtration, and the obtained calcium content of Na ₂ SO ₄ crude brine was 852.52 mg/L. Magnesium content 103.67mg / L, SS content 3127.54mg / L, and then sent to the ceramic membrane module 2 for filtration, can remove CaCO ₃ precipitate and Mg (OH) ₂ colloid, using a zirconia ceramic with an average pore diameter of 50nm Membrane, 19 channels, channel inner diameter 4mm, cross flow rate 5m / s, operating pressure 0.3MPa, to obtain ceramic membrane concentrate and After the supernatant of the ceramic membrane, a ceramic membrane serum calcium content 22.66mg / L, a magnesium content of 31.38mg / L.

Claims (23)

1. A brine refining method based on a membrane technology, comprising the steps of: adding a CO ₃ ^2- and/or OH ^- ion as a precipitant to a crude brine, and performing a precipitation reaction with a cationic impurity in the crude brine to form a precipitate, It is further sent to a ceramic membrane for filtration to remove precipitates, and purified brine is obtained on the permeate side of the ceramic membrane.
2. The membrane technology-based brine refining method according to claim 1, wherein the crude brine refers to a brine mainly containing NaCl, KCl or Na ₂ SO ₄ ; the cationic impurity is selected from Ca ²⁺ , Mg ²⁺ , Cs ⁺ or Ni ⁺ ions.
3. The membrane technology-based brine refining method according to claim 2, wherein when the crude brine refers to brine mainly containing NaCl, the crude brine is selected from brine, seawater mainly containing NaCl or dissolved by NaCl crude salt. When the crude brine refers to the brine containing mainly KCl, the crude brine is the brine obtained by dissolving the crude salt of KCl; when the crude brine refers to the brine containing mainly Na ₂ SO ₄ , the crude brine refers to Na ₂ The brine obtained after dissolving the SO ₄ crude salt is either a brine containing mainly Na ₂ SO ₄ .
4. The membrane-based brine refining method according to claim 1 or 2, wherein the cation in the precipitant is the same as the cation of the main component in the crude brine.
5. The membrane-based brine refining method according to claim 4, wherein the precipitating agent is selected from one or a mixture of NaOH, Na ₂ CO ₃ , KOH or K ₂ CO ₃ , each of which is precipitated. The amount of agent added is greater than the amount required to completely precipitate the impurity cations.
6. The membrane-based brine refining method according to claim 1, wherein the ceramic membrane refers to a ceramic microfiltration membrane or a ceramic ultrafiltration membrane.
7. The membrane-based brine refining method according to claim 6, wherein the microfiltration membrane has an average pore diameter of from 0.05 μm to 5 μm.
8. The membrane-based brine refining method according to claim 6, wherein the ultrafiltration membrane has an average pore diameter of from 0.005 μm to 0.05 μm or a molecular weight cutoff of from 1,000 to 200,000 Da.
9. A membrane-based brine refining process according to claim 1 wherein the crude brine is pre-filtered prior to the addition of the precipitating agent.
10. The membrane-based brine refining method according to claim 1, wherein after the precipitation reaction, the brine is filtered through a coarse filter and then sent to a ceramic membrane for filtration.
11. The membrane-based brine refining method according to claim 1, characterized in that before the crude brine is sent to the ceramic membrane for filtration, chlorine is added thereto; the chlorine is added in the form of chlorine or hypochlorite.
12. The membrane-based brine refining method according to claim 11, wherein the addition of chlorine is intermittently added every 4 to 12 hours; the amount of addition is 50 to 100 mg/l, and the addition time lasts. 1 to 2 hours; then unreacted chlorine was neutralized by adding Na ₂ SO ₃ to the ceramic membrane supernatant.
13. The membrane technology-based brine refining method according to claim 1, characterized in that the turbidity of the ceramic membrane supernatant is monitored on-line, and the ceramic membrane supernatant entering the turbidity detector is diluted to make the ceramic membrane clear. The content of the main component in the liquid is less than 80% of its saturated solubility, and then the turbidity is detected.
14. A brine refining apparatus based on a membrane technology, comprising: a reaction tank (26) and a ceramic membrane module (2) connected in series.
15. The membrane-based brine refining apparatus according to claim 14, wherein a dosing device for CO ₃ ^2- and/or OH ^- ion precipitating agent is connected to the reaction tank (26).
16. The membrane technology-based brine refining device according to claim 14, wherein the device is further provided with a salt tank (9), and the bottom of the salt tank (9) is provided with a water inlet (10), and the upper portion is provided with The overflow port (11) and the overflow port (11) are connected to the reaction tank (9).
17. The membrane refining device according to claim 16, characterized in that the overflow port (11) is connected to the reaction tank (26) through the baffling groove (28); the baffle (28) is provided with Filter (30); filter (30) is hangable.
18. A membrane-based brine refining apparatus according to claim 14, wherein the reaction tank (26) is connected to the ceramic membrane module (2) through a coarse filter (29).
19. A membrane-based brine refining apparatus according to claim 18, wherein said coarse filter (29) is a titanium mesh filter; and said titanium mesh has an equivalent of titanium plate opening (33) The diameter is less than 0.5mm.
20. A membrane-based brine refining apparatus according to claim 14, wherein a component communication chamber (1), a ceramic membrane element in the ceramic membrane module (2) is disposed under the ceramic membrane module (2) The raw material liquid flow channel communicates with the component communication cavity (1), the component communication cavity body (2) is provided with a liquid liquid inlet (3), and the material liquid inlet (3) is connected with the reaction tank (26), and the component is connected to the cavity ( 1) Both ends are provided with a drain port (4) that can be opened.
21. A membrane-based brine refining apparatus according to claim 14 or 20, wherein the ceramic membrane element mounted in the ceramic membrane module (2) is a single-tube type or a multi-channel type, and the raw material flow of the ceramic membrane element The road is perpendicular to the water level.
22. The membrane technology-based brine refining device according to claim 14, characterized in that the permeate tube (5) of the ceramic membrane module (2) is further provided with a liquid collecting pipe (6) and a liquid collecting pipe ( 6) Connected to the turbidimeter (7); a dilution tube (8) is also provided on the liquid collection tube (6).
23. The membrane technology-based brine refining device according to claim 14, wherein the chemical salt tank (9) is further provided with a raw material funnel (12), and the raw material funnel (12) comprises a funnel cavity ( 13), below the funnel cavity (13) is a discharge port (14), in the middle of the funnel cavity (13) is provided a rotating shaft (15), the rotating shaft (15) is provided with a spiral blade (16), in the rotating shaft A turntable (17) is arranged above the (15), and an eccentric shaft (18) is arranged on the turntable (17), and the eccentric shaft (18) An active connection is connected to one end of the first connecting rod (19); a limiting plate (21) is arranged outside the funnel cavity (13), and a limiting slot (22) is arranged on the limiting plate (21), the limiting slot (22) is sleeved with a second connecting rod (20), one end of the second connecting rod (20) is movably connected with the other end of the first connecting rod (19), and faces the limit on the funnel cavity (13) An opening (24) is defined on one side of the plate (21), and a baffle (23) is disposed outside the opening (24), and the baffle (23) is connected to the other end of the second link (20); the funnel cavity ( 13) The lower radius is smaller than the upper radius; the discharge port (14) is provided with a card plate (25).

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