CN115304082A - Process for recovering NaCl in salt mud for chlor-alkali production - Google Patents
Process for recovering NaCl in salt mud for chlor-alkali production Download PDFInfo
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- CN115304082A CN115304082A CN202211237188.2A CN202211237188A CN115304082A CN 115304082 A CN115304082 A CN 115304082A CN 202211237188 A CN202211237188 A CN 202211237188A CN 115304082 A CN115304082 A CN 115304082A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
- C01D3/06—Preparation by working up brines; seawater or spent lyes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/08—Filter cloth, i.e. woven, knitted or interlaced material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/08—Filter cloth, i.e. woven, knitted or interlaced material
- B01D39/083—Filter cloth, i.e. woven, knitted or interlaced material of organic material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/08—Filter cloth, i.e. woven, knitted or interlaced material
- B01D39/086—Filter cloth, i.e. woven, knitted or interlaced material of inorganic material
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Abstract
The invention relates to a process for recovering NaCl from salt mud for chlor-alkali production, which belongs to the technical field of chlor-alkali production and comprises the following steps: the method comprises the following steps that firstly, slurry is discharged from a preprocessor and a Kjean membrane filter, the slurry enters a salt slurry tank, then the slurry is conveyed to a filter press by a slurry pump to be made into a slurry cake, the salt water discharged by filter pressing is recycled, the salt slurry is conveyed into the preprocessor for preprocessing, then the salt slurry is filtered by an HVM membrane filter, the discharged filter slurry is conveyed into a salt slurry tank, then the salt slurry is conveyed into a primary filter press by a primary slurry pump, primary salt slurry and primary pressure filtrate are formed after filter pressing, the primary salt slurry is discharged into a washing pool and dissolved and washed by primary water, the primary pressure filtrate is conveyed into a brine pool, when the salt content of the primary salt slurry is reduced to 1% by mixing and dissolving the primary salt slurry and the primary water, the primary salt slurry is conveyed into a secondary filter press by a secondary slurry pump, and secondary filtrate formed after filter pressing overflows into the salt slurry tank and is conveyed into the primary filter press by the primary slurry pump again; realizes the regeneration and utilization of waste and reduces the discharge pressure of solid waste.
Description
Technical Field
The invention belongs to the technical field of chlor-alkali production, and particularly relates to a process for recovering NaCl from salt mud in chlor-alkali production.
Background
At present, brine is refined once by using a preprocessor and a Kjean membrane filter process, firstly slurry discharged by the preprocessor and the Kjean membrane filter enters a salt slurry tank, then the slurry is conveyed to a filter press by a slurry pump to be made into a mud cake, the brine discharged by filter pressing is recycled, the discharged salt slurry is discharged after the discharged salt slurry is made into a cake by a plate-and-frame filter press, and a certain amount of available chlorine contained in the salt slurry corrodes filter cloth. The mud cake that produces after the filter-pressing composition is complicated, and the principal ingredients are calcium carbonate, magnesium hydrate and silt, and the mud cake contains the salt content height, is difficult to utilize, and along with the increase of environmental protection treatment dynamics, discharge pressure is big, is unfavorable for the cleaner production of enterprise.
The invention relates to a method for separating a large amount of sodium chloride, partial sodium carbonate and magnesium hydroxide from a mud cake, reducing the salt content and the amount of discharged salt mud, realizing the regeneration and utilization of wastes and reducing the solid waste discharge pressure of a company.
Disclosure of Invention
In order to solve the technical problem, the invention provides a process for recovering NaCl from salt mud in chlor-alkali production.
The purpose of the invention can be realized by the following technical scheme:
a NaCl recovery process in salt mud for chlor-alkali production comprises the following steps:
after the salt mud is treated by a preprocessor, floating mud formed on the surface is discharged to a salt mud tank through upper mud discharge, settled mud is discharged to the salt mud tank through a lower mud discharge port, clear liquid overflowing from a clear liquid outlet enters an HVM membrane filter, the pretreated crude salt water contains a large amount of calcium ions, a small amount of mechanical impurities and a small amount of magnesium hydroxide precipitate, sodium carbonate solution is added for reaction, the calcium ions are generated into calcium carbonate precipitate, then the impurities are filtered and removed through an HVM membrane to obtain refined salt water, the refined salt water is sent to the salt mud tank and then sent to a primary filter press through a primary slurry pump, primary salt mud and primary pressure filtrate are formed after filter pressing, the primary salt mud is discharged to a washing pool and dissolved and washed by primary water, the primary pressure filtrate is sent to a halogen water pool, when the salt content of the primary salt mud is reduced to 1 percent by mixing and dissolving with the primary water, a secondary slurry pump is used for filter pressing, secondary filtrate formed after filter liquid overflows to the salt mud tank and the primary salt mud tank is sent to the primary filter press again through the primary pump, the primary salt mud tank is washed, the sodium carbonate filter cake in the pipeline is further reduced, the sodium chloride filter cake, the sodium carbonate filter tank is separated, and the primary salt mud filter cake is sent to the primary salt mud filter cake, and the sodium hydroxide filter cake is separated, and then is sent to the sodium carbonate filter cake, and the sodium carbonate filter cake is sent to form a clean sodium carbonate filter cake.
Further: and corrosion-resistant filter cloth is arranged in both the first-stage filter press and the second-stage filter press.
Further: the corrosion-resistant filter cloth is prepared by the following steps:
step S1, drying polyacrylonitrile powder at 75-80 ℃ for 12 hours, then adding the dried polyacrylonitrile powder into dimethyl sulfoxide, slowly stirring, heating to 75-80 ℃ at a heating rate of 3-5 ℃/min, then preserving heat for 4 hours, transferring the polyacrylonitrile powder to a vacuum drying oven with the pressure of-0.10 MPa and the temperature of 80 ℃ for 10 hours to remove bubbles in vacuum to prepare a spinning solution, controlling the using amount ratio of the polyacrylonitrile powder to the dimethyl sulfoxide to be 15-18 g: 100mL, then preheating a spinning machine to 80 ℃, pouring the spinning solution into the spinning solution, spinning the spinning solution into a coagulating bath at a spinning rate of 2.5m/min to prepare nascent fiber, flushing the nascent fiber, then placing the nascent fiber into a boiling water bath to extend by 4-6 times, then freezing for 24 hours to prepare precursor fiber, then placing the precursor fiber into the drying oven, heating to 180-200 ℃ at a heating rate of 5-10 ℃/min, and carrying out heat preservation treatment for 4-6 hours to prepare treated fiber;
s2, slowly pouring ethyl orthosilicate onto the surface of anhydrous aluminum trichloride, sequentially adding isopropyl ether and anhydrous dichloromethane, magnetically stirring for 2 hours, then placing the mixture into a drying oven, heating to 100-105 ℃, and drying for 1 hour to obtain dry gel, wherein the dosage ratio of the ethyl orthosilicate to the anhydrous aluminum trichloride to the isopropyl ether to the anhydrous dichloromethane is controlled to be 0.20-0.22mL to 0.5g to 0.5mL to 15-20mL; mixing alcoholic solution of polyvinylpyrrolidone with xerogel, stirring at a constant speed, adding absolute ethyl alcohol, continuously stirring for 15min, adding N, N-dimethylformamide, magnetically stirring for 1h to prepare spinning solution, controlling the dosage ratio of polyvinylpyrrolidone, xerogel, absolute ethyl alcohol and N, N-dimethylformamide to be 0.5-0.8 g: 0.3-0.5 g: 2-2.5 mL: 1.5mL, carrying out electrostatic spinning to prepare composite fiber, then calcining at 1200 ℃ for 1h to prepare porous fiber, and weaving according to warp yarn density of 150/cm and weft yarn density of 180/cm to prepare base cloth;
in the step S2, ethyl orthosilicate and aluminum trichloride are used as raw materials, xerogel which is mullite gel is prepared by a sol-gel method, then alcoholic solution of polyvinylpyrrolidone is added to prepare spinning solution, electrostatic spinning is carried out to prepare mullite and PVP composite fiber, and then calcination and PVP decomposition are carried out to form porous fiber.
And S3, uniformly mixing the treated fibers and the polypropylene fibers according to the weight ratio of 2-3: 7-8 to prepare mixed fibers, then opening and opening twice to prepare a fiber group, carding into a fiber net, then cross lapping, adding base cloth, carrying out pre-needling at the frequency of 100 needling/min, then carrying out main needling, and finishing to prepare the corrosion-resistant filter cloth.
Further, the method comprises the following steps: in the step S1, the coagulating bath is formed by mixing dimethyl sulfoxide and deionized water according to the volume ratio of 1: 1.
Further: the alcohol solution of polyvinylpyrrolidone in the step S2 is formed by mixing polyvinylpyrrolidone and absolute ethyl alcohol according to the dosage ratio of 0.5-0.8 g: 8-10 mL.
Further, the method comprises the following steps: and S3, controlling the needling frequency to be 150 needling/min during main needling, wherein the needling channel number is 2, and the needling depth is 6mm.
The invention has the beneficial effects that:
the method can recover a large amount of sodium chloride, partial sodium carbonate and magnesium hydroxide in the salt mud cake, not only reduces the consumption of raw salt, sodium carbonate and magnesium hydroxide in the salt water refining process, but also reduces the salt content and the amount in the discharged salt mud, realizes the regeneration and utilization of wastes, and reduces the discharge pressure of solid wastes; the corrosion-resistant filter cloth is prepared by preparing a treated fiber from polyacrylonitrile powder, wherein the fiber is a pre-oxidized polyacrylonitrile fiber which has excellent high-temperature resistance, lower price than carbon fiber and lower cost, so the corrosion-resistant filter cloth is an excellent filter material.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of the process for recovering NaCl from salt mud in chlor-alkali production according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Referring to fig. 1, the present invention is a process for recovering NaCl from salt mud in chlor-alkali production, comprising the following steps:
former salt mud is once refined and is used preprocessor + kay membrane filter technology, and preprocessor and kay membrane filter arrange mud earlier and get into the salt mud jar, carry to the pressure filter again through the sediment stuff pump and make the mud cake, and the salt solution recycle that the filter-pressing goes out, and this salt mud is wherein through testing: according to the mass percentage, the magnesium is 13.8 percent, the sodium chloride is 2.6 percent, the calcium is 39.2 percent, the water is 32.5 percent, and the balance is other impurities; after the salt mud is treated by a preprocessor, floating mud formed on the surface is discharged to a salt mud tank through upper mud discharge, settled mud is discharged to the salt mud tank through a lower mud discharge outlet, clear liquid overflowing from a clear liquid outlet enters an HVM membrane filter, pretreated crude salt water contains a large amount of calcium ions, a small amount of mechanical impurities and a small amount of magnesium hydroxide precipitate, sodium carbonate solution is added for reaction, the calcium ions are generated into calcium carbonate precipitate, then the impurities are filtered and removed through the HVM membrane to obtain refined salt water, the refined salt water is sent to the salt mud tank and then sent to a primary filter press through a primary slurry pump, primary salt mud and primary pressure filtrate are formed after filter pressing, the primary salt mud is discharged to a washing pool and dissolved and washed by primary water, the first-stage pressure filtrate is conveyed to a brine pool, when the first-stage salt slurry is mixed with primary water through stirring to be dissolved and reduce the salt content to 1%, the first-stage salt slurry is conveyed to a second-stage filter press by a second-stage slurry pump, second-stage filtrate formed after filter pressing overflows to a salt slurry tank, the second-stage filtrate is conveyed to the first-stage filter press by the first-stage slurry pump again, the salt slurry in the pipeline is washed, the contents of sodium chloride, sodium carbonate and magnesium hydroxide in the salt slurry are further reduced, a raw filtrate tank and a filtrate pump are stopped, clean salt slurry after physically separating a large amount of sodium chloride and partial sodium carbonate and magnesium hydroxide is discharged to the salt slurry pool to be circulated, formed second-stage filter cakes are conveyed to the salt slurry pool, the pressure filtrate in the brine pool is recrystallized, the filtration and washing are carried out, and the detection component contents are as follows: 0.22% of sodium chloride, 10.83% of magnesium, 15.94% of calcium, 28.9% of water and the balance of impurities.
And corrosion-resistant filter cloth is arranged in each of the primary filter press and the secondary filter press.
Example 2
A NaCl recovery process in salt mud for chlor-alkali production comprises the following steps:
former salt mud is once refined and is used preprocessor + kay membrane filter technology, and preprocessor and kay membrane filter arrange mud earlier and get into the salt mud jar, carry to the pressure filter again through the sediment stuff pump and make the mud cake, and the salt solution recycle that the filter-pressing goes out, and this salt mud is wherein through testing: according to the mass percentage, 13.7 percent of magnesium, 3.3 percent of sodium chloride, 38.6 percent of calcium, 32.3 percent of water and the balance of other impurities; after the salt mud is treated by a preprocessor, floating mud formed on the surface is discharged to a salt mud tank through upper mud discharge, settled mud is discharged to the salt mud tank through a lower mud discharge outlet, clear liquid overflowing from a clear liquid outlet enters an HVM membrane filter, pretreated crude salt water contains a large amount of calcium ions, a small amount of mechanical impurities and a small amount of magnesium hydroxide precipitate, sodium carbonate solution is added for reaction, the calcium ions are generated into calcium carbonate precipitate, then the impurities are filtered and removed through the HVM membrane to obtain refined salt water, the refined salt water is sent to the salt mud tank and then sent to a primary filter press through a primary slurry pump, primary salt mud and primary pressure filtrate are formed after filter pressing, the primary salt mud is discharged to a washing pool and dissolved and washed by primary water, the first-stage pressure filtrate is conveyed to a brine pool, when the first-stage salt slurry is mixed with primary water through stirring to be dissolved and reduce the salt content to 1%, the first-stage salt slurry is conveyed to a second-stage filter press by a second-stage slurry pump, second-stage filtrate formed after filter pressing overflows to a salt slurry tank, the second-stage filtrate is conveyed to the first-stage filter press by the first-stage slurry pump again, the salt slurry in the pipeline is washed, the contents of sodium chloride, sodium carbonate and magnesium hydroxide in the salt slurry are further reduced, a raw filtrate tank and a filtrate pump are stopped, clean salt slurry after physically separating a large amount of sodium chloride and partial sodium carbonate and magnesium hydroxide is discharged to the salt slurry pool to be circulated, formed second-stage filter cakes are conveyed to the salt slurry pool, the pressure filtrate in the brine pool is recrystallized, the filtration and washing are carried out, and the detection component contents are as follows: 0.43 percent of sodium chloride, 10.12 percent of magnesium, 15.1 percent of calcium, 28.7 percent of water and the balance of impurities.
And corrosion-resistant filter cloth is arranged in both the first-stage filter press and the second-stage filter press.
Example 3
The corrosion-resistant filter cloth is prepared by the following steps:
step S1, drying polyacrylonitrile powder at 75 ℃ for 12 hours, then adding the dried polyacrylonitrile powder into dimethyl sulfoxide, slowly stirring, heating to 75 ℃ at a heating rate of 3 ℃/min, then preserving heat for 4 hours, transferring the polyacrylonitrile powder to a vacuum drying oven with the pressure of-0.10 MPa and the temperature of 80 ℃ for vacuum defoaming for 10 hours after heat preservation is finished, preparing a spinning solution, controlling the using amount ratio of the polyacrylonitrile powder to the dimethyl sulfoxide to be 15 g: 100mL, then preheating a spinning machine to 80 ℃, pouring the spinning solution, spinning into a coagulating bath at the spinning rate of 2.5m/min to prepare nascent fiber, flushing, placing the nascent fiber in a boiling water bath for extending for 4 times, then freezing for 24 hours to prepare protofilament, then placing the protofilament in the drying oven, heating to 180 ℃ at the heating rate of 5 ℃/min, and preserving heat for 4 hours to prepare treated fiber;
the coagulating bath is formed by mixing dimethyl sulfoxide and deionized water according to the volume ratio of 1: 1.
S2, slowly pouring tetraethoxysilane onto the surface of anhydrous aluminum trichloride, sequentially adding isopropyl ether and anhydrous dichloromethane, magnetically stirring for 2 hours, then placing the mixture into a drying box, heating to 100 ℃, and drying for 1 hour to obtain dry gel, wherein the dosage ratio of tetraethoxysilane, anhydrous aluminum trichloride, isopropyl ether and anhydrous dichloromethane is controlled to be 0.20 mL: 0.5 g: 0.5 mL: 15mL; mixing an alcoholic solution of polyvinylpyrrolidone with the dry gel, stirring at a constant speed, adding absolute ethyl alcohol, continuously stirring for 15min, adding N, N-dimethylformamide, magnetically stirring for 1h to prepare a spinning solution, controlling the dosage ratio of polyvinylpyrrolidone, dry gel, absolute ethyl alcohol and N, N-dimethylformamide to be 0.5 g: 0.3 g: 2 mL: 1.5mL, carrying out electrostatic spinning to prepare a composite fiber, then calcining for 1h at 1200 ℃ to prepare a porous fiber, and weaving according to the warp density of 150/cm and the weft density of 180/cm to prepare a base fabric;
the alcohol solution of the polyvinylpyrrolidone is formed by mixing the polyvinylpyrrolidone and absolute ethyl alcohol according to the dosage ratio of 0.5g to 8 mL.
And S3, uniformly mixing the treated fibers and the polypropylene fibers according to the weight ratio of 2: 8 to prepare mixed fibers, then opening and opening twice to prepare fiber clusters, carding into fiber nets, then cross lapping, adding base cloth, carrying out pre-needling at the frequency of 100 needling/min, then carrying out main needling, and finishing to prepare the corrosion-resistant filter cloth.
The needling frequency is controlled to be 150 needling/min during main needling, the needling number is 2, and the needling depth is 6mm.
Example 4
The corrosion-resistant filter cloth is prepared by the following steps:
step S1, drying polyacrylonitrile powder at 78 ℃ for 12 hours, then adding the dried polyacrylonitrile powder into dimethyl sulfoxide, slowly stirring, heating to 78 ℃ at a heating rate of 4 ℃/min, then preserving heat for 4 hours, transferring the polyacrylonitrile powder to a vacuum drying box with the pressure of-0.10 MPa and the temperature of 80 ℃ for vacuum defoaming for 10 hours after heat preservation is finished to prepare a spinning solution, controlling the using ratio of the polyacrylonitrile powder to the dimethyl sulfoxide to be 16 g: 100mL, then preheating a spinning machine to 80 ℃, pouring the spinning solution into the spinning solution, spinning the polyacrylonitrile powder into a coagulating bath at the spinning rate of 2.5m/min to prepare nascent fiber, flushing the nascent fiber, placing the nascent fiber into a boiling water bath for 5 times of elongation, then freezing the nascent fiber for 24 hours to prepare precursor fiber, then placing the precursor into the drying box, heating to 190 ℃ at the heating rate of 8 ℃/min, and carrying out heat preservation treatment for 5 hours to prepare the treated fiber;
the coagulating bath is formed by mixing dimethyl sulfoxide and deionized water according to the volume ratio of 1: 1.
Step S2, slowly pouring ethyl orthosilicate onto the surface of anhydrous aluminum trichloride, sequentially adding isopropyl ether and anhydrous dichloromethane, magnetically stirring for 2 hours, then placing the mixture into a drying box, heating to 105 ℃, and drying for 1 hour to obtain dry gel, wherein the dosage ratio of the ethyl orthosilicate to the anhydrous aluminum trichloride to the isopropyl ether to the anhydrous dichloromethane is controlled to be 0.21 mL: 0.5 g: 0.5 mL: 18mL; mixing an alcoholic solution of polyvinylpyrrolidone with the xerogel, stirring at a constant speed, adding absolute ethyl alcohol, continuously stirring for 15min, adding N, N-dimethylformamide, magnetically stirring for 1h to prepare a spinning solution, controlling the dosage ratio of polyvinylpyrrolidone, xerogel, absolute ethyl alcohol and N, N-dimethylformamide to be 0.6 g: 0.4 g: 2.2 mL: 1.5mL, carrying out electrostatic spinning to prepare a composite fiber, then calcining at 1200 ℃ for 1h to prepare a porous fiber, and weaving according to the warp density of 150/cm and the weft density of 180/cm to prepare a base fabric;
and S3, uniformly mixing the treated fibers and the polypropylene fibers according to the weight ratio of 3: 7 to prepare mixed fibers, then opening and opening twice to prepare fiber clusters, carding into fiber nets, then cross lapping, adding base cloth, carrying out pre-needling at the frequency of 100 needling/min, then carrying out main needling, and finishing to prepare the corrosion-resistant filter cloth.
The needling frequency is controlled to be 150 punches/min during main needling, the number of needling channels is 2, and the needling depth is 6mm.
Example 5
The corrosion-resistant filter cloth is prepared by the following steps:
step S1, drying polyacrylonitrile powder at 80 ℃ for 12h, then adding the dried polyacrylonitrile powder into dimethyl sulfoxide, slowly stirring, heating to 80 ℃ at a heating rate of 5 ℃/min, then preserving heat for 4h, transferring the polyacrylonitrile powder to a vacuum drying box with the pressure of-0.10 MPa and the temperature of 80 ℃ for vacuum defoaming for 10h after heat preservation is finished to prepare a spinning solution, controlling the using ratio of the polyacrylonitrile powder to the dimethyl sulfoxide to be 18 g: 100mL, then preheating a spinning machine to 80 ℃, pouring the spinning solution, spinning into a coagulating bath at the spinning rate of 2.5m/min to prepare nascent fiber, flushing, placing the nascent fiber in a boiling water bath for 6 times, then freezing for 24h to prepare protofilament, then placing the protofilament in the drying box, heating to 200 ℃ at the heating rate of 10 ℃/min, and preserving heat for 6h to prepare treated fiber;
the coagulating bath is formed by mixing dimethyl sulfoxide and deionized water according to the volume ratio of 1: 1.
Step S2, slowly pouring ethyl orthosilicate onto the surface of anhydrous aluminum trichloride, sequentially adding isopropyl ether and anhydrous dichloromethane, magnetically stirring for 2 hours, then placing the mixture into a drying oven, heating to 105 ℃, and drying for 1 hour to obtain dry gel, wherein the dosage ratio of the ethyl orthosilicate to the anhydrous aluminum trichloride to the isopropyl ether to the anhydrous dichloromethane is controlled to be 0.22mL to 0.5g to 0.5mL to 20mL; mixing an alcoholic solution of polyvinylpyrrolidone with the xerogel, stirring at a constant speed, adding absolute ethyl alcohol, continuously stirring for 15min, adding N, N-dimethylformamide, magnetically stirring for 1h to prepare a spinning solution, controlling the dosage ratio of polyvinylpyrrolidone, xerogel, absolute ethyl alcohol and N, N-dimethylformamide to be 0.8 g: 0.5 g: 2.5 mL: 1.5mL, carrying out electrostatic spinning to prepare a composite fiber, then calcining at 1200 ℃ for 1h to prepare a porous fiber, and weaving according to the warp density of 150/cm and the weft density of 180/cm to prepare a base fabric;
and S3, uniformly mixing the treated fibers and the polypropylene fibers according to the weight ratio of 3: 7 to prepare mixed fibers, then opening and opening twice to prepare fiber clusters, carding into fiber nets, then cross lapping, adding base cloth, carrying out pre-needling at the frequency of 100 needling/min, then carrying out main needling, and finishing to prepare the corrosion-resistant filter cloth.
The needling frequency is controlled to be 150 needling/min during main needling, the needling number is 2, and the needling depth is 6mm.
Comparative example 1
This comparative example is compared with example 3, in which a corrosion-resistant filter cloth was prepared using polyacrylonitrile fiber, polypropylene fiber, and mullite fiber according to the process of step S3, and the same fiber as that of example 3 was used without modification or treatment.
Comparative example 2
This comparative example is a commercially available corrosion resistant filter cloth produced by a company, the procedure is as follows:
adding 10 parts by weight of polyethylene powder and 8 parts by weight of polypropylene powder into 150 parts by weight of hot water with the temperature of more than 70 ℃, stirring for 10 minutes, then adding 80 parts by weight of absolute ethyl alcohol, heating to boil, keeping for 5 minutes, filtering, and drying at 100 ℃ to obtain a mixture; adding the mixture into 130 parts of dichloroethane, heating to 70 ℃ under the protection of nitrogen, reacting for 45 minutes, cooling, filtering, washing with acetone, and drying to obtain a solid; mixing 10 parts of PET, 6 parts of polytetrafluoroethylene emulsion, 5 parts of liquid nitrile rubber, 5 parts of diphenyl silanediol and 3 parts of modified graphene with a solid, heating to 105 ℃ at a heating rate of 2 ℃/min under a vacuum condition of 0.01MPa of vacuum degree, keeping for 30 min, then cooling to 60 ℃, keeping for 80 min, and cooling to room temperature to obtain a reactant; adding 0.5 part of lubricant into the reactant, performing melt extrusion through a double-screw extruder, performing spinning through a spinneret plate of a spinning box, cooling and sizing to obtain a mesh, wherein the lubricant is talcum powder, and the particle size is 1000 meshes; weaving the net into a net, wherein the diameter of the warp is 0.18-0.21mm, and the diameter of the weft is 0.20-0.25mm; the warp density of the woven net is 23-28 pieces/cm, and the weft density is 14-16 pieces/cm, so as to obtain the filter cloth. The corrosion-resistant filter cloths prepared in examples 3 to 5 and comparative examples 1 to 2 were tested, and the results are shown in table 1 below:
soaking a sample to be tested in HCl and NaOH with the mass concentration of 10% for 500h respectively, observing the surface state, and testing the tensile fracture degree;
TABLE 1 test results of examples and comparative examples
It can be seen from table 1 above that the corrosion-resistant filter cloth prepared by the example of the present invention has excellent corrosion resistance.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing is merely exemplary and illustrative of the principles of the present invention and various modifications, additions and substitutions of the specific embodiments described herein may be made by those skilled in the art without departing from the principles of the present invention or exceeding the scope of the claims set forth herein.
Claims (6)
1. A NaCl recovery process in salty mud for chlor-alkali production is characterized by comprising the following steps: the method comprises the following steps:
treating the salt mud through a preprocessor, discharging the generated floating mud to a salt mud tank through upper and lower rows of mud, discharging clear liquid into an HVM membrane filter to prepare refined salt water, discharging the refined salt water to the salt mud tank, performing filter pressing through a first-stage filter press and a second-stage filter press in sequence, and then sending the refined salt water to a salt mud warehouse;
the first-stage salt mud and the first-stage pressure filtrate are formed after filter pressing of the first-stage filter press, the first-stage salt mud is discharged into a washing tank and then added with primary water for dissolving and washing, and the first-stage pressure filtrate is conveyed to a brine tank;
and (3) detecting the salt content when the primary salt mud is dissolved and washed by primary water, conveying the salt content to a secondary filter press when the salt content is 1%, performing filter pressing, overflowing the formed secondary filtrate to a salt mud tank, conveying the salt mud tank to the primary filter press again, circulating, and conveying the formed secondary filter cake to a salt mud warehouse.
2. The process for recovering NaCl from salty mud used in chlor-alkali production according to claim 1, characterized by the fact that: and corrosion-resistant filter cloth is arranged in both the first-stage filter press and the second-stage filter press.
3. The process for recovering NaCl from salty mud for chlor-alkali production according to claim 2, characterized by: the corrosion-resistant filter cloth is prepared by the following steps:
step S1, drying polyacrylonitrile powder for 12 hours, then adding the dried polyacrylonitrile powder into dimethyl sulfoxide, stirring, heating to 75-80 ℃, keeping the temperature for 4 hours, transferring the polyacrylonitrile powder and the dimethyl sulfoxide to a vacuum drying oven for vacuum defoaming for 10 hours after keeping the temperature to prepare spinning solution, controlling the dosage ratio of the polyacrylonitrile powder to the dimethyl sulfoxide to be 15-18 g: 100mL, then preheating a spinning machine to 80 ℃, pouring the spinning solution into a coagulation bath to prepare nascent fiber, placing the nascent fiber in a boiling water bath for extending for 4-6 times after washing, then freezing for 24 hours to prepare protofilament, then placing the protofilament in the drying oven, heating to 180-200 ℃, and keeping the temperature for 4-6 hours to prepare treated fiber;
s2, slowly pouring ethyl orthosilicate onto the surface of anhydrous aluminum trichloride, sequentially adding isopropyl ether and anhydrous dichloromethane, magnetically stirring for 2 hours, then placing the mixture into a drying oven, heating to 100-105 ℃, and drying for 1 hour to obtain dry gel, wherein the dosage ratio of the ethyl orthosilicate to the anhydrous aluminum trichloride to the isopropyl ether to the anhydrous dichloromethane is controlled to be 0.20-0.22mL to 0.5g to 0.5mL to 15-20mL; mixing alcoholic solution of polyvinylpyrrolidone with xerogel, stirring at a constant speed, adding absolute ethyl alcohol, continuously stirring for 15min, adding N, N-dimethylformamide, magnetically stirring for 1h to prepare spinning solution, controlling the dosage ratio of polyvinylpyrrolidone, xerogel, absolute ethyl alcohol and N, N-dimethylformamide to be 0.5-0.8 g: 0.3-0.5 g: 2-2.5 mL: 1.5mL, carrying out electrostatic spinning to prepare composite fiber, then calcining at 1200 ℃ for 1h to prepare porous fiber, and weaving according to warp yarn density of 150/cm and weft yarn density of 180/cm to prepare base cloth;
and S3, uniformly mixing the treated fibers and the polypropylene fibers according to the weight ratio of 2-3: 7-8 to prepare mixed fibers, then opening and loosening twice to prepare a fiber group, carding into a fiber net, then cross lapping, adding base cloth, carrying out pre-needling at the frequency of 100 needling/min, then carrying out main needling, and finishing to prepare the corrosion-resistant filter cloth.
4. The process for recovering NaCl from salty mud for chlor-alkali production according to claim 3, characterized by: in the step S1, the coagulating bath is formed by mixing dimethyl sulfoxide and deionized water according to the volume ratio of 1: 1.
5. The process for recovering NaCl from salty mud for chlor-alkali production according to claim 3, characterized by: the alcohol solution of polyvinylpyrrolidone in the step S2 is formed by mixing polyvinylpyrrolidone and absolute ethyl alcohol according to the dosage ratio of 0.5-0.8 g: 8-10 mL.
6. The process for recovering NaCl from salty mud used in chlor-alkali production according to claim 3, characterized by comprising the following steps: and S3, controlling the needling frequency to be 150 needling/min during main needling, wherein the needling channel number is 2, and the needling depth is 6mm.
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