CN111960437B - Circulating purification balance treatment system, equipment and method for stable separation of salt and nitrate - Google Patents
Circulating purification balance treatment system, equipment and method for stable separation of salt and nitrate Download PDFInfo
- Publication number
- CN111960437B CN111960437B CN202010892359.XA CN202010892359A CN111960437B CN 111960437 B CN111960437 B CN 111960437B CN 202010892359 A CN202010892359 A CN 202010892359A CN 111960437 B CN111960437 B CN 111960437B
- Authority
- CN
- China
- Prior art keywords
- sodium sulfate
- sodium chloride
- purification unit
- nitrate
- salt
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
- B01D61/026—Reverse osmosis; Hyperfiltration comprising multiple reverse osmosis steps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/0036—Crystallisation on to a bed of product crystals; Seeding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/0081—Use of vibrations, e.g. ultrasound
-
- 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
- C01D3/14—Purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/16—Purification
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D2009/0086—Processes or apparatus therefor
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Water Supply & Treatment (AREA)
- Crystallography & Structural Chemistry (AREA)
- Nanotechnology (AREA)
- Heat Treatment Of Water, Waste Water Or Sewage (AREA)
Abstract
The invention relates to a circulating purification balance treatment system and equipment for stable salt and nitrate separation, which comprise a primary purification unit, a secondary purification unit and a tertiary purification unit, wherein the tertiary purification unit at least comprises an NF membrane separation device, and the NF membrane separation device enables the generated nitrate-poor sodium chloride-rich produced water to enter a sodium chloride production unit and enables the nitrate-rich sodium chloride-low concentrated water to flow back to the secondary purification unit in a manner of meeting the sodium chloride concentration required by a sodium chloride production unit; tertiary purification unit includes filter equipment at least for further getting rid of the impurity of freezing poor nitre mother liquor according to the mode that accords with NF membrane separator impurity concentration requirement and obtaining impurity liquid, filter equipment's impurity liquid export and one-level purification unit intercommunication to make one-level purification unit can contain the miscellaneous salt that contains sodium sulfate crystal and sodium chloride crystal according to the mode purification of roughly balanced salt concentration in the waste water.
Description
Technical Field
The invention relates to the technical field of salt-containing wastewater purification, in particular to a circulating purification balance treatment system, equipment and method for stable separation of salt and nitrate.
Background
High salt waste water, desulfurization waste water, hydrophobic water and the like generated in industries such as the coal chemical industry, the stone chemical industry, electric power, cogeneration, coal mine hydrophobic water, metallurgy, nonferrous materials, pharmacy, papermaking, natural gas purification, comprehensive park industrial waste water and the like generally have high salt content, high hardness, complex components such as silicon, fluorine, organic matters and the like, are not treated, are stored and placed, and tend to cause pollution factors to the surrounding environment, and serious regional environmental pollution is caused after long-term accumulation. In view of the requirements of tail water treatment in the industries, the tail water cannot meet the environmental protection requirements through simple treatment, and serious pollution is caused to the received water body and underground water after discharge, so that near zero discharge of high-salinity wastewater gradually becomes a final treatment trend and approach of the high-salinity wastewater in order to protect the ecological environment for people to live and meet the self requirements of resource utilization. In the design of the comprehensive high-salt-content wastewater treatment zero-emission process, the final solid product can be separated out at higher purity, about 90% of sodium sulfate and sodium chloride in high-salt water can be sold as a zero-emission byproduct as industrial raw materials, the impurity salt amount in the zero-emission treatment process is greatly reduced, a large amount of sodium sulfate and sodium chloride are not treated as solid hazardous waste, the environment-friendly benefit and the resource recycling value are very high, about 10% of the impurity salt in the near place is treated as the hazardous waste, and the cost and the resource are saved remarkably.
Comprehensive high-salt concentrated water (generally TDS is more than 5000 mg/l) discharged by enterprises and accepted by gardens at present, high-salt wastewater contains a large amount of organic matters and complex impurities, and is generally not suitable for removing the organic matters by adopting traditional biological treatment degradation, and the more commonly adopted pretreatment comprises' hardness removal double-alkali softening pretreatment → reduction → high-salt water advanced treatment for hardness removal, silicon removal, fluorine removal and the like → NF → lean sodium nitrate and chloride production water → concentration → evaporative crystallization → sodium chloride; NF → concentrated water of sodium sulfate and low in sodium nitrate and low in sodium sulfate → organic matter removal (measures such as advanced oxidation, resin adsorption and high-temperature treatment) → evaporative crystallization → sodium sulfate; the purity of the finally generated sodium sulfate and sodium chloride crystal salt is not high, the impurity content is higher, the quality of the sodium sulfate and sodium chloride obtained by the process route is unstable and poor, and the aim of comprehensively utilizing the salt and the nitrate as industrial raw materials is difficult to achieve; the process route has the advantages that the amount of the generated miscellaneous salt is large, the miscellaneous salt contains a large amount of organic matters and complex components, the generated miscellaneous salt is solid dangerous waste and needs to be treated by qualified professional companies, the cost for treating the solid dangerous waste in China is basically more than 3000-4000 yuan/ton, the treatment cost is very high, the treatment bottleneck of a large amount of zero-discharge crystalline salt is formed, the small-scale treatment capacity of the professional companies is very limited at present, and the treatment requirement of the large amount of miscellaneous salt generated by the zero-discharge treatment of the waste water of a plurality of industrial enterprises cannot be met.
Furthermore, on the one hand, due to the differences in understanding to those skilled in the art; on the other hand, since the inventor has studied a lot of documents and patents when making the present invention, but the space is not limited to the details and contents listed in the above, however, the present invention is by no means free of the features of the prior art, but the present invention has been provided with all the features of the prior art, and the applicant reserves the right to increase the related prior art in the background.
Disclosure of Invention
Aiming at the defects of the prior art: the most main components in the comprehensive high-salt wastewater are sodium chloride and sodium sulfate, the ratio of the two salts to the total salt is relatively high, usually more than 90%, so the current mainstream technical route is as follows: pretreatment → reduction → reprocessing → NF → reduction of sodium nitrate-rich and low-sodium sulfate concentrated water respectively → reprocessing → salt separation evaporation crystallization and sodium chloride-poor water production → concentration (optional) → salt separation evaporation crystallization; pretreatment → NF → low sodium sulfate and high concentration water rich in nitrate are reduced respectively → retreatment → salt separation evaporation crystallization and water production of low sodium chloride and nitrate → concentration → salt separation evaporation crystallization; in the process, NF is contacted with a large amount of organic impurities, the frequent chemical cleaning of the NF membrane is considered, and the permeation of small molecular organic matters enters an evaporative crystallization system, so that the stable operation of salt separation through the process route and the frequent use cost of replacement of the NF membrane are caused, the evaporative crystallization of sodium chloride and sodium sulfate is influenced by the adverse effect of low impurities on the purity, or a large amount of miscellaneous salts is generated, particularly the content of sodium nitrate in high-salt water is high, and the amount of miscellaneous salts is increased more.
The invention provides a circulating purification balance treatment system for stable salt and nitrate separation, which comprises a primary purification unit, a secondary purification unit and a tertiary purification unit, wherein the tertiary purification unit at least comprises an NF (NF) membrane separation device, which is used for further separating sodium chloride and sodium sulfate in frozen lean nitrate mother liquor discharged by the secondary purification unit; the third-stage purification unit at least comprises a filter device, the filter device is arranged between the NF membrane separation device and the second-stage purification unit and is used for further removing impurities of the frozen nitrate-poor mother liquor in a mode meeting the requirement of the impurity concentration of the NF membrane separation device to obtain impurity liquid, and an impurity liquid outlet of the filter device is communicated with the first-stage purification unit, so that the first-stage purification unit can purify mixed salt containing sodium sulfate crystals and sodium chloride crystals in a mode of approximately balancing the impurity concentration in the salt-containing wastewater.
According to a preferable embodiment, the NF membrane separation device has a sodium sulfate rejection rate of 95-98% and a sodium chloride rejection rate of-10%.
According to a preferred embodiment, the secondary purification unit freezes sodium sulfate in the form of crystals of sodium nitrate decahydrate while producing sodium sulfate and sodium chloride crystals purified by evaporative crystallization in the primary purification unit as a nitrate-rich mother liquor in a saturated state.
According to a preferred embodiment, the primary purification unit and the secondary purification unit are provided with separation units for controlling the water content of the mixed salt, and the water content of the mixed salt is 4% -5%.
According to a preferred embodiment, the secondary purification unit uses a secondary refrigerant to separate out sodium sulfate in a cooling process in a supersaturation state in a decahydrate form under the condition that a precooling feed liquid is obtained by precooling the sodium sulfate and sodium chloride solution which are based on a near-saturation state of mixed salt hot-melt blending, and the secondary refrigerant can reduce the temperature of the precooling feed liquid to minus 5-0 ℃ to obtain a freezing feed liquid.
According to a preferred embodiment, the sodium sulfate decahydrate is prepared into a near-saturated sodium nitrate solution in a sodium sulfate production unit through at least hot melting and condensed water hot melting, the sodium nitrate solution and the condensed water are subjected to heat exchange and heating, and the sodium sulfate solution is concentrated through multi-effect concurrent evaporation crystallization, so that sodium sulfate in the solution is continuously concentrated to be supersaturated and separated out, and gradually grows and deposits on sodium sulfate foot.
According to a preferred embodiment, the frozen feed liquid enters the tertiary purification unit from the nitrate-poor mother liquid obtained by settling, and the tertiary purification unit comprises a nanofiltration device capable of intercepting sulfate ions, so that the water produced by the tertiary purification unit can be used for producing sodium chloride by a sodium chloride production unit.
According to a preferred embodiment, concentrated brine wastewater is concentrated at least once before entering the primary purification unit, so that the TDS value of the concentrated brine wastewater is 6 to 20 ten thousand ppm.
According to a preferred embodiment, the invention provides a circulating type purification balance treatment device for stable salt and nitrate separation, which comprises an NF membrane separation device, a low-sulfur sodium nitrate-rich water production unit and a low-sodium nitrate-rich water production unit, wherein the NF membrane separation device is used for further separating sodium chloride and sodium sulfate in frozen nitrate-poor mother liquor discharged by a secondary purification unit; the NF membrane separation device can be communicated with the filtering device, the filtering device can be communicated with the second-stage purification unit, the filtering device is used for further removing impurities of the frozen mirabilite-poor mother liquor in a mode meeting the impurity concentration requirement of the NF membrane separation device to obtain impurity liquid, and an impurity liquid outlet of the filtering device is communicated with the first-stage purification unit, so that the first-stage purification unit can purify mixed salt containing sodium sulfate crystals and sodium chloride crystals in the salt-containing wastewater in an approximately balanced mode.
According to a preferred embodiment, the rejection rate of the NF membrane separation device to sodium sulfate is 95 to 98 percent, and the rejection rate to sodium chloride is-10 to 10 percent.
Drawings
FIG. 1 is a block diagram of a processing system provided by the present invention;
FIG. 2 is a settler provided by the present invention;
FIG. 3 is a preferred stirring blade provided by the present invention;
FIG. 4 is a schematic block diagram of a portion of a preferred recycling system of the present invention;
FIG. 5 is a crystal bump according to the present invention.
List of reference numerals
100: primary purification unit 400: sodium sulfate production unit
200: a secondary purification unit 500: sodium chloride production unit
300: tertiary purification unit 200a: settling vessel
200a-1: feed inlet 200a-2: poor nitre mother liquor outlet
200a-3: a liquid outlet 200a-4 of nitre decahydrate slurry: stirring mechanism
200a-401: stirring shafts 200a-402: stirring blade
200a-402a: crystallized bumps 200a-403: skirt edge
300a: the filter device 300b: NF membrane separation device
300b-1: primary nanofiltration device 300b-2: secondary nanofiltration device
300b-n: n-grade nanofiltration device
Detailed Description
This is described in detail below with reference to fig. 1-4.
In the invention, english abbreviations and corresponding Chinese paraphrases are as follows:
TDS: total dissolved solids, total amount of all solutes in water, i.e.: total amount of soluble solids. Generally, organic matter and inorganic matter in molecular form contained in natural water are not considered, and therefore the salt content is referred to as TDS.
NF: and (4) a nanofiltration device. Nanofiltraction, nanofiltration, is used to separate out relatively small molecular mass materials, such as sodium chloride, from the solvent.
MVR: the vapor mechanically recompresses the evaporator.
TVR: a vapor thermal recompression evaporator.
DTRO: dish tubular reverse osmosis unit.
ED: and an electrodialysis device.
And (3) RO: a reverse osmosis device.
Example 1
The embodiment discloses a circulating purification balance treatment system and equipment for stable separation of salt and nitrate. Including a primary purification unit 100, a secondary purification unit 200, and a tertiary purification unit 300.
Primary purification unit 100: the method comprises the steps that the high-salt-content wastewater enters a thermal method (MVR/multiple-effect/TVR) evaporation crystallization system after passing through a pretreatment system, generated magma is thickened, concentrated, separated and dehydrated to produce sodium sulfate and sodium chloride (mixed salt), sodium chloride and sodium sulfate mixed salt with low impurity content are obtained preliminarily, sodium sulfate and sodium chloride separated out through main crystallization are isolated from high-content organic matters in enriched mother liquor and impurities such as sodium nitrate, fluoride ions and silicon, and the process is a primary salt and nitrate purification process. The isolated impurities do not enter secondary purification unit 200 and tertiary purification unit 300, and particularly do not block the membrane pores in tertiary purification unit 300, so that tertiary purification unit 300 can be continuous. Part of the mixed salt mother liquor discharged from the primary purification unit 100 enters a mixed salt production unit (adopting a thermal method for drying) to produce the mixed salt mainly containing organic substances, sodium nitrate, salt nitrate and impurities.
Secondary purification unit 200: sodium chloride and sodium sulfate produced by purification, evaporation, crystallization and separation enter a dissolving and stirring tank or a tank, condensed water is added and stirred for dissolution, sodium sulfate and sodium chloride solution with saturated concentration are prepared, salt and nitrate solution enters a liquid storage barrel and is pumped into a freezing and crystallizing system, the temperature of the feed liquid is controlled through a crystallizer of the freezing and crystallizing system, sodium nitrate decahydrate is crystallized and separated, the produced sodium nitrate decahydrate is redissolved and then enters a sodium sulfate production unit 400 (a multi-effect sodium nitrate evaporation and crystallization device is adopted), finally, sodium sulfate liquid is evaporated and concentrated through steam heating to obtain supersaturated sodium sulfate crystals, and high-purity sodium sulfate (commonly called anhydrous sodium sulfate) is obtained through thickening, separation and drying;
three-stage purification unit 300: the nitre-poor mother liquor generated by freezing crystallization enters a three-stage purification unit 300 (provided with an NF membrane separation device) for further separating sodium chloride and sodium sulfate. Concentrating the sodium chloride water (sodium chloride water) or directly feeding the sodium chloride water into a sodium chloride evaporative crystallization system, heating the sodium chloride feed liquid by steam, circularly evaporating to reach supersaturation, separating out a large amount of sodium chloride crystals from the feed liquid, thickening, concentrating, separating and drying to obtain high-purity sodium chloride; and the NF membrane separation device generates rich sodium nitrate and low sodium sulfate concentrated water and returns the rich sodium nitrate and low sodium sulfate concentrated water to the freezing crystallizer, and the sodium sulfate in the rich sodium nitrate and low sodium sulfate concentrated water is extracted. The invention can ensure the stability and high-efficiency operation of the salt separation crystallization system when the water quantity and the water quality of the system fluctuate, realize the complete separation of sodium chloride and sodium sulfate, is not influenced by organic matters, nitrate and impurities, particularly has the advantages of obviously prolonged one-time use time and high stability of a membrane structure in the three-stage purification unit 300, high purity of the produced sodium chloride and sodium sulfate and high recovery rate of product salt after multi-stage purification, can reduce the amount of miscellaneous salt in the system to the maximum extent, and has low yield of miscellaneous salt.
As shown in fig. 4, the three-stage purification unit 300 includes at least a filtering device 300a and an NF membrane separation device 300b. The filter device 300a may be a tube filter, a cartridge filter. The filtering device 300a is arranged between the secondary purification unit 200 and the NF membrane separation device 300b, and is used for filtering the frozen lean nitre mother liquor so as to further reduce the impurity concentration of the NF membrane separation device 300b, and meet the liquid inlet requirement of the NF membrane separation device 300b. On one hand: the aperture of the nanofiltration membrane of the NF membrane separation device 300b is small, and the NF membrane separation device 300b is easily blocked due to overlarge impurity particle size, so that the arrangement of the filtration device 300a can reduce the probability that the nanofiltration membrane is blocked, effectively improve the separation efficiency of the NF membrane separation device 300b, and improve the purity of the obtained sodium chloride; on the other hand, the impurity liquid of the filtering apparatus 300a can be used as the quenching and tempering liquid of the wastewater with high salt content, and when the concentration of the impurities in the wastewater with high salt content is too high or too low, the impurity liquid and the wastewater with high salt content can be mixed to control the concentration of the impurities within the range of the required concentration of the impurities of the first-stage purification unit 100, so that the mixed salt can be more easily separated out.
Preferably, the NF membrane separation apparatus 300b includes at least one nanofiltration device. As shown in fig. 4, when the number of the nanofiltration devices is greater than or equal to 2, the former stage of nanofiltration device is connected in series and communicated in a manner that the water produced by the poor sodium nitrate and chloride can be discharged to the next nanofiltration device, the content of sodium sulfate in the water produced by the poor sodium nitrate and chloride is reduced in a multistage manner, and the interception rate of sodium sulfate is controlled between 95% and 98%; and the concentrated water rich in nitrate and low in sodium sulfate generated by each stage of nanofiltration device is discharged to a second-stage purification unit 200 and is further used for nitrate extraction. Preferably, as shown in fig. 4, the NF membrane separation apparatus 300b includes a primary nanofiltration apparatus 300b-1, a secondary nanofiltration apparatus 300b-2, and an N-stage nanofiltration apparatus 300b-N (N is greater than or equal to 3). Through a pilot test, the interception rate of the sodium sulfate is controlled to gradually increase according to the flow direction of the produced water, and when the interception rate of the sodium sulfate reaches 95 to 98 percent, the NF membrane separation device 300b discharges the nitrate-poor sodium chloride produced water to the sodium chloride production unit 500; and if the interception rate of the sodium sulfate does not reach 95-98%, the upper-stage nanofiltration device discharges the sodium nitrate and chloride poor water to the lower-stage nanofiltration device. Preferably, the NF membrane separation apparatus 300b comprises a primary, secondary or tertiary nanofiltration apparatus, which is preferred, i.e. the purity of the produced sodium chloride is increased at the best cost. The interception rate of sodium sulfate is controlled to gradually increase according to the flowing direction of produced water, and the sodium sulfate content in the concentrated water rich in nitrate and low sodium sulfate discharged by the primary nanofiltration device, the secondary nanofiltration device, the grade I nanofiltration device and the grade II nanofiltration device is gradually reduced, so that the concentrated water rich in nitrate and low sodium sulfate discharged by the primary nanofiltration device can be directly discharged to a precipitator 200a after being cooled and directly used for crystallization; and concentrated water rich in nitrate, low in sodium sulfate and discharged by a secondary grade 8230A nano-filtration device and low in sodium sulfate and n grade nano-filtration device needs to be further concentrated.
Example 2
This embodiment may be a further improvement and/or a supplement to embodiment 1, and repeated contents are not described again. The preferred embodiments of the present invention are described in whole or in part with reference to the following examples, which are intended to supplement the present invention and are not intended to be limiting.
Preferably, the system may further comprise a pre-treatment unit and a concentration unit. The pretreatment unit is mainly used for mixing and adjusting the comprehensive high-salinity wastewater, softening and removing hardness and suspended matters, filtering, removing hardness by resin, reducing and concentrating by membranes, retreating and removing silicon and fluorine by the concentrated high-salinity wastewater, removing organic matters by advanced oxidation, adsorbing by active carbon (the advanced oxidation and the active carbon are arranged at the position before the advanced reduction according to the impurity content or after the advanced oxidation and the active carbon are reduced or between two-stage membranes, recycling and reusing the reduced produced water, and the reduced produced concentrated water enters the concentration unit, for example,
preferably, the reduced concentrated water enters a concentration process (ED, DTRO, MVR falling film evaporation concentration or multiple effect evaporation) and is concentrated to about 6 to 20 ppm (preferably 10 to 20 ppm), and then enters the first-stage purification unit 100: the multi-effect evaporative crystallization and the steam circularly exchange heat in the heating chamber, the feed liquid reaches the boiling point and is subjected to flash evaporation in the evaporation chamber, the circularly-performed feed liquid is concentrated, each effect feed liquid is gradually concentrated, the concentration of sodium sulfate and sodium chloride in the last effect feed liquid is continuously increased until reaching supersaturation and being separated out and gradually grown up and deposited on salt feet, the salt slurry liquid is discharged, wet salt sodium sulfate and sodium chloride are obtained through a thickening and centrifugal separation channel, and the water produced by the evaporator is completely recycled after heat exchange with the feed liquid. The content of impurities such as organic matters, silicon, fluorine and the like in the evaporative crystallization feed liquid is continuously enriched and increased through cyclic concentration of the evaporative crystallization feed liquid, a certain amount of mother liquid needs to be discharged, the total impurity content of an evaporative system is balanced by the impurity content of the discharged mother liquid, and the impurities of the evaporative crystallization system are approximately kept in a certain balance range, so that the ion content in the primary purification unit 100 can ensure the purity of the precipitated sodium sulfate and sodium chloride.
Preferably, the system further comprises a miscellaneous salt production unit: the mixed salt mother liquor which is discharged from a mixed salt crystallizer in the primary purification unit 100 and is used for balancing feed liquid impurities enters a mixed salt mother liquor adjusting tank, evaporation crystallization is continuously carried out through a mixed salt evaporation crystallizer to obtain mixed salt slurry, cyclone separation is carried out, the underflow mixed salt slurry enters a centrifugal machine for separation to obtain mixed salt, the water content of the mixed salt is about 10-20%, and the mixed salt is treated; and (3) evaporating and crystallizing the mixed salt, discharging the mother liquor, allowing the mother liquor to enter a mixed salt mother liquor storage tank, and allowing the mother liquor to enter a mixed salt mother liquor curing system for drying treatment to obtain the mixed salt.
Preferably, there is a separation unit between primary purification unit 100 and secondary purification unit 200. The separation unit controls the water content of the mixed salt of the crystalline sodium sulfate and the sodium chloride to be between about 4 and 5 percent by adopting a centrifugal separation mode. And (3) carrying out hot melting on the mixed salt of the crystalline sodium sulfate and the sodium chloride in a stirring tank by utilizing condensed water generated by the system to prepare nearly saturated sodium sulfate and sodium chloride solutions. And overflowing the sodium sulfate and sodium chloride solution into a mixed solution storage barrel, and then sending into a precooler for precooling and cooling. And (3) when the precooled feed liquid reaches a precooling design temperature (generally between 22 and 27 degrees, preferably 25 degrees), the feed liquid enters a freezing crystallizer. The pre-cooled feed liquid is circulated and exchanges heat and is cooled with a secondary refrigerant (ethylene glycol solution or calcium chloride solution is selected, the preparation concentration is 15% -25%, and the optimal concentration is 20%) under the action of a crystallization chamber and a heat exchanger recirculation pump of a freezing crystallization system, sodium sulfate in the solution is separated out in the form of sodium sulfate decahydrate, and the final feed liquid operation temperature is controlled to be in the range of-5 ℃ to 0 ℃. The decahydrate crystals are separated out from the feed liquid, the decahydrate crystals are settled and the supersaturation degree is eliminated, decahydrate solid is separated out through a centrifugal machine, and the decahydrate is subjected to hot melting and condensed water hot melting and then enters a unit 400 (mainly comprising nitrate evaporative crystallization) for producing sodium sulfate to obtain the sodium sulfate.
Preferably, secondary purification unit 200 includes a settler 200a. The settler 200a comprises at least one feed inlet 200a-1, at least one lean nitre mother liquor outlet 200a-2, at least one decahydrate slurry outlet 200a-3, and an agitation mechanism 200a-4. And the feed inlet 200a-1 can be communicated with the freezing crystallizer to guide supersaturated freezing feed liquid into the settler 200a. And a lean nitrate mother liquor outlet 200a-2 is communicated with the third-stage purification unit 300, and the lean nitrate mother liquor is discharged from the settler. And a decahydrate slurry outlet 200a-3 which is communicated with the sodium sulfate production unit 400 and discharges the decahydrate slurry out of the settler 200a. The stirring mechanism 200a-4 comprises a stirring driving device, stirring shafts 200a-401 and stirring blades 200a-402. The opposite ends of the stirring shafts 200a-401 are respectively connected with stirring driving devices and stirring blades 200a-402. The stirring blades 200a-402 are positioned at the lower side of the lean nitrate mother liquor outlet 200a-2 and the upper side of the decahydrate slurry outlet 200a-3, and the part is a region for further separating out the decahydrate. When the stirring shafts 200a to 401 are driven, due to the influence of supersaturation degree and the seed crystals in the frozen feed liquid, when the stirring blades 200a to 402 generate centrifugal force, the frozen feed liquid generates micro vibration in the cavity, so that sodium sulfate in the frozen feed liquid is further crystallized, the content of sodium sulfate in the lean sodium sulfate mother liquid is reduced, and the purity of the sodium sulfate and the sodium chloride can be improved.
Preferably, the agitating blades 200a-402 may be arranged as follows: are mounted at different heights on the stirring shafts 200a-401, and can stir pre-cooled solutions at different depths. The stirring vanes 200a to 402 are circumferentially installed on the stirring shafts 200a to 401 in such a manner as to extend in the radial direction of the settler as viewed in plan.
Preferably, the agitating blades 200a-402 have crystallized protrusions 200a-402a thereon. The crystallization protrusions 200a to 402a may be provided in such a manner as to have vibration when the agitating blades 200a to 402 rotate, so as to increase the crystallization rate of the sodium decahydrate. For example, the crystallization protrusions 200a to 402a may be spring-mounted to the stirring blades 200a to 402.
Preferably, as shown in FIG. 2, the mounting density of the crystallization protrusions 200a-402a is gradually increased in the extending direction of the agitating blades 200a-402. Under the influence of centrifugal force, solid particles or grains are closer to the far ends of the stirring blades 200a-402, so that the crystallization protrusions 200a-402a generate vibration waves when the colony generates micro-vibration to promote the crystallization of the sodium decahydrate at the far ends of the stirring blades. For this purpose, as shown in fig. 2, the lower end of the settler 200a is formed in a V shape, and when the stirring shaft stops rotating, the decahydrate slurry flows toward a decahydrate slurry outlet 200a-3 by gravity. Therefore, only a small amount of decahydrate crystal grains need to be separated from the precooled feed liquid in the freezing crystallizer, and then the crystal grains are vibrated and crystallized in the settler, so that the separation efficiency of the decahydrate can be greatly improved, and the quantity of the secondary refrigerant needed by the freezing crystallizer is effectively reduced.
Preferably, as shown in fig. 3, the positions of the crystalloid lobes 200a-402a of two stirring blades adjacent in the circumferential direction may be different in the radial direction. The vibration intensities of the crystallization protrusions 200a-402a at different positions are also inconsistent, so that the movement of the precooled feed liquid in the settler is irregular, and the crystallization of the sodium nitrate decahydrate is promoted.
Preferably, the rotation speed of the stirring shaft is set in such a manner that the crystal protrusions 200a-402a have different vibration intensities, so that more sodium sulfate is precipitated as decahydrate. Such as: rotation speed of the stirring shaft: increasing, then fluctuating sinusoidally, and then decreasing. However, the rotation speed of the stirring shaft cannot be changed abruptly.
Preferably, as shown in fig. 5, the crystallization protrusions 200a-402a may be designed in a column shape or a rod shape. As shown in fig. 5, the widths of the crystallization protrusions 200a-402a are set to decrease first to form pits and then to increase along the axial direction thereof. Or when the stirring shaft rotates, the frozen material liquid can generate turbulent flow at the pit due to the change of the cross section, and the strength of the turbulent flow is increased to easily generate micro vortex under the action of the exciting force of the spring. Under the action of the micro vortex, the crystal grains adsorbed on the surfaces of the crystal protrusions 200a-402a are carried away by the micro vortex, so that the number of the crystal grains on the crystal protrusions 200a-402a is reduced. Meanwhile, the micro vortex generates micro vibration wave, which also promotes the nitrate decahydrate to accelerate to grow and separate out crystal grains.
Preferably, the distal ends of the stirring vanes at the same height are connected together by skirts 200 a-403.
Preferably, the temperature of the frozen feed liquid in the settler is kept between-5 ℃ and 0 ℃ by the settler in a cold insulation manner. For example, the outer wall of the settler is provided with a cold insulation material.
Preferably, the settler 200a further comprises a drainage plate which is obliquely disposed at the lower end of the feed inlet 200a-1 and drains the freezing feed liquid to the central region of the settler 200a. Preferably, because the saturated freezing feed liquid contains the seed crystal, the concentrated water rich in sodium sulfate and nitrate can directly flow into the settler 200a to crystallize in a vibration mode after being cooled to reach the supersaturated state, and can not enter the freezing crystallizer, so as to reduce the processing load of the freezing crystallizer.
Preferably, the sodium sulfate production unit 400: preparing a nearly saturated sodium sulfate solution from sodium sulfate decahydrate through hot melting and hot dissolving of condensed water, performing heat exchange heating on the sodium sulfate decahydrate and the condensed water, feeding the sodium sulfate decahydrate and the condensed water into a sodium sulfate evaporation crystallization system, concentrating a sodium sulfate solution through multiple-effect forward flow evaporation crystallization, continuously concentrating sodium sulfate in the solution to achieve supersaturation, separating out the sodium sulfate solution, gradually growing up and precipitating the sodium sulfate solution on sodium sulfate feet, discharging a sodium sulfate slurry liquid, obtaining wet sodium sulfate through thickening and centrifugal separation, drying through a sodium sulfate drying bed, and packaging to obtain a sodium sulfate product; a small amount of mother liquor discharged from the last effect of sodium sulfate evaporative crystallization returns to a pre-freezing or mixed salt crystallizer unit, and condensed water produced by an evaporative crystallization system exchanges heat with the feed of the system and is recycled;
preferably, three-stage purification unit 300: the frozen supernatant mother liquor obtained after sedimentation of the sodium chloride-nitrate-poor solution produced by the secondary purification unit 200 is discharged into a membrane filtration unit for treatment, partial impurities are removed to prevent the impurities from damaging the structure of the nanofiltration membrane, and the filtered concentrated water returns to the mixed salt evaporation crystallization feeding tank of the primary purification unit 100. The filtered produced water of the frozen material liquid is adjusted and then enters a subsequent NF device to purify the poor sodium nitrate and sodium chloride material liquid, the NF treatment mainly uses sodium chloride as a small amount of sodium sulfate solution, the concentrated water rich in sodium nitrate and low sodium sulfate returns to a freezing crystallizer (and/or a settler) of the secondary purification unit 200 to continuously recover sodium sulfate, and the produced water of the poor sodium nitrate and sodium chloride directly enters a sodium chloride production unit 500: sodium chloride evaporative crystallizer or water produced is concentrated (the water with large quantity and low concentration is matched (RO or ED or DTRO or MVR) and then enters into the sodium chloride evaporative crystallization system;
sodium chloride production unit 500: the sodium chloride-poor water produced enters a sodium chloride evaporative crystallization system, sodium chloride solution is concentrated through multiple-effect concurrent evaporative crystallization, sodium chloride in the solution is continuously concentrated to be supersaturated and separated out, and gradually grows up and deposits on salt feet, salt slurry liquid is discharged, wet sodium chloride salt is obtained through a thickening and centrifugal separation channel, and then the wet sodium chloride salt is dried and packaged through a salt drying bed to obtain a sodium chloride product; a small amount of mother liquor discharged at the end of sodium chloride evaporative crystallization returns to a NF front or mixed salt crystallizer unit, and condensed water produced by an evaporative crystallization system is recycled after heat exchange with the feeding material of the system.
Example 3
This embodiment may be a further improvement and/or a supplement to embodiments 1, 2 or a combination thereof, and repeated contents are not described again. This example discloses that, without creating conflicts or inconsistencies, the entire contents and/or parts of preferred implementations of other examples may supplement this example.
The embodiment discloses a multistage balance purification method for high-salt-content wastewater, in particular to a multistage balance salt and nitrate separating process method for high-salt-content wastewater, which comprises the following process steps:
(1) Carrying out pretreatment of removing impurities such as hardness, silicon, fluorine and part of organic matters on the high-salinity wastewater after homogenizing the incoming water of the wastewater, and enabling the pretreated high-salinity wastewater to enter a concentration system to obtain high-salinity concentrated water containing saltpeter;
(2) The concentrated high-salinity concentrated water obtained in the step (1) generally has a TDS of about 6-20 ten thousand ppm, is subjected to MVR and multi-effect forced circulation evaporation crystallization to enable saltpeter to reach a supersaturated state, sodium sulfate and sodium chloride mixed salt crystals are separated out, sodium sulfate and sodium chloride crystal slurry discharged from an evaporation crystallizer is subjected to thickening separation to obtain sodium sulfate and sodium chloride mixed salt with the water content of 4-5%, meanwhile, part of miscellaneous salt mother liquor discharged from the evaporation crystallization system is subjected to impurity removal and drying, organic matters, sodium nitrate and other impurities of saturated concentrated feed liquid enter an evaporation crystallization tank are mainly balanced, and produced water in the process is subjected to heat exchange and then is sent to a produced water recycling system;
(3) Sodium sulfate and sodium chloride which are subjected to concentration, salt precipitation and purification in the step (2) and are subjected to moisture removal enter a hot-melt treatment unit to prepare nearly saturated sodium sulfate and sodium chloride solution;
(4) The high-concentration saltpeter feed liquid prepared by the saltpeter hot melting after the secondary purification II in the step (3) is firstly fed into a purification unit II for purifying sodium chloride and recovering sodium sulfate;
(5) The sodium sulfate is supersaturated in the form of crystal water through the secondary purification of the step (4), sodium sulfate decahydrate crystals (sodium nitrate decahydrate) are separated out through crystallization, the sodium sulfate decahydrate crystals enter a sodium nitrate decahydrate hot-melting or hot-melting system through thickening, concentration and crystallization, and the sodium sulfate is separated out through evaporation, concentration and crystallization of the sodium nitrate evaporation and crystallization system; the produced water after the thermal dissolution and the evaporation crystallization after the melting is sent to a produced water recycling system through heat exchange;
(6) The mother liquor after salt purification in the step (5) enters a filtering system for three-stage purification;
(7) The solution filtered in the step (6) enters three-stage purification;
(8) Feeding the high-salinity concentrated water obtained after the purification III is concentrated in the step (7) into a feeding tank before secondary purification;
(9) Carrying out evaporative crystallization on the purified water (sodium chloride solution) obtained in the step (8), concentrating, and then carrying out evaporative crystallization to separate out sodium chloride;
(10) And (3) purifying and discharging a small amount of mother liquor, introducing the small amount of mother liquor into a mixed salt mother liquor curing system, mainly balancing impurities such as organic matters, sodium nitrate, soluble silicon and the like in the system, controlling the concentration of the impurities such as the enriched organic matters and the sodium nitrate, and treating the mixed salt produced by drying and curing the mixed salt mother liquor separately or uniformly mixing the small amount of mixed salt mother liquor and sewage for biochemical treatment and the like.
Preferably, the process steps are further detailed as follows: sodium sulfate and sodium chloride generated by I-stage purification are subjected to hot melting and then sent into a purification II to reduce nitrate content so as to purify the sodium chloride, and crystal nitrate containing water generated by the purification II is subjected to hot melting and hot melting, wherein feed liquid after hot melting is filtered in the step (6) and subjected to water inlet heat exchange with condensed water generated by a system so as to improve the temperature of circulating liquid, meet the water inlet requirement of entering the purification III, the temperature is about 25-35 ℃, the produced water of the purification III system mainly contains sodium chloride and is sent to the step (9) to be concentrated and crystallized so as to recover high-purity sodium chloride; and (4) returning purified III concentrated water which mainly contains sodium sulfate to the step (8) for further recovering the sodium sulfate.
Preferably, in the purification II system, the temperature of the purification II is controlled to be-5-0 ℃, and the refrigerant adopts ethylene glycol solution or calcium chloride solution, and the preparation concentration is 20%.
Preferably, in the purification III system, the rejection rate of sodium sulfate is controlled to be 95-98%, and the rejection rate of sodium chloride is controlled to be-10%. The reason why negative rejection occurs is that: because the salt content is high, the permeability of sodium ions is increased, the permeability of chloride ions is greater than that of sulfate ions, and more chloride ions are needed to permeate the nanofiltration membrane for the electrical balance of the two sides of the nanofiltration membrane, so that the rejection rate of chloride ions is negative.
Preferably, the control concentration of each pollutant in the effluent of the purification treatment system is controlled as follows: CODCr is less than or equal to 2000mg/l (TDS 20 ten thousand ppm is upper limit), TDS low and TDS high are respectively low value and high value, total hardness (calculated by CaCO 3) is less than 5mg/l, total alkalinity (calculated by CaCO 3) is 10-30 mg/l; the control concentration of each pollutant in the effluent water of the first-stage purification unit 100 (mixed salt crystallization system I) is controlled as follows: CODCr is less than or equal to 50000mg/l, and silicon is less than 1000mg/l.
Preferably, the temperature of the frozen feed liquid is controlled to be in a range of-5-0 ℃, separated nitre decahydrate solid is produced and dehydrated through centrifugal separation, the solid is subjected to hot melting by using condensed water, a saturated sodium sulfate solution is prepared, a nitre removing evaporation crystallization system is used, nitre is produced at high temperature, a high-purity sodium sulfate product is prepared, a small amount of enriched impurities are returned to a mixed salt evaporation system, sodium sulfate is continuously recovered, and meanwhile, a small amount of impurity enriched substances in the nitre evaporation crystallization system are balanced through reflux;
preferably, the rejection rate of the NF system to sodium sulfate is more than or equal to 98 percent, and the rejection rate to sodium chloride is negative. Negative retention refers to: the sodium chloride solution was allowed to pass completely.
Example 4
The present embodiment also discloses a crystallization system that may be implemented by the present invention in combination with a system unit and/or other alternative components. For example, the method of the present invention may be implemented using various components of the system of the present invention.
Preferably, the circulating purification balance treatment equipment for stably separating salt and nitrate. The invention provides circulating purification balance treatment equipment for stable salt and nitrate separation, which comprises an NF membrane separation device, wherein the NF membrane separation device is used for further separating sodium chloride and sodium sulfate in frozen poor nitrate mother liquor discharged by a secondary purification unit; the NF membrane separation device can be communicated with the filtering device, the filtering device can be communicated with the second-stage purification unit, the filtering device is used for further removing impurities of the frozen mirabilite-poor mother liquor in a mode meeting the impurity concentration requirement of the NF membrane separation device to obtain impurity liquid, and an impurity liquid outlet of the filtering device is communicated with the first-stage purification unit, so that the first-stage purification unit can purify mixed salt containing sodium sulfate crystals and sodium chloride crystals in the salt-containing wastewater in an approximately balanced mode. The rejection rate of the NF membrane separation device to sodium sulfate is 95-98%, and the rejection rate to sodium chloride is-10%.
The purification equilibrium processing apparatus of the present invention further comprises:
1) A pretreatment device: a membrane concentration system is used for obtaining high-salinity concentrated water containing a large amount of organic matters, sodium nitrate and other impurities, and the produced water is recycled;
2) The concentrated high-salt water is subjected to mixed salt purification I, and sodium sulfate and sodium chloride are separated through evaporative crystallization to obtain relatively pure mixed salt of sodium sulfate and sodium chloride;
3) The first-stage purification unit is used for carrying out purification treatment on the high-salinity concentrated water by using salt and nitrate; isolating the concentrated organic matter, sodium nitrate, silicon, fluorine and other impurity substances in the feed liquid to obtain relatively pure salt and nitrate mixed salt with the water content of about 5%;
4) Salt and nitre generated by a first-stage purification unit are heated and added with a small amount of condensed water for redissolution to obtain pure sodium sulfate and sodium chloride solution saturated in crystallization; the nearly saturated mixed solution of sodium sulfate and sodium chloride enters a purification unit II;
5) The secondary purification unit is used for cooling the nearly saturated feed liquid of sodium sulfate and sodium chloride to separate out a low-temperature saturated sodium sulfate solution from sodium sulfate by sodium sulfate decahydrate crystallization, so that pure sodium sulfate decahydrate crystals containing 10 crystal waters are obtained, and the purification treatment of the sodium chloride solution in the feed liquid is realized;
6) The sodium sulfate-sodium decahydrate purification system comprises a first-stage purification unit, a second-stage purification unit, a sodium sulfate-sodium decahydrate crystallization system and a mixed salt crystallizer, wherein the first-stage purification unit is used for producing sodium decahydrate;
the purified feed liquid of the purification unit II is filtered, the filtered discharge liquid returns to a feed tank before the purification unit II, the filtered clear liquid enters an adjusting tank for blending, then enters the purification unit III, and the blended sodium sulfate solution which mainly contains sodium chloride and is small in amount is purified again;
7) The third-stage purification unit generates a nitrate-rich solution and returns the nitrate-rich solution to the second-stage purification unit; the purification unit III is used for generating a poor nitrate solution, and the poor nitrate solution enters a sodium chloride evaporation crystallizer to be evaporated and crystallized to separate out high-purity sodium chloride salt; the condensed water produced by the sodium chloride evaporative crystallizer after evaporation and crystallization is completely recycled through heat exchange;
sodium chloride is evaporated and crystallized to generate a small amount of mother liquor, the mother liquor returns to the purification unit I, and sodium chloride is further recovered; a small amount of mother liquor discharged by salt evaporation crystallization returns to a primary purification unit to recover sodium chloride and a small amount of impurities which are balanced and enriched in the mother liquor, the mother liquor enters a mixed salt crystallizer, and the impurities are balanced and removed by the impurity-removing mother liquor;
8) And (3) enabling the mixed salt mother liquor discharged from the purification unit I to enter a mixed salt treatment system, separating out the mixed salt through evaporation and crystallization, and removing the mother liquor from the mixed salt mother liquor discharged from a mixed salt evaporation crystallizer to perform solidification treatment to obtain the mixed salt, wherein the impurity content of the system is mainly balanced.
Preferably, the multistage purification impurity separation salt separation crystallization system comprises a mixed salt evaporation crystallization treatment system, a mixed salt hot-melt sodium sulfate and sodium chloride saturated solution freezing crystallization treatment system, a sodium nitrate decahydrate hot-melt (hot-melt) sodium sulfate evaporation crystallization system, a freezing mother liquor NF separation treatment system and a sodium chloride salt evaporation crystallization separation system.
Preferably, the pretreatment system comprises an AOP unit such as hardness-removing softening sedimentation clarification, a filter or membrane filtration, resin softening, advanced oxidation unit activated carbon and the like, so as to remove most of hardness, alkalinity, heavy metals, suspended substances, part of silicon, part of fluorine, alkali liquor for reaction, part of organic matters and other impurities in the wastewater.
Preferably, the purification, evaporation and crystallization processing system I comprises a crystallization process device such as multi-effect forced circulation evaporation crystallization, TVR evaporation crystallization, MVR falling film evaporation + forced circulation evaporation crystallization, flash evaporation and the like, wherein sodium sulfate and sodium chloride are separated out from the evaporation and concentration feed liquid when the evaporation and concentration feed liquid is salt nitrate in an oversaturated state, and mixed salt solids, CODcr, silicon, fluoride, suspended matters, alkali liquor obtained by reaction of pretreatment residues, scale inhibitors added by pretreatment, impurities of corrosion inhibitors remaining in the system and the like are thoroughly isolated, so that subsequent recrystallization and purification units ii and iii are carried out in a relatively alcoholic solution to respectively obtain pure sodium sulfate and sodium chloride solids; CODCr, silicon, fluoride, suspended solids, alkali liquor which is added in the pretreatment residue and is enriched in feed liquid, impurities of scale inhibitor which is added in the pretreatment residue and corrosion inhibitor which is remained in the system enter a mixed salt system through mother liquor discharge, the mother liquor is discharged through mixed salt evaporation crystallization and is solidified for disposal, and the balance system is enriched with higher CODCr, silicon, fluoride, suspended solids, alkali liquor which is added in the pretreatment residue and is enriched in the impurities of scale inhibitor which is added in the pretreatment residue and corrosion inhibitor which is remained in the system.
In this example, purification I corresponds to a first purification unit 100, purification II corresponds to a second purification unit 200, and purification III corresponds to a third purification unit 300
Example 5
This embodiment can be implemented by the systems in embodiments 1, 2 and 4 without causing conflicts. The embodiment discloses a multistage purification circulation method for high-salt-content wastewater, which at least comprises the following steps:
s1: evaporating and crystallizing the pretreated strong salt wastewater to obtain mixed salt of sodium chloride and sodium sulfate,
s2: preparing the mixed salt into a nitrate-rich mother solution in a saturated state, and freezing to obtain nitrate decahydrate and a nitrate-poor mother solution;
s3: and separating the poor-nitrate mother liquor by adopting a membrane separation mode to obtain a sodium chloride solution and rich-nitrate low-sodium sulfate concentrated water. The sodium sulfate-rich and low-sodium sulfate concentrated water can be frozen according to the method of S2 to obtain the sodium sulfate decahydrate.
After step S2, evaporating the sodium decahydrate in a hot-melt state to obtain sodium sulfate;
after step S3, the sodium chloride solution is evaporated to obtain sodium chloride.
It should be noted that the above-mentioned embodiments are exemplary, and that those skilled in the art, having benefit of the present disclosure, may devise various arrangements that are within the scope of the present disclosure and that fall within the scope of the invention. It should be understood by those skilled in the art that the present specification and figures are illustrative only and are not intended to be limiting on the claims. The scope of the invention is defined by the claims and their equivalents.
Claims (5)
1. A circulating purification balance treatment system for stable separation of salt and nitrate comprises a first-stage purification unit (100), a second-stage purification unit (200) and a third-stage purification unit (300);
it is characterized in that the preparation method is characterized in that,
primary purification unit (100): the high-salt-content wastewater enters a thermal evaporation crystallization system after passing through a pretreatment system, generated magma is thickened, concentrated, separated and dehydrated to produce sodium sulfate and sodium chloride, sodium chloride and sodium sulfate mixed salt with low impurity content are obtained preliminarily, and the crystallized sodium sulfate and sodium chloride are isolated from high-content organic matters, sodium nitrate, fluoride ions and silicon impurities in the enriched mother liquor, wherein the process is a primary salt and nitrate purification process;
secondary purification unit (200): sodium chloride and sodium sulfate produced by purification, evaporation, crystallization and separation enter a dissolving and stirring tank or a tank, condensed water is added and stirred for dissolution, sodium sulfate and sodium chloride solution with saturated concentration are prepared, salt and nitrate solution enters a liquid storage barrel and is pumped into a freezing and crystallizing system, the temperature of the feed liquid is controlled through a crystallizer of the freezing and crystallizing system, sodium nitrate decahydrate is crystallized and separated, the produced sodium nitrate decahydrate is redissolved and enters a sodium sulfate production unit (400), finally, sodium sulfate feed liquid is evaporated and concentrated through steam heating to reach supersaturation to produce sodium sulfate crystals, and high-purity sodium sulfate is obtained through thickening, separation and drying;
tertiary purification unit (300): the nitre-poor mother liquor generated by freezing crystallization enters a three-stage purification unit (300) for further re-separation of sodium chloride and sodium sulfate; the three-stage purification unit (300) at least comprises a filtering device (300 a) and an NF membrane separation device (300 b), the NF membrane separation device (300 b) comprises at least one nanofiltration device, the filtering device (300 a) is a tubular micro-filter or a cartridge filter, and the filtering device (300 a) is arranged between the two-stage purification unit (200) and the NF membrane separation device (300 b) and is used for filtering the frozen nitrate-poor mother liquor so as to further reduce the impurity concentration of the NF membrane separation device (300 b) and meet the feed liquor requirement of the NF membrane separation device (300 b); on one hand, the aperture of the nanofiltration membrane of the NF membrane separation device (300 b) is small, and the NF membrane separation device (300 b) is easily blocked due to overlarge impurity particle size, so that the arrangement of the filtration device (300 a) can reduce the probability of blockage of the nanofiltration membrane, effectively improve the separation efficiency of the NF membrane separation device (300 b), and improve the purity of the obtained sodium chloride; on the other hand, an impurity liquid outlet of the filtering device (300 a) is communicated with the primary purification unit (100), the impurity liquid of the filtering device (300 a) is used as a tempering liquid of the high-salinity wastewater, and when the impurity concentration in the high-salinity wastewater is too high or too low, the impurity liquid and the high-salinity wastewater are mixed so as to control the impurity concentration within the range of the required impurity concentration of the primary purification unit (100), so that mixed salt can be more easily separated out; concentrating the sodium chloride lean product water or directly feeding the sodium chloride lean product water into a sodium chloride evaporative crystallization system, heating the sodium chloride feed liquid through steam to achieve supersaturation after circulating evaporation, separating out a large amount of sodium chloride crystals from the feed liquid, and thickening, concentrating, separating and drying the sodium chloride feed liquid to obtain high-purity sodium chloride; the NF membrane separation device (300 b) generates concentrated water rich in sodium sulfate and nitrate and returns to the freezing crystallizer, and sodium sulfate in the concentrated water rich in sodium sulfate and nitrate is extracted;
the secondary purification unit (200) comprises a settler (200 a), wherein the settler (200 a) comprises at least one feed inlet (200 a-1), at least one lean nitre mother liquor outlet (200 a-2), at least one decahydrate slurry outlet (200 a-3) and a stirring mechanism (200 a-4); the feed inlet (200 a-1) is communicated with the freezing crystallizer, and the supersaturated freezing feed liquid is guided into the settler (200 a); a lean nitrate mother liquor outlet (200 a-2) is communicated with the third-stage purification unit (300), and the lean nitrate mother liquor is discharged out of the settler; a decahydrate slurry outlet (200 a-3) is communicated with a sodium sulfate production unit (400) and discharges the decahydrate slurry out of the settler (200 a); the stirring mechanism (200 a-4) comprises a stirring driving device, a stirring shaft (200 a-401) and a stirring blade (200 a-402); the two opposite ends of the stirring shaft (200 a-401) are respectively connected with a stirring driving device and a stirring blade (200 a-402); the stirring blades (200 a-402) are positioned at the lower side of the lean nitrate mother liquor outlet (200 a-2) and the upper side of the decahydrate slurry outlet (200 a-3); when the stirring shaft (200 a-401) is driven, due to the influence of supersaturation degree and seed crystals in the frozen feed liquid, when the stirring blade (200 a-402) generates centrifugal force, the frozen feed liquid generates micro vibration in the cavity, so that sodium sulfate in the frozen feed liquid is further crystallized, the content of sodium sulfate in the lean nitrate mother liquid is reduced, and the purity of sodium sulfate and sodium chloride can be improved;
the stirring blades (200 a-402) are arranged at different heights of the stirring shaft (200 a-401) and are used for stirring precooled solution at different depths, and the stirring blades (200 a-402) are circumferentially arranged on the stirring shaft (200 a-401) in a manner of extending in the radial direction of the settler when viewed in a top view;
the stirring blades (200 a-402) are provided with crystallization bulges (200 a-402 a), and the crystallization bulges (200 a-402 a) are arranged in a mode of vibrating when the stirring blades (200 a-402) rotate so as to improve the crystallization speed of the sodium sulfate decahydrate;
the installation density of the crystal protrusions (200 a-402 a) is gradually increased in the extending direction of the stirring blades (200 a-402);
the positions of the crystallization bulges (200 a-402 a) of two circumferentially adjacent stirring blades in the radial direction are different, and the vibration intensities of the crystallization bulges (200 a-402 a) at different positions are inconsistent, so that the precooled feed liquid does not move regularly in the settler, and the crystallization of the sodium sulfate decahydrate is promoted;
the rotation speed of the stirring shaft is set in a manner that the crystal protrusions (200 a-402 a) have different vibration intensities, so that more sodium sulfate is separated out as sodium nitrate decahydrate;
the width of the crystallized projections (200 a-402 a) is set to decrease first to form pits and then increase along the axial direction thereof.
2. The processing system according to claim 1, wherein the NF membrane separation device (300 b) has a sodium sulfate rejection of 95 to 98% and a sodium chloride rejection of-10 to 10%.
3. The processing system of claim 1, wherein a separation unit for controlling a water content of the mixed salt is disposed between the primary purification unit (100) and the secondary purification unit (200), wherein the water content of the mixed salt is 4% -5%.
4. The treatment system according to claim 3, wherein the secondary purification unit (200) uses a coolant to separate out sodium sulfate in a cooling process in a supersaturated state in a decahydrate form under the condition that a near-saturated sodium sulfate and sodium chloride solution prepared based on the mixed salt hot melting is precooled to obtain a precooled feed liquid, and the coolant can reduce the temperature of the precooled feed liquid to minus 5 ℃ to 0 ℃ to obtain a frozen feed liquid.
5. The treatment system of claim 4, wherein the concentrated salt wastewater is concentrated at least once to a TDS value of 6 to 20 ppm before entering the primary purification unit (100).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010892359.XA CN111960437B (en) | 2020-08-28 | 2020-08-28 | Circulating purification balance treatment system, equipment and method for stable separation of salt and nitrate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010892359.XA CN111960437B (en) | 2020-08-28 | 2020-08-28 | Circulating purification balance treatment system, equipment and method for stable separation of salt and nitrate |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111960437A CN111960437A (en) | 2020-11-20 |
| CN111960437B true CN111960437B (en) | 2022-11-29 |
Family
ID=73400468
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010892359.XA Active CN111960437B (en) | 2020-08-28 | 2020-08-28 | Circulating purification balance treatment system, equipment and method for stable separation of salt and nitrate |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111960437B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114314907A (en) * | 2021-12-17 | 2022-04-12 | 烟台金正环保科技有限公司 | Purification system and method for producing miscellaneous salt through wastewater treatment |
| CN115193090B (en) * | 2022-07-25 | 2023-08-29 | 青岛润扬环境科技有限公司 | Continuous quality-dividing crystallization purification device for mixed salt in zero-emission process |
| CN115403057A (en) * | 2022-09-22 | 2022-11-29 | 倍杰特集团股份有限公司 | Salt-nitrate separation wastewater treatment system and method based on condensate recovery |
| CN115465995A (en) * | 2022-09-22 | 2022-12-13 | 倍杰特集团股份有限公司 | Membrane separation salt and nitrate-based salt-containing wastewater recycling treatment system and method |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106823419A (en) * | 2017-01-18 | 2017-06-13 | 合山锌业科技有限公司 | Interior heating crystalline evaporator |
| WO2017181696A1 (en) * | 2016-04-21 | 2017-10-26 | 广州市心德实业有限公司 | Method for treating and recycling brine wastewater containing sodium chloride and sodium sulfate |
| CN206645853U (en) * | 2017-03-20 | 2017-11-17 | 科莱环境工程（北京）有限公司 | A kind of system of sub-prime crystallization technique processing brine waste |
| CN107619144A (en) * | 2017-10-20 | 2018-01-23 | 侯新春 | A kind of high slat-containing wastewater divides salt process for reclaiming and system |
| CN108947064A (en) * | 2018-07-02 | 2018-12-07 | 广州汉泰环境技术有限公司 | A kind of the sub-prime crystallization processes and its system of brine waste |
| CN108996785A (en) * | 2018-07-02 | 2018-12-14 | 广州汉泰环境技术有限公司 | A kind of high slat-containing wastewater thoroughly divides salt crystallization processes and its system |
| CN109292797A (en) * | 2018-11-02 | 2019-02-01 | 江苏中圣高科技产业有限公司 | A kind of brine waste sub-prime recovery method |
-
2020
- 2020-08-28 CN CN202010892359.XA patent/CN111960437B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017181696A1 (en) * | 2016-04-21 | 2017-10-26 | 广州市心德实业有限公司 | Method for treating and recycling brine wastewater containing sodium chloride and sodium sulfate |
| CN106823419A (en) * | 2017-01-18 | 2017-06-13 | 合山锌业科技有限公司 | Interior heating crystalline evaporator |
| CN206645853U (en) * | 2017-03-20 | 2017-11-17 | 科莱环境工程（北京）有限公司 | A kind of system of sub-prime crystallization technique processing brine waste |
| CN107619144A (en) * | 2017-10-20 | 2018-01-23 | 侯新春 | A kind of high slat-containing wastewater divides salt process for reclaiming and system |
| CN108947064A (en) * | 2018-07-02 | 2018-12-07 | 广州汉泰环境技术有限公司 | A kind of the sub-prime crystallization processes and its system of brine waste |
| CN108996785A (en) * | 2018-07-02 | 2018-12-14 | 广州汉泰环境技术有限公司 | A kind of high slat-containing wastewater thoroughly divides salt crystallization processes and its system |
| CN109292797A (en) * | 2018-11-02 | 2019-02-01 | 江苏中圣高科技产业有限公司 | A kind of brine waste sub-prime recovery method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN111960437A (en) | 2020-11-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111960437B (en) | Circulating purification balance treatment system, equipment and method for stable separation of salt and nitrate | |
| CN106830465B (en) | Salt separation and purification recovery method of salt-containing wastewater | |
| CN112028363B (en) | Stable salt separation system and method for high-salt-content wastewater | |
| CN108623050B (en) | Desulfurization wastewater treatment method and system | |
| CN112047362B (en) | Multistage purification equipment and process for high-salt-content wastewater | |
| CN108275815B (en) | High-salinity wastewater zero-discharge evaporation crystallization salt quality-grading system and method | |
| CA3103575C (en) | Methods for producing potassium sulfate and sodium chloride from wastewater | |
| CN112919505B (en) | Device and method for continuously producing lithium hydroxide from salt lake lithium-rich brine | |
| CN110127925B (en) | Method for recycling mixed salt produced by waste acid treatment | |
| CN216639187U (en) | Treatment system for salt-containing wastewater and CO 2-containing waste gas | |
| CN111547916A (en) | Salt and nitrate separation method for nitrate-rich wastewater | |
| CN112028364B (en) | Multistage purification system and method for high-salt-content wastewater | |
| CN117120380A (en) | Garbage leachate purification method | |
| CN109607582B (en) | Method and system for recovering magnesium salt from desulfurization wastewater | |
| CN115465995A (en) | Membrane separation salt and nitrate-based salt-containing wastewater recycling treatment system and method | |
| CN115676856B (en) | Method and system for extracting lithium from salt lake | |
| CN110923452A (en) | Process for recovering potassium and sodium salts from lithium-precipitated liquid of lepidolite by using ethanol | |
| CN103265056B (en) | Method for extracting industrial slat from salt mixture | |
| CN106430771B (en) | salt separation system and salt separation method | |
| CN116964247A (en) | System and method for direct production of lithium hydroxide | |
| CN111620497A (en) | Method and system for treating Enbipu pharmaceutical wastewater | |
| CN220999474U (en) | Brine recovery system | |
| CN111362490A (en) | Desulfurization wastewater treatment method and system | |
| CN115849487B (en) | Method for separating single salt and water from multi-component wastewater based on cascade concentrated eutectic freezing | |
| CN114890629B (en) | Method for recycling high-salt wastewater |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |