CN106185996A

CN106185996A - A kind of salt extraction process and salt making system

Info

Publication number: CN106185996A
Application number: CN201610515930.XA
Authority: CN
Inventors: 熊日华; 卫昶; 何灿
Original assignee: Shenhua Group Corp Ltd; National Institute of Clean and Low Carbon Energy
Current assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Priority date: 2016-07-01
Filing date: 2016-07-01
Publication date: 2016-12-07
Anticipated expiration: 2036-07-01
Also published as: CN106185996B

Abstract

The present invention relates to water treatment field, disclose a kind of salt extraction process and salt making system.The method includes: brackish water is carried out nanofiltration separation process, obtains nanofiltration and produces water and the dense water of nanofiltration；Carry out Crystallization Separation after being cooled down by dense for nanofiltration water, obtain crystallizing water outlet and crystal salt, moisture will be crystallized out and for backflow crystallization water outlet and crystallize dense water；The dense water that dense for crystallization water and the second evaporative crystallization refluxed carries out alternating temperature evaporative crystallization separating treatment, obtains dianion salt, univalent anion salt and the dense water of the second evaporative crystallization, is the second evaporative crystallization dense water of backflow and dense water of system by the second dense moisture of evaporative crystallization；Brackish water includes raw water and backflow crystallization water outlet, and in raw water, < when 5%, meeting R1 < X/ (5 X), R1 is the volume flow ratio that water is produced in the dense water of crystallization and nanofiltration to dianion salt mass percentage content X%.The method of the present invention can prepare highly purified one-component salt, and investment and operating cost can be greatly reduced and improve the response rate of salt.

Description

A kind of salt extraction process and salt making system

Technical field

The present invention relates to water treatment field, in particular it relates to a kind of salt extraction process and salt making system.

Background technology

Along with the continuous lifting of environmental requirement, the contradictions such as water resource is not enough and environmental carrying capacity is limited highlight day by day.At stone In the production processes such as oiling work, Coal Chemical Industry, electric power, iron and steel and desalinization, substantial amounts of brine waste can be produced.In order to reduce Outer displacement, improves the service efficiency of water, and current brine waste generally uses reuse after the embrane method based on reverse osmosis processes, Improve the service efficiency of water to a certain extent.Requiring the occasion of zero liquid discharge, reverse osmosis concentrated water is used steaming further Send out crystallization processes, obtain distilled water and solid carnallite.Owing to these solid carnallites usually containing Organic substance, and meet water and be prone to Dissolving, therefore its safe disposal problem obtains extensive concern, and cost of disposal is high simultaneously, has become as the load-bearing burden of enterprise.

Under this background, how during zero liquid emission treatment of waste water, it is thus achieved that the single solid that purity is higher Salt is a kind of good try.Due to the extensive application of ion exchange technique, the polyvalent cation in waste water can be easier Be exchanged into sodium ion, and in natural water, anion is mainly made up of chloride ion and sulfate ion, and therefore waste water processes Concentrate in waste water mainly sodium sulfate and the mixed solution of sodium chloride, other component, as less in potassium salt, nitrate equal size.

Currently, the mode of point salt-pepper noise widely used substep evaporation of industrial sodium sulfate and sodium chloride is carried out.This side Method is not only invested greatly, energy consumption high, and this process operation interval is limited, unstable product quality, and the salt of whole process reclaims effect Rate is relatively low.It is therefore desirable to propose the salt producing craft of a kind of improvement, the one-component salt that can not only obtain higher degree is made For salable industry byproduct, and the investment of process, operating cost can be reduced and improve the response rate of salt.

Summary of the invention

The invention aims to overcome drawbacks described above present in prior art, it is provided that a kind of salt extraction process and salt manufacturing System, the salt extraction process of the present invention can prepare highly purified one-component salt, and investment and operating cost can be greatly reduced And improve the response rate of salt.

To achieve these goals, first aspect, the invention provides a kind of salt extraction process, the method includes:

(1) brackish water containing dianion salt and univalent anion salt is carried out nanofiltration separation process, obtain rich one The dense water of nanofiltration that the nanofiltration product water of valency anion salt and dianion salt are concentrated；

(2) the dense water of nanofiltration that step (1) obtains is carried out cooling process, the dense water of nanofiltration after being cooled down；

(3) the dense water of nanofiltration after cooling step (2) obtained carries out Crystallization Separation process, obtains crystallizing water outlet and crystallization Salt, is two strands by the described moisture that crystallizes out, and is back to the nanofiltration separation described in step (1) respectively as backflow crystallization water outlet and processes Follow-up alternating temperature evaporative crystallization separating treatment is carried out with as the dense water of crystallization；

(4) the dense water of crystallization step (3) obtained and the second evaporative crystallization dense water of backflow are carried out as evaporative crystallization Alternating temperature evaporative crystallization separating treatment, described alternating temperature evaporative crystallization separating treatment includes at the first evaporative crystallization separation of carrying out successively Reason and the second evaporative crystallization separating treatment, for by control evaporating temperature obtain dianion salt, univalent anion salt and The second dense water of evaporative crystallization, is two strands by the described second dense moisture of evaporative crystallization, respectively as the second evaporative crystallization dense water of backflow It is back to described alternating temperature evaporative crystallization separating treatment and carries out post processing as the dense water of system；

Wherein, in step (1), the described brackish water containing dianion salt and univalent anion salt include raw water and Backflow crystallization water outlet described in step (3)；And the weight/mass percentage composition X% of dianion salt < when 5%, meets in raw water < X/ (5-X), R1 are the volume flow ratio crystallizing dense water with nanofiltration product water to relational expression R1.

Second aspect, the invention provides a kind of salt making system, and this system includes: nanofiltration separation unit, cooling unit, knot Brilliant separative element, the first evaporative crystallization separative element and the second evaporative crystallization separative element,

Described nanofiltration separation unit is for carrying out nanofiltration by the brackish water containing dianion salt and univalent anion salt Separating treatment, obtains the dense water of nanofiltration that water is produced in the nanofiltration of rich univalent anion salt and dianion salt is concentrated；

Described cooling unit, for the dense water of nanofiltration from described nanofiltration separation unit is carried out cooling process, is cooled down After the dense water of nanofiltration；

Described Crystallization Separation unit, for the dense water of nanofiltration from described cooling unit is carried out Crystallization Separation process, obtains Crystallization water outlet and crystal salt, and described Crystallization Separation unit be connected with described nanofiltration separation unit at least partially crystallized go out Water is back to described nanofiltration separation unit；

Described first evaporative crystallization separative element is not for being back to nanofiltration separation from described Crystallization Separation unit The partially crystallizable water outlet of unit and the second evaporative crystallization from described second evaporative crystallization separative element reflux dense water as steaming Send out crystallization water inlet and carry out the first evaporative crystallization separating treatment, obtain dianion salt or univalent anion salt and the first evaporation Crystallize dense water；

Described second evaporative crystallization separative element is for by the first evaporation from described first evaporative crystallization separative element Crystallize dense water and carry out the second evaporative crystallization separating treatment, obtain univalent anion salt or dianion salt and the second evaporation knot Brilliant dense water, and described second evaporative crystallization separative element is connected for will be at least partly with described first evaporative crystallization separative element Second evaporative crystallization concentrate recirculation is to described first evaporative crystallization separative element.

Use the method and system of the present invention, realize once dividing salt by nanofiltration separation unit and Crystallization Separation unit, will Major part sodium chloride separates to nanofiltration and produces water and obtain pure salt by evaporative crystallization；Meanwhile, by using alternating temperature evaporative crystallization to divide Divide salt from evaporative crystallization water inlet (crystallizing dense water and the second evaporative crystallization dense water of backflow) is carried out secondary, significantly improve overall work The salt organic efficiency of skill.Meanwhile, the method for the present invention can be greatly reduced investment and operating cost and improve the purity of salt.

Other features and advantages of the present invention will be described in detail in detailed description of the invention part subsequently.

Accompanying drawing explanation

Fig. 1 is the schematic flow sheet of the salt extraction process of one embodiment of the present invention.

Fig. 2 is the schematic flow sheet of the salt extraction process of another embodiment of the invention.

Fig. 3 is the schematic flow sheet of the salt extraction process of comparative example 1 of the present invention.

Detailed description of the invention

Hereinafter the detailed description of the invention of the present invention is described in detail.It should be appreciated that described herein specifically Embodiment is merely to illustrate and explains the present invention, is not limited to the present invention.

The end points of scope disclosed in this article and any value are not limited to this accurate scope or value, these scopes or Value should be understood to the value comprised close to these scopes or value.For numerical range, between the endpoint value of each scope, respectively Between endpoint value and the single point value of individual scope, and can obtain one or more between single point value with combination with one another New numerical range, these numerical rangies should be considered the most specifically to disclose.

First aspect, the invention provides a kind of salt extraction process, and the method includes:

In the method for the present invention, it will be understood by those skilled in the art that pending nanofiltration separation processes containing two The brackish water of valency anion salt and univalent anion salt be Crystallization Separation process obtain, be back to nanofiltration separation process at least Partially crystallizable water outlet is mixed into feed liquid with raw water.

In the method for the present invention, for the weight/mass percentage composition of dianion salt in raw water, there is no particular limitation, Can be the common various content in this area, when in raw water dianion salt weight/mass percentage composition X% < when 5%, in order to It is capable of producing the purpose reclaiming dianion salt continuously, relational expression R1 < X/ (5-X) must be met；When bivalence in raw water During weight/mass percentage composition X%>=5% of anion salt, it is not necessary to meet relational expression R1<X/ (5-X).

In the method for the present invention, the present inventor finds the most in surprise, crystallizes the body of dense water and nanofiltration product water For whether realizing the present invention, long-pending flow-rate ratio R1 produces that to reclaim the purpose of dianion salt most important continuously, when X < when 5, Choosing of R1 is relevant to the weight/mass percentage composition X% of dianion salt in raw water, produces back continuously to realize the present invention Receive the purpose of dianion salt, it is necessary to meet relational expression R1 < X/ (5-X)；And, inventor sends out under study for action the most further Existing, in the case of meeting R1 < X/ (5-X), meet R1 < 3X/ (50-3X) further, the response rate of one-component salt is the most relatively High (> 70%).Such as, in order to improve the response rate of one-component salt further, when the quality of dianion salt in raw water During percentage composition X%=3%, crystallize dense water and nanofiltration produce the volume flow ratio R1 of water meet R1 < 3*3/ (50 3*3), i.e. R1 < 0.22；And as the weight/mass percentage composition X%=1% of dianion salt in raw water, crystallize dense water and nanofiltration and produce the body of water Long-pending flow-rate ratio R1 meets R1 < 3*1/ (50 3*1), i.e. R1 < 0.064.

The present inventor is under study for action it has further been found that the volume flow ratio R2 that water is produced in the dense water of nanofiltration and nanofiltration is Another vital parameter, in raw water dianion salt weight/mass percentage composition X% < when 5%, R2 choose with X% and the dense water of crystallization are related with the volume flow ratio R1 that water is produced in nanofiltration, produce recovery continuously to preferably realize the present invention The purpose of dianion salt also makes the method operate under suitable pressure condition, under preferable case, meets relational expression R2 > {(R1+1)*X/5–R1}.Such as, as the weight/mass percentage composition X%=3% of dianion salt in raw water, dense water is crystallized When producing the volume flow ratio R1=0.1 of water with nanofiltration, R2 > (0.1+1) * 3/5-0.1, i.e. R2 > 0.56.Meanwhile, in order to avoid because of Nanofiltration concentrated stream amount is excessive causes Crystallization Separation unit size, cost of investment and system energy consumption excessive, and R2 typically requires to be less than 4, preferably scope is R2 < 3, further preferred R2 < 1.5.

In the method for the present invention, in order to improve the separating effect of dianion salt and univalent anion salt further and return Yield, under preferable case, in step (1), on the basis of the weight of raw water, by percentage to the quality, in raw water, bivalence is cloudy The concentration of ion salt and univalent anion salt is than for 1:0.1-9, more preferably 1:0.25-4.

In the method for the present invention, in order to improve the separating effect of dianion salt and univalent anion salt further and return Yield, under preferable case, in step (1), the condition that nanofiltration separation processes includes: temperature is 10-40 DEG C, more preferably 15-30℃；Pressure is 1-6MPa, more preferably 2-4MPa.The present inventor is under study for action it has further been found that receive Filter dense water and nanofiltration to produce the volume flow of water and be compared to that energy consumption size, system investments be how many, the total tune performance of system has weight Affecting, the volume flow ratio of water is produced in the dense water of suitable nanofiltration and nanofiltration can significantly reduce energy consumption, reduces system investments, improves The total tune performance of system, therefore, in order to significantly reduce energy consumption, reduces system investments, improves the total tune performance of system, The volume flow ratio that the dense water of nanofiltration produces water with nanofiltration is preferably 0.2-3:1, more preferably 0.5-1.5:1.The present invention carries And pressure be gauge pressure.

In the method for the present invention, for nanofiltration separation process the NF membrane component requirements used have relatively low monovalence cloudy from Alite rejection, to improve dianion salt and the separating effect of univalent anion salt and the response rate, under preferable case, step (1), in, it is less than 20% to the rejection of univalent anion salt in brackish water that nanofiltration separation processes the NF membrane element used NF membrane element, such as, can be GE DL series NF membrane element, GE SWSR series NF membrane element, DOW NF270 series The NE8040-40 NF membrane element of NF membrane element or TCK company of Korea S.

In the method for the present invention, in order to improve the response rate of dianion salt further and avoid dianion salt to exist Crystallization in cooling process, under preferable case, in step (2), the method that cooling processes includes: dense for nanofiltration water is passed through heat exchange The mode processed is cooled to crystallization temperature, and described crystallization temperature is less than 5 DEG C and is higher than the freezing point temperature of the dense water of described nanofiltration, enters one Step is preferably-2～2 DEG C；And control the dense water of described nanofiltration heat exchange process in flow velocity be 1-20m/s, more preferably 2- 5m/s。

Preferably, heat exchange processes and carries out in spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger, and described The dense water of nanofiltration flows in spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger as tube side fluid, described heat exchange The thermal medium that adds processed can be steam, hot water or other thermal source.Those skilled in the art can select to change according to practical situation The concrete kind of hot device, this is well known to those skilled in the art, and does not repeats them here.

In the method for the present invention, in order to improve the response rate of dianion salt further, under preferable case, step (3) In, the condition that Crystallization Separation processes includes: temperature less than 5 DEG C and higher than the freezing point temperature of the dense water of nanofiltration, more preferably-2 ～2 DEG C.It will be understood by those skilled in the art that at said temperatures, dianion salt is such as in Crystallization Separation processes The dissolubility of sodium sulfate is relatively low, and a part of dianion salt can crystallization under supersaturation promotes.

The present inventor is under study for action it has further been found that suitably crystallize the volume flow of dense water and nanofiltration product water Ratio can significantly improve the response rate of one-component salt, therefore, in order to significantly improve the response rate of one-component salt, crystallizes dense water The volume flow ratio producing water with nanofiltration is preferably 0.02-1:1, more preferably 0.04-0.25:1.

In the method for the present invention, it is cloudy that the crystallization water outlet processed in order to avoid being back to nanofiltration separation separates out bivalence in pipeline Ion salt crystallizes and blocking pipeline, can be effectively improved the temperature being mixed into feed liquid that nanofiltration separation processes, it is ensured that nanofiltration simultaneously Separating treatment be in higher operation temperature without produce fouling, under preferable case, the method also includes: by backflow crystallization Before effluent recycling processes to nanofiltration separation, described backflow crystallization water outlet is carried out hyperthermic treatment.It is further preferred that described liter The embodiment that temperature processes is that heat exchange processes.There is no particular limitation, as long as can for the concrete operation method processed for heat exchange The temperature being back to the backflow crystallization water outlet that nanofiltration separation processes is brought up to suitable temperature so that pending nanofiltration separation processes The temperature being mixed into feed liquid meet the operation temperature that nanofiltration separation processes, this is well known to those skilled in the art, This repeats no more.Specifically, heat exchange processes to enter in spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger OK, the thermal medium that adds that described heat exchange processes can be steam, hot water or other thermal source.Those skilled in the art can be according to reality Situation selects the concrete kind of heat exchanger, and this is well known to those skilled in the art, and does not repeats them here.

In the case of process of the present invention it is preferred, dianion weight/mass percentage composition in raw water is 0.2%- 5%；It is further preferred that described dianion salt contains sodium sulfate, described univalent anion salt contains sodium chloride；More enter one Preferably, described dianion salt is sodium sulfate to step, and described univalent anion salt is sodium chloride.

It will be understood by those skilled in the art that nanofiltration separation processes and Crystallization Separation processes respectively higher and relatively low Operating under two different temperature conditionss, the operation temperature that wherein nanofiltration separation processes is 10-40 DEG C (preferably 15-30 DEG C), Dianion salt is illustrated with sodium sulfate, and now, sodium sulfate dissolubility in aqueous is higher, about 10-50g, can be right Sodium sulfate realizes effectively being concentrated into the most higher concentration range of 5-10wt% without causing it to tie at NF membrane element surface Dirt；The operation temperature that Crystallization Separation processes is that near zero is (less than 5 DEG C and higher than the freezing point temperature of the dense water of described nanofiltration, preferably For-2～2 DEG C), but it is guaranteed on the freezing point of the dense water of nanofiltration, now sodium sulfate dissolubility in aqueous is 5g or more Low, the nanofiltration dense water sufficient crystallising containing 5-10wt% even more high concentration sodium sulfate can be separated out sulfate crystal salt, makes The sodium sulfate concentration that must crystallize water outlet is reduced to about 5wt%.Nanofiltration separation process is discharged water to by being back to small part crystallization, Concentration again and the circulation crystallization of sodium sulfate can be realized, therefore can realize comparing separation and the crystallization of sodium sulfate thoroughly, And making whole operating process realize continuous operation, stable state produces salt.

In the case of process of the present invention it is preferred, in step (4), described first evaporative crystallization separating treatment and second is steamed The evaporating temperature sending out Crystallization Separation process differs more than 20 DEG C, further preferably difference 30-50 DEG C；Described first evaporative crystallization divides It is 90-110 DEG C from the evaporating temperature processed, and the evaporating temperature of described second evaporative crystallization separating treatment is 50-70 DEG C；Or The evaporating temperature of described first evaporative crystallization separating treatment is 50-70 DEG C, and the evaporation of described second evaporative crystallization separating treatment Temperature is 90-110 DEG C.

It will be understood by those skilled in the art that by controlling aforementioned temperature condition, sodium sulfate can be in operation temperature Obtaining in higher evaporative crystallization separating treatment, sodium chloride can obtain in the evaporative crystallization separating treatment that temperature is relatively low, i.e. By controlling aforementioned temperature condition, the first evaporative crystallization separating treatment can obtain sodium sulfate, the second evaporative crystallization separating treatment Sodium chloride can be obtained；Or the first evaporative crystallization separating treatment can obtain sodium chloride, and the second evaporative crystallization separating treatment can To obtain sodium sulfate.

In the case of process of the present invention it is preferred, in step (4), the described second evaporative crystallization dense water of backflow is dense with system The volume flow ratio of water is 5-100:1, more preferably 30-60:1.

In the case of process of the present invention it is preferred, in step (4), the method for described post processing includes: by dense for described system Water is evaporated crystallization, obtains containing univalent anion salt and the salt-mixture of dianion salt.

In the case of process of the present invention it is preferred, the method also includes: water and reverse osmosis are produced in nanofiltration step (1) obtained Saturating dense water carries out electrodialysis process as electrodialysis, obtains electric osmose division water and the dense water of electrodialysis；

Described electric osmose division water is carried out reverse-osmosis treated, obtains reverse osmosis produced water and reverse osmosis concentrated water, and by described instead Infiltration concentrate recirculation is to described electrodialysis process.

Preferably, the method also includes: dense for described electrodialysis water is evaporated crystallization, obtains univalent anion salt.

Preferably, the condition of electrodialysis process includes: the voltage of every pair of diaphragm is 0.4-1.2V, more preferably 0.5- 1V；The volume flow ratio of electric osmose division water and the dense water of electrodialysis is 2-50:1, more preferably 10-30:1.

Preferably, the condition of reverse-osmosis treated includes: temperature is 5-45 DEG C, more preferably 15-30 DEG C；Pressure is 1- 8MPa, more preferably 1.5-7MPa；The volume flow ratio of reverse osmosis produced water and reverse osmosis concentrated water is 1-5:1, the most excellent Elect 2-4:1 as.

In the case of process of the present invention it is preferred, the method also includes: carry out alternating temperature evaporative crystallization separating treatment it Before, the dense water of crystallization step (3) obtained is evaporated processing, and to be concentrated by dense for described crystallization water, obtains evaporating dense water, Then the dense water that dense for described evaporation water and described second evaporative crystallization refluxed carries out alternating temperature evaporative crystallization as evaporative crystallization Separating treatment.

Preferably, the concentration rate of described evaporation process is 3-5 times.

Second aspect, as shown in Figure 1 or 2, the invention provides a kind of salt making system, and this system includes: nanofiltration separation Unit, cooling unit, Crystallization Separation unit, the first evaporative crystallization separative element and the second evaporative crystallization separative element,

In the system of the present invention, the NF membrane component requirements for nanofiltration separation unit has relatively low univalent anion salt Rejection, to improve dianion salt and the separating effect of univalent anion salt and the response rate, under preferable case, nanofiltration separation Unit includes at least one NF membrane element, it is further preferred that NF membrane element is to univalent anion salt in this brackish water Rejection less than 20% NF membrane element, can be such as GE DL series NF membrane element, GE SWSR series NF membrane Element, DOWNF270 series NF membrane element or the NE8040-40 NF membrane element of TCK company of Korea S；It is further preferred that Nanofiltration separation unit includes at least two NF membrane elements being used in series.

In the system of the present invention, for cooling unit, there is no particular limitation, can be commonly used in the art various can Carrying out the cooling unit of aforementioned cooling process, under preferable case, cooling unit includes heat exchanger, it is further preferred that described in change Hot device is spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger.Those skilled in the art can be according to practical situation Selecting the concrete kind of heat exchanger, this is well known to those skilled in the art, and does not repeats them here.

In the system of the present invention, under preferable case, Crystallization Separation unit includes crystalline element and solid-liquid separation unit, described Crystalline element carries out crystallization treatment for the dense water of nanofiltration of self-cooling mono unit in the future, obtains crystallizing water outlet and crystallization solid-liquid mixing Thing, described solid-liquid separation unit, for the crystallization solidliquid mixture from crystalline element is carried out solid-liquid separation process, is tied Brilliant salt and the crystalline mother solution used as crystallization water outlet.It will be understood by those skilled in the art that the knot that crystallization treatment obtains Brilliant water outlet is identical with the crystalline mother solution component that solid-liquid separation processes, and all uses as crystallization water outlet.

For concrete crystalline element and solid-liquid separation unit, there is no particular limitation, can be commonly used in the art various Crystallization apparatus and equipment for separating liquid from solid, this is well known to those skilled in the art, and does not repeats them here.Those skilled in the art should It should be appreciated that, Crystallization Separation unit can also include built-in cooling unit, for reducing receiving of pending Crystallization Separation process Filter the temperature of dense water.

In the system of the present invention, under preferable case, described salt making system also includes intensification unit, for will be from crystallization Before at least partly crystallization water outlet of separative element is back to nanofiltration separation unit, described at least part of crystallization water outlet is risen Temperature processes.

In the system of the present invention, for intensification unit, there is no particular limitation, as long as nanofiltration separation list can will be back to The temperature of at least partly crystallization water outlet of unit brings up to suitable temperature so that what pending nanofiltration separation processed is mixed into feed liquid Temperature meets the operation temperature that nanofiltration separation processes.Under preferable case, intensification unit includes heat exchanger, further preferably Ground, heat exchanger is spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger.Those skilled in the art can be according to reality Situation selects the concrete kind of heat exchanger, and this is well known to those skilled in the art, and does not repeats them here.

In the system of the present invention, under preferable case, the first evaporative crystallization separative element includes the first crystallizing evaporator and One solid-liquid separation unit, described first crystallizing evaporator, for described evaporative crystallization is evaporated crystallization treatment, obtains The first dense water of evaporative crystallization and the first evaporative crystallization solidliquid mixture, described first solid-liquid separation unit is for will be from described the First evaporative crystallization solidliquid mixture of one crystallizing evaporator carries out solid-liquid separation process, obtains crystal salt and as the first evaporation Crystallize the evaporative crystallization mother solution that dense water uses.It will be understood by those skilled in the art that evaporative crystallization processes first obtained The dense water of evaporative crystallization is identical with the evaporative crystallization mother solution component that solid-liquid separation processes, and all uses as the first dense water of evaporative crystallization.

In the system of the present invention, under preferable case, the second evaporative crystallization separative element includes the second crystallizing evaporator and Two solid-liquid separation units, described second crystallizing evaporator is for by the first evaporation from described first evaporative crystallization separative element Crystallize dense water and be evaporated crystallization treatment, obtain the second dense water of evaporative crystallization and the second evaporative crystallization solidliquid mixture, described Two solid-liquid separation units divide for the second evaporative crystallization solidliquid mixture from described second crystallizing evaporator is carried out solid-liquid From process, obtain crystal salt and the evaporative crystallization mother solution used as the second dense water of evaporative crystallization.Those skilled in the art should Being understood by, evaporative crystallization processes the second dense water of evaporative crystallization obtained and the evaporative crystallization mother solution component phase of solid-liquid separation process With, all use as the second dense water of evaporative crystallization.

In the system of the present invention, under preferable case, this system also includes: electrodialysis cell and reverse osmosis units, described electricity Dialysis unit is for producing water and the reverse osmosis concentrated water from described reverse osmosis units by the nanofiltration from described nanofiltration separation unit Carry out electrodialysis process as electrodialysis, obtain electric osmose division water and the dense water of electrodialysis；

Described reverse osmosis units, for the electric osmose division water from described electrodialysis cell is carried out reverse-osmosis treated, obtains Reverse osmosis produced water and reverse osmosis concentrated water, and described reverse osmosis units is connected with described electrodialysis cell for by described reverse osmosis concentrated Water is back to described electrodialysis cell.

Preferably, described system also includes crystallizing evaporator, for by the dense water of electrodialysis from described electrodialysis cell It is evaporated crystallization, obtains univalent anion salt.

In the system of the present invention, under preferable case, this system also includes evaporation element, and described evaporation element is for will be from The partially crystallizable water outlet not being back to nanofiltration separation unit of described Crystallization Separation unit is evaporated processing, and obtains evaporating dense Water；

And described first evaporative crystallization separative element is for by the dense water of evaporation from described evaporation element with from described The second evaporative crystallization dense water of backflow of the second evaporative crystallization separative element carries out the first evaporative crystallization as evaporative crystallization and divides From process.

For reverse osmosis units, electrodialysis cell and evaporation element, there is no particular limitation, can be commonly used in the art Various reverse osmosis units, electrodialysis cell and evaporation element, such as reverse osmosis units can be one section of counter-infiltration system of one-level, electricity Dialysis unit can be to comprise tertiary effluent power series electrical dialysis membrane stack and corresponding aid system, and evaporation element can be evaporation Device, this is well known to the skilled person, and does not repeats them here.

Embodiment

Hereinafter will be described the present invention by embodiment, but and be not so limited the scope of the present invention.Below In embodiment, if no special instructions, the method used is method commonly used in the art.

Inductively coupled plasma (ICP) method and chromatography of ions (IC) is used to determine each component in water and content thereof.

Using synthesis brackish water analog raw material water, its component is the most as shown in Table 1 and Table 2.

Table 1

Project	Na⁺	Cl^-	SO₄ ^2-
				Unit	mg/L	mg/L	mg/L
Numerical value	10643.9	8784.2	10221.8

Table 2

Project	Na⁺	Cl^-	SO₄ ^2-
				Unit	mg/L	mg/L	mg/L
Numerical value	31771.6	42313.4	9093.5

Embodiment 1

In conjunction with Fig. 1, the present embodiment is for illustrating the salt extraction process of the present invention.

In the present embodiment use nanofiltration separation unit be include by singly prop up putamina form, its built with 6 series connection GE One section of nanofiltration system of one-level of DSL NF8040 NF membrane element；Crystallization Separation unit includes that the volume of a band heat-insulation layer is 4.0m³Rustless steel container and centrifugal separating device；Evaporation element be a heat exchange area be 5.0m²Mechanical compression type evaporation Device；First evaporative crystallization separative element includes that a heat exchange area is 1.0m²Forced-circulation evaporation crystallizer and centrifugation Device；Second evaporative crystallization separative element includes that a heat exchange area is 4.0m²Forced-circulation evaporation crystallizer and centrifugal point From device；It is 80m that electrodialysis cell comprises a total membrane area²Tertiary effluent power series electrical dialysis membrane stack and assist system accordingly System；Reverse osmosis units be include by singly prop up putamina form, its built with 6 series connection DOW BW30FR-400 reverse-osmosis membrane elements One section of counter-infiltration system of one-level.The flow of inlet water of constitutive material water is 3.67m³/ h, concrete technology flow process is as follows:

(1) it is 3.67m by flow³/ h, temperature are that the synthesis brackish water shown in table 1 of 25 DEG C is with flow as raw water 1.33m³After/h, temperature are the backflow crystallization water outlet mixing of 25 DEG C, with 5.0m³The total flow of/h, the temperature of 25 DEG C are mixed as nanofiltration Close water inlet to supply to nanofiltration separation unit, at 25 DEG C, carry out nanofiltration separation process.Wherein, nanofiltration separation unit uses part Dense water circulation operator scheme, dense water circulating load is 5.0m³/ h, the intake pressure of nanofiltration separation unit is 3.0MPa.Through nanofiltration After separative element processes, obtaining flow is 3.33m³/ h, temperature are that to produce water and flow be 1.67m for the nanofiltration of 25 DEG C³/ h, temperature are The dense water of nanofiltration of 25 DEG C.In the dense water of nanofiltration, the concentration of sodium sulfate is 7.17%.

(2) to flow be 1.67m³/ h, temperature are that the dense water of nanofiltration of 25 DEG C is cooled to 0 DEG C by spiral tube exchanger After, supply to Crystallization Separation unit carries out low temperature (0 DEG C) Crystallization Separation and processes.Due to sodium sulfate dissolubility the most drastically Reducing, part of sulfuric acid sodium separates out in Crystallization Separation unit, obtains crystallization water outlet and the crystallization solidliquid mixture of clarification, will crystallization Solidliquid mixture centrifugal separating device is centrifuged separating treatment, obtains sulfate crystal salt and (after deduction water of crystallization is 37.7kg/h) and crystalline mother solution, the crystallization water outlet that composition is identical is divided into two strands after mixing with crystalline mother solution, and one flow is 1.33m³/ h, temperature be 0 DEG C backflow crystallization water outlet and another plume amount be 0.34m³/ h, temperature are the dense water of crystallization of 0 DEG C.Will Backflow crystallization water outlet supply enters nanofiltration separation unit after mixing with raw water to step (1) and is circulated process.

(3) it is 0.34m by flow³/ h, temperature are after the dense water of crystallization of 0 DEG C is heated to 105 DEG C by tubular heat exchanger As evaporation water inlet supply to evaporation element, at 105 DEG C, it is evaporated concentration.Control the concentration rate of evaporation element extremely 5.0 times, obtaining flow is 0.27m³Water is produced in the evaporation of/h and flow is 0.07m³/ h, temperature are the dense water of evaporation of 105 DEG C.

(4) it is 0.07m by flow³/ h, temperature be the dense water of evaporation and the flow of 105 DEG C be 0.20m³/ h, temperature are 60 DEG C Second evaporative crystallization refluxes after dense water mixes and supplies to the first evaporative crystallization separative element, at 100 DEG C as evaporative crystallization water inlet Under be evaporated Crystallization Separation process.Owing to sodium sulfate reaches saturated prior to sodium chloride, part of sulfuric acid sodium separates out, and uses centrifugal point After device is centrifuged separating treatment, obtain sulfate crystal salt (for 15.2kg/h after deduction water of crystallization).Simultaneously, it is thus achieved that stream Amount is 0.06m³The distilled water of/h and flow are 0.21m³/ h, temperature are the first dense water of evaporative crystallization of 100 DEG C.

(5) it is 0.21m by flow³/ h, temperature are that the first dense water of evaporative crystallization of 100 DEG C is cooled to through tubular heat exchanger Supply after 60 DEG C to the second evaporative crystallization separative element, at 60 DEG C, be evaporated Crystallization Separation process.At this temperature, due to Sodium chloride reaches saturated prior to sodium sulfate, and partial oxidation sodium separates out, after using centrifugal separating device to be centrifuged separating treatment, To sodium chloride crystal salt (3.95kg/h).Simultaneously, it is thus achieved that flow is 0.006m³The distilled water of/h and flow are 0.204m³/ h, temperature Degree is the second dense water of evaporative crystallization of 60 DEG C.It is two strands by the second dense moisture of evaporative crystallization, will flow be wherein 0.20m³/ h's One sends the first evaporative crystallization separative element circular treatment in step (4) back to as the second evaporative crystallization dense water of backflow, will stream Amount is 0.004m³Another stock of/h is evaporated crystallization treatment as the supply of system dense water to crystallizing evaporator, is mainly wrapped Sodium chloride-containing and the salt-mixture of sodium sulfate.

(6) it is 3.33m by flow³/ h, temperature are that to produce water and flow be 1.0m for the nanofiltration of 25 DEG C³/ h, temperature are 25 DEG C anti- After permeating the mixing of dense water, with 4.33m³The total flow of/h, the temperature of 25 DEG C supply to electrodialysis cell as electrodialysis water inlet, Electrodialysis process is carried out at 25 DEG C.Wherein, the average voltage of electrodialysis cell every pair diaphragm is 0.76 volt.Through electrodialysis list After unit processes, obtaining flow is 4.0m³/ h, temperature are the electric osmose division water of 25 DEG C and flow is 0.33m³/ h, temperature are 25 DEG C The dense water of electrodialysis.The supply of dense for electrodialysis water is evaporated crystallization treatment to crystallizing evaporator, is mainly comprised sodium chloride Crystal salt.

(7) it is 4.0m by flow³/ h, temperature are that the electric osmose division water of 25 DEG C supplies to reverse osmosis units, at 25 DEG C Carry out reverse-osmosis treated.Wherein, reverse osmosis units uses part dense water circulation operator scheme, and dense water circulating load is 6.0m³/ h, instead The intake pressure of permeation unit is 1.6MPa.After reverse osmosis units processes, obtaining flow is 3.0m³/ h, temperature are 25 DEG C Reverse osmosis produced water and flow be 1.0m³/ h, temperature are the reverse osmosis concentrated water of 25 DEG C.Reverse osmosis concentrated water is sent back to step (6) exist Electrodialysis cell is circulated process.

Table 3 gives flow and the component of each material stream in embodiment 1.

Table 3

From table 3 it can be seen that the raw water that temperature is 25 DEG C contains higher sodium ion, chloride ion and sulphuric acid simultaneously Root, obtain after mix with the backflow crystallization water outlet that temperature is 25 DEG C temperature be 25 DEG C, sodium sulfate concentration be 2.42% nanofiltration mixed Closing water inlet, after being processed by nanofiltration separation, the sodium sulfate concentration of the dense water of nanofiltration obtained is 7.17%, owing to sodium sulfate is at 25 DEG C Dissolubility in Shi Shui is higher (about 30g), and the dense water of now nanofiltration is stable.The dense water of nanofiltration is after cooling, due to sulfur Acid sodium dissolubility in water when low temperature drastically reduces (being about 4.9 grams when 0 DEG C), separates out sulfur in low temperature crystallization separation process Acid sodium solid, the sodium sulfate concentration of backflow crystallization water outlet drops to 4.91%, close to saturation, reaches a kind of new stablizing State, is back to nanofiltration separation unit and is circulated process after intensification.This circular treatment makes the response rate of sodium sulfate increase Add.In the present embodiment, the response rate of the sodium sulfate of the combined system being made up of nanofiltration separation unit and Crystallization Separation unit is 67.9%.Simultaneously as use extremely low but high to divalent salts (sodium sulfate) rejection to monovalent salt (sodium chloride) rejection NF membrane, nanofiltration is produced the concentration of sodium chloride in water and, far above sodium sulfate, is beaten for the follow-up sodium chloride crystal salt obtaining purity higher Lower basis.

Simultaneously as use electrodialysis to concentrate nanofiltration product water further with the combined system of reverse osmosis so that sodium chloride Concentration produce that 1.44% water is concentrated in the dense water of electrodialysis from nanofiltration 14.2%, the correspondingly volume of sodium-chloride water solution From 3.33m³/ h reduces to 0.33m³/ h so that subsequent evaporation crystallization obtains the energy consumption of sodium chloride crystal salt and is greatly reduced 91.0%.

On the other hand, in order to improve the response rate of crystal salt further, the present embodiment does not returns for Crystallization Separation unit Stream low temperature crystallization water outlet uses evaporation element, the first evaporative crystallization separative element (100 DEG C) and the second evaporative crystallization separative element The combination evaporator crystal system of (60 DEG C) is further processed, and utilizes the solubility with temperature of sodium sulfate and sodium chloride to change Difference (in the range of 60 DEG C-100 DEG C, sodium sulfate solubility with temperature in water raises and reduces, the dissolubility of sodium chloride with The rising of temperature and raise), furthermore achieved that sodium sulfate separates with sodium chloride.In the present embodiment, tied by combination evaporator The process of crystallographic system system, has reclaimed the sodium sulfate of 27.4% and the sodium chloride of 7.43% further, so that system-wide sulphuric acid The response rate of sodium and sodium chloride is up to 95.3% and 98.4% respectively.

Embodiment 2

In conjunction with Fig. 2, the present embodiment is for illustrating the salt extraction process of the present invention.

In the present embodiment use nanofiltration separation unit be include by singly prop up putamina form, its built with 6 series connection GE One section of nanofiltration system of one-level of DSL NF8040 NF membrane element；Crystallization Separation unit includes that the volume of a band heat-insulation layer is 4.0m³Rustless steel container and centrifugal separating device；Evaporation element be a heat exchange area be 5.0m²Mechanical compression type evaporation Device；First evaporative crystallization separative element includes that a heat exchange area is 1.0m²Forced-circulation evaporation crystallizer and centrifugation Device；Second evaporative crystallization separative element includes that a heat exchange area is 1.0m²Forced-circulation evaporation crystallizer and centrifugal point From device；It is 100m that electrodialysis cell comprises a total membrane area²Tertiary effluent power series electrical dialysis membrane stack and assist accordingly System；Reverse osmosis units be include by singly prop up putamina form, its built with 6 series connection DOW SW30XHR-400i seawater reverse osmosis One section of counter-infiltration system of the one-level of membrane element.The flow of inlet water of constitutive material water is 3.67m³/ h, concrete technology flow process is as follows:

(1) it is 3.67m by flow³/ h, temperature are that the synthesis brackish water shown in table 2 of 25 DEG C is with flow as raw water 1.33m³After/h, temperature are the backflow crystallization water outlet mixing of 25 DEG C, with 5.0m³The total flow of/h, the temperature of 25 DEG C are mixed as nanofiltration Close water inlet to supply to nanofiltration separation unit, at 25 DEG C, carry out nanofiltration separation process.Wherein, nanofiltration separation unit uses part Dense water circulation operator scheme, dense water circulating load is 5.0m³/ h, the intake pressure of nanofiltration separation unit is 3.4MPa.Through nanofiltration After separative element processes, obtaining flow is 3.33m³/ h, temperature are that to produce water and flow be 1.67m for the nanofiltration of 25 DEG C³/ h, temperature are The dense water of nanofiltration of 25 DEG C.In the dense water of nanofiltration, the concentration of sodium sulfate is 6.80%.

(2) to flow be 1.67m³/ h, temperature are that the dense water of nanofiltration of 25 DEG C is cooled to 0 DEG C by spiral tube exchanger After, supply to Crystallization Separation unit carries out low temperature (0 DEG C) Crystallization Separation and processes.Due to sodium sulfate dissolubility the most drastically Reducing, part of sulfuric acid sodium separates out in Crystallization Separation unit, obtains crystallization water outlet and the crystallization solidliquid mixture of clarification, will crystallization Solidliquid mixture centrifugal separating device is centrifuged separating treatment, obtains sulfate crystal salt and (after deduction water of crystallization is 31.6kg/h) and crystalline mother solution, the crystallization water outlet that composition is identical is divided into two strands after mixing with crystalline mother solution, and one flow is 1.33m³/ h, temperature be 0 DEG C backflow crystallization water outlet and another plume amount be 0.34m³/ h, temperature are the dense water of crystallization of 0 DEG C.Will Backflow crystallization water outlet supply enters nanofiltration separation unit after mixing with raw water to step (1) and is circulated process.

(3) it is 0.34m by flow³/ h, temperature are after the dense water of crystallization of 0 DEG C is heated to 105 DEG C by tubular heat exchanger As evaporation water inlet supply to evaporation element, at 105 DEG C, it is evaporated concentration.Control the concentration rate of evaporation element extremely 3.0 times, obtaining flow is 0.23m³Water is produced in the evaporation of/h and flow is 0.11m³/ h, temperature are the dense water of evaporation of 105 DEG C.

(4) it is 0.11m by flow³/ h, temperature be the dense water of evaporation and the flow of 105 DEG C be 0.20m³/ h, temperature are 100 DEG C The second evaporative crystallization reflux to supply to the first evaporative crystallization as evaporative crystallization water inlet after dense water mix and is cooled to 60 DEG C and divide From unit, at 60 DEG C, it is evaporated Crystallization Separation processes.Owing to sodium chloride reaches saturated prior to sodium sulfate, partial oxidation sodium is analysed Go out, after using centrifugal separating device to be centrifuged separating treatment, obtain sodium chloride crystal salt (for 13.0kg/ after deduction water of crystallization h).Simultaneously, it is thus achieved that flow is 0.06m³The distilled water of/h and flow are 0.25m³/ h, temperature are that first evaporative crystallization of 60 DEG C is dense Water.

(5) it is 0.25m by flow³/ h, temperature are that the first dense water of evaporative crystallization of 60 DEG C is warming up to through tubular heat exchanger Supply after 100 DEG C to the second evaporative crystallization separative element, at 100 DEG C, be evaporated Crystallization Separation process.At this temperature, by Reaching saturated in sodium sulfate prior to sodium chloride, part of sulfuric acid sodium separates out, after using centrifugal separating device to be centrifuged separating treatment, Obtain sulfate crystal salt (5.16kg/h).Simultaneously, it is thus achieved that flow is 0.01m³The distilled water of/h and flow are 0.24m³/ h, temperature Degree is the second dense water of evaporative crystallization of 100 DEG C.It is two strands by the second dense moisture of evaporative crystallization, will flow be wherein 0.20m³/ h's One sends the first evaporative crystallization separative element circular treatment in step (4) back to as the second evaporative crystallization dense water of backflow, will stream Amount is 0.04m³Another stock of/h is evaporated crystallization treatment as the supply of system dense water to crystallizing evaporator, is mainly comprised Sodium chloride and the salt-mixture of sodium sulfate.

(6) it is 3.33m by flow³/ h, temperature are that to produce water and flow be 1.83m for the nanofiltration of 25 DEG C³/ h, temperature are 25 DEG C After reverse osmosis concentrated water mixing, with 5.16m³The total flow of/h, the temperature of 25 DEG C supply to electrodialysis cell as electrodialysis water inlet In, at 25 DEG C, carry out electrodialysis process.Wherein, the average voltage of electrodialysis cell every pair diaphragm is 0.95 volt.Through electric osmose After analysis cell processing, obtaining flow is 3.66m³/ h, temperature are the electric osmose division water of 25 DEG C and flow is 1.50m³/ h, temperature are The dense water of electrodialysis of 25 DEG C.The supply of dense for electrodialysis water is evaporated crystallization treatment to crystallizing evaporator, is mainly comprised chlorine Change the crystal salt of sodium.

(7) it is 3.66m by flow³/ h, temperature are that the electric osmose division water of 25 DEG C supplies to reverse osmosis units, at 25 DEG C Carry out reverse-osmosis treated.Wherein, reverse osmosis units uses part dense water circulation operator scheme, and dense water circulating load is 6.33m³/ h, The intake pressure of reverse osmosis units is 6.7MPa.After reverse osmosis units processes, obtaining flow is 1.83m³/ h, temperature are 25 DEG C reverse osmosis produced water and flow be 1.83m³/ h, temperature are the reverse osmosis concentrated water of 25 DEG C.Reverse osmosis concentrated water is sent back to step (6) Process it is circulated in electrodialysis cell.

Table 4 gives flow and the component of each material stream in embodiment 2.

Table 4

From table 4, it can be seen that the raw water that temperature is 25 DEG C contains higher sodium ion, chloride ion and sulphuric acid simultaneously Root, obtain after mix with the backflow crystallization water outlet that temperature is 25 DEG C temperature be 25 DEG C, sodium sulfate concentration be 2.29% nanofiltration mixed Closing water inlet, after being processed by nanofiltration separation, the sodium sulfate concentration of the dense water of nanofiltration obtained is 6.80%, owing to sodium sulfate is at 25 DEG C Dissolubility in Shi Shui is higher (about 30g), and the dense water of now nanofiltration is stable.The dense water of nanofiltration is after cooling, due to sulfur Acid sodium dissolubility in water when low temperature drastically reduces (being about 4.9 grams when 0 DEG C), separates out sulfur in low temperature crystallization separation process Acid sodium solid, the sodium sulfate concentration of backflow crystallization water outlet drops to 4.91%, close to saturation, reaches a kind of new stablizing State, is back to nanofiltration separation unit and is circulated process after intensification.This circular treatment makes the response rate of sodium sulfate increase Add.In the present embodiment, the response rate of the sodium sulfate of the combined system being made up of nanofiltration separation unit and Crystallization Separation unit is 64.1%.Simultaneously as use extremely low but high to divalent salts (sodium sulfate) rejection to monovalent salt (sodium chloride) rejection NF membrane, nanofiltration is produced the concentration of sodium chloride in water and, far above sodium sulfate, is beaten for the follow-up sodium chloride crystal salt obtaining purity higher Lower basis.

Simultaneously as use electrodialysis to concentrate nanofiltration product water further with the combined system of reverse osmosis so that sodium chloride Concentration produce that 6.96% water is concentrated in the dense water of electrodialysis from nanofiltration 15.4%, the correspondingly volume of sodium-chloride water solution From 3.33m³/ h reduces to 1.50m³/ h so that subsequent evaporation crystallization obtains the energy consumption of sodium chloride crystal salt and is greatly reduced 55.0%.

On the other hand, in order to improve the response rate of crystal salt further, the present embodiment does not returns for Crystallization Separation unit Stream low temperature crystallization water outlet uses evaporation element, the first evaporative crystallization separative element (60 DEG C) and the second evaporative crystallization separative element The combination evaporator crystal system of (100 DEG C) is further processed, and utilizes the solubility with temperature of sodium sulfate and sodium chloride to change Difference (in the range of 60 DEG C-100 DEG C, sodium sulfate solubility with temperature in water raises and reduces, the dissolubility of sodium chloride Raise with the rising of temperature), furthermore achieved that sodium sulfate separates with sodium chloride.In the present embodiment, pass through combination evaporator The process of crystal system, has reclaimed the sodium sulfate of 10.5% and the sodium chloride of 5.07% further, so that system-wide sulfur The response rate of acid sodium and sodium chloride is up to 74.6% and 95.8% respectively.

Comparative example 1

This comparative example uses flow process shown in Fig. 3, for the advance of the salt extraction process of the comparative illustration present invention.

The nanofiltration separation unit used in this comparative example is same as in Example 1；First evaporation element and the second evaporation element Being respectively heat exchange area is 60m²And 6m²Mechanical compression type vaporizer.The flow of inlet water of constitutive material water is 3.67m³/ h, tool Body technology flow process is as follows:

(1) it is 3.67m by flow³/ h, temperature are that the synthesis brackish water shown in table 1 of 25 DEG C supplies extremely as nanofiltration water inlet Nanofiltration separation unit, carries out nanofiltration separation process at 25 DEG C.Wherein, nanofiltration separation unit uses part dense water circulation operation mould Formula, dense water circulating load is 6.33m³/ h, the intake pressure of nanofiltration separation unit is 4.0MPa.Through nanofiltration separation cell processing After, obtaining flow is 3.15m³/ h, temperature are that to produce water and flow be 0.52m for the nanofiltration of 25 DEG C³/ h, temperature are that the nanofiltration of 25 DEG C is dense Water.In the dense water of nanofiltration, the concentration of sodium sulfate is 10.4%.

(2) it is 3.15m by flow³/ h, temperature are that the nanofiltration of 25 DEG C is produced after water is heated to 105 DEG C by tubular heat exchanger Supply, to the first evaporation element, is evaporated concentration at 105 DEG C.The concentration rate controlling the first evaporation element is 17 Times, obtaining flow is 2.96m³Water is produced in the condensation of/h and flow is 0.19m³/ h, temperature are the first dense water of evaporation element of 105 DEG C.

(3) it is 0.52m by flow³/ h, temperature are after the dense water of nanofiltration of 25 DEG C is heated to 105 DEG C by tubular heat exchanger Supply, to the second evaporation element, is evaporated concentration at 105 DEG C.The concentration rate controlling the second evaporation element is 2.5 Times, obtaining flow is 0.31m³Water is produced in the condensation of/h and flow is 0.21m³/ h, temperature are the second dense water of evaporation element of 105 DEG C.

(4) respectively the first dense water of evaporation element and the supply of the second evaporation element dense water are evaporated to evaporative crystallization unit Crystallization treatment, obtains two kinds of crystal salt.

Table 5 gives flow and the component of each material stream in comparative example 1.

Table 5

As can be seen from Table 5, temperature contains higher sodium ion, chloride ion and sulphuric acid in being the raw water of 25 DEG C simultaneously Root, after being processed by nanofiltration separation, the calcium sulfate degree of supersaturation of the dense water of nanofiltration obtained is 10.4% (operation pressure is close to the upper limit 4.0MPa), harsher than the service condition of embodiment 1.Separate single yet with the low temperature crystallization not introduced in embodiment 1 Unit and combination evaporator Crystallization Separation unit, salt-mixture containing sodium sulfate and sodium chloride in the dense water of nanofiltration (wherein sodium sulfate and The content of sodium chloride is respectively 87.5% and 12.5%).

In this comparative example, owing to using nanofiltration separation, it is 85.7% that the response rate of sodium chloride in water is produced in nanofiltration, far below real Executing the response rate (98.4%) of sodium chloride in example 1, and sodium sulfate is owing to obtaining with pure salt form, the response rate is 0, especially without Method compares with the high-recovery (95.3%) of sodium sulfate in embodiment 1.

Simultaneously as do not introduce electrodialysis cell to carry out reconcentration process with reverse osmosis units, this comparative example needs The water yield of evaporation is the former water yield, is 3.67m³/ h, for total evaporation (0.67m in embodiment 1³/ h) 5.5 times, evaporate energy Consumption is corresponding to be increased.

The preferred embodiment of the present invention described in detail above, but, the present invention is not limited in above-mentioned embodiment Detail, in the technology concept of the present invention, technical scheme can be carried out multiple simple variant, this A little simple variant belong to protection scope of the present invention.

It is further to note that each the concrete technical characteristic described in above-mentioned detailed description of the invention, at not lance In the case of shield, can be combined by any suitable means, in order to avoid unnecessary repetition, the present invention to various can The compound mode of energy illustrates the most separately.

Additionally, combination in any can also be carried out between the various different embodiment of the present invention, as long as it is without prejudice to this The thought of invention, it should be considered as content disclosed in this invention equally.

Claims

1. a salt extraction process, it is characterised in that the method includes:

(1) brackish water containing dianion salt and univalent anion salt is carried out nanofiltration separation process, obtain rich monovalence cloudy The dense water of nanofiltration that the nanofiltration product water of ion salt and dianion salt are concentrated；

(3) the dense water of nanofiltration after cooling step (2) obtained carries out Crystallization Separation process, obtains crystallizing water outlet and crystal salt, Be two strands by the described moisture that crystallizes out, respectively as backflow crystallization water outlet be back to nanofiltration separation described in step (1) process and Follow-up alternating temperature evaporative crystallization separating treatment is carried out as crystallizing dense water；

(4) the dense water of crystallization step (3) obtained and the second evaporative crystallization dense water of backflow carry out alternating temperature as evaporative crystallization Evaporative crystallization separating treatment, described alternating temperature evaporative crystallization separating treatment include the first evaporative crystallization separating treatment of carrying out successively and Second evaporative crystallization separating treatment, for obtaining dianion salt, univalent anion salt and second by control evaporating temperature The dense water of evaporative crystallization, is two strands by the described second dense moisture of evaporative crystallization, respectively as the second evaporative crystallization backflow concentrate recirculation To described alternating temperature evaporative crystallization separating treatment and carry out post processing as the dense water of system；

Wherein, in step (1), the described brackish water containing dianion salt and univalent anion salt includes raw water and step (3) the backflow crystallization water outlet described in；And the weight/mass percentage composition X% of dianion salt < when 5%, meets relation in raw water < X/ (5-X), R1 are the volume flow ratio crystallizing dense water with nanofiltration product water to formula R1.

Method the most according to claim 1, wherein, the method also includes: water and reverse osmosis are produced in nanofiltration step (1) obtained Saturating dense water carries out electrodialysis process as electrodialysis, obtains electric osmose division water and the dense water of electrodialysis；

Described electric osmose division water is carried out reverse-osmosis treated, obtains reverse osmosis produced water and reverse osmosis concentrated water, and by described reverse osmosis Concentrate recirculation is to described electrodialysis process；

Method the most according to claim 1 and 2, wherein, the method also includes: carrying out alternating temperature evaporative crystallization separating treatment Before, the dense water of crystallization step (3) obtained is evaporated processing, and to be concentrated by dense for described crystallization water, obtains evaporating dense Water, the dense water that then dense for described evaporation water and described second evaporative crystallization refluxed carries out alternating temperature evaporation knot as evaporative crystallization Brilliant separating treatment；

4. according to the method described in any one in claim 1-3, wherein, in step (1), dianion salt in raw water Weight/mass percentage composition X% < when 5%, R1 < 3X/ (50-3X).

5. according to the method described in any one in claim 1-4, wherein, in step (1), dianion salt in raw water Weight/mass percentage composition X%<when 5%, 4>R2>{ (R1+1) * X/5 R1}, R2 are the dense water of nanofiltration and the volume flow of water is produced in nanofiltration Ratio.

6. according to the method described in any one in claim 1-5, wherein, in step (1), with the weight of raw water as base Standard, by percentage to the quality, in raw water, the concentration of dianion salt and univalent anion salt ratio is for 1:0.1-9, is preferably 1:0.25-4；

Preferably, dianion weight/mass percentage composition in described raw water is 0.2%-5%；

Preferably, described dianion salt is sodium sulfate, and described univalent anion salt is sodium chloride.

7. according to the method described in any one in claim 1-6, wherein, in step (1), the bar that described nanofiltration separation processes Part includes: temperature is 10-40 DEG C, preferably 15-30 DEG C；Pressure is 1-6MPa, preferably 2-4MPa；The dense water of described nanofiltration and institute The volume flow ratio stating nanofiltration product water is 0.2-3:1, preferably 0.5-1.5:1.

8., according to the method described in any one in claim 1-7, wherein, in step (1), described nanofiltration separation processes and uses NF membrane element be to the rejection of univalent anion salt in described brackish water less than 20% NF membrane element.

9. according to the method described in any one in claim 1-8, wherein, in step (2), the method bag that described cooling processes Including: dense for nanofiltration water is cooled to by the way of heat exchange processes crystallization temperature, described crystallization temperature is received less than 5 DEG C and described in being higher than Filter the freezing point temperature of dense water, be preferably-2～2 DEG C；And control the dense water of described nanofiltration heat exchange process in flow velocity be 1-20m/s, It is preferably 2-5m/s；

Preferably, described heat exchange processes and carries out in spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger, and described The dense water of nanofiltration flows in spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger as tube side fluid.

10., according to the method described in any one in claim 1-9, wherein, in step (3), described Crystallization Separation processes Condition includes: temperature is less than 5 DEG C and is higher than the freezing point temperature of the dense water of nanofiltration, is preferably-2～2 DEG C.

11. according to the method described in any one in claim 1-10, and wherein, in step (3), the dense water of described crystallization is with described It is 0.02-1:1, preferably 0.04-0.25:1 that the volume flow ratio of water is produced in nanofiltration.

12. according to the method described in any one in claim 1-11, and wherein, the method also includes: by described backflow knot Before brilliant effluent recycling processes to described nanofiltration separation, described backflow crystallization water outlet is carried out hyperthermic treatment；

Preferably, the embodiment of described hyperthermic treatment is that heat exchange processes.

13. according to the method described in any one in claim 1-12, and wherein, in step (4), described first evaporative crystallization divides More than 20 DEG C are differed, preferably difference 30-50 DEG C from the evaporating temperature processed with the second evaporative crystallization separating treatment；Described first steams The evaporating temperature sending out Crystallization Separation process is 90-110 DEG C, and the evaporating temperature of described second evaporative crystallization separating treatment is 50- 70 DEG C, or the evaporating temperature of described first evaporative crystallization separating treatment is 50-70 DEG C, and at described second evaporative crystallization separation The evaporating temperature of reason is 90-110 DEG C.

14. according to the method described in any one in claim 1-13, and wherein, in step (4), described second evaporative crystallization returns The volume flow ratio flowing dense water and the dense water of system is 5-100:1, preferably 30-60:1.

15. according to the method described in any one in claim 1-14, wherein, in step (4), and the method bag of described post processing Include: dense for described system water is evaporated crystallization, obtains containing univalent anion salt and the salt-mixture of dianion salt.

16. methods according to claim 2, wherein, the condition of described electrodialysis process includes: the voltage of every pair of diaphragm is 0.4-1.2V, preferably 0.5-1V；The volume flow ratio of electric osmose division water and the dense water of electrodialysis is 2-50:1, preferably 10-30: 1。

17. according to the method described in claim 2 or 16, and wherein, the condition of described reverse-osmosis treated includes: temperature is 5-45 DEG C, preferably 15-30 DEG C；Pressure is 1-8MPa, preferably 1.5-7MPa；Reverse osmosis produced water and the volume flow of reverse osmosis concentrated water Ratio is 1-5:1, preferably 2-4:1.

18. 1 kinds of salt making systems, it is characterised in that this system includes: nanofiltration separation unit, cooling unit, Crystallization Separation unit, First evaporative crystallization separative element and the second evaporative crystallization separative element,

Described nanofiltration separation unit is for carrying out nanofiltration separation by the brackish water containing dianion salt and univalent anion salt Process, obtain the dense water of nanofiltration that water is produced in the nanofiltration of rich univalent anion salt and dianion salt is concentrated；

Described cooling unit is for carrying out cooling process, after being cooled down by the dense water of nanofiltration from described nanofiltration separation unit The dense water of nanofiltration；

Described Crystallization Separation unit, for the dense water of nanofiltration from described cooling unit is carried out Crystallization Separation process, is crystallized Water outlet and crystal salt, and described Crystallization Separation unit is connected with described nanofiltration separation unit and returns at least partially crystallized water outlet It flow to described nanofiltration separation unit；

Described first evaporative crystallization separative element is not for being back to nanofiltration separation unit from described Crystallization Separation unit Partially crystallizable water outlet and from described second evaporative crystallization separative element second evaporative crystallization reflux dense water as evaporation knot Crystalline substance carries out the first evaporative crystallization separating treatment, obtains dianion salt or univalent anion salt and the first evaporative crystallization Dense water；

Described second evaporative crystallization separative element is for by the first evaporative crystallization from described first evaporative crystallization separative element Dense water carries out the second evaporative crystallization separating treatment, obtains univalent anion salt or dianion salt and the second evaporative crystallization is dense Water, and described second evaporative crystallization separative element is connected for by least part of second with described first evaporative crystallization separative element Evaporative crystallization concentrate recirculation is to described first evaporative crystallization separative element.

19. salt making systems according to claim 18, wherein, this system also includes: electrodialysis cell and reverse osmosis units,

Described electrodialysis cell is for producing water and from described reverse osmosis units by the nanofiltration from described nanofiltration separation unit Reverse osmosis concentrated water carries out electrodialysis process as electrodialysis, obtains electric osmose division water and the dense water of electrodialysis；

Described reverse osmosis units, for the electric osmose division water from described electrodialysis cell is carried out reverse-osmosis treated, obtains reverse osmosis Thoroughly produce water and reverse osmosis concentrated water, and described reverse osmosis units is connected for being returned by described reverse osmosis concentrated water with described electrodialysis cell It flow to described electrodialysis cell；

Preferably, described system also includes crystallizing evaporator, for being carried out by the dense water of electrodialysis from described electrodialysis cell Evaporative crystallization, obtains univalent anion salt.

20. according to the salt making system described in claim 18 or 19, and wherein, this system also includes evaporation element, described evaporation list Unit is used for being evaporated the partially crystallizable water outlet not being back to nanofiltration separation unit from described Crystallization Separation unit processing, Obtain evaporating dense water；

And described first evaporative crystallization separative element is for by the dense water of evaporation from described evaporation element with from described second The second evaporative crystallization dense water of backflow of evaporative crystallization separative element is carried out at the first evaporative crystallization separation as evaporative crystallization Reason.

21. according to the salt making system described in any one in claim 18-20, wherein, described nanofiltration separation unit include to A few NF membrane element, described NF membrane element is less than 20% to the rejection of univalent anion salt in described brackish water NF membrane element；

Preferably, described nanofiltration separation unit includes at least two NF membrane elements being used in series.

22. according to the salt making system described in any one in claim 18-21, and wherein, described cooling unit includes heat exchanger, Preferably, described heat exchanger is spiral tube exchanger, tubular heat exchanger or double pipe heat exchanger.

23. according to the salt making system described in any one in claim 18-22, and wherein, described Crystallization Separation unit includes knot Brilliant unit and solid-liquid separation unit,

Described crystalline element, for the dense water of nanofiltration from described cooling unit is carried out crystallization treatment, obtains crystallizing water outlet and knot Brilliant solidliquid mixture,

Described solid-liquid separation unit, for the crystallization solidliquid mixture from described crystalline element is carried out solid-liquid separation process, obtains To crystal salt with as crystallizing the crystalline mother solution that water outlet uses.

24. according to the salt making system described in any one in claim 18-23, and wherein, described system also includes intensification unit, For before at least partly crystallization water outlet from described Crystallization Separation unit is back to described nanofiltration separation unit, by institute State at least partly crystallization water outlet and carry out hyperthermic treatment；

Preferably, described intensification unit includes heat exchanger, it is further preferred that described heat exchanger is spiral tube exchanger, tubulation Formula heat exchanger or double pipe heat exchanger.

25. according to the salt making system described in any one in claim 18-24, and wherein, described first evaporative crystallization separates single Unit includes the first crystallizing evaporator and the first solid-liquid separation unit,

Described first crystallizing evaporator, for described evaporative crystallization is evaporated crystallization treatment, obtains the first evaporative crystallization Dense water and the first evaporative crystallization solidliquid mixture,

Described first solid-liquid separation unit is for by the first evaporative crystallization solidliquid mixture from described first crystallizing evaporator Carry out solid-liquid separation process, obtain crystal salt and the evaporative crystallization mother solution used as the first dense water of evaporative crystallization.

26. salt making systems according to claim 25, wherein, described second evaporative crystallization separative element includes the second evaporation Crystallizer and the second solid-liquid separation unit,

Described second crystallizing evaporator is for entering the first dense water of evaporative crystallization from described first evaporative crystallization separative element Row evaporative crystallization processes, and obtains the second dense water of evaporative crystallization and the second evaporative crystallization solidliquid mixture,

Described second solid-liquid separation unit is for by the second evaporative crystallization solidliquid mixture from described second crystallizing evaporator Carry out solid-liquid separation process, obtain crystal salt and the evaporative crystallization mother solution used as the second dense water of evaporative crystallization.