CN106430771B - salt separation system and salt separation method - Google Patents
salt separation system and salt separation method Download PDFInfo
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- CN106430771B CN106430771B CN201610617684.9A CN201610617684A CN106430771B CN 106430771 B CN106430771 B CN 106430771B CN 201610617684 A CN201610617684 A CN 201610617684A CN 106430771 B CN106430771 B CN 106430771B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/048—Purification of waste water by evaporation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
- C02F1/60—Silicon compounds
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F2001/5218—Crystallization
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Abstract
the invention discloses a salt separation system and a salt separation method. The salt separation system of the invention comprises: a nanofiltration device for separating a first concentrate entering from an inlet of the nanofiltration device into a first dialysate in which the content of monovalent anions is higher than the content of divalent anions and a second concentrate in which the content of divalent anions is higher than the content of monovalent anions; the first evaporative crystallization device is connected with a first outlet of the nanofiltration device and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions; and the second evaporative crystallization device is connected with a second outlet of the nanofiltration device and is used for evaporating and crystallizing the second concentrated solution to obtain the salt containing the divalent anions. The salt separation method adopts the salt separation system, and comprises the following steps: a nanofiltration step, a first evaporative crystallization step and a second evaporative crystallization step.
Description
Technical Field
the invention belongs to the field of coal chemical industry sewage treatment, and particularly relates to a salt separation system and a salt separation method.
background
With the increasing severity of domestic environmental pollution and the shortage of water resources in China, the coal chemical industry sewage discharge technology is more and more paid attention.
After the treatment of anoxic/aerobic (A/O) biochemical treatment, flocculation precipitation, ultrafiltration, reverse osmosis and the like, the recovery rate of the coal chemical industry sewage can reach 90 percent, and how to treat the residual 10 percent of concentrated brine becomes the technical bottleneck of the coal chemical industry sewage discharge process.
The common method for treating the coal chemical industry strong brine comprises the following steps: an efflux method, an evaporation pond method and a multi-effect evaporation method. Wherein, the direct discharge of the waste liquid by the discharge method not only causes secondary pollution of the environment, but also wastes a large amount of resources; the evaporation pond method has high requirements on regions and seasons, and wastes a large amount of resources because wastes at the later stage are difficult to treat; the multiple-effect evaporation method is characterized in that strong brine is evaporated and crystallized through a plurality of multiple-effect evaporation tanks, the obtained solid components are complex, only solid waste treatment can be carried out, the utilization rate of water is low, resource recycling is not realized, and a large amount of resources are wasted.
At present, there is a method for preparing industrial salt by separating, evaporating and crystallizing strong brine in coal chemical industry, and the specific process flow is as follows: firstly, introducing coal chemical industry strong brine added with lime milk, coagulant and magnesium agent into a clarification tank or a coagulating sedimentation tank for chemical precipitation treatment to obtain strong brine after chemical precipitation; then adjusting the pH value of the strong brine to be neutral, and removing carbonate in the strong brine through a stripping device; then the dialysate enters an ultrafiltration device, the dialysate produced by ultrafiltration enters a nanofiltration device, and the dialysate produced by nanofiltration only leaves low-valent ions; and finally, evaporating and crystallizing dialysate produced by nanofiltration to obtain sodium chloride crystals, and drying to obtain the industrial salt.
the method has the following defects: the method does not treat the concentrated water produced by ultrafiltration and the concentrated water produced by nanofiltration, and does not really realize zero discharge of the coal chemical industry wastewater; the method only extracts chloride in the concentrated brine, does not extract sulfate and nitrate in the concentrated brine, and does not deeply utilize resources, thereby wasting partial resources; the precipitated sludge obtained by the method by using the lime milk, the coagulant and the magnesium agent has complex components and is not easy to treat; the method has low water recovery rate and wastes partial resources; the evaporation crystallization has higher water quantity, so that the evaporation crystallization cost is higher; the process does not mention the treatment of soluble silicon in concentrated brine.
Disclosure of Invention
The invention provides a salt separation system and a salt separation method, which solve the problems that different salts cannot be effectively separated, the resource is wasted, and the evaporation crystallization cost is high in the prior art.
according to an aspect of the present invention, there is provided a salt separation system, the system comprising:
a nanofiltration device for separating a first concentrate entering from an inlet of the nanofiltration device into a first dialysate, in which a content of monovalent anions is higher than a content of divalent anions, and a second concentrate, in which a content of divalent anions is higher than the content of monovalent anions;
the first evaporative crystallization device is connected with a first outlet of the nanofiltration device and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions;
and the second evaporative crystallization device is connected with a second outlet of the nanofiltration device and is used for evaporating and crystallizing the second concentrated solution to obtain the salt containing the divalent anions.
Optionally, according to the salt separation system of the present invention, the first evaporative crystallization device is a multi-effect evaporator or an MVR evaporator.
optionally, according to the salt separation system of the present invention, the second evaporative crystallization device is a multi-effect evaporator or an MVR evaporator.
Optionally, according to the salt separation system of the present invention, the system further comprises:
And the high-pressure reverse osmosis device is arranged between the nanofiltration device and the first evaporative crystallization device and is used for carrying out high-pressure reverse osmosis treatment on the first dialysate to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device.
optionally, according to the salt separation system of the present invention, the system further comprises:
the flue gas circulating evaporation device is arranged between the nanofiltration device and the second evaporative crystallization device and is used for concentrating the second concentrated solution into a fourth concentrated solution;
and the first filtering device is arranged between the flue gas circulation evaporation device and the second evaporation crystallization device and is used for filtering solid impurities in the fourth concentrated solution.
And the ion exchange device is arranged between the first filtering device and the second evaporative crystallization device and is used for adjusting the hardness of the fourth concentrated solution.
optionally, according to the salt separation system of the present invention, the system further comprises:
A chemical silicon removal device arranged between the nanofiltration device and the second evaporative crystallization device and used for removing soluble silicon in the second concentrated solution;
and the second filtering device is arranged between the chemical silicon removal device and the second evaporative crystallization device and is used for filtering out insoluble solid substances in the second concentrated solution.
According to another aspect of the present invention, there is provided a salt separation method using the salt separation system of the present invention, the salt separation system comprising: the device comprises a nanofiltration device, a first evaporative crystallization device and a second evaporative crystallization device; and the number of the first and second groups,
The method comprises the following steps:
And (3) nanofiltration: treating the first concentrated solution in the nanofiltration device, and separating to obtain a first dialysate and a second concentrated solution, wherein the content of the monovalent anions in the first dialysate is higher than that of the divalent anions, and the content of the divalent anions in the second concentrated solution is higher than that of the monovalent anions;
A first evaporative crystallization step: carrying out evaporative crystallization on the first dialysate in the first evaporative crystallization device to obtain a salt containing monovalent anions;
A second evaporation crystallization step: and carrying out evaporative crystallization on the second concentrated solution in the second evaporative crystallization device to obtain a salt containing divalent anions.
Optionally, according to the salt separation method provided by the invention, the salt separation system adopted by the method further comprises a high-pressure reverse osmosis device, and the high-pressure reverse osmosis device is arranged between the nanofiltration device and the first evaporative crystallization device; and
The method also comprises a high-pressure reverse osmosis step between the nanofiltration step and the first evaporative crystallization step: and carrying out high-pressure reverse osmosis treatment on the first dialysate through the high-pressure reverse osmosis device to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device.
Optionally, according to the salt separation method of the present invention, the salt separation system adopted by the method further includes: the flue gas circulating evaporation device is arranged between the nanofiltration device and the second evaporative crystallization device; the first filtering device is arranged between the circulating evaporation device and the second evaporation crystallization device; the ion exchange device is arranged between the first filtering device and the second evaporative crystallization device; and
The method further comprises the following steps:
Flue gas circulating evaporation: the second concentrated solution is in circulating contact with hot flue gas through the flue gas circulating evaporation device to exchange heat, and the second concentrated solution is concentrated into a fourth concentrated solution;
Solid impurity filtering: filtering solid impurities in the fourth concentrated solution by the filtering device;
And (3) hardness adjustment: and adjusting the hardness of the fourth concentrated solution in the ion exchange device.
Optionally, according to the salt separation method of the present invention, the salt separation system adopted by the method further includes: a chemical silicon removal device arranged between the nanofiltration device and the second evaporative crystallization device; the second filtering device is arranged between the chemical silicon removal device and the second evaporative crystallization device; and the number of the first and second groups,
the method comprises the following steps:
Chemical silicon removal: passing said second concentrate through said chemical desiliconization apparatus to remove soluble silicon from said second concentrate;
And (3) filtering: and removing solid insoluble substances in the second concentrated solution after the silicon removal in the second filtering device.
The invention has the following beneficial effects:
according to the salt separation system, monovalent anions and divalent anions in the coal chemical industry strong brine can be separated, monovalent salts and divalent salts in the coal chemical industry strong brine are purified, the monovalent salts and the divalent salts obtained through evaporation and crystallization reach the industrial level, zero discharge and resource recycling of the coal chemical industry wastewater are realized, and resources are saved; the water in the strong brine can be recovered, so that resource recycling is realized, water resources are saved, the water amount during evaporation crystallization is reduced, and the investment cost of evaporation crystallization is saved; in addition, the flue gas with low cost is utilized to remove soluble silicon in the strong brine, so that the scaling of an evaporation crystallizer is prevented, the operation of the evaporation crystallizer is stable, and the service life of the evaporation crystallizer is prolonged; on the other hand, the purity of the monovalent salt and the divalent salt obtained by evaporative crystallization is improved.
according to the salt separation method, the salt separation system is adopted, monovalent anions and divalent anions in the coal chemical industry strong brine can be separated, and monovalent salts and divalent salts in the coal chemical industry strong brine are purified, so that the monovalent salts and the divalent salts obtained through evaporation and crystallization reach the industrial level, zero emission and resource recycling of the coal chemical industry wastewater are realized, and resources are saved; the water in the strong brine can be recycled, so that resource recycling is realized, water resources are saved, the water quantity during evaporation and crystallization is reduced, and the evaporation and crystallization cost is saved; in addition, the flue gas with low cost is used for removing soluble silicon in the concentrated brine, and the purity of monovalent salt and divalent salt obtained by evaporation crystallization is improved.
Drawings
FIG. 1 is a salt separation system according to one embodiment of the present invention;
FIG. 2 is a salt separation system according to one embodiment of the present invention;
FIG. 3 is a salt separation system according to one embodiment of the present invention;
FIG. 4 is a salt separation system according to one embodiment of the present invention;
FIG. 5 is a flow diagram of a method for salt separation according to one embodiment of the present invention;
FIG. 6 is a flow diagram of a method for salt separation according to one embodiment of the present invention;
FIG. 7 is a flow diagram of a method for salt separation according to one embodiment of the present invention;
FIG. 8 is a flow diagram of a salt separation method according to one embodiment of the present invention.
the reference signs are:
The device comprises a nanofiltration device 1, a first evaporative crystallization device 2, a second evaporative crystallization device 3, a high-pressure reverse osmosis device 4, a flue gas circulation evaporation device 5, a first filtering device 6, an ion exchange device 7, a chemical silicon removal device 8 and a second filtering device 9.
Detailed Description
The embodiments are merely illustrative of the invention and should not be construed as limiting the scope of the invention, which is further illustrated and described in connection with the accompanying drawings and detailed description.
According to an aspect of the present invention, there is provided a salt separation system, as shown in fig. 1, comprising:
a nanofiltration device 1 for separating a first concentrate entering from an inlet of the nanofiltration device into a first dialysate, in which the content of monovalent anions is higher than the content of divalent anions, and a second concentrate, in which the content of divalent anions is higher than the content of monovalent anions;
The first evaporative crystallization device 2 is connected with a first outlet of the nanofiltration device 1, and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions;
and the second evaporative crystallization device 3, the second evaporative crystallization device 3 is connected with a second outlet of the nanofiltration device 1 and is used for evaporating and crystallizing the second concentrated solution to obtain the salt containing the divalent anions.
according to the salt separating system of the present invention, the nanofiltration device 1 is mainly used for separating the first concentrated solution into the first dialyzed solution and the second concentrated solution, and the silicon and organic matters in the first concentrated solution are filtered into the second concentrated solution, wherein the amount of the organic matters is represented by Chemical Oxygen Demand (COD), and the COD is the amount of reducing substances (generally organic matters) to be oxidized in a water sample measured by a chemical method, wherein the content of monovalent anions in the first dialyzed solution is higher than that of divalent anions, and the content of divalent anions in the second concentrated solution is higher than that of monovalent anions.
The first evaporative crystallization device 2 carries out evaporative crystallization on the first dialysate to obtain monovalent salts (such as sodium chloride and sodium nitrate) with higher purity; the second evaporative crystallization device carries out evaporative crystallization on the second concentrated solution to obtain divalent salt (such as sulfate) with higher purity.
according to the salt separation system, monovalent salt (such as sodium chloride and sodium nitrate) and divalent salt (such as sodium sulfate) with higher purity are obtained, so that resource recycling is realized, and the problem of resource waste is solved.
according to one embodiment of the salt separation system of the present invention, the first evaporative crystallization device is a multiple effect evaporator or MVR evaporator.
according to the salt separation system, when the first evaporative crystallization device adopts a multi-effect evaporator and the salt obtained by evaporative crystallization is sodium chloride and sodium nitrate, the sodium chloride crystal can be crystallized by the first n-effect (for example, n is 1 or 2) and the sodium nitrate crystal can be crystallized by the second n-effect (n is 3 or 4), so that the sodium chloride crystal and the sodium nitrate crystal are separated, and the sodium chloride crystal and the sodium nitrate crystal with higher purity are obtained.
The first evaporative crystallization device can select a multi-effect evaporator or an MVR evaporator, and only the heating modes of the first evaporative crystallization device and the MVR evaporator are different.
According to one embodiment of the salt separation system of the present invention, the second evaporative crystallization device is a multiple effect evaporator or an MVR evaporator.
the second evaporative crystallization device adopts a multi-effect evaporator, so that first n effects (for example, n is 1 or 2) can crystallize out one divalent salt, and then n effects (n is 3 or 4) can crystallize out another divalent salt, so that a plurality of divalent salts can be separated, and divalent salt crystals with higher purity can be obtained.
the second evaporative crystallization device can also select an MVR evaporator, and the heating modes of the second evaporative crystallization device and the MVR evaporator are different.
According to the salt separating system of the present invention, as shown in fig. 2, the system further comprises:
And the high-pressure reverse osmosis device 4 is arranged between the nanofiltration device 1 and the first evaporative crystallization device 2, and is used for performing high-pressure reverse osmosis treatment on the first dialysate to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device 2.
according to the salt separation system, the first dialysate is treated by the high-pressure reverse osmosis device 4 to obtain the second dialysate and the third concentrated solution, wherein the second dialysate is clear water which can be used as water for a circulating water supplementing system, so that water resources are saved, the amount of water required to be evaporated when the second concentrated solution is evaporated and crystallized is reduced, and the cost of evaporation and crystallization is reduced.
In one embodiment of the salt separation system according to the present invention, as shown in fig. 3, the system further comprises:
the flue gas circulating evaporation device 5 is arranged between the nanofiltration device 1 and the second evaporative crystallization device 3, and is used for concentrating the second concentrated solution into a fourth concentrated solution;
And the first filtering device 6 is arranged between the flue gas circulation evaporation device 5 and the second evaporation crystallization device 3, and is used for filtering solid impurities in the fourth concentrated solution.
And the ion exchange device 7 is arranged between the first filtering device 6 and the second evaporative crystallization device 3, and is used for adjusting the hardness of the fourth concentrated solution.
according to the salt separating system of the invention, the flue gas circulation evaporation device 5 comprises: a flue gas evaporation tower and a flue gas evaporation circulation pool; flue gas enters from a gas inlet of the flue gas evaporation tower, the temperature of the gas inlet is more than 100 ℃, a second concentrated solution is sprayed on the flue gas evaporation tower to contact with the flue gas for heat exchange, the second concentrated solution is evaporated, and the flue gas is discharged from a gas outlet of the flue gas evaporation tower; the evaporated second concentrated solution is discharged from a liquid outlet of the flue gas evaporation tower and enters a flue gas evaporation circulation pool, the temperature of the second concentrated solution is 40-50 ℃, meanwhile, due to acid gases such as carbon dioxide and sulfur dioxide in the flue gas, the pH value of the second concentrated solution entering the flue gas evaporation circulation pool is reduced to 7-8, the content of silicon in the second concentrated solution is reduced to 140-190 mg/L and the hardness is 700mg/L under the temperature and the pH value, wherein the hardness comprises magnesium hardness and calcium hardness, and after the content of silicon is reduced to 140-190 mg/L, the content of silicon does not influence the evaporation and crystallization steps; and the second concentrated solution in the flue gas evaporation circulating pool enters the flue gas evaporation tower again to continue to contact and exchange heat, and finally, a saturated fourth concentrated solution is obtained. 15-25% of the volume of the second concentrated solution can be evaporated in the process of contacting and heat exchanging the second concentrated solution with the flue gas, so that the investment cost in evaporation and crystallization can be reduced; conveying the insoluble silicon settled at the bottom of the circulating tank to a filter press by using a sludge pump, and pressing into a mud cake; adjusting the pH value of the fourth concentrated solution discharged from the outlet of the circulating evaporation device to 4.0-4.4 by using sulfuric acid; then filtering solid impurities in the fourth concentrated solution by a first filtering device 6, wherein the filtering device can be a multi-medium filter or a sand filter; the fourth concentrated solution with solid impurities filtered is passed through an ion exchange device 7, and the hardness of the fourth concentrated solution is adjusted, mainly calcium ions and/or magnesium ions are adsorbed in the fourth concentrated solution.
In another embodiment of the salt separating system according to the present invention, as shown in fig. 4, the system further includes:
A chemical silicon removal device 8, wherein the chemical silicon removal device 8 is arranged between the nanofiltration device and the second evaporative crystallization device 3 and is used for removing soluble silicon in the second concentrated solution;
And the second filtering device 9 is arranged between the chemical silicon removal device 8 and the second evaporative crystallization device 3 and is used for filtering solid insoluble substances in the second concentrated solution.
a chemical silicon removal device is adopted in the system, and the second concentrated solution is adjusted to be neutral or slightly alkaline so as to remove soluble silicon; then, a coagulant and a flocculant are added to the second concentrated solution to adsorb the removed silicon, and the silicon is precipitated. And (3) enabling the supernatant after precipitation to enter a second filtering device 9 to filter out insoluble solids, and enabling the filtered solution to enter a second evaporative crystallization device 3 for evaporative crystallization.
according to another aspect of the present invention, there is provided a salt separation method according to the present invention, the salt separation system comprising: the device comprises a nanofiltration device, a first evaporative crystallization device and a second evaporative crystallization device; and the number of the first and second groups,
And, the method comprises the steps of:
And (3) nanofiltration: treating the first concentrated solution in a nanofiltration device, and separating to obtain a first dialysate and a second concentrated solution, wherein the content of monovalent anions in the first dialysate is higher than that of divalent anions, and the content of divalent anions in the second concentrated solution is higher than that of monovalent anions;
A first evaporative crystallization step: carrying out evaporative crystallization on the first dialysate in a first evaporative crystallization device to obtain a salt containing monovalent anions;
A second evaporation crystallization step: and (4) carrying out evaporative crystallization on the second concentrated solution in a second evaporative crystallization device to obtain the salt containing the divalent anions.
According to the salt separation method, in the nanofiltration step, the operating pressure of the nanofiltration device is controlled to be about 2.0 Mpa; the water hardness of the first concentrated solution entering the nanofiltration device is below 10mg/L, the pH value is 8-11, and when the pH value is 8-11, the solubility of silicon in the first concentrated solution is good, so that the damage to the nanofiltration membrane is small; the nanofiltration step can separate the concentrate into a first dialysate and a second concentrate, and remove silicon and organic substances from the first concentrate.
According to the salt separation method, the salt separation system provided by the invention is adopted, and monovalent salt (such as sodium chloride and sodium nitrate) with higher purity and divalent salt (such as sodium sulfate) with higher purity are obtained through the nanofiltration device, the first evaporative crystallization device and the second evaporative crystallization device, so that the resource recycling is realized, and the problem of resource waste is solved.
according to one embodiment of the salt separation method, the salt separation system adopted by the method further comprises a high-pressure reverse osmosis device, and the high-pressure reverse osmosis device is arranged between the nanofiltration device and the first evaporative crystallization device; and
the method also comprises a high-pressure reverse osmosis step between the nanofiltration step and the first evaporative crystallization step: and (3) carrying out high-pressure reverse osmosis treatment on the first dialysate through a high-pressure reverse osmosis device to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device.
according to the salt separation method, the first dialysate is subjected to high-pressure reverse osmosis treatment to obtain not only the third concentrated solution, but also the second dialysate, and the second dialysate has good water quality and can be used as supplementary water for circulating water of a system, so that water resources are saved; meanwhile, the water amount of the third concentrated solution during evaporative crystallization is reduced, and the evaporative crystallization cost is reduced.
According to an embodiment of the salt separation method of the present invention, the salt separation system adopted in the method further comprises: the flue gas circulating evaporation device is arranged between the nanofiltration device and the second evaporative crystallization device; the filtering device is arranged between the circulating evaporation device and the second evaporation crystallization device; the ion exchange device is arranged between the filtering device and the second evaporative crystallization device; and
the method further comprises the following steps:
Flue gas circulating evaporation: the second concentrated solution is in circulating contact with hot flue gas through a flue gas circulating evaporation device to exchange heat, and the second concentrated solution is concentrated into a fourth concentrated solution;
solid impurity filtering: filtering the fourth concentrated solution by a filtering device to remove solid impurities in the fourth concentrated solution;
and (3) hardness adjustment: and (4) carrying out hardness adjustment on the fourth concentrated solution in an ion exchange device.
According to the salt separation method, 15-25% of the volume of the second concentrated solution can be evaporated in the circulating evaporation step, so that the cost for evaporation and crystallization can be reduced; in addition, silicon contained in the second concentrated solution can be effectively filtered.
According to an embodiment of the salt separation method of the present invention, the salt separation system adopted in the method further comprises: the chemical silicon removal device is arranged between the nanofiltration device and the second evaporative crystallization device; the second filtering device is arranged between the chemical silicon removal device and the second evaporative crystallization device; and the number of the first and second groups,
The method comprises the following steps:
chemical silicon removal: passing the second concentrated solution through a chemical silicon removal device to remove soluble silicon in the second concentrated solution;
and (3) filtering: and removing solid insoluble substances in the second concentrated solution after the silicon removal in a second filtering device.
In the method, in the step of chemical silicon removal, the second concentrated solution is adjusted to be neutral or slightly alkaline, so that soluble silicon is removed; then, a coagulant and a flocculant are added to the second concentrated solution to adsorb the removed silicon, and the silicon is precipitated. And enabling the supernatant after precipitation to enter a second filtering device for filtering so as to remove insoluble solids, and enabling the filtered solution to enter a second evaporative crystallization device for evaporative crystallization.
it can be seen that the liquid separating system and the liquid separating method according to the present invention have many optional factors, and different embodiments can be combined according to the claims of the present invention, but the embodiments according to the present invention are only used for illustrating the present invention and do not limit the present invention. The method of separating liquids according to the invention will now be described by way of example.
example 1
a salt separation method using a salt separation system according to the present invention, the system comprising: a nanofiltration device 1 for separating a first concentrate entering from an inlet of the nanofiltration device into a first dialysate and a second concentrate; the first evaporative crystallization device 2 is connected with a first outlet of the nanofiltration device 1, and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions; and the second evaporative crystallization device 3, the second evaporative crystallization device 3 is connected with a second outlet of the nanofiltration device 1 and is used for evaporating and crystallizing the second concentrated solution to obtain the salt containing the divalent anions.
and, as shown in fig. 5, the method comprises: a nanofiltration step S1: treating the first concentrated solution in a nanofiltration device, and separating to obtain a first dialysate and a second concentrated solution, wherein the content of monovalent anions in the first dialysate is higher than that of divalent anions, and the content of divalent anions in the second concentrated solution is higher than that of monovalent anions; first evaporative crystallization step S2: carrying out evaporative crystallization on the first dialysate in a first evaporative crystallization device to obtain a salt containing monovalent anions; second evaporative crystallization step S3: and (4) carrying out evaporative crystallization on the second concentrated solution in a second evaporative crystallization device to obtain the salt containing the divalent anions.
example 2
a salt separation method using the salt separation system according to the present invention, a nanofiltration device 1 for separating a first concentrate, which enters from an inlet of the nanofiltration device, into a first dialysate in which a content of monovalent anions is higher than a content of divalent anions and a second concentrate in which a content of divalent anions is higher than the content of monovalent anions; the first evaporative crystallization device 2 is connected with a first outlet of the nanofiltration device 1, and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions; the second evaporative crystallization device 3 is connected with a second outlet of the nanofiltration device 1 and is used for evaporating and crystallizing the second concentrated solution to obtain salt containing divalent anions; the system further comprises: and the high-pressure reverse osmosis device 4 is arranged between the nanofiltration device 1 and the first evaporative crystallization device 2.
And, as shown in fig. 6, the method comprises: a nanofiltration step S1: treating the first concentrated solution in a nanofiltration device, and separating to obtain a first dialysate and a second concentrated solution, wherein the content of monovalent anions in the first dialysate is higher than that of divalent anions, and the content of divalent anions in the second concentrated solution is higher than that of monovalent anions; first evaporative crystallization step S2: carrying out evaporative crystallization on the first dialysate in a first evaporative crystallization device to obtain a salt containing monovalent anions; second evaporative crystallization step S3: evaporating and crystallizing the second concentrated solution in a second evaporation and crystallization device to obtain a salt containing divalent anions; the method also comprises a high-pressure reverse osmosis step S4 between the nanofiltration step and the first evaporative crystallization step: and (3) carrying out high-pressure reverse osmosis treatment on the first dialysate through a high-pressure reverse osmosis device to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device.
Example 3
A salt separation method using the salt separation system according to the present invention, a nanofiltration device 1 for separating a first concentrate, which enters from an inlet of the nanofiltration device, into a first dialysate in which a content of monovalent anions is higher than a content of divalent anions and a second concentrate in which a content of divalent anions is higher than the content of monovalent anions; the first evaporative crystallization device 2 is connected with a first outlet of the nanofiltration device 1, and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions; the second evaporative crystallization device 3 is connected with a second outlet of the nanofiltration device 1 and is used for evaporating and crystallizing the second concentrated solution to obtain salt containing divalent anions; the system further comprises: and the high-pressure reverse osmosis device 4 is arranged between the nanofiltration device 1 and the first evaporative crystallization device 2. The system further comprises: the flue gas circulating evaporation device 5 is arranged between the nanofiltration device and the second evaporative crystallization device and is used for concentrating the second concentrated solution into a fourth concentrated solution; the first filtering device 6 is arranged between the flue gas circulating evaporation device and the second evaporation crystallization device and is used for filtering solid impurities in the fourth concentrated solution; and the ion exchange device 7 is arranged between the first filtering device and the second evaporative crystallization device and is used for adjusting the hardness of the fourth concentrated solution.
And, as shown in fig. 7, the method comprises: a nanofiltration step S1: treating the first concentrated solution in a nanofiltration device, and separating to obtain a first dialysate and a second concentrated solution, wherein the content of monovalent anions in the first dialysate is higher than that of divalent anions, and the content of divalent anions in the second concentrated solution is higher than that of monovalent anions; first evaporative crystallization step S2: carrying out evaporative crystallization on the first dialysate in a first evaporative crystallization device to obtain a salt containing monovalent anions; second evaporative crystallization step S3: evaporating and crystallizing the second concentrated solution in a second evaporation and crystallization device to obtain a salt containing divalent anions; the method also comprises a high-pressure reverse osmosis step S4 between the nanofiltration step and the first evaporative crystallization step: and (3) carrying out high-pressure reverse osmosis treatment on the first dialysate through a high-pressure reverse osmosis device to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device.
The method further comprises the following steps: flue gas circulating and evaporating step S5: the second concentrated solution is in circulating contact with hot flue gas through a flue gas circulating evaporation device to exchange heat, and the second concentrated solution is concentrated into a fourth concentrated solution; s6 solid impurity filtering step: filtering solid impurities in the fourth concentrated solution by a first filtering device; s7 hardness adjusting step: and (4) carrying out hardness adjustment on the fourth concentrated solution in an ion exchange device.
Example 4
A salt separation method using the salt separation system according to the present invention, a nanofiltration device 1 for separating a first concentrate, which enters from an inlet of the nanofiltration device, into a first dialysate in which a content of monovalent anions is higher than a content of divalent anions and a second concentrate in which a content of divalent anions is higher than the content of monovalent anions; the first evaporative crystallization device 2 is connected with a first outlet of the nanofiltration device 1, and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions; the second evaporative crystallization device 3 is connected with a second outlet of the nanofiltration device 1 and is used for evaporating and crystallizing the second concentrated solution to obtain salt containing divalent anions; the system further comprises: and the high-pressure reverse osmosis device 4 is arranged between the nanofiltration device 1 and the first evaporative crystallization device 2. The salt separation system adopted by the method also comprises: the chemical silicon removal device is arranged between the nanofiltration device and the second evaporative crystallization device; the second filtering device is arranged between the chemical silicon removal device and the second evaporative crystallization device;
And, as shown in fig. 8, the method comprises: a nanofiltration step S1: treating the first concentrated solution in a nanofiltration device, and separating to obtain a first dialysate and a second concentrated solution, wherein the content of monovalent anions in the first dialysate is higher than that of divalent anions, and the content of divalent anions in the second concentrated solution is higher than that of monovalent anions; first evaporative crystallization step S2: carrying out evaporative crystallization on the first dialysate in a first evaporative crystallization device to obtain a salt containing monovalent anions; second evaporative crystallization step S3: evaporating and crystallizing the second concentrated solution in a second evaporation and crystallization device to obtain a salt containing divalent anions; the method also comprises a high-pressure reverse osmosis step S4 between the nanofiltration step and the first evaporative crystallization step: and (3) carrying out high-pressure reverse osmosis treatment on the first dialysate through a high-pressure reverse osmosis device to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device.
The method further comprises the following steps: chemical silicon removal step S8: passing the second concentrated solution through a chemical silicon removal device to remove soluble silicon in the second concentrated solution; filtering step S9: and removing solid impurities in the second concentrated solution after the silicon removal in a filtering device.
according to the salt separation method of the embodiment 1-4, the salt separation system provided by the invention can be used for purifying monovalent salt and divalent salt in the concentrated brine in the coal chemical industry, so that the monovalent salt and the divalent salt obtained by evaporation and crystallization reach the industrial grade, zero discharge and resource recycling of the wastewater in the coal chemical industry are realized, and resources are saved; and the water in the strong brine can be recycled, so that resource recycling is realized, water resources are saved, the water quantity during evaporative crystallization is reduced, and the evaporative crystallization cost is saved.
it will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (6)
1. a salt separation system, comprising:
a nanofiltration device for separating a first concentrate entering from an inlet of the nanofiltration device into a first dialysate in which a content of monovalent anions is higher than a content of divalent anions and a second concentrate in which a content of divalent anions is higher than the content of monovalent anions;
the first evaporative crystallization device is connected with a first outlet of the nanofiltration device and is used for carrying out evaporative crystallization on the first dialysate to obtain salt containing monovalent anions;
the second evaporative crystallization device is connected with a second outlet of the nanofiltration device and is used for carrying out evaporative crystallization on the second concentrated solution to obtain a salt containing divalent anions;
the system further comprises:
The high-pressure reverse osmosis device is arranged between the nanofiltration device and the first evaporative crystallization device and is used for carrying out high-pressure reverse osmosis treatment on the first dialysate to obtain a second dialysate and a third concentrated solution and conveying the third concentrated solution to the first evaporative crystallization device;
The system further comprises:
The flue gas circulating evaporation device is arranged between the nanofiltration device and the second evaporative crystallization device and is used for concentrating the second concentrated solution into a fourth concentrated solution; the flue gas circulation evaporation plant includes: a flue gas evaporation tower and a flue gas evaporation circulation pool; the flue gas enters from a gas inlet of the flue gas evaporation tower, the temperature of the gas inlet is more than 100 ℃, the second concentrated solution is sprayed on the flue gas evaporation tower to contact with the flue gas for heat exchange, the second concentrated solution is evaporated, and the flue gas is discharged from a gas outlet of the flue gas evaporation tower; discharging the evaporated second concentrated solution from a liquid outlet of the flue gas evaporation tower, and feeding the second concentrated solution into the flue gas evaporation circulation tank, wherein the temperature of the second concentrated solution is 40-50 ℃, meanwhile, due to carbon dioxide and sulfur dioxide acid gases in the flue gas, the pH value of the second concentrated solution fed into the flue gas evaporation circulation tank is reduced to 7-8, the content of silicon in the second concentrated solution is reduced to 140-190 mg/L under the temperature and the pH value, and the hardness is 700mg/L, wherein the hardness comprises magnesium hardness and calcium hardness; the second concentrated solution in the flue gas evaporation circulation pool enters the flue gas evaporation tower again to continuously contact and exchange heat, and a saturated fourth concentrated solution is finally obtained;
the first filtering device is arranged between the flue gas circulating evaporation device and the second evaporative crystallization device and is used for filtering solid impurities in the fourth concentrated solution;
and the ion exchange device is arranged between the first filtering device and the second evaporative crystallization device and is used for adjusting the hardness of the fourth concentrated solution.
2. the salt separating system of claim 1, wherein the first evaporative crystallization device is a multiple effect evaporator or an MVR evaporator.
3. the salt separating system of claim 1, wherein the second evaporative crystallization device is a multiple effect evaporator or an MVR evaporator.
4. The salt dispersal system as defined in claim 1, further comprising:
a chemical silicon removal device arranged between the nanofiltration device and the second evaporative crystallization device and used for removing soluble silicon in the second concentrated solution;
And the second filtering device is arranged between the chemical silicon removal device and the second evaporative crystallization device and is used for filtering out solid insoluble substances in the second concentrated solution.
5. a salt separation method using the salt separation system of claim 1, wherein the salt separation system comprises: the device comprises a nanofiltration device, a first evaporative crystallization device and a second evaporative crystallization device; the salt separation system also comprises a high-pressure reverse osmosis device, and the high-pressure reverse osmosis device is arranged between the nanofiltration device and the first evaporative crystallization device; the salt separation system further comprises: the flue gas circulating evaporation device is arranged between the nanofiltration device and the second evaporative crystallization device; the first filtering device is arranged between the circulating evaporation device and the second evaporation crystallization device; an ion exchange device disposed between the filtration device and the second evaporative crystallization device; and the number of the first and second groups,
the method comprises the following steps:
And (3) nanofiltration: treating the first concentrated solution in the nanofiltration device, and separating to obtain a first dialysate and a second concentrated solution, wherein the content of the monovalent anions in the first dialysate is higher than that of the divalent anions, and the content of the divalent anions in the second concentrated solution is higher than that of the monovalent anions;
a first evaporative crystallization step: carrying out evaporative crystallization on the first dialysate in the first evaporative crystallization device to obtain a salt containing monovalent anions;
a second evaporation crystallization step: carrying out evaporative crystallization on the second concentrated solution in the second evaporative crystallization device to obtain a salt containing divalent anions;
the method also comprises a high-pressure reverse osmosis step between the nanofiltration step and the first evaporative crystallization step: carrying out high-pressure reverse osmosis treatment on the first dialysate through the high-pressure reverse osmosis device to obtain a second dialysate and a third concentrated solution, and conveying the third concentrated solution to the first evaporative crystallization device;
The method further comprises the following steps:
Flue gas circulating evaporation: the second concentrated solution is in circulating contact with hot flue gas through the flue gas circulating evaporation device to exchange heat, and the second concentrated solution is concentrated into a fourth concentrated solution;
solid impurity filtering: filtering solid impurities in the fourth concentrated solution by the first filtering device;
And (3) hardness adjustment: and adjusting the hardness of the fourth concentrated solution in the ion exchange device.
6. The salt separating method according to claim 5, wherein the salt separating system adopted by the method further comprises: a chemical silicon removal device arranged between the nanofiltration device and the second evaporative crystallization device; the second filtering device is arranged between the chemical silicon removal device and the second evaporative crystallization device; and the number of the first and second groups,
the method comprises the following steps:
Chemical silicon removal: passing said second concentrate through said chemical desiliconization apparatus to remove silicon from said second concentrate;
and (3) filtering: and removing solid insoluble substances in the second concentrated solution after the silicon removal in the second filtering device.
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