The content of the invention
The present invention is based on the deficiencies in the prior art, there is provided a kind of method that crude salt is extracted from concentrated seawater, the party
Method can efficiently separate the multivalent ion in concentrated seawater, improve crude salt purity, and can reach the mesh of concentration sodium chloride brine
, mitigate subsequent evaporation pressure, so as to produce the refined salt of higher degree by evaporation process;Additionally it has been significantly increased and has been
The overall Water Sproading rate of system.
To achieve the above object, the technical solution adopted by the present invention is:
A kind of method that crude salt is extracted from concentrated seawater, the method are:
(1) electrodialysis process is carried out to the concentrated seawater from desalinator, the electrodialysis process includes three-level
Operation:
First order operation is to use the first order electrodialysis membrane stack equipped with Monovalent selectivity amberplex to be handled, will
Concentrated seawater and deionized water are separately added into the desalting chamber and enriched chamber of first order electrodialysis membrane stack, and it is molten to add sodium sulphate in the liquid chamber of pole
Liquid, is the terminal of first order operation when the electrical conductivity of processing to desalinization liquor is less than 20ms/cm, first order operation at this time is tied
Beam, obtains desalinization liquor I and concentrate I, wherein desalinization liquor I is after chemical precipitation removes calcium and magnesium ion, back to sea water desalination
Factory's preparing fresh again;And concentrate I is operated into the second level;
The second level operation be use equipped with conventional ion exchange membrane second level electrodialysis membrane stack to concentrate I at
Reason, adds concentrate I, pole liquid chamber adds metabisulfite solution, works as place toward the enriched chamber of second level electrodialysis membrane stack and desalting chamber
Reason to desalinization liquor electrical conductivity less than 5ms/cm when, be the second level operation terminal, the second level operation terminates, obtain desalinization liquor II
Operated with concentrate II, wherein concentrate II into the third level, desalinization liquor II, which can be back in first order membrane stack, (adds concentration
Room);
The third level operation be use equipped with conventional ion exchange membrane second level electrodialysis membrane stack to concentrate II at
Reason, adds concentrate II, pole liquid chamber adds metabisulfite solution, works as place toward the enriched chamber of third level electrodialysis membrane stack and desalting chamber
Reason to desalinization liquor electrical conductivity less than 5ms/cm when, be the third level operation terminal, the third level operation terminates, obtain desalinization liquor
III and concentrate III, wherein desalinization liquor III can be back in first order membrane stack and (add enriched chamber);
(2) crude salt is made through evaporating in concentrate III.
Further, the mass fraction for the metabisulfite solution that pole liquid chamber adds is preferably 3-5% in three-level operation, is most preferably
3%.
Further, in first order operation, desalinization liquor I can remove calcium and magnesium ion by following chemical precipitation method:Toward desalination
Sodium hydroxide and sodium carbonate are added in liquid, precipitates calcium and magnesium ion, so as to remove a large amount of calcium and magnesium ions.
In the method for the invention, the amount that feed liquid adds in each compartment is determined according to the size of film size, and usual each compartment adds
The volume entered is identical.
First order electrodialysis membrane stack of the present invention is alternately arranged by Monovalent selectivity anion and cation exchange membrane to be formed, and
Membrane stack is respectively put into a pole film adjacent to electrode plate both sides, for protecting Monovalent selectivity film so that formed pole liquid chamber, enriched chamber and
Desalting chamber;The second level, third level electrodialysis membrane stack are alternately arranged composition by common anion and cation exchange membrane, respectively shape
Poling liquid chamber, enriched chamber and desalting chamber.
Further, (i.e. an anode membrane adds number of repeat unit in the first order, the second level, third level electrodialysis membrane stack
One cavity block adds an anode membrane again) respectively preferably 5 (i.e. 6 anode membranes and 5 cavity blocks altogether).
Further, in the first order electrodialysis membrane stack, Monovalent selectivity anion and cation exchange membrane is Japanese Asahi Chemical Industry
Monovalent selectivity anode membrane, Japanese Asahi Chemical Industry Monovalent selectivity cavity block, and pole film is Japan AGC pole film.
Further, in the second level, third level electrodialysis membrane stack, common anion and cation exchange membrane is Japanese Asahi Chemical Industry
Anode membrane, Japanese Asahi Chemical Industry cavity block.
Further, in the electrodialysis system, electrode plate used is by titanium plating ruthenium processing.
Further, in the first order electrodialysis membrane stack, partition plate is provided between adjacent two films, it is by polypropylene system
Into.
Further, in the second level, third level electrodialysis membrane stack, partition plate is provided between negative and positive film, it is by poly- third
Made of alkene.
Further, in first order operation, preferred operations current density is 4mA/cm2, each compartment flow is 40L/h.
Further, in the second level and third level operation, preferred operations current density is 10mA/cm2, each compartment flow is equal
For 40L/h.
In the present invention, the electrodialysis process can be necessary to determine whether to need according to the composition and processing of concentrated seawater into
One step increases electrodialysis operation.
In the present invention, the concentrated seawater electrical conductivity from desalinator is 55-75ms/cm, and calcium and magnesium ion concentration is distinguished
For 600-700mg/L, 1400-1600mg/L, Na ion concentration 14000-16000mg/L, chlorine ion concentration 21000-
24000mg/L, sulfate ion concentration 2800-3200mg/L, potassium concentration 300-500mg/L, bromide ion concentration are
80-90mg/L.For above-mentioned concentrated seawater, preferably described electrodialysis process is operated by the first order, the second level operates and third level behaviour
Form.
The present invention has the advantages that compared with prior art:
(1) electrodialysis system that the present invention designs can efficiently separate the multivalent ion in concentrated seawater, can improve crude salt
Purity, and can achieve the purpose that concentrate sodium chloride brine, mitigate subsequent evaporation pressure so that by evaporation process produce compared with
The refined salt of high-purity.In addition, can after the first order desalinization liquor produced through system removes substantial amounts of calcium and magnesium ion by chemical precipitation
Back to desalinator again preparing fresh, and the second level and third level desalinization liquor can also be back to first order operation, from
And the overall Water Sproading rate of system is significantly increased.
(2) the more traditional concentrated seawater treatment technology of electrodialysis system that designs of the present invention, have expend less, easy to operate, ring
The advantages that border is friendly;Marine environmental pollution problem caused by avoiding concentrated seawater discharge at the same time, realizes the sustainable profit of resource
With.
Embodiment 1
This example is using the electrodialysis system shown in Fig. 1.Specifically include:One is equipped with Monovalent selectivity amberplex
Electrodialysis membrane stack and two electrodialysis membrane stacks that common amberplex is housed.In addition, also a vaporising device is used to steam
The final concentrate rich in sodium chloride of hair.The specification of three electrodialysis membrane stacks is just the same.The repetition of each membrane stack
Unit number is 5.The area of every film is 11cm × 27cm.By the electrodialytic membranes equipped with Monovalent selectivity amberplex
The first order of system is stacked in, Monovalent selectivity amberplex used is respectively Japanese Asahi Chemical Industry Monovalent selectivity anode membrane
(NEOSEPTA CIMS), Japanese Asahi Chemical Industry's Monovalent selectivity cavity block (NEOSEPTA ACS), and membrane stack is each adjacent to electrode plate both sides
A Japan AGC pole film (SELEMION CMTE) is put into, for protecting Monovalent selectivity film.And two equipped with it is common from
The second level of the electrodialysis membrane stack of proton exchange respectively as system, the third level, conventional ion exchange membrane used is respectively day
This Asahi Chemical Industry anode membrane (NEOSEPTA CMX), Japanese Asahi Chemical Industry's cavity block (NEOSEPTA AMX).Electrode plate used passes through titanium
Plate ruthenium processing;The baffle dimensions being placed between two films are also 11cm × 27cm, are made up of polypropylene.
As shown in Figure 1, by 1L concentrated seawaters, (the concentrated seawater electrical conductivity is 60ms/cm, and calcium and magnesium ion concentration is respectively
665mg/L, 1546mg/L, Na ion concentration 15117mg/L, chlorine ion concentration 23525mg/L, sulfate ion concentration are
3041mg/L, potassium concentration 392mg/L, bromide ion concentration 89mg/L) and 1L deionized waters be separately added into first order film
The desalting chamber and enriched chamber of heap, it is 3% metabisulfite solution that pole liquid chamber, which adds 1L mass fractions,.Operation electric current density is 4mA/cm2,
Each compartment flow is 40L/h.When the electrical conductivity of desalting chamber's solution is less than 20ms/cm (i.e. salt rejection rate is higher than 70%), the
Level-one operation terminates.Then the feed liquid in enriched chamber is put into fluid reservoir, and first order desalinization liquor removes greatly by chemical precipitation
After the calcium and magnesium ion of amount, back to desalinator again preparing fresh.Several batch experiments are repeated, are made in fluid reservoir
Feed liquid reaches the demand of second level operation.Found by detection, enriched chamber's feed liquid electrical conductivity is left in 50ms/cm in each batch
The right side, wherein calcium and magnesium ion concentration drop to 175mg/L, 200mg/L or so respectively.Show to operate by the first order, can be significantly
Separate the multivalent ion in concentrated seawater.Then second level enriched chamber is pumped into first order concentrate 1L with desalting chamber;The third level is dense
Contracting room is pumped into second level concentrate 1L with desalting chamber, and it is 3% metabisulfite solution that pole liquid chamber, which adds 1L mass fractions,;Operation electricity
Current density is 10mA/cm2, each compartment flow is 40L/h, and it is equal to work as desalinization liquor electrical conductivity in the second level, third level membrane stack
Less than 5ms/cm, operation terminates.And the second level, third level desalinization liquor can be back in first order membrane stack.Finally obtain at this time
Concentrate electrical conductivity rich in sodium chloride close to 110ms/cm, wherein calcium and magnesium ion concentration be respectively 976mg/L, 1432mg/
L or so.Finally crude salt is produced by evaporation process again.By repeat experiment find, the crude salt purity stabilization of extraction 85%, and
Concentrated seawater is only 56% without the crude salt purity that system is handled.