WO2000029327A1 - Method for production of magnesium chloride from sea water - Google Patents

Method for production of magnesium chloride from sea water Download PDF

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Publication number
WO2000029327A1
WO2000029327A1 PCT/NO1999/000342 NO9900342W WO0029327A1 WO 2000029327 A1 WO2000029327 A1 WO 2000029327A1 NO 9900342 W NO9900342 W NO 9900342W WO 0029327 A1 WO0029327 A1 WO 0029327A1
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WIPO (PCT)
Prior art keywords
solution
sea water
gypsum
magnesium chloride
unit
Prior art date
Application number
PCT/NO1999/000342
Other languages
French (fr)
Inventor
Thor G. Thorsen
Roger I. Hagen
Ole Waernes
Birger Langseth
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Norsk Hydro Asa
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Publication date
Application filed by Norsk Hydro Asa filed Critical Norsk Hydro Asa
Priority to AU11913/00A priority Critical patent/AU1191300A/en
Publication of WO2000029327A1 publication Critical patent/WO2000029327A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • B01D61/0271—Nanofiltration comprising multiple nanofiltration steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/58—Multistep processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • B01D61/026—Reverse osmosis; Hyperfiltration comprising multiple reverse osmosis steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/04—Feed pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/08—Prevention of membrane fouling or of concentration polarisation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/26—Magnesium halides
    • C01F5/30—Chlorides
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/04—Specific process operations in the feed stream; Feed pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/16—Use of chemical agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/147—Microfiltration

Definitions

  • the invention concerns a method for production of concentrated magnesium chloride (MgCI 2 ) from sea water.
  • the magnesium chloride is meant for use as raw material in the production of magnesium metal.
  • a typical sea water composition has the following content of major constituents: 10.5 g/l Na + , 1.3 g/l Mg + , 0.4 g/l Ca 2+ , 0.4 g/l K + and 2.6 g/l SO 4 2 ⁇
  • Concentration of bicarbonate (HCO 3 ) amounts to 0.1373 g/kg sea water at a salinity of 33.9 g/kg.
  • the first stage in the production is a process based upon precipitation of magnesium with alkali, mostly burnt dolomite.
  • the separated hydroxide is concentrated in Dorr-thickeners and dewatered by following filtration and drying.
  • CO 2 emission from the production of burnt dolomite and in addition raw materials have to be transported to the plant as dolomite.
  • the object of the invention is thus to produce magnesium chloride directly from sea water by use of membrane technology. Another object is to obtain a high concentration of magnesium chloride without concentrating the content of sodium chloride at the same time. It is also important to obtain a product free from impurities.
  • Figure 1 shows a flow sheet of the process.
  • Figure 2 shows one possible configuration of the last concentration step.
  • the invention concerns a method for production of concentrated sulphate free magnesium chloride brine from sea water.
  • Sea water is fed to a first nanofiltration unit with selective concentration of divalent ions in solution (e.g. Mg 2+ , Ca 2+ , SO 2" ) and therefore sodium chloride is reduced relatively and gradually removed with the permeate.
  • the solution from the first unit is fed to a second nanofiltration unit with selective concentration of divalent ions, so that calcium sulphate (gypsum) precipitates inside the filter and is thereafter removed as solid gypsum from the resulting concentrated solution and the sodium chloride is gradually removed with the permeate.
  • Any rest content of sulphate is removed from the solution in an anion -exchanger before the resulting magnesium chloride solution is concentrated further in a third nanofiltration unit and sodium chloride is gradually removed with the permeate.
  • Nucleation crystals can be recycled from the gypsum precipitation step to the second nanofiltration step in order to prevent blockage of the membrane surface. It is preferred to remove sulphate and calcium as gypsum by the use of sedimentation and clarification or by cross-flow micro filtration.
  • the feed sea water may be pre-treated by acid supply and stripping of CO 2 to prevent precipitation of carbonates.
  • An acid could be supplied before the first or second nanofiltration unit.
  • the ion exchanger is regenerated by a sulphate free sodium chloride solution from the first or third nanofiltration unit.
  • Membranes with high selectivity in the rejection of Mg-ions are preferably used.
  • the membranes used in nanofiltration unit 3 have a carefully selected permeability for magnesium chloride so that sodium chloride is less rejected and the osmotic back pressure difference across the membranes is mainly from the magnesium chloride.
  • the brine could be concentrated to more than 100 g MgCI 2 /l.
  • Mg-ions It is essential to this process that special membranes with high selectivity in the rejection of Mg-ions are used.
  • the rejection of Mg will be dependent on the mixture of ions that is present in the solution besides Mg.
  • the rejection of the individual ions will depend much on the membrane and will change along the membrane throughout the plant.
  • the rejection of MgSO will be highest of the salts. Calcium may be rejected a little less than Mg, and Na will show very low rejection.
  • the plant flow sheet is shown in figure 1.
  • the process is shown divided into 6 process steps: Step 1 - pre-treatment, Step 2 - nanofilter unit 1 (NF1 ), Step 3 - nanofilter unit 2 (NF2), Step 4 - gypsum separator, Step 5 - sulphate ion exchanger and Step 6 - nanofilter unit 3 (NF3).
  • Step 1 - pre-treatment Step 2 - nanofilter unit 1
  • Step 3 - nanofilter unit 2 NF2
  • Step 4 - gypsum separator Step 5 - sulphate ion exchanger
  • Step 6 - nanofilter unit 3 NF3
  • the sea water is pre-treated in Step 1 to remove membrane fouling agents as humic acid, silicates and particles and to prevent unintentional precipitation of carbonates on the membrane.
  • the pre-treatment will preferably include the use of a sand filter or another type of media filter, followed by a cartridge or sieve filter. These filters will remove particles in the feed.
  • the pre-treatment may further consist of a stripping unit to remove CO 2 to prevent carbonate precipitation, optionally an acid can be added to lower the pH to a value between 2 and 5, to improve the divalent ion selectivity in the following nanofilter units.
  • Step 2 the sea water is treated in a nanofiltration unit NF1 which will preconcentrate divalent ions in true solution with an operating pressure provided by process pump 1 (PP1). NaCI solution is gradually removed with the permeate.
  • nanofiltration unit NF2 which will further concentrate divalent ions, but with simultaneous gypsum precipitation and separation of this compound from the concentrate flow.
  • the nucleation crystals added to the main feed are taken from a gypsum crystal separation unit in process Step 4.
  • This separation unit preferably consists of a conventional sedimentation and clarification apparatus.
  • it can consist of a separate membrane filter specially adapted for slurry concentration, using ultra- or cross flow micro filtration membranes with pore sizes between 0.01 and 10 micrometers.
  • process Step 5 is an anion exchanger.
  • sulphate ions are separated by ion exchange in one or more internal ion exchange units.
  • the ion exchanger(s) may be regenerated with sulphate-free NaCI-solution from the following nanofilter or from the previous nanofilters, which have low sulphate concentration and sufficient volume. Most volume flows are reduced significantly before the gypsum separation unit and the ion exchanger.
  • a flow of 6250 m 3 /h sea water with a magnesium content of 1.3 g/l is first pre-treated and thereafter fed to a first nanofiltration unit, NF1 (see figure 1 ).
  • This unit should operate at about 20 bar pressure and reduce the process stream to a residual volume of 3200 m 3 /h, which will have a magnesium content of 2.5 g/l .
  • Process pump 2 PP2
  • PP2 Process pump 2
  • the flow leaving NF2 is reduced to about 625 m 3 /h and has a magnesium concentration of about 13 g/l and contains all gypsum that has been precipitated internally in the concentrate flow within the unit.
  • nanofiltration unit 2 and gypsum separation After nanofiltration unit 2 and gypsum separation almost all calcium has been removed, and the sulphate concentration has increased to about 20 g/l and is well above the initial level in sea water. This solution is well suited for effective removal of sulphate.
  • the osmotic back-pressure in the following nanofiltration unit NF3 will almost entirely come from magnesium chloride, which makes the further concentration as effective as possible.
  • the feed to NF3 will have the same magnesium content as the flow leaving NF2 and the NaCI concentration will have increased to about 45 g/l.
  • NF3 operates at a pressure of about 60 bar.
  • the concentration in NF3 is carried out up to 200 g MgCI 2 /l, the concentration of NaCI in the magnesium chloride brine will still be about 45 g/l, as will also the concentration of NaCI in the permeate from this unit.
  • the permeate will be almost pure NaCI solution.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Nanotechnology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

A method is described for the production of magnesium chloride from sea water to be used in the production of magnesium metal. The method is based on the use of selective nanofiltration membranes to separate the magnesium directly from the sea water.

Description

METHOD FOR PRODUCTION OF MAGNESIUM CHLORIDE FROM SEA WATER
The invention concerns a method for production of concentrated magnesium chloride (MgCI2) from sea water. The magnesium chloride is meant for use as raw material in the production of magnesium metal.
Today magnesium is being recovered from sea water in several industrial plants throughout the world. A typical sea water composition has the following content of major constituents: 10.5 g/l Na+, 1.3 g/l Mg +, 0.4 g/l Ca2+, 0.4 g/l K+ and 2.6 g/l SO4 2\ Concentration of bicarbonate (HCO3 ) amounts to 0.1373 g/kg sea water at a salinity of 33.9 g/kg. Generally, the first stage in the production is a process based upon precipitation of magnesium with alkali, mostly burnt dolomite. The separated hydroxide is concentrated in Dorr-thickeners and dewatered by following filtration and drying. In the existing production there is a considerable CO2 emission from the production of burnt dolomite, and in addition raw materials have to be transported to the plant as dolomite.
It is possible to separate Mg directly from sea water using nanofiltration. This process will be similar to reverse osmosis as applied in the desalination of sea water for the production of drinking water. The basic layout of the process and the considerations regarding scaling are also similar. The membranes used in reverse osmosis are semipermeable membranes that are permeable by water but not salts. If a high operating pressure is applied to sea water that is fed to one side of the membrane, fresh water will appear on the other side of the membrane.
In contrast to these processes we are not interested in increasing the concentration of NaCI, only the concentration of MgCI2. Therefore, slightly different membranes are selected, that are partially permeable to salts. These membranes are called nanofiltration membranes. The permeability to various salts will have to be carefully selected to suit process needs. It is also a major difference to other processes based on sea water, that the concentration is carried out up to a very high level (120 - 200g/l). As the molar concentration of MgCI2 is far less than that of NaCI, the osmotic back pressure is also much less. This means that the operating pressure and therefore the power consumption of the pump will be less, provided that the selected membrane has high permeability to NaCI. The object of the invention is thus to produce magnesium chloride directly from sea water by use of membrane technology. Another object is to obtain a high concentration of magnesium chloride without concentrating the content of sodium chloride at the same time. It is also important to obtain a product free from impurities.
These and other objects of the invention are achieved by the method for production of magnesium chloride as described below. The invention is further described and characterised by the enclosed patent claims.
The invention will be further described with reference to the drawings, where:
Figure 1 shows a flow sheet of the process.
Figure 2 shows one possible configuration of the last concentration step.
The invention concerns a method for production of concentrated sulphate free magnesium chloride brine from sea water. Sea water is fed to a first nanofiltration unit with selective concentration of divalent ions in solution (e.g. Mg2+, Ca2+, SO 2") and therefore sodium chloride is reduced relatively and gradually removed with the permeate. The solution from the first unit is fed to a second nanofiltration unit with selective concentration of divalent ions, so that calcium sulphate (gypsum) precipitates inside the filter and is thereafter removed as solid gypsum from the resulting concentrated solution and the sodium chloride is gradually removed with the permeate. Any rest content of sulphate is removed from the solution in an anion -exchanger before the resulting magnesium chloride solution is concentrated further in a third nanofiltration unit and sodium chloride is gradually removed with the permeate.
Nucleation crystals can be recycled from the gypsum precipitation step to the second nanofiltration step in order to prevent blockage of the membrane surface. It is preferred to remove sulphate and calcium as gypsum by the use of sedimentation and clarification or by cross-flow micro filtration. The feed sea water may be pre-treated by acid supply and stripping of CO2 to prevent precipitation of carbonates. An acid could be supplied before the first or second nanofiltration unit. Preferably the ion exchanger is regenerated by a sulphate free sodium chloride solution from the first or third nanofiltration unit. Membranes with high selectivity in the rejection of Mg-ions are preferably used. It is preferred that the membranes used in nanofiltration unit 3 have a carefully selected permeability for magnesium chloride so that sodium chloride is less rejected and the osmotic back pressure difference across the membranes is mainly from the magnesium chloride. The brine could be concentrated to more than 100 g MgCI2/l.
It is essential to this process that special membranes with high selectivity in the rejection of Mg-ions are used. The rejection of Mg will be dependent on the mixture of ions that is present in the solution besides Mg. The rejection of the individual ions will depend much on the membrane and will change along the membrane throughout the plant. In solutions with similar ion ratios as in sea water, the rejection of MgSO will be highest of the salts. Calcium may be rejected a little less than Mg, and Na will show very low rejection.
The plant flow sheet is shown in figure 1. The process is shown divided into 6 process steps: Step 1 - pre-treatment, Step 2 - nanofilter unit 1 (NF1 ), Step 3 - nanofilter unit 2 (NF2), Step 4 - gypsum separator, Step 5 - sulphate ion exchanger and Step 6 - nanofilter unit 3 (NF3). The basic unit operation steps inn the process are described below:
The sea water is pre-treated in Step 1 to remove membrane fouling agents as humic acid, silicates and particles and to prevent unintentional precipitation of carbonates on the membrane. The pre-treatment will preferably include the use of a sand filter or another type of media filter, followed by a cartridge or sieve filter. These filters will remove particles in the feed. The pre-treatment may further consist of a stripping unit to remove CO2 to prevent carbonate precipitation, optionally an acid can be added to lower the pH to a value between 2 and 5, to improve the divalent ion selectivity in the following nanofilter units.
In Step 2 the sea water is treated in a nanofiltration unit NF1 which will preconcentrate divalent ions in true solution with an operating pressure provided by process pump 1 (PP1). NaCI solution is gradually removed with the permeate. This step is followed by nanofiltration unit NF2 which will further concentrate divalent ions, but with simultaneous gypsum precipitation and separation of this compound from the concentrate flow.
As the filtration progresses the concentrations of Mg2+, SO 2" and Ca2+ increase. Eventually the solubility of gypsum will be exceeded and precipitation starts. The precipitated gypsum will be separated by the membrane in a similar way as described in US patent 4 207 183, where nucleation crystals in the fluid stream passing through the separation apparatus will cause preferential precipitation of the solute thereby eliminating the formation of deposits on the membrane barrier. This have the benefit of a reduction in sulphate and calcium concentrations further on in the process. As the sulphate concentration is higher than the calcium concentration, the final concentration of calcium will be very low. CaCO3 will not precipitate in the plant even if stripping of carbon dioxide is not performed on the feed.
The nucleation crystals added to the main feed are taken from a gypsum crystal separation unit in process Step 4. This separation unit preferably consists of a conventional sedimentation and clarification apparatus. Optionally, it can consist of a separate membrane filter specially adapted for slurry concentration, using ultra- or cross flow micro filtration membranes with pore sizes between 0.01 and 10 micrometers.
After the calcium ions are effectively removed in nanofilter unit NF2 and the gypsum separator, the process stream continues to process Step 5, which is an anion exchanger. In this step sulphate ions are separated by ion exchange in one or more internal ion exchange units. The ion exchanger(s) may be regenerated with sulphate-free NaCI-solution from the following nanofilter or from the previous nanofilters, which have low sulphate concentration and sufficient volume. Most volume flows are reduced significantly before the gypsum separation unit and the ion exchanger.
After the ion exchanger step follows process Step 6 with a concentration of the magnesium chloride solution in nanofilter unit NF3. A principle sketch of one possible configuration within this step is shown in figure 2 as an illustration. In this step high concentration of magnesium chloride brine is achieved by two or more nanofilter sub-units in a recycle configuration. By using two or more units it is possible to divide osmotic backpressure from the magnesium chloride solution between more than one membrane passage, and in this way the nanofilter membranes can be operated within their tolerances regarding operating pressure. The membranes used in this step will be carefully selected for their selectivity for magnesium chloride separation. The number of sub-units that are necessary will vary depending on the properties of the membranes and the final concentration of the magnesium chloride brine. The final concentration is preferentially between 120 and 200 g/l and is selected according to the economic optimum which is dependent on further processing of the magnesium chloride brine for the Mg production.
The invention will be illustrated by a non-limiting example with reference to the figure. Example
An illustrating example of possible process parameters is as follows. Several existing nanofilter membranes can be used. In laboratory tests the properties of type NF45 from Dow Chemical Company have been measured. These properties have been applied in a simulation to find process parameters throughout the process concerning the concentrations.
A flow of 6250 m3/h sea water with a magnesium content of 1.3 g/l is first pre-treated and thereafter fed to a first nanofiltration unit, NF1 (see figure 1 ). This unit should operate at about 20 bar pressure and reduce the process stream to a residual volume of 3200 m3/h, which will have a magnesium content of 2.5 g/l . Process pump 2 (PP2) should apply an operating pressure of about 30 bar in the first part of the nanofilter unit NF2. This pressure should be increased internally to 45 bar for the last part of the unit. The flow leaving NF2 is reduced to about 625 m3/h and has a magnesium concentration of about 13 g/l and contains all gypsum that has been precipitated internally in the concentrate flow within the unit.
After nanofiltration unit 2 and gypsum separation almost all calcium has been removed, and the sulphate concentration has increased to about 20 g/l and is well above the initial level in sea water. This solution is well suited for effective removal of sulphate. After removal of the sulphate in the ion exchanger the osmotic back-pressure in the following nanofiltration unit NF3 will almost entirely come from magnesium chloride, which makes the further concentration as effective as possible. The feed to NF3 will have the same magnesium content as the flow leaving NF2 and the NaCI concentration will have increased to about 45 g/l. NF3 operates at a pressure of about 60 bar. If the concentration in NF3 is carried out up to 200 g MgCI2/l, the concentration of NaCI in the magnesium chloride brine will still be about 45 g/l, as will also the concentration of NaCI in the permeate from this unit. The permeate will be almost pure NaCI solution.
The flow values as given above are calculated as if it was no loss of magnesium through the process. This is not quite true, but the losses are expected to be relatively low. They can be calculated according to the characteristics of the membranes.

Claims

1. Method for production of concentrated sulphate free magnesium chloride brine from sea water, characterised by the following steps: a) sea water is fed to a first nanofiltration unit with selective concentration of divalent ions in solution (e.g. Mg2+, Ca+, SO4 2'), and, therefore, sodium chloride is reduced relatively and gradually removed with the permeate, b) the solution from the first unit is fed to a second nanofiltration unit with selective concentration of divalent ions so that calcium sulphate (gypsum) precipitates inside the filter and is thereafter removed as solid gypsum from the resulting concentrated solution, and where sodium chloride is gradually removed with the permeate, c) any remaining content of sulphate is removed from the solution in an anion-exchanger before, d) the resulting magnesium chloride solution is concentrated further in a third nanofiltration unit and sodium chloride is gradually removed with the permeate.
2. Method according to claim 1 , characterised in that the gypsum is removed by sedimentation and clarification.
3. Method according to claim 1 , characterised in that gypsum is removed by cross-flow micro filtration.
4. Method according to claim 1 , characterised in that nucleation crystals are recycled from the gypsum removal step to the second nanofiltration step in order to prevent blockage of the membrane surfaces.
5. Method according to claim 1 , characterised in that the feed sea water is pre-treated by acid supply and stripping of CO2 to prevent precipitation of carbonates.
6. Method according to claim 5, characterised in that an acid is supplied before the first or second nanofiltration unit.
7. Method according to claim 1 , characterised in that the ion exchanger is regenerated by a sulphate free sodium chloride solution from the first or third nanofiltration unit.
8. Method according to claim 1 , characterised in that membranes are used with high selectivity in the rejection of Mg-ions.
9. Method according to claim 8, characterised in that the membranes used in nanofiltration unit 3 have a carefully selected permeability for magnesium chloride so that sodium chloride is less rejected and the osmotic pressure difference across the membrane is mainly from the magnesium chloride.
10. Method according to claim 1 , characterised in that the brine is concentrated to more than 100 g MgCI2/l.
PCT/NO1999/000342 1998-11-13 1999-11-12 Method for production of magnesium chloride from sea water WO2000029327A1 (en)

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NO985322A NO985322L (en) 1998-11-13 1998-11-13 Process for the preparation of magnesium chloride from seawater
NO19985322 1998-11-13

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2395946A (en) * 2002-12-05 2004-06-09 Thomas Altmann Extracting sodium chloride from seawater, using nanofiltration
CN100515959C (en) * 2006-10-09 2009-07-22 叶建荣 Manual collecting and filtering apparatus
WO2011015041A1 (en) * 2009-08-07 2011-02-10 无锡尚德太阳能电力有限公司 Wastewater treatment method and system using the method
CN104261443A (en) * 2014-09-25 2015-01-07 池州西恩新材料科技有限公司 Process for calcium-method production of magnesium hydrate by using nanofiltration membrane
US20160368800A1 (en) * 2013-06-24 2016-12-22 Fmc Kongsberg Subsea As Subsea seawater filtration and treatment system
US10648061B2 (en) 2015-08-28 2020-05-12 Albemarle Corporation Processes for recovering lithium values from lithium-containing brines
CN112956488A (en) * 2020-12-22 2021-06-15 天津海源汇科技有限公司 Preparation method of sea salt disinfectant

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB541450A (en) *
GB536266A (en) * 1939-11-13 1941-05-08 Ocean Salts Products Ltd Preparation of magnesium chloride from sea water
NO303324B1 (en) * 1996-11-13 1998-06-29 Norsk Hydro As Procedure for Removing Sulfate from Concentrated MgCl2 Solutions

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB541450A (en) *
GB536266A (en) * 1939-11-13 1941-05-08 Ocean Salts Products Ltd Preparation of magnesium chloride from sea water
NO303324B1 (en) * 1996-11-13 1998-06-29 Norsk Hydro As Procedure for Removing Sulfate from Concentrated MgCl2 Solutions

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2395946A (en) * 2002-12-05 2004-06-09 Thomas Altmann Extracting sodium chloride from seawater, using nanofiltration
GB2395946B (en) * 2002-12-05 2006-01-18 Thomas Altmann Method for the production of sodium chloride from seawater
CN100515959C (en) * 2006-10-09 2009-07-22 叶建荣 Manual collecting and filtering apparatus
WO2011015041A1 (en) * 2009-08-07 2011-02-10 无锡尚德太阳能电力有限公司 Wastewater treatment method and system using the method
CN101987765B (en) * 2009-08-07 2012-06-27 无锡尚德太阳能电力有限公司 Sewage treatment method and system used by same
US20160368800A1 (en) * 2013-06-24 2016-12-22 Fmc Kongsberg Subsea As Subsea seawater filtration and treatment system
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