Process for producing a highly concentrated pure aqueous solution of magnesium hydrogencarbonate or calcium hydrogencarbonate and pressure vessel for storing and / or dosing the solution into the water to be optimized
Patent Information
- Application Number
- EP2023768797
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-09-08
- Filing Date
- 2023-09-05
- Publication Date
- 2025-07-16
AI Technical Summary
Existing methods for producing magnesium and calcium hydrogen carbonate solutions are limited by impurities, slow reaction rates, and the inability to achieve high concentrations due to the poor solubility of their carbonates, which also leads to scale formation and precipitation issues.
A method involving an anion exchanger loaded with hydrogen carbonate ions, where a mixture of weakly, medium, or strongly basic ion exchange materials is used to exchange chloride ions from magnesium or calcium chloride solutions, producing a highly concentrated, pure magnesium or calcium hydrogen carbonate solution, which is then stored and dosed using a pressure vessel to prevent precipitation.
This method enables the production of high-quality, highly concentrated magnesium or calcium hydrogen carbonate solutions with minimal impurities, allowing for efficient enrichment of water with magnesium and calcium bicarbonates, reducing the need for large amounts of additives and preventing carbonate precipitation.
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Figure 1.1
Abstract
Description
[0001] Process for producing a highly concentrated pure aqueous solution of magnesium bicarbonate or calcium bicarbonate and pressure vessel for storing and / or dosing the solution into the water to be optimized
[0002] Description
[0003] For many applications, water, especially water used for drinking or for preparing hot drinks such as coffee, requires that the composition of the water be as consistent as possible.
[0004] For example, in the industrial production of table water, or water that is subsequently processed into a hot or cold beverage such as coffee, beer, or soft drinks, it is common practice to first demineralize the water. A defined amount of salt is then added to the purified and virtually salt-free water to ensure a sufficient electrolyte concentration for human consumption.
[0005] Bicarbonates, e.g. NaHCO3, KHCO3, which are present as solids and dissolve easily, are particularly suitable for dosing.
[0006] Magnesium and calcium salts are more nutritionally valuable than sodium and potassium salts. Therefore, it is particularly desirable for the water to contain primarily magnesium and calcium as minerals.
[0007] Unlike the alkali salts sodium bicarbonate and potassium bicarbonate, the bicarbonates of the alkaline earth metals calcium and magnesium do not exist as solids. Rather, the bicarbonates of calcium and magnesium exist only in dissolved form. Evaporation and concentration of the solution is not possible, as this process converts the dissolved calcium or magnesium bicarbonate into calcium or magnesium carbonate, CO2, and H2O:
[0008] Ca(HCO3)2CaCO3+ H2O + CO2(1) or
[0009] Mg(HCO3)2MgCO3+ H2O + CO2(2) The carbonates of magnesium and calcium are poorly soluble and are the main cause of scale formation in installations and hot water heaters.
[0010] The bicarbonates of calcium and magnesium metals can be prepared from two solutions. Typically, one solution consists of potassium or magnesium.
[0011] Sodium bicarbonate and the other solution of magnesium chloride or calcium chloride. Mixing the two solutions together produces the desired calcium or magnesium bicarbonate.
[0012] However, the solution obtained in this way is not pure, but also contains undesirable sodium or potassium chloride.
[0013] As an example, the preparation of a 1% solution, or 10 g / l, of magnesium bicarbonate is cited.
[0014] In this case, an additional 8 g / l NaCl is formed.
[0015] Another possibility is the production of calcium or
[0016] Magnesium bicarbonate from magnesium or calcium carbonate and carbonic acid.
[0017] CaCO3+ CO2+ H2O Ca(HCO3)2(4)
[0018] Analogous for Mg:
[0019] In both cases, pure bicarbonate of calcium or magnesium is formed, but the reaction of CO2 with the respective carbonate is quite slow, since CO2 or H2CO3 dissolved in water is only a weak acid (pKsl = 6.3 or pKs2 = 10.3).
[0020] The respective carbonate dissolves only slowly and with a high stoichiometric excess of CO2. The object of the invention
[0021] The object of the present invention is to produce a magnesium or calcium hydrogen carbonate solution that is as pure as possible and which is stoichiometric and has a fast reaction rate.
[0022] Summary of the invention
[0023] The object of the invention is already achieved by a process for producing magnesium and calcium hydrogen carbonate, by treated water and by a pressure vessel according to one of the independent claims.
[0024] Preferred embodiments and further developments of the invention can be found in the subject matter of the dependent claims, the description and the drawings.
[0025] The invention relates to a process for producing magnesium and / or calcium bicarbonate. The process is intended, in particular, to produce a highly concentrated calcium and / or magnesium bicarbonate solution.
[0026] This preferably has a total hardness of over 200° dH, particularly preferably over 400° dH, in particular 400°-800° dH.
[0027] According to the invention, an anion exchanger loaded with hydrogen carbonate, i.e. bicarbonate, ions is provided.
[0028] The ion exchanger can be designed as a weakly basic, medium-basic, or strongly basic anion exchanger. A mixture of weakly basic, medium-basic, and strongly basic ion exchange material can also be used.
[0029] Basic ion exchangers can, in particular, contain amino groups as a functional group. The ion exchanger can, in particular, be present as a bed in a cartridge, which has an inlet and an outlet for the concentrate to be enriched with magnesium or calcium bicarbonate.
[0030] Furthermore, according to the invention, a solution containing magnesium and / or calcium salts is passed over the anion exchanger loaded with bicarbonate ions. Chlorides are preferably used as the magnesium or calcium salts. Magnesium sulfate can also be used as the magnesium salt.
[0031] To produce the desired magnesium or calcium bicarbonate solution, a solution of magnesium chloride and / or calcium chloride is passed over a weak and / or medium and / or strong anion exchanger which is in the bicarbonate form, whereby the chloride ion of the solution is exchanged for the bicarbonate ion of the anion exchanger.
[0032] The concentration of the feed solution of magnesium chloride and / or calcium chloride is in the range of 0.05 mol / l to 0.3 mol / l.
[0033] It has been shown that a highly concentrated solution containing calcium bicarbonate or magnesium bicarbonate can be produced in this way. The concentration of the bicarbonate solution can be close to the solubility limit, in particular.
[0034] The solution can be prepared in a single pass through the ion exchanger. The resulting magnesium or calcium bicarbonate solution is of high quality and free of impurities. This highly concentrated solution can then be used to enrich water, especially demineralized water, with magnesium and / or calcium bicarbonate. Due to the high concentration, only small quantities are required. In particular, one liter of the solution is sufficient for up to 200–1000 liters of water, depending on the concentration.
[0035] For the solution containing magnesium and / or calcium salt, readily soluble magnesium chloride and / or calcium chloride or magnesium sulfate can be used.
[0036] According to one embodiment of the invention, chloride-free and / or sodium-free water can be provided. Chloride-free or sodium-free is understood to mean a concentration of less than 1 mmol / l, preferably less than 0.1 mmol / l.
[0037] The desired concentration of magnesium and / or calcium bicarbonate can be adjusted in particular based on the electrical conductivity of the water.
[0038] In this way, a control valve can be controlled based on conductivity.
[0039] In particular, a target value for the conductivity of 50-2000 pS / cm for drinking water and / or preferably 100-300 pS / cm for coffee water can be set.
[0040] The concentrated solution may contain 2-25 g / l, in particular 5-20 g / l magnesium and / or calcium hydrogen carbonate.
[0041] In a further development of the invention, the solution is fed into a pressure vessel, in particular an expansion tank. The overpressure in the pressure vessel can be, in particular, between 1.5 and 10 bar.
[0042] A pressure vessel can be used to easily prevent carbon dioxide from escaping, which would otherwise lead to the precipitation of magnesium or calcium carbonates. If the pressure vessel is designed as an expansion vessel, the magnesium or calcium bicarbonate-containing concentrate can be easily added to the water being treated, particularly without the use of a pump.
[0043] The expansion vessel can, in particular, be designed as a diaphragm expansion vessel. In such a vessel, an elastic diaphragm separates a gas volume from the concentrate. The pressure vessel can be pressurized via the gas volume throughout its entire use, particularly until the concentrate is consumed. The diaphragm can be designed, for example, as an intermediate wall or an inserted bladder.
[0044] In one embodiment of the invention, the pressure vessel is filled with carbon dioxide on the gas side. In particular, the gas volume of the pressure vessel can comprise or consist of carbon dioxide.
[0045] This avoids a concentration gradient with regard to carbon dioxide, which could lead to the carbon dioxide escaping through the membrane, which in turn can lead to precipitation of the carbonates.
[0046] In a preferred embodiment of the invention, the anion exchanger is converted into the bicarbonate form with sodium and / or potassium bicarbonate before passing the magnesium or calcium salt-containing solution through it. In particular, the anion exchanger can then be present in the bicarbonate form to at least 30%, preferably 50%-100%, and particularly preferably 80%-100% of its total capacity (according to DIN 54402:2009-04).
[0047] The anion exchanger is preferably pre-charged with chloride ions. Chloride ions, in particular, lead to high selectivity, i.e., rapid exchange into the bicarbonate form. This ensures that the chloride ions are almost completely removed from the solution even during the passage through the anion exchanger.
[0048] The invention further relates to a treated water which was produced using the method described above.
[0049] The water can, in particular, be chloride- and / or sodium-free. Preferably, the water has a carbonate hardness of 5°dH - 20°dH for use as drinking water and a carbonate hardness of 2°dH - 8°dH for use as coffee water.
[0050] The invention further relates to a pressure vessel which is designed in particular as an equalizing vessel.
[0051] This comprises a solution containing calcium and / or magnesium bicarbonate. In particular, the pressure vessel comprises a solution as prepared as described above. Furthermore, the pressure vessel may additionally contain a solution containing magnesium chloride and / or magnesium sulfate or magnesium chloride and / or calcium chloride, which is dosed separately.
[0052] The total hardness of the solution can be above 200°dH, especially between 400° and 800°dH.
[0053] The pressure in the pressure vessel is preferably 1.5 - 10 bar.
[0054] The invention further relates to an installation system comprising the pressure vessel.
[0055] The installation system preferably further comprises a sensor for the electrical conductivity of the treated water and a valve which is controlled based on the measured conductivity.
[0056] The calcium and / or magnesium bicarbonate-containing concentrate is easily added via the valve, and the mineral concentration, i.e. the hardness of the water, can thus be easily adjusted.
[0057] Description of an embodiment
[0058] The concentrate is produced, in particular, according to the process described below. In a first step, a weakly basic, medium-basic, or strongly basic ion exchanger, or a mixture of weakly basic, medium-basic, and / or strongly basic ion exchangers, is converted, preferably from the chloride form, into the bicarbonate form. The bicarbonate solution can consist, for example, of sodium or potassium bicarbonate.
[0059] The concentration of the bicarbonate solution can be between 5 and 10 g / l for sodium bicarbonate. When using potassium bicarbonate, the solution can also be more concentrated, for example, 15-25 g / l.
[0060] The loading of the ion exchanger is carried out as follows: R- HCOß' + CF (R= basic ion exchanger)(6)
[0061] The starting solution of the ion exchanger therefore contains predominantly Na or KCl.
[0062] In a second step, the anion exchanger loaded with bicarbonate ions is passed through an aqueous solution of magnesium or calcium chloride. The bicarbonate ion of the anion exchanger is exchanged for the chloride ion of MgCl or CaCl2, respectively, forming magnesium or calcium bicarbonate.
[0063] The concentration of calcium and / or magnesium bicarbonate flowing out of the ion exchanger can be adjusted via the concentration of calcium and / or magnesium chloride in the inlet.
[0064] The concentration of the magnesium bicarbonate produced in this way can be almost up to the solubility limit, usually up to 25 g / l Mg(HCO3)2. After the production of the bicarbonate, the anion exchanger is again in the chloride form (R-Cl), and the process can be repeated according to Eq. (6) and Eq. (7) or Eq. (8).
[0065] Instead of chloride salts, the whole process can also be carried out with nitrate salts.
[0066] If a highly concentrated solution of calcium or magnesium bicarbonate is produced, it can only be stored or transported for a longer period of time if magnesium carbonate does not precipitate due to the outgassing of CO2 in the solution.
[0067] According to a further aspect of the invention, the solution is filled into a pressure vessel. This preferably has an overpressure of 0.5 bar to 10 bar.
[0068] To treat or produce water, for example drinking water, coffee water, tea water, which preferably consists of pure calcium or magnesium-containing bicarbonate solution, the concentrated solution is dosed from a pressure vessel.
[0069] For this purpose, the water can be demineralized using a process such as reverse osmosis, a mixed bed exchanger or membrane distillation.
[0070] The solution from the pressure tank can then be dosed into the salt-free or almost salt-free demineralization process without a dosing pump via an adjustable valve, e.g. a ball valve, a needle valve, etc.
[0071] Short description of the drawings
[0072] The subject matter of the invention will be explained in more detail below with reference to the drawings Fig. 1 to Fig. 4.
[0073] Fig 1 shows schematically the loading of the anion exchanger with hydrogen carbonate ions.
[0074] Fig. 2 shows the production of the concentrate. Fig. 3 schematically shows the use of the concentrate for water treatment.
[0075] Fig. 4 is a flowchart according to an embodiment of the invention.
[0076] Detailed description of the drawings
[0077] Figure 1 shows a schematic view of a cartridge 1 with an anion exchanger. In a first step, a solution containing sodium bicarbonate is passed over the anion exchanger, which is in chloride form.
[0078] The ion exchanger is then almost completely converted into the bicarbonate form.
[0079] As shown schematically in Fig. 2, magnesium chloride is then passed over the cartridge 1 containing the anion exchange material.
[0080] This produces a concentrate containing magnesium bicarbonate, which is fed into a pressure vessel 10 via inlet 13.
[0081] The pressure vessel 10 is designed as a membrane compensation vessel and comprises a membrane 11 which separates the gas volume from the liquid.
[0082] Carbon dioxide, for example, can be added via gas inlet 12. This reduces the risk of carbon dioxide escaping.
[0083] A solution containing magnesium chloride and / or magnesium sulfate or magnesium chloride and / or calcium chloride can additionally be added to the pressure vessel via inlet 14.
[0084] Fig 3 shows an installation system.
[0085] This includes a water connection 2.
[0086] The incoming water is demineralized from water connection 2. In this embodiment, a reverse osmosis system 20 is provided for this purpose.
[0087] This comprises a membrane 21 which separates the chamber of the reverse osmosis system 20 into a concentrate side 22 and a permeate side 23.
[0088] The saline concentrate is fed to the effluent, while the permeate is almost salt-free and flows further via line 3.
[0089] In order to enrich the permeate with a defined amount of magnesium and / or calcium hydrogen carbonate, the pressure vessel 10 containing the concentrate is coupled to the line 3 via a valve 4.
[0090] The valve 4 is controlled by the electrical conductivity of the outlet water measured by the conductivity sensor 5.
[0091] The water can then be used for a coffee machine 6, in this embodiment a portafilter machine, to prepare coffee.
[0092] Because the control system maintains a consistent composition of the source water, the brewed coffee always tastes the same. In particular, the coffee machine's optimized settings (pressure temperature, grind size) do not need to be changed.
[0093] Fig. 4 is a flowchart of an embodiment of the method according to the invention.
[0094] First, an anion exchanger loaded with chloride is converted into the bicarbonate form by introducing a solution containing sodium bicarbonate.
[0095] A magnesium chloride solution is then passed over the anion exchanger.
[0096] The resulting magnesium bicarbonate concentrate is filled into an equalizing vessel.
[0097] A solution containing magnesium chloride and / or magnesium sulfate or magnesium chloride and / or calcium chloride can be added to the pressure vessel via inlet 14. The compensation vessel is pressurized by introducing carbon dioxide.
[0098] The concentrate is then used to specifically treat demineralized water.
[0099] The expansion tank is connected to a water pipe through which the desalinated incoming water flows.
[0100] The concentrate is then dosed in a controlled manner via conductivity.
[0101] The water is then used, for example, to make coffee.
[0102] The invention has made it possible to provide a process in a simple and effective manner by means of which a highly concentrated solution containing calcium and / or magnesium bicarbonate can be produced.
[0103] List of reference symbols:
[0104] 1 cartridge with anion exchanger
[0105] 2 Connection 3 Line
[0106] 4 valve
[0107] 5 Conductivity sensor
[0108] 6 coffee machines
[0109] 10 Pressure vessel 11 Membrane
[0110] 12 Gas inlet
[0111] 13 Entrance / Exit
[0112] 14 Entrance
[0113] 20 Reverse osmosis system 21 Membrane
[0114] 22 Concentrate page
[0115] 23 Permeate side
Claims
Claims:
1. A process for producing magnesium and / or calcium bicarbonate, wherein an anion exchanger loaded with bicarbonate ions is provided and then a solution containing magnesium and / or calcium salt is passed over the anion exchanger.
2. Method according to the preceding claim, characterized in that the solution is fed to a pressure vessel, in particular a compensation vessel, in particular a membrane compensation vessel.
3. Method according to one of the preceding claims, characterized in that a A solution containing magnesium and / or calcium salt is used which contains magnesium sulfate and / or magnesium chloride and / or calcium chloride.
4. Method according to one of the preceding claims, characterized in that the Hydrogen carbonate solution is then added to water to be treated, in particular demineralized water, the water being used in particular for preparing beverages.
5. Method according to the preceding claim, characterized in that the Dosing is regulated based on the electrical conductivity of the water, in particular with 50 to 2000 pS / cm for use as drinking water, preferably 100 to 300 pS / cm as the target value for coffee preparation.
6. Method according to one of the preceding claims, characterized in that the Solution is enriched with 2 to 25 g / l, in particular with 5 to 20 g / l magnesium and / or calcium hydrogen carbonate.
7. Method according to the preceding claim, characterized in that the Pressure vessel is filled with CO2 on the gas side, in particular a gas volume of the pressure vessel.
8. Method according to one of the preceding claims, characterized in that the Anion exchanger is converted into the bicarbonate form with sodium and / or potassium bicarbonate before passing through the solution containing magnesium and / or calcium salt, in particular to at least 30%, preferably to 50 - 100%, particularly preferably to 80 - 100% of its total capacity (according to DIN 54402: 2009-04).
9. Method according to the preceding claim, characterized in that the Anion exchanger is converted from the chloride form to the bicarbonate form.
10. Treated water produced by a process according to any one of the preceding claims.
11. Treated water according to the preceding claim, characterized in that the water is free of chloride and / or sodium.
12. Treated water according to one of the preceding claims, characterized in that the drinking water, e.g. for coffee preparation, has a carbonate hardness of 1.5 to 8° dH.
13. Pressure vessel, in particular an expansion vessel, comprising a calcium and / or magnesium bicarbonate-containing solution, in particular a solution prepared according to one of the preceding claims.
14. Installation system comprising a pressure vessel according to the preceding claim.
15. Installation system according to the preceding claims, characterized in that the installation system comprises a conductivity sensor and a valve which is controlled based on the measured conductivity.