Method and system for extracting salt from a layer of earth

Abstract

Method (2) for obtaining a salt (3) from a layer of earth (7), wherein - a first pump of a salt extraction system (1) pumps water into a layer of earth (7) (20) in which a salt (3) is arranged, and the pumped water dissolves the salt (3) from the layer of earth (7) to form a brine (5); - a second pump of the salt production system (1) pumps the formed brine (5) into a distillation unit (10) of the salt production system (1) (21) and the distillation unit (10) extracts the dissolved salt (3) from the pumped brine (5) by distillation (22); and - distilled water produced during distillation (6) is pumped into the layer of earth (7) (20).

Description

[0001] The invention relates to a method for extracting salt from a layer of earth, in which a first pump of a salt extraction system pumps water into a layer of earth containing salt, the pumped water dissolves the salt from the earth layer, forming a brine, a second pump of the salt extraction system pumps the brine formed into a distillation unit of the salt extraction system, and the distillation unit extracts the dissolved salt from the pumped brine by distillation. The invention further relates to a salt extraction system.

[0002] Methods for separating a salt from a brine, i.e. an aqueous solution of the salt, are in various forms part of the state of the art and serve to separate the water as the solvent of the salt from the salt dissolved in the water.

[0003] One purpose of such processes is to extract water from the brine.

[0004] DE 10 2015 109 119 A1 discloses a device and a method for desalinating seawater. Salt-free distilled water is obtained from the seawater by means of vacuum distillation.

[0005] JP 2012 091 108 A also discloses a device and a method for distilling water. In this method, the water to be distilled is continuously distilled under reduced pressure and heated by solar thermal energy.

[0006] WO 2020 048 577 A1 also discloses a device for the low-pressure distillation of water. The device uses the weight of the water to be distilled to provide a low pressure in the distillation chamber.

[0007] On the other hand, such processes can aim to extract the salt from the brine. The process described at the beginning is used, for example, in Argentina, Chile, and Bolivia to extract lithium carbonate and is an alternative to the also possible extraction of lithium carbonate in a mine, such as those operated in Australia. From DE 15 83 829 A1 and DE 14 58 622 A1, processes are known in which an unsaturated salt solution is pumped into a mixed salt formation containing sodium chloride and potassium chloride in order to obtain potassium chloride by cooling the brine.

[0008] The brine produced is usually pumped into large evaporation basins, from which the water evaporates, leaving behind the dissolved salt in the brine. This evaporation releases large quantities of water into the Earth's atmosphere, thereby affecting the Earth's climate and accelerating human-induced climate change. Such a process is known from DE 34 22 481 A1.

[0009] This negative consequence of brine extraction can be prevented by distilling the brine in a distillation plant instead of allowing it to evaporate. However, the water consumption for brine production is very high. To obtain the amount of lithium carbonate needed for an electric vehicle, approximately 10 m³ of water are required. 3Water is consumed. If the brine is produced using groundwater, the local groundwater level drops as a result of the brine extraction. Especially in the highlands of South America, local groundwater levels are naturally low.

[0010] One object of the invention is to propose a method for extracting salt from a layer of earth that is environmentally and climate-friendly. A further object of the invention is to provide a salt extraction system, i.e., a system for obtaining salt.

[0011] An object of the invention is a method for extracting salt from a layer of earth, in which a first pump of a salt extraction system pumps water into a layer of earth containing salt. The pumped water dissolves the salt from the earth layer, forming a brine. A second pump of the salt extraction system pumps the brine to a distillation unit of the salt extraction system, and the distillation unit extracts the dissolved salt from the pumped brine by distillation. The layer of earth is typically located on the earth's surface, i.e., an upper layer of the earth's crust, which may have a thickness of approximately 40 cm. The salt may be present in the earth layer as a crystalline salt or as a mineral salt. The water is a solvent for the salt. The brine is an aqueous solution of the salt. The dissolved salt is concentrated in a distillation sump, as is customary.

[0012] According to the invention, the distilled water produced during distillation is pumped into the soil layer. This distilled water is the distillate produced during distillation. The distillate is then reused to dissolve another salt from the soil layer. In this way, evaporation of the distilled water, i.e., its release into the Earth's atmosphere, is prevented, thus avoiding or at least reducing any negative impact on the Earth's climate caused by the process. Furthermore, the water is cyclically reused as a solvent, resulting in low consumption of externally supplied water. This low consumption of externally supplied water reduces the environmental damage caused by the process.

[0013] The method according to the invention is ideally carried out continuously.

[0014] The brine produced is preferably distilled at low pressure and / or low temperature. Low pressure refers to gas pressure and, relative to atmospheric pressure at the Earth's surface (air pressure), is a vacuum, i.e., less than 1 bar. Pressures below 0.3 bar are referred to as a vacuum. Distillation at a gas pressure above 0.3 bar is called low-pressure distillation, while distillation at a gas pressure below 0.3 bar is called vacuum distillation.

[0015] Distillation involves raising the temperature of the brine above its boiling point. The boiling point depends on the gas pressure and decreases with decreasing gas pressure. Consequently, the brine can be distilled at a lower or much lower temperature than its boiling point at atmospheric pressure using low-pressure or vacuum distillation. Distillation at a low temperature is called low-temperature distillation. While providing the reduced pressure or vacuum does consume electrical energy, heating the brine to the low temperature requires less energy than heating it to its boiling point at atmospheric pressure.

[0016] Additionally, groundwater can be extracted and pumped into the ground. In other words, groundwater is supplied externally to the salt production system. Thanks to the cyclical reuse of the distilled water, however, the salt production system consumes only 10% of the amount of groundwater used in conventional evaporation ponds. This prevents or at least significantly reduces the lowering of the local groundwater level, thus minimizing any ecological damage caused by the process.

[0017] Ideally, the distilled water produced is temporarily stored and heated in a water tank within the salt production system before being pumped into the ground. The water tank ensures continuous operation of the salt production system. Heating the distilled water allows for a higher concentration of dissolved salt in the resulting brine.

[0018] Advantageously, solar thermal energy supplied by a heat exchanger in the salt production system is stored in a thermal storage unit within the system. This stored solar thermal energy is then used to heat the distilled water produced. The thermal storage unit ensures the continuous operation of the salt production system. The thermal energy stored in the unit is climate-neutral and free of charge. As a result, the distilled water is heated purely by solar thermal energy.

[0019] Alternatively or additionally, thermal energy provided by an electrically operated heating element of the salt production system can be stored in the thermal storage unit. The electrically operated heating element allows for the exclusive or supplementary storage of thermal energy when solar thermal energy is unavailable or insufficient, for example, due to cloud cover and / or at night. Thanks to the heating element, the continuity and productivity of the process are not affected by weather or time of day.

[0020] In one embodiment, lithium carbonate is obtained as the salt. Lithium carbonate, Li₂CO₃, contains lithium, Li. The lithium is needed for the production of electrical storage devices, which are used, for example, in mobile devices such as smartphones and the like, or in electric vehicles. In view of the increasing demand for lithium and the greater environmental and climate impact associated with conventional lithium extraction, the process according to the invention improves the life cycle assessment and the climate impact, particularly for the rapidly developing field of electromobility.

[0021] Advantageously, a compaction stage of the salt production plant mechanically compacts the recovered lithium carbonate. The lithium carbonate can then be pressed from the compaction stage into a strand. Elemental lithium can be extracted from the strand in a manner known per se, for example, by chemical or physical processes such as high-temperature distillation. Extracting the lithium from the strand is a subsequent step in the process according to the invention and is not part of the process itself.

[0022] Preferably, the salt production system is operated exclusively by means of regeneratively generated electrical energy provided by an electrical energy storage system, a solar power system, and / or a wind turbine of the salt production system. The electrical energy storage system ensures continuous operation of the salt production system. Ideally, the electrical energy storage system is charged exclusively with electrical energy provided by the solar power system and / or the wind turbine. The primary energy demand of the salt production system is met without the combustion of fossil fuels, thereby further improving the environmental and climate footprint of the process according to the invention.

[0023] The production of distilled water can involve condensing water vapor generated during distillation on a cold trap located between a vacuum pump and a vacuum chamber of the distillation system. The cold trap prevents the water vapor flowing towards the vacuum pump from leaving the distillation system through the pump.

[0024] Another aspect of the invention is a salt extraction system with a distillation unit. The salt extraction system is a system for obtaining salt from a layer of earth and is suitable for dissolving a crystalline or mineral salt located in the layer of earth to form a brine and for extracting the dissolved salt from the brine by distillation.

[0025] According to the invention, the salt extraction system is configured to carry out a method according to one embodiment of the invention. The salt extraction system enables the environmentally friendly and climate-friendly extraction of salt from a layer of earth.

[0026] A significant advantage of the process according to the invention is that it is environmentally friendly and has minimal impact on the ecosystem surrounding the salt production system, in particular consuming very little groundwater. A further advantage is that it has virtually no impact on the global climate, especially that water input into the atmosphere is minimal and that the CO2 balance can be at least substantially neutralized.

[0027] The invention is schematically illustrated in the drawings with reference to one embodiment and is further described with reference to the drawings. The drawings show: Fig. 1 a salt extraction system according to an embodiment of the invention; and Fig. 2 a flowchart of a process according to an embodiment of the invention for obtaining a salt from a layer of earth.

[0028] Fig. Figure 1 shows a salt production system 1 according to an embodiment of the invention. The salt production system 1 comprises a distillation unit 10. The distillation unit 10 can be configured as a low-pressure distillation unit or as a vacuum distillation unit. The distillation unit 10 can therefore include a vacuum pump, an inlet chamber, at least one vacuum chamber, an outlet lock, and, in particular, a cold trap arranged between the vacuum pump and the at least one vacuum chamber. Furthermore, the salt production system 1 can include a water tank 11, an electrical energy storage device 12, a heat storage device 13, and a mechanical compression stage 17 (see Figure 1). Fig. 2) include. The heat storage unit 13 may include an electrically operated heating element 130.

[0029] The salt extraction system 1 may also include a first pump configured to pump water into a layer of earth 7 and / or a second pump configured to pump brine from the layer of earth 7 into the distillation plant 10.

[0030] Furthermore, the salt production system 1 can include a heat exchanger 14 for solar thermal energy extraction, a solar power system 15 for photovoltaic conversion of solar light energy into electrical energy and / or a wind power plant 16 for conversion of kinetic wind energy into electrical energy.

[0031] Fig. Figure 1 further shows an energy flow 8, 9 during operation of the salt production system 1. The energy flow 8 of the salt production system 1 during a day comprises the following sections. The thermal storage unit 13 is heated with thermal energy provided by the heat exchanger 14. The electrical energy storage unit 12 is charged with electrical energy provided by the solar power plant 15 and / or the wind turbine 16.

[0032] The heating element 130 is operated with electrical energy provided by the solar power system 15 and / or the wind turbine 16. The distillation unit 10 is operated with electrical energy provided by the electrical energy storage unit 12, the solar power system 15, and / or the wind turbine 16. The water tank 11 is heated with thermal energy provided by the heat storage unit 13.

[0033] The energy flow 9 of the salt production system 1 during a night comprises the following sections. The electrical energy storage unit 12 is charged with electrical energy provided by the wind turbine 16. The heating element 130 is operated with electrical energy provided by the electrical energy storage unit 12 and / or the wind turbine 16. The distillation unit 10 is operated with electrical energy provided by the electrical energy storage unit 12 and / or the wind turbine 16. The water tank 11 is heated with thermal energy provided by the heat storage unit 13.

[0034] The salt extraction system 1 is configured to extract a salt 3 from a layer of earth 7 by carrying out a process 2 as follows.

[0035] Fig. Figure 2 shows a flowchart of the process 2 according to an embodiment of the invention for obtaining a salt 3 from a layer of earth 7.

[0036] A first pump of a salt extraction system 1 pumps 20 liters of water into a layer of earth 7 in which a salt 3 is located. The pumped water dissolves the salt 3 from the layer of earth 7, forming a brine 5.

[0037] A second pump of the salt production system 1 pumps 21 the brine 5 formed into the distillation unit 10 of the salt production system 1. The distillation unit 10 extracts 22 the dissolved salt 3 from the pumped brine 5 by distillation. Preferably, the brine 5 formed is distilled at a low pressure and / or at a low temperature.

[0038] The distilled water 6 produced during distillation is pumped into the soil layer 7. The production of the distilled water 6 can include condensing water vapor generated during distillation on a cold trap of the distillation plant 10, which is located between a vacuum pump and a negative pressure chamber of the distillation plant 10. Additionally, groundwater 4 can be extracted and pumped into the soil layer 7 23.

[0039] The distilled water 6 produced is advantageously temporarily stored and heated in the water tank 11 of the salt production system 1 before being pumped into the layer of earth 7.

[0040] Solar thermal energy provided by the heat exchanger 14 of the salt production system 1 can be stored in the thermal storage tank 13 of the salt production system 1. Alternatively or additionally, thermal energy provided by the electrically operated heating element 130 of the salt production system 1 can be stored in the thermal storage tank 13. The distilled water 6 produced can be heated using the stored thermal energy.

[0041] For example, lithium carbonate is obtained as salt 3. The mechanical compaction stage 17 can mechanically compact the obtained lithium carbonate.

[0042] Ideally, the salt production system 1 is operated exclusively by means of regeneratively generated electrical energy provided by the electrical energy storage system 12, the solar power plant 15 and / or the wind power plant 16 of the salt production system 1. REFERENCE MARK LIST: 1 Salt extraction system 10 distillation plants 11 Water tank 12 electrical energy storage devices 13 Heat storage 130 heating element 14 heat exchangers (solar thermal) 15 Solar power system (photovoltaics) 16 wind turbines 17 mechanical compaction stage 2 procedures 20 water pumps 21 brine pumps 22 Extracting the salt 23 groundwater pumps 24 Caches 3 Salt 4 Groundwater 5 Sole 6 distilled water 7 Earth layer

Claims

[1] Method (2) for obtaining a salt (3) from a layer of earth (7), wherein - a first pump of a salt extraction system (1) pumps water into a layer of earth (7) (20) in which a salt (3) is arranged, and the pumped water dissolves the salt (3) from the layer of earth (7) to form a brine (5); - a second pump of the salt production system (1) pumps the formed brine (5) into a distillation unit (10) of the salt production system (1) (21) and the distillation unit (10) extracts the dissolved salt (3) from the pumped brine (5) by distillation (22); and - distilled water produced during distillation (6) is pumped into the layer of earth (7) (20). [2] Method according to claim 1, wherein the brine formed (5) is distilled at a low pressure and / or at a low temperature and / or additionally groundwater (4) is extracted (23) and pumped into the earth layer (7). [3] Method according to claim 1 or 2, wherein the produced distilled water (6) is temporarily stored (24) and heated in a water tank (11) of the salt production system (1) before being pumped into the layer of earth (7). [4] Method according to claim 3, wherein solar thermal energy provided by a heat exchanger (14) of the salt production system (1) is stored in a heat storage unit (13) of the salt production system (1) and the produced distilled water (6) is heated by means of the stored thermal energy. [5] Method according to claim 3 or 4, wherein heat energy provided by an electrically operated heating element (130) of the salt production system (1) is stored in the heat storage unit 13. [6] Method according to any one of claims 1 to 5, wherein lithium carbonate is obtained as the salt (3). [7] Method according to claim 6, wherein a mechanical compaction stage (17) of the salt recovery system (1) mechanically compacts the recovered lithium carbonate. [8] Method according to any one of claims 1 to 7, wherein the salt production system is operated exclusively by means of regeneratively generated electrical energy provided by an electrical energy storage device (12), a solar power plant (15) and / or a wind power plant (16) of the salt production system (1). [9] Method according to any one of claims 1 to 8, wherein the production of the distilled water (6) comprises condensing water vapor produced during distillation on a cold trap of the distillation plant (10) arranged between a vacuum pump of the distillation plant (10) and a low pressure chamber of the distillation plant (10). [10] Salt extraction system (1) comprising a distillation apparatus (10) and configured to carry out a process (2) according to any one of claims 1 to 9.

Images