Water softening apparatus and method

Abstract

The application relates to the technical field of water treatment, in particular to a water softening device and method. The water softening device comprises an electrolysis assembly, a crystallizer and a separator. The electrolysis assembly comprises an anode chamber and a cathode chamber which are not communicated with each other. A crystallization chamber is communicated with a cathode water outlet of the cathode chamber through a water outlet pipeline. A check valve assembly is arranged on the water outlet pipeline, and the check valve assembly only allows the alkaline liquid to flow in one direction towards the crystallizer. The alkaline liquid in the cathode chamber generates a crystallization reaction under the action of a crystal seed, and the generated crystal slurry is discharged through a crystal discharge port. The obtained softened water is discharged through an overflow port. The separator is used for separating the crystal slurry discharged from the crystallizer. A first outlet is used for discharging a first mixed medium containing coarse crystals, and a second outlet is used for discharging a second mixed medium containing fine crystal seeds. The second mixed medium is returned to the crystallization chamber of the crystallizer. The application can avoid the participation of the cathode in crystallization, and solves the problems of cathode fouling and poor crystallization effect.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a water softening device and method. Background Technology

[0002] In electrochemical water softening technology, precipitation and crystallization are concentrated on the cathode surface and near the boundary layer. The precipitation rate is strictly limited by the cathode geometry and mass transfer conditions, and there are also problems such as easy scaling on the cathode and poor crystallization effect. To address this, existing technologies use diaphragm electrolysis combined with an external crystallizer, but problems still exist such as crystallization slurry reflux into the cathode area, the electrolysis unit still retaining the crystallization induction environment, and the use of fixed-bed packing for the crystallization interface. The cathode still directly or indirectly participates in the crystallization process, failing to fundamentally solve this problem. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a water softening device that achieves isolation between the anode and cathode, while utilizing an external crystallizer and water circuit design to completely prevent cathode participation in crystallization, thus avoiding cathode scaling and improving the crystallization effect.

[0004] This invention also proposes a water softening method that can automatically adjust operating parameters according to water quality fluctuations, making it highly adaptable.

[0005] The water softening device of this invention includes an electrolysis component, a crystallizer, and a separator. The electrolysis component includes an electrolytic cell and a cation exchange membrane disposed within the electrolytic cell. The cation exchange membrane divides the electrolytic cell into an independent and non-communicating anode chamber and a cathode chamber. An anode is disposed in the anode chamber, and a cathode is disposed in the cathode chamber. The anode and cathode are electrically connected to the positive and negative terminals of a DC power supply, respectively. The crystallizer includes a crystallization chamber, a crystal discharge port, and an overflow port. The crystallization chamber is connected to the cathode outlet of the cathode chamber via a water outlet pipe. A check valve component is provided on the water outlet pipe, which only allows alkaline liquid in the cathode chamber to flow towards the crystallizer. The crystallizer operates in a unidirectional flow; seed crystals are provided in the crystallization chamber, and the alkaline liquid in the cathode chamber undergoes a crystallization reaction under the action of the seed crystals. The resulting crystal slurry is discharged through the crystal discharge port, and the softened water is discharged through the overflow port. The separator includes an inlet, a first outlet, and a second outlet. The inlet is connected to the crystal discharge port of the crystallizer, and the second outlet is connected to the crystallization chamber. The separator is used to separate the crystal slurry discharged from the crystallizer. The first outlet is used to discharge a first mixed medium containing coarse crystals, and the second outlet is used to discharge a second mixed medium containing fine seed crystals. The second mixed medium flows back into the crystallization chamber of the crystallizer.

[0006] The water softening device of this invention effectively suppresses cathode scaling by spatially separating the electrolytic alkali production and the crystallization process, thus extending the continuous operation cycle of the device. At the same time, it utilizes seed crystals to induce heterogeneous nucleation, thereby improving the separation performance of the crystallization products and overcoming the limitation of cathode surface area on processing capacity.

[0007] In some embodiments, the crystallizer further includes a flow guiding structure and / or a circulation structure, the flow guiding structure and / or circulation structure being used to keep the seed crystals suspended in the crystallization chamber;

[0008] The flow guiding structure includes a flow guiding plate with a U-shaped cross-section, and the U-shaped opening side of the flow guiding plate faces the crystal discharge port; The circulation structure includes an inner circulation component and / or an outer circulation component. The inner circulation component includes at least one of a stirrer, an air-lift device, and an inner circulation pump. The outer circulation component includes an outer circulation pipe and an outer circulation pump disposed on the outer circulation pipe.

[0009] In some embodiments, the seed crystal is at least one of calcite, aragonite, spheroidal aragonite, and inert seed carrier; and / or, the seed crystal size in the crystallizer is 10 μm to 800 μm; and / or, the seed crystal mass concentration in the crystallizer is 0.5 g / L to 50 g / L.

[0010] In some embodiments, the separator is a hydrocyclone separator, which is used to perform particle size classification separation of crystal slurry, and the separated coarse crystals have a particle size greater than 300 μm and fine seed crystals have a particle size less than or equal to 300 μm.

[0011] In some embodiments, the water softening device further includes a slag discharge pipe and a seed crystal return pipe. The slag discharge pipe connects the crystal discharge port of the crystallizer with the water inlet of the separator, and a slag discharge valve is provided on the slag discharge pipe. The seed crystal return pipe connects the second outlet of the separator with the crystallization chamber of the crystallizer, and a seed crystal return pump is provided on the seed crystal return pipe.

[0012] In some embodiments, the water softening device further includes a cathode inlet pipe, an anode inlet pipe, a flow meter, a pH meter, an overflow pipe, and a control system. The cathode inlet pipe is connected to the cathode chamber and is equipped with a cathode inlet pump and a first analyzer. The anode inlet pipe is connected to the anode chamber and is equipped with an anode inlet pump. The flow meter and pH meter are located on the outlet pipe. The overflow pipe is connected to the overflow port and is equipped with a second analyzer and a conductivity meter. Both the first analyzer and the second analyzer are used to detect the contents of their respective pipes. The system measures the hardness and alkalinity of the water. It is electrically connected to the pH meter, flow meter, first analyzer, second analyzer, conductivity meter, DC power supply, circulation structure, cathode inlet pump, anode inlet pump, seed reflux pump, and slag discharge valve. Based on the detection information fed back from the first analyzer, second analyzer, flow meter, pH meter, and conductivity meter, the system adjusts at least one of the following: the current and / or voltage of the DC power supply, the on / off state and opening degree of the slag discharge valve, the power of the cathode inlet pump, the power of the anode inlet pump, the power of the seed reflux pump, and the operating state of the circulation structure.

[0013] The water softening device of this invention can overcome the limitation of cathode surface area on sedimentation rate, fundamentally inhibit cathode scaling, realize controllable crystal particle size and sedimentation performance, reduce overall energy consumption and device volume, and improve the feasibility of continuous industrial applications.

[0014] The water softening method of this invention is implemented by any of the water softening devices described above, and includes the following steps: S1. Electrolysis for Alkali Production: Raw water is introduced into the cathode and anode chambers of the electrolytic cell, respectively. A direct current is applied using the DC power supply, causing a water reduction reaction at the cathode to generate OH-. - An alkaline liquid is obtained in the cathode chamber; S2. Alkaline liquid transfer: The alkaline liquid in the cathode chamber is sent into the crystallizer through the outlet pipe, and the alkaline liquid is prevented from flowing back into the cathode chamber by the check valve on the outlet pipe; S3. Crystallization reaction: The alkaline liquid is thoroughly mixed with the seed crystals in the crystallization chamber, and the Ca²⁺ in the alkaline liquid… + With CO3² - Heterogeneous nucleation and crystal growth occur on the surface of the seed crystal, generating settleable CaCO3 crystal particles, and the resulting softened water is discharged through the overflow port of the crystallizer; S4. Separation and Seed Circulation: The crystal slurry discharged from the crystallizer is sent to the separator for graded separation. The second mixed medium containing fine seed crystals obtained by separation is returned to the crystallization chamber of the crystallizer, and the first mixed medium containing coarse crystals is discharged and recycled.

[0015] In some embodiments, in step S1, the hydraulic residence time of the cathode chamber is controlled to be 1s to 15s, the water flow velocity in the cathode chamber is 0.3m / s to 1.2m / s, and the current density in the cathode chamber is 50A / m² to 2000A / m².

[0016] In some embodiments, in step S3, the hydraulic residence time in the crystallization chamber is controlled to be 1 min to 60 min, the pH value of the water in the crystallization chamber is 8.5 to 11.5, and the seed crystal concentration in the crystallization chamber is 0.5 g / L to 50 g / L.

[0017] In some embodiments, the water softening method further includes step S5: pH adjustment: mixing the acidic liquid generated in the anode chamber of the electrolytic cell with the softened water discharged through the overflow port to adjust the pH value of the softened water to neutral or weakly alkaline.

[0018] The water softening method of this invention makes the electrolytic alkali production and heterogeneous nucleation crystallization process stable and controllable by limiting the hydraulic residence time, water flow velocity, current density, pH value and seed concentration parameters of the cathode chamber and crystallization chamber. Attached Figure Description

[0019] Figure 1 This is the overall flowchart of the present invention.

[0020] Figure 2 This is a connection diagram of the control system of the present invention.

[0021] Figure label: 1. Electrolysis assembly; 101. Electrolytic cell; 102. Cation exchange module; 103. Anode chamber; 104. Cathode chamber; 105. Anode; 106. Cathode; 107. DC power supply; 108. Cathode inlet pipe; 109. Cathode inlet pump; 110. Anode inlet pipe; 111. Anode inlet pump; 2. Crystallizer; 201. Crystallization chamber; 202. Flow guiding structure; 203. Crystal discharge port; 204. Overflow port; 3. Separator; 301. Inlet; 302. First outlet; 303. Second outlet; 4. Water outlet pipe; 41. Check valve assembly; 5. Slag discharge pipe; 51. Slag discharge valve; 6. Seed reflux pipeline; 61. Seed reflux pump; 7. Flow meter; 8. pH meter; 9. First analyzer; 10. Second analyzer; 11. Conductivity meter; 12. Control system. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] like Figures 1-2 As shown, the water softening device of this embodiment includes an electrolysis component 1, a crystallizer 2, and a separator 3. The electrolysis component 1 includes an electrolysis cell 101 and a cation exchange membrane disposed within the electrolysis cell 101. The cation exchange membrane divides the electrolysis cell 101 into an independent and non-communicating anode chamber 103 and a cathode chamber 104. An anode 105 is disposed in the anode chamber 103, and a cathode 106 is disposed in the cathode chamber 104. The anode 105 and cathode 106 are electrically connected to the positive and negative terminals of a DC power supply 107, respectively. The crystallizer 2 includes a crystallization chamber 201, a crystal discharge port 203, and an overflow port 204. The crystallization chamber 201 is connected to the outlet of the cathode 106 of the cathode chamber 104 via a water outlet pipe 4. A check valve component 41 is provided on the water outlet pipe 4, which only allows the cathode chamber to flow back. The alkaline liquid in the cathode chamber 104 flows unidirectionally toward the crystallizer 2; the crystallization chamber 201 is provided with seed crystals, and the alkaline liquid in the cathode chamber 104 undergoes a crystallization reaction under the action of the seed crystals. The generated crystal slurry is discharged through the crystal discharge port 203, and the obtained softened water is discharged through the overflow port 204; the separator 3 includes an inlet 301, a first outlet 302, and a second outlet 303. The inlet 301 is connected to the crystal discharge port 203 of the crystallizer 2, and the second outlet 303 is connected to the crystallization chamber 201; the separator 3 is used to separate the crystal slurry discharged from the crystallizer 2. The first outlet 302 is used to discharge the first mixed medium containing coarse crystals, and the second outlet 303 is used to discharge the second mixed medium containing fine seed crystals. The second mixed medium flows back into the crystallization chamber 201 of the crystallizer 2.

[0024] In this embodiment, the water softening device separates the electrolytic alkali production and crystallization reaction in terms of space and function. The cathode chamber 104 is solely responsible for hydroxide ion generation, while the crystallization process is completed in a separate crystallizer 2. This prevents scaling on the cathode 106 surface, allowing the device to operate continuously and stably for extended periods without frequent shutdowns for cleaning.

[0025] The water softening device in this embodiment includes an electrolysis unit 1, a crystallizer 2, and a separator 3.

[0026] Electrolysis assembly 1 includes an electrolytic cell 101 and a cation exchange membrane disposed within the electrolytic cell 101. The cation exchange membrane divides the electrolytic cell 101 into an independent and non-communicating anode chamber 103 and a cathode chamber 104. An anode 105 is disposed in the anode chamber 103, and a cathode 106 is disposed in the cathode chamber 104. The anode 105 and cathode 106 are electrically connected to the positive and negative terminals of a DC power supply 107, respectively. During operation, raw water enters through the inlet of the cathode chamber 104. Under the action of DC current, a water reduction reaction occurs in the cathode 106, generating hydroxide ions, thus forming an alkaline liquid in the cathode chamber 104. Simultaneously, an oxidation reaction occurs in the anode chamber 103, generating an acidic liquid. The cation exchange membrane allows cations such as sodium and calcium ions to migrate from the anode chamber 103 to the cathode chamber 104 to maintain charge balance, but effectively prevents the acidic liquid in the anode chamber 103 from mixing with the alkaline liquid in the cathode chamber 104.

[0027] The crystallizer 2 includes a crystallization chamber 201, a crystal discharge port 203, and an overflow port 204. The crystallization chamber 201 is connected to the cathode 106 outlet of the cathode chamber 104 via a water outlet pipe 4. A check valve assembly 41 is provided on the water outlet pipe 4. The check valve assembly 41 allows alkaline liquid in the cathode chamber 104 to flow unidirectionally towards the crystallizer 2, preventing liquid in the crystallizer 2 from flowing back into the cathode chamber 104. The check valve assembly 41 can adopt common one-way valve structures such as lift type, swing type, or spring type, or it can be replaced by other anti-backflow devices with one-way flow function, such as an electric shut-off valve with liquid level or pressure interlock control, or a non-mechanical anti-backflow design such as a U-shaped bend with air isolation. As long as it can achieve the function of allowing alkaline liquid to flow from the cathode chamber 104 to the crystallizer 2 while preventing reverse flow, the check valve assembly 41 can be replaced.

[0028] Seed crystals are pre-added to the crystallization chamber 201. Alkaline liquid from the cathode chamber 104 enters the crystallization chamber 201 and mixes thoroughly with the seed crystals suspended within the chamber. Calcium and carbonate ions in the alkaline liquid reach a supersaturated state on the seed crystal surface, preferentially undergoing heterogeneous nucleation, followed by gradual crystal growth. The resulting calcium carbonate crystals settle to the bottom of the crystallization chamber 201, forming a crystal slurry, which is discharged through the crystal outlet 203. After the crystallization reaction is complete, the clear liquid at the top, which is softened water, is discharged through the overflow outlet 204.

[0029] The separator 3 includes an inlet 301, a first outlet 302, and a second outlet 303. The inlet 301 is connected to the crystal discharge port 203 of the crystallizer 2 and is used to receive the crystal slurry discharged from the crystallizer 2. The second outlet 303 is connected to the crystallization chamber 201. The separator 3 separates the incoming crystal slurry. The first outlet 302 discharges a first mixed medium containing coarse crystals, which can be externally transported and used as industrial packing material. The second outlet 303 discharges a second mixed medium containing fine crystal seeds. The second mixed medium flows back into the crystallization chamber 201 of the crystallizer 2 to continue participating in subsequent crystallization reactions as crystal seeds, maintaining the concentration and activity of the crystal seeds within the crystallization chamber 201. Specifically, the separator 3 can be a settling tank, a hydrocyclone separator, a filter, or a combination thereof, achieving both coarse and fine filtration and flow separation.

[0030] During the entire operation of the device, the two processes of alkali production by electrolysis and crystallization precipitation are completed in independent spaces. The cathode chamber 104 does not participate in the crystallization process, which reduces the possibility of precipitate adhering to the surface of the cathode 106 from the source. The crystallization process is controlled by seed induction, and the generated crystal particles have a relatively uniform particle size, which facilitates subsequent solid-liquid separation. At the same time, the recycling of seed crystals can reduce the system operating cost.

[0031] In some embodiments, the crystallizer 2 further includes a flow guiding structure 202 and / or a circulation structure, which are used to keep the seed crystals suspended in the crystallization chamber 201. The flow guiding structure 202 includes a flow guiding plate with a U-shaped cross-section, and the U-shaped opening side of the flow guiding plate faces the crystal discharge port 203; The circulation structure includes an internal circulation component and / or an external circulation component. The internal circulation component includes at least one of a stirrer, an air-lift device, and an internal circulation pump. The external circulation component includes an external circulation pipe and an external circulation pump disposed on the external circulation pipe.

[0032] In this embodiment, the crystallizer 2 is equipped with a flow guiding structure 202 or a circulation structure to keep the seed crystals in a uniform suspended state in the crystallization chamber 201, avoiding the seed crystals from settling and accumulating at the bottom, thereby increasing the contact opportunity between the seed crystals and the alkaline liquid, which is conducive to the continuous and stable crystallization reaction.

[0033] The flow guiding structure 202 includes a U-shaped flow guiding plate. The flow guiding plate is installed inside the crystallization chamber 201, with its U-shaped opening facing the crystal discharge port 203. During the operation of the crystallizer 2, the alkaline liquid enters the crystallization chamber 201 through the inlet 301 and diffuses upwards or to both sides along the U-shaped flow channel of the flow guiding plate, causing the seed crystals suspended in the liquid to form an orderly internal circulation flow. The design of the U-shaped opening facing the crystal discharge port 203 allows coarser crystals that have settled to the bottom to be guided to the vicinity of the crystal discharge port 203 for easy discharge, while finer seed crystals rise with the liquid along the outer or inner side of the flow guiding plate and re-participate in the crystallization reaction.

[0034] The circulation structure includes at least one of an internal circulation component and an external circulation component. The internal circulation component can be an agitator, a lift-up device, or an internal circulation pump. The agitator is installed inside the crystallization chamber 201, and its rotating blades drive the liquid and seed crystals together. The lift-up device introduces gas into the bottom of the crystallization chamber 201, using the lifting force generated by the rising bubbles to carry the seed crystals and liquid upwards. The internal circulation pump is located inside the crystallizer 2 or on a bypass, drawing the slurry from the lower part of the crystallization chamber 201 and sending it to the upper part to re-enter the chamber. The external circulation component includes an external circulation pipe and an external circulation pump installed on the external circulation pipe. The inlet and outlet of the external circulation pipe are connected to different locations in the crystallization chamber 201. After the external circulation pump starts, it draws the slurry in the crystallization chamber 201 from the inlet and sends it back to the crystallization chamber 201 from the outlet through the external circulation pipe, thus forming an external circulation flow. Any of the above circulation structures can effectively prevent seed crystal deposition in the crystallization chamber 201, maintaining the seed crystals in a suspended state.

[0035] In practical applications, the flow guiding structure 202 can be used in conjunction with the circulation structure: the flow guiding plate provides a directional flow path for the seed crystals, and the circulation structure provides the driving force; the combination of the two can achieve a better suspension effect. Alternatively, only one of the structures can be used, as long as it can keep the seed crystals suspended within the crystallization chamber 201.

[0036] In some embodiments, the seed crystal is at least one of calcite, aragonite, spheroidal aragonite, and inert seed carrier; and / or, the seed crystal size in the crystallizer 2 is 10 μm to 800 μm; and / or, the seed crystal mass concentration in the crystallizer 2 is 0.5 g / L to 50 g / L.

[0037] This embodiment provides a good nucleation interface for crystallizer 2 by selecting appropriate seed crystal type, particle size range, and mass concentration. This allows calcium ions in the alkaline liquid to more easily undergo heterogeneous nucleation on the seed crystal surface, resulting in a more stable crystal growth rate, uniform crystal particle size, and less likelihood of fine slime formation.

[0038] Seed crystals can be at least one of calcite, aragonite, or aragonite. Calcite is the most stable crystal form of calcium carbonate, with stable chemical properties and is not prone to phase transitions; aragonite has a high growth rate under certain conditions, which is beneficial for rapid hardness removal; aragonite, as a metastable crystal form, has high surface activity and a short nucleation induction period. These three seed crystals can be used individually or in combination, depending on the raw water quality and treatment objectives. In addition, seed crystals can also include inert seed carriers. Inert seed carriers can be ceramic microparticles, quartz sand, or glass beads. These materials themselves do not participate in the crystallization reaction but can provide a smooth surface for calcium carbonate deposition, making them particularly suitable for system start-up phases or situations where the source of natural seed crystals is limited.

[0039] The particle size of the seed crystals in crystallizer 2 can be controlled within the range of 10 μm to 800 μm. If the particle size is too small, it is easily lost with the effluent, increasing the burden on subsequent separation; if the particle size is too large, the specific surface area provided per unit mass is small, resulting in insufficient nucleation sites. In actual operation, an appropriate particle size range can be selected according to the particle size requirements of the target product and the performance of the separation equipment, for example, preferably 50 μm to 300 μm.

[0040] The mass concentration of seed crystals in crystallizer 2 can be controlled within the range of 0.5 g / L to 50 g / L. If the mass concentration is too low, there will be insufficient nucleation surface available in crystallizer 2, which will easily induce homogeneous nucleation and generate a large number of fine-particle crystals, affecting the subsequent solid-liquid separation effect. If the mass concentration is too high, although there will be sufficient nucleation surface, it will increase the energy consumption of circulating stirring and may also cause excessive wear of seed crystals.

[0041] The restrictions on seed type, particle size, and mass concentration can be implemented individually or in any combination. For example, selecting calcite as the seed crystal, controlling its average particle size to 100 μm, and initially adding it at a mass concentration of 10 g / L can achieve a good crystallization softening effect. Alternatively, at the initial stage of system startup, calcite and a small amount of inert seed carrier can be added simultaneously. After the seed crystal circulation stabilizes, the inert seed carrier is gradually encapsulated by calcium carbonate, eventually transforming into a seed crystal system dominated by calcium carbonate.

[0042] In some embodiments, the separator 3 is a hydrocyclone separator 3, which is used to perform particle size classification separation of the crystal slurry. The separated coarse crystals have a particle size greater than 300 μm, and the fine seed crystals have a particle size less than or equal to 300 μm.

[0043] In this embodiment, a hydrocyclone separator 3 is used as the separator, which uses centrifugal force to classify the crystal slurry according to particle size. In this way, the larger coarse crystals are discharged from the bottom, while the smaller fine crystals are returned to the crystallizer 2 from the overflow port 204, realizing automatic screening and recycling of the crystals without the need for additional classification equipment.

[0044] The hydrocyclone separator 3 is a device that uses centrifugal force generated by fluid rotation to achieve solid-liquid fractional separation. The crystal slurry discharged from the crystal outlet 203 of the crystallizer 2 enters the hydrocyclone separator 3 tangentially. Under the action of centrifugal force, particles larger than 300 μm are thrown against the separator wall and move downwards along a spiral path, eventually discharging from the first outlet 302 at the bottom. This first mixed medium mainly contains coarse crystals. Particles with a diameter of 300 μm or less experience less centrifugal force and move with the liquid towards the central low-pressure zone, forming an upward-flowing internal vortex, eventually discharging from the second outlet 303 at the top. This second mixed medium mainly contains fine seed crystals.

[0045] Through the aforementioned staged separation, the hydrocyclone separator 3 divides the crystal slurry into two streams: the first mixed medium containing coarse crystals is discharged and recycled, and can be used as an industrial raw material; the second mixed medium containing fine seed crystals is returned to the crystallization chamber 201 of the crystallizer 2 to continue participating in the crystallization reaction as seed crystals. In this way, the seed crystal particle size in the crystallizer 2 is controlled below 300 μm, maintaining a high specific surface area and nucleation activity, while avoiding excessive growth of coarse crystals in the crystallizer 2, which would consume the number of seed crystals or affect the flow pattern.

[0046] In actual operation, the structural parameters (such as column diameter, cone angle, overflow pipe insertion depth, etc.) and operating parameters (such as feed pressure, flow rate, etc.) of the hydrocyclone separator 3 can be adjusted according to the target product particle size requirements and the seed particle size distribution in the crystallizer 2, so that the classification particle size can be adjusted to around 300μm to obtain a better separation effect.

[0047] In some embodiments, the water softening device further includes a slag discharge pipe 5 and a seed crystal return pipe 6. The slag discharge pipe 5 connects the crystal discharge port 203 of the crystallizer 2 with the water inlet 301 of the separator 3, and a slag discharge valve 51 is provided on the slag discharge pipe 5. The seed crystal return pipe 6 connects the second outlet 303 of the separator 3 with the crystallization chamber 201 of the crystallizer 2, and a seed crystal return pump 61 is provided on the seed crystal return pipe 6.

[0048] In some embodiments, the water softening device further includes a cathode 106 inlet pipe, an anode 105 inlet pipe, a flow meter 7, a pH meter 8, an overflow pipe, and a control system 12. The cathode 106 inlet pipe is connected to the cathode chamber 104, and a cathode 106 inlet pump and a first analyzer 9 are installed on the cathode 106 inlet pipe. The anode 105 inlet pipe is connected to the anode chamber 103, and an anode 105 inlet pump is installed on the anode 105 inlet pipe. The flow meter 7 and the pH meter 8 are installed on the outlet pipe 4. The overflow pipe is connected to the overflow port 204, and a second analyzer 10 and a conductivity meter 11 are installed on the overflow pipe. Both the first analyzer 9 and the second analyzer 10 are used to detect the water in the corresponding pipes. The hardness and alkalinity values ​​are measured. The control system 12 is electrically connected to the pH meter 8, flow meter 7, first analyzer 9, second analyzer 10, conductivity meter 11, DC power supply 107, circulation structure, cathode 106 inlet pump, anode 105 inlet pump, seed reflux pump 61, and slag discharge valve 51, respectively. The control system 12 adjusts at least one of the following based on the detection information fed back by the first analyzer 9, second analyzer 10, flow meter 7, pH meter 8, and conductivity meter 11: the current and / or voltage of the DC power supply 107, the on / off state and opening degree of the slag discharge valve 51, the power of the cathode 106 inlet pump, the power of the anode 105 inlet pump, the power of the seed reflux pump 61, and the working state of the circulation structure.

[0049] This embodiment achieves automatic seed crystal reflux circulation, controllable slag discharge, and closed-loop regulation throughout the entire process by setting up dedicated pipelines, valves, pumps, and an online monitoring and control system 12. In this way, the system can automatically adjust the electrolysis current and circulation intensity according to changes in the influent water quality, maintaining a stable seed crystal concentration within the crystallizer 2, and matching the slag discharge frequency to the processing load, which is beneficial for long-term unattended continuous operation.

[0050] In terms of material conveying, the device also includes a slag discharge pipe 5 and a seed crystal return pipe 6. The slag discharge pipe 5 connects the crystal discharge port 203 of the crystallizer 2 with the water inlet 301 of the separator 3, and a slag discharge valve 51 is installed on the slag discharge pipe 5. When the crystal slurry in the crystallizer 2 accumulates to a certain level, the slag discharge valve 51 opens, and the crystal slurry is sent to the separator 3 for processing through the slag discharge pipe 5. The seed crystal return pipe 6 connects the second outlet 303 of the separator 3 with the crystallization chamber 201 of the crystallizer 2, and a seed crystal return pump 61 is installed on the seed crystal return pipe 6. The second mixed medium containing fine seed crystals separated by the separator 3 is pumped back to the crystallization chamber 201 of the crystallizer 2 through the seed crystal return pipe 6 by the seed crystal return pump 61 to maintain the concentration and activity of the seed crystals in the crystallizer 2.

[0051] For water intake and monitoring, the device also includes a cathode 106 inlet pipe, an anode 105 inlet pipe, a flow meter 7, a pH meter 8, and an overflow pipe. The cathode 106 inlet pipe is connected to the cathode chamber 104, and is equipped with a cathode 106 inlet pump and a first analyzer 9. The cathode 106 inlet pump delivers raw water into the cathode chamber 104, and the first analyzer 9 monitors the hardness and alkalinity of the incoming water in real time. The anode 105 inlet pipe is connected to the anode chamber 103, and is equipped with an anode 105 inlet pump to deliver raw water or other water sources into the anode chamber 103. The outlet pipe 4 is equipped with a flow meter 7 and a pH meter 8, used to monitor the flow rate and pH value of the alkaline liquid flowing from the cathode chamber 104 to the crystallizer 2, respectively. The overflow pipe is connected to the overflow port 204 of the crystallizer 2. The overflow pipe is equipped with a second analyzer 10 and a conductivity meter 11, which are used to detect the hardness, alkalinity and conductivity of the softened water.

[0052] The device is also equipped with a control system 12. The control system 12 is electrically connected to the pH meter 8, flow meter 7, first analyzer 9, second analyzer 10, conductivity meter 11, DC power supply 107, circulation structure, cathode 106 inlet pump, anode 105 inlet pump, seed crystal reflux pump 61, and slag discharge valve 51. The control system 12 receives detection information from the aforementioned instruments and sensors, including inlet water hardness, alkalinity, outlet water flow rate, cathode 106 outlet water pH, crystallizer 2 outlet water hardness, alkalinity, and conductivity. Based on this information, the control system 12 performs at least one of the following adjustment operations: adjusting the current or voltage of the DC power supply 107 to change the alkali production rate of the cathode chamber 104, so that the pH at the inlet of the crystallizer 2 is maintained within a set range; adjusting the on / off state and opening degree of the slag discharge valve 51 to control the discharge frequency and discharge volume of the crystal slurry; adjusting the power of the cathode 106 inlet pump to change the inlet flow rate; adjusting the power of the anode 105 inlet pump; adjusting the power of the seed return pump 61 to control the seed return speed; and adjusting the working state of the circulation structure to change the suspension degree and mixing intensity of the seeds in the crystallizer 2. Through such closed-loop control, the system can automatically adapt to fluctuations in raw water quality and changes in treatment load, maintaining a stable softening effect. In addition, the control system 12 can also perform supersaturation control: by coordinating the control of the current of the DC power supply 107, the flow rate of raw water, the seed concentration, the temperature, and, if necessary, the backflow of CO2 or acid, the system preferentially promotes heterogeneous growth and inhibits homogeneous nucleation and fine sludge formation.

[0053] A water softening method, using a water softening apparatus as described in any of the above embodiments, includes the following steps: S1. Electrolysis for Alkali Production: Raw water is introduced into the cathode chamber 104 and anode chamber 103 of the electrolytic cell 101, respectively. A direct current is applied using a DC power supply 107, causing a water reduction reaction to occur at the cathode 106 to generate OH-. - An alkaline liquid is obtained in the cathode chamber 104; S2. Alkaline liquid transfer: The alkaline liquid in the cathode chamber 104 is sent into the crystallizer 2 through the water outlet pipe 4. The check valve component 41 on the water outlet pipe 4 prevents the alkaline liquid from flowing back into the cathode chamber 104. S3. Crystallization reaction: The alkaline liquid is thoroughly mixed with the seed crystals in crystallization chamber 201, and the Ca²⁺ in the alkaline liquid… + With CO3² - Heterogeneous nucleation and crystal growth occur on the surface of the seed crystal, generating settleable CaCO3 crystal particles. The resulting softened water is discharged through the overflow port 204 of the crystallizer 2. S4. Separation and Seed Circulation: The crystal slurry discharged from the crystallizer 2 is sent to the separator 3 for graded separation. The second mixed medium containing fine seed crystals obtained by separation is returned to the crystallization chamber 201 of the crystallizer 2, and the first mixed medium containing coarse crystals is discharged and recycled.

[0054] The water softening method in this embodiment sequentially connects four steps: electrolytic alkali production, alkaline liquid transfer, crystallization reaction, and separation and seed crystal circulation, forming a continuous operation process. In this method, the electrochemical unit is only responsible for generating hydroxide ions, and the crystallization process is entirely completed within the external crystallizer 2 using seed crystals. Therefore, the cathode 106 is less prone to scaling and can operate continuously for extended periods without frequent shutdowns for cleaning. Specifically, it includes the following steps.

[0055] Step S1: Electrolysis to produce alkali.

[0056] Raw water is introduced into the cathode chamber 104 and anode chamber 103 of the electrolysis cell 101, respectively. The DC power supply 107 is turned on, applying DC current to the anode 105 and cathode 106. A reduction reaction occurs on the surface of the cathode 106, generating hydroxide ions, which gradually transforms the water in the cathode chamber 104 into an alkaline liquid. Simultaneously, an oxidation reaction occurs in the anode chamber 103, generating an acidic liquid. A cation exchange membrane separates the two chambers, preventing acid-base neutralization and ensuring the continuous accumulation of alkalinity in the alkaline liquid within the cathode chamber 104.

[0057] Step S2: Alkaline liquid transfer.

[0058] The alkaline liquid generated in the cathode chamber 104 is led out from the outlet of the cathode 106 and sent to the crystallizer 2 through the outlet pipe 4. The outlet pipe 4 is designed as a short-distance pipeline to reduce alkalinity loss during transportation. A check valve assembly 41 is installed on the outlet pipe 4. The check valve assembly 41 only allows liquid to flow from the cathode chamber 104 to the crystallizer 2. Once the pressure in the crystallizer 2 increases or a backflow tendency occurs, the check valve assembly 41 automatically closes to prevent the seed-containing slurry in the crystallizer 2 from flowing back into the cathode chamber 104, thereby ensuring that the cathode chamber 104 is never contaminated by seed crystals.

[0059] Step S3: Crystallization reaction.

[0060] After the alkaline liquid enters the crystallizer 2, it mixes thoroughly with the seed crystals, which have been pre-added and kept in suspension in the crystallization chamber 201. Calcium and carbonate ions in the alkaline liquid reach a supersaturated state on the seed crystal surface, preferentially undergoing heterogeneous nucleation, followed by crystal growth. This process generates settleable calcium carbonate crystal particles, which settle to the bottom of the crystallization chamber 201 to form a crystal slurry. Simultaneously, the supernatant transforms into softened water and is discharged through the overflow port 204 of the crystallizer 2, completing the hardness removal process.

[0061] Step S4: Separation and Seed Cycle.

[0062] The crystal slurry discharged from the bottom of crystallizer 2 is sent to separator 3. Separator 3 performs a fractional separation process on the crystal slurry. The first mixed medium obtained after separation contains coarse crystals with larger particle sizes and is discharged and recovered from the first outlet 302, where it can be used as industrial filler or building material raw material. The second mixed medium obtained after separation contains fine seed crystals with smaller particle sizes and is returned to the crystallization chamber 201 of crystallizer 2 from the second outlet 303 via a reflux pipe, continuing to participate in subsequent crystallization reactions as seed crystals. Through this cycle, the seed crystal concentration and activity within crystallizer 2 are maintained, and the system does not require frequent replenishment of new seed crystals.

[0063] In some embodiments, in step S1, the hydraulic residence time of the cathode chamber 104 is controlled to be 0.5s to 60s, the water flow velocity of the cathode chamber 104 is 0.1m / s to 2.0m / s, and the current density of the cathode chamber 104 is 50A / m² to 2000A / m².

[0064] In some embodiments, in step S3, the hydraulic residence time in the crystallization chamber 201 is controlled to be 1 min to 60 min, the pH value of the water in the crystallization chamber 201 is 8.5 to 11.5, and the seed crystal concentration in the crystallization chamber 201 is 0.5 g / L to 50 g / L.

[0065] In some embodiments, the water softening method further includes step S5: pH adjustment: mixing the acidic liquid generated by the anode chamber 103 of the electrolytic cell 101 with the softened water discharged through the overflow port 204 to adjust the pH value of the softened water to neutral or weakly alkaline.

[0066] This embodiment comprehensively controls the operating parameters of the cathode chamber 104, the reaction conditions of the crystallization chamber, and the pH adjustment of the effluent, making the electrochemical alkali production process more efficient and stable. The crystallization process is carried out under suitable supersaturation and seed conditions, and the final effluent pH meets the requirements for direct discharge or reuse. The coordination of various parameters is conducive to achieving low energy consumption and high hardness removal rate under continuous operation conditions.

[0067] This embodiment defines the key parameters in steps S1 and S3, and adds step S5 to adjust the pH of the effluent. These will be explained below.

[0068] Parameter control in step S1.

[0069] In the alkali production step via electrolysis, the hydraulic residence time in the cathode chamber 104 is controlled to be between 0.5 s and 60 s. If the residence time is too short, the water reduction reaction is incomplete, and the OH-... - Insufficient OH- generation and excessive residence time may increase the risk of localized oversaturation on the cathode 106 surface, which is detrimental to scale inhibition. Simultaneously, the linear velocity of the water flow in the cathode chamber 104 should be controlled between 0.1 m / s and 2.0 m / s. A higher linear velocity helps to promptly remove the OH- generated near the cathode 106.- To prevent excessively high pH levels within the boundary layer, which could induce localized crystallization, the current density in cathode chamber 104 is controlled between 50 A / m² and 2000 A / m². Too low a current density results in insufficient alkali production, while too high a current density may lead to increased side reactions or higher energy consumption. In practice, adjustments can be made within these ranges based on the influent hardness and flow rate. For example, a hydraulic retention time of 1 s to 15 s, a linear velocity of 0.2 m / s to 1.2 m / s, and a current density of 200 A / m² to 800 A / m² can be selected to achieve better alkali production and lower scaling tendency.

[0070] Parameter control in step S3.

[0071] In the crystallization reaction step, the hydraulic residence time in crystallization chamber 201 is controlled to be 1 min to 60 min. A shorter residence time results in insufficient crystal growth and high residual hardness in the effluent; a longer residence time increases the required equipment volume. The pH value of the water in crystallization chamber 201 is controlled to be 8.5 to 11.5. If the pH value is too low, the carbonate concentration is insufficient, and the crystallization driving force is weak; if the pH value is too high, it may cause magnesium ion precipitation or an increase in homogeneous nucleation. The seed crystal concentration in crystallization chamber 201 is controlled to be 0.5 g / L to 50 g / L. If the seed crystal concentration is too low, the heterogeneous nucleation surface is insufficient, easily producing fine-particle crystals; if the concentration is too high, the circulation energy consumption increases. In actual operation, adjustments can be made within the above ranges according to the influent water quality and treatment objectives. For example, selecting a hydraulic residence time of 5 min to 25 min, a pH value of 9.2 to 10.8, and a seed crystal concentration of 5 g / L to 25 g / L is beneficial for obtaining crystal products with concentrated particle size distribution and good settling performance.

[0072] Step S5: pH callback.

[0073] The method in this embodiment also includes step S5. In step S5, the acidic liquid generated in the anode chamber 103 of the electrolytic cell 101 is collected and mixed with softened water discharged through the overflow port 204. The acidic liquid generated in the anode chamber 103 during electrolysis contains a high concentration of hydrogen ions. Using it to neutralize the residual alkalinity of the softened water can restore the pH value of the softened water to a neutral or slightly alkaline range, meeting the standards for subsequent use or direct discharge. This approach eliminates the need for additional acid additives, achieving resource utilization of electrolysis byproducts. The mixing ratio can be adjusted according to the pH value of the softened water and the acidity of the acidic liquid in the anode chamber 103. If necessary, a static mixer or stirring device can be installed to ensure uniform mixing. In addition, H2 released from the cathode chamber and O2 (or Cl2 generated from chlorinated water) that may be released from the anode chamber can be discharged safely or utilized as resources through a gas-liquid separator.

[0074] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0075] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0076] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0077] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0078] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A water softening device, characterized in that, include: An electrolysis assembly includes an electrolytic cell and a cation exchange membrane disposed within the electrolytic cell. The cation exchange membrane divides the electrolytic cell into an independent and non-communicating anode chamber and a cathode chamber. An anode is disposed in the anode chamber, and a cathode is disposed in the cathode chamber. The anode and the cathode are electrically connected to the positive and negative terminals of a DC power supply, respectively. A crystallizer includes a crystallization chamber, a crystal discharge port, and an overflow port. The crystallization chamber is connected to the cathode outlet of the cathode chamber via a water outlet pipe. The water outlet pipe is equipped with a check valve, which allows alkaline liquid in the cathode chamber to flow unidirectionally toward the crystallizer. Seed crystals are provided in the crystallization chamber. Under the action of the seed crystals, the alkaline liquid in the cathode chamber undergoes a crystallization reaction. The generated crystal slurry is discharged through the crystal discharge port, and the resulting softened water is discharged through the overflow port. A separator is provided, comprising an inlet, a first outlet, and a second outlet. The inlet is connected to the crystal discharge port of the crystallizer, and the second outlet is connected to the crystallization chamber. The separator is used to separate the crystal slurry discharged from the crystallizer. The first outlet is used to discharge a first mixed medium containing coarse crystals, and the second outlet is used to discharge a second mixed medium containing fine crystal seeds. The second mixed medium is returned to the crystallization chamber of the crystallizer.

2. The water softening device according to claim 1, characterized in that, The crystallizer further includes a flow guiding structure and / or a circulation structure, which are used to keep the seed crystals suspended in the crystallization chamber. The flow guiding structure includes a flow guiding plate with a U-shaped cross-section, and the U-shaped opening side of the flow guiding plate faces the crystal discharge port; The circulation structure includes an inner circulation component and / or an outer circulation component. The inner circulation component includes at least one of a stirrer, an air-lift device, and an inner circulation pump. The outer circulation component includes an outer circulation pipe and an outer circulation pump disposed on the outer circulation pipe.

3. The water softening device according to claim 1, characterized in that, The seed crystal is at least one of calcite, aragonite, spheroidal aragonite, and inert seed carrier; and / or, the seed crystal size in the crystallizer is 10 μm to 800 μm; and / or, the seed crystal concentration in the crystallizer is 0.5 g / L to 50 g / L.

4. The water softening device according to claim 1, characterized in that, The separator is a hydrocyclone separator, which is used to classify and separate the crystal slurry by particle size. The separated coarse crystals have a particle size greater than 300 μm, and the fine seed crystals have a particle size less than or equal to 300 μm.

5. The water softening device according to claim 1, characterized in that, Also includes: A slag discharge pipe is provided, which connects the crystal discharge port of the crystallizer to the water inlet of the separator, and a slag discharge valve is provided on the slag discharge pipe. A seed reflux pipeline is provided, which connects the second outlet of the separator to the crystallization chamber of the crystallizer, and a seed reflux pump is provided on the seed reflux pipeline.

6. The water softening device according to any one of claims 1-5, characterized in that, Also includes: A cathode inlet water pipe is connected to the cathode chamber, and a cathode inlet water pump and a first analyzer are installed on the cathode inlet water pipe; An anode inlet pipe is connected to the anode chamber, and an anode inlet pump is installed on the anode inlet pipe; A flow meter and a pH meter are provided on the outlet pipe; An overflow pipe is connected to the overflow outlet, and a second analyzer and a conductivity meter are installed on the overflow pipe; The control system includes a first analyzer and a second analyzer, both used to detect the hardness and alkalinity values ​​of the water in the corresponding pipeline. The control system is electrically connected to the pH meter, flow meter, first analyzer, second analyzer, conductivity meter, DC power supply, circulation structure, cathode inlet pump, anode inlet pump, seed reflux pump, and slag discharge valve. Based on the detection information fed back from the first analyzer, second analyzer, flow meter, pH meter, and conductivity meter, the control system adjusts at least one of the following: the current and / or voltage of the DC power supply, the on / off state and opening degree of the slag discharge valve, the power of the cathode inlet pump, the power of the anode inlet pump, the power of the seed reflux pump, and the operating state of the circulation structure.

7. A water softening method, characterized in that, The water softening device used as described in any one of claims 1-6 includes the following steps: S1. Electrolysis for Alkali Production: Raw water is introduced into the cathode and anode chambers of the electrolytic cell, respectively. A direct current is applied using the DC power supply, causing a water reduction reaction at the cathode to generate OH-. - An alkaline liquid is obtained in the cathode chamber; S2. Alkaline liquid transfer: The alkaline liquid in the cathode chamber is sent into the crystallizer through the outlet pipe, and the alkaline liquid is prevented from flowing back into the cathode chamber by the check valve on the outlet pipe; S3. Crystallization reaction: The alkaline liquid is thoroughly mixed with the seed crystals in the crystallization chamber, and the Ca²⁺ in the alkaline liquid… + With CO3² - Heterogeneous nucleation and crystal growth occur on the surface of the seed crystal, generating settleable CaCO3 crystal particles, and the resulting softened water is discharged through the overflow port of the crystallizer; S4. Separation and Seed Circulation: The crystal slurry discharged from the crystallizer is sent to the separator for graded separation. The second mixed medium containing fine seed crystals obtained by separation is returned to the crystallization chamber of the crystallizer, and the first mixed medium containing coarse crystals is discharged and recycled.

8. The water softening method according to claim 7, characterized in that, In step S1, the hydraulic residence time of the cathode chamber is controlled to be 1s to 15s, the linear velocity of the water flow in the cathode chamber is 0.3m / s to 1.2m / s, and the current density of the cathode chamber is 50A / m² to 2000A / m².

9. The water softening method according to claim 7, characterized in that, In step S3, the hydraulic residence time in the crystallization chamber is controlled to be 1 min to 60 min, the pH value of the water in the crystallization chamber is 8.5 to 11.5, and the seed crystal concentration in the crystallization chamber is 0.5 g / L to 50 g / L.

10. The water softening method according to claim 7, characterized in that, It also includes step S5: pH adjustment: mixing the acidic liquid generated in the anode chamber of the electrolytic cell with the softened water discharged through the overflow port to adjust the pH value of the softened water to neutral or weakly alkaline.

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