Device for controlling pH of feedwater raw water through micro-nano bubble liquid generated by reinforcing carbon dioxide dissolution coupling cold energy recovery

Abstract

The invention discloses a device for controlling the pH value of feedwater raw water through micro-nano bubble liquid generated by reinforcing carbon dioxide dissolution coupling cold energy recovery, and belongs to the technical field of feedwater treatment. The device comprises a cold water tank, a pressure pump, a dissolved air tank, a pressure relief tank, a pH regulating tank, a water inlet and outlet system and a PLC control box, according to the device, water and carbon dioxide are efficiently mixed through sudden change of the flow rate and pressure of liquid in a venturi tube of a dissolved air tank; according to the device, the water temperature is reduced through cold energy released during heat absorption gasification of liquid carbon dioxide for subsequent gas dissolving in the gas dissolving tank, and the cold energy released during gasification of the carbon dioxide is fully utilized to reduce the water temperature to promote gas dissolving; according to the device, the gas dissolving amount under the pressure reduction condition is further guaranteed through the pressure relief tank and the venturi tube, so that gas dissolving water rich in carbon dioxide micro-nano bubbles is stably generated and used for being mixed with raw water of a water supply plant according to different proportions, then pH control is achieved, and the utilization rate of carbon dioxide is increased.

Description

A device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply. Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro-nano bubble liquid for controlling the pH of raw water. Background Technology

[0002] In recent years, many cities in China have faced the significant water quality problem of high raw water pH levels and the resulting excessive aluminum concentration in treated water. According to the 2024 "Report on the State of China's Ecological Environment," the eutrophication of lakes (reservoirs) in my country continues to worsen, with over 30% of related water bodies now eutrophic, and seasonal algal blooms occurring frequently. Algal proliferation consumes large amounts of carbon dioxide in the water, disrupting the carbonic acid balance and causing a decrease in bicarbonate and carbonate concentrations, leading to a significant increase in pH. Production data shows that the raw water pH can reach as high as 8.5–9.0 during peak algal bloom periods. This high pH environment severely affects the coagulation and sedimentation process, easily leading to increased aluminum concentration in the coagulation and sedimentation effluent and causing "aluminum leakage" in sand filtration processes, seriously impacting drinking water safety.

[0003] To address the aforementioned issues, water treatment plants typically lower the pH by adding acidifying coagulants, increasing the coagulant dosage, or directly adding acid to the raw water. However, these methods all have significant drawbacks: the former two not only increase reagent costs and easily lead to excessive residual aluminum, but also the frequent adjustments to the coagulant dosage affect process stability; directly adding acid to the raw water requires the construction of a new acidification system, and strong acids are corrosive, so drinking water generally does not use strong acid treatment, posing safety hazards. In recent years, the technology of adjusting the pH of raw water using carbon dioxide has received widespread attention and has been extensively researched and applied both domestically and internationally. Carbon dioxide dissolves in water to form a carbonic acid system, which can gradually release H₂. + This method gently and stably lowers pH and is non-corrosive, making it relatively safe. However, it currently suffers from problems such as low carbon dioxide dissolution efficiency, significant gas escape, and reliance on experience-based dosage judgment, leading to high operating costs and unsatisfactory adjustment effects. Therefore, optimizing the carbon dioxide dosing method and improving its mass transfer and dissolution efficiency are key to advancing the practical application of this technology and achieving efficient and stable operation. This also plays a crucial supporting and promoting role in achieving the "dual carbon" target.

[0004] Micro-nano aeration technology is a novel and highly efficient water treatment technology that primarily purifies water by generating bubbles ranging in size from micrometers to nanometers. Micro-nano bubbles (MNBs) are bubbles with diameters ranging from hundreds of nanometers to tens of micrometers. They possess extremely strong adsorption capacity, high mass transfer efficiency, and high surface potential, significantly enhancing the solubility and utilization of gases in water, rapidly bringing dissolved gases to a supersaturated state. Addressing the problems of low carbon dioxide dosage efficiency and severe leakage in raw water pH adjustment, the use of micro-nano aeration technology to enhance carbon dioxide dissolution and mass transfer is considered an effective way to improve gas utilization and achieve precise pH control. This method can significantly reduce carbon dioxide dosage while stably adjusting pH, saving operating costs. Although existing technologies (such as CN102268374A) have reported the use of micro-nano aerators to generate micro-nano bubbles from carbon dioxide for microalgae cultivation, directly applying this approach to pH adjustment of raw water in water treatment plants has significant limitations. Simply using micro-nano aerators to introduce carbon dioxide to adjust the pH of raw water is insufficient for the scale of water treatment plants, and the required electricity is too high, making it impractical for actual production. Furthermore, the Venturi tube microbubble generator solution provided in CN114849508A1 is prone to problems such as unstable pH control and poor scale-up in practical applications, and it cannot guarantee the carbon dioxide dissolution and residence time, easily leading to carbon dioxide escape and waste. Therefore, there is an urgent need to develop a green treatment device that can efficiently, energy-savingly, and stably control the pH of raw water in water treatment plants and significantly improve carbon dioxide utilization. Summary of the Invention

[0005] To address the problems associated with carbon dioxide dosing, this invention proposes a technological innovation using micro-nano carbon dioxide aeration. This invention provides a device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro-nano bubble liquid for controlling the pH of raw water. Liquid carbon dioxide vaporizes and absorbs heat in the vaporizer within the cold water tank, lowering the temperature of the water entering the dissolved air tank and promoting increased carbon dioxide dissolution efficiency and volume. The dissolved air tank utilizes the abrupt changes in liquid flow rate and pressure within a Venturi tube to efficiently mix water and carbon dioxide. Simultaneously, the dissolved air tank is equipped with an annular packing layer to increase the gas-liquid contact surface, enhancing gas-liquid mass transfer and thus stably generating dissolved air water rich in carbon dioxide micro-nano bubbles. The pressure relief tank reduces pressure while utilizing a Venturi tube for secondary gas dissolution, minimizing carbon dioxide escape due to pressure reduction. The dissolved air water rich in carbon dioxide micro-nano bubbles is mixed with raw water in different proportions to achieve efficient control of the raw water pH.

[0006] To achieve the purpose of this invention, the device of this invention adopts a carbon dioxide micro-nano reactor as the main structure, including a cold water tank, a gasifier, a dissolved gas tank, a pressure relief tank, a first Venturi tube, a second Venturi tube, and a pH adjustment tank.

[0007] A vaporizer is installed inside the cold water tank to vaporize the introduced liquid carbon dioxide and cool the water in the tank. The dissolved gas tank contains a first Venturi tube and a packing layer to enhance the dissolution of carbon dioxide under pressure. The gas outlet of the vaporizer is connected via pipelines to the throat of the first Venturi tube and the internal space of the dissolved gas tank. The inlet of the first Venturi tube is connected to the outlet of the cold water tank. The pressure relief tank contains a second Venturi tube connected to the outlet of the dissolved gas tank for secondary dissolution of the dissolved gas water from the dissolved gas tank. The pH adjustment tank is connected to the outlet of the pressure relief tank.

[0008] The principle of this invention is as follows: Based on the sudden change in the flow rate and pressure of the liquid in the Venturi tube, water and carbon dioxide can be mixed efficiently. At the same time, a high-pressure environment and a packing layer are used to promote dissolved air. Combined with the heat absorption of liquid carbon dioxide vaporization to reduce the inlet water temperature of the dissolved air tank and increase the amount of dissolved air, it can continuously and stably produce dissolved air water with a high carbon dioxide concentration for adjusting the pH of the raw water. This realizes the efficient adjustment of the pH of a large volume of raw water in the water supply plant using a small amount of dissolved air water with a high carbon dioxide concentration, thus solving the problem of high pH of raw water in the water supply plant.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention designs a highly efficient dissolved air device structure, utilizes the Venturi tubes in the dissolved air tank and the pressure relief tank to change the pressure by controlling the fluid flow rate, thereby absorbing carbon dioxide to generate dissolved air water rich in micro-nano bubbles, and provides an annular packing layer in the middle of the dissolved air tank to increase the gas-liquid contact surface, which can improve the dissolved water efficiency and dissolved water volume of carbon dioxide, thereby further improving its utilization rate; the Venturi tubes in the pressure relief tank can ensure that more carbon dioxide can dissolve in water, prevent excessive gas from escaping due to the decrease in gas pressure, minimize gas waste caused by gas escape, achieve efficient utilization of carbon dioxide, and achieve a significant reduction in aeration volume.

[0010] 2. In this invention, the cold energy is fully utilized to promote the dissolution of carbon dioxide in water. Taking advantage of the characteristic that liquid carbon dioxide needs to absorb heat during vaporization, the cold energy released by its heating is used to lower the water temperature of the tap water in the subsequent carbon dioxide dissolution tank, thereby achieving efficient utilization of cold energy, promoting the dissolution of carbon dioxide in water, and improving the dissolution efficiency and the amount of water dissolved.

[0011] 3. This invention utilizes dissolved air water rich in carbon dioxide micro-nano bubbles to adjust the pH of raw water, and increases the dissolved air volume through micro-nano aeration technology, achieving a volume of 1 m³. 3 / h of dissolved air water applied to more than 100 m 3 The effective pH control of the raw water ensures that the pH remains stable within the required range. Compared to conventional carbon dioxide aeration technology, under the same pH control conditions, micro-nano aeration can significantly reduce the amount of carbon dioxide aeration, saving production costs. Attached Figure Description

[0012] Figure 1 is a schematic diagram of a device for controlling the pH of raw water supply by enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro-nano bubble liquid.

[0013] In Figure 1: 1-Carbon dioxide storage tank, 2-Pressure gauge, 3-Pressure reducing valve, 4-Cold water tank, 5-Inlet valve, 6-Tap water inlet pipe, 7-Cold water tank pH meter, 8-Cold water tank level gauge, 9-Vaporizer, 10-Drain pipe, 11-Drain valve, 12-Gas flow meter, 13-Boosting pump, 14-Inlet valve, 15-Inlet flow meter, 16-Dissolved gas tank, 17-First Venturi tube, 18-Pressure sensor, 19-Packaging layer, 20-Dissolved gas water valve, 21-Pressure relief tank level gauge, 22 - Pressure gauge for pressure relief tank, 23- Pressure relief tank, 24- Second Venturi tube, 25- Dissolved air water valve, 26- Dissolved air water outlet flow meter, 27- pH meter for regulating tank, 28- Carbon dioxide content analyzer, 29- Level gauge for regulating tank, 30- pH regulating tank, 31- Agitator, 32- Release device, 33- Air outlet, 34- Raw water inlet pipe, 35- First outlet valve, 36- Second outlet valve, 37- Third outlet valve, 38- Raw water outlet pipe, 39- Control box, 40- Control box display screen.

[0014] Figure 2 shows the effect of carbon dioxide depressurization and gasification cooling energy recovery on reducing water temperature.

[0015] Figure 3 shows a comparison of the pH adjustment effects of carbon dioxide micro-nano aeration and conventional aeration on raw water.

[0016] Figure 4 shows the pH change effect of dissolved air water and raw water adjusted at different ratios. Detailed Implementation

[0017] The following provides a more detailed description of specific embodiments of the present invention. It should be noted that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0019] Example 1: A device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro-nano bubble liquid for controlling the pH of raw water. This example provides a device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro-nano bubble liquid for controlling the pH of raw water. Referring to Figure 1, the device mainly includes a cold water tank 4, a vaporizer 9, a dissolved gas tank 16, a pressurizing pump 13, a pressure relief tank 23, a first Venturi tube 17, a second Venturi tube 24, a control box 39, and a pH adjustment tank 30.

[0020] A vaporizer 9 is installed in the cold water tank 4 to vaporize the introduced liquid carbon dioxide and cool the water in the cold water tank 4. The dissolved gas tank 16 is equipped with a first Venturi tube 17 and a packing layer 19 to enhance the dissolution of carbon dioxide under pressure. The gas outlet of the vaporizer 9 is connected to the throat of the first Venturi tube 17 and the internal space of the dissolved gas tank 16 through an air inlet pipe. The outlet of the cold water tank 4 is connected to the inlet of the first Venturi tube 17 through a pressure pump 13. The pressure relief tank 23 is equipped with a second Venturi tube 24 that communicates with the outlet of the dissolved gas tank 16 for secondary dissolution of the dissolved gas water from the dissolved gas tank 16. The outlet of the pressure relief tank 23 is connected to the pH adjustment tank 30 through a release device 32. The release device 32 is used to release the dissolved gas water after secondary dissolution and mix it with the original water. The pH adjustment tank 30 is equipped with a stirrer 31.

[0021] It also includes a carbon dioxide storage tank 1, which is connected to the liquid carbon dioxide inlet of the vaporizer 9 via a pipeline.

[0022] The system also includes an inlet system and a drainage system. The inlet system includes a tap water inlet pipe 6 connected to the cold water tank 4 and a raw water inlet pipe 34 connected to the raw water source and leading to the pH adjustment tank 30. An inlet valve 5 is installed on the inlet pipe 6. The drainage system includes a drain pipe 10 connected to the cold water tank 4 and a raw water outlet pipe 38 connected to the pH adjustment tank 30. A drain valve 11 is installed on the drain pipe 10. The side wall of the pH adjustment tank 30 is provided with a plurality of first outlet valves 35, second outlet valves 36 and third outlet valves 37 along the height direction. The first outlet valves 35, second outlet valves 36 and third outlet valves 37 are all connected to the drain pipe 38.

[0023] The carbon dioxide storage tank 1 is equipped with a pressure gauge 2 and a pressure reducing valve 3; the cold water tank 4 is equipped with a cold water tank pH meter 7 and a cold water tank level gauge 8, and an inlet valve 14 and an inlet flow meter 15 are installed on the pipeline between the outlet of the cold water tank 4 and the inlet of the first Venturi tube 17; a gas flow meter 12 is installed on the gas inlet pipeline connected to the gas outlet of the vaporizer 9; a pressure sensor 18 is installed in the dissolved gas tank 16; a pressure relief tank level gauge 21 and a pressure relief tank pressure gauge 22 are installed on the pressure relief tank 23, and a dissolved gas water valve 25 and a dissolved gas water outlet flow meter 26 are installed on the pipeline between the outlet of the pressure relief tank 23 and the release device 32; a pH adjustment tank is equipped with an adjustment tank pH meter 27, a carbon dioxide content measuring device 28, and an adjustment tank level gauge 29.

[0024] The pressure pump 13, stirrer 31, carbon dioxide content analyzer 28, valves, level gauges, pH meters, flow meters, and pressure sensor 18 are all connected to and controlled by the control box 39.

[0025] The control box 39 controls the pH control and temperature monitoring of each tank, as well as the operation of the pressure pump 13, level gauge, carbon dioxide content measuring device 28 and agitator 31.

[0026] The control box 39 is a PLC control cabinet, which is equipped with a control box display screen 40.

[0027] In this embodiment, the device utilizes the first Venturi tube 17 to generate a local vacuum (negative pressure), thereby automatically and efficiently drawing in and initially breaking down carbon dioxide gas. At the same time, the carbon dioxide gas is broken into extremely fine bubbles and dissolved in water to form a gas-liquid mixture through pressurized gas dissolution. Due to their large specific surface area and slow rising speed, these bubbles can remain in the water for a long time, thereby efficiently generating dissolved air water rich in micro-nano bubbles.

[0028] Liquid carbon dioxide is supplied by carbon dioxide storage tank 1, and after being depressurized by pressure reducing valve 3, it enters vaporizer 9 in cold water tank 4 for endothermic vaporization. The vaporized carbon dioxide gas enters the dissolved gas tank 16 from the top. Tap water in cold water tank 4 is pumped by booster pump 13 and injected into dissolved gas tank 16 in jet form through first venturi tube 17. A ring-shaped packing layer 19 is provided in the middle of dissolved gas tank 16 to increase the gas-liquid contact area. At the same time, the first venturi tube 17 in dissolved gas tank 16 uses its negative pressure suction property to draw in a portion of the carbon dioxide from the inlet pipe and initially mix it with the tap water; another portion of the carbon dioxide from the inlet pipe enters from the top of dissolved gas tank 16, and through the pressure change in the first venturi tube 17, micro-nano bubbles are formed by strong turbulent shearing. The high-pressure environment of dissolved gas tank 16 and the characteristic of packing layer 19 to increase the gas-liquid contact area further enhance the dissolved gas.

[0029] After the carbon dioxide is fully dissolved, the dissolved air water enters the pressure relief tank 23 for depressurization. The pressure relief tank 23 is equipped with a second Venturi tube 24 to reduce carbon dioxide escape caused by depressurization. The depressurized dissolved air water then enters the pH adjustment tank 30 via the pressure difference through the release device 32 to mix with the raw water, thereby adjusting the pH of the raw water. By adjusting the carbon dioxide intake rate, water intake rate, pressure in the dissolved air tank 16, and pressure in the pressure relief tank 23, dissolved air water with different carbon dioxide concentrations can be generated, thus flexibly controlling the pH value of the raw water supply.

[0030] In this embodiment, the material of the annular packing layer 19 in the dissolved gas tank 16 is polypropylene, which has the characteristics of large specific surface area, high porosity and good permeability, as well as acid corrosion resistance, light weight and long-term stability.

[0031] In this embodiment, the carbon dioxide storage tank 1, the vaporizer 9, and the release device 32 are all existing technologies and will not be described in detail here.

[0032] Example 2: Recovery of Cooling Energy from Liquid Carbon Dioxide Vaporization and Utilization of Dissolved Gas. This example is based on the device described in Example 1, and utilizes its cold water pool 4 for cooling energy recovery. Active cooling of the water body is achieved by recovering the latent heat of phase change during the liquid carbon dioxide vaporization process.

[0033] During operation, high-pressure liquid carbon dioxide enters the vaporizer 9, which is submerged in the cold water pool 4, from the gas source (carbon dioxide storage tank 1) via the pressure reducing valve 3. Within the vaporizer 9, depressurization and heat absorption vaporization are completed. This process continuously absorbs heat from the water in the cold water pool 4, causing the pool water temperature to decrease. Temperature monitoring points confirm that this device can achieve a stable decrease in the water temperature of the cold water pool 4, as shown in Figure 2. The cooled pool water is then pumped into the dissolved carbon dioxide tank 16 via the pressure pump 13. Due to the lower inlet water temperature, the solubility of carbon dioxide in water increases, meaning that more carbon dioxide gas can dissolve under the same pressure conditions, generating dissolved carbon dioxide water with a higher concentration.

[0034] This embodiment demonstrates that cold energy recovery can achieve active cooling of water by monitoring temperature changes at different monitoring points in both the no-cold-energy-recovery mode and the cold-energy-recovery mode. Figure 2 shows the reaction parameters as follows: influent flow rate is 0.6 m³ / s. 3 The dissolved air tank 16 has a carbon dioxide inlet flow rate of 2.5 L / min, a pressure of 0.35 MPa in both the dissolved air tank 16 and the pressure of the pressure relief tank 23 is 0.35 MPa, and the vaporizer 9 has the following parameters: external dimensions 400 mm * 400 mm * 160 mm, and a heat exchange area of ​​3.84 m². 2 It is made of 304 stainless steel.

[0035] The results show that in the mode without cold energy recovery, the temperature of the dissolved air water outlet is 0.3 ℃ higher than that of the inlet water due to the work of the pressurization pump 13. However, after the cold energy recovery is turned on, the tap water inlet is cooled down by the vaporization of liquid carbon dioxide in the vaporizer 9 in the cold water pool 4. The temperature of the dissolved air water outlet can be reduced by 0.1 ℃ under the conditions of carbon dioxide inlet flow rate of 2.5 L / min and pressure of 0.35 MPa in the subsequent dissolved air tank 16, which reduces the temperature by 0.1 ℃ compared with the mode without cold energy recovery, as shown in Figure 2.

[0036] In this embodiment, it is necessary to ensure that carbon dioxide enters the vaporizer 9 in liquid form to absorb heat and vaporize. The pipeline between the pressure reducing valve 3 and the vaporizer 9 should be as short as possible. At the same time, it is necessary to ensure the required pressure for the liquid state and that the inlet pipe has corresponding heat insulation measures.

[0037] In this embodiment, the water level in the cold water tank 4 is above the vaporizer 9 to achieve cold energy recovery. The water volume in the cold water tank 4 should be sufficient to ensure the normal operation of the booster pump 13, while minimizing the water volume in the cold water tank 4 to ensure that the water in the cold water tank 4 can be effectively cooled, thereby promoting the improvement of the gas dissolving effect in the subsequent gas dissolving tank.

[0038] Example 3: Method for adjusting the pH of raw water by enhancing carbon dioxide dissolution with micro-nano bubbles. This example uses the device in Example 1 to carry out the micro-nano enhanced carbon dioxide dissolution reaction to adjust the pH of raw water. Its structure is shown in Figure 1.

[0039] First, open the cold water inlet valve 5. After the water level completely submerges the vaporizer 9, open the liquid carbon dioxide storage tank and adjust the pressure reducing valve 3 to stably deliver liquid carbon dioxide to the vaporizer 9 for endothermic vaporization. The generated gaseous carbon dioxide enters the dissolved gas tank 16 through two paths via the inlet pipe. The water, cooled by the vaporizer 9, enters the dissolved gas tank 16 under the action of the pressure pump 13, achieving efficient gas dissolution through the first Venturi tube 17 and the annular packing layer 19. The resulting dissolved gas water then flows by gravity into the pressure relief tank 23, where the second Venturi tube 24 further suppresses gas escape, ensuring a stable dissolved gas concentration. Finally, it flows by gravity through a pipeline into the pH adjustment tank 30 to adjust the pH of the raw water.

[0040] The micro-nano aeration experiment calculated the corresponding carbon dioxide consumption based on the flow rate of gaseous carbon dioxide before entering the dissolved air tank 16 and the pressure of the pressure reducing valve. The carbon dioxide content was determined by absorbing the effluent from the pressure relief tank 23 with sodium hydroxide solution and back-titrifying with hydrochloric acid. Conventional aeration refers to directly introducing carbon dioxide into the raw water through an aeration head for pH adjustment; its experiment calculated the corresponding carbon dioxide consumption based on the carbon dioxide flow rate and gas pressure. Figure 3 compares the relationship between carbon dioxide consumption and raw water pH changes under conventional aeration and micro-nano enhanced dissolved air conditions. The micro-nano enhanced group's pH change was reflected by measuring the pH change after mixing and stirring the dissolved air water with the raw water, while the conventional aeration group's pH change was directly reflected by the corresponding raw water pH changes for different carbon dioxide consumption levels.

[0041] The results show that, using the micro-nano bubble enhanced dissolution technology of this embodiment, the required carbon dioxide consumption is significantly lower than that of conventional aeration when achieving the same raw water pH adjustment target. Throughout the entire pH adjustment range (e.g., from an initial pH of approximately 8.5 to 7.5), the carbon dioxide utilization rate of the micro-nano aeration technology is approximately 40%-50% higher than that of conventional aeration technology. Based on the comparison of experimental results between micro-nano aeration and conventional aeration, it is clear that using micro-nano aeration technology to enhance carbon dioxide dissolution can effectively reduce the required amount of carbon dioxide. For the same raw water pH change, micro-nano aeration technology can save 40-50% of carbon dioxide compared to conventional aeration.

[0042] In this embodiment, the inlet flow rate of the pressurizing pump 13 is controlled by adjusting the regulating valve in front of the dissolved air tank 16 to control the carbon dioxide concentration of the dissolved air water.

[0043] In this embodiment, before gaseous carbon dioxide enters the dissolved air tank 16, the gas flow rate and pressure need to be controlled by adjusting the flow meter and the pressure reducing valve in order to control the carbon dioxide concentration in the subsequent dissolved air water effluent.

[0044] In this embodiment, the pressure range of the dissolved air tank 16 is 0.3-0.50 MPa. The pressure range needs to take into account the withstand range of the dissolved air tank material, as well as the pressure of the pressurizing pump and the carbon dioxide storage tank 1, and ensure a stable air inlet flow rate and water inlet flow rate.

[0045] In this embodiment, the pressure range of the pressure relief tank 23 is 0.1-0.30 MPa. The pressure range needs to take into account the material tolerance of the pressure relief tank 23 and needs to be lower than the pressure of the dissolved air tank so that the dissolved air water generated by the dissolved air tank 16 can flow smoothly into the pressure relief tank 23. At the same time, the pressure inside the pressure relief tank 23 should be as high as possible to allow the dissolved air water to flow into the pH adjustment tank 30 for pH adjustment of the raw water.

[0046] Example 4: Adjusting the pH of raw water by mixing dissolved air water with different carbon dioxide concentrations in different proportions. In this example, the device in Example 1 is used to adjust different operating parameters to produce dissolved air water with different carbon dioxide concentrations. Its structure is shown in Figure 1.

[0047] In this embodiment, by adjusting the ratio of raw water inlet flow rate to dissolved air inlet flow rate in pH adjustment tank 30, the pH change before and after mixing of raw water can be measured. The pH change caused by different mixing ratios and the corresponding carbon dioxide consumption can be obtained, and the response relationship between mixing ratio and pH change can be established, as shown in Figure 4.

[0048] The device in Example 1 can generate dissolved air water with a stable carbon dioxide concentration, and the pH can be fine-tuned by changing the mixing ratio of the dissolved air water and the raw water. Alternatively, the carbon dioxide concentration of the dissolved air water can be changed by adjusting the equipment parameters of the device in Example 1, and the pH of the raw water can be controlled over a wide range according to a fixed mixing ratio of dissolved air water and raw water. Combining these two control methods can efficiently maintain the stability of the raw water pH. By rationally adjusting the equipment parameters and mixing ratio according to the actual situation of the water supply plant, the desired pH control effect can be achieved.

[0049] This embodiment adjusts the mixing ratio of dissolved air water and raw water by controlling the flow rates of dissolved air water entering the pH adjustment tank, thereby adjusting the pH of the raw water. The carbon dioxide concentration in the dissolved air water is 0.608 g / L, the initial pH of the raw water is 8.04, and the mixing and residence time in the pH adjustment tank is 6 minutes. The results show that under different mixing ratios of dissolved air water and raw water, the pH of the raw water can be effectively reduced, and the higher the proportion of dissolved air water, the more significant the pH reduction effect. As shown in Figure 4, when the mixing ratio of dissolved air water to raw water is 1:150, the pH of the raw water with an initial pH of 8.04 can only be reduced to 7.60, failing to reach the ideal pH range below 7.50. When the mixing ratio is controlled in the range of 1:100 to 1:50, the pH of the raw water can be reduced to 7.48-7.17, meeting the pH control requirements without significantly affecting the subsequent coagulation and sedimentation process. At this time, the carbon dioxide consumption per ton of water is 6-12 g, achieving both treatment effectiveness and economy.

[0050] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, characterized in that, The system includes a cold water tank (4), a vaporizer (9), a dissolved carbon dioxide tank (16), a pressure relief tank (23), a first Venturi tube (17), a second Venturi tube (24), and a pH adjustment tank (30). The vaporizer (9) is located in the cold water tank (4) and is used to vaporize the introduced liquid carbon dioxide and cool the water in the cold water tank (4). The dissolved carbon dioxide tank (16) is equipped with a first Venturi tube (17) and a packing layer (19) to enhance the dissolution of carbon dioxide under pressure. The gas outlet of the vaporizer (9) is connected to the throat of the first venturi tube (17) and the internal space of the dissolved gas tank (16) through pipelines, and the inlet of the first venturi tube (17) is connected to the outlet of the cold water pool (4); the pressure relief tank (23) is provided with a second venturi tube (24) connected to the outlet of the dissolved gas tank (16) for secondary gas dissolution of the dissolved gas water from the dissolved gas tank (16); the pH adjustment tank (30) is connected to the outlet of the pressure relief tank (23).

2. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 1, is characterized in that... The outlet of the pressure relief tank (23) is connected to the pH adjustment tank (30) through the release device (32), which is used to release the dissolved air water after secondary dissolved air treatment and mix it with the original water.

3. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 1, is characterized in that... It also includes a carbon dioxide storage tank (1), which is connected to the liquid carbon dioxide inlet of the vaporizer (9) via a pipeline.

4. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 1, is characterized in that... The dissolved gas tank (16) maintains high pressure to increase dissolved gas, and its operating pressure range is 0.3-0.5 MPa.

5. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 1, is characterized in that... The filler layer (19) is made of polypropylene.

6. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 1, is characterized in that... The operating pressure range of the pressure relief tank (23) is 0.1-0.3 MPa.

7. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 1, is characterized in that... The pH adjustment tank (30) is equipped with a stirrer (31).

8. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 1, is characterized in that... It also includes an inlet system and a drainage system. The inlet system includes a tap water inlet pipe (6) connected to the cold water tank (4) and a raw water inlet pipe (34) connected to the raw water source and leading to the pH adjustment tank (30). The drainage system includes a drain pipe (10) connected to the cold water tank (4) and a raw water outlet pipe (38) connected to the pH adjustment tank (30).

9. The device for enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid for controlling the pH of raw water supply, as described in claim 8, is characterized in that... Multiple outlet valves are installed on the raw water outlet pipe (38) and at different heights corresponding to the pH adjustment tank (30).

10. A device for controlling the pH of raw water supply by enhancing carbon dioxide dissolution coupled with cold energy recovery to generate micro / nano bubble liquid according to any one of claims 1-9, characterized in that, It also includes a control box (39); the cold water tank (4) is equipped with a cold water tank pH meter (7) and a cold water tank level gauge (8); the dissolved gas tank (16) is equipped with a pressure sensor (18); the pressure relief tank (23) is equipped with a pressure relief tank level gauge (21); the pH adjustment tank (30) is equipped with an adjustment tank pH meter (27), a carbon dioxide content measuring device (28) and an adjustment tank level gauge (29); the cold water tank pH meter (7), the cold water tank level gauge (8), the pressure sensor (18), the pressure tank level gauge (21), the adjustment tank pH meter (27), the carbon dioxide content measuring device (28) and the adjustment tank level gauge (29) are all connected to the control box (39).

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