Electrochemical descaling-filtration crystallization combined descaling system with serrated cathode structure

Abstract

The present invention discloses an electrochemical scale removal-filtration crystallization combined descaling system with a serrated cathode structure, comprising an electrochemical scale removal module and a filtration crystallization module. The cathode in the electrochemical scale removal module has a serrated structure, and the outlet of the electrochemical scale removal module is connected to the inlet of the filtration crystallization module. The system has a high descaling efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical descaling, and relates to an electrochemical descaling-filtration and crystallization combined descaling system with a sawtooth cathode structure. Background Art

[0002] Scaling is a widespread phenomenon in industrial circulating cooling water systems, reducing their heat transfer efficiency and increasing their operating energy consumption. Given the significant water consumption of industrial circulating cooling water systems, controlling scale deposition in these systems ensures safe and stable operation, significantly reduces energy consumption, and fully utilizes water resources. This contributes to China's ongoing "carbon peak and carbon neutrality" initiatives, offering significant social and economic benefits.

[0003] To address the scaling problem in circulating cooling water systems, researchers have proposed a number of treatment methods, including chemical agents, magnetization and electromagnetic technology, ultrasonic technology, and electrochemical descaling technology. Electrochemical descaling technology is an active descaling and anti-scaling technology that can precipitate scaling ions in water in solid form, thereby reducing the scaling tendency of circulating water, increasing the concentration factor, reducing the amount of wastewater discharged and the amount of water replenished, and saving water resources. At the same time, the electrochemical anode can produce a large amount of strong oxidizing active substances during the reaction process, making this technology also have a good killing and inhibitory effect on microorganisms and algae in circulating cooling water systems.

[0004] The main problem with electrochemical scale removal at present is still the low treatment efficiency. A series of works (Ind.Eng.Chem.Res.2018,57,6585; Separation and Purification Technology, 2019,210:943; Separation and Purification Technology, 2018,191:216)) show that the hardness removal efficiency obtained by electrochemical scale removal technology is in the range of 10-25%. Since scale needs to be precipitated in the cathode area and deposited on the cathode plate, the material, usage area and surface state of the cathode will become the key factors affecting scale precipitation, provided that the other factors are optimized. Most of the cathodes currently used adopt a flat plate structure, which has a small available area, is not conducive to the precipitation of scale at the cathode, and the scale removal efficiency is low. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an electrochemical descaling-filtration crystallization combined descaling system with a serrated cathode structure, which has a high descaling efficiency.

[0006] To achieve the above-mentioned purpose, the electrochemical scale removal-filtration crystallization combined scale removal system with a serrated cathode structure described in the present invention includes an electrochemical scale removal module and a filtration crystallization module, wherein the cathode in the electrochemical scale removal module is a serrated structure, and the outlet of the electrochemical scale removal module is connected to the inlet of the filtration crystallization module.

[0007] The cathode in the electrochemical scale removal module is formed by extruding cathode material through a mold.

[0008] To ensure the treatment effect, the angle of the cathode serrated folding plate should be controlled within the range of 10° to 90°.

[0009] The length and width of the cathode are determined according to the selected cathode serrated folding plate angle and the actual size of the electrolytic cell and anode. The distance between the edges of the cathode plate on both sides and the reaction container is greater than or equal to 10 cm.

[0010] The length of the cathode in the electrochemical scale removal module is the same as the length of the anode, and the width of the cathode in the electrochemical scale removal module is the same as the width of the anode.

[0011] The electrochemical descaling module is a manual descaling system or an automatic descaling system.

[0012] The outlet of the electrochemical scale removal module is connected to the inlet at the bottom of the filtration crystallization module through a flow regulating valve.

[0013] An overflow port is provided on the top of the filtration crystallization module.

[0014] The filtration crystallization module is a circular tubular structure.

[0015] The filler filled in the filtration crystallization module is artificial zeolite, quartz sand or molecular sieve.

[0016] The present invention has the following beneficial effects:

[0017] In the electrochemical descaling-filtration crystallization combined descaling system with a serrated cathode structure described in the present invention, the cathode in the electrochemical scale removal module is a serrated structure, wherein the tip of the serrated cathode has a lower surface potential and a higher current density than the smooth part, and the cathode hydrogen evolution reaction is more intense, thereby forming a local strong alkaline environment near the tip of the cathode, making it easier to generate CaCO3 and Mg(OH)2 precipitation, thereby improving its descaling rate. Through the implementation of the present invention, the descaling rate can exceed 10g / (m 2·h). Moreover, the scale layer at the tip is easier to fall off, which promotes the renewal of the cathode surface. The flat part can also provide a place for the subsequent cathode reaction after the tip is covered by the scale layer. At the same time, because the surface area of the serrated cathode is larger than that of the flat plate, the cathode deactivation time is prolonged through the synergistic effect of the tip area and the flat area, and its voltage is lower at the same current, which ultimately makes the serrated cathode energy consumption lower. Through the implementation of the present invention, the energy consumption can be made no higher than 10kWh / kg CaCO3. At the same time, the effluent water of the electrochemical treatment process of the electrochemical scale removal module contains a large amount of scale ions and hydroxide ions. The removal efficiency of the scale ions is improved by the filtration and crystallization module, and the non-deposited scale particles in the water are intercepted and filtered. In addition, due to the ohmic heating effect during the electrochemical treatment process, the outlet water temperature is increased, resulting in a weakening of the heat exchange effect of the circulating water. Therefore, the present invention adds a filtration and crystallization module to the circulating water to add a heat dissipation process, effectively alleviate the situation of water temperature increase, which is conducive to ensuring the heat exchange capacity of the circulating water. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the cathode in the electrochemical scale removal module of the present invention;

[0019] Figure 2 This is a graph showing voltage changes during the descaling process for the present invention and a flat-plate cathode;

[0020] Figure 3 A schematic diagram of the system of the present invention;

[0021] Figure 4 A comparison chart of hardness removal between the present invention and the electrochemical system;

[0022] Figure 5 This is a comparison chart of the temperature changes of the present invention and the electrochemical system. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0024] The accompanying drawings illustrate schematic diagrams of the structures of the disclosed embodiments of the present invention. These figures are not drawn to scale; for the purpose of clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0025] The electrochemical scale removal and filtration crystallization combined descaling system with a serrated cathode structure described in the present invention includes an electrochemical scale removal module and a filtration crystallization module, wherein the cathode in the electrochemical scale removal module is a serrated structure, and the outlet of the electrochemical scale removal module is connected to the inlet of the filtration crystallization module.

[0026] Specifically, the length and width of the cathode are determined according to the actual sizes of the electrolytic cell and the anode, wherein the length of the cathode is the same as the length of the anode, and the width of the cathode is the same as the width of the anode.

[0027] The sawtooth length and sawtooth angle of the sawtooth structure are selected and adjusted according to the actual situation. If the sawtooth length is too short, the distance between the cathode and the anode will increase, the cell pressure will increase, and the shielding effect between different sawtooth will increase, resulting in a decrease in the descaling rate and an increase in energy consumption. However, if the sawtooth length is too long, the OH generated at the cathode tip will be - With H near the anode + Neutralization occurs, and the calcium and magnesium ions in the solution cannot be removed, resulting in a lower descaling rate and increased energy consumption.

[0028] The reduction of the sawtooth angle will increase the reaction area of the cathode and reduce the cell pressure. At the same time, it will also make the cathode tip part more, the current density of the tip part is larger, the reaction rate is faster, and the hydrogen evolution reaction is more intense. It can make the scale layer growing on the cathode detach from the cathode surface under the action of hydrogen bubbles, promote the renewal of the cathode surface, that is, the tip effect. The smaller the angle, the more obvious the tip effect, which increases the descaling rate and effectively reduces energy consumption.

[0029] The electrochemical scale removal module is a manual descaling system or an automatic descaling system; the outlet of the electrochemical scale removal module is connected to the inlet at the bottom of the filtration crystallization module through a flow regulating valve, and an overflow port is provided at the top of the filtration crystallization module; the filtration crystallization module is a circular tubular structure; the filler filled in the filtration crystallization module is artificial zeolite, quartz sand or molecular sieve.

[0030] Example 1

[0031] The cathode is extruded from a 0.1 mm thick stainless steel plate using a mold. The serrations are 10 mm long and 30° in angle. The projected cathode length is 60 mm and the width is 70 mm. The electrochemical descaling device has a volume of 200 mL and consists of two 60 mm x 70 mm TiO electrodes and a cathode of the same size arranged in parallel, with a center-to-center spacing of 15 mm between the cathode and anode. The water quality parameters for the treated water sample are: hardness 700 mg / L, alkalinity 350 mg / L, pH 8.2, and conductivity 2.5 mS / cm.

[0032] When the applied current value is 0.4A, the descaling rate of the present invention can reach 11.23g / (m 2 ·h), the energy consumption is only 6.82kWh / kg CaCO3, which is much lower than other reports.

[0033] For comparison, the zigzag cathode was replaced with a stainless steel plate of the same projection size, and the experimental results were compared. Figure 2 As shown in the figure, the voltage of the electrochemical descaling device with a sawtooth plate and a flat plate cathode was monitored under the condition of a current of 0.4A. The results show that the voltage will rise during the electrochemical descaling process, but the voltage of the sawtooth cathode is always about 4% lower than the voltage of the flat plate. Therefore, when running at the same current for the same time, the sawtooth cathode consumes about 4% less electricity than the flat plate cathode.

[0034] Example 2

[0035] The treatment conditions of the present invention (abbreviated as EC-FC system) and the electrochemical system (abbreviated as EC system) are compared. The difference between the two is whether the filtration crystallization system (abbreviated as FC system) is added. The reaction conditions of the EC system are: the inlet water hardness is 300mg·L -1 , hardness: alkalinity = 1:1, the anode is a Ti4O7 electrode, the cathode is a serrated stainless steel cathode, the water inlet peristaltic pump speed is 10 rpm, and the current density is 6 mA cm -2 , the reaction time is 60min. The parameters of the FC system are: the module is a plexiglass tube with an inner diameter of 2cm and a length of 25cm, with overflow water at the upper end and a flow regulating valve at the lower end to control the water flow rate, and 100g of pre-treated artificial zeolite is filled inside. Artificial zeolite is sieved with a sieve before use, and particles in the range of 40-60 mesh are collected. They are soaked and washed three times with deionized water, each time for 30 minutes, and can be used after drying. In the EC-FC system, the water to be treated flows through the electrochemical module and the FC module in sequence, such as Figure 3 shown.

[0036] Depend on Figure 4It can be seen that the hardness removal rate change trend of the EC-FC system is consistent with that of the EC system. The removal rate is high in the initial stage (0-10min) and tends to be stable after 10min. The six groups of hardness removal rate data in the stable stage (10-60min) are averaged and the hardness removal rate of the EC-FC system is 16.50% (±0.45%), which is higher than the 9.75% (±1.24%) of the EC system. This shows that the hardness removal ability of the EC-FC system is stronger than that of the EC system. When other conditions are the same, the improvement in the hardness removal ability is due to the post-placed FC module.

[0037] The experimental results show that the ohmic heating phenomenon during electrolysis will cause the water temperature to rise, such as Figure 5 As shown, the post-FC system can effectively alleviate this temperature rise phenomenon. Taking the reaction time of 60 minutes as an example, the water temperature of the EC system increases by 1.75°C, while the corresponding water temperature increase of the EC-FC system is only 0.55°C. This is because the water sample has sufficient time to exchange heat with the air in the FC module, so that the ohmic heat is released to a certain extent. In the actual operation of circulating cooling water, it can effectively alleviate the impact of electrochemical equipment on the heat exchange capacity of the circulating water system. The above results show that the introduction of the FC module can effectively improve the performance of the EC-FC system in hardness removal, TDS removal and water temperature increase.

[0038] Example 3

[0039] Influent hardness is an important water quality parameter that affects the treatment effect. Table 1 shows the changes in different indicators of the EC-FC system and the EC system during the descaling process at different influent hardness values. The reaction conditions of the EC system are: influent hardness 300 mg·L -1 , hardness: alkalinity = 1:1, the anode is a Ti4O7 electrode, the cathode is a serrated stainless steel cathode, the water inlet peristaltic pump speed is 10 rpm, and the current density is 6 mA cm -2 The reaction time was 60 minutes. The FC system parameters were as follows: the module consisted of a 2cm inner diameter, 25cm long organic glass tube, with overflow water at the top and a flow control valve at the bottom to control the water flow rate. The tube was filled with 100g of pre-treated quartz sand. Before use, the quartz sand was sieved with a sieve to collect particles with a mesh size of 40-60. The sand was then rinsed with deionized water three times for 30 minutes each time and allowed to air dry before use.

[0040] As shown in Table 1, at different inlet water hardness values, the hardness removal rate, alkalinity removal rate, TDS removal rate, and temperature difference index of the EC-FC system are all better than those of the EC system, which fully demonstrates that the FC module can effectively improve the treatment efficiency of the EC-FC system.

[0041] Table 1

[0042]

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. An electrochemical descaling-filtration crystallization combined descaling system with a sawtooth cathode structure, characterized in that: It includes an electrochemical scale removal module and a filtration crystallization module, wherein the cathode in the electrochemical scale removal module is a serrated structure, and the outlet of the electrochemical scale removal module is connected to the inlet of the filtration crystallization module; The cathode in the electrochemical scale removal module is made by extruding cathode material through a mold; The serrated folding angle of the cathode is controlled within the range of 10° to 90°, and its length and width are determined according to the selected serrated folding angle and the actual size of the electrolytic cell and anode. The distance between the two sides of the cathode plate and the reaction vessel is greater than or equal to 10 cm; The length of the cathode in the electrochemical scale removal module is the same as the length of the anode, and the width of the cathode in the electrochemical scale removal module is the same as the width of the anode.

2. The electrochemical descaling-filtration crystallization combined descaling system with a sawtooth cathode structure according to claim 1 is characterized in that: The electrochemical descaling module is a manual descaling system or an automatic descaling system.

3. The electrochemical descaling-filtration crystallization combined descaling system with a sawtooth cathode structure according to claim 1 is characterized in that: The outlet of the electrochemical scale removal module is connected to the inlet at the bottom of the filtration crystallization module through a flow regulating valve.

4. The electrochemical descaling-filtration crystallization combined descaling system with a sawtooth cathode structure according to claim 1 is characterized in that: An overflow port is provided on the top of the filtration crystallization module.

5. The electrochemical descaling-filtration crystallization combined descaling system with a sawtooth cathode structure according to claim 1 is characterized in that: The filtration crystallization module is a circular tubular structure.

6. The electrochemical descaling-filtration crystallization combined descaling system with a sawtooth cathode structure according to claim 1 is characterized in that: The filler filled in the filtration crystallization module is artificial zeolite, quartz sand or molecular sieve.

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