A system and method for wastewater electrolysis coupled with carbon reduction

Abstract

This invention proposes a system and method for wastewater electrolysis coupled with carbon reduction. The system includes an electrolytic cell, a collection component, an absorption cell, and a recovery component. The electrolytic cell is energized to electrolyze the electrolyte and generate electrolytic gas. The collection component includes a gas-liquid separator connected to the electrolytic cell. The absorption cell is connected to the gas-liquid separator and includes an alkali inlet for introducing an alkaline absorbent and a gas inlet for introducing a carbon dioxide mixture. The recovery component is connected to the absorption cell to separate the electrolyte discharged from the absorption cell and generate byproducts. The recovery component is also connected to the electrolytic cell to allow the electrolyte containing byproducts to be introduced back into the electrolytic cell. This invention provides a wastewater electrolysis coupled with carbon reduction system with high electrolysis efficiency and high safety.

Description

Technical Field

[0001] This invention relates to the field of wastewater electrolysis treatment technology, and more specifically, to a system and method for wastewater electrolysis coupled with carbon reduction. Background Technology

[0002] Alcohol-containing wastewater is a very common type of wastewater. Conventional biological treatment methods cannot recover and reuse alcohols from wastewater, resulting in additional costs and significant resource waste. Electrochemical oxidation of alcohols into acids is a clean and effective method for value-added treatment of alcohol-containing pollutants. However, the electrochemical reaction in wastewater produces hydrogen gas at the cathode, which is highly hazardous and poses a threat to the safety of the wastewater treatment process. Summary of the Invention

[0003] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0004] The inventors discovered that during the electrochemical oxidation of alcohol-containing wastewater, since oxidation does not produce oxygen, the anode and cathode membranes of conventional electrolytic reactors can be removed. However, this leads to the mixing of a small amount of gaseous impurities generated at the anode with the cathode products, causing difficulties in the subsequent purification and storage of the cathode products, such as poisoning the storage medium. At the same time, the cations generated at the anode come into contact more easily with the scale-forming anions such as hydroxides and carbonates generated at the cathode, making it easier to generate scale and causing electrode passivation.

[0005] 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 wastewater electrolysis coupled with carbon reduction system. This system can simultaneously achieve wastewater electrochemical conversion and carbon reduction, as well as in-situ product impurity removal and a highly flexible and adjustable system. It achieves simultaneous improvement in cathode by-product gas purity and anodic oxidation efficiency, reduces electrode fouling through flexible adjustment of the electrolyte reflux flow rate, and achieves a high degree of system compatibility with renewable energy sources.

[0006] The wastewater electrolysis coupled carbon reduction system of this invention includes:

[0007] An electrolytic cell, wherein electricity is supplied to electrolyze the electrolyte within the cell and generate electrolytic gas;

[0008] A collection component, comprising a gas-liquid separation device connected to the electrolytic cell, for receiving the electrolyte and electrolytic gas after electrolysis in the electrolytic cell;

[0009] An absorption tank is connected to the gas-liquid separation device. The absorption tank includes an alkali inlet and a gas inlet. The alkali inlet is used to introduce an alkaline absorbent, and the gas inlet is used to introduce a carbon dioxide mixture, so that the electrolyte discharged from the gas-liquid separation device reacts with the carbon dioxide mixture and the alkaline absorbent in the absorption tank.

[0010] A recovery component is connected to the absorption cell to separate the electrolyte discharged from the absorption cell and generate by-products. The recovery component is also connected to the electrolytic cell to allow the electrolyte containing the by-products to be introduced into the electrolytic cell.

[0011] In some embodiments, the collection assembly further includes a gas collection device connected to the gas-liquid separator for collecting gas discharged from the gas-liquid separator.

[0012] In some embodiments, the absorption cell further includes an electrolyte outlet, which is connected to the electrolytic cell so that the absorption cell can supply electrolyte to the electrolytic cell through the electrolyte outlet.

[0013] In some embodiments, the recycling assembly includes a by-product recycling device and a conditioning device. The by-product recycling device is connected to the absorption tank, and the conditioning device is connected between the electrolytic cell and the by-product recycling device. The conditioning device is used to adjust the pH value of the electrolyte discharged from the by-product recycling device.

[0014] In some embodiments, the electrolytic cell is a diaphragm-less electrolytic cell.

[0015] The wastewater electrolysis coupled carbon reduction method of this invention is completed using the wastewater electrolysis coupled carbon reduction system described in any one of the above embodiments, and includes the following steps:

[0016] Inside the electrolytic cell, the electrolyte is electrolyzed after being energized, and the electrolyzed electrolyte and the generated gas are then passed into the collection assembly.

[0017] The electrolyte and electrolytic gas are separated using a collection component, and the separated electrolyte is then passed into an absorption cell.

[0018] A mixture of alkaline substances and carbon dioxide is introduced into the absorption tank to remove impurity gases from the electrolyte in the absorption tank.

[0019] The electrolyte, after impurity gases have been removed, is passed into a collection assembly. After obtaining byproducts using a conditioning device, the electrolyte is then passed into an electrolytic cell for electrolysis.

[0020] In some embodiments, the wastewater electrolytic coupling carbon reduction method of the present invention further includes the following steps:

[0021] The gas discharged from the gas-liquid separator is collected using a collection device.

[0022] In some embodiments, before the electrolyte for removing impurity gases is introduced into the collection assembly, the method further includes the following step:

[0023] The electrolyte solution used to remove impurity gases in the absorption cell is passed into the electrolytic cell.

[0024] In some embodiments, the introduction of a mixture of alkaline substance and carbon dioxide into the absorption tank satisfies the following relationship:

[0025] q ac = Q c n, where q ac Q is the amount of alkali added to the absorption tank; Q is the flow rate of the carbon dioxide mixture introduced into the absorption tank; c is the stoichiometric ratio, taken as 0.5; n is the absorption efficiency, taken as 0.8~0.9.

[0026] In some embodiments, the carbon dioxide mixture contains 10% to 40% carbon dioxide. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the wastewater electrolysis coupled carbon reduction system according to an embodiment of the present invention.

[0028] Figure label:

[0029] 1. Electrolytic cell; 11. Electrolyte outlet; 12. Electrolyte inlet.

[0030] 2. Collection component; 21. Gas-liquid separation device; 211. First liquid inlet; 212. First liquid outlet; 213. First exhaust outlet; 22. Gas collection device; 221. Gas collection inlet.

[0031] 3. Absorption tank; 31. Alkali inlet; 32. Second liquid inlet; 33. Second liquid outlet; 34. Electrolyte outlet; 35. Gas inlet; 36. Gas outlet.

[0032] 4. Recycling component; 41. By-product recycling device; 411. Third liquid inlet; 412. By-product outlet; 413. Third liquid outlet; 414. Additive inlet; 42. Conditioning device. Detailed Implementation

[0033] 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.

[0034] The wastewater electrolytic coupling carbon reduction system of the present invention is described below with reference to the accompanying drawings.

[0035] like Figure 1 As shown, the wastewater electrolysis coupled carbon reduction system of this embodiment of the invention includes: an electrolytic cell 1, a collection component 2, an absorption cell 3, and a recovery component 4.

[0036] Electrolytic cell 1 is energized to electrolyze the electrolyte within it and generate electrolytic gas. Collection assembly 2 includes a gas-liquid separator 21 connected to electrolytic cell 1 to receive the electrolyte and electrolytic gas after electrolysis. Absorption cell 3 is connected to the gas-liquid separator 21 and includes an alkali inlet 31 and a gas inlet 35. The alkali inlet 31 is used to introduce an alkaline absorbent, and the gas inlet 35 is used to introduce a carbon dioxide mixture, so that the electrolyte discharged from the gas-liquid separator 21 reacts with the carbon dioxide mixture and the alkaline absorbent within the absorption cell 3. Recovery assembly 4 is connected to the absorption cell 3 to separate the electrolyte discharged from the absorption cell 3 and generate byproducts. Recovery assembly 4 is also connected to electrolytic cell 1 to allow the electrolyte containing byproducts to be reintroduced into electrolytic cell 1.

[0037] Specifically, such as Figure 1 As shown, the electrolytic cell 1 includes an electrolyte outlet 11 and an electrolyte inlet 12. The gas-liquid separation device 21 includes a first liquid inlet 211, a first liquid outlet 212, and a first exhaust port 213. The electrolyte outlet 11 and the first liquid inlet 211 are connected by a pipe so that after the electrolyte in the electrolytic cell 1 undergoes an electrolytic reaction, the electrolyzed electrolyte and the gas generated by the electrolysis can be introduced into the gas-liquid separation device 21 through the pipe, thereby separating the electrolyte and the electrolyzed gas in the gas-liquid separation device 21.

[0038] It is understandable that the gas-liquid separation device 21 can be a gas-liquid separator, that is, the electrolyte and the electrolytic gas are separated in the gas-liquid separation device 21 according to the action of gravity.

[0039] like Figure 1 As shown, the absorption tank 3 also includes a second inlet 32, a second outlet 33, an electrolyte outlet 34, and a gas outlet 36. The second inlet 32 ​​is connected to the first outlet 212 through a pipe so that the absorption tank 3 can receive the electrolyte discharged from the gas-liquid separation device 21. The alkali addition port 31 is used to add alkaline substances, such as potassium hydroxide solution.

[0040] After a mixture of carbon dioxide and alkaline substances is introduced into the absorption tank 3, the electrolyte comes into contact with the carbon dioxide-containing gas and alkaline substances within the absorption tank 3. The carbon dioxide reacts with the alkaline substances added to the absorption tank 3 and is converted into carbonate ions. The residual gas from decarbonization can carry away any small amounts of gas remaining in the electrolyte (such as carbon monoxide and impurity gases). The gas inlet can be connected to a carbon dioxide emission outlet, such as the outlet of a thermal power plant flue. The gas outlet 36 can be connected to an vent or a carbon removal gas collection device 22 to prevent the emitted carbon dioxide from polluting the air.

[0041] It should be noted that, depending on the reaction conditions in the absorption tank 3, the amount of alkali added and the gas-liquid flow ratio in the absorption tank 3 can be adjusted in order to obtain the target carbon absorption and electrolyte impurity removal and desorption effects.

[0042] In other words, the wastewater electrolysis coupled carbon reduction system of this invention can improve the system's operational flexibility (i.e., electrolyte reflux ratio or system power) while ensuring certain system conversion rate requirements or product purity requirements, and has a high compatibility with renewable energy. The system can simultaneously obtain CO, organic by-products, wastewater treatment, and flue gas decarbonization effects, resulting in high comprehensive benefits.

[0043] In some embodiments, the collection assembly 2 further includes a gas collection device 22, which is connected to the gas-liquid separator 21 for collecting the gas discharged from the gas-liquid separator 21.

[0044] It is understandable that, such as Figure 1 As shown, the gas collection device 22 can receive the gas discharged from the gas-liquid separator 21, avoiding the direct discharge of electrolytic gas into the air and reducing environmental pollution.

[0045] In some embodiments, the absorption cell 3 further includes an electrolyte outlet 34, which is connected to the electrolytic cell 1 so that the absorption cell 3 can supply electrolyte to the electrolytic cell 1 through the electrolyte outlet 34.

[0046] It is understandable that, such as Figure 1 As shown, the electrolyte outlet 34 is connected to the electrolyte inlet 12 via a pipe. The electrolyte in the absorption tank 3 is alkaline, and the alkaline substance added to the absorption tank 3 has the same composition as the electrolyte. Therefore, by passing the electrolyte with impurities removed into the electrolytic cell 1 through the electrolyte outlet 34, the electrolyte can be recycled. Furthermore, since the electrolyte is free of impurities, the electrolyte return flow rate can be adjusted according to the requirements for cleaning the electrode surface of the electrolytic cell 1, ensuring that excessive amounts of impurities are not carried back and mixed with the original electrolyte in the electrolytic cell 1.

[0047] It should be noted that both the alkali addition port and the gas inlet are equipped with control valves. By adjusting the opening of the control valves, the operator can control the amount of alkaline substances and carbon dioxide introduced into the absorption tank, thus ensuring the adjustable relative amounts of gas and liquid inside the absorption tank.

[0048] In some embodiments, the recycling component 4 includes a by-product recycling device 41 and a conditioning device 42. The by-product recycling device 41 is connected to the absorption tank 3, and the conditioning device 42 is connected between the electrolytic cell 1 and the by-product recycling device 41. The conditioning device 42 is used to adjust the pH value of the electrolyte discharged from the by-product recycling device 41.

[0049] Understandably, the by-product recovery device 41 includes a third inlet 411, a third outlet 413, a by-product discharge outlet 412, and an additive inlet 414. The third inlet 411 is connected to the second outlet 33 via a pipe to receive a portion of the electrolyte discharged from the absorption tank 3. The third outlet is connected to the fourth inlet via a pipe to allow the by-product recovery device 41 to pass the electrolyte into the conditioning device 42. The additive inlet 414 is used to add additives so that the electrolyte and additives mix in the by-product recovery device 41 to generate by-products, which are then discharged through the by-product discharge outlet 412.

[0050] In other words, a portion of the electrolyte enters the recovery component 4, where it undergoes pH adjustment and other processes to obtain corresponding byproducts (such as benzoic acid). The electrolyte after separating the byproducts flows back into the electrolytic cell 1 for reuse.

[0051] Preferably, electrolytic cell 1 is a diaphragm-less electrolytic cell. It is understood that in electrolytic cell 1, the reaction occurring at the anode is a gas-free oxidation reaction, such as the oxidation of an alcohol to an acid, and no gas is generated in the reaction; a carbon reduction reaction occurs at the cathode, producing carbon monoxide. Optionally, the standard electrode potential is below 1.23V.

[0052] Therefore, the wastewater electrolysis coupled carbon reduction system of this embodiment of the invention can control the gas impurity removal efficiency by controlling the amount of gas introduced into the absorption tank, thereby obtaining a higher reaction efficiency in the electrolysis tank (for example, the reaction conversion rate is increased from 80% to 95%, and the concentration of the main reactant in the system is reduced to a lower level. At this time, some side reactions that produce gas may occur (such as oxygen, sulfur oxides, carbon oxides, etc.), which are removed by the absorption tank to avoid excessive impurities in hydrogen gas).

[0053] Furthermore, the membrane-free electrolytic cell can achieve wastewater treatment and carbon reduction, avoiding the additional costs associated with membrane investment and fouling; and it produces no hydrogen, ensuring high system safety.

[0054] The following describes a wastewater electrolytic coupling carbon reduction method according to an embodiment of the present invention.

[0055] The wastewater electrolysis coupled carbon reduction method of this invention is implemented using the wastewater electrolysis coupled carbon reduction system of any of the above embodiments, and includes the following steps:

[0056] Inside the electrolytic cell, the electrolyte is electrolyzed after electricity is applied, and the resulting electrolyte and gas are then passed into a collection assembly. It should be noted that this is a diaphragm-less electrolytic cell; that is, the anode reaction uses the oxidation of organic matter in wastewater, and the main reaction does not produce gas, thus avoiding the mixing of large amounts of oxygen with hydrogen at the cathode. To address the potential oxygen-generating side reaction at the anode, an inert carrier gas is used during electrolyte circulation to remove a small amount of oxygen.

[0057] The electrolyte and electrolytic gas are separated using a collection component, and the separated electrolyte is then passed into an absorption cell.

[0058] A mixture of alkaline substances and carbon dioxide is introduced into the absorption tank to remove impurity gases from the electrolyte in the absorption tank.

[0059] The electrolyte, after impurity gases have been removed, is passed into a collection assembly. After obtaining byproducts using a conditioning device, the electrolyte is then passed into an electrolytic cell for electrolysis.

[0060] In some embodiments, the wastewater electrolytic coupling carbon reduction method of the present invention further includes the following steps:

[0061] The gas discharged from the gas-liquid separator is collected using a collection device. This prevents the gas from being directly released into the air, reducing air pollution.

[0062] In some embodiments, before introducing the electrolyte for removing impurity gases into the collection assembly, the following step is further included:

[0063] The electrolyte solution, after impurity gases have been removed from the absorption tank, is passed into the electrolytic cell. In other words, the electrolyte solution, after impurity gases have been removed, can be passed back into the electrolytic cell, ensuring the reuse of the electrolyte and reducing production costs.

[0064] In some embodiments, a mixture of alkaline substance and carbon dioxide gas is introduced into the absorption tank, satisfying the following relationship: q ac = Q c n, where q ac Q is the amount of alkali added to the absorption tank; Q is the flow rate of the carbon dioxide mixture introduced into the absorption tank; c is the stoichiometric ratio, taken as 0.5; n is the absorption efficiency, taken as 0.8~0.9.

[0065] It is understandable that the greater the flow rate of the carbon dioxide mixture introduced into the absorption tank, the shorter the residence time of the gas absorption reaction and the lower the absorption efficiency.

[0066] Preferably, the carbon dioxide content in the carbon dioxide mixture is 10% to 40%. It should be noted that if the carbon dioxide content is too low, the yield of carbon reduction products will be low; if the carbon dioxide content is too high, the carbon absorption reaction will take too long (i.e., a longer residence time is required), which is not conducive to improving the overall reaction efficiency.

[0067] 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 are not intended to 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 system for wastewater electrolysis coupled with carbon reduction, characterized in that, include: An electrolytic cell is provided, wherein an electrolytic cell is energized to electrolyze the electrolyte in the cell and generate electrolytic gas. The electrolytic cell is a diaphragm-free electrolytic cell used to electrolyze alcohol-containing wastewater. The anode undergoes an oxidation reaction that oxidizes the alcohol to an acid, and the main reaction does not produce gas. The cathode undergoes a carbon dioxide reduction reaction and generates carbon monoxide. A collection component, comprising a gas-liquid separation device connected to the electrolytic cell, for receiving the electrolyte and electrolytic gas after electrolysis in the electrolytic cell; An absorption tank is connected to the gas-liquid separation device. The absorption tank includes an alkali inlet and a gas inlet. The alkali inlet is used to introduce an alkaline absorbent, and the gas inlet is used to introduce a carbon dioxide mixture, so that the electrolyte discharged from the gas-liquid separation device reacts with the carbon dioxide mixture and the alkaline absorbent in the absorption tank. The absorption tank is used to contact the electrolyte with the carbon dioxide mixture and the alkaline absorbent, so that the carbon dioxide is absorbed by the alkaline absorbent and converted into carbonate ions. At the same time, the inert component in the carbon dioxide mixture is used as a carrier gas to strip and carry away the impurities dissolved in the electrolyte. A recovery component is connected to the absorption cell to separate the electrolyte discharged from the absorption cell and generate by-products. The recovery component is also connected to the electrolytic cell to allow the electrolyte containing the by-products to be introduced into the electrolytic cell.

2. The wastewater electrolysis coupled carbon reduction system according to claim 1, characterized in that, The collection assembly also includes a gas collection device connected to the gas-liquid separator for collecting the gas discharged from the gas-liquid separator.

3. The wastewater electrolysis coupled carbon reduction system according to claim 2, characterized in that, The absorption cell also includes an electrolyte outlet, which is connected to the electrolytic cell so that the absorption cell can supply electrolyte to the electrolytic cell through the electrolyte outlet.

4. The wastewater electrolysis coupled carbon reduction system according to claim 3, characterized in that, The recycling component includes a by-product recycling device and a conditioning device. The by-product recycling device is connected to the absorption tank, and the conditioning device is connected between the electrolytic cell and the by-product recycling device. The conditioning device is used to adjust the pH value of the electrolyte discharged from the by-product recycling device.

5. A method for wastewater electrolysis coupled with carbon reduction, characterized in that, The wastewater electrolysis coupled with carbon reduction method is performed using the wastewater electrolysis coupled with carbon reduction system as described in any one of claims 1-4, and includes the following steps: Inside the electrolytic cell, the electrolyte is electrolyzed after being energized, and the electrolyzed electrolyte and the generated gas are then passed into the collection assembly. The electrolyte and electrolytic gas are separated using a collection component, and the separated electrolyte is then passed into an absorption cell. A mixture of alkaline substances and carbon dioxide is introduced into the absorption tank to remove impurity gases from the electrolyte in the absorption tank. The electrolyte, after impurity gases have been removed, is passed into a collection assembly. After obtaining byproducts using a conditioning device, the electrolyte is then passed into an electrolytic cell for electrolysis.

6. The wastewater electrolysis coupled with carbon reduction method according to claim 5, characterized in that, It also includes the following steps: The gas discharged from the gas-liquid separator is collected using a collection device.

7. The wastewater electrolysis coupled with carbon reduction method according to claim 5, characterized in that, Before introducing the electrolyte containing the removed impurity gas into the collection assembly, the method further includes the following steps: The electrolyte solution used to remove impurity gases in the absorption cell is passed into the electrolytic cell.

8. The wastewater electrolysis coupled with carbon reduction method according to claim 5, characterized in that, The introduction of a mixture of alkaline substance and carbon dioxide into the absorption tank satisfies the following relationship: q ac = Q c n, where q ac Q is the amount of alkali added to the absorption tank; Q is the flow rate of the carbon dioxide mixture introduced into the absorption tank; c is the stoichiometric ratio, taken as 0.5; n is the absorption efficiency, taken as 0.8~0.

9.

9. The method for wastewater electrolysis coupled with carbon reduction according to claim 5, characterized in that, The carbon dioxide mixture contains 10% to 40% carbon dioxide.

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