A self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation

Abstract

The present invention discloses a self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation. The photocatalytic oxidation reactor is a circulating tubular reactor with an internal circulation pipe. The circulating tubular reactor is provided with a reaction pipe section with continuously changing contraction and expansion. The circulating tubular reactor is provided with a main reactor and a secondary reactor connected by a circulation pipe. A circulation pump is arranged in the circulation pipe. The main and secondary reactors are independently installed with light sources inside or / and outside. The present invention can conveniently adjust the residence time of materials without affecting the fluidization of the solid photocatalyst; the unique structure of the contraction and expansion of the reaction pipe can make the gas evenly distributed in the liquid phase and will not be affected by the coalescence of bubbles in the liquid phase; the unique structure of the contraction and expansion of the reaction pipe enables the reactor wall to have a self-cleaning function, preventing the catalyst mud from adhering to the reactor wall and having a higher light utilization rate. The structure of the present invention is simple and reasonable, with high light energy utilization rate, uniform material distribution, adjustable residence time and high reaction efficiency.

Description

Technical Field

[0001] The present invention relates to a photocatalytic reactor, and more particularly to a self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation. Background Art

[0002] As a green technology, photocatalytic technology has important application prospects in the fields of energy and environment. Under the irradiation of light, organic wastewater can be degraded into carbon dioxide and water, which is considered a revolutionary breakthrough in the field of environmental purification in the 21st century by the environmental protection community. Photocatalytic reactors and photocatalytic catalysts are the core of photocatalytic reactions. The core factors to be considered in the design of gas-liquid-solid multiphase photocatalytic reactors are whether the reactants are in sufficient contact and whether the utilization rate of light is sufficient, etc. Among them, the contradictory problems of residence time adjustment and catalyst fluidization, the coalescence phenomenon of bubbles in the liquid phase, and whether the light utilization rate is sufficient are the difficulties in the design of photocatalytic reactors.

[0003] Regarding the design difficulty of the contradictory problems of residence time adjustment and catalyst fluidization, in order to ensure sufficient residence time, the flow rate often needs to be reduced. If the flow rate is insufficient, the catalyst cannot be fluidized or the fluidization effect is poor, and ensuring the fluidization effect of the catalyst may lead to too short residence time and unable to ensure sufficient contact of the reactants. The design difficulty regarding the coalescence phenomenon of bubbles in the liquid phase lies in that it is inconvenient to install a stirring device in the photoreactor. There are mainly two reasons for the low light utilization rate. One reason is that the catalyst mud adheres to the reactor wall, hindering the contact between light and reactants; the other reason is that light is absorbed by the reactor during the propagation process, and the light energy is converted into heat energy and lost.

[0004] Chinese invention patent CN109745937B provides a two-dimensional photocatalytic fluidized bed device, and the two-dimensional photocatalytic fluidized bed device includes a plurality of two-dimensional fluidized beds arranged side by side and made of transparent materials, that is, the patent optimizes the light utilization rate through the structure of superimposing two-dimensional fluidized beds. This patent optimizes the light utilization rate and reduces the problem of light being converted into heat energy loss. However, it does not solve the problems that the coalescence phenomenon of bubbles in the liquid phase hinders gas flow and causes uneven gas distribution, and the catalyst mud adheres to the reactor wall and hinders the utilization of light.

[0005] Chinese invention CN112794532A discloses an integrated activated carbon ozone photocatalytic internal circulation fluidized bed reaction device. Through an integrated method, this invention integrates a variety of functional structures together to improve the sufficient contact degree of reactants and achieve composite water treatment.

[0006] Chinese utility model patent CN219003018U provides a fluidized bed photocatalytic reactor, and through the design improvement of the fluidized bed, the convenience of catalyst feeding, discharging and recycling is realized.

[0007] The above-mentioned existing technologies have all solved the problems existing in the photocatalytic reactor to a certain extent. However, at present, the contradictory problems of residence time and catalyst fluidization, the coalescence phenomenon of bubbles in the liquid phase hindering the uneven gas distribution, and the catalyst mud adhering to the reactor wall hindering the utilization of light resulting in low light utilization rate and other technical problems still have not been well solved. Especially to solve these problems simultaneously is a very great challenge. Summary of the Invention

[0008] Aiming at the technical problems such as the contradiction between residence time and catalyst fluidization, the coalescence phenomenon of bubbles in the liquid phase hindering the uneven gas distribution, and the catalyst mud adhering to the reactor wall hindering the utilization of light resulting in low light utilization rate, the present invention provides a self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation, which has a reasonable structural design and can simultaneously solve the contradictory problems of residence time and catalyst fluidization, the coalescence phenomenon of bubbles in the liquid phase hindering gas flow resulting in uneven gas distribution, the problem of light being absorbed by the reactor wall and other and converted into heat energy and lost, and the problem of catalyst mud adhering to the reactor wall hindering the utilization of light and light energy being converted into heat energy and lost, thereby significantly improving the light energy utilization rate and reaction efficiency.

[0009] The technical solution of the present invention to solve the above technical problems is as follows:

[0010] A self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation is a circulating tube reactor with an internal circulation tube, and the circulating tube reactor is provided with a reaction tube section with continuously changing contraction and expansion.

[0011] Furthermore, a circulation pump is arranged in the internal circulation tube.

[0012] The reaction materials are circulated through the internal circulation tube and the circulation pump, so that the internal circulation speed can be freely adjusted under the condition of constant total flow rate to adjust the total residence time of the materials. In this way, not only can the residence time of the materials be extended to ensure the contact time, but also the fluidized state of the catalyst will not be changed, ensuring that the catalyst is in a good fluidized state and making the reaction more sufficient.

[0013] The design of the reaction tube section with continuously changing contraction and expansion can make the fluid continuously change between positive pressure and negative pressure, which can well prevent the occurrence of bubble coalescence phenomenon. Even if large bubbles are generated due to the coalescence phenomenon during the process, they can be quickly broken, ensuring that the gas flow is unobstructed, so that the gas is more evenly distributed in the liquid phase and is more conducive to the smooth progress of the reaction; at the same time, this continuous change of the fluid between positive pressure and negative pressure can cause the flow rate to change, so as to achieve the effect of flushing the reactor wall, enabling the reactor wall to achieve self-cleaning, preventing the catalyst mud from adhering to the reactor wall, and ensuring a higher light utilization rate.

[0014] Further, the degree of contraction and expansion is preferably such that the ratio of the minimum partial area to the maximum partial area is 0.01 - 0.8, more preferably 0.04 - 0.4, and further preferably 0.0625 - 0.25.

[0015] Further, the circulating tube reactor is provided with a main reactor and a secondary reactor. The main reactor and the secondary reactor are connected through an internal circulation pipe. The main reactor and the secondary reactor are independently installed with light sources inside or / and outside. For example, the main reactor is internally provided with a lamp tube, and the secondary reactor is externally provided with a light strip, and a sleeve is arranged outside the light strip; both the main reactor and the secondary reactor are internally provided with lamp tubes; both the main reactor and the secondary reactor are externally provided with light strips, and a sleeve is arranged outside the light strips; the main reactor is externally provided with a light strip, and the secondary reactor is internally provided with a lamp tube, and so on.

[0016] Further, the light source is an ultraviolet lamp.

[0017] Further, the light source can be made of a rigid material or a flexible material. The rigid material is such as a lamp tube, and the flexible material is such as a light strip.

[0018] Further, a reflective material is attached to the outer surface of the reactor with an internally installed light source or / and the inner surface of the sleeve outside the reactor with an externally installed light source, so that the light can be reflected back into the reactor; for example, a reflective material can be attached to the outer surface of the main reactor with an internally installed lamp tube and the inner surface of the sleeve outside the light strip of the secondary reactor with an externally installed light strip, so as to realize reflecting the light back into the reactor and making the light further utilized.

[0019] Further, the structures of the secondary reactor and the main reactor can be the same or different.

[0020] Further, a gas distributor is arranged at the lower part of the main reactor.

[0021] Further, the circulating tube reactor is made of a transparent material, such as transparent plexiglass.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention can conveniently adjust the residence time of the material without affecting the fluidization of the solid photocatalyst, and can completely solve the contradiction problem between the residence time and the catalyst fluidization.

[0024] (2) The unique structure of the contraction and expansion of the reaction tube of the present invention can make the gas uniformly distributed in the liquid phase and is not affected by the coalescence phenomenon of bubbles in the liquid phase.

[0025] (3) The unique structure of the contraction and expansion of the reaction tube of the present invention enables the reactor wall to have a self-cleaning function, prevents the catalyst mud from adhering to the reactor wall, and ensures a higher light utilization rate.

[0026] (4)The light reflection material can achieve a higher light energy utilization rate.

[0027] (5)The structure of the present invention is simple and reasonable, with a high light energy utilization rate, uniform material distribution, adjustable residence time, and high reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. is a schematic structural diagram of Embodiment 1 of the present invention. 1. Gas inlet pipe, 2-1. Sub-reactor, 3-1. Sub-reactor light source, 4-1. Transparent light source protection sleeve for the sub-reactor, 5. Circulation pump, 6. Catalyst feeding port, 7. Transparent light source protection sleeve for the main reactor, 8. Filter screen of the discharge pipe, 9. Discharge pipe, 10. Main reactor light source, 11. Main reactor, 12. Filter screen of the feed pipe, 13. Feed pump, 14. Feed pipe, 15. Gas distributor, 16. Catalyst discharge port.

[0029] Figure 2 FIG. is a schematic structural diagram of Embodiment 2 of the present invention. 1. Gas inlet pipe, 2-2. Sleeve, 3-2. Sub-reactor, 4-2. Strip light source, 5. Circulation pump, 6. Catalyst feeding port, 7. Transparent light source protection sleeve, 8. Filter screen of the discharge pipe, 9. Discharge pipe, 10. Light source, 11. Main reactor, 12. Filter screen of the feed pipe, 13. Feed pump, 14. Feed pipe, 15. Gas distributor, 16. Catalyst discharge port. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto. DETAILED DESCRIPTION OF THE EMBODIMENT 1

[0032] The schematic structural diagram of Embodiment 1 of the present invention is as shown in Figure 1As shown in the figure, a self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation is a circulating tube reactor with an internal circulation tube. The circulating tube reactor is provided with a continuously varying reaction tube section with contraction and expansion, including a main reactor 11 and a sub-reactor 2-1. The ratio of the minimum part area to the maximum part area of the main reactor 11 is 1:4, and the ratio of the minimum part area to the maximum part area of the sub-reactor 2-1 is 1:4. The main reactor 11 and the sub-reactor 2-1 are completely connected through an internal circulation tube. A circulation pump 5 is arranged in the internal circulation tube. A light source 10 is arranged inside the main reactor 11. The lamp tube 10 is provided with a transparent protective sleeve 7. The outer surface of the main reactor 11 is pasted with a light-reflecting material. A light source 10 and a strip-shaped light source 3-1 are arranged inside the sub-reactor 2-1. The lamp tube 3-1 is provided with a transparent protective sleeve 4-1. The outer surface of the sub-reactor 2-1 is pasted with a light-reflecting material. A gas distributor 15 is arranged at the bottom of the main reactor 11. A gas feed pipe 1 is connected to the gas distributor 15. The lower part of the main reactor 11 is connected to a feed pipe 14. A feed pipe filter 12 and a feed pump 13 are arranged in the feed pipe 14. The upper part of the main reactor 11 is connected to a discharge pipe 9. A discharge pipe filter 8 is arranged on the discharge pipe 9. A catalyst feeding port 6 is arranged at the top of the circulating tube reactor, and a catalyst discharging port 16 is arranged at the bottom. Example 1

[0033] Reactor parameters: (1) Plexiglass main reactor: diameter 100 mm, height 800 mm, with an upper feeding port and a lower discharging port. (2) Plexiglass sub-reactor: diameter 100 mm, height 800 mm. (3) Ultraviolet light source, power 300 W, 2 units. (4) Stainless steel self-priming gas-liquid mixing dissolved air pump, power 550 W, voltage 220 V. Quantity 2 units. (5) Liquid flowmeter: flow range 3 - 400 L / h, quantity 2 units. (6) Gas flowmeter: flow range 0.25 - 2.5 m3 / h, quantity 1 unit. (7) Oil-free silent air compressor: power 550 W, exhaust volume 36 L / min, rated exhaust pressure 0.8 MPa.

[0034] The organic wastewater enters the main reactor 11 with reflective material on its outer surface through the feed pipe 14 under the action of the feed pump 13. Air or pure oxygen enters the main reactor 11 through the gas distributor 15 via the gas feed pipe 1. The catalyst is added through the catalyst feeding port 6 and can be unloaded through the catalyst discharging port 16 for regeneration when deactivated. Under the illumination of the light source 10, a photocatalytic reaction occurs between the organic wastewater and oxygen on the surface of the catalyst. The contraction and expansion of the main reactor channel can change the flow rate, with the pressure decreasing and increasing, resulting in positive and negative pressure differences in the front and back pressure differences. This causes the generated bubbles to break and be evenly distributed in the liquid phase. At the same time, the variable-speed fluid will also impact the reactor surface, achieving a self-cleaning effect on the reactor surface. Under the action of the circulation pump 5, the reaction liquid circulates and enters the secondary reactor 2-1 for further reaction. The secondary reactor 2-1 has the same structure as the main reactor 11. After the reaction is completed, the reaction liquid is discharged from the discharge pipe 9, and the backmixing and residence time of the reaction liquid in the entire reactor are adjusted by regulating the speed of the circulating liquid and the speed of the discharged liquid. When the air flow rate is 1 m 3 / h; catalyst: covalent triazine framework / sepiolite composite; wastewater flow rate containing propranolol hydrochloride (PRO, 400 µmol / L): 10 L / h; internal circulation flow rate: 100 L / h; the degradation rate of propranolol hydrochloride at the outlet reaches 99%. Specific Embodiment 2

[0036] The structural schematic diagram of Specific Embodiment 2 of the present invention is as shown in Figure 2 Figure. A self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation is a circulating tube reactor with an internal circulation tube. The circulating tube reactor is provided with a continuously changing reaction tube section with contraction and expansion, including a main reactor 11 and a secondary reactor 3-2. The ratio of the minimum part area to the maximum part area of the main reactor 11 is 1:4, and the ratio of the minimum part area to the maximum part area of the secondary reactor 3-2 is 1:4. The main reactor 11 and the secondary reactor 3-2 are completely connected through the internal circulation tube, and a circulation pump 5 is arranged inside the internal circulation tube. A light source 10 is installed inside the main reactor 11, and the lamp tube 10 is provided with a transparent protective sleeve 7. The outer surface of the main reactor 11 is pasted with a light-reflecting material. A strip-shaped light source 4-2 is installed outside the secondary reactor 3-2, and a sleeve 2-2 is arranged outside the strip-shaped light source 4-2. The inner surface of the sleeve 2-2 is pasted with a light-reflecting material. A gas distributor 15 is arranged at the bottom of the main reactor 11, and the gas feed pipe 1 is connected to the gas distributor 15. The lower part of the main reactor 11 is connected to the feed pipe 14, and a feed pipe filter screen 12 and a feed pump 13 are arranged inside the feed pipe 14. The upper part of the main reactor 11 is connected to the discharge pipe 9, and a discharge pipe filter screen 8 is arranged on the discharge pipe 9. A catalyst feeding port 6 is arranged at the top of the circulating tube reactor, and a catalyst discharging port 16 is arranged at the bottom. Example 2

[0037] Under the action of the feed pump 13, the organic wastewater enters the main reactor 11 with reflective materials attached to its outer surface through the feed pipe 14. Air or pure oxygen enters the main reactor 11 through the gas feed pipe 1 and the gas distributor 15. The catalyst is added through the catalyst feeding port 6 and can be discharged through the catalyst discharging port 16 for regeneration when deactivated. Under the illumination of the light source 10, the organic wastewater and oxygen undergo a photocatalytic reaction on the surface of the catalyst. The contraction and expansion of the main reactor channel can increase and decrease the flow rate, and the pressure changes, resulting in the changes of positive and negative pressure differences in the front and back pressure differences. This causes the generated bubbles to break and be evenly distributed in the liquid phase. At the same time, the variable-speed fluid will also impact the surface of the reactor, achieving a self-cleaning effect on the reactor surface. Under the action of the circulation pump 5, the reaction liquid circulates and enters the secondary reactor 3-2 for further reaction. The structure of the secondary reactor 3-2 is similar to that of the main reactor 11, with a continuously contracting and expanding channel structure. A strip light source is wound around the outer surface of the secondary reactor, and a sleeve with a light-reflecting material attached to its inner surface is put on the strip light source to avoid light energy loss. After the reaction is completed, the reaction liquid is discharged from the discharge pipe 9, and the backmixing and residence time of the reaction liquid in the entire reactor are adjusted by regulating the speed of the circulating liquid and the speed of the discharging liquid.

Claims

1. A self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation, Characterized in that, The photocatalytic oxidation reactor is a circulating tube reactor with an internal circulation tube, and the circulating tube reactor is provided with a continuously varying reaction tube section with contraction and expansion; the circulating tube reactor is provided with a main reactor and a secondary reactor, and the main reactor and the secondary reactor are connected through an internal circulation tube. The main reactor and the secondary reactor are independently installed with light sources inside or / and outside. The outer surface of the reactor with a light source installed inside or / and the inner surface of the sleeve outside the reactor with a light source installed outside is pasted with a reflective material, so that light can be reflected back into the reactor; a gas distributor is arranged at the lower part of the main reactor.

2. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1, Characterized in that, A circulation pump is arranged in the internal circulation tube.

3. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1 or 2, Characterized in that, The degree of contraction and expansion is such that the ratio of the area of the smallest part to the area of the largest part is 0.01 to 0.

8.

4. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1 or 2, Characterized in that, The degree of contraction and expansion is such that the ratio of the area of the smallest part to the area of the largest part is 0.04 to 0.

4.

5. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1 or 2, Characterized in that, The degree of contraction and expansion is such that the ratio of the area of the smallest part to the area of the largest part is 0.0625 to 0.

25.

6. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1 or 2, Characterized in that, The light source is an ultraviolet lamp.

7. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1 or 2, Characterized in that, The light source is made of a rigid material or a flexible material.

8. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1 or 2, Characterized in that, The structure of the secondary reactor is the same as or different from that of the main reactor.

9. The self-cleaning gas-liquid-solid multiphase photocatalytic oxidation reactor with internal circulation according to claim 1 or 2, Characterized in that, The circulating tube reactor is made of a transparent material.

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