A gas-liquid-solid internal circulation reaction device and a method for the Fenton reaction

Abstract

This invention provides a gas-liquid-solid internal circulation reactor and a method for Fenton reaction, comprising a coaxially arranged middle cylinder and outer cylinder, and at least one inner cylinder disposed within the middle cylinder. The bottoms of the inner cylinder, middle cylinder, and outer cylinder are connected. Each inner cylinder has at least one gas inlet at its bottom. The upper end of the inner cylinder extends to the upper part of the middle cylinder, and its upper opening communicates with the middle cylinder. At least one liquid inlet is provided at the top of the middle cylinder. The bottom of the outer cylinder is conical, and a liquid outlet is provided on the outer cylinder wall. The liquid outlet is positioned below the reaction liquid level within the reactor. Using this device for Fenton reaction, the separation of the carrier and liquid is located at the lower end of the reactor, solving the short-circuit problem in traditional fluidized bed reactions. Gas-driven carrier flow eliminates the need for external circulation, significantly reducing energy consumption. Compared to the catalytic carrier filling amount in traditional fluidized beds, it is increased from 30% to over 60%. This higher filling amount further improves the catalytic oxidation effect and reduces the amount of iron added. It also increases the amount of ferric iron crystallized on the carrier surface, reducing iron sludge production.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, and more specifically, relates to a gas-liquid-solid internal circulation reaction device and a method for treating wastewater by using the device to perform Fenton reaction. Background Technology

[0002] Fenton oxidation technology is an oxidation technique that uses hydrogen peroxide to generate hydroxyl radicals under the action of ferrous iron to oxidize organic matter. It has strong oxidizing power, and the generated ferric iron also has a flocculating effect, making it effective in treating industrial wastewater containing recalcitrant organic matter. However, the Fenton reaction requires acidic conditions and produces a large amount of iron sludge, causing secondary pollution. This results in high acid and alkali consumption and high treatment costs. To overcome the shortcomings of Fenton technology, fluidized bed Fenton oxidation technology has been developed. This technology crystallizes and precipitates iron ions in the solution on the surface of carrier particles, reducing the iron content in the effluent and lowering the iron sludge production. The carrier particles also have heterogeneous catalytic activity, enhancing the oxidation effect. However, in this technology, the carrier filling volume in fluidized bed Fenton oxidation is less than 30%, which limits its catalytic effect and the crystallization rate of ferric iron to some extent. Furthermore, a high reflux ratio is required to achieve fluidization, resulting in high energy consumption. Patent CN210393862U modified the internal packing structure, increasing the treatment effect, but the fluidized bed still suffers from high circulation volume and low carrier filling volume. Patents CN109455796A and CN212222543U, due to their solid-liquid separation at the top of the reactor, are prone to short-circuiting and obstructed influent diffusion, severely limiting the pH requirements of the Fenton reaction influent. Furthermore, the use of liquid fluidization necessitates a large external circulation volume. Problems such as high reflux rate, high energy consumption, low carrier packing density, and insufficient catalytic effect are hindering the development of fluidized bed Fenton reactors. Currently, there is an urgent need to develop new technologies to improve catalytic efficiency and reduce reflux and energy consumption. Summary of the Invention

[0003] To address the above shortcomings, this invention provides a gas-liquid-solid internal circulation reactor and a method for conducting Fenton reactions using it, solving the problems of large reflux flow and low catalyst carrier filling rate in traditional Fenton fluidized beds, improving catalytic oxidation effect, reducing iron dosage, increasing the amount of ferric iron crystallization on the carrier surface, and reducing iron sludge production.

[0004] To achieve the above technical objectives, the technical solution of the present invention is as follows:

[0005] The technical objective of the first aspect of this invention is to provide a gas-liquid-solid internal circulation reaction device, comprising a coaxially arranged middle cylinder and an outer cylinder, and at least one inner cylinder disposed within the middle cylinder. The bottoms of the inner cylinder, the middle cylinder, and the outer cylinder are connected. Each inner cylinder has at least one air inlet at its bottom. The upper end of the inner cylinder extends to the upper middle part of the middle cylinder, and its upper opening is connected to the middle cylinder. At least one liquid inlet is disposed at the top of the middle cylinder. The bottom of the outer cylinder is conical, and a liquid outlet is disposed on the outer cylinder wall. The position of the liquid outlet is lower than the reaction liquid level inside the reaction device.

[0006] Furthermore, an air distribution device is installed directly above the inner cylinder inside the middle cylinder. This air distribution device is a device that can redistribute the upward airflow from below to the side.

[0007] Furthermore, preferably, the air distribution device is an inverted cone, which redistributes the upward airflow from below to the side. Even more preferably, the cone surface of the inverted cone is a concave curved surface; the smooth curved surface facilitates the formation of vortices, achieving thorough distribution and mixing.

[0008] Furthermore, the gas distribution device not only redistributes the gas but also rapidly mixes the reaction liquid entering from the upper part of the cylinder with the internal liquid. Preferably, the gas distribution device has a structure formed by an upper cone and a lower inverted cone. The upper cone structure distributes and mixes the downward-flowing liquid, while the lower inverted cone redistributes the upward-flowing gas to both sides, allowing for more thorough mixing of the two gas streams. As a further preferred embodiment, the conical surface of the lower inverted cone is a concave curved surface; the smooth curved surface facilitates the formation of vortices, achieving thorough distribution and mixing.

[0009] Furthermore, the number of inner cylinders is 1-10, preferably 1-5, and the bottom opening of the inner cylinder is an outward-facing trumpet shape.

[0010] Furthermore, the ratio of the cross-sectional area of ​​the outer cylinder to the cross-sectional area of ​​the middle cylinder is 100:25~90, preferably 100:49~82; the ratio of the cross-sectional area of ​​the middle cylinder to the sum of the cross-sectional areas of the inner cylinder is 100:1~50, preferably 100:4~25.

[0011] Furthermore, each inner cylinder has 2-4 air inlets at its bottom. Preferably, the air inlets extend into the inner cylinder at different heights, with at least one high-level air inlet and at least one low-level air inlet. This arrangement facilitates control of the ventilation rate during startup and operation, and makes it easier to control the fluidization of the internal solids.

[0012] The technical objective of the second aspect of this invention is to provide a method for the Fenton reaction, utilizing a gas-liquid-solid internal circulation reaction device. The reaction device includes a coaxially arranged middle cylinder and an outer cylinder, and at least one inner cylinder disposed within the middle cylinder. The bottoms of the inner cylinder, the middle cylinder, and the outer cylinder are connected. Each inner cylinder has at least one air inlet at its bottom. The upper end of the inner cylinder extends to the upper part of the middle cylinder, and its upper opening communicates with the middle cylinder. At least one liquid inlet is provided at the top of the middle cylinder. The bottom of the outer cylinder is conical, and a liquid outlet is provided on the outer cylinder wall. The position of the liquid outlet is lower than the reaction liquid level inside the reaction device.

[0013] In the above-mentioned device, a carrier is filled in the inner cylinder and between the inner and middle cylinders. Air enters the inner cylinder through the air inlet. The wastewater to be treated and Fenton's reagent are introduced through the liquid inlet above. They come into contact with the carrier between the inner and middle cylinders and carry the carrier downwards, completing the reaction simultaneously. At the bottom of the middle cylinder, the carrier carries the liquid into the conical area at the bottom of the outer cylinder. Under the action of the introduced gas, the carrier and part of the liquid rise from the inner cylinder, while the other part of the liquid enters the space between the outer and middle cylinders from the bottom and exits through the water outlet.

[0014] Furthermore, the particle size of the carrier is 0.1~5mm, preferably 0.5-2mm. The carrier is selected from one or a mixture of several of quartz sand, ceramsite, building sand, and resin.

[0015] Furthermore, the Fenton reagent is a ferrous solution and a hydrogen peroxide solution.

[0016] Furthermore, an air distribution device is installed directly above the inner cylinder inside the middle cylinder. This air distribution device is a device that can redistribute the upward airflow from below to the side.

[0017] Furthermore, preferably, the air distribution device is an inverted cone, which redistributes the upward airflow from below to the side. Even more preferably, the cone surface of the inverted cone is a concave curved surface; the smooth curved surface facilitates the formation of vortices, achieving thorough distribution and mixing.

[0018] Furthermore, the gas distribution device not only redistributes the gas but also rapidly mixes the reaction liquid entering from the upper part of the cylinder with the internal liquid. Preferably, the gas distribution device has a structure formed by an upper part being a cone and a lower part being an inverted cone. As a further preferred embodiment, the cone surface of the inverted cone in the lower part is a concave curved surface, and the smooth curved surface facilitates the formation of vortices, achieving full distribution and mixing.

[0019] The gas separator with the above structure rapidly mixes the influent water and Fenton's reagent with the reaction solution to achieve the required pH range for rapid reaction. Furthermore, the pH of the reaction solution gradually decreases during the Fenton reaction, thus relaxing the pH requirement for the influent water. The pH of the wastewater to be treated is 3-10, preferably 5-8. After mixing, the mixture enters between the inner and middle cylinders, where heterogeneous and homogeneous catalytic oxidation reactions occur, improving the removal rate of organic matter. Simultaneously, using the carrier as a crystallization nucleus, the ferric iron produced in the reaction crystallizes on the surface of the carrier particles, reducing iron sludge production while also achieving a heterogeneous catalytic effect.

[0020] Furthermore, the residence time of the wastewater to be treated in the reaction device is 0.1~6h, preferably 0.2-1.5h.

[0021] Furthermore, the bottom opening of the inner cylinder is an outward-facing trumpet shape.

[0022] Furthermore, the ratio of the cross-sectional area of ​​the outer cylinder to the cross-sectional area of ​​the middle cylinder is 100:25~90, preferably 100:49~82; the ratio of the cross-sectional area of ​​the middle cylinder to the sum of the cross-sectional areas of the inner cylinder is 100:1~50, preferably 100:4~25.

[0023] Furthermore, each inner cylinder has 2-4 air inlets at its bottom. Preferably, the air inlets extend into the inner cylinder at different heights, with at least one high-level air inlet and at least one low-level air inlet. This arrangement facilitates control of the ventilation rate during startup and operation, and makes it easier to control the fluidization of the internal solids.

[0024] In the above-mentioned device, by controlling the air intake and water output, the fluidization rate of the reactants inside the reaction device can be controlled, and the carrier can be prevented from entering the outer cylinder in large quantities.

[0025] The technical solution of the present invention has the following advantages:

[0026] (1) The gas-liquid-solid internal circulation reaction device of the present invention can realize the internal circulation of gas, liquid and solid three-phase materials inside the device. The solid-liquid separation is set at the lower end of the reactor to solve the short circuit problem in the reaction process. The gas drives the carrier to flow, eliminating the need for external circulation and greatly reducing energy consumption. Furthermore, it increases the carrier filling amount and improves the reaction efficiency.

[0027] (2) The Fenton reaction of the present invention adopts an internal circulation reaction device, and the solid-liquid separation of the carrier and the reaction liquid is set at the bottom of the reactor, which solves the short-circuit problem in the traditional fluidized bed reaction process; the carrier is driven by gas, eliminating the need for external circulation and greatly reducing energy consumption; and compared with the catalytic carrier filling amount of the traditional fluidized bed, it is increased from 30% to more than 60%. The high catalytic carrier filling amount can further improve the catalytic oxidation effect and reduce the amount of iron added; increase the amount of trivalent iron crystallization on the carrier surface and reduce the iron sludge production.

[0028] (3) After setting up a gas separator with a specific structure, the reaction liquid, Fenton reagent and the original reaction liquid in the device are rapidly mixed, quickly reaching the pH range required for the reaction, and the reaction is rapid; and the pH requirement of the Fenton reaction on the influent water is reduced, and the pH of the influent water of the Fenton reaction is increased.

[0029] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0030] Figure 1 This invention relates to a gas-liquid-solid internal circulation reaction device;

[0031] Figure 2 , Figure 3 and Figure 4 These are the front view, top view, and side view of the gas distribution device;

[0032] Figure 5 A schematic diagram of the conventional Fenton fluidized bed used in Comparative Example 1. Detailed Implementation

[0033] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0034] Example 1

[0035] This embodiment discloses a gas-liquid-solid internal circulation reaction device, including an inner cylinder 1, a middle cylinder 2, and an outer cylinder 3 arranged coaxially. The bottoms of the inner cylinder 1, middle cylinder 2, and outer cylinder 3 are connected. The bottom opening of the inner cylinder 1 is an outward-facing trumpet shape, and an air inlet I 11 and an air inlet II 12 are also provided at the bottom. The two air inlets are sleeve-type, with air inlet I 11 located at a lower position and air inlet II 12 located at a higher position. The air inlet pipe connected to air inlet II 12 is sleeved inside the air inlet pipe connected to air inlet I 11. The upper end of the inner cylinder 1 extends to the upper middle part of the middle cylinder 2, and the upper end opening is connected to the middle cylinder 2. The top of the middle cylinder 2 is provided with liquid inlet I 21 and liquid inlet II 22. A gas distribution device 23 is provided directly above the inner cylinder inside the middle cylinder. The gas distribution device 23 is a structure formed by the combination of an upper part of a cone and a lower part of an inverted cone. Its front view is shown below. Figure 2 As shown, the top view is as follows Figure 3 As shown, the side view is as follows Figure 4 As shown; the bottom of the outer cylinder 3 is conical, and liquid outlet I 31 and liquid outlet II 32 are provided on the outer cylinder wall. The positions of liquid outlet I 31 and liquid outlet II 32 are lower than the reaction liquid level inside the reaction device.

[0036] The ratio of the cross-sectional area of ​​the outer cylinder to that of the middle cylinder is 100:55, and the ratio of the cross-sectional area of ​​the middle cylinder to that of the inner cylinder is 100:10.

[0037] Example 2

[0038] This embodiment provides a method for performing the Fenton reaction using the reaction apparatus of Example 1:

[0039] A carrier is filled between the inner cylinder 1 and the middle cylinder 2. Air enters the inner cylinder 1 through air inlet I11 and air inlet II12. The wastewater to be treated is introduced through liquid inlet I21, and Fenton reagent is introduced through liquid inlet II22. A water inlet zone 100 is formed in the upper part of the middle cylinder 2. Under the action of the gas separator 23, the water and the internal liquid are rapidly mixed in the mixing zone 200 and enter the catalytic reaction zone 300 between the inner cylinder 1 and the middle cylinder 2 to contact the carrier and carry the carrier downwards, completing the reaction at the same time. At the bottom of the middle cylinder 2, the carrier carries the liquid into the solid-liquid separation zone 400 at the bottom of the outer cylinder. Under the action of the introduced gas, the carrier and part of the liquid rise from the inner cylinder 1 to the gas lifting zone 500, and the other part of the liquid enters from the bottom between the outer cylinder 3 and the middle cylinder 2 and exits through liquid outlet I31 and liquid outlet II32.

[0040] The carrier is 20-40 mesh ceramsite with a carrier volume charge of 60%. The wastewater to be treated contains Acid Red 3R (pH 9, total organic carbon TOC = 65 mg / L). Fenton's reagent consists of ferrous sulfate solution (207 mg / L concentration) and hydrogen peroxide solution (200 mg / L). The residence time of the wastewater in the reaction device is 20 min.

[0041] Comparative Example 1

[0042] A traditional Fenton fluidized bed reactor was used to treat the same wastewater. The influent and return liquid were pumped together from the bottom of the reactor for reaction. After reaction, the wastewater was discharged from the top of the reactor, with a portion being returned and a portion discharged. A schematic diagram of the reactor is shown below. Figure 5 As shown in the figure. The carrier is 20-40 mesh ceramsite, and the carrier volume filler is 30%. The residence time of wastewater in the reaction device is 20 minutes.

[0043] Comparative Example 2

[0044] A conventional homogeneous Fenton reaction was used to continuously react the same wastewater, with mixing achieved by stirring. There were no carrier particles in the reactor. The residence time of the wastewater in the reaction apparatus was 20 minutes.

[0045] The processing results of Example 2, Comparative Example 1, and Comparative Example 2 are shown in Table 1.

[0046] Table 1.

[0047]

[0048] As shown in Table 1, the reaction apparatus of this invention can significantly increase the filling volume of the fluidized bed carrier, thereby improving the oxidation effect, reducing the TOC content in the effluent, and significantly reducing the amount of iron sludge produced compared to the traditional Fenton reaction. The reaction apparatus of this invention does not require reflux water for Fenton oxidation, which can significantly reduce the energy consumption of wastewater treatment and lower treatment costs.

Claims

1. A method for the Fenton reaction, characterized in that, A gas-liquid-solid internal circulation reaction device is provided. The reaction device includes a coaxially arranged middle cylinder and an outer cylinder, and at least one inner cylinder disposed within the middle cylinder. The bottoms of the inner cylinder, middle cylinder, and outer cylinder are connected. Each inner cylinder has an air inlet at its bottom, and the air inlets extend into the inner cylinder at different heights, with at least one high-level air inlet and at least one low-level air inlet. The upper end of the inner cylinder extends to the upper middle part of the middle cylinder, and its upper opening communicates with the middle cylinder. At least one liquid inlet is provided at the top of the middle cylinder. The bottom of the outer cylinder is conical, and a liquid outlet is provided on the outer cylinder wall. The liquid outlet is positioned below the reaction liquid level inside the reaction device. A gas distribution device is provided directly above the inner cylinder inside the middle cylinder. The gas distribution device is a device that can redistribute the upward airflow from below to the side. In the gas-liquid-solid internal circulation reaction device, a carrier is filled in the inner cylinder and between the inner and middle cylinders. Air enters the inner cylinder through the air inlet, and the wastewater to be treated and Fenton's reagent are introduced through the liquid inlet above. They come into contact with the carrier between the inner and middle cylinders and carry the carrier downwards, completing the reaction simultaneously. At the bottom of the middle cylinder, the carrier carries the liquid into the conical area at the bottom of the outer cylinder. Under the action of the introduced gas, the carrier and part of the liquid rise from the inner cylinder, while the other part of the liquid enters from the bottom between the outer and middle cylinders and exits through the water outlet.

2. The method according to claim 1, characterized in that, The gas distribution device is an inverted cone.

3. The method according to claim 2, characterized in that, The gas distribution device is an inverted cone with a concave curved surface.

4. The method according to claim 2, characterized in that, The gas distribution device has a structure formed by combining an upper part of a cone and a lower part of an inverted cone.

5. The method according to claim 4, characterized in that, The lower half of the inverted cone has a concave curved surface.

6. The method according to claim 1, characterized in that, The inner cylinder consists of 1-10 cylinders, with their bottom openings in an outward-facing trumpet shape.

7. The method according to claim 1, characterized in that, The ratio of the cross-sectional area of ​​the outer cylinder to the cross-sectional area of ​​the middle cylinder is 100:25~90; the ratio of the cross-sectional area of ​​the middle cylinder to the sum of the cross-sectional areas of the inner cylinder is 100:1~50.

8. The method according to claim 7, characterized in that, The ratio of the cross-sectional area of ​​the outer cylinder to the cross-sectional area of ​​the middle cylinder is 100:49~82; the ratio of the cross-sectional area of ​​the middle cylinder to the sum of the cross-sectional areas of the inner cylinder is 100:4~25.

9. The method according to claim 1, characterized in that, Each inner cylinder has 2-4 air inlets at its bottom.

10. The method according to claim 1, characterized in that, The carrier is selected from one or a mixture of several of the following: quartz sand, ceramsite, building sand, and resin; the particle size of the carrier is 0.1~5mm.

11. The method according to claim 10, characterized in that, The particle size of the carrier is 0.5-2 mm.

12. The method according to claim 1, characterized in that, The Fenton reagent is a ferrous solution and a hydrogen peroxide solution.

13. The method according to claim 1, characterized in that, The pH of the wastewater to be treated is 3-10.

14. The method according to claim 13, characterized in that, The pH of the wastewater to be treated is 5-8.

15. The method according to claim 1, characterized in that, The residence time of the wastewater to be treated in the reaction device is 0.1~6h.

16. The method according to claim 15, characterized in that, The residence time of the wastewater to be treated in the reaction device is 0.2-1.5 hours.

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