Two-stage Fenton catalytic oxidation reaction device and method

Abstract

The invention discloses a two-stage Fenton catalytic oxidation reaction device and method. The device comprises a pre-reactor and a main reactor communicated with the pre-reactor, the two sides of the upper portion of the pre-reactor are connected with a water inlet pipe and a water outlet pipe, a baffle is arranged on one side of the pre-reactor, the water inlet pipe is connected to the side, close to the outer wall of the pre-reactor, of the baffle, and the baffle and the closer inner wall of the pre-reactor form a dosing area. According to the method provided by the invention, a pre-dosing reaction is adopted in the device, then a main reaction is performed, a Fenton catalyst is added in a traditional Fenton reaction area, the catalyst and added ferrous sulfate are subjected to a synergistic reaction in a fluidized state, hydrogen peroxide is jointly catalyzed and excited to quickly generate a large number of hydroxyl free radicals, and the yield of the hydroxyl free radicals is increased. The reaction pH range is widened to 4.5-5.5, the reaction efficiency is effectively improved, the retention time of the reactor is shortened, and the occupied area of the reactor is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of heterogeneous Fenton reactors, and in particular relates to a two-stage Fenton catalytic oxidation reaction device and method. Background Art

[0002] Conventional biochemical treatment processes in industrial wastewater treatment plants cannot remove refractory organic matter, making it difficult to meet COD standards for some industrial wastewater treatment. The traditional Fenton advanced oxidation process is to remove refractory organic matter from wastewater by reacting Fe2+ and H2O2 under strong acidic conditions (pH≈3). The traditional Fenton process has disadvantages such as Fe3+ being easily hydrolyzed and difficult to reduce, large iron sludge production, and a narrow pH working range.

[0003] The heterogeneous Fenton-like reaction is that H2O2 molecules generate hydroxyl radicals on the surface of Fenton solid catalysts, which then oxidize and degrade organic pollutants. Heterogeneous Fenton catalytic oxidation can broaden the pH conditions of the Fenton reaction and reduce the generation of large amounts of iron sludge. Although the heterogeneous Fenton reaction can solve some problems of the traditional Fenton process, in engineering applications, the sewage treatment efficiency is low and it is difficult to operate efficiently and stably. In addition, most of the reactors on the market are single-stage Fenton reactors. The single-stage Fenton reactor has the following disadvantages in engineering applications: it cannot react in time when the influent changes, which affects the effluent compliance rate, the consumption of ferrous sulfate and hydrogen peroxide is large and cannot be accurately controlled, and the economy and stability of the Fenton process need to be improved. Summary of the invention

[0004] The purpose of the present invention is to provide a two-stage Fenton catalytic oxidation reaction device and method to address the problems of low efficiency of heterogeneous Fenton reaction, high cost of single-stage Fenton reaction reagents, and easy precipitation of catalysts.

[0005] In a first aspect of the present invention, a two-stage Fenton catalytic oxidation reaction device is provided, comprising a pre-reactor and a main reactor connected to the pre-reactor; the pre-reactor is a cylinder, the upper two sides of the pre-reactor are connected to a water inlet pipe and a water outlet pipe, a baffle is provided on one side of the pre-reactor, the water inlet pipe is connected to a side of the baffle close to the outer wall of the pre-reactor, the baffle and the inner wall of the pre-reactor close to form a dosing area, and an emptying pipe is provided at the bottom of the pre-reactor; The outlet pipe is connected to the top of the main reactor, and a water inlet pump is arranged on the outlet pipe. A dosing mixing box is arranged on the top of the main reactor, and the outlet pipe is connected to the dosing mixing box. Ferrous sulfate dosing pipes, hydrogen peroxide dosing pipes, concentrated sulfuric acid dosing pipes and COD monitors are arranged in the dosing mixing box and in the dosing area, and a pH monitor is also arranged on the inlet pipe; a drainage pipe is arranged at the bottom of the dosing mixing box, and the drainage pipe is connected to the lower end of the main reactor. A horizontal centrifugal pump is connected to the drainage pipe for sewage transportation, so that the main reactor finally inlets water from the bottom; A circular tube guide is arranged at the bottom of the main reactor, and a water outlet guide area and a triangular weir outlet trough are arranged at the top of the main reactor; Figure 2 As shown, the circular tube guide 20 uses a plurality of parallel circular tubes to evenly replenish the sewage, ensuring that the sewage entering the reaction zone from the bottom of the main reactor 13 is evenly distributed, which can improve the reaction efficiency and the utilization rate of the catalyst.

[0006] The middle part of the pre-reactor contains Fenton catalyst to form a fluidized area; the middle part of the main reactor contains Fenton catalyst to form a catalyst reaction zone.

[0007] Preferably, the baffle is made of 316L stainless steel, and the distance between the lower end of the baffle and the bottom of the pre-reactor is controlled to be 20-40 cm.

[0008] Preferably, a drain pipe is provided at the bottom of the main reactor, and the diameter of the drain pipe is controlled to be 10-15 cm.

[0009] Preferably, a fluidization state observation port is provided in the middle of the main reactor, and the diameter of the observation port is controlled at 15-20 cm; and a COD monitor is provided in the water outlet area of ​​the main reactor.

[0010] A second aspect of the present invention provides a two-stage Fenton catalytic oxidation reaction method, using a two-stage Fenton catalytic oxidation reaction device as described in any one of the above 4, specifically comprising: The pre-reactor is constructed with a height-to-diameter ratio of 3:2, and a Fenton catalyst is added to the pre-reactor in advance; the residence time of the sewage after being transported to the pre-reactor is 15-30 seconds, and the pH of the sewage is adjusted to 4.5-5.5 after entering the pre-reactor. After the sewage enters from the top of the pre-reactor, it first enters the dosing area, and ferrous sulfate and hydrogen peroxide are metered and added to the dosing area; The influent water of the pre-reactor is mixed with ferrous sulfate and hydrogen peroxide and then passes through the bottom of the baffle to enter the reaction zone to form a fluidized state. The catalyst achieves a synergistic reaction with the added ferrous sulfate in the fluidized state, jointly catalyzing and stimulating the hydrogen peroxide to produce a hydroxyl reaction, generating hydroxyl free radical substances with strong oxidizing ability and oxidizing organic pollutants in the wastewater; The effluent from the pre-reactor flows out from the top outlet pipe and is lifted to the dosing mixing box at the top of the main reactor by the water inlet pump. Ferrous sulfate and hydrogen peroxide are metered and added to the dosing mixing box. After dosing and mixing, the water flows out through the drainage pipe and enters the bottom of the main reactor under the action of the horizontal centrifugal pump. The sewage passes through the circular pipe guide at the bottom of the main reactor and rises evenly for water distribution. A Fenton catalyst is added inside the main reactor, and the catalyst and the mixed liquid form a fluidized reaction, and are fully mixed to cause a homogeneous Fenton reaction and a heterogeneous Fenton reaction, so that the catalyst can achieve a synergistic reaction with the added ferrous sulfate in a fluidized state, jointly catalyzing and stimulating the hydrogen peroxide to produce a hydroxyl reaction, generating hydroxyl free radical substances with strong oxidizing ability and oxidizing organic pollutants in the wastewater; Control the residence time of sewage in the main reactor to 0.25-0.4h; The wastewater after the reaction enters the outlet diversion area, and then enters the outlet trough through the triangular weir. The catalyst contacts the steel plate in the diversion area and stays in the main reactor.

[0011] Preferably, the Fenton catalyst is a transition metal oxide.

[0012] Preferably, the reaction control mode of the pre-reactor and the main reactor is divided into process one and process two according to the different pH values. The pH range of process one is 4.5-5.0, and the pH range of process two is 5.0-5.5. If the detected pH exceeds the interval value, the pH is adjusted, and concentrated sulfuric acid is added in the dosing area of ​​the pre-reactor to adjust the pH; wherein, in the front-end predictive control of the pre-reactor, the dosage of hydrogen peroxide in the pre-reactor is determined according to the COD concentration value A1 of the pre-reactor inlet water, and the calculation formula of the dosage of hydrogen peroxide Y1 is: Y1=15%×A1×N; Among them, Y1 is the dosage of hydrogen peroxide; A1 is the COD concentration of the pre-reactor inlet; N is the ratio of the hydrogen peroxide dosage to the COD concentration when the pH is 4.5-5 or 5-5.5, and the COD is reduced from A1 to the expected target; in the front-end predictive control of the main reactor, the main reactor inlet COD concentration A2 is used to determine the main reactor hydrogen peroxide dosage, and the hydrogen peroxide dosage Y2 calculation formula is: Y2=A2×N; Among them, Y2 is the dosage of hydrogen peroxide; A2 is the COD concentration of the main reactor inlet; N is the ratio of the dosage of hydrogen peroxide to the COD concentration when the pH is 4.5-5 or 5-5.5, reducing the COD from A2 to the expected target.

[0013] Preferably, the COD concentration value of the pre-reactor influent is A1, the theoretical set value of the effluent is set to 85%A1, and the actual effluent of the pre-reactor, that is, the COD concentration value of the actual influent of the main reactor is A2. If ︱85%A1-A2︱ / 85%A1≤8%, the dosage of ferrous sulfate and hydrogen peroxide is not adjusted; If ︱85%A1-A2︱ / 85%A1>8%, adjust the dosage of ferrous sulfate and hydrogen peroxide in the pre-reactor. The actual dosage of hydrogen peroxide Y3 is calculated as follows: Y3=Y1+×N; Among them, Y3 is the actual dosage of hydrogen peroxide; A1 is the COD concentration of the pre-reactor inlet; N is the ratio of the amount of hydrogen peroxide added to the COD concentration when the pH is 4.5-5 or 5-5.5, when the COD is reduced from A2 to the expected target; At the same time, the dosage ratio of hydrogen peroxide to ferrous sulfate in the pre-reactor is controlled at 1:1-1:3.

[0014] Preferably, the actual influent COD mass concentration value of the main reactor is A2, and the theoretical set value of the effluent is M%A2, where the M value is based on the designed effluent index and a certain amount of surplus is considered; The actual effluent COD mass concentration value of the main reactor is A3. If ︱M%A2-A3︱ / M%A2≤5%, the dosage of ferrous sulfate and hydrogen peroxide in the main reactor will not be adjusted.

[0015] If |M%A2-A3| / M%A2>4%, adjust the dosage of ferrous sulfate and hydrogen peroxide in the main reactor. The actual dosage of hydrogen peroxide Y4 is calculated as follows: Y4=Y2+×N; At the same time, the dosage ratio of hydrogen peroxide to ferrous sulfate in the main reactor is controlled at 1:1-1:3.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a two-stage Fenton catalytic oxidation reaction device and method. In the traditional Fenton reaction area, a Fenton catalyst is added. The catalyst achieves a synergistic reaction with the added ferrous sulfate in a fluidized state, and jointly catalyzes and excites hydrogen peroxide to quickly generate a large number of hydroxyl free radicals, thereby widening the reaction pH range to 4.5-5.5, effectively improving the reaction efficiency, reducing the reactor residence time, and reducing the reactor footprint.

[0017] The setting of the pre-reactor effectively ensures that the effluent from the main reactor meets the standards. Through the water quality data of the inlet and outlet water of the pre-reactor, it is possible to respond promptly to changes in the incoming water and the reaction between the incoming water and Fenton, and adjust the operating parameters of the main reactor in time to ensure that the main reactor operates stably and meets the standards.

[0018] The present invention proposes a dosing device and a dosing control method for a two-stage Fenton catalytic oxidation reactor, which can achieve accurate dosing of hydrogen peroxide and ferrous sulfate according to changes in influent water, effectively reduce the dosage of the reagents, and thus reduce operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of an embodiment of the present invention.

[0020] Figure 2 A schematic structural diagram of a circular tube flow guide in an embodiment of the present invention.

[0021] In the above drawings: 1. pre-reactor; 2. water inlet pipe; 3. water outlet pipe; 4. baffle; 5. ferrous sulfate dosing pipe; 6. hydrogen peroxide dosing pipe; 7. concentrated sulfuric acid dosing pipe; 8. COD monitor; 9. pH monitor; 10. drain pipe; 11. water inlet pump; 12. dosing area; 13. main reactor; 14. dosing mixing box; 15. drainage pipe; 16. horizontal centrifugal pump; 17. fluidization area; 18. catalyst reaction area; 19. observation port; 20. circular tube guide; 21. outlet diversion area; 22. triangular weir outlet trough. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1-Figure 2 As shown, as a preferred embodiment of the present invention, this embodiment provides a two-stage Fenton catalytic oxidation reaction device, including a pre-reactor 1 and a main reactor 13 connected to the pre-reactor, both of which are made of 316L stainless steel; the pre-reactor 1 is a cylinder, and the upper two sides of the pre-reactor 1 are connected to the water inlet pipe 2 and the water outlet pipe 3, a baffle 4 is provided on one side of the pre-reactor, the water inlet pipe 2 is connected to the side of the baffle 4 close to the outer wall of the pre-reactor 1, the baffle 4 and the inner wall of the pre-reactor 1 that is closer form a dosing area 12, and an emptying pipe 10 is provided at the bottom of the pre-reactor 1, and the diameter is controlled to be 8-10cm; The outlet pipe 3 is connected to the top of the main reactor 13, and a water inlet pump 11 is arranged on the outlet pipe 3. A dosing mixing box 14 is arranged on the top of the main reactor 13. The outlet pipe 3 is connected to the dosing mixing box 14. The dosing mixing box 14 and the dosing area 12 are both provided with a ferrous sulfate dosing pipe 5, a hydrogen peroxide dosing pipe 6, a concentrated sulfuric acid dosing pipe 7 and a COD monitor 8. A pH monitor 9 is also arranged on the inlet pipe 3; a drainage pipe 15 is arranged at the bottom of the dosing mixing box 14, and the drainage pipe 15 is connected to the lower end of the main reactor 13. A horizontal centrifugal pump 16 is connected to the drainage pipe 15 for sewage transportation, so that the main reactor 13 finally inflows water from the bottom; A circular pipe guide 20 is provided at the bottom of the main reactor 13, and a water outlet guide area 21 and a triangular weir water outlet trough 22 are provided at the top of the main reactor 13; A Fenton catalyst is contained in the middle of the pre-reactor 1 to form a fluidized area 17 ; a Fenton catalyst is contained in the middle of the main reactor 13 to form a catalyst reaction zone 18 .

[0024] In some preferred embodiments, the baffle plate 4 is made of 316L stainless steel, and the distance between the lower end of the baffle plate 4 and the bottom of the pre-reactor 1 is controlled to be 20-40 cm.

[0025] In some preferred embodiments, a drain pipe 23 is provided at the bottom of the main reactor 13, and the diameter of the drain pipe 23 is controlled to be 10-15 cm.

[0026] In some preferred embodiments, in order to facilitate observation of the sulfidation state in the main reactor, a fluidization state observation port 19 is provided in the middle of the main reactor 13, and the diameter of the observation port 19 is controlled at 15-20 cm; a COD monitor is provided in the outlet area of ​​the main reactor 13.

[0027] When the above embodiment is implemented, the pre-reactor 1 is first constructed with a height-to-diameter ratio of 3:2, and the Fenton catalyst is added to the pre-reactor 1 in advance; the residence time of the sewage after being transported to the pre-reactor 1 is 15-30 seconds, and the pH of the sewage is adjusted to 4.5-5.5 after entering the pre-reactor 1. After the sewage enters from the top of the pre-reactor 1, it first enters the dosing area 12, and ferrous sulfate and hydrogen peroxide are metered and added to the dosing area 12; The water in the pre-reactor 1 is mixed with ferrous sulfate and hydrogen peroxide and then passes through the bottom of the partition 4 to enter the reaction zone to form a fluidized state. The catalyst achieves a synergistic reaction with the added ferrous sulfate in the fluidized state, jointly catalyzing and exciting the hydrogen peroxide to produce a hydroxyl reaction, generating hydroxyl free radical substances with strong oxidizing ability and oxidizing organic pollutants in the wastewater; The effluent of the pre-reactor 1 flows out from the top outlet pipe 3, and is lifted to the dosing mixing box 14 at the top of the main reactor 13 by the water inlet pump 11. Ferrous sulfate and hydrogen peroxide are metered and added to the dosing mixing box 14. After dosing and mixing, the water flows out through the drainage pipe 15, and enters the bottom of the main reactor 13 under the action of the horizontal centrifugal pump 16. The sewage passes through the circular pipe guide 20 at the bottom of the main reactor 13 and is evenly distributed. A Fenton catalyst is added to the main reactor 13, and the catalyst and the mixed liquid form a fluidized reaction, and are fully mixed to cause a homogeneous Fenton reaction and a heterogeneous Fenton reaction, so that the catalyst and the added ferrous sulfate can achieve a synergistic reaction in a fluidized state, and jointly catalyze and stimulate the hydrogen peroxide to produce a hydroxyl reaction, generate hydroxyl free radical substances with strong oxidizing ability, and oxidize organic pollutants in the wastewater; Control the residence time of sewage in the main reactor 13 to be 0.25-0.4h; The wastewater after the reaction enters the outlet diversion area 21, and then enters the outlet trough 22 through the triangular weir. The catalyst contacts the steel plate of the diversion area and stays in the main reactor 13.

[0028] Among them, the Fenton catalyst is preferably a transition metal oxide, such as Fe3O4, Cu2O, etc.

[0029] In a further sewage treatment method, that is, the method of using the device in the present invention, the reaction control mode of the pre-reactor 1 and the main reactor 13 is divided into process one and process two according to the different pH values. The pH range of process one is 4.5-5.0, and the pH range of process two is 5.0-5.5. If the detected pH exceeds the interval value, the pH is adjusted, and concentrated sulfuric acid is added to the dosing area of ​​the pre-reactor 1 to adjust the pH; wherein, in the front-end predictive control of the pre-reactor, the dosage of hydrogen peroxide in the pre-reactor is determined according to the COD concentration value A1 of the pre-reactor inlet water, and the calculation formula of the dosage of hydrogen peroxide Y1 is: Y1=15%×A1×N; Among them, Y1 is the amount of hydrogen peroxide added in mg / L; A1 is the COD concentration of the pre-reactor inlet in mg / L; N is the ratio of the amount of hydrogen peroxide added in mg / L to the COD concentration in mg / L when the pH is 4.5-5 or 5-5.5, to reduce COD from A1 to the expected target; in the front-end predictive control of the main reactor, the amount of hydrogen peroxide added in the main reactor is determined by the COD concentration value A2 of the main reactor inlet, and the calculation formula of the hydrogen peroxide dosage Y2 is: Y2=A2×N; Among them, Y2 is the amount of hydrogen peroxide added in mg / L; A2 is the COD concentration of the main reactor inlet in mg / L; N is the ratio of the amount of hydrogen peroxide added in mg / L to the COD concentration in mg / L when the pH is 4.5-5 or 5-5.5, to reduce the COD from A2 to the expected target.

[0030] In a further sewage treatment method, the COD concentration value of the pre-reactor influent is A1, the theoretical set value of the effluent is set to 85%A1, and the actual effluent of the pre-reactor, i.e., the COD concentration value of the actual influent of the main reactor is A2. If ︱85%A1-A2︱ / 85%A1≤8%, the dosage of ferrous sulfate and hydrogen peroxide is not adjusted; If ︱85%A1-A2︱ / 85%A1>8%, adjust the dosage of ferrous sulfate and hydrogen peroxide in the pre-reactor. The actual dosage of hydrogen peroxide Y3 is calculated as follows: Y3=Y1+85%A1-A2×N; Among them, Y3 is the actual dosage of hydrogen peroxide in mg / L; A1 is the COD concentration of the pre-reactor inlet in mg / L; N is the ratio of the amount of hydrogen peroxide in mg / L to the COD concentration in mg / L when the pH is 4.5-5 or 5-5.5, to reduce the COD from A2 to the expected target; At the same time, the dosage ratio of hydrogen peroxide to ferrous sulfate in the pre-reactor is controlled at 1:1-1:3.

[0031] In a further sewage treatment method, the actual influent COD mass concentration value of the main reactor is A2, and the theoretical set value of the effluent is M%A2, where the M value is based on the designed effluent index and a certain surplus amount is considered; The actual effluent COD mass concentration value of the main reactor is A3. If ︱M%A2-A3︱ / M%A2≤5%, the dosage of ferrous sulfate and hydrogen peroxide in the main reactor will not be adjusted.

[0032] If |M%A2-A3| / M%A2>4%, adjust the dosage of ferrous sulfate and hydrogen peroxide in the main reactor. The actual dosage of hydrogen peroxide Y4 is calculated as follows: Y4=Y2+M%A2-A3×N; At the same time, the dosage ratio of hydrogen peroxide to ferrous sulfate in the main reactor is controlled at 1:1-1:3.

[0033] During operation, the effluent quality of the pre-reactor 1 is not only the basis for adjusting the dosage of hydrogen peroxide and ferrous sulfate in the main reactor 13, but also can be used to determine the cause of failure to meet the effluent standards over time and with changes in water inflow, and to timely analyze the cause and adjust the operation control of the main reactor 13.

[0034] In addition, according to the operation experience statistics, the operation data is continuously accumulated during the operation process, and the operation parameters are optimized and adjusted; if maintenance is required, the pre-reactor 1 and the main reactor 13 can be emptied through the drain pipe.

[0035] During the reaction process, the main reactor 13 is provided with a fluidization state observation port 19 for observing the fluidization state of the crystals.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A two-stage Fenton catalytic oxidation reaction device, characterized in that: The invention comprises a pre-reactor (1) and a main reactor (13) connected to the pre-reactor; the pre-reactor (1) is a cylinder; the upper two sides of the pre-reactor (1) are connected to a water inlet pipe (2) and a water outlet pipe (3); a baffle (4) is provided on one side of the pre-reactor; the water inlet pipe (2) is connected to a side of the baffle (4) close to the outer wall of the pre-reactor (1); the baffle (4) and the inner wall of the pre-reactor (1) close to the baffle form a dosing area (12); and a drain pipe (10) is provided at the bottom of the pre-reactor (1); The water outlet pipe (3) is connected to the top of the main reactor (13), and a water inlet pump (11) is provided on the water outlet pipe (3). A dosing mixing box (14) is provided on the top of the main reactor (13). The water outlet pipe (3) is connected to the inside of the dosing mixing box (14). A ferrous sulfate dosing pipe (5), a hydrogen peroxide dosing pipe (6), a concentrated sulfuric acid dosing pipe (7) and a COD monitor (8) are provided in the dosing mixing box (14) and the dosing area (12). A pH monitor (9) is also provided on the water inlet pipe (3). A drainage pipe (15) is provided at the bottom of the dosing mixing box (14), and the drainage pipe (15) is connected to the lower end of the main reactor (13). A horizontal centrifugal pump (16) is connected to the drainage pipe (15) for sewage transportation, so that water finally enters the main reactor (13) from the bottom. A circular tube guide (20) is arranged at the bottom of the main reactor (13), and a water outlet guide area (21) and a triangular weir water outlet trough (22) are arranged at the top of the main reactor (13); The pre-reactor (1) contains a Fenton catalyst in the middle to form a fluidized area (17); the main reactor (13) contains a Fenton catalyst in the middle to form a catalyst reaction zone (18).

2. A two-stage Fenton catalytic oxidation reaction device according to claim 1, characterized in that: The baffle (4) is made of 316L stainless steel, and the distance between the lower end of the baffle (4) and the bottom of the pre-reactor (1) is controlled to be 20-40 cm.

3. A two-stage Fenton catalytic oxidation reaction device according to claim 1, characterized in that: An exhaust pipe (23) is provided at the bottom of the main reactor (13), and the diameter of the exhaust pipe (23) is controlled to be 10-15 cm.

4. A two-stage Fenton catalytic oxidation reaction device according to claim 1, characterized in that: A fluidization state observation port (19) is provided in the middle of the main reactor (13), and the diameter of the observation port (19) is controlled to be 15-20 cm; a COD monitor is provided in the outlet area of ​​the main reactor (13).

5. A two-stage Fenton catalytic oxidation reaction method, characterized in that: A two-stage Fenton catalytic oxidation reaction device according to any one of claims 1 to 4, specifically comprising: The pre-reactor (1) is constructed with a height-to-diameter ratio of 3:2, and a Fenton catalyst is added to the pre-reactor (1) in advance; the residence time of the sewage after being transported to the pre-reactor (1) is 15-30 seconds, and after the sewage enters the pre-reactor (1), the pH value is adjusted to 4.5-5.5, and after the sewage enters from the top of the pre-reactor (1), it first enters the dosing area (12), and ferrous sulfate and hydrogen peroxide are metered and added to the dosing area (12); The influent water of the pre-reactor (1) is mixed with ferrous sulfate and hydrogen peroxide and then passes through the bottom of the partition (4) to enter the reaction zone, forming a fluidized state. The catalyst achieves a synergistic reaction with the added ferrous sulfate in the fluidized state, jointly catalyzing and stimulating the hydrogen peroxide to produce a hydroxyl reaction, thereby generating hydroxyl free radical substances with strong oxidizing ability and oxidizing organic pollutants in the wastewater; The effluent of the pre-reactor (1) flows out from the top effluent pipe (3), is lifted to the dosing and mixing box (14) at the top of the main reactor (13) by the water inlet pump (11), ferrous sulfate and hydrogen peroxide are metered and added to the dosing and mixing box (14), and after the dosing and mixing, the effluent flows out through the drainage pipe (15), and enters the bottom of the main reactor (13) under the action of the horizontal centrifugal pump (16), and the sewage flows through the circular pipe guide (20) at the bottom of the main reactor (13) and is evenly distributed upward; A Fenton catalyst is added into the main reactor (13), and the catalyst and the mixed liquid form a fluidized reaction, and are fully mixed to generate a homogeneous Fenton reaction and a heterogeneous Fenton reaction, so that the catalyst and the added ferrous sulfate can achieve a synergistic reaction in a fluidized state, and jointly catalyze and stimulate the hydrogen peroxide to generate a hydroxyl reaction, thereby generating a hydroxyl free radical substance with strong oxidizing ability and oxidizing organic pollutants in the wastewater; Control the residence time of the sewage in the main reactor (13) to be 0.25-0.4h; The wastewater after the reaction enters the outlet diversion area (21), and then enters the outlet trough (22) through the triangular weir. The catalyst contacts the steel plate of the diversion area and remains in the main reactor (13).

6. A two-stage Fenton catalytic oxidation reaction method according to claim 5, characterized in that: The Fenton catalyst is preferably a transition metal oxide.

7. A two-stage Fenton catalytic oxidation reaction method according to claim 5, characterized in that: The reaction control modes of the pre-reactor (1) and the main reactor (13) are divided into process one and process two according to the different pH values. The pH range of process one is 4.5-5.0, and the pH range of process two is 5.0-5.

5. If the detected pH value exceeds the interval value, the pH is adjusted, and concentrated sulfuric acid is added to the dosing area of ​​the pre-reactor (1) to adjust the pH. In the front-end predictive control of the pre-reactor, the dosage of hydrogen peroxide in the pre-reactor is determined according to the COD concentration value A1 of the pre-reactor influent. The calculation formula of the dosage of hydrogen peroxide Y1 is: Y1=15%×A1×N; Among them, Y1 is the amount of hydrogen peroxide added (mg / L); A1 is the COD concentration of the pre-reactor inlet (mg / L); N is the ratio of the amount of hydrogen peroxide added (mg / L) to the COD concentration (mg / L) when the pH is 4.5-5 or 5-5.5, which reduces the COD from A1 to the expected target; in the front-end predictive control of the main reactor, the amount of hydrogen peroxide added to the main reactor is determined by the COD concentration value A2 of the main reactor inlet, and the calculation formula of the hydrogen peroxide dosage Y2 is: Y2=A2×N; Wherein, Y2 is the dosage of hydrogen peroxide (mg / L); A2 is the COD concentration of the main reactor inlet (mg / L); N is the ratio of the dosage of hydrogen peroxide (mg / L) to the COD concentration (mg / L) when the pH is 4.5-5 or 5-5.5, to reduce the COD from A2 to the expected target.

8. A two-stage Fenton catalytic oxidation reaction method according to claim 7, characterized in that: It also includes pre-reactor feedback control: the COD concentration value of the pre-reactor inlet water is A1, the theoretical set value of the outlet water is set to 85%A1, the actual outlet water of the pre-reactor, that is, the COD concentration value of the actual inlet water of the main reactor is A2, if ︱85%A1-A2︱ / 85%A1≤8%, the dosage of ferrous sulfate and hydrogen peroxide is not adjusted; If ︱85%A1-A2︱ / 85%A1>8%, adjust the dosage of ferrous sulfate and hydrogen peroxide in the pre-reactor. The actual dosage of hydrogen peroxide Y3 is calculated as follows: Y3=Y1+(85%A1-A2)×N; Among them, Y3 is the actual dosage of hydrogen peroxide (mg / L); A1 is the COD concentration of the pre-reactor inlet (mg / L); N is the ratio of the hydrogen peroxide dosage (mg / L) to the COD concentration (mg / L) when the pH is 4.5-5 or 5-5.5, to reduce the COD from A2 to the expected target; At the same time, the dosage ratio of hydrogen peroxide to ferrous sulfate in the pre-reactor is controlled at 1:1-1:

3.

9. A two-stage Fenton catalytic oxidation reaction method according to claim 7 or 8, characterized in that: It also includes the main reactor feedback control: the actual influent COD mass concentration value of the main reactor is A2, and the theoretical set value of the effluent is M%A2, where the M value is based on the designed effluent index and a certain amount of surplus is considered; The actual effluent COD mass concentration value of the main reactor is A3. If ︱M%A2-A3︱ / M%A2≤5%, the dosage of ferrous sulfate and hydrogen peroxide in the main reactor will not be adjusted. If |M%A2-A3| / M%A2>4%, adjust the dosage of ferrous sulfate and hydrogen peroxide in the main reactor. The actual dosage of hydrogen peroxide Y4 is calculated as follows: Y4=Y2+(M%A2-A3)×N; At the same time, the dosage ratio of hydrogen peroxide to ferrous sulfate in the main reactor is controlled at 1:1-1:3.

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