Fluidized bed system based on fenton reaction and method for treating wastewater using the same

Abstract

The application relates to a fluidized bed system based on a Fenton reaction and a method for treating sewage by using the same. The system comprises a fluidized bed main body, a first water inlet arranged at the lower end of the fluidized bed main body, a first water outlet arranged at the upper end of the fluidized bed main body, a filler layer arranged in the fluidized bed main body, and a crystallization layer arranged above the filler layer. The method comprises the following steps: pretreating sewage, inducing crystallization on the surface of particles in the crystallization layer after ferrous ions are converted into ferric ions, and depositing the ferric ions on the surface of the particles, and discharging the treated sewage. The application can solve the problem that the catalyst is easy to flow away in the sewage treatment process based on the Fenton reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sewage treatment, and particularly relates to a fluidized bed system based on Fenton reaction and a method for treating sewage by using the same. BACKGROUND

[0002] Sewage treatment is a process involving the removal of harmful pollutants in wastewater. Fenton reaction is a method of decomposing harmful pollutants in wastewater through redox reaction. In sewage treatment, Fenton reaction is often used to treat wastewater containing organic compounds such as benzene and toluene. This reaction requires the addition of hydrogen peroxide and iron ions in the wastewater to generate highly active hydroxyl radicals, which can oxidize and decompose organic pollutants. During the Fenton reaction, organic compounds in the wastewater are decomposed into smaller molecules that can be more easily biodegraded or removed by other sewage treatment methods. Therefore, Fenton reaction plays an important role in sewage treatment, especially in the case of treating high-concentration organic wastewater, it can effectively degrade organic pollutants and convert them into safer compounds, thereby reducing the impact on the environment.

[0003] However, the conventional Fenton reaction is a homogeneous reaction, so the catalyst is easy to flow out, resulting in secondary pollution and increasing the operation cost. In addition, a large amount of chemical sludge is generated during the reaction process, which increases the cost of sludge treatment in the plant. In addition, during actual operation, residual H2O2 can cause sludge to float and COD value to increase, thus restricting the further promotion and application of this process. SUMMARY

[0004] In order to overcome the defects of the prior art, the technical problem to be solved by the present application is to provide a fluidized bed system based on Fenton reaction and a method for treating sewage by using the same, which solves the problem of easy loss of catalyst in the sewage treatment process based on Fenton reaction.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] The present application provides a fluidized bed system based on Fenton reaction, which comprises a fluidized bed main body, a first water inlet is arranged at the lower end of the fluidized bed main body, a first water outlet is arranged at the upper end of the fluidized bed main body, a filler layer and a crystallization layer are arranged inside the fluidized bed main body, and the crystallization layer is located above the filler layer.

[0007] The fluidized bed system based on Fenton reaction is a combination of induced crystallization principle and fluidized bed technology. In order to improve the shortcomings of conventional Fenton process, the fluidized bed reactor and Fenton technology are organically combined, and by introducing external particles and setting a crystallization layer, heterogeneous crystallization of Fe 3+ is realized, and Fe 3+The FeOOH is coated on the surface of the filler in the form of crystal, so as to achieve the interception of Fe 3+ , strengthen the Fenton reaction. The wastewater enters from the bottom of the reactor at a certain flow rate, so that the crystals are in a suspended state, and then a composite material with crystal seeds as the core is obtained. The crystal nucleus acts as a "condensation nucleus", and the presence of the crystal nucleus can enrich the ions participating in the reaction in the water phase on the surface of the crystal nucleus, thereby causing the local ion concentration around the crystal nucleus to rise to a supersaturated state, accelerating the deposition and attachment on the surface of the crystal nucleus. The reaction process is cyclically carried out by the following steps:

[0008] 1) Formation of FeOOH: the catalytic component Fe 2+ in the ferrous reagent decomposes H2O2 to generate OH· and Fe 3+ , Fe 3+ crystallizes on the surface of the particles of the crystalline layer to form FeOOH, and the hydroxyl radical OH· can be used to oxidize organic matter with poor biodegradability and large molecular weight, thereby treating wastewater;

[0009] 2) Dissolution and reduction of FeOOH: in addition, the crystalline FeOOH forms a complex precursor with organic matter, releases organic groups and Fe 2+ , Fe 2+ continuously generates OH· and Fe 3+ by decomposing H2O2, thereby avoiding the loss of the catalytic component Fe 2+ .

[0010] The preferred technical scheme of the present application is that the water distribution well is located on one side of the fluidized bed body, one end of the water distribution well is provided with a second water inlet, the other end of the water distribution well is provided with a second water outlet, the second water outlet and the first water inlet are connected by pipelines, and a reagent inlet is arranged between the second water inlet and the second water outlet.

[0011] The preferred technical scheme of the present application is that the reagent inlet sequentially comprises a sulfuric acid inlet, a ferrous inlet and a hydrogen peroxide inlet.

[0012] The preferred technical scheme of the present application is that the inner side wall of the fluidized bed body is further provided with an air injection port, and the air injection port faces the crystalline layer.

[0013] The preferred technical scheme of the present application is that the crystalline layer is fine sand, and the filler layer is composed of pebbles and quartz sand.

[0014] The preferred technical scheme of the present application is that the inner side wall of the fluidized bed body is further provided with an air injection port, and the air injection port faces the crystalline layer.

[0015] The preferred technical scheme of the present application is that the filter unit is composed of a filter beam and a filter column arranged from top to bottom.

[0016] The preferred technical scheme of the present application is that a water distribution layer is further arranged between the filtering unit and the supporting plate.

[0017] The present application provides a method for treating sewage by using the fluidized bed system, comprising the following steps:

[0018] S0: Before opening the valve of the first water inlet, add sulfuric acid, ferrous reagent and hydrogen peroxide to the sewage to be treated to obtain pretreated sewage;

[0019] S1: The pretreated sewage is sent into the interior of the fluidized bed main body through the first water inlet, and the pollutants in the pretreated sewage are degraded by Fenton reaction, and the ferrous ions are converted into trivalent iron ions which induce crystallization on the surface of the particles in the crystallization layer and are deposited on the surface of the particles;

[0020] S2: The pretreated sewage after treatment is discharged from the first water outlet.

[0021] The preferred technical scheme of the present application is that in S0, the amount of ferrous reagent is adjusted by detecting the pH value at the crystallization layer.

[0022] The present application has the following beneficial effects:

[0023] The fluidized bed system based on Fenton reaction provided by the present application is characterized in that the interior of the fluidized bed main body is provided with a filler layer and a crystallization layer, the pollutants in the pretreated sewage are degraded by Fenton reaction, the ferrous ions are converted into trivalent iron ions which induce crystallization on the surface of the particles in the crystallization layer and are deposited on the surface of the particles, realizing heterogeneous crystallization of Fe 3+ , the Fe 3+ generated in the Fenton reaction process is coated on the surface of the filler in the form of crystallization, and the Fe 3+ is intercepted in the form of FeOOH, thereby reducing the loss of the catalyst Fe 2+ , reducing the use of ferrous reagent, reducing the operation cost, avoiding the generation of a large amount of chemical sludge, reducing the sludge treatment cost of the plant, the Fenton reaction involving hydrogen peroxide is more sufficient and is not easy to remain, thereby avoiding the floating of sludge and the increase of COD value. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0025] Figure 1 It is a top view structural schematic diagram of the fluidized bed system based on Fenton reaction of the present application.

[0026] Figure 2 The structure diagram of the fluidized bed main body in the fluidized bed system based on Fenton reaction of the present application;

[0027] Figure 3 The sewage flow direction diagram of the fluidized bed system based on Fenton reaction of the present application;

[0028] Figure 4 The flow chart of the method for treating sewage by using the fluidized bed system based on Fenton reaction of the present application.

[0029] In the figure:

[0030] 1-fluidized bed main body; 21-first water inlet; 22-first water outlet; 23-air injection port; 31-packing layer;

[0031] 32-crystallization layer; 33-supporting plate; 34-filtration unit; 341-filter beam; 342-filter column; 35-water distribution layer;

[0032] 4-distribution well; 41-second water inlet; 42-second water outlet; 43-reagent inlet; 431-sulfuric acid inlet;

[0033] 432-ferrous iron inlet; 433-hydrogen peroxide inlet. DETAILED DESCRIPTION

[0034] The technical solutions of the present application will be further illustrated by specific embodiments in combination with the accompanying drawings.

[0035] Please refer to Figures 1-3 The fluidized bed system based on Fenton reaction provided in the embodiment comprises a fluidized bed main body 1, the lower end of the fluidized bed main body 1 is provided with a first water inlet 21, the upper end of the fluidized bed main body 1 is provided with a first water outlet 22, the inside of the fluidized bed main body 1 is provided with a packing layer 31 and a crystallization layer 32, and the crystallization layer 32 is located above the packing layer 31. The packing layer mainly plays a role in supporting the crystallization layer. In the embodiment, the crystallization layer 32 is fine sand, and the packing layer 31 is pebbles and quartz sand. The fine sand particles on the crystallization layer are used for the attachment of ferric ions as catalysts in the Fenton reaction, so as to prevent the catalyst from flowing out of the fluidized bed system together with the treated sewage, causing loss. When the concentration of iron ions is too high, the iron ions will wrap the microorganisms, so as to isolate the nutrients outside the microorganisms, so that the active microorganisms lack nutrients and the respiration rate is slowed down, and the denitrification performance is greatly weakened, thereby causing secondary pollution. After the iron ions are attached to the packing layer, the occurrence of the above situation can be reduced. Moreover, the heterogeneous crystallization of Fe 3+ is realized, the Fe 3+ produced in the Fenton reaction process is coated on the surface of the packing in the form of crystallization, and the Fe 3+The use of ferrous reagent can be reduced, the operation cost can be reduced, the Fenton reaction with hydrogen peroxide is more sufficient, and the hydrogen peroxide is not easy to remain, so that sludge floating and COD value rising are avoided.

[0036] Specifically, the water distribution well 4 is arranged on one side of the fluidized bed body 1, one end of the water distribution well 4 is provided with a second water inlet 41, the other end of the water distribution well 4 is provided with a second water outlet 42, the second water outlet 42 and the first water inlet 21 are connected by pipelines, and the second water inlet 41 and the second water outlet 42 are provided with a reagent inlet 43. The arrangement of the water distribution well is beneficial to locally increasing the concentration of the Fenton reagent in the sewage to be treated, and is beneficial to increasing the reaction rate and the cleaning efficiency of the sewage.

[0037] Preferably, the reagent inlet 43 sequentially comprises a sulfuric acid inlet 431, a ferrous inlet 432, and a hydrogen peroxide inlet 433. The sulfuric acid, the ferrous reagent, and the hydrogen peroxide are respectively added through the above-mentioned inlets. The ferrous reagent can be ferrous sulfate, ferrous chloride, and ferrous nitrate, etc. In this embodiment, ferrous chloride is selected because ferrous chloride is more easily oxidized to iron ions in water, and chloride ions in water can form iron oxide precipitates with iron ions. In addition, the solubility of ferrous chloride is higher than that of ferrous sulfate, which can release ferrous ions more quickly, accelerate the reaction rate, and more easily adhere to the fine sand of the crystalline layer. The sulfuric acid is first added to the sewage, which can neutralize the alkaline substances in the water, so that the reaction system maintains a certain acidity, which is beneficial to maintaining the activity of ferrous ions. The activity of ferrous ions requires the presence of sulfuric acid, so the ferrous inlet is after the sulfuric acid inlet. After the generation of ferrous ions, oxidation reaction with pollutants occurs, thereby degrading organic substances. Hydrogen peroxide acts as an oxidizing agent in the reaction, which can further enhance the effect of oxidative degradation. Therefore, the hydrogen peroxide inlet should be after the ferrous reagent is added, so as to form sufficient iron ions in the reactor to maximize the oxidation capacity of hydrogen peroxide.

[0038] Preferably, the inside side wall of the fluidized bed body 1 is also provided with a gas injection port 23, which faces the crystalline layer 32, so that the fine sand of the crystalline layer is sprayed up to form a more uniform system, so that the gas and solid particles in the fluidized bed form a circulating flow system, so that the reactants can continuously flow, maintain the stability and uniformity of the entire Fenton reaction process, and also facilitate the collection and separation of the products. At the same time, it also avoids the fine sand of the crystalline layer from falling to the position of the filler layer.

[0039] Specifically, the inside of the fluidized bed body 1 is provided with a supporting plate 33, the supporting plate 33 is provided with through holes for water to pass through, the filler layer 31 is located on the supporting plate 33, and the supporting plate 33 is provided with a filtering unit 34 below.

[0040] Preferably, the filtering unit 34 is a filter beam 341 and a filter column 342 arranged in sequence from top to bottom. Both the filter beam and the filter column are used to filter impurities and small particles in the incoming pretreated sewage, playing an important role in protecting the crystallization layer and the reactor equipment.

[0041] In order to fully spread the incoming sewage and improve the treatment efficiency, preferably, a water distribution layer 35 is arranged between the filtering unit 34 and the supporting plate 33, and specifically, the water distribution layer 35 is a PVC perforated water distribution plate.

[0042] Please refer to Figure 4 The method for treating sewage by using the fluidized bed system provided by the embodiment comprises the following steps:

[0043] S0: Before opening the valve of the first water inlet, add sulfuric acid, ferrous reagent and hydrogen peroxide to the sewage to be treated to obtain pretreated sewage;

[0044] S1: The pretreated sewage is sent into the interior of the fluidized bed body through the first water inlet, the first water inlet is arranged at the bottom of the fluidized bed body, and the pretreated sewage flows from the bottom to the top of the fluidized bed body. When passing through the filler layer and the crystallization layer in the interior of the fluidized bed body, a Fenton reaction occurs, the pollutant in the pretreated sewage is degraded by the Fenton reaction, and the ferrous ion is converted into ferric ion, which induces crystallization on the surface of the particles in the crystallization layer and is deposited on the surface of the particles, and is not easy to flow away with the sewage, so as to continuously catalyze the subsequent sewage;

[0045] S2: The pretreated sewage after treatment overflows at the top of the fluidized bed body and is discharged through the first water outlet.

[0046] Preferably, in S0, the amount of ferrous reagent is adjusted by detecting the pH value at the crystallization layer. In the embodiment, a pH tester is arranged for detection. The technical scheme of adjusting the amount of ferrous reagent by detecting the pH value at the crystallization layer is a real-time feedback control strategy, which has the following advantages: 1. High precision. The amount of ferrous reagent is adjusted by detecting the pH value at the crystallization layer, so that the acid-base condition of the reaction environment can be grasped in real time during the reaction, thereby the amount of ferrous reagent is accurately controlled, the reaction reaches the best state, and the reaction efficiency and reaction rate are improved; 2. Saving reagent. Since the amount of ferrous reagent can be adjusted according to the real-time feedback of the pH value, the situation of over-adding or under-adding is avoided, thereby the amount of reagent used can be effectively saved, and the processing cost is reduced; 3. Good stability. The amount of ferrous reagent is adjusted by controlling the pH value of the reaction environment, so that the stability of the reaction environment can be maintained, and the reaction out of control caused by under-adding or over-adding of reagent is prevented, thereby the stability and reliability of the treatment are ensured.

[0047] The technical scheme of the embodiment adopts the fluidized bed system based on Fenton reaction and the method for treating wastewater, so that the adding amount of ferrous reagent is reduced in the whole wastewater treatment process, and the adding amount is calculated to be 20% less than that of the same period. Meanwhile, since the ferric ion as the catalyst is in a heterogeneous state and attached to the surface of the particles in the crystalline layer, the amount of chemical sludge generated in the process is less than that of the traditional Fenton oxidation tower by more than 20%, which greatly reduces the operation burden of the plant sludge system and achieves the purpose of sludge reduction.

[0048] The application is described by preferred embodiments, and those skilled in the art know that various changes or equivalent replacements can be made to the features and embodiments without departing from the spirit and scope of the application. The application is not limited by the specific embodiments disclosed herein, and other embodiments falling within the claims of the application are within the scope of protection of the application.

Claims

1. A method for treating wastewater by using a fluidized bed system based on Fenton reaction, characterized in that: the fluidized bed system based on Fenton reaction comprises a fluidized bed body (1), a first water inlet (21) is arranged at the lower end of the fluidized bed body (1), and a first water outlet (22) is arranged at the upper end of the fluidized bed body (1); an inner part of the fluidized bed body (1) is provided with a filler layer (31) and a crystallization layer (32), and the crystallization layer (32) is located above the filler layer (31); a water distribution well (4) is further arranged on one side of the fluidized bed body (1); a second water inlet (41) is arranged at one end of the water distribution well (4), a second water outlet (42) is arranged at the other end of the water distribution well (4), the second water outlet (42) is connected with the first water inlet (21) in a pipeline mode, and a reagent inlet (43) is arranged between the second water inlet (41) and the second water outlet (42); the reagent inlet (43) comprises a sulfuric acid inlet (431), a ferrous inlet (432) and a hydrogen peroxide inlet (433) in sequence; a gas injection port (23) is further arranged on the inner side wall of the fluidized bed body (1), and the gas injection port (23) faces the crystallization layer (32); and the method comprises the following steps: S0, before opening the valve of the first water inlet, adding sulfuric acid, ferrous reagent and hydrogen peroxide into the wastewater to be treated to obtain pretreated wastewater; S1, feeding the pretreated wastewater into the inner part of the fluidized bed body through the first water inlet, degrading the pollutant in the pretreated wastewater by Fenton reaction, and inducing crystallization on the surface of particles on the crystallization layer after the ferrous ion is converted into ferric ion and then depositing on the surface of the particles; S2, discharging the pretreated wastewater after treatment from the first water outlet; and in S0, adjusting the addition amount of the ferrous reagent by detecting the pH value at the crystallization layer.

2. The method according to claim 1, characterized in that: the crystallization layer (32) is fine sand; and the filler layer (31) is cobble and quartz sand.

3. The method according to claim 1, characterized in that: a supporting plate (33) is arranged in the inner part of the fluidized bed body (1), and a through hole for water passing through is arranged on the supporting plate (33); the filler layer (31) is arranged on the supporting plate (33), and a filter unit (34) is arranged below the supporting plate (33).

4. The method according to claim 3, characterized in that: the filter unit (34) comprises a filter beam (341) and a filter column (342) arranged in sequence from top to bottom.

5. The method according to claim 4, characterized in that: a water distribution layer (35) is further arranged between the filter unit (34) and the supporting plate (33). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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