Heterogeneous Fenton-like catalyst, preparation method, reaction device and pretreatment method thereof

Abstract

The invention discloses a heterogeneous Fenton-like catalyst, a preparation method, a reaction device and a pretreatment method thereof. According to the catalyst, high-iron-content ash is used as a base material, porous magnetic particles of 3-5 mm are prepared through biomass reduction, magnetic separation enrichment, bonding granulation and roasting, the specific surface area is 200-300 m < 2 > / g, and the porosity is 70-80%. The device is of a closed vertical three-area structure, a pipeline mixer and a tangential nozzle are adopted to form rotational flow, and a gas collecting hood collects waste gas and is provided with a backwashing loop from bottom to top. During operation, H2O2 is added according to 1-1.5 times of the COD (Chemical Oxygen Demand) of inlet water under the nearly neutral condition that the pH value is 5-7, and the catalyst stays for 30-60 minutes, so that high-salt high-chlorine refractory organic wastewater can be efficiently degraded, iron mud can be reduced, backwashing and recycling are easy, the operation cost is reduced, and the method has engineering popularization value and is stable and reliable in operation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to a magnetic heterogeneous Fenton-like catalyst taking high-iron-content ash as a base material, a preparation method of the catalyst, and a fixed-bed Fenton-like reaction device and a pretreatment method using the catalyst. BACKGROUND

[0002] A large amount of wastewater with high salt content and containing refractory organic matter is generated in industrial production processes, which cannot be directly introduced into a biological treatment unit and needs to be pretreated.

[0003] Fenton oxidation is a typical advanced oxidation technology. Hydroxyl radicals (·OH) generated in the oxidation process can effectively degrade organic pollutants in wastewater as a strong oxidant. The traditional Fe 2+ (pentahydrate) is oxidized to Fe 3+ and generates iron sludge Fe(OH)3, causing iron salt consumption and sludge problems, and the operation pH range is narrow. The heterogeneous Fenton-like system uses a solid catalyst to replace the soluble iron ions (such as Fe 2+ ) in the homogeneous system, effectively broadening the pH range, greatly reducing the secondary pollution caused by iron sludge, and having broad application prospects.

[0004] Utility model patent ZL 201920688565.1 discloses an integrated fixed-bed Fenton device for industrial wastewater treatment. The middle section is a fixed-bed reactor with a trapezoidal structure, and the lower section is a pH adjustment tank provided with a spiral agitator. The trapezoidal device can make the sludge be pumped away at the bottom of the middle section. The reactor and the adjustment tank are combined in design, which can save the land occupation, but the maintenance difficulty is greatly increased when the agitator in the adjustment tank fails, and the engineering application feasibility is poor.

[0005] Invention patent ZL202110342908.0 relates to a high-efficiency heterogeneous Fenton-like reactor for high-salt refractory wastewater and a high-salt refractory wastewater treatment method, but it needs to inject circulating water into the interlayer for temperature control, which increases the complexity of the system and has poor engineering application feasibility. SUMMARY

[0006] In order to solve the problems of large amount of iron sludge, narrow pH range and poor adaptability to high-salt / high-chlorine refractory wastewater in the traditional Fenton process, the application provides a magnetic heterogeneous Fenton-like catalyst with high-iron-content ash as a base material and a preparation method thereof, and a fixed-bed Fenton-like reaction device and a pretreatment method matched therewith. The catalyst is prepared by reduction of the high-iron-content ash as the base material, realizes the resource utilization of waste, has low cost and wide application prospect, has the advantages of strong adsorption capacity, large specific surface area, large porosity and large loading capacity, and has magnetism for facilitating recovery. The heterogeneous fixed-bed Fenton-like pretreatment process is suitable for pretreatment of high-salt / high-chlorine refractory organic wastewater, and no iron sludge is generated in the reaction process, and waste gas can be collected and disposed.

[0007] According to a first aspect of the application, a heterogeneous Fenton-like catalyst is provided, which takes high-iron-content ash as a base material, and converts iron elements in the base material into magnetic iron oxides under reducing conditions, and after magnetic separation enrichment, is mixed with an inorganic binder to form and calcine to obtain a granular catalyst.

[0008] In some technical solutions, the high-iron-content ash contains 50-70wt% of iron oxides, 20-25wt% of MoO3, 6-12wt% of NiO, 2-8wt% of SiO2, 1-5wt% of CoO and 1-2wt% of Al2O3.

[0009] In some technical solutions, the granular catalyst has a particle size of 3-5mm, a specific surface area of 200-300m 2 / g, a porosity of 70-80%, and magnetism.

[0010] According to a second aspect of the application, a method for preparing the above-mentioned heterogeneous Fenton-like catalyst is further provided, which comprises the following steps:

[0011] Screening the high-iron-content ash;

[0012] Using biomass as a reducing agent to convert Fe 3+ in the ash into Fe3O4 with magnetism;

[0013] Magnetic separation and washing;

[0014] Mixing with an inorganic binder, drying and calcining to obtain a granular catalyst.

[0015] In some technical solutions, one or more of the following preparation conditions is used:

[0016] The particle size of the screening is 50-80 mesh;

[0017] The reduction temperature is 300-700℃;

[0018] The washing is alternately performed with deoxygenated water and anhydrous ethanol;

[0019] The drying temperature is 100-120℃, the drying time is 4-8h, the calcination temperature is 800-1000℃, and the calcination time is 20-60min;

[0020] The inorganic binder is silica sol or pseudo-boehmite;

[0021] The biomass is agricultural waste.

[0022] According to the third aspect of the present application, a fixed-bed Fenton-like reaction device is further provided, comprising a closed shell, in which a water inlet mixing zone, a catalyst packing zone and a water outlet zone are sequentially formed from bottom to top;

[0023] The water inlet mixing zone is communicated with a water inlet pipeline, and the water inlet pipeline is communicated with an H2O2 adding branch through a pipeline mixer;

[0024] The catalyst packing zone carries the heterogeneous Fenton-like catalyst prepared by the above method or by the above method;

[0025] The water outlet zone is communicated with a water outlet pipeline; and

[0026] The water outlet zone is provided with a gas collecting member for collecting reaction gas, and the gas collecting member is communicated with an external waste gas treatment system.

[0027] In some technical solutions, the outlet end of the water inlet pipeline is communicated with multiple nozzles arranged tangentially and obliquely to the inner wall of the shell through a distribution pipe, for forming a cyclone in the water inlet mixing zone;

[0028] The installation angle of the nozzles is 30-45°, the number of the nozzles is 2, 4 or 8, and each nozzle is arranged equidistantly along the circumference of the shell and is phase-shifted.

[0029] In some technical solutions, the water outlet zone comprises a water outlet groove fixed to the inner wall of the shell and a water outlet weir located above the water outlet groove away from the inner wall of the shell, the water outlet groove is communicated with the external water outlet pipeline through a water outlet port, and the water outlet weir is a triangular weir or a trapezoidal weir.

[0030] In some technical solutions, the gas collecting member is a reverse horn-shaped gas collecting cover, which is located above the catalyst packing zone and is communicated with the waste gas treatment system through a waste gas discharge port.

[0031] In some technical solutions, an acid adding port and a water inlet pH online monitoring assembly are arranged on the side of the water inlet mixing zone and communicated with the zone; a water inlet COD online monitoring assembly is arranged on the water inlet pipeline; a water outlet pH and ORP online monitoring assembly is arranged in the water outlet zone; a water outlet COD online monitoring assembly is arranged on the water outlet pipeline; and

[0032] The online monitoring components are respectively electrically connected with corresponding actuators to form interlocking control, including: water inflow COD and H2O2 dosing interlocking, water inflow pH and acid dosing interlocking, water outflow COD and water outflow valve interlocking.

[0033] In some technical solutions, a backwashing circuit with the water outflow of the reaction device as a water source is further provided; the circuit comprises a backwashing water pump in communication with the water outflow tank, a backwashing water inlet arranged at the lower part of the shell, and a backwashing water outlet tank arranged in the water outflow area below the water outflow tank and fixed to the inner wall of the shell; the backwashing water outlet tank is provided with a backwashing water discharge port.

[0034] In some technical solutions, the catalyst packing area is supported by the water distribution partition plate, and the catalyst filling rate is 50-70% of the total volume of the reaction device.

[0035] In some technical solutions, a plurality of reaction devices are arranged in parallel to maintain continuous water inflow operation by other devices when a single device is backwashed or stopped.

[0036] According to a fourth aspect of the present application, a fixed-bed Fenton-like pretreatment method is further provided, which uses the above reaction device to treat high-salt or high-chlorine refractory organic wastewater, and comprises the following steps:

[0037] The water inflow and hydrogen peroxide are mixed in the pipeline mixer and then enter the water inflow mixing area through nozzles in multiple paths to form a cyclone;

[0038] The mixed solution is uniformly distributed to enter the catalyst packing area for contact reaction;

[0039] The treated water is discharged from the water outflow area; during the reaction process, waste gas is collected by the gas collection member and sent to a waste gas treatment system;

[0040] The substandard water outflow is returned to the water inflow end for reprocessing.

[0041] In some technical solutions, one or more of the following treatment conditions is included:

[0042] The H2O2 dosage is controlled at 1-1.5 times the water inflow COD;

[0043] The catalyst contact time is 30-60 min;

[0044] The pH in the water inflow mixing area is 5-7, the pH of the water outflow is 6-8, the water outflow ORP is 200-300 mV, and the residence time of the reaction device is 1-2 h;

[0045] Backwashing is performed every 3-4 months, and the backwashing intensity is 10-15 L / m 2 ·s, and the backwashing time is 15-20 min.

[0046] The above technical solutions of the present application at least have the following beneficial effects:

[0047] 1. The present application uses high-iron-containing industrial ash as a raw material for catalyst, converts iron in the ash into magnetic iron oxide under reducing conditions, and makes porous magnetic particles after magnetic separation and enrichment, to construct a heterogeneous fixed-bed Fenton-like system for pretreatment of high-salt, high-chlorine and refractory organic wastewater. This approach not only realizes the resource utilization of solid waste and reduces material costs, but also avoids the generation of a large amount of iron sludge in the conventional homogeneous Fenton reaction by fixing iron phases on the catalyst, thereby significantly reducing the sludge disposal burden and improving the environmental and economic performance of the system;

[0048] 2. The particle catalyst prepared in the present application is a porous magnetic particle (preferably with a particle size of 3-5 mm, a specific surface area of about 200-300 m 2 / g, and a porosity of about 70-80%), which provides a large adsorption area and mass transfer channel, facilitating the migration of refractory macromolecular organic matter to the catalyst surface and enrichment, and the porous structure enhances the effective exposure of the active sites, and the magnetism facilitates backwashing and electromagnetic recovery, thereby balancing reaction efficiency and maintenance convenience. The metal oxides of Co, Ni and other metals inherently present in the ash can also act as cocatalytic elements to promote the redox cycle of Fe 3+ / Fe 2+ on the surface of the catalyst, enhancing the sustained production of ·OH free radicals and delaying catalyst deactivation;

[0049] 3. The present application adopts a closed vertical three-zone structure (water inlet mixing zone-catalyst packing zone-water outlet zone), and configures a pipeline mixer and multiple tangential / tilted nozzles in the water inlet mixing zone to form strong cyclone. This mass transfer enhancement design can make H2O2 and water mix quickly and fully, and distribute the mixed liquid evenly to the catalyst packing layer, thereby shortening the initial reaction time and increasing the treatment intensity per unit volume; at the same time, the cyclone and the water distribution partition cooperate to help suppress local short circuiting and plugging of the packing layer, ensuring the overall utilization rate of the catalyst layer; the cooperation of the gas collection member set at the top and the annular water outlet groove / water outlet weir can realize the centralized collection of volatile organic matter or gas in the reaction and send it into the waste gas treatment system, reducing secondary pollution;

[0050] 4. The present application can significantly reduce reagent waste and manual adjustment intensity while ensuring reaction effect, thereby reducing operating cost and improving system stability, by monitoring the influent COD, influent pH, effluent COD, effluent pH and ORP online, and forming interlocking control with H2O2, acid (HCl) dosing device and effluent valve (for example, the H2O2 dosage is automatically adjusted by 1-1.5 times of the influent COD, the influent pH is interlocked with acid dosing to achieve the control of the set interval 5-7, and the effluent COD is automatically backflowed for reprocessing when it does not meet the standard); in combination with the characteristics of the catalyst in the present application that it can still efficiently catalyze the generation of ·OH under near neutral pH conditions (avoiding the strong dependence of traditional Fenton on low pH), the overall process has obvious economic advantages in acid and alkali consumption and sludge disposal;

[0051] 5. The present application designs a bottom-up backwashing circuit with effluent as water source, and the backwashing water passes through the catalyst packing zone from bottom to top by backwashing water pump and is discharged by the backwashing water outlet groove fixed on the inner wall of the shell; the backwashing system (preferably the cycle is 3-4 months, the backwashing intensity is 10-15 L / m 2 ·s, and the backwashing time is 15-20 min) can effectively remove adsorptive sludge or flocculent pollutants without removing the catalyst layer, restore water permeability and prolong the operation cycle, and in combination with the arrangement of multiple devices operating in parallel, the continuous treatment capacity of the system can be ensured when a single device is backwashed or shut down for maintenance, thereby improving the engineering reliability and applicability;

[0052] 6. The heterogeneous catalytic system of the present application realizes the surface circulation of Fe 3+ / Fe 2+ on the surface of the catalyst, efficiently generates hydroxyl radicals (·OH) to break the carbon-carbon and carbon-oxygen bonds of organic matter by reacting with hydrogen peroxide, degrades into small molecule products and improves the biodegradability; the chloride ions present in the ash can also promote the reaction rate of Fe3O4 and H2O2 at a certain concentration, enhance the generation of ·OH, so that the present process has better adaptability in high-chlorine environment;

[0053] In summary, the present application overcomes the disadvantages of high reagent consumption, large amount of sludge, strong pH dependence, etc. of traditional Fenton method in high-salt and high-chlorine wastewater treatment through the systematic synergy of catalyst material innovation, particle engineering treatment, mass transfer and gas collection structure design, online interlocking control and backwashing maintenance system, realizes a fixed bed Fenton pretreatment scheme with low cost, stable operation, less secondary pollution and engineering implementation. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced and the labels in the drawings will be briefly introduced. Obviously, the drawings described below only represent some of the embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0055] Figure 1 The structure schematic diagram of the fixed bed Fenton-like reaction device described in the embodiments of the present application;

[0056] Figure 2 The nozzle arrangement schematic diagram described in the embodiments of the present application;

[0057] Figure 3 The principle diagram of the fixed bed Fenton-like pretreatment method described in the embodiments of the present application.

[0058] The meanings of the labels in the drawings are as follows:

[0059] 1—housing;

[0060] 10—water inlet mixing area, 11—pipeline mixer, 12—nozzle;

[0061] 20—catalyst packing area;

[0062] 30—water outlet area, 31—water outlet weir, 32—annular water outlet groove, 33—gas collecting cover;

[0063] 41—backwashing water pump, 42—backwashing water outlet groove. DETAILED DESCRIPTION

[0064] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings described below only represent some of the embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings, and other embodiments can also be obtained.

[0065] In order to make the drawing simple and clear, only the parts related to the present application are shown in each drawing, and they do not represent the actual structure of the product. In addition, in order to make the drawing simple and easy to understand, in some drawings, only one of the parts with the same structure or function is shown, or only one of them is labeled. In this paper, "one" not only means "only one", but also means "more than one".

[0066] It should be further understood that the term "and / or" as used in the specification and in the claims, if any, means any of the possibilities of combination of one or more of the associated listed items and all possible combinations and includes these combinations.

[0067] In this document, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0068] In addition, in the description of the present application, the terms "first", "second" and the like are only used for differentiation and description, and cannot be understood as indicating or implying relative importance.

[0069] According to one embodiment of the present application, a heterogeneous Fenton-like catalyst and a preparation method thereof are provided. A high-iron-content ash is selected, which mainly contains iron oxides 50-70wt%, and also contains MoO320-25wt%, NiO 6-12wt%, SiO22-8wt%, CoO 1-5wt% and Al2O31-2wt%. The high-iron-content ash is crushed and sieved to 50-80 mesh to obtain a raw material powder with uniform particle size, which is used as the substrate of the present embodiment. Subsequently, the ash is uniformly mixed with chopped agricultural waste biomass (such as rice husk) in a suitable ratio, and is heated and treated in a reducing furnace under a reducing atmosphere, so that Fe 3+ is reduced and phase-transformed into Fe3O4 phase with magnetism in the range of 300-700℃; after reduction, the magnetic components are enriched by magnetic separation with a strong magnetic field, so as to enrich Fe3O4 and its associated Co, Ni and other metal components. The material obtained by magnetic separation is washed three times alternately with deoxidized water and anhydrous ethanol to remove surface soluble impurities and dehydrate, and then the obtained magnetic powder is mixed with inorganic binders such as silica sol (or pseudo-boehmite) to granulate, the wet granules are dried at 100-120℃ for 4-8h, and finally the granular catalyst with densification and retained porous structure is obtained by calcination at 800-1000℃ for 20-60min.

[0070] The obtained catalyst is a porous magnetic granule, the particle size is controlled to be 3-5mm by granulation, the specific surface area is about 200-300m 2 / g by measurement, the porosity is about 70-80%, and it shows good magnetic response, which is convenient for rapid recovery by electromagnetic device during shutdown or maintenance. The catalyst of the present embodiment shows strong surface adsorption capacity, smooth mass transfer channel and surface Fe 3+ / Fe 2+Easy to circulate, suitable for fixed bed Fenton-like system of the application.

[0071] According to another embodiment of the application, a fixed bed Fenton-like reaction device is provided, such as Figure 1 The reaction device is a closed vertical cylindrical shell, the shell 1 is arranged from bottom to top in sequence with water inlet mixing zone 10, catalyst packing zone 20 and water outlet zone 30. The external water inlet is detected by the water inlet COD online monitoring component before entering the device, and the water inlet COD signal is detected. The water inlet pipeline is connected with the H2O2 addition branch through the pipeline mixer 11, which is used for rapid premixing of H2O2 added according to the water inlet COD interlock, and the outlet of the pipeline mixer 11 is connected with the annular distribution pipe. The annular distribution pipe evenly distributes the mixed liquid to a plurality of nozzles 12. As Figure 2 The nozzles 12 are arranged tangentially and obliquely relative to the inner wall of the shell. In this embodiment, the combination of the annular distribution pipe and the tangential nozzle makes the mixed liquid act on the inner wall of the shell in a tangential and oblique (preferably 30-45°) spraying manner, forming a circumferential rotational flow field. The rotational flow field cooperates with the downstream water distribution baffle to uniformly distribute the mixed liquid and reduce the inlet short circuit, significantly improving the contact efficiency and mass transfer rate of H2O2 and water phase, thereby improving the treatment intensity per unit volume.

[0072] In a specific design, the number of nozzles 12 can be selected as 2, 4 or 8, and they are arranged at equal intervals along the circumference and are phase-shifted to improve the uniformity of the annular distribution; the connection between the nozzles 12 and the annular distribution pipe adopts standard flanges or detachable threaded joints and is provided with sealing pads, which is convenient for on-site replacement and maintenance; a check element (check valve) is preferably arranged between the annular distribution pipe and the pipeline mixer 11, which is used to prevent backwashing water from flowing back to the pipeline mixer 11 during backwashing, and to protect the pipeline mixer 11 from liquid backflushing and contamination. This mass transfer and maintenance design takes into account the operation efficiency and process robustness.

[0073] The catalyst packing zone 20 is located in the middle and is supported by the water distribution baffle. The catalyst is prepared as a porous magnetic particle (particle size 3-5 mm) according to the foregoing embodiments, and the filling rate is controlled at 50%-70% of the total volume of the device. The arrangement and pore size design of the water distribution baffle are used to make the rotational flow water from the nozzles 12 be distributed uniformly before entering the catalyst layer, which avoids local erosion and inhibits channeling and plugging, and ensures the geometric utilization rate of the catalyst layer. A gas collecting member is arranged above the catalyst packing zone 20 along the axis of the shell 1, which is preferably a reverse horn-shaped gas collecting cover 33. The gas collecting cover 33 is connected with the external waste gas treatment system through the waste gas discharge port.

[0074] The water outlet area 30 is a combination of a ring-shaped water outlet groove 32 and a water weir 31. The ring-shaped water outlet groove 32 is fixed to the inner wall of the shell, and the water weir 31 (preferably a triangular weir or a trapezoidal weir) is arranged on the inner side. The water outlet is discharged through the water outlet or returned to the water inlet through the backflow pipeline for reprocessing when it does not meet the standard. The water outlet area 30 is also provided with a water outlet pH and ORP online monitoring assembly and a water outlet COD online monitoring assembly. The monitoring signals are used to constitute interlocking control with the actuators (water outlet valve, dosing pump, etc.), so as to ensure that the water outlet meets the standard stably.

[0075] In order to ensure long-term continuous operation and facilitate maintenance, the device is provided with a backwashing circuit taking the water outlet as the water source. The water outlet is subjected to backwashing from the lower part of the shell 1 by the backwashing water pump 41, passes through the catalyst layer from bottom to top, and the sewage after backwashing is collected in the backwashing water outlet groove 42 located below the water outlet area 30 and fixed to the inner wall of the shell, and is discharged from the backwashing water discharge port. The inner edge bottom surface of the backwashing water outlet groove 42 is preferably inclined to the center of the shell 1, so as to facilitate the flow of backwashing liquid and guide the released gas to the collection port of the gas collection hood 33 in cooperation with the gas collection hood 33. The design of the backwashing process enables the recovery of the layer permeability without disassembling the catalyst layer. The backwashing period is preferably 3-4 months, and the backwashing intensity is 10-15 L / m 2 ·s, the backwashing time is 15-20 min; and it is appropriate to connect multiple devices in the plant area in parallel so as to maintain the continuous treatment capacity of the system by other units when a single unit is backwashed or maintained. This parallel redundancy improves the engineering availability and treatment continuity.

[0076] In terms of control and electrical connection, the device is provided with an automatic control unit. The control unit is electrically connected with the online monitoring assemblies of the inlet water COD, inlet water pH, outlet water COD, outlet water pH and ORP, and is electrically connected with the H2O2 and acid (HCl) dosing pumps, outlet water valve, backwashing water pump 41, electromagnetic recovery device and other actuators, so as to realize the interlocking of inlet water COD and H2O2 addition, interlocking of inlet water pH and acid addition, and interlocking of outlet water COD and outlet water valve, thereby reducing the reagent waste and manual intervention frequency while ensuring the treatment effect. In order to facilitate maintenance and catalyst replacement, the device can be provided with an upper or lateral electromagnetic recovery device. The magnetic particles are quickly sucked by the magnetic force during shutdown or maintenance, which is convenient for offline regeneration or replacement.

[0077] The advantages of the structure and connection relationship of the embodiment are: ① The tangential inclined nozzle-cyclone-water distribution baffle system significantly improves the contact and mass transfer efficiency of H2O2 and wastewater, reduces the reagent consumption and shortens the treatment volume; ② The porous magnetic particle catalyst cooperates with the backwashing circuit to realize long-term operation with low iron sludge and easy maintenance; ③ The gas collection hood 33 cooperates with the backwashing geometry to reduce VOCs emission and facilitate centralized treatment; ④ The online monitoring and interlocking control improve the automation and economy, and the whole system has good implementability and maintainability in engineering.

[0078] According to another embodiment of the present application, a fixed bed Fenton-like pretreatment method is provided, and the reaction device of the above embodiment is taken as the operation object. Before starting, the granular catalyst prepared in the above embodiment is filled into the catalyst packing area 20 according to the design, and the filling rate is adjusted to 50% to 70% (preferably 60%) of the total volume of the device. The seal connection of the annular distribution pipe with each nozzle is checked, and the good electrical connection of the check valve, backwash water pump 41, water outlet valve, dosing pump, and online monitoring components (inlet water COD, inlet water pH, outlet water COD, outlet water pH, outlet water ORP) with the control unit is confirmed, and it is confirmed that the gas hood 33 is in communication with the waste gas treatment system, the backwash water outlet tank 42 and the discharge pipeline are unobstructed.

[0079] After the system is transported and purged in a closed and qualified detection, the water inlet pipeline is opened to supply water, and the real-time COD value is measured by the inlet water COD online monitoring component; the control unit starts and adjusts the H2O2 dosing pump according to the inlet water COD signal at a preset ratio (preferably 1.0 to 1.5 times) to make hydrogen peroxide fully mixed with the inlet water at the pipeline mixer 11; the mixed solution is injected into the inlet water mixing area 10 by the nozzle 12 through the annular distribution pipe and forms a cyclone, and the cyclone uniformly enters the catalyst packing area 20 after being stabilized at the water distribution baffle, so that the organic matter on the surface of the catalyst undergoes the following oxidation-reduction cycle reaction process (mechanism reference Figure 3 ):

[0080] Fe 2+ +H2O2→Fe 3+ +·OH+OH -

[0081] Fe 3+ +H2O2→Fe 2+ +·OOH+H +

[0082] Fe 3+ +·OOH→Fe 2+ +O 2 +H +

[0083] The inlet water pH is adjusted and maintained in the target interval of 5 to 7 by the inlet water pH online monitoring interlock control acid (HCl) dosing on the inlet water side, so as to take into account the catalytic activity and alkali consumption; the outlet water overflows to the outlet through the annular outlet tank 32 through the outlet weir 31 and is determined by the outlet water COD online monitoring whether the outlet water meets the standard, and when it does not meet the standard, it is automatically returned to the inlet end for reprocessing by the valve route; the volatile components or gases generated during the reaction are collected by the gas hood 33 and sent to the waste gas treatment system for treatment; the operation parameters (H2O2 dosing amount, inlet / outlet water pH, outlet water ORP) are recorded by the control unit and automatically fine-tuned according to the preset threshold value, so as to maintain the outlet water ORP preferably in the range of 200 to 300 mV to maintain the reaction activity.

[0084] In a specific design, the hydrogen peroxide dosage is controlled at 1-1.5 times the influent COD, the catalyst contact time is controlled at 30-60 min, the total residence time (including mixing and catalyst packing zone) is controlled at 1-2 h, the influent pH is 5-7, and the effluent pH is maintained at 6-8. The combination of the above parameters with the device of the preceding embodiment can still maintain a high COD removal efficiency under the condition of high-salinity and high-Cl wastewater, compared with the traditional homogeneous Fenton process, the chemical consumption is reduced and no subsequent iron sludge flocculation and sedimentation treatment is required, thereby saving operating costs and reducing secondary pollution.

[0085] To maintain the water permeability and activity of the catalyst layer, the backwashing cycle is set to be once every 3-4 months according to operating experience. The backwashing process is to stop the influent, start the backwashing water pump 41 to make the effluent pass through the catalyst layer from bottom to top and be discharged from the backwashing water outlet tank 42. The backwashing intensity is preferably 10-15 L / m 2 s, and the backwashing time is preferably 15-20 min. During backwashing, the backwashing water is prevented from flowing back to the pipeline mixer 11 through the check valve and control logic. After backwashing, the influent is restored and the treatment is continued by the other devices in parallel to ensure the continuity of the system. If the water permeability or activity of the catalyst does not recover to the specified standard after backwashing, the catalyst is removed for offline regeneration or replacement using the electromagnetic recovery device of the device.

[0086] This embodiment realizes efficient pretreatment of high-salinity / high-chlorine wastewater under near-neutral pH conditions through structural optimization of the reaction device (nozzle cyclone, water distribution baffle, geometric coordination of gas collection hood 33 and backwashing outlet tank) and material advantages of the granular catalyst (ash resourceization, magnetic particles, endogenous catalytic aid), significantly reduces operating costs and secondary pollution, and ensures long-term continuous operation and easy maintenance through backwashing and parallel redundancy mechanisms.

[0087] In order to have a clearer understanding of the technical solutions of the present application and their technical effects, the following examples are given, including Comparative Examples 1-3 and Examples 1-6.

[0088] Comparative Example 1

[0089] The wastewater of a certain chemical park contains coal chemical enterprises, fine chemical enterprises, etc. The wastewater has high COD concentration, COD 8000 mg / L, and high content of refractory organic matter, B / C about 0.12, and Cl - content as high as 3000 mg / L. The conventional Fenton process is used for treatment, the H2O2 dosage is 5000 mg / L, HCl is added to adjust the reaction pH to 3-4, the reaction time is 30 min, the COD of the effluent after reaction is reduced to 4640 mg / L, the COD removal rate is 42%, and the B / C is increased to 0.33. The amount of iron sludge produced is 10 g / L. After one month of operation, the COD removal rate is reduced to 30%. The Cl -The Fenton reaction effect will be reduced.

[0090] Example 1

[0091] The wastewater of a certain chemical industrial park contains coal chemical enterprises, fine chemical enterprises, etc. The wastewater has high COD concentration, COD 8000 mg / L, and high content of refractory organic matter, B / C about 0.12, and high salt content, TDS 12000 mg / L. The wastewater is treated by the fixed bed Fenton process of the patent, H2O2 dosage 4000 mg / L, reaction pH adjusted to 5-6, reaction time 30 min, and the effluent COD reduced to 3360 mg / L, COD removal rate 58%, B / C increased to 0.38. No iron sludge is produced. After one month of operation, the COD removal rate is 60%, and the Cl - The formation of hydroxyl radicals can be accelerated, thereby strengthening the catalytic reaction.

[0092] Example 2

[0093] The wastewater of a certain chemical industrial park contains coal chemical enterprises, fine chemical enterprises, etc. The wastewater has high COD concentration, COD 8000 mg / L, and high content of refractory organic matter, B / C about 0.12, and high salt content, TDS 12000 mg / L. The wastewater is treated by the fixed bed Fenton process of the patent, H2O2 dosage 4000 mg / L, reaction pH adjusted to 5-6, reaction time 60 min, and the effluent COD reduced to 2920 mg / L, COD removal rate 63.5%, B / C increased to 0.42. No iron sludge is produced.

[0094] Comparative Example 2

[0095] The wastewater of a certain chemical industrial park contains coal chemical enterprises, fine chemical enterprises, etc. The wastewater has high COD concentration, COD 8000 mg / L, and high content of refractory organic matter, B / C about 0.12, and high salt content, TDS 12000 mg / L. The wastewater is treated by the fixed bed Fenton process of the patent, H2O2 dosage 4000 mg / L, reaction pH adjusted to 5-6, reaction time 30 min, and the effluent COD reduced to 4320 mg / L, COD removal rate 46%, B / C increased to 0.35.

[0096] The treatment effect of the commercial catalyst is worse than that of the catalyst of the patent.

[0097] Comparative Example 3

[0098] A printing and dyeing wastewater, COD concentration is 8610mg / L, B / C is about 0.15, difficult to directly biodegradation, need to be pretreated, using conventional Fenton process for treatment, reaction pH is adjusted to about 3, catalyst contact time 30min, after the reaction of effluent COD decreased to 4380mg / L, COD removal rate of 49%, B / C increased to 0.38, after the reaction of effluent into the neutralization tank, in the neutralization tank dosing liquid alkali, the wastewater pH is adjusted to neutral; Neutralization tank wastewater flows into the degassing tank, by blowing agitation, remove a small amount of gas bubble in the wastewater; Degassing tank effluent flows into the coagulation reaction tank, dosing flocculant PAM and fully reacted, the wastewater in the iron mud flocculation; Coagulation after the wastewater flows into the sedimentation tank, the iron mud in the supernatant, the sludge pump to the original sludge treatment system for treatment, the supernatant into the subsequent A-O biochemical treatment unit.

[0099] Example 3

[0100] A printing and dyeing wastewater, COD concentration is 8610mg / L, B / C is about 0.15, difficult to directly biodegradation, need to be pretreated, using the fixed bed Fenton process of the patent for treatment, reaction pH is adjusted to 5-6, catalyst contact time 30min, after the reaction of effluent COD decreased to 3013mg / L, COD removal rate of 65%, B / C increased to 0.44. Pretreated effluent pH back to 7-8, continue to enter the subsequent A-O biochemical treatment unit. No iron mud production, no need to degassing.

[0101] Compared with the conventional Fenton process, using the fixed bed Fenton process of the patent, can greatly save the amount of acid and alkali required for pH adjustment, save the cost of iron mud treatment, at the same time can be in a reactor for gas-liquid separation collection of waste gas, greatly shorten the process flow.

[0102] Example 4

[0103] The reactor in the above example 3, after running for 3 months, backwash, backwash intensity is 12L / m2·s, backwash time is 15min, backwash water is discharged to the backwash pool. Backwash after rewater, COD removal efficiency is basically not affected.

[0104] Example 5

[0105] The reactor in the above example 3, after running for a period of time, due to the low load operation of the process device, the COD concentration of the wastewater is reduced to 6000mg / L, the reactor effluent COD is 1800mg / L, the COD removal rate is 70%. Low load operation is conducive to the removal of COD.

[0106] Example 6

[0107] The reactor in the above-mentioned embodiment 3, the catalyst in the device needs to be completely taken out during overhaul, the magnetic catalyst can be taken out by using the electromagnet device, the operation is simple and convenient, and automation can be realized.

[0108] The above-mentioned embodiments only express several implementation manners of the present application, the description is more specific and detailed, but it cannot be understood as the limitation of the patent scope of the present application. It should be pointed out that for ordinary skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A heterogeneous Fenton-like catalyst, characterized in that, Using high-iron-content ash slag as a base material, the iron element in the base material is converted into magnetic iron oxide under reducing conditions. After magnetic separation and enrichment, it is mixed with an inorganic binder, molded, and calcined to obtain a particulate catalyst.

2. The heterogeneous Fenton-like catalyst according to claim 1, characterized in that, The high-iron ash slag has an iron oxide content of 50-70 wt%, and also contains 20-25 wt% MoO3, 6-12 wt% NiO, 2-8 wt% SiO2, 1-5 wt% CoO and 1-2 wt% Al2O3.

3. The heterogeneous Fenton-like catalyst according to claim 1, characterized in that, The particulate catalyst has a particle size of 3-5 mm, a specific surface area of ​​200-300 m² / g, a porosity of 70-80%, and is magnetic.

4. A method for preparing the heterogeneous Fenton-like catalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: Screening of ash and slag with high iron content; Using biomass as a reducing agent, Fe in ash is reduced. 3+ It is transformed into magnetic Fe3O4; Perform magnetic separation and washing; The catalyst is obtained by mixing with an inorganic binder, granulating, drying, and calcining.

5. The method according to claim 4, characterized in that, Use one or more of the following preparation conditions: The particle size of the sieve is 50-80 mesh; The reduction temperature is 300–700℃; Washing is performed using alternating amounts of deoxygenated water and anhydrous ethanol; The drying temperature is 100-120℃ and the time is 4-8h; the calcination temperature is 800-1000℃ and the time is 20-60min. The inorganic binder is silica sol or boehmite; Biomass is agricultural waste.

6. A fixed-bed Fenton reactor, characterized in that, It includes a sealed shell, inside which, from bottom to top, are formed an inlet mixing zone, a catalyst packing zone, and an outlet zone; The water inlet mixing zone is connected to the water inlet pipeline, and the water inlet pipeline is connected to the H2O2 dosing branch through the pipeline mixer; The catalyst packing region carries the heterogeneous Fenton catalyst according to any one of claims 1 to 3 or the heterogeneous Fenton catalyst prepared by the method according to any one of claims 4 to 5; The water outlet area is connected to the water outlet pipeline; and The effluent zone is equipped with a gas collecting component for collecting the reaction gases, and the gas collecting component is connected to an external waste gas treatment system.

7. The fixed-bed Fenton reactor according to claim 6, characterized in that, The outlet of the water inlet pipe is connected to multiple nozzles arranged tangentially and obliquely relative to the inner wall of the shell via a distribution pipe, which are used to form a swirling flow in the water mixing zone. The nozzles are installed at an angle of 30 to 45°, and there are 2, 4 or 8 of them. Each nozzle is arranged at equal intervals along the circumference of the shell and is staggered in phase.

8. The fixed-bed Fenton reactor according to claim 6, characterized in that, The water outlet area includes a water outlet trough fixed around the inner wall of the shell and a water outlet weir located above the water outlet trough on the side away from the inner wall of the shell. The water outlet trough is connected to an external water outlet pipeline through a water outlet, and the water outlet weir is a triangular weir or a trapezoidal weir.

9. The fixed-bed Fenton reactor according to claim 6, characterized in that, The gas collection component is an inverted trumpet-shaped gas collection hood, located above the catalyst packing area and connected to the waste gas treatment system through the waste gas emission port.

10. The fixed-bed Fenton reactor according to claim 6, characterized in that, An acid dosing port and an online pH monitoring unit for the influent are installed on the side of the influent mixing zone, connected to this zone; an online COD monitoring unit for the influent is installed on the influent pipeline; online pH and ORP monitoring units for the effluent are installed in the effluent zone, and an online COD monitoring unit for the effluent is installed on the effluent pipeline; and... The aforementioned online monitoring components are electrically connected to their respective actuators to form interlocking controls, including: influent COD and H2O2 dosing interlock, influent pH and acid dosing interlock, and effluent COD and effluent valve interlock.

11. The fixed-bed Fenton reactor according to claim 6, characterized in that, It also includes a backwash circuit that uses the effluent from the reaction device as a water source; the circuit includes: a backwash water pump connected to the effluent tank, a backwash water inlet located at the bottom of the shell, and a backwash water outlet tank located in the effluent area and below the effluent tank, fixed around the inner wall of the shell, wherein the backwash water outlet tank is provided with a backwash water discharge port.

12. The fixed-bed Fenton reactor according to claim 6, characterized in that, The catalyst packing zone is supported by a water distribution baffle, and the catalyst filling rate is 50-70% of the total volume of the reaction device.

13. The fixed-bed Fenton reactor according to claim 6, characterized in that, Multiple reaction units are connected in parallel so that when a single unit is backwashed or shut down, the other units can maintain continuous water intake.

14. A fixed-bed Fenton pretreatment method, characterized in that, The reaction apparatus according to any one of claims 6 to 13 is used to treat high-salt or high-chlorine recalcitrant organic wastewater, comprising the following steps: After the influent and hydrogen peroxide are mixed in the pipeline mixer, they are divided into multiple streams and enter the influent mixing zone through nozzles to form a swirling flow. The mixture is evenly distributed with water to allow it to enter the catalyst packing zone for contact reaction. The treated water is discharged from the effluent area; during the reaction process, the waste gas is collected by the gas collection component and sent to the waste gas treatment system. Water that fails to meet standards is returned to the inlet for further treatment.

15. The fixed-bed Fenton pretreatment method according to claim 14, characterized in that, Includes one or more of the following processing conditions: The H2O2 dosage should be controlled at 1 to 1.5 times the COD of the influent; The catalyst contact time is 30–60 min; The pH in the influent mixing zone is 5-7, the pH in the effluent is 6-8, the effluent ORP is 200-300mV, and the residence time in the reaction device is 1-2 hours. Backwashing should be performed every 3 to 4 months, with a backwashing intensity of 10 to 15 L / m²·s and a backwashing time of 15 to 20 minutes.

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