Nitrate-nitrogen-containing wastewater treatment method and device combined with catalyst regeneration

Abstract

The invention belongs to the technical field of waste catalyst regeneration and wastewater treatment, and discloses a nitrate-nitrogen-containing wastewater treatment method combined with catalyst regeneration, and the method comprises the following steps: S1, catalyst preparation: dipping and adding a metal precursor on a carrier, drying, and calcining to obtain a catalyst; s2, H2S purification: the catalyst is used for purification treatment of coal gas, and the catalyst is inactivated after being used; s3, filler preparation: inputting the deactivated catalyst into a filler preparation unit, and mixing the deactivated catalyst with the biological liquid and the wastewater to prepare the sulfur autotrophic denitrification filler; s4, wastewater treatment: inputting the sulfur autotrophic denitrification filler into a wastewater treatment unit, treating nitrate-nitrogen-containing wastewater, and performing biological membrane separation on the used filler; and S5, regenerating the catalyst: enabling the deactivated catalyst obtained by separating the biological membrane to enter a regeneration unit, regenerating the deactivated catalyst into the catalyst, and circularly repeating the steps S2-S5. According to the method, waste elemental sulfur can be recycled, and the economic performance of the sulfur autotrophic denitrification process is improved.

Description

Technical Field

[0001] This invention belongs to the field of waste catalyst regeneration and wastewater treatment technology, specifically, it relates to a method and apparatus for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration. Background Technology

[0002] H2S is a major component of odorous gases and is highly toxic. It mainly originates from waste gas from crude oil refining, natural gas industry, coal chemical industry, and steel industry. Currently, the Claus process is commonly used for desulfurization of various H2S-containing pollutants, but this process can only recover about 95% of the sulfur content. The low concentration of H2S in the Claus process tail gas requires efficient treatment. Selective catalytic oxidation technology using Fe-based catalysts can achieve H2S removal and recovery; however, the deactivation of Fe-based catalysts leads to high catalyst consumption and cost, frequent catalyst replacements, and the generation of hazardous waste. Currently, high-temperature heating oxidation is commonly used to oxidize the elemental sulfur deposited on the surface of the deactivated catalyst to sulfur dioxide, thereby restoring catalyst activity. However, high-temperature heating generates high energy consumption and the released SO2 causes secondary environmental pollution. Achieving low-energy catalyst regeneration and recycling can significantly improve the economic and environmental performance of this process.

[0003] For the treatment of nitrate-containing wastewater from industrial plants, sulfur autotrophic denitrification technology has significant advantages over traditional heterotrophic denitrification technology, requiring no carbon source and producing low sludge content. However, the sulfur autotrophic denitrification packing material is a significant cost component, resulting in high wastewater treatment costs. Utilizing waste resources to produce sulfur autotrophic denitrification packing material is an important means to further improve the economic and environmental benefits of sulfur autotrophic denitrification technology. Furthermore, the sulfur autotrophic denitrification process is affected by pH decreases and NO2... - Accumulation leads to a deterioration in process performance, hindering the preparation of self-regulating pH and adaptive NO2. - Sulfur-autotrophic denitrification packing is an important means to improve the process operation effect.

[0004] Patent document CN1 16173924A discloses a method for preparing and regenerating a bimetallic Fe-Cu-BTC desulfurizer. This invention uses ferric nitrate, copper nitrate and trimesic acid as raw materials to prepare a bimetallic Fe-Cu-BTC desulfurizer in a one-step hydrothermal method for selective catalytic oxidation of H2S. For deactivated catalysts, heating oxidation is mainly used to oxidize the elemental sulfur on the catalyst surface into SO2 to regenerate the catalyst. However, this process generates SO2, which forms secondary pollutants, and requires a heating device, resulting in high energy consumption.

[0005] Patent document CN1 15925111A discloses a sulfur-autotrophic denitrification slow-release composite filler, its preparation method, and its application. This invention involves mixing and grinding sulfur powder, zinc carbonate powder, activated magnesium oxide powder, and clay in a specific ratio, then granulating them with a sodium alginate aqueous solution, and finally drying them under vacuum to obtain the target product. The filler preparation involves many components, is costly, requires a vacuum environment, and is complex to operate.

[0006] Patent document CN116903137A discloses a sulfur-autotrophic denitrification packing material and its preparation method. This invention uses sulfur powder, siderite powder, thiosulfate, activated clay, propylene glycol alginate, binder, volatile agent, hydrogen sulfide removal agent, neutralizing agent, digesting agent, and denitrifying thiobacillus to prepare the sulfur-autotrophic denitrification packing material. The packing material preparation involves many components, resulting in high cost, and the obtained packing material lacks the ability to control the process pH and resist NO2. - The ability to accumulate. Summary of the Invention

[0007] The high energy consumption of selective catalytic oxidation (SCO) catalysts for H2S-containing flue gas leads to increased costs due to catalyst regeneration, and the catalyst regeneration operation is complex. Furthermore, the high cost of preparing sulfur-autotrophic denitrification packing material required for the deep treatment of nitrate-containing wastewater exacerbates the problem of pollutant removal costs. The purpose of this invention is to provide a method and apparatus for treating nitrate-containing wastewater with combined catalyst regeneration. This method utilizes deactivated catalysts and uses waste Fe-based catalysts as self-regulating pH and adaptive NO2 catalysts. - The sulfur autotrophic denitrification packing material can treat wastewater containing nitrate and nitrogen, while simultaneously regenerating and reusing the catalyst, reducing the energy consumption of catalyst regeneration, and achieving synergistic treatment of pollutants. This can improve the economic and environmental performance of H2S selective catalytic oxidation and sulfur autotrophic denitrification processes.

[0008] A first aspect of the present invention provides a method for treating nitrate-containing nitrogen wastewater using a combined catalyst regeneration method, the method comprising the following steps:

[0009] S1. Catalyst preparation: A metal precursor is impregnated onto a support, then dried and calcined to obtain the catalyst;

[0010] S2 and H2S purification: The catalyst is used for the purification of coal gas, and the catalyst is deactivated after use;

[0011] S3. Packing material preparation: The deactivated catalyst is fed into the packing material preparation unit and mixed with biological liquid and wastewater to produce sulfur autotrophic denitrification packing material;

[0012] S4. Wastewater treatment: The sulfur autotrophic denitrification packing is fed into the wastewater treatment unit to treat the nitrate-nitrogen-containing wastewater. The used packing is subjected to biofilm separation, and the obtained biofilm is made into a biological liquid and returned to the packing preparation unit.

[0013] S5. Catalyst regeneration: The deactivated catalyst obtained from biofilm separation enters the regeneration unit and is regenerated into a catalyst. Steps S2-S5 are repeated in a cycle.

[0014] A second aspect of the present invention provides a nitrogen-containing wastewater treatment device with combined catalyst regeneration used in the above-described method. The device includes: a catalyst preparation unit, a desulfurization tower, a packing preparation unit, a wastewater treatment unit, and a catalyst regeneration unit. The wastewater treatment unit is provided with a wastewater treatment pond and a biological liquid preparation unit.

[0015] The catalyst preparation unit is connected to the desulfurization tower. The catalyst recovery pipe of the desulfurization tower is connected to the packing preparation unit. The packing preparation unit is connected to the wastewater treatment pond through the packing conveying pipe. The packing outlet of the wastewater treatment pond is connected to the biological liquid preparation unit. The biological liquid preparation unit is connected to the packing preparation unit through the biological reflux pipe. The deactivated catalyst outlet of the biological liquid preparation unit is connected to the catalyst regeneration unit. The catalyst outlet of the catalyst regeneration unit is connected to the desulfurization tower.

[0016] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0017] 1. Achieve low-energy regeneration of H2S selective catalytic oxidation catalyst, avoid high-temperature processes, and simplify process operation;

[0018] 2. Utilize waste elemental sulfur to improve the economic performance of sulfur autotrophic denitrification process and achieve self-regulating pH and adaptive NO2. - Sulfur autotrophic denitrification packing for wastewater;

[0019] 3. Achieve waste-to-waste treatment, reuse waste catalysts, and improve the environmental performance of the process;

[0020] 4. Innovate the equipment structure to improve the selective catalytic oxidation performance after catalyst regeneration and enhance the process operation efficiency.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the nitrogen-containing wastewater treatment device with combined catalyst regeneration according to the present invention.

[0023] Figure 2 This is a schematic diagram of the wastewater treatment unit of the present invention.

[0024] Figure 3 This is a schematic diagram of the biological liquid preparation unit in the wastewater treatment unit of the present invention.

[0025] Figure 4 This is a schematic diagram of the flow guide plate in the wastewater treatment unit of the present invention.

[0026] Figure 5 This is a comparison chart showing the treatment capacity of the packing materials prepared in Example 1 and Comparative Example 4 of the present invention for simulated wastewater No. 1.

[0027] Figure 6 This is a comparison chart showing the treatment capacity of the packing materials prepared in Example 1 and Comparative Example 4 of the present invention for simulated wastewater No. 2.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Catalyst preparation unit, 2. Catalyst conveying pipe, 3. Desulfurization tower, 4. Flue gas inlet, 5. Flue gas outlet, 6. Catalyst recovery pipe, 7. Packing material preparation unit, 8. Packing material conveying pipe, 9. Wastewater treatment unit, 10. Biological reflux pipe, 11. Packing material recovery pipe, 12. Packing material discharge pipe, 13. Catalyst regeneration conveying pipe, 14. Catalyst regeneration unit, 15. Regenerated catalyst conveying pipe;

[0030] 9-1. Packing material inlet; 9-2. Wastewater outlet; 9-3. Wastewater treatment tank; 9-4. Baffle plate; 9-5. Packing material conveying screw; 9-6. Packing material output channel; 9-7. Packing material output screw; 9-8. Wastewater inlet; 9-9. Packing material outlet; 9-10. Biological liquid preparation unit; 9-10-1. Packing material input channel; 9-10-2. Biological separation channel; 9-10-3. Ultrasonic generator; 9-10-4. Packing material output channel; 9-10-5. Elastic limiter;

[0031] A. Guide vane, A-1. Conveying section, A-2. Drop section, α. Inclination angle. Detailed Implementation

[0032] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0033] According to a first aspect of the present invention, the present invention provides a method for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration, the method comprising the following steps:

[0034] S1. Catalyst preparation: A metal precursor is impregnated onto a support, then dried and calcined to obtain the catalyst;

[0035] S2 and H2S purification: The catalyst is used for the purification of coal gas, and the catalyst is deactivated after use;

[0036] S3. Packing material preparation: The deactivated catalyst is fed into the packing material preparation unit and mixed with biological liquid and wastewater to produce sulfur autotrophic denitrification packing material;

[0037] S4. Wastewater treatment: The sulfur autotrophic denitrification packing is fed into the wastewater treatment unit to treat the nitrate-nitrogen-containing wastewater. The used packing is subjected to biofilm separation, and the obtained biofilm is made into a biological liquid and returned to the packing preparation unit.

[0038] S5. Catalyst regeneration: The deactivated catalyst obtained from biofilm separation enters the regeneration unit and is regenerated into a catalyst. Steps S2-S5 are repeated in a cycle.

[0039] The catalyst used in this invention is a conventional catalyst for H2S purification, such as an Fe-based catalyst. The catalyst is prepared using conventional materials and methods.

[0040] According to the present invention, in step S1, the calcination conditions may include: the calcination atmosphere being a weakly reducing gas such as air, nitrogen, or helium; the calcination temperature being 200-1100℃, preferably 500-800℃; and the calcination time being 1-12h, preferably 2-5h.

[0041] In step S2 of the present invention, the feed space velocity can be 500-15000 mL / (g·h), preferably 3000-5000 mL / (g·h).

[0042] According to the present invention, in step S3, the flow rate of the wastewater can be 0-10 L / h, preferably 2-4 L / h, and the wastewater is the wastewater treated by the sulfur autotrophic denitrification packing. The residence time of the deactivated catalyst in the packing preparation unit can be 1-100 h, preferably 24-36 h.

[0043] In step S4 of this invention, the residence time of wastewater in the wastewater treatment unit can be 1-10 hours, preferably 4-6 hours. The residence time of the packing material in the wastewater treatment unit can be 1-10 days, preferably 3-4 days. The reflux rate of the biological liquid can be 0-10 L / h, preferably 2-4 L / h.

[0044] According to the present invention, in step S5, within the regeneration unit, the deactivated catalyst is regenerated by exchanging heat with coal gas and then spraying with Na2CO3 solution. The temperature of the deactivated catalyst after heat exchange can be 51-122℃, preferably 85-101℃. The mass ratio of Na2CO3 to the mass of the deactivated catalyst in the Na2CO3 solution is 1:(200-5000), preferably 1:(1500-2000).

[0045] In this invention, the catalyst can have a lifespan of 1-100 cycles, preferably 20-40 cycles.

[0046] According to a second aspect of the present invention, the present invention provides a nitrogen-containing wastewater treatment device with combined catalyst regeneration used in the above-described method, the device comprising: a catalyst preparation unit, a desulfurization tower, a packing preparation unit, a wastewater treatment unit and a catalyst regeneration unit, wherein the wastewater treatment unit is provided with a wastewater treatment pond and a biological liquid preparation unit;

[0047] The catalyst preparation unit is connected to the desulfurization tower. The catalyst recovery pipe of the desulfurization tower is connected to the packing preparation unit. The packing preparation unit is connected to the wastewater treatment pond through the packing conveying pipe. The packing outlet of the wastewater treatment pond is connected to the biological liquid preparation unit. The biological liquid preparation unit is connected to the packing preparation unit through the biological reflux pipe. The deactivated catalyst outlet of the biological liquid preparation unit is connected to the catalyst regeneration unit. The catalyst outlet of the catalyst regeneration unit is connected to the desulfurization tower.

[0048] In this invention, the wastewater treatment tank is equipped with a guide plate, and adjacent guide plates are respectively arranged on the opposite side walls of the wastewater treatment tank, so that the material flows in an "S" shape.

[0049] Preferably, the upper surface of the guide vane is stepped, having a conveying section and a drop section. The guide vane is inclined, and the angle between the conveying section and the horizontal plane, and the angle between the drop section and the vertical plane, constitute the inclination angle of the guide vane. The inclination angle is 1-45°, more preferably 15-20°. The number of guide vanes is affected by the inclination angle; the larger the inclination angle, the fewer guide vanes can be installed.

[0050] According to the present invention, the biofluid preparation unit includes a biofilm separation device, which is provided with a bioseparation channel and an ultrasonic generator.

[0051] Preferably, the biofilm separation device includes guide columns, forming a bioseparation channel between the guide columns and between the guide columns and the inner wall of the biofilm separation device. The bioseparation channel is wavy along the material flow direction, and an ultrasonic generator is installed on the guide columns. During the descent of the packing material into the bioseparation channel, it is continuously squeezed and vibrated by the channel wall, causing the biofilm on the surface of the packing material to detach.

[0052] The bioseparation channel of the present invention can be of any size as required. Preferably, the diameter of the bioseparation channel is 1.05-1.15 times the average diameter of the packing material.

[0053] More preferably, the guide columns are connected to each other and to the inner wall of the biofilm separation device by elastic limiters. The elastic limiters restrict the degree of compression of the channel by vibration, thus protecting the packing particles.

[0054] The substances, parameters, and devices not limited in this invention can be selected according to existing technology and are conventional technical means in this field.

[0055] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0056] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0057] Example 1

[0058] use Figure 1-4 The device shown treats coal gas and wastewater. The coal gas has an H2S concentration of 2658 mg / L and a temperature of 136℃. The wastewater contains NO3. - The content is 42 mg / L, NO2 - The concentration is 3 mg / L, and the pH is 7.6;

[0059] S1: Catalyst Preparation

[0060] In P 25 - 2wt% Fe(NO3)3·9H2O was added to the TiO2 support as a metal precursor, impregnated and mixed, and then evaporated and dried. The dried material was calcined at 600℃ in N2 atmosphere for 4h and then naturally cooled to obtain H2S selective catalytic oxidation catalyst.

[0061] S2: H2S purification

[0062] The processed gas is 5m 3 A flow rate of 50 g / h enters the desulfurization tower 3 through the flue gas inlet 4, moves upward, and exits through the flue gas outlet 5. The prepared catalyst and the resource-recycling catalyst enter the upper part of the desulfurization tower through the catalyst delivery pipe 2 and the regenerated catalyst delivery pipe 15 at a total flow rate of 50 g / h. The coal gas being treated in the desulfurization tower comes into countercurrent contact with the catalyst, achieving selective catalytic oxidation of H2S in the coal gas to form sulfur. The catalyst in the desulfurization tower is kept present in the tower by controlling the inflow and outflow rates, forming a fixed bed at the bottom of the desulfurization tower for selective catalytic oxidation of H2S. The space velocity is maintained at 5000 mL / (g·h). After the process cycle stabilizes, the H2S content in the coal gas discharged from the flue gas outlet is 103 mg / L, and the desulfurization rate is 96.12%. During the purification process, elemental sulfur is deposited on the catalyst surface, resulting in a decrease in catalytic activity. The catalyst after the reaction is discharged from the desulfurization tower through the catalyst recovery pipe 6 and enters the packing preparation unit 7. The average deposition amount of elemental sulfur on the catalyst is about 83.5 mg S / g catalyst (surface S). 0 and HS - sum);

[0063] S3: Packing material preparation

[0064] The reacted catalyst is mixed with biological liquid at a flow rate of 2 L / h and treated wastewater at a flow rate of 2 L / h from biological return pipe 10 in the packing preparation unit 7, with a residence time of 24 h, to form sulfur autotrophic denitrification packing.

[0065] S4: Wastewater Treatment

[0066] The prepared sulfur-autotrophic denitrification packing material is fed into the wastewater treatment unit 9 through the packing material delivery pipe 8. The wastewater to be treated is fed into the wastewater treatment unit at a flow rate of 36 L / h, with a wastewater retention time of 4 h and a packing material retention time of 3 d. The structure of the wastewater treatment unit is as follows: Figure 2 and Figure 3 As shown, the packing material enters the wastewater treatment tank 9-3 through the packing inlet 9-1. Guided by the baffle plate 9-4, it moves in an "S" shaped path by gravity to the bottom of the wastewater treatment tank. It is then conveyed to the packing output channel 9-6 by the bottom packing conveying screw 9-5, and further conveyed to the packing outlet 9-9 by the vertically upward packing output screw 9-7, entering the biological liquid preparation unit 9-10. Wastewater enters the packing conveying channel through the wastewater inlet 9-8, and then, after being guided by the baffle plate within the wastewater treatment tank, moves upward in an "S" shaped path, contacting the packing material counter-currently to achieve denitrification. It then overflows and is discharged through the wastewater outlet 9-2. The baffle plate 9-4 is a stepped baffle plate (taking the left baffle plate as an example). Figure 4 As shown, the material first contacts the guide plate from the left side and moves along the conveying section A-1. When it reaches the falling section A-2, it will undergo a rolling and falling process, realizing the rotation of the packing and releasing the N2 generated on the surface of the packing due to the sulfur autotrophic denitrification process. When the guide plate is set, the angle between the conveying section and the horizontal plane is α, and the angle between the falling section and the vertical plane is also maintained at α. α is defined as the tilt angle of the guide plate. In this embodiment, the tilt angle of the guide plate is 15°. The number of guide plates is affected by the tilt angle. The larger the tilt angle of the guide plate, the fewer guide plates can be installed. The packing material entering the bio-liquid preparation unit 9-10 first enters the packing input channel 9-10-1, and after passing through a branch path, enters the bio-separation channel 9-10-2. This channel has a wavy, downward-facing shape, and its diameter is 1.05-1.15 times the average diameter of the packing material. Under the action of the ultrasonic generator 9-10-3, ultrasonic vibration is generated, causing the packing material to be continuously squeezed and vibrated by the channel as it falls within the bio-separation channel. This causes the biofilm on the packing surface to detach. During this process, the elastic limiter 9-10-5 limits the degree of compression of the channel by the vibration, thus protecting the packing particles. After passing through the bio-separation channel, the packing material and the detached biofilm are discharged through the packing output channel 9-10-4. The packing material is then transported to the subsequent packing recovery pipe 11. The biofilm is continuously mixed with treated wastewater at a flow rate of 2 L / h to produce bio-liquid, which is then returned to the packing preparation unit. After the process cycle stabilizes, NO3- is discharged from the wastewater treatment unit 9. -The content is 3 mg / L, NO2 - The content was 0 mg / L, the pH was 7.3, and the denitrification rate was 93.3%.

[0067] S5: Catalyst Regeneration

[0068] The packing material is discharged from the wastewater treatment unit through the packing material recovery pipe. Part of the packing material is sent to the resource recovery unit through the packing material discharge pipe 12 at a flow rate of 1.5 g / h to recover TiO2 in the packing material. The remaining packing material is sent to the catalyst regeneration unit 14 through the catalyst regeneration conveying pipe 13 at a flow rate of 48.5 g / h. In the catalyst regeneration unit, the packing material exchanges heat with the treated coal gas at a flow rate of 6 L / h. After heat exchange, the temperature of the packing material reaches 92℃. At the same time, a Na2CO3 solution (0.2 g / L) of 0.15 L / h is sprayed to regenerate the catalyst. The catalyst at the end of the regeneration is sent back to the desulfurization tower 3 through the regenerated catalyst conveying pipe 15 for reuse. The catalyst is circulated in the desulfurization tower, the packing material preparation unit, the wastewater treatment unit, and the catalyst regeneration unit to improve the catalyst utilization rate. The average catalyst utilization rate can reach 33 cycles.

[0069] Example 2

[0070] use Figure 1-4 The device shown treats coal gas and wastewater. The coal gas has an H2S concentration of 1726 mg / L and a temperature of 122°C. The wastewater contains NO3. - The content is 28 mg / L, NO2 - The concentration was 21 mg / L, and the pH was 8.1.

[0071] S1: Catalyst Preparation

[0072] In P 25 - 2wt% FeCl3·6H2O was added to the TiO2 support as a metal precursor, impregnated and mixed, and then evaporated and dried. The dried material was calcined at 500℃ in N2 atmosphere for 3h and then naturally cooled to obtain the H2S selective catalytic oxidation catalyst.

[0073] S2: H2S purification

[0074] The processed gas is in 10m³ 3A flow rate of 80 g / h enters the desulfurization tower 3 through the flue gas inlet 4, moves upward, and exits through the flue gas outlet 5. The prepared catalyst and the resource-recycling catalyst enter the upper part of the desulfurization tower through the catalyst delivery pipe 2 and the regenerated catalyst delivery pipe 15 at a total flow rate of 80 g / h. The coal gas being treated in the desulfurization tower comes into countercurrent contact with the catalyst, achieving selective catalytic oxidation of H2S in the coal gas to form sulfur. The catalyst in the desulfurization tower is kept present in the tower by controlling the inflow and outflow rates, forming a fixed bed at the bottom of the desulfurization tower for selective catalytic oxidation of H2S. The space velocity is maintained at 3000 mL / (g·h). The H2S content in the coal gas discharged from the flue gas outlet is 48 mg / L, and the desulfurization rate is 97.2%. During the purification process, elemental sulfur is deposited on the catalyst surface, resulting in a decrease in catalytic activity. The catalyst after the reaction is discharged from the desulfurization tower through the catalyst recovery pipe 6 and enters the packing preparation unit 7. The average deposition amount of elemental sulfur on the catalyst is 73.3 mg S / g catalyst (surface S). 0 and HS - sum);

[0075] S3: Packing material preparation

[0076] The reacted catalyst is mixed with biological liquid at a flow rate of 4 L / h and treated wastewater at a flow rate of 3 L / h from biological return pipe 10 in the packing preparation unit 7, with a residence time of 24 h, to form sulfur autotrophic denitrification packing.

[0077] S4: Wastewater Treatment

[0078] The prepared sulfur-autotrophic denitrification packing material is fed into the wastewater treatment unit 9 through the packing material delivery pipe 8. The wastewater to be treated is fed into the wastewater treatment unit at a flow rate of 46 L / h, with a wastewater retention time of 5 h and a packing material retention time of 3 days. The structure of the wastewater treatment unit is as follows: Figure 2 and Figure 3As shown, the packing material enters the wastewater treatment tank 9-3 through the packing inlet 9-1. Guided by the baffle plate 9-4, it moves in an "S" shaped path by gravity to the bottom of the wastewater treatment tank. It is then conveyed to the packing output channel 9-6 by the bottom packing conveying screw 9-5, and further conveyed to the packing outlet 9-9 by the vertically upward packing output screw 9-7, entering the biological liquid preparation unit 9-10. Wastewater enters the packing conveying channel through the wastewater inlet 9-8, and then moves upward in an "S" shaped path within the wastewater treatment tank after being guided by the baffle plate, contacting the packing material counter-currently to achieve denitrification. It then overflows and is discharged through the wastewater outlet 9-2. The baffle plate 9-4 is a stepped baffle plate. The material moves along the conveying section A-1 and rolls and falls when it reaches the falling section A-2. The inclination angle of the baffle plate is 15°. The number of baffle plates is affected by the inclination angle; the larger the inclination angle, the fewer baffle plates can be installed. The packing material entering the bio-liquid preparation unit 9-10 first enters the packing input channel 9-10-1, and after passing through a branch path, enters the bio-separation channel 9-10-2. This channel has a wavy, downward-facing shape, and its diameter is 1.05-1.15 times the average diameter of the packing material. Under the action of the ultrasonic generator 9-10-3, ultrasonic vibration is generated, causing the packing material to be continuously squeezed and vibrated by the channel as it falls within the bio-separation channel. This causes the biofilm on the packing surface to detach. During this process, the elastic limiter 9-10-5 limits the degree of compression of the channel by the vibration, thus protecting the packing particles. After passing through the bio-separation channel, the packing material and the detached biofilm are discharged through the packing output channel 9-10-4. The packing material is then transported to the subsequent packing recovery pipe 11. The biofilm is continuously mixed with treated wastewater at a flow rate of 2 L / h to produce bio-liquid, which is then returned to the packing preparation unit. After the process cycle stabilizes, NO3- is discharged from the wastewater treatment unit 9. - The content is 2 mg / L, NO2 - The concentration was 2 mg / L, the pH was 7.5, and the denitrification rate was 91.8%.

[0079] S5: Catalyst Regeneration

[0080] The packing material is discharged from the wastewater treatment unit through the packing material recovery pipe. Part of the packing material is sent to the resource recovery unit through the packing material discharge pipe 12 at a flow rate of 2 g / h to recover TiO2 in the packing material. The remaining packing material is sent to the catalyst regeneration unit 14 through the catalyst regeneration conveying pipe 13 at a flow rate of 78 g / h. In the catalyst regeneration unit, the packing material exchanges heat with the treated coal gas at a flow rate of 13 L / h. After heat exchange, the temperature of the packing material reaches 96℃. At the same time, a Na2CO3 solution (0.1 g / L) of 0.4 L / h is sprayed to regenerate the catalyst. The catalyst at the end of the regeneration is sent back to the desulfurization tower through the regenerated catalyst conveying pipe 15 for reuse. The catalyst is circulated in the desulfurization tower, the packing material preparation unit, the wastewater treatment unit, and the catalyst regeneration unit to improve the catalyst utilization rate. The average catalyst utilization rate can reach 40 cycles.

[0081] Examples A1-A10

[0082] Using the apparatus and operating parameters of Example 1, the amount of catalyst inside the desulfurization tower was adjusted during process S2, thereby controlling the gas space velocity of the coal gas treated on the catalyst surface. The desulfurization rate of the coal gas, the sulfur content deposited on the catalyst surface, and the denitrification rate of the wastewater in the corresponding process are shown in Table 1.

[0083] Table 1

[0084] serial number <![CDATA[Air velocity / mL·g -1 h -1 > Desulfurization rate / % <![CDATA[Sulfur deposition content / mg S·g -1 Catalyst]]> Denitrification rate / % Example 1 5000 96.1 83.5 93.3 Example A1 4000 96.5 76.5 91.8 Example A2 3000 96.8 68.3 90.3 Example A3 2000 97.1 57.4 88.2 Example A4 1000 97.5 43.2 83.3 Example A5 500 98.0 32.1 78.9 Example A6 6000 94.2 84.7 93.5 Example A7 7000 92.1 86.5 93.7 Example A8 8000 89.3 88.1 93.8 Example A9 9000 86.6 89.5 93.9 Example A10 10000 82.3 90.3 94.1 Example A11 15000 71.6 91.2 94.2

[0085] Comparison reveals that changes in the catalyst content at the bottom of the desulfurization tower alter the space velocity of the gas treated on the catalyst surface, affecting the desulfurization rate of the gas and the sulfur deposition content on the catalyst surface within the tower, ultimately impacting the nitrogen removal rate of the wastewater. When the space velocity is between 3000-5000 mL·g... -1 h -1 The process of this invention operates best within the specified range, with the space velocity below 3000 mL·g. -1 h -1 When the amount of coal gas processed per unit catalyst is low, the desulfurization rate of the coal gas will be increased, but the sulfur deposition content on the catalyst surface will decrease, resulting in insufficient sulfur source for the downstream wastewater denitrification process, thus leading to a decrease in the denitrification rate, which is below 90%. When the space velocity is higher than 5000 mL·g -1 h -1 At that time, the amount of coal gas processed by a unit catalyst increases, which leads to faster catalyst deactivation and a decrease in the desulfurization rate of coal gas, below 95%.

[0086] Examples B1-B25

[0087] Using the apparatus and operating parameters described in Example 1, the biological liquid reflux rate, wastewater flow rate, and catalyst residence time in the biological reflux pipe inside the packing preparation unit were adjusted during the packing preparation process. The corresponding wastewater denitrification rates are shown in Table 2.

[0088] Table 2

[0089]

[0090]

[0091] Comparing Examples 1 and B1-B7, it can be found that the biological liquid return flow rate affects the denitrification rate of the wastewater by the process of the present invention. When the biological liquid return flow rate is in the range of 2-4 L / h, the denitrification rate of the wastewater is relatively high. When the biological liquid return flow rate is less than 2 L / h, the biological liquid has poor fluidity before being transported to the packing preparation unit, and the biomass carried decreases, resulting in poor surface bioaccumulation effect during packing preparation. When the biological liquid return flow rate is greater than 4 L / h, the degree of biological dispersion in the packing preparation unit is high, and the contact efficiency between the packing surface and the biological decreases, resulting in poor biological deposition and enrichment effect on the packing surface.

[0092] Comparing Examples 1 and B8-B14, it can be found that when the wastewater flow rate is in the range of 2-4 L / h, the prepared packing material has a good denitrification effect on the wastewater. When the wastewater flow rate is less than 2 L / h, the nitrate nitrogen content is insufficient during the packing material preparation process, which limits the growth and reproduction of microorganisms on the packing material surface. When the wastewater flow rate is higher than 4 L / h, the biodispersion in the packing material preparation unit is high, the contact efficiency between the packing material surface and the organism decreases, resulting in poor biodeposition and enrichment effect on the packing material surface.

[0093] Comparing Examples 1 and B15-B25, it can be found that the catalyst residence time in the packing preparation unit affects the denitrification efficiency of the process for wastewater. When the catalyst residence time is in the range of 24-36h, the process operation effect is better. When the catalyst residence time is less than 24h, the biofilm formation effect on the packing surface is poor, and the initial denitrification activity is low when entering the wastewater treatment unit. When the catalyst residence time is greater than 36h, the biofilm on the surface of the packing will age and fall off in the later stage of the residence time in the wastewater treatment unit, resulting in a decrease in the wastewater treatment effect.

[0094] Examples C1-C9, Comparative Example 1

[0095] Using the device and operating parameters in Example 1, the tilt angle of the guide plate inside the wastewater treatment device was adjusted during process S4, and the corresponding wastewater denitrification rate results are shown in Table 3.

[0096] Table 3

[0097] serial number Tilt angle / ° Denitrification rate / % Example 1 15 93.3 Example C1 10 90.5 Example C2 5 88.6 Example C3 1 83.2 Example C4 20 93.1 Example C5 25 91.6 Example C6 30 90.2 Example C7 35 87.3 Example C8 40 82.8 Example C9 45 78.6 Comparative Example 1 No deflector 62.6

[0098] Comparing Examples 1 and C1-C9 reveals that the tilt angle of the guide plates designed within the wastewater treatment device significantly affects the denitrification effect of the device and process. When the tilt angle is within the range of 15-20°, the denitrification efficiency exceeds 90%. The main function of the guide plates is to significantly improve the contact efficiency between the packing material and the wastewater, enhance the mass transfer process, and promote the packing material's rolling motion along the guide plates under its own weight. This prevents N2 generated during the sulfur autotrophic denitrification process from blocking the packing surface and affecting the mass transfer contact between the packing material and nitrate nitrogen. When the tilt angle of the guide plates is less than 15°, the packing material's movement changes from rolling to pushing, reducing the nitrogen removal effect. When the tilt angle of the guide plates is greater than 20°, the number of guide plates decreases, the contact efficiency between the packing material and the wastewater decreases, resulting in a reduction in the wastewater treatment effect.

[0099] Comparing Example 1 and Comparative Example 1, it can be found that without the guide plate, nitrogen removal by the packing is difficult to achieve, and the contact efficiency between the packing and the wastewater decreases, resulting in a significant reduction in the denitrification efficiency of the wastewater. This proves the effectiveness of the stepped guide plate (such as...) installed in the device of the present invention. Figure 4 As shown, the use of the sulfur autotrophic denitrification packing material prepared by the resource recycling of waste catalysts in this invention has a significant promoting effect.

[0100] Examples D1-D22, Comparative Example 2

[0101] Using the apparatus and operating parameters in Example 2, the gas flow rate in the catalyst regeneration unit during process S5 was adjusted, thereby controlling the temperature of the deactivated catalyst and the ratio of the mass of Na2CO3 sprayed in the catalyst regeneration unit to the mass of the deactivated catalyst. The desulfurization rate of the gas in the desulfurization tower corresponding to different catalyst regeneration conditions and the results of the surface moisture content of the catalyst (the result of the weight comparison before and after drying at 105℃) obtained by sampling at the outlet of the catalyst regeneration unit are shown in Table 4.

[0102] Table 4

[0103]

[0104]

[0105] Comparing Example 2 with Examples D1-D11, it was found that the catalyst surface temperature in the catalyst regeneration unit significantly affects the desulfurization rate of the gas by the device and process of the present invention. Comparing Example 2 with Examples D12-D22, it was found that the mass ratio of Na2CO3 sprayed in the catalyst regeneration unit to the mass of the catalyst also affects the desulfurization rate of the gas.

[0106] The catalyst regeneration temperature mainly affects two aspects: 1. Removing residual biofilm from the catalyst surface at a certain temperature, exposing catalytic active sites for coal gas desulfurization; 2. Maintaining a certain water film on the catalyst surface, which promotes the adsorption of H2S on the catalyst surface during coal gas desulfurization, enhancing mass transfer. When the catalyst surface temperature in the catalyst regeneration unit is within the range of 85-101℃, the process operates well, and the catalytic activity is high after catalyst regeneration. When the catalyst surface temperature is below 85℃, the biofilm on the catalyst surface is not completely removed, and some active sites are covered. A certain amount of time is needed for regeneration to remove the biofilm during coal gas desulfurization, leading to a decrease in desulfurization efficiency. Simultaneously, excessive water content on the catalyst surface covers the active sites, inhibiting O2 adsorption and thus reducing the H2S oxidation process. When the catalyst surface temperature is above 101℃, the water film on the catalyst surface decreases significantly, the water content decreases, and the adsorption and mass transfer efficiency of H2S on the regenerated catalyst surface decreases, resulting in reduced catalytic activity.

[0107] The role of Na2CO3 sprayed during catalyst regeneration is to increase the alkalinity within the water film on the catalyst surface, further promoting the adsorption of H2S on the catalyst surface. When the mass ratio of Na2CO3 to the mass of the regenerated catalyst is within the range of 1:(1500-2000), the process and equipment of this invention operate well, and the catalytic activity of the catalyst after regeneration is high. When the mass ratio of Na2CO3 to the mass of the regenerated catalyst is higher than 1:1500, the Na2CO3 content is high, the alkalinity of the catalyst surface is high, and excessive alkalinity will occupy metal active sites, and excessive alkalinity will excessively promote the adsorption of sulfur on the catalyst surface, accelerating the occurrence of sulfur poisoning of the catalyst. When the mass ratio of Na2CO3 to the mass of the regenerated catalyst is lower than 1:2000, the amount of Na2CO3 added is low, the promoting adsorption effect of the water film on the surface of the regenerated catalyst on H2S decreases, resulting in a decrease in the catalytic activity of the catalyst after regeneration, thereby leading to a decrease in the desulfurization rate in the coal gas.

[0108] Examples E1-E8, Comparative Example 3

[0109] Using the apparatus and operating parameters in Example 2, the flow rate of the packing discharged from the packing discharge pipe during process S5 was adjusted to control the number of times the catalyst circulated in the process unit and flow. The results of the gas desulfurization rate, wastewater denitrification rate and catalyst usage in the process corresponding to different number of cycles are shown in Table 5.

[0110] Table 5

[0111]

[0112]

[0113] Comparing Examples 2 and E1-E8, it can be found that when the catalyst cycle count is within the range of 20-40, the process and apparatus of the present invention have high purification efficiency for coal gas and wastewater, with a desulfurization rate of over 97% and a denitrification rate of over 91%. When the catalyst cycle count exceeds 40 times, the catalyst is used too many times, leading to catalyst aging and reduced regeneration efficiency, resulting in a decrease in both desulfurization and denitrification rates. When the catalyst cycle count is below 20 times, the catalyst consumption is too high, exceeding 100 g / d, reducing the economic efficiency of the process.

[0114] Comparing Example 2 and Comparative Example 3, it can be found that if the catalyst is not recycled in the process, the catalyst consumption is extremely high, resulting in huge economic costs. Although the denitrification efficiency of wastewater is increased to 92.6%, the desulfurization efficiency of coal gas is only 91.3%. This reflects that in the process and apparatus of the present invention, the alkaline water film generated on the catalyst surface by the catalyst regeneration unit has a significant promoting effect on the desulfurization process in coal gas, making the catalyst catalytic activity higher than that of fresh catalyst. This proves that the process flow and process apparatus designed in the present invention achieve resource recycling and efficient regeneration of catalyst, optimize the desulfurization effect of coal gas, and have excellent environmental and economic performance.

[0115] Comparative Example 4

[0116] In addition to enabling low-cost regeneration and resource recovery of sulfur-autotrophic denitrification packing from coal gas desulfurization catalysts, the method and apparatus of this invention optimize the regeneration process while enhancing the selective catalytic oxidation activity of the regenerated catalyst for H2S. Furthermore, during the recycling process, the regenerated catalyst undergoes further deactivation and regeneration to prepare the sulfur-autotrophic denitrification packing, resulting in packing with self-regulating pH and adaptive NO2 properties. - The function was implemented using the operating mode of Example 1, but all the sulfur autotrophic denitrification packing used was a single-use desulfurization catalyst from coal gas (catalyst that had not undergone packing preparation and regeneration). The obtained packing was labeled as packing x, and the packing generated in the circulation process in Example 1 was labeled as packing c. Packing x and packing c were collected separately and tested in different wastewaters. The first simulated wastewater had a pH of 6.5 and NO3 content of 1. - The content is 42 mg / L, NO2 - The concentration was 3 mg / L; the pH of the second simulated wastewater was 7.6, and the NO3 content was... - The content is 105 mg / L, NO2 - The content was 80 mg / L; the treatment effects of filler x and filler c on simulated wastewater No. 1 and simulated wastewater No. 2, respectively, using the same filler quantity, wastewater volume, and reaction device as in Example 1, are as follows: Figure 5-6 As shown.

[0117] Comparison of the treatment results of simulated wastewater No. 1 revealed that, due to the low pH (6.5), which is below the optimal pH range for the sulfur autotrophic denitrification process, the denitrification rate of packing material x after stabilization was less than 50%, while that of packing material c after stabilization reached over 90%. Sampling of wastewater treated by different packing materials showed that, after 20 hours of treatment, the pH of wastewater treated by packing material x was 6.5, indicating that packing material x did not exhibit a self-regulating effect on pH. In contrast, the pH of simulated wastewater No. 1 treated by packing material c obtained during the process and apparatus of this invention was 7.2 after 20 hours of sampling. Characterization of packing material c revealed the presence of a certain amount of Na2CO3 on its surface, which plays a self-regulating role in pH during the sulfur autotrophic denitrification process, thereby ensuring efficient denitrification by microorganisms on the packing material.

[0118] Comparing the results of the second simulated wastewater treatment revealed that the wastewater contained a high concentration of NO2. - It is easy to produce biotoxicity to microorganisms, thus leading to a decrease in biological activity. After stabilization, the denitrification rate of packing material X is less than 40%, while that of packing material C is close to 90%. Tests on samples taken after 20 hours of wastewater treatment revealed that NO3 in the wastewater treated by packing material X was significantly higher than that of packing material C. - The content is 54 mg / L, NO2 - The concentration was 69 mg / L. Sampling tests of the second simulated wastewater treated by packing material c after 20 hours revealed NO3. - The content is 13 mg / L, NO2 - The concentration was 6 mg / L. Characterization of filler c revealed that, in addition to the presence of a large amount of elemental sulfur generated by the selective oxidation of H2S as a raw material for sulfur autotrophic denitrification, the surface alkaline solution also absorbed a portion of free H2S. - It can also be used as a feedstock for sulfur autotrophic denitrification, and it can preferentially react with NO2 in the No. 2 simulated wastewater. - Reaction, avoid NO2 - Accumulation leads to biotoxicity, thus exhibiting adaptive NO2 - The function.

[0119] In summary, the above analysis leads to the conclusion that the process and apparatus of this invention achieve low-cost regeneration of deactivated catalysts while simultaneously producing self-regulating pH and adaptive NO2. - The sulfur-autotrophic denitrification packing material improves the treatment efficiency of wastewater denitrification.

[0120] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for treating nitrate-containing nitrogen wastewater using a combined catalyst regeneration process, characterized in that, The method includes the following steps: S1. Catalyst preparation: A metal precursor is impregnated onto a support, then dried and calcined to obtain the catalyst; S2 and H2S purification: The catalyst is used for the purification of coal gas, and the catalyst is deactivated after use; S3. Packing material preparation: The deactivated catalyst is fed into the packing material preparation unit and mixed with biological liquid and wastewater to produce sulfur autotrophic denitrification packing material; S4. Wastewater treatment: The sulfur autotrophic denitrification packing is fed into the wastewater treatment unit to treat the nitrate-nitrogen-containing wastewater. The used packing is subjected to biofilm separation, and the obtained biofilm is made into a biological liquid and returned to the packing preparation unit. S5. Catalyst regeneration: The deactivated catalyst obtained from biofilm separation enters the regeneration unit and is regenerated into a catalyst. Steps S2-S5 are repeated in a cycle.

2. The method for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration according to claim 1, wherein, In step S1, the calcination conditions include: the calcination atmosphere is air, nitrogen or helium; the calcination temperature is 200-1100℃, preferably 500-800℃; and the calcination time is 1-12h, preferably 2-5h.

3. The method for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration according to claim 1, wherein, In step S2, the feed space velocity is 500-15000 mL / (g·h), preferably 3000-5000 mL / (g·h).

4. The method for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration according to claim 1, wherein, In step S3, the flow rate of the wastewater is 0-10 L / h, preferably 2-4 L / h; the residence time of the deactivated catalyst in the packing preparation unit is 1-100 h, preferably 24-36 h.

5. The method for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration according to claim 1, wherein, In step S4, the residence time of wastewater in the wastewater treatment unit is 1-10 hours, preferably 4-6 hours; the residence time of the packing material in the wastewater treatment unit is 1-10 days, preferably 3-4 days; and the reflux rate of the biological liquid is 0-10 L / h, preferably 2-4 L / h.

6. The method for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration according to claim 1, wherein, In step S5, within the regeneration unit, the deactivated catalyst is regenerated by exchanging heat with coal gas and then spraying Na2CO3 solution; the temperature of the deactivated catalyst after heat exchange is 51-122℃, preferably 85-101℃; the mass ratio of Na2CO3 to the mass of deactivated catalyst in the Na2CO3 solution is 1:(200-5000), preferably 1:(1500-2000).

7. The method for treating nitrate-containing nitrogen wastewater by combined catalyst regeneration according to claim 1, wherein, The catalyst has a service life of 1-100 cycles, preferably 20-40 cycles.

8. The nitrogen-containing wastewater treatment device with combined catalyst regeneration used in the method according to any one of claims 1-7, characterized in that, The device includes: a catalyst preparation unit, a desulfurization tower, a packing preparation unit, a wastewater treatment unit, and a catalyst regeneration unit. The wastewater treatment unit is equipped with a wastewater treatment pond and a biological liquid preparation unit. The catalyst preparation unit is connected to the desulfurization tower. The catalyst recovery pipe of the desulfurization tower is connected to the packing preparation unit. The packing preparation unit is connected to the wastewater treatment pond through the packing conveying pipe. The packing outlet of the wastewater treatment pond is connected to the biological liquid preparation unit. The biological liquid preparation unit is connected to the packing preparation unit through the biological reflux pipe. The deactivated catalyst outlet of the biological liquid preparation unit is connected to the catalyst regeneration unit. The catalyst outlet of the catalyst regeneration unit is connected to the desulfurization tower.

9. The nitrogen-containing wastewater treatment device with combined catalyst regeneration according to claim 8, wherein, The wastewater treatment tank is equipped with a flow guide plate, with adjacent flow guide plates respectively located on opposite side walls of the wastewater treatment tank, so that the material flows in an "S" shape; Preferably, the upper surface of the guide plate is stepped, having a conveying section and a drop section. The guide plate is inclined, and the angle between the conveying section and the horizontal plane and the angle between the drop section and the vertical plane are the inclination angles of the guide plate, which are 1-45°, more preferably 15-20°.

10. The nitrogen-containing wastewater treatment device with combined catalyst regeneration according to claim 8, wherein, The biological fluid preparation unit includes a biofilm separation device, which is equipped with a biological separation channel and an ultrasonic generator. Preferably, the biofilm separation device is provided with guide columns, and a bioseparation channel is formed between the guide columns and between the guide columns and the inner wall of the biofilm separation device. The bioseparation channel is wavy along the material flow direction, and an ultrasonic generator is provided on the guide columns. More preferably, the flow guide columns are connected to each other and to the inner wall of the biofilm separation device by elastic limiters.

Images