A staged acid precipitation process and apparatus for polyurethane wastewater

Abstract

This invention relates to the field of industrial wastewater treatment technology and discloses a segmented acid precipitation process for polyurethane wastewater, comprising the following steps: Acid precipitation reaction step: Polyurethane wastewater is introduced into the acid precipitation reaction zone, and the pH is adjusted to acidic, causing pollutants in the wastewater to precipitate and form initial fine flocs, resulting in a floc-containing mixture; Fluctuation buffer step: The floc-containing mixture is introduced into a fluctuation buffer zone, utilizing the dynamic volume adjustment capability of this zone to smooth influent flow and water quality fluctuations, allowing the mixture to enter subsequent treatment in a relatively stable flow state. This invention no longer relies on traditional filtration equipment to passively trap flocs, but instead constructs a dynamic and controllable floc growth environment through a vortex flocculation and recombination device. In this environment, the fine flocs achieve "self-growth" and "self-settling" through continuous collisions with the dynamic collision medium, fundamentally solving the physical problem of small, difficult-to-settle flocs. This marks a fundamental breakthrough in the concept of solid-liquid separation in acid precipitation.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to a method and apparatus for staged acid precipitation treatment of polyurethane production wastewater with high concentration and large fluctuations in water quality. Background Technology

[0002] Polyurethane materials are widely used in foam plastics, elastomers, coatings, adhesives and other fields due to their excellent properties. During their production, a large amount of high-concentration organic wastewater is generated. Experimental data shows that polyurethane wastewater has typical characteristics of high concentration and strong fluctuations: the chemical oxygen demand (CODcr) fluctuates greatly (37,000–100,000 mg / L), and the total nitrogen also fluctuates significantly (700–2,500 mg / L). These water quality characteristics pose a significant challenge to subsequent treatment.

[0003] For this type of wastewater, acid precipitation is a commonly used pretreatment method. By adding acid to adjust the pH of the wastewater to acidic (usually 2-3), some organic pollutants in the wastewater (such as high molecular weight polymers, emulsified substances, etc.) precipitate out and form flocs due to charge neutralization and decreased solubility, thereby achieving the initial separation and removal of pollutants.

[0004] However, existing acid precipitation treatment technologies face a long-neglected core problem in engineering applications: the flocs formed by acid precipitation have extremely poor settling performance. In laboratory studies, the treatment effect is usually evaluated by "adjusting the pH to 2 and measuring the filtrate quality after filtration." This in itself implies that relying on natural gravity settling cannot effectively achieve solid-liquid separation; filtration is still necessary. Extending this problem to the level of engineering practice, it manifests in the following unavoidable shortcomings:

[0005] 1. Filtration equipment is overburdened and operating costs are high: Due to the fine size and stickiness of floc particles, the filter pores of traditional solid-liquid separation equipment such as plate and frame filter presses and filter cloth filters are easily and quickly blocked. This leads to frequent shutdowns for cleaning and replacement of filter cloths, which not only increases the cost of manual maintenance, but also seriously restricts the continuous operation and processing efficiency of the treatment system.

[0006] 2. The effluent quality is difficult to meet the standards, threatening the subsequent biological treatment system: A large number of fine flocs can penetrate the tiny pores of the filter media and enter the subsequent biological treatment unit with the effluent. These suspended solids not only cause the final effluent to exceed the suspended solids standard, but may also cause sludge bulking in the biological treatment system, or cause toxic shocks to activated sludge microorganisms due to the biological inhibitory substances they may carry, seriously threatening the stable operation of the entire wastewater treatment plant.

[0007] 3. Fluctuations in influent water quality exacerbate the separation dilemma: The dramatic fluctuations in CODcr of polyurethane wastewater mean that the amount of flocs produced by acid precipitation also fluctuates accordingly. When the influent concentration suddenly increases, the large amount of flocs generated instantaneously can cause the filtration system to quickly become paralyzed due to blockage, and the system has extremely weak resistance to shock loads.

[0008] Existing technological improvements are mostly limited to adjusting operating parameters, such as trying different pH values, adding various flocculants or coagulants. These methods may improve floc properties to some extent, but they have not broken out of the traditional framework of "first forming flocs and then filtering them out." They have not fundamentally solved the core contradiction of flocs being difficult to settle and easy to clog from the physical mechanism of solid-liquid separation. Therefore, a completely new process approach and supporting equipment are urgently needed to fundamentally break through the technical bottleneck of acid precipitation treatment of polyurethane wastewater. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing polyurethane wastewater acid precipitation treatment, such as poor floc settling performance, easy clogging of filtration equipment, and weak resistance to shock loads. It provides a polyurethane wastewater segmented acid precipitation process and device that achieves floc self-aggregation and self-separation at the flow field dynamics level through multi-stage segmented treatment, so as to achieve efficient, stable, and low-maintenance wastewater pretreatment.

[0010] On the one hand, the present invention proposes a staged acid precipitation process for polyurethane wastewater, comprising the following steps:

[0011] Acid precipitation reaction steps: Polyurethane wastewater is introduced into the acid precipitation reaction zone, and the pH is adjusted to acidic, so that the pollutants in the wastewater precipitate out to form initial fine flocs, and a floc-containing mixed liquid is obtained;

[0012] Fluctuation buffering step: The floc-containing mixture is introduced into the fluctuation buffer zone. The dynamic volume regulation capability of this zone is used to smooth the fluctuation of influent flow and water quality, so that the mixture enters the subsequent treatment in a relatively stable flow state.

[0013] Vortex flocculation and recapture step: The mixture after wave buffering is introduced tangentially into the vortex flocculation and recapture zone to generate a rotating upward flow field. In this flow field, the fine flocs in the mixture continuously collide, adhere and grow with the dynamic collision medium pre-set in the flow field, gradually aggregating into large flocs that are easy to settle, and then settling and separating under the action of gravity to obtain a preliminary clarified liquid.

[0014] Dynamic particle filter bed separation step: The preliminary clarified liquid is introduced into the dynamic particle filter bed separation zone, so that it flows from bottom to top through the particle filter media layer in a slightly expanded or fluidized state. Through the adsorption and interception effect on the surface of the filter media particles, the residual fine flocs are further removed, and finally purified water is obtained.

[0015] On the other hand, the present invention also proposes an apparatus for implementing the above-mentioned staged acid precipitation process for polyurethane wastewater, comprising:

[0016] The acid precipitation reaction tank is used to contain polyurethane wastewater and carry out an acid precipitation reaction to form a flocculent mixed liquid.

[0017] A fluctuation buffer, whose inlet is connected to the outlet of the acid precipitation reaction tank, is used to receive the flocculent mixture and smooth its flow rate and water quality fluctuations.

[0018] The vortex flocculation and heavy precipitator has its inlet connected to the outlet of the wave buffer. The inlet direction of the vortex flocculation and heavy precipitator is set to create a rotating upward flow field inside. It is equipped with a dynamic collision medium inside to promote the collision, aggregation and sedimentation of fine flocs.

[0019] The dynamic particle filter bed separator has its inlet connected to the outlet of the vortex flocculation and gravity trap. Inside, there is a particle filter media layer that is slightly expanded or fluidized under the action of rising water flow, which is used for deep filtration of the preliminary clarified liquid.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention no longer relies on traditional filtration equipment to passively trap flocs. Instead, it constructs a dynamic and controllable floc growth environment through a vortex flocculation and gravity trap. In this environment, the fine flocs achieve "self-growth" and "self-settling" through continuous collisions with the dynamic collision medium, fundamentally solving the physical problem of small flocs and difficulty in settling. This marks a fundamental breakthrough in the concept of acid precipitation solid-liquid separation.

[0022] 2. The process consists of four stages: acid precipitation, wave buffer, vortex flocculation, and dynamic filter bed. Each unit has a clear function and works together. Acid precipitation completes the initial precipitation of pollutants, wave buffer provides stable hydraulic conditions for subsequent units, vortex flocculation realizes the aggregation and removal of the main flocs, and dynamic filter bed acts as a gatekeeper to ensure the quality of the effluent. This gradient pollutant reduction path greatly improves the system's adaptability and treatment stability for high-concentration and highly fluctuating wastewater.

[0023] 3. The vortex flocculation and gravity trap cleverly utilizes the kinetic energy of the incoming water. Through the design of tangential water inlet and guide plate, a stable rotating upward flow field is formed. The flocculation balls suspended on the flexible central rope swing and rotate freely in the flow field, forming an adaptive three-dimensional collision space. The entire process of floc attachment, growth, weight gain and detachment on the surface of the ball is automatically cyclical without any manual or automated control, realizing a truly "passive" high-efficiency flocculation.

[0024] 4. The dynamic particle filter bed separator uses suspended particle filter media with a density slightly less than that of water. Under the action of rising water flow, it forms a micro-boiling state. The dynamic friction between the filter media particles causes the trapped flocs to fall off continuously and be discharged through the flushing pipe, realizing the online self-cleaning of the filter layer. This avoids the disadvantages of traditional fixed filter beds that are prone to clogging and require frequent backwashing, ensuring the long-term continuous and stable operation of the system.

[0025] 5. The fluctuation buffer can absorb and release water instantly through the displacement of the floating baffle, and smooth out the drastic fluctuations in the influent flow and water quality. This allows the entire acid precipitation treatment system to maintain a stable and efficient operating state when faced with situations such as irregular drainage and sudden changes in concentration in the production workshop. It is particularly suitable for industrial wastewater treatment scenarios with large fluctuations in water quality and quantity, such as polyurethane wastewater.

[0026] 6. Apart from the necessary inlet pump, the entire device has almost no other power components. The "self-cleaning" characteristics of vortex flocculation and dynamic filter bed greatly reduce the frequency of manual intervention and maintenance. Compared with the traditional solution that relies on frequent replacement of filter cloth, the operating cost and maintenance workload of the present invention are significantly reduced.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 This is a schematic cross-sectional view of the vortex flocculation and gravity trap of the present invention.

[0030] Figure 3 This is a schematic diagram of the front structure of the flocculant balls of the present invention;

[0031] Figure 4 This is a top view cross-sectional structural diagram of the flocculant balls of the present invention;

[0032] Figure 5 This is a schematic cross-sectional view of the dynamic particle filter bed separator of the present invention;

[0033] Figure 6 This is a front cross-sectional view of the fluctuation buffer of the present invention.

[0034] Figure 7 This is a side cross-sectional view of the fluctuation buffer of the present invention.

[0035] Figure Descriptions: 1. Acid precipitation reaction tank; 2. Fluctuation buffer; 3. Vortex flocculation and gravity trap; 31. Tank body; 32. Sludge hopper; 33. Sludge discharge valve; 34. Vortex guide plate; 35. Flow stabilizing cylinder; 36. Flexible central rope; 37. Flocculation ball; 38. Limiting ring; 39. Flexible sleeve; 4. Dynamic particle filter bed separator; 41. First cylindrical shell; 42. Second cylindrical shell; 43. Conical shell; 44. Suspended particle filter media zone; 45. Filter media interception screen; 5. First connecting pipe; 6. Second connecting pipe; 7. Annular water collection tank; 8. Water distributor; 9. Overflow pipe; 10. Water outlet pipe; 11. Flushing pipe; 12. Floating baffle; 13. Guide rail; 14. Flow gap; 15. Buffer spring assembly; 16. Elastic sealing skirt; 17. Branch pipe. Detailed Implementation

[0036] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0038] Please see Figure 1 The polyurethane wastewater staged acid precipitation device proposed in this invention includes four core units in sequence along the wastewater treatment process: acid precipitation reaction tank 1, wave buffer 2, vortex flocculation and recombination device 3, and dynamic particle filter bed separator 4. The units are connected by pipelines to form a complete staged treatment system.

[0039] in,

[0040] The outlet of the acid precipitation reaction tank 1 and the inlet of the wave buffer 2 are connected by the first connecting pipe 5.

[0041] The outlet of the turbulent buffer 2 is connected to the inlet of the vortex flocculation and gravity trap 3 via a second connecting pipe 6.

[0042] The upper end of the vortex flocculation and gravity trap 3 is provided with an annular water collection tank 7, and the side of the annular water collection tank 7 is provided with an overflow pipe 9. The other end of the overflow pipe 9 is connected to the lower water inlet of the dynamic particle filter bed separator 4 through a water distributor 8.

[0043] The upper side of the dynamic particle filter bed separator 4 has an outlet pipe 10 and a flushing pipe 11 located below the outlet pipe 10.

[0044] In one embodiment, the acid precipitation reaction tank 1 is a conventional wastewater reaction tank, equipped with a stirring device (not shown in the figure) and a pH online monitoring and control system. After the polyurethane raw water enters the tank, the pH is adjusted to the acidic range (such as pH=2-3) by adding acidic solutions such as sulfuric acid or hydrochloric acid, so that the organic pollutants in the wastewater precipitate out and form the initial fine flocs.

[0045] In one embodiment, see Figure 1 , Figure 6 and Figure 7 The main body of the fluctuation buffer 2 is a rectangular box structure. Its function is to smooth the flow rate and water quality fluctuations of the water coming from the upstream acid precipitation reaction tank, and to provide stable hydraulic conditions for the downstream treatment unit.

[0046] A floating baffle 12 is vertically installed inside the chamber, dividing the interior into a water inlet chamber on the left and a water outlet chamber on the right. The upper part of the water inlet chamber has a water inlet and is connected to the acid precipitation reaction tank 1 through a first connecting pipe 5. The lower part of the water outlet chamber has a water outlet and is connected to the vortex flocculation and gravity trap 3 through a second connecting pipe 6.

[0047] The floating baffle 12 is made of rigid lightweight sheet material (such as reinforced plastic sheet) with closed-cell foam floats embedded inside, which enables it to float in water. A guide rail 13 is installed on the upper part of the inner cavity of the tank along the length direction. The upper end of the floating baffle 12 is slidably assembled with the guide rail 13 to ensure that it can only move horizontally left and right and cannot tilt or rotate. A flow gap 14 is left between the lower end of the floating baffle 12 and the bottom surface of the inner cavity of the tank to connect the inlet chamber and the outlet chamber.

[0048] The floating baffle 12 is equipped with elastic sealing skirts 16 (such as rubber or silicone skirts) on both sides of the inner wall of the long side of the tank. These skirts are tightly attached to the inner wall to prevent water from flowing directly from both sides without affecting the horizontal movement of the floating baffle.

[0049] A buffer spring assembly 15 is installed in the water outlet chamber. Its two ends are fixedly connected to the side of the floating baffle 12 and the end side wall of the wave buffer 2, respectively, to promote the reset of the floating baffle and improve the dynamic balance performance.

[0050] A branch pipe 17 located above the second connecting pipe 6 can also be added to the side wall of the water outlet chamber. The other end of the branch pipe 17 extends to the outside of the wave buffer 2 and connects with the second connecting pipe 6 to increase the flow capacity.

[0051] After the system starts, water flows into the inlet chamber and through the flow gap 14 into the outlet chamber. During stable operation, the water level H1 in the inlet chamber is slightly higher than the water level H2 in the outlet chamber. The static pressure generated by the difference ΔH drives the water flow through the flow gap 14 at a speed equal to the inlet flow rate. When the inlet flow rate increases instantaneously, the water level H1 in the inlet chamber rises, ΔH increases, and at the same time, the floating baffle 12 is subjected to net pressure in the direction of the outlet chamber and moves to the right, increasing the volume of the inlet chamber, absorbing excess water, and inhibiting H1 from rising too quickly. At the same time, the increase in ΔH accelerates the flow velocity at the bottom, and the water output of the outlet chamber gradually increases until it is in balance with the new inlet flow. When the inlet flow rate decreases, the process is reversed, thereby achieving automatic buffering of inlet fluctuations.

[0052] In one embodiment, see Figure 2 The vortex flocculation and gravity trap 3 is the core unit for achieving "self-flocculation". Its function is to use the rotating flow field to make fine flocs attach and grow on the dynamic collision medium, form large flocs and settle and separate.

[0053] Its structure includes a tank 31, a sludge hopper 32 and a sludge discharge valve 33 connected from top to bottom. A tangential water inlet is provided on the lower side of the tank 31. The outlet of the second connecting pipe 6 is connected to the water inlet, and the axis of the second connecting pipe 6 is tangent to the cross-sectional circle of the tank. A coaxially aligned vortex guide plate 34 (spiral guide plate) is installed on the inner wall of the tank 31 to ensure that a high-speed rotating upward flow field is generated after the water flows in.

[0054] A flow stabilizer 35 is installed at the center of the top of the inner cavity of the tank 31. Its lower end extends into the innermost ring of the vortex guide plate 34 with a certain gap. An annular space is formed between the outer wall of the flow stabilizer 35 and the inner wall of the upper end of the tank 31. After the water flow that rises through the tangential inlet and the guide plate enters the annular space, the rotation intensity is weakened and the flow velocity is reduced, creating a stable area for floc settling. An overflow port connecting the annular space and the annular water collection tank 7 is opened at the top of the tank 31.

[0055] The lower end of the flow stabilizer 35 is equipped with a flexible central rope 36, which is made of a high-strength, corrosion-resistant flexible material (such as PTFE-coated stainless steel wire rope). The upper end is fixed to the center of the top of the flow stabilizer by a universal lifting ring, allowing it to swing freely, while the lower end is suspended in the middle of the tank.

[0056] Multiple flocculants 37 are installed at intervals along the length of the flexible central rope 36 to form a flocculant unit. Each flocculant 37 is installed on the flexible central rope through a movable connector, so that it can slide up and down the rope within a small range and can rotate freely around the connection point.

[0057] like Figure 3 , Figure 4 As shown, the movable connector includes two upper and lower limiting rings 38 and a flexible sleeve 39 connecting the two. The flocculant ball 37 has a through hole in the middle and is movably fitted on the flexible sleeve 39, which can rotate freely on the outer wall of the sleeve and float up and down slightly.

[0058] The flocculant ball 37 is a lightweight porous sphere with a diameter approximately 1 / 5 to 1 / 4 of the tank diameter. It is made of rough-surfaced polypropylene or polyethylene, with a surface covered with micropores and protrusions (pore diameter 1-3 mm). The interior is hollow or filled with a lightweight material, with a density slightly less than water (approximately 0.9-0.95 g / cm³). Its outer wall may also have circumferentially distributed radial streamlined grooves to increase the surface area and promote rotation in the vortex.

[0059] After the flocculated wastewater enters the tank 31 tangentially, it generates a rotating upward flow field. The flexible central rope 36 and the flocculent balls 37 swing and rotate randomly in the vortex, forming a dynamic three-dimensional collision space. The fine flocs continuously collide, attach, and grow with the surface of the flocculent balls in the vortex, gradually agglomerating into large particles. After the flocs attached to the surface of the flocculent balls grow to a certain thickness, they automatically fall off due to the shear force of the water flow and gravity, and settle into the sludge collection hopper 32. They are periodically discharged through the sludge discharge valve 33. The surface of the desorbed flocculent balls is re-exposed, and new flocs continue to attach, forming an automatic cycle of "attachment-growth-falling off-reattachment". The preliminary clarified liquid after treatment by this unit enters the annular water collection tank 7 from the top overflow port.

[0060] In one embodiment, see Figure 5 The dynamic particle filter bed separator 4 is the final control unit. Its function is to use fluidized particle filter media to deeply intercept the fine flocs remaining in the preliminary clarified liquid.

[0061] Its structure includes a first cylindrical shell 41 and a second cylindrical shell 42 that are distributed vertically and coaxially aligned. The diameter of the first cylindrical shell 41 is larger than that of the second cylindrical shell 42. The two are connected by a conical shell 43. A suspended particulate filter media area 44 is provided inside the conical shell 43 and at the lower part of the first cylindrical shell 41. The area is filled with suspended particulate filter media, preferably expanded polystyrene or polyethylene particles (3-8 mm in diameter, with a density slightly less than that of water). A filter media interception screen 45 is installed at the upper end of the inner cavity of the first cylindrical shell 41, located below the water outlet pipe 10, to prevent the filter media from flowing out.

[0062] The water distributor 8 has a porous water distribution plate extending to the lower end of the inner cavity of the second cylindrical shell 42 for uniform water distribution. The flushing pipe 11 is located on the lower side of the first cylindrical shell 41, in the upper middle part of the suspended particle filter media area 44 in a static state. Its inner end extends into the filter media area and is provided with a filter screen, and its outer end is provided with a pipe port with a valve.

[0063] The preliminary clarified liquid containing residual flocs enters evenly from the bottom of the second cylindrical shell 42 through the water distributor 8, and passes upward through the suspended particle filter media zone 44. Under the action of the rising water flow, the filter media particles are in a state of slight boiling, and the filter layer expands to 1.2-1.5 times the static height, forming dynamic pores. The flocs are adsorbed or intercepted by the surface of the filter media particles, and the clear water is discharged from the outlet pipe 10.

[0064] As the number of trapped flocs increases, the filtration resistance increases, the filter layer expands more intensely, and the collision and friction between filter media particles intensifies. The trapped flocs are rubbed off. At this time, the flushing pipe 11 valve is opened, and part of the water flow carries the detached flocs out of the flushing pipe 11 (which can be returned to the acid precipitation reaction tank), realizing online self-cleaning of the filter media without the need to stop the machine for backwashing.

[0065] The polyurethane wastewater staged acid precipitation process proposed in this invention is implemented using the above-mentioned apparatus and specifically includes the following steps:

[0066] Step S1: Acid precipitation reaction

[0067] Polyurethane wastewater enters acid precipitation reaction tank 1 continuously or intermittently. Acid is added under stirring to adjust the pH to a set value (e.g., 2.0-3.0). Organic pollutants in the wastewater precipitate out, forming initial fine flocs, and a floc-containing mixed liquid is obtained.

[0068] Step S2: Fluctuation Buffer

[0069] The flocculent mixture enters the inlet chamber of the wave buffer 2 through the first connecting pipe 5. Inside the wave buffer 2, the flow rate and water quality fluctuations of the incoming water are automatically suppressed by the follow-up displacement of the floating baffle 12 and the synergistic effect of the buffer spring group 15, so that the mixture flows out from the outlet chamber through the second connecting pipe 6 in a relatively stable flow state.

[0070] Step S3: Vortex flocculation and recapture

[0071] The buffered mixture enters the vortex flocculation and gravity collector 3 tangentially, forming a rotating upward flow field in the tank 31. The fine flocs in the mixture continuously collide, adhere, and grow with multiple flocs 37 suspended on the flexible central rope 36 in the flow field. The grown flocs settle to the sludge collection hopper 32 under gravity and are periodically discharged. The preliminary clarified liquid after this step enters the annular water collection tank 7 from the top overflow port and flows to the dynamic particle filter bed separator 4 through the overflow pipe 9.

[0072] Step S4: Dynamic particle filter bed separation

[0073] The initial clarified liquid enters evenly from the bottom of the dynamic particle filter bed separator 4 through the water distributor 8, and flows from bottom to top through the suspended particle filter media zone 44, which is in a slightly expanded state. The remaining fine flocs are adsorbed or trapped by the filter media particles. The purified water is discharged from the outlet pipe 10 and enters the subsequent treatment unit or is reused. The trapped flocs are continuously detached in the dynamic friction of the filter media particles and are periodically discharged from the flushing pipe 11 with part of the water flow, realizing the self-cleaning of the filter layer.

[0074] The scope of protection of this invention is not limited to the specific embodiments described above. For example, the dynamic collision medium is not limited to a spherical shape, but can also be a porous suspension of other shapes; the floating baffle driving method of the wave buffer is not limited to buoyancy plus spring, but can also adopt other mechanical or hydraulic feedback methods; the vortex flow field can be generated by tangential water inlet and guide plates, or by the principle of a stirrer or hydrocyclone. Any variation or equivalent substitution based on the core concept of "segmented treatment, vortex self-flocculation, and dynamic filter bed self-cleaning" of this invention should be considered to fall within the scope of protection of this invention.

Claims

1. A staged acid precipitation process for polyurethane wastewater, characterized in that, Includes the following steps: S1. Introduce polyurethane wastewater into the acid precipitation reaction zone, adjust the pH to acidic, so that pollutants precipitate out to form fine flocs, and obtain a floc-containing mixed liquid; S2. Introduce the flocculent mixture into the fluctuation buffer adjustment zone to smooth out its flow rate and water quality fluctuations; S3. The buffered mixture is introduced into the vortex flocculation and settling zone, so that it comes into contact with the dynamic collision medium in the rotating upward flow field, which promotes the collision and aggregation of fine flocs and their sedimentation and separation to obtain a preliminary clarified liquid. S4. The preliminary clarified liquid is introduced into the dynamic granular filter bed filtration zone, so that it flows from bottom to top through the fluidized granular filter media layer, and the residual flocs are further removed by adsorption and interception to obtain purified effluent.

2. The staged acid precipitation process for polyurethane wastewater according to claim 1, characterized in that, The vortex flocculation sedimentation zone is equipped with a flexible suspended dynamic collision medium that can move with the flow field. Fine flocs attach to, grow, and automatically detach and settle on the surface of this medium.

3. The staged acid precipitation process for polyurethane wastewater according to claim 1, characterized in that, The density of the granular filter media in the dynamic granular filter bed filtration zone is slightly less than that of water. Under the action of the rising water flow, it is in a state of slight expansion or fluidization. The trapped flocs are automatically detached in the dynamic friction of the filter media particles and discharged through the flushing liquid.

4. A staged acid precipitation apparatus for polyurethane wastewater to implement the process described in any one of claims 1-3, characterized in that, include: Acid precipitation reaction tank (1) is used to contain polyurethane wastewater and carry out acid precipitation reaction; A fluctuation buffer (2) has its inlet connected to the outlet of the acid precipitation reaction tank (1) and is used to receive the floc-containing mixture and smooth its fluctuations. The vortex flocculation and heavy trap (3) has its inlet connected to the outlet of the wave buffer (2) and is configured to have tangential water inlet to form a rotating upward flow field inside it. It is equipped with a dynamic collision medium to promote the collision and aggregation of fine flocs inside it. The dynamic particle filter bed separator (4) has its inlet connected to the outlet of the vortex flocculation and gravity trap (3), and its interior is provided with a particle filter media layer (44) that is fluidized under the action of rising water flow.

5. The polyurethane wastewater staged acid precipitation device according to claim 4, characterized in that, The vortex flocculation heavy trap (3) includes a tank (31) and a flexible central rope (36) disposed inside the tank (31). The dynamic collision medium is a plurality of flocculation balls (37) installed at intervals on the flexible central rope (36). The lower side of the tank (31) is provided with a tangential water inlet, and the inner wall of the tank is provided with a vortex guide plate (34).

6. The polyurethane wastewater staged acid precipitation device according to claim 5, characterized in that, The flocculant ball (37) is a porous, lightweight sphere with a rough surface and a density less than that of water. The flocculant ball (37) is mounted on a flexible central rope (36) via a movable connector, allowing it to rotate freely and / or slide axially with a small amplitude.

7. The polyurethane wastewater staged acid precipitation device according to claim 4, characterized in that, The dynamic particle filter bed separator (4) includes two shells with different diameters distributed vertically, and a conical transition section connecting the two shells. The particle filter media layer (44) is located in the lower shell and the conical transition section. The upper side wall of the dynamic particle filter bed separator (4) is provided with a water outlet pipe (10), and the lower side wall is provided with a flushing pipe (11) for discharging concentrated water containing detached flocs.

8. The polyurethane wastewater staged acid precipitation device according to claim 4, characterized in that, The fluctuation buffer (2) includes a tank and a floating baffle (12) disposed in the tank. The floating baffle (12) divides the inside of the tank into an inlet chamber and an outlet chamber. A flow gap (14) is formed between the lower end of the floating baffle (12) and the bottom surface of the tank. The floating baffle (12) can move horizontally in response to changes in water level to automatically adjust the volume on both sides.

9. The polyurethane wastewater staged acid precipitation device according to claim 8, characterized in that, The upper end of the floating baffle (12) is slidably mounted on the guide rail (13) at the top of the inner cavity of the box, and a buffer spring assembly (15) is provided between the side of the floating baffle (12) and the side wall of the box.

10. The polyurethane wastewater staged acid precipitation device according to claim 4, characterized in that, The upper end of the vortex flocculation and heavy precipitator (3) is provided with an annular water collection tank (7), which is connected to the water distributor (8) through an overflow pipe (9). The water distributor (8) is connected to the lower inlet of the dynamic particle filter bed separator (4).

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