Wastewater treatment device and method for PVB (Polyvinyl Butyral) resin production

Abstract

The invention provides a wastewater treatment device and method for PVB (Polyvinyl Butyral) resin production. The wastewater treatment device comprises a tower body, and a liquid distributor, a filler layer and an aeration device are sequentially arranged in the tower body from top to bottom; the top of the tower body is provided with an air outlet, and the bottom of the tower body is provided with a water outlet; the liquid distributor is connected with a water inlet pipe; the aeration device is connected with an air inlet pipe; and a foam trapping device is arranged between the air outlet and the liquid distributor. Through the arrangement of the foam trapping device, total cross-section interception of rising foams, complete collection of fractured liquid, thorough separation of gas and liquid in space and reflux treatment of concentrated liquid can be realized; therefore, the problems of liquid accumulation, blockage, corrosion and the like of a gas-phase pipeline caused by foam escape when the PVB resin production wastewater is treated by the existing air stripping tower are effectively solved, and the technical problem that the pollutant removal efficiency is overestimated is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a wastewater treatment device and method for PVB resin production. Background Technology

[0002] The content in this section only provides background information related to this invention and may not constitute prior art.

[0003] PVB (polyvinyl butyral) resin, as an important chemical raw material, generates a certain amount of wastewater during its production. This wastewater mainly originates from the synthesis reaction mother liquor, washing processes, and equipment rinsing water. This type of wastewater has a complex composition, typically containing substances such as n-butyraldehyde, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), hydrochloric acid, and sodium chloride. It is characterized by high organic matter concentration, low pH value, and high salt content. Among these, n-butyraldehyde is toxic and volatile, and it inhibits microorganisms, resulting in poor biodegradability of the wastewater, making direct biological treatment unsuitable.

[0004] Currently, air stripping is commonly used as a pretreatment process for PVB resin production wastewater. Air stripping utilizes contact between air and wastewater to transfer volatile pollutants (mainly n-butyraldehyde) from the liquid phase to the gas phase, thus achieving removal. After air stripping pretreatment, the wastewater can be further treated using processes such as iron-carbon micro-electrolysis, Fenton oxidation, and biochemical treatment to ensure that the effluent meets discharge standards.

[0005] However, existing stripping towers have a long-overlooked technical problem when applied to PVB resin production wastewater treatment. Because PVB resin production wastewater contains high-molecular-weight surfactants such as polyvinyl alcohol (PVA), a large amount of extremely stable microfoam is generated during aeration and stripping. Due to the action of surfactants, these microfoam films accumulate higher concentrations of pollutants such as butyraldehyde, PVA, and PVB than the main wastewater, becoming "concentrated carriers" of pollutants. Existing stripping towers typically install wire mesh demisters or baffle demisters upstream of the outlet to break up the foam, but these demisters can only break larger bubbles and are ineffective at intercepting stable microfoam. Unbroken microfoam may carry pollutants into the gas phase pipeline, causing problems such as liquid accumulation, blockage, and corrosion. More insidiously, pollutants "escape" to the gas phase in foam form and are not actually removed from the water, leading to an overestimation of pollutant removal efficiency and affecting the stable operation of subsequent biological treatment. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a wastewater treatment device and method for PVB resin production, so as to solve the technical problem that when the existing stripping tower treats PVB resin production wastewater, the surfactants in the wastewater generate stable micro foam, which causes the foam to carry pollutants into the gas phase pipeline, resulting in pipeline blockage and overestimation of pollutant removal efficiency.

[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a wastewater treatment device for PVB resin production, comprising a tower body, wherein a liquid distributor, a packing layer, and an aeration device are sequentially arranged from top to bottom inside the tower body; an air outlet is provided at the top of the tower body, and a water outlet is provided at the bottom of the tower body; the liquid distributor is connected to a water inlet pipe; the aeration device is connected to an air inlet pipe; a foam collection device is provided between the air outlet and the liquid distributor; the foam collection device includes: The trapping hood includes a sealing surface, a bubble-breaking inclined surface adjacent to the sealing surface, and a connecting plane; the sealing surface is used to seal and connect with the circumferential inner wall of the tower body; along the axial direction of the tower body from top to bottom, the bubble-breaking inclined surface extends obliquely to the center of the tower body to guide the liquid formed after the intercepted foam breaks to its bottom; the connecting plane is located at the bottom of the bubble-breaking inclined surface and faces the bottom of the tower body; A liquid collector is located below the connecting plane and defines a liquid collection chamber with an open top; the projection of the opening of the liquid collection chamber onto the outer edge of the connecting plane in the axial direction of the tower body; a reflux port is provided at the bottom of the liquid collection chamber; A venting tube; the bottom end of the venting tube extends into the liquid collection chamber and has a gap between it and the bottom surface of the liquid collection chamber; the top end of the venting tube passes through the connecting plane and is sealed and fixed thereto; the top end of the venting tube is connected to the air outlet. Return pipe; one end of the return pipe is connected to the return port, and the other end of the return pipe is connected to the inlet pipe.

[0008] Optionally, a bubble-breaking screen is provided at the opening of the liquid collection chamber; the air guide tube passes through the bubble-breaking screen and is fixedly connected to the bubble-breaking screen.

[0009] Optionally, the mesh size of the bubble-breaking mesh is 0.5-1mm.

[0010] Optionally, the bubble-breaking inclined surface is provided with protrusions; the height of the protrusions is 0.2-0.5mm, and the distribution density is 10-50 per square centimeter.

[0011] Optionally, the trapping hood has a heating chamber inside; the heating chamber contains a heat-conducting medium and a heating element for heating the heat-conducting medium.

[0012] Optionally, the wastewater treatment device for PVB resin production further includes a controller; the controller is electrically connected to both the heating element and the flow detection element on the air inlet pipe, and is used to adjust the heating temperature of the heat-conducting medium according to the air intake.

[0013] Optionally, the air guide tube passes through the heating chamber; the air guide tube is made of a thermally conductive material.

[0014] Optionally, the bubble-breaking inclined surface is provided with an anti-stick coating.

[0015] Optionally, a one-way valve is provided on the return pipe.

[0016] Secondly, the present invention provides a method for treating wastewater from PVB resin production, employing the wastewater treatment apparatus for PVB resin production as described above, comprising the following steps: The wastewater to be treated is introduced into the liquid distributor through the inlet pipe. After being evenly distributed by the liquid distributor, the wastewater flows downward. At the same time, air is introduced into the aeration device through the air inlet pipe. The aeration device generates bubbles that flow upward. In the packing layer, the gas and liquid come into contact, and the n-butyraldehyde in the wastewater volatilizes into the gas phase. The rising gas carries foam into the foam collection device. The foam impacts and breaks the bubble-breaking slope of the collection hood. The liquid formed after breaking flows along the bubble-breaking slope to the connecting plane and drips from the outer edge of the connecting plane. The gas flows along the bubble-breaking slope and enters the liquid collection chamber. It then enters the gas guide tube through the gap at the bottom of the gas guide tube and finally flows out from the gas outlet after passing through the top of the gas guide tube. The dripping liquid falls into the collection chamber, and after accumulating at the bottom of the collection chamber, the liquid flows through the return pipe into the inlet pipe, mixes with the new wastewater in the inlet pipe, and then re-enters the tower for treatment. The treated wastewater is discharged from the outlet.

[0017] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: The wastewater treatment device provided by this invention achieves full-section interception of rising foam through a sealed connection between the collection hood and the inner wall of the tower, ensuring that the foam cannot escape. Based on the principle of foam impact and rupture, the device uses a rupture slope to intercept the foam and guide the liquid formed after the foam ruptures to the connecting plane for dripping. The structure is simple and has a good flow guiding effect. The projection of the liquid collection chamber opening covers the outer edge of the connecting plane, ensuring that all dripping liquid is collected without leakage. A gap is reserved between the bottom end of the gas guide pipe and the bottom surface of the liquid collection chamber, providing a smooth channel for gas to enter the gas guide pipe. At the same time, the liquid will not enter the gas guide pipe after accumulating at the bottom of the liquid collection chamber, achieving complete separation of gas and liquid in space. The return pipe is connected to the water inlet pipe. Based on the principle of material balance, the collected concentrated liquid is mixed with new wastewater and then re-enters the tower for treatment, avoiding the local accumulation of non-volatile substances such as polyvinyl alcohol and polyvinyl butyral at the bottom of the tower. At the same time, it makes the concentration of the effluent at the bottom of the tower more stable, which is beneficial to subsequent treatment. The entire device has a simple structure, requires no external power, and operates stably and reliably. It effectively solves the problems of liquid accumulation, blockage, and corrosion in the gas phase pipeline caused by foam escape when the existing stripping tower treats PVB resin production wastewater, as well as the technical problem of overestimation of pollutant removal efficiency. Attached Figure Description

[0018] Figure 1 A schematic diagram of a wastewater treatment device for PVB resin production provided in an embodiment of the present invention; Figure 2 for Figure 1 Enlarged view of the local structure at point A; Figure 3 for Figure 2 Enlarged view of the local structure at point B; Figure 4 A partial structural diagram of a foam collection device provided for an embodiment of the present invention; it shows the general structure of the liquid collector, the air guide tube, and the bubble-breaking net.

[0019] Icons: 10-Tower body, 11-Air outlet, 12-Water outlet, 20-Liquid distributor, 30-Packing layer, 40-Aeration device, 50-Water inlet pipe, 60-Air inlet pipe, 70-Foam collection device, 71-Collection hood, 711-Sealing surface, 712-Bubble-breaking slope, 713-Connecting plane, 714-Heating chamber, 715-Inlet and outlet, 72-Liquid collector, 721-Liquid collection chamber, 722-Return port, 723-Guide slope, 73-Air guide pipe, 74-Return pipe, 75-One-way valve, 76-Bubble-breaking net, 77-Heating element. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. The same reference numerals in the accompanying drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the described embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] Compared to the embodiments shown in the accompanying drawings, feasible embodiments within the scope of protection of this invention may have fewer components, other components not shown in the drawings, different components, components with different arrangements, or components with different connections, etc. Furthermore, two or more components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components.

[0022] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. Example 1

[0023] Please refer to Figures 1 to 4 As shown, Embodiment 1 of the present invention provides a wastewater treatment device for PVB resin production, and in particular a stripping tower for pretreating wastewater generated during the PVB resin production process.

[0024] Specifically, such as Figure 1 As shown, the wastewater treatment device includes a tower body 10. Inside the tower body 10, from top to bottom, are arranged a liquid distributor 20, a packing layer 30, and an aeration device 40. The top of the tower body 10 has an air outlet 11, and the bottom of the tower body 10 has a water outlet 12. The liquid distributor 20 is connected to an inlet pipe 50, which is used to supply wastewater to be treated. The aeration device 40 is connected to an air inlet pipe 60, which is used to supply air.

[0025] Furthermore, a foam collection device 70 is provided between the air outlet 11 and the liquid distributor 20. The foam collection device 70 is mainly used to collect the foam generated during the wastewater treatment process.

[0026] Reference Figure 2As shown, the foam trapping device 70 includes a trapping hood 71, a liquid collector 72, a gas guide pipe 73, and a return pipe 74. The trapping hood 71 is generally frustum-shaped, wider at the top and narrower at the bottom, and includes a sealing surface 711, a bubble-breaking inclined surface 712 adjacent to the sealing surface 711, and a connecting plane 713. The sealing surface 711 is used to seal against the circumferential inner wall of the tower body 10, ensuring that the rising gas and its carried foam must impact the trapping hood 71 and cannot escape from the gap between the circumferential outer wall of the trapping hood 71 and the inner wall of the tower body 10. Along the axial direction of the tower body 10 from top to bottom, the bubble-breaking inclined surface 712 extends obliquely towards the center of the tower body 10, used to intercept and break the foam, and to guide the liquid formed after the foam breaks to its bottom. The connecting plane 713 is located at the bottom of the bubble-breaking inclined surface 712 and faces the bottom of the tower body 10, used for liquid collection and dripping, and for connecting to the gas guide pipe 73. Specifically, the outer edge of the connecting plane 713, that is, the connection between the connecting plane 713 and the bubble-breaking slope 712, can be regarded as the liquid collection and dripping area. During the wastewater treatment process, the liquid formed after the foam breaks down will eventually collect in the liquid collection and dripping area under the guidance of the bubble-breaking slope 712 and drip down after forming droplets.

[0027] The liquid collector 72 is located below the connecting plane 713 and defines a top-open liquid collection chamber 721. The projection of the opening of the liquid collection chamber 721 onto the axial direction of the tower body 10 covers the outer edge of the connecting plane 713, ensuring that all liquid dripping from the outer edge of the connecting plane 713 (i.e., the liquid collection and dripping area) falls into the liquid collection chamber 721 and does not drip to the outside. A reflux port 722 is provided at the bottom of the liquid collection chamber 721.

[0028] The bottom end of the gas guide pipe 73 extends into the liquid collection chamber 721, with a gap reserved between it and the bottom surface of the liquid collection chamber 721. This gap serves as the inlet for gas to enter the gas guide pipe 73. The top end of the gas guide pipe 73 passes through the connecting plane 713 axially upward along the tower body 10 and is sealed and fixed thereto, ensuring that gas can only flow from inside the gas guide pipe 73 and will not leak from the connecting plane 713. The top end of the gas guide pipe 73 communicates with the gas outlet 11 to exhaust gas outside the tower. Exemplarily, the top end of the gas guide pipe 73 can be directly connected to the gas outlet 11, or it can be indirectly connected to the gas outlet 11 through the sealed space above the trap hood 71, see [link to relevant documentation]. Figure 1 .

[0029] One end of the reflux pipe 74 is connected to the reflux port 722, and the other end of the reflux pipe 74 is connected to the inlet pipe 50. It is used to collect the liquid collected in the liquid collection chamber 721 into the inlet pipe 50, mix it with the new wastewater in the inlet pipe 50, and then re-enter the tower for treatment.

[0030] As a preferred option, refer to Figure 2As shown, a one-way valve 75 is provided on the return pipe 74. This one-way valve 75 only allows liquid to enter the inlet pipe 50 from the return pipe 74, so as to prevent wastewater in the inlet pipe 50 from flowing back into the return pipe 74. The one-way valve 75 can be set at any position on the return pipe 74, but it is preferably set near the connection between the return pipe 74 and the inlet pipe 50, so as to prevent wastewater in the inlet pipe 50 from flowing back into the return pipe 74 to the greatest extent.

[0031] According to an embodiment of the present invention, the working process of the provided wastewater treatment device is roughly as follows: During operation, the wastewater to be treated enters the liquid distributor 20 through the inlet pipe 50. After being evenly distributed by the liquid distributor 20, the wastewater flows downward along the axial direction of the tower body 10, passing sequentially through the packing layer 30 and the area where the aeration device 40 is located. Simultaneously, air enters the aeration device 40 through the air inlet pipe 60. The aeration device 40 generates a large number of fine bubbles that flow upward and come into full contact with the downward-flowing wastewater in the packing layer 30. Volatile pollutants such as n-butyraldehyde in the wastewater evaporate from the liquid phase into the gas phase and move upward along the axial direction of the tower body 10 along with the bubbles. Because the wastewater contains high-molecular-weight surfactants such as polyvinyl alcohol, a large number of stable micro-foams are generated during the aeration process. The liquid film of these foams is enriched with high concentrations of pollutants such as n-butyraldehyde, polyvinyl alcohol, and polyvinyl butyral. The foam moves upward along the axial direction of the tower body 10 along with the gas.

[0032] The rising gas, carrying foam, enters the foam collection device 70. Because the sealing surface 711 of the collection hood 71 is sealed to the inner wall of the tower body 10, the rising gas and foam cannot escape through the gap between the circumferential outer wall of the collection hood 71 and the inner wall of the tower body 10, and must impact the bubble-breaking inclined surface 712 of the collection hood 71. The foam ruptures upon impact with the bubble-breaking inclined surface 712. The principle is that when foam impacts a solid surface, the liquid film vibrates and deforms under the impact force. When the thickness of the liquid film decreases to a critical value, the surface tension cannot maintain the stability of the liquid film, thus causing the foam to rupture. The liquid formed after rupture flows downward along the bubble-breaking inclined surface 712 under the action of gravity, is guided to the connecting plane 713 at the bottom of the bubble-breaking inclined surface 712, and drips from the outer edge of the connecting plane 713. Because the projection of the opening of the liquid collection chamber 721 in the axial direction of the tower body 10 covers the outer edge of the connecting plane 713, all the dripping liquid falls into the liquid collection chamber 721. Simultaneously, after impacting the bubble-breaking inclined plane 712, the gas loses its vertical momentum and is forced to change direction, flowing horizontally towards the center along the bubble-breaking inclined plane 712. The deflected gas enters the liquid collecting chamber 721, and then enters the gas guiding pipe 73 through the gap between the bottom end of the gas guiding pipe 73 and the bottom surface of the liquid collecting chamber 721. This gap is designed using the gas adhesion effect and pressure difference driving principle, allowing the gas to smoothly enter the gas guiding pipe 73 without being disturbed by the accumulation of liquid in the liquid collecting chamber 721. The gas flows upward along the gas guiding pipe 73, and finally exits from the top of the gas guiding pipe 73 through the gas outlet 11, thus being discharged outside the tower and sent for further processing.

[0033] The liquid falling into the collection chamber 721 accumulates at the bottom of the chamber and then enters the return pipe 74 through the return port 722. After flowing along the return pipe 74, it flows into the inlet pipe 50, mixes with the new wastewater in the inlet pipe 50, and re-enters the tower for further treatment. This design of mixing the returned liquid with the wastewater provided by the inlet pipe 50 is based on the principle of material balance: polyvinyl alcohol and polyvinyl butyral are non-volatile substances and will not be discharged with the gas. If they are only returned to the bottom of the tower, they may accumulate locally, forming a high-concentration zone. However, by flowing them into the inlet pipe 50 and mixing them evenly with the new wastewater, they can be evenly distributed in the inlet water and ultimately discharged with the effluent, avoiding the problem of local accumulation. The treated wastewater is finally discharged from the outlet 12 at the bottom of the tower body 10 and enters subsequent biological treatment or other processes.

[0034] The wastewater treatment device provided in this embodiment of the invention achieves full-section interception of rising foam through a sealed connection between the collection hood 71 and the inner wall of the tower body 10, ensuring that the foam cannot escape. Based on the principle of foam impact and rupture, the foam is intercepted by the ruptured bubble slope 712, and the liquid formed after the foam ruptures is guided to the connecting plane 713 to drip down. The structure is simple and the flow guiding effect is good. The projection of the opening of the liquid collection chamber 721 covers the outer edge of the connecting plane 713, ensuring that all the dripping liquid is collected without leakage. The bottom end of the air guide pipe 73 is connected to... A pre-reserved gap at the bottom of the liquid collection chamber 721 provides a smooth passage for gas to enter the gas guide pipe 73. Simultaneously, liquid accumulated at the bottom of the liquid collection chamber 721 will not enter the gas guide pipe 73, achieving complete gas-liquid separation in space. The return pipe 74 is connected to the water inlet pipe 50. Based on the material balance principle, the collected concentrated liquid is mixed with new wastewater and then reintroduced into the tower for treatment. This avoids the localized accumulation of non-volatile substances such as polyvinyl alcohol and polyvinyl butyral at the bottom of the tower, and also makes the concentration of the effluent at the bottom of the tower more stable, which is beneficial for subsequent treatment. The entire device has a simple structure, requires no external power, and operates stably and reliably. It effectively solves the problems of liquid accumulation, blockage, and corrosion in the gas phase pipeline caused by foam escape when treating PVB resin production wastewater in existing stripping towers, as well as the technical problem of overestimating the pollutant removal efficiency.

[0035] In a preferred embodiment of the present invention, reference is made to Figure 3 and Figure 4 As shown, a defoaming mesh 76 is provided at the opening of the liquid collection chamber 721. A gas guide tube 73 passes through the defoaming mesh 76 and is fixedly connected to it. Specifically, the defoaming mesh 76 is a horizontally arranged mesh structure, with its outer edge fixedly connected to the inner wall of the opening of the liquid collection chamber 721 to seal the opening. An opening is made in the center of the defoaming mesh 76 for the gas guide tube 73 to pass through, and it is fixedly connected to the outer wall of the gas guide tube 73. The mesh size of the defoaming mesh 76 is 0.5-1 mm.

[0036] In this embodiment, the bubble-breaking net 76 serves two functions: first, as a structural component to fix the position of the liquid collector 72. Since the outer edge of the bubble-breaking net 76 is fixed to the liquid collector 72 and the center is fixed to the air guide pipe 73, the liquid collector 72 is firmly suspended on the air guide pipe 73 without the need for additional connecting arms or support structures, making the overall structure simpler; second, as a functional component to perform secondary bubble-breaking treatment on the dripping liquid. When the liquid drips from the outer edge of the connecting plane 713 and passes through the bubble-breaking net 76 into the liquid collection chamber 721, if the droplet contains incompletely broken or newly formed micro bubbles, these bubbles will collide with the mesh wires when passing through the mesh holes of the bubble-breaking net 76, and the liquid film of the foam will be punctured by the mesh wires, thereby releasing the liquid encapsulated within.

[0037] Specifically, although the aforementioned bubble-breaking slope 712 effectively intercepts and breaks down foam, it is still possible that some foam may not completely break down or that foam may reform as the liquid drips. If the droplets dripping from the outer edge of the connecting plane 713 contain incompletely broken or newly formed foam, when these foams pass through the mesh of the bubble-breaking net 76, the liquid film of the foam collides with the mesh wires of the bubble-breaking net 76. Since the diameter of the mesh wires is much smaller than the diameter of the foam, the mesh wires can penetrate the foam liquid film, disrupting the surface tension balance of the liquid film and causing the foam to break down. The liquid released after breaking down continues to fall along with the original droplets and eventually enters the bottom of the liquid collection chamber 721. Due to the presence of the bubble-breaking net 76, the liquid entering the liquid collection chamber 721 is basically free of foam, avoiding the problem of secondary accumulation or re-foaming of foam in the liquid collection chamber 721.

[0038] Preferably, the pore size of the defoaming net 76 used in this embodiment of the invention is 0.5-1 mm. This range is based on the inventors' in-depth research on the foam characteristics of PVB resin production wastewater. Studies have shown that the diameter of the microfoam generated in PVB wastewater is typically between 0.5-3 mm, with foam smaller than 1 mm being the most stable and least prone to spontaneous breakage. When the pore size of the defoaming net 76 is 0.5-1 mm, it can effectively intercept and puncture the vast majority of microfoam, while ensuring that the pore size is not too small to cause blockage or liquid stagnation. If the pore size is greater than 1 mm, some microfoam may pass directly through the mesh without being punctured; if the pore size is less than 0.5 mm, the mesh is easily clogged due to liquid surface tension or impurities in the water, increasing the maintenance frequency.

[0039] By setting up the bubble-breaking net 76, firstly, the liquid collector 72 can be fixed to the air guide pipe 73 with the help of the bubble-breaking net 76, eliminating the need for a separate support structure for the liquid collector 72, further simplifying the device structure and reducing manufacturing costs; secondly, the bubble-breaking net 76 can puncture any foam that may exist in the dripping droplets, ensuring that the liquid entering the liquid collection chamber 721 is as pure as possible, avoiding the problem of foam accumulation or re-foaming in the liquid collection chamber 721; thirdly, the 0.5-1mm mesh aperture is an optimized design for the foam characteristics of PVB wastewater, which can effectively break bubbles while also taking into account anti-clogging performance; fourthly, the bubble-breaking net 76 is set at the opening of the liquid collection chamber 721, located on the inevitable path of the dripping liquid, making full use of the kinetic energy of the falling droplets, and achieving secondary bubble breaking without additional power.

[0040] In a preferred embodiment of the present invention, a plurality of protrusions (not shown in the figure) are provided on the bubble-breaking inclined surface 712 of the trapping hood 71. These protrusions can be evenly distributed on the surface of the bubble-breaking inclined surface 712, the height of the protrusions is 0.2-0.5 mm, and the distribution density of the protrusions is 10-50 per square centimeter.

[0041] It is worth noting that when foam impacts the bubble-breaking ramp 712, the liquid film of the foam needs to reach a certain degree of deformation before it ruptures. If the bubble-breaking ramp 712 is smooth, some foam may slide along the ramp 712 without rupturing after impact, especially if the ramp 712 itself is wet, in which case the foam may remain intact for a long time without rupturing. However, with protrusions on the bubble-breaking ramp 712, when foam impacts, the tips of the protrusions actively pierce the liquid film of the foam, creating stress concentration in the local area of ​​the liquid film. This causes the liquid film to thin first at that point and eventually rupture, a process similar to puncturing a bubble with a needle. Even if the foam does not rupture immediately, the presence of the protrusions increases the resistance to the foam's movement on the bubble-breaking ramp 712, prolonging the foam's residence time on the ramp 712. This facilitates the discharge of liquid from the liquid film under gravity, thus thinning the liquid film, reducing its strength, and causing it to continuously collide with other protrusions as it flows downwards along the bubble-breaking ramp 712, eventually rupturing.

[0042] Furthermore, the height of the protrusions is set to 0.2-0.5 mm. This range allows for effective penetration into the foam liquid film without significantly obstructing the flow of the liquid. If the protrusion height is less than 0.2 mm, it will be difficult to effectively penetrate the liquid film, resulting in poor bubble-breaking effect; if the protrusion height is greater than 0.5 mm, it may obstruct the flow of liquid along the bubble-breaking slope 712, leading to liquid stagnation or poor flow. Even further, by setting the density of the protrusions to 10-50 per square centimeter, this range ensures a sufficient number of bubble-breaking points on the bubble-breaking slope 712, while avoiding excessively dense protrusions that could cause liquid stagnation between the protrusions.

[0043] In a preferred embodiment of the present invention, an anti-stick coating (not shown in the figure) is provided on the bubble-breaking slope 712 of the trapping hood 71. Preferably, the anti-stick coating is made of a material with low surface energy, good corrosion resistance and temperature resistance, such as polytetrafluoroethylene (PTFE), ceramic coating or diamond-like carbon coating. The anti-stick coating uniformly covers the entire surface of the bubble-breaking slope 712, and its thickness is controlled within a range that can effectively perform the anti-stick function without affecting the original geometry of the bubble-breaking slope 712, typically 0.05-0.2 mm.

[0044] The inventors of this invention discovered that PVB resin production wastewater contains high molecular weight substances such as polyvinyl alcohol, which have high viscosity and easily adhere to ordinary metal or plastic surfaces. When the liquid flows along the bubble-breaking slope 712, if the affinity between the bubble-breaking slope 712 and the liquid is strong, the liquid may spread and remain on the bubble-breaking slope 712, forming a liquid film or droplet residue. After long-term operation, these residues will gradually accumulate and dry, forming a scale layer that is difficult to remove, affecting the flow guiding effect of the bubble-breaking slope 712 and even blocking the liquid flow path. In contrast, the anti-stick coating has a low surface energy, and the liquid has a large contact angle on it, making it difficult to spread and adhere. As a result, the droplets on the coating surface are spherical and easily roll off, thus effectively preventing the liquid from remaining and accumulating on the bubble-breaking slope 712.

[0045] In summary, by setting an anti-stick coating, it is possible to effectively prevent the adhesion of highly viscous substances such as polyvinyl alcohol to the bubble-breaking slope 712, avoiding the problem of poor flow due to the accumulation of adhering substances; at the same time, the low surface energy characteristics of the anti-stick coating make it easier for the liquid to flow down, accelerating the speed at which the liquid converges to the connecting plane 713; in addition, the anti-stick coating reduces the frequency of cleaning and maintenance of the bubble-breaking slope 712, reducing the operating cost of the device.

[0046] In a preferred embodiment of the present invention, reference is made to Figure 3 As shown, the liquid collector 72 is also roughly frustum-shaped, with its outer bottom surface forming a guide slope 723. When some of the rising gas, along with the foam, comes into contact with the guide slope 723, this part of the gas and foam is guided to move upward along the guide slope 723, and finally concentrates and rushes towards the bubble-breaking slope 712 on the collection hood 71, thereby improving the foam conveying efficiency and collection effect.

[0047] In a preferred embodiment of the present invention, reference is made to Figure 2 As shown, a heating chamber 714 is provided inside the collection hood 71. The heating chamber 714 contains a heat-conducting medium and a heating element 77 for heating the heat-conducting medium. Specifically, the collection hood 71 adopts a hollow internal design, with its internal space serving as the sealed heating chamber 714. The heating chamber 714 is filled with a heat-conducting medium, which can be selected from substances with good thermal conductivity and heat capacity, such as heat-conducting oil, water, or phase change materials. Additionally, an inlet / outlet 715 can be provided at the top of the collection hood 71 to facilitate the replacement or addition of the heat-conducting medium.

[0048] Heating element 77 is disposed inside heating chamber 714 and can be an electric heating tube, electric heating wire, or other form of electric heating element, used to heat the heat-conducting medium. Heating element 77 is connected to an external power source, and the heating temperature is adjusted by controlling the power-on state. After the heat-conducting medium is heated, it transfers heat to the inner and outer walls of the trapping shroud 71, especially to the bubble-breaking inclined surface 712 that is in contact with the foam.

[0049] The inventors of this invention further discovered that the high molecular weight substances such as polyvinyl alcohol contained in PVB resin production wastewater have high viscosity, and the viscosity of these substances decreases significantly with increasing temperature. When the temperature of the bubble-breaking slope 712 increases, the viscosity of the liquid formed after rupture decreases, its fluidity increases, and it flows more easily down the bubble-breaking slope 712, reducing liquid retention and adhesion on the bubble-breaking slope 712. At the same time, the increased temperature also helps the trace amounts of n-butyraldehyde remaining in the captured liquid film to volatilize again. During the flow of the liquid film on the bubble-breaking slope 712, due to the increased temperature, the saturated vapor pressure of n-butyraldehyde increases, and the volatilization rate accelerates. This portion of the residual n-butyraldehyde volatilizes from the liquid film, enters the gas phase, and is discharged from the gas guide pipe 73 along with the deflected gas, thereby further improving the total removal rate of n-butyraldehyde.

[0050] Preferably, the heating temperature range of the heat-conducting medium is controlled between 40-60℃. It should be noted that if the heating temperature is below 40℃, the viscosity reduction effect of polymers such as polyvinyl alcohol is not significant, and the anti-sticking and flow-promoting effects are limited; if the temperature is above 60℃, although the viscosity is further reduced, energy consumption increases, and it may adversely affect other components in the wastewater. Furthermore, high temperatures may accelerate certain corrosion processes. A temperature range of 40-60℃ effectively reduces viscosity and promotes secondary volatilization while balancing energy consumption and equipment safety.

[0051] In another preferred embodiment of the invention, the heating control method of the heating element 77 is further optimized. Specifically, the wastewater treatment device also includes a controller (not shown in the figure). The controller is electrically connected to both the heating element 77 and a flow detection element (e.g., a flow valve, not shown in the figure) on the air inlet pipe 60, and is used to adjust the heating temperature of the heat transfer medium according to the air intake.

[0052] Specifically, a flow detection element is installed on the air inlet pipe 60 to detect the amount of air entering the aeration device 40 in real time and transmit the air volume signal to the controller. The controller has a pre-set control logic, which can be a PID control algorithm or a lookup table control method based on empirical data. Based on the received air volume signal, the controller calculates the corresponding target heating temperature according to the pre-set control logic, and then controls the power output of the heating element 77 to make the temperature of the heat transfer medium reach or approach the target temperature.

[0053] This control method is designed based on the following technical principles: In the wastewater treatment device provided in this embodiment of the invention, the removal of n-butyraldehyde mainly relies on two pathways: one is the stripping effect during gas-liquid contact in the packing layer 30, determined by the air intake; the other is the secondary volatilization effect during heating the bubble-breaking inclined surface 712 in the foam collection device 70, determined by the heating temperature. These two pathways are complementary. When the air intake is large, the gas-liquid contact is sufficient, and the n-butyraldehyde in the wastewater has been sufficiently stripped in the packing layer 30, leaving less n-butyraldehyde remaining in the foam liquid film. In this case, the heating temperature can be appropriately reduced to save energy. When the air intake is small, the stripping effect is relatively weak, leaving more n-butyraldehyde remaining in the foam liquid film. In this case, the heating temperature needs to be increased to enhance the secondary volatilization effect and compensate for the insufficient stripping. Therefore, dynamically adjusting the heating temperature according to the air intake can achieve an optimized balance between energy consumption and treatment effect.

[0054] Specifically, the controller's control logic can be set to decrease the heating temperature when the intake air volume increases and increase the heating temperature when the intake air volume decreases, so that the heating temperature is continuously adjusted within the range of 40-60℃ according to the change in intake air volume. For example, a linear interpolation method can be used, so that when the intake air volume changes from the minimum to the maximum value, the heating temperature correspondingly decreases linearly from 60℃ to 40℃. This dynamic adjustment method ensures good processing results under different operating conditions while avoiding unnecessary energy consumption. The minimum intake air volume corresponds to the highest heating temperature, and the maximum intake air volume corresponds to the lowest heating temperature.

[0055] In another preferred embodiment of the invention, reference is made to Figure 2 As shown, the air guide tube 73 passes through the heating chamber 714, and the air guide tube 73 is made of a heat-conducting material.

[0056] Specifically, the top end of the air guide tube 73 enters through the connecting plane 713, first passes through the interior of the heating chamber 714, and then exits through the top surface of the trapping shroud 71 to communicate with the air outlet 11. The contact area between the air guide tube 73 and the heating chamber 714 maintains a good thermally conductive connection. This can be achieved by directly passing the air guide tube 73 through the heating chamber 714 and sealing it at the exit point, or by coiling or placing a portion of the air guide tube 73 inside the heating chamber 714. The air guide tube 73 is made of a material with good thermal conductivity, such as copper, aluminum, or stainless steel, to ensure good heat transfer efficiency.

[0057] Based on the above configuration, when the heat-conducting medium in the heating chamber 714 is heated, the heat from the heating chamber 714 is conducted through the wall of the gas guide pipe 73 to the interior of the gas guide pipe 73, thus heating the gas flowing through the gas guide pipe 73. After being heated, the gas temperature increases and its density decreases, creating natural convection within the gas guide pipe 73. That is, the driving force for the hot gas to flow upwards is enhanced. This natural convection effect can assist in gas discharge, reduce gas flow resistance, and lower the requirements for system pressure differential.

[0058] Meanwhile, after the gas in the duct 73 is heated, any trace amounts of water vapor or organic matter it may carry will not condense on the pipe wall, avoiding pipe wall adhesion and blockage problems caused by condensation. Furthermore, the design of the duct 73 passing through the heating chamber 714 also works in conjunction with the aforementioned temperature control strategy. When the controller adjusts the heating temperature according to the intake air volume, the gas temperature in the duct 73 changes accordingly. Specifically, when the intake air volume is small, the heating temperature increases, and the natural convection of the gas in the duct 73 is enhanced after heating, resulting in a more significant effect on auxiliary gas discharge and compensating for insufficient stripping. When the intake air volume is large, the heating temperature decreases, and natural convection weakens. At this point, the stripping effect itself is already sufficient, and the demand for auxiliary exhaust is correspondingly reduced. This coordinated relationship ensures that the natural convection effect matches the exhaust demand under different operating conditions, further optimizing the gas discharge effect. Example 2

[0059] Based on Example 1, Example 2 of the present invention provides a method for treating wastewater from PVB resin production, using the wastewater treatment device for PVB resin production described in Example 1 above.

[0060] Specifically, the wastewater treatment method includes the following steps: The wastewater to be treated enters the liquid distributor 20 through the inlet pipe 50. Under the action of the liquid distributor 20, the wastewater is evenly distributed across the entire cross-section inside the tower body 10, forming a uniform liquid flow that flows downwards along the axial direction of the tower body 10, sequentially passing through the packing layer 30 and the area containing the aeration device 40. Simultaneously, air enters the aeration device 40 through the air inlet pipe 60, dispersing the air into a large number of fine bubbles and releasing them into the tower body 10. These bubbles flow upwards along the axial direction of the tower body 10. In the packing layer 30 area, the downward-flowing wastewater comes into gas-liquid contact with the upward-flowing bubbles. According to the gas-liquid mass transfer theory, when the partial pressure of a volatile component in the gas phase is lower than its equilibrium partial pressure in the liquid phase, the component will transfer from the liquid phase to the gas phase. In this system, n-butyraldehyde in the wastewater has high volatility, and its partial pressure in the gas phase is much lower than its equilibrium partial pressure. Therefore, n-butyraldehyde rapidly evaporates from the liquid phase into the interior of the bubbles and moves upwards with them.

[0061] Because PVB resin production wastewater contains high-molecular-weight surfactants such as polyvinyl alcohol, these substances reduce surface tension, causing a stable liquid film to form on the surface of the bubbles as they rise, generating a large number of fine bubbles. These fine foam liquid films are enriched with high concentrations of pollutants such as n-butyraldehyde, polyvinyl alcohol, and polyvinyl butyral. The foam moves upward along the tower body 10 with the gas and enters the foam collection device 70.

[0062] As the rising gas carrying foam enters the foam collection device 70, it first encounters the collection hood 71. Because the sealing surface 711 of the collection hood 71 is sealed to the inner wall of the tower body 10, the rising gas and foam cannot escape from the edge and must impact the bubble-breaking inclined surface 712 of the collection hood 71. When the foam impacts the bubble-breaking inclined surface 712, it is subjected to impact force, causing the liquid film to vibrate and deform. When the liquid film thickness decreases to a critical value, the surface tension can no longer maintain the stability of the liquid film, causing the foam to rupture and release the concentrated liquid encapsulated within. The liquid formed after rupture flows downward along the bubble-breaking inclined surface 712 under the action of gravity, is guided to the connecting plane 713 at the bottom of the bubble-breaking inclined surface 712, and drips from the outer edge of the connecting plane 713.

[0063] Simultaneously, after impacting the bubble-breaking inclined surface 712, the gas loses its vertical momentum and is forced to change direction, flowing horizontally towards the center along the bubble-breaking inclined surface 712. The deflected gas enters the liquid collection chamber 721, and then enters the gas guide pipe 73 through the pre-reserved gap between the bottom end of the gas guide pipe 73 and the bottom surface of the liquid collection chamber 721. Afterward, the gas flows upward along the gas guide pipe 73, and finally exits from the top of the gas guide pipe 73 through the gas outlet 11, thus being discharged from the tower and sent for further processing.

[0064] Because the projection of the opening of the liquid collecting chamber 721 onto the axial direction of the tower body 10 covers the outer edge of the connecting plane 713, all the liquid dripping from the outer edge of the connecting plane 713 falls into the liquid collecting chamber 721 and does not drip to the outside. After accumulating at the bottom of the liquid collecting chamber 721, the liquid enters the return pipe 74 through the return port 722, flows along the return pipe 74, and then flows into the water inlet pipe 50, where it mixes with the new wastewater in the water inlet pipe 50 and re-enters the tower for further treatment.

[0065] The treated wastewater is finally discharged from the outlet 12 at the bottom of the tower 10 and enters subsequent biological treatment or other processes. For example, it can sequentially enter the equalization tank, the biological reaction tank, and the high-efficiency activated carbon adsorption tower for deep purification. The entire treatment process is continuous, with wastewater constantly entering and being discharged after treatment. The foam collection device 70 operates continuously to ensure that the system can stably and efficiently remove pollutants.

[0066] The wastewater treatment method provided in this embodiment of the invention, by adopting the wastewater treatment device provided in the aforementioned embodiment 1, at least possesses the beneficial effects of the wastewater treatment device provided in embodiment 1, effectively solving the problems of liquid accumulation, blockage, and corrosion in the gas phase pipeline caused by foam escape when the existing stripping tower treats PVB resin production wastewater, as well as the technical problem of overestimation of pollutant removal efficiency.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wastewater treatment device for PVB resin production, comprising a tower body, wherein a liquid distributor, a packing layer, and an aeration device are arranged sequentially from top to bottom inside the tower body; an air outlet is provided at the top of the tower body, and a water outlet is provided at the bottom of the tower body; the liquid distributor is connected to a water inlet pipe; and the aeration device is connected to an air inlet pipe; characterized in that, A foam trapping device is provided between the air outlet and the liquid distributor; the foam trapping device includes: The trapping hood includes a sealing surface, a bubble-breaking inclined surface adjacent to the sealing surface, and a connecting plane; the sealing surface is used to seal and connect with the circumferential inner wall of the tower body; along the axial direction of the tower body from top to bottom, the bubble-breaking inclined surface extends obliquely to the center of the tower body to guide the liquid formed after the intercepted foam breaks to its bottom; the connecting plane is located at the bottom of the bubble-breaking inclined surface and faces the bottom of the tower body; A liquid collector is located below the connecting plane and defines a liquid collection chamber with an open top; the projection of the opening of the liquid collection chamber onto the outer edge of the connecting plane in the axial direction of the tower body; a reflux port is provided at the bottom of the liquid collection chamber; A venting tube; the bottom end of the venting tube extends into the liquid collection chamber and has a gap between it and the bottom surface of the liquid collection chamber; the top end of the venting tube passes through the connecting plane and is sealed and fixed thereto; the top end of the venting tube is connected to the air outlet. Return pipe; one end of the return pipe is connected to the return port, and the other end of the return pipe is connected to the inlet pipe.

2. The wastewater treatment device for PVB resin production according to claim 1, characterized in that, A bubble-breaking screen is provided at the opening of the liquid collection chamber; the air guide tube passes through the bubble-breaking screen and is fixedly connected to the bubble-breaking screen.

3. The wastewater treatment device for PVB resin production according to claim 2, characterized in that, The mesh size of the bubble-breaking net is 0.5-1mm.

4. The wastewater treatment device for PVB resin production according to claim 1, characterized in that, The bubble-breaking inclined surface is provided with protrusions; the height of the protrusions is 0.2-0.5mm, and the distribution density is 10-50 per square centimeter.

5. The wastewater treatment device for PVB resin production according to claim 1, characterized in that, The trapping hood has a heating chamber inside; the heating chamber contains a heat-conducting medium and a heating element for heating the heat-conducting medium.

6. The wastewater treatment device for PVB resin production according to claim 5, characterized in that, It also includes a controller; the controller is electrically connected to both the heating element and the flow detection element on the air intake pipe, and is used to adjust the heating temperature of the heat-conducting medium according to the air intake volume.

7. The wastewater treatment device for PVB resin production according to claim 5, characterized in that, The air guide tube passes through the heating chamber; the air guide tube is made of a thermally conductive material.

8. The wastewater treatment device for PVB resin production according to claim 1, characterized in that, The bubble-breaking inclined surface is provided with an anti-stick coating.

9. The wastewater treatment device for PVB resin production according to claim 1, characterized in that, The return pipe is equipped with a one-way valve.

10. A method for treating wastewater from PVB resin production, comprising using the wastewater treatment apparatus for PVB resin production as described in any one of claims 1 to 9, characterized in that, Includes the following steps: The wastewater to be treated is introduced into the liquid distributor through the inlet pipe. After being evenly distributed by the liquid distributor, the wastewater flows downward. At the same time, air is introduced into the aeration device through the air inlet pipe. The aeration device generates bubbles that flow upward. In the packing layer, the gas and liquid come into contact, and the n-butyraldehyde in the wastewater volatilizes into the gas phase. The rising gas carries foam into the foam collection device. The foam impacts and breaks the bubble-breaking slope of the collection hood. The liquid formed after breaking flows along the bubble-breaking slope to the connecting plane and drips from the outer edge of the connecting plane. The gas flows along the bubble-breaking slope and enters the liquid collection chamber. It then enters the gas guide tube through the gap at the bottom of the gas guide tube and finally flows out from the gas outlet after passing through the top of the gas guide tube. The dripping liquid falls into the collection chamber, and after accumulating at the bottom of the collection chamber, the liquid flows through the return pipe into the inlet pipe, mixes with the new wastewater in the inlet pipe, and then re-enters the tower for treatment. The treated wastewater is discharged from the outlet.

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