A distillation apparatus and method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation.

Abstract

This application relates to the field of molecular distillation equipment technology, and more particularly to a distillation apparatus and method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. The distillation apparatus includes a rotary motor, an inner cylinder, an outer cylinder, and a scraper. The inner cylinder is nested within the outer cylinder and connected to the output end of the rotary motor. The scraper is fixedly connected to the rotating surface of the inner cylinder, and the scraping surface of the scraper is spaced apart from the inner wall of the outer cylinder. The inner wall of the outer cylinder has at least two sets of grooves, the included angle between the planes of the two sets of grooves being 80° to 90°, and the two sets of grooves are evenly distributed in the upper and lower parts of the outer cylinder. The length of each groove set is less than or equal to 0.50 of the height of the inner wall of the outer cylinder. Through parameter design and structural optimization of the groove sets in the outer cylinder, this distillation apparatus achieves synergistic improvements in flow path extension, mass transfer process enhancement, and anti-clogging, resulting in a purity of over 40% for the heavy component discharged from the outlet, while the distillation apparatus remains free of clogging.

Description

Technical Field

[0001] This application relates to the field of molecular distillation equipment technology, and in particular to a distillation apparatus and method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. Background Technology

[0002] If titanium dioxide waste acid is not effectively treated, direct discharge will not only cause serious environmental pollution but also result in a severe waste of resources. Currently, traditional methods for treating titanium dioxide waste acid mainly include neutralization and traditional waste acid concentration. However, these methods typically suffer from high investment costs, high energy consumption, easy clogging of evaporation pipes, and unstable equipment operation.

[0003] Molecular distillation is a special liquid-liquid separation technology that relies on the difference in the mean free path of molecules of different substances to achieve separation. It has wide applications in industries such as food, pharmaceuticals, and fine chemicals. Traditional molecular distillation equipment generally consists of a heating device and a condensing device. The incoming liquid is distilled once using the molecular distillation equipment to obtain the distillate.

[0004] However, traditional molecular distillation typically involves only one distillation cycle, meaning the feed liquid undergoes only one mass transfer process upon entering the equipment, resulting in low purity of the distillate. Furthermore, traditional molecular distillation equipment suffers from problems such as liquid phase retention and difficulty in smooth discharge. Summary of the Invention

[0005] This application provides a distillation apparatus and method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, in order to solve the following technical problem: how to reduce the risk of clogging in molecular distillation equipment under the premise of multiple distillations.

[0006] In a first aspect, embodiments of this application provide a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. The distillation apparatus includes a rotary motor, an inner cylinder, an outer cylinder, and a scraper. The inner cylinder is nested inside the outer cylinder, and the inner cylinder is connected to the output end of the rotary motor to drive the inner cylinder to rotate inside the outer cylinder. The scraper is fixedly connected to the rotating surface of the inner cylinder, and the scraping surface of the scraper is spaced apart from the inner wall of the outer cylinder. The inner wall of the outer cylinder is provided with at least two sets of grooves, the included angle between the planes of the two sets of grooves is 80° to 90°, and the two sets of grooves are evenly distributed in the upper and lower parts of the outer cylinder; the length of the groove set is less than or equal to 0.50 of the height of the inner wall of the outer cylinder.

[0007] Optionally, the groove group includes an upper groove group and a lower groove group. The upper groove group includes a first upper groove and a second upper groove. The lower groove group includes a first lower groove and a second lower groove. The first upper groove and the second upper groove are symmetrically arranged with respect to the center plane of the outer cylinder. The first lower groove and the second lower groove are also symmetrically arranged with respect to the center plane of the outer cylinder.

[0008] Optionally, the lengths of the first upper groove, the second upper groove, the first lower groove, and the second lower groove are 0.46 to 0.50 of the height of the inner wall of the outer cylinder.

[0009] Optionally, the center lines of the first upper groove and the second upper groove are located in a first plane, and the center lines of the first lower groove and the second lower groove are located in a second plane, with the included angle between the first plane and the second plane being 85° to 90°.

[0010] Optionally, the grooves in the groove group are circular grooves.

[0011] Optionally, the radius R of the circular groove satisfies: λ1<δ-d+R≤λ2, In the formula, δ is the gap distance between the scraping surface of the scraper and the inner wall of the outer cylinder, which is 0.30 mm to 1.0 mm; d represents the dynamic liquid film thickness formed by the operation of the scraper; λ1 is the mean free path of the heavy components to be separated in the titanium dioxide waste acid; λ2 is the mean free path of the light component to be separated in the titanium dioxide waste acid.

[0012] Optionally, the distillation apparatus further includes a light component outlet and a heavy component outlet. The light component outlet is located on the surface of the outer cylinder, and the heavy component outlet penetrates the outer cylinder and extends into the lower part of the inner cylinder. The outlet directions of the light component outlet and the heavy component outlet are perpendicular to each other.

[0013] Secondly, embodiments of this application provide a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. The distillation method is adapted to the distillation apparatus described in the first aspect, and the distillation method includes: The waste acid from titanium dioxide containing sulfuric acid is pretreated to obtain pretreated waste acid solution; Under vacuum conditions, the pretreated waste acid solution is subjected to multi-stage molecular distillation using the distillation apparatus described in the first aspect to remove water from the pretreated waste acid solution and obtain sulfuric acid.

[0014] Optionally, the multi-stage molecular distillation includes a heating section and a condensation section, wherein the final temperature of the heating section is 60°C to 80°C, and the temperature of the condensation section is 20°C to 35°C.

[0015] Optionally, the pressure of the vacuum environment is from 0.05 kPa to 0.10 kPa.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. Based on the structure of the inner and outer cylinders, the apparatus optimizes the internal structure of the outer cylinder and incorporates two sets of grooves. The included angle between the planes of the two sets of grooves is controlled to be 80° to 90°, and the two sets of grooves are evenly distributed in the upper and lower portions of the outer cylinder. The length of each groove set is less than or equal to 0.50 of the height of the inner wall of the outer cylinder. This allows the grooves to form staggered but non-overlapping guide channels on the inner wall of the outer cylinder. These staggered guide channels can guide the flow of the scraper... The propelled liquid material continuously flows from the upper part of the outer cylinder to the lower part, achieving a stepped flow of the liquid material. This stepped flow path extends the flow distance and time of the liquid material, and promotes the mass transfer process driven by the concentration gradient that may exist between different levels during the flow, thus constructing a multi-stage molecular distillation system. In addition, these staggered guide channels can guide the liquid material to flow faster and more directionally on the inner wall of the outer cylinder, and improve the smoothness of condensate accumulation, which helps to overcome the condensate discharge blockage problem in traditional distillation equipment. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided for an embodiment of this application;

[0020] Figure 2 A schematic diagram of the outer cylinder in a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided for an embodiment of this application;

[0021] Figure 3A schematic diagram of the distribution of groove groups in a distillation device for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided for an embodiment of this application;

[0022] Figure 4 A diagram showing the groove distribution in a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided in this application embodiment;

[0023] Figure 5 A schematic diagram of a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided for an embodiment of this application;

[0024] Figure 6 A schematic diagram of the actual process of a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided for an embodiment of this application;

[0025] Among them, 1-rotary motor, 2-inner cylinder, 3-outer cylinder, 4-scraper, 5-upper groove group, 501-first upper groove, 502-second upper groove, 6-lower groove group, 601-first lower groove, 602-second lower groove, 7-light component outlet, 8-heavy component outlet, 9-heating device, 10-condensing jacket, 11-liquid distributor, 12-waste acid inlet. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] The range descriptions used in this application, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "comprising" and others used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in this document, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained by purchasing from the market or by existing methods.

[0028] It should be noted that the existing improved solution is a multi-stage molecular distillation apparatus. This apparatus uses a "multi-stage series molecular distillation column" structural design. Unlike traditional single-stage molecular distillation apparatus, this apparatus achieves multi-stage molecular distillation through the series connection of three distillation columns. Each distillation column adopts a concentric circle design with "external heating and internal cooling," meaning the outer cylinder wall serves as the evaporation surface, and the central vertical condenser serves as the condensation surface. This structure is quite typical in molecular distillation apparatuses, but the key improvement of this apparatus in typical molecular distillation apparatuses is the realization of three-stage linkage. In addition, this apparatus also incorporates several structural details: a scraper that prevents scaling on the evaporation surface through a rotating scraper; a guide channel design at the liquid outlet to ensure precise separation of light and heavy fractions; and an integrated design of the vacuum system and hot oil circulation system.

[0029] However, while this distillation equipment improves the purity of the distilled products, it introduces new drawbacks: the system complexity increases dramatically, and energy consumption rises. Therefore, there is an urgent need to develop new solutions that combine efficient mass transfer with a simplified structure.

[0030] Figure 1 An exemplary schematic diagram of a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation is shown in an embodiment of this application. Figure 2 An exemplary schematic diagram of the outer cylinder of a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided in an embodiment of this application, is shown. like Figure 1 and Figure 2As shown in the figure, this application provides a distillation device for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. The distillation device includes a rotary motor 1, an inner cylinder 2, an outer cylinder 3, and a scraper 4. The inner cylinder 2 is nested inside the outer cylinder 3, and the inner cylinder 2 is connected to the output end of the rotary motor 1 to drive the inner cylinder 2 to rotate inside the outer cylinder 3. The scraper 4 is fixedly connected to the rotating surface of the inner cylinder 2, and the scraping surface of the scraper 4 is spaced apart from the inner wall of the outer cylinder 3. The inner wall of the outer cylinder 3 is provided with at least two sets of grooves, the included angle between the planes of the two sets of grooves is 80° to 90°, and the two sets of grooves are evenly distributed in the upper and lower parts of the outer cylinder 3; the length of the groove set is less than or equal to 0.50 of the height of the inner wall of the outer cylinder 3.

[0031] The included angle between the planes on which the two groove groups are located can be 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°, 89° or 90°.

[0032] It should be noted that this groove group is based on the existing multi-stage molecular distillation equipment, and uniquely introduces two sets of grooves with different arrangements on the inner wall of the outer cylinder 3. These grooves can serve as flow guides to guide the liquid phase material of titanium dioxide waste acid to flow in a directional and rapid manner under the action of the scraper 4, so as to avoid the liquid phase material from clogging the inner cylinder 2 and the outer cylinder 3.

[0033] It should be noted that the arrangement of this groove group can be used in conjunction with the scraper 4 of the rotating inner cylinder 2. The scraper 4 can continuously scrape the condensation surface of the inner wall of the outer cylinder 3, forcibly moving any liquid phase material film that may be trapped, and guiding it to different inner walls of the outer cylinder 3 through the guiding effect of the groove group. This not only prevents the increase in heat and mass transfer resistance caused by an excessively thick liquid phase material film, but also achieves high-frequency renewal of the liquid on the condensation surface of the inner wall of the outer cylinder 3, significantly enhancing the mass transfer rate. The scraper 4 can use a scraping blade.

[0034] It should be noted that the scraper 4 and the inner wall (i.e., the condensation wall) of the outer cylinder 3 are provided with a certain and small gap, which can prevent the material in the titanium dioxide waste acid from directly colliding with the inner wall of the outer cylinder 3, thereby reducing wear.

[0035] It should be noted that a heating device 9 can be installed inside the distillation apparatus, and the output end of the heating device 9 can be located on the surface of the inner cylinder 2 to increase the temperature of the titanium dioxide waste acid. In addition, a liquid distributor 11 can be installed between the top of the inner cylinder 2 and the inner wall of the outer cylinder 3 to increase the uniformity of dispersion of the titanium dioxide waste acid.

[0036] It should be noted that the outer wall of the inner cylinder 2 can be improved by using a condensing jacket 10 to enhance the condensation effect of the outer cylinder 3. This is beneficial for the directional and rapid flow of the two sets of grooves and helps to overcome the blockage of condensate discharge in traditional distillation equipment.

[0037] It should be noted that the distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation provided in this application embodiment has a double-layer structure of inner cylinder 2 and outer cylinder 3 as its basic framework. Through precise optimization of the internal structure of the outer cylinder 3, a significant improvement in the distillation concentration efficiency of titanium dioxide waste acid is achieved. Specifically: In terms of core structural design, the device incorporates two independent sets of grooves on the inner wall of the outer cylinder 3. This design is crucial for achieving multi-stage molecular distillation. To maximize the flow guidance effect, the included angle between the planes of the two sets of grooves is strictly controlled between 80° and 90°. This angle setting avoids overlapping interference between groove trajectories while forming mutually cooperating flow guidance paths. Furthermore, the two sets of grooves are not concentrated but evenly distributed in the upper and lower parts of the outer cylinder 3, with the length of each set less than or equal to 0.50 of the height of the inner wall of the outer cylinder 3. This length and distribution design allows the grooves to naturally form an interlaced, non-overlapping network of flow channels on the inner wall of the outer cylinder 3, providing a structured guiding channel for the flow of liquid materials.

[0038] These staggered flow channels optimize the distillation process in several ways. First, as the scraper 4 pushes the liquid material along the inner wall of the outer cylinder 3, the flow channels guide the material continuously from the upper part to the lower part of the outer cylinder 3, forming a stepped flow path. This path design significantly extends the flow distance and residence time of the liquid material on the inner wall of the outer cylinder 3, allowing the material more time to contact the heat source, promoting the volatilization and separation of light components, and laying the foundation for efficient distillation.

[0039] Secondly, during the stepped flow process, the materials in the upper and lower parts naturally form a concentration gradient due to their different degrees of volatilization. The staggered structure of the guide channels provides favorable conditions for mass transfer between different levels, promoting the concentration gradient-driven mass transfer process. Through this enhanced mass transfer between levels, the device successfully constructs a multi-stage molecular distillation system, achieving a separation effect similar to multiple distillations, and significantly improving the concentration and purity of the effective components in titanium dioxide waste acid.

[0040] Furthermore, the staggered guide channels address two major pain points of traditional distillation equipment. On one hand, the directional structure of the guide channels guides the liquid material to flow faster and in a more directional manner on the inner wall of the outer cylinder 3, avoiding material stagnation and accumulation in local areas and improving the uniformity and stability of material flow. On the other hand, the groove structure of the guide channels provides a clear channel for the accumulation of condensate, accelerating the discharge rate of condensate and effectively overcoming the common problem of condensate discharge blockage in traditional distillation equipment, thus ensuring the long-term stability of the unit's operation.

[0041] In summary, the present application provides a distillation device for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. Through precise parameter design and structural optimization of the outer cylinder 3 groove group, the distillation device achieves synergistic improvement in terms of flow path extension, mass transfer process enhancement, and anti-clogging, providing a reliable technical solution for the efficient concentration of titanium dioxide waste acid.

[0042] Figure 3 An exemplary schematic diagram of the distribution of the groove group in a distillation device for concentrating titanium dioxide waste acid based on multi-stage molecular distillation according to an embodiment of this application is shown; In some alternative implementations, such as Figure 3 As shown, the groove group includes an upper groove group 5 and a lower groove group 6. The upper groove group 5 includes a first upper groove 501 and a second upper groove 502. The lower groove group 6 includes a first lower groove 601 and a second lower groove 602. The first upper groove 501 and the second upper groove 502 are symmetrically arranged with respect to the center plane of the outer cylinder 3, and the first lower groove 601 and the second lower groove 602 are symmetrically arranged with respect to the center plane of the outer cylinder 3.

[0043] In these embodiments, the groove group is designed as an upper groove group 5 and a lower groove group 6, and the upper groove group includes a first upper groove 501 and a second upper groove 502, and the lower groove group 6 includes a first lower groove 601 and a second lower groove 602. The different upper and lower grooves are arranged relatively symmetrically, which can make the grooves in the upper groove group 5 and the lower groove group 6 in an alternating distribution state. This is beneficial to the discharge of condensate from the inner wall of the outer cylinder 3 and the directional flow speed of liquid phase materials, thus overcoming the condensate discharge blockage problem of traditional distillation equipment.

[0044] In some alternative embodiments, the lengths of the first upper groove 501, the second upper groove 502, the first lower groove 601, and the second lower groove 602 are 0.46 to 0.50 of the height of the inner wall of the outer cylinder 3.

[0045] In these embodiments, the first upper groove 501, the second upper groove 502, the first lower groove 601, and the second lower groove 602, with a length of 0.46 to 0.50 of the height of the inner wall of the outer cylinder 3, have sufficient length to allow the condensate on the inner wall of the outer cylinder 3 to be introduced from the upper part of the inner wall of the outer cylinder 3 to the lower part of the inner wall of the outer cylinder 3, thereby realizing the stepped flow of the liquid phase material driven by the scraper 4 to construct a multi-stage molecular distillation system. In addition, the sufficient length of the first upper groove 501, the second upper groove 502, the first lower groove 601, and the second lower groove 602 can effectively promote the directional and rapid flow of the liquid phase material, which is beneficial to overcoming the condensate discharge blockage problem in traditional distillation equipment.

[0046] It should be noted that the actual lengths of the first upper groove 501, the second upper groove 502, the first lower groove 601, and the second lower groove 602 need to be determined based on the end structure of the outer cylinder 3 and the inner cylinder 2, as well as the strength of the working conditions. For example, if the length of the groove is less than or equal to the axial length of the scraper 4, liquid accumulation in the unscraped area can be avoided. In addition, the groove design area needs to be maintained in the middle area of ​​the inner wall of the outer cylinder 3. To a certain extent, it is necessary to ensure that the starting and ending points of the grooves are separated from the top or bottom of the outer cylinder 3 by an un-grooved transition section. In practice, the length of the transition section needs to be greater than or equal to 0.02 to 0.05 of the height of the outer cylinder 3 to avoid the opening of the groove being too close to the end of the outer cylinder 3 under actual working conditions, which could lead to cracking of the distillation device due to the low strength of the edge material. Therefore, in practice, the length of each groove can be compressed to 0.45 to 0.48 of the height of the inner wall of the outer cylinder 3.

[0047] In some alternative embodiments, the center lines of the first upper groove 501 and the second upper groove 502 are located in a first plane, and the center lines of the first lower groove 601 and the second lower groove 602 are located in a second plane, with the included angle between the first plane and the second plane being 85° to 90°.

[0048] In these embodiments, controlling the center lines of the first upper-level groove 501 and the second upper-level groove 502 to be located in the first plane and the center lines of the first lower-level groove 601 and the second lower-level groove 602 to be located in the second plane with an angle of 80° to 90°, can form uniformly and staggered grooves among the first upper-level groove 501, the second upper-level groove 502, the first lower-level groove 601 and the second lower-level groove 602. These grooves can further promote the directional and rapid flow of liquid phase materials, and the flow direction is radial, which is beneficial to overcoming the blockage of condensate discharge in traditional distillation equipment.

[0049] The angle between the first plane and the second plane can be 85°, 86°, 87°, 88°, 89° or 90°.

[0050] In some alternative embodiments, the grooves in the groove group are circular grooves.

[0051] In these embodiments, the use of circular grooves optimizes the cross-section of the grooves. Since circular grooves lack sharp corners, they avoid the blockage of distillation equipment caused by particle or crystal deposition, compared to grooves with square, rectangular, or triangular cross-sections. This is particularly effective in preventing the deposition and blockage of metal ions in titanium dioxide waste acid.

[0052] Figure 4 An exemplary diagram of the groove distribution in a distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided in an embodiment of this application, is shown. In some alternative implementations, such as Figure 4 As shown, the radius R of the circular groove satisfies: λ1<δ-d+R≤λ2, In the formula, δ is the gap distance between the scraping surface of the scraper 4 and the inner wall of the outer cylinder 3, and the value is from 0.30mm to 1.0mm; d is the dynamic liquid film thickness formed by the operation of the scraper 4; λ1 is the mean free path of the heavy components to be separated in the titanium dioxide waste acid; λ2 is the mean free path of the light component to be separated in the titanium dioxide waste acid.

[0053] In these embodiments, a circular groove with radius R satisfying λ1<δ-d+R≤λ2 can have sufficient depth to accommodate a large amount of liquid material and promote the directional and rapid flow of the liquid material, which helps to overcome the blockage of condensate discharge in traditional distillation equipment.

[0054] It should be noted that, as Figure 4 As shown, after the scraper 4 is fixedly connected to the inner cylinder 2, the rotation speed of the scraper 4 can be controlled by controlling the rotation speed of the inner cylinder 2, so that a uniform dynamic film of liquid phase material can be formed on the surface of the scraper 4. The thickness of this dynamic film can be controlled according to the rotation speed of the inner cylinder 2. If the inner cylinder 2 rotates at a uniform speed, the thickness d of this dynamic film can be maintained at a certain level. The length of the motion path obtained by subtracting the thickness d of the dynamic film from the gap distance between the scraping surface of the scraper 4 and the inner wall of the outer cylinder 3, and adding it to the radius R of each groove, needs to be the same as the motion path of the light and heavy components of titanium dioxide waste acid between the inner cylinder 2 and the outer cylinder 3 to meet the separation requirements of titanium dioxide waste acid.

[0055] In some optional embodiments, the distillation apparatus further includes a light component outlet 7 and a heavy component outlet 8. The light component outlet 7 is located on the surface of the outer cylinder 3, and the heavy component outlet 8 penetrates the outer cylinder 3 and extends into the lower part of the inner cylinder 2. The discharge directions of the light component outlet 7 and the heavy component outlet 8 are perpendicular to each other.

[0056] In these embodiments, by vertically arranging the light component outlet 7 and the heavy component outlet 8 of the distillation apparatus, the light component can flow out from the light component outlet 7 and the heavy component can flow out from the heavy component outlet 8, based on the characteristics of the light and heavy components of the titanium dioxide waste acid and the arrangement of the two sets of grooves.

[0057] It should be noted that the distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation provided in this application embodiment has the following usage process: After pretreatment, the titanium dioxide waste acid enters through the waste acid inlet 12 of the distillation apparatus (generally located at the top of the distillation apparatus) and flows evenly to the wall of the inner cylinder 2 via the liquid distributor 11 above the inner cylinder 2. Symmetrically distributed scrapers 4 are installed on the wall of the inner cylinder 2, and the scrapers 4 are linked to a rotary motor 1 above the inner cylinder 2. When the rotary motor 1 is started, the scrapers 4 rotate synchronously with the inner cylinder 2, forcing the titanium dioxide waste acid flowing downwards along the inner wall of the outer cylinder 3 to form a thin and uniformly distributed dynamic liquid film. Simultaneously, the heating device 9 equipped in the inner cylinder 2 operates, raising the temperature of the dynamic liquid film. Under high vacuum, the molecules on the surface of the dynamic liquid film evaporate freely. Due to the different evaporation rates of different components, water (as a lighter component) evaporates preferentially, and its molecules have a larger mean free path. As these water molecules escape from the surface of the dynamic liquid film, they cross the gap between the inner cylinder 2 and the outer cylinder 3, impacting the cooler inner wall of the outer cylinder 3 (which is continuously cooled by the condensing jacket 10 on the outer wall) and condensing to form condensate. The condensate collects and is discharged from the light component outlet 7 connected to the outer cylinder 3. Meanwhile, the waste acid (as a heavy component), which has a slower evaporation rate and a smaller mean free path, mainly remains in the dynamic liquid film of the inner cylinder 2, and eventually flows out through the heavy component outlet 8 connected to the bottom of the inner cylinder 2, thus achieving the separation of water and waste acid.

[0058] Figure 5 An exemplary schematic diagram of a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, provided in an embodiment of this application, is shown. Figure 6 An exemplary schematic diagram of the actual process of a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation according to an embodiment of this application is shown. Based on a general inventive concept, such as Figure 5 and Figure 6As shown, this application provides a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. The distillation method is adapted to the distillation apparatus described in the first aspect, and the distillation method includes: S1. Pre-treat the waste acid from titanium dioxide containing sulfuric acid to obtain pre-treated waste acid solution; S2. Under vacuum conditions, the pretreated waste acid solution is subjected to multi-stage molecular distillation using the distillation apparatus to remove water from the pretreated waste acid solution and obtain sulfuric acid.

[0059] The distillation method is based on the distillation apparatus described above. The specific structure of the distillation apparatus can be referred to in the above embodiments. Since the distillation method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0060] It should be noted that this pretreatment mainly removes excess impurity ions from the titanium dioxide waste acid in order to improve the purity of the pretreated waste acid solution.

[0061] In some alternative embodiments, the multistage molecular distillation includes a heating section and a condensation section, wherein the heating section has an end temperature of 60°C to 80°C and the condensation section has a temperature of 20°C to 35°C.

[0062] In these embodiments, the heating section with an end temperature of 60°C to 80°C allows the titanium dioxide waste acid to be fully heated, promoting the distillation of the light components of the titanium dioxide waste acid to form gaseous light components, which is beneficial to the operation of the condensation section; in addition, the condensation section with a temperature of 20°C to 35°C allows the gaseous light components to be condensed to form condensate.

[0063] The final temperature of this heating section can be 60℃, 65℃, 70℃, 75℃ or 80℃.

[0064] The temperature of the condensation section can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 30℃ or 35℃.

[0065] In some alternative embodiments, the pressure of the vacuum environment is from 0.05 kPa to 0.10 kPa.

[0066] In these embodiments, a vacuum environment with a pressure of 0.05 kPa to 0.10 kPa allows the heating and condensation stages of the light components of titanium dioxide waste acid to proceed freely, effectively separating the light and heavy components of the titanium dioxide waste acid.

[0067] The pressure of the vacuum environment can be 0.05 kPa, 0.06 kPa, 0.07 kPa, 0.08 kPa, 0.09 kPa or 0.10 kPa.

[0068] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0069] Example 1 like Figure 1 and Figure 3 As shown, a distillation device for concentrating titanium dioxide waste acid based on multi-stage molecular distillation is disclosed. The distillation device includes a rotary motor 1, an inner cylinder 2, an outer cylinder 3, and a scraper 4. The inner cylinder 2 is nested inside the outer cylinder 3, and the inner cylinder 2 is connected to the output end of the rotary motor 1 to drive the inner cylinder 2 to rotate inside the outer cylinder 3. The scraper 4 is fixedly connected to the rotating surface of the inner cylinder 2. The inner wall of the outer cylinder 3 is provided with at least two sets of groove groups, including an upper groove group 5 and a lower groove group 6. The upper groove group 5 includes a first upper groove 501 and a second upper groove 502, and the lower groove group 6 includes a first lower groove 601 and a second lower groove 602. The first upper groove 501 and the second upper groove 502 are symmetrically arranged with respect to the center plane of the outer cylinder 3, and the first lower groove 601 and the second lower groove 602 are symmetrically arranged with respect to the center plane of the outer cylinder 3.

[0070] The lengths of the first upper groove 501, the second upper groove 502, the first lower groove 601, and the second lower groove 602 are 0.48 times the height of the inner wall of the outer cylinder 3.

[0071] The center lines of the first upper groove 501 and the second upper groove 502 are located in the first plane, and the center lines of the first lower groove 601 and the second lower groove 602 are located in the second plane. The included angle between the first plane and the second plane is 90°.

[0072] The grooves in the groove group are circular grooves.

[0073] The radius R of the circular groove satisfies: λ1<δ-d+R≤λ2, In the formula, δ is the gap distance between the scraping surface of the scraper 4 and the inner wall of the outer cylinder 3, and the value is 0.30mm; d represents the dynamic liquid film thickness formed by the operation of the scraper 4; λ1 is the mean free path of the heavy components to be separated in the titanium dioxide waste acid; λ2 is the mean free path of the light component to be separated in the titanium dioxide waste acid.

[0074] The calculated value of R is between 0.20 mm and 0.90 mm.

[0075] The distillation apparatus also includes a light component outlet 7 and a heavy component outlet 8. The light component outlet 7 is located on the surface of the outer cylinder 3, and the heavy component outlet 8 penetrates the outer cylinder 3 and extends into the lower part of the inner cylinder 2. The discharge directions of the light component outlet 7 and the heavy component outlet 8 are perpendicular to each other.

[0076] like Figure 5 and Figure 6 As shown, a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation is described. The distillation method is adapted to a distillation apparatus, including: S1. Pre-treat the waste acid from titanium dioxide containing sulfuric acid to obtain pre-treated waste acid solution; S2. Under vacuum conditions, the pretreated waste acid solution is subjected to multi-stage molecular distillation using the distillation apparatus to remove water from the pretreated waste acid solution and obtain sulfuric acid.

[0077] Multistage molecular distillation includes a heating section and a condensation section. The final temperature of the heating section is 60°C to 80°C, and the temperature of the condensation section is 20°C to 35°C.

[0078] The pressure in the vacuum environment is 0.05 kPa to 0.10 kPa.

[0079] Example 2

[0080] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The lengths of the first upper groove 501, the second upper groove 502, the first lower groove 601, and the second lower groove 602 are 0.50 times the height of the inner wall of the outer cylinder 3.

[0081] Example 3

[0082] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The lengths of the first upper groove 501 and the second upper groove 502 are 0.46 times the height of the inner wall of the outer cylinder 3, and the lengths of the first lower groove 601 and the second lower groove 602 are 0.50 times the height of the inner wall of the outer cylinder 3.

[0083] Example 4

[0084] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The angle between the first plane and the second plane is 85°.

[0085] Example 5

[0086] Compared to Example 1, the differences in this example are as follows, while the rest are the same: The angle between the first plane and the second plane is 80°.

[0087] Comparative Example 1

[0088] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same: Instead of using two sets of grooves, a traditional molecular distillation apparatus can be used directly.

[0089] Comparative Example 2

[0090] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same: The lengths of the first upper groove 501 and the second upper groove 502 are 0.55 times the height of the inner wall of the outer cylinder 3, and the lengths of the first lower groove 601 and the second lower groove 602 are 0.45 times the height of the inner wall of the outer cylinder 3.

[0091] Comparative Example 3

[0092] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same: The lengths of the first upper groove 501 and the second upper groove 502 are 0.60 times the height of the inner wall of the outer cylinder 3, and the lengths of the first lower groove 601 and the second lower groove 602 are 0.40 times the height of the inner wall of the outer cylinder 3.

[0093] Comparative Example 4

[0094] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same: The angle between the first plane and the second plane is 60°.

[0095] Comparative Example 5

[0096] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same: The angle between the first plane and the second plane is 45°.

[0097] Comparative Example 6

[0098] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same: The angle between the first plane and the second plane is 30°.

[0099] Relevant experimental and effect data: The purity of the material (generally regenerated sulfuric acid) at the discharge port of each embodiment and comparative example was statistically analyzed, and the results are shown in Table 1.

[0100] Table 1. Purity of regenerated sulfuric acid from the discharge port of each embodiment and comparative example.

[0101] As shown in Table 1, the distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation provided in this application embodiment achieves synergistic improvements in flow path extension, mass transfer process enhancement, and anti-clogging through precise parameter design and structural optimization of the outer cylinder groove assembly. This provides a reliable technical solution for the efficient concentration of titanium dioxide waste acid. The purity of the heavy component (regenerated sulfuric acid) discharged from the heavy component material outlet 8 reaches over 40%, and no clogging occurs in the distillation apparatus.

[0102] Compared to Example 1, Comparative Example 1 uses a conventional molecular distillation apparatus without grooves, which results in lower purity of the regenerated sulfuric acid and frequent clogging, affecting the use of the apparatus.

[0103] Compared to Example 1, the length of the groove group used in Comparative Example 2 and Comparative Example 3 is higher or lower than the height of the inner wall of the outer cylinder 3, which will result in a lower purity of the final regenerated sulfuric acid.

[0104] Compared to Example 1, the included angle between the two groove groups used in Comparative Examples 4, 5, and 6 is less than 80°. This results in lower purity of the final regenerated sulfuric acid. Furthermore, when the included angle is too small, partial blockage still occurs. This is because the two groove groups are distributed relatively close together, making it difficult to ensure uniform distribution of titanium dioxide waste acid during the working stage of the scraper 4, thus causing blockage of the distillation device. In addition, the narrower included angle used in Comparative Example 6 is approximately such that both groove groups are axially distributed, which cannot meet the requirements of multi-stage molecular distillation.

[0105] In summary, the present application provides a distillation device for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. Through precise parameter design and structural optimization of the groove group of the outer cylinder 3, and based on the structural design of "staggered grooves + uniform rotation of the scraper 3", the distillation device can efficiently achieve smooth discharge of condensate, enhanced mass transfer, and single-machine multi-stage molecular distillation effect with relatively simplified distillation equipment (only one unit is needed) and lower operational complexity.

[0106] In addition, the present application provides a distillation device for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. This distillation device is significantly different from the complex scheme in the prior art that requires multiple molecular distillation towers to be connected in series to achieve multi-stage molecular distillation. It only uses a single distillation device and only needs to set a few sets of grooves to achieve smooth discharge of condensate, enhanced mass transfer and single-machine multi-stage molecular distillation effect, which can effectively reduce the overall treatment cost of titanium dioxide waste acid.

[0107] Furthermore, this application provides a distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation. This distillation method relies on the aforementioned distillation apparatus and only requires pretreatment of the titanium dioxide waste acid. Combined with the multi-stage molecular distillation of the distillation apparatus, it can achieve smooth discharge of the condensate of the titanium dioxide waste acid, enhanced mass transfer, and the effect of multi-stage molecular distillation.

[0108] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A distillation apparatus for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, the distillation apparatus comprising a rotary motor, an inner cylinder, an outer cylinder, and a scraper, wherein the inner cylinder is nested within the outer cylinder and is connected to the output end of the rotary motor to drive the inner cylinder to rotate within the outer cylinder; the scraper is fixedly connected to the rotating surface of the inner cylinder, and the scraping surface of the scraper is spaced apart from the inner wall of the outer cylinder; The inner wall of the outer cylinder is provided with at least two sets of grooves, the included angle between the planes of the two sets of grooves is 80° to 90°, and the two sets of grooves are evenly distributed in the upper and lower parts of the outer cylinder; the length of the groove set is less than or equal to 0.50 of the height of the inner wall of the outer cylinder.

2. The distillation apparatus according to claim 1, characterized in that, The groove group includes an upper groove group and a lower groove group. The upper groove group includes a first upper groove and a second upper groove. The lower groove group includes a first lower groove and a second lower groove. The first upper groove and the second upper groove are symmetrically arranged with respect to the center plane of the outer cylinder. The first lower groove and the second lower groove are also symmetrically arranged with respect to the center plane of the outer cylinder.

3. The distillation apparatus according to claim 2, characterized in that, The lengths of the first upper groove, the second upper groove, the first lower groove, and the second lower groove are 0.46 to 0.50 of the height of the inner wall of the outer cylinder.

4. The distillation apparatus according to claim 2, characterized in that, The center lines of the first upper groove and the second upper groove are located in a first plane, and the center lines of the first lower groove and the second lower groove are located in a second plane. The included angle between the first plane and the second plane is 85° to 90°.

5. The distillation apparatus according to claim 1 or 2, characterized in that, The grooves in the groove group are circular grooves.

6. The distillation apparatus according to claim 5, characterized in that, The radius R of the circular groove satisfies: λ1<δ-d+R≤λ2, In the formula, δ is the gap distance between the scraping surface of the scraper and the inner wall of the outer cylinder, which is 0.30 mm to 1.0 mm; d represents the dynamic liquid film thickness formed by the operation of the scraper; λ1 is the mean free path of the heavy components to be separated in the titanium dioxide waste acid; λ2 is the mean free path of the light component to be separated in the titanium dioxide waste acid.

7. The distillation apparatus according to claim 1, characterized in that, The distillation apparatus further includes a light component outlet and a heavy component outlet. The light component outlet is located on the surface of the outer cylinder, and the heavy component outlet penetrates the outer cylinder and extends into the lower part of the inner cylinder. The outlet directions of the light component outlet and the heavy component outlet are perpendicular to each other.

8. A distillation method for concentrating titanium dioxide waste acid based on multi-stage molecular distillation, wherein the distillation method is adapted to the distillation apparatus as described in any one of claims 1 to 7, and the distillation method comprises: The waste acid from titanium dioxide containing sulfuric acid is pretreated to obtain pretreated waste acid solution; Under vacuum conditions, the pretreated waste acid solution is subjected to multi-stage molecular distillation using the distillation apparatus as described in any one of claims 1 to 7 to remove water from the pretreated waste acid solution and obtain sulfuric acid.

9. The distillation method according to claim 8, characterized in that, The multi-stage molecular distillation includes a heating section and a condensation section, wherein the final temperature of the heating section is 60°C to 80°C and the temperature of the condensation section is 20°C to 35°C.

10. The distillation method according to claim 8, characterized in that, The pressure of the vacuum environment is between 0.05 kPa and 0.10 kPa.

Images