Gas-liquid turbulent mass transfer device and method for low-temperature gas stripping purification of thermosensitive material

Abstract

The invention discloses a gas-liquid turbulent mass transfer device and method for low-temperature gas stripping purification of thermosensitive materials, the device comprises a tower body, the top of the tower body is provided with a liquid feed port and a gas discharge port, and the bottom of the tower body is provided with a liquid discharge port and a gas feed port; a turbulent element is arranged in the tower body and comprises a partition plate coaxially arranged in the gravity direction, a small rotational flow cavity, a large rotational flow cavity, a downcomer, a liquid seal circular groove and a plurality of connecting rib plates for fixing the liquid seal circular groove on the downcomer, and the small rotational flow cavity, the large rotational flow cavity and the downcomer are communicated in sequence; and a tangential gas inlet is formed in the side wall of the large rotational flow cavity. According to the invention, gas-liquid turbulent enhanced mass transfer is realized through the turbulent element, volatile components in the thermosensitive material are removed at low consumption on the premise of avoiding deterioration of the thermosensitive material, and meanwhile, the liquid seal circular groove is arranged to realize liquid seal at a lower liquid amount, so that the retention time of the thermosensitive material is shortened, and the energy consumption and the purification and separation cost are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical equipment, and in particular relates to a gas-liquid turbulent mass transfer device and method for low-temperature gas lift purification of heat-sensitive materials. Background Art

[0002] Heat-sensitive materials are widely used in industrial production and daily life. Many organic monomers and intermediates, fine chemical products, medicines and fragrances are heat-sensitive. Removing volatile components from heat-sensitive materials is an important part of the refined production of heat-sensitive materials. Compared with liquid-liquid extraction, gas-liquid mass transfer through carrier gas or steam does not introduce solvents or dissolved water, and is an efficient drying and separation method.

[0003] However, traditional steam stripping must increase the temperature of heat-sensitive materials, and heat-sensitive materials are very likely to undergo decomposition, polymerization, oxidation and other deterioration reactions when exposed to heat, causing significant economic losses. Therefore, heating of heat-sensitive materials should be avoided in industrial production.

[0004] At present, the main way to remove volatile components from heat-sensitive materials is to inject low-temperature carrier gas into heat-sensitive materials to reduce the partial pressure of volatile components and then achieve gas stripping separation of volatile components. However, low temperature conditions slow down the molecular diffusion rate of volatile components in the material, causing problems such as slow separation and low separation progress. Traditionally, the method of increasing the carrier gas injection amount of the packed tower or plate tower is used to increase the gas-liquid interface area and the gas-liquid turbulence degree, thereby compensating for the lack of gas-liquid mass transfer. However, excessive carrier gas injection means excessively high operating costs and excessive material volatilization losses. Summary of the invention

[0005] Aiming at the shortcomings of low-temperature gas lift purification of heat-sensitive materials in the prior art, the present invention proposes a gas-liquid turbulent mass transfer device and method for low-temperature gas lift purification of heat-sensitive materials.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention is to provide a gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials, comprising a tower body, wherein the top of the tower body is provided with a liquid feed inlet and a gas discharge port, and the bottom of the tower body is provided with a liquid discharge port and a gas feed inlet; a turbulent element is provided inside the tower body, wherein:

[0008] The turbulent element includes a baffle coaxially arranged along the gravity direction, a small cyclone cavity, a large cyclone cavity and a downcomer connected in sequence, a liquid sealing circular groove, and a plurality of connecting ribs for fixing the liquid sealing circular groove on the downcomer;

[0009] The upper side of the small cyclone cavity is fixed in the partition, and the top of the small cyclone cavity is higher than the upper surface of the partition;

[0010] The side wall of the large cyclone cavity is provided with a gas tangential inlet;

[0011] The bottom end of the downcomer is located in the liquid-sealed circular groove.

[0012] The present invention is further configured such that the number of the turbulence elements is one or more; when there are multiple turbulence elements, the multiple turbulence elements are arranged in series in the tower body along the gravity direction, which can increase the number of countercurrent contact units and the gas lift purification efficiency.

[0013] The present invention is further configured such that the height difference H between the top of the small cyclone cavity and the upper surface of the partition is 1 It is 10-20mm.

[0014] The present invention is further configured such that the large cyclone cavity and the small cyclone cavity are both cylindrical, wherein the diameter of the large cyclone cavity is 50-500 mm; and the ratio of the diameter of the small cyclone cavity to the large cyclone cavity is 0.3-0.7.

[0015] The present invention is further configured such that the number of the gas tangential inlets is one or more, and if there are multiple, they are evenly distributed; the cross-section of the gas tangential inlet is a narrow and long rectangle, and the ratio of the length of the long side a to the short side b of the narrow and long rectangle is 2-10.

[0016] The second aspect of the present invention is to provide a gas-liquid turbulent mass transfer method for low-temperature gas stripping purification of heat-sensitive materials based on the above device, comprising the following steps:

[0017] Liquid material is injected from the top of the tower body and forms a liquid layer above the partition. When the height of the liquid layer exceeds the top of the small cyclone cavity, it enters the small cyclone cavity. Gas material enters from the bottom of the tower body and enters the large cyclone cavity through the gas tangential inlet. The rising gas material and the descending liquid material complete turbulent mass transfer in the large cyclone cavity and the small cyclone cavity to remove the volatile components in the liquid material.

[0018] Subsequently, the gaseous material enters the top of the partition from the small cyclone cavity and is discharged from the top of the tower body; the liquid material enters the downcomer and the liquid seal groove in sequence from the large cyclone cavity and is finally discharged from the bottom of the tower body;

[0019] When a plurality of turbulent elements are connected in series in the tower body, the liquid overflowing from the liquid-sealed circular groove forms a liquid layer on the partition of the next-stage turbulent element; the gas above the partition enters the gas tangential inlet of the previous-stage turbulent element, and the above-mentioned turbulent mass transfer process is repeated, and finally the gas is discharged from the top of the tower body, and the liquid with the volatile components removed is discharged from the bottom of the tower body.

[0020] The present invention is further configured such that the ratio of the volume flow rates of the gas material and the liquid material, that is, the gas-liquid ratio, is 0.8-100. Under conditions of too small a gas-liquid ratio, liquid turbulence cannot be driven, and under conditions of too large a gas-liquid ratio, mist entrainment is prone to occur.

[0021] The present invention is further configured such that the velocity of the gas material at the gas tangential inlet is 0.5-20 m / s, and the gas Reynolds number Re inside the large cyclone cavity is 10-100.

[0022] The present invention is further configured such that the viscosity of the gas material is 0.002-0.1 cP;

[0023] When the gas viscosity is 0.002-0.02cP, the gas resistance is 0.1-1kPa, and the liquid seal level height is 0.01-0.1m; when the gas viscosity is 0.02-0.1cP, the gas resistance is 1-2kPa, and the liquid seal level height is 0.1-0.2m.

[0024] The present invention is further configured such that, in the operation link, liquid material should be injected first to form a liquid sealing area in the liquid sealing circular groove, and then gas material should be injected to prevent gas from entering the large cyclone cavity from the liquid sealing area.

[0025] The beneficial effects of the present invention are as follows:

[0026] The device of the present invention realizes gas-liquid turbulence enhanced mass transfer through turbulent elements, removes volatile components in heat-sensitive materials at low consumption while avoiding deterioration of heat-sensitive materials, and simultaneously provides a liquid seal circular groove to realize liquid seal at a lower liquid volume, thereby reducing the residence time of heat-sensitive materials. In addition, compared with the existing heat-sensitive material gas lift purification method, the present invention does not need to use steam, vacuum equipment and antioxidants, etc., greatly reducing energy consumption and purification and separation costs, and solving the problem that heat-sensitive materials are difficult to purify at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the gas-liquid turbulent mass transfer device for low-temperature gas lift purification of heat-sensitive materials according to the present invention.

[0028] Figure 2 It is a schematic diagram of the structure of the turbulent element.

[0029] Figure 3 yes Figure 2 Cross-sectional view along the AA direction.

[0030] Figure 4 It is a schematic diagram of the gas-liquid countercurrent contact form in the device of the present invention.

[0031] In the figure:

[0032] 10-tower body; 11-liquid feed port; 12-liquid discharge port; 13-gas feed port; 14-gas discharge port;

[0033] 20-turbulent element; 21-partition plate; 22-small cyclone cavity; 23-large cyclone cavity; 24-downcomer; 25-liquid seal groove; 26-connecting rib plate; 27-gas tangential inlet. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is clearly and comprehensively described below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the following embodiments are only part of the embodiments of the present invention. Other embodiments obtained by those skilled in the art without creative work still fall within the scope of protection of the present invention.

[0035] like Figure 1 The gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials shown in the figure comprises a tower body 10, the top of the tower body 10 is provided with a liquid feed port 11 and a gas discharge port 14, and the bottom of the tower body 10 is provided with a liquid discharge port 12 and a gas feed port 13; the interior of the tower body 10 is provided with a turbulent element 20, wherein:

[0036] Combination Figure 2 and Figure 3 As shown, the turbulent element 20 includes a baffle 21 coaxially arranged along the gravity direction, a small cyclone cavity 22, a large cyclone cavity 23 and a downcomer 24 that are sequentially connected, a liquid sealing circular groove 25, and a plurality of connecting ribs 26 for fixing the liquid sealing circular groove 25 on the downcomer 24;

[0037] The upper side of the small cyclone cavity 22 is fixed in the partition 21, and the top of the small cyclone cavity 22 is higher than the upper surface of the partition 21.

[0038] The side wall of the large cyclone cavity 23 is provided with a gas tangential inlet 27;

[0039] The bottom end of the downcomer 24 is located in the liquid-sealed circular groove 25 .

[0040] like Figure 4 As shown, the principle of mass transfer enhancement by the turbulent element 20 is as follows:

[0041] The gas is injected from the gas tangential inlet 27 on the side wall of the large cyclone cavity 23, and forms a gas-liquid cyclone flow with the descending liquid. Specifically, during the top-down movement of the liquid, the liquid is subjected to the centrifugal force of the gas cyclone and moves toward the side wall of the large cyclone cavity 23, and the gas and liquid form a turbulent countercurrent contact. The gas cyclones while penetrating the liquid, forming a large relative slip velocity between the gas and the liquid. According to the surface renewal mass transfer theory, gas-liquid equilibrium can be achieved in a very short time, and the effect of enhanced mass transfer can be achieved.

[0042] Furthermore, the number of the turbulence elements 20 is one or more; Figure 1 As shown, when there are multiple turbulence elements 20, the multiple turbulence elements 20 are arranged in series along the gravity direction in the tower body 10, which can increase the number of countercurrent contact units and the gas lift purification efficiency.

[0043] Furthermore, the height difference H between the top of the small cyclone cavity 22 and the upper surface of the partition 21 is 1 (like Figure 4 As shown) is 10-20mm.

[0044] Furthermore, the large cyclone cavity 23 and the small cyclone cavity 22 are both cylindrical, wherein the diameter of the large cyclone cavity 23 is 50-500 mm; and the ratio of the diameter of the small cyclone cavity 22 to the large cyclone cavity 23 is 0.3-0.7.

[0045] Furthermore, the number of the gas tangential inlet 27 is one or more, and if there are multiple, they are evenly distributed; Figure 3 As shown, the cross section of the gas tangential inlet 27 is a long and narrow rectangle, and the ratio of the length of the long side a to the short side b of the long and narrow rectangle is 2-10.

[0046] like Figure 1 and Figure 4 As shown, the gas-liquid turbulent mass transfer method for low-temperature gas stripping purification of heat-sensitive materials based on the above device includes the following steps:

[0047] Liquid material (i.e., heat-sensitive material including volatile components) is injected from the top of the tower body 10 and forms a liquid layer above the partition 21. When the height of the liquid layer exceeds the top of the small cyclone cavity 22, it enters the small cyclone cavity 22; gas material enters from the bottom of the tower body 10 and enters the large cyclone cavity 23 through the gas tangential inlet 27. The rising gas material and the descending liquid material complete turbulent mass transfer in the large cyclone cavity 23 and the small cyclone cavity 22 to remove the volatile components in the liquid material;

[0048] Subsequently, the gaseous material enters the top of the partition 21 from the small cyclone cavity 22 and is discharged from the top of the tower body 10; the liquid material enters the downcomer 24 and the liquid seal groove 25 from the large cyclone cavity 23 in sequence and is finally discharged from the bottom of the tower body 10;

[0049] When a plurality of turbulent elements 20 connected in series are arranged in the tower body 10, the liquid overflowing from the liquid-sealed circular groove 25 forms a liquid layer on the partition 21 of the next-stage turbulent element 20; the gas above the partition 21 enters the gas tangential inlet 27 of the previous-stage turbulent element 20, and the above-mentioned turbulent mass transfer process is repeated, and finally the gas is discharged from the top of the tower body 10, and the liquid with the volatile components removed is discharged from the bottom of the tower body 10.

[0050] Furthermore, the ratio of the volume flow rates of the gas material and the liquid material, that is, the gas-liquid ratio, is 0.8-100. If the gas-liquid ratio is too small, the liquid turbulence cannot be driven, and if the gas-liquid ratio is too large, mist entrainment is likely to occur.

[0051] Furthermore, the velocity of the gas material at the gas tangential inlet 27 is 0.5-20 m / s, and the gas Reynolds number Re inside the large cyclone cavity 23 is 10-100.

[0052] The gas Reynolds number can reflect the degree of turbulence. Wherein, D is the diameter of the large cyclone cavity 23, u is the gas velocity at the gas tangential inlet 27, and ρ G is the gas density, μ G is the gas viscosity.

[0053] Furthermore, the viscosity of the gas material is 0.002-0.1 cP. When the gas viscosity is high, the resistance of the gas moving from the tangential gas inlet 27 to the top of the partition 21 is large, and the gas resistance determines the height of the liquid seal level (e.g. Figure 4 As shown), the required liquid seal level is also larger, specifically:

[0054] When the gas viscosity is 0.002-0.02cP, the gas resistance is 0.1-1kPa, and the liquid seal level height is 0.01-0.1m; when the gas viscosity is 0.02-0.1cP, the gas resistance is 1-2kPa, and the liquid seal level height is 0.1-0.2m.

[0055] Furthermore, the height of the liquid layer above the partition 21 is 10-20 mm, so as to minimize the residence time of the heat-sensitive material while maintaining the mass transfer effect.

[0056] Furthermore, in the operation link, liquid material should be injected first to form a liquid seal circular groove 25 as shown in FIG. Figure 4 The liquid seal area shown is then injected with gas material to prevent the gas from entering the large cyclone cavity 23 from the liquid seal area.

[0057] Application Examples

[0058] Polyether polyols are typical heat-sensitive materials with poor thermal stability. When heated, they will undergo oxidation reactions, causing the material to turn yellow. In the traditional polyether polyol production process, multiple steps such as raw materials, side reactions, and post-processing will lead to the generation of volatile substances (aldehydes), which are difficult to separate.

[0059] Total aldehyde content test method: Use Shimadzu LC-20AT liquid chromatography instrument, UV detector, chromatographic column model VenusilXBPC18 (2), and the mobile phase is a mixture of water, acetonitrile and tetrahydrofuran (the mass ratio of the three is 53:31:16); after the sample is derivatized with 2,4-dinitrophenylhydrazine, aldehyde substances are determined by HPLC.

[0060] Example 1

[0061] The above-mentioned gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials was used to carry out nitrogen stripping treatment on polyether polyols to remove aldehyde volatile substances. The specific parameters and process conditions were set as follows:

[0062] Liquid flow rate is 0.1m 3 / h, nitrogen flow rate 3.6m 3 / h, gas-liquid ratio is 36;

[0063] The gas velocity at the gas tangential inlet 27 is 10 m / s, and the gas Reynolds number inside the large cyclone cavity 23 is 67.

[0064] The gas viscosity is 0.018 cP, the gas resistance is 0.18 kPa, and the liquid seal level height is 0.18 m.

[0065] The height of the liquid layer formed above the partition 21 is 10 mm;

[0066] The diameter of the large cyclone cavity 23 is 100 mm, the ratio of the diameter of the small cyclone cavity 22 to the diameter of the large cyclone cavity 23 is 0.5, and the ratio of the length of the long side a to the short side b of the gas tangential inlet 27 is 4.

[0067] Comparative Example 1

[0068] The polyether polyol was stripped by a method disclosed in CN106543427A for removing volatile substances from the polyether polyol and reducing odor. An antioxidant and a reducing agent were added to the polyether polyol. Then, water vapor was used as a stripping agent. The ratio of the water vapor flow rate to the volume flow rate of the polyether polyol was adjusted to 2.5. The stripping operation was carried out at 140°C and 0.08MPa.

[0069] Comparative Example 2

[0070] On the basis of the device of Example 1, the gas tangential inlet 27 of the turbulence element 20 is changed to eight radial inlets, and nitrogen stripping treatment is carried out at the same gas-liquid flow rate.

[0071] The treatment effect data of the above-mentioned embodiment 1 and comparative examples 1-2 are shown in the following table 1:

[0072] Table 1 Treatment effect data

[0073] Example 1 Comparative Example 1 Comparative Example 2 Initial total aldehyde content / ppm 200 200 200 Residual total aldehyde content / ppm 4 4 30 Purification efficiency 98％ 98％ 85％

[0074] From the results in Table 1, it can be seen that the device of the present invention can achieve a removal effect comparable to that of Comparative Example 1 without the addition of an antioxidant and a reducing agent, and significantly reduces the aldehyde substances in the polyether polyol. In addition, the present application adopts low-temperature stripping, which reduces the steam consumption, antioxidant consumption, and power consumption of the vacuum moving equipment of the steam stripping technology compared to Comparative Example 1.

[0075] In comparative example 2, the eight radial gas inlets reduce the gas velocity and fail to form a gas vortex in the large vortex cavity 23, resulting in a decrease in the turbulence level and failure to obtain effective gas lift separation.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials, characterized in that: The tower body comprises a tower body, wherein the top of the tower body is provided with a liquid feed port and a gas discharge port, and the bottom of the tower body is provided with a liquid discharge port and a gas feed port; a turbulent element is provided inside the tower body, wherein: The turbulent element includes a baffle coaxially arranged along the gravity direction, a small cyclone cavity, a large cyclone cavity and a downcomer connected in sequence, a liquid sealing circular groove, and a plurality of connecting ribs for fixing the liquid sealing circular groove on the downcomer; The upper side of the small cyclone cavity is fixed in the partition, and the top of the small cyclone cavity is higher than the upper surface of the partition; The side wall of the large cyclone cavity is provided with a gas tangential inlet; The bottom end of the downcomer is located in the liquid-sealed circular groove.

2. The gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials according to claim 1, characterized in that: The number of the turbulence elements is one or more; when there are multiple turbulence elements, the multiple turbulence elements are arranged in series in the tower body along the gravity direction.

3. The gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials according to claim 1, characterized in that: The height difference H1 between the top of the small cyclone cavity and the upper surface of the partition is 10-20 mm.

4. The gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials according to claim 1, characterized in that: The large cyclone cavity and the small cyclone cavity are both cylindrical, wherein the diameter of the large cyclone cavity is 50-500 mm; and the ratio of the diameter of the small cyclone cavity to the large cyclone cavity is 0.3-0.

7.

5. The gas-liquid turbulent mass transfer device for low-temperature gas stripping purification of heat-sensitive materials according to claim 1, characterized in that: The number of the gas tangential inlet is one or more, and if there are multiple inlets, they are evenly distributed; the cross-section of the gas tangential inlet is a narrow and long rectangle, and the ratio of the length of the long side a to the short side b of the narrow and long rectangle is 2-10.

6. A gas-liquid turbulent mass transfer method for low-temperature gas stripping purification of heat-sensitive materials, characterized in that: The gas-liquid turbulent mass transfer device for low-temperature gas stripping and purification of heat-sensitive materials according to any one of claims 1 to 5 comprises the following steps: Liquid material is injected from the top of the tower body and forms a liquid layer above the partition. When the height of the liquid layer exceeds the top of the small cyclone cavity, it enters the small cyclone cavity. Gas material enters from the bottom of the tower body and enters the large cyclone cavity through the gas tangential inlet. The rising gas material and the descending liquid material complete turbulent mass transfer in the large cyclone cavity and the small cyclone cavity to remove the volatile components in the liquid material. Subsequently, the gaseous material enters the top of the partition from the small cyclone cavity and is discharged from the top of the tower body; the liquid material enters the downcomer and the liquid seal groove in sequence from the large cyclone cavity and is finally discharged from the bottom of the tower body; When a plurality of turbulent elements are connected in series in the tower body, the liquid overflowing from the liquid-sealed circular groove forms a liquid layer on the partition of the next-stage turbulent element; the gas above the partition enters the gas tangential inlet of the previous-stage turbulent element, and the above-mentioned turbulent mass transfer process is repeated, and finally the gas is discharged from the top of the tower body, and the liquid with the volatile components removed is discharged from the bottom of the tower body.

7. The gas-liquid turbulent mass transfer method for low-temperature gas stripping purification of heat-sensitive materials according to claim 6, characterized in that: The ratio of the volume flow of the gas material to the liquid material, that is, the gas-liquid ratio, is 0.8-100.

8. The gas-liquid turbulent mass transfer method for low-temperature gas stripping purification of heat-sensitive materials according to claim 6, characterized in that: The velocity of the gas material at the gas tangential inlet is 0.5-20 m / s, and the gas Reynolds number Re inside the large cyclone cavity is 10-100.

9. The gas-liquid turbulent mass transfer method for low-temperature gas stripping purification of heat-sensitive materials according to claim 6, characterized in that: The viscosity of the gas material is 0.002-0.1 cP; When the gas viscosity is 0.002-0.02cP, the gas resistance is 0.1-1kPa, and the liquid seal level height is 0.01-0.1m; when the gas viscosity is 0.02-0.1cP, the gas resistance is 1-2kPa, and the liquid seal level height is 0.1-0.2m.

10. The gas-liquid turbulent mass transfer method for low-temperature gas stripping purification of heat-sensitive materials according to claim 6, characterized in that: During the operation, liquid material should be injected first to form a liquid seal area in the liquid seal circular groove, and then gas material should be injected to prevent gas from entering the large cyclone cavity from the liquid seal area.

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