Low-temperature rectification device control system for preparing high-purity carboxylic ester

Abstract

The invention relates to the technical field of low-temperature rectification, in particular to a low-temperature rectification device control system for preparing high-purity carboxylic ester, which comprises a distiller main body used for purifying a carboxylic ester coarse material and comprising a feeding assembly, a distillation assembly and a spraying assembly, the distillation assembly comprises a filler layer used for increasing the contact area of the carboxylic ester steam coarse material and the purified liquid and an ultrasonic imaging device arranged above the filler layer and used for obtaining a dry-wet distribution image; a temperature control mechanism; a pressure regulating mechanism; the control mechanism is used for determining the spraying mode of the spraying assembly according to the dry-wet distribution image and the air pressure difference of the filler layer and adjusting the distance between the upper surface of the feeding assembly and the filler layer according to the air pressure difference of the filler layer. And respectively determining the change rate of the internal air pressure of the distiller main body and the conversion frequency of the spraying mode according to the viscosity of the purified liquid. According to the invention, the purification efficiency of the carboxylic ester is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic distillation, and in particular to a control system of a cryogenic distillation device for preparing high-purity carboxylic acid esters. Background Art

[0002] In the prior art, control devices for high-purity carboxylic acid ester distillation include a tank body, a top cover, a collecting cover, a screw, a fixed heating coil, a movable heating coil, and other components. To achieve precise control of the heating coil, an adjustment assembly is typically also provided. This adjustment assembly includes a drive gear, a clamping plate, and an electric push rod. The extension and contraction of the electric push rod can drive the drive gear and the connecting gear to engage or disengage with each other, and the rotation of the drive motor drives the screw to rotate. The rotation of the screw drives the clamping block to move along the interior of the tank body, thereby squeezing the movable heating coil at the bottom, causing it to evenly contract and move toward the bottom, corresponding to the liquid level inside the tank. The control device for high-purity carboxylic acid ester distillation also focuses on improving heating efficiency and mixing effects. The rotation of the screw drives the movement of the movable heating coil, which in turn drives the nozzle toward the bottom. When liquid is added, it is added to the nozzle through a conduit, causing the liquid to mix with the liquid at the top. The rotation of the drive motor also drives the conduit and nozzle to rotate, further promoting solution mixing.

[0003] Chinese Patent Publication No. CN107141199A discloses a method and apparatus for low-temperature distillation of methanol mother liquor without reflux, comprising the following steps: a. steam is heated in a reboiler and then directed to the bottom of a distillation tower for heating, a portion of the methanol mother liquor is pumped into a preheater, and after preheating in the preheater, it enters the first distillation stage of the distillation tower for continuous distillation; a portion of the methanol mother liquor is pumped into the second distillation stage for distillation; b. the overhead fraction is condensed in a condenser and then directed to a methanol transfer tank, with the methanol in the methanol transfer tank being directly returned to the process system for reuse; c. a portion of the bottom liquid is directed to an ammonium chloride concentration section, and a portion is returned to a reboiler for evaporation and then re-enters the distillation tower. It can be seen from this that the method and apparatus for low-temperature distillation of methanol mother liquor without reflux has problems such as preferential crystallization in pits due to the rough surface of the packing, with the crystallization position protruding from the surface, thereby causing liquid bypass and reducing distillation efficiency; and a pressure difference caused by low-pressure cooling slows the flow rate of small-volume and light-weight liquid, which is concentrated on the upper side of the packing layer, resulting in uneven liquid distribution and reduced distillation purity. Summary of the Invention

[0004] To this end, the present invention provides a control system for a cryogenic distillation device for preparing high-purity carboxylic acid esters, which is designed to overcome the problems in the prior art of preferential crystallization in pits due to the rough surface of the packing, with the crystal positions protruding from the surface, thereby causing liquid bypass and reduced distillation efficiency; and the pressure difference caused by low-pressure cooling causes the flow rate of small-volume and light-weight liquid to slow down and concentrate on the upper side of the packing layer, resulting in uneven liquid distribution and reduced distillation purity.

[0005] To achieve the above-mentioned object, the present invention provides a control system for a cryogenic distillation device for preparing high-purity carboxylic acid esters, comprising: A distiller body for purifying carboxylic acid ester concentrate from carboxylic acid ester crude material comprises a feed assembly for introducing the carboxylic acid ester crude material into the distiller body to form a carboxylic acid ester crude vapor material, a distillation assembly disposed above the feed assembly for providing a purification area for the carboxylic acid ester crude vapor material, and a spray assembly disposed above the distillation assembly for spraying a purification liquid onto the distillation assembly and collecting the viscosity of the purified liquid. The distillation assembly includes a packing layer for increasing the contact area between the carboxylic acid ester steam crude material and the purified liquid, and an ultrasonic imaging device disposed above the packing layer for obtaining a dry-wet distribution image of a vertical plane of the packing layer; a temperature control mechanism connected to the distiller body and used to adjust the internal temperature of the distiller body; a pressure regulating mechanism connected to the distiller body and used to regulate the internal air pressure of the distiller body; A control mechanism is respectively connected to the distiller body, the temperature control mechanism and the pressure regulating mechanism, and is used to determine the spraying mode of the spraying component according to the dry-wet distribution image and the pressure difference between the upper and lower environments of the packing layer, adjust the distance between the upper surface of the feed component and the packing layer according to the pressure difference, and determine the rate of change of the internal air pressure of the distiller body and the switching frequency of the spraying mode according to the viscosity of the purified liquid.

[0006] Furthermore, the feed assembly comprises: A feed channel for conveying the carboxylic acid ester crude material; A feed pump is connected to the feed channel and is used for providing conveying power for the carboxylic acid ester crude material.

[0007] Furthermore, the voltage regulating component includes: a vacuum pump disposed on one side of the distiller body near the nozzle; a first air pressure sensor, which is arranged above the packing layer and is used to detect the air pressure above the packing layer and is recorded as a first air pressure; The second air pressure sensor is arranged below the packing layer and is used to detect the air pressure below the packing layer and record it as the second air pressure.

[0008] Furthermore, the spray assembly includes: a nozzle, which is arranged above the vacuum pump; a viscometer connected to the nozzle and used to collect the viscosity of the purified liquid; Wherein, the lower surface of the nozzle is provided with a knob for adjusting the spraying angle of the purified liquid.

[0009] Furthermore, the control mechanism is respectively connected to the ultrasonic imaging device, the first air pressure sensor, and the second air pressure sensor to obtain the echo signal, the first air pressure, and the second air pressure of the packing layer, and establishes a dry-wet distribution image of the liquid phase area with attached liquid and the dry area without attached liquid inside the packing layer according to the intensity distribution of the echo signal, and calculates the air pressure difference of the packing layer according to the first air pressure and the second air pressure; If the liquid phase region in the dry-wet distribution image appears in a prism-shaped distribution on the vertical plane of the packing layer, and the number of prism-shaped distributions is greater than or equal to a preset number, the dry-wet distribution type is determined to be a bypass type; If the distribution area of ​​the liquid phase region in the upper half of the vertical plane of the packing layer in the dry-wet distribution image is larger than the distribution area of ​​the lower half, and the air pressure difference is greater than or equal to the preset air pressure difference, the dry-wet distribution type is determined to be a laminar type.

[0010] Furthermore, the air pressure difference is the difference between the preset second air pressure and the preset first air pressure.

[0011] Furthermore, the control mechanism is connected to the nozzle and the viscometer respectively, so as to obtain the viscosity of the purified liquid under the condition that the dry-wet distribution type is a circumferential flow type. If the viscosity is less than the preset viscosity, the spraying mode of the nozzle is adjusted from the wide-angle atomizing spraying mode to a spraying mode that alternates between the wide-angle atomizing spraying mode and the rotary supercharged pulse spraying mode.

[0012] Furthermore, the control mechanism is connected to the feed assembly and is used to increase the distance between the upper surface of the feed assembly and the packing layer according to the air pressure difference under the condition that the dry-wet distribution type is a laminar flow type. Wherein, the distance between the upper surface of the feed assembly and the filler layer is positively correlated with the air pressure difference.

[0013] Furthermore, the control mechanism is respectively connected to the vacuum pump and the nozzle, so as to reduce the rate of change of the internal air pressure and increase the switching frequency of the spraying mode when the dry-wet distribution type is a circumferential flow type and the viscosity is greater than or equal to the preset viscosity.

[0014] Furthermore, the switching frequency of the spraying mode is the ratio of the number of switching times from the wide-angle atomizing spraying mode to the wide-angle atomizing spraying mode and the rotary supercharged pulse spraying mode to the unit switching time.

[0015] Compared with the prior art, the beneficial effect of the present invention is that the system of the present invention is provided with a distiller body, a temperature control mechanism, a pressure regulating mechanism and a control mechanism, and monitors the liquid distribution state of the packing layer through an ultrasonic imaging device. In combination with the pressure difference detected by the first air pressure sensor and the second air pressure sensor, it can identify different flow modes such as liquid vortex or laminar flow, and adjust the spraying mode of the nozzle and the distance between the upper surface of the feed component and the packing layer accordingly. Since the packing layer preferentially crystallizes at the pits, a distribution of vertical prismatic dry areas and liquid areas appears on the surface, and the presence of the prismatic dry areas will cause the liquid flow path on the surface of the packing layer to change, so that the liquid preferentially flows along the edge of the prismatic dry areas, forming The eddy current will cause the residence time of the liquid in the packing layer to be uneven. The residence time of the liquid in some areas is too long, while that in some areas is too short, thereby affecting the distillation efficiency. By changing the spraying mode of the nozzle and increasing the disturbance of the liquid, the liquid can be more evenly distributed in the packing layer, thereby improving the distillation efficiency. Due to the pressure difference of low-pressure cooling, the flow rate of the small-volume and light-weight liquid slows down and then concentrates on the upper side of the packing layer, thereby slowing down the downward flow rate of the carboxylic acid ester component, and the effect of separation achieved by the vapor-liquid interaction decreases, affecting the distillation purity. By adjusting the distance between the upper surface of the feed component and the packing layer, the degree of vapor-liquid interaction is increased, and the separation effect of the carboxylic acid ester crude material is improved.

[0016] Furthermore, the method of the present invention optimizes the distillation process by providing a feeding assembly, a pressure regulating assembly, and a spraying assembly, and flexibly adjusting the internal air pressure and the distance between the upper surface of the feeding assembly and the packing layer according to actual working conditions. The vacuum pump in the pressure regulating assembly maintains the air pressure inside the distiller body stable, and achieves low-temperature distillation by reducing the pressure. By controlling the feeding rate of the crude carboxylic acid ester material, the material is ensured to be evenly distributed in the distiller body, thereby further improving the distillation efficiency. The spraying assembly realizes the change of the spraying mode by controlling the spraying angle, avoiding the uneven distribution of the liquid in the packing layer, thereby improving the stability and efficiency of the distillation process.

[0017] Furthermore, the method of the present invention determines the dry-wet distribution type. Due to the low gas-liquid interaction efficiency of the packing layer caused by the circumferential and laminar flow types, which leads to reduced distillation efficiency, and the random distribution of dry and wet areas in the packing layer, which leads to unstable mass transfer area, the packing layer's moisture distribution is monitored by sensors and the distribution type of dry and wet areas is analyzed. When low efficiency caused by circumferential or laminar flow is detected, the corresponding distillation zoning process is implemented to reduce the uneven distribution of dry and wet areas, improve the gas-liquid interaction efficiency of the packing layer, stabilize the mass transfer area, and achieve improved distillation efficiency.

[0018] Furthermore, the method of the present invention adjusts the spraying mode of the nozzle from a wide-angle atomizing spraying mode to a spraying mode alternating between a wide-angle atomizing spraying mode and a rotary pressurized pulse spraying mode under the condition that the dry-wet distribution type is a circumferential flow type. The circumferential flow caused by the crystallization position on the protruding surface of the side wall of the packing layer will make the flow of the liquid in the packing layer uneven, and the liquid flow rate in some areas is faster, and the liquid flow rate in some areas is slower, thereby affecting the mixing effect and distillation efficiency of the liquid. By adjusting the spraying mode of the nozzle to an alternating between a wide-angle atomizing spraying mode and a rotary pressurized pulse spraying mode, the distribution of the liquid in the packing layer can be made more uniform, and at the same time, each position of the packing plate is flushed to increase the disturbance degree of the liquid, thereby improving the mixing effect and distillation efficiency of the liquid. A single spraying mode is prone to cause liquid phase deviation, and pulse spraying causes pressure oscillation to affect the separation effect and can also effectively avoid the formation of dead corners of the liquid in the packing layer, further improving the distillation effect.

[0019] Furthermore, the system of the present invention reduces the distance between the upper surface of the feed assembly and the packing layer according to the air pressure difference. The air pressure difference caused by low-pressure cooling will slow down the flow rate of small-volume and light-weight liquid, thereby concentrating it on the upper side of the packing layer, resulting in uneven liquid distribution, affecting the purity and efficiency of distillation. The air pressure fluctuation amplitude of the lower surface of the packing layer is large due to the evaporation of the gas generated by the feed port during the distillation process. By increasing the distance between the upper surface of the feed assembly and the packing layer, when the evaporating gas contacts the side wall of the packing layer after climbing, Its energy has been attenuated, thus reducing the impact on the packing layer and the problem of uneven liquid distribution caused by direct impact of the gas on the packing layer. The increased distance also enables the gas to better exchange heat with the liquid in the packing layer during the climbing process, reducing the accumulation of liquid in the packing layer, allowing the liquid to be more evenly distributed in the packing layer, increasing the area and time of gas-liquid interaction, thereby improving the purity and efficiency of distillation, reducing the excessive flow rate of liquid in the packing layer, reducing the back mixing of liquid, and further improving the distillation effect.

[0020] Furthermore, the system of the present invention reduces the rate of change of the internal air pressure and the switching frequency of the spraying mode. When the viscosity of the liquid is high, the fluidity of the liquid is weakened and the response speed to the change of air pressure becomes slower. By adopting a more stable air pressure regulation system, the rapid change of air pressure and the increase in viscosity caused by low temperature are reduced, thereby reducing the flow resistance. Since the pulse spraying pressure accumulates due to high viscosity liquid, the flow pattern conversion process is prone to interface disturbance. By increasing the switching frequency to avoid blockage or uneven spraying, the stability of the spraying is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is a schematic diagram of the overall structure of a control system of a cryogenic distillation device for preparing high-purity carboxylic acid esters according to an embodiment of the present invention; Figure 2 This is a block diagram of the overall structure of a control system for a cryogenic distillation device for preparing high-purity carboxylic acid esters according to an embodiment of the present invention; Figure 3 This is a block diagram of the main structure of the distiller of the control system of the cryogenic distillation device for preparing high-purity carboxylic acid esters according to an embodiment of the present invention; Figure 4 This is a structural block diagram of a spraying component of a control system of a cryogenic distillation device for preparing high-purity carboxylic acid esters according to an embodiment of the present invention; Explanation of the accompanying numbers: 1-distillation vessel body, 2-knob, 3-vent, 4-nozzle, 5-vacuum pump, 6-ultrasonic imaging device, 7-packing layer, 8-feed channel, 9-feed pump, 10-temperature control mechanism, 11-second air pressure sensor, 12-first air pressure sensor. DETAILED DESCRIPTION

[0022] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0023] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0025] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0026] See also Figure 1 、 Figure 2 、 Figure 3 as well as Figure 4, which are respectively a schematic diagram of the overall structure of the control system of a cryogenic distillation device for preparing high-purity carboxylic acid esters according to an embodiment of the present invention, a block diagram of the overall structure, a block diagram of the main structure of the distiller, and a block diagram of the structure of the spray assembly. A control system of a cryogenic distillation device for preparing high-purity carboxylic acid esters according to the present invention comprises: A distiller body 1 is used to purify a carboxylic acid ester concentrate from a carboxylic acid ester crude material, comprising a feed assembly for introducing the carboxylic acid ester crude material into the distiller body 1 to form a carboxylic acid ester crude vapor material, a distillation assembly disposed above the feed assembly for providing a purification area for the carboxylic acid ester crude vapor material, and a spray assembly disposed above the distillation assembly for spraying a purification liquid onto the distillation assembly and collecting the viscosity of the purified liquid. The distillation assembly includes a packing layer 7 for increasing the contact area between the carboxylic acid ester steam crude material and the purified liquid, and an ultrasonic imaging device 6 disposed above the packing layer 7 for obtaining a dry-wet distribution image of the vertical plane of the packing layer 7; a temperature control mechanism 10 connected to the distiller body 1 for adjusting the internal temperature of the distiller body 1; a pressure regulating mechanism connected to the distiller body 1 for regulating the internal air pressure of the distiller body 1; A control mechanism is respectively connected to the distiller main body 1, the temperature control mechanism 10 and the pressure regulating mechanism, and is used to determine the spraying mode of the spraying component according to the dry-wet distribution image and the pressure difference between the upper and lower environments of the packing layer 7, adjust the distance between the upper surface of the feed component and the packing layer 7 according to the pressure difference, and determine the rate of change of the internal air pressure of the distiller main body 1 and the switching frequency of the spraying mode according to the viscosity of the purified liquid.

[0027] Specifically, embodiments of the temperature control mechanism 10 include an electric heating ring and an attached heater.

[0028] Specifically, the types of crude carboxylic acid ester materials include purified ethyl acetate, dibutyl phthalate, and methyl methacrylate. The impurity components in the crude carboxylic acid ester materials include incompletely reacted raw materials, such as carboxylic acids and alcohols, acid anhydrides generated by self-condensation of carboxylic acids, such as acetic anhydride and propionic anhydride, and dialkyl ethers generated by dehydration of alcohols, such as diethyl ether and dipropyl ether.

[0029] Specifically, when the carboxylate crude material is ethyl acetate, the environmental parameters in the distiller body 1 are: The vacuum degree range is [8kpa, 14kpa]; The range of cryogenic distillation temperature is [-20℃, 18℃]; When the carboxylate crude material is dibutyl phthalate, the environmental parameters in the distiller body 1 are: The vacuum degree range is [0.1kpa, 1kpa]; The range of cryogenic distillation temperature is [50℃, 80℃]; When the carboxylate crude material is methyl methacrylate, the environmental parameters in the distiller body 1 are: The vacuum degree range is [10kpa, 20kpa]; The temperature range of cryogenic distillation is [-10℃, 30℃].

[0030] Specifically, the crude carboxylate material is a carboxylate with a concentration of less than 90%; the refined carboxylate material is a carboxylate with a concentration of 99%.

[0031] Specifically, the crude carboxylate ester vapor is a vaporized form of the crude carboxylate ester.

[0032] Specifically, the purified liquid is an ethylene glycol solution with a concentration ratio of 55% ethylene glycol and 45% water.

[0033] Specifically, embodiments of the ultrasonic imaging device 6 include a focused 3D imager and a scanning imager.

[0034] Specifically, a gas release port 3 for releasing the distilled impurities in the form of gas is provided on the side wall of the distiller body near the nozzle.

[0035] In practice, the system of the present invention is provided with a distiller body 1, a temperature control mechanism 10, a pressure regulating mechanism and a control mechanism, and monitors the liquid distribution state of the packing layer 7 through an ultrasonic imaging device 6. In combination with the pressure difference detected by the first air pressure sensor 12 and the second air pressure sensor 11, it is possible to identify different flow modes such as liquid vortex or laminar flow, and adjust the spraying mode of the nozzle 4 and the distance between the upper surface of the feed assembly and the packing layer 7 accordingly. Since the packing layer 7 preferentially crystallizes at the pits, a distribution of vertical prismatic dry areas and liquid areas appears on the surface, and the presence of the prismatic dry areas causes the liquid flow path on the surface of the packing layer 7 to change, so that the liquid preferentially flows along the edges of the prismatic dry areas, forming vortex. The bypass flow will cause the residence time of the liquid in the packing layer 7 to be uneven, with the residence time of the liquid in some areas being too long and that in some areas being too short, thereby affecting the distillation efficiency. By changing the spraying mode of the nozzle 4 and increasing the disturbance of the liquid, the liquid can be more evenly distributed in the packing layer 7, thereby improving the distillation efficiency. Due to the pressure difference caused by low-pressure cooling, the flow rate of the small-volume and light-weight liquid slows down and is concentrated on the upper side of the packing layer 7, thereby slowing down the downward flow rate of the carboxylic acid ester component, reducing the effect of separation achieved by the vapor-liquid interaction, and affecting the distillation purity. By adjusting the distance between the upper surface of the feed component and the packing layer 7, the degree of vapor-liquid interaction is increased, and the separation effect of the carboxylic acid ester crude material is improved.

[0036] Specifically, the feed assembly includes: A feed channel 8 for conveying the carboxylate crude material; A feed pump 9 is connected to the feed channel 8 and is used to provide conveying power for the carboxylic acid ester crude material.

[0037] Specifically, the feed channel 8 is a pipe that can transport liquid. The material of the pipe is not limited here as long as it can transport carboxylic acid ester.

[0038] Specifically, the voltage regulating component includes: a vacuum pump 5 , which is provided on one side of the distiller body 1 near the nozzle 4 ; a first air pressure sensor 12, which is arranged above the packing layer 7 and is used to detect the air pressure above the packing layer 7 and is recorded as a first air pressure; The second air pressure sensor 11 is disposed below the packing layer 7 and is used to detect the air pressure below the packing layer 7 and record it as the second air pressure.

[0039] Specifically, the spray assembly includes: a nozzle 4, which is arranged above the vacuum pump 5; a viscometer (not shown), connected to the nozzle 4, for collecting the viscosity of the purified liquid; The lower surface of the nozzle 4 is provided with a knob 2 for adjusting the spraying angle of the purified liquid.

[0040] Specifically, the nozzle 4 adjusts the spraying angle by adjusting the size of the spraying cross section.

[0041] Specifically, an exhaust port is provided on the side wall of the distiller body 1 near the nozzle 4 .

[0042] Specifically, examples of the viscometer include a digital viscometer, a capillary viscometer, a falling rod viscometer, a rotational viscometer, a falling ball viscometer, and a vibration viscometer.

[0043] During implementation, the method of the present invention optimizes the distillation process by setting a feeding component, a pressure regulating component, and a spraying component, and flexibly adjusting the internal air pressure and the distance between the upper surface of the feeding component and the packing layer 7 according to actual working conditions. The vacuum pump 5 in the pressure regulating component maintains the air pressure inside the distiller body 1 stable, and realizes low-temperature distillation by reducing the pressure. By controlling the feeding rate of the crude carboxylic acid ester material, the material is ensured to be evenly distributed in the distiller body 1, thereby further improving the distillation efficiency. The spraying component realizes the change of the spraying mode by controlling the spraying angle, avoiding the uneven distribution of the liquid in the packing layer 7, thereby achieving the improvement of the stability and efficiency of the distillation process.

[0044] Specifically, the control mechanism is connected to the ultrasonic imaging device 6, the first air pressure sensor 12, and the second air pressure sensor 11, respectively, to obtain the echo signal, the first air pressure, and the second air pressure of the packing layer 7, and establish a dry-wet distribution image of the liquid phase area with attached liquid and the dry area without attached liquid inside the packing layer 7 according to the intensity distribution of the echo signal, and calculate the air pressure difference of the packing layer 7 according to the first air pressure and the second air pressure; If the liquid phase region in the dry-wet distribution image has a prismatic distribution on the vertical plane of the packing layer 7, and the number of prismatic distributions is greater than or equal to a preset number, the dry-wet distribution type is determined to be a circumferential flow type; If the distribution area of ​​the liquid phase region in the upper half of the vertical plane of the packing layer 7 in the dry-wet distribution image is larger than the distribution area in the lower half, and the air pressure difference is greater than or equal to the preset air pressure difference, the dry-wet distribution type is determined to be a laminar type.

[0045] Specifically, the air pressure difference is the difference between the preset second air pressure and the preset first air pressure.

[0046] Specifically, establishing a dry-wet distribution image of the liquid phase area with attached liquid and the dry area without attached liquid in the vertical plane inside the packing layer 7 based on the intensity distribution of the echo signal is an existing technology well known to those skilled in the art and will not be described in detail here.

[0047] Specifically, under the conditions that the carboxylic acid ester crude material is ethyl acetate, the radius of the packing layer 7 is 0.3m, and the height is 0.03m, the general value range of the preset number is [6, 15], and the general value range of the preset air pressure difference is [40Pa, 80Pa]; the preferred embodiment of the preset number is 10, and the preferred embodiment of the preset air pressure difference is 50Pa.

[0048] Those skilled in the art will understand that the optional range of the preset quantity and the preset air pressure difference provided in this embodiment and the preferred embodiment are the values ​​selected in this embodiment under the conditions that the carboxylic acid ester crude material is ethyl acetate, the radius of the packing layer 7 is 0.4m, and the height is 30mm, which are the best values ​​for the technical problem solved by the technical solution of the present invention. In actual applications or experiments, those skilled in the art can adaptively adjust the preset quantity and the preset air pressure difference according to the actual application environment and application scenario.

[0049] In practice, the method of the present invention determines the dry-wet distribution type. Due to the low gas-liquid interaction efficiency in packing layer 7 caused by eddy and laminar flow, which leads to reduced distillation efficiency, and the random distribution of dry and wet areas in packing layer 7, resulting in an unstable mass transfer area, sensors are used to monitor the moisture distribution in packing layer 7 and analyze the distribution type of dry and wet areas. When low efficiency caused by eddy or laminar flow is detected, the corresponding distillation zoning process is implemented to reduce the uneven distribution of dry and wet areas, increase the gas-liquid interaction efficiency in packing layer 7, stabilize the mass transfer area, and achieve improved distillation efficiency.

[0050] Specifically, the control mechanism is respectively connected to the nozzle 4 and the viscometer to obtain the viscosity of the purified liquid under the condition that the dry-wet distribution type is a circumferential flow type. If the viscosity is less than the preset viscosity, the spraying mode of the nozzle 4 is adjusted from the wide-angle atomizing spraying mode to a spraying mode that alternates between the wide-angle atomizing spraying mode and the rotary supercharged pulse spraying mode.

[0051] Specifically, the spraying angle is the angle between two sides of the purified liquid sprayed from the nozzle 4 on a vertical plane.

[0052] Specifically, the maximum spray angle of the wide-angle atomizing spray mode is 75°, the minimum spray angle of the rotary boost pulse spray mode is 10°, the minimum rotation rate of knob 2 is 2 rpm, and the maximum pressure of the pulse spray is 0.28 MPa. The maximum pressure is calculated based on a fluid mechanics model with a porosity of 38% for the packing layer 7 and a gas phase Reynolds number Re=2200. The calculation process is well known to those skilled in the art and will not be described in detail here. When performing the rotary pressurized pulse spraying mode, the pulse pressure maintains a fluctuation threshold of ±0.02Mpa.

[0053] In implementation, the method of the present invention adjusts the spraying mode of the nozzle 4 from a wide-angle atomizing spraying mode to a spraying mode alternating between a wide-angle atomizing spraying mode and a rotary pressurized pulse spraying mode under the condition that the dry-wet distribution type is a circumferential flow type. The circumferential flow caused by the crystallization position on the protruding surface of the side wall of the packing layer 7 will make the flow of the liquid in the packing layer 7 uneven, and the liquid flow rate in some areas is faster, and the liquid flow rate in some areas is slower, thereby affecting the mixing effect and distillation efficiency of the liquid. By adjusting the spraying mode of the nozzle 4 to an alternating between a wide-angle atomizing spraying mode and a rotary pressurized pulse spraying mode, the distribution of the liquid in the packing layer 7 can be made more uniform, and at the same time, each position of the packing plate is flushed to increase the disturbance degree of the liquid, thereby improving the mixing effect and distillation efficiency of the liquid. A single spraying mode is prone to cause liquid phase deviation, and pulse spraying causes pressure oscillation to affect the separation effect and can also effectively avoid the formation of dead corners of the liquid in the packing layer 7, further improving the distillation effect.

[0054] Specifically, the control mechanism is connected to the feed assembly and is used to increase the distance between the upper surface of the feed assembly and the packing layer 7 according to the air pressure difference under the condition that the dry-wet distribution type is laminar flow type. The distance between the upper surface of the feed assembly and the packing layer 7 is positively correlated with the air pressure difference.

[0055] Specifically, an embodiment of adjusting the distance between the upper surface of the feeding assembly and the filler layer 7 is to increase the distance by reducing the feeding amount.

[0056] In implementation, under the conditions that the carboxylic acid ester crude material is ethyl acetate, the radius of the packing layer 7 is 0.3m, and the height is 0.03m, if the difference between the air pressure difference and the preset air pressure difference increases by 5Pa, the distance between the upper surface of the feeding component and the packing layer 7 increases by 5mm. For example, if the difference between the air pressure difference and the preset air pressure difference is 10Pa, and the distance between the upper surface of the current feeding component and the packing layer 7 is 300mm, the distance increases to 300mm+5mm+5mm=310mm.

[0057] In practice, the system of the present invention reduces the distance between the upper surface of the feed component and the packing layer 7 according to the air pressure difference. The air pressure difference caused by low-pressure cooling will slow down the flow rate of small-volume and light-weight liquid, thereby concentrating it on the upper side of the packing layer 7, resulting in uneven liquid distribution, affecting the purity and efficiency of distillation. The air pressure fluctuation amplitude of the lower surface of the packing layer 7 is large due to the evaporation of the gas generated by the feed port during the distillation process. By increasing the distance between the upper surface of the feed component and the packing layer 7, when the evaporating gas contacts the side wall of the packing layer 7 after climbing, its The energy has been attenuated, thus reducing the impact on the packing layer 7 and the problem of uneven liquid distribution caused by the direct impact of the gas on the packing layer 7. The increased distance also enables the gas to better exchange heat with the liquid in the packing layer 7 during the climbing process, reducing the accumulation of the liquid in the packing layer 7, allowing the liquid to be more evenly distributed in the packing layer 7, increasing the area and time of gas-liquid interaction, thereby improving the purity and efficiency of the distillation, reducing the excessive flow rate of the liquid in the packing layer 7, reducing the back mixing of the liquid, and further improving the distillation effect.

[0058] Specifically, the control mechanism is connected to the vacuum pump 5 and the nozzle 4, respectively, and is used to reduce the rate of change of the internal air pressure and increase the switching frequency of the spraying mode when the dry-wet distribution type is a circumferential flow type and the viscosity is greater than or equal to the preset viscosity.

[0059] Specifically, the switching frequency of the spraying mode is the ratio of the number of switching times from the wide-angle atomizing spraying mode to the wide-angle atomizing spraying mode and the rotary supercharged pulse spraying mode to the unit switching time.

[0060] Specifically, the unit switching time is 1 minute.

[0061] Preferably, under the conditions that the carboxylate coarse material is ethyl acetate, the radius of the packing layer 7 is 0.3m, the height is 0.03m, the porosity of the packing layer 7 is 38%, and the gas phase Reynolds number Re=2200, the switching frequency of the spraying mode is increased to twice the ratio of the number of switching times from the wide-angle atomizing spraying mode to the wide-angle atomizing spraying mode and the rotary supercharged pulse spraying mode to the unit switching time, and the switching is performed according to the alternating frequency. Specifically, the rate of change of the internal air pressure is the amount of change of the internal air pressure of the vacuum pump 5 per unit depressurization time during the depressurization process.

[0062] Specifically, under the conditions that the carboxylic acid ester crude material is ethyl acetate, the radius of the packing layer 7 is 0.3m, the height is 0.03m, the porosity of the packing layer 7 is 38%, and the gas phase Reynolds number Re=2200, the general value of the preset viscosity is [10Pa·s, 14Pa·s], and the preferred embodiment of the preset viscosity is 12.5MPa·s.

[0063] Those skilled in the art will understand that the optional range of the preset viscosity and the preferred embodiment provided in this embodiment are the values ​​selected under the conditions that the carboxylic acid ester crude material is ethyl acetate, the radius of the packing layer 7 is 0.3m, the height is 0.03m, the porosity of the packing layer 7 is 38%, and the gas phase Reynolds number Re=2200 to achieve the best effect on the technical problem solved by the technical solution of the present invention. In actual applications or experiments, those skilled in the art can adaptively adjust the preset viscosity according to the actual application environment and application scenarios.

[0064] In practice, if the difference between the viscosity and the preset viscosity exceeds 0.5 MPa·s, the rate of change of the internal pressure is reduced to 0.95 of the original value. For example, if the viscosity is 14 MPa·s and the current rate of change of the internal pressure is 100 Pa / s, the rate of change of the internal pressure is reduced to .

[0065] In practice, the system of the present invention reduces the rate of change of the internal air pressure and the switching frequency of the spraying mode. When the viscosity of the liquid is high, the fluidity of the liquid is weakened and the response speed to the air pressure change is slowed down. By adopting a more stable air pressure regulation system, the rapid change of air pressure and the increase in viscosity caused by low temperature are reduced, thereby reducing the flow resistance. Since the pulse spraying pressure accumulates due to high viscosity liquid, the flow pattern conversion process is prone to interface disturbance. By increasing the switching frequency to avoid blockage or uneven spraying, the stability of the spraying is improved.

[0066] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A control system for a cryogenic distillation device for preparing high-purity carboxylic acid esters, characterized in that: include: A distiller body for purifying carboxylic acid ester concentrate from carboxylic acid ester crude material comprises a feed assembly for introducing the carboxylic acid ester crude material into the distiller body to form a carboxylic acid ester crude vapor material, a distillation assembly disposed above the feed assembly for providing a purification area for the carboxylic acid ester crude vapor material, and a spray assembly disposed above the distillation assembly for spraying a purification liquid onto the distillation assembly and collecting the viscosity of the purified liquid. The distillation assembly includes a packing layer for increasing the contact area between the carboxylic acid ester steam crude material and the purified liquid, and an ultrasonic imaging device disposed above the packing layer for obtaining a dry-wet distribution image of a vertical plane of the packing layer; a temperature control mechanism connected to the distiller body and used to adjust the internal temperature of the distiller body; a pressure regulating mechanism connected to the distiller body and used to regulate the internal air pressure of the distiller body; A control mechanism is respectively connected to the distiller body, the temperature control mechanism and the pressure regulating mechanism, and is used to determine the spraying mode of the spraying component according to the dry-wet distribution image and the pressure difference between the upper and lower environments of the packing layer, adjust the distance between the upper surface of the feed component and the packing layer according to the pressure difference, and determine the rate of change of the internal air pressure of the distiller body and the switching frequency of the spraying mode according to the viscosity of the purified liquid.

2. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 1, characterized in that: The feed assembly comprises: A feed channel for conveying the carboxylic acid ester crude material; A feed pump is connected to the feed channel and is used for providing conveying power for the carboxylic acid ester crude material.

3. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 2, characterized in that: The voltage regulating component comprises: a vacuum pump disposed on one side of the distiller body near the nozzle; a first air pressure sensor, which is arranged above the packing layer and is used to detect the air pressure above the packing layer and is recorded as a first air pressure; The second air pressure sensor is arranged below the packing layer and is used to detect the air pressure below the packing layer and record it as the second air pressure.

4. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 3, characterized in that: The spray assembly comprises: a nozzle, which is arranged above the vacuum pump; a viscometer connected to the nozzle and used to collect the viscosity of the purified liquid; Wherein, the lower surface of the nozzle is provided with a knob for adjusting the spraying angle of the purified liquid.

5. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 4, characterized in that: The control mechanism is connected to the ultrasonic imaging device, the first air pressure sensor, and the second air pressure sensor, respectively, to obtain the echo signal of the packing layer, the first air pressure, and the second air pressure, and to establish a dry-wet distribution image of the liquid phase area with attached liquid and the dry area without attached liquid inside the packing layer according to the intensity distribution of the echo signal, and calculate the air pressure difference of the packing layer according to the first air pressure and the second air pressure; If the liquid phase region in the dry-wet distribution image appears in a prism-shaped distribution on the vertical plane of the packing layer, and the number of prism-shaped distributions is greater than or equal to a preset number, the dry-wet distribution type is determined to be a bypass type; If the distribution area of ​​the liquid phase region in the upper half of the vertical plane of the packing layer in the dry-wet distribution image is larger than the distribution area of ​​the lower half, and the air pressure difference is greater than or equal to the preset air pressure difference, the dry-wet distribution type is determined to be a laminar type.

6. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 5, characterized in that: The air pressure difference is the difference between the preset second air pressure and the preset first air pressure.

7. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 6, characterized in that: The control mechanism is connected to the nozzle and the viscometer respectively, and is used to obtain the viscosity of the purified liquid under the condition that the dry-wet distribution type is a circumferential flow type. If the viscosity is less than the preset viscosity, the spraying mode of the nozzle is adjusted from the wide-angle atomizing spraying mode to a spraying mode that alternates between the wide-angle atomizing spraying mode and the rotary supercharged pulse spraying mode.

8. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 7, characterized in that: The control mechanism is connected to the feed assembly and is used to increase the distance between the upper surface of the feed assembly and the packing layer according to the air pressure difference under the condition that the dry-wet distribution type is a laminar flow type. Wherein, the distance between the upper surface of the feed assembly and the filler layer is positively correlated with the air pressure difference.

9. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 8, characterized in that: The control mechanism is connected to the vacuum pump and the nozzle respectively, and is used to reduce the rate of change of the internal air pressure and increase the switching frequency of the spraying mode when the dry-wet distribution type is a circumferential flow type and the viscosity is greater than or equal to the preset viscosity.

10. The control system for a cryogenic distillation device for preparing high-purity carboxylic acid ester according to claim 9, characterized in that: The switching frequency of the spraying mode is the ratio of the number of switching times from the wide-angle atomizing spraying mode to the wide-angle atomizing spraying mode and the rotary supercharged pulse spraying mode to the unit switching time.

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