Sub-boiling distillation apparatus using constant-boiling heat supply

Abstract

The application discloses a sub-boiling distillation device using constant-boiling heat supply and belongs to the technical field of distillation and purification. The device comprises a constant-boiling evaporation part, a sub-boiling distillation part nested in a constant-boiling chamber, a condensate circulation control part and an integrated jacket structure. The device uses constant-boiling evaporation heat supply, automatically maintains a sub-boiling state through a temperature gradient and does not need complex temperature control. The device is cooperatively controlled by a non-contact liquid level sensor and a condensate buffer tank, avoids secondary pollution and can adjust pressure or change the composition of a constant-boiling zone to accurately control evaporation temperature. The device has two modes of single sub-boiling and continuous two-stage distillation. Surface area enhancing internal components can be additionally arranged in the sub-boiling chamber, a liquid column is formed by using surface tension and the distillation efficiency is significantly improved. The device has the advantages of simple structure, high thermal efficiency, good purification effect and suitability for laboratory preparation of high-purity reagents.

Description

Technical Field

[0001] This invention relates to the field of distillation and purification technology, and more specifically to a sub-boiling distillation apparatus that utilizes azeotropic heating. Background Technology

[0002] Distillation is a method of separating and purifying substances by heating a liquid to vaporize it and then condensing the vapor. It is commonly used to purify liquid substances. Among common distillation methods, boiling distillation is widely used due to its simplicity and high throughput. However, because the liquid is heated to its boiling point, the boiling vaporization process produces a large number of aerosol particles. These aerosol particles often carry metal ions and solid particles present in the liquid phase. Therefore, the purification effect of boiling distillation is quite limited, and the metal ion content of the reagents obtained through boiling distillation does not change significantly, making it difficult to meet the requirements of high-purity applications.

[0003] To obtain reagents with higher purity, sub-boiling distillation technology was developed. The biggest difference between this technique and boiling distillation is that the liquid temperature is below its boiling point, typically controlled at 10-20°C below the boiling point. Because the vapor pressure at the liquid surface still exists below the boiling point, sub-boiling distillation can control temperature and pressure to continuously generate vapor at the liquid surface without causing violent boiling inside the liquid. Since sub-boiling distillation is slower than azeotropic distillation, the process control often depends on the diffusion mass transfer step, which can usually be designed with a larger liquid phase surface area to improve evaporation efficiency.

[0004] Because vigorous boiling of the liquid is avoided, the formation of aerosol particles is greatly reduced, thus preventing impurities (such as metal ions and solid particles) from being carried into the vapor. This allows for the purification of organic reagents containing trace metals in the laboratory. High-purity organic solvents with strictly controlled impurity content are widely used in trace analysis and high-precision experiments in the laboratory, such as in high-precision analysis, pharmaceuticals, and electronics manufacturing. Sub-boiling distillation is suitable for preparing such small quantities of high-purity reagents.

[0005] Existing patent application CN202320524249.7 discloses a quartz sub-boiling distillation apparatus for removing trace metallic impurities from chlorosilane materials. This apparatus is equipped with a temperature control device with at least three temperature sensors to detect the liquid phase temperature, gas phase temperature, and condensate temperature, respectively. Conventional sub-boiling distillation apparatuses typically require precise temperature control to prevent the liquid from boiling, which increases both the operational complexity and cost. Patent application CN87201984 discloses an azeotropic and sub-boiling dual high-purity water evaporator. This device uses a float valve structure based on the communicating vessel principle to control the system liquid level. This structure is inconvenient to manufacture and limits the density of the reagent to be purified. The device uses a glass bulb with a slightly movable air vent as a condensate reflux valve, resulting in inaccurate control of the azeotropic liquid temperature and pressure. Furthermore, its long heat utilization path leads to low efficiency and heat loss. A prior art patent with application number CN202321965473.6 discloses a PFA sub-boiling distillation apparatus, which uses a thermal radiation lamp to radiate heat onto the evaporator, causing the liquid inside to reach a sub-boiling state for sub-boiling distillation. The evaporation efficiency of this apparatus is limited by the liquid phase surface area, which is constrained by the cross-sectional area inside the evaporator, resulting in low evaporation efficiency.

[0006] Therefore, to address the aforementioned problems, this invention provides a sub-boiling distillation apparatus utilizing azeotropic heating. An integrated jacket structure nests a sub-boiling evaporator within an azeotropic evaporator, utilizing the heat energy from the boiling of the azeotropic liquid as a heat source. The sub-boiling evaporation temperature is automatically controlled via the temperature gradient of heat transfer. Simultaneously, a non-contact capacitive liquid level sensor and a condensate reflux valve are introduced to achieve intelligent control, solving the problems of complex structure, low control precision, low thermal efficiency, and susceptibility to secondary pollution in existing technologies. Furthermore, based on biomimetic principles, this apparatus designs a surface-enhanced star-shaped concave structured packing. This packing utilizes the capillary effect of the liquid, allowing it to rise from the horizontal liquid phase surface along the structure of this component. Through rational structural design and combination, a large number of liquid columns capable of mass exchange with the gas phase are formed on the liquid surface, avoiding the limitation of the liquid phase surface area by the evaporator cross-sectional area, providing a large gas-liquid exchange surface, and improving the sub-boiling distillation efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a sub-boiling distillation apparatus that utilizes azeotropic heating and has a surface area-enhanced star-shaped concave structured packing, in order to solve the problems of complex structure, low control precision, low thermal efficiency, easy introduction of secondary pollution, and evaporation efficiency limited by the cross-sectional area of ​​the container in the prior art.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A sub-boiling distillation apparatus utilizing azeotropic heating includes an azeotropic evaporation section, a sub-boiling distillation section, a condensate circulation control section, and an integrated jacket structure. The azeotropic evaporation section includes an azeotropic chamber 1, an azeotropic condenser 3, an electric heating platform 12, a feed valve 7, a condensate reflux valve 6, and a non-contact capacitive level sensor 10. The electric heating platform 12 is located at the bottom of the azeotropic chamber 1 for heating; the feed valve 7 is located at the top of the azeotropic chamber 1 for replenishing the condensate.

[0010] The condensate return valve 6 is located at the top of the azeotropic chamber 1 to regulate the pressure inside the chamber; the non-contact capacitive liquid level sensor 10 is attached to the outer wall of the azeotropic chamber 1 for non-contact detection of the liquid level.

[0011] The subboiling distillation section includes a subboiling chamber 2, a subboiling condenser 8, a liquid collection bottle 9, and a temperature probe 14. The top of the subboiling chamber 2 is provided with an interface communicating with the outlet of the condensate buffer tank 4, a steam outlet communicating with the inlet of the subboiling condenser 8, and an interface for installing the temperature probe 14. The temperature probe 14 is located at the interface at the top of the subboiling chamber 2 and is used to monitor the steam temperature inside the subboiling chamber 2. The subboiling condenser 8 is connected to the steam outlet of the subboiling chamber 2, and its outlet is connected to the liquid collection bottle 9.

[0012] The condensate circulation control section includes a condensate buffer tank 4, a condensate outlet valve 5, and a condensate return valve 6; the bottom outlet of the azeotropic condenser 3 is connected to the top inlet of the condensate buffer tank 4, and the bottom of the condensate buffer tank 4 is provided with two outlets, one of which is connected to the top interface of the sub-boiling chamber 2 through the condensate outlet valve 5, and the other of which is connected to the azeotropic chamber 1 through the condensate return valve 6.

[0013] The integrated jacket structure nests and fixes the sub-boiling chamber 2 inside the azeotropic chamber 1, ensuring that the evaporating portion of the sub-boiling chamber 2 is completely immersed in the boiling liquid and its vapor atmosphere within the azeotropic chamber 1. For a given liquid composition, at a constant pressure, its boiling point remains constant. Therefore, the temperature within the azeotropic evaporator remains constant and uniform, unaffected by fluctuations in heating power and ambient temperature. This creates an extremely stable heat source for the sub-boiling evaporator. The temperature gradient from heat transfer automatically controls the liquid temperature within the sub-boiling chamber 2 to remain below its boiling point, achieving heat supply from azeotropic evaporation to sub-boiling evaporation. Utilizing the heat energy generated by azeotropic evaporation eliminates the need for additional heating devices. Furthermore, due to the temperature gradient, a complex temperature control system is unnecessary to automatically maintain the sub-boiling state, simplifying the equipment structure and reducing manufacturing costs.

[0014] Preferably, the outer wall of the azeotropic chamber 1 is covered with an insulation sleeve 11 to reduce heat loss and improve thermal efficiency. The design of the insulation sleeve effectively reduces heat radiation and convective heat dissipation from the azeotropic chamber to the external environment, allowing more of the heat generated by azeotropic evaporation to be used to heat the sub-boiling chamber, thus improving energy utilization efficiency. At the same time, it also makes the boiling state inside the azeotropic chamber more stable, which is conducive to maintaining a constant temperature in the sub-boiling chamber.

[0015] Preferably, the non-contact capacitive liquid level sensor 10 includes at least two sensors, corresponding to preset upper and lower liquid level thresholds respectively. The sensor signal output terminals are connected to the control system, which controls the opening or closing of the feed valve 7 based on the received signals to achieve automatic liquid replenishment. This non-contact detection method avoids the problems of metal ion precipitation and particulate matter contamination that may occur when traditional float valves or probe-type liquid level gauges come into direct contact with high-purity solvents, ensuring the purity of the reagent throughout the distillation process. Simultaneously, the automatic liquid replenishment function allows the device to operate unattended for extended periods, improving operational convenience and safety.

[0016] Preferably, the azeotropic chamber 1, the sub-boiling chamber 2, and the azeotropic condenser 3 are all made of high-purity quartz glass; the sub-boiling condenser 8, the liquid collection bottle 9, and the pipeline connecting the sub-boiling condenser 8 and the liquid collection bottle 9 are all made of soluble polytetrafluoroethylene (PFA). This graded material design ensures excellent thermal stability and chemical inertness while avoiding secondary pollution introduced by material precipitation.

[0017] Preferably, the condensate buffer tank 4 and the condensate reflux valve 6 are used to adjust the pressure in the azeotropic chamber 1 according to the Antoine equation, thereby precisely controlling the boiling point temperature of the azeotropic liquid, and indirectly adjusting the evaporation temperature of the liquid in the sub-boiling chamber 2. According to the Antoine equation... For a liquid with a specific composition, there is a definite correlation between saturated vapor pressure and temperature. By adjusting the opening of the condensate reflux valve 6 to control the amount of hot condensate flowing back to the azeotropic chamber 1, the liquid level in the condensate buffer tank 4 can be changed, thereby regulating the vapor pressure balance within the azeotropic chamber 1 and achieving precise control of the boiling point temperature. This pressure regulation method is more precise and stable than directly controlling the heating power, and can meet the different requirements of various reagents for sub-boiling distillation temperatures.

[0018] Preferably, the device can adjust the azeotropic temperature in the azeotropic chamber by changing the composition of the liquid within the azeotropic zone. Because the interactions between different molecules in the mixture are different, the boiling point of the mixture will change. The azeotropic temperature of the binary mixture with a certain composition can be obtained through the Txy phase diagram of the binary mixture. This method of changing the composition of the azeotropic liquid can change the boiling temperature of the azeotropic liquid, and thus adjust the evaporation temperature in the sub-boiling chamber through heat transfer. This method of changing the composition of the azeotropic liquid can also conveniently change the temperature of sub-boiling distillation.

[0019] Preferably, the device has two operating modes: when the condensate outlet valve 5 is closed and the condensate reflux valve 6 is opened, a separate sub-boiling distillation purification mode is achieved where the azeotropic chamber 1 provides a heat source for the sub-boiling chamber 2; when the condensate outlet valve 5 is opened, a continuous purification mode is achieved where the first-stage azeotropic distillation and the second-stage sub-boiling distillation are connected in series. This dual-mode design allows the device to adapt to different purification needs, improving the versatility and practicality of the equipment.

[0020] Preferably, a surface area enhancement internal component 13 can be placed inside the subboiling chamber 2 to form a liquid column on the surface of the component using the surface tension of the liquid, thereby increasing the gas-liquid interface and significantly improving the subboiling distillation efficiency without boiling, thus solving the problem of slow subboiling distillation rate in traditional methods.

[0021] Preferably, the surface area-enhancing internal component 13 is formed by longitudinally stacking the smallest structural units. The liquid columns formed by the longitudinal stacking do not contact each other and air columns exist, thus achieving a larger gas-liquid interface. The smallest structural unit is designed with a star-shaped line structure and adjustable-thickness support pillars. This design is particularly suitable for common organic solvents with surface tension lower than water, such as alcohols like methanol, ethanol, and isopropanol; alkanes like cyclohexane, n-hexane, and n-heptane; ketones like acetone and butanone; and benzene-based reagents like benzene, toluene, and xylene, effectively promoting the formation of stable liquid columns.

[0022] Preferably, the connections between the sub-boiling chamber 2 and the azeotropic chamber 1, as well as between the components, are all sealed with standard frosted glass joints. This standard frosted glass joint connection not only ensures airtightness and prevents vapor leakage, but also facilitates disassembly, cleaning, and maintenance of the device. When handling different types of reagents or performing deep cleaning, the components can be easily disassembled and processed separately, avoiding the risk of cross-contamination.

[0023] Preferably, this device, based on the process of water transport from the roots by the xylem vessels in trees, designs an open surface area-enhancing internal component. This internal component is composed of many columns, each with a periodically varying unit structure. The geometry of this unit structure causes the cross-sectional area of ​​the liquid flow to change regularly. Each unit structure is equivalent to a tiny capillary, continuously providing adhesive force to the liquid, eventually reaching a point where the provided adhesive force balances with the total weight of the liquid in the column. Furthermore, referring to the top view of this internal component, the spacing between each column ensures that each liquid column is in contact with the gas on all sides, forming a larger liquid surface agent and enhancing the efficiency of sub-boiling distillation.

[0024] Preferably, this device features a 3D-printed surface-area-reinforced internal component. The central portion of its unit structure employs a star-shaped concave design, enabling the formation of effective liquid columns for common organic solvents with surface tension lower than water, such as alcohols like methanol, ethanol, and isopropanol; low-boiling-point alkanes like cyclohexane, n-hexane, and n-heptane; and ketones like acetone and butanone. Each unit structure is equivalent to a tiny capillary tube, calculated according to the liquid capillary force formula: The surface tension γ of organic liquids is much lower than that of water. With the same channel radius r, the pressure difference ΔP of the liquid rises is smaller. Compared to units without this design, the star-shaped structure reduces the channel radius at its original location, enhances the liquid pressure difference, and strengthens the liquid adhesion, allowing even organic liquids with lower surface tension to automatically form stable liquid columns without breaking. Simultaneously, the thickness of the support pillars in the surface-area-enhanced internal component 13 can be adjusted to further regulate the size of the fluid channel radius, thereby handling liquids with even lower surface tension.

[0025] The working mechanism of this invention is based on the temperature gradient effect of heat transfer and the principle of phase change heat transfer. An electric heating stage 12 heats the solvent in the azeotropic chamber 1 to boiling. The boiling liquid and vapor are completely enclosed within the sub-boiling chamber 2. For a given solvent composition, its boiling point only changes with pressure. The temperature within the azeotropic evaporator remains constant and uniform, unaffected by fluctuations in heating power or ambient temperature. Heat is spontaneously transferred from the high-temperature azeotropic liquid to the sub-boiling chamber 2. Due to the inherent temperature gradient in heat transfer, the liquid temperature in the sub-boiling chamber 2 is automatically locked at a sub-boiling state slightly below the boiling point, eliminating the need for active temperature control. In the sub-boiling state, the liquid only evaporates smoothly on the surface without violent boiling, completely avoiding the entrainment of vapors caused by bubble bursting. This allows non-volatile impurities such as metal ions and solid particles to be trapped in the residual liquid, while only volatile components enter the vapor phase, achieving deep impurity removal. Meanwhile, the evaporation efficiency in the sub-boiling state is also controlled by the gas-liquid surface area. The surface area enhancement internal component 13 is placed inside the sub-boiling chamber 2, utilizing liquid surface tension to form a liquid column on the liquid surface, thereby increasing the gas-liquid surface area and achieving more efficient sub-boiling distillation. The condensate reflux valve 6 can adjust the pressure in the azeotropic chamber 1, changing the boiling point temperature, and thus indirectly controlling the sub-boiling evaporation temperature. Through the condensate buffer tank 4 and corresponding valves, two modes can be achieved: individual sub-boiling distillation or continuous two-stage distillation. The non-contact capacitive liquid level sensor 10 is attached to the outer wall of the azeotropic chamber 1, enabling contactless automatic liquid replenishment and avoiding secondary contamination. The device is manufactured using high-purity quartz glass and PFA materials in a graded manner, with a standard frosted port sealing connection to ensure purity control throughout the entire process.

[0026] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0027] 1. This invention achieves efficient utilization of thermal energy and automatic temperature control through an integrated jacket structure. The sub-boiling chamber is completely nested inside the azeotropic chamber, immersing the sub-boiling chamber in a boiling liquid and steam atmosphere. The heat energy generated by azeotropic evaporation is used as the heat source for sub-boiling evaporation, avoiding the need for additional heating devices. At the same time, by utilizing the inherent temperature gradient during heat transfer, the liquid temperature inside the sub-boiling chamber is automatically locked at a sub-boiling state slightly below the boiling point, eliminating the need for a complex active temperature control system, simplifying the device structure and reducing manufacturing costs.

[0028] 2. This invention achieves precise regulation of the sub-boiling evaporation temperature through a condensate reflux valve. By adjusting the pressure inside the azeotropic chamber according to the Antoni equation, the boiling point temperature of the azeotropic liquid is changed, thereby indirectly controlling the evaporation temperature of the sub-boiling chamber through heat transfer. This pressure regulation method is more precise and stable than directly controlling the heating power, and can meet the different requirements of different reagents for sub-boiling distillation temperature, significantly expanding the applicability of the device.

[0029] 3. This invention uses a non-contact capacitive liquid level sensor to achieve contactless automatic liquid replenishment. The sensor is attached to the outer wall of the azeotropic chamber and determines the liquid level by sensing changes in the dielectric constant. This avoids the problems of metal ion precipitation and particulate matter contamination that may occur when traditional liquid level gauges come into direct contact with high-purity solvents. At the same time, the automatic liquid replenishment function allows the device to operate unattended for a long time, improving the convenience and safety of operation.

[0030] 4. This invention has two switchable working modes to adapt to different purification needs: when the condensate outlet valve is closed, a single sub-boiling distillation purification mode is achieved, and industrial-grade reagents can be used as the heat source medium to reduce preparation costs; when the condensate outlet valve is open, a continuous purification mode of first-stage azeotropic distillation and second-stage sub-boiling distillation in series is achieved, and the same raw material is treated in two stages, which significantly improves the purification effect; the dual-mode design makes the device more adaptable and flexible.

[0031] 5. This invention employs a graded material design and standard frosted port connection to ensure the purity of the entire process. The azeotropic chamber, sub-boiling chamber, and azeotropic condenser are made of high-purity quartz glass, while the sub-boiling condenser, liquid collection bottle, and connecting pipelines are made of PFA material. This ensures excellent thermal stability and chemical inertness while avoiding secondary pollution introduced by material precipitation. All connections are sealed with standard frosted ports, facilitating disassembly and cleaning, effectively preventing cross-contamination, and extending the service life of the device.

[0032] 6. The device of the present invention is designed with an open surface area enhancement internal component based on bionics. This internal component is composed of many columns with periodically changing unit structures. Several unit structures are equivalent to tiny capillaries continuously connected in series, spontaneously forming liquid columns on the liquid surface. The columns are spaced apart from each other so that the surrounding area of ​​each liquid column is in contact with the gas, forming a larger gas-liquid phase surface and greatly enhancing the sub-boiling distillation efficiency.

[0033] 7. The device of the present invention adopts a star-shaped concave design in the central part of the unit structure, which reduces the flow cross-sectional area at the original position and increases the adhesion force compared with the unit without this design, so that organic liquids with low surface tension can automatically form a stable liquid column without breaking; at the same time, the thickness of the support in the surface area enhancement internal component 13 can be adjusted to further adjust the size of the fluid channel radius, thereby dealing with liquids with even lower surface tension. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be made based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the sub-boiling distillation apparatus utilizing azeotropic heating in Embodiment 1 of the present invention;

[0036] Figure 2 This is a schematic diagram of the minimum unit structure of the surface area enhanced internal component 13 and the column formed by the minimum unit structure in Embodiment 1 of the present invention;

[0037] Figure 3 This is a top view of the surface area-enhanced internal component 13 in Embodiment 1 of the present invention;

[0038] Among them, 1-Azeotropic chamber; 2-Sub-boiling chamber; 3-Azeotropic condenser; 4-Condensate buffer tank; 5-Condensate outlet valve; 6-Condensate reflux valve; 7-Feed valve; 8-Sub-boiling condenser; 9-Liquid collection bottle; 10-Non-contact capacitive liquid level sensor; 11-Insulation jacket; 12-Electric heating platform; 13-Surface area reinforced internal component; 14-Temperature probe. Detailed Implementation

[0039] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific implementation schemes are now described in detail.

[0040] The present invention will be further described below with reference to embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0041] Example 1

[0042] See appendix Figure 1 - Appendix Figure 3 This embodiment provides a sub-boiling distillation apparatus utilizing azeotropic heating, the structure of which is as follows: Figure 1 As shown, it specifically includes an azeotropic evaporation section, a sub-boiling distillation section, a condensate circulation control section, and an integrated jacket structure.

[0043] The azeotropic evaporation section includes an azeotropic chamber 1, an azeotropic condenser 3, an electric heating platform 12, a feed valve 7, a condensate return valve 6, and a non-contact capacitive level sensor 10. The electric heating platform 12 is located at the bottom of the azeotropic chamber 1 for heating; the feed valve 7 is located at the top of the azeotropic chamber 1 for replenishing liquid; the condensate return valve 6 is located at the top of the azeotropic chamber 1 for regulating the pressure inside the azeotropic chamber; and the non-contact capacitive level sensor 10 is attached to the outer wall of the azeotropic chamber 1 for non-contact detection of the liquid level.

[0044] The sub-boiling distillation section includes a sub-boiling chamber 2, a sub-boiling condenser 8, a liquid collection bottle 9, and a temperature probe 14. The top of the sub-boiling chamber 2 is provided with an interface connecting to the outlet of the condensate buffer tank 4, a steam outlet interface connecting to the inlet of the sub-boiling condenser 8, and an interface for installing the temperature probe 14. The temperature probe 14 is located at the interface on the top of the sub-boiling chamber 2 and is used to monitor the liquid phase temperature within the sub-boiling chamber 2. The sub-boiling condenser 8 is connected to the steam outlet of the sub-boiling chamber 2, and its outlet is connected to the liquid collection bottle 9.

[0045] The condensate circulation control system includes a condensate buffer tank 4, a condensate outlet valve 5, and a condensate return valve 6. The condensate buffer tank 4 is located below the azeotropic condenser 3, allowing condensate to flow spontaneously to it. The bottom outlet of the azeotropic condenser 3 is connected to the top inlet of the condensate buffer tank 4 via a pipeline. The bottom of the condensate buffer tank 4 has two outlets: one connected to the azeotropic chamber 1 via the condensate return valve 6, and the other connected to the top interface of the sub-boiling chamber 2 via the condensate outlet valve 5.

[0046] The integrated jacket structure nests and fixes the sub-boiling chamber 2 inside the azeotropic chamber 1, so that the evaporation part of the sub-boiling chamber 2 is completely immersed in the boiling liquid and its vapor atmosphere in the azeotropic chamber 1.

[0047] The outer wall of the azeotropic chamber 1 is covered with an insulation sleeve 11. The non-contact capacitive level sensor 10 includes two sensors, corresponding to preset upper and lower liquid level thresholds respectively, with the sensor signal output connected to the control system. The azeotropic chamber 1, the sub-boiling chamber 2, and the azeotropic condenser 3 are all made of high-purity quartz glass. The sub-boiling condenser 8, the liquid collection bottle 9, and the piping connecting the sub-boiling condenser 8 and the liquid collection bottle 9 are all made of PFA material. The connections between the sub-boiling chamber 2 and the azeotropic chamber 1, as well as between all components, are sealed with standard frosted glass.

[0048] The operating process of this apparatus in the standalone sub-boiling distillation mode is as follows: Industrial-grade n-hexane is injected into azeotropic chamber 1 as a heat source medium, and analytical-grade n-hexane to be purified is injected into sub-boiling chamber 2. The condensate outlet valve 5 is closed, the condensate reflux valve 6 is opened, and the electric heating platform 12 is turned on for heating. The n-hexane in azeotropic chamber 1 boils upon heating, generating constant vapor that completely surrounds sub-boiling chamber 2. Heat is transferred to sub-boiling chamber 2 through the vessel wall, and the temperature gradient automatically locks the liquid temperature in sub-boiling chamber 2 at a sub-boiling state 3-5°C below the boiling point. The temperature of n-hexane in the sub-boiling zone is detected by temperature probe 14. The liquid surface in sub-boiling chamber 2 evaporates steadily, and the pure vapor enters the sub-boiling condenser 8, condenses, and is collected in the liquid collection bottle 9. A non-contact capacitive liquid level sensor 10 monitors the liquid level in azeotropic chamber 1 in real time. When the liquid level is below the lower threshold, the feed valve 7 is automatically opened to replenish the liquid; when the liquid level reaches the upper threshold, replenishment stops. The condensate return valve 6 remains open to ensure that all condensate in the condensate buffer tank 4 is returned to the azeotropic chamber 1, preventing liquid accumulation in the buffer tank and maintaining normal pressure operation.

[0049] Example 2

[0050] This embodiment is based on Embodiment 1 above, and the similarities with Embodiment 1 will not be repeated. The differences between this embodiment and Embodiment 1 are as follows:

[0051] Open the condensate outlet valve 5 to achieve a continuous purification mode of primary azeotropic distillation and secondary sub-boiling distillation in series.

[0052] The working process of this embodiment is as follows: Industrial-grade isopropanol to be purified is injected into the azeotropic chamber 1, and the subboiling chamber 2 is initially empty. The electric heating platform 12 is turned on, and the isopropanol in the azeotropic chamber 1 boils upon heating, generating vapor which is condensed by the azeotropic condenser 3 and flows into the condensate buffer tank 4. The vapor then flows into the subboiling chamber 2 through the opened condensate outlet valve 5. The opening of the condensate reflux valve 6 is adjusted to prevent excessive liquid accumulation in the condensate buffer tank 4. After the subboiling chamber 2 collects the condensate from the first-stage azeotropic distillation, it enters a subboiling evaporation state under the thermal coupling effect of the boiling liquid in the azeotropic chamber 1. The generated secondary vapor is condensed by the subboiling condenser 8 and collected in the liquid collection bottle 9. This embodiment achieves the series processing of the first-stage azeotropic distillation and the second-stage subboiling distillation of the same raw material.

[0053] Example 3

[0054] This embodiment is based on Embodiment 1 above, and the similarities with Embodiment 1 will not be repeated. The differences between this embodiment and Embodiment 1 are as follows:

[0055] By adjusting the pressure inside the azeotropic chamber 1 through the condensate buffer tank 4 and the condensate return valve 6, precise control of the sub-boiling evaporation temperature can be achieved.

[0056] The working process of this embodiment is as follows: Industrial-grade acetone is injected into azeotropic chamber 1, and analytical-grade acetone to be purified is injected into sub-boiling chamber 2. The pressure value corresponding to the target evaporation temperature is calculated according to the Antoine equation. The condensate reflux valve 6 is partially closed, and the reflux flow rate is adjusted to raise the pressure in azeotropic chamber 1 to the calculated value. The boiling point of azeotropic acetone increases with increasing pressure, and the evaporation temperature of acetone in sub-boiling chamber 2 is correspondingly increased through heat transfer. The temperature of acetone in the sub-boiling zone is detected by the temperature probe 14, and the system stabilizes after reaching the target temperature. This embodiment achieves precise customization of the sub-boiling evaporation temperature through pressure regulation.

[0057] Example 4

[0058] This embodiment is based on Embodiment 1 above, and the similarities with Embodiment 1 will not be repeated. The differences between this embodiment and Embodiment 1 are as follows:

[0059] By changing the liquid composition within the azeotropic chamber 1, the temperature within the azeotropic chamber 1 can be controlled, thereby achieving precise regulation of the sub-boiling evaporation temperature.

[0060] The working process of this embodiment is as follows: Industrial-grade acetone is injected into azeotropic chamber 1. Based on the acetone-chloroform Txy isobaric phase diagram, the acetone-chloroform composition corresponding to the target azeotropic temperature is calculated. A certain molar fraction of chloroform / acetone mixed solution is injected into azeotropic chamber 1. The condensate reflux valve 6 is fully opened to maintain atmospheric pressure within azeotropic chamber 1. The addition of chloroform increases the azeotropic temperature of the acetone-chloroform mixture. Through heat transfer, the evaporation temperature of acetone in sub-boiling chamber 2 is correspondingly increased. The temperature of acetone in the sub-boiling zone is monitored by temperature probe 14. After reaching the target temperature, the system stabilizes. This embodiment achieves precise customization of the sub-boiling evaporation temperature by changing the composition of the liquid in the azeotropic chamber.

[0061] Example 5

[0062] This embodiment is based on the above embodiment 1. The similarities with the above embodiment 1 will not be repeated. The difference between this embodiment and the above embodiment 1 is that the non-contact capacitive liquid level sensor 10 uses three sensors, which correspond to the low liquid level alarm threshold, the lower liquid level control threshold and the upper liquid level control threshold, respectively.

[0063] In this embodiment, when the liquid level drops to the lower liquid level control threshold, the control system opens the feed valve 7 to replenish the liquid; when the liquid level rises to the upper liquid level control threshold, the control system closes the feed valve 7; when the liquid level drops to the low liquid level alarm threshold, the control system issues an alarm and automatically reduces the power of the electric heating platform 12 to prevent dry burning. This embodiment improves the safety and reliability of the device operation through multiple threshold settings.

[0064] Example 6

[0065] This embodiment is based on Embodiment 1 above, and the similarities with Embodiment 1 will not be repeated. The differences between this embodiment and Embodiment 1 are as follows:

[0066] A surface area-enhancing internal component 13 was placed inside the sub-boiling chamber 2.

[0067] The working process of this embodiment is as follows: the process is the same as in Embodiment 1. In the sub-boiling chamber 2, cyclohexane forms many tiny liquid columns on the surface area enhancement internal component 13 due to liquid surface tension, resulting in a larger gas-liquid mass transfer area. This embodiment increases the yield of the device per unit time by setting the surface area enhancement internal component without any change in purity.

[0068] Example 7

[0069] This embodiment is based on the above embodiment 6. The similarities with the above embodiment 6 will not be repeated. The difference between this embodiment and the above embodiment 6 is that the internal liquid columns of the surface area enhanced internal component 13 adopt an arrangement structure that is connected to each other and no interval is set.

[0070] Comparative Example 1

[0071] This comparative example provides a conventional sub-boiling distillation apparatus, which differs from Example 1 in that it does not employ an integrated jacket structure and does not include an azeotropic evaporation section as a heat source.

[0072] The apparatus for this comparative example includes a sub-boiling distillation flask, an electric heating mantle, a temperature controller, a condenser, and a collection bottle. A temperature probe is installed inside the sub-boiling distillation flask, and the temperature controller adjusts the power of the electric heating mantle based on probe feedback to precisely control the liquid temperature inside the flask at 5°C below its boiling point. The apparatus has no azeotropic heat source and no automatic liquid replenishment function; manual monitoring of the liquid level and manual replenishment are required.

[0073] Comparative Example 2

[0074] This comparative example is based on the above-mentioned comparative example 1. The similarities with the above-mentioned comparative example 1 will not be repeated. The difference between this comparative example and the above-mentioned comparative example 1 is that boiling distillation is used to make the liquid in the distillation flask reach the boiling point and carry out vigorous boiling distillation.

[0075] The apparatus for this comparative example includes a distillation flask, an electric heating mantle, a condenser, and a collection bottle. The electric heating mantle heats the liquid in the distillation flask at full power, causing it to boil violently; the vapor is then collected after condensation. The apparatus has no temperature control or liquid level control.

[0076] Comparative Example 3

[0077] This comparative example is based on the above-described Example 1. The similarities with Example 1 will not be repeated. The difference between this comparative example and Example 1 is that: a non-contact capacitive liquid level sensor 10 is not set, and a traditional float valve structure is used to control the liquid level.

[0078] In this comparative example, a float valve is installed in the azeotropic chamber 1. The float rises and falls with the liquid level, controlling the opening and closing of the feed valve 7 via a linkage mechanism. The float and linkage mechanism are in direct contact with the liquid inside the azeotropic chamber.

[0079] Using the apparatus described in the above embodiments and comparative examples, n-hexane purification experiments were conducted using industrial-grade n-hexane as raw material (initial metal ion content is shown in Table 1). After purification, the products obtained from each apparatus were collected, concentrated, and then wet-digested to obtain a digestate. The metal ion content was then detected using inductively coupled plasma mass spectrometry (ICP-MS). Simultaneously, the energy consumption, processing rate, and operational stability of each apparatus were recorded. The detection results are shown in Table 1.

[0080] Table 1

[0081]

[0082] As can be seen from Table 1: In Example 1, using the integrated jacket structure of the present invention, the Na content in the obtained product under the single sub-boiling distillation mode is... + Ca 2+ Fe 3+ The impurity content was reduced to 0.9 ppb, 0.6 ppb, and 0.5 ppb, respectively, with an impurity removal rate of over 99.9%, significantly better than the boiling distillation of Comparative Example 2 (where the impurity residue was as high as several hundred ppb). Compared with the conventional sub-boiling distillation of Comparative Example 1, the impurity content of Example 1 was slightly lower, while the energy consumption was reduced by about 33%, demonstrating the advantage of efficient thermal energy utilization of the present invention.

[0083] Example 2 employs a continuous purification mode combining a primary azeotropic stage and a secondary sub-boiling stage, which further improves the purity of the obtained product, with the metal ion content all below 2 ppb, demonstrating that the two-stage tandem purification mode has a more thorough removal effect on impurities.

[0084] Example 3 shows that by adjusting the pressure in the azeotropic chamber through the condensate buffer tank 4 and the condensate reflux valve 6, the sub-boiling evaporation temperature was successfully and precisely controlled at 52°C. The impurity concentration of the obtained product was less than 5 ppb, and the processing rate was faster, which verifies the effective control capability of the pressure regulation method on the sub-boiling evaporation temperature.

[0085] Example 4 uses a method of changing the composition of the azeotropic liquid. The azeotropic zone uses an acetone-chloroform mixture of 85.7 wt%, which, compared to using 98 wt% acetone, successfully controls the sub-boiling evaporation temperature from 52.1℃ to 53.3℃. The quality of the product obtained is comparable to that of Example 3, and the evaporation efficiency is improved. This verifies the effective control capability of changing the composition of the azeotropic liquid on the sub-boiling evaporation temperature.

[0086] Example 5 uses a three-sensor liquid level control mode, which has very stable operation. No abnormal liquid level occurred during the entire experiment, which proves the positive effect of multi-threshold settings on improving the safety and reliability of the device.

[0087] Example 6 employed a surface area-enhanced internal component 13, increasing the processing efficiency to 0.45 L / h, while maintaining a concentration comparable to that of Example 1 (Fe). 3+ The low concentration (as low as 0.1 ppb) demonstrates that this structure can effectively increase the gas-liquid phase mass transfer area without introducing contaminants.

[0088] Example 7 also uses surface area-enhanced internal components 13, but because the liquid columns are connected to each other and there are no gaps, the processing efficiency decreases from 0.45 L / h to 0.40 L / h compared to Example 6, which proves the importance of maintaining gaps between the liquid columns in the component to improve mass transfer efficiency.

[0089] Although conventional sub-boiling distillation in Comparative Example 1 can obtain products with higher purity, its energy consumption is significantly higher than that in Example 1, and it requires manual monitoring of the liquid level, making it less convenient to operate.

[0090] The impurity content in the boiling distillation product of Comparative Example 2 was as high as several hundred ppb, and the impurity removal rate was less than 30%, proving that the gas-liquid entrainment phenomenon during boiling does indeed lead to a large number of impurities entering the distillate.

[0091] Comparative Example 3 uses a float valve to control the liquid level. Although other structures are the same as in Example 1, the metal ion content in the product is significantly increased, especially Na. + Reaching 18.6 ppb, which is more than 5 times that of Example 1, proves that direct contact between the float valve and the solvent does indeed introduce metal ion contamination, thus verifying the superiority of the non-contact liquid level sensor of this invention.

[0092] In summary, this invention integrates a sub-boiling chamber within an azeotropic chamber using a jacketed structure. It utilizes azeotropic evaporation for heating and automatically maintains the sub-boiling state via a temperature gradient, eliminating the need for complex temperature control. Pressure regulation via a condensate reflux valve allows for precise control of the evaporation temperature. A non-contact liquid level sensor enables automatic liquid replenishment without contact, preventing secondary contamination. It features dual modes: individual sub-boiling and continuous two-stage distillation, adapting to different purification needs. The use of high-purity quartz glass and PFA materials in graded manufacturing ensures purity control throughout the entire process. This invention reduces energy consumption and operational complexity while maintaining high-purity purification, demonstrating significant technological advancement and practical value.

[0093] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0094] The embodiments described above merely illustrate more specific and detailed implementations of the present invention, and should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A sub-boiling distillation apparatus utilizing azeotropic heating, characterized in that, include: The azeotropic evaporation section includes an azeotropic chamber (1), an azeotropic condenser (3), an electric heating platform (12), a feed valve (7), a condensate return valve (6), and a non-contact capacitive level sensor (10). The electric heating platform (12) is located at the bottom of the azeotropic chamber (1) for heating. The feed valve (7) is located at the top of the azeotropic chamber (1) for replenishing liquid. The condensate return valve (6) is located at the top of the azeotropic chamber (1) for regulating the pressure inside. The non-contact capacitive level sensor (10) is attached to the outer wall of the azeotropic chamber (1) for non-contact detection of the liquid level. The subboiling distillation section includes a subboiling chamber (2), a subboiling condenser (8), a liquid collection bottle (9), and a temperature probe (14). The top of the subboiling chamber (2) is provided with an interface communicating with the outlet of the condensate buffer tank (4), a steam outlet interface communicating with the inlet of the subboiling condenser (8), and an interface for installing the temperature probe (14). The temperature probe (14) is located at the interface at the top of the subboiling chamber (2) and is used to monitor the steam temperature inside the subboiling chamber (2). The subboiling condenser (8) is connected to the steam outlet of the subboiling chamber (2), and its outlet is connected to the liquid collection bottle (9). The condensate circulation control section includes a condensate buffer tank (4), a condensate outlet valve (5), and a condensate return valve (6). The bottom outlet of the azeotropic condenser (3) is connected to the top inlet of the condensate buffer tank (4). The bottom of the condensate buffer tank (4) is provided with two outlets, one of which is connected to the top interface of the sub-boiling chamber (2) through the condensate outlet valve (5), and the other is connected to the azeotropic chamber (1) through the condensate return valve (6). And an integrated jacket structure, wherein the integrated jacket structure nests and fixes the sub-boiling chamber (2) inside the azeotropic chamber (1), so that the evaporation part of the sub-boiling chamber (2) is completely immersed in the boiling liquid and its steam atmosphere in the azeotropic chamber (1), and the temperature of the liquid in the sub-boiling chamber (2) is automatically controlled to be lower than its boiling point through the temperature gradient of heat transfer, so as to realize the heating from azeotropic evaporation to sub-boiling evaporation.

2. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 1, characterized in that, The non-contact capacitive liquid level sensor (10) includes at least two sensors, which correspond to the preset upper liquid level threshold and lower liquid level threshold respectively. Its signal output terminal is connected to the control system. The control system controls the opening and closing of the feed valve (7) according to the received signal to realize automatic liquid replenishment.

3. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 1, characterized in that, The outer wall of the azeotropic chamber (1) is covered with an insulation sleeve (11) to reduce heat loss and improve thermal efficiency.

4. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 1, characterized in that, The azeotropic chamber (1), sub-boiling chamber (2) and azeotropic condenser (3) are all made of high-purity quartz glass; the sub-boiling condenser (8), liquid collection bottle (9) and its connecting pipes are all made of soluble polytetrafluoroethylene material.

5. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 1, characterized in that, The condensate buffer tank (4) works in conjunction with the condensate return valve (6) to control the pressure in the azeotropic chamber (1) by adjusting the condensate return flow rate, thereby indirectly adjusting the evaporation temperature of the liquid in the sub-boiling chamber (2) according to the Antoni equation.

6. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 1, characterized in that, The device has two working modes: when the condensate outlet valve (5) is closed and the condensate reflux valve (6) is opened, a separate sub-boiling distillation purification mode is achieved where the azeotropic chamber (1) only provides a heat source for the sub-boiling chamber (2); when the condensate outlet valve (5) is opened, a continuous purification mode is achieved where the first-stage azeotropic distillation and the second-stage sub-boiling distillation are connected in series.

7. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 1, characterized in that, The subboiling chamber (2) can be filled with a surface area enhancement internal component (13) to form a liquid column on the surface of the component by utilizing the surface tension of the liquid, thereby increasing the gas-liquid interface and improving the subboiling distillation efficiency.

8. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 7, characterized in that, The surface area enhancement internal component (13) is formed by longitudinally stacking the smallest structural units. The liquid columns formed by the longitudinal stacking do not contact each other and there are air columns. The smallest structural unit is designed with a star-shaped line structure and adjustable support columns.

9. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 7 or 8, characterized in that, The surface area enhancement internal component (13) is suitable for organic solvents with a surface tension lower than that of water. The organic solvent is selected from one or more of alcohols, alkanes, ketones or benzenes, wherein the alcohol is methanol, ethanol or isopropanol, the alkane is cyclohexane, n-hexane or n-heptane, the ketone is acetone or butanone, and the benzene is benzene, toluene or xylene.

10. The sub-boiling distillation apparatus utilizing azeotropic heating according to claim 1, characterized in that, The connection between the sub-boiling chamber (2) and the azeotropic chamber (1), as well as between the components, are all sealed with standard frosted joints.

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