An ammonia distillation tower using multi-frequency ultrasound to improve heat and mass transfer performance

Abstract

The present invention discloses an ammonia distillation tower that uses multi-frequency ultrasonic waves to enhance heat and mass transfer performance. The tower is used for separating ammonia in an ammonia absorption refrigeration system. The tower comprises four sections, sequentially arranged from top to bottom: a condensation section, a rectification section, a stripping section, and a generator section. The tower includes an ammonia outlet, a condenser, a cooling water outlet, a cooling water inlet, a steam conduit, a reflux liquid conduit, an atomizer oscillator, an ultrasonic atomizer, an atomizing tank, a bubble cap, an ultrasonic oscillator, a tower plate, a solution conduit, a concentrated solution inlet, a heating fluid outlet, a through-hole, a partition, a heating tube, a heating fluid inlet, and a dilute solution outlet. Mist droplets replace the filler in conventional distillation towers to reduce the overall tower mass. The stripping and rectifying sections of the tower are each equipped with several sets of ultrasonic atomizers that generate ammonia mist droplets. Ultrasonic oscillators are installed on the tower plates to enhance gas-liquid heat and mass exchange. The generator section at the bottom of the tower utilizes an off-tube falling film evaporation method. This improves the heat and mass transfer characteristics of the ammonia distillation process.

Description

Technical Field

[0001] The present invention relates to a distillation tower used in an ammonia absorption refrigeration system, which mainly uses ultrasonic atomization and ultrasonic oscillation technologies to enhance the heat and mass transfer effects of the distillation process. Background Art

[0002] If the vast reserves of low-grade heat sources can be effectively utilized, it will be of great significance to solving the energy crisis. The ammonia absorption refrigeration cycle is a typical heat-driven refrigeration cycle that can achieve the heating and quality improvement of low-grade heat sources. However, ammonia and water have similar boiling points, and the steam generated by directly heating the ammonia solution has a high water content, so the concentration of the gaseous ammonia component needs to be further increased through distillation. The distillation tower is the key heat and mass exchange equipment in the ammonia absorption refrigeration system. The improvement of its heat and mass transfer effect is of great significance to the system performance and equipment size optimization.

[0003] A distillation tower primarily consists of four sections: the fractional condenser, the rectifying section, the stripping section, and the generating section. The concentrated solution enters the center of the distillation tower and flows downward under gravity through the stripping section to the bottom of the tower, where it exchanges heat between the heating tubes and produces steam and a dilute solution. The dilute solution exits the bottom of the tower, while the steam continues upward to the fractional condenser at the top of the tower. The steam in the fractional condenser is condensed by cooling water, resulting in a gaseous phase of extremely pure ammonia vapor and a liquid phase of saturated ammonia solution with a high ammonia content. The ammonia vapor exits the top of the tower, while the remaining liquid ammonia in the fractional condenser flows downward, where it is ultrasonically atomized into micron-sized droplets, which then contact the ascending ammonia vapor for heat and mass exchange, achieving the desired distillation effect.

[0004] Traditional distillation towers mainly fall into two types: plate towers and packed towers. Plate distillation towers were the first to be used and the most thoroughly researched. The plates, which play a decisive role in volumetric efficiency, are the core components for heat and mass transfer. The insufficient gas-liquid contact surface within plate towers is a major factor affecting the volumetric efficiency of distillation towers. Packed towers use hollow towers filled with fillers of various shapes. The liquid adheres to the surface of the filler and comes into contact with the steam. Compared to plate towers, the specific surface area of the filler and the volumetric heat and mass transfer efficiency are significantly improved. However, further improving the performance of packed towers faces bottlenecks. Due to the influence of liquid viscosity and surface tension, the flow channels within the tower are prone to scaling and clogging. The packing is expensive, and the weight of packed towers is large, which is unfavorable for installation and maintenance. Summary of the Invention

[0005] Technical problem: In order to overcome the problems of large size and low heat and mass exchange efficiency of traditional distillation tower equipment and to improve the compactness of absorption refrigeration equipment, the present invention provides an ammonia distillation tower that uses multi-frequency ultrasound to enhance heat and mass transfer performance. The ammonia distillation tower has a higher volumetric mass transfer coefficient, thus reducing the volume of the equipment. Compared with traditional distillation towers, the ammonia distillation tower removes most of the tower plates and all the fillers, and instead installs an ultrasonic atomizer and an ultrasonic oscillator inside it. The ultrasonic atomizer atomizes the solution into micron-sized droplets to increase the vapor-liquid contact area, and the ultrasonic oscillator can reduce the resistance of the gas-liquid heat and mass transfer process in the tower plates, thereby reducing the size of the distillation tower and reducing the concentration of the dilute solution at the outlet.

[0006] Technical solution: To achieve the above purpose, the present invention adopts an ammonia distillation tower that uses multi-frequency ultrasound to improve heat and mass transfer performance, which is sequentially provided with four parts from top to bottom: a condensation section, a distillation section, a stripping section and a generating section; wherein,

[0007] The fractional condensation section is located at the top of the distillation tower, and includes an ammonia outlet, a fractional condenser, a cooling water outlet, a cooling water inlet, a steam conduit, and a reflux liquid conduit; the ammonia outlet is located at the upper part of the fractional condenser, the cooling water outlet and the cooling water inlet are located on one side of the fractional condenser, the steam conduit is located on the other side of the fractional condenser and connected to the upper part of the distillation section, and the reflux liquid conduit is located at the lower part of the fractional condenser and connected to the atomization tank of the distillation section;

[0008] The distillation section is located at the upper part of the distillation tower, and includes an atomizer vibrator, an ultrasonic atomizer, an atomization tank, a bubble cap, an ultrasonic oscillator, a tower plate, and a solution conduit. This section is divided into three layers. The first layer includes an ultrasonic atomizer consisting of an atomizer vibrator, an ultrasonic atomizer, and an atomization tank; the second layer includes an ultrasonic oscillator consisting of a bubble cap, an ultrasonic oscillator, and a tower plate, and a solution conduit is provided in the middle of the ultrasonic oscillator; the third layer has the same structure as the first layer.

[0009] The stripping section includes two layers of ultrasonic oscillators consisting of bubble caps, ultrasonic oscillators, and trays; the stripping section is also provided with a concentrated solution inlet;

[0010] The generating section includes a heating fluid outlet, a through hole, a partition, a heating tube, a heating fluid inlet, and a dilute solution outlet; the lower part of the heating tube is connected to the heating fluid inlet, and the upper part of the heating tube is connected to the heating fluid outlet to form a heater, and a through hole is provided on the heater, and the dilute solution flows from the heating tube to the dilute solution outlet through the through hole.

[0011] The ultrasonic atomizer is installed in the center of the atomization tank, 1-2 cm below the liquid level to obtain the best atomization effect.

[0012] The atomizer tank is an inverted hollow circular concave structure with a bottom diameter larger than the diameter of the ultrasonic atomizer. This ensures that large-diameter droplets produced by the ultrasonic atomizer fall back into the tank, while small-diameter droplets can diffuse throughout the vapor phase. The larger diameter at the bottom of the atomizer tank provides ample installation space for the ultrasonic atomizer.

[0013] The atomization tanks are grouped into six and symmetrically distributed in a regular hexagon; a group of atomization tanks is installed on each layer of the distillation tower to provide droplets for the distillation section and the stripping section respectively; each atomization tank is connected by a solution conduit to ensure uniform liquid level in the tank.

[0014] The frequency of the ultrasonic oscillator is 20-68kHz, and six oscillators form a group and are symmetrically distributed in a regular hexagon. The ultrasonic oscillator is installed at the bottom of the tower plate in a trumpet shape and is installed through a hole in the tower plate.

[0015] The tower plate is a perforated plate structure, with evenly distributed equal-diameter circular holes at the oscillator installation position for the installation of the ultrasonic oscillator. A solution conduit is installed at the center of the tower plate, which is slightly higher than the tower plate. The overflow solution flows along the solution conduit into the atomization tank by falling film.

[0016] The oscillation frequency of the ultrasonic atomizer is 1.7MHz-2.4MHz. The ultrasonic atomization effect causes the solution to generate droplets. The top atomizer atomizes the high-concentration ammonia reflux liquid in the partial condenser to provide small-sized droplets for the distillation section. The middle atomizer is installed below the tower plate to atomize the solution in the tower plate to provide small-sized droplets for the stripping section.

[0017] A solution conduit for connecting the tower plate and the atomization tank is installed in the tower plate; the solution conduit is slightly higher than the bottom of the tower plate. After the solution overflows, it flows in the solution conduit as a falling film. The bottom is connected to the atomization tank to provide solution to the atomizer. The falling film flow increases the heat and mass exchange area between the solution and the gas, enhances the heat and mass transfer characteristics of the solution and steam, and the solution conduit also provides support for the atomization tank.

[0018] The present invention adopts a distillation method of an ammonia distillation tower that uses multi-frequency ultrasonic waves to improve the heat and mass transfer performance. The concentrated solution in the distillation tower flows into the tower plate from the concentrated solution inlet, mixes with the falling droplets inside the tower plate, and is evenly distributed to the inside of the ultrasonic atomizer through the solution conduit and the atomization tank. The ultrasonic oscillator installed on the tower plate stirs the mixing process; the solution inside the atomization tank is atomized into micron-level droplets by the ultrasonic atomizer oscillator installed in the center of the ultrasonic atomizer; the droplets fall onto the heating fluid outlet water tank under the action of gravity, and the solution flows onto the partition through the through-holes of the outlet water tank. The partition has a hole larger than the outer diameter of the heating tube. After the solution overflows on the partition, it flows along the outside of the heating tube to generate a thin thermal boundary layer. The outside of the heating tube has a higher heat transfer coefficient, which strengthens the steam generation process inside the generator; the dilute solution is collected on the heating fluid inlet water tank and flows out of the dilute solution outlet at the bottom of the distillation tower; the steam generated in the heating process rises under the action of buoyancy, and heat transfer between the stripping section and the droplets. After mass transfer, the steam continues to ascend through the bubble cap installed on the tower plate, passes through the distillation section, and then enters the partial condenser through the steam duct for condensation; the cooling coil is immersed in the partial condenser, and cooling water flows into the cooling coil from the cooling water inlet, cools the liquid phase in the partial condenser, and then flows out from the cooling water outlet; the steam condenses in the partial condenser, the upper steam is high-purity saturated ammonia steam, which flows out of the distillation tower through the ammonia outlet, and the lower part condenses into a high-concentration solution, flows into the atomization tank on the upper layer of the distillation tower through the reflux liquid duct and the atomization tank for atomization; under the action of gravity, the droplets generated in the upper atomization tank descend, exchange heat and mass with the ascending steam, and then fall to the middle tower plate to be mixed with the concentrated solution from the concentrated solution inlet.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0020] 1. The ultrasonic frequency in the ultrasonic atomizer of the present invention provides energy for the liquid unit to overcome the liquid gravity and surface tension, and the atomization is carried out as droplets instead of fillers, which significantly increases the gas-liquid contact area and volume mass transfer coefficient inside the distillation tower, while reducing the overall mass of the distillation tower.

[0021] 2. The ultrasonic oscillator in the present invention can, on the one hand, cause internal disturbances in the fluid through cavitation and mechanical effects, reduce the thickness of the boundary layer, promote mixing and heat and mass transfer within the solution, and also promote heat and mass transfer between gas and liquid, thereby improving the efficiency of heat and mass transfer; on the other hand, the high-frequency pressure changes generated inside the solution induce the generation of bubbles inside the solution. The bubbles serve as vaporization cores, reduce the superheat of the liquid phase, and thus improve the evaporation capacity of the solution.

[0022] In summary, the present invention can significantly improve the distillation effect of the distillation tower, obtain a lower concentration of the final solution, reduce the circulation rate of the absorption refrigeration system, and at the same time reduce the overall mass and volume of the distillation tower, thereby reducing the energy consumption and size of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings and examples.

[0024] Figure 1 is a cross-sectional schematic diagram of the present invention,

[0025] Figure 2 This is a top view of the atomizing slot distribution of the present invention.

[0026] Figure 3 is a top view of a tray of the present invention,

[0027] Figure 4 is a schematic cross-sectional view of a tray of the present invention,

[0028] Figure 5 is the occurrence section of the present invention, Figure 1 Cross-section at AA;

[0029] The figure shows: ammonia outlet 1; partial condenser 2; cooling water outlet 3; cooling water inlet 4; steam conduit 5; reflux liquid conduit 6; atomizer oscillator 7; ultrasonic atomizer 8; atomizing tank 9; bubble cap 10; ultrasonic oscillator 11; tower plate 12; solution conduit 13; concentrated solution inlet 14; heating fluid outlet 15; through hole 16; partition 17; heating tube 18; heating fluid inlet 19; dilute solution outlet 20. DETAILED DESCRIPTION

[0030] The present invention is further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0031] The ammonia distillation tower of the present invention adopts multi-frequency ultrasound to improve heat and mass transfer performance, and improves the heat and mass transfer performance of the ammonia distillation process based on ultrasonic atomization technology and ultrasonic oscillation technology.

[0032] exist Figure 1 Middle: The distillation tower of the present invention comprises, from top to bottom, a fractional condensation section, a distillation section, a stripping section, and a generating section. The fractional condensation section is located at the top of the distillation tower and includes an ammonia outlet 1, a partial condenser 2, a cooling water outlet 3, a cooling water inlet 4, a steam conduit 5, and a reflux liquid conduit 6; the ammonia outlet 1 is located at the upper part of the partial condenser 2, the cooling water outlet 3 and the cooling water inlet 4 are located on one side of the partial condenser 2, the steam conduit 5 is located on the other side of the partial condenser 2 and connected to the upper part of the distillation section, and the reflux liquid conduit 6 is located at the lower part of the partial condenser 2 and connected to the atomization tank 9 of the distillation section;

[0033] The distillation section is located at the upper part of the distillation tower, and includes an atomizer vibrator 7, an ultrasonic atomizer 8, an atomization tank 9, a bubble cap 10, an ultrasonic oscillator 11, a tower plate 12, and a solution conduit 13. This section is divided into three layers. The first layer includes an ultrasonic atomizer consisting of the atomizer vibrator 7, the ultrasonic atomizer 8, and the atomization tank 9; the second layer includes an ultrasonic oscillator consisting of the bubble cap 10, the ultrasonic oscillator 11, and the tower plate 12, and a solution conduit 13 is provided in the middle of the ultrasonic oscillator; the third layer has the same structure as the first layer.

[0034] The stripping section includes two layers of ultrasonic oscillators consisting of bubble caps 10, ultrasonic oscillators 11, and trays 12; a concentrated solution inlet 14 is also provided in the stripping section;

[0035] The generating section includes a heating fluid outlet 15, a through hole 16, a partition 17, a heating tube 18, a heating fluid inlet 19, and a dilute solution outlet 20; the lower part of the heating tube 18 is connected to the heating fluid inlet 19, and the upper part of the heating tube 18 is connected to the heating fluid outlet 15 to form a heater, and a through hole 16 is provided on the heater, and the dilute solution flows from the heating tube 18 to the dilute solution outlet 20 through the through hole 16.

[0036] The rectifying and stripping sections are separated by tray 12. The partial condenser 2 is a conventional shell-and-tube heat exchanger. Low-temperature cooling water flows in through the cooling water inlet 4 and out through the cooling water outlet 3. Nearly saturated steam enters the partial condenser 2 through the steam conduit 5 and is liquefied. At this point, the upper portion of the partial condenser 2 is saturated steam at the corresponding temperature. The lower the cooling water temperature, the purer the corresponding saturated ammonia steam. Nearly pure ammonia vapor from the upper portion of the partial condenser 2 flows out of the rectifying column through the ammonia outlet 1 as the product. The liquid ammonia at the bottom passes through the reflux conduit 6 and the atomization tank 9 and is evenly dispersed into the ultrasonic atomizer 8. The ultrasonic atomizer oscillator 7, mounted in the center of the atomization tank 9, atomizes the liquid. The droplets diffuse throughout the rectifying section and slowly descend under the combined effects of gravity, buoyancy, and drag. During their descent, they fully contact and exchange heat and mass with the steam in the rectifying section. Due to their large surface area and small diameter, the micron-sized droplets quickly reach thermal and phase equilibrium with the steam. During steady-state operation, the temperature of the distillation tower gradually decreases from bottom to top, so the droplet concentration gradually decreases. The tower plate 12 is installed on several layers in the distillation tower. The dilute solution flows into the tower plate 12 from the concentrated solution inlet 14, and after being evenly mixed with the falling droplets, it is introduced into the atomization tank 9 installed in the distillation section by the solution conduit 13 for a new round of atomization. The ultrasonic oscillator 11 is installed on the tower plate 12 to strengthen the mixing process and ensure uniform mixing. The atomized droplets fall from the through hole onto the partition 17, overflow from the opening on the partition, and continuously evaporate along the heating tube by falling film flow to generate saturated steam. The hot fluid flows into the heating tube 18 from the heating fluid inlet 19 and flows out from the heating fluid outlet 15. The solution in the generating section and the heating tube 18 undergo heat exchange. The steam generated by the heated solution moves upward, and the remaining liquid flows out of the dilute solution outlet 20 at the bottom of the distillation tower.

[0037] exist Figure 2 The structural distribution of the atomization tank and the installation method of the atomizer are described: the ultrasonic atomizer 8 is installed in the center of the atomization tank 9, 1-2 cm below the liquid level to obtain the best atomization effect.

[0038] The atomizer tank 9 is an inverted hollow circular concave structure with a bottom diameter larger than that of the ultrasonic atomizer 8. This ensures that large-diameter droplets produced by the ultrasonic atomizer 8 fall back into the atomizer tank 9, while small-diameter droplets can diffuse throughout the vapor phase. The bottom diameter of the atomizer tank 9 is larger than the top diameter, providing ample installation space for the ultrasonic atomizer.

[0039] The atomization slots 9 are grouped into six and symmetrically distributed in a regular hexagon. A group of atomization slots is installed on each layer of the distillation tower to provide droplets for the distillation section and the stripping section respectively. Each atomization slot 9 is connected by a solution conduit 13 to ensure uniform liquid level in the slot.

[0040] The atomizing tank 9 is distributed in a regular hexagonal shape, and the center of the circumscribed circle of the hexagon coincides with the axis of the distillation tower, so as to provide droplets that are dispersed throughout the entire distillation tower as much as possible. The solution drained by the reflux liquid conduit 6 and the solution conduit 13 located in the center is distributed to each ultrasonic atomizer 8 through the conduit of the atomizing tank 9 for atomization. The ultrasonic atomizer 8 is installed in the center of the bottom of the atomizing tank 9, and generates a high-frequency ultrasonic wave of 1.7-2.4MHz under the action of high-frequency electronic oscillation, causing the phase interface to rupture and atomize, and producing droplets with an average diameter of tens of microns. Large-sized droplets have a limited radial movement range because their gravity is larger than the resistance, and therefore they will quickly fall back into the atomizing tank 9, while small-sized droplets are subject to relatively large resistance and can be diffused throughout the space.

[0041] exist Figure 3 The structure of the tower plate is described as follows: the tower plate 12 is a perforated plate structure, and uniformly distributed circular holes of equal diameter are opened at the oscillator installation position for the installation of the ultrasonic oscillator 11. A solution conduit 13 is installed at the center of the tower plate 12. The solution conduit is slightly higher than the tower plate, and the overflow solution flows along the solution conduit into the atomization tank 9 in a falling film manner.

[0042] A solution conduit 13 for connecting the tower plate and the atomization tank is installed in the tower plate 12; the solution conduit is slightly higher than the bottom of the tower plate. After the solution overflows, it flows in the solution conduit as a falling film. The bottom is connected to the atomization tank to provide solution to the atomizer. The falling film flow increases the heat and mass exchange area between the solution and the gas, enhances the heat and mass transfer characteristics of the solution and steam, and the solution conduit also provides support for the atomization tank.

[0043] The diameter of the tower plate 12 is equal to the inner diameter of the distillation tower and is fixed at a suitable height of the distillation tower by welding or latching. The ultrasonic oscillators 11 are symmetrically distributed and installed in the openings of the tower plate 12. The ultrasonic oscillators 11 are processed into an inverted frustum and installed between the tower plate 12 by welding to avoid leakage in the installation gap. Under the action of high-frequency electronic pulses, the ultrasonic oscillator 11 generates oscillations with a frequency of tens of kilohertz on the contact surface of the solution, generating an ultrasonic field in the solution. After the ultrasonic field acts on the solution, it will violently disturb the solution due to cavitation and mechanical effects, promoting the mixing and vaporization process of the fluid inside the tower plate 12.

[0044] exist Figure 4 The layout of the trays and solution conduits is described in [1]. Bubble caps 10 and ultrasonic oscillators are evenly and densely arranged on tray 12 to ensure that vapor from the stripping section can flow upward into the rectifying section. The lower ends of bubble caps 10 are flush with the bottom of tray 12 and immersed in the liquid on the tray. The solution conduits are slightly higher than the tray supports. After uniform mixing, the solution flows as a falling film along the inner wall of solution conduit 13.

[0045] exist Figure 5The installation layout of the generator section is described in the following example: Droplets fall under the influence of gravity onto the heating fluid outlet tank 15, which has five through-holes 16. The solution flows through these through-holes and onto a baffle 17, which has a circular hole slightly larger than the outer diameter of the heating tube. The edge of the hole is set at a certain height, allowing the solution to overflow from the baffle 17. The solution flows along the outside of the heating tube 18, creating a thin flow boundary layer and thermal boundary layer. This results in a higher heat transfer coefficient outside the tube, enhancing the steam generation process within the generator. As the tower temperature decreases upwards, the uneven temperature field drives the bottom steam upwards through the holes in baffle 17 under the influence of buoyancy. The dilute solution then converges at the heating fluid inlet tank 19 and exits the dilute solution outlet 20 at the bottom of the distillation tower. The higher the heating fluid temperature, the lower the concentration of ammonia in the outlet dilute solution.

[0046] The distillation method of the ammonia distillation tower using multi-frequency ultrasound to improve heat and mass transfer performance of the present invention is as follows: the concentrated solution of the distillation tower flows into the tower plate 12 from the concentrated solution inlet 14, mixes with the falling droplets inside the tower plate, and is evenly distributed to the inside of the ultrasonic atomizer 8 through the solution conduit 13 and the atomization tank 9. The ultrasonic oscillator 11 installed on the tower plate 12 stirs the mixing process; the solution inside the atomization tank 9 is atomized into micron-level droplets by the ultrasonic atomizer oscillator 7 installed in the center of the ultrasonic atomizer 8; the droplets fall onto the heating fluid outlet 15 water tank under the action of gravity, and the solution flows to the partition 17 through the through hole 16 of the outlet water tank. The partition 17 has a hole larger than the outer diameter of the heating tube. After the solution overflows on the partition 17, it flows along the outside of the heating tube 18 to generate a thin thermal boundary layer. The outside of the heating tube 18 has a higher heat transfer coefficient, which strengthens the steam generation process inside the generator; the dilute solution is collected on the heating fluid inlet 19 water tank and flows out of the dilute solution outlet 20 at the bottom of the distillation tower; the steam generated in the heating process rises under the action of buoyancy, and After the droplets have fully contacted and transferred heat and mass, they continue to ascend through the bubble cap 10 installed on the tower plate, pass through the distillation section, and then enter the partial condenser 2 through the steam conduit 5 for condensation; the cooling coil is immersed in the partial condenser, and cooling water flows into the cooling coil from the cooling water inlet 4, cools the liquid phase in the partial condenser, and then flows out from the cooling water outlet 3; the steam condenses in the partial condenser, the upper steam is high-purity saturated ammonia steam, which flows out of the distillation tower through the ammonia outlet 1, and the lower part condenses into a high-concentration solution through the reflux liquid conduit 6 and the atomization tank 9 to flow into the atomization tank 9 on the upper layer of the distillation tower for atomization; under the action of gravity, the droplets generated in the upper atomization tank 9 descend and exchange heat and mass with the ascending steam, and then fall to the middle tower plate 12 and mix with the concentrated solution from the concentrated solution inlet 14.

[0047] In summary, this distillation tower utilizes ultrasonic atomization technology to transform the solution into droplets, replacing filler. This reduces overall mass while significantly improving the mass transfer coefficient, thereby reducing tower size. Furthermore, ultrasonic oscillation technology promotes heat transfer between the solution and the heating fluid, reducing the superheat of the outlet solution and effectively lowering the dilute solution concentration. By reducing the size of ammonia absorption refrigeration systems and improving their overall energy efficiency, this novel distillation tower provides a significant solution to the constraints that have limited their commercial application.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An ammonia distillation tower that uses multi-frequency ultrasound to improve heat and mass transfer performance, used for separating ammonia in an ammonia absorption refrigeration system, characterized by The ammonia distillation tower is sequentially provided with four parts from top to bottom: the fractionation section, the distillation section, the stripping section and the generating section; wherein, The condensation section is located at the top of the distillation tower, and comprises an ammonia outlet (1), a condenser (2), a cooling water outlet (3), a cooling water inlet (4), a steam conduit (5), and a reflux liquid conduit (6); the ammonia outlet (1) is located at the upper part of the condenser (2), the cooling water outlet (3) and the cooling water inlet (4) are located on one side of the condenser (2), the steam conduit (5) is located on the other side of the condenser (2) and is connected to the upper part of the distillation section, and the reflux liquid conduit (6) is located at the lower part of the condenser (2) and is connected to the atomization tank (9) of the distillation section; The distillation section is located at the upper part of the distillation tower, and includes an atomizer vibrator (7), an ultrasonic atomizer (8), an atomizing tank (9), a bubble cap (10), an ultrasonic oscillator (11), a tower plate (12), and a solution conduit (13); the section is divided into three layers, the first layer includes an ultrasonic atomizer composed of an atomizer vibrator (7), an ultrasonic atomizer (8), and an atomizing tank (9); the second layer includes an ultrasonic oscillator composed of a bubble cap (10), an ultrasonic oscillator (11), and a tower plate (12), and a solution conduit (13) is provided in the middle of the ultrasonic oscillator; the third layer has the same structure as the first layer; The stripping section comprises two layers of ultrasonic oscillators consisting of a bubble cap (10), an ultrasonic oscillator (11), and a tray (12); a concentrated solution inlet (14) is also provided in the stripping section; The generating section comprises a heating fluid outlet (15), a through hole (16), a partition (17), a heating tube (18), a heating fluid inlet (19), and a dilute solution outlet (20); the lower portion of the heating tube (18) is connected to the heating fluid inlet (19), and the upper portion of the heating tube (18) is connected to the heating fluid outlet (15) to form a heater, and a through hole (16) is provided on the heater, and the dilute solution flows past the heating tube (18) through the through hole (16) to the dilute solution outlet (20).

2. The ammonia distillation tower using multi-frequency ultrasound to improve heat and mass transfer performance according to claim 1, characterized in that: The ultrasonic atomizer (8) is installed in the center of the atomization tank (9), 1-2 cm below the liquid level to obtain the best atomization effect.

3. The ammonia distillation tower using multi-frequency ultrasound to improve heat and mass transfer performance according to claim 1, characterized in that: The ultrasonic oscillator (11) has a frequency of 20-68 kHz, and six oscillators form a group and are symmetrically distributed in a regular hexagon. The ultrasonic oscillator (11) is installed at the bottom of the tower plate (12) in a trumpet shape and is installed through a hole in the tower plate (12).

4. The ammonia distillation tower using multi-frequency ultrasound to improve heat and mass transfer performance according to claim 3, characterized in that: The tower plate (12) is a perforated plate structure, with uniformly distributed circular holes of equal diameter opened at the oscillator installation position for the installation of the ultrasonic oscillator (11). A solution conduit (13) is installed at the center of the tower plate (12). The solution conduit is slightly higher than the tower plate, and the overflow solution flows along the solution conduit into the atomization tank (9) in a falling film manner.

5. The ammonia distillation tower using multi-frequency ultrasound to improve heat and mass transfer performance according to claim 2, characterized in that: The oscillation frequency of the ultrasonic atomizer (8) is 1.7 MHz to 2.4 MHz, and the ultrasonic atomization effect causes the solution to generate droplets. The first layer of atomizers is located in the distillation section at the upper part of the distillation tower, and atomizes the high-concentration ammonia reflux liquid in the partial condenser to provide small-sized droplets for the distillation section. The second layer of atomizers is installed below the tower plate, and atomizes the solution in the tower plate to provide small-sized droplets for the stripping section.

6. The ammonia distillation tower using multi-frequency ultrasound to improve heat and mass transfer performance according to claim 4, characterized in that: The tower plate (12) is provided with a solution conduit (13) for connecting the tower plate and the atomization tank. The solution conduit is slightly higher than the bottom of the tower plate. After the solution overflows, it flows in a falling film in the solution conduit. The bottom is connected to the atomization tank to provide the solution to the atomizer. The falling film flow increases the heat and mass exchange area between the solution and the gas, thereby enhancing the heat and mass transfer characteristics of the solution and the steam. The solution conduit also provides support for the atomization tank.

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