Cascaded axial flow type salt water crystallization system and use method thereof

Abstract

The invention discloses a cascading axial flow type salt water crystallization system and a using method thereof.The system comprises a photo-thermal salt collecting module and a Fresnel salt collecting module which are installed on a support side by side, and a salt outlet of the photo-thermal salt collecting module is communicated with a salt inlet of the Fresnel salt collecting module through an electromagnetic valve; the center lines of the photo-thermal salt collecting module, the electromagnetic valve and the Fresnel salt collecting module are coaxial to form an axial flow cascade body, a first spiral scraper mechanism is arranged in the first heat collecting pipe to push materials to the second heat collecting pipe, and a second spiral scraper mechanism is arranged in the second heat collecting pipe to push the materials to the salt discharging opening. Through a cascading axial flow technical means of photo-thermal salt collection and Fresnel salt collection, salt water is subjected to high-efficiency preheating, primary crystallization and secondary crystallization, and salt water vapor is condensed and recycled, so that zero-energy-consumption water-salt resource collection of the salt water is realized. The problems that existing salt water evaporative crystallization is large in energy consumption and low in efficiency are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of saline water crystallization treatment, and particularly relates to a cascaded axial-flow saline water crystallization system, and also relates to a method for using the cascaded axial-flow saline water crystallization system. Background Art

[0002] Saline water can cause soil salinization and acid-baseification, harm the growth of plants, reduce the quality of crops, and lead to environmental water pollution and ecological damage. The saline water in China is mainly distributed in the arid regions of the northwest and the eastern coastal areas. The total amount of saline water far exceeds that of fresh water. The saline water resources are rich and have great potential for development and utilization. At present, there has been certain development and utilization in related fields. For example, methods for producing salt, alkali, and chlorine from saline water such as the solar salt production method, boiling method, lake salt method, evaporation pond method, electrolysis method, ion exchange method, etc. Compared with other methods, the evaporation method uses industrial means to heat saline water and uses heat energy to promote the evaporation of saline water. This method has high energy consumption and low efficiency. The solar light resources in nature can transfer heat energy through radiation and are widespread. The related technologies of concentrating solar heat, light-selective membrane solar heat collection, vacuum solar heat collection, and lens solar heat collection are also relatively mature. If these existing technologies can be effectively combined and an innovative natural force-driven solar heat collection method using solar radiation energy is proposed, and a new saline water salt collection system driven by this natural force is developed, it will provide innovative theories and technologies for the resource utilization of saline water resources.

[0003] Therefore, it is very necessary and urgent to study a cascaded axial-flow saline water crystallization system. Summary of the Invention

[0004] The purpose of the present invention is to provide a cascaded axial-flow saline water crystallization system and a method for using the same to solve the problems of high energy consumption and low efficiency in the existing evaporation and crystallization of saline water.

[0005] The technical solution adopted by the present invention is that a cascaded axial-flow saline water crystallization system includes a solar heat salt collection module and a Fresnel salt collection module fixedly installed side by side on a bracket. The solar heat salt collection module includes a first heat collection pipe and a reflector. The first heat collection pipe is fixedly installed above the bracket, and the reflector is fixedly installed below the first heat collection pipe, and the light focused by the reflector can irradiate the first heat collection pipe for heating. The first heat collection pipe is provided with an inner cavity for accommodating saline water, and a water inlet, a salt outlet, and a steam outlet communicating with the inner cavity. The Fresnel salt collection module includes a second heat collection pipe and a linear Fresnel convex lens. The second heat collection pipe is fixedly installed on the bracket, and a linear Fresnel convex lens is fixedly installed above the second heat collection pipe. The light focused by the linear Fresnel convex lens can irradiate the second heat collection pipe for heating. The second heat collection pipe is provided with an inner cavity and a salt inlet and a salt outlet communicating with the inner cavity, and the salt outlet communicates with the salt inlet.

[0006] Preferably, a solenoid valve is installed on the pipeline connecting the salt outlet and the salt inlet. The center lines of the solar thermal salt collection module, the solenoid valve, and the Fresnel salt collection module are coaxial to form an axial flow cascade body. A first spiral scraper mechanism is arranged in the first heat collecting pipe. The first spiral scraper mechanism can push the materials in the first heat collecting pipe to the second heat collecting pipe. A second spiral scraper mechanism is arranged in the second heat collecting pipe. The second spiral scraper mechanism can push the materials in the second heat collecting pipe to the salt discharge port.

[0007] Preferably, the water inlet of the first heat collecting pipe is arranged at the head end, and the water inlet is connected to the brine outlet of the heat exchanger through a first pipeline. The heat exchanger is installed on a bracket. The heat exchanger is also provided with a brine inlet. A condensate outlet is arranged at one end of the side wall of the heat exchanger close to the brine inlet. A steam inlet is arranged at one end of the side wall of the heat exchanger close to the brine outlet. The steam inlet is connected to the exhaust port of the first heat collecting pipe through a second pipeline. The condensate outlet is connected to a water collecting pipe.

[0008] Preferably, the first heat collecting pipe is installed inside the first vacuum tube and both ends are hermetically extended out of the first vacuum tube. A one-way light coating layer and a heat insulation coating layer are arranged on the inner wall of the first vacuum tube from the inside to the outside. First upper and lower flanges are respectively arranged at both ends of the first heat collecting pipe. The first spiral scraper mechanism includes a first driving motor with a first communication hole arranged inside and a solar thermal salt collection auger fixedly connected to the first rotor inside it. The first rotor is of a sleeve structure. The solar thermal salt collection auger is axially installed in the first heat collecting pipe and is in movable contact with the inner wall of the first heat collecting pipe. A first discharge inner hole is arranged axially on the solar thermal salt collection auger. One end of the first stator of the first driving motor is fixedly connected to the first upper flange, and the other end of the first stator of the first driving motor is fixedly connected to the flange of the first pipeline. The first lower flange is fixedly connected to the input end of the solenoid valve.

[0009] Preferably, the solar thermal salt collection auger includes a first spiral blade with an L-shaped cross section and a first fixing flange fixedly installed at its head end. The first fixing flange is fixedly connected to the first rotor. A first heat insulation layer is arranged on the inner wall of the first rotor between the first fixing flange and the first rotor. A first seal for sealing the motor and the first pipeline is arranged at one end of the first heat insulation layer away from the first fixing flange. The outer cylindrical surface of the first seal is set as a plurality of annular seal platform structures with a trapezoidal cross section. The first stator is fixedly and hermetically connected to the first pipe flange of the first pipeline and the first upper flange respectively.

[0010] Preferably, the above-mentioned second heat collecting tube is installed inside the second vacuum tube and its two ends are hermetically extended out of the second vacuum tube. There is a cavity between the second heat collecting tube and the second vacuum tube, and a spiral heat conductor is installed on the outer section of the second heat collecting tube inside the cavity. A solution inlet and a solution outlet passing through the side wall of the second heat collecting tube are respectively arranged at the upper and lower ends of the spiral heat conductor. The solution inlet and the solution outlet are respectively close to the salt inlet and the salt outlet. Second upper flange and second lower flange are respectively arranged at both ends of the second heat collecting tube. The second upper flange is fixedly connected to the output end of the solenoid valve. The second spiral scraper mechanism includes a second driving motor and a Fresnel salt collecting auger fixedly connected to its second rotor. The Fresnel salt collecting auger is axially installed inside the second heat collecting tube and keeps active contact with the inner wall of the second heat collecting tube. Both ends of the second stator of the second driving motor are fixedly connected to the second lower flange and the third pipe flange of the third output pipe respectively.

[0011] Preferably, the above-mentioned Fresnel salt collecting auger includes a second spiral blade with a trapezoidal cross-section and a second fixed flange fixedly installed at its end. The second spiral blade is provided with a second inner hole for feeding. The cross-section of the second spiral blade becomes smaller from the feeding end to the discharging end. The second fixed flange is fixedly connected to the second rotor. A second heat insulation layer is integrally arranged between the second fixed flange and the second rotor and on the inner wall of the second rotor. A second seal is arranged at one end of the second heat insulation layer away from the second fixed flange. The outer cylindrical surface of the second seal is set as a structure of multiple annular seal platforms with a trapezoidal cross-section.

[0012] Preferably, an output valve is arranged on the above-mentioned salt outlet. The output end of the third pipeline is connected to a salt collecting box, and the salt collecting box is installed at the lower part of the bracket.

[0013] Preferably, the above-mentioned reflector is fixedly installed below the first heat collecting tube through a reflector bracket. The reflector is a strip-shaped parabolic structure, and a mirror heat insulation and reflective coating is sprayed on the inner wall of the parabolic surface. The central axis of the first heat collecting tube is set at the focal position of the parabolic surface; the linear Fresnel convex mirror is fixedly installed above the second heat collecting tube through a Fresnel mirror bracket. The central axis of the second heat collecting tube is set at the focal length of the linear Fresnel convex mirror.

[0014] Preferably, the bracket comprises a cross bar and a left vertical plate and a right vertical plate fixed at both ends of the cross bar, a first neutral plate and a second neutral plate are symmetrically arranged between the left vertical plate and the right vertical plate, a left mounting hole for heat collecting tube and a right mounting hole for heat collecting tube are respectively arranged at the top of the left vertical plate and the right vertical plate, the end of the second heat collecting tube is fixedly connected to the left vertical plate through the left mounting hole of the heat collecting tube, the head end of the first heat collecting tube is fixedly connected to the right vertical plate through the right mounting hole of the heat collecting tube, a left mounting hole for heat exchanger and a right mounting hole for heat exchanger are arranged at the top of the first neutral plate and the second neutral plate, the left end and the right end of the heat exchanger are respectively fixedly connected to the first neutral plate and the second neutral plate through the left mounting hole of the heat exchanger and the right mounting hole of the heat exchanger, the salt water outlet of the heat exchanger is arranged at the right end and connected to the first pipe through a flange, a right through hole is arranged in the middle of the right vertical plate corresponding to the first pipe, the first pipe is connected to the first heat collecting tube after passing through the right through hole of the right vertical plate, and a left through hole is arranged on the left vertical plate corresponding to the right through hole.

[0015] Preferably, the middle part of the bottom end of the above-mentioned bracket is fixedly connected to the output end of the first rotary motor, the input end of the first rotary motor is fixedly connected to the output end of the second rotary motor, the input end of the second rotary motor is fixedly connected to the output end of the third motor, and the axes of the first rotary motor, the second rotary motor and the third rotary motor are perpendicular to each other, together forming an orthogonal RRR three-axis transmission system, providing spherical motion for the axial flow cascade body and the heat exchanger.

[0016] Preferably, the input end of the third motor is fixedly connected to the top of the pole, the bottom of the pole is fixed to the ground through a flange, the middle of the pole is connected to a salt collecting box through a throat clamp, the salt collecting box is connected to the salt discharge port through a third pipeline, a salt collecting port is opened at the bottom of the salt collecting box, and a valve is provided at the salt collecting port.

[0017] A method for using a cascade axial flow salt water crystallization system is as follows: salt water is pressed into a heat exchanger for preheating, and the salt water with a temperature of 60°C-80°C enters the first heat collecting tube of the photothermal salt collecting module from the heat exchanger, and the first drive motor drives the photothermal salt collecting auger in reverse to stir the salt water so that the salt water is evenly heated, and the temperature of the salt water reaches 85°C-160°C, which promotes the evaporation of water in the salt water, and discharges the steam to the heat exchanger through the second pipe, and the salt water that has just entered is preheated and the steam is condensed inside the heat exchanger. After a period of time, the first drive motor rotates forward, and the first rotating blade of the photothermal salt collecting auger is used to stir the crystals in the The viscous crystalline salt inside and on the inner wall of the first heat collecting tube is scraped and transported; the solenoid valve is opened, and the photothermal salt collecting auger outputs the viscous crystalline salt to the Fresnel salt collecting module. With the support of the linear Fresnel mirror, the second vacuum tube and the spiral heat conductor, the internal temperature of the second heat collecting tube reaches above 200°C, and the second drive motor drives the Fresnel salt collecting auger in reverse to stir the viscous crystalline salt, causing the viscous crystalline salt to undergo secondary heating and evaporation. After a period of time, the second drive motor drives forward, and uses the second spiral blade to scrape off the crystalline salt adhered to the inner wall of the second heat collecting tube, and finally outputs the crystalline salt through the third pipeline.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the axial flow technology of the present invention for solar thermal salt collection and Fresnel salt collection, first, the saline water is subjected to solar thermal salt collection to reach a set temperature and undergo primary crystallization to obtain viscous crystalline salt. The obtained viscous crystalline salt is then sent to the Fresnel salt collection for secondary crystallization, enabling the saline water to salt crystallization to achieve single-end entry and single-end output, reducing the original water-vapor-thermal three-phase separation process, and the structure is simpler; the saline water crystallization process is gradually heated, and the temperature is higher than that of a single solar thermal salt collection system or Fresnel salt collection system, making the saline water crystallization process more efficient; realizing low-energy water-salt resource collection of saline water and solving the problems of high energy consumption and low efficiency in the existing evaporation crystallization of saline water; (2) The solenoid valve is used to connect the solar thermal salt collection module and the Fresnel salt collection module in series to form an axial flow structure, and in cooperation with the first spiral scraper mechanism and the second spiral scraper mechanism, it can stir and quickly send out the crystalline salt of the solar thermal salt collection module and stir and quickly send out the crystalline salt of the Fresnel salt collection module respectively. Stirring in the Fresnel salt collection module enables the re-crystallization of the crystalline salt after primary crystallization to obtain sufficient and rapid secondary crystallization, with higher crystallization efficiency; (3) The steam is collected by the heat exchanger to preheat the saline water. The preheated saline water enters the solar thermal salt collection module for primary crystallization, reducing the heating time of the saline water, shortening the crystallization time, further improving the crystallization efficiency and realizing energy recovery; (4) The first vacuum tube is provided with a unidirectional light coating layer and a heat insulation coating layer, which can achieve the aggregation of light and reduce heat dissipation, improving the energy utilization rate of light; the first spiral scraper mechanism can ensure that the driving motor drives the solar thermal salt collection auger to rotate to send out the crystalline salt while passing the material; (5) The first spiral blade with an L-shaped cross-section promotes the stirring effect during the evaporation crystallization of saline water, and can better roll and drive the transportation of crystalline salt (or salt viscous liquid) when the re-crystallized salt is output. Moreover, the L-shaped spiral blade has higher rigidity and strength, higher rotational stability, and the L-shaped structure is also more conducive to stirring and transporting after the production of crystalline salt; (6) The second heat collection tube is installed with a spiral heat conductor, which, in cooperation with Fresnel heating, makes the second heat collection tube more evenly heated, with a higher temperature, faster crystallization, higher efficiency, and more stable crystallization; (7) The trapezoidal second spiral blade, compared with the rectangular blade, increases the contact area of the crystalline salt, and uses the propelling effect of the trapezoidal inclined surface to further improve the propelling process of the crystalline salt. The sharp blade at the small end of the trapezoid can also be used to increase the scraping force of the blade on the crystalline salt adhered to the inner wall of the second heat collection tube; (8) Through the output valve, the crystallized salt can be conveyed into the salt collection tank through the second spiral blade, which is convenient for collection and then transportation. The first rotary motor, the second rotary motor, and the third rotary motor form an orthogonal RRR three-axis transmission system. Compared with the RR two-axis transmission system of the solar thermal salt collection system or the Fresnel salt collection system, the light tracking is more accurate, greatly improving the utilization efficiency of solar energy. (9) Placing the focus of the reflector on the central axis of the first heat collection tube, or the focal length of the linear Fresnel convex mirror on the central axis of the second heat collection tube, can maximize the heating effect and improve the utilization of light energy. (10) The usage method of the brine crystallization system: Preheat the brine to 60°C - 80°C through a heat exchanger and then enter the first heat collection tube of the solar thermal salt collection module to be heated to 85°C - 160°C for primary crystallization. After reaching the set time, it is sent into the second heat collection tube to be heated to above 200°C for crystallization, which can improve the crystallization efficiency and energy utilization rate. (11) This system can utilize the solar light resources in nature and drive the heat collection method through the natural force of radiant energy to collect, evaporate, condense, and recycle the water in the brine resources; concentrate, crystallize, and collect the salt in the brine resources, realizing the water-salt resource treatment of the brine resources, providing beneficial technical support for the treatment of saline-alkali land in arid areas and brine in coastal areas of our country. In summary, the present invention uses the axial flow cascade technical means of heat exchangers, solar thermal salt collection, and Fresnel salt collection, and condenses and recovers the brine vapor to achieve low-energy consumption water-salt resource collection of brine. It solves the problems of high energy consumption and low efficiency in the existing brine evaporation and crystallization. Compared with a single solar thermal salt collection system or a Fresnel salt collection system, it has the following advantages: ① Through the axial flow cascade technology, the brine to salt crystallization realizes single-end entry and single-end output, reducing the original water-vapor-heat three-phase separation process, and the structure is simpler. ② Adopting the axial flow cascade structure, the brine crystallization process is gradually heated, and the temperature is higher than that of a single solar thermal salt collection system or a Fresnel salt collection system, making the brine crystallization process more efficient. ③ Compared with the Fresnel salt collection system, a spiral heat conductor and a vacuum tube are added outside the second heat collection tube, making the second heat collection tube more evenly heated and the temperature higher. ④ The first rotary motor, the second rotary motor, and the third rotary motor are newly added to form an orthogonal RRR three-axis transmission system. Compared with the RR two-axis transmission system of the solar thermal salt collection system or the Fresnel salt collection system, the light tracking is more accurate, greatly improving the utilization efficiency of solar energy. ⑤ The L-shaped first spiral blade is newly added to promote the stirring effect during the brine evaporation and crystallization process, and can better drive the transportation of the recrystallized salt (or salt viscous liquid) during the output of the recrystallized salt. ⑥The newly added trapezoidal second spiral blade increases the contact area of the crystal salt compared with the rectangular blade. By utilizing the propelling effect of the inclined surface of the trapezoid, the propelling process of the crystal salt is further improved. Additionally, the sharp cutting edge at the small end of the trapezoid can be used to increase the scraping force of the blade on the crystal salt adhered to the inner wall of the second heat collecting pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. 6 is a three-dimensional structural schematic diagram of a cascaded axial-flow type saline water crystal salt system; Figure 2 FIG. 7 is a side view of a cascaded axial-flow type saline water crystal salt system; Figure 3 FIG. 8 is a front view structural schematic diagram of a cascaded axial-flow type saline water crystal salt system; Figure 4 is Figure 3 the schematic diagram of the A-A sectional structure in FIG. Figure 5 FIG. 10 is a schematic diagram of the structure at the first heat collecting pipe; Figure 6 FIG. 11 is a schematic diagram of the structure of the vertical rod and bracket of a cascaded axial-flow type saline water crystal salt system; Figure 7 FIG. 12 is a schematic diagram of the heat exchanger structure of a cascaded axial-flow type saline water crystal salt system; Figure 8 FIG. 13 is a schematic diagram of the solar thermal salt collection module structure of a cascaded axial-flow type saline water crystal salt system; Figure 9 FIG. 14 is a schematic diagram of the Fresnel salt collection module structure of a cascaded axial-flow type saline water crystal salt system; Figure 10 FIG. 15 is a schematic assembly diagram of the spiral heat conductor of a cascaded axial-flow type saline water crystal salt system; Figure 11 is Figure 4 the enlarged schematic diagram of part A in FIG. Figure 12 is Figure 4 the enlarged schematic diagram of part B in FIG. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present invention will be further explained below in conjunction with the drawings of the specification, so as to be better understood by those skilled in the art.

[0021] Embodiment 1 As Figures 1-12 shown, a cascaded axial-flow type saline water crystallization system includes a solar thermal salt collection module 1, a Fresnel salt collection module 2, a heat exchanger 3, a bracket 4, a first driving motor 5, a second driving motor 6, a solenoid valve 7, a first pipeline 8, a second pipeline 9, a third pipeline 10, a first rotary motor 11, a second rotary motor 12, a third rotary motor 13, a vertical rod 14, and a salt collection tank 15.

[0022] The above-mentioned solar thermal salt collection module 1 and Fresnel salt collection module 2 are fixedly installed on the bracket 4. The solar thermal salt collection module 1 includes a first heat collection pipe 101 and a reflector 102. The first heat collection pipe 101 is fixedly installed above the bracket 4, and the reflector 102 is fixedly installed below the first heat collection pipe 101, and the light focused by the reflector 102 can irradiate the first heat collection pipe 101 for heating. The first heat collection pipe 101 is internally provided with a cavity for accommodating brine, and a water inlet 103, a salt outlet 104, and a steam outlet 105 communicated with the cavity; the Fresnel salt collection module 2 includes a second heat collection pipe 201 and a linear Fresnel convex lens 202. The second heat collection pipe 201 is fixedly installed on the bracket 4, and a linear Fresnel convex lens 202 is fixedly installed above the second heat collection pipe 201. The light focused by the linear Fresnel convex lens 202 can irradiate the second heat collection pipe 201 for heating. The second heat collection pipe 201 is internally provided with a cavity and a salt inlet 203 and a salt outlet 204 communicated with the cavity, and the salt outlet 104 is communicated with the salt inlet 203. Through the axial flow cascade technology of solar thermal salt collection and Fresnel salt collection, first, the brine is heated to a set temperature through solar thermal salt collection and undergoes primary crystallization to obtain viscous crystalline salt. Then, the obtained viscous crystalline salt is sent to the Fresnel salt collection for secondary crystallization, enabling the brine to achieve single-end entry and single-end output during the salt crystallization process, reducing the original water-vapor-thermal three-phase separation process, and the structure is simpler; the brine crystallization process is gradually heated, and the temperature is higher than that of a single solar thermal salt collection system or Fresnel salt collection system, making the brine crystallization process more efficient; realizing low-energy water-salt resource collection of brine and solving the problems of high energy consumption and low efficiency in the existing brine evaporation crystallization.

[0023] An electromagnetic valve 7 is installed on the pipeline where the salt outlet 104 is communicated with the salt inlet 203. The central axes of the solar thermal salt collection module 1, the electromagnetic valve 7, and the Fresnel salt collection module 2 are coaxial, forming an axial flow cascade body. A first spiral scraper mechanism is provided in the first heat collection pipe 101, and the first spiral scraper mechanism can push the materials in the first heat collection pipe 101 into the second heat collection pipe 201. A second spiral scraper mechanism is provided in the second heat collection pipe 201, and the second spiral scraper mechanism can push the materials in the second heat collection pipe into the salt outlet 204. Using the electromagnetic valve to connect the solar thermal salt collection module and the Fresnel salt collection module in series to form an axial flow cascade structure, and cooperating with the first spiral scraper mechanism and the second spiral scraper mechanism, it can stir and quickly send out the crystalline salt of the solar thermal salt collection module respectively, and stir and quickly send out the crystalline salt of the Fresnel salt collection module. Stirring in the Fresnel salt collection module enables sufficient and rapid secondary crystallization of the crystalline salt after primary crystallization, and the crystallization efficiency is higher.

[0024] The water inlet 103 of the first heat pipe is arranged at the head end, and the water inlet is connected to the brine outlet 301 of the heat exchanger 3 through the first pipeline 8. The heat exchanger 3 is installed on the bracket 4. The heat exchanger 3 is also provided with a brine inlet 302. One end of the side wall of the heat exchanger 3 close to the brine inlet 302 is provided with a condensate outlet 303. One end of the side wall of the heat exchanger 3 close to the brine outlet 301 is provided with a steam inlet 304. The steam inlet 304 is connected to the exhaust port 104 of the first heat pipe 101 through the second pipeline 9. The condensate outlet 303 is connected to the water collecting pipe. The heat exchanger is used to collect steam to preheat the brine. The preheated brine enters the solar thermal salt collection module for primary crystallization, reducing the heating time of the brine, shortening the crystallization time, further improving the crystallization efficiency and realizing energy recovery.

[0025] To improve the light utilization efficiency of the system, the above-mentioned reflector 102 is fixedly installed below the first heat collecting tube 101 through a reflector bracket 109. The reflector is a strip-shaped parabolic structure, and a mirror heat-insulating and reflecting coating is provided on the inner wall of the parabolic surface. The center of the first heat collecting tube 101 is set at the focal position of the parabolic surface to achieve mirror focusing and maximize the utilization efficiency of light energy. The central axis of the first heat collecting tube 101 is set at the focal position of the parabolic surface. The first heat collecting tube 101 is made of stainless steel. The first vacuum tube 106 is made of glass. The first heat collecting tube 101 is installed inside the first vacuum tube 106 and both ends are hermetically extended out of the first vacuum tube 106. The first heat collecting tube 101 and the first vacuum tube 106 are made by a vacuum sintering and sealing process to form a vacuum heat collector. A one-way light coating layer 110 and a heat-insulating coating layer 111 are provided on the inner wall of the first vacuum tube 106 from the inside to the outside to prevent light from escaping from the first vacuum tube 106 and transfer the temperature to the first heat collecting tube 101. First upper flanges 107 and first lower flanges 108 are respectively provided at both ends of the first heat collecting tube 101. The first spiral scraper mechanism includes a first driving motor 5 provided with a first communication hole and a solar heat collecting salt auger 16 fixedly connected to a first rotor 501 inside it. The first driving motor 5 is flange-connected to the first upper flange 107. The other end of the first driving motor 5 is flange-connected to a first pipe 8. The first lower flange 108 is flange-connected to the input end of a solenoid valve 7.The first rotor 501 is of a bushing structure. The solar thermal salt-collecting auger 16 is axially installed inside the inner wall of the first heat-collecting pipe 101 and keeps in movable contact. The solar thermal salt-collecting auger 16 is axially provided with a first discharge inner hole 113. The solar thermal salt-collecting auger 16 includes a first spiral blade 1602 with an L-shaped cross section and a first fixed flange 1601 fixedly installed at the head end of the first spiral blade 1602. The first fixed flange 1601 is fixedly connected to the first rotor 501 of the first driving motor 5. The first fixed flange 1601 and the first spiral blade 1602 are driven to rotate by the first rotor 501 to scrape the crystalline salt on the inner wall of the first heat-collecting pipe 101 and push it to the end of the first heat-collecting pipe 101 to the greatest extent. In order to protect the normal operation of the first rotor 501, a first heat insulation layer 502 is provided between the first fixed flange 1601 and the inner wall of the first rotor 501. One end of the first heat insulation layer 502 away from the first fixed flange 1601 is provided with a first seal 503 between the sealed motor and the first pipe 8. The outer cylindrical surface of the first seal 503 is set as a structure of multiple annular seal platforms with a trapezoidal cross section to ensure the connection sealing performance between the first fixed flange 1601 and the first driving motor 5. In order to ensure the driving force of the first driving motor 5 on the first spiral scraper mechanism, one end of the first stator 501 of the first driving motor 5 is fixedly connected to the first upper flange 107, the other end of the first stator 501 of the first driving motor 5 is fixedly connected to the flange of the first pipe 8, the first lower flange is fixedly connected to the input end of the solenoid valve 7, and first seal washers 505 and second seal washers 506 are respectively provided between the first stator 504 and the first pipe flange 801 and the first upper flange 107, and are fastened by a bolt group. Among them, the first spiral scraper mechanism can ensure that the driving motor can drive the solar thermal salt-collecting auger to rotate to send out the crystalline salt while passing through the material. The first spiral blade with an L-shaped cross section promotes the stirring effect during the evaporation and crystallization of brine, can better roll and drive the transportation of crystalline salt (or viscous salt liquid) during the output of crystalline salt, and the L-shaped spiral blade has higher rigidity and strength, higher rotational stability, and the L-shaped structure is also more conducive to stirring and transportation after the generation of crystalline salt.

[0026] The linear Fresnel convex mirror 202 is fixedly installed above the second heat collecting pipe 201 through the Fresnel mirror bracket 211. The center of the second heat collecting pipe 201 is set at the focal length of the linear Fresnel convex mirror 202 to improve the utilization rate of light energy. The second heat collecting pipe 201 is made of stainless steel, and the second vacuum tube 205 is made of glass. The second heat collecting pipe 201 is installed inside the second vacuum tube 205 and both ends are hermetically extended out of the second vacuum tube 205. The second heat collecting pipe 201 and the second vacuum tube 205 are made by a vacuum sintering and sealing process. There is a cavity between the second heat collecting pipe 201 and the second vacuum tube 205, and a spiral heat conductor 206 is spirally installed on the outer side section of the second heat collecting pipe 201 in the cavity. The upper and lower ends of the spiral heat conductor 206 are respectively provided with a solution inlet 209 and a solution outlet 210 passing through the side wall of the second heat collecting pipe 201. The solution inlet 209 and the solution outlet 210 are respectively close to the salt inlet 203 and the salt outlet 204. The installation of the spiral heat conductor 206 on the second heat collecting pipe 201, combined with Fresnel heating, makes the second heat collecting pipe 201 more evenly heated, with a higher temperature, faster crystallization, higher efficiency, and more stable crystallization.

[0027] Both ends of the second heat pipe 201 are respectively provided with a second upper flange 207 and a second lower flange 208. The second upper flange 207 is fixedly connected to the output end of the electromagnetic valve 7. The second spiral scraper mechanism includes a second driving motor 6 and a Fresnel salt-collecting auger 17 fixedly connected to its second rotor 601. The second driving motor 6 is fixedly connected to the second lower flange 208. The Fresnel salt-collecting auger 17 is axially installed along the inside of the second heat pipe 201 and is in movable contact with the inner wall of the second heat pipe. The Fresnel salt-collecting auger 17 includes a second spiral blade 1702 with a trapezoidal cross-section and a second fixed flange 1701 fixedly installed at the end of the second spiral blade 1702. The second spiral blade 1702 is provided with a second inner hole 1703 for feeding. The cross-section of the second spiral blade 1702 becomes smaller from the feed end to the discharge end. The trapezoidal second spiral blade 1702 increases the contact area of the crystal salt compared with a rectangular blade, and uses the pushing effect of the trapezoidal inclined surface to further improve the pushing process of the crystal salt. The sharp cutting edge at the small end of the trapezoid can also be used to increase the scraping force of the blade on the crystal salt adhered to the inner wall of the second heat pipe. The second fixed flange 1701 is fixedly connected to the second rotor 601 of the second driving motor 6. The second rotor 601 drives the second fixed flange 1701 and the second spiral blade 1702 to rotate, scraping the crystal salt on the inner wall of the second heat pipe 201 and pushing it towards the salt discharge port 204 to the greatest extent. To prevent the second rotor from being deformed by high temperature and affecting the operation, a second heat insulation layer 602 is integrally provided between the second fixed flange 1701 and the second rotor 601 and on the inner wall of the second rotor. One end of the second heat insulation layer 601 away from the second fixed flange 1701 is provided with a second seal 603 that elastically seals the salt discharge port 204 of the second heat pipe 201 and the second rotor 601. The outer cylindrical surface of the second seal 603 is provided with a structure of multiple annular seal platforms with a trapezoidal cross-section. The second stator 604 of the second driving motor 6 is respectively fixedly connected to the third pipe flange 1001 of the third pipe 10 and the second lower flange 208. Third and fourth sealing washers 605 and 606 are respectively provided between the second stator 604 and the third pipe flange 1001 and the second lower flange 208, and are fastened with a bolt group.

[0028] The salt discharge port 204 of the second heat pipe 201 is provided at the end, and an output valve 18 is provided on the salt discharge port 204, which is used to seal the second heat pipe 201 during crystallization. The salt discharge port 204 is fixedly connected to the second drive motor 6, and the other end of the second drive motor 6 is connected to the third pipe 10. The output end of the third pipe 10 is flange-connected to the salt collection tank 15. The salt collection tank 15 is installed at the lower part of the bracket 4. Through the output valve, the crystallized salt can be conveyed into the salt collection tank through the second spiral blade, which is convenient for collection and then transportation. A solution inlet 209 is provided at one end of the side wall of the second heat pipe 201 close to the salt inlet 203, and a solution outlet 211 is provided at one end close to the salt discharge port 204. Clean water can be pressed into the second heat pipe through the solution inlet for flushing and flows out from the solution outlet. During use, the solution inlet and the solution outlet are closed.

[0029] Further, the above-mentioned bracket 4 includes a cross bar 401 and left and right vertical plates 402 and 403 fixed at both ends of the cross bar 401. A first middle vertical plate 404 and a second middle vertical plate 405 are provided between the left and right vertical plates 402 and 403. The first middle vertical plate 404 and the second middle vertical plate 405 are axisymmetric with the center of the cross bar 401. Left and right through holes 4021 and 4031 for installing the heat pipe are respectively opened at the tops of the left and right vertical plates 402 and 403. The end of the second heat pipe 201 is fixedly connected to the left vertical plate 402 through the left through hole 4021 for installing the heat pipe, and the first heat pipe 101 is fixedly connected to the right vertical plate 403 through the right through hole 4031 for installing the heat pipe. Heat exchanger left and right through holes 4041 and 4042 are provided at the tops of the first middle vertical plate 404 and the second middle vertical plate 405. The left and right ends of the heat exchanger 3 are respectively fixedly connected to the first middle vertical plate 404 and the second middle vertical plate 405 through the heat exchanger left and right through holes 4041 and 4051. The brine outlet of the heat exchanger 3 is provided at the right end and is flange-connected to the first pipe 8. A right through hole 4032 corresponding to the first pipe 8 is opened in the middle of the right vertical plate 403. The first pipe 8 passes through the right through hole 4032 and penetrates the right vertical plate 403 and then is connected to the first drive motor 5. A left through hole 4031 corresponding to the right through hole 4032 is opened on the left vertical plate 402.

[0030] The middle part of the cross bar 401 of the above-mentioned bracket 4 is fixedly connected to the output end of the first rotary motor 11. The first rotary motor 11 drives the bracket 4 to swing left and right. The input end of the first rotary motor 11 is fixedly connected to the output end of the second rotary motor 12. The second rotary motor 12 drives the first rotary motor 11 and the bracket to pitch. The input end of the second rotary motor 12 is fixedly connected to the output end of the third motor 13. The third rotary motor 13 makes a rotational motion. The axes of the first rotary motor 11, the second rotary motor 12, and the third rotary motor 13 are perpendicular to each other, jointly forming an orthogonal RRR three-axis transmission system, which provides spherical motion for the axial flow stage body and the heat exchanger. The first rotary motor, the second rotary motor, and the third rotary motor form an orthogonal RRR three-axis transmission system. Compared with the RR two-axis transmission system of the solar thermal salt collection system or the Fresnel salt collection system, the light tracking is more accurate, greatly improving the utilization efficiency of solar energy.

[0031] Among them, a light sensor tracking system is installed on the bracket 4. The light sensor tracking system includes a sensing unit and a control unit. The sensing unit is used to collect parameters such as the rotation angle, pitch angle, wind speed, temperature, humidity, and light intensity. The control unit receives the data from the sensing unit and controls the motion of the three-axis transmission system to adjust the axial flow stage body to the optimal posture.

[0032] Furthermore, the input end of the above-mentioned third motor 13 is fixedly connected to the top end of the vertical rod 14. The bottom end of the vertical rod 14 is fixed to the ground through a flange. The middle part of the vertical rod 14 is connected with a salt collection tank 15 through a hose clamp. The salt collection tank 15 is connected to the salt discharge port 204 through a third pipeline 10.

[0033] Embodiment 2 A method for using a staged axial flow type brine crystallization system, the method is as follows: Press the brine into the heat exchanger for preheating. The brine with a temperature of 60°C - 80°C enters the first heat collecting pipe of the solar thermal salt collection module from the heat exchanger. The first driving motor reversely drives the solar thermal salt collection auger to stir the brine, so that the brine is evenly heated. The temperature of the brine reaches 85°C - 160°C, promoting the evaporation of water in the brine, and discharging the steam through the second pipeline to the heat exchanger, where the newly entered brine is preheated and the steam is condensed inside the heat exchanger. After a period of time, the first driving motor rotates forward, and the first rotating blade of the solar thermal salt collection auger is used to scrape and convey the viscous crystal salt crystallized inside and on the inner wall of the first heat collecting pipe; the solenoid valve is opened, and the solar thermal salt collection auger outputs the viscous crystal salt to the Fresnel salt collection module. With the assistance of the linear Fresnel mirror, the second vacuum tube, and the spiral heat conductor, the internal temperature of the second heat collecting pipe reaches above 200°C, and the air pressure is 80 kPa. The second driving motor reversely drives the Fresnel salt collection auger to stir the viscous crystal salt, promoting the secondary heating evaporation of the viscous crystal salt. After a period of time, the second driving motor drives forward, and the second spiral blade is used to scrape off the crystal salt adhered to the inner wall of the second heat collecting pipe, and finally the crystal salt is output through the third pipeline.

[0034] The usage method of the brine crystallization system preheats the brine to 60°C - 80°C through a heat exchanger and then enters the first heat collecting pipe of the solar thermal salt collection module to be heated to 85°C - 160°C for primary crystallization. After reaching the set time, it is sent into the second heat collecting pipe to be heated to above 200°C for crystallization, which can improve the crystallization efficiency and energy utilization rate.

[0035] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit and principles of the present invention, various deformations and improvements made by those skilled in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A cascaded axial-flow brackish water crystallization system, characterized in that, It includes a solar thermal salt collection module (1) and a Fresnel salt collection module (2) fixedly installed side by side on a bracket (4). The solar thermal salt collection module (1) includes a first heat collection pipe (101) and a reflector (102). The first heat collection pipe (101) is fixedly installed above the bracket (4), and the reflector (102) is fixedly installed below the first heat collection pipe (101), and the sunlight focused by the reflector (102) can irradiate the first heat collection pipe (101) for heating. The first heat collection pipe (101) is provided with an inner cavity for containing brine, and a water inlet (103), a salt outlet (104) and a steam outlet (105) communicated with the inner cavity; the Fresnel salt collection module (2) includes a second heat collection pipe (201) and a linear Fresnel convex mirror (202). The second heat collection pipe (201) is fixedly installed on the bracket (4), and a linear Fresnel convex mirror (202) is fixedly installed above the second heat collection pipe (201). The sunlight focused by the linear Fresnel convex mirror (202) can irradiate the second heat collection pipe (201) for heating. The second heat collection pipe (201) is provided with an inner cavity and a salt inlet (203) and a salt discharge port (204) communicated with the inner cavity, and the salt outlet (104) is communicated with the salt inlet (203).

2. The axial flow type brackish water crystallization system according to claim 1, wherein An electromagnetic valve (7) is installed on the pipeline where the salt outlet (104) is communicated with the salt inlet (203). The central lines of the solar thermal salt collection module (1), the electromagnetic valve (7) and the Fresnel salt collection module (2) are coaxial to form an axial flow cascade body. A first spiral scraper mechanism is arranged in the first heat collection pipe (101), and the first spiral scraper mechanism can push the materials in the first heat collection pipe (101) into the second heat collection pipe (201). A second spiral scraper mechanism is arranged in the second heat collection pipe (201), and the second spiral scraper mechanism can push the materials in the second heat collection pipe into the salt discharge port (204).

3. The axial-flow brackish water crystallization system according to claim 1, wherein The water inlet (103) of the first heat collection pipe (101) is arranged at the head end, and the water inlet (103) is connected to the brine outlet (302) of the heat exchanger (3) through a first pipeline (8). The heat exchanger (3) is installed on the bracket (4). The heat exchanger (3) is also provided with a brine inlet (301). A condensate outlet (303) is arranged at one end of the side wall of the heat exchanger (3) close to the brine outlet (302), and a steam inlet (304) is arranged at one end of the side wall of the heat exchanger (3) close to the brine inlet (301). The steam inlet (304) is connected to the steam outlet (104) of the first heat collection pipe (101) through a second pipeline (9), and the condensate outlet (303) is connected to a water collecting pipe.

4. The axial-flow brackish water crystallization system according to claim 2, wherein The first heat pipe (101) is installed inside the first vacuum tube (106) and its two ends are hermetically extended out of the first vacuum tube (106). The inner wall of the first vacuum tube (106) is provided with a one-way light coating layer (110) and a heat insulation coating layer (111) from the inside to the outside. The two ends of the first heat pipe (101) are respectively provided with a first upper flange (107) and a first lower flange (108). The first spiral scraper mechanism includes a first driving motor (5) and a solar heat collection auger (16) fixedly connected to a first rotor (501) inside it. The first rotor (501) is of a bushing structure. The solar heat collection auger (16) is axially installed inside the first heat pipe (101) and is in movable contact with the inner wall of the first heat pipe (101). A first discharge inner hole (112) is arranged axially on the solar heat collection auger (16). One end of a first stator (504) of the first driving motor (5) is fixedly and hermetically connected to the first upper flange (107). The other end of the first stator (504) of the first driving motor (5) is fixedly and hermetically connected to a first pipe flange (801) of a first pipe (8). The first lower flange (108) is fixedly connected to the input end of a solenoid valve (7).

5. The axial-flow type brackish water crystallization system according to claim 4, wherein The solar heat collection auger (16) includes a first spiral blade (1601) with an L-shaped cross section and a first fixed flange (1602) fixedly installed at its head end. The first fixed flange (1601) is fixedly connected to the first rotor (501). A first heat insulation layer (502) integrated with each other is arranged between the first fixed flange (1601) and the first rotor (501) and on the inner wall of the first rotor (501). One end of the first heat insulation layer (502) away from the first fixed flange (1601) is provided with a first seal (503) for sealing between the motor and the first pipe (8). The outer cylindrical surface of the first seal (503) is set as a structure of a plurality of annular seal platforms with a trapezoidal cross section.

6. The axial-flow type brackish water crystallization system according to claim 4 or 5, characterized in that The second heat collecting pipe (201) is installed in the second vacuum tube (205) and its two ends are hermetically extended out of the second vacuum tube (205). There is a cavity between the second heat collecting pipe (201) and the second vacuum tube (205), and a spiral heat conductor (206) is installed on the outer section of the second heat collecting pipe (201) in the cavity. The upper and lower ends of the spiral heat conductor (206) are respectively provided with a solution inlet (209) and a solution outlet (210) passing through the side wall of the second heat collecting pipe (201). The solution inlet (209) and the solution outlet (210) are respectively close to the salt inlet (203) and the salt discharge port (204). Second upper flange (207) and second lower flange (208) are respectively provided at both ends of the second heat collecting pipe (201). The second upper flange (207) is fixedly connected to the output end of the electromagnetic valve (7). The second spiral scraper mechanism includes a second driving motor (6) and a Fresnel salt collecting auger (17) fixedly connected to its second rotor (601). The Fresnel salt collecting auger (17) is installed axially along the inside of the second heat collecting pipe (201) and keeps moving contact with the inner wall of the second heat collecting pipe. The two ends of the second stator (604) of the second driving motor (6) are respectively fixedly connected to the second lower flange (208) and the third pipe flange (1001) of the third output pipe (10).

7. A staged axial flow brackish water crystallization system according to claim 6, characterized in that, The Fresnel salt collecting auger (17) includes a second spiral blade (1702) with a trapezoidal cross-section and a second fixed flange (1701) fixedly installed at its end. The second spiral blade (1702) is provided with a second inner hole (1703) for feeding. The cross-section of the second spiral blade (1702) becomes smaller from the feeding end to the discharging end. The second fixed flange (1701) is fixedly connected to the second rotor (601). A second heat insulation layer (602) is integrally provided between the second fixed flange (1701) and the second rotor (601) and on the inner wall of the second rotor (601). One end of the second heat insulation layer (602) away from the second fixed flange (1701) is provided with a second seal (603) that elastically seals the salt discharge port (204) of the second heat collecting pipe (201) and the second rotor (601). The outer cylindrical surface of the second seal (603) is set as a structure of multiple annular seal platforms with a trapezoidal cross-section.

8. The axial-flow brackish water crystallization system according to claim 6, characterized in that, An output valve (18) is provided on the salt discharge port (204). The output end of the third pipeline (10) is connected to a salt collecting tank (15). The salt collecting tank (15) is installed at the lower part of the bracket (4). The middle of the bottom end of the bracket (4) is fixedly connected to the output end of a first rotary motor (11). The input end of the first rotary motor (11) is fixedly connected to the output end of a second rotary motor (12). The input end of the second rotary motor (12) is fixedly connected to the output end of a third motor (13). The axes of the first rotary motor (11), the second rotary motor (12), and the third rotary motor (13) are perpendicular to each other, jointly forming an orthogonal RRR three-axis transmission system to provide spherical motion for the axial flow stage body and the heat exchanger.

9. The axial-flow type brackish water crystallization system according to claim 1, wherein The reflector (102) is fixedly mounted below the first heat collecting tube (101) via a reflector bracket (109); the reflector is a strip-shaped parabolic structure, and a mirror heat-insulating reflective coating is provided on the inner wall of the parabola; the central axis of the first heat collecting tube (101) is arranged at the focal position of the parabola; the linear Fresnel convex mirror (202) is fixedly mounted above the second heat collecting tube (201) via a Fresnel mirror bracket (211), and the central axis of the second heat collecting tube (201) is arranged at the focal length of the linear Fresnel convex mirror (202).

10. The method of using a cascaded axial-flow desalination crystallization system according to claim 6, wherein, The method comprises the following steps: the salt water is pressed into a heat exchanger for preheating, the salt water with a temperature of 60°C-80°C enters the first heat collecting tube of the photothermal salt collecting module from the heat exchanger, the first driving motor drives the photothermal salt collecting auger in reverse to stir the salt water so that the salt water is evenly heated, the temperature of the salt water reaches 85°C-160°C, the water in the salt water evaporates, the steam generated by the evaporation is discharged to the heat exchanger through the second pipe, the salt water just entering is preheated and the steam is condensed inside the heat exchanger, after the set time is reached, the first driving motor rotates forward, and the first rotating blade of the photothermal salt collecting auger is used to scrape and transport the viscous crystallized salt inside and on the inner wall of the first heat collecting tube; The solenoid valve opens, and the photothermal salt collecting auger outputs the viscous crystalline salt to the Fresnel salt collecting module. With the support of the linear Fresnel mirror, the second vacuum tube and the spiral heat conductor, the internal temperature of the second heat collecting tube reaches above 200°C. The second drive motor drives the Fresnel salt collecting auger in reverse to stir the viscous crystalline salt, causing the viscous crystalline salt to undergo secondary heating and evaporation. After a period of time, the second drive motor drives forward and uses the second spiral blade to scrape off the crystalline salt adhered to the inner wall of the second heat collecting tube, and finally outputs the crystalline salt through the third pipeline.

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