CN114249373B - Solar water desalination device and method based on tubular hydrophobic ceramic membrane - Google Patents

Abstract

The invention discloses a solar water desalination device and a method based on a tubular hydrophobic ceramic membrane, which belong to the technical field of solar seawater desalination and comprise a membrane distillation system, an interface evaporation-condensation double-effect system, a circulation control water tank group and a photovoltaic power supply system, wherein a raw water inlet end and a raw water outlet end of the membrane distillation system are communicated with the circulation control water tank group; the steam outlet end of the membrane distillation system is communicated with the interface evaporation-condensation double-effect system; the interface evaporation-condensation double-effect system is communicated with the circulating control water tank group; the photovoltaic power supply system supplies power for the device. The water desalination device and the method comprehensively utilize the solar direct-drive membrane distillation technology, the thermal interface distillation technology and the spray falling film distillation technology, realize integrated collaborative operation and miniaturization of the solar water desalination device, and remarkably improve the solar energy utilization rate and the system operation efficiency of the water desalination device.

Description

Solar water desalination device and method based on tubular hydrophobic ceramic membrane

Technical Field

The invention relates to the technical field of solar seawater/brackish water desalination, in particular to a solar water desalination device and method based on a tubular hydrophobic ceramic membrane.

Background

The solar membrane distillation technology is a branch of the solar distillation technology, the technology utilizes the evaporation-condensation process of the hydrophobic microporous membrane and raw water to achieve the purpose of sea water/brackish water desalination, the evaporation-condensation process occurs at two sides of the hydrophobic microporous membrane, the sea water/brackish water heated by solar energy is evaporated near the evaporation side hydrophobic interface of the membrane, and the high-temperature water vapor is driven by the vapor pressure difference at two sides of the membrane to penetrate through the micropores inside the hydrophobic membrane to reach the condensation side of the membrane to be condensed to form fresh water.

The interface evaporation is a novel high-efficiency water desalination technology, when an extremely thin raw water film is formed at the evaporation interface, the raw water film at the evaporation interface is quickly vaporized in a heat conduction or direct heat absorption mode by utilizing renewable energy sources such as waste heat, waste heat or solar energy, and then liquid fresh water is produced through a condensation link.

The ultrasonic atomization technology utilizes the high-frequency resonance effect (the oscillation frequency is 1.7MHz or 2.4MHz, which is larger than the hearing range of human body, and the electronic oscillation does not harm human body and animals) of the ceramic atomizing sheet to disperse raw water into mist liquid drop groups with small particle size. The technology does not need extra heat source and chemical reagent, and compared with the heating type atomization technology, the ultrasonic atomization energy consumption can be reduced by more than 90 percent.

The existing most solar water desalination devices have single desalination modes, so that the energy consumption of a water desalination system is high, and the water yield, the solar energy utilization rate and the latent heat recovery rate of the water desalination system are low. According to the invention, the solar energy utilization technology is organically combined with the membrane distillation technology, the interfacial evaporation technology, the ultrasonic atomization technology and the spray falling film evaporation technology, and an integrated cooperative operation mechanism is implemented, so that the solar energy utilization rate and the water production capacity of the desalted water system can be greatly improved, and the operation efficiency of the device is further improved.

Disclosure of Invention

In order to solve the defects in the prior art, the invention aims to provide a solar water desalination device and a solar water desalination method based on a tubular hydrophobic ceramic membrane, which comprehensively utilize a solar direct-driven membrane distillation technology, a thermal method interface distillation technology and a spray falling film distillation technology, and adopt a trough type condensation heat collection technology, an enhanced heat and mass transfer technology, a vortex generation technology, an ultrasonic atomization technology, a latent heat recovery type interface evaporation-condensation integrated design, a single-shaft solar tracking technology and a spray liquid film generation technology to comprehensively enhance an evaporation process and a condensation process, so that the solar water desalination device realizes integrated collaborative operation and miniaturization, and the solar energy utilization rate and the system operation efficiency of the water desalination device are remarkably improved.

The technical scheme adopted for solving the technical problems is as follows:

the solar water desalination device based on the tubular hydrophobic ceramic membrane comprises a membrane distillation system, an interface evaporation-condensation double-effect system, a circulation control water tank group and a photovoltaic power supply system, wherein a raw water inlet end and a raw water outlet end of the membrane distillation system are communicated with the circulation control water tank group; the steam outlet end of the membrane distillation system is communicated with the interface evaporation-condensation double-effect system; the interface evaporation-condensation double-effect system is communicated with the circulating control water tank group; the photovoltaic power supply system supplies power for the device.

Further, the solar energy collecting system also comprises a spraying falling film evaporation system and a solar tracking system; the inlet end of the spray falling film evaporation system is communicated with the raw water outlet end of the film distillation system, and the spray falling film evaporation system is also communicated with the interface evaporation-condensation double-effect system; the solar tracking system controls the tilt angle of the membrane distillation system.

Further, the circulation control water tank group comprises a circulation bin, a raw water bin and a fresh water collection bin, wherein the circulation bin is communicated with the raw water bin through a pipe orifice; the spraying falling film evaporation system is positioned in the circulating bin, and the interface evaporation-condensation double-effect system is positioned above the raw water bin and is communicated with the raw water bin; the fresh water collecting bin is positioned below the raw water bin and is communicated with the interface evaporation-condensation double-effect system, raw water in the raw water bin can be evaporated and condensed in the interface evaporation-condensation double-effect system in sequence, and finally flows into the fresh water collecting bin.

Further, the membrane distillation system comprises a small groove type condenser array and a decompression membrane distillation assembly arranged at the focal line position of the groove type condenser;

the vacuum membrane distillation assembly comprises a straight-through vacuum heat collecting pipe and a tubular hydrophobic ceramic membrane, wherein the tubular hydrophobic ceramic membrane is concentrically arranged inside the straight-through vacuum heat collecting pipe, the straight-through vacuum heat collecting pipe is a straight-through vacuum heat collecting pipe, the upper part of the outer side surface of the fresh water collecting bin is also communicated with a negative pressure pump, high-temperature water vapor flows out from a vapor outlet of the vacuum membrane distillation assembly under the suction effect of the negative pressure pump, flows into the interface evaporation-condensation double-effect system, and finally flows into the fresh water collecting bin;

the outer surface of the tubular hydrophobic ceramic membrane is provided with spiral circulation fins, and vortex generators parallel to the axis of the tubular hydrophobic ceramic membrane are uniformly arranged on the spiral circulation fins.

Further, the evaporation and condensation double-effect system comprises a heat exchange unit, wherein the heat exchange unit is of a cross-flow plate type and comprises condensation chambers and evaporation chambers, and the condensation chambers and the evaporation chambers are sequentially and alternately arranged;

the inlet end of the condensing chamber is communicated with the steam outlet end of the decompression membrane distillation assembly, and the outlet end is communicated with the fresh water collecting bin; the inlet end of the evaporating chamber is communicated with the raw water bin, and the outlet end of the evaporating chamber is communicated with the inlet end of the condensing chamber.

Furthermore, the inner side wall surfaces in the evaporation chamber are all hydrophilic evaporation interfaces, the bottom of the evaporation chamber is provided with an infiltration cotton stick and ultrasonic oscillation atomization sheet combination, the lower surface of the ultrasonic atomization sheet is closely contacted with the upper end surface of the infiltration cotton stick, and the infiltration cotton stick is fixedly arranged and penetrates into the raw water below the water surface; the inner side interfaces in the condensing chamber are all hydrophobic evaporation interfaces;

the evaporation and condensation pipe network is arranged in the raw water bin and comprises a vertical pipe, a converging transverse pipe and a main pipe, the upper end openings of the vertical pipe are communicated with the bottom of the condensation chamber, and the outlet of the main pipe is communicated with the fresh water collecting bin.

Specifically, the infiltration cotton stick is fixedly installed and has a length of 2/3 that of the infiltration cotton stick to be deep under the water surface of the raw water.

Further, a porous spraying unit and a falling film evaporation plate are arranged in the spraying falling film evaporation system, an inlet of the porous spraying unit is communicated with a raw water outlet end of the film distillation system, and the upper part of the spraying falling film evaporation system is communicated with the condensation chamber through a pipeline; the spray falling film evaporation system also comprises a vapor-liquid separation fan.

Further, the sun tracking system comprises a tracking platform for installing a fixed film distillation system and a photovoltaic power supply system, a combined module of a rotating member is adopted below the tracking platform to be connected with a fixed support, the tracking platform is driven to rotate through an electric screw rod connecting rod mechanism, and a two-quadrant light balance sensor is arranged on the sunny side of the tracking platform fixed support.

The solar water desalination method uses the solar water desalination device, and the specific method comprises the following steps:

solar direct-drive type membrane distillation: the membrane distillation system heats raw water, and hot steam formed after heating flows through the interface evaporation-condensation double-effect system and is condensed to form fresh water;

latent heat driven interfacial distillation: the interface evaporation-condensation double-effect system is communicated with the raw water bin, and the raw water flows through the interface evaporation-condensation double-effect system and forms fresh water after evaporation and condensation;

spray falling film distillation: the membrane distillation system heats raw water, the heated raw water flows through the spray falling film evaporation system, tiny liquid drops are formed after being sprayed out of the spray falling film evaporation system, the tiny liquid drops are heated again in the spray falling film evaporation system, and vapor generated after evaporation enters the interface evaporation-condensation double-effect system, and fresh water is formed after condensation.

Compared with the prior art, the invention has the beneficial effects that:

1. the solar water desalination device and the method comprehensively utilize the solar direct-driven membrane distillation technology, the thermal interface distillation technology and the spray falling film distillation technology, integrate the trough type condensation heat collection technology, the enhanced heat and mass transfer technology, the vortex generation technology, the ultrasonic atomization technology, the latent heat recovery type interface evaporation-condensation integrated design, the single-shaft solar tracking technology and the spray type liquid film generation technology into the comprehensive enhanced evaporation process and the condensation process, realize integrated collaborative operation and miniaturization of the solar water desalination device, and remarkably improve the solar energy utilization rate and the system operation efficiency of the water desalination device;

2. according to the solar water desalination device and the method, the tubular hydrophobic ceramic membrane is concentrically embedded in the straight-through type vacuum heat collection tube, so that the problems of scaling and tube explosion of the inner wall surface of the straight-through type vacuum heat collection tube by a direct distillation method are solved to a certain extent, the retention rate of salt ions, microorganisms and the like is effectively improved, and the quality of fresh water is improved; the cylindrical vortex generators are arranged at the equal radian positions of the spiral circulation fins, countless fine vortices are formed when raw water flows through the surfaces of the vortex generators, the generation and the falling of the vortices effectively destroy a thermal boundary layer and a speed boundary layer near the outer hydrophobic interface of the tubular hydrophobic ceramic membrane, the spiral circulation fins synchronously aggravate the disturbance of the raw water to the hydrophobic membrane interface, the destruction and disturbance behaviors of the boundary layer obviously improve the vaporization rate and the vaporization quantity of the raw water near the hydrophobic membrane interface, and the desalination water performance of the tubular hydrophobic ceramic membrane is further enhanced;

3. according to the solar water desalination device and the method, the condensation chambers and the evaporation chambers are orderly and alternately arranged in a meshed mode by utilizing the cross-flow plate type heat exchange unit. The method comprises the steps that super-hydrophilic nano materials are compounded at the evaporation interface inside an evaporation chamber, an infiltration cotton stick and an ultrasonic oscillation atomization sheet combination are arranged at the bottom of the evaporation chamber, raw liquid at the upper end face of the infiltration cotton stick is atomized into fine liquid drops by the ultrasonic oscillation atomization sheet combination, the fine liquid drops are adsorbed by a hydrophilic evaporation interface in the evaporation chamber of an interface evaporation-condensation double-effect system in the ascending process, meanwhile, the whole hydrophilic evaporation interface is rapidly distributed under the action of capillary force, an extremely thin liquid film is continuously formed at the hydrophilic evaporation interface, film-shaped condensation is carried out on high-temperature water vapor in a condensation chamber while high-efficiency interface evaporation is realized by utilizing the heat conduction of a shared wall surface, and then the double functions of second-efficiency interface evaporation of raw water and primary condensation of high-temperature water vapor are exerted;

4. according to the solar water desalination device and method, the inlet end of the porous spraying unit in the spraying falling film evaporation system is communicated with the raw water outlet end of the solar trough type concentrating type decompressing film distillation system, and high-temperature raw water heated by the solar trough type concentrating type decompressing film distillation system is sprayed out through the porous spraying unit to form a large number of fine liquid drops, so that the contact area of the raw water and hot air in a circulating bin is increased, water vapor molecules are easier to break loose from the constraint of other surrounding liquid water molecules, and the vaporization rate and vaporization quantity of the raw water in the circulating bin are improved, namely the first effect is enhanced; the gas-liquid separation fan can strengthen the convection heat transfer and mass transfer intensity between the high-temperature air flow in the circulation bin and the fine raw water droplets, so that the evaporation rate and the evaporation capacity of the surfaces of the fine droplets are further improved, namely the second effect is strengthened; under the action of gravity, the unevaporated raw water droplets form an extremely thin raw water film on the surface of the falling film evaporation plate and are in a flowing state, and when the falling film evaporation plate is electrified and heated, liquid raw water at the liquid film is continuously and efficiently evaporated, so that spray falling film distillation is realized, and the evaporation rate and evaporation quantity of raw water in a circulation bin are further improved, namely third effect reinforcement.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the following drawings, in which:

FIG. 1 is a schematic diagram of the structure of the present invention;

FIG. 2 is a schematic view of another view angle structure of the present invention;

FIG. 3 is a schematic diagram of a pressure-reducing membrane distillation assembly according to the present invention;

FIG. 4 is a schematic structural view of a tubular hydrophobic ceramic membrane member of the invention;

FIG. 5 is a schematic diagram of the structure of the interfacial evaporation-condensation dual-effect system and the spray falling film evaporation system of the present invention;

FIG. 6 is a schematic diagram of the internal structure of the interfacial evaporation-condensation dual-purpose system of the present invention;

FIG. 7 is a schematic diagram of the porous spray unit structure of the present invention.

In the figure: the device comprises a 1-small tank type condenser, a 2-decompression membrane distillation assembly, a 3-raw water inlet, a 4-raw water outlet, a 5-steam outlet, a 6-circulation control water tank group, a 7-vapor-liquid separation fan, an 8-water pressure sensor, a 9-negative pressure pump, a 10-electromagnetic valve, an 11-fresh water auxiliary collecting bottle, a 12-photovoltaic power supply system, a 13-tubular hydrophobic ceramic membrane, a 14-spiral circulation rib, a 15-vortex generator, a 16-heat exchange unit, a 17-condensation chamber, an 18-evaporation chamber, a 19-raw water bin, a 20-evaporation condensation pipe network, a 21-infiltration cotton stick, a 22-ultrasonic oscillation atomizing sheet, a 23-fresh water collecting bin, a 24-circulation bin, a 25-porous spraying unit, a 26-falling film evaporation sheet, a 27-two-quadrant light balance sensor, a 28-lead screw, a 29-fixed support, a 30-adjustment connecting rod, a 31-driving motor, a 32-lead screw, a 33-direct current circulation pump and a 34-vacuum heat collecting pipe.

Detailed Description

The present application is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be noted that, for convenience of description, only the portions related to the invention are shown in the drawings.

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

As shown in fig. 1-2, the embodiment provides a solar water desalination device based on a tubular hydrophobic ceramic membrane, which comprises a membrane distillation system, an interface evaporation-condensation double-effect system, a spray falling film evaporation system, a solar tracking system and a photovoltaic power supply system. Specific:

the membrane distillation system is a solar trough condensation type decompression membrane distillation system and comprises a straight-through vacuum heat collecting tube 34, a small trough condenser 1 array, a tubular hydrophobic ceramic membrane 13, a spiral circulation rib 14, a negative pressure pump 9 and a condensing device (namely a condensing chamber 17 and an evaporation condensing pipe network 20). In this embodiment, the condenser array is composed of 6 small-sized groove-type condensers 1 and a positioning plate, the small-sized groove-type condensers 1 are transversely installed and longitudinally arranged on the positioning plate, two adjacent groove-type condensers 1 are fixedly connected by positioning bolts and nuts, and the bottom of each small-sized groove-type condenser 1 is fixedly connected with the positioning plate by the positioning bolts and nuts. The central line of the straight-through vacuum heat collecting tube 34 is overlapped with the focal line of the small trough condenser 1, and the two ends are fixed and limited by a buckle; the straight-through type vacuum heat collecting pipe 34 is a metal-glass straight-through type vacuum heat collecting pipe. In order to make the buckle closely contact with the straight-through type vacuum heat collecting pipe 34 and ensure that the buckle does not cause rigid damage to the straight-through type vacuum heat collecting pipe 34, a silica gel buffer protection pad with the thickness of about 1mm is arranged at the contact part of the inner ring of the buckle and the vacuum pipe.

As shown in fig. 3-4, the straight-through vacuum heat collecting tube 34 is internally provided with a tubular hydrophobic ceramic membrane 13 and a spiral circulation rib 14 with a columnar vortex generator 15. The tubular hydrophobic ceramic membrane 13 has only one end opening (i.e. the steam outlet 5 end), the half section is U-shaped, the wall thickness of the hydrophobic ceramic membrane is 5mm, the steam outlet 5 end is sealed by a special end cover (inner end cover), the material is silica gel, the end cover comprises a top cover and an inner plug, and the center of the end cover is provided with a nozzle with the inner diameter of 10mm, the wall thickness of 2mm and the length of 30mm for connecting a steam conveying pipeline. The outer diameter of the inner plug of the end cover is slightly larger than the inner diameter of the tubular hydrophobic ceramic membrane 13, and because the inner plug is made of silica gel, extrusion deformation (interference fit) can be generated when the inner plug is plugged into the inner wall of the tubular hydrophobic ceramic membrane 13, so that good air tightness is ensured. The spiral circulation rib 14 is formed by rolling a hastelloy with the thickness of 1mm, and the hastelloy is used as a tungsten-containing nickel-chromium-molybdenum alloy, has good corrosion resistance and thermal stability, and can effectively prevent high-temperature seawater/brackish water from corroding the rib; the columnar vortex generator 15 is made of a Ha-type alloy, and has a diameter of 6mm and a length of 800mm.

Before installation, the spiral circulation fins 14 are wound on the outer side surface of the tubular hydrophobic ceramic membrane 13 at equal intervals, the spiral interval is set to be 20mm, after the inner ring of the spiral circulation fins 14 is tightly attached to the outer surface of the tubular ceramic membrane 13 for fixed installation, three groups of positioning holes with the diameter of 6mm are formed in the center position of the annular band of the spiral circulation fins 14 in parallel with the central line of the tubular hydrophobic ceramic membrane 13 in equal radian by using a laser cutting machine, then three columnar vortex generators 15 are synchronously inserted into the three rows of positioning holes, and finally the three groups of positioning holes are bonded and fixed by using high-temperature-resistant waterproof glue. In order to prevent the outer surface of the tubular hydrophobic ceramic film and the inner surface of the straight-through vacuum tube from being scratched by the ribs during installation, a layer of flexible material thin layer is sprayed on the inner side and the outer side of the spiral circulation rib 14, and the sum of the width of the annular belt of the ribs, the outer radius of the ceramic film and the thickness of the flexible material thin layer is slightly smaller than the inner diameter of the vacuum tube. The tubular hydrophobic ceramic film 13 with the spiral circulation fins 14 is stretched in from the outlet end of the straight-through vacuum heat collecting tube 34, and finally the special outer end cover is used for sealing the inlet end and the outlet end of the straight-through vacuum heat collecting tube 34.

The outer end cover mainly comprises a top cover, an inner plug and a skirt sleeve. The connecting mode is the same as that of the inner end cover, the outer end cover and the through-type vacuum heat collecting pipe 34 are connected by interference fit, when the connecting device is installed, the inner plug is forcefully plugged into the through-type vacuum heat collecting pipe 34, and meanwhile, the skirt sleeve is spread, so that the outer end cover can be sleeved on the outer surface of the inlet end and the outlet end of the through-type vacuum heat collecting pipe 34. The outer end cap of the outlet end is provided with two through holes which are respectively positioned at the center position and the edge position (close to the inner wall of the straight-through vacuum heat collecting tube 34). The diameter of the through hole at the center is 13mm (slightly smaller than the outer diameter of the nozzle), namely the nozzle of the inner end cover can just extend out of the middle round hole, so that the high-temperature-resistant high-elasticity hose can be conveniently connected; the edge is provided with a convex spray pipe type through hole, the inner diameter of the through hole is 10mm, the wall thickness is 2mm, and the length is 20mm. The center of the outer end cover of the inlet end is also provided with a convex circular through hole, the inner diameter of the through hole is 10mm, the wall thickness is 2mm, the length is 20mm, and the through hole is connected by adopting a high-temperature-resistant high-elasticity hose. When the device is operated, in order to prevent the high-temperature-resistant high-elasticity hose from falling off due to pressure mutation, special binding belts are used for assisting in reinforcement at the outer sides of the skirt sleeve and the hose. The inner pressure of the tubular hydrophobic ceramic membrane 13 is far lower than the outer pressure of the tubular hydrophobic ceramic membrane under the influence of the suction effect of the negative pressure pump 9, and the inner end cover is firmly adsorbed at the steam outlet 5 of the tubular hydrophobic ceramic membrane 13 under the action of the inner pressure and the outer pressure difference, so that the inner end cover can be reinforced in an auxiliary way without a skirt sleeve or a special binding belt.

As shown in fig. 5-6, the dual-purpose system for interfacial evaporation-condensation is a dual-purpose system for interfacial evaporation-condensation driven by latent heat, the core component of which is a cross-flow plate type heat exchange unit 16, the vapor condensation side of the heat exchange unit 16 is called a condensation chamber 17, and the cavities adjacent to the condensation chamber 17 and having a common wall are called evaporation chambers 18, namely the condensation chambers 17 and the evaporation chambers 18 are alternately arranged in sequence. The latent heat of condensation released by the high-temperature water vapor in the condensing chamber 17 is transferred to the evaporating chamber 18 through the common wall, thereby rapidly and efficiently evaporating the raw water film at the evaporation interface inside the evaporating chamber 18. Wherein the common wall is made of brass material with good heat conduction performance and has a thickness of about 1mm. The spacing between adjacent common walls (i.e., the internal widths of the condensing and evaporating chambers) is about 5mm. All evaporation interfaces in the evaporation chamber 18 are compounded with super-hydrophilic nano materials, piezoelectric ultrasonic oscillation atomization sheets 22 are arranged at the bottom positions of all the evaporation chambers 18, the rated power is 2W, the working voltage is 5V-12V, the inlet end of each evaporation chamber 18 is communicated with a raw water bin 19, and in the embodiment, the inlet end of each evaporation chamber is connected into the raw water bin 19 through a soaking cotton stick 21; a temperature sensor is arranged at the middle part of the height of the evaporation chamber 18 and is connected with a controller; the outlet of the evaporating chamber 18 is communicated with the condensing chamber 17 through a gas type one-way four-way valve; all walls inside the condensation chamber 17 are hydrophobic interfaces.

As shown in fig. 5, the circulation control water tank group 6 comprises a circulation bin 24, a raw water bin 19 and a fresh water collection bin 23, wherein the bins are isolated by a heat-insulating waterproof partition board. The spray falling film evaporation system is embedded in the circulation bin 24 and comprises a porous spray unit 25, an internal circulation gas-liquid separation fan 7 and a falling film evaporation plate 26. In this embodiment, as shown in fig. 7, the porous spray unit 25 is formed by connecting a main pipe and 8 auxiliary pipes, wherein 4 auxiliary pipes are respectively distributed on two sides of the main pipe, a plurality of densely distributed fine micropores are uniformly formed below each auxiliary pipe, the main pipe is installed at the top of the circulation bin 24, and the inlet end of the main pipe is communicated with the raw water outlet 4 of the vacuum membrane distillation assembly 2. The installation position of the gas-liquid separation fan 7 is slightly higher than the highest point of the falling film evaporation plate 26, the air outlet and the air inlet are equal in height and are both communicated with the circulation bin 24, and a high-strength hot air circulation flow field can be formed on the upper part of the falling film evaporation plate 26. The water pressure sensor 8 is arranged at the center height of the water outlet of the raw water bin 19, the water pressure sensor 8 is connected with the control system, when the water pressure is lower than the lowest set value, the controller controls the electromagnetic valve 10 to be opened, and raw water can be supplemented to the raw water bin 19 (the electromagnetic valve 10 is connected with a tap water supplementing port, not shown in the figure); when the water pressure is higher than the highest set value, the controller controls the electromagnetic valve 10 to be closed; the outlet of the raw water bin 19 is provided with a direct current circulating pump 33, so that raw water can be driven to continuously circulate, and the aim of heat absorption and vaporization is further realized.

The raw water bin 19 is internally provided with a steam condensation pipe network 20, the steam condensation pipe network 20 is communicated in a series-parallel mixed mode by 57 parallel vertical pipes, 19 converging transverse pipes and 1 main pipe, and the openings at the upper ends of all the vertical pipes are communicated with the bottom of the condensation chamber 17. The upper part of the outer side surface of the fresh water collection bin 23 is communicated with a negative pressure pump 9, and under the dual actions of gravity and the negative pressure pump 9, excessive steam and liquid fresh water in the condensation chamber 17 synchronously flow into the steam condensation pipe network 20, the excessive steam performs convection heat exchange with low-temperature raw water in the raw water bin 19 through the steam condensation pipe network 20, so that all the steam is condensed into the liquid fresh water, and meanwhile, the low-temperature raw water in the raw water bin 19 is primarily preheated. In order to make the liquid fresh water flow into the fresh water collecting bin 23 smoothly, all the transverse pipes are provided with a slight inclination angle. The negative pressure pump 9 is in communication with the fresh water collection sump 23 via a suction line. Considering that the condensation phenomenon of micro water vapor can occur in the converging pipeline of the vapor outlet 5 in the pressure reducing membrane distillation assembly 2, the fresh water auxiliary collecting bottle 11 is arranged at the lowest point of the converging pipeline of the vapor outlet 5, and the fresh water auxiliary collecting bottle 11 is connected with the converging pipeline of the vapor outlet 5 through a detachable bolt and nut structure.

The solar tracking system comprises a tracking platform for installing a fixed film distillation system and a photovoltaic power supply system, a combined module of a rotating member is adopted below the tracking platform to be connected with a fixed support, the tracking platform is driven to rotate through an electric lead screw connecting rod mechanism, and a two-quadrant light balance sensor 27 is arranged on the sunny side of the tracking platform. Specifically, the solar tracking system is integrally installed towards the front south, and the two-quadrant optical balance sensor 27 is installed at a tracking platform which does not affect the lighting of the array of the small-sized groove-type concentrators 1 and the photovoltaic module and is connected to the controller. The electric screw rod connecting rod mechanism consists of a driving motor 31, a screw rod 28, a screw rod 32 and an adjusting connecting rod 30, the central position of the back of the tracking platform is connected with the top end of the adjusting connecting rod 30 through a rotating piece, and the bottom end of the adjusting connecting rod 30 is connected with the screw rod 32 through a rotating piece. The controller controls the driving motor 31 to rotate forward and backward and drives the screw 32 to move forward and backward through the screw 28.

The two-quadrant light balance sensor 27 transmits the received light intensity signal data to the controller in real time, and the controller judges the rotation direction of the tracking platform according to the light intensity signal difference, so that the driving motor 31 is controlled to rotate, and the purpose of tracking the solar altitude in real time is achieved. When the driving motor 31 drives the screw rod 28 to rotate forwards, the screw rod 32 moves in a direction away from the driving motor 31, and the adjusting connecting rod 30 slightly increases the inclination angle of the tracking platform under the driving of the screw rod 32; when the driving motor 31 drives the screw rod 28 to reversely rotate, the screw rod 32 moves towards the direction approaching to the driving motor 31, and the adjusting connecting rod 30 slightly reduces the inclination angle of the tracking platform under the driving of the screw rod 32. The inclination angle change range of the tracking platform is preferably set to be 30-60 degrees according to the latitude and longitude range and the weather condition of the past year of China. The adjustment ratio of the length of the link 30, the length of the lead screw 28, and the tracking platform width is set to 1:2:2 v 3 according to the setting conditions.

The method for desalting the sea water/brackish water by utilizing the solar water desalting device comprises the following steps:

the solar water desalination process adopts a solar direct-driven membrane distillation, latent heat driven interfacial distillation, spray falling film distillation and photovoltaic power supply system integrated cooperative operation method, and combines a plurality of evaporation and condensation strengthening methods to realize the high-efficiency, high-yield and zero-conventional energy consumption operation of the water desalination system.

Solar direct-drive type membrane distillation: the membrane distillation system heats raw water, and hot steam formed after heating flows through the interface evaporation-condensation double-effect system and is condensed to form fresh water;

latent heat driven interfacial distillation: the interface evaporation-condensation double-effect system is communicated with the raw water bin, and the raw water flows through the interface evaporation-condensation double-effect system and forms fresh water after evaporation and condensation;

spray falling film distillation: the membrane distillation system heats raw water, the heated raw water flows through the spray falling film evaporation system, tiny liquid drops are formed after being sprayed out of the spray falling film evaporation system, the tiny liquid drops are heated again in the spray falling film evaporation system, and water vapor generated after evaporation enters the interface evaporation-condensation double-effect system and forms fresh water after condensation.

The solar energy directly drives raw water to continuously and efficiently vaporize near an external hydrophobic evaporation interface of the tubular hydrophobic ceramic membrane 13, meanwhile, the photovoltaic power supply system 12 drives the negative pressure pump 9 to continuously operate, and then high-temperature water vapor is driven to permeate the tubular hydrophobic ceramic membrane 13 through the internal and external pressure difference of the tubular hydrophobic ceramic membrane 13, the high-temperature water vapor permeated through the tubular hydrophobic ceramic membrane 13 flows into the condensing chamber 17 to be condensed under the action of negative pressure suction to form liquid fresh water, and finally flows into the fresh water collecting bin 23 through the steam condensing pipe network 20;

meanwhile, the photovoltaic power supply system 12 drives the falling film evaporation plate 26 to keep a higher temperature continuously, the photovoltaic power supply system 12 drives the vapor-liquid separation fan 7 to run continuously, liquid high-temperature raw water which is not vaporized near the external hydrophobic interface of the tubular hydrophobic ceramic membrane 13 flows into the spray falling film evaporation system through the raw water outlet 4 of the decompression membrane distillation assembly 2, a large number of fine raw liquid drops are formed after the liquid high-temperature raw water is sprayed out through the porous spray unit 25, the vapor-liquid separation fan 7 drives high-temperature air flow at the upper part of the circulation bin 24 to circulate at a high speed and generate high-efficiency convection heat exchange and mass transfer with the fine raw liquid drops, high-efficiency vaporization is further generated at the vapor-liquid interface of the fine raw liquid drops, the fine raw liquid drops which are not vaporized are further heated and vaporized by the falling film evaporation plate 26 in the spray falling film evaporation system, water vapor formed by vaporization of the high-temperature raw liquid drops in the circulation bin 24 flows into the condensation chamber 17 to condense under the action of negative pressure suction, and finally flows into the fresh water collection bin 23 through the vapor condensation pipe network 20;

meanwhile, the photovoltaic power supply system 12 drives the ultrasonic oscillation atomizing sheet 22 group to atomize the stock solution at the upper end face of the infiltration cotton stick into tiny liquid drops, the tiny liquid drops are adsorbed by a hydrophilic evaporation interface in the evaporation chamber 18 of the interface evaporation-condensation double-effect system in the ascending process, meanwhile, the whole hydrophilic evaporation interface is rapidly distributed under the action of capillary force, an extremely thin liquid film is continuously formed at the hydrophilic evaporation interface, the interface evaporation phenomenon continuously occurs under the driving of condensation latent heat in the condensation chamber 17 of the interface evaporation-condensation double-effect system, and water vapor flowing out of the evaporation chamber 18 flows into the condensation chamber 17 to be condensed under the action of negative pressure suction to form liquid fresh water, and finally flows into the fresh water collection bin 23 through the vapor condensation pipe network 20;

in summary, the solar water desalination device based on the tubular hydrophobic ceramic membrane synchronously realizes integrated collaborative operation of solar direct-driven membrane distillation, latent heat driven interfacial distillation, spray falling film distillation and photovoltaic power supply system.

Further, the evaporation and condensation strengthening method provided by the invention comprises the following steps:

the spiral circulation fins 14 and the vortex generator 15 positioned on the outer surface of the tubular hydrophobic ceramic membrane 13 improve the vaporization rate and vaporization amount of raw water in the straight-through vacuum heat collecting tube, thereby increasing the membrane flux of the decompression membrane distillation assembly 2;

the vapor-liquid separation fan 7 and the falling film evaporation plate 26 in the circulation bin 24 improve the evaporation rate and evaporation amount of the surface of the original liquid drops in the circulation bin, so that the water yield of the spraying falling film evaporation system is increased;

the combination of the infiltration cotton stick 21 and the ultrasonic oscillation atomizing sheet 22 in the evaporation-condensation double-effect system and the hydrophilic evaporation interface improve the interfacial evaporation capacity of the liquid film surface in the evaporation chamber, and meanwhile, the high-temperature steam in the condensation chamber is cooled and condensed, so that the evaporation efficiency and the condensation efficiency of the interfacial evaporation-condensation double-effect system are greatly improved;

the steam condensation pipe network 20 carries out primary preheating on raw water in the raw water bin while condensing residual water steam, thereby greatly improving the overall water yield and the solar energy utilization rate of the desalted water system.

Specific:

solar direct-drive type membrane distillation: raw water flows into the decompression membrane distillation assembly 2 from the raw water bin 19 through the raw water inlet 3 under the drive of the direct current circulating pump 33, when the system operates, solar rays are focused by the small trough type condenser 1 and then are injected into the position of about 1/2 outer tube of the direct current vacuum heat collecting tube 34 facing the condenser, the direct current solar rays are directly injected into the position of about 1/2 outer tube of the direct current vacuum heat collecting tube 34 facing away from the condenser, and solar radiation energy transmitted to the position of the inner tube heat absorption coating through the outer tube of the direct current vacuum heat collecting tube 34 is fully absorbed by the raw water, namely, the solar radiation energy is converted into the internal energy of the raw water; the heat convection loss and the heat radiation loss of the through vacuum heat collection tube 34 are negligible because the interlayer of the inner tube and the outer tube of the through vacuum heat collection tube 34 has higher vacuum degree and the emissivity of the heat absorption coating is extremely low; the steam outlet 5, the condensing chamber 17, the steam condensing pipe network 20, the fresh water collecting bin 23 and the negative pressure pump 9 of the tubular hydrophobic ceramic membrane 13 are sequentially communicated, when the negative pressure pump 9 operates, a great steam pressure difference is generated on the inner side and the outer side of the tubular hydrophobic ceramic membrane 13, so raw water is vaporized near the hydrophobic evaporation interface on the outer side of the tubular hydrophobic ceramic membrane 13 to generate a great amount of steam, and the steam is transmitted to the inner side of the tubular hydrophobic ceramic membrane 13 under the drive of the steam pressure difference; the vapor inside the tubular hydrophobic ceramic membrane 13 flows into the condensation chamber 17 of the interface evaporation-condensation double-effect system for primary condensation under the suction action of the negative pressure pump 9, then flows into the vapor condensation pipe network 20 for final-stage full condensation, and finally the liquid fresh water flows into the fresh water collecting bin 23. Under the diversion effect of the spiral circulation rib 14, raw water flowing into the straight-through type vacuum heat collecting pipe 34 is tightly adhered to the outer wall of the tubular hydrophobic ceramic membrane 13 to perform spiral circulation flow, so that the effective sweeping area of the raw water at the outer wall of the tubular hydrophobic ceramic membrane 13 is remarkably increased, disturbance of the raw water on a hydrophobic membrane interface is synchronously aggravated, and the vaporization rate and vaporization amount of the raw water near the hydrophobic membrane interface are remarkably improved; in addition, the cylindrical vortex generators 15 are uniformly arranged at the spiral circulation fins 13, countless tiny vortices are formed when raw water flows through the surfaces of the vortex generators 15, and the generation and the falling of the vortices effectively destroy a thermal boundary layer and a velocity boundary layer near the outer hydrophobic interface of the tubular hydrophobic ceramic membrane 13, so that the desalinating water performance of the tubular hydrophobic ceramic membrane 13 is further enhanced.

Latent heat driven thermal interfacial distillation:

after the piezoelectric ultrasonic oscillation atomizing sheet 22 is powered on, constant pressure pointing to the raw water liquid level at the upper end face of the infiltration cotton stick 21 is formed on the surface of the piezoelectric ultrasonic oscillation atomizing sheet, so that the surface of the raw water is raised, cavitation phenomenon occurs on the raised raw water liquid level, the raw water is atomized into fine liquid drops, the fine liquid drops are adsorbed by the hydrophilic evaporation interface in the evaporation chamber 18 of the interface evaporation-condensation double-effect system in the rising process, meanwhile, the whole hydrophilic evaporation interface is rapidly distributed under the action of capillary force, an extremely thin liquid film is continuously formed at the hydrophilic evaporation interface, and high-efficiency interface evaporation is realized in the evaporation chamber 18 by utilizing the heat conduction action of the shared wall surface. Since the inner side interface of the condensation chamber 17 is a hydrophobic surface, the fresh water droplets generated after the condensation of the high-temperature vapor in the condensation chamber 17 cannot be suspended at the hydrophobic interface for a long time, when the fresh water droplets grow to a certain volume, the fresh water droplets flow into the fresh water collection bin 23 through the vapor condensation pipe network 20 under the action of gravity, the process can be approximately regarded as a beaded condensation process, and the hydrophobic design of the condensation chamber 17 can greatly improve the condensation efficiency because the heat transfer coefficient of the beaded condensation process is far greater than that of the film-like condensation process. The evaporating chamber 18 is communicated with the condensing chamber 17 through a gas four-way check valve, and when the water vapor generated in the evaporating chamber 18 flows into the condensing chamber 17 and the vapor condensing pipe network 20 under the action of negative pressure suction, the water vapor is efficiently condensed into liquid fresh water and finally flows into the fresh water collecting bin 23. When the solar radiation intensity is reduced, the membrane flux and the water vapor temperature of the reduced pressure membrane distillation assembly are relatively low, so that the temperature at the evaporation interface in the evaporation chamber 18 is synchronously reduced, at this time, when the ultrasonic oscillation atomizing sheet 22 still operates at the original atomization speed, the liquid film at the hydrophilic evaporation interface is thickened, so that the interface evaporation speed and the interface evaporation amount are reduced, the latent heat loss is increased, and the input voltage of the ultrasonic oscillation atomizing sheet 22 can be adjusted according to the temperature range in the evaporation chamber 18 through a controller, so that the interface evaporation speed and the atomization speed are always in a dynamic balance state.

Contact convection evaporation and spray falling film distillation:

after the high-temperature raw water heated by the solar trough type concentrating type vacuum membrane distillation system is sprayed out by the porous spraying unit 25, a large number of fine liquid drops can be formed, so that the contact area of the raw water and hot air in the circulating bin 24 is increased, water vapor molecules are easier to break loose from the constraint of other surrounding liquid water molecules, and the evaporation rate and evaporation amount of the raw water in the circulating bin 24 are improved, namely the first effect is enhanced. When the vapor-liquid separation fan 7 runs synchronously, convection mixing occurs between the high-temperature air in the circulation bin 24 and the fine liquid drops, so that the convection heat transfer and mass transfer intensity between the high-temperature air in the circulation bin 24 and the fine raw water liquid drops is further improved, and the evaporation rate and evaporation quantity of the fine liquid drop surfaces are improved, namely the second effect is enhanced. The falling film evaporation plates 26 are designed into two-stage type, 2 groups are total, each group of falling film evaporation plates 26 comprises 4 specially-made direct current heating falling film evaporation plates 26, and the required electric energy is provided by the photovoltaic power supply system 12. The first stage of the falling film evaporation plate 26 is in an inverted-V shape, the second stage is in a positive herringbone shape, the top of the second stage direct current heating falling film evaporation plate 26 is slightly higher than the bottom of the first stage direct current heating falling film evaporation plate 26, under the action of gravity, the unevaporated liquid film and the unexplained liquid drops preferentially fall onto the surface of the first stage direct current heating falling film evaporation plate 26 to form an extremely thin raw water liquid film and conduct flow dynamic interface distillation, the raw water liquid film and the liquid drops which are not distilled by the first stage direct current heating falling film evaporation plate 26 continuously flow into the second stage direct current heating falling film evaporation plate 26 through the bottom outlet of the liquid film and the liquid drops to conduct flow dynamic interface distillation until flowing through 2 groups of falling film evaporation plates 26, and the rest raw water is collected into the raw water bin 24, so that spray falling film distillation is realized, and the evaporation rate and evaporation quantity of raw water in a circulating bin are further improved, namely third effect is enhanced. The vapor generated in the circulation bin 24 is collected into the condensation chamber 17 in the interface evaporation-condensation double-effect system through the gas type one-way four-way valve by the top vapor outlet 5 under the suction effect of the negative pressure pump 9 for primary condensation, and then flows through the vapor condensation pipe network 20 to realize final condensation, and all the vapor is condensed into liquid fresh water and flows into the fresh water collection bin 23.

It will be appreciated by persons skilled in the art that the scope of the invention referred to in this application is not limited to the specific combinations of features described above, but it is intended to cover other embodiments in which any combination of features described above or equivalents thereof is possible without departing from the spirit of the invention. Such as the above-described features and technical features having similar functions (but not limited to) disclosed in the present application are replaced with each other.

Claims (6)

1. The solar water desalination device based on the tubular hydrophobic ceramic membrane is characterized by comprising a membrane distillation system, an interface evaporation-condensation double-effect system, a circulation control water tank group and a photovoltaic power supply system, wherein a raw water inlet end and a raw water outlet end of the membrane distillation system are communicated with the circulation control water tank group; the steam outlet end of the membrane distillation system is communicated with the interface evaporation-condensation double-effect system; the interface evaporation-condensation double-effect system is communicated with the circulating control water tank group; the photovoltaic power supply system supplies power for the device;

the spray falling film evaporation system is also included; the inlet end of the spray falling film evaporation system is communicated with the raw water outlet end of the film distillation system, and the spray falling film evaporation system is also communicated with the interface evaporation-condensation double-effect system;

the circulating control water tank group comprises a circulating bin, a raw water bin and a fresh water collecting bin, and the circulating bin is communicated with the raw water bin through a pipe orifice; the spraying falling film evaporation system is positioned in the circulating bin, and the interface evaporation-condensation double-effect system is positioned above the raw water bin and is communicated with the raw water bin; the fresh water collecting bin is positioned below the raw water bin and is communicated with the interface evaporation-condensation double-effect system, raw water in the raw water bin is sequentially evaporated and condensed in the interface evaporation-condensation double-effect system, and finally flows into the fresh water collecting bin;

the interface evaporation-condensation double-effect system comprises a heat exchange unit, wherein the heat exchange unit is of a cross-flow plate type and comprises a condensation chamber and an evaporation chamber, and the condensation chamber and the evaporation chamber are sequentially and alternately arranged;

the inlet end of the condensing chamber is communicated with the steam outlet end of the decompression membrane distillation assembly, and the outlet end of the condensing chamber is communicated with the fresh water collecting bin; the inlet end of the evaporation chamber is communicated with the raw water bin, and the outlet end of the evaporation chamber is communicated with the inlet end of the condensation chamber;

the spray falling film evaporation system is internally provided with a porous spray unit and a falling film evaporation plate, an inlet of the porous spray unit is connected with a raw water outlet end of the film distillation system, and the upper part of the spray falling film evaporation system is communicated with the condensation chamber through a pipeline; the spray falling film evaporation system also comprises a vapor-liquid separation fan.

2. A tubular hydrophobic ceramic membrane based solar water desalination apparatus as claimed in claim 1 further comprising a solar tracking system controlling the tilt angle of the membrane distillation system.

3. The solar water desalination device based on a tubular hydrophobic ceramic membrane according to claim 2, wherein the membrane distillation system comprises a small trough condenser array and a decompression membrane distillation assembly arranged at the focal line position of the trough condenser;

the vacuum membrane distillation assembly comprises a straight-through vacuum heat collecting pipe and a tubular hydrophobic ceramic membrane, the tubular hydrophobic ceramic membrane is concentrically arranged inside the straight-through vacuum heat collecting pipe, the upper part of the lateral surface of the outside of the fresh water collecting bin is also communicated with a negative pressure pump, and high-temperature water vapor flows out from a vapor outlet of the vacuum membrane distillation assembly under the suction effect of the negative pressure pump, flows into the interface evaporation-condensation double-effect system and finally flows into the fresh water collecting bin;

the outer surface of the tubular hydrophobic ceramic membrane is provided with spiral circulation fins, and vortex generators parallel to the axis of the tubular hydrophobic ceramic membrane are uniformly arranged on the spiral circulation fins.

4. The solar water desalination device based on the tubular hydrophobic ceramic membrane according to claim 2, wherein the inner side wall surfaces in the evaporation chamber are hydrophilic evaporation interfaces, an infiltration cotton stick is installed at the bottom of the evaporation chamber and combined with an ultrasonic oscillation atomization sheet, the lower surface of the ultrasonic oscillation atomization sheet is closely contacted with the upper end surface of the infiltration cotton stick, and the infiltration cotton stick is fixedly installed and penetrates into the raw water below the water surface; the inner side interfaces in the condensing chamber are all hydrophobic evaporation interfaces;

the evaporation and condensation pipe network is arranged in the raw water bin and comprises a vertical pipe, a converging transverse pipe and a main pipe, the upper end openings of the vertical pipe are communicated with the bottom of the condensation chamber, and the outlet of the main pipe is communicated with the fresh water collecting bin.

5. The solar water desalination device based on the tubular hydrophobic ceramic membrane according to claim 2, wherein the solar tracking system comprises a tracking platform for installing a fixed membrane distillation system and a photovoltaic power supply system, a combined module of a rotating member is adopted below the tracking platform to be connected with a fixed support, the tracking platform is driven to rotate through an electric screw rod connecting rod mechanism, and a two-quadrant light balance sensor is arranged on the sunny side of the tracking platform.

6. A method for desalinating water by solar energy, which is characterized in that a solar energy desalinating water device as claimed in any one of claims 2-5 is used, and the specific method comprises the following steps:

solar direct-drive type membrane distillation: the membrane distillation system heats raw water, and hot steam formed after heating flows through the interface evaporation-condensation double-effect system and is condensed to form fresh water;

latent heat driven interfacial distillation: the interface evaporation-condensation double-effect system is communicated with the raw water bin, and the raw water flows through the interface evaporation-condensation double-effect system and forms fresh water after evaporation and condensation;

spray falling film distillation: the membrane distillation system heats raw water, the heated raw water flows through the spray falling film evaporation system, tiny liquid drops are formed after being sprayed out of the spray falling film evaporation system, the tiny liquid drops are heated again in the spray falling film evaporation system, and vapor generated after evaporation enters the interface evaporation-condensation double-effect system, and fresh water is formed after condensation.

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