A seawater desalination system and method coupled with multi-stage flash evaporation and multi-effect distillation

Abstract

The invention relates to the technical field of seawater desalination, and specifically discloses a seawater desalination system and method coupled with multi-stage flash evaporation and multi-effect distillation, comprising a multi-stage flash tank and a multi-stage flash coupling tank, wherein each stage of the flash tank corresponds to a flash coupling tank; the flash coupling tank comprises a first flash chamber, a reheater, a sprayer and a flash assembly which are arranged in sequence from bottom to top, wherein the fresh water generated by condensation of the flash tank enters the reheater of the corresponding flash coupling tank, the sprayer sprays the seawater entering the flash coupling tank of this stage from the outside on the steam generated by the reheater, and the steam generated by the sprayer is condensed into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber; the invention couples the multi-stage flash evaporation with the multi-effect distillation, and can make full use of the waste heat of fresh water generated by condensation of the existing flash tank, thereby improving the energy efficiency ratio of the system and increasing the fresh water output.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater desalination, and in particular to a seawater desalination system and method coupled with multi-stage flash evaporation and multi-effect distillation. Background Art

[0002] In the context of severe shortage of fresh water resources and serious water pollution, seawater desalination technology came into being. The current mainstream seawater desalination technologies include thermal evaporation seawater desalination, reverse osmosis and nanofiltration seawater desalination, and electrodialysis seawater desalination.

[0003] Multi-stage flash desalination technology is a type of thermal evaporation desalination technology. It is a desalination technology proposed to solve the scaling and corrosion problems of multi-effect distillation desalination technology. At the same time, due to its high energy efficiency ratio, it is highly respected in the Middle East countries and countries around the Mediterranean.

[0004] Multi-stage flash desalination technology is divided into straight-through multi-stage flash desalination technology and brine circulation multi-stage flash desalination technology according to whether the concentrated brine is recovered and discharged. Whether it is straight-through or brine circulation multi-stage flash desalination technology, the system workflow includes the steps of preheating the seawater in the heat exchange tube bundle after the steam is generated in each stage of the flash tank, and collecting it for backup after condensing it into fresh water. However, the fresh water generated after condensation still has a considerable amount of waste heat that has not been fully utilized, so that the energy efficiency ratio of the system can never break through the existing bottleneck. Summary of the invention

[0005] In view of the problem that the waste heat of fresh water generated by condensation in the above-mentioned multi-stage flash evaporation seawater desalination is not fully utilized, the present invention provides a seawater desalination system and method coupling multi-stage flash evaporation with multi-effect distillation. By coupling multi-stage flash evaporation with multi-effect distillation, the waste heat of fresh water generated by condensation in the existing flash tank can be fully utilized, thereby improving the energy efficiency ratio of the system and increasing the fresh water output.

[0006] In order to solve the above technical problems, the specific solutions provided by the present invention are as follows:

[0007] A seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation comprises a multi-stage flash tank and a multi-stage flash coupling tank, wherein each stage of the flash tank corresponds to a flash coupling tank;

[0008] The flash coupling tank comprises a first flash chamber, a reheater, a sprayer and a flash assembly which are arranged in sequence from bottom to top, wherein the fresh water generated by condensation in the flash tank enters the reheater of the corresponding flash coupling tank, the sprayer sprays the seawater entering the flash coupling tank of this stage from the outside on the steam generated by the reheater, and the steam is condensed into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber.

[0009] In some embodiments, the flash assembly includes a first demister, a first fresh water tray, and a first heat exchange tube bundle, which are arranged in sequence from bottom to top. The first demister removes salt particles rising with the steam, so that the steam condenses into fresh water after reaching the first heat exchange tube bundle and drips onto the first fresh water tray.

[0010] In some embodiments, a vacuum pump assembly, a water pump assembly, and a heating module are also included;

[0011] The vacuum pump assembly is connected to the multi-stage flash tank, and the water pump assembly is connected to the multi-stage flash tank and the multi-stage flash coupling tank;

[0012] Among them, the first-stage flash tank is connected to the heating module, and the last-stage flash tank is connected to the first-stage flash coupling tank.

[0013] In some embodiments, the flash tank includes a second flash chamber, a second demister, a second fresh water tray, and a second heat exchange tube bundle arranged in sequence from bottom to top;

[0014] The second heat exchange tube bundle of the first-stage flash tank is connected to the input end of the heating module, and the output end of the heating module is connected to the second flash chamber of the first-stage flash tank.

[0015] In some embodiments, the heating module includes a solar energy component and an air energy component connected to the solar energy component.

[0016] In some embodiments, the solar energy component includes a solar thermal array, a heat storage tank and a heat exchanger, the solar thermal array is connected to the heat storage tank, the heat storage tank is connected to the heat exchanger, and the heat exchanger is connected to the air energy component.

[0017] In some embodiments, the multi-stage flash coupling tank is divided into a heat recovery part and a heat discharge part, the flash assembly of the first-stage flash coupling tank of the heat discharge part is connected to a first separator, the first separator is connected to a mixer, and the mixer is connected to the flash assembly of the last-stage flash coupling tank of the heat recovery part;

[0018] The flash chamber of the final flash coupling tank of the heat discharge part is further connected with a second separator, and the second separator is connected with a mixer.

[0019] The present invention also provides a seawater desalination method, based on any of the above-mentioned seawater desalination systems and solar thermal systems, the method comprising:

[0020] After the seawater enters the last-stage flash coupling tank, it enters the previous-stage flash coupling tank in sequence until the seawater enters the first-stage flash coupling tank;

[0021] After the seawater enters the last-stage flash tank from the first-stage flash coupling tank, it enters the previous-stage flash tank in sequence until the seawater enters the first-stage flash tank;

[0022] The seawater enters the solar thermal system from the first-stage flash tank for heating and then returns to the first-stage flash tank, and then returns to the last-stage flash coupling tank in sequence;

[0023] The seawater heated by the solar thermal system enters the flash tanks at each level and the output fresh water enters the reheater of the corresponding flash coupling tank. The sprayer of the flash coupling tank sprays seawater on the reheater to generate steam, and the steam is condensed into fresh water under the action of the flash assembly.

[0024] In some embodiments, the method further comprises:

[0025] After the seawater heated by the solar thermal system returns to each stage of flash coupling tanks in turn, the seawater in the flash coupling tank evaporates to form steam. The steam passes through the first demister to remove the salt particles rising with the steam, so that the steam reaches the first heat exchange tube bundle and condenses into fresh water, which drips onto the first fresh water tray.

[0026] In some embodiments, the method further comprises:

[0027] The multi-stage flash coupling tank is divided into a heat recovery part and a heat discharge part. The heat discharge part separates a part of the unsalted seawater through a separator and then enters the heat recovery part through a mixer.

[0028] The present invention provides a seawater desalination system and method coupled with multi-stage flash evaporation and multi-effect distillation, comprising a multi-stage flash tank and a multi-stage flash coupling tank, wherein each stage of the flash tank corresponds to a flash coupling tank; the flash coupling tank comprises a first flash chamber, a reheater, a sprayer and a flash assembly which are arranged in sequence from bottom to top, wherein fresh water generated by condensation in the flash tank enters the reheater of the corresponding flash coupling tank, and since the fresh water carries waste heat, when the sprayer sprays seawater entering the flash coupling tank of this stage from the outside on the reheater, the generated steam is condensed into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber, which, on the one hand, improves the fresh water production, and on the other hand, can make full use of the waste heat of the fresh water generated by condensation in the flash tank, thereby improving the energy efficiency ratio of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a seawater desalination system in the prior art;

[0030] Figure 2 A schematic diagram of a flash tank provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of a flash coupling tank provided in an embodiment of the present application;

[0032] Figure 4A schematic diagram of a seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation provided in an embodiment of the present application;

[0033] Figure 5 A schematic diagram of a seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation provided in another embodiment of the present application;

[0034] Among them, 1 is a flash tank; 11 is a second flash chamber; 12 is a second demister; 13 is a second fresh water tray; 14 is a second heat exchange tube bundle; 2 is a flash coupling tank; 21 is a first flash chamber; 22 is a reheater; 23 is a sprayer; 24 is a first demister; 25 is a first fresh water tray; 26 is a first heat exchange tube bundle; 3 is a vacuum pump assembly; 4 is a water pump assembly; 5 is a heating module; 51 is an air energy assembly; 52 is a solar thermal array; 53 is a heat storage tank; 54 is a heat exchanger; 6 is a first separator; 7 is a mixer; 8 is a second separator. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them.

[0036] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] For example, a seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation includes a multi-stage flash tank and a multi-stage flash coupling tank, each stage of the flash tank corresponds to a flash coupling tank; the flash coupling tank includes a first flash chamber, a reheater, a sprayer and a flash assembly arranged in sequence from bottom to top, wherein the seawater in the flash chamber of the upper stage flash coupling tank enters the sprayer of the lower stage flash coupling tank, and the fresh water condensed in the flash tank enters the reheater of the corresponding flash coupling tank, and the steam generated by the sprayer spraying seawater on the reheater is condensed into fresh water under the action of the flash assembly.

[0038] The present embodiment provides a seawater desalination system and method that couples multi-stage flash evaporation with multi-effect distillation. The multi-stage flash evaporation is coupled with multi-effect distillation to fully utilize the waste heat of fresh water generated by condensation in an existing flash tank, thereby improving the energy efficiency of the system and increasing the fresh water output.

[0039] Embodiment 1:

[0040] In the prior art, multi-stage flash desalination technology is divided into direct multi-stage flash desalination technology and brine circulation multi-stage flash desalination technology according to whether the concentrated brine discharged is recovered or not. Figure 1 As shown, the flash tank 1 includes a second flash chamber 11, a second demister 12, a second fresh water tray 13 and a second heat exchange tube bundle 14. The straight-through multi-stage flash desalination system consists of a multi-stage flash tank 1, a heating module 5, a vacuum pump assembly 3 and a water pump assembly 4. The flash tanks 1 at each stage are connected in sequence. The working process is that after the vacuum pump assembly 3 is operated, the air pressure inside each stage of the flash tank 1 is reduced and gradually decreased. The seawater first enters the second heat exchange tube bundle 14 of the last stage of the flash tank 1 for preheating, and at the same time condenses the steam of the flash tank 1 at this stage, and then enters the second heat exchange tube bundle 14 of the previous stage of the flash tank 1 until the seawater enters the second heat exchange tube bundle 1 of the first stage of the flash tank 1. After preheating, the seawater is further increased by heat exchange with the heating module 5 through the heating module 5, and then the seawater returns to the first-stage flash tank 1. Since the air pressure in the flash tank 1 is much lower than the corresponding saturated vapor pressure at the temperature, the seawater evaporates instantly to generate steam. The steam passes through the second demister 12 to remove the tiny salt particles rising with the steam, and then reaches the outside of the second heat exchange tube bundle 14 in the flash tank 1 to release latent heat, preheating the seawater in the second heat exchange tube bundle 14, condensing itself into fresh water and dripping onto the second fresh water tray 13. The unevaporated seawater enters the second-stage flash tank 1 under the action of the pressure difference to continue evaporating, and the whole seawater desalination work is completed by analogy.

[0041] The difference between the brine circulation multi-stage flash desalination system and the straight-through multi-stage flash desalination system is that part of the discharged concentrated brine is recovered for desalination. However, in the brine circulation multi-stage flash desalination system and the straight-through multi-stage flash desalination system, the fresh water generated after condensation in each stage of the flash tank still has a considerable amount of waste heat that is not fully utilized, so that the energy efficiency ratio of the system can never break through the existing bottleneck.

[0042] refer to Figure 2-Figure 4 , Figure 2 A schematic diagram of a flash tank provided in an embodiment of the present application; Figure 3 A schematic diagram of a flash coupling tank provided in an embodiment of the present application; Figure 4 Schematic diagram of a seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation provided in an embodiment of the present application.

[0043] A seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation provided in this example includes a multi-stage flash tank 1 and a multi-stage flash coupling tank 2. Each stage of the flash tank 1 corresponds to a flash coupling tank 2, that is, the number of flash coupling tanks 2 is equal to or greater than the number of flash tanks 1, so as to ensure that the waste heat of fresh water generated by condensation of each stage of the flash tank 1 can be reused. The flash tanks 1 of each stage are connected in sequence, and the flash coupling tanks 2 of each stage are connected in sequence. For example, the first-stage flash tank 1 corresponds to the first-stage flash coupling tank 2, the second-stage flash tank 1 corresponds to the second-stage flash coupling tank 2, and so on.

[0044] Flash tank 1 is a container with relatively low pressure where high-pressure saturated water enters. Due to the sudden drop in pressure, the saturated water becomes steam under a portion of the container pressure. It can be applied to seawater desalination technology, that is, high-pressure seawater enters a relatively low-pressure flash tank 1. Due to the sudden drop in pressure, the seawater evaporates instantly to produce steam, and the steam condenses to produce fresh water.

[0045] The flash coupling tank 2 couples flash evaporation with distillation, and includes a first flash chamber 21, a reheater 22, a sprayer 23 and a flash assembly arranged in sequence from bottom to top, wherein the fresh water generated by condensation in the flash tank 1 enters the reheater 22 of the corresponding flash coupling tank 2. Since the fresh water still has waste heat, when the sprayer 23 sprays the seawater entering the flash coupling tank 2 of this stage from the outside on the reheater, steam will be generated. The steam is condensed into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber 21, that is, the waste heat of the fresh water generated by condensation in the flash tank 1 is fully utilized, thereby improving the energy efficiency ratio of the system and increasing the fresh water output.

[0046] For example, a multi-stage flash tank includes a first-stage flash tank and a second-stage flash tank, and a multi-stage flash coupling tank includes a first-stage flash coupling tank and a second-stage flash coupling tank. The first-stage flash tank, the second-stage flash tank, the first-stage flash coupling tank and the second-stage flash coupling tank can be connected in sequence. Seawater enters the first-stage flash tank for condensation to generate fresh water, and the remaining seawater enters the second-stage flash tank to continue condensing to generate fresh water. The remaining seawater in the second-stage flash tank enters the first-stage flash coupling tank to continue condensing to generate fresh water, and so on. The fresh water condensed in the first-stage flash tank enters the reheater of the first-stage flash coupling tank. The sprayer of the first-stage flash coupling tank sprays the seawater entering the flash coupling tank of the second-stage flash tank on the reheater. The generated steam condenses to generate fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber. The seawater in the first flash chamber of the first flash coupling tank enters the sprayer of the second-stage flash coupling tank. The fresh water generated by condensation in the second-stage flash tank enters the reheater of the second-stage flash coupling tank. The sprayer of the second-stage flash coupling tank sprays the seawater entering the first-stage flash coupling tank onto the reheater. The generated steam condenses into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber.

[0047] It should be noted that the sprayer sprays the seawater entering the flash coupling tank of this stage from the outside onto the reheater. The outside here may refer to the flash coupling tank of the previous stage or the flash tank connected to the flash coupling tank of this stage, or a device independent of the flash coupling tank of this stage.

[0048] A seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation is provided in this example. By coupling multi-stage flash evaporation and multi-effect distillation, the waste heat of fresh water generated by condensation in the existing flash tank can be fully utilized, thereby improving the energy efficiency ratio of the system and increasing the fresh water production.

[0049] Embodiment 2:

[0050] refer to Figure 3 The flash assembly of the flash coupling tank 2 provided in this example includes a first demister 24, a first fresh water tray 25 and a first heat exchange tube bundle 26 arranged in sequence from bottom to top, wherein the first demister 24 removes salt particles rising with the steam, so that the steam condenses into fresh water after reaching the first heat exchange tube bundle 26 and drips onto the first fresh water tray 25.

[0051] In the seawater desalination process, the flash coupling tank 2 not only sprays the seawater entering the flash coupling tank 2 from the outside onto the reheater 22 through the sprayer 23 and condenses the generated steam into fresh water using the first heat exchange tube bundle 26, but also preheats the seawater entering the first heat exchange tube bundle 26 through the first heat exchange tube bundle 26 to increase the temperature of the seawater, thereby improving the energy efficiency ratio of the system and the seawater desalination output.

[0052] Embodiment three:

[0053] refer to Figure 4 In this example, the seawater desalination system also includes a vacuum pump assembly 3, a water pump assembly 4 and a heating module 5; the vacuum pump assembly 3 is connected to the multi-stage flash tank 1, and the water pump assembly 4 is connected to the multi-stage flash tank 1 and the multi-stage flash coupling tank 2; wherein, the first-stage flash tank 1 is connected to the heating module 5, and the flash tanks 1 at each stage and the flash coupling tanks 2 at each stage are connected in sequence, and the last-stage flash tank 1 is connected to the first-stage flash coupling tank 2.

[0054] The flash tank 1 includes a second flash chamber 11, a second demister 12, a second fresh water tray 13 and a second heat exchange tube bundle 14 which are arranged in sequence from bottom to top; the second heat exchange tube bundle 14 of the first-stage flash tank 1 is connected to the input end of the heating module 5, and the output end of the heating module 5 is connected to the second flash chamber 11 of the first-stage flash tank 1.

[0055] refer to Figure 4 In the specific working process, after the vacuum pump assembly is running, the air pressure inside each stage of the flash tank is reduced and gradually decreased. The seawater first enters the first heat exchange tube bundle of the last stage flash coupling tank for preheating, and condenses the steam of the flash coupling tank of this stage, and then enters the first heat exchange tube bundle of the previous stage flash coupling tank, and then enters the second heat exchange tube bundle of the last stage flash tank from the first stage flash coupling tank, until the seawater enters the second heat exchange tube bundle of the first stage flash tank from the second stage flash tank for preheating, and then exchanges heat with the heating module through the heating module, and the temperature is further increased, and then the seawater returns to the second stage flash tank. Back to the first-stage flash tank, since the air pressure in this stage of flash tank is much lower than the corresponding saturated vapor pressure at this temperature, the seawater evaporates instantly to produce steam. The steam passes through the second demister to remove the tiny salt particles that rise with the steam, and then reaches the outside of the second heat exchange tube bundle inside the flash tank of this stage to release latent heat, preheating the seawater in the second heat exchange tube bundle, condensing itself into fresh water and dripping onto the second fresh water tray. The unevaporated seawater enters the second-stage flash tank under the action of the pressure difference to continue evaporating. By analogy, the unevaporated seawater enters the last-stage flash coupling tank and is finally discharged outside the last-stage flash coupling tank.

[0056] In this example, the unevaporated seawater between the flash coupling tanks of each stage is changed from flowing spontaneously under the pressure difference to being sprayed by a sprinkler so that the seawater is evenly sprayed on the reheater.

[0057] The fresh water produced by each level of flash tanks enters the reheater of the corresponding flash coupling tank. Since the fresh water still has waste heat, when the sprayer sprays the seawater entering the flash coupling tank of this level on the reheater, steam will be generated. The steam is condensed into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber, which means that the waste heat of the fresh water generated by the condensation of the flash tank is fully utilized, thereby improving the energy efficiency of the system and increasing the fresh water output.

[0058] Since the last stage flash tank is connected to the first stage flash coupling tank, the unevaporated seawater in the last stage flash tank enters the sprayer of the first stage flash coupling tank under the action of pressure difference. After the sprayer sprays the seawater on the reheater, the generated steam condenses into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber. The unevaporated seawater in the first stage flash coupling tank enters the sprayer of the second stage flash coupling tank, and so on, completing the entire seawater desalination work.

[0059] It should be noted that, since the air pressure in each flash tank is much lower than the corresponding saturated vapor pressure at the temperature after heating, the seawater evaporates instantly to generate steam. The steam passes through the second demister to remove the tiny salt particles rising with the steam, and then reaches the outside of the second heat exchange tube bundle inside the flash tank of this stage to release latent heat, preheating the seawater in the second heat exchange tube bundle, and condenses itself into fresh water and drips onto the second fresh water tray. The method of generating part of the fresh water in the flash coupling tanks of each stage is the same as that of the flash tanks of each stage. In addition, the flash coupling tanks of each stage can also utilize the waste heat of the fresh water generated by the flash tanks of each stage to generate fresh water again. Specifically, the fresh water generated by condensation in the flash tank enters the reheater of the corresponding flash coupling tank. Since the fresh water still has waste heat, when the sprayer sprays the seawater entering the flash coupling tank of this stage from the outside on the reheater, steam is generated, and the steam is condensed into fresh water under the action of the flash assembly.

[0060] For the fresh water generated by the flash coupling tanks at each level through two methods, it can be collected uniformly or separately, and the specific setting can be made according to actual needs.

[0061] Embodiment 4:

[0062] refer to Figure 5 The multi-stage flash coupling tank is divided into a heat recovery part and a heat discharge part. The flash component of the first-stage flash coupling tank 2 of the heat discharge part is connected to a first separator 6, the first separator 6 is connected to a mixer 7, and the mixer 7 is connected to the flash component of the last-stage flash coupling tank 2 of the heat recovery part; the first flash chamber of the last-stage flash coupling tank 2 of the heat discharge part is also connected to a second separator 8, and the second separator 8 is connected to the mixer 7.

[0063] In the specific working process, after the vacuum pump assembly is running, the air pressure inside each stage of the flash tank and each stage of the flash coupling tank is reduced and gradually decreased. The seawater first enters the first heat exchange tube bundle of the last stage flash coupling tank of the heat discharge part for preheating, and condenses the steam of the flash coupling tank of this stage. Then, it enters the first heat exchange tube bundle of the previous stage flash coupling tank, and then enters the first heat exchange tube bundle of the last stage flash coupling tank of the heat recovery part from the first stage flash coupling tank of the heat recovery part, until it enters the second heat exchange tube bundle of the last stage flash tank from the first heat exchange tube bundle of the first stage flash coupling tank of the heat recovery part. Finally, the seawater enters the second heat exchange tube bundle of the first stage flash tank from the second stage flash tank for preheating. , through the heating module, the temperature is further increased by exchanging heat with the heating module, and then the seawater returns to the first-stage flash tank. Since the air pressure in the flash tank of this stage is much lower than the corresponding saturated vapor pressure at this temperature, the seawater evaporates instantly to produce steam. The steam passes through the second demister to remove the tiny salt particles rising with the steam, and then reaches the outside of the second heat exchange tube bundle inside the flash tank of this stage to release latent heat, preheating the seawater in the second heat exchange tube bundle, condensing itself into fresh water and dripping onto the second fresh water tray. The unevaporated seawater enters the second-stage flash tank to continue evaporating, and so on. The unevaporated seawater enters the last-stage flash coupling tank of the heat discharge part, and is finally discharged outside the last-stage flash coupling tank.

[0064] It should be noted that when seawater enters the first heat exchange tube bundle of the final flash coupling tank of the heat recovery part from the first heat exchange tube bundle of the first flash coupling tank of the heat discharge part, the seawater is first separated from the condensed water by the first separator, and then enters the first heat exchange tube bundle of the final flash coupling tank of the heat recovery part through the mixer; when the final flash coupling tank of the heat discharge part discharges unevaporated seawater, part of the seawater is separated by the second separator and enters the first heat exchange tube bundle of the final flash coupling tank of the heat recovery part through the mixer, and the discharged seawater is recovered as a desalination raw material.

[0065] This example provides a seawater desalination system that couples brine circulation multi-stage flash evaporation with multi-effect distillation. In terms of system composition, the multi-stage flash evaporation coupling tank is divided into a heat recovery part and a heat discharge part. Figure 5 The fresh water produced by the multi-stage flash tank is used as the reheat source of the multi-stage flash coupling tank. For different operating conditions, such as the seawater temperature entering the first-stage flash tank, the concentrated seawater temperature discharged from the last-stage flash coupling tank and other condition parameters, in order to achieve the highest energy efficiency ratio, for a system with a total flash stage of n+m, it is often necessary to divide the entire system into j parts (2≤j≤n+m), where the fresh water produced in the i-th part is used as the reheat source of the l+1-th part (i<j). Of course, it can also be adjusted according to other needs, and no specific restrictions are made here.

[0066] Embodiment five:

[0067] refer to Figure 4 and Figure 5 In this example, the heating module 5 includes a solar energy component and an air energy component 51 connected to the solar energy component. The solar energy component includes a solar thermal array 52, a heat storage tank 53 and a heat exchanger 54. The solar thermal array 52 is connected to the heat storage tank 53, the heat storage tank 53 is connected to the heat exchanger 54, and the heat exchanger 54 is connected to the air energy component 51.

[0068] After being heated by the solar thermal array, the heat transfer oil enters the heat storage tank. The function of the heat storage tank is to ensure that the mass flow rate of the heat transfer oil in the system can remain stable. Then it enters the heat exchanger to heat the seawater preheated by the flash tank, and then enters the air energy component for the last round of heating. After that, it enters the second flash chamber of the first-stage flash tank as a desalination raw material. In the above energy supply, the air energy component is used as a supplementary heat source for the solar energy component. Under sunny environmental conditions, if the temperature of the seawater reaches the system set inlet temperature after being heated by the heat exchanger, the air energy component can be turned off; the air energy component is to reduce the demand for the heat exchange area of ​​the solar thermal array and reduce the system cost. When the water output of the system is too large, resulting in the corresponding amount of seawater that needs to be heated exceeding the load of the air energy component, multiple ultra-high temperature air energy hot water pumps can be connected in series and in parallel, or electric heaters can be used as subsequent supplementary heat sources for air energy.

[0069] Solar thermal technology is heavily dependent on the weather and the topography of the desalination plant. For some desalination plant construction sites where the sunlight is insufficient to heat the desalination system, using air energy to heat the system requires the use of air energy heat pump series and parallel technology, which will increase the system's energy supply design and equipment purchase costs. For countries in the Middle East and the Mediterranean region with sufficient traditional fossil energy, direct use of electric heating will be more in line with local actual conditions. In addition, the desalination system coupled with multi-stage flash evaporation and multi-effect distillation mentioned in this case can use four heat source combinations of electric heating, air energy heat pumps, solar thermal energy, and power plant waste heat to supply energy.

[0070] Embodiment six:

[0071] The present invention also provides a seawater desalination method, based on any of the above-mentioned seawater desalination systems and solar thermal systems, the method comprising:

[0072] 101. After the seawater enters the last-stage flash coupling tank, it enters the previous-stage flash coupling tank in sequence until the seawater enters the first-stage flash coupling tank.

[0073] The seawater first enters the first heat exchange tube bundle of the last stage flash coupling tank for preheating, and condenses the steam of the flash coupling tank of this stage, and then enters the first heat exchange tube bundle of the previous stage flash coupling tank.

[0074] 102. After the seawater enters the last-stage flash tank from the first-stage flash coupling tank, it enters the previous-stage flash tank in sequence until the seawater enters the first-stage flash tank.

[0075] The seawater enters the second heat exchange tube bundle of the last stage flash tank from the first stage flash coupling tank, until the seawater enters the second heat exchange tube bundle of the first stage flash tank from the second stage flash tank for preheating.

[0076] 103. The seawater enters the solar thermal system from the first-stage flash tank for heating and then returns to the first-stage flash tank, and then returns to the last-stage flash coupling tank in sequence.

[0077] Through the solar thermal system, the temperature is further increased by exchanging heat with the solar thermal system. Then the seawater returns to the first-stage flash tank. Since the air pressure in the flash tank is much lower than the corresponding saturated vapor pressure at this temperature, the seawater evaporates instantly to produce steam. The steam passes through the second demister to remove the tiny salt particles that rise with the steam, and then reaches the outside of the second heat exchange tube bundle inside the flash tank to release latent heat, preheating the seawater in the second heat exchange tube bundle, condensing itself into fresh water and dripping onto the second fresh water tray. The unevaporated seawater enters the second-stage flash tank under the action of the pressure difference to continue evaporating. By analogy, the unevaporated seawater enters the last-stage flash coupling tank. Between the flash coupling tanks at each stage, the unevaporated seawater changes from spontaneous flow under the pressure difference to spraying through a sprinkler so that the seawater is evenly sprayed on the reheater.

[0078] 104. The seawater heated by the solar thermal system enters into the flash tanks at each level, and the fresh water output after flash evaporation enters into the reheater of the corresponding flash coupling tank. The sprayer of the flash coupling tank sprays the seawater on the reheater to generate steam, and the steam is condensed into fresh water under the action of the flash assembly.

[0079] Since there is waste heat in the fresh water, when the sprayer sprays the seawater entering the flash coupling tank of this stage onto the reheater, steam will be generated. The steam will condense into fresh water under the action of the flash assembly, and the unevaporated seawater will fall into the first flash chamber, thus making full use of the waste heat of the fresh water generated by the condensation of the flash tank, improving the energy efficiency of the system and increasing the fresh water production.

[0080] In some embodiments, the method further comprises:

[0081] After the seawater heated by the solar thermal system returns to each stage of flash coupling tanks in turn, the seawater in the flash coupling tank evaporates to form steam. The steam passes through the first demister to remove the salt particles rising with the steam, so that the steam reaches the first heat exchange tube bundle and condenses into fresh water, which drips onto the first fresh water tray.

[0082] Since the air pressure in each flash tank is much lower than the corresponding saturated vapor pressure at the heated temperature, the seawater evaporates instantly to generate steam. The steam passes through the second demister to remove the tiny salt particles rising with the steam, and then reaches the outside of the second heat exchange tube bundle inside the flash tank of this stage to release latent heat, preheating the seawater in the second heat exchange tube bundle, and condenses itself into fresh water and drips onto the second fresh water tray. The generation method of part of the fresh water in the flash coupling tanks of each stage is the same as that of the flash tanks of each stage. In addition, the flash coupling tanks of each stage can also use the waste heat of the fresh water generated by the flash tanks of each stage to generate fresh water again. Specifically, the fresh water generated by the condensation of the flash tank enters the reheater of the corresponding flash coupling tank. Since the fresh water still has waste heat, when the sprayer sprays the seawater entering the flash coupling tank of this stage from the outside on the reheater, steam will be generated, and the steam will condense into fresh water under the action of the flash assembly.

[0083] In some embodiments, the method further comprises:

[0084] The multi-stage flash coupling tank is divided into a heat recovery part and a heat discharge part. The heat discharge part separates a part of the unsalted seawater through a separator and then enters the heat recovery part through a mixer.

[0085] Specifically, after the vacuum pump assembly is operated, the air pressure inside each stage of the flash tank and each stage of the flash coupling tank is reduced and gradually decreased. The seawater first enters the first heat exchange tube bundle of the last stage flash coupling tank of the heat discharge part for preheating, and condenses the steam of the flash coupling tank of this stage. Then, it enters the first heat exchange tube bundle of the previous stage flash coupling tank, and then enters the first heat exchange tube bundle of the last stage flash coupling tank of the heat recovery part from the first stage flash coupling tank of the heat discharge part, until it enters the second heat exchange tube bundle of the last stage flash tank from the first heat exchange tube bundle of the first stage flash coupling tank of the heat recovery part. Finally, the seawater enters the second heat exchange tube bundle of the first stage flash tank from the second stage flash tank for preheating, and then passes through After passing through the heating module, the temperature is further increased by exchanging heat with the heating module. Then the seawater returns to the first-stage flash tank. Since the air pressure in the flash tank is much lower than the corresponding saturated vapor pressure at this temperature, the seawater evaporates instantly to generate steam. The steam passes through the second demister to remove the tiny salt particles rising with the steam, and then reaches the outside of the second heat exchange tube bundle inside the flash tank of this stage to release latent heat, preheating the seawater in the second heat exchange tube bundle, condensing itself into fresh water and dripping onto the second fresh water tray. The unevaporated seawater enters the second-stage flash tank to continue evaporating. By analogy, the unevaporated seawater enters the last-stage flash coupling tank of the heat discharge part, and is finally discharged outside the last-stage flash coupling tank.

[0086] It should be noted that when seawater enters the first heat exchange tube bundle of the final flash coupling tank of the heat recovery part from the first heat exchange tube bundle of the first flash coupling tank of the heat discharge part, the seawater is first separated from the condensed water by the first separator, and then enters the first heat exchange tube bundle of the final flash coupling tank of the heat recovery part through the mixer; when the final flash coupling tank of the heat discharge part discharges unevaporated seawater, part of the seawater is separated by the second separator and enters the first heat exchange tube bundle of the final flash coupling tank of the heat recovery part through the mixer, and the discharged seawater is recovered as a desalination raw material.

[0087] In summary, the present invention provides a seawater desalination system and method coupled with multi-stage flash evaporation and multi-effect distillation, which couples multi-stage flash evaporation with multi-effect distillation, and can fully utilize the waste heat of fresh water generated by condensation in the existing flash tank, thereby improving the energy efficiency ratio of the system and increasing the fresh water output. At the same time, solar thermal energy and air energy are combined as the heat source of the system, effectively alleviating the current situation of energy shortage.

[0088] In the description of the present invention, it is necessary to understand that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0089] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0090] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0091] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

Claims

1. A seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation, characterized in that: It comprises a multi-stage flash tank (1) and a multi-stage flash coupling tank (2), wherein each stage of the flash tank (1) corresponds to a flash coupling tank (2); The flash coupling tank couples flash evaporation with distillation, and the flash coupling tank (2) comprises a first flash chamber (21), a reheater (22), a sprayer (23) and a flash assembly, which are arranged in order from bottom to top, wherein the fresh water generated by condensation in the flash tank (1) enters the reheater (22) of the corresponding flash coupling tank (2), and the sprayer (23) sprays the seawater entering the flash coupling tank (2) at the same level onto the steam generated by the reheater (22), and the steam is condensed into fresh water under the action of the flash assembly, and the unevaporated seawater falls into the first flash chamber (21); The flash tanks of each stage are connected in sequence, and the flash coupling tanks of each stage are connected in sequence. After the vacuum pump assembly is operated, the air pressure inside each flash tank is reduced and gradually decreased. The seawater first enters the first heat exchange tube bundle of the last flash coupling tank for preheating, and condenses the steam of the flash coupling tank of this stage, and then enters the first heat exchange tube bundle of the previous flash coupling tank, and then enters the second heat exchange tube bundle of the last flash tank from the first flash coupling tank, until the seawater enters the second heat exchange tube bundle of the first flash tank from the second flash tank for preheating, and then exchanges heat with the heating module through the heating module, and the temperature is further increased. Then the seawater returns to the first flash tank. Since the air pressure in the flash tank of this stage is much lower than the corresponding saturated vapor pressure at this temperature, the seawater evaporates instantly to generate steam, and the unevaporated seawater enters the second flash tank under the action of the pressure difference to continue evaporating. By analogy, the unevaporated seawater enters the last flash coupling tank and is finally discharged outside the last flash coupling tank.

2. The seawater desalination system coupled with multi-stage flash evaporation and multiple-effect distillation according to claim 1, characterized in that: The flash steam assembly comprises a first demister (24), a first fresh water tray (25) and a first heat exchange tube bundle (26) which are arranged in sequence from bottom to top. The first demister (24) removes salt particles that rise with the steam, so that the steam condenses into fresh water after reaching the first heat exchange tube bundle (26) and drips onto the first fresh water tray (25).

3. The seawater desalination system coupled with multi-stage flash evaporation and multiple-effect distillation according to claim 2, characterized in that: It also includes a vacuum pump assembly (3), a water pump assembly (4) and a heating module (5); The vacuum pump assembly (3) is connected to the multi-stage flash tank (1), and the water pump assembly (4) is connected to the multi-stage flash tank (1) and the multi-stage flash coupling tank (2); The first-stage flash tank (1) is connected to the heating module (5), and the last-stage flash tank (1) is connected to the first-stage flash coupling tank (2).

4. The seawater desalination system coupled with multi-stage flash evaporation and multiple-effect distillation according to claim 3, characterized in that: The flash tank (1) comprises a second flash chamber (11), a second demister (12), a second fresh water tray (13) and a second heat exchange tube bundle (14) which are arranged in sequence from bottom to top; The second heat exchange tube bundle (14) of the first-stage flash tank (1) is connected to the input end of the heating module (5), and the output end of the heating module (5) is connected to the second flash chamber (11) of the first-stage flash tank (1).

5. The seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation according to claim 3, characterized in that: The heating module (5) comprises a solar energy component and an air energy component (51) connected to the solar energy component.

6. The seawater desalination system coupled with multi-stage flash evaporation and multiple-effect distillation according to claim 5, characterized in that: The solar energy component comprises a solar thermal array (52), a heat storage tank (53) and a heat exchanger (54); the solar thermal array (52) is connected to the heat storage tank (53), the heat storage tank (53) is connected to the heat exchanger (54), and the heat exchanger (54) is connected to the air energy component (51).

7. The seawater desalination system coupled with multi-stage flash evaporation and multi-effect distillation according to any one of claims 1 to 6, characterized in that: The multi-stage flash coupling tank is divided into a heat recovery part and a heat discharge part. The flash component of the first-stage flash coupling tank of the heat discharge part is connected to a first separator (6), the first separator (6) is connected to a mixer (7), and the mixer (7) is connected to the flash component of the last-stage flash coupling tank of the heat recovery part. The flash chamber of the final flash coupling tank of the heat discharge part is also connected to a second separator (8), and the second separator (8) is connected to the mixer (7).

8. A method for desalination of seawater, characterized in that: Based on the seawater desalination system according to any one of claims 1 to 7, the method comprises: After the seawater enters the last-stage flash coupling tank, it enters the previous-stage flash coupling tank in sequence until the seawater enters the first-stage flash coupling tank; After the seawater enters the last stage flash tank from the first stage flash coupling tank, it enters the previous stage flash tank in sequence until the seawater enters the first stage flash tank; The seawater enters the solar thermal system from the first-stage flash tank for heating and then returns to the first-stage flash tank, and then returns to the last-stage flash coupling tank in sequence; The seawater heated by the solar thermal system enters the flash tanks at each level and the output fresh water enters the reheater of the corresponding flash coupling tank. The sprayer of the flash coupling tank sprays seawater on the reheater to generate steam, and the steam is condensed into fresh water under the action of the flash assembly.

9. The seawater desalination method according to claim 8, characterized in that: The method further comprises: After the seawater heated by the solar thermal system returns to each stage of the flash coupling tank in turn, the seawater in the flash coupling tank evaporates to form steam. The steam passes through the first demister to remove the salt particles rising with the steam, so that the steam reaches the first heat exchange tube bundle and condenses into fresh water, which drips onto the first fresh water tray.

10. The seawater desalination method according to claim 8, characterized in that: The method further comprises: The multi-stage flash coupling tank is divided into a heat recovery part and a heat discharge part. The heat discharge part separates a part of the unsalted seawater through a separator and then enters the heat recovery part through a mixer.

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