A system and method for extracting lithium from seawater using industrial waste heat and solar energy

Abstract

A seawater desalination and lithium extraction system and method based on industrial waste heat and solar energy belong to the technical field of seawater lithium extraction and seawater desalination. In view of the low lithium concentration in seawater and the waste heat and solar energy of seawater desalination plants, industrial waste heat and solar energy are used to drive seawater desalination and seawater lithium extraction. Concentrated seawater after low-temperature multi-effect evaporation is further evaporated and concentrated in a plate evaporator. The costs of seawater desalination and seawater lithium extraction are reduced through deep coupling of the two processes of seawater desalination evaporation and seawater evaporation lithium extraction. Based on the differences in heat source quality and evaporation and concentration processing capacity, industrial waste heat and solar hot water are reasonably matched as heat sources for seawater desalination evaporation and concentrated seawater evaporation lithium extraction in terms of heat source quality and flow rate. Three working conditions are adopted to reasonably allocate industrial waste heat and solar energy to achieve all-weather seawater desalination and lithium extraction operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of seawater lithium extraction and desalination, and in particular relates to a seawater desalination lithium extraction system and method based on industrial waste heat and solar energy. Background Art

[0002] As a new green material, lithium boasts strong electrochemical activity and ductility, making it widely used in batteries, aerospace, and pharmaceuticals. However, with the rapid growth of global demand for lithium resources, the lithium resources found in solid lithium ore and salt lake brines are no longer sufficient to meet the rapidly expanding market demand. The total amount of lithium in the ocean is nearly 3,000 times greater than that on land, making seawater lithium extraction a crucial resource for future lithium resource development.

[0003] The lithium concentration in seawater is one thousandth of that found in terrestrial lithium mines. High costs and low seawater concentration ratios are the technical bottlenecks hindering seawater lithium extraction. Existing seawater concentration consumes high-pressure steam and electricity, resulting in high energy costs. Currently, desalinated seawater is discharged directly into the sea, leaving the lithium mineral resources in the desalinated seawater unutilized. Limitations such as reduced flow resistance and scaling on heat exchange surfaces make it difficult to effectively increase the seawater concentration ratio, limiting the cost reduction and separation efficiency improvement of existing seawater lithium extraction technologies, including co-precipitation, ion exchange adsorption, solvent extraction, and membrane separation. Therefore, utilizing waste heat from coastal industries and solar energy to extract lithium from seawater could help reduce the cost of lithium extraction.

[0004] Chinese patent publication number CN113293292B, "A Solar-Powered Seawater Lithium Extraction System and Preparation Method," proposes a solar-powered seawater lithium extraction system. Under sunlight, photogenerated electrons generated by a semiconductor flow through an external current into a cathode. The cathode material receives the photogenerated electrons and, to maintain electrical neutrality, captures lithium ions from seawater, thereby enriching the system. However, its limitations lie in its sole use of solar energy and the low lithium concentration in seawater, which results in low efficiency and hinders practical engineering applications.

[0005] Chinese patent publication number CN114291952B, "A System and Method for Extracting Lithium from Seawater in a Thermal Power Plant," proposes a system for extracting lithium from seawater in a thermal power plant. This system uses the plant's surplus electricity to power a desalination unit, which is then heated by the plant's steam turbine extraction system. Concentrated seawater produced by the desalination unit is used as a raw material for extracting lithium from seawater. However, the load of the desalination unit in this system depends on the power and heating loads of the thermal power plant, resulting in low or unstable desalination load output. The high-quality electricity and extraction steam consumed by desalination make the costs of desalination and lithium extraction from seawater excessively high.

[0006] The Chinese patent publication number CN117210704A, "A Seawater Lithium Extraction System and Method Based on Solar Nanofluids," proposes a seawater lithium extraction system and method based on solar nanofluids. Nanofluids are built into the top of the seawater preheating component to absorb solar energy to heat seawater, thereby achieving the purpose of concentrating seawater. However, the concentration of the concentrated seawater is low and cannot be used directly for lithium extraction.

[0007] The Chinese patent publication number CN109593973A, "A process for extracting lithium from seawater or salt lake water," proposes a process for extracting lithium from seawater or salt lake water. The process uses graphene solar cell power generation and an intelligent power storage management system coupled with a graphene ceramic membrane lithium ion absorber system to extract lithium from seawater or salt lake water. However, the low concentration of lithium in seawater makes the efficiency of extracting lithium directly from seawater too low.

[0008] Chinese patent publication number CN115386740A, "A Method and Apparatus for Extracting Lithium from Brine or Seawater Based on Electrodialysis Principles," proposes a method and apparatus for extracting lithium from seawater based on the principle of electrodialysis. This method utilizes the preferential permeability of a solid-state electrolyte to lithium ions. An external electric field is applied to induce lithium ions in the seawater in the positive electrode region to migrate toward the negative electrode, thereby enriching the seawater in the negative electrode region. However, this method consumes electrical energy during operation, and the accumulation of contaminants on the surface of the solid electrolyte can severely reduce its ability to selectively transport lithium ions.

[0009] To summarize, the existing problems of the seawater desalination lithium extraction system and method in the prior art are as follows:

[0010] 1. Existing seawater desalination and lithium extraction technologies consume high-pressure steam and electricity, resulting in high energy costs. However, power plants, steel mills, and other facilities with desalination plants generate a large amount of low-quality industrial waste heat that cannot be used for desalination and lithium extraction.

[0011] 2. Existing seawater lithium extraction technology simplifies the seawater desalination evaporation and seawater lithium extraction processes into one process, with seawater desalination as the goal and concentrated seawater as a by-product. This makes the cost of seawater desalination and seawater lithium extraction too high, and does not aim to reduce the cost of seawater desalination and seawater lithium extraction by resource utilization of lithium in seawater.

[0012] 3. Industrial waste heat-driven low-temperature multi-effect evaporation seawater desalination technology is limited by the scaling of the outer tube wall during the falling film evaporation process outside the horizontal tube. The seawater concentration ratio is low, and the concentrated seawater containing low concentration of lithium ions cannot meet the lithium ion concentration requirements of the next concentrated seawater adsorption process for lithium extraction, resulting in low adsorption lithium extraction efficiency. It is necessary to develop a high-concentration ratio seawater evaporation lithium extraction technology coupled with low-temperature multi-effect evaporation seawater desalination technology.

[0013] 4. Both the seawater desalination evaporation and concentrated seawater evaporation lithium extraction processes use steam as the evaporation heat source. There is no difference in the heat source quality and material evaporation processing capacity between the two evaporation processes. Compared with the concentrated seawater evaporation and lithium extraction process after seawater desalination evaporation and concentration, seawater desalination evaporation has higher requirements on the quality of the evaporation heat source and the evaporation processing volume of large seawater, resulting in excessively high energy consumption for concentrated seawater evaporation and lithium extraction. It is necessary to adopt the principle of energy use according to quality to match the heat sources of the two evaporation processes to reduce the cost of seawater desalination and lithium extraction.

[0014] 5. Solar energy is intermittent at night and fluctuates during the day. It is necessary to rationally distribute industrial waste heat and solar energy between the two processes of seawater desalination and evaporation, and concentrated seawater evaporation and lithium extraction, so as to achieve economical and stable operation of the seawater lithium extraction process around the clock. Summary of the Invention

[0015] In response to the shortcomings of existing seawater lithium extraction technologies, the present invention proposes a seawater desalination lithium extraction system and method based on industrial waste heat and solar energy.

[0016] In view of the low lithium concentration in seawater and the characteristics of waste heat and solar energy in seawater desalination plants, the present invention rationally matches industrial waste heat and solar hot water as heat sources for seawater desalination evaporation and concentrated seawater evaporation and lithium extraction in terms of heat source quality and flow rate, based on the differences in heat source quality and evaporation concentration processing capacity. This achieves the use of high-quality industrial waste heat for low-temperature multi-effect evaporation desalination of large seawater volumes, and the use of low-quality solar hot water for plate-type concentrated seawater evaporation and lithium extraction with small processing capacity and high concentration ratio, ensuring all-weather seawater desalination and lithium extraction operation. The costs of seawater desalination and seawater lithium extraction are reduced through the deep coupling of the two processes of seawater desalination evaporation and seawater evaporation and lithium extraction.

[0017] The present invention adopts the following technical solution: a seawater desalination and lithium extraction system based on industrial waste heat and solar energy, which includes a low-temperature multi-effect evaporation seawater desalination unit and a multi-effect plate-type concentrated seawater evaporation and lithium extraction unit.

[0018] The low-temperature multi-effect evaporation seawater desalination unit comprises an industrial waste heat steam electric regulating valve, a multi-effect horizontal tube falling film evaporator, a condenser, a seawater electric regulating valve, a seawater pump, a fresh water tank and a concentrated seawater tank;

[0019] The multi-effect plate-type concentrated seawater evaporation and lithium extraction unit comprises a solar collector, a solar hot water tank, a multi-effect plate-type seawater desalination device, a concentrated lithium water tank and a concentrated lithium water pump;

[0020] The horizontal tube falling film evaporator is provided with a liquid distributor, a heat exchange tube bundle, a secondary steam outlet, a concentrated seawater drain outlet, and a condensed water outlet; the industrial waste heat steam is divided into two routes and connected to the horizontal tube falling film evaporator and the industrial waste heat steam electric regulating valve through pipelines respectively, and the industrial waste heat steam is connected to the condenser from the horizontal tube falling film evaporator; the seawater is diverted to the condenser and enters the liquid distributor on the horizontal tube falling film evaporator through the condenser. The condenser is also connected to the solar water tank of the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit. The concentrated seawater drain outlet on the horizontal tube falling film evaporator is connected to the concentrated seawater tank, and the condensed water outlet on the horizontal tube falling film evaporator is connected to the fresh water tank.

[0021] The multi-effect plate-type seawater desalination device comprises a multi-effect plate-type evaporator and a plate-type condenser; a solar collector is connected to a solar water heater tank to form a solar heating cycle, the solar water heater tank circulates with the multi-effect plate-type evaporator, the outlet of the electric regulating valve for industrial waste heat steam is respectively connected to the waste heat steam inlet of the solar water heater tank and the hot water inlet of the multi-effect plate-type evaporator, the concentrated seawater tank is connected to the plate-type condenser via a pipeline through the concentrated seawater inlet of the plate-type condenser, the concentrated seawater outlet of the plate-type condenser is connected to the multi-effect plate-type evaporator via the concentrated seawater inlet of the multi-effect plate-type evaporator, the secondary steam enters the plate-type condenser and is then connected to the fresh water tank, and the concentrated lithium water outlet of the multi-effect plate-type evaporator is connected to the concentrated lithium water tank.

[0022] The plate condenser is provided with a plate condenser condensed water outlet, a plate condenser concentrated seawater inlet, and a plate condenser concentrated seawater outlet.

[0023] The multi-effect plate evaporator is provided with a multi-effect plate evaporator hot water outlet, a multi-effect plate evaporator hot water inlet, a multi-effect plate evaporator concentrated seawater inlet and a multi-effect plate evaporator concentrated lithium water outlet.

[0024] A method for extracting lithium from seawater by desalination based on industrial waste heat and solar energy, comprising the following steps:

[0025] Step 1: Under sunlight conditions, the industrial waste heat steam enters the heat exchange tube bundle of the first-effect horizontal tube falling film evaporator. Under nighttime conditions, 50-65% of the industrial waste heat steam enters the first-effect heat exchange tube bundle, and the remaining industrial waste heat steam enters the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit. Under sunlight conditions and when the hot water tank temperature is lower than the set temperature, the industrial waste heat steam electric regulating valve is adjusted to distribute the industrial waste heat steam into the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit. The industrial waste heat releases latent heat of vaporization in the heat exchange tube bundle of the first-effect horizontal tube falling film evaporator, and the condensed water flows out of the evaporator. The secondary steam generated in the evaporator is sequentially connected in series to enter the subsequent several-effect horizontal tube falling film evaporators to repeat the steam condensation process, and the generated condensed water enters the fresh water tank.

[0026] Step 2: The seawater is adjusted in proportion by the electric seawater regulating valve and then enters different horizontal tube falling film evaporators. After the seawater is pressurized, it is preheated to 40-45°C in the condenser and sprayed onto the heat exchange tube bundles through the liquid distributor. The seawater outside the heat exchange tube bundle absorbs the latent heat of vaporization of the steam inside the heat exchange tube bundle and evaporates and concentrates. It then flows out from the concentrated seawater outlet and is collected and enters the concentrated seawater tank.

[0027] Step 3: In the multi-effect plate concentrated seawater evaporation and lithium extraction unit, under sunlight conditions, hot water heated by the solar collector circulates between the solar water tank and the multi-effect plate desalination device, is heated by the solar collector, and then circulates to release heat; under nighttime conditions, 35-50% of the industrial waste heat steam at a temperature of 55-60°C enters the multi-effect plate evaporator, releases latent heat of vaporization, and is then condensed into condensed water, and the 55-60°C condensed water flows into the solar water tank; under transient conditions, part of the hot water in the solar water tank absorbs the latent heat of vaporization of the secondary steam generated by the terminal horizontal tube falling film evaporator in the multi-effect horizontal tube falling film evaporator in the condenser, and the preheated 40-45°C hot water returns to the solar water tank from the condenser, and the industrial waste heat steam is mixed with the hot water in the solar water tank for heating. After being heated by the solar collector and the industrial waste heat steam, the heated hot water releases sensible heat in the multi-effect plate evaporator and then returns to the solar water tank;

[0028] Step 4: In the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit, the concentrated seawater enters the plate condenser from the concentrated seawater tank. After absorbing the latent heat of secondary steam vaporization and being preheated, the concentrated seawater enters the multi-effect plate evaporator to be heated and evaporated and concentrated. The concentrated lithium water after evaporation and concentration enters the concentrated lithium water tank, and the concentrated lithium water is used as the raw material for subsequent lithium extraction.

[0029] The beneficial effects of the present invention are as follows: the present application designs a system and method for lithium extraction from seawater using industrial waste heat and solar energy, with the goal of resource utilization of lithium in seawater, and divides the process of lithium extraction from seawater into two processes: deep-coupled low-temperature multi-effect evaporation seawater desalination and plate-type concentrated seawater evaporation for lithium extraction. The plate-type concentrated seawater evaporation technology has the advantage of low scaling and crystallization restrictions, and the concentrated seawater after low-temperature multi-effect evaporation desalination is further evaporated and concentrated in the plate evaporator, and the lithium ion concentration requirement for the next step of lithium extraction by adsorption is met by increasing the seawater concentration ratio; the proposed method for lithium extraction from seawater does not require the consumption of high-quality high-pressure steam and electricity, and utilizes low-grade industrial waste heat and solar energy to respectively realize seawater desalination and concentrated seawater evaporation for lithium extraction, thereby saving energy consumption for lithium extraction from seawater desalination. It greatly reduces the cost of seawater desalination and seawater lithium extraction; uses industrial waste heat steam with higher quality than solar water heating as the heat source for low-temperature multi-effect evaporation seawater desalination with large seawater treatment capacity, and utilizes the abundant solar thermal resources in the northern coastal areas to produce hot water. Solar water heating is suitable for concentrated seawater evaporation and lithium extraction processes, which have low requirements for heat source quality and small concentrated seawater treatment capacity. Matching the evaporation treatment capacity according to different heat source qualities can effectively reduce the cost of seawater desalination and seawater lithium extraction; removes the latent heat of vaporization of the condenser of the low-temperature multi-effect evaporation seawater desalination system to preheat the seawater entering the evaporator, and mainly uses it to preheat the hot water in the solar water heating tank, reducing the heat loss of low-temperature multi-effect evaporation seawater desalination and reducing the cost of solar heat collection; for the intermittent solar energy and volatility, three operating conditions are adopted to achieve a reasonable distribution between industrial waste heat steam and solar hot water. The first design condition, that is, the heat source for concentrated seawater evaporation and lithium extraction is completely provided by solar hot water, and the industrial waste heat steam is completely used for low-temperature multi-effect evaporation of seawater desalination. Under the design condition, the fresh water output of seawater desalination and the concentrated liquid output of concentrated seawater evaporation and lithium extraction are the largest; the second night condition, that is, when there is no sunshine, industrial waste heat steam is used as a common heat source for the two processes of low-temperature multi-effect evaporation and lithium extraction of seawater. 50% to 65% of the industrial waste heat steam is used for low-temperature multi-effect evaporation and seawater desalination, and the remaining industrial waste heat steam is used for multi-effect plate concentrated seawater evaporation and lithium extraction. The amount of seawater treated by low-temperature multi-effect evaporation is based on the amount of industrial waste heat steam relative to the design condition. The amount of industrial waste heat steam used for lithium extraction from concentrated seawater is adjusted according to the difference between the hot water temperature in the solar water tank and the set temperature of the hot water. The amount of seawater evaporated and treated by the low-temperature multi-effect evaporation desalination system varies in proportion to the reduction in the amount of industrial waste heat steam relative to the design operating conditions. The three operating modes are used to realize all-weather seawater desalination and lithium extraction operation, solving the problem of reasonable allocation of industrial waste heat steam and solar energy under changing sunlight conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a flow chart of a system and method for extracting lithium from seawater by desalination based on industrial waste heat and solar energy.

[0031] Name of the label in the figure:

[0032] 0. Industrial waste heat steam electric regulating valve;

[0033] 1. First-effect horizontal tube falling film evaporator, 11. First-effect liquid distributor, 12. First-effect heat exchange tube bundle, 13. First-effect secondary steam outlet, 14. First-effect concentrated seawater outlet, 15. First-effect condensate outlet;

[0034] 2. Second-effect horizontal tube falling film evaporator, 21. Second-effect liquid distributor, 22. Second-effect heat exchange tube bundle, 23. Second-effect secondary steam outlet, 24. Second-effect concentrated seawater outlet, 25. Second-effect condensate outlet;

[0035] 3. Third-effect horizontal tube falling film evaporator, 31. Third-effect liquid distributor, 32. Third-effect heat exchange tube bundle, 33. Third-effect secondary steam outlet, 34. Third-effect concentrated seawater outlet, 35. Third-effect condensate outlet;

[0036] 4. Condenser, 41. Condenser seawater inlet, 42. Condenser seawater outlet, 43. Condenser solar hot water inlet, 44. Condenser solar hot water outlet, 45. Condenser steam inlet;

[0037] 5. Seawater electric regulating valve;

[0038] 6. Seawater pump;

[0039] 7. Fresh water tank, 71. Fresh water tank inlet;

[0040] 8. Concentrated sea water tank, 81. Concentrated sea water tank inlet, 82. Concentrated sea water tank outlet;

[0041] 9. Solar thermal collector, 91. Solar thermal collector water inlet, 92. Solar thermal collector water outlet;

[0042] 10. Solar water heater, 101. Water outlet of solar water heater, 102. Water inlet of solar water heater, 103. Hot water inlet of solar water heater, 104. Hot water outlet of solar water heater, 105. Waste heat steam inlet of solar water heater;

[0043] 16. Multi-effect plate-type seawater desalination device, 161. Multi-effect plate-type evaporator, 162. Plate-type condenser, 163. Plate-type condenser condensate outlet, 164. Multi-effect plate-type evaporator hot water outlet, 165. Multi-effect plate-type evaporator hot water inlet, 166. Plate-type condenser concentrated seawater inlet, 167. Plate-type condenser concentrated seawater outlet, 168. Multi-effect plate-type evaporator concentrated seawater inlet, 169. Multi-effect plate-type evaporator concentrated lithium water outlet;

[0044] 17. Concentrated lithium water pump;

[0045] 18. Concentrated lithium water tank. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0047] Example 1: Figure 1 A seawater desalination and lithium extraction system based on industrial waste heat and solar energy is shown, which includes a low-temperature multi-effect evaporation seawater desalination unit and a multi-effect plate-type concentrated seawater evaporation and lithium extraction unit. More specifically:

[0048] The low-temperature multi-effect evaporation seawater desalination unit comprises: an industrial waste heat steam electric regulating valve 0, a first-effect horizontal tube falling film evaporator 1, a second-effect horizontal tube falling film evaporator 2, a third-effect horizontal tube falling film evaporator 3, a condenser 4, a seawater electric regulating valve 5, a seawater pump 6, a fresh water tank 7 and a concentrated seawater tank 8, wherein the first-effect horizontal tube falling film evaporator 1, the second-effect horizontal tube falling film evaporator 2 and the third-effect horizontal tube falling film evaporator 3 respectively comprise a first-effect liquid distributor 11, a first-effect heat exchange tube bundle 12, and a first-effect secondary steam outlet 13. , first effect concentrated seawater drain port 14, first effect condensed water outlet 15, second effect liquid distributor 21, second effect heat exchange tube bundle 22, second effect secondary steam outlet 23, second effect concentrated seawater drain port 24, second effect condensed water outlet 25, third effect liquid distributor 31, third effect heat exchange tube bundle 32, third effect secondary steam outlet 33, third effect concentrated seawater drain port 34, third effect condensed water outlet 35; the industrial waste heat steam is divided into two routes and connected to the first effect heat exchange tube bundle 12 and the industrial waste heat steam electric power plant respectively through pipelines. The first-effect secondary steam outlet 13 is connected to the second-effect heat exchange tube bundle 22 via a pipeline, the second-effect secondary steam outlet 23 is connected to the third-effect heat exchange tube bundle 32 via a pipeline, and the third-effect secondary steam outlet 33 is connected to the condenser steam inlet 45 via a pipeline; the seawater is connected to the condenser seawater inlet 41 via the seawater electric regulating valve 5 and the seawater pump 6, and the condenser seawater outlet 42 is connected to the first-effect liquid distributor 11, the second-effect liquid distributor 21 and the third-effect liquid distributor 31 via pipelines, and the condenser solar water inlet 4 3 and the condenser solar hot water outlet 44 are respectively connected to the solar hot water tank outlet 101 and the solar hot water tank inlet 102 of the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit through pipelines, the first effect concentrated seawater drain outlet 14, the second effect concentrated seawater drain outlet 24 and the third effect concentrated seawater drain outlet 34 are connected to the concentrated seawater tank inlet 81 through pipelines, and the first effect condensed water outlet 15, the second effect condensed water outlet 25, the third effect condensed water outlet 35 and the condenser condensed water outlet 46 are connected to the fresh water tank inlet 71 through pipelines.

[0049] The multi-effect plate-type concentrated seawater evaporation and lithium extraction unit comprises: a solar collector 9, a solar hot water tank 10, a multi-effect plate-type seawater desalination device 16, a concentrated lithium water tank 18 and a concentrated lithium water pump 17, the multi-effect plate-type seawater desalination device 16 comprises a multi-effect plate-type evaporator 161, a plate-type condenser 162, a plate-type condenser condensed water outlet 163, a multi-effect plate-type evaporator hot water outlet 164, a multi-effect plate-type evaporator hot water inlet 165, a plate-type condenser concentrated seawater inlet 166, a plate-type condenser concentrated seawater outlet 167, a multi-effect plate-type evaporator concentrated seawater inlet 168 and a multi-effect plate-type evaporator concentrated lithium water outlet 169; a solar collector water inlet 91, a solar collector water outlet 92, a solar hot water tank water inlet 102 and a solar hot water tank water outlet 101 are connected via pipelines to form a solar heating cycle, and the solar hot water tank is connected to the water inlet 91 of the solar collector. The hot water outlet 104 of the energy water tank is connected to the hot water inlet 165 of the multi-effect plate evaporator, and the hot water outlet 164 of the multi-effect plate evaporator is connected to the hot water inlet 103 of the solar water tank. The outlet of the industrial waste heat steam electric regulating valve 0 is divided into two routes and respectively connected to the waste heat steam inlet 105 of the solar water tank and the hot water inlet 165 of the multi-effect plate evaporator. The concentrated sea water tank outlet 82 is connected to the plate condenser 162 through a pipeline via the concentrated sea water inlet 166 of the plate condenser. The concentrated sea water outlet 167 of the plate condenser is connected to the multi-effect plate evaporator 161 via the concentrated sea water inlet 168 of the multi-effect plate evaporator. After the secondary steam enters the plate condenser 162, it is connected to the fresh water tank inlet 71 by the condensed water outlet 163 of the plate condenser. The concentrated lithium water outlet 169 of the multi-effect plate evaporator is connected to the concentrated lithium water tank 18 via the concentrated lithium water pump 17.

[0050] Example 2: A method for extracting lithium from seawater using industrial waste heat and solar energy disclosed in Example 1 is used. The specific steps for extracting lithium using this method are as follows:

[0051] Step 1: Industrial waste heat steam with a temperature of 55-60°C, under the design working condition, which is under sunlight and can meet the solar heating demand, all enters the first-effect heat exchange tube bundle 12;

[0052] During nighttime operation, i.e., when there is no sunlight, 65% of the industrial waste heat steam with a temperature of 55-60°C enters the first-effect heat exchange tube bundle 1b, and the remaining 35% enters the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit through the industrial waste heat steam electric regulating valve 0;

[0053] In the transitional working condition, that is, during the day when the hot water temperature in the solar water heater 10 does not reach the hot water set temperature of 75-80°C, the opening of the industrial waste heat steam electric regulating valve 0 is dynamically adjusted according to the difference between the hot water temperature in the solar water heater 10 and the hot water set temperature, and the proportion of the industrial waste heat steam entering the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit is allocated; the industrial waste heat steam releases the latent heat of vaporization in the first-effect heat exchange tube bundle 12, and the condensed water flows out of the first-effect evaporator 1 through the first-effect condensed water outlet 15, and the secondary steam generated by evaporation in the first-effect evaporator 1 enters the second-effect through the first-effect secondary steam outlet 13. The steam condensation process is repeated in the heat exchange tube bundle 22. The secondary steam generated by evaporation in the second effect evaporator 2 enters the third effect heat exchange tube bundle 32 through the second effect secondary steam outlet 23 to repeat the steam condensation process. The secondary steam generated by evaporation in the third effect evaporator 3 enters the condenser 4 through the third effect secondary steam outlet 33 and the condenser steam inlet 45 to be condensed into fresh water. The condensed water flows out from the first effect condensed water outlet 15, the second effect condensed water outlet 25, the third effect condensed water outlet 35 and the condenser condensed water outlet 46 respectively, and then flows into the fresh water tank 7 through the fresh water tank inlet 71.

[0054] Step 2: The proportion of industrial waste heat steam entering the low-temperature multi-effect evaporation seawater desalination unit under the three working conditions described in step 1 is 20°C, salinity is 3.2%, and lithium concentration is 0.25. mg / L seawater is adjusted in the same proportion by the seawater electric regulating valve 6 and enters the first effect horizontal tube falling film evaporator 1, the second effect horizontal tube falling film evaporator 2 and the third effect horizontal tube falling film evaporator 3. The seawater is pressurized by the seawater pump 5 and preheated to 40-45°C in the condenser 4. After preheating, the seawater is evenly divided into three paths and respectively passes through the first effect liquid distributor 11, the second effect liquid distributor 21 and the third effect liquid distributor 31, and then sprayed onto the outside of the first effect heat exchange tube bundle 12, the second effect heat exchange tube bundle 22 and the third effect heat exchange tube bundle 32. The seawater outside the tube bundle absorbs the latent heat of vaporization of the steam in the tube and then evaporates and concentrates. It flows out from the first effect concentrated seawater outlet 14, the second effect concentrated seawater outlet 24 and the third effect concentrated seawater outlet 34 and is then collected. The concentrated seawater with a temperature of 48.4-53.4°C, a salinity of 6.4% and a lithium concentration of 0.50 mg / L enters the concentrated seawater tank 8;

[0055] Step 3: In the multi-effect plate-type concentrated seawater evaporation lithium extraction unit,

[0056] Under the design operating conditions, after being heated by the solar collector 9, hot water at 75-80°C flows out from the hot water outlet 104 of the solar water tank and enters the multi-effect plate desalination device 16. The hot water releases sensible heat in the multi-effect plate evaporator 161, and the hot water at 55-60°C returns to the solar water tank 10 through the hot water outlet 164 of the multi-effect plate evaporator and the hot water inlet 103 of the solar water tank, and is circulated and heated by the solar collector 9.

[0057] During nighttime operation, 35% of the industrial waste heat steam at a temperature of 55-60°C enters the multi-effect plate evaporator 161 from the multi-effect plate evaporator hot water inlet 165 to release the latent heat of vaporization and then condenses into condensed water. The 55-60°C condensed water flows out of the multi-effect plate evaporator 161 and enters the solar water heater 10.

[0058] In the transitional operating condition, part of the hot water in the solar water tank 10 absorbs the latent heat of vaporization of the secondary steam generated in the third-effect horizontal tube falling film evaporator 3 in the condenser 4. After preheating, the 40-45°C hot water returns to the solar water tank 10 through the condenser solar water outlet 44 and the solar water tank inlet 102. The industrial waste heat steam enters the solar water tank 10 through the solar water tank waste heat steam inlet 105 and is directly mixed with the hot water for heating. After being heated by the solar collector 9 and the industrial waste heat steam, the hot water at a temperature of 75-80°C releases sensible heat in the multi-effect plate evaporator 161 and returns to the solar water tank 10.

[0059] Step 4: In the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit, concentrated seawater with a temperature of 48-53°C, a salinity of 6.4%, and a lithium concentration of 0.50 mg / L flows out from the concentrated seawater tank outlet 82 and enters the plate condenser 162. After absorbing the latent heat of secondary steam vaporization and preheating to 50-55°C, the concentrated seawater enters the multi-effect plate evaporator 161 through the plate condenser concentrated seawater outlet 167 and the multi-effect plate evaporator concentrated seawater inlet 168 to be heated and evaporated and concentrated. After evaporation and concentration, concentrated lithium water with a temperature of 52-57°C, a salinity of 32%, and a lithium concentration of 2.5 mg / L enters the concentrated lithium water tank 18 through the multi-effect plate evaporator concentrated lithium water outlet 169 via the concentrated lithium water pump 17. The concentrated lithium water is used as the raw material for subsequent lithium extraction.

[0060] By adopting the above technical scheme, a seawater desalination and lithium extraction system and method based on industrial waste heat and solar energy is used. Seawater desalination and lithium extraction do not require the consumption of high-quality high-pressure steam and electricity. Industrial waste heat and solar energy are used to drive seawater desalination and seawater lithium extraction, and the concentrated seawater after low-temperature multi-effect evaporation seawater desalination is further evaporated and concentrated in a plate evaporator. By increasing the seawater concentration ratio, the cost of seawater desalination and lithium extraction is significantly reduced; industrial waste heat and solar hot water are reasonably matched as heat sources for seawater desalination evaporation and concentrated seawater evaporation and lithium extraction in terms of heat source quality and flow rate, industrial waste heat steam with higher quality than solar hot water is used as the heat source for low-temperature multi-effect evaporation seawater desalination with a large seawater treatment capacity, and solar hot water is used as the heat source for concentrated seawater evaporation and lithium extraction with a small concentrated seawater treatment capacity; a condenser is used to preheat the hot water in the solar hot water tank, thereby reducing the heat loss of the discharged seawater in the original low-temperature multi-effect evaporation seawater desalination; three working conditions are adopted to reasonably allocate industrial waste heat and solar energy, thereby realizing all-weather seawater desalination and lithium extraction operation, and extending the operation time of seawater desalination and lithium extraction.

[0061] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may modify the technical solutions described in the aforementioned embodiments or replace some or all of the technical features therein with equivalents; such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A seawater desalination and lithium extraction system based on industrial waste heat and solar energy, characterized by: It includes a low-temperature multi-effect evaporation seawater desalination unit and a multi-effect plate-type concentrated seawater evaporation lithium extraction unit; The low-temperature multi-effect evaporation seawater desalination unit comprises an industrial waste heat steam electric regulating valve, a multi-effect horizontal tube falling film evaporator, a condenser, a seawater electric regulating valve, a seawater pump, a fresh water tank and a concentrated seawater tank; The multi-effect plate-type concentrated seawater evaporation and lithium extraction unit comprises a solar collector, a solar hot water tank, a multi-effect plate-type seawater desalination device, a concentrated lithium water tank and a concentrated lithium water pump; The horizontal tube falling film evaporator is provided with a liquid distributor, a heat exchange tube bundle, a secondary steam outlet, a concentrated seawater drain outlet, and a condensed water outlet; the industrial waste heat steam is divided into two paths and connected to the horizontal tube falling film evaporator and the industrial waste heat steam electric regulating valve through pipelines, and the industrial waste heat steam is connected to the condenser from the horizontal tube falling film evaporator; the seawater is diverted to the condenser and enters the liquid distributor on the horizontal tube falling film evaporator through the condenser. The condenser is also connected to the solar water tank of the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit. The concentrated seawater drain outlet on the horizontal tube falling film evaporator is connected to the concentrated seawater tank, and the condensed water outlet on the horizontal tube falling film evaporator is connected to the fresh water tank. The multi-effect plate-type seawater desalination device includes a multi-effect plate-type evaporator and a plate-type condenser; a solar collector is connected to a solar water heater tank to form a solar heating cycle, the solar water heater tank circulates with the multi-effect plate-type evaporator, the outlet of the industrial waste heat steam electric regulating valve is respectively connected to the waste heat steam inlet of the solar water heater tank and the hot water inlet of the multi-effect plate-type evaporator, the concentrated seawater tank is connected to the plate-type condenser through a pipeline via the concentrated seawater inlet of the plate-type condenser, the concentrated seawater outlet of the plate-type condenser is connected to the multi-effect plate-type evaporator via the concentrated seawater inlet of the multi-effect plate-type evaporator, the secondary steam enters the plate-type condenser and is then connected to the fresh water tank, and the concentrated lithium water outlet of the multi-effect plate-type evaporator is connected to the concentrated lithium water tank; the plate-type condenser is provided with a plate-type condenser condensate water outlet, a plate-type condenser concentrated seawater inlet, and a plate-type condenser concentrated seawater outlet.

2. The seawater desalination and lithium extraction system based on industrial waste heat and solar energy as claimed in claim 1, characterized in that: The multi-effect plate evaporator is provided with a multi-effect plate evaporator hot water outlet, a multi-effect plate evaporator hot water inlet, a multi-effect plate evaporator concentrated seawater inlet and a multi-effect plate evaporator concentrated lithium water outlet.

3. A lithium extraction method for a seawater desalination system based on industrial waste heat and solar energy according to any one of claims 1 to 2 is adopted, comprising the following steps: Step 1: Under sunlight conditions, the industrial waste heat steam enters the heat exchange tube bundle of the first-effect horizontal tube falling film evaporator. Under nighttime conditions, 50-65% of the industrial waste heat steam enters the first-effect heat exchange tube bundle, and the remaining industrial waste heat steam enters the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit. Under sunlight conditions and when the hot water tank temperature is lower than the set temperature, the industrial waste heat steam electric regulating valve is adjusted to distribute the industrial waste heat steam into the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit. The industrial waste heat releases latent heat of vaporization in the heat exchange tube bundle of the first-effect horizontal tube falling film evaporator, and the condensed water flows out of the evaporator. The secondary steam generated in the evaporator is sequentially connected in series to enter the subsequent several-effect horizontal tube falling film evaporators to repeat the steam condensation process, and the generated condensed water enters the fresh water tank. Step 2: The seawater is adjusted in proportion by the electric seawater regulating valve and then enters different horizontal tube falling film evaporators. After the seawater is pressurized, it is preheated to 40-45°C in the condenser and sprayed onto the heat exchange tube bundles through the liquid distributor. The seawater outside the heat exchange tube bundle absorbs the latent heat of vaporization of the steam inside the heat exchange tube bundle and evaporates and concentrates. It then flows out from the concentrated seawater outlet and is collected and enters the concentrated seawater tank. Step 3: In the multi-effect plate concentrated seawater evaporation and lithium extraction unit, under sunlight conditions, hot water heated by the solar collector circulates between the solar water tank and the multi-effect plate desalination device, is heated by the solar collector, and then circulates to release heat; under nighttime conditions, 35-50% of the industrial waste heat steam at a temperature of 55-60°C enters the multi-effect plate evaporator, releases latent heat of vaporization, and is then condensed into condensed water, and the 55-60°C condensed water flows into the solar water tank; under transient conditions, part of the hot water in the solar water tank absorbs the latent heat of vaporization of the secondary steam generated by the terminal horizontal tube falling film evaporator in the multi-effect horizontal tube falling film evaporator in the condenser, and the preheated 40-45°C hot water returns to the solar water tank from the condenser, and the industrial waste heat steam is mixed with the hot water in the solar water tank for heating. After being heated by the solar collector and the industrial waste heat steam, the heated hot water releases sensible heat in the multi-effect plate evaporator and then returns to the solar water tank; Step 4: In the multi-effect plate-type concentrated seawater evaporation and lithium extraction unit, the concentrated seawater enters the plate condenser from the concentrated seawater tank. After absorbing the latent heat of secondary steam vaporization and being preheated, the concentrated seawater enters the multi-effect plate evaporator to be heated and evaporated and concentrated. The concentrated lithium water after evaporation and concentration enters the concentrated lithium water tank, and the concentrated lithium water is used as the raw material for subsequent lithium extraction.

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