System for producing desalinated water from high-salinity water and method of production

Abstract

The application discloses a system for preparing desalination water by using high-salt water and a preparation method. Because the anions and cations in water are not separated, when the temperature fluctuation exceeds 70 DEG C, the heat exchange surface will be scaled and crystallized. The system comprises a first evaporation tower, a second evaporation tower, a third evaporation tower, a mechanical acceleration clarification stirring pool (6) and a driving liquid system. The clarification water outlet of the mechanical acceleration clarification stirring pool is communicated with a clarification water tank (9), and the clarification water outlet of the clarification water tank is communicated with the driving liquid outlet of the driving liquid system through a pipeline and connected with the inlet of a first anion exchange membrane device (12). The anion liquid outlet of the first anion exchange membrane device is communicated with the dehumidification section (2) of the first evaporation tower, the cation liquid outlet is communicated with a carbon remover (13), and the outlet of the carbon remover is communicated with the dehumidification section of the first evaporation tower. The application is used for preparing desalination water.

Description

Technical Field

[0001] The invention relates to a system and a method for preparing desalinated water by utilizing high-salt water. Background Art

[0002] In current desalinated water production systems, the evaporation tower typically maintains a maximum water temperature of 42°C to prevent scaling on the heat exchange surfaces. The corresponding moisture content of the air is 54.8 g / kg of dry air. Even with an electromagnetic scale inhibitor to raise the water temperature to 70°C, the moisture content is only 276 g / kg of dry air. Because the anions and cations in the water remain inseparable, scaling and crystallization will form on the heat exchange surfaces when the temperature fluctuates above 70°C. The evaporation tower heats the water and air to 70°C for humidification and dehumidification, requiring large amounts of circulating water and air, which in turn increases transmission power consumption and equipment investment. Summary of the Invention

[0003] The purpose of the present invention is to remedy the deficiencies of the prior art and to provide a system and method for preparing desalinated water using high-salt water.

[0004] The above purpose is achieved through the following technical solutions:

[0005] A system for preparing desalinated water using high-salt water comprises: a No. 1 evaporation tower, a No. 2 evaporation tower, a No. 3 evaporation tower, a mechanically accelerated clarification and stirring tank, and a drive liquid system. The clarified water outlet of the mechanically accelerated clarification and stirring tank is connected to a clarified water tank. The clarified water outlet of the clarified water tank and the drive liquid outlet of the drive liquid system are connected to the inlet of a primary anion exchange membrane device via a pipeline.

[0006] The anion liquid outlet of the first-stage anion exchange membrane device is connected to the dehumidification section of the first evaporation tower, and the cationic liquid outlet is connected to the decarbonizer, and the outlet of the decarbonizer is connected to the dehumidification section of the first evaporation tower;

[0007] The cation concentrate separated from the humidification section of the No. 1 evaporation tower passes through a calcium ion remover and then flows into an anion and cation mixer together with the separated anion concentrate;

[0008] The brine outlet of the anion and cation mixer is connected to the inlet of the nanofiltration membrane device, the ion liquid outlet of the nanofiltration membrane device is respectively connected to the dehumidification section of the No. 2 evaporation tower and the secondary anion exchange membrane, and the ion liquid outlet of the secondary anion exchange membrane is connected to the dehumidification section of the No. 3 evaporation tower.

[0009] The system for preparing desalinated water using high-salt water, the driving liquid system includes a driving liquid tank, a sodium hydroxide dosing device, a flue gas pipe and a desalted water tank, the flue gas pipe is inserted into the driving liquid tank, and the desalted water tank is connected to the driving liquid tank.

[0010] The system for preparing desalinated water by utilizing high-salt water has a flue gas pipe inserted into the mechanically accelerated clarification stirring tank.

[0011] In the system for preparing desalinated water using high-salt water, the clarified water outlet of the mechanically accelerated clarification stirring tank is connected to the clarified water tank, and the residue outlet is connected to the dryer.

[0012] A method for preparing a desalinated water system using high-salt water, the method comprising the following steps: using an anion exchange membrane + nanofiltration membrane + evaporation dew point method;

[0013] (1) Seawater or high-salinity wastewater enters the mechanical clarification accelerated stirring tank, in which sodium hydroxide is added to adjust the pH value of the water to 8.7-9. Cooled and purified flue gas is introduced to remove 90% of the calcium ions and 60% of the magnesium ions in the water. The residue formed by calcium and magnesium hardness is dehydrated into a solid state by a dryer and sent to the storage yard. Some calcium and magnesium ions and carbon dioxide are solidified and no longer enter the water system. The dried water enters the clarification tank for recycling;

[0014] (2) The driving liquid is made of carbon dioxide gas and desalinated water. Hydrochloric acid is added to adjust the pH value of the driving liquid to 8.3-8.4, so that the carbon dioxide gas in the driving liquid is converted into bicarbonate ions, and the driving liquid enters the anion exchange membrane system;

[0015] All the anions in the water enter the driving liquid, and the bicarbonate ions in the driving liquid enter the water. After the replacement, the driving liquid contains chloride ions, sulfate ions, and bromide ions, and the water contains bicarbonate, sodium ions, magnesium ions, potassium ions, and calcium ions. The carbon dioxide converted from the bicarbonate ions is removed by the decarbonizer and recycled, and finally the water is divided into two streams of anion and cation water;

[0016] (3) The anion (cation) ions enter the No. 1 evaporation tower and dehumidification tower separately, and are heated to 92°C by the latent heat of vaporization of the wet air. They are then heated by the hot end heat exchanger. The heating temperature is determined based on the temperature of the hot air at the outlet of the humidification tower, which is 95°C. They then enter the top of the humidification tower, release heat to humidify the dry air, and the water evaporates into the air. The anion (cation) ion liquid is concentrated into a slurry and transported to the anion and cation mixer by two independent slurry pumps. The separated sodium chloride crystals are transported to the storage yard, and the leachate forms brine.

[0017] (4) The brine contains monovalent chloride ions, potassium ions, trace amounts of sodium and bromide ions, divalent sulfate ions, magnesium ions and trace amounts of calcium ions. The brine is transported to the nanofiltration membrane device to separate two ionic liquids, one for monovalent ionic liquid and the other for divalent ionic liquid;

[0018] (5) The 33°C monovalent ion liquid is transported to the No. 3 evaporation tower for further concentration into potassium chloride crystals;

[0019] (6) The 33°C divalent ion liquid enters the secondary anion exchange membrane, and the sulfate ion liquid and the magnesium ion liquid are separated in one way and in another way, and then enter the No. 3 evaporation tower in two independent loops to crystallize magnesium sulfate crystals. Beneficial effects

[0020] 1. This invention utilizes waste heat from flue gas to cool it down to below its dew point, separating sulfuric acid from the flue gas while also improving the purity of the carbon dioxide. One channel of carbon dioxide is used to remove calcium and magnesium hardness from the water, solidifying the carbon dioxide and calcium and magnesium hardness, preventing them from circulating in the water system. Another channel of carbon dioxide is used as a driving fluid raw material and is reused repeatedly in the water system, replacing the consumption of soda ash.

[0021] 2. The present invention uses only anion exchange membrane to separate anions and cations in water, saving the investment cost of cation exchange membrane.

[0022] 3. The present invention uses a nanofiltration membrane system to separate monovalent ions and divalent ions, which not only improves the purity of potassium chloride crystals and magnesium sulfate crystals, but also prevents scaling and crystal precipitation in the heat exchange parts of the heat exchanger and evaporation tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Attachment Figure 1 It is a schematic diagram of the present invention;

[0024] In the figure: 1. Humidification section of evaporation tower No. 1; 2. Dehumidification section of evaporation tower No. 1; 3. Humidification section of evaporation tower No. 3; 4. Dehumidification section of evaporation tower No. 3; 5. Flue heat exchanger; 6. Mechanically accelerated clarification stirring tank; 7. Dryer; 8. Sodium hydroxide dosing device; 9. Clarification water tank; 10. Demineralized water tank; 11. Drive liquid tank; 12. Primary anion exchange membrane device; 13. Decarbonizer; 14. Secondary anion exchange membrane; 15. Nanofiltration membrane device; 16. Anion and cation mixer; 17. Dehumidification section of evaporation tower No. 2; 18. Humidification section of evaporation tower No. 2; 19. Flue gas inlet pipe; 20. Calcium ion remover. DETAILED DESCRIPTION

[0025] Reference Figure 1 A system for preparing desalinated water using high-salt water, comprising: a No. 1 evaporation tower, a No. 2 evaporation tower, a No. 3 evaporation tower, a mechanically accelerated clarification stirring tank 6, and a drive liquid system, wherein the clarified water outlet of the mechanically accelerated clarification stirring tank is connected to a clarified water tank 9, and the clarified water outlet of the clarified water tank and the drive liquid outlet of the drive liquid system are connected to the inlet of a primary anion exchange membrane device 12 via a pipeline;

[0026] The anionic liquid outlet of the primary anion exchange membrane device is connected to the dehumidification section 2 of the first evaporation tower, and the cationic liquid outlet is connected to the decarbonizer 13. The outlet of the decarbonizer is connected to the dehumidification section of the first evaporation tower;

[0027] The cation concentrate separated from the humidification section 1 of the first evaporation tower passes through the calcium ion remover 20 and then flows into the anion and cation mixer 16 together with the separated anion concentrate;

[0028] The brine outlet of the anion and cation mixer is connected to the inlet of the nanofiltration membrane device 15, and the ion liquid outlet of the nanofiltration membrane device is respectively connected to the dehumidification section 17 of the No. 2 evaporation tower and the secondary anion exchange membrane, and the ion liquid outlet of the secondary anion exchange membrane is connected to the dehumidification section 4 of the No. 3 evaporation tower.

[0029] The driving liquid system includes a driving liquid tank 11, a sodium hydroxide dosing device, a flue gas pipe 19 and a desalted water tank 10. The flue gas pipe is inserted into the driving liquid tank, and the desalted water tank is connected to the driving liquid tank.

[0030] A flue gas supply pipe is inserted into the mechanical accelerated clarification stirring tank. The flue gas supply pipe of the driving liquid system and the flue gas supply pipe of the mechanical accelerated clarification stirring tank are both from the flue heat exchanger 5 of the No. 3 evaporation tower.

[0031] The clarified water outlet of the mechanically accelerated clarification stirring tank is connected to the clarified water tank, and the residue outlet is connected to the dryer 7.

[0032] The method for preparing a desalinated water system using high-salt water comprises the following steps: using an anion exchange membrane + nanofiltration membrane + evaporation dew point method;

[0033] (1) Seawater or high-salinity wastewater enters the mechanical clarification accelerated stirring tank, in which sodium hydroxide is added to adjust the pH value of the water to 8.7-9. Cooled and purified flue gas is introduced to remove 90% of the calcium ions and 60% of the magnesium ions in the water. The residue formed by calcium and magnesium hardness is dehydrated into a solid state by a dryer and sent to the storage yard. Some calcium and magnesium ions and carbon dioxide are solidified and no longer enter the water system. The dried water enters the clarification tank for recycling;

[0034] (2) The driving liquid is made of carbon dioxide gas and desalinated water. Hydrochloric acid is added to adjust the pH value of the driving liquid to 8.3-8.4, so that the carbon dioxide gas in the driving liquid is converted into bicarbonate ions, and the driving liquid enters the anion exchange membrane system;

[0035] All the anions in the water enter the driving liquid, and the bicarbonate ions in the driving liquid enter the water. After the replacement, the driving liquid contains chloride ions, sulfate ions, and bromide ions, and the water contains bicarbonate, sodium ions, magnesium ions, potassium ions, and calcium ions. The carbon dioxide converted from the bicarbonate ions is removed by the decarbonizer and recycled, and finally the water is divided into two streams of anion and cation water;

[0036] (3) The anion (cation) ions enter the No. 1 evaporation tower and dehumidification tower separately, and are heated to 92°C by the latent heat of vaporization of the wet air. They are then heated by the hot end heat exchanger. The heating temperature is determined based on the temperature of the hot air at the outlet of the humidification tower, which is 95°C. They then enter the top of the humidification tower, release heat to humidify the dry air, and the water evaporates into the air. The anion (cation) ion liquid is concentrated into a slurry and transported to the anion and cation mixer by two independent slurry pumps. The separated sodium chloride crystals are transported to the storage yard, and the leachate forms brine.

[0037] (4) The brine contains monovalent chloride ions, potassium ions, trace amounts of sodium and bromide ions, divalent sulfate ions, magnesium ions and trace amounts of calcium ions. The brine is transported to the nanofiltration membrane device to separate two ionic liquids, one for monovalent ionic liquid and the other for divalent ionic liquid;

[0038] (5) The 33°C monovalent ion liquid is transported to the No. 3 evaporation tower for further concentration into potassium chloride crystals;

[0039] (6) The 33°C divalent ion liquid enters the secondary anion exchange membrane, and the sulfate ion liquid and the magnesium ion liquid are separated in one way and in another way, and then enter the No. 3 evaporation tower in two independent loops to crystallize magnesium sulfate crystals.

Claims

1. A system for preparing desalinated water using high-salt water, comprising: The No. 1 evaporation tower, the No. 2 evaporation tower, the No. 3 evaporation tower, the mechanical accelerated clarification stirring tank and the drive liquid system are characterized in that: the clarified water outlet of the mechanical accelerated clarification stirring tank is connected to the clarified water tank, and the clarified water outlet of the clarified water tank and the drive liquid outlet of the drive liquid system are connected to the inlet of the primary anion exchange membrane device through a pipeline; The anion liquid outlet of the first-stage anion exchange membrane device is connected to the dehumidification section of the first evaporation tower, and the cationic liquid outlet is connected to the decarbonizer, and the outlet of the decarbonizer is connected to the dehumidification section of the first evaporation tower; The cation concentrate separated from the humidification section of the No. 1 evaporation tower passes through a calcium ion remover and then flows into an anion and cation mixer together with the separated anion concentrate; The brine outlet of the anion and cation mixer is connected to the inlet of the nanofiltration membrane device, and the monovalent ion liquid and divalent ion liquid outlets of the nanofiltration membrane device are respectively connected to the dehumidification section of the No. 2 evaporation tower and the secondary anion exchange membrane. The monovalent ion liquid enters the No. 2 evaporation tower, and the divalent ion liquid enters the secondary anion exchange membrane device. The ion liquid outlet of the secondary anion exchange membrane device is connected to the dehumidification section of the No. 3 evaporation tower.

2. The system for preparing desalinated water using high-salt water according to claim 1, characterized in that: The driving liquid system includes a driving liquid tank, a sodium hydroxide dosing device, a flue gas pipe and a desalted water tank. The flue gas pipe is inserted into the driving liquid tank, and the desalted water tank is connected to the driving liquid tank.

3. The system for preparing desalinated water using high-salt water according to claim 2, characterized in that: A flue gas pipe is inserted into the mechanical accelerated clarification stirring tank.

4. The system for preparing desalinated water using high-salt water according to claim 3, characterized in that: The clarified water outlet of the mechanically accelerated clarification stirring tank is communicated with the clarified water tank, and the residue outlet is communicated with the drying machine.

5. A method for preparing a desalinated water system using high-salt water according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: adopting an anion exchange membrane + nanofiltration membrane + evaporation dew point method; (1) Seawater or high-salinity wastewater enters the mechanical clarification accelerated stirring tank, in which sodium hydroxide is added to adjust the pH value of the water to 8.7-9. Cooled and purified flue gas is introduced to remove 90% of the calcium ions and 60% of the magnesium ions in the water. The residue formed by calcium and magnesium hardness is dehydrated into a solid state by a dryer and sent to the storage yard. Some calcium and magnesium ions and carbon dioxide are solidified and no longer enter the water system. The dried water enters the clarification tank for recycling; (2) The driving liquid is made of carbon dioxide gas and desalinated water. The pH value of the driving liquid is adjusted to 8.3-8.4, so that the carbon dioxide gas in the driving liquid is converted into bicarbonate ions, and the driving liquid enters the anion exchange membrane system; All the anions in the water enter the driving liquid, and the bicarbonate ions in the driving liquid enter the water. After the replacement, the driving liquid contains chloride ions, sulfate ions, and bromide ions, and the water contains bicarbonate, sodium ions, magnesium ions, potassium ions, and calcium ions. The carbon dioxide converted from the bicarbonate ions is removed by the decarbonizer and recycled, and finally the water is divided into two streams of anion and cation water; (3) The anion (cation) ions enter the No. 1 evaporation tower and dehumidification tower separately, and are heated to 92°C by the latent heat of vaporization of the wet air. They are then heated by the hot end heat exchanger. The heating temperature is determined based on the temperature of the hot air at the outlet of the humidification tower, which is 95°C. They then enter the top of the humidification tower, release heat to humidify the dry air, and the water evaporates into the air. The anion (cation) ion liquid is concentrated into a slurry and transported to the anion and cation mixer by two independent slurry pumps. The separated sodium chloride crystals are transported to the storage yard, and the leachate forms brine. (4) The brine contains monovalent chloride ions, potassium ions, trace amounts of sodium and bromide ions, divalent sulfate ions, magnesium ions and trace amounts of calcium ions. The brine is transported to the nanofiltration membrane device to separate two ionic liquids, one for monovalent ionic liquid and the other for divalent ionic liquid; (5) The 33°C monovalent ion liquid is transported to the second evaporation tower for further concentration into potassium chloride crystals; (6) The 33°C divalent ion liquid enters the secondary anion exchange membrane, and the sulfate ion liquid and the magnesium ion liquid are separated in one way and then enter the No. 3 evaporation tower in two independent loops to crystallize magnesium sulfate crystals.

Images