Mechanical vapor recompression and multi-effect evaporation salt production system

Abstract

The invention relates to the technical field of salt manufacturing equipment, in particular to a mechanical vapor recompression and multi-effect evaporation salt manufacturing system which comprises a preheating unit, an autoclave, an evaporation unit, a saltpeter manufacturing unit, a flash tank, a vapor recompression unit and a condensation unit. The preheating unit is used for heating raw materials, the output end of the preheating unit is connected with the input end of the autoclave, the nitrate-containing liquid output end of the autoclave is connected with the input end of the evaporation unit, the waste liquid output end of the autoclave is connected with the input end of the flash tank, and the output end of the flash tank is connected with the evaporation unit. The nitrate-containing liquid output end of the evaporation unit is connected with the input end of the nitrate preparation unit, the gas output end of the evaporation unit is connected with the input end of the condensation unit, and the gas output end of the nitrate preparation unit is connected with the condensation unit; the preheating unit, the evaporation unit and the saltpeter preparation unit can be flexibly used according to different components in brine through independent use or combined use of the preheating unit, the evaporation unit and the saltpeter preparation unit, so that a multi-path combined process is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of salt-making equipment, and particularly to a mechanical vapor recompression and multi-effect evaporation salt-making system. Background Art

[0002] In the mining of well and rock salt, the components of the brine are affected by factors such as the thickness of the rock layer, the depth of the mineral deposit, and the position of brine extraction. For example, the sulfate ion concentration in the brine of the Zhongyan Jintan Company's PetroChina gas storage area is about 8.5 g / l. The sulfate ion concentration in the brines of the Sinopec gas storage area and the Honghua gas storage area is relatively high compared to the brine in the middle of the salt basin. Currently, the sulfate ion concentration in the mixed brine of the two gas storage areas has reached about 11 g / l. Moreover, with the deepening of the mining degree, the sulfate ion concentration will continue to increase. It has now been found that the highest sulfate ion concentration in a single well reaches 25 g / l. In order to meet the fluctuating demands of the raw brine in different brine extraction areas, a single evaporation salt-making device has insufficient production capacity or poor quality of the prepared finished product. In addition, the hot steam generated by the system is directly discharged into the environment, which will cause damage to the environment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: to overcome the problems in the prior art that a single evaporation salt-making device has insufficient production capacity or poor quality of the prepared finished product, and the hot steam generated by the system is directly discharged into the environment, which will cause damage to the environment, and to provide a mechanical vapor recompression and multi-effect evaporation salt-making system.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a mechanical vapor recompression and multi-effect evaporation salt-making system, including:

[0005] A preheating unit, a hot press tank, an evaporation unit, a nitrate production unit, a flash tank, a vapor recompression unit, and a condensation unit;

[0006] The preheating unit is used to heat the raw material. The output end of the preheating unit is connected to the input end of the hot press tank. The nitrate-containing liquid output end of the hot press tank is connected to the input end of the evaporation unit. The waste liquid output end of the hot press tank is connected to the input end of the flash tank. The output end of the flash tank is connected to the evaporation unit. The nitrate-containing liquid output end of the evaporation unit is connected to the input end of the nitrate production unit. The gas output end of the evaporation unit is connected to the input end of the condensation unit. The gas output end of the nitrate production unit is connected to the condensation unit. The vapor recompression unit is connected to the hot press tank. The waste liquid output end of the nitrate production unit is connected to the input end of the flash tank. The evaporation unit is used to refine salt and nitrate-containing liquid. By using the preheating unit, evaporation unit, and nitrate production unit alone or in combination, it can be flexibly used according to the different components in the brine, realizing a multi-path combined process.

[0007] To solve the problem of how to arrange the preheating unit, it is further included that the preheating unit includes a primary preheater, a secondary preheater, and a tertiary preheater. The output end of the primary preheater is connected to the input end of the secondary preheater, the output end of the secondary preheater is connected to the input end of the tertiary preheater, and the output end of the tertiary preheater is connected to the input end of the autoclave.

[0008] To solve the problem of how to arrange the evaporation unit, it is further included that the evaporation unit includes a first-effect evaporation tank, a second-effect evaporation tank, a third-effect evaporation tank, and a fourth-effect evaporation tank.

[0009] The nitrate-containing liquid output end of the autoclave is connected to the input end of the first-effect evaporation tank, the nitrate-containing liquid output end of the first-effect evaporation tank is connected to the input end of the second-effect evaporation tank, the nitrate-containing liquid output end of the second-effect evaporation tank is connected to the input end of the third-effect evaporation tank, the nitrate-containing liquid output end of the third-effect evaporation tank is connected to the input end of the fourth-effect evaporation tank, and the nitrate-containing liquid output end of the fourth-effect evaporation tank is connected to the input end of the nitrate production unit.

[0010] The gas-liquid output end of the first-effect evaporation tank is connected to the input end of the second-effect evaporation tank, the gas output end of the second-effect evaporation tank is connected to the input end of the third-effect evaporation tank, the gas output end of the third-effect evaporation tank is connected to the input end of the condensation unit, and the gas output end of the fourth-effect evaporation tank is connected to the input end of the condensation unit.

[0011] It is further included that the output end of the flash tank is connected to the input end of the fourth-effect evaporation tank.

[0012] It is further included that the nitrate production unit includes a nitrate preheater, a nitrate production tank, a centrifuge, and a dryer.

[0013] The input end of the nitrate preheater is connected to the output end of the evaporation unit, the output end of the nitrate preheater is connected to the input end of the nitrate production tank, the nitrate liquid output end of the nitrate production tank is connected to the input end of the centrifuge, the output end of the centrifuge is connected to the input end of the dryer, the waste liquid output end of the nitrate production tank is connected to the input end of the flash tank, and the gas output end of the nitrate production tank is connected to the condensation unit.

[0014] It is further included that the steam recompression unit includes a demister, a scrubber, a droplet separator, a steam compressor, and a sprayer.

[0015] The steam output end of the autoclave is connected to the input end of the demister, the output end of the demister is connected to the input end of the scrubber, the output end of the scrubber is connected to the input end of the droplet separator, the output end of the droplet separator is connected to the input end of the steam compressor, the output end of the steam compressor is connected to the input end of the sprayer, and the output end of the sprayer is connected to the input end of the autoclave.

[0016] Further comprising a condensation unit including an atmospheric condenser, a primary steam ejector pump, an auxiliary condenser, a secondary steam ejector pump, and a circulating cooling water system. The input end of the atmospheric condenser is connected to the gas output end of the evaporation unit and the gas output end of the nitrate production unit. The output end of the atmospheric condenser is connected to the input end of the primary steam ejector pump. The output end of the primary steam ejector pump is connected to the input end of the auxiliary condenser. The output end of the auxiliary condenser is connected to the input end of the secondary steam ejector pump. The atmospheric condenser is connected in a cycle with the circulating cooling water system, and the circulating cooling water system is connected in a cycle with the auxiliary condenser.

[0017] The beneficial effects of the present invention are as follows: A mechanical vapor recompression and multi-effect evaporation salt production system provided by the present invention

[0018] 1. The combined operation mode of mechanical vapor recompression and multi-effect evaporation for cogeneration can achieve a large production capacity with less investment and minimum power consumption.

[0019] 2. The salt production of this application can be used flexibly according to the different components in the brine by using the preheating unit, evaporation unit, and nitrate production unit alone or in combination, realizing a multi-path combined process.

[0020] 3. By using the condensation unit, this application can also utilize the additional steam and non-condensable gas generated in the system and complete the recycling of water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the drawings and embodiments.

[0022] Figure 1 is a schematic structural diagram of the present invention.

[0023] In the figure: 1. Preheating unit, 11. Primary preheater, 12. Secondary preheater, 13. Tertiary preheater, 2. Hot press tank, 3. Evaporation unit, 31. First-effect evaporation tank, 32. Second-effect evaporation tank, 33. Third-effect evaporation tank, 34. Fourth-effect evaporation tank, 4. Nitrate production unit, 41. Nitrate preheater, 42. Nitrate production tank, 43. Centrifuge, 44. Dryer, 5. Flash tank, 6. Vapor recompression unit, 61. Demister, 62. Scrubber, 63. Liquid droplet separator, 64. Vapor compressor, 65. Sprayer, 7. Condensation unit, 71. Atmospheric condenser, 72. Primary steam ejector pump, 73. Auxiliary condenser, 74. Secondary steam ejector pump, 75. Circulating cooling water system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Now, the present invention will be further described in detail with reference to the drawings. These drawings are all simplified schematic diagrams, only illustrating the basic structure of the present invention in a schematic manner, so they only show the components related to the present invention.

[0025] As Figure 1 is a schematic structural diagram of the present invention, a mechanical vapor recompression and multi-effect evaporation salt production system, comprising:

[0026] a preheating unit 1, a hot pressing tank 2, an evaporation unit 3, a nitrate production unit 4, a flash tank 5, a vapor recompression unit 6, and a condensation unit 7;

[0027] The preheating unit 1 is used to heat raw materials. The output end of the preheating unit 1 is connected to the input end of the hot pressing tank 2. The nitrate-containing liquid output end of the hot pressing tank 2 is connected to the input end of the evaporation unit 3. The waste liquid output end of the hot pressing tank 2 is connected to the input end of the flash tank 5. The output end of the flash tank 5 is connected to the evaporation unit 3. The nitrate-containing liquid output end of the evaporation unit 3 is connected to the input end of the nitrate production unit 4. The gas output end of the evaporation unit 3 is connected to the input end of the condensation unit 7. The gas output end of the nitrate production unit 4 is connected to the condensation unit 7. The vapor recompression unit 6 is connected to the hot pressing tank 2. The waste liquid output end of the nitrate production unit 4 is connected to the input end of the flash tank 5. The evaporation unit 3 is used to refine table salt and nitrate-containing liquid, and the hot pressing tank 2 can produce table salt and discharge it.

[0028] The preheating unit 1 includes a primary preheater 11, a secondary preheater 12, and a tertiary preheater 13. The output end of the primary preheater 11 is connected to the input end of the secondary preheater 12. The output end of the secondary preheater 12 is connected to the input end of the tertiary preheater 13. The output end of the tertiary preheater 13 is connected to the input end of the hot pressing tank 2, and the tertiary preheater 13 is connected to the first-effect evaporation tank 31.

[0029] The evaporation unit 3 includes a first-effect evaporation tank 31, a second-effect evaporation tank 32, a third-effect evaporation tank 33, and a fourth-effect evaporation tank 34. The first-effect evaporation tank 31, the second-effect evaporation tank 32, the third-effect evaporation tank 33, and the fourth-effect evaporation tank 34 can all prepare the product table salt.

[0030] The nitrate-containing liquid output end of the hot pressing tank 2 is connected to the input end of the first-effect evaporation tank 31. The nitrate-containing liquid output end of the first-effect evaporation tank 31 is connected to the input end of the second-effect evaporation tank 32. The nitrate-containing liquid output end of the second-effect evaporation tank 32 is connected to the input end of the third-effect evaporation tank 33. The nitrate-containing liquid output end of the third-effect evaporation tank 33 is connected to the input end of the fourth-effect evaporation tank 34. The nitrate-containing liquid output end of the fourth-effect evaporation tank 34 is connected to the input end of the nitrate production unit 4. The non-condensable gas in the hot pressing tank 2 is directly discharged into the atmosphere. The hot pressing tank 2 is a high-temperature and high-pressure container, mainly used for heating, high-pressure treatment, and sealing materials;

[0031] The gas-liquid output end of the first-effect evaporator 31 is connected to the input end of the second-effect evaporator 32, the gas output end of the second-effect evaporator 32 is connected to the input end of the third-effect evaporator 33, the gas output end of the third-effect evaporator 33 is connected to the input end of the condensation unit 7, and the gas output end of the fourth-effect evaporator 34 is connected to the input end of the condensation unit 7. That is, the non-condensable gas of the first-effect evaporator 31 is discharged into the second-effect evaporator 32, the non-condensable gas of the second-effect evaporator 32 is discharged into the third-effect evaporator 33, the non-condensable gas of the third-effect evaporator 33 is discharged into the atmospheric condenser 71 of the condensation unit 7, and the non-condensable gas of the fourth-effect evaporator 34 is discharged into the atmospheric condenser 71 of the condensation unit 7.

[0032] The output end of the flash tank 5 is connected to the input end of the fourth-effect evaporator 34, so as to realize the re-refining of the waste liquid, thereby improving the extraction efficiency and resource utilization rate.

[0033] The refined brine preheated by the preheating unit 1 is sent to the evaporation unit 3. In the evaporation unit 3, part of the water is evaporated, the salt is crystallized, and the salt crystals settle and are collected in the salt tank.

[0034] A certain amount of brine leaves the evaporator through the circulation pipe separation area.

[0035] The salt collected in the salt tank is cooled by the washing brine, replacing the mother liquor containing high-concentration Na2SO4 and impurities (solution), flushing the small salt solids back into the evaporator, ensuring the further growth of the crystal particle size, fluidizing the salt bed in the salt leg, diluting the solid-liquid concentration of the slurry discharged to the centrifuge, and cooling the salt slurry to a lower temperature, which is convenient for solid-liquid separation in the pusher centrifuge and for the salt to be transported on the belt.

[0036] The mother liquor from EV-100 is discharged into the evaporator EV-201. The water in the mother liquor is evaporated in the multi-effect evaporation device, and the salt crystallizes.

[0037] The nitrate production unit 4 includes a nitrate preheater 41, a nitrate production tank 42, a centrifuge 43, and a dryer 44;

[0038] The input end of the nitrate preheater 41 is connected to the output end of the evaporation unit 3, the output end of the nitrate preheater 41 is connected to the input end of the nitrate production tank 42, the nitrate liquid output end of the nitrate production tank 42 is connected to the input end of the centrifuge 43, the output end of the centrifuge 43 is connected to the input end of the dryer 44, the waste liquid output end of the nitrate production tank 42 is connected to the input end of the flash tank 5, the gas output end of the nitrate production tank 42 is connected to the condensation unit 7, the non-condensable gas of the nitrate production tank 42 is discharged into the atmospheric condenser 71 of the condensation unit 7, and the nitrate production unit 4 can extract anhydrous nitrate.

[0039] The steam recompression unit 6 includes a demister 61, a scrubber 62, a droplet separator 63, a steam compressor 64, and a sprayer 65. The steam recompression unit 6 can recompress and utilize steam and remove impurities therein.

[0040] The steam from the autoclave 2 is sent to the scrubber 62. Before the steam enters the scrubber 62, the halogen droplets carried in the steam are separated by the demister 61. The steam flows down along the middle part of the scrubber 62, where the recycled steam condensate is sprayed. The steam is cooled to the saturation temperature and the remaining halogen droplets are separated. After passing through this part, the flow direction is changed, and the steam passes through the droplet separator 63 before leaving the scrubber and entering the steam compressor 64.

[0041] The steam output end of the autoclave 2 is connected to the input end of the demister 61. The output end of the demister 61 is connected to the input end of the scrubber 62. The output end of the scrubber 62 is connected to the input end of the droplet separator 63. The output end of the droplet separator 63 is connected to the input end of the steam compressor 64. The output end of the steam compressor 64 is connected to the input end of the sprayer 65. The output end of the sprayer 65 is connected to the input end of the autoclave 2.

[0042] The condensation unit 7 includes an atmospheric condenser 71, a primary steam ejector 72, an auxiliary condenser 73, a secondary steam ejector 74, and a circulating cooling water system 75. The input end of the atmospheric condenser 71 is connected to the gas output ends of the evaporation unit 3 and the nitrate production unit 4. The output end of the atmospheric condenser 71 is connected to the input end of the primary steam ejector 72. The output end of the primary steam ejector 72 is connected to the input end of the auxiliary condenser 73. The output end of the auxiliary condenser 73 is connected to the input end of the secondary steam ejector 74. The atmospheric condenser 71 is connected in a cycle with the circulating cooling water system 75. The circulating cooling water system 75 is connected in a cycle with the auxiliary condenser 73. The condensation unit 7 can condense steam and non-condensable gases and then discharge them into the atmosphere, avoiding the impact on the environment during direct discharge.

[0043] The corrosion of the evaporation salt-making heating tubes and other parts is extremely severe, including both chemical corrosion and electrochemical corrosion. In particular, some non-condensable gases, such as oxygen, carbon dioxide, hydrogen sulfide, etc., affect equipment corrosion and scaling, and also reduce the heat transfer efficiency.

[0044] The presence of oxygen causes corrosion both inside and outside the tubes. The principle is as follows:

[0045] At the cathode: Fe → Fe++ + 2 electrons

[0046] And oxygen in the solution

[0047] (acidic) O2 + 2H+ + 4 electrons → 2OH －

[0048] (Alkaline) O2 + 2H2O + 4 electrons → 4OH －

[0049] At the anode, Fe++ + 2OH － → Fe(OH)2

[0050] 4Fe(OH)2 + O2 + 2H2O → 4Fe(OH)3

[0051] Further oxidation

[0052] 2Fe(OH)3 → Fe2O3﹒nH2O (reddish-brown)

[0053] 2Fe(OH)3 + Fe(OH)2 → Fe3O4 (black)

[0054] Ca 2 Ca++ + Fe3O4n·H2O + Fe2O3n·H2O → CaFe2O4

[0055] Therefore, control the calcium ion content in the brine before evaporation, and the calcium content in the brine is less than or equal to 1.0 mg / L; at the same time, discharge the non-condensable gas during the evaporation process from the system to reduce the corrosion and scaling of different components in the gas on the equipment, because the corrosion products will also affect the purity and chromaticity of the salt products.

[0056] If the non-condensable gas stays in the tube wall of the heating chamber or preheater and accumulates continuously, the wall surface will be surrounded by a layer of non-condensable gas, blocking the contact between the steam and the wall surface of the heating chamber or heat exchanger. For the steam to transfer heat to the brine, it must first pass through the "gas film". However, the thermal conductivity of the gas is very small, the thermal resistance is very large, and the heat is not easily transferred, resulting in a significant reduction in the heat transfer coefficient. When the steam contains 1% non-condensable gas, the condensation heat transfer coefficient is reduced by 60%.

[0057] After the purified refined brine is preliminarily treated by preheating unit 1, it enters the hot press tank 2, the first-effect evaporation tank 31, the second-effect evaporation tank 32, the third-effect evaporation tank 33, and the fourth-effect evaporation tank 34 in sequence to produce salt-containing mother liquor. The salt-containing mother liquor is then heated by the nitrate preheater 41 and enters the nitrate production tank 42 (i.e., the nitrate evaporation tank). After the mother liquor is fully crystallized, the mother liquor passes through the flash tank 5 and is transferred to the fourth-effect evaporation tank 34 for recrystallization. The salt slurry discharged from the hot press tank 2, the first-effect evaporation tank 31, the second-effect evaporation tank 32, the third-effect evaporation tank 33, and the fourth-effect evaporation tank 34 enters the centrifuge for dehydration and drying, and then is transported to the packaging workshop through the belt conveyor and loaded onto the ship at the dock; similarly, the nitrate discharged from the nitrate production tank 42 enters the centrifuge 43 for dehydration, is dried by the dryer 44, and then is transported to the nitrate packaging machine through the belt conveyor for packaging and warehousing.

[0058] In actual use, a multi-path combination process is set up to meet the requirements of different raw brine components:

[0059] When the sulfate ion in the feed brine ≤ 6 g / L, the preheating unit 1 + the nitrate production unit 4 of the operating system are run;

[0060] When the sulfate ion in the feed brine is 6 - 18 g / L, the preheating unit 1 + the evaporation unit 3 + the nitrate production unit 4 of the operating system are run;

[0061] When the sulfate ion in the feed brine is 18 - 30 g / L, the evaporation unit 3 + the nitrate production unit 4 of the operating system are run;

[0062] When the sulfate ion in the feed brine ≥ 30 g / L, the nitrate production unit 4 of the operating system is run.

[0063] According to the different compositions of the brine, the output will have some changes, and this system can increase the output by 30% - 60%.

[0064] Example 1:

[0065] After the brine is purified, the main components of the brine are: the sodium chloride content is 290 - 300 g / L, and the sodium sulfate content is 1 - 5 g / L. After the brine is preheated by the first - stage, second - stage, and third - stage preheaters 11, 12, and 13, it enters the hot - press tank 2 for evaporation and crystallization. The evaporated crystals are washed, cooled, and then sent to the centrifuge 43. After dehydration and drying, high - purity salt is obtained, and the sodium chloride content in the dry salt is greater than or equal to 99.9%; the supernatant liquid generated by the hot - press tank 2 is transferred to the flash tank 5 for flash cooling and then sent to the four - effect evaporation tank 34 for salt production. The evaporated crystals are washed, cooled, and then sent to the centrifuge 43 for dehydration. After drying, industrial salt is obtained, and the dry - basis sodium chloride content in the industrial salt is greater than or equal to 99.5%. The supernatant liquid generated by the four - effect evaporation tank 34 is preheated by the nitrate preheater 41 and then sent to the nitrate production tank 42. The nitrate slurry in the nitrate production tank 42 is washed and then sent to the centrifuge 43 and the dryer 44 for drying, and anhydrous sodium sulfate (also known as anhydrous nitrate) is obtained. The sodium sulfate content in the anhydrous nitrate product is greater than or equal to 99.0%.

[0066] The secondary steam generated by the evaporation of the hot - press tank 2 is separated from salt mist by the demister 61. The conductivity of the secondary steam is less than or equal to 180 μS / cm. Then, the steam is washed by the washer 62, and the conductivity of the washed steam is less than or equal to 40 μS / cm. After removing the liquid moisture therein by the droplet separator 63, it enters the steam compressor 64 for compression to high - temperature and high - pressure supersaturated steam. After being sprayed and cooled by the sprayer 65, it reaches saturated steam and enters the heating chamber of the hot - press tank 2 to heat the brine for evaporation and crystallization to separate salt. The secondary steam of the hot - press tank 2 circulates in this way, and finally the recycling of the secondary steam is realized.

[0067] The non-condensable gases in the secondary steam of the autoclave 2, such as carbon dioxide, oxygen, nitrogen, etc., are directly discharged to the atmosphere through the non-condensable gas pipeline to improve the heat exchange efficiency of the heating chamber. The non-condensable gases contained in the steam in the primary preheater, secondary preheater, and tertiary preheater are discharged to the atmospheric condenser. The non-condensable gases in the secondary steam of the quadruple-effect evaporator 34 and the nitrate-making tank 42 are discharged to the atmospheric condenser. The secondary steam generated by the quadruple-effect evaporator 34 is cooled by circulating cooling water to instantly form a negative pressure. The medium-pressure steam pumps the non-condensable gases in the atmospheric condenser to the primary steam jet pump, and then the secondary steam contained in the non-condensable gases is condensed into water by the auxiliary condenser. The medium-pressure steam discharges the non-condensable gases to the atmosphere through the secondary steam jet.

[0068] Example 2:

[0069] After the brine is purified, the main components of the brine are: the sodium chloride content is 290 - 300 g / L, and the sodium sulfate content is 15 g / L. After the brine is preheated by the primary, secondary, and tertiary preheaters 11, 12, and 13, it enters the autoclave 2 for evaporation and crystallization. The evaporated crystals are washed and cooled and then sent to the centrifuge 43. After dehydration and drying, high-purity salt is obtained, and the sodium chloride content in the dry salt is greater than or equal to 99.9%. The supernatant liquid generated by the autoclave 2 is transferred to the first-effect evaporator 31, the supernatant liquid of the first-effect evaporator 31 is transferred to the second-effect evaporator 32, the supernatant liquid of the second-effect evaporator 32 is transferred to the third-effect evaporator 33, and the supernatant liquid of the third-effect evaporator 33 is transferred to the quadruple-effect evaporator 34. The crystals evaporated from the first-effect evaporator 31 / second-effect evaporator 32 / third-effect evaporator 33 / quadruple-effect evaporator 34 are washed and cooled and then sent to the centrifuge 43 for dehydration. After drying, dry salt is obtained, and the dry basis sodium chloride content in the dry salt is greater than or equal to 99.8%. The supernatant liquid generated by the quadruple-effect evaporator 34 is preheated by the nitrate preheater 41 and then sent to the nitrate-making tank 42. The nitrate slurry in the nitrate-making tank 42 is washed and then sent to the centrifuge 43 and the dryer 44 for drying to obtain anhydrous sodium sulfate (also known as: anhydrous nitrate), and the sodium sulfate content in the anhydrous nitrate product is greater than or equal to 99.0%.

[0070] The secondary steam generated by the evaporation of the autoclave 2 undergoes salt mist separation by the demister 61, and the conductivity of the secondary steam is less than or equal to 200 μS / cm. Then, the steam is washed by the washer 62, and the conductivity of the washed steam is less than or equal to 45 μS / cm. After removing the liquid moisture therein by the droplet separator 63, it enters the steam compressor 64 for compression to high-temperature and high-pressure supersaturated steam, and then is sprayed and cooled by the sprayer 65 to reach saturated steam and enter the heating chamber of the autoclave 2 to heat the brine for evaporation and crystallization to separate salt. The secondary steam of the autoclave 2 circulates in this way, and finally the recycling of the secondary steam is realized.

[0071] The non-condensable gases in the secondary steam of the autoclave 2, such as carbon dioxide, oxygen, nitrogen, etc., are directly discharged to the atmosphere through the non-condensable gas pipeline to improve the heat exchange efficiency of the heating chamber. The non-condensable gases contained in the steam in the primary preheater 11, secondary preheater 12, and tertiary preheater 13 are discharged to the atmospheric condenser. The non-condensable gases in the secondary steam of the quadruple-effect evaporator 34 and the nitre-making tank 42 are discharged to the atmospheric condenser. The secondary steam generated by the quadruple-effect evaporator 34 is cooled by circulating cooling water to instantly form a negative pressure. The medium-pressure steam pumps the non-condensable gases in the atmospheric condenser to the primary steam ejector 72, and then the secondary steam contained in the non-condensable gases is condensed into water by the auxiliary condenser. The medium-pressure steam discharges the non-condensable gases to the atmosphere through the secondary steam ejector 74.

[0072] Example 3:

[0073] After the brine is purified, the main components of the brine are: the sodium chloride content is 290 - 300 g / L, and the sodium sulfate content is 25 g / L. The brine enters the first-effect evaporator 31 after being preheated by the primary, secondary, and tertiary preheaters 11, 12, and 13. The supernatant of the first-effect evaporator 31 is transferred to the second-effect evaporator 32, the supernatant of the second-effect evaporator 32 is transferred to the third-effect evaporator 33, and the supernatant of the third-effect evaporator 33 is transferred to the quadruple-effect evaporator 34. The crystals after evaporation in the first-effect evaporator 31 / second-effect evaporator 32 / third-effect evaporator 33 / quadruple-effect evaporator 34 are washed and cooled and then sent to the centrifuge 43 for dehydration, and dry salt is obtained after drying. The sodium chloride dry basis content in the dry salt is greater than or equal to 99.8%. The supernatant generated by the quadruple-effect evaporator 34 is preheated by the nitre preheater 41 and then sent to the nitre-making tank 42. The nitre slurry in the nitre-making tank 42 is washed and then sent to the centrifuge 43 and the dryer 44 for drying to obtain anhydrous sodium sulfate (also known as anhydrous nitre). The sodium sulfate content in the anhydrous nitre product is greater than or equal to 98.8%.

[0074] The non-condensable gases contained in the steam in the primary preheater 11, secondary preheater 12, and tertiary preheater 13 are discharged to the atmospheric condenser. The non-condensable gases in the secondary steam of the quadruple-effect evaporator 34 and the nitre-making tank 42 are discharged to the atmospheric condenser. The secondary steam generated by the quadruple-effect evaporator 34 is cooled by circulating cooling water to instantly form a negative pressure. The medium-pressure steam pumps the non-condensable gases in the atmospheric condenser to the primary steam ejector 72, and then the secondary steam contained in the non-condensable gases is condensed into water by the auxiliary condenser. The medium-pressure steam discharges the non-condensable gases to the atmosphere through the secondary steam ejector 74.

[0075] Example 4:

[0076] After the impurities are removed from the brine, the main components of the brine are as follows: the sodium chloride content is 290 - 300 g / L, and the sodium sulfate content is 40 g / L. The brine enters the quadruple-effect evaporation tank 34 after being preheated by the first-stage, second-stage, and third-stage preheaters 11, 12, and 13. The crystals after evaporation in the quadruple-effect evaporation tank 34 are sent to the centrifuge 43 for dehydration after being washed and cooled, and dry salt is obtained after drying. The sodium chloride dry basis content in the dry salt is greater than or equal to 99.5%. The supernatant liquid generated by the quadruple-effect evaporation tank 34 is sent to the sodium nitrate production tank 42 after being preheated by the sodium nitrate preheater 41. After the sodium nitrate slurry in the sodium nitrate production tank 42 is washed, it is sent to the centrifuge 43 and the dryer 44 for drying, and anhydrous sodium sulfate (also known as anhydrous sodium nitrate) is obtained. The sodium sulfate content in the anhydrous sodium nitrate product is greater than or equal to 98.5%.

[0077] The non-condensable gas contained in the steam in the first-stage preheater, second-stage preheater, and third-stage preheaters 11, 12, and 13 is discharged to the atmospheric condenser. The non-condensable gas in the secondary steam of the quadruple-effect evaporation tank 34 and the sodium nitrate production tank 42 is discharged to the atmospheric condenser. The secondary steam generated by the quadruple-effect evaporation tank 34 is cooled by circulating cooling water to instantly form a negative pressure. The medium-pressure steam pumps the non-condensable gas in the atmospheric condenser to the first-stage steam ejector, and then the secondary steam contained in the non-condensable gas is condensed into water by the auxiliary condenser. The medium-pressure steam discharges the non-condensable gas to the atmosphere through the second-stage steam ejector. The enrichment of non-condensable gas is reduced, and the heat exchange efficiency of the heating chamber and the preheater is improved; at the same time, the negative pressure formed by the instant condensation of the secondary steam generated by the quadruple-effect evaporation tank 34 into water ensures the negative pressure difference between each evaporation tank, realizing low-temperature salt production.

[0078] Inspired by the ideal embodiments of the present invention described above, through the above description, relevant staff can make various changes and modifications completely within the scope without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A mechanical vapor recompression and multi-effect evaporation salt production system, characterized in that, Comprising: A preheating unit (1), an autoclave (2), an evaporation unit (3), a nitrate production unit (4), a flash tank (5), a steam recompression unit (6), and a condensation unit (7); The preheating unit (1) is used to heat the raw materials. The output end of the preheating unit (1) is connected to the input end of the autoclave (2). The nitrate-containing liquid output end of the autoclave (2) is connected to the input end of the evaporation unit (3). The waste liquid output end of the autoclave (2) is connected to the input end of the flash tank (5). The output end of the flash tank (5) is connected to the evaporation unit (3). The nitrate-containing liquid output end of the evaporation unit (3) is connected to the input end of the nitrate production unit (4). The gas output end of the evaporation unit (3) is connected to the input end of the condensation unit (7). The gas output end of the nitrate production unit (4) is connected to the condensation unit (7). The steam recompression unit (6) is connected to the autoclave (2). The waste liquid output end of the nitrate production unit (4) is connected to the input end of the flash tank (5). The evaporation unit (3) is used to refine salt and nitrate-containing liquid.

2. The mechanical vapor recompression and multiple-effect evaporation salt production system according to claim 1, wherein: The preheating unit (1) includes a primary preheater (11), a secondary preheater (12), and a tertiary preheater (13). The output end of the primary preheater (11) is connected to the input end of the secondary preheater (12). The output end of the secondary preheater (12) is connected to the input end of the tertiary preheater (13). The output end of the tertiary preheater (13) is connected to the input end of the autoclave (2).

3. A mechanical vapor recompression and multi-effect evaporation salt production system as described in claim 1, characterized in that: The evaporation unit (3) includes a first-effect evaporator (31), a second-effect evaporator (32), a third-effect evaporator (33), and a fourth-effect evaporator (34). The nitrate-containing liquid output end of the autoclave (2) is connected to the input end of the first-effect evaporator (31). The nitrate-containing liquid output end of the first-effect evaporator (31) is connected to the input end of the second-effect evaporator (32). The nitrate-containing liquid output end of the second-effect evaporator (32) is connected to the input end of the third-effect evaporator (33). The nitrate-containing liquid output end of the third-effect evaporator (33) is connected to the input end of the fourth-effect evaporator (34). The nitrate-containing liquid output end of the fourth-effect evaporator (34) is connected to the input end of the nitrate production unit (4). The gas-liquid output end of the first-effect evaporator (31) is connected to the input end of the second-effect evaporator (32). The gas output end of the second-effect evaporator (32) is connected to the input end of the third-effect evaporator (33). The gas output end of the third-effect evaporator (33) is connected to the input end of the condensation unit (7). The gas output end of the fourth-effect evaporator (34) is connected to the input end of the condensation unit (7).

4. The mechanical vapor recompression and multi-effect evaporation salt production system according to claim 3, wherein: The output end of the flash tank (5) is connected to the input end of the fourth-effect evaporator (34).

5. A mechanical vapor recompression and multi-effect evaporation salt production system according to claim 1, characterized in that: The nitrate production unit (4) includes a nitrate preheater (41), a nitrate production tank (42), a centrifuge (43), and a dryer (44). The input end of the nitrate preheater (41) is connected to the output end of the evaporation unit (3), the output end of the nitrate preheater (41) is connected to the input end of the nitrate production tank (42), the nitrate solution output end of the nitrate production tank (42) is connected to the input end of the centrifuge (43), the output end of the centrifuge (43) is connected to the input end of the dryer (44), the waste liquid output end of the nitrate production tank (42) is connected to the input end of the flash tank (5), and the gas output end of the nitrate production tank (42) is connected to the condensation unit (7).

6. The mechanical vapor recompression and multi-effect evaporation salt production system according to claim 1, characterized in that: The steam recompression unit (6) includes a demister (61), a scrubber (62), a droplet separator (63), a steam compressor (64), and a sprayer (65). The steam output end of the autoclave (2) is connected to the input end of the demister (61), the output end of the demister (61) is connected to the input end of the scrubber (62), the output end of the scrubber (62) is connected to the input end of the droplet separator (63), the output end of the droplet separator (63) is connected to the input end of the steam compressor (64), the output end of the steam compressor (64) is connected to the input end of the sprayer (65), and the output end of the sprayer (65) is connected to the input end of the autoclave (2).

7. A mechanical vapor recompression and multiple-effect evaporation salt-making system according to claim 1, characterized in that: The condensation unit (7) includes an atmospheric condenser (71), a primary steam jet pump (72), an auxiliary condenser (73), a secondary steam jet pump (74), and a circulating cooling water system (75). The input end of the atmospheric condenser (71) is connected to the gas output ends of the evaporation unit (3) and the nitrate production unit (4). The output end of the atmospheric condenser (71) is connected to the input end of the primary steam jet pump (72). The output end of the primary steam jet pump (72) is connected to the input end of the auxiliary condenser (73). The output end of the auxiliary condenser (73) is connected to the input end of the secondary steam jet pump (74). The atmospheric condenser (71) is connected in a cycle with the circulating cooling water system (75), and the circulating cooling water is connected in a cycle with the auxiliary condenser (73).

8. A mechanical vapor recompression and multiple-effect evaporation salt production system according to claim 1, characterized in that: The tertiary preheater (13) is connected to the first-effect evaporation tank (31).

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