Efficient MVR (mechanical vapor recompression) evaporation system and use method thereof

Abstract

The invention relates to the technical field of MVR (mechanical vapor recompression) evaporation systems, in particular to an efficient MVR evaporation system and a using method thereof.The efficient MVR evaporation system comprises a stock solution evaporation and crystallization subsystem, a vapor compression subsystem and a condensate water waste heat recovery subsystem which are mutually coupled, and the stock solution evaporation and crystallization subsystem comprises a chemical reaction module and an evaporation and crystallization module; the chemical reaction module comprises a chemical reactor for containing a stock solution, the chemical reactor is connected with a solid-liquid separator, the solid outlet end of the solid-liquid separator is connected with the inlet end of a first sodium chloride solid tank, and the liquid outlet end of the solid-liquid separator is sequentially connected with a cold side channel of a first heat exchanger and a first circulating pump in series; the evaporative crystallization module comprises a buffer tank and a first evaporator, the first circulating pump is connected with the buffer tank, the structure and the technological process of the MVR system are optimized, the efficient heat exchanger design is adopted, the heat exchange efficiency is improved, the heat loss is reduced, the energy efficiency and the stability of the system are remarkably improved, the operation cost is reduced, and wide application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of MVR evaporation systems, and more particularly to an efficient MVR evaporation system and a method for using the same. Background Art

[0002] The MVR (Mechanical Vapor Recompression) system is an efficient evaporation and concentration technology, which is widely used in industries such as chemical engineering, food, and medicine. Its working principle is to provide the heat required for the evaporation process through mechanical energy to achieve the evaporation and concentration process. The MVR system mainly consists of components such as an evaporator, a compressor, a condenser, and an expansion valve, and the evaporation and concentration process is achieved through the coordinated operation of these components. The system compresses the low-temperature and low-pressure steam into high-temperature and high-pressure steam through the compressor, releases the heat to the evaporator, thereby realizing the evaporation and concentration process. The low-temperature and low-pressure steam after evaporation is cooled and condensed into a liquid through the condenser, and at the same time, the heat is released and then returned to the compressor for circulation.

[0003] The core of MVR technology is to use the thermal energy of the secondary steam to increase its temperature as a heat source to replace the fresh steam by compression, that is, to apply a part of the work done by the compressor to achieve cyclic evaporation. Thus, it is not necessary to use external fresh steam, and the evaporation and concentration purpose can be achieved by relying on the self-circulation of the evaporation system. In this way, the originally wasted steam is fully utilized, the latent heat is recovered, and the thermal efficiency is improved. Theoretically, using an MVR evaporator can save more than 60%-80% of energy compared with a traditional evaporator and save more than 90% of cooling water.

[0004] However, the traditional MVR system has deficiencies in terms of preheating efficiency and system composition complexity. For example, the preheating efficiency is low, the time is long, and the system composition is complex. In addition, when the traditional MVR system processes specific industrial waste liquids, such as the waste liquid generated during the conversion of potassium chloride to potassium sulfate, there may be no optimized design for the characteristics of these waste liquids, resulting in low treatment efficiency, low resource recovery rate, and possible environmental pollution problems. Therefore, it is of great significance to develop an efficient, energy-saving, and environmentally friendly waste liquid treatment system.

[0005] In the process of converting potassium chloride to produce potassium sulfate (chemical production), the waste liquid usually contains a large amount of potassium chloride, sodium chloride, and a small amount of organic amines. If these waste liquids are directly discharged, they will cause serious pollution to the environment. When the traditional MVR system processes such waste liquids, there are problems such as low energy utilization efficiency and high operating costs. Existing MVR systems often face challenges such as poor system stability, low energy efficiency, and high maintenance costs when processing waste liquids with high concentration, high viscosity, or containing scale-forming components. Summary of the Invention

[0006] The technical problem to be solved by the present invention is as follows: In order to solve the problems that in the existing MVR system when treating waste liquid with high concentration, high viscosity or containing scale-forming components, due to low preheating efficiency, long time, and complex system composition, the treatment efficiency is not high, the resource recovery rate is low, and there may be environmental pollution problems, an efficient MVR evaporation system and its usage method are provided herein.

[0007] The technical solution adopted by the present invention to solve its technical problem is: An efficient MVR evaporation system, including a raw liquid evaporation and crystallization subsystem, a steam compression subsystem, and a condensate waste heat recovery subsystem that are coupled to each other;

[0008] The raw liquid evaporation and crystallization subsystem includes a chemical reaction module and an evaporation and crystallization module. The chemical reaction module includes a chemical reactor for containing the raw liquid. The chemical reactor is connected to a solid-liquid separator. The solid outlet end of the solid-liquid separator is connected to the inlet end of the first sodium chloride solid tank. The liquid outlet end of the solid-liquid separator is sequentially connected in series with the cold side channel of the first heat exchanger and the first circulation pump;

[0009] The evaporation and crystallization module includes a buffer tank and a first evaporator. The first circulation pump is connected to the buffer tank. The buffer tank is sequentially connected in series with the raw liquid channel of the first evaporator and the first separator. The first separator is connected to the second sodium chloride solid tank. The first separator is sequentially connected in series with the second evaporator, the second separator, the third evaporator, the third separator, and the liquid outlet. The second separator is sequentially connected in series with the first thickener, the first centrifuge, the mother liquid tank, the second circulation pump, and the liquid passage of the first evaporator. The third separator is sequentially connected in series with the second thickener, the second centrifuge, the residual liquid tank, the third circulation pump, and the liquid passage of the first evaporator;

[0010] The steam compression subsystem is used to converge the steam separated from the first separator, the second separator, and the third separator in the corresponding evaporator into a compressor for compression and temperature rise to become secondary steam, and perform gas-liquid separation on the secondary steam. The separated steam is provided for step-by-step use in each evaporator, and the separated liquid is transported to the third evaporator for re-evaporation;

[0011] The condensate waste heat recovery subsystem is used to exchange heat between the condensate water in the first evaporator, the second evaporator, and the third evaporator and the first heat exchanger, and transport the heat-exchanged condensate water after reheating to the steam compression subsystem for re-steaming or put it into the chemical reactor together with the outlet concentrated hydrochloric acid for secondary utilization.

[0012] In some preferred embodiments, the vapor compression subsystem includes a compressor. The gas outlets of the first separator and the second separator are respectively connected to one end and the other end of a first three-way valve through pipelines. The first three-way valve is connected to a second valve and one end of a third three-way valve through a pipeline. The third separator is connected in series between the cold-side channel of the second heat exchanger, the other end of the third three-way valve, a second pressure sensor, the compressor, and the gas-liquid separator through pipelines. The compressor is connected to the hot-side channel of the second heat exchanger through a pipeline. One end of the gas-liquid separator is connected in series between a fifth valve, a liquid storage tank, and a third evaporator through pipelines. The other end of the gas-liquid separator is connected in series between a fourth flow sensor, a first temperature sensor, a third pressure sensor, and one end of a fourth three-way valve through pipelines. The outlet end of the fourth three-way valve is connected in series between the gas channel of the first evaporator, a fourth temperature sensor, the gas channel of the second evaporator, a fifth temperature sensor, and the gas channel of the third evaporator through pipelines.

[0013] In some preferred embodiments, the condensate waste heat recovery subsystem includes a condensate tank. The condensates of the third evaporator and the second evaporator are connected in series between one end and the other end of a fifth three-way valve through pipelines. The outlet end of the fifth three-way valve is connected in series between a third temperature sensor, a fifth pressure sensor, a seventh flow sensor, and one end of a sixth three-way valve through pipelines. The condensate of the first evaporator is connected to the other end of the sixth three-way valve through a pipeline. The sixth three-way valve is connected in series between the hot-side channel of the first heat exchanger, a fourth circulation pump, the condensate tank, a sixth valve, and the other end of the fourth three-way valve through pipelines.

[0014] In some preferred embodiments, an electric heater is connected in series between the sixth valve and the other end of the fourth three-way valve.

[0015] In some preferred embodiments, a first valve is connected in series between the first circulation pump and the buffer tank, and a first pressure sensor is connected in series between the first circulation pump and the first evaporator.

[0016] In some preferred embodiments, the buffer tank is connected to the first pressure sensor, and the first pressure sensor is located between the buffer tank and the first evaporator.

[0017] In some preferred embodiments, a first flow sensor is connected in series between the first separator and the second evaporator through a liquid pipeline, a third flow sensor is connected in series between the second separator and the third evaporator, and a sixth flow sensor, a fourth pressure sensor, a second temperature sensor, and an eighth valve are connected in series between the third separator and the liquid outlet in sequence.

[0018] Preferably, in some embodiments, a second flow sensor is connected in series between the first centrifuge and the mother liquor tank, a third valve is provided between the mother liquor tank and the second circulation pump, the output end of the second circulation pump is connected to one end of a second three-way valve, a fifth flow sensor is provided between the second centrifuge and the residual liquid tank, a seventh valve is provided between the residual liquid tank and the third circulation pump, and the output end of the third circulation pump is connected to the other end of the second three-way valve.

[0019] Preferably, in some embodiments, a fourth valve is provided between the outlet end of the second three-way valve and the liquid passage of the first evaporator.

[0020] A method of using an efficient MVR evaporation system as described above includes the following steps:

[0021] S1. Process of evaporating and crystallizing the stock solution: The stock solution first reacts with excessive concentrated hydrochloric acid in the chemical reactor to generate sodium chloride solid precipitate, which enters the first sodium chloride solid tank and then flows through the first heat exchanger, the first circulation pump, and the first pressure sensor in sequence. When the first pressure sensor detects excessive pressure, the first valve is opened to allow the stock solution to flow into the buffer tank to balance the pressure of the system. Then, it flows through the first pressure sensor, the first evaporator, and the first separator in sequence, and appropriate temperatures are set for evaporation and concentration. The separated sodium chloride solid is returned to the production line as raw material for continued use. The separated liquid contains a large amount of potassium chloride, concentrated hydrochloric acid, and a small amount of sodium chloride and organic amine. Then, it flows through the first flow sensor and the second evaporator, and appropriate temperatures are set in the second evaporator. One stream of liquid in the second evaporator goes to the second separator, the first thickener, and the first centrifuge to separate out potassium chloride precipitate. After precipitation, it then flows through the second flow sensor, the mother liquor tank, the third valve, the second circulation pump, and the fourth valve and returns to the first evaporator for continued evaporation and concentration. The liquid separated by the second separator contains a large amount of concentrated hydrochloric acid and a small amount of sodium chloride and organic amine, and passes through the third flow sensor, the third evaporator, the third separator, the sixth flow sensor, the fourth pressure sensor, the second temperature sensor, and the eighth valve and is discharged through the liquid outlet. One stream of the third evaporator flows through the third separator, the second thickener, and the second centrifuge in sequence to separate out solid impurities. Then, the remaining liquid flows through the fifth flow sensor, the residual liquid tank, the seventh valve, and the third circulation pump, and then returns to the first evaporator through the second three-way valve together with the liquid in the mother liquor tank. The residual liquid tank contains corrosive organic amine. If the flow rate is small, the second three-way valve is closed and the mother liquor reflux is not carried out.

[0022] S2. Steam compression to supplement secondary steam process: The steam in the first separator and the second separator sequentially passes through the first three-way valve, the second valve, the third three-way valve, and the second pressure sensor and enters the compressor for compression and temperature rise to become secondary steam. The steam in the third separator flows into the second heat exchanger. The waste heat in the compressor enters the second heat exchanger through the air to exchange heat with the steam, and then sequentially flows through the third three-way valve, the second pressure sensor, the compressor, and the gas-liquid separator. The gas-liquid separator filters out the liquid and flows into the liquid storage tank and the third evaporator for continuous evaporation and concentration. The secondary steam separated by the gas-liquid separator sequentially flows through the fourth flow sensor, the first temperature sensor, the third pressure sensor, and the fourth three-way valve. The secondary steam first enters the first evaporator for evaporation and concentration, and then enters the second evaporator and the third evaporator for cascaded utilization of the secondary steam;

[0023] S3. Condensate waste heat recovery process: The condensate in the third evaporator and the second evaporator converges through the fifth three-way valve and sequentially enters the third temperature sensor, the fifth pressure sensor, and the seventh flow sensor, and then converges with the condensate of the first evaporator through the sixth three-way valve and flows into the hot side channel of the first heat exchanger to exchange heat with the stock solution in the cold side channel. After heat exchange, the condensate flows into the condensate tank through the fourth circulation pump. The condensate can either supplement the secondary steam or be put into the chemical reactor together with the outlet concentrated hydrochloric acid for secondary utilization.

[0024] The beneficial effects of the present invention are as follows: When the high-efficiency MVR evaporation system and its usage method of the present invention are in use, the combined design of multiple evaporators and separators is adopted to achieve cascaded utilization of energy. The secondary steam generated by each stage of the evaporator is introduced into the next stage as a heat source, effectively improving the utilization rate of thermal energy;

[0025] At the same time, the condensate is recycled through the condensate tank, reducing the consumption of fresh water, significantly improving the utilization efficiency of water resources, reducing the overall energy consumption of the system. The system realizes multi-stage evaporation through multiple evaporators (primary, secondary, and tertiary evaporators). The secondary steam generated by each stage of the evaporator is guided to the next stage as a heat source to make full use of the heat, thereby effectively improving the utilization rate of thermal energy and further enhancing the overall productivity of the system. The evaporator and the chemical reactor are integrally designed to make the evaporation process and the chemical reaction proceed synchronously. It can not only pre-treat the stock solution, remove impurities, adjust the composition, etc., but also improve the working efficiency of the subsequent evaporator, creating more favorable conditions for the subsequent evaporation process;

[0026] Multiple separators and centrifuges are equipped in the system, and through the series connection method, the solid particles in the solution can be separated and concentrated more effectively, not only improving the purity and quality of the product, but also reducing the generation of solid waste, which is beneficial to environmental protection and resource recovery, achieving a win-win situation of economic benefits and environmental benefits;

[0027] The present invention contains multiple temperature, pressure, and flow sensors, which can receive and record different physical signals to provide comprehensive operating condition parameters. The data is used to control the opening and closing of different valves, improving the controllability and safety of the system operation.

[0028] By optimizing the structure and process flow of the MVR system and adopting an efficient heat exchanger design, the present invention improves the heat transfer efficiency, reduces heat loss, significantly enhances the energy efficiency and stability of the system, reduces the operating cost, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below in conjunction with the drawings and embodiments.

[0030] Figure 1 It is the MVR system diagram in the present invention;

[0031] Figure 2 It is the raw liquid evaporation and crystallization subsystem diagram in the present invention;

[0032] Figure 3 It is the steam compression subsystem diagram in the present invention;

[0033] Figure 4 It is the condensate waste heat recovery subsystem diagram in the present invention.

[0034] In the figure: 1. Chemical reactor; 2. Solid-liquid separator; 3. First sodium chloride solid tank; 4. First heat exchanger; 5. First circulation pump; 6. First valve; 7. Buffer tank; 8. First pressure sensor; 9. First evaporator; 10. First separator; 11. Second sodium chloride solid tank; 12. First flow sensor; 13. Second evaporator; 14. Second separator; 15. First three-way valve; 16. Second valve; 17. First thickener; 18. First centrifuge; 19. Second flow sensor; 20. Mother liquor tank; 21. Third valve; 22. Second circulation pump; 23. Second three-way valve; 24. Fourth valve; 25. Third flow sensor; 26. Third evaporator; 27. Third separator; 28. Second heat exchanger; 29. Third three-way valve; 30. Second pressure sensor; 31. Compressor; 32. Gas-liquid separator; 33. Fifth valve; 34. Liquid storage tank; 35. Fourth flow sensor; 36. First temperature sensor; 37. Third pressure sensor; 38. Fourth three-way valve; 39. Electric heater; 40. Sixth valve; 41. Second thickener; 42. Second centrifuge; 43. Fifth flow sensor; 44. Residual liquid tank; 45. Seventh valve; 46. Third circulation pump; 47. Sixth flow sensor; 48. Fourth pressure sensor; 49. Second temperature sensor; 50. Eighth valve; 51. Fifth three-way valve; 52. Third temperature sensor; 53. Fifth pressure sensor; 54. Seventh flow sensor; 55. Sixth three-way valve; 56. Fourth circulation pump; 57. Condensate tank; 58. Fourth temperature sensor; 59. Fifth temperature sensor. Detailed implementation manners

[0035] The present invention will be further described in detail below in conjunction with embodiments:

[0036] The present invention is not limited to the following specific implementation manners. Those of ordinary skill in the art can implement the present invention in other various specific implementation manners according to the content disclosed in the present invention, or those that adopt the design structure and idea of the present invention and make simple changes or modifications all fall within the protection scope of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0037] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0038] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0039] Embodiment 1

[0040] As Figures 1-4 shown, an efficient MVR evaporation system includes a raw liquid evaporation and crystallization subsystem, a steam compression subsystem, and a condensate waste heat recovery subsystem that are coupled to each other;

[0041] The raw liquid evaporation and crystallization subsystem includes a chemical reaction module and an evaporation and crystallization module. The chemical reaction module includes a chemical reactor 1. The raw liquid is connected to the inlet end of the chemical reactor 1 through a pipeline. The chemical reactor 1 is connected to a solid-liquid separator 2 through a pipeline. The solid outlet end of the solid-liquid separator 2 is connected to the inlet end of a first sodium chloride solid tank 3 through a pipeline. The liquid outlet end of the solid-liquid separator 2 is connected to the cold side channel of a first heat exchanger 4 and a first circulation pump 5 in sequence through a pipeline. The raw liquid in the chemical reactor 1 reacts with concentrated hydrochloric acid to pretreat the raw liquid and improve the subsequent reaction efficiency;

[0042] The evaporation and crystallization module includes a buffer tank 7. The first circulation pump 5 is connected to the first pressure sensor 8 and the first valve 6 through pipelines simultaneously. The first valve 6 is connected to the buffer tank 7 through a pipeline. The buffer tank 7 is connected to the first pressure sensor 8 through a pipeline. The first pressure sensor 8 is connected to the stock solution channel of the first evaporator 9 and the first separator 10 through pipelines. The first separator 10 is connected to the second sodium chloride solid tank 11 through a solid pipeline. The first separator 10 is connected to the first flow sensor 12, the second evaporator 13, the second separator 14, the third flow sensor 25, the third evaporator 26, the third separator 27, the sixth flow sensor 47, the fourth pressure sensor 48, the second temperature sensor 49, the eighth valve 50, and the liquid outlet through liquid pipelines. The second separator 14 is connected to the first thickener 17, the first centrifuge 18, the second flow sensor 19, the mother liquor tank 20, the third valve 21, the second circulation pump 22, and one end of the second three-way valve 23 through pipelines in sequence. The third separator 27 is connected to the second thickener 41, the second centrifuge 42, the fifth flow sensor 43, the residual liquid tank 44, the seventh valve 45, the third circulation pump 46, and the other end of the second three-way valve 23 through pipelines in sequence. The outlet end of the second three-way valve 23 is connected to the liquid channel of the first evaporator 9 through pipelines in sequence via the fourth valve 24. Among them, the evaporation and crystallization module adopts a multi-stage evaporator design, with each stage equipped with an independent evaporator and separator, realizing staged evaporation and heat recovery, improving the energy efficiency of the system. A buffer tank 7 is added to the system to stabilize the feed flow rate and pressure, reduce system fluctuations, and improve operational stability.

[0043] The vapor compression subsystem is used to converge the steam in the first separator 10, the second separator 14, and the third separator 27 into the compressor 31 for compression and temperature increase to become secondary steam, and supply it to the corresponding first evaporator 9, second evaporator 13, and third evaporator 26 respectively. The gas outlets of the first separator 10 and the second separator 14 are connected to one end and the other end of the first three-way valve 15 through pipelines respectively. The first three-way valve 15 is connected to the second valve 16 and one end of the third three-way valve 29 through a pipeline. The third separator 27 is connected to the cold side channel of the second heat exchanger 28, the other end of the third three-way valve 29, the second pressure sensor 30, the compressor 31, and the gas-liquid separator 32 through pipelines in sequence. The compressor 31 is connected to the hot side channel of the second heat exchanger 28 through a pipeline. One end of the gas-liquid separator 32 is connected to the fifth valve 33, the liquid storage tank 34, and the third evaporator 26 through pipelines in sequence. The other end of the gas-liquid separator 32 is connected to the fourth flow sensor 35, the first temperature sensor 36, the third pressure sensor 37, and one end of the fourth three-way valve 38 through pipelines in sequence. The outlet end of the fourth three-way valve 38 is connected to the gas channel of the first evaporator 9, the fourth temperature sensor 58, the gas channel of the second evaporator 13, the fifth temperature sensor 59, and the gas channel of the third evaporator 26 through pipelines in sequence.

[0044] The condensate waste heat recovery subsystem is used to exchange heat between the condensate water in the first evaporator 9, the second evaporator 13 and the third evaporator 26 and the first heat exchanger 4, and convey the heat-exchanged condensate water to the steam compression subsystem for re-steaming or put it into the chemical reactor 1 together with the outlet concentrated hydrochloric acid for secondary utilization; the condensate waste heat recovery subsystem includes the first evaporator 9, the second evaporator 13, the third evaporator 26, the third temperature sensor 52, the fifth pressure sensor 53, the seventh flow sensor 54, the first heat exchanger 4, the fourth circulation pump 56, and the condensate water tank 57. The condensate water of the third evaporator 26 and the second evaporator 13 is sequentially connected to one end and the other end of the fifth three-way valve 51 through pipelines. The outlet end of the fifth three-way valve 51 is sequentially connected to the third temperature sensor 52, the fifth pressure sensor 53, the seventh flow sensor 54, and one end of the sixth three-way valve 55 through pipelines. The condensate water of the first evaporator 9 is connected to the other end of the sixth three-way valve 55 through a pipeline. The sixth three-way valve 55 is sequentially connected to the hot side channel of the first heat exchanger 4, the fourth circulation pump 56, the condensate water tank 57, the sixth valve 40, and the electric heater 39 through pipelines. The electric heater 39 is connected to the other end of the fourth three-way valve 38 through a pipeline.

[0045] Among them, the first heat exchanger 4 and the second heat exchanger 28 in this embodiment both include a cold side channel and a hot side channel. The first evaporator 9, the second evaporator 13, and the third evaporator 26 all include a raw liquid outlet and an inlet, a secondary steam inlet, and a condensate water outlet. The first separator 10, the second separator 14, and the third separator 27 all include a raw liquid outlet and an inlet. The first valve 6, the second valve 16, the third valve 21, the fourth valve 24, the fifth valve 33, the sixth valve 40, the seventh valve 45, and the eighth valve 50 all include an outlet and an inlet. The first three-way valve 15, the second three-way valve 23, the third three-way valve 29, the fourth three-way valve 38, the fifth three-way valve 51, and the sixth three-way valve 55 all include two inlets and one outlet. The first circulation pump 5, the second circulation pump 22, the third circulation pump 46, and the fourth circulation pump 56 all include an outlet and an inlet. The compressor 31 includes a steam channel and an air channel. The recording functions of each sensor are provided by a data collector connected to the sensor. In this solution, the switches of each branch are all provided by electric gate valves. The remote control and precise adjustment of the valves are realized through electric actuators, which greatly improves the automation degree and operation efficiency of the system. The evaporator and pipelines are made of corrosion-resistant and high-temperature-resistant materials, which prolongs the service life of the equipment and reduces the maintenance cost.

[0046] Embodiment 2

[0047] Embodiment 2 is a usage method of the system in Embodiment 1. Specifically: A usage method of the efficient MVR evaporation system as described above is as follows:

[0048] S1. Process of evaporation and crystallization of stock solution: As Figure 2 shown, the stock solution first reacts with excessive concentrated hydrochloric acid in the chemical reactor 1 to form sodium chloride solid precipitate, which enters the first sodium chloride solid tank 3 through the solid-liquid separator 2. Then it flows through the first heat exchanger 4, the first circulation pump 5, and the first pressure sensor 8 in sequence. If the first pressure sensor 8 detects excessive pressure, the first valve 6 is opened to allow the stock solution to flow into the buffer tank 7 to balance the system pressure. Then it flows through the first pressure sensor 8, the first evaporator 9, and the first separator 10, where appropriate temperatures are set for evaporation and concentration. The separated sodium chloride solid is returned to the production line as raw material for continued use. Then it flows through the first flow sensor 12 and the second evaporator 13. In the second evaporator 13, appropriate temperatures are set, and one stream further goes to the second separator 14, the first thickener 17, and the first centrifuge 18 to separate potassium chloride precipitate. The remaining liquid flows through the second flow sensor 19, the mother liquor tank 20, the third valve 21, the second circulation pump 22, and the fourth valve 24, and then returns to the first evaporator 9 for continued evaporation and concentration. It then passes through the third flow sensor 25, the third evaporator 26, the third separator 27, the sixth flow sensor 47, the fourth pressure sensor 48, the second temperature sensor 49, and the eighth valve 50. Another stream continues to enter the third evaporator 26 for evaporation and concentration. Then one stream flows through the third separator 27, the second thickener 41, and the second centrifuge 42 to separate solid impurities. Then the remaining liquid flows through the fifth flow sensor 43, the residue tank 44, the seventh valve 45, and the third circulation pump 46. Then it returns to the first evaporator 9 through the second three-way valve 23 together with the liquid in the mother liquor tank 20. The residue tank 44 contains corrosive organic amine. If the value of the flow sensor is small, the valve is closed and the mother liquor reflux is not carried out.

[0049] S2. Process of steam compression to supplement secondary steam: As Figure 3 shown, the steam in the first separator 10 and the second separator 14 sequentially passes through the first three-way valve 15, the second valve 16, the third three-way valve 29, and the second pressure sensor 30 and enters the compressor 31 for compression and temperature increase to become secondary steam. The steam in the third separator 27 flows into the second heat exchanger 28. The waste heat in the compressor 31 enters the second heat exchanger 28 through the air to exchange heat with the steam. Then it flows through the third three-way valve 29, the second pressure sensor 30, the compressor 31, and the gas-liquid separator 32 in sequence. The filtered liquid flows into the liquid storage tank 34 and the third evaporator 26 for continued evaporation and concentration. The secondary steam sequentially passes through the fourth flow sensor 35, the first temperature sensor 36, the third pressure sensor 37, and the fourth three-way valve 38. The secondary steam first enters the first evaporator 9 for evaporation and concentration, and then enters the second evaporator 13 and the third evaporator 26 for cascade utilization of the secondary steam. When the secondary steam is insufficient, the water in the condensate tank 57 can be heated by the electric heater 39 to supplement the secondary steam.

[0050] S3. Condensate waste heat recovery process: As Figure 4 shown, the condensate water in the third evaporator 26 and the second evaporator 13 converges through the fifth three-way valve 51 and sequentially enters the third temperature sensor 52, the fifth pressure sensor 53, and the seventh flow sensor 54, and then converges with the condensate water of the first evaporator 9 through the sixth three-way valve 55 and flows into the hot side channel of the first heat exchanger 4 to exchange heat with the stock solution in the cold side channel. After heat exchange, the condensate water flows into the condensate water tank 57 through the fourth circulation pump 56. The condensate water can either supplement the secondary steam or be put into the chemical reactor 1 together with the outlet concentrated hydrochloric acid for secondary utilization.

[0051] Based on the ideal embodiments of the present invention as an inspiration, through the above description, relevant staff can completely make various changes and modifications 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 high efficiency MVR evaporation system, characterized by: It includes mutually coupled raw liquid evaporation crystallization subsystem, steam compression subsystem and condensed water waste heat recovery subsystem; The stock solution evaporation and crystallization subsystem comprises a chemical reaction module and an evaporation and crystallization module, wherein the chemical reaction module comprises a chemical reactor for containing the stock solution, the chemical reactor is connected to a solid-liquid separator, the solid outlet end of the solid-liquid separator is connected to the inlet end of the first sodium chloride solid tank, and the liquid outlet end of the solid-liquid separator is connected in series with the cold side channel of the first heat exchanger and the first circulation pump in sequence; The evaporation and crystallization module comprises a buffer tank and a first evaporator, a first circulation pump is connected to the buffer tank, the buffer tank is sequentially connected in series with the first evaporator raw liquid channel and the first separator, the first separator is connected to the second sodium chloride solid tank, the first separator is sequentially connected in series with the second evaporator, the second separator, the third evaporator, the third separator and the liquid outlet, the second separator is sequentially connected in series with the first thickener, the first centrifuge, the mother liquid tank, the second circulation pump and the first evaporator liquid, and the third separator is sequentially connected in series with the second thickener, the second centrifuge, the residual liquid tank, the third circulation pump and the first evaporator liquid channel; The steam compression subsystem is used to combine the steam separated from the first separator, the second separator and the third separator in the corresponding evaporator into the compressor to compress and heat it into secondary steam, and perform gas-liquid separation on the secondary steam. The separated steam is provided to each evaporator for use step by step, and the separated liquid is transported to the third evaporator for re-evaporation; The condensed water waste heat recovery subsystem is used to exchange heat between the condensed water in the first evaporator, the second evaporator and the third evaporator and the first heat exchanger, and to reheat the condensed water after heat exchange and then transport it to the steam compression subsystem for re-steaming or to put it into a chemical reactor together with the outlet concentrated hydrochloric acid for secondary utilization.

2. A high-efficiency MVR evaporation system according to claim 1, characterized in that: The steam compression subsystem includes a compressor, and the gas outlets of the first separator and the second separator are connected to one end of the first three-way valve and two ends of the first three-way valve respectively through pipelines. The first three-way valve is connected to the second valve and one end of the third three-way valve through a pipeline. The third separator is connected in series with the cold side channel of the second heat exchanger, the two ends of the third three-way valve, the second pressure sensor, the compressor and the gas-liquid separator through a pipeline. The compressor is connected to the hot side channel of the second heat exchanger through a pipeline, one end of the gas-liquid separator is connected in series with the fifth valve, the liquid storage tank and the third evaporator through a pipeline, the two ends of the gas-liquid separator are connected in series with the fourth flow sensor, the first temperature sensor, the third pressure sensor and one end of the fourth three-way valve through a pipeline, and the outlet end of the fourth three-way valve is connected in series with the first evaporator gas channel, the fourth temperature sensor, the second evaporator gas channel, the fifth temperature sensor and the third evaporator gas channel through a pipeline.

3. A high-efficiency MVR evaporation system according to claim 2, characterized in that: The condensed water waste heat recovery subsystem includes a condensed water tank, the condensed water of the third evaporator and the second evaporator are connected in series with one end of the fifth three-way valve and between two ends of the fifth three-way valve through pipelines, the outlet end of the fifth three-way valve is connected in series with the third temperature sensor, the fifth pressure sensor, the seventh flow sensor, and one end of the sixth three-way valve through pipelines, the condensed water of the first evaporator is connected with two ends of the sixth three-way valve through pipelines, and the sixth three-way valve is connected in series with the hot side channel of the first heat exchanger, the fourth circulation pump, the condensed water tank, the sixth valve and between two ends of the fourth three-way valve through pipelines.

4. A high-efficiency MVR evaporation system according to claim 3, characterized in that: An electric heater is connected in series between two ends of the sixth valve and the fourth three-way valve.

5. A high-efficiency MVR evaporation system according to claim 4, characterized in that: A first valve is connected in series between the first circulation pump and the buffer tank, and a first pressure sensor is connected in series between the first circulation pump and the first evaporator.

6. A high-efficiency MVR evaporation system according to claim 5, characterized in that: The buffer tank is connected to a first pressure sensor, and the first pressure sensor is located between the buffer tank and the first evaporator.

7. A high-efficiency MVR evaporation system according to claim 6, characterized in that: A first flow sensor is connected in series between the first separator and the second evaporator through a liquid pipeline, a third flow sensor is connected in series between the second separator and the third evaporator, and a sixth flow sensor, a fourth pressure sensor, a second temperature sensor and an eighth valve are connected in series between the third separator and the liquid outlet.

8. A high-efficiency MVR evaporation system according to claim 7, characterized in that: A second flow sensor is connected in series between the first centrifuge and the mother liquid tank, a third valve is provided between the mother liquid tank and the second circulation pump, the output end of the second circulation pump is connected to one end of the second three-way valve, a fifth flow sensor is provided between the second centrifuge and the residual liquid tank, a seventh valve is provided between the residual liquid tank and the third circulation pump, and the output end of the third circulation pump is connected to two ends of the second three-way valve.

9. A high-efficiency MVR evaporation system according to claim 8, characterized in that: A fourth valve is arranged between the outlet end of the second three-way valve and the first evaporator liquid channel.

10. A method for using a high-efficiency MVR evaporation system according to claim 9, characterized in that: The steps include: S1. Evaporation and crystallization process of raw liquid: the raw liquid first reacts with excess concentrated hydrochloric acid in a chemical reactor to generate sodium chloride solid precipitate which enters the first sodium chloride solid tank and flows through the first heat exchanger, the first circulation pump, and the first pressure sensor in sequence. When the first pressure sensor detects that the pressure is too high, the first valve is opened to allow the raw liquid to flow into the buffer tank to balance the pressure of the system. Then, it flows through the first pressure sensor, the first evaporator, and the first separator in sequence and is set at a suitable temperature for evaporation and concentration. The separated sodium chloride solid is returned to the production line as a raw material for continued use. The separated liquid then flows through the first flow sensor and the second evaporator, and a suitable temperature is set in the second evaporator. A stream of liquid in the second evaporator flows to the second separator, the first thickener, and the first centrifuge to separate it. Potassium chloride precipitates, and then flows through the second flow sensor, the mother liquid tank, the third valve, the second circulation pump, and the fourth valve to return to the first evaporator to continue evaporation and concentration. The liquid separated by the second separator passes through the third flow sensor, the third evaporator, the third separator, the sixth flow sensor, the fourth pressure sensor, the second temperature sensor, and the eighth valve and is discharged through the liquid outlet. One of the streams of the third evaporator flows through the third separator, the second thickener, and the second centrifuge in sequence to separate solid impurities. Then the remaining liquid flows through the fifth flow sensor, the residual liquid tank, the seventh valve, and the third circulation pump, and then flows back to the first evaporator with the liquid in the mother liquid tank through the second three-way valve. The residual liquid tank contains corrosive organic amines. If the flow rate is small, the second three-way valve is closed without reflux of the mother liquid. S2, steam compression to supplement secondary steam process: the steam in the first separator and the second separator passes through the first three-way valve, the second valve, the third three-way valve, and the second pressure sensor in turn, enters the compressor for compression and temperature increase to become secondary steam, the steam in the third separator flows into the second heat exchanger, the waste heat in the compressor enters the second heat exchanger through the air to exchange heat with the steam, and then flows through the third three-way valve, the second pressure sensor, the compressor and the gas-liquid separator in turn, the gas-liquid separator filters out liquid and flows into the liquid storage tank and the third evaporator to continue evaporation and concentration, the secondary steam separated by the gas-liquid separator flows through the fourth flow sensor, the first temperature sensor, the third pressure sensor and the fourth three-way valve in turn, the secondary steam first enters the first evaporator for evaporation and concentration, and then enters the second evaporator and the third evaporator for secondary steam cascade utilization; S3, condensed water waste heat recovery process: the condensed water in the third evaporator and the second evaporator is combined through the fifth three-way valve and enters the third temperature sensor, the fifth pressure sensor and the seventh flow sensor in turn, and then is combined with the condensed water in the first evaporator through the sixth three-way valve and flows into the hot side channel of the first heat exchanger to exchange heat with the original liquid in the cold side channel. The condensed water after heat exchange flows into the condensed water tank through the fourth circulation pump. The condensed water can be used to supplement secondary steam or put into a chemical reactor together with the outlet concentrated hydrochloric acid for secondary utilization.

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