Three-cycle high-salinity wastewater low-temperature scraper drying system and working method thereof

Abstract

The invention relates to a triple-cycle high-salinity wastewater low-temperature scraper drying system and a working method thereof. The triple-cycle high-salinity wastewater low-temperature scraper drying system comprises a roller scraper dryer, a steam condensation chamber, a condensation water tank and a vacuum pump. The vacuum pump vacuumizes the drying cavity through the condensate water tank and the steam condensation chamber. The first heat exchange cycle is suitable for exchanging heat absorbed by the steam condensation chamber to the third heat exchange cycle; the second heat exchange cycle is suitable for exchanging heat of the third heat exchange cycle to the water jacket; and the heat exchange ends on the two sides of the third heat exchange cycle are connected with the first heat exchange cycle and the second heat exchange cycle correspondingly. The three heat exchange cycles work cooperatively, the heat of the first heat exchange cycle is reduced, the heat provided for the second heat exchange cycle by the third heat exchange cycle is reduced, and the hot water in the second heat exchange cycle can still heat the materials in the drying cavity by exceeding the boiling point rise through the auxiliary heat, so that the low water content of the dry materials is effectively ensured.

Description

Technical Field

[0001] The invention relates to the field of environmental protection, and in particular to a three-circulation high-salt wastewater low-temperature scraper drying system and a working method thereof. Background Art

[0002] In recent years, due to the rigid demand for wastewater treatment and water reuse, membrane treatment technologies including reverse osmosis and nanofiltration have been widely used. The clear liquid from the membrane is reused as a clean water resource, while the concentrated liquid from the membrane contains high salt content and COD, total nitrogen and other substances that cannot be completely removed. After further concentration by evaporation or other methods, it cannot be formed into a solid by traditional crystallization. Therefore, drying technology becomes a good choice.

[0003] The current drying technologies for high-salt wastewater include evaporation drying technology, spray drying technology and drum drying technology. Among them, evaporation drying technology includes flue evaporation drying and bypass flue evaporation drying, which is mainly used in thermal power plants. It combines the heat of high-temperature flue gas for drying and has requirements for the use scenario. Spray drying technology requires that the high-salt wastewater be atomized and contacted with filtered and preheated air to evaporate the water quickly to obtain a dry solid. The use of this technology has high requirements for the surface tension, viscosity and other impurities in the high-salt water. Otherwise, the high-salt wastewater cannot form an atomized state, thus affecting the drying effect. Drum drying is divided into outer drum drying and inner drum drying. The heat source of outer drum drying is inside the drum, while the heat source of inner drum drying is in the outer jacket of the outer wall of the drum. The moisture of the high-salt wastewater in the outer drum is evaporated after contacting the rotating outer wall of the drum, while the high-salt wastewater in the inner drum is quickly evaporated in the drum through convection heat transfer and radiation heat transfer formed by the heat source in the outer wall jacket. With the development of technology, the focus has gradually been on inner drum scraper drying, which has lower water quality requirements for high-salt wastewater than spray drying, and higher thermal efficiency than outer drum scraper drying.

[0004] In order to further reduce energy consumption and make the device adapt to the use scenarios without steam heat source or thermal oil heat source, low-temperature heat pump drum scraper drying technology has gradually emerged. Patent No. CN211215519U invented a heat pump type low-temperature crystallizer, which combines heat pump and drying, and uses thermal medium to cool the secondary steam in the steam condensation chamber while obtaining heat. After further work by the refrigeration compressor, it becomes a high-temperature and high-pressure gas, and then returns to the jacket of the drum scraper to release heat to the wastewater to be evaporated and crystallized in the drum scraper, so that the water in the wastewater evaporates to form secondary steam that enters the steam condensation chamber. After releasing heat, the thermal medium becomes liquid, and after passing through the throttle valve, it becomes a low-temperature and low-pressure liquid and then returns to the steam condensation chamber to absorb the heat in the secondary steam. In this patent, the hot and cold cycles of the thermal medium realize the evaporation and drying of the wastewater and the condensation of the secondary steam, but there are also two major disadvantages: first, the jacket of the drum scraper is filled with high-temperature and high-pressure thermal medium, which is relatively sensitive, and requires a high pressure resistance level of the drum scraper equipment body, and the equipment manufacturing cost is high; second, as the evaporation of the material proceeds, the water molecules with high mobility on the surface of the material and the water molecules with high diffusion ability in the middle layer evaporate, and the water molecules in the innermost layer of the material have a low evaporation rate, and the amount of secondary steam formed in the drum scraper dryer gradually decreases, and the heat obtained by the thermal medium from the secondary steam in the condenser decreases accordingly, and the heat provided to the outer jacket of the drum scraper dryer is less, which ultimately leads to the dry material formed by drying still containing a high moisture content and cannot be completely dried. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, provide a three-circulation high-salt wastewater low-temperature scraper drying system and its working method, and solve the technical problems of high manufacturing cost and low drying quality of previous roller scraper equipment.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] First aspect:

[0008] Provide a three-cycle high-salt wastewater low-temperature scraper drying system, including

[0009] A drum scraper dryer, a steam condensation chamber, a condensate tank and a vacuum pump; the steam condensation chamber is connected to the drying chamber of the drum scraper dryer, the condensate tank is connected to the condensate outlet of the steam condensation chamber, the condensate tank outlet is connected to the water outlet pump, the vacuum pump is connected to the condensate tank, and the vacuum pump evacuates the drying chamber through the condensate tank and the steam condensation chamber;

[0010] A first heat exchange cycle, one heat exchange end of which is connected to the steam condensation chamber, and the other heat exchange end of which is connected to the third heat exchange cycle, wherein the first heat exchange cycle is suitable for exchanging heat absorbed by the steam condensation chamber to the third heat exchange cycle;

[0011] A second heat exchange cycle, one heat exchange end of which is connected to the water jacket of the drum scraper dryer, and the other heat exchange end of which is connected to the third heat exchange cycle, wherein the second heat exchange cycle is suitable for exchanging heat from the third heat exchange cycle to the water jacket;

[0012] The third heat exchange cycle has heat exchange ends on both sides connected to the first heat exchange cycle and the second heat exchange cycle respectively.

[0013] Further, the first heat exchange cycle includes a condenser, a first heat exchanger, a first circulation pipeline and a circulation pump;

[0014] The condenser is arranged in the steam condensation chamber, the condenser and the shell cavity of the first heat exchanger form a first circulation pipeline, and the circulation pump is arranged on the first circulation pipeline.

[0015] Furthermore, the second heat exchange cycle includes a second heat exchanger and a second circulation pipeline;

[0016] The second circulation pipeline is connected to the water jacket and the second heat exchanger shell cavity.

[0017] Furthermore, electric auxiliary heating is arranged on the second circulation pipeline.

[0018] Further, the third heat exchange cycle includes a first heat exchanger, a second heat exchanger, a compressor, a third circulation pipeline and a throttle valve;

[0019] The compressor and the throttle valve are arranged on a second circulation pipeline, and the second circulation pipeline is respectively connected to the tube cavity of the first heat exchanger and the tube cavity of the second heat exchanger.

[0020] Second aspect:

[0021] A working method of the above three-circulation high-salt wastewater low-temperature scraper drying system is provided, and the method is as follows:

[0022] Start the second heat exchange cycle, heat the water jacket by electric auxiliary heating, and start feeding into the drying chamber when the heating temperature rises to 55-65°C;

[0023] Start the vacuum pump and control the vacuum degree to 82-88%. The steam in the drying chamber is pumped into the steam condensation chamber for condensation through the vacuum pump, and the condensed water is pumped into the condensed water tank;

[0024] Start the first heat exchange cycle, adjust the flow rate of the heat exchange medium in the circulation pump so that the temperature range of the heat exchange medium entering the condenser is 30-40°C, and the temperature range of the heat exchange medium leaving the condenser is controlled at 40-50°C; the temperature range of the heat exchange medium entering the first heat exchanger is controlled at 40-50°C, and the temperature of the heat exchange medium leaving the first heat exchanger is controlled at 30-40°C;

[0025] Start the third heat exchange cycle, start the compressor and the throttle valve, control the temperature range of the heat exchange medium entering the first heat exchanger to be controlled at 25-30°C, and the temperature range of the heat exchange medium leaving the first heat exchanger to be controlled at 35-45°C; after the compressor does work, the temperature is controlled at 90-100°C;

[0026] Stop the electric auxiliary heating, and in the second heat exchange cycle, the temperature range of hot water entering the second heat exchanger is controlled at 55-65°C, and after heat exchange with the second heat exchanger, the temperature range of hot water leaving the second heat exchanger is controlled at 75-85°C;

[0027] Through the liquid level interlock of the outlet pump and the condensate tank, the liquid level of the condensate tank is controlled within the range of 30-80%;

[0028] The speed of the scraper in the drum scraper dryer is controlled at 4-10rpm. After the dry material is discharged, the moisture content is tested and the moisture content is controlled within 10% by adjusting the speed.

[0029] When the feeding is all finished, the boiling point of the material in the drum scraper dryer rises, and the secondary steam gradually decreases, the electric auxiliary heating is started again to keep the temperature of the hot water entering the water jacket in the second heat exchange cycle not lower than 80℃;

[0030] Finally, the compressor is stopped, the throttle valve is closed, and the third heat exchange cycle is stopped;

[0031] Stop the circulation pump and stop the first heat exchange cycle;

[0032] Stop the electric auxiliary heating and stop the second heat exchange cycle;

[0033] When all dry materials in the drum scraper dryer have been discharged, stop the vacuum pump.

[0034] The beneficial effects of the present invention are:

[0035] The three-circulation high-salt wastewater low-temperature scraper drying system of the present invention does not need to use traditional heat sources such as steam or heat-conducting oil, and can work only by powering on.

[0036] Avoiding the direct filling of expensive and highly sensitive thermal media into the jacket of the drum scraper dryer reduces the pressure resistance level and manufacturing difficulty of the drum scraper dryer equipment body.

[0037] When the system is started, electric auxiliary heating is used to heat the low-temperature hot water in the jacket, thus avoiding the problem of insufficient secondary steam in the startup phase causing the heater to provide too little heat to the thermal medium; and the automatic start of electric auxiliary heating in the shutdown phase can fully ensure that the boiling point of complex materials rises after concentration, even if the amount of secondary steam is gradually reduced.

[0038] The three heat exchange cycles work together, the heat of the first heat exchange cycle is reduced, and the heat provided to the second heat exchange cycle by the third heat exchange cycle is reduced. The hot water in the second heat exchange cycle can still heat the material in the drying chamber above the boiling point through auxiliary heat, thereby effectively ensuring a lower moisture content of the dry material. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention is further described below in conjunction with the accompanying drawings.

[0040] Figure 1 It is a schematic diagram of the three-circulation high-salt wastewater low-temperature scraper drying system of the present invention;

[0041] Among them, 1. Drum scraper dryer, 11. Water jacket, 2. Steam condensation chamber, 3. Condensate tank, 31. Water outlet pump, 4. Vacuum pump;

[0042] 51. a first heat exchanger, 52. a second heat exchanger;

[0043] 61. condenser, 62. circulation pump;

[0044] 71. Electric auxiliary heating;

[0045] 81. Compressor, 82. Throttle valve. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] The present application provides a three-circulation high-salt wastewater low-temperature scraper drying system, which is described in detail below. It should be noted that the description order of the following embodiments is not intended to limit the preferred order of the embodiments of the present application. In the following embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0048] In order to solve the technical problems of high manufacturing cost and low drying quality of the roller scraper equipment in the prior art, an embodiment of the present application provides a three-circulation high-salinity wastewater low-temperature scraper drying system, which is described in detail below.

[0049] like Figure 1 As shown, a three-circulation high-salinity wastewater low-temperature scraper drying system includes

[0050] A drum scraper dryer 1, a steam condensation chamber 2, a condensed water tank 3 and a vacuum pump 4; the steam condensation chamber 2 is connected to the drying chamber of the drum scraper dryer 1, the condensed water tank 3 is connected to the condensed water outlet of the steam condensation chamber 2, the outlet of the condensed water tank 3 is connected to the water outlet pump 31, the vacuum pump 4 is connected to the condensed water tank 3, and the vacuum pump 4 evacuates the drying chamber through the condensed water tank 3 and the steam condensation chamber 2;

[0051] A first heat exchange cycle, one heat exchange end of which is connected to the steam condensation chamber 2, and the other heat exchange end of which is connected to the third heat exchange cycle, wherein the first heat exchange cycle is suitable for exchanging the heat absorbed by the steam condensation chamber 2 to the third heat exchange cycle;

[0052] A second heat exchange cycle, one heat exchange end of which is connected to the water jacket 11 of the drum scraper dryer 1, and the other heat exchange end of which is connected to the third heat exchange cycle, wherein the second heat exchange cycle is suitable for exchanging heat from the third heat exchange cycle to the water jacket 11;

[0053] The third heat exchange cycle has heat exchange ends on both sides connected to the first heat exchange cycle and the second heat exchange cycle respectively.

[0054] Specifically, as an optional implementation in this embodiment, Figure 1 As shown, the first heat exchange cycle includes a condenser 61, a first heat exchanger 51, a first circulation pipeline and a circulation pump 62;

[0055] The condenser 61 is disposed in the steam condensation chamber 2 . The condenser 61 and the shell cavity of the first heat exchanger 51 form a first circulation pipeline. The circulation pump 62 is disposed on the first circulation pipeline.

[0056] In this embodiment, the heat exchange medium in the first circulation pipeline is a mixed refrigerant of R410A, R452B, and R454B.

[0057] When the drum scraper drying is in operation, the steam generated by the waste water in the drying chamber enters the steam condensation chamber 2, and is liquefied into condensed water after encountering the condenser 61. While condensing the secondary steam, the condenser 61 absorbs the heat of the secondary steam and turns it into high-temperature water, which is transmitted to the first heat exchanger 51. In the first heat exchanger 51, the heat is released to the heat exchange medium and the self-cooling is completed, turning it into low-temperature water. The low-temperature water flows back to the condenser 61 under the action of the circulation pump 62.

[0058] After being cooled in the steam condensation chamber 2, the secondary steam becomes condensed water and flows from the bottom of the steam condensation chamber 2 to the condensed water tank, and is transported to the reuse point through the outlet pump 31.

[0059] The vacuum degree in the scraper drum dryer 1 is adjusted using a vacuum pump 4. The vacuum degree in the condensed water tank is connected to the vacuum degree in the steam condensation chamber 2 and the drying chamber, and the vacuum degree is adjusted to about 85%, so that the evaporation temperature of the waste water in the scraper drum dryer 1 is controlled at about 60°C.

[0060] Specifically, as an optional implementation in this embodiment, Figure 1 As shown, the second heat exchange cycle includes a second heat exchanger 52 and a second circulation pipeline;

[0061] The second circulation pipeline is connected to the water jacket 11 and the shell cavity of the second heat exchanger 52 .

[0062] The heat exchange medium in the second circulation pipeline is water.

[0063] The hot water in the water jacket 11 heats the material inside the drum scraper dryer 1 and becomes low-temperature hot water, which exchanges heat with the heat exchange medium that absorbs heat in the first heat exchange cycle through the second heat exchanger 52. The heat exchange medium releases heat in the second heat exchanger 52, and the low-temperature hot water becomes high-temperature hot water and returns to the water jacket 11 of the drum scraper dryer 1 to provide heat for the internal material.

[0064] Specifically, as an optional implementation in this embodiment, Figure 1 As shown, the second circulation pipeline is provided with electric auxiliary heating 71.

[0065] Specifically, as an optional implementation in this embodiment, Figure 1 As shown, the third heat exchange cycle includes a first heat exchanger 51, a second heat exchanger 52, a compressor 81, a third circulation pipeline and a throttle valve 82;

[0066] The compressor 81 and the throttle valve 82 are arranged on a second circulation pipeline, and the second circulation pipeline is connected to the tube cavity of the first heat exchanger 51 and the tube cavity of the second heat exchanger 52 respectively.

[0067] The heat exchange medium in the third circulation pipeline is a mixed refrigerant of R410A, R452B, and R454B.

[0068] Energy cycle of the heat exchange medium: the heat exchange medium absorbs the heat of the high-temperature water in the first heat exchange cycle in the first heat exchanger 51 and then becomes a high-temperature and high-pressure gas after work is done by the compressor 81. The heat exchange medium heats the low-temperature hot water in the second heat exchange cycle in the second heat exchanger 52 and then becomes a low-temperature and low-pressure liquid. After passing through the throttle valve 82, the heat exchange medium returns to the first heat exchange cycle to absorb the heat of the high-temperature water in the first heat exchange cycle.

[0069] During the startup and shutdown stages of the drum scraper drying equipment, electric auxiliary heating 71 is used to heat the low-temperature hot water in the jacket, thereby avoiding the problem of insufficient secondary steam in the startup stage causing the first heat exchanger 51 to provide too little heat to the heat exchange medium. Starting the electric auxiliary heating 71 during the shutdown stage can fully ensure that after the boiling point of the material is increased after concentration, the water molecules with a low evaporation rate in the innermost layer of the material cannot be evaporated due to lack of sufficient heat, thereby causing the dry material to have too high a moisture content.

[0070] Taking 5t / d feed rate as an example, the specific working method of the present invention is as follows:

[0071] The second heat exchange cycle is started, and the water jacket 11 is heated by the electric auxiliary heat 71. When the heating temperature rises to 55-65°C, the material is fed into the drying chamber; the feeding amount is 250-300 kg / h.

[0072] Start the vacuum pump 4, control the vacuum degree to 82-88%, and pump the steam in the drying chamber into the steam condensation chamber 2 through the vacuum pump 4 for condensation, and the condensed water is pumped into the condensed water tank 3;

[0073] Start the first heat exchange cycle, adjust the flow rate of the heat exchange medium in the circulation pump 62, so that the temperature range of the heat exchange medium entering the condenser 61 is 30-40°C, and the temperature range of the heat exchange medium leaving the condenser 61 is controlled at 40-50°C; the temperature range of the heat exchange medium entering the first heat exchanger 51 is controlled at 40-50°C, and the temperature of the heat exchange medium leaving the first heat exchanger 51 is controlled at 30-40°C;

[0074] Start the third heat exchange cycle, start the compressor 81 and the throttle valve 82, control the temperature range of the heat exchange medium entering the first heat exchanger 51 to be controlled at 25-30°C, and the temperature range of the heat exchange medium leaving the first heat exchanger 51 to be controlled at 35-45°C; after the compressor 81 does work, the temperature is controlled at 90-100°C;

[0075] The electric auxiliary heating 71 is stopped, and the temperature range of the hot water entering the second heat exchanger 52 in the second heat exchange cycle is controlled to be 55-65° C., and after heat exchange with the second heat exchanger 52, the temperature range of the hot water leaving the second heat exchanger 52 is controlled to be 75-85° C.;

[0076] Through the liquid level interlock of the water outlet pump 31 and the condensate tank, the liquid level of the condensate tank is controlled to be in the range of 30-80%;

[0077] The speed of the scraper in the drum scraper dryer 1 is controlled at 4-10 rpm. After the dry material is discharged, the moisture content is tested and the moisture content is controlled within 10% by adjusting the speed.

[0078] When the feeding is all finished, the boiling point of the material in the drum scraper dryer 1 increases, and the secondary steam gradually decreases, the electric auxiliary heat 71 is started again to keep the temperature of the hot water entering the water jacket 11 in the second heat exchange cycle not lower than 80°C;

[0079] Finally, stop the compressor 81, close the throttle valve 82, and stop the third heat exchange cycle.

[0080] Stop the circulation pump 62 and stop the first heat exchange cycle.

[0081] Stop the electric auxiliary heating 71 and stop the second heat exchange cycle.

[0082] When all the dry materials in the drum scraper dryer 1 are completely discharged, stop the vacuum pump 4.

[0083] For each device selected in this application, the components without specific structures described are all common standard components or components known to those skilled in the art. Their structures and principles can all be learned by those skilled in the art through technical manuals or obtained through conventional experimental methods.

[0084] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can 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 according to specific situations.

[0085] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0086] In several embodiments provided by the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there can be other division methods. For another example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some communication interfaces. The indirect coupling or communication connection of the devices or units can be in an electrical, mechanical, or other forms.

[0087] The unit described as a separation component may or may not be physically separated. The component shown as a unit may or may not be a physical unit, that is, it may be located in one place or distributed across multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0088] In addition, each functional unit in various embodiments of the present invention may be integrated in a processing unit, may exist separately as individual physical units, or two or more units may be integrated in one unit.

[0089] Based on the ideal embodiments of the present invention as described above, 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 three-cycle high-salt wastewater low-temperature scraper drying system, characterized in that: include A roller scraper dryer (1), a steam condensation chamber (2), a condensate tank (3) and a vacuum pump (4); the steam condensation chamber (2) is connected to the drying chamber of the roller scraper dryer (1), the condensate tank (3) is connected to the condensate outlet of the steam condensation chamber (2), the outlet of the condensate tank (3) is connected to a water outlet pump (31), the vacuum pump (4) is connected to the condensate tank (3), and the vacuum pump (4) evacuates the drying chamber through the condensate tank (3) and the steam condensation chamber (2); a first heat exchange cycle, one heat exchange end of which is connected to the steam condensation chamber (2) and the other heat exchange end of which is connected to the third heat exchange cycle, wherein the first heat exchange cycle is suitable for exchanging heat absorbed by the steam condensation chamber (2) to the third heat exchange cycle; a second heat exchange cycle, one heat exchange end of which is connected to the water jacket (11) of the drum scraper dryer (1), and the other heat exchange end of which is connected to the third heat exchange cycle, wherein the second heat exchange cycle is suitable for exchanging heat from the third heat exchange cycle to the water jacket (11); The third heat exchange cycle has heat exchange ends on both sides connected to the first heat exchange cycle and the second heat exchange cycle respectively.

2. A three-circulation high-salinity wastewater low-temperature scraper drying system according to claim 1, characterized in that: The first heat exchange cycle comprises a condenser (61), a first heat exchanger (51), a first circulation pipeline and a circulation pump (62); The condenser (61) is arranged in the steam condensation chamber (2), the condenser (61) and the shell cavity of the first heat exchanger (51) form a first circulation pipeline, and the circulation pump (62) is arranged on the first circulation pipeline.

3. A three-circulation high-salt wastewater low-temperature scraper drying system according to claim 1, characterized in that: The second heat exchange cycle includes a second heat exchanger (52) and a second circulation pipeline; The second circulation pipeline is connected to the water jacket (11) and the shell cavity of the second heat exchanger (52).

4. A three-circulation high-salinity wastewater low-temperature scraper drying system according to claim 3, characterized in that: The second circulation pipeline is provided with electric auxiliary heating (71).

5. A three-circulation high-salinity wastewater low-temperature scraper drying system according to claim 1, characterized in that: The third heat exchange cycle comprises a first heat exchanger (51), a second heat exchanger (52), a compressor (81), a third circulation pipeline and a throttle valve (82); The compressor (81) and the throttle valve (82) are arranged on a second circulation pipeline, and the second circulation pipeline is respectively connected to the tube cavity of the first heat exchanger (51) and the tube cavity of the second heat exchanger (52).

6. The working method of the three-circulation high-salinity wastewater low-temperature scraper drying system according to any one of claims 1 to 5, characterized in that the method as follows: The second heat exchange cycle is started, and the water jacket (11) is heated by the electric auxiliary heat (71). When the heating temperature rises to 55-65° C., the material is fed into the drying chamber; The vacuum pump (4) is started to control the vacuum degree to be 82-88%, and the steam in the drying chamber is pumped into the steam condensation chamber (2) through the vacuum pump (4) for condensation, and the condensed water is pumped into the condensed water tank (3); Starting the first heat exchange cycle, adjusting the flow rate of the heat exchange medium in the circulation pump (62) so that the temperature of the heat exchange medium entering the condenser (61) is in the range of 30 to 40° C., and the temperature of the heat exchange medium exiting the condenser (61) is controlled in the range of 40 to 50° C.; the temperature of the heat exchange medium entering the first heat exchanger (51) is controlled in the range of 40 to 50° C., and the temperature of the heat exchange medium exiting the first heat exchanger (51) is controlled in the range of 30 to 40° C.; Starting the third heat exchange cycle, starting the compressor (81) and the throttle valve (82), controlling the temperature range of the heat exchange medium entering the first heat exchanger (51) to be controlled within 25 to 30° C., and the temperature range of the heat exchange medium exiting the first heat exchanger (51) to be controlled within 35 to 45° C.; and controlling the temperature of the heat exchange medium after the compressor (81) does work to be controlled within 90 to 100° C.; The electric auxiliary heating (71) is stopped, and the temperature range of the hot water entering the second heat exchanger (52) in the second heat exchange cycle is controlled to be 55-65° C., and after heat exchange with the second heat exchanger (52), the temperature range of the hot water leaving the second heat exchanger (52) is controlled to be 75-85° C.; The liquid level of the condensate tank is controlled within a range of 30 to 80% by interlocking the liquid level of the water outlet pump (31) and the condensate tank; The speed of the scraper in the drum scraper dryer (1) is controlled at 4 to 10 rpm. After the dry material is discharged, the moisture content is tested and the moisture content is controlled within 10% by adjusting the speed. When the feeding is completed, the boiling point of the material in the drum scraper dryer (1) increases, and the secondary steam gradually decreases, the electric auxiliary heating (71) is started again to maintain the temperature of the hot water entering the water jacket (11) in the second heat exchange cycle not less than 80°C; Finally, the compressor (81) is stopped, the throttle valve (82) is closed, and the third heat exchange cycle is stopped; Stopping the circulation pump (62) to stop the first heat exchange cycle; Stop the electric auxiliary heating (71) and stop the second heat exchange cycle; When all the dry materials in the scraper drum dryer (1) have been discharged, the vacuum pump (4) is stopped.

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