Triple-effect evaporation treatment device and method for salt-containing sewage

Abstract

The invention discloses a triple-effect evaporation treatment device and method for salt-containing sewage, and belongs to the technical field of sewage chemical treatment. The invention relates to a triple-effect evaporation treatment device for salt-containing sewage. The triple-effect evaporation treatment device comprises an external heat source, and a first-effect reaction unit, a second-effect reaction unit and a triple-effect reaction unit which are connected in sequence, the first-effect reaction unit is provided with a first-effect evaporation chamber, the second-effect reaction unit is provided with a second-effect evaporation chamber, the third-effect reaction unit is provided with a third-effect evaporation chamber, and the first-effect evaporation chamber is connected with an external heat source to evaporate sewage; the first-effect reaction unit is one or two of the first-effect reaction unit, the second-effect reaction unit and the third-effect reaction unit, the heater is arranged in an evaporation chamber of the first-effect reaction unit, the heater is approximately annular, and an area enclosed by the annular heater is a first area; the annular heater and the inner wall of the evaporation chamber form a second area; and the first region is communicated with the second region. Self-circulation of sewage in the evaporation chamber is realized, the evaporation rate and the heat transfer rate are high, the energy consumption is low, the equipment manufacturing is simple, and the like.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and more specifically to a triple-effect evaporation treatment device and method for saline sewage. Background Art

[0002] The saline wastewater produced in industrial production usually has the characteristics of high salt, high COD and poor material fluidity. The salt concentration can reach 10% to 13%, and the COD concentration can reach 50,000 to 60,000 mg / L. If the wastewater is not effectively treated and discharged directly, it is easy to cause serious pollution to the environment. Multi-effect evaporation is a treatment equipment that uses the secondary steam generated by the previous evaporation as the heat source for the next evaporation. It is widely used in the treatment of high-salt wastewater in the fields of chemical industry, pharmaceutical industry, etc. The current multi-effect evaporator usually has the characteristics of high operating energy consumption and slow evaporation rate.

[0003] The Chinese patent with the publication number CN211971803U discloses a novel three-effect evaporation system for physical and chemical wastewater, in which the three-effect evaporation system is a countercurrent evaporation, including a first-effect evaporator, a second-effect evaporator and a third-effect evaporator, and a first-effect separator, a second-effect separator and a third-effect separator are provided accordingly. A forced circulation pump is provided between each first-effect evaporator and the corresponding separator so that the liquid material circulates between the separator and the evaporator and boils and evaporates in the evaporator. When the liquid material evaporates to a set concentration, the liquid material in the separator is transported to the next-effect separator by a discharge pump. Then, the liquid material is evaporated by circulating boiling between the next-effect evaporator and the separator. This cycle is repeated until the three-effect evaporation is completed to complete the concentration and crystallization of the liquid material.

[0004] However, in the above technical solution, each effect evaporator and the corresponding separator are separately arranged, and liquid circulation is realized by a forced circulation pump. In the application, the evaporator plays the role of a heater, and the heating chamber in the evaporator is shell-side heating, and the separator plays the role of an evaporation chamber. Therefore, when evaporating in each effect, there will be problems such as slow evaporation rate and poor heat transfer rate; under the action of the forced circulation pump, the liquid circulates between the evaporator and the separator of each effect to evaporate and concentrate, which will cause the problem of increased energy consumption of the forced circulation pump, resulting in an increase in the overall energy consumption of the three-effect evaporator. Summary of the invention

[0005] 1. Technical problem to be solved by the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art that the evaporation rate of materials in the evaporator is slow and the overall operating energy consumption of the triple-effect evaporator is high, and to provide a triple-effect evaporation treatment device for saline sewage, which can realize the self-circulation of sewage in the evaporation chamber, improve the evaporation rate and heat transfer rate of the wastewater, and reduce the overall operating energy consumption of the device.

[0007] 2. Technical solution

[0008] In order to achieve the above object, the technical solution provided by the present invention is:

[0009] A triple-effect evaporation treatment device for saline wastewater of the present invention comprises an external heat source and a reaction unit;

[0010] The reaction unit comprises a first-effect reaction unit, a second-effect reaction unit, and a third-effect reaction unit connected in sequence;

[0011] The first-effect reaction unit is provided with a first-effect evaporation chamber, the second-effect reaction unit is provided with a second-effect evaporation chamber, and the third-effect reaction unit is provided with a third-effect evaporation chamber; the salt-containing sewage is transported into the second-effect evaporation chamber via the third-effect evaporation chamber, and then transported into the first-effect evaporation chamber from the second-effect evaporation chamber;

[0012] The first-effect reaction unit further comprises a first-effect heater, which is arranged outside the first-effect evaporation chamber, and the saline wastewater is transported from the first-effect evaporation chamber to the first-effect heater, and then transported from the first-effect heater to the first-effect evaporation chamber;

[0013] The first-effect heater is connected to an external heat source, and the first-effect evaporation chamber evaporates to generate secondary steam, and the secondary steam acts on the evaporation of sewage in the second-effect evaporation chamber;

[0014] The second-effect evaporation chamber evaporates to generate secondary steam, and the secondary steam acts on the evaporation of sewage in the third-effect evaporation chamber;

[0015] Any one or both of the two-effect reaction unit and the three-effect reaction unit further comprises a heater disposed inside the evaporation chamber thereof;

[0016] The heater is roughly annular, and the area enclosed by the annular heater is the first area;

[0017] The annular heater and the inner wall of the evaporation chamber form a second area;

[0018] The first region is connected to the second region.

[0019] It should be noted that when the sewage is heated and evaporated in the evaporation chamber, the sewage can circulate between the edge of the heater body and the center of the heater in the first area, and can also circulate between the center of the heater in the first area and the second area; thereby, the kinetic energy consumption of external circulation heating by a water pump in traditional sewage multi-effect evaporation treatment is eliminated; moreover, the secondary steam directly heats the sewage in the evaporation chamber, avoiding the heat loss of the traditional external heater, and achieving high energy utilization.

[0020] Furthermore, the three-effect evaporation chamber includes a liquid inlet and a liquid outlet;

[0021] The second-effect evaporation chamber comprises a liquid inlet and a liquid outlet;

[0022] The first-effect evaporation chamber comprises a first liquid inlet, a second liquid inlet and a liquid outlet;

[0023] Wherein, the liquid outlet of the three-effect evaporation chamber is connected to the liquid inlet of the two-effect evaporation chamber, and the liquid outlet of the two-effect evaporation chamber is connected to the liquid inlet of the one-effect evaporation chamber;

[0024] The liquid outlet of the first-effect evaporation chamber is connected to a first-effect heater;

[0025] The second liquid inlet of the first-effect evaporation chamber is connected to the first-effect heater.

[0026] Furthermore, a three-effect material transfer pump is connected between the liquid outlet of the three-effect evaporation chamber and the liquid inlet of the two-effect evaporation chamber;

[0027] A second-effect material transfer pump is connected between the liquid outlet of the second-effect evaporation chamber and the liquid inlet of the first-effect evaporation chamber.

[0028] Furthermore, a heater is provided inside the three-effect evaporation chamber, and the heater is a three-effect heater; a heater is provided inside the two-effect evaporation chamber, and the heater is a two-effect heater;

[0029] The three-effect evaporation chamber includes an air outlet;

[0030] The second-effect evaporation chamber includes an air outlet;

[0031] The first-effect evaporation chamber includes an air outlet;

[0032] The triple-effect heater comprises an air inlet and an air outlet;

[0033] The two-effect heater includes an air inlet and an air outlet;

[0034] The single-effect heater comprises a liquid inlet and a liquid outlet, an air inlet and an air outlet;

[0035] The air inlet of the three-effect heater is connected to the air outlet of the two-effect evaporation chamber, and the air inlet of the two-effect heater is connected to the air outlet of the one-effect evaporation chamber; the air inlet of the one-effect heater is connected to an external heat source;

[0036] The liquid inlet of the first-effect heater is connected to the liquid outlet of the first-effect evaporation chamber;

[0037] The liquid outlet of the first-effect heater is connected to the second liquid inlet of the first-effect evaporation chamber.

[0038] Furthermore, the single-effect reaction unit further comprises a single-effect circulation pump and a discharge pump;

[0039] The first-effect circulation pump is arranged between the liquid outlet of the first-effect evaporation chamber and the liquid inlet of the first-effect heater;

[0040] The liquid outlet of the first-effect evaporation chamber is also connected to a discharge pump.

[0041] Furthermore, the exteriors of the first-effect evaporation chamber, the second-effect evaporation chamber, and the third-effect evaporation chamber are respectively provided with shell heating layers;

[0042] The shell heating layer comprises an air inlet and an air outlet, and the air inlet is connected to an external heat source.

[0043] Furthermore, the outsides of the first-effect evaporation chamber, the second-effect evaporation chamber and the third-effect evaporation chamber are respectively provided with a first-effect shell heating layer, a second-effect shell heating layer and a third-effect shell heating layer;

[0044] The first-effect shell heating layer includes an air inlet and an air outlet; the air inlet is connected to an external heat source.

[0045] The two-effect shell heating layer includes an air inlet and an air outlet;

[0046] The three-effect shell heating layer includes an air inlet and an air outlet;

[0047] The air inlet of the first-effect shell heating layer, the air inlet of the second-effect shell heating layer and the air inlet of the third-effect shell heating layer are all connected to an external heat source.

[0048] Furthermore, the device also includes a gas-liquid separation unit, and the gas-liquid separation unit includes a second-effect gas-liquid separation tank and a third-effect gas-liquid separation tank;

[0049] The liquid inlet of the second-effect gas-liquid separation tank is connected to the gas outlet of the second-effect heater, the liquid outlet of the second-effect gas-liquid separation tank is connected to the liquid inlet of the triple-effect gas-liquid separation tank, and the gas outlet of the second-effect gas-liquid separation tank is connected to the gas inlet of the triple-effect heater.

[0050] Further, the device also includes a preheating unit, and the preheating unit includes a preheater and a feed pump;

[0051] The feed pump comprises a liquid inlet and a liquid outlet;

[0052] The preheater comprises a liquid inlet, a liquid outlet, a preheating liquid inlet and a preheating liquid outlet;

[0053] The liquid inlet of the feed pump is connected to the saline sewage, and the liquid outlet of the feed pump is connected to the liquid inlet of the preheater;

[0054] The liquid outlet of the preheater is connected to the liquid inlet of the triple-effect evaporation chamber;

[0055] The air outlet of the shell heating layer is connected to the preheating liquid inlet of the preheater;

[0056] The gas outlet of the first-effect heater is connected to the preheating liquid inlet of the preheater.

[0057] Furthermore, the preheating liquid inlet of the preheater is connected to the gas outlets of the first-effect heater, the first-effect shell heating layer, the second-effect shell heating layer and the third-effect shell heating layer.

[0058] Furthermore, the device also includes a condensing unit, which includes a condenser, a water tank, an air pumping device and a water pumping device;

[0059] The gas inlet of the condenser is connected to the gas outlet of the three-effect evaporation chamber and the gas outlet of the three-effect gas-liquid separation tank, and the condenser is connected to the water tank;

[0060] The liquid inlet of the water tank is connected to the liquid outlet of the triple-effect gas-liquid separation tank, and the liquid outlet of the water tank is connected to the pumping equipment;

[0061] The water tank is also provided with an air extraction device.

[0062] The present invention also provides a method for using a triple-effect evaporation treatment device for saline wastewater, comprising the following steps:

[0063] S1. Before the device starts evaporation, inject the salty sewage into the three-effect evaporation chamber, the second-effect evaporation chamber and the first-effect evaporation chamber in sequence to the 1 / 2 to 3 / 4 liquid level of each effect evaporation chamber;

[0064] S2, start the first-effect circulation pump, and adjust the flow rate of the outlet pipe of the first-effect circulation pump to 1-2m / s;

[0065] S3, start the operation of the condenser;

[0066] S4. Turn on the exhaust equipment to exhaust the air in the system and control the pressure of the evaporation system at -0.5~-0.05MPa;

[0067] S5. Turn on the raw steam for heating, control the sewage temperature in the first-effect evaporation chamber to 95-100°C, control the sewage temperature in the second-effect evaporation chamber to 85-95°C, and control the sewage temperature in the third-effect evaporation chamber to 80-90°C.

[0068] 3. Beneficial effects

[0069] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0070] (1) An annular heater is provided inside the evaporation chamber in the two-effect reaction unit or the three-effect reaction unit of the present invention, wherein a first area is formed inside the heater; the heater and the inner wall of the evaporation chamber form a second area; the first area and the second area are connected, and when treating sewage, a large amount of low-temperature sewage in the evaporation chamber quickly and over a large area exchanges heat with the secondary steam in the heater through the tube wall, resulting in a faster heat transfer rate, and sewage close to the heater body quickly heats up and has a lower density, while sewage far from the heater heats up slowly and has a higher density, thereby forming a density difference of sewage at different parts inside the evaporation chamber, thereby realizing self-circulation of sewage inside the evaporation chamber, that is, the sewage circulates between the edge of the heater body in the first area and the center of the heater, and can also circulate between the center of the heater in the first area and the second area, thereby eliminating the kinetic energy consumption of external circulation heating by a water pump in the traditional sewage multi-effect evaporation treatment; moreover, the secondary steam directly heats the sewage in the evaporation chamber, thereby avoiding the heat loss of the traditional external heater, and achieving high energy utilization.

[0071] (2) The provision of the shell heating layer of the present invention expands the heat exchange area of ​​the evaporated sewage. The shell heating layer uses fresh steam, the sewage temperature difference is large, the heat exchange speed is fast, and the evaporation power is sufficient, ensuring the stability of the evaporation system. Moreover, in the form of heating of the evaporation chamber shell, the sewage near the evaporation chamber shell is quickly heated up and the density decreases; the sewage far from the evaporation chamber shell is heated up slowly and has a high density; the density difference between different parts of the sewage is generated, which enhances the effect of the sewage self-circulating between the center of the heater in the first area and the second area, eliminating the kinetic energy consumption of the traditional external circulation. Moreover, when the heat of the secondary steam does not meet the heating and evaporation of the sewage in the second-effect evaporation chamber or the third-effect evaporation chamber, it can also provide heat to the evaporation chamber to ensure normal evaporation of the sewage.

[0072] (3) By setting up a second-effect gas-liquid separation tank, the non-condensable gas in the condensate of the second-effect heater is further transported to the third-effect heater to heat the sewage, thus achieving deep utilization of waste heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a structural schematic diagram of a triple-effect evaporation treatment device for saline wastewater in the present invention;

[0074] Figure 2 It is a top cross-sectional schematic diagram of a second-effect evaporation chamber and a second-effect heater in a three-effect evaporation treatment device for saline wastewater in the present invention;

[0075] Figure 3 The present invention is a schematic structural diagram of another second-effect evaporation chamber and a second-effect heater in a three-effect evaporation treatment device for saline wastewater.

[0076] Explanation of the symbols in the schematic diagram:

[0077] 101. Feed pump; 102. Preheater;

[0078] 201, first-effect evaporation chamber; 202, first-effect heater; 203, first-effect circulation pump; 204, discharge pump; 205, first-effect shell heating layer; 206, first-effect heating steam valve; 207, first-effect shell heating steam valve;

[0079] 301, second-effect evaporation chamber; 302, second-effect heater; 3021, annular pipe; 3022, tube array; 303, second-effect material transfer pump; 304, second-effect shell heating layer; 305, second-effect gas-liquid separation tank; 306, second-effect shell heating steam valve;

[0080] 401, triple-effect evaporation chamber; 402, triple-effect heater; 403, triple-effect material transfer pump; 404, triple-effect shell heating layer; 405, triple-effect gas-liquid separation tank; 406, triple-effect shell heating steam valve;

[0081] 501. Condenser; 502. Water tank; 503. Air extraction equipment; 504. Water pumping equipment; 505. Circulating water supply valve; 506. Circulating water return valve. DETAILED DESCRIPTION

[0082] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.

[0083] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and so on quoted in this specification are only for the convenience of description, and are not used to limit the scope of implementation. The change or adjustment of their relative relationship should also be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0084] The present invention will be further described below in conjunction with the embodiments.

[0085] Example

[0086] Combination Figure 1 and Figure 2, a triple-effect evaporation treatment device for saline sewage of the present invention comprises an external heat source and a reaction unit, wherein the reaction unit comprises a first-effect reaction unit, a second-effect reaction unit, and a third-effect reaction unit connected in sequence, and further comprises a preheating unit and a condensing unit connected to the third-effect reaction unit. In this embodiment, the external heat source is raw steam. The raw steam enters the first-effect reaction unit, and the saline sewage enters the third-effect reaction unit after being preheated by the preheating unit, which is countercurrent heating evaporation. Specifically, the salt in the saline sewage can be sulfate, chloride, etc., and the mass concentration of the salt in the saline sewage is generally 2% to 15%. The corresponding salt can be obtained after the saline sewage passes through the multi-effect evaporation of the treatment device. As an optional embodiment, the salt in the saline sewage can be any one of sulfate and chloride, for example, potassium sulfate. As another optional embodiment, the saline sewage can also be saline sewage containing organic matter. The first-effect reaction unit is provided with a first-effect evaporation chamber 201, the second-effect reaction unit is provided with a second-effect evaporation chamber 301, and the third-effect reaction unit is provided with a third-effect evaporation chamber 401; the saline wastewater is transported into the second-effect evaporation chamber 301 through the third-effect evaporation chamber 401, and then transported into the first-effect evaporation chamber 201 from the second-effect evaporation chamber 301. A second-effect transfer pump 303 is connected between the liquid inlet 1 of the first-effect evaporation chamber 201 and the liquid outlet of the second-effect evaporation chamber 301; a third-effect transfer pump 403 is connected between the liquid inlet of the second-effect evaporation chamber 301 and the liquid outlet of the third-effect evaporation chamber 401, and the second-effect transfer pump 303 and the third-effect transfer pump 403 are used to transport wastewater.

[0087] Any one or two of the two-effect reaction unit and the three-effect reaction unit also includes a heater arranged inside the evaporation chamber. The heater is roughly annular, and the area surrounded by the annular heater is the first area; the annular heater and the inner wall of the evaporation chamber form the second area; the first area and the second area are connected. When the sewage is heated and evaporated in the evaporation chamber, a large amount of low-temperature sewage in the evaporation chamber quickly and widely exchanges heat with the secondary steam in the heater through the tube wall, and the heat transfer rate is faster. The sewage close to the heater body heats up quickly and the density decreases. The sewage away from the heater heats up slowly and has a higher density. Therefore, a density difference of sewage is formed in different parts of the evaporation chamber, and the self-circulation of sewage in the evaporation chamber is realized. The sewage can circulate between the edge of the heater body in the first area and the center of the heater, and can also circulate between the center of the heater in the first area and the second area; the kinetic energy consumption of the external circulation heating of the water pump in the traditional sewage multi-effect evaporation treatment is eliminated; moreover, the secondary steam directly heats the sewage in the evaporation chamber, avoiding the heat loss of the traditional external heater, and the energy utilization rate is high. As an optional embodiment, the annular heater can be a spiral coil heater or a tube heater.

[0088] The first-effect reaction unit includes a first-effect heater 202, a first-effect evaporation chamber 201, a first-effect circulation pump 203 and a discharge pump 204. The first-effect heater 202 is arranged outside the first-effect evaporation chamber 201. The raw steam is connected to the air inlet of the first-effect heater 202 through a pipeline, and a first-effect heating steam valve 206 is arranged on the pipeline to control the introduction, closing and flow rate of the raw steam; the liquid outlet of the first-effect heater 202 is connected to the second liquid inlet of the first-effect evaporation chamber 201, and the liquid outlet of the first-effect evaporation chamber 201 is connected to the inlet of the first-effect circulation pump 203, and the outlet of the first-effect circulation pump 203 is connected to the liquid inlet at the bottom of the first-effect heater 202. Through the first-effect circulation pump 203, the circulating heating and evaporation of sewage in the first-effect evaporation chamber 201 and the first-effect heater 202 is realized.

[0089] The liquid outlet of the first-effect evaporation chamber 201 is also connected to a discharge pump 204. Furthermore, the inlet end of the discharge pump 204 can be connected to the inlet main pipe of the first-effect circulation pump 203. A concentration detector is provided in the first-effect evaporation chamber 201. When the salt concentration in the sewage is detected to reach a set value, which is usually the critical saturation point of the salt concentration, the discharge pump 204 automatically discharges part of the mother liquid to the drying treatment section, and then the second-effect transfer pump 303 automatically replenishes part of the liquid to the first-effect evaporation chamber 201. On the other hand, the third-effect transfer pump 403 will also automatically replenish part of the liquid to the second-effect evaporation chamber 301, and then the feed pump 101 in the preheating unit will also automatically replenish part of the liquid to the third-effect evaporation chamber 401.

[0090] The sewage entering the first-effect evaporation chamber 201 has a high salt concentration and a high COD concentration; during the continuous cycle heating evaporation process, the concentration of materials such as salt and organic matter in the sewage is even higher, and crystallized salt and organic matter are prone to adhere to the wall. The first-effect heater 202 is arranged outside the first-effect evaporation chamber 201, and is used in conjunction with the first-effect evaporation chamber 201 to prevent the precipitated crystal salt and organic matter from adhering to the heater and calcium ions or magnesium ions from scaling on the heater, thereby affecting the heat transfer rate of the heater. As a specific implementation, the first-effect heater 202 can adopt a shell-and-tube heat exchanger.

[0091] The second-effect reaction unit includes a second-effect transfer pump 303, a second-effect evaporation chamber 301 and a second-effect heater 302 arranged in the second-effect evaporation chamber 301, and the second-effect heater 302 is a ring heater. The air outlet of the first-effect evaporation chamber 201 is connected to the air inlet of the second-effect heater 302, and the secondary steam generated by evaporation in the first-effect evaporation chamber 201 is passed into the second-effect heater 302 to heat the sewage in the second-effect evaporation chamber 301. A liquid level gauge is provided in the second-effect evaporation chamber 301. When the liquid level in the second-effect evaporation chamber 301 decreases, the three-effect transfer pump 403 automatically starts to replenish the material to the set value. As an optional embodiment, the second-effect heater 302 is coaxially arranged with the second-effect evaporation chamber 301, so that the circulation flow of the sewage is more uniform. As another optional embodiment, when the sewage is treated in the second-effect evaporation chamber 301, the second-effect heater 302 should be located in the sewage. Specifically, when sewage is treated in the second-effect evaporation chamber 301 , the liquid level of the sewage is located at 1 / 2 to 3 / 4 of the liquid level of the second-effect evaporation chamber 301 , and the second-effect heater 302 should always be below the sewage liquid level in the evaporation chamber.

[0092] The triple-effect reaction unit includes a triple-effect transfer pump 403, a triple-effect evaporation chamber 401 and a triple-effect heater 402 arranged in the triple-effect evaporation chamber 401, and the triple-effect heater 402 is a ring heater. The air outlet of the second-effect evaporation chamber 301 is connected to the air inlet of the triple-effect heater 402, and the secondary steam of the second-effect evaporation chamber 301 is passed into the triple-effect heater 402 through a pipeline, which is used to heat the sewage in the triple-effect evaporation chamber 401. A liquid level gauge is provided in the triple-effect evaporation chamber 401. When the liquid level in the triple-effect evaporation chamber 401 decreases, the feed pump 101 automatically starts to replenish the material to the set value. As an optional embodiment, the triple-effect heater 402 is coaxially arranged with the triple-effect evaporation chamber 401, so that the circulation flow of the sewage is more uniform. As another optional embodiment, when the sewage is treated in the triple-effect evaporation chamber 401, the triple-effect heater 402 should be located in the sewage. Specifically, when sewage is treated in the three-effect evaporation chamber 401, the liquid level of the sewage is located at 1 / 2 to 3 / 4 of the liquid level of the three-effect evaporation chamber 401, and the three-effect heater 402 should always be below the sewage liquid level in the evaporation chamber.

[0093] Both the two-effect reaction unit and the three-effect reaction unit include a heater arranged inside the evaporation chamber. A large amount of low-temperature sewage in the evaporation chamber can quickly exchange heat with the secondary steam in the heater, and the heat transfer rate is faster. The sewage close to the heater body, such as the sewage in the second area and the sewage close to the heater at the edge of the first area, heats up quickly and the density decreases; the sewage far away from the heater, such as the sewage at the center of the heater, heats up slowly and has a higher density, so a density difference of sewage is formed in different parts of the evaporation chamber, realizing the self-circulation of sewage inside the evaporation chamber, that is, circulating between the edge of the heater body in the first area and the center of the heater, and also circulating between the center of the heater in the first area and the second area, eliminating the kinetic energy consumption of external circulation heating by the water pump in the traditional sewage multi-effect evaporation treatment; moreover, the secondary steam directly heats the sewage in the evaporation chamber, avoiding the heat loss of the traditional external heater, and the energy utilization rate is high.

[0094] In addition, the diameter D1 of the heater is smaller than the diameter D2 of the evaporation chamber, and the diameter D1 of the heater is 80% to 90% of the diameter D2 of the evaporation chamber. The diameter D1 of the heater within this range is conducive to the circulation of sewage between the edge of the heater body in the first area and the center of the heater, and also between the center of the heater in the first area and the second area. The diameter of the heater is too large and it is not convenient to install.

[0095] Moreover, the secondary steam directly heats the sewage in the evaporation chamber, avoiding the heat loss of the traditional external heater, and the energy utilization rate is high. Since the sewage material concentration in the second-effect evaporation chamber 301 and the third-effect evaporation chamber 401 is low, salt and organic matter will not adhere to the surface of the heater to affect the normal use of the heater.

[0096] As an optional implementation of the embodiment, in combination with Figure 1 and Figure 2 The second-effect heater 302 in the second-effect evaporation chamber 301 is a spiral coil heater. The area surrounded by the pipes of the spiral coil heater is the first area, and the area between the spiral coil heater and the inner wall of the second-effect evaporation chamber 301 is the second area. The diameter of the spiral coil heater is smaller than the diameter of the second-effect evaporation chamber 301, and is 80%-90% of the diameter of the second-effect evaporation chamber 301, so as to ensure the stability of the water flow state when the sewage is circulating in two ways, and it is also convenient for installation. The secondary steam is passed into the spiral coil heater to heat the sewage, which can realize the circulation of sewage between the edge of the heater body in the first area and the center of the heater and the circulation between the center of the heater in the first area and the second area, eliminating the kinetic energy consumption of external circulation heating by the water pump in the traditional sewage multi-effect evaporation treatment. As a specific embodiment, the coil steel pipe size of the spiral coil heater can be DN25~DN40.

[0097] As an optional embodiment, the triple-effect heater 402 in the triple-effect evaporation chamber 401 may also be a spiral coil heater, the area surrounded by the pipes of the spiral coil heater is the first area, and the area between the spiral coil heater and the inner wall of the triple-effect evaporation chamber 401 is the second area. The diameter of the spiral coil heater is smaller than the diameter of the triple-effect evaporation chamber 401, and is 80% to 90% of the diameter of the triple-effect evaporation chamber 401, so as to ensure the stability of the water flow state when the sewage is circulating in two ways, and it is also convenient for installation. The secondary steam is passed into the spiral coil heater to heat the sewage, which can realize the circulation of the sewage between the edge of the heater body in the first area and the center of the heater and the circulation between the center of the heater in the first area and the second area, eliminating the kinetic energy consumption of the external circulation heating of the water pump in the traditional sewage multi-effect evaporation treatment. As a specific embodiment, the coil steel pipe size of the spiral coil heater can be DN25 to DN40, and the secondary steam can be passed into the steel pipe to heat the sewage.

[0098] Combination Figure 3 As another optional implementation of the embodiment, the second-effect heater 302 is a tube-in-tube heater, which includes two annular tubes 3021 arranged opposite to each other, a plurality of tubes 3022 are arranged between the two annular tubes 3021, and the upper and lower annular tubes 3021 are connected to the tubes 3022. As a preferred implementation, the upper and lower annular tubes 3021 are circular annular tubes of the same size, and the plurality of tubes 3022 are arranged at equal intervals; secondary steam can be passed into the annular tubes 3021 and the tubes 3022 to heat the sewage. The area surrounded by the annular tube 3021 and the plurality of tubes 3022 is the first area, and the area between the tube-in-tube heater and the inner wall of the second-effect evaporation chamber 301 is the second area; the diameter of the tube-in-tube heater is smaller than the diameter of the second-effect evaporation chamber 301, and is 80% to 90% of the diameter of the second-effect evaporation chamber 301, so as to ensure the stability of the water flow state when the sewage is circulating in two ways, and is also convenient for installation. In addition, the interval between each two adjacent tubes is not less than 5cm. The secondary steam heats the sewage through the shell-and-tube heater, so that the sewage circulates between the edge of the heater body and the center of the heater in the first area and between the center of the heater in the first area and the second area, eliminating the kinetic energy consumption of external circulation heating. Similarly, the triple-effect heater 402 also adopts a shell-and-tube heater with the same structure to achieve the effect of ensuring the circulation of sewage and facilitate installation.

[0099] As another implementation of the embodiment, the first-effect evaporation chamber 201, the second-effect evaporation chamber 301 and the third-effect evaporation chamber 401 are respectively provided with a shell heating layer outside; the shell heating layer includes an air inlet and an air outlet, and the air inlet is connected to an external heat source to heat the sewage in the evaporation chamber. As a specific implementation, a steam pipe is provided in the shell heating layer, and the steam pipe surrounds the outer wall of the evaporation chamber, and steam can be passed to heat the evaporation chamber. Specifically, the steam pipe can be a semicircular pipe and surrounds the outer wall of the evaporation chamber.

[0100] More specifically, the first-effect evaporation chamber 201, the second-effect evaporation chamber 301 and the third-effect evaporation chamber 401 are respectively provided with a first-effect shell heating layer 205, a second-effect shell heating layer 304 and a third-effect shell heating layer 404 outside, and the air inlets of the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the third-effect shell heating layer 404 are respectively connected to the raw steam through a pipeline. The connecting pipelines between the air inlets of the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the third-effect shell heating layer 404 and the raw steam are respectively provided with a first-effect shell heating steam valve 207, a second-effect shell heating steam valve 306 and a third-effect shell heating steam valve 406 to control the entry, closing and flow rate of steam in each shell heating layer.

[0101] By setting the shell heat exchange layer, including the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the third-effect shell heating layer 404, the heat exchange area of ​​the evaporated sewage in each effect evaporation chamber is expanded. The shell heating layer uses fresh raw steam, the sewage temperature difference is large, the heat exchange speed is fast, and the evaporation power is sufficient, ensuring the stability of the evaporation system. Among them, due to the heating form of the evaporation chamber shell by the second-effect shell heating layer 304 and the third-effect shell heating layer 404, the sewage close to the evaporation chamber shell quickly heats up and the density drops quickly; the sewage far from the evaporation chamber shell heats up slowly and the density drops slowly; the density difference of different parts of the sewage is generated, and the effect of the self-circulation flow of the sewage between the center of the heater in the first area and the second area is enhanced. The second-effect shell heating layer 304 and the second-effect heater 302 enhance the self-circulation effect of the sewage inside the second-effect evaporation chamber 301, improve the heat transfer rate and evaporation rate, and also eliminate the kinetic energy consumption of the traditional external circulation. Similarly, the three-effect shell heating layer 404 and the three-effect heater 402 work together to enhance the self-circulation effect of sewage in the three-effect evaporation chamber 401, increase the heat transfer rate and evaporation rate, and also eliminate the kinetic energy consumption of the traditional external circulation.

[0102] In the triple-effect evaporation treatment device, when the heat of the secondary steam is not enough to heat and evaporate the sewage in the second-effect evaporation chamber 301 or the third-effect evaporation chamber 401, the raw steam can provide additional heat to the evaporation chamber through the shell heating layer to enable the evaporation of the sewage to proceed normally, thereby solving the problem of insufficient secondary steam in countercurrent evaporation.

[0103] The device also includes a gas-liquid separation unit, which includes a second-effect gas-liquid separation tank 305 and a third-effect gas-liquid separation tank 405. The liquid inlet of the second-effect gas-liquid separation tank 305 is connected to the gas outlet of the second-effect heater 302, so that the condensate from the second-effect heater 302 is separated from the non-condensable gas. The liquid outlet of the second-effect gas-liquid separation tank 305 is connected to the liquid inlet of the third-effect gas-liquid separation tank 405, so that the condensate enters the water tank 502 through the third-effect gas-liquid separation tank 405. The gas outlet of the second-effect gas-liquid separation tank 305 is connected to the gas inlet of the third-effect heater 402, so that the separated non-condensable gas is recovered to the third-effect heater 402 to heat the sewage, thereby realizing the deep utilization of waste heat. The liquid inlet of the third-effect gas-liquid separation tank 405 is connected to the gas outlet of the third-effect heater 402, so that the condensate from the third-effect heater 402 is separated from the non-condensable gas.

[0104] The triple-effect reaction unit is also connected to a preheating unit and a condensing unit. The condensing unit includes a condenser 501, a water tank 502, an exhaust device 503 and a pumping device 504. The condenser 501 is connected to a circulating water supply valve 505 and a circulating water return valve 506, which are always kept open when the device is running to circulate water to the condenser 501 to meet the condensation requirements. As an optional embodiment, the condenser 501 can be a shell and tube heat exchanger. The condenser 501 is connected to the air outlet of the triple-effect evaporation chamber 401, and the condenser 501 is connected to the water tank 502. The condenser 501 can cool the secondary steam generated by the triple-effect evaporation chamber 401 and the non-condensable gas separated by the triple-effect gas-liquid separation tank 405.

[0105] The liquid inlet of the water tank 502 is connected to the liquid outlet of the triple-effect gas-liquid separation tank 405 . Specifically, the water tank 502 is arranged below the condenser 501 . The water tank 502 can recover the liquid in the triple-effect gas-liquid separation tank 405 and the liquid condensed by the condenser 501 .

[0106] The liquid outlet of the water tank 502 is connected to an air extraction device 503, so that the device can evaporate and operate under negative pressure, which reduces the operating temperature of the system and avoids the problems of high equipment requirements and complex manufacturing caused by high temperature and high pressure during positive pressure evaporation. The water tank 502 is also connected to a water extraction device 504, which can discharge water outside the device for reprocessing after the water level in the water tank 502 reaches a set value. As a specific implementation, the water extraction device 504 is a water pump, and the air extraction device 503 is a vacuum pump.

[0107] The preheating unit includes a preheater 102 and a feed pump 101, and the feed pump 101 includes a liquid inlet and a liquid outlet; the preheater 102 includes a liquid inlet, a liquid outlet, a preheating liquid inlet and a preheating liquid outlet. The liquid outlet of the preheater 102 is connected to the liquid inlet of the three-effect evaporation chamber 401; the liquid outlet of the feed pump 101 is connected to the liquid inlet of the preheater 102, and the liquid inlet of the feed pump 101 is connected to the saline sewage. The saline sewage is transported to the preheater 102 for preheating by the feed pump 101, and the preheated saline sewage is transported to the three-effect evaporation chamber 401 for heating and evaporation. The preheating liquid inlet of the preheater 102 is connected to the gas outlets of the first-effect heater 202, the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the three-effect shell heating layer 404. Among them, the heat source of the preheater 102 is the high-temperature condensate of the raw steam coming out of the outlet of the first-effect heater 202, the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the third-effect shell heating layer 404, thereby realizing the deep utilization of the waste heat of the raw steam. The raw steam condensate after the waste heat is utilized is recovered and reused outside the preheating liquid outlet discharge device of the preheater 102.

[0108] A method for using a triple-effect evaporation treatment device for saline wastewater according to the present invention comprises the following steps:

[0109] S1. Before the raw steam is introduced into the treatment device, the saline wastewater enters the three-effect evaporation chamber 401 after passing through the feed pump 101 and the preheater 102, and is transferred to the second-effect evaporation chamber 301 by the three-effect transfer pump 403; and then the saline wastewater is transferred to the first-effect evaporation chamber 201 by the second-effect transfer pump 303, until the liquid level of the saline wastewater in each effect evaporation chamber is located at the 1 / 2 to 3 / 4 liquid level of each effect evaporation chamber.

[0110] S3. Restart the first-effect circulation pump 203 and adjust the outlet pipeline flow rate of the first-effect circulation pump 203 to 1-2 m / s, which can prevent the evaporation system from being blocked and is economical.

[0111] S3, opening the circulating water supply valve 505 and the circulating water return valve 506 of the condenser 501, and condensing the secondary steam generated by the three-effect evaporation chamber 401 and the non-condensable gas separated by the three-effect separation tank in the condenser 501.

[0112] S4, open the exhaust device 503, remove the air in the device system, control the pressure of each evaporation chamber at -0.5 to -0.05 MPa, reduce the boiling point of the sewage, and thus reduce the operating temperature of the device;

[0113] S5. Open the first-effect heating steam valve 206, the first-effect shell heating steam valve 207, the second-effect shell heating steam valve 306 and the third-effect shell heating steam valve 406; turn on the raw steam for heating to ensure that each effect evaporation chamber is in a boiling state, control the sewage temperature of the first-effect evaporation chamber 201 to 95-100°C to achieve normal flow of sewage, control the sewage temperature of the second-effect evaporation chamber 301 to 85-95°C, and control the sewage temperature of the third-effect evaporation chamber 401 to 80-90°C.

[0114] Specifically, when the treatment device is running to heat and evaporate the sewage, the flow direction of the sewage in the treatment device is as follows: when the material concentration in the first-effect evaporation chamber 201 reaches the set value, the discharge pump 204 automatically starts to discharge the material in a partially saturated state, and when the liquid level in the first-effect evaporation chamber 201 drops to a low level, the second-effect transfer pump 303 starts to transport the material in the second-effect evaporation chamber 301 to the evaporation chamber 201 until the high liquid level is reached. When the liquid level in the second-effect evaporation chamber 301 drops to a low level, the third-effect transfer pump 403 starts to transport the material in the third-effect evaporation chamber 401 to the second-effect evaporation chamber 301 until the high liquid level is reached. When the liquid level in the third-effect evaporation chamber 401 drops, the feed pump 101 starts to transport the sewage outside the boundary to the third-effect evaporation chamber 401 until the high liquid level is reached. Among them, the salt-containing sewage enters the preheater 102 for preheating through the feed pump 101, and the preheated salt-containing sewage enters the third-effect evaporation chamber 401.

[0115] The flow direction of the raw steam in the treatment device is as follows: the raw steam is connected to the air inlet of the first-effect heater 202 through a pipeline, and heats the sewage in the first-effect heater 202; the air inlets of the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the third-effect shell heating layer 404 are each connected to the raw steam through a pipeline, and are used for the raw steam to heat the sewage in each effect evaporation chamber. The connecting pipelines between the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the third-effect shell heating layer 404 and the raw steam are respectively provided with a first-effect shell heating steam valve 207, a second-effect shell heating steam valve 306 and a third-effect shell heating steam valve 406 to control the entry, closing and flow size of the steam in each shell heating layer. After the raw steam heats the sewage in the first-effect heater 202, the first-effect shell heating layer 205, the second-effect shell heating layer 304 and the third-effect shell heating layer 404, it is condensed into high-temperature condensate and connected through various pipelines to enter the preheater 102 to preheat the salt-containing sewage.

[0116] The flow direction of the secondary steam in the processing device is as follows: the secondary steam generated in the evaporation process of the first-effect evaporation chamber 201 is passed into the second-effect heater 302 to heat the material, and after the secondary steam comes out of the second-effect heater 302, it will enter the second-effect gas-liquid separation tank 305; the secondary steam generated in the evaporation process of the second-effect evaporation chamber 301 is passed into the triple-effect heater 402 to heat the material, and after the secondary steam comes out of the triple-effect heater 402, it will enter the triple-effect gas-liquid separation tank 405; the secondary steam generated in the evaporation process of the triple-effect evaporation chamber 401 is passed into the condenser 501 for condensation.

[0117] The concentration detector in the first-effect evaporation chamber 201 is interlocked with the discharge pump 204 for control; the second-effect transfer pump 303, the third-effect transfer pump 403 and the feed pump 101 are interlocked with the liquid level of the first-effect evaporation chamber 201, the liquid level of the second-effect evaporation chamber 301 and the liquid level of the third-effect evaporation chamber 401 respectively for control; a pumping device 504 is provided to operate automatically according to the liquid level of the water tank 502.

[0118] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A triple-effect evaporation treatment device for saline wastewater, characterized in that: The device includes an external heat source and a reaction unit; The reaction unit comprises a first-effect reaction unit, a second-effect reaction unit, and a third-effect reaction unit connected in sequence; The first-effect reaction unit is provided with a first-effect evaporation chamber (201), the second-effect reaction unit is provided with a second-effect evaporation chamber (301), and the third-effect reaction unit is provided with a third-effect evaporation chamber (401); the salt-containing sewage is transported from the third-effect evaporation chamber (401) into the second-effect evaporation chamber (301), and then transported from the second-effect evaporation chamber (301) into the first-effect evaporation chamber (201); The first-effect reaction unit further comprises a first-effect heater (202), wherein the first-effect heater (202) is arranged outside the first-effect evaporation chamber (201), and the saline wastewater is transported from the first-effect evaporation chamber (201) to the first-effect heater (202), and then transported from the first-effect heater (202) to the first-effect evaporation chamber (201); The first-effect heater (202) is connected to an external heat source, and the first-effect evaporation chamber (201) evaporates to generate secondary steam, and the secondary steam is used to evaporate the sewage in the second-effect evaporation chamber (301); The second-effect evaporation chamber (301) evaporates to generate secondary steam, and the secondary steam is used to evaporate the sewage in the third-effect evaporation chamber (401); Any one or both of the two-effect reaction unit and the three-effect reaction unit further comprises a heater disposed inside the evaporation chamber thereof; The heater is roughly annular, and the area enclosed by the annular heater is the first area; The annular heater and the inner wall of the evaporation chamber form a second area; The first area is connected to the second area.

2. The triple-effect evaporation treatment device for saline wastewater according to claim 1, characterized in that: The three-effect evaporation chamber (401) comprises a liquid inlet and a liquid outlet; The second-effect evaporation chamber (301) comprises a liquid inlet and a liquid outlet; The first-effect evaporation chamber (201) comprises a first liquid inlet, a second liquid inlet and a liquid outlet; The liquid outlet of the third-effect evaporation chamber (401) is connected to the liquid inlet of the second-effect evaporation chamber (301), and the liquid outlet of the second-effect evaporation chamber (301) is connected to the liquid inlet of the first-effect evaporation chamber (201); The liquid outlet of the first-effect evaporation chamber (201) is connected to the first-effect heater (202); The second liquid inlet of the first-effect evaporation chamber (201) is connected to the first-effect heater (202).

3. The triple-effect evaporation treatment device for saline wastewater according to claim 2 is characterized in that: A three-effect material transfer pump (403) is connected between the liquid outlet of the three-effect evaporation chamber (401) and the liquid inlet of the two-effect evaporation chamber (301); A second-effect material transfer pump (303) is connected between the liquid outlet of the second-effect evaporation chamber (301) and the liquid inlet of the first-effect evaporation chamber (201).

4. The triple-effect evaporation treatment device for saline wastewater according to any one of claims 1 to 3, characterized in that: A heater is provided inside the triple-effect evaporation chamber (401), and the heater is a triple-effect heater (402); A heater is provided inside the second-effect evaporation chamber (301), and the heater is a second-effect heater (302); The three-effect evaporation chamber (401) comprises an air outlet; The second-effect evaporation chamber (301) comprises an air outlet; The first-effect evaporation chamber (201) comprises an air outlet; The triple-effect heater (402) comprises an air inlet and an air outlet; The two-effect heater (302) comprises an air inlet and an air outlet; The first-effect heater (202) comprises a liquid inlet and a liquid outlet, an air inlet and an air outlet; The air inlet of the triple-effect heater (402) is connected to the air outlet of the second-effect evaporation chamber (301), and the air inlet of the second-effect heater (302) is connected to the air outlet of the first-effect evaporation chamber (201); the air inlet of the first-effect heater (202) is connected to an external heat source; The liquid inlet of the first-effect heater (202) is connected to the liquid outlet of the first-effect evaporation chamber (201); The liquid outlet of the first-effect heater (202) is connected to the second liquid inlet of the first-effect evaporation chamber (201).

5. The triple-effect evaporation treatment device for saline wastewater according to claim 4 is characterized in that: The first-effect reaction unit further comprises a first-effect circulation pump (203) and a discharge pump (204); The first-effect circulation pump (203) is arranged between the liquid outlet of the first-effect evaporation chamber (201) and the liquid inlet of the first-effect heater (202); The liquid outlet of the first-effect evaporation chamber (201) is also connected to a discharge pump (204).

6. The triple-effect evaporation treatment device for saline wastewater according to claim 5, characterized in that: The exteriors of the first-effect evaporation chamber (201), the second-effect evaporation chamber (301) and the third-effect evaporation chamber (401) are respectively provided with shell heating layers; The shell heating layer comprises an air inlet and an air outlet, and the air inlet is connected to an external heat source.

7. The triple-effect evaporation treatment device for saline wastewater according to claim 6 is characterized in that: The device further comprises a gas-liquid separation unit, wherein the gas-liquid separation unit comprises a second-effect gas-liquid separation tank (305) and a third-effect gas-liquid separation tank (405); The liquid inlet of the second-effect gas-liquid separation tank (305) is connected to the gas outlet of the second-effect heater (302), the liquid outlet of the second-effect gas-liquid separation tank (305) is connected to the liquid inlet of the third-effect gas-liquid separation tank (405), and the gas outlet of the second-effect gas-liquid separation tank (305) is connected to the gas inlet of the third-effect heater (402).

8. The triple-effect evaporation treatment device for saline wastewater according to claim 7, characterized in that: The device further comprises a preheating unit, wherein the preheating unit comprises a preheater (102) and a feed pump (101); The feed pump (101) comprises a liquid inlet and a liquid outlet; The preheater (102) comprises a liquid inlet, a liquid outlet, a preheating liquid inlet and a preheating liquid outlet; The liquid inlet of the feed pump (101) is connected to the saline wastewater, and the liquid outlet of the feed pump (101) is connected to the liquid inlet of the preheater (102); The liquid outlet of the preheater (102) is connected to the liquid inlet of the triple-effect evaporation chamber (401); The air outlet of the shell heating layer is connected to the preheating liquid inlet of the preheater (102); The gas outlet of the first-effect heater (202) is connected to the preheating liquid inlet of the preheater (102).

9. The triple-effect evaporation treatment device for saline wastewater according to claim 8, characterized in that: The device further comprises a condensing unit, wherein the condensing unit comprises a condenser (501), a water tank (502), an air extraction device (503) and a water extraction device (504); The gas inlet of the condenser (501) is connected to the gas outlet of the triple-effect evaporation chamber (401) and the gas outlet of the triple-effect gas-liquid separation tank (405), and the condenser (501) is connected to the water tank (502); The liquid inlet of the water tank (502) is connected to the liquid outlet of the triple-effect gas-liquid separation tank (405), and the liquid outlet of the water tank (502) is connected to the pumping equipment (504); The water tank (502) is also connected to an air extraction device (503).

10. The method for using the triple-effect evaporation treatment device for saline wastewater according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Before the device performs evaporation, the salty sewage to be treated is sequentially injected into the three-effect evaporation chamber (401), the second-effect evaporation chamber (301) and the first-effect evaporation chamber (201) to a liquid level of 1 / 2 to 3 / 4 of each effect evaporation chamber; S2, start the first-effect circulation pump (203), and adjust the flow rate of the outlet pipeline of the first-effect circulation pump (203) to 1-2 m / s; S3, start the operation of the condenser (501); S4, open the exhaust device (503), exhaust the air in the system, and control the pressure of each evaporation chamber to -0.5 to -0.05 MPa; S5. Turn on the raw steam heating to perform boiling evaporation, control the sewage temperature in the first-effect evaporation chamber (201) to 95-100° C., control the sewage temperature in the second-effect evaporation chamber (301) to 85-95° C., and control the sewage temperature in the third-effect evaporation chamber (401) to 80-90° C.

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