MVR evaporator system

Abstract

The invention discloses an MVR evaporator system which comprises an evaporator, a compressor, a liquid separation unit and a control unit. Wherein the bottom of a liquid separation cylinder of the liquid separation unit is provided with a liquid separation cylinder conveying port, the liquid separation cylinder conveying port is communicated with a bottom discharge port of the evaporator through a first branch, and the first branch is provided with a first bottom valve; the delivery port of the liquid separation cylinder is further connected with a second branch communicated with the outside of the system, and a second bottom valve is arranged on the second branch; the first density sensor is used for measuring the liquid density rho 2b at the bottom of the liquid separation cylinder in real time; the control unit is configured to control the opening and closing states of the first bottom valve and the second bottom valve at least based on rho 2b after liquid in the liquid separation cylinder is subjected to standing layering, so that heavy-component pollutants located on the lower layer and light-component pollutants located on the upper layer after standing layering are discharged to the outside of the system through the second branch, and the heavy-component pollutants located on the lower layer and the light-component pollutants located on the upper layer are discharged to the outside of the system through the third branch. And the liquid in the middle layer is conveyed back to the evaporator through the first branch. According to the evaporator system, the evaporator can still continuously evaporate under the condition of high concentration of wastewater, and the treatment efficiency of the system is greatly improved.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and more specifically to an MVR evaporator system including a liquid separation unit. Background Technology

[0002] Evaporators are common chemical equipment widely used in chemical, environmental protection, pharmaceutical, food, textile, and energy industries. Evaporators typically utilize the difference in boiling points between water and other solutes in a solution. By heating the water, it boils and vaporizes, escaping from the solution, thus achieving separation of water and solute, and concentration of the solution.

[0003] In recent years, evaporators such as Mechanical Vapor Recompression (MVR) evaporators have been widely used in wastewater treatment, especially for highly polluted and concentrated industrial wastewater, such as electroplating wastewater, organic wastewater, and oily wastewater. They offer advantages such as wide adaptability, short process chains, and high levels of automation.

[0004] However, when treating wastewater, the concentration of wastewater inside the evaporator continuously increases as evaporation proceeds. When the concentration reaches a certain level, factors such as a decrease in water content and increased pollution, or salt precipitation and crystallization, may occur, hindering continuous evaporation and forcing the evaporator to interrupt the evaporation process and discharge the concentrated liquid. In other words, the evaporation time of existing evaporators is limited, making it difficult to continuously treat wastewater at high concentrations, thus affecting treatment efficiency. Summary of the Invention

[0005] One of the objectives of this application is to provide an MVR evaporator system including a liquid separation unit, which can separate and discharge the concentrate in the evaporator online through the liquid separation unit, so that the evaporator can continue to evaporate even when the wastewater has a high concentration, without interruption, which greatly improves the system's treatment efficiency.

[0006] This application provides an MVR evaporator system, including an evaporator, a compressor, a liquid distribution unit, and a control unit. The evaporator contains an evaporative heat exchanger, the tube side of which is connected to the compressor's suction port via a gas phase outlet at the top of the evaporator, and the compressor's discharge port is connected to the shell-side inlet of the evaporator heat exchanger. The liquid distribution unit includes a liquid distribution cylinder and a first density sensor. The liquid distribution cylinder has a liquid distribution cylinder delivery port at its bottom, which is connected to the bottom discharge port of the evaporator via a first branch, and a first bottom valve is installed on the first branch. The liquid distribution cylinder delivery port is also connected to a second branch connecting to the outside of the system, and a second bottom valve is installed on the second branch. The first density sensor is installed at the bottom of the liquid distribution cylinder for real-time measurement of the liquid density ρ at the bottom of the liquid distribution cylinder.2b The control unit is configured to: after the liquid has settled and separated into layers in the separating cylinder, at least based on the ρ 2b The system controls the opening and closing states of the first bottom valve and the second bottom valve to discharge the heavy component pollutants in the lower layer and the light component pollutants in the upper layer to the outside of the system via the second branch, and to transport the liquid in the middle layer back to the evaporator via the first branch.

[0007] In one possible implementation, the control unit is specifically configured as follows: In ρ 2b ≥Second density threshold ρ d2 In this case, the first bottom valve is controlled to be closed and the second bottom valve is controlled to be open, so as to discharge the lower layer of heavy component pollutants through the second branch; Second density threshold ρ d2 >ρ 2b > First density threshold ρ d1 In this case, the second bottom valve is controlled to be closed and the first bottom valve is controlled to be open, so as to transport the liquid in the middle layer back to the evaporator via the first branch; In ρ 2b ≤ First density threshold ρ d1 In this case, the first bottom valve is controlled to be closed and the second bottom valve is controlled to be open, so as to discharge the upper light component pollutants through the second branch.

[0008] In one possible implementation, the system further includes a second density sensor and a third density sensor; the second density sensor is mounted on the upper part of the dispensing cylinder and is used to measure the liquid density ρ at the upper part of the dispensing cylinder. 2a The third density sensor is used to measure the initial density ρ1 of the liquid to be treated entering the system. The control unit is also configured to: Calculate the weighted value λ = (ρ1 - ρ3) / (ρ1 - ρ2); where ρ2 is the highest concentration of the liquid in the separatory cylinder. When the lighter component contaminants are greater than the heavier component contaminants in the separatory cylinder, ρ2 = ρ 2a When the heavy component contaminant is greater than the light component contaminant in the separatory cylinder, ρ2 = ρ 2b ρ3 is the average density of the liquid in the separatory cylinder. ρ(h) is the curve of liquid density as a function of liquid level height measured by the first density sensor, and hs is the total liquid height in the dispensing cylinder; Calculate ρ d1 and ρ d2 ; where the light component pollutant is greater than the heavy component pollutant in the separating cylinder, ρ d1=ρ3+λ(ρ2-ρ3), ρ d2 =1; When the heavy component contaminants are greater than the light component contaminants in the separatory cylinder, ρ d1 =1,ρ d2 =ρ3+λ(ρ2-ρ3).

[0009] In one possible implementation, the liquid dispensing unit further includes a first liquid level sensor for real-time detection of the liquid level height in the liquid dispensing cylinder; The control unit is also configured to: Record the total height hs of the liquid in the separating cylinder after settling and stratification during the nth separation. n The liquid level height h1 after the heavy component pollutants are discharged n And the liquid height h2 after the middle layer of liquid has been discharged. n ; The volume ratio of the liquid in the middle layer to the total liquid volume in the separating cylinder during the nth separation is calculated as kn = (h2) / (h2). n -h1 n ) / hs n ; Determine the rate of change of k based on k(n-m+1)…k(n-2), k(n-1), kn for m consecutive separations; When the rate of change of k decreases to the first preset threshold, the interval t(n+1) of the next separation is shortened. If the rate of change of k rises to the second preset threshold, the interval t(n+1) of the next separation is extended.

[0010] In one possible implementation of the first aspect, the MVR evaporator system further includes a vacuum system, which is connected to the upper part of the dispensing cylinder via a first vacuum line equipped with a first suction valve; The control unit is configured to control the opening of the first suction valve before opening the first bottom valve to deliver the liquid in the evaporator to the dispensing cylinder.

[0011] In one possible implementation, the upper part of the liquid separator is also connected to a first compressed gas pipeline, and a liquid separator pressurization valve is provided on the first compressed gas pipeline. The control unit is configured to: after the liquid in the separating cylinder stops boiling, control the closing of the first suction valve and the opening of the pressure valve of the separating cylinder.

[0012] In one possible implementation, the liquid separation unit further includes a liquid separation cylinder heat exchanger disposed on the outer periphery of the liquid separation cylinder; wherein the inlet of the liquid separation cylinder heat exchanger is connected to the exhaust port of the compressor and a liquid separation cylinder heating valve is disposed between the two; and the drain port of the liquid separation cylinder heat exchanger is connected to a liquid separation cylinder drain valve.

[0013] In one possible implementation, the MVR evaporator system further includes a preheating unit, which includes a preheating cylinder and a preheating cylinder heat exchanger disposed on the outer periphery of the preheating cylinder; the preheating cylinder inlet of the preheating cylinder is connected to the evaporator; the inlet of the preheating cylinder heat exchanger is connected to the shell-side steam outlet disposed on the shell side; the drain outlet of the preheating cylinder heat exchanger is connected to a preheating cylinder drain valve; the gas outlet of the preheating cylinder heat exchanger is connected to the gas phase outlet disposed on the upper part of the evaporator, and a return gas valve is disposed between the two.

[0014] In one possible implementation, the upper part of the preheating cylinder is connected to the vacuum system via a second vacuum line equipped with a second suction valve; the upper part of the preheating cylinder is also connected to a second compressed gas line, on which a preheating cylinder pressurization valve is provided. The control unit is configured to: when the preheating unit heats the liquid in the preheating cylinder, control the closing of the second suction valve and the opening of the preheating cylinder pressurization valve, so that the gas pressure in the preheating cylinder is greater than the gas pressure in the evaporator.

[0015] In one possible implementation, the preheating cylinder is further provided with a preheating cylinder heater and a second temperature sensor, the second temperature sensor being used to detect the temperature of the wastewater in the preheating cylinder; The control unit is configured to control the preheating cylinder heater to turn on when the wastewater temperature in the preheating cylinder drops below the wastewater temperature in the evaporator. Attached Figure Description

[0016] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of an exemplary implementation of the MVR evaporation system of this application.

[0018] Figure 2 An exemplary schematic diagram of the liquid distribution in the liquid separation unit of this application after stratification.

[0019] Explanation of reference numerals in the attached figures: Evaporator 100; Vapor outlet 1001; Discharge port 1002; Evaporative heat exchanger 101; Tube side 102; Shell side 103; Shell side inlet 1031; Shell side vapor outlet 1032; Shell side distilled water outlet 1033; Liquid inlet pipe 111; Exhaust pipe 112; Evaporator liquid inlet valve 121; Exhaust valve 122; Third liquid level sensor 131; Third density sensor 132; Third pressure sensor 133; Third temperature sensor 134; Compressor 201; compressor intake port 2011; compressor exhaust port 2012; Preheating cylinder 301; preheating cylinder heat exchanger 302; steam inlet 3021 of preheating cylinder heat exchanger; gas outlet 3022; distilled water inlet 3023 of preheating cylinder heat exchanger; drain outlet 3024 of preheating cylinder heat exchanger; preheating cylinder heater 303; preheating cylinder liquid inlet valve 321; return gas valve 322; preheating cylinder pressurization valve 323; preheating cylinder drain valve 324; fourth density sensor 331; second liquid level sensor 332; second temperature sensor 333; Separating cylinder 401; Separating cylinder delivery port 4011; Separating cylinder heat exchanger 402; Separating cylinder heat exchanger inlet 4021; Separating cylinder heat exchanger outlet 4022; First branch 411; Second branch 412; First bottom valve 421; Second bottom valve 422; Separating cylinder pressurizing valve 423; Separating cylinder heating valve 424; Separating cylinder drain valve 425; First density sensor 431; Second density sensor 432; First liquid level sensor 433; Circulating water pump 501; circulating water tank 502; ejector 503; first vacuum line 511; first suction valve 521; second vacuum line 512; second suction valve 522. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of the embodiments of this application, the application will be described below in conjunction with the accompanying drawings and specific implementation methods.

[0021] MVR evaporator systems typically involve several stages in their wastewater treatment process, including influent, heating, evaporation, and discharge. Only during the evaporation stage can wastewater be concentrated and distilled into water; other stages, such as influent, heating, and discharge, cannot be evaporated. To improve system efficiency, the time spent in non-evaporation stages should be minimized. In conventional evaporators, during the evaporation stage, the wastewater concentration continuously increases, while the steam generated from boiling gradually decreases, reducing the evaporator's heat exchange efficiency and heat transfer capacity. When the maximum concentration is reached, the evaporator cannot continue evaporation, requiring the process to stop, the high-concentration wastewater to be discharged, and the system to proceed to the next treatment stage, involving influent and heating of the wastewater again. This results in insufficient system efficiency.

[0022] This application provides an MVR evaporator system including a liquid separation unit. The liquid separation unit can separate and discharge the concentrate in the evaporator online during the evaporation stage of the system, without having to interrupt the evaporation due to excessively high solution concentration, salt precipitation, crystallization, or other reasons. This achieves continuous evaporation processing and improves the system's processing efficiency.

[0023] See Figure 1 This application provides an MVR evaporator system, including an evaporator 100, a compressor 201, and a liquid distribution unit.

[0024] Evaporator 100 is used to contain wastewater and is the main equipment for wastewater evaporation treatment in the system. Evaporator 100 can be, by example, a pressure vessel made of corrosion-resistant material (such as 316L stainless steel).

[0025] An evaporative heat exchanger 101 is installed inside the evaporator 100. The evaporative heat exchanger 101 is mainly used to provide the heat required for the evaporation of wastewater within the evaporator 100. In some possible implementations, the evaporative heat exchanger 101 can be a shell-and-tube heat exchanger, installed in the lower middle part of the evaporator 100. The shell side 103 of the evaporative heat exchanger 101, that is, the space surrounding the heat exchange tube bundle, is the place where the high-temperature medium releases heat. The tube side 102 of the evaporative heat exchanger 101, that is, the space formed by the internal interconnection of all the heat exchange tubes, serves as the heating and evaporation chamber for the wastewater. The wastewater to be treated circulates within this chamber, exchanging heat with the high-temperature medium in the shell side 103, and after receiving heat, some of the water evaporates into steam.

[0026] The evaporator 100 is provided with a gas phase outlet 1001 at the top, which is connected to the suction port 2011 of the compressor 201 through a pipe. In this way, the tube side 102 of the evaporator heat exchanger 101 forms a gas passage with the suction port 2011 of the compressor 201, and the steam generated in the tube side 102 can be continuously extracted.

[0027] Compressor 201 is primarily used to compress low-quality steam, which is relatively cold and low-pressure, drawn from tube side 102. The compression process significantly increases the steam pressure and corresponding saturation temperature, transforming it into high-quality steam (e.g., pressure from 0.5 bar(a) to 1.2 bar(a), and saturation temperature from approximately 81°C to over 104°C). The exhaust port 2012 of compressor 201 is connected to the shell-side inlet 1031 via a high-temperature, high-pressure resistant pipe, thereby delivering the compressed, heated, and pressurized high-quality steam to the shell side 103 of evaporative heat exchanger 101 as a heat source for heating the wastewater in tube side 102. The latent heat of the high-quality steam can be transferred to the wastewater in tube side 102 through the tube walls, causing the water to evaporate, while the steam itself condenses into distilled water, achieving separation of water and pollutants from the original wastewater solution. This cycle provides the heat required for evaporation to tube side 102, realizing internal heat recycling, reducing dependence on external fresh steam, and allowing the system to operate primarily on electrical energy, thus reducing the demand for external energy. Compressor 201 may be selected, for example, as a centrifugal compressor or a Roots compressor.

[0028] The shell side 103 is also provided with a shell side steam outlet 1032 and a shell side distilled water outlet 1033 for discharging steam and distilled water from the shell side 103. For example, the steam outlet 1032 may be located at the upper part of the shell side 103, and the distilled water outlet 1033 may be located at the bottom of the shell side 103.

[0029] The upper part of the evaporator 100 can also be connected to an exhaust pipe 112, which connects to the outside of the system. An exhaust valve 122 can be installed on the exhaust pipe 112. By setting the exhaust pipe 112, gases, such as non-condensable gases, in the evaporator 100 can be discharged from the system when needed, so as to avoid excessive accumulation of non-condensable gases in the evaporator 100, which would affect the heat exchange efficiency.

[0030] The evaporator 100 is also equipped with an evaporator inlet for introducing new wastewater as needed. The evaporator inlet is connected to an inlet pipe 111, which may be equipped with an evaporator inlet valve 121. Optionally, a third liquid level sensor 131 may be installed in the evaporator 100 to measure whether the wastewater in the evaporator 100 has reached a preset liquid level. When liquid is introduced into the evaporator 100, if the third liquid level sensor 131 detects that the wastewater in the evaporator 100 has reached the preset liquid level, the evaporator inlet valve 121 can be closed to stop the liquid introduction.

[0031] Optionally, a third density sensor 132 can be installed in the evaporator 100 to measure the density of the wastewater in the evaporator 100. Changes in the density of the wastewater in the evaporator 100 can reflect the pollutant content and concentration of the wastewater. As evaporation proceeds, the density of the wastewater in the evaporator 100 continuously increases (or decreases). When the density reaches a set value, a portion of the waste liquid in the evaporator 100 can be transferred to the liquid distribution unit, causing the liquid distribution unit to start operating. Optionally, if the main pollutants in the wastewater are conductive, the third density sensor 132 can be replaced with a conductivity sensor. By measuring the conductivity of the wastewater, the pollutant content and concentration of the wastewater can also be reflected.

[0032] Optionally, a third pressure sensor 133 may also be installed inside the evaporator 100 to detect the gas pressure inside the evaporator 100. A third temperature sensor 134 may also be installed inside the evaporator 100 to detect the temperature of the wastewater inside the evaporator 100. Through the third pressure sensor 133 and the third temperature sensor 134, pressure and temperature data inside the evaporator 100 can be acquired in real time for monitoring operating conditions and control. On the other hand, it can also be used to determine whether the wastewater in the tube side 102 has reached the saturation temperature, thereby determining the operating stage of the evaporation system, such as whether to switch from the heating stage to the evaporation stage.

[0033] The liquid separation unit is mainly used to separate the concentrated liquid discharged from the evaporator 100 after it has been concentrated to a certain concentration. The liquid is then separated into high-concentration concentrate and ordinary concentrate. The high-concentration concentrate is discharged to the outside of the system, for example, to a concentrate storage tank, while the ordinary concentrate is returned to the evaporator 100 to continue evaporation.

[0034] The liquid separation unit may include a liquid separation cylinder 401 and a first density sensor 431.

[0035] The separating cylinder 401 is the main body of the container for settling and separation. A separating cylinder delivery port 4011 is located at the bottom of the separating cylinder 401, which is connected to two branches. The first branch 411 is connected to the bottom discharge port 1002 of the evaporator 100, and a first bottom valve 421 is installed on the first branch 411. The second branch 412 is connected to the outside of the system, and a second bottom valve 422 is installed on the second branch 412.

[0036] The first density sensor 431 is installed at the bottom of the dispensing cylinder 401 to measure the liquid density at the bottom of the dispensing cylinder 401 in real time, denoted as ρ. 2b .

[0037] When the liquid in the separating tank 401 settles and separates, the heavier components in the waste liquid (such as crystals, heavy metals, solid particles, etc.), also known as heavy component pollutants, will flow to the bottom of the separating tank 401; the lighter components in the waste liquid (such as oil, suspended solids, organic solvents, etc.), also known as light component pollutants, will flow to the top of the separating tank 401; and water and liquids with a density close to that of water will remain in the middle position.

[0038] After a period of settling, the separation is basically complete. Based on the different densities of the wastewater layer, the wastewater can be divided into three parts: a lower section with a high concentration of heavy pollutants (density greater than water), a middle section with a density close to that of the original wastewater and water, and an upper section with a high concentration of light pollutants (density less than water). The heavy and light pollutants are discharged from the system, while a portion of the wastewater is returned to the evaporator 100 for further treatment. Since the wastewater passes through the first density sensor 431 located at the bottom of the separating cylinder 401 when it is discharged, the density can be monitored in real time. 2b The density of wastewater layers at different heights after stratification is detected to determine the classification of wastewater layers at a certain liquid level, thereby determining when to use the second branch 412 to discharge heavy component pollutants and light component pollutants, and when to use the first branch 411 to transport the liquid in the middle layer back to the evaporator 100 for further treatment.

[0039] The above-described operation process, as well as any subsequent possible operation processes, can be implemented, exemplarily, by a configured control unit. The control unit can be implemented, exemplarily, by a PLC or microprocessor, which connects to various sensors and actuators (e.g., valves) to control each actuator.

[0040] The separation process of the liquid separation unit separates heavy and light pollutants from the wastewater, resulting in wastewater with a concentration much lower than the existing wastewater in the evaporator 100. Of course, the evaporator 100 will also open the evaporator inlet valve 121 to replenish the wastewater. This achieves the effect of reducing the wastewater concentration in the evaporator 100, thereby extending the evaporation time of the evaporator 100, enabling continuous evaporation treatment, and improving the system's processing efficiency.

[0041] If the density is greater than the second density threshold ρ d2 It belongs to the category of recombinant pollutants, with a density less than the first density threshold ρ. d1 It belongs to the category of light component pollutants, with a density at ρ d2 and ρ d1 The wastewater in between belongs to the intermediate layer. Next, the density can be measured in real-time by the first density sensor 431. 2b , and ρ d2 ρ d1Based on the comparison results, the heavy component pollutants and light component pollutants are discharged from the system, and the wastewater from the intermediate layer is partially discharged back into the evaporator 100 for further treatment.

[0042] Optionally, the control unit can be specifically configured as follows: In ρ 2b ≥ρ d2 In this case, the first bottom valve is controlled to be closed and the second bottom valve is controlled to be open, so as to discharge the lower layer of heavy component pollutants through the second branch. In ρ d2 >ρ 2b >ρ d1 In this case, the second bottom valve is controlled to be closed and the first bottom valve is controlled to be open, so as to transport the liquid in the middle layer back to the evaporator via the first branch. In ρ 2b ≤ρ d1 In this case, the first bottom valve is controlled to be closed and the second bottom valve is controlled to be open, so as to discharge the upper light component pollutants through the second branch.

[0043] First density threshold ρ d1 Second density threshold ρ d2 It can be determined in a variety of possible ways.

[0044] In some implementations, ρ can be d1 and ρ d2 Set to a fixed empirical value. For example, for wastewater mainly composed of heavy component pollutants, ρ can be set to... d1 =1.0 (water density), ρ d2 =1.15. For example, for wastewater mainly composed of light pollutants, ρ can be set... d1 =0.85, ρ d2 =1.0. These values ​​can be determined based on multiple experimental measurements and calculations on a specific wastewater treatment.

[0045] In some implementations, the ρ measured by the first density sensor after static stratification can be used. 2b Subtract a preset offset, and that becomes ρ. d2 Optionally, the liquid dispensing unit may further include a second density sensor 432. The second density sensor 432 is mounted on the upper part of the dispensing cylinder 401 and is used to measure the liquid density in the upper part of the dispensing cylinder 401, denoted as ρ. 2a The ρ measured by the first density sensor after static stratification can be used to... 2a Add an offset, as ρ d2 .

[0046] In other implementations, the first density threshold ρ can be calculated based on the liquid density measured by the third density sensor when the evaporator delivers waste liquid to the liquid distribution unit, using a preset functional relationship or by adding or subtracting an offset. d1 Second density threshold ρ d2 .

[0047] In some implementations, a weighted value λ can be introduced to calculate the first density threshold ρ for two different scenarios: one with more heavy component pollutants and the other with more light component pollutants. d1 Second density threshold ρ d2 This allows for adjustments to pollutant discharge based on the wastewater conditions during the separation process, further improving separation efficiency. In this implementation, the first density threshold ρ... d1 Second density threshold ρ d2 The calculation process may include the following steps S601 to S606.

[0048] S601, obtain the initial density ρ1 of the liquid to be processed.

[0049] Optionally, the evaporation system may further include a fourth density sensor 331 for measuring the initial density ρ1 of the liquid to be treated entering the system. Exemplarily, the fourth density sensor 331 may be installed on the inlet pipe of the liquid to be treated, or in the preheating cylinder 301 described below. Since the wastewater in the preheating cylinder 301 comes directly from external wastewater, placing the fourth density sensor 331 in the preheating cylinder 301 allows the detected wastewater density to be used as the initial density of the wastewater.

[0050] S602, based on the initial density ρ1 and the density change trend measured by the third density sensor, determine whether there are more light component pollutants than heavy component pollutants in the liquid separator.

[0051] If the pollutants in the wastewater in evaporator 100 are mostly light components, the initial density of the wastewater will be less than 1. Furthermore, as evaporation proceeds, the water content decreases, the pollutant concentration increases, and the wastewater density gradually decreases. If the pollutants in the wastewater in evaporator 100 are mostly heavy components, the initial density of the wastewater will be greater than 1. Furthermore, as evaporation proceeds, the water content decreases, the pollutant concentration increases, and the wastewater density gradually increases. Therefore, by determining whether the initial density of the wastewater is greater than 1, and whether the density of the wastewater in the evaporator (i.e., the density of the wastewater measured by the third density sensor 132) gradually increases or decreases with increasing concentration, it is easy to determine whether the pollutants in the wastewater are predominantly light components or heavy components.

[0052] S603, determine the maximum concentration ρ2 of the liquid in the separatory cylinder; where, when the lighter component contaminants are greater than the heavier component contaminants in the separatory cylinder, ρ2 = ρ 2a When the heavy component contaminant is greater than the light component contaminant in the separatory cylinder, ρ2 = ρ 2b .

[0053] When the pollutants are mainly light components, after settling and stratification, the pollutants tend to accumulate at the top of the separator. At this point, the second density sensor at the top of the separator will detect the density of the most concentrated wastewater, i.e., ρ2 = ρ 2a When the pollutants are mainly heavy components, after settling and stratification, the pollutants tend to accumulate at the bottom of the separatory tank. At this point, the first density sensor at the bottom of the separatory tank will detect the density of the most concentrated wastewater, i.e., ρ2 = ρ 2b .

[0054] S604, determine the average density ρ3 of the liquid in the separatory cylinder.

[0055] During the process of waste liquid flowing from the evaporator to the dispensing cylinder, the real-time density of the wastewater can be detected by the first density sensor at the bottom, and the density change curve ρ(h) as a function of liquid level height h can be continuously recorded. Therefore, the average density of the liquid in the dispensing cylinder at a liquid level of h can be estimated using the following function: .

[0056] After the liquid filling is completed, the total liquid level height hs is obtained. The average density of the liquid in the entire dispensing cylinder is calculated by integration: .

[0057] ρ3 is the overall average concentration of all the concentrated liquids that have entered the separatory tank this time. It reflects the overall concentration of this part of the material transferred from the evaporator.

[0058] S605, calculate the weighted value λ=(ρ1-ρ3) / (ρ1-ρ2).

[0059] (ρ1-ρ3) represents the degree of concentration from the original wastewater to the current average state in the separatory tank. The larger this difference, the more concentrated the liquid transferred in this operation is. (ρ1-ρ2) represents the potential concentration space from the original wastewater to the most concentrated state in the current separatory tank. The larger this difference, the greater the density difference between the pollutants in the wastewater and the most concentrated state, and the greater the separation potential.

[0060] λ quantifies the degree of concentration in this separation. When λ is closer to 0, it means ρ3 is close to ρ1, indicating a very low overall concentration of the separated liquid, almost no concentration. When λ is closer to 1, it means ρ3 is close to ρ2, indicating a very high overall concentration of the separated liquid, very close to its contaminant enrichment limit. Compared to the general determination method, the introduction of λ acts as a dynamic adjustment factor. It makes the values ​​of the first and second density thresholds no longer static, but closely linked to the real-time concentration state of the separated liquid, thus enabling more efficient and accurate density differentiation and separation.

[0061] S606, determine ρ d1 and ρ d2 .

[0062] When the light component contaminant is greater than the heavy component contaminant in the separatory cylinder, ρd1=ρ3+λ(ρ2-ρ3), ρd2=1.

[0063] In this scenario, if λ is small, it means the overall concentration is low, with ρd1 close to ρ3. Less of the light component should be discharged, only the very low-density portion at the top, to retain more liquid for return to the evaporator. If λ is large, it means the liquid is already quite concentrated, and more of the light component should be discharged, with a wider density range to more thoroughly remove upper-layer contaminants and prevent their backflow into the evaporator. Furthermore, in this case, because heavy components are scarce, the lower layer is mainly water and a small amount of heavy components. The density of water (1) serves as the dividing line; components with a density greater than 1 are considered heavy components and discharged. This simplifies the determination of the lower layer, allowing the liquid-liquid separation operation to focus more on separating light component contaminants.

[0064] When the heavy component contaminant is greater than the light component contaminant in the separatory cylinder, ρd1=1, ρd2=ρ3+λ(ρ2-ρ3).

[0065] In this scenario, if λ is small, it means the overall concentration is not high, and ρd2 is close to ρ3. Less heavy components should be discharged, only the bottommost, highest-density portion, to retain more liquid for return to the evaporator. If λ is large, it means the liquid is already very concentrated, and more heavy components should be discharged, with a wider density range to more thoroughly remove lower-layer sediments and prevent their backflow into the evaporator. Furthermore, in this case, because light components are scarce, the upper layer is mainly water and a small amount of light components. The density of water (1) is used as the dividing line; components with a density less than 1 are considered light components and discharged. This simplifies the determination of the upper layer, allowing the liquid-liquid separation operation to focus more on the separation of heavy component pollutants.

[0066] By adopting the above approach, through the introduction of λ and fixing a density threshold of 1 (the density of water) according to the pollutant type, the separation of non-primary pollutants is simplified, while dynamic calculation is used for primary pollutants. This not only enables more accurate liquid separation but also makes the control strategy clearer and more efficient.

[0067] Optionally, a first liquid level sensor 433 may be installed in the separating cylinder 401 to detect the liquid level of the wastewater in the separating cylinder 401. The first liquid level sensor 433 may, exemplarily, be a continuous liquid level sensor. The first liquid level sensor 433 can record changes in the liquid level within the separating cylinder 401, such as recording the total liquid level height in the separating cylinder 401, the height of the discharged liquid, etc. See also... Figure 2 After the liquid in the separatory cylinder has settled and separated into layers, the total height of the liquid level at this point can be recorded as hs. Open the second bottom valve to discharge the high-concentration heavy component pollutants from the bottom out of the system. When the first density sensor detects the wastewater density ρ... 2b =ρ d2 At this point, record the drop in liquid level as h1, and close the second bottom valve. Then open the first bottom valve to discharge the middle layer wastewater with higher water content back into the evaporator. When the first density sensor detects the wastewater density ρ... 2b =ρ d1 At this point, record the height of the drop in liquid level as h2, and close the first bottom valve. Then open the second bottom valve to discharge the high-concentration, light-component pollutants with lower density from the wastewater out of the system.

[0068] In addition, the liquid level data detected by the first liquid level sensor 433 can also be used to control the lower limit of liquid discharge in the liquid dispensing cylinder 401. Once the liquid level detected by the first liquid level sensor 433 is lower than the preset lower limit, the first bottom valve and the second bottom valve are closed to stop the discharge.

[0069] Each time the liquid is separated, the values ​​of hs, h1, and h2 can be recorded. The liquid level height of the heavy component pollutant is h1, the liquid level height of the middle layer liquid is h2-h1, and the liquid level height of the light component pollutant is hs-h2.

[0070] Wherein, the total height of the liquid in the separating cylinder after settling and stratification during the nth separation is denoted by hs. n This indicates the liquid level height h1 after the heavy component pollutants have been discharged. n The liquid height h2 after the middle layer of liquid has been drained n The volume ratio of the liquid in the middle layer to the total liquid volume in the separating cylinder during the nth separation is calculated as kn = (h2) / (h2). n -h1 n ) / hs n .

[0071] When the wastewater concentration in the evaporator is high, it means that the total amount and concentration of light and heavy pollutants are large. After this high-concentration wastewater is sent to the separatory tank for settling, the light component stratification and heavy component stratification will be relatively thicker, while the middle layer will be relatively thinner. Therefore, during discharge, (h2) n -h1 nThe concentration of pollutants in the wastewater will decrease, leading to a lower calculated kn value. Conversely, if the concentration in the evaporator is low, the amount of pollutants in the wastewater fed into the separatory cylinder will be less, resulting in a thicker middle layer after stratification and a higher kn value. In other words, a decreasing kn value indicates that the concentration in the evaporator is increasing; an increasing kn value indicates that the concentration is decreasing. The kn value is inversely correlated with the real-time wastewater concentration in the evaporator.

[0072] In some implementations, by comparing the sequence of kn values ​​over the most recent m times (e.g., 3-5 times): k(n-m+1)…k(n-2), k(n-1), kn, the working interval of the dispensing cylinder can be adjusted based on the trend of the kn values, allowing the wastewater in the evaporator to maintain a more stable concentration. For example, when kn drops to the third preset threshold, the interval t(n+1) for the next dispensing is shortened. If kn decreases significantly, it indicates that the wastewater concentration in the evaporator is increasing, and the proportion of low-concentration wastewater is decreasing. Therefore, the interval between two dispensing operations in the dispensing cylinder can be shortened, resulting in a relatively lower wastewater concentration in the evaporator during the next dispensing operation. When kn rises to the fourth preset threshold, the interval t(n+1) for the next dispensing is extended. If kn increases significantly, it indicates that the wastewater concentration is decreasing, and the proportion of low-concentration wastewater is increasing. Therefore, the dispensing interval t(n+1) can be extended, allowing higher-concentration wastewater to enter the dispensing cylinder during the next dispensing operation.

[0073] In other implementations, the rate of change of k can be calculated by comparing the most recent m kn value sequences. This not only reveals the concentration of the wastewater but also the trend of concentration change. By analyzing this trend, the working interval of the dispensing cylinder can be adjusted, allowing for more robust and forward-looking adjustments. For example, if the rate of change of k decreases to a first preset threshold, the interval t(n+1) of the next dispensing cycle is shortened; if the rate of change of k increases to a second preset threshold, the interval t(n+1) of the next dispensing cycle is extended.

[0074] Optionally, the liquid separation unit may further include a liquid separation cylinder heat exchanger 402 disposed around the outer periphery of the liquid separation cylinder 401. The liquid separation cylinder heat exchanger 402 may, exemplarily, be a jacketed heater. The liquid separation cylinder heat exchanger inlet 4021 is connected to the exhaust port 2012 of the compressor 201, and a liquid separation cylinder heating valve 424 is disposed between them. The drain port of the liquid separation cylinder heat exchanger 402 is connected to a liquid separation cylinder drain valve 425. The liquid separation cylinder drain valve 425 may be independently connected to the outside of the system or connected to the lower part of the shell side 103, so that the condensate generated in the liquid separation cylinder heat exchanger 402 and the condensate generated in the evaporation heat exchanger 101 are both discharged from the shell side distilled water outlet 1033. With this design, during the operation of the liquid separation unit, when the liquid separation cylinder 401 is under vacuum and boiling evaporation is carried out using residual heat, the liquid separation cylinder heating valve 424 and the liquid separation cylinder drain valve 425 can be opened to introduce some steam from the exhaust port 2012 of the compressor 201 to actively heat the liquid separation cylinder 401. The wastewater in the liquid separation cylinder 401 can evaporate more quickly under vacuum, achieving secondary concentration. After a set time, the liquid separation cylinder heating valve 424 and the liquid separation cylinder drain valve 425 can be closed, the first suction valve 521 can be closed, and the liquid separation cylinder pressurization valve 423 can be opened, then entering the settling stage. In this way, the high-quality steam generated by the compressor 201 can be directly used to heat and evaporate the wastewater in the liquid separation cylinder 401, achieving secondary concentration and further improving the subsequent settling and stratification effect. At the same time, the concentration of the middle layer liquid subsequently sent back to the evaporator 100 is also relatively lower.

[0075] Optionally, the evaporation system may also include a preheating unit. The preheating unit is primarily used to preheat the wastewater to be treated before it enters the evaporator. This improves the evaporator's processing efficiency and prevents drastic temperature fluctuations in the evaporator during large-scale replenishment. When wastewater evaporated to a certain concentration in the evaporator is transported to the liquid separation unit, a large amount of new wastewater needs to be added to the evaporator. If the added wastewater is at a low temperature, the overall temperature of the wastewater in the evaporator will drop significantly, affecting the stability and continuity of evaporation. Therefore, introducing a preheating unit in addition to the aforementioned liquid separation unit in the evaporator system facilitates continuous, efficient, and stable evaporation treatment.

[0076] The preheating unit includes a preheating cylinder 301 and a preheating cylinder heat exchanger 302.

[0077] The preheating cylinder 301 is the main container for preheating waste liquid. The preheating cylinder 301 may be equipped with a preheating cylinder delivery port, which can be connected to the evaporator inlet via the liquid inlet pipe 111 to deliver the preheated waste liquid to the evaporator 100. The preheating cylinder 301 may also be equipped with a preheating cylinder inlet, which can be the same connection port as the preheating cylinder delivery port, or they can be two separate connection ports; this application does not limit this. A preheating cylinder inlet valve 321 may be installed on the pipe connecting the preheating cylinder inlet or the preheating cylinder delivery port.

[0078] The heat exchanger 302 of the preheating cylinder is located on the outer periphery of the preheating cylinder 301 and is mainly used to provide heat for heating the liquid in the preheating cylinder 301.

[0079] The steam inlet 3021 of the preheating cylinder heat exchanger is connected to the shell-side steam outlet 1032 provided on the shell side 103. The drain outlet 3024 of the preheating cylinder heat exchanger is connected to a preheating cylinder drain valve 324. Optionally, the distilled water inlet 3023 of the preheating cylinder heat exchanger can be located at the lower part of the preheating cylinder heat exchanger 302, connected to the shell-side distilled water outlet 1033 at the lower part of the shell side 103, and the distilled water inlet 3023 of the preheating cylinder heat exchanger is connected to the drain outlet 3024 of the preheating cylinder heat exchanger.

[0080] With this connection method, the steam in the shell side 103 of the evaporator heat exchanger 101 can be introduced into the preheating cylinder heat exchanger 302, and the condensate in the evaporator 100 can also flow into the preheating cylinder heat exchanger 302 and be discharged from the system through the drain port 3024 of the preheating cylinder heat exchanger 302 and the preheating cylinder drain valve 324.

[0081] The preheating cylinder heat exchanger 302 is also provided with a gas outlet 3022, which is connected to the gas phase outlet 1001 provided on the upper part of the evaporator 100, and a return gas valve 322 is provided between the two. Exemplarily, the connecting pipes of the gas outlet 3022 and the gas phase outlet 1001 can partially overlap with the exhaust pipe 112 connecting the evaporator 100, such as... Figure 1 As shown.

[0082] Optionally, a second liquid level sensor 332 may be installed in the preheating tank 301 to measure whether the wastewater in the preheating tank 301 has reached a preset liquid level. The second liquid level sensor 332 may, exemplarily, be a continuous liquid level sensor.

[0083] As evaporation proceeds, the concentration of wastewater in evaporator 100 continuously increases, which may reduce the amount of steam generated in evaporator 100. Consequently, the amount of secondary steam heated and pressurized by compressor 201 also decreases, resulting in insufficient steam in preheating cylinder heat exchanger 302. This, in turn, prevents the wastewater in preheating cylinder 301 from being preheated to its original temperature, thus affecting the continuous and stable operation of the evaporation process. To address this, optionally, preheating cylinder 301 is also equipped with a preheating cylinder heater 303 and a second temperature sensor 333. The second temperature sensor 333 is used to detect the temperature of the wastewater in preheating cylinder 301. When the second temperature sensor 333 detects that the wastewater temperature in preheating cylinder 301 has dropped and is lower than the wastewater temperature in evaporator 100, the control unit is configured to: control the preheating cylinder heater 303 to open, thereby supplementing heating and raising the temperature of the wastewater in preheating cylinder 301. In this way, when replenishing liquid to evaporator 100, drastic temperature fluctuations can be avoided, maintaining the continuity and stability of the main evaporation process.

[0084] The MVR evaporation system may also include a vacuum system, which can at least provide a vacuum environment for the evaporation system. The vacuum system can employ existing solutions, and this application is not limited thereto. Exemplarily, the vacuum system includes a circulating water tank 502, a circulating water pump 501, and an ejector 503. The outlet of the circulating water tank 502 is connected to the inlet of the circulating water pump 501, the outlet of the circulating water pump 501 is connected to the inlet of the ejector 503, the outlet of the ejector 503 is connected to the inlet of the circulating water tank 502, and the suction port of the ejector 503 can be connected to the space to be evacuated. The circulating water pump 501 pressurizes the working liquid (usually water) in the circulating water tank 502 and delivers it at high speed into the nozzle of the ejector 503. According to Bernoulli's principle, a strong vacuum effect is generated in the mixing chamber and suction chamber of the ejector 503, thereby evacuating the space connected to the suction port.

[0085] Optionally, in this embodiment, the suction port of the ejector 503 can be connected to the upper part of the separating cylinder 401 via a first vacuum line 511 equipped with a first suction valve 521, which can evacuate the separating cylinder 401 when needed. The control unit can be configured to open the first suction valve before opening the first bottom valve to deliver the liquid in the evaporator to the separating cylinder. By designing the first vacuum line 511, a vacuum can be evacuated from the separating cylinder 401 during liquid separation. This allows the height of the separating cylinder 401 to be designed to be higher, so that the liquid level in the separating cylinder 401 exceeds the liquid level in the evaporator 100, which is more conducive to static stratification and obtaining a better separation effect. On the other hand, by evacuating, the saturation temperature of the liquid entering the separating cylinder 401 can be lowered. In this way, the waste liquid that has just entered the separating cylinder 401 from the evaporator 100 can continue to evaporate some water using residual heat, further increasing the concentration of wastewater in the separating cylinder 401.

[0086] Optionally, in this embodiment, the suction port of the ejector 503 can be connected to the upper part of the preheating cylinder 301 via a second vacuum pipeline 512 equipped with a second suction valve 522, so that the preheating cylinder 301 can be evacuated when needed. For example, when the preheating cylinder 301 needs to be replenished with new wastewater from the outside, the wastewater under normal external pressure can be drawn into the preheating cylinder 301 due to the pressure difference through the second vacuum pipeline 512, eliminating the need for structures such as mechanical feed pumps.

[0087] The MVR evaporation system may also include a pressurization system for regulating the pressure within the dispensing cylinder 401 and / or the preheating cylinder 301.

[0088] Optionally, a first compressed gas pipeline can be connected to the upper part of the separating cylinder 401, and a separating cylinder pressurization valve 423 is installed on the first compressed gas pipeline. During static separation, for example, after the liquid in the separating cylinder 401 has stopped boiling, the control unit can be configured to close the first suction valve 521 and open the separating cylinder pressurization valve 423. This method can pressurize the separating cylinder 401, which helps to eliminate foam and air bubbles in the separating cylinder 401 more quickly and achieve a better separation effect.

[0089] If wastewater is added to the evaporator 100 from the preheating cylinder 301, and the temperature of the liquid added to the evaporator 100 is significantly lower than the original temperature of the liquid in the evaporator 100, it may affect or even interrupt the evaporation process. To address this, optionally, a second compressed gas pipeline can be connected to the upper part of the preheating cylinder 301, and a preheating cylinder pressurization valve 323 is installed on the second compressed gas pipeline. When the preheating unit heats the liquid in the preheating cylinder 301, the control unit is configured to: close the second suction valve 522 and open the preheating cylinder pressurization valve 323, so that the gas pressure in the preheating cylinder 301 is greater than the gas pressure in the evaporator 100. In this way, the saturation temperature that the wastewater in the preheating cylinder 301 can be heated to will be higher than that of the wastewater in the evaporator 100. When wastewater is added to the evaporator 100 from the preheating cylinder 301, it can be ensured that the evaporation temperature of the evaporator 100 will not drop, further contributing to the efficient and stable evaporation process of the evaporator system.

[0090] The following section will further explain the working process of the MVR evaporator system.

[0091] First, the system enters the liquid inlet stage. Compressor 201 is started. Under the suction action of compressor 201, the pressure in the tube side 102 of evaporator 100 will form a negative pressure, for example, dropping to 0.5-0.7 bar. The preheating cylinder inlet valve 321 and the evaporator inlet valve 121 are opened. Due to the negative pressure, the wastewater to be treated is drawn into evaporator 100. When the third liquid level sensor 131 in tube side 102 is triggered, the evaporator inlet valve 121 is closed, and the system enters the heating stage.

[0092] When the evaporator liquid inlet is complete, the evaporator liquid inlet valve 121 is closed, while the preheating cylinder liquid inlet valve 321 remains open. The second suction valve 522 located on the preheating cylinder 301 is then opened. The preheating unit generates negative pressure under the action of the vacuum system, drawing wastewater into the preheating cylinder 301. When the second liquid level sensor 332 detects that the wastewater in the preheating cylinder 301 has reached the designated level, the preheating cylinder liquid inlet valve 321 and the second suction valve 522 are closed. Then, the preheating cylinder pressurization valve 323 is opened. One end of the preheating cylinder pressurization valve 323 is connected to compressed air, with a pressure of approximately 1 bar. Opening the preheating cylinder pressurization valve 323 maintains a pressure of 1 bar (gauge pressure) in the preheating cylinder 301, preventing boiling when the liquid temperature in the preheating cylinder 301 is high.

[0093] The system then enters the heating stage. During this stage, the gas in tube side 102 is compressed in compressor 201, its temperature rises, and it exits from compressor 2012, entering the shell side 103 of evaporator heat exchanger 101 to heat the wastewater in tube side 102. The gas in shell side 103 then passes through shell side steam outlet 1032 and enters preheating cylinder heat exchanger 302 to preheat the wastewater in preheating cylinder 301. After heat exchange, the condensate in preheating cylinder heat exchanger 302 is discharged from the system through preheating cylinder heat exchanger 302's drain outlet 3024 and preheating cylinder drain valve 324. The remaining gas can then return to tube side 102 of evaporator 100 through return gas valve 322.

[0094] The pressure and temperature data measured by the third pressure sensor 133 and the third temperature sensor 134 can determine whether the wastewater in tube 102 has reached its saturation temperature. When the water temperature in tube 102 reaches the saturation temperature, it will boil and generate steam. The system then enters the evaporation stage. During the evaporation stage, the return gas valve 322 is closed; when there is non-condensable gas in the evaporator 100, the exhaust valve 122 is opened, and the non-condensable gas is discharged through the exhaust pipe 112.

[0095] As evaporation proceeds, the wastewater in evaporator 100 decreases. When the third liquid level sensor 131 in evaporator 100 detects a drop in liquid level, the evaporator inlet valve 121 can be opened to allow wastewater at a certain temperature in the preheater (preheating cylinder 301) to replenish evaporator 100. Since the pressure in preheating cylinder 301 can be controlled to be higher than the pressure in evaporator 100 via preheating cylinder pressure valve 323, the wastewater in preheating cylinder 301 can be heated to a relatively higher saturation temperature. Using this method, when preheating cylinder 301 replenishes wastewater to evaporator 100, the evaporation temperature of evaporator 100 can be ensured not to drop, further contributing to efficient and stable evaporation processing of the evaporator system.

[0096] When the second liquid level sensor 332 detects that the wastewater level in the preheating cylinder 301 is low, the preheating cylinder pressurization valve 323 is closed, the second suction valve 522 is opened, and the preheating cylinder inlet valve 321 is opened to replenish new wastewater into the preheating cylinder 301 from the outside.

[0097] As the wastewater continues to evaporate, the concentration of wastewater in evaporator 100 gradually increases. Once a set value is reached, the wastewater in evaporator 100 is discharged into separator 401 for separation to remove some pollutants and reduce the wastewater concentration. Of course, since the concentrated wastewater is discharged, the wastewater in the preheater (preheating cylinder 301) can also be replenished to evaporator 100. In this way, the concentration of wastewater in evaporator 100 can be reduced during the system's evaporation process, preventing or prolonging the time it takes for the wastewater in evaporator 100 to reach its maximum concentration and cease evaporation. This allows evaporator 100 to remain in an evaporation state for an extended period, improving its processing efficiency.

[0098] For the liquid separation unit, when wastewater from the evaporator 100 needs to be discharged into the liquid separation cylinder 401, the first suction valve 521 is opened to create a vacuum inside the liquid separation cylinder 401. The first bottom valve 421 is then opened, and under the vacuum, the wastewater from the evaporator 100 is drawn into the liquid separation cylinder 401. When the first liquid level sensor 433 detects that the liquid level in the liquid separation cylinder 401 has risen to a set level, the first bottom valve 421 is closed. Due to the vacuum, the liquid level in the liquid separation cylinder 401 can exceed the liquid level in the evaporator 100, allowing the height of the liquid separation cylinder 401 to be set higher, thus making it easier for the wastewater to separate into layers and achieving a better separation effect. Also due to the vacuum, the saturation temperature of the liquid in the liquid separation cylinder 401 drops significantly. Therefore, the wastewater entering the liquid separation cylinder 401 from the evaporator 100 will continue to boil until the wastewater temperature drops below the saturation temperature corresponding to the negative pressure. The water vapor generated during this continued boiling process will be drawn away by the vacuum system through the first vacuum line 511, and the concentration of the waste liquid will increase slightly after entering the separatory cylinder 401.

[0099] After boiling stops, close the first suction valve 521 and open the separatory cylinder pressure valve 423. One end of the separatory cylinder pressure valve 423 is connected to compressed air, and the other end is connected to the separatory cylinder 401. After opening the separatory cylinder pressure valve 423, the pressure inside the separatory cylinder 401 can rise to 5-7 bar. The separatory unit enters a static state. Under pressure, the foam and bubbles generated by boiling in the separatory cylinder 401 will quickly disappear, and the liquid in the separatory cylinder 401 will begin to separate into layers.

[0100] After a certain period of settling, the stratification is basically completed. Based on the different densities of the wastewater layers, the wastewater is divided into three parts: a lower layer with high concentrations of heavy pollutants, a middle layer with densities similar to the original wastewater solution and water, and an upper layer with high concentrations of light pollutants. At this point, the separation unit can enter the evacuation stage.

[0101] Open the second bottom valve 422 to make the bottom density greater than ρ. d2 The pollutants are discharged to the outside of the system through the second branch 412. When the first density sensor 431 detects that the density of the wastewater is greater than ρ... d2 It becomes equal to ρ d2 When the pollutants have been completely discharged, the second bottom valve 422 is closed and the first bottom valve 421 is opened, allowing the intermediate wastewater portion to return to the evaporator 100 through the first branch 411. When the first density sensor 431 detects that the wastewater density has decreased to equal ρ... d1 When the discharge of the intermediate layer of wastewater is completed, the first bottom valve 421 is closed and the second bottom valve 422 is opened to discharge the light component pollutants to the outside of the system through the second branch 412.

[0102] Whether discharging into the evaporator 100 or to the outside of the system, if the first liquid level sensor 433 detects a low liquid level in the dispensing cylinder 401, the first bottom valve 421 and the second bottom valve 422 are closed, thus completing one dispensing process. During the dispensing process in the dispensing unit, the wastewater concentration in the evaporator 100 decreases due to the replenishment of new wastewater to be treated and the intermediate layer wastewater from the dispensing unit, allowing for continuous evaporation. After a period of evaporation, when the wastewater concentration in the evaporator 100 is detected to have reached a set value, the dispensing unit restarts the dispensing process, and this cycle continues.

[0103] It is understood that the MVR evaporation system in this application embodiment may also include other possible components, and in actual use it may also be connected to other possible components, parts, systems, etc., which is not limited in this application. Exemplarily, in some possible implementations, the MVR evaporation system may also include a concentrate storage tank, which can be connected to the dispensing cylinder delivery port through a second branch.

[0104] It should be understood that in the description of this application, the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., generally indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These directions and positional relationships are for ease of description and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0105] It should also be understood that, unless otherwise explicitly specified, the terms "installation," "connection," "assembly," "fixing," etc., in the description of this application should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0106] It should also be understood that, unless otherwise explicitly specified, "multiple" means two or more.

[0107] The same or similar parts among the various embodiments in this specification can be referred to interchangeably. Different implementations in the above embodiments can be combined with each other as long as they do not contradict each other. The above implementation methods do not constitute a limitation on the scope of protection of this application.

Claims

1. An MVR evaporator system, characterized in that, It includes an evaporator, compressor, liquid distribution unit, and control unit; among which, An evaporator heat exchanger is provided inside the evaporator. The tube side of the evaporator heat exchanger is connected to the suction port of the compressor through the gas phase outlet at the top of the evaporator, and the discharge port of the compressor is connected to the shell side inlet of the evaporator heat exchanger. The liquid separation unit includes a liquid separation cylinder and a first density sensor. The liquid separation cylinder has a liquid separation cylinder inlet at its bottom, which is connected to the bottom discharge port of the evaporator via a first branch, and a first bottom valve is installed on the first branch. The liquid separation cylinder inlet is also connected to a second branch connecting to the outside of the system, and a second bottom valve is installed on the second branch. The first density sensor is installed at the bottom of the liquid separation cylinder to measure the liquid density ρ at the bottom of the liquid separation cylinder in real time. 2b ; The control unit is configured to: after the liquid has settled and separated in the separating cylinder, at least based on the ρ 2b The system controls the opening and closing states of the first bottom valve and the second bottom valve to discharge the heavy component pollutants in the lower layer and the light component pollutants in the upper layer to the outside of the system via the second branch, and to transport the liquid in the middle layer back to the evaporator via the first branch.

2. The MVR evaporator system according to claim 1, characterized in that, The control unit is specifically configured as follows: In ρ 2b ≥Second density threshold ρ d2 In this case, the first bottom valve is controlled to be closed and the second bottom valve is controlled to be open, so as to discharge the lower layer of heavy component pollutants through the second branch; Second density threshold ρ d2 >ρ 2b > First density threshold ρ d1 In this case, the second bottom valve is controlled to be closed and the first bottom valve is controlled to be open, so as to transport the liquid in the middle layer back to the evaporator via the first branch; In ρ 2b ≤ First density threshold ρ d1 In this case, the first bottom valve is controlled to be closed and the second bottom valve is controlled to be open, so as to discharge the upper light component pollutants through the second branch.

3. The MVR evaporator system according to claim 2, characterized in that, The system also includes a second density sensor and a third density sensor; the second density sensor is installed on the upper part of the dispensing cylinder and is used to measure the liquid density ρ in the upper part of the dispensing cylinder. 2a The third density sensor is used to measure the initial density ρ1 of the liquid to be treated entering the system. The control unit is also configured to: Calculate the weighted value λ = (ρ1 - ρ3) / (ρ1 - ρ2); Where ρ2 is the highest concentration of the liquid in the separatory cylinder. When the lighter component contaminants are greater than the heavier component contaminants in the separatory cylinder, ρ2 = ρ 2a When the heavy component contaminant is greater than the light component contaminant in the separatory cylinder, ρ2 = ρ 2b ρ3 is the average density of the liquid in the separatory cylinder. ρ(h) is the curve of liquid density as a function of liquid level height measured by the first density sensor, and hs is the total liquid height in the dispensing cylinder; Calculate ρ d1 and ρ d2 ; where the light component contaminants are greater than the heavy component contaminants in the separating cylinder, ρ d1 =ρ3+λ(ρ2-ρ3), ρ d2 =1; When the heavy component contaminants are greater than the light component contaminants in the separatory cylinder, ρ d1 =1,ρ d2 =ρ3+λ(ρ2-ρ3).

4. The MVR evaporator system according to claim 1, characterized in that, The liquid separation unit also includes a first liquid level sensor for real-time detection of the liquid level in the liquid separation cylinder; The control unit is also configured to: Record the total height hs of the liquid in the separating cylinder after settling and stratification during the nth separation. n The liquid level height h1 after the heavy component pollutants are discharged n And the liquid height h2 after the middle layer of liquid has been discharged. n ; The volume ratio of the liquid in the middle layer to the total liquid volume in the separating cylinder during the nth separation is calculated as kn = (h2) / (h2). n -h1 n ) / hs n ; Determine the rate of change of k based on k(n-m+1)…k(n-2), k(n-1), kn for m consecutive separations; When the rate of change of k decreases to the first preset threshold, the interval t(n+1) of the next separation is shortened. If the rate of change of k rises to the second preset threshold, the interval t(n+1) of the next separation is extended.

5. The MVR evaporator system according to any one of claims 1 to 4, characterized in that, It also includes a vacuum system, which is connected to the upper part of the liquid separator via a first vacuum line equipped with a first suction valve; The control unit is configured to control the opening of the first suction valve before opening the first bottom valve to deliver liquid in the evaporator to the dispensing cylinder.

6. The MVR evaporator system according to claim 5, characterized in that, The upper part of the liquid separator is also connected to a first compressed gas pipeline, and a liquid separator pressurization valve is installed on the first compressed gas pipeline. The control unit is configured to: after the liquid in the separating cylinder stops boiling, control the closing of the first suction valve and the opening of the pressure valve of the separating cylinder.

7. The MVR evaporator system according to any one of claims 1 to 4, characterized in that, The liquid separation unit also includes a liquid separation cylinder heat exchanger disposed on the outer periphery of the liquid separation cylinder; wherein, the inlet of the liquid separation cylinder heat exchanger is connected to the exhaust port of the compressor and a liquid separation cylinder heating valve is disposed between the two; the drain port of the liquid separation cylinder heat exchanger is connected to a liquid separation cylinder drain valve.

8. The MVR evaporator system according to any one of claims 1 to 4, characterized in that, It also includes a preheating unit, which includes a preheating cylinder and a preheating cylinder heat exchanger disposed on the outer periphery of the preheating cylinder; the preheating cylinder inlet is connected to the evaporator; the inlet of the preheating cylinder heat exchanger is connected to the shell-side steam outlet disposed on the shell side; the drain outlet of the preheating cylinder heat exchanger is connected to a preheating cylinder drain valve; the gas outlet of the preheating cylinder heat exchanger is connected to the gas phase outlet disposed on the upper part of the evaporator, and a return gas valve is disposed between the two.

9. The MVR evaporator system according to claim 8, characterized in that, The upper part of the preheating cylinder is connected to the vacuum system through a second vacuum pipeline equipped with a second suction valve; the upper part of the preheating cylinder is also connected to a second compressed gas pipeline, and a preheating cylinder pressurization valve is installed on the second compressed gas pipeline; The control unit is configured to: when the preheating unit heats the liquid in the preheating cylinder, control the closing of the second suction valve and the opening of the preheating cylinder pressurization valve, so that the gas pressure in the preheating cylinder is greater than the gas pressure in the evaporator.

10. The MVR evaporator system according to claim 8, characterized in that, The preheating cylinder is also equipped with a preheating cylinder heater and a second temperature sensor, the second temperature sensor being used to detect the temperature of the wastewater in the preheating cylinder. The control unit is configured to control the preheating cylinder heater to turn on when the wastewater temperature in the preheating cylinder drops below the wastewater temperature in the evaporator.

Images