MVR (Mechanical Vapor Recompression) evaporation device with convertible operation modes

Abstract

The utility model discloses an MVR (Mechanical Vapor Recompression) evaporation mode and device capable of changing operation modes. According to the MVR evaporation mode capable of changing the operation mode, the MVR evaporation device and the common evaporation devices connected in series are respectively used for forming two sections of evaporation devices, and heat source steam and steam output by a compressor in the MVR evaporation device are used for providing evaporation heat sources for the two sections of evaporation devices in parallel; control valves are respectively arranged on steam supply pipelines through which heat source steam and steam output by a compressor in the MVR evaporation device are parallel to the two sections of evaporation devices, so that independent heat supply channels for the two sections of evaporation devices are realized.

Description

Technical Field

[0001] The utility model relates to an MVR evaporation device with switchable operating modes, and more particularly to an evaporation device capable of processing different types of materials or the same material with significantly varying output concentrations and temperatures within the same MVR evaporation system. The MVR evaporation device with switchable operating modes comprises a steam compressor and at least one evaporator, along with interconnected steam piping, a distilled condensate output pipe, a waste liquid input pipe for processing, a treated concentrated waste liquid discharge pipe, pumps or circulation pumps for conveying various liquids, and control valves disposed on each pipe. Background Art

[0002] Evaporation systems play a crucial role in national production activities, with a wide range of applications. They can be used in some industrial processes for material concentration and drying, product extraction and separation, seawater desalination for production and domestic water, and various other functions, such as material crystallization and separation, and resource recycling and reuse. Evaporation system configurations primarily include multi-effect evaporation, MVR evaporation, and a combination of multi-effect and MVR evaporation. For example, CN105536276 A and CN 108217797 A disclose a combined evaporation device consisting of a steam compressor and two evaporators. Multi-effect evaporation systems utilize vacuum evaporation. The first-effect evaporator uses fresh steam as the power heat source, while each subsequent evaporator uses the secondary steam generated by the previous effect, after being compressed by the compressor, as the evaporation heat source. However, the secondary steam from the last-effect evaporator is rendered useless due to its very low pressure and temperature, and must be condensed using circulating cooling water to create a vacuum. This creates a significant pressure and temperature gradient between the preceding and succeeding devices, ensuring smooth and continuous evaporation. The advantages of multi-effect evaporation lie in its numerous process steps and flexible design. It's easy to find the right point in the system to achieve complex process goals based on diverse requirements. However, its disadvantages are also obvious. First, it requires a large footprint, numerous process control steps, a complex process, and high operating costs. Furthermore, since the final effect operates very close to a vacuum, achieving more economical performance requires increasing the number of effects and raising the pressure and temperature of the fresh steam in the first-effect evaporator to ensure pressure and temperature differences between the devices. However, when the number of effects reaches a certain level, costs rise significantly, while the increase in operating efficiency is extremely limited, resulting in generally low operating efficiency. MVR evaporation combines multiple effects in a single unit, allowing for a large heat exchange area. It also features minimal control steps, a small footprint, and very low operating costs. It is essentially powered entirely by electricity, with secondary steam heated and pressurized by a steam compressor and then returned to the evaporator to provide the heat source for evaporation. All steam is effectively utilized, with no exhaust, effectively utilizing the steam's latent heat. This results in high operating efficiency, enabling a large evaporated water volume from a single unit, while being energy-efficient and environmentally friendly. However, this type of equipment system is suitable for relatively simple process links and cannot achieve complex process objectives. For materials with high boiling point rise values, multiple steam compressors must be used in series, which significantly reduces the economic efficiency of investment. To utilize the flexible characteristics of multi-effect evaporation and the ease of achieving complex goals, while also meeting the needs of low operating costs and land conservation, multi-effect and MVR combined evaporation has emerged, which can largely meet the needs of certain conditions. However, the combination of two evaporation systems leads to more complex process links, requiring the use of various control methods to achieve process objectives, requiring a larger site, and significantly increasing project investment. Summary of the Invention

[0003] The utility model provides an MVR evaporation device with a switchable operating mode, which can overcome the shortcomings of the prior art.

[0004] This utility model discloses an MVR evaporator with switchable operating modes. It utilizes two evaporators, one in the front section and one in the rear section. The front section consists of an MVR evaporator, while the rear section consists of a conventional evaporator. After treatment in the MVR evaporator, the liquid feed can be selectively fed into the feed port of the conventional evaporator in the rear section or directly discharged through a concentrated liquid feed pipe via controlled valves. Both evaporators can utilize heat source steam or steam output from the MVR evaporator's compressor as the evaporation heat source. Control valves are installed on the parallel steam supply lines for the heat source steam and steam output from the MVR evaporator's compressor to the two evaporators. By adjusting the opening and closing of different valves on the steam pipelines, various separate heat supply channels to the two evaporators can be selected. In this utility model, the control of different control valves enables the device to switch between different operating modes.

[0005] Preferably, the utility model is an MVR evaporation device with a switchable operation mode, comprising a steam compressor and an evaporator, as well as interconnected steam pipelines, distilled condensate output pipes, waste liquid input pipelines to be treated and concentrated waste liquid discharge pipelines after treatment, and pumps or circulation pumps for conveying various liquids and control valves arranged on each pipeline. The utility model is provided with a front and rear two-stage evaporation device, wherein: the MVR evaporation device composed of at least one steam compressor and at least one evaporator constitutes a first-stage evaporation device; the ordinary evaporation device constitutes a second-stage evaporation device, in which: the feed liquid input end of the primary evaporator is connected to the feed liquid supply end of the material to be treated. The feed pipes are connected, the feed liquid output end of the previous evaporator is connected to the feed liquid input end of the next evaporator, the feed liquid output end of the final evaporator is respectively connected to the feed end of the second-stage evaporator and the concentrated liquid discharge pipe, the heat source steam and the compressor steam outlet end of the MVR evaporator are respectively connected to the heating steam input end of the first evaporator and the second evaporator, and control valves are provided on the steam pipelines connecting the discharge end of the first evaporator and the second evaporator with the concentrated liquid discharge pipe, and connecting the first evaporator and the second evaporator with the heat source steam and the evaporator. Circulation pipes with circulation pumps are respectively provided on each stage of the first evaporator and the second evaporator. The two-stage evaporation device described in the present invention can adopt any existing evaporator, such as a tubular evaporator or a plate evaporator. Of course, the forced circulation evaporator with a heater and flash evaporator in the embodiment of the present invention can also be used.

[0006] Preferably, the MVR evaporation device with a switchable operating mode of the present invention comprises a two-stage evaporation and heating device comprising a flash evaporator and a two-stage evaporation heater. A two-stage evaporation heater circulation pipe with a circulation pump is disposed between the discharge and feed ends of the flash evaporator, and the circulation pipe is serially connected between the feed and discharge ends of the two-stage evaporation heater. Specifically, in the MVR evaporation device with a switchable operating mode of the present invention, the two-stage evaporation device utilizes a forced circulation evaporator comprising a heater and a flash evaporator. A two-stage evaporation heater circulation pipe with a circulation pump is disposed between the heater and the flash evaporator, and the circulation pipe is serially connected between the feed and discharge ends of the two-stage evaporation heater.

[0007] Preferably, in a MVR evaporation device with a switchable operation mode of the present invention, a first-stage evaporation device is composed of a steam compressor and two evaporators, each consisting of a first-stage evaporator and a second-stage evaporator. The liquid output end of the first-stage evaporator of the first-stage evaporator is connected to the liquid input end of the second-stage evaporator, the discharge end of the second-stage evaporator is respectively connected to the liquid input end and the concentrated liquid discharge pipe of the second-stage evaporator, the secondary steam outlet ends of each stage of the evaporator of the first-stage evaporator and the secondary steam output end of the second-stage evaporator are connected to the input end of the steam compressor, the heating ends of the two-stage evaporators of the first-stage evaporator and the heating end of the second-stage evaporator are respectively connected to the steam output pipe of the steam compressor and the heat source steam pipe, and at the same time, the secondary steam pipe (37) of the second-stage evaporator is also connected to the steam inlet main pipe (26) of the first-stage evaporator, and the setting function is realized by switching the valve. Control valves are provided on the steam pipes connecting the discharge ends of the first-stage evaporator and the second-stage evaporator with the concentrated liquid discharge pipe, and connecting the first-stage evaporator and the second-stage evaporator with the heat source steam and the evaporator.

[0008] More preferably, the MVR evaporation device with a switchable operating mode of the present invention is controlled by a DCS automatic control system.

[0009] The device of this utility model is equipped with a two-stage evaporation device. The first stage evaporation device consists of a steam compressor and multiple evaporators, thus forming a multi-stage evaporation device that fully adopts the MVR evaporation method. The first stage evaporation device generates secondary steam, which is driven by electricity and then heated and pressurized by the steam compressor and returned to the evaporator to provide the evaporation heat source, prompting the evaporator to generate secondary steam again, forming a continuous, stable and reliable evaporation process. After the first stage evaporation, the concentration of the processed material increases and the flow rate decreases. Then, it is fed through the material transfer pipe through the control valve to the second stage evaporator of the second stage evaporation device. If the boiling point of the material to be processed increases significantly after the concentration reaches a certain level, the heat source steam of the evaporator needs to be at a higher temperature and pressure. In this case, the power heat source of the second-stage evaporation heater in the two-stage evaporation device of the present invention uses the heat source steam from the pipeline network, which is exchanged with the material to form clean condensate and sent away. The concentration of the material to be processed continues to increase in the second-stage evaporator and is discharged from the concentrated liquid discharge pipe through the control valve after meeting the process requirements. If the process conditions permit or require, such as the material to be processed is very heat-sensitive, or the temperature of the material in the evaporator needs to be controlled to avoid the material from coking or long molecular chain breakage under high temperature conditions, the heat supply of the second-stage evaporation heater can be switched to the heat supply of the steam compressor, which has a relatively low saturated vapor pressure and temperature, and the material temperature is also low, thus avoiding the sensitive temperature of the material. The utility model can also mix the secondary steam of the second evaporation and the secondary steam of the first evaporation before the steam compressor, and enter the steam compressor together. After the steam is heated and pressurized by electricity, it is all sent to the first evaporator to provide the evaporation heat source. If the opposite is true, the viscosity of certain materials is highly sensitive to temperature, and basic fluidity can only be guaranteed by increasing the material temperature. In this case, the secondary steam from the second-stage evaporator can be connected to the outlet of the steam compressor. The saturated vapor pressure of the secondary steam is consistent with that of the steam compressor outlet. As the steam pressure increases, the corresponding material temperature also rises significantly, ensuring that the material can maintain a higher temperature without a significant increase in viscosity, and still maintain good fluidity. The secondary steam from the second-stage evaporation and the secondary steam from the first-stage evaporation are mixed after the steam compressor, and then enter the first-stage evaporator for heat transfer exchange, forming effective evaporation.

[0010] If the boiling point rise of the material at concentrated outlet is not significantly higher than that of the first-stage evaporation, the present invention switches the power heat source for the second-stage evaporation to the MVR evaporation mode. This means that the fresh steam supply to the second-stage evaporation is cut off, and the motive steam for evaporation is supplied by the steam compressor outlet instead. Simultaneously, the secondary steam generated by the second-stage evaporation is mixed with the secondary steam from the first-stage evaporation before entering the steam compressor. After electrical work is performed, the steam is heated and pressurized, and then distributed to the first and second-stage evaporators to provide evaporation heat. At this point, the secondary steam from all the first and second-stage evaporators enters the steam compressor, where it is heated and pressurized by electrical work, and then distributed to all the first and second-stage evaporators, forming an MVR operating mode with overall parallel operation.

[0011] In this way, the device of the present invention can realize the change of operation mode during operation, so that a single device can be applicable to the requirements of multiple different processes and the requirements of different operation modes in the same process.

[0012] The present invention comprises a single-stage evaporator comprising a steam compressor and multiple evaporators. The multi-stage evaporators within the single-stage evaporator enable progressive concentration or feed rotation, and are self-cleaning. A multi-stage evaporator configuration is possible. The primary evaporator generates secondary steam, which is electrically driven and returned to the evaporator after being heated and pressurized by the steam compressor to provide a heat source for evaporation. This encourages the generation of secondary steam within the evaporator, resulting in a continuous, stable, and reliable evaporation process. After the primary evaporator, the processed material's concentration increases and its flow rate decreases. The material is then fed through a feed pipe via a control valve to a secondary evaporator. If the boiling point elevation of the processed material increases significantly after reaching a certain concentration, requiring a higher temperature and pressure for the evaporator's heat source, the secondary evaporator in the present invention utilizes fresh steam from the pipeline network as its power source. This steam exchanges heat with the processed material, forming clean condensate that is then transported away. The processed material's concentration continues to increase within the secondary evaporator until it reaches process requirements and is discharged from the concentrate discharge pipe via a control valve.

[0013] As a preferred structure of the utility model, the one-stage evaporation device consists of a steam compressor and two evaporators. On the one hand, it can form multi-stage evaporation, and at the same time, it can gradually concentrate or rotate the feed to achieve a self-cleaning effect, or isolate one of the evaporators during operation for cleaning and maintenance operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attachment Figure 1 This is a schematic structural diagram of the first embodiment of the present invention, Figure 2 This is a schematic structural diagram of a second embodiment of the present invention, wherein:

[0015] 1 is the feed pipe for the material to be processed, 2 is the feed control valve, 3 is the first-stage evaporator of a section evaporation device, 4 is the circulating pump of the first-stage evaporator, 5 is the condensed water collecting pipe of a section evaporation device, 6 is the condensed water drainage control valve of the first-stage evaporator, 7 is the circulating pipe of the first-stage evaporator, 8 is the steam inlet pipe of the first-stage evaporator, 9 is the non-condensable gas control valve of the first-stage evaporator, 10 is the non-condensable gas collecting pipe of a section evaporation device, 11 is the condensed water tank of a section evaporation device, 12 is the condensed water outlet pipe of the surface condenser, 13 is the surface condenser, 14 is the non-condensable gas discharge pipe, 15 is the circulating cooling water supply pipe, 16 is the circulating cooling water return pipe, 17 is The condensate pump of the first stage evaporation device, 18 is the condensate pipe of the first stage evaporation device, 19 is the feed control valve, 20 is the second stage evaporator of the first stage evaporation device, 21 is the circulation pump of the second stage evaporator, 22 is the condensate drainage control valve of the second stage evaporator, 23 is the circulation pipe of the second stage evaporator, 24 is the steam inlet pipe of the second stage evaporator, 25 is the steam inlet control valve of the second stage evaporator, 26 is the inlet steam main pipe of the first stage evaporation device, 27 is the steam inlet control valve of the first stage evaporator, 28 is the secondary steam control valve of the first stage evaporator, 29 is the secondary steam control valve of the second stage evaporator, 30 is the secondary steam inlet of the steam compressor Steam input main pipe, 31 is the steam compressor steam output main pipe, 32 is the steam compressor, 33 is the steam supply control valve from the steam compressor to the second stage evaporation device, 34 is the steam inlet pipe of the second stage evaporation device, 35 is the heat source steam pipe for the first stage evaporation device, 36 is the secondary steam of the second stage evaporation device into the steam compressor outlet control valve, 37 is the secondary steam pipe of the second stage evaporation device, 38 is the secondary steam of the second stage evaporation device into the steam compressor inlet pipe, 39 is the secondary steam of the second stage evaporation device into the steam compressor inlet control valve, 40 is the flash evaporator, 41 is the steam supply control valve of the heat source steam to the first stage evaporation device, 42 is The heat source steam supply pipe, 43 is the heat source steam to the second stage evaporation steam supply control valve, 44 is the second stage outlet heater circulation pipe, 45 is the second stage evaporation heater, 46 is the second stage evaporation condensate tank, 47 is the second stage evaporation condensate pump, 48 is the second stage evaporation condensate pipe, 49 is the concentrated liquid feed pipe, 50 is the second stage evaporation discharge pipe, 51 is the second stage evaporation heater condensate outlet pipe, 52 is the second stage evaporation discharge control valve, 53 is the second stage evaporation circulation pump, 54 is the second stage inlet heater circulation pipe, 55 is the flash evaporator circulating liquid discharge pipe, 56 is the second stage evaporation feed control valve, 57 is the first stage evaporation discharge pipe, and 58 is the first stage evaporation discharge control valve. DETAILED DESCRIPTION

[0016] The present invention will be described below with reference to the embodiments and accompanying drawings.

[0017] Figure 1This is the first embodiment of the present invention. In this embodiment, the evaporator 3 and the compressor 32 form a one-stage evaporation device. In this embodiment, only the I-stage evaporator is set in the one-stage evaporation device, and the flash evaporator 40 and the second-stage evaporation heater 45 form a two-stage evaporation device. Among them: the feed end of the evaporator 3 in the first-stage evaporation device is connected to the feed liquid to be processed through a pipeline with a feed control valve 2, and an evaporator circulation pipe 7 with a circulation pump 4 is provided between the discharge end and the feed end of the evaporator 3. The steam inlet pipe 8 of the first-stage evaporator of the evaporator 3 is connected to the steam output main pipe 31 of the steam compressor and the heat source steam pipe 42 provided with a steam supply control valve 41 to the first-stage evaporation device through a heating steam pipeline 26 with a control valve 27. The secondary steam output end of the evaporator 3 is connected to the air inlet end of the compressor through a pipeline 30 provided with a secondary steam control valve 28 of the first-stage evaporator. The evaporator circulation pipe 7 of the evaporator 3 is located downstream of the circulation pump, and a first-stage evaporation discharge pipe 57 with a feed control valve 19 thereon is used to connect the feed end of the second-stage evaporation device and the concentrated liquid feeding pipe 49 respectively. In the second-stage evaporation unit, a second-stage heater circulation pipe 44, equipped with a second-stage circulation pump 53, is installed between the liquid inlet and outlet of the flash evaporator 40 and connected in series between the feed and outlet of the second-stage heating evaporator 45. Downstream of the circulation pump 53, the second-stage heater circulation pipe 44 is connected to the concentrate feed pipe 49 via a tee and the second-stage evaporation heater circulation pipe 50, equipped with a second-stage evaporation discharge control valve 52. A second-stage evaporation heater condensate outlet pipe 51 directs condensate from the second-stage evaporation heater into the second-stage evaporation condensate tank 46. The heating steam input of the second-stage evaporation heater 45 is connected to the heat source steam pipe 42 and the steam compressor steam output manifold 31 via pipelines. A heat source steam supply control valve 43 is installed on the pipeline connecting the heat source steam pipe 42 and the heating steam input of the second-stage evaporation heater 45. In this embodiment, the non-condensable gas from evaporator 3 of the first-stage evaporation device is fed into a surface condenser 13 via a non-condensable gas control valve 9 for the evaporator and a first-stage non-condensable gas collection pipe 10. Condensate from evaporator 3 is fed into a first-stage evaporation condensate tank 11 via an evaporation condensate collection pipe 5 equipped with a condensate drain control valve 6. Condensate from surface condenser 13 is also fed into the first-stage evaporation condensate tank 11 via a surface condenser condensate outlet pipe 12, while the non-condensable gas is discharged through a non-condensable gas discharge pipe 14.

[0018] In this embodiment, reed is used as the papermaking raw material. The dilute black liquor sent from pulping is stored in the dilute black liquor tank and then fed by the feed pump through the material feed pipe 1 to be processed into the evaporator 3 of the first-stage evaporation device. During normal operation, the feed amount is accurately and automatically controlled by the feed control valve 2. The secondary steam generated by the treated material in the first stage evaporator 3 is collected in the secondary steam main pipe 30 of the steam compressor and enters the steam compressor 32. After the steam compressor 32 performs work, the temperature and pressure are increased, and the steam main pipe 31 of the steam compressor is sent through the heating end of the evaporator 3 to heat the liquid in the evaporator 3. The liquid is circulated and heated by the circulation pump 4 through the circulation pipe 7 of the evaporator 3, and the black liquor at the bottom of the equipment is circulated to the upper part of the heater, forming a uniform and consistent film on the surface of the heater and flowing downward, and fully heat exchanging with the steam from the steam compressor 32. After receiving heat, the black liquor boils and is concentrated and evaporated, and the concentration gradually increases. The steam after heat exchange in the evaporator 3 is condensed to form condensed water and discharged through the condensate drain control valve 6. The generated secondary steam is collected in the secondary steam main pipe 30 and enters the steam compressor 32. After the steam compressor 32 performs work, the temperature and pressure are increased, and it is sent out through the steam main pipe 31 of the steam compressor and enters the evaporator 3 through the heating steam inlet control valve 27 of the evaporator 3 and the steam inlet pipe 8 respectively, to achieve a stable evaporation process. During this process, the black liquor gradually concentrates to a higher concentration. The resulting condensate is collected in the first-stage evaporation condensate tank 11 and pumped to the preceding process stage by the first-stage evaporation condensate pump 17 for reuse as hot water. When the required concentration is reached, the black liquor flows through the first-stage evaporation discharge pipe 57, the feed control valve 19, and the second-stage evaporation feed control valve 56 into the second-stage evaporation unit for evaporation.

[0019] In this embodiment, the second-stage evaporation employs forced circulation evaporation to address the issue of equipment scaling, which is particularly prone to inorganic salt crystallization when the reed pulp black liquor concentration is high. During operation, the black liquor is fed through the second-stage evaporation feed control valve 56 and the second-stage evaporation heater circulation pipe 54, and then enters the second-stage evaporation heater 45 for circulation heating via the second-stage evaporation circulation pump 53. The heated liquid is fed through the rear end 44 of the second-stage heater circulation pipe into the flash evaporator 40 for flash evaporation. During the second-stage evaporation, the black liquor is continuously and uninterruptedly fed into the second-stage evaporation heater 45 by the second-stage evaporation circulation pump 53, concentrating and producing a higher concentration of black liquor. At this point, the boiling point elevation of the operating medium is very high. The steam compressor's steam supply control valve 33 to the second-stage evaporation is closed, and the fresh steam supply control valve 43 to the second-stage evaporation is opened. At this point, the second-stage evaporation operates in the heat source steam supply mode. The high-temperature heat source steam undergoes sufficient heat exchange within the secondary evaporator heater 45. Fresh steam is condensed to form condensed water, which is collected in the secondary evaporator condensate tank 46 and then pumped to the production system's water points for use by the secondary evaporator condensate pump 47. Black liquor, heated to a desired temperature, flows through the secondary heater outlet circulation pipe 44 and enters the flash evaporator 40 for flash evaporation, generating a large amount of secondary steam, creating a continuous and stable evaporation process. If the black liquor requires a higher temperature to maintain good fluidity, the secondary evaporator secondary steam inlet control valve 39 is closed and the secondary evaporator secondary steam outlet control valve 36 is opened. This connects the secondary steam from the secondary evaporator to the outlet of the steam compressor 32, aligning the saturated vapor pressure of the secondary evaporator secondary steam with the outlet of the steam compressor 32. This increases the steam pressure and, consequently, the material temperature, ensuring a high material temperature. In this mode, the secondary steam from the secondary evaporator and the primary evaporator secondary steam mix after the steam compressor before entering the primary evaporator for heat exchange, resulting in efficient evaporation. Conversely, if the required output concentration for the second-stage evaporation is low, or a lower temperature is required to achieve other process steps, the second-stage evaporation secondary steam inlet control valve 39 is opened, and the second-stage evaporation secondary steam inlet control valve 36 is closed. At this time, the secondary steam of the second-stage evaporator is connected to the inlet of the steam compressor 32. The saturated vapor pressure of the second-stage evaporation secondary steam is consistent with the steam compressor inlet, and the corresponding secondary steam saturated vapor pressure is lower, which in turn reduces the material temperature, achieving the process requirement of lower temperature discharge. The secondary steam of the second-stage evaporation and the secondary steam of the first-stage evaporation are mixed before the steam compressor and enter the steam compressor together. After the electric power is used to heat and pressurize the steam, it is all sent to the first-stage evaporator to provide the evaporation heat source.

[0020] During operation of this embodiment, if the boiling point elevation of the produced material at the time of concentrated output is not significantly compared with that of the first-stage evaporation, or if the effective concentration does not need to be too high and the boiling point elevation of the material does not change much, the steam supply control valve 33 from the steam compressor to the second-stage evaporation is opened, the steam supply control valve 43 from the heat source steam to the second-stage evaporation is closed, the inlet control valve 39 for the second-stage evaporation secondary steam entering the steam compressor is opened, and the outlet control valve 36 for the second-stage evaporation secondary steam entering the steam compressor is closed. At this time, the power heat source for the second-stage evaporation is switched to the MVR evaporation operation mode, that is, the supply of fresh steam to the second-stage evaporation is cut off, and the outlet of the steam compressor 32 is used to supply the power steam for evaporation. At the same time, the secondary steam generated by the second-stage evaporation and the secondary steam of the first-stage evaporation are mixed before the steam compressor 32 and enter the steam compressor together. After the electric power is used to work, the steam is heated and pressurized and then respectively allocated to the first and second-stage evaporators to provide evaporation heat sources. In this case, the secondary steam from all the first and second stage evaporators enters the steam compressor, and after being heated and pressurized by work, it is distributed to all the first and second stage evaporators, forming an overall parallel operation MVR operation mode. Example

[0021] See attached Figure 2 The two-stage evaporation device of this embodiment is exactly the same as that of the embodiment. The difference is that the one-stage evaporation device uses two evaporators, a first-stage evaporator and a second-stage evaporator, which are arranged in series to treat the feed liquid. In this embodiment, the evaporator 3 is the first-stage evaporator, and its pipeline equipped with a feed valve 19 is connected to the second-stage evaporator circulation pipe 23 of the second-stage evaporator 20. The second-stage evaporator circulation pipe 23 is connected to the second-stage evaporator circulation pipe 23.

[0022] The downstream end of pump 21 is connected to the first-stage evaporation discharge pipe 57 via a tee. The connection between the first-stage evaporation discharge pipe 57 and the second-stage evaporation device is similar to the previous embodiment. In this embodiment, the secondary steam engine output of stage II evaporator 20 is also connected to the input of compressor 32. The heating steam input of stage II evaporator 20 is connected to the heat source steam pipe 35 and the first-stage evaporation inlet steam main pipe 26 of compressor 32, respectively. Control valves 25 and 27 are installed on the pipeline connecting the evaporation inlet steam main pipe 26 to the heating steam input of stage II evaporator 20 and the steam inlet pipe 8 of stage I evaporator 3, respectively.

[0023] During operation in this embodiment, the dilute black liquor delivered from the pulping process is stored in a dilute black liquor tank and then fed by a feed pump through the material feed pipe 1 to the first-stage evaporator 3 of the first-stage evaporator. During normal operation, the feed rate is precisely and automatically controlled by the feed control valve 2. The processed medium material in the first-stage evaporator 3 is initially concentrated and then enters the second-stage evaporator 20 of the first-stage evaporator through the feed control valve 19. The processed material is further concentrated and evaporated in the second-stage evaporator 20 of the first-stage evaporator, further increasing its concentration. After reaching the concentration required by the process, it enters the second-stage evaporator through the second-stage evaporator feed control valve 56 for further evaporation and concentration.

[0024] The secondary steam generated by the I-stage evaporator 3 and the II-stage evaporator 20 is collected in the steam compressor secondary steam main 30 and enters the steam compressor 32. After working in the steam compressor 32, it is heated and pressurized, then discharged from the steam compressor outlet steam main 31. It is regulated and controlled by the steam inlet control valve 27 of the evaporator inlet and the steam inlet control valve 25 of the evaporator B, respectively, before entering the I-stage evaporator 3 and the II-stage evaporator 20. The circulating pump 4 of the I-stage evaporator 3 delivers the black liquor at the bottom of the equipment to the top of the heater, where it forms a uniform and consistent film on the heater surface and flows downward, fully exchanging heat with the steam from the steam compressor. The steam is condensed to form condensate, which is discharged through the I-stage evaporator condensate drain control valve 6. The black liquor in the I-stage evaporator 3 absorbs the heat and boils, generating secondary steam, achieving a stable evaporation process. Similarly, the circulating pump 21 of the second-stage evaporator 20 pumps black liquor from the bottom of the equipment into the upper portion of the heater, where it forms a uniform and consistent film on the heater surface and flows downward, exchanging sufficient heat with the steam from the steam compressor. The steam condenses to form condensed water, which is then discharged through the condensate drain control valve 22 of the second-stage evaporator 20. The black liquor in the second-stage evaporator 20 absorbs the heat and boils, generating secondary steam, achieving a stable evaporation process and further increasing the black liquor concentration. Therefore, the processed material enters the first-stage evaporator in a sequential and staged manner, first entering the first-stage evaporator 3 of the first-stage evaporator and, after initial concentration, entering the second-stage evaporator 20 of the first-stage evaporator. The secondary steam and the power heat source steam entering their respective evaporators are distributed in parallel. This arrangement maximizes the effective temperature difference based on the different boiling point elevations of the material at different concentrations, maximizing the large effective temperature difference and high evaporation intensity, thereby improving the operating efficiency of the evaporation system. Of course, in actual applications, a reverse operation mode can also be implemented, where the black liquor is first fed to the first-stage evaporator 3 and then discharged through the second-stage evaporator 20, or first fed to the second-stage evaporator 20 and then discharged through the first-stage evaporator 3. This can take advantage of the different concentrations of black liquor within the equipment to achieve a self-cleaning effect. When the treated black liquor in the first-stage evaporation unit reaches the required concentration, it enters the second-stage evaporation unit through the first-stage evaporation discharge pipe 57, the feed control valve 19, and the second-stage evaporation feed control valve 56 for evaporation. The subsequent processing process is the same as that of the previous embodiment and will not be repeated here.

[0025] The utility model device can also adopt more evaporators to form a one-stage evaporation device.

[0026] Through the above two embodiments of the present invention, it can be seen that the present invention can realize different operation modes in one device. If automatic control valves and related automatic control devices are used in the device, the operation mode can be switched very conveniently and automatically.

[0027] The embodiments of the present invention should not be regarded as limiting the scope of protection of the present invention. Related improvements based on the methods and devices of the present invention also fall within the scope of protection of the present invention.

Claims

1. An MVR evaporation device with a switchable operating mode, characterized in that A front and rear two-stage evaporation device is adopted. The front evaporation device is composed of an MVR evaporation device, and the rear evaporation device is composed of an ordinary evaporation device. The liquid treated by the MVR evaporation device can be selectively sent to the feed end or the concentrated liquid feeding pipe of the ordinary evaporation device in the rear section through controlled valves. Both evaporation devices can use heat source steam or steam output by the compressor in the MVR evaporation device to provide evaporation heat source. Control valves are respectively set on the parallel steam supply pipelines of the heat source steam and the steam output by the compressor in the MVR evaporation device to the two evaporation devices, and various separate heating channels to the two evaporation devices are selected by adjusting the opening and closing of different valves on the steam pipelines.

2. The MVR evaporation device with a switchable operating mode according to claim 1 is characterized in that The evaporation device includes a steam compressor and an evaporator, as well as interconnected steam pipelines, distilled condensed water output pipes, waste liquid input pipes to be treated and treated concentrated waste liquid discharge pipes, and pumps or circulation pumps for conveying various liquids and control valves arranged on each pipe. The evaporation device is provided with two-stage evaporation devices, wherein: an MVR evaporation device composed of at least one steam compressor and at least one evaporator constitutes a first-stage evaporation device; a second-stage evaporation device is composed of a common evaporation device, in which: the feed liquid input end of the primary evaporator is connected to the feed pipe of the material to be treated, and the feed liquid input end of the previous stage evaporator is connected to the feed pipe of the material to be treated. The liquid feed output end is connected to the liquid feed input end of the next stage evaporator, the liquid feed output end of the final evaporator is respectively connected to the feed end and the concentrated liquid discharge pipe of the second stage evaporator, the heat source steam and the compressor steam outlet ends of the MVR evaporator are respectively connected to the heating steam input ends of the first stage evaporator and the second stage evaporator, control valves are provided on the steam pipelines connecting the discharge ends of the first stage evaporator and the second stage evaporator and the concentrated liquid discharge pipe, and connecting the first stage evaporator and the second stage evaporator with the heat source steam and the evaporator, and circulation pipes with circulation pumps are respectively provided on each stage of the first stage evaporator and the second stage evaporator.

3. The MVR evaporation device with a switchable operating mode according to claim 2, characterized in that The two-stage evaporation device is composed of a two-stage evaporation heating device consisting of a flash evaporator and a two-stage evaporation heater. A two-stage evaporation heater circulation pipe with a circulation pump is provided between the discharge end and the feed end of the flash evaporator, and the circulation pipe is connected in series between the feed end and the discharge end of the two-stage evaporation heater.

4. The MVR evaporation device with a switchable operating mode according to claim 2 or 3, characterized in that The first-stage evaporation device consists of a steam compressor and two evaporators consisting of a first-stage evaporator and a second-stage evaporator. The feed liquid output end of the first-stage evaporator of the first-stage evaporator is connected to the feed liquid input end of the second-stage evaporator, and the discharge end of the second-stage evaporator is respectively connected to the feed liquid input end and the concentrated liquid discharge pipe of the second-stage evaporation device. The secondary steam outlet ends of the evaporators of each stage of the first-stage evaporation device and the secondary steam output end of the second-stage evaporation device are both connected to the input end of the steam compressor. The heating ends of the two-stage evaporators of the first-stage evaporation device and the heating end of the second-stage evaporation device are respectively connected to the steam output pipe of the steam compressor and the heat source steam pipe. Control valves are provided on the steam pipelines connecting the discharge ends of the first-stage evaporation device and the second-stage evaporation device with the concentrated liquid discharge pipe, and connecting the first-stage evaporation device and the second-stage evaporation device with the heat source steam and the evaporator.

5. The MVR evaporation device with a switchable operating mode according to claim 4, characterized in that The device is controlled by a DCS automatic control system.

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