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

Abstract

The invention 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, an MVR evaporation device and common evaporation devices connected in series are 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 present invention relates to an MVR evaporation device with a switchable operation mode, and in particular to an evaporation device for treating different types of materials or the same material with greatly varying effective concentration and temperature requirements in the same MVR evaporation system. The MVR evaporation device with a switchable operation mode of the present invention comprises a steam compressor and at least one evaporator, as well as interconnected steam pipelines, a distilled condensed water output pipe, a waste liquid input pipeline to be treated, and a concentrated waste liquid discharge pipeline after treatment, as well as pumps or circulation pumps for conveying various liquids and control valves arranged on each pipeline. Background Art

[0002] The evaporation system occupies a very important position in national production activities, and its application range is very wide. It can realize the concentration and drying of materials, or the extraction and separation of products in some industrial production, and can also desalinate seawater for production and living water. At the same time, it can also realize the crystallization separation of materials, resource recycling and reuse and other functions. The configuration mode of the evaporation system mainly includes multiple-effect evaporation, MVR evaporation and multiple-effect and MVR combined evaporation. For example: CN105536276 A, CN 108217797 A and other public disclosures use a combined evaporation device consisting of a steam compressor and two evaporators. The multiple-effect evaporation system uses vacuum evaporation. The first-effect evaporator uses fresh steam as the power heat source. After that, each effect evaporator uses the secondary steam generated by the previous effect after the compressor is sterilized as the evaporation heat source. However, the secondary steam of the last effect evaporator has lost its utilization value due to its low pressure and temperature. It can only be condensed by circulating cooling water to form a vacuum, thereby forming a significant pressure and temperature gradient between the front and rear equipment, so that the evaporation can be kept stable and continuous. The advantages of multi-effect evaporation are that it has many process links, flexible and free design, and it is always possible to find the right point in the system to achieve more complex process goals according to different requirements. But its disadvantages are also obvious. First of all, it occupies a large area, has many process control links, is complex in process, and has high operating costs. At the same time, since the operating conditions of the last effect are very close to vacuum, if you want to obtain more economical operating indicators, you can only increase the number of effects of the equipment and increase the pressure and temperature of the fresh steam of the first effect evaporator to ensure the pressure difference and temperature difference between the equipment. However, when the number of effects increases to a certain extent, the cost increases significantly, while the increase in operating efficiency is extremely limited, so the operating efficiency is generally not high. MVR evaporation integrates multiple effect evaporation areas. A single device can accommodate a large heat exchange area, has few control links, occupies a small area, and has very low operating costs. It is basically all powered by electricity. The secondary steam is heated and pressurized by the steam compressor and then returned to the evaporator to provide evaporation heat source. All steam can be effectively utilized, there is no steam discharge, and the steam latent heat is fully utilized. The operating efficiency is very high, and a large amount of evaporated water can be obtained with a single device, which is energy-saving and environmentally friendly. However, this type of equipment system is suitable for relatively simple process links and cannot achieve complex process goals. For materials with high boiling point rise values, multiple steam compressors need to be used in series, and the investment economy is significantly reduced. In order to take advantage of the characteristics of multi-effect evaporation process flexibility and easy realization of complex goals, while taking into account the needs of low operating costs and land conservation, multi-effect and MVR combined evaporation came into being, which can meet the needs of certain conditions to a large extent. However, the combination of the two evaporation systems makes the process links more complicated, and various control methods are required to achieve process goals. The site occupies a wider area and the project investment has increased significantly. Summary of the invention

[0003] The present invention provides an MVR evaporation method and device with a switchable operation mode, which can overcome the shortcomings of the prior art.

[0004] The present invention discloses an MVR evaporation method with a switchable operation mode, which adopts two evaporation devices in front and back sections. The evaporation device in the front section is composed of an MVR evaporation device, and the evaporation device in the back section is composed of an ordinary evaporation device. After being processed by the MVR evaporation device, the feed liquid can be selectively sent to the feed end of the ordinary evaporation device in the back section through a controlled valve or directly sent out through a concentrated liquid feeding pipe. Both evaporation devices can use heat source steam or steam output by a compressor in the MVR evaporation device to provide evaporation heat sources. Control valves are respectively arranged on parallel steam supply pipelines of the heat source steam and steam output by the compressor in the MVR evaporation device to the two evaporation devices, and various separate heat supply channels to the two evaporation devices are selected by adjusting the opening and closing of different valves on the steam pipeline. The method of the present invention can switch the device to operate in different operation modes by controlling different control valves.

[0005] The present invention discloses an MVR evaporation device with a switchable operation mode, comprising a steam compressor and an evaporator, as well as interconnected steam pipelines, a distilled condensed water output pipe, a waste liquid input pipe to be treated and a concentrated waste liquid discharge pipe after treatment, and a pump or a circulation pump for conveying various liquids and a control valve arranged on each pipeline. The device of the present invention is provided with front and rear two-stage evaporation devices, 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 pipe of the material to be treated The feed liquid output end of the first stage evaporator is connected to the feed liquid input end of the second stage evaporator, the feed liquid output end of the last stage 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 end of the MVR evaporator are respectively connected to the heating steam input end of the first stage evaporator and the second stage evaporator, and the steam pipeline connecting the discharge end 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 are all provided with control valves, and the evaporators of each stage of the first stage evaporator and the second stage evaporator are respectively provided with circulation pipes with circulation pumps. The two-stage evaporator described in the present invention can adopt any existing evaporator, such as a tubular evaporator or a plate evaporator, and of course, the forced circulation evaporator with a heater and a flash evaporator in the embodiment of the present invention can also be used.

[0006] Preferably, the two-stage evaporation device in the MVR evaporation device with a switchable operation mode of the present invention is a forced circulation evaporator composed of a heater and a flash evaporator. A two-stage evaporation heater circulation pipe with a circulation pump is arranged between the heater and 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.

[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, which are composed of a first-stage evaporator and a second-stage evaporator. The liquid output end of the first-stage evaporator is connected to the liquid input end of the second-stage evaporator, and 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 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 connected to the input end of the steam compressor. The heating end of the two-stage evaporator 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. At the same time, the secondary steam pipe (37) of the second-stage evaporation device is also connected to the inlet steam main pipe (26) of the first-stage evaporation device, and the setting function is realized by switching the valve. 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.

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

[0009] The device of the present invention is provided with two-stage evaporation devices, one of which is composed of a steam compressor and multiple evaporators, thus forming a multi-stage evaporation device that fully adopts the MVR evaporation form. The first stage evaporation device drives the secondary steam generated by itself by electricity, and returns it to the evaporator after heating and pressurizing by the steam compressor to provide an evaporation heat source, prompting the evaporator to generate secondary steam again, forming a continuous, stable and reliable evaporation process. After the first stage of evaporation, the concentration of the processed material increases, the flow rate decreases, and then it is sent to the second stage evaporator of the second stage evaporation device through the material transfer pipeline through the control valve. If the boiling point of the material to be processed increases significantly after the concentration is increased to a certain degree, the heat source steam of the evaporator needs a higher temperature and pressure. At this time, the power heat source of the second-stage evaporation heater in the second-stage evaporation device of the present invention adopts the heat source steam from the pipe network, and forms clean condensed water after heat exchange with the material to be processed and is 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 reaching the process requirements; and when the process conditions permit or require, such as the material to be processed is very heat-sensitive, or it is necessary to control the temperature of the material in the evaporator, to avoid the material from coking under high temperature conditions or long molecular chain rupture and property change, the heat supply of the second-stage evaporation heater can be switched to the heat supply due to the steam compressor, and the corresponding steam saturated vapor pressure and temperature are relatively low, and the material temperature is also low, thus avoiding the sensitive temperature of the material. The present invention can also mix the secondary steam of the second-stage evaporation and the secondary steam of the first-stage evaporation before the steam compressor, and enter the steam compressor together. After the electric power works, the steam is heated and pressurized and all are sent to the first-stage evaporator to provide evaporation heat source. If the situation is the opposite, the viscosity of some materials is very sensitive to temperature, and only by increasing the material temperature can basic fluidity be guaranteed. At this time, the secondary steam of 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 the outlet of the steam compressor. When the steam pressure is increased, the corresponding material temperature also rises significantly, ensuring that the material can have a higher temperature, the viscosity does not increase significantly, and it still has good fluidity. The secondary steam of the second-stage evaporation and the secondary steam of the first-stage evaporation are mixed after the steam compressor, and then enter the first-stage evaporator for heat transfer exchange to form effective evaporation.

[0010] If the boiling point increase value of the material when it is concentrated is not obvious compared with the first stage evaporation, the present invention switches the power heat source of the second stage evaporation to the MVR evaporation operation mode, that is, the second stage evaporation cuts off the supply of fresh steam, and changes to the outlet of the steam compressor 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 in front of the steam compressor and enter the steam compressor together. After the electric power works, the steam is heated and pressurized and respectively allocated to the first and second stage evaporators to provide evaporation heat source. At this time, the secondary steam of all the evaporators in the first and second stages all enter the steam compressor, and after the work is done to heat and pressurize, it is allocated to all the first and second stage evaporators, forming an MVR operation mode of 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 is 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 steam compressor and a plurality of evaporators to form a one-stage evaporation device. Through the function of the multi-stage evaporators in the one-stage evaporation device, the concentration can be gradually increased or the feeding operation can be rotated, and the self-cleaning function can be realized, and the multi-stage evaporator can be set. The one-stage evaporation drives the secondary steam generated by itself by electricity, and returns it to the evaporator after being heated and pressurized by the steam compressor to provide an evaporation heat source, so as to promote the generation of secondary steam again in the evaporator, forming a continuous, stable and reliable evaporation process. After the first stage evaporation, the concentration of the processed material increases, the flow rate decreases, and then it is sent to the second stage evaporator through the material passing pipe through the control valve. If the boiling point rise value of the material to be processed increases significantly after the concentration is increased to a certain extent, the heat source steam of the evaporator requires a higher temperature and pressure. At this time, the power heat source of the second stage evaporator in the present invention adopts fresh steam from the pipe network, and forms clean condensed water after heat exchange with the processed material and sends it away. The concentration of the processed material continues to increase in the second stage evaporator, and after meeting the process requirements, it is discharged from the concentrated liquid discharge pipe through the control valve.

[0013] As a preferred structure of the present invention, the one-stage evaporation device is composed 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 them during operation to perform cleaning and maintenance operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attached Figure 1 This is an embodiment of the present invention in which only a first-stage evaporator is provided. Figure 2 For the present invention, only the embodiment of the first-stage evaporator and the second-stage evaporator is provided.

[0015] In the attached drawings: 1 is a feed pipe for the material to be processed, 2 is a feed control valve, 3 is a first-stage evaporator of a section evaporation device, 4 is a circulating pump of the first-stage evaporator, 5 is a first-stage evaporation condensate collection pipe, 6 is a first-stage evaporator condensate drainage control valve, 7 is a first-stage evaporator circulation pipe, 8 is a first-stage evaporator steam inlet pipe, 9 is a first-stage evaporator non-condensable gas control valve, 10 is a first-stage evaporation device non-condensable gas collection pipe, 11 is a first-stage evaporation device condensate tank, 12 is a surface condenser condensate outlet pipe, 13 is a surface condenser, 14 is a non-condensable gas discharge pipe, 15 is a circulating cooling water supply pipe, 16 is a circulating cooling water return pipe, 17 is a condensate pump for a first-stage evaporation device, 18 is a condensate pipe for a first-stage evaporation device, 19 is a feed control valve, 20 is a second-stage evaporator for a first-stage evaporation device, 21 is a circulation pump for the second-stage evaporator, 22 is a condensate drainage control valve for the second-stage evaporator, 23 is a circulation pipe for the second-stage evaporator, 24 is a steam inlet pipe for the second-stage evaporator, 25 is a steam inlet control valve for the second-stage evaporator, 26 is an inlet steam main pipe for a first-stage evaporation device, 27 is a steam inlet control valve for the first-stage evaporator, 28 is a secondary steam control valve for the first-stage evaporator, 29 is a secondary steam control valve for the second-stage evaporator, and 30 is an inlet steam compressor The secondary 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 4 is the steam supply pipe for heat source steam, 43 is the steam supply control valve for heat source steam to the second-stage evaporation, 44 is the circulation pipe for the second-stage outlet heater, 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 feeding pipe, 50 is the second-stage evaporation discharge pipe, 51 is the condensate outlet pipe of the second-stage evaporation heater, 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 is explained below with reference to embodiments and drawings.

[0017] Figure 1This is the first embodiment of the present invention. In this embodiment, an evaporator 3 and a compressor 32 form a one-stage evaporation device. In this embodiment, only a first-stage evaporator is set in the one-stage evaporation device, and a flash evaporator 40 and a 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 treated through a pipeline with a feed control valve 2, an evaporator circulation pipe 7 with a circulation pump 4 is arranged between the discharge end and the feed end of the evaporator 3, the steam input port pipe 8 of the first-stage evaporator of the evaporator 3 is connected to the steam compressor steam output main pipe 31 and the heat source steam pipe 42 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 with a secondary steam control valve 28 of the first-stage evaporator, and the evaporator circulation pipe 7 of the evaporator 3 is located downstream of the circulation pump. The first-stage evaporation discharge pipe 57 with a feed control valve 19 is connected to the feed end of the second-stage evaporation device and the concentrated liquid feeding pipe 49 respectively. A second-stage heater circulation pipe 44 with a second-stage circulation pump 53 thereon and connected in series between the feed end and the discharge end of the second-stage heating evaporator 45 is arranged between the liquid inlet end and the liquid outlet end of the flash evaporator 40 in the second-stage evaporation device. The second-stage heater circulation pipe 44 is located downstream of the circulation pump 53 and is connected to the concentrated liquid feeding pipe 49 by a tee and the second-stage evaporation heater circulation pipe 50 with a second-stage evaporation discharge control valve 52 thereon. The second-stage evaporation heater condensate outlet pipe 51 guides the condensate of the second-stage evaporation heater into the second-stage evaporation condensate tank 46, and the heating steam input end of the second-stage evaporation heater 45 is connected to the heat source steam pipe 42 and the steam compressor steam output main pipe 31 by pipelines, and the heat source steam to the second-stage evaporation steam supply control valve 43 is arranged on the pipeline connecting the heat source steam pipe 42 and the heating steam input end of the second-stage evaporation heater 45. In this embodiment, the non-condensable gas of the evaporator 3 of the first stage evaporation device is sent to the surface condenser 13 through the non-condensable gas control valve 9 for the evaporator and the first stage non-condensable gas collection pipe 10, and the condensed water of the evaporator 3 is sent to the first stage evaporation condensed water tank 11 through the evaporation condensed water collection pipe 5 with the condensed water drainage control valve 6. The condensed water of the surface condenser 13 is also sent to the first stage evaporation condensed water tank 11 through the surface condenser condensed water outlet pipe 12, and the non-condensable gas is discharged through the non-condensable gas discharge pipe 14.

[0018] In this embodiment, reed is used as the papermaking raw material for example. The dilute black liquor sent from pulping is stored in the dilute black liquor tank and then fed into the evaporator 3 of the first-stage evaporation device through the material feeding pipe 1 to be processed by the feed pump. 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 when the treated material treats the medium material is collected in the secondary steam main pipe 30 of the steam compressor and enters the steam compressor 32. After the steam compressor 32 does work and the temperature is increased and pressurized, the liquid in the evaporator 3 is heated by the steam main pipe 31 of the steam compressor through the heating end of the evaporator 3. These liquids are circulated and heated by the circulation pipe 7 of the evaporator 3 under the action of the circulation pump 4, 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 exchanging heat with the steam from the steam compressor 32. After receiving the heat, the black liquor boils and is concentrated and evaporated, and the concentration gradually increases. The steam after the heat exchange in the evaporator 3 is condensed to form condensed water and discharged through the condensed water drainage 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 does work and the temperature is increased and pressurized, it is sent out by the steam main pipe 31 of the steam compressor, and enters the evaporator 3 through the heating steam inlet control valve 27 and the steam inlet pipe 8 of the evaporator 3 respectively, so as to realize a stable evaporation process. In this process, the concentration of black liquor is gradually concentrated to a higher concentration, and the generated condensed water is collected in the first stage evaporation condensed water tank 11, and sent to the previous process section by the first stage evaporation condensed water pump 17 for reuse as hot water. When the concentration reaches the process requirement, the black liquor enters the second stage evaporation device through the first stage evaporation discharge pipe 57 and the feed control valve 19, and the second stage evaporation feed control valve 56 for evaporation treatment.

[0019] In this embodiment, the second stage evaporation adopts forced circulation evaporation to solve the problem that the equipment is particularly prone to scaling due to the crystallization of inorganic salts when the concentration of reed pulp black liquor is high. When the second stage evaporation device is in 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 enters the second stage evaporation heater 45 for circulation heating through the action of the second stage evaporation circulation pump 53. The heated liquid is sent to the flash evaporator 40 for flash evaporation through the rear end 44 of the second stage heater circulation pipe. In the second stage evaporation, the black liquor is transported by the second stage evaporation circulation pump 53 and continuously enters the second stage evaporation heater 45 without interruption, and is concentrated to produce a higher concentration of black liquor. The boiling point rise value of the operating medium is very high at this time. The steam compressor is closed to the second stage evaporation steam supply control valve 33, and the fresh steam is opened to the second stage evaporation steam supply control valve 43. At this time, the operation steam supply mode of the second stage evaporation is heat source steam supply. The high-temperature heat source steam generates sufficient heat exchange in the second-stage evaporation heater 45, and the fresh steam is condensed to form condensed water, which is collected in the second-stage evaporation condensation water tank 46 and then sent to the water point of the production system by the second-stage evaporation condensation water pump 47 for use. The black liquor heated to a certain temperature enters the flash evaporator 40 from the second-stage outlet heater circulation pipe 44 for flash evaporation, generating a large amount of secondary steam, forming a continuous and stable evaporation process. If the effective black liquor needs a higher temperature to maintain good fluidity, the second-stage evaporation secondary steam inlet steam compressor inlet control valve 39 is closed, and the second-stage evaporation secondary steam inlet steam compressor outlet control valve 36 is opened. At this time, the secondary steam of the second-stage evaporator is connected to the outlet of the steam compressor 32, and the saturated vapor pressure of the second-stage evaporation secondary steam is consistent with the outlet of the steam compressor 32. The steam pressure increases, and the corresponding material temperature also increases accordingly. It ensures that the material has a higher temperature. In this mode, the secondary steam of the second-stage evaporation and the secondary steam of the first-stage evaporation are mixed after the steam compressor, and then enter the first-stage evaporator for heat transfer exchange to form effective evaporation. On the contrary, if the effective concentration requirement of the second stage evaporation is not high, or a lower temperature is required to realize other process, it is necessary to open the second stage evaporation secondary steam inlet steam compressor inlet control valve 39, close the second stage evaporation secondary steam inlet steam compressor outlet control valve 36, 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, the corresponding secondary steam saturated vapor pressure is low, and the material temperature is also low, so as to realize the process requirement of low 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 works, the steam is heated and pressurized and all are sent to the first stage evaporator to provide evaporation heat source.

[0020] During the operation of this embodiment, if the boiling point rise value of the produced material at the time of concentration is not obvious compared with that of the first stage evaporation, or the effective concentration does not need to be too high, and the boiling point rise value of the material does not change much, then the steam compressor to the second stage evaporation steam supply control valve 33 is opened, the heat source steam to the second stage evaporation steam supply control valve 43 is closed, the second stage evaporation secondary steam into the steam compressor inlet control valve 39 is opened, and the second stage evaporation secondary steam into the steam compressor outlet control valve 36 is closed. At this time, the power heat source of the second stage evaporation is switched to the MVR evaporation operation mode, that is, the second stage evaporation cuts off the supply of fresh steam, and changes to the outlet of the steam compressor 32 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 in front of the steam compressor 32 and enter the steam compressor together. After the electric power does work, the steam is heated and pressurized and respectively allocated to the first and second stage evaporators to provide evaporation heat sources. In this case, the secondary steam of all the first and second stage evaporators enters the steam compressor, and is distributed to all the first and second stage evaporators after being heated and pressurized, 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, except that the one-stage evaporation device uses two evaporators, a Class I evaporator and a Class II evaporator, which are arranged in series to process the feed liquid. In this embodiment, the evaporator 3 is a Class I evaporator, and its pipeline equipped with a feed valve 19 is connected to the Class II evaporator circulation pipe 23 of the Class II evaporator 20. The Class II evaporator circulation pipe 23 is connected to the Class II evaporator circulation pipe 23. The downstream of the pump 21 is connected to the first stage evaporation discharge pipe 57 by a tee, and the connection method of the first stage evaporation discharge pipe 57 and the second stage evaporation device is the same as before. In this embodiment, the secondary steam engine output end of the second stage evaporator 20 is also connected to the input end of the compressor 32, and the heating steam input end of the second stage evaporator 20 is respectively connected to the heat source steam pipe 35 and the first stage evaporation inlet steam main pipe 26 of the compressor 32. The pipeline connecting the evaporation inlet steam main pipe 26 and the heating steam input end of the second stage evaporator 20 and the steam inlet pipe 8 of the first stage evaporator 3 are respectively provided with control valves 25 and 27.

[0022] During operation of this embodiment, the diluted black liquor sent from pulping is stored in the diluted black liquor tank and then fed into the first-stage evaporator 3 of the first-stage evaporation device by the feed pump through the material feed pipe 1 to be processed. During normal operation, the feed amount is accurately and automatically controlled by the feed control valve 2. The treated medium material of the first-stage evaporator 3 is initially concentrated, and then enters the second-stage evaporator 20 of the first-stage evaporation device through the feed control valve 19. The treated material is concentrated and evaporated again in the second-stage evaporator 20 of the first-stage evaporation device, and the concentration is further increased. After reaching the concentration required by the process, it enters the second-stage evaporation device through the second-stage evaporation feed control valve 56 for further evaporation and concentration.

[0023] The secondary steam generated by the I-level evaporator 3 and the II-level evaporator 20 is collected in the secondary steam main pipe 30 of the steam compressor and enters the steam compressor 32. After the steam compressor 32 does work, it is heated and pressurized and then sent out from the steam main pipe 31 of the steam compressor. It is regulated and controlled by the steam inlet control valve 27 of the evaporator and the steam inlet control valve 25 of the evaporator B, respectively, and enters the I-level evaporator 3 and the II-level evaporator 20. The circulating pump 4 of the I-level evaporator 3 sends the black liquor at the bottom of the equipment to the upper part of the heater, forming a uniform and consistent film on the surface of the heater and flowing downward, and fully exchanging heat with the steam from the steam compressor. After the steam is condensed, it forms condensed water and is discharged through the I-level evaporator condensate drainage control valve 6. After receiving the heat, the black liquor in the I-level evaporator 3 forms a boiling phenomenon, generating secondary steam, and realizing a stable evaporation process. Similarly, the circulating pump 21 of the second-stage evaporator 20 sends the black liquor at the bottom of the equipment to the upper part of the heater, forming a uniform and consistent film on the surface of the heater and flowing downward, and fully exchanging heat with the steam from the steam compressor. After the steam is condensed, it forms condensed water and is discharged through the condensate drainage control valve 22 of the second-stage evaporator 20. After receiving heat, the black liquor in the second-stage evaporator 20 forms a boiling phenomenon, generates secondary steam, realizes a stable evaporation process, and the concentration of black liquor is increased again. Therefore, the processed materials enter the first-stage evaporator in a sequence and classification, that is, they first enter the first-stage evaporator 3 of the first-stage evaporation device, and then enter the second-stage evaporator 20 of the first-stage evaporation device after preliminary concentration, and the secondary steam and the power heat source steam entering each evaporator are distributed in parallel. This arrangement can form different effective temperature differences as much as possible according to the different boiling point rise values ​​of the materials at different concentrations, maximize the use of the properties of large effective temperature difference and high evaporation intensity, and improve the operating efficiency of the evaporation system. Of course, in actual application, it is also possible to implement a reverse operation mode of first feeding to the first-stage evaporator 3 and then sending out through the second-stage evaporator 20, or first feeding to the second-stage evaporator 20 and then sending out through the first-stage evaporator 3, and utilizing the different concentrations of black liquor inside the equipment to achieve the self-cleaning effect of the equipment. When the treated black liquor in the first-stage evaporation device reaches the concentration required by the process, it enters the second-stage evaporation device through the first-stage evaporation discharge pipe 57 and the material control valve 19 and the second-stage evaporation feed control valve 56 for evaporation treatment. The subsequent treatment process is the same as that of the previous embodiment, and will not be repeated here.

[0024] In the device of the present invention, more evaporators can also be used to form a one-stage evaporation device.

[0025] Through the above two embodiments of the present invention, it can be known that the present invention can realize operations in different operating modes in a set of devices. If automatic control valves and related automatic control devices are used in the device, the operating mode can be switched very conveniently and automatically. DCS automatic control system The embodiments of the present invention should not be regarded as limiting the protection scope of the present invention, and related improvements formed on the basis of the methods and devices of the present invention also belong to the protection scope of the present invention.

Claims

1. A MVR evaporation method with a switchable operation 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 feed liquid treated by the MVR evaporation device can be selectively sent to the feed end or the concentrated liquid feeding pipe of the rear ordinary evaporation device through controlled valves. The two 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 pipeline.

2. A MVR evaporation device with a switchable operation mode for implementing the method described in claim 1, comprising a steam compressor and an evaporator, as well as interconnected steam pipelines, distilled condensed water 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, characterized in that The device is provided with front and rear 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 with the feed pipe of the material to be processed, the feed liquid output end of the previous stage evaporator is connected with the feed liquid input end of the next stage evaporator, the feed liquid output end of the final stage evaporator is respectively connected with the feed end and the concentrated liquid discharge pipe of the second-stage evaporation device, the heat source steam and the compressor steam outlet end of the MVR evaporation device are respectively connected with the heating steam input end of the first evaporation device and the second stage evaporation device, the discharge end connecting the first evaporation device and the second stage evaporation device with the concentrated liquid discharge pipe, and the steam pipeline connecting the first evaporation device and the second stage evaporation device with the heat source steam and the evaporator are all provided with control valves, and the evaporators of the first evaporation device and the second stage evaporation device are respectively provided with circulation pipes with circulation pumps.

3. The MVR evaporation device with a switchable operation 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 arranged between the discharge end and the feed end of the flash evaporator, and the circulation pipe is serially connected between the feed end and the discharge end of the two-stage evaporation heater.

4. The MVR evaporation device with a switchable operation mode according to claim 2 or 3, characterized in that The one-stage evaporation device is composed 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 one-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 one-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 end of the two-stage evaporator of the one-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 arranged on the steam pipelines connecting the discharge ends of the one-stage evaporation device and the second-stage evaporation device with the concentrated liquid discharge pipe, and connecting the one-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 operation mode according to claim 4, characterized in that The device is controlled by a DCS automatic control system.

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