An MVR system based on thermal flash evaporation circulating rising film heat transfer

Abstract

This invention relates to an MVR system based on thermally stimulated flash evaporation and circulating rising film heat exchange, comprising a rising film heat exchanger, a vapor-liquid separator, a preheater, a thermally stimulated heater, and a throttling device. The preheater is connected to the thermally stimulated heater, and the condensate inlet of the preheater is connected to the condensate outlet of the rising film heat exchanger. The material outlet of the thermally stimulated heater is connected to the feed inlet of the rising film heat exchanger through the throttling device. The rising film heat exchanger is connected to the vapor-liquid separator so that the secondary steam in the rising film heat exchanger enters the vapor-liquid separator. The separated vapor phase is compressed and then fed back into the rising film heat exchanger as a heat source. The concentrated liquid flowing out of the vapor-liquid separator and the rising film heat exchanger is collected when its concentration is qualified; otherwise, it is pressurized and reinjected into the thermally stimulated heater for reuse. This invention can form a stable annular flow without relying on a large temperature difference, matching the narrow temperature difference heat transfer characteristics of the MVR system and significantly reducing the high-grade energy consumption of the rising film heat exchanger.

Description

Technical Field

[0001] This invention relates to the field of evaporation and concentration technology, specifically to an MVR system based on thermal flash evaporation circulating rising film heat exchange. Background Technology

[0002] Mechanical vapor recompression (MVR) systems, with their heat recycling characteristics, have become the mainstream energy-saving evaporation technology. MVR systems use a compressor to recover, pressurize, and heat the secondary steam generated during evaporation, reusing it as a heat source, thus significantly reducing energy consumption. A rising film heat exchanger is a key component in the energy cycle of an MVR system. High-temperature, high-pressure secondary steam enters the shell side of the rising film heat exchanger, heating the material in the tube side to its boiling point and causing it to evaporate. By recovering the latent heat of the secondary steam, the demand for external fresh steam is significantly reduced. Rising film heat exchangers are characterized by high heat transfer efficiency, short material residence time, and compact design, and are widely used in the evaporation and concentration of low-viscosity, heat-sensitive, and easily foaming materials. The evolution of the flow pattern in existing rising film heat exchange technologies involves five stages: single-phase liquid flow, bubbly flow, slug flow, annular flow, and mist flow. Among these, the annular flow stage offers the best heat transfer effect, but its formation is highly dependent on a large heat transfer temperature difference of over 20°C to ensure rapid vaporization of the material and the generation of sufficient vapor phase kinetic energy.

[0003] The heat source for the MVR system is compressed secondary steam. Due to limitations in the boiling point of the material and the ultimate pressure ratio of the compressor, the heat transfer temperature difference of the MVR system heat exchanger is generally no higher than 10℃, with a design value typically between 4 and 10℃, representing a typical narrow temperature difference operating condition. When using compressed secondary steam as the heat source for the rising film heat exchanger through the MVR system, the low heat flux density of the heat exchanger leads to insufficient vaporization of the inlet material. The vapor phase velocity is difficult to reach the critical velocity required for rising film, and the flow pattern inside the heat exchange tube remains stagnant in inefficient flow states such as bubbly or slug-like structures. This prevents the achievement of efficient heat exchange in circulating rising film, thus significantly reducing the energy-saving evaporation effect.

[0004] To compensate for insufficient rising film kinetic energy, existing technologies employ a forced circulation pump. This approach increases the apparent velocity of the vapor-liquid mixture within the heat exchange tubes by increasing the feed rate. However, due to the significant increase in the liquid-to-liquid ratio, the flow pattern within the heat exchange tubes degenerates into a typical bubbly flow pattern, failing to achieve a true circulating rising film heat exchange effect. This results in a reduction in the heat exchange efficiency of the rising film heat exchanger in the MVR system, thereby decreasing the evaporation efficiency of the solution. Summary of the Invention

[0005] The present invention aims to provide an MVR system based on thermal flash evaporation circulating rising film heat exchange to overcome the shortcomings of the prior art. The technical problem to be solved by the present invention is achieved through the following technical solution.

[0006] An MVR system based on thermally stimulated flash evaporation circulating rising film heat exchange includes a rising film heat exchanger, a vapor-liquid separator, a preheater, a thermally stimulated heater, and a throttling component.

[0007] The material outlet of the preheater is connected to the material inlet of the heat shock heater so that the preheated liquid enters the heat shock heater after being pressurized. The condensate inlet of the preheater is connected to the condensate outlet of the rising film heat exchanger so that the steam condensate in the shell side of the rising film heat exchanger flows into the preheater, thereby using the waste heat of the steam condensate to preheat the liquid.

[0008] The material outlet of the thermal shock heater is connected to the feed inlet of the rising film heat exchanger through the throttling component. The thermal shock heater is used to heat the liquid with high-temperature live steam. After being heated, the liquid flows through the throttling component and is throttled and depressurized, and then undergoes isenthalpic flash evaporation. The flashed liquid is converted into a vapor-liquid two-phase flow and then enters the heat exchange tube of the rising film heat exchanger. Driven by the expansion kinetic energy of the vapor phase, the liquid rises along the inner wall of the heat exchange tube to form a stable liquid film.

[0009] The secondary steam outlet at the top of the rising film heat exchanger is connected to the secondary steam inlet of the vapor-liquid separator, so that the secondary steam in the rising film heat exchanger enters the vapor-liquid separator. The separated vapor phase is compressed and then introduced into the rising film heat exchanger through the heating steam inlet of the rising film heat exchanger, and used as a heat source for the rising film heat exchanger.

[0010] The concentrated liquid flowing out of the vapor-liquid separator and the rising film heat exchanger is collected when the concentration is qualified; otherwise, it is pressurized and reinjected into the heat-shock heater through the material inlet of the heat-shock heater for reuse.

[0011] Preferably, a booster pump is provided between the material outlet of the preheater and the material inlet of the heat stimulator. The booster pump is used to pressurize the liquid material from the preheater and send it into the heat stimulator.

[0012] Preferably, the device also includes a compressor, the inlet of which is connected to the secondary steam outlet of the vapor-liquid separator, and the outlet of which is connected to the heating steam inlet of the rising film heat exchanger.

[0013] Preferably, the outlet of the compressor is connected to the inlet of the rising film heat exchanger, and a flow regulating valve and a check valve are provided between the outlet of the compressor and the inlet of the rising film heat exchanger.

[0014] Preferably, it also includes a concentrate tank, the concentrate inlet of which is connected to the concentrate outlet of the rising film heat exchanger and the separated liquid outlet of the vapor-liquid separator, and the concentrate outlet of the concentrate tank is connected to the material inlet of the heat-induced heater.

[0015] Preferably, the device further includes a condensate tank, wherein the condensate inlet of the condensate tank is connected to the steam condensate outlet of the rising film heat exchanger, and the condensate outlet of the condensate tank is connected to the condensate inlet of the preheater.

[0016] Preferably, it also includes a measurement and control system, which includes a temperature sensor, a pressure sensor, a flow sensor, a level gauge, and a PLC controller.

[0017] Preferably, a vapor-liquid distributor is provided inside the lower end cap of the rising film heat exchanger.

[0018] Preferably, the temperature of the feed liquid after thermal shock in the thermal shock heater needs to be 5-20°C higher than the evaporation temperature of the rising film heat exchanger.

[0019] Preferably, the temperature difference between the vapor phase, after separation by the vapor-liquid separator and compression, and the liquid in the heat exchange tubes of the rising film heat exchanger is 4~10℃.

[0020] The MVR system based on thermal flash evaporation circulating rising film heat exchange provided by this invention has the following beneficial effects:

[0021] This invention provides sufficient kinetic energy to the vapor phase flow velocity in the rising film heat exchanger through the thermal flash evaporation process of the thermally activated heater and throttling component. This allows the vapor-liquid two-phase flow to skip inefficient flow patterns such as single-phase liquid flow, bubbly flow, and slug flow, and directly form a highly efficient annular rising film flow pattern. This improves the heat transfer efficiency by more than 30% compared to traditional rising film heat exchange technology. As a result, the temperature of the secondary steam after compression by the compressor is only within 10°C higher than the evaporation temperature of the rising film heat exchanger to achieve highly efficient annular rising film heat exchange. It does not require a large temperature difference to form a stable annular flow, which is more compatible with the narrow temperature difference evaporation characteristics of the MVR system and significantly reduces the high-grade energy consumption of the rising film heat exchanger.

[0022] The thermal flash evaporation process, achieved through the thermal shock heater and throttling components, enables the system to utilize the latent heat of steam more efficiently. It only requires additional power to the compressor, resulting in a high evaporation rate, low power consumption, and better energy-saving performance.

[0023] Rising film heat exchangers that operate under a stable annular flow pattern for extended periods can avoid problems such as localized dry walls and coking in the internal heat exchange tubes, thus extending the service life of the heat exchanger. Attached Figure Description

[0024] Figure 1 This is a structural block diagram of one embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of one embodiment of the rising film heat exchanger in this invention;

[0026] Figure 3 This is a schematic diagram of one embodiment of the vapor-liquid distributor in this invention;

[0027] Figure 4(a) shows the evolution of the rising film heat exchange flow pattern in a traditional rising film heat exchanger;

[0028] Figure 4(b) is a diagram showing the evolution of the rising film heat exchange flow pattern in a rising film heat exchanger in one embodiment of the present invention;

[0029] Figure 5 This is a structural block diagram of another embodiment of the present invention.

[0030] The reference numerals in the attached figures are, in order: 1. Rising film heat exchanger, 2. Compressor, 3. Vapor-liquid separator, 4. Concentrate tank, 5. Reflux pump, 6. Condensate tank, 7. Condensate pump, 8. Preheater, 9. Booster pump, 10. Thermal shock heater, 11. Measurement and control system, 12. Throttling component, 13. Vapor-liquid distributor, 14. Flow regulating valve. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] Example 1:

[0033] Reference Figure 1 As shown, an MVR system based on thermally stimulated flash evaporation circulating rising film heat exchange is improved in that it includes a rising film heat exchanger 1, a vapor-liquid separator 3, a preheater 8, a thermally stimulated heater 10, and a throttling component 12.

[0034] The material outlet of the preheater 8 is connected to the material inlet of the heat-induced heating heater 10 so that the preheated liquid enters the heat-induced heating heater 10 after being pressurized. The condensate inlet of the preheater 8 is connected to the condensate outlet of the rising film heat exchanger 1 so that the steam condensate in the shell side of the rising film heat exchanger 1 flows into the preheater 8, thereby using the waste heat of the steam condensate to preheat the liquid.

[0035] The material outlet of the thermal shock heater 10 is connected to the feed inlet of the rising film heat exchanger 1 through the throttling component 12. The thermal shock heater 10 is used to heat the liquid with high-temperature live steam. After being heated, the liquid flows through the throttling component 12 and is throttled and depressurized, and then undergoes isenthalpic flash evaporation. The flashed liquid is converted into a vapor-liquid two-phase flow and then enters the heat exchange tube of the rising film heat exchanger 1. Driven by the expansion kinetic energy of the vapor phase, the liquid rises along the inner wall of the heat exchange tube to form a stable liquid film.

[0036] The secondary steam outlet at the top of the rising film heat exchanger 1 is connected to the secondary steam inlet of the vapor-liquid separator 3, so that the secondary steam in the rising film heat exchanger 1 enters the vapor-liquid separator 3. The separated vapor phase is compressed and then introduced into the rising film heat exchanger 1 through the heating steam inlet of the rising film heat exchanger 1, and used as a heat source for the rising film heat exchanger 1.

[0037] The concentrated liquid flowing out of the vapor-liquid separator 3 and the rising film heat exchanger 1 is collected when the concentration is qualified; otherwise, it is pressurized and reinjected into the heat-stimulating heater 10 through the material inlet for reuse.

[0038] Furthermore, a booster pump 9 is provided between the material outlet of the preheater 8 and the material inlet of the heat stimulator 10. The booster pump 9 is used to pressurize the liquid material from the preheater 8 and send it into the heat stimulator 10. The material outlet of the preheater 8 is connected to the inlet of the booster pump 9, and the outlet of the booster pump 9 is connected to the material inlet of the heat stimulator 10.

[0039] Furthermore, it also includes a compressor 2, the inlet of which is connected to the secondary steam outlet of the vapor-liquid separator 3, and the outlet of the compressor 2 is connected to the heating steam inlet of the rising film heat exchanger 1.

[0040] Furthermore, the compressor 2 is one of a centrifugal compressor, a Roots compressor, a twin-screw compressor, or a single-screw compressor.

[0041] Furthermore, the compressor 2 is a single-stage or multi-stage compressor.

[0042] Furthermore, it also includes a concentrate tank 4, the concentrate inlet of which is connected to the concentrate outlet of the rising film heat exchanger 1 and the separated liquid outlet of the vapor-liquid separator 3, respectively, and the concentrate outlet of the concentrate tank 4 is connected to the material inlet of the heat-induced heater 10.

[0043] Furthermore, a reflux pump 5 is installed at the outlet of the concentrate tank 4. The outlet of the concentrate tank 4 is connected to the inlet of the reflux pump 5, and one outlet of the reflux pump 5 is used to collect concentrate, while the other outlet is connected to the inlet of the booster pump 9.

[0044] Furthermore, it also includes a condensate tank 6, the condensate inlet of which is connected to the steam condensate outlet of the rising film heat exchanger 1, and the condensate outlet of the condensate tank 6 is connected to the condensate inlet of the preheater 8.

[0045] Furthermore, a condensate pump 7 is installed between the condensate outlet of the condensate tank 6 and the condensate inlet of the preheater 8. The condensate outlet of the condensate tank 6 is connected to the inlet of the condensate pump 7, and the outlet of the condensate pump 7 is connected to the condensate inlet of the hot side channel of the preheater 8. The condensate is discharged from the condensate outlet of the preheater 8.

[0046] Furthermore, the temperature of the liquid after thermal shock in the thermal shock heater 10 needs to be 5-20°C higher than the evaporation temperature of the rising film heat exchanger 1.

[0047] Furthermore, the temperature difference between the vapor phase, which is separated by the vapor-liquid separator 3 and then compressed before being introduced into the rising film heat exchanger 1, and the liquid in the heat exchange tube of the rising film heat exchanger 1 is 4~10℃.

[0048] In this embodiment, the rising film heat exchanger 1 is a vertical shell-and-tube structure with a length-to-diameter ratio of 100-150 for the heat exchange tubes. The upper outlet of the heat exchange tubes is 100-200 mm higher than the upper tube sheet. The shell side of the rising film heat exchanger 1 is the hot medium side. The upper side wall of the shell of the rising film heat exchanger 1 is provided with a heating steam inlet, and the lower side wall of the shell is provided with a steam condensate outlet. The tube side of the rising film heat exchanger 1 is the cold medium side. The lower head of the rising film heat exchanger 1 is provided with a feed inlet, and a vapor-liquid distributor 13 is provided inside the lower head. A wire mesh demister is provided inside the vapor-liquid separator 3. A secondary steam outlet is provided at the top of the upper head, and a concentrate outlet is provided on the side wall of the upper head.

[0049] The preheater 8 is used to preheat the feed through secondary steam condensate. The cold side channel is equipped with a material inlet and a material outlet, and the hot side channel is equipped with a condensate inlet and a condensate outlet.

[0050] Furthermore, the preheater 8 is a partitioned heat exchanger structure, and the preheater 8 is one of a plate heat exchanger, a shell-and-tube heat exchanger, a spiral plate heat exchanger, or a coaxial heat exchanger.

[0051] The function of the heat shock heater 10 is to heat the liquid material after it has been preheated by the preheater 8 at high temperature, thereby storing the high temperature heat energy into the internal energy of the liquid material. The cold side channel of the heat shock heater 10 is provided with a material inlet and a material outlet, and the hot side channel is provided with a live steam inlet and a steam condensate outlet.

[0052] Furthermore, the heat shock heater 10 has a partition wall heat exchanger structure, and the heat shock heater 10 is one of a plate heat exchanger, a shell and tube heat exchanger, or a spiral plate heat exchanger.

[0053] The function of the throttling component 12 is to throttle and reduce the pressure of the high-temperature liquid after thermal shock heating, so that the liquid undergoes isenthalpic throttling flash evaporation. Through throttling flash evaporation, the internal energy accumulated by the thermal shock heating of the liquid is converted into the expansion kinetic energy of the vapor and liquid phases after flash evaporation.

[0054] Furthermore, the throttling component is one of the following: throttling valve, orifice plate, reducer, reducer, or windowed structured packing.

[0055] Furthermore, a vapor-liquid distributor 13 is provided inside the lower end cap of the rising film heat exchanger 1. The function of the vapor-liquid distributor 13 is to ensure that the vapor and liquid phases after throttling and flash evaporation enter each heat exchange tube of the rising film heat exchanger 1 in a uniform proportion, thereby avoiding uneven vapor-liquid distribution in the heat exchange tubes.

[0056] Furthermore, the vapor-liquid distributor 13 is a conical perforated plate or a hydrocyclone.

[0057] Furthermore, it also includes a measurement and control system, which comprises temperature sensors, pressure sensors, flow sensors, level gauges, and a PLC controller. The temperature control system is used to monitor the temperature, pressure, flow rate, and other parameters of each key node in the MVR system in real time, enabling the start-up and shutdown control of compressor 2, reflux pump 5, condensate pump 7, and booster pump 9, as well as the adjustment of the frequency of compressor 2 and the opening degree of throttling component 12.

[0058] Furthermore, the temperature sensor and pressure sensor are disposed between the thermal heater 10 and the throttling component 12.

[0059] Furthermore, a pressure sensor is provided between the throttling component 12 and the rising film heat exchanger 1.

[0060] In this embodiment, the working process of the MVR system is as follows:

[0061] The material to be processed first enters the preheater 8, where the waste heat from the condensate of the rising film heat exchanger 1 is used for preheating, reducing the subsequent heating load. After preheating, the liquid is pressurized by the booster pump 9 and sent to the thermal shock heater 10 to be heated by high-temperature live steam, completing the storage of thermal energy into internal energy. The high-pressure saturated liquid flows through the throttling device 12 and undergoes isenthalpic flash evaporation, rapidly converting the internal energy of the thermal shock liquid into the kinetic energy of the vapor-liquid two-phase flow, generating a high-kinetic-energy vapor-liquid two-phase flow. The vapor-liquid two-phase flow is evenly distributed to each heat exchange tube of the rising film heat exchanger 1 by the vapor-liquid distributor 13. The expansion kinetic energy of the vapor phase drives the liquid to climb along the inner wall of the heat exchange tube and form a uniform and stable liquid film, directly entering the high-efficiency annular flow stage. The shell of the rising film heat exchanger 1... The secondary steam, compressed and heated by compressor 2, is introduced into the heat exchanger tubes, forming a narrow temperature difference of 4~10℃ with the tube-side material to maintain the phase change heat transfer of the rising film heat exchanger 1. The secondary steam at the tube-side outlet of the rising film heat exchanger 1 enters the vapor-liquid separator 3. The separated vapor phase enters compressor 2, is compressed and heated, and then returns to the shell side of the rising film heat exchanger 1 as a heat source, realizing the recycling of evaporation heat. The separated liquid phase is combined with the concentrate of the rising film heat exchanger 1 and enters the concentrate tank 4. After the concentration of the liquid phase is detected, it is collected when the concentration reaches the preset concentration requirement. If the concentration is not qualified, it is returned to the inlet of the booster pump 9 for reprocessing via reflux pump 5. The condensate of the shell side of the rising film heat exchanger 1 flows into the condensate tank 6, and is discharged from the system after passing through the condensate pump 7 and the preheater 8.

[0062] Example 2:

[0063] Based on Example 1, this example uses the evaporation and concentration of sodium chloride solution as an application scenario to provide a detailed description of the specific operating parameters, operation process, and application effects of the MVR system based on thermal flash evaporation circulating rising film heat exchange.

[0064] The feed solution to be treated is an aqueous sodium chloride solution with a feed temperature of 30℃, a feed flow rate of 10t / h, and a feed mass concentration of 5%. It is required that after evaporation and concentration by the MVR system, the mass concentration of sodium chloride in the output is not less than 15%, and the evaporation temperature of the rising film heat exchanger is 85℃.

[0065] Reference Figure 1 As shown, an MVR system based on thermally stimulated flash evaporation circulating rising film heat exchange includes a rising film heat exchanger 1, a compressor 2, a vapor-liquid separator 3, a concentrate tank 4, a reflux pump 5, a condensate tank 6, a condensate pump 7, a preheater 8, a booster pump 9, a thermally stimulated heater 10, a measurement and control system 11, a throttling component 12, and a vapor-liquid distributor 13.

[0066] Reference Figure 2As shown, the rising film heat exchanger 1 is a vertical shell-and-tube heat exchanger with a length-to-diameter ratio of 13:1, a tube diameter of 19 mm, and a height of 2500 mm. The upper outlet of the heat exchanger tube is 100 mm higher than the upper tube sheet. The shell side of the rising film heat exchanger 1 is the hot medium side, with a heating steam inlet on the upper side wall and a steam condensate outlet on the lower side wall. The tube side of the rising film heat exchanger 1 is the cold medium side. The lower head of the rising film heat exchanger 1 has a feed inlet, and a vapor-liquid distributor 13 is installed inside the lower head. The top of the upper head has a secondary steam outlet, and the side wall of the upper head has a concentrate outlet. The compressor 2 is a centrifugal compressor. The compressor is a single-stage compressor; the vapor-liquid separator 3 is a tank-type structure with a secondary steam inlet on the side wall, a secondary steam outlet at the top, and a separated liquid outlet at the bottom. The vapor-liquid separator 3 is equipped with a wire mesh demister inside; the concentrate tank 4 has a concentrate inlet at the top and a concentrate outlet at the bottom; the condensate tank 6 has a condensate inlet at the top and a condensate outlet at the bottom; the preheater 8 preheats the feed by using secondary steam condensate; the preheater 8 adopts a partition wall heat exchanger structure, with a material inlet and material outlet on the cold side channel and a condensate inlet and condensate outlet on the hot side channel; the preheater 8 uses a plate heat exchanger.

[0067] The function of the heat shock heater 10 is to heat the preheated liquid at high temperature, completing the storage of high-temperature thermal energy into the internal energy of the liquid. The heat shock heater 10 is a shell-and-tube heat exchanger, with a material inlet and outlet on the cold side and a live steam inlet and steam condensate outlet on the hot side. The heat shock heater 10 adopts a shell-and-tube heat exchanger. The function of the throttling component 12 is to throttle and reduce the pressure of the high-temperature liquid after heat shock heating, realizing isenthalpic throttling flash evaporation of the liquid. Through throttling flash evaporation, the internal energy stored in the liquid after heat shock heating is converted into the expansion kinetic energy of the vapor and liquid phases after flash evaporation. The throttling component adopts a throttling valve. The function of the vapor-liquid distributor 13 is to ensure that the vapor and liquid phases after throttling flash evaporation enter each heat exchange tube of the rising film heat exchanger in a uniform proportion, avoiding uneven vapor-liquid distribution in the heat exchange tubes. Figure 3 As shown, the vapor-liquid distributor 13 is a conical perforated plate; the vapor-liquid distributor 13 is located inside the lower head of the rising film heat exchanger 1.

[0068] The measurement and control system 11 includes a temperature sensor, a pressure sensor, a flow sensor, a level gauge, and a PLC controller; it is used to monitor the temperature, pressure, and flow parameters of each key measuring point in the MVR system in real time; and to realize the start and stop control of the compressor 2, the reflux pump 5, the condensate pump 7, and the booster pump 9, as well as the adjustment of the compressor frequency and the opening degree of the throttling component 12.

[0069] In this embodiment, the secondary steam outlet of the rising film heat exchanger 1 is connected to the secondary steam inlet of the vapor-liquid separator 3; the secondary steam outlet of the vapor-liquid separator 3 is connected to the inlet of the compressor 2; the outlet of the compressor 2 is connected to the heating steam inlet of the rising film heat exchanger 1; the steam condensate outlet of the rising film heat exchanger 1 is connected to the condensate inlet of the condensate tank 6; the condensate outlet of the condensate tank 6 is connected to the inlet of the condensate pump 7, and the outlet of the condensate pump 7 is connected to the condensate inlet of the hot side channel of the preheater 8, and the condensate is discharged from the condensate outlet of the preheater 8; the feed pipeline is connected to the material inlet of the preheater 8, and the material outlet of the preheater 8 is connected to the heating steam inlet of the compressor 2. The inlet of the booster pump 9 is connected to the material inlet of the heat-induced shock heater 10, and the material outlet of the heat-induced shock heater 10 is connected to the throttling device 12. Temperature and pressure sensors are installed on the connecting pipeline. The other side of the throttling device 12 is connected to the feed inlet of the rising film heat exchanger 1, and a pressure sensor is installed on the connecting pipeline. The concentrate outlet of the rising film heat exchanger 1 and the separated liquid outlet of the vapor-liquid separator 3 are both connected to the concentrate inlet of the concentrate tank 4. The concentrate outlet of the concentrate tank 4 is connected to the inlet of the reflux pump 5. One outlet of the reflux pump 5 is used for sampling, and the other outlet is connected to the inlet of the booster pump 9.

[0070] The working process of the MVR system in this embodiment is as follows:

[0071] A feed liquid with a flow rate of 10 t / h and a temperature of 30°C is fed into preheater 8, where it is preheated using 90°C condensate from rising film heat exchanger 1, reducing the subsequent heating load. The preheated material is then pressurized to 150-200 kPa by booster pump 9 and fed into thermal shock heater 10, where it is heated to 100°C by 150°C high-temperature live steam, completing the storage of thermal energy into internal energy. The high-pressure saturated feed liquid flows through throttling device 12, where its pressure is reduced to approximately 50 kPa. After being throttled by the 100°C sodium chloride solution, it undergoes intense isenthalpic flash evaporation under low-pressure conditions, rapidly converting the internal energy of the thermally stimulated feed liquid into a vapor-liquid two-phase flow. The flow kinetic energy generates a high-kinetic-energy vapor-liquid two-phase flow, which enters the heat exchange tubes of the rising film heat exchanger 1 after passing through the vapor-liquid distributor. As shown in Figure 4(a), the flow pattern evolution of traditional rising film heat exchangers requires sequentially going through single-phase liquid flow, bubbly flow, slug flow, annular flow, and mist flow. Under the narrow temperature difference conditions of MVR, it is often difficult to cross the inefficient stages such as bubbly flow and slug flow, and a stable annular flow cannot be formed. However, as shown in Figure 4(b), this embodiment pre-generates a high-kinetic-energy vapor-liquid two-phase flow through thermal flash evaporation, directly skipping the inefficient flow pattern stages and quickly entering the efficient annular flow stage, significantly shortening the flow pattern transformation process and improving heat exchange efficiency and stability. The evaporation temperature of the rising film heat exchanger 1 is 85℃, and the evaporation pressure is about 50kPa (a). The secondary steam from the tube-side outlet of rising film heat exchanger 1 enters vapor-liquid separator 3. The separated vapor phase enters compressor 2 for compression and heating. The compressed secondary steam, at 90°C, is then introduced into the shell side of rising film heat exchanger 1, forming a narrow heat transfer temperature difference of 4-6°C with the material in the tube side. The latent heat of the evaporating secondary steam is recovered through mechanical vapor recompression, realizing the recycling of heat energy in the evaporation process. The separated liquid phase is combined with the concentrate from rising film heat exchanger 1 and enters concentrate tank 4. After concentration detection, the liquid phase is collected when the concentration reaches the preset requirement of 15%. When the concentration is below 15%, it is returned to the inlet of booster pump 9 for reprocessing via reflux pump 5. The condensate from the shell side of rising film heat exchanger 1 flows into condensate tank 6, and is discharged from the system after passing through condensate pump 7 and preheater 8. The condensate discharge rate is approximately 6.67 t / h.

[0072] This embodiment provides an MVR system based on thermally stimulated flash evaporation and circulating rising film heat exchange. Through an independent kinetic energy pre-generation mechanism, a stable annular flow can be formed without relying on a large temperature difference. The starting temperature difference for rising film heat exchange is reduced to within 10°C, perfectly matching the narrow temperature difference heat transfer characteristics of the MVR system. Furthermore, the thermally stimulated flash process directly propels the flow pattern inside the rising film heat exchanger tubes into a highly efficient annular flow stage, improving heat transfer efficiency by more than 30% compared to traditional rising film technology. This enables the reuse of latent heat of secondary steam, reduces system energy consumption, and ensures the efficient operation of the MVR system under narrow temperature difference conditions.

[0073] Example 3:

[0074] Based on Example 2, referring to Figure 5As shown, an MVR system based on thermally stimulated flash evaporation circulating rising film heat exchange in this embodiment includes a rising film heat exchanger 1, a compressor 2, a vapor-liquid separator 3, a concentrate tank 4, a reflux pump 5, a condensate tank 6, a condensate pump 7, a preheater 8, a booster pump 9, a thermally stimulated heater 10, a measurement and control system 11, a throttling component 12, a vapor-liquid distributor 13, and a flow regulating valve 14.

[0075] The outlet of the compressor 2 is connected to the inlet of the rising film heat exchanger 1, and a flow regulating valve 14 and a one-way valve are provided between the outlet of the compressor 2 and the inlet of the rising film heat exchanger 1.

[0076] The equipment structure and system connection method of this embodiment are the same as those of embodiment 2. The difference from embodiment 2 is that the outlet of the compressor 2 is divided into two, one of which is connected to the heating steam inlet of the rising film heat exchanger 1, and the other is connected to the feed inlet of the rising film heat exchanger 1. A flow regulating valve 14 and a check valve are installed on this connecting pipeline.

[0077] In this embodiment of the MVR system, the feed liquid is heated to at least the evaporation temperature of the rising film heat exchanger 1 by the heat-shock heater 10. The secondary steam required to drive the rising film heat exchanger 1 to form a film comes partly from the flash evaporation of the heat-shock feed liquid and partly from the high-pressure steam at the outlet of the compressor 2. The vapor content at the inlet of the rising film heat exchanger 1 is adjusted by supplementing the steam at the outlet of the compressor 2, ensuring that the vapor content at the inlet of the rising film heat exchanger 1 is within the required range for circulating rising film. This embodiment is mainly applicable to application conditions where the live steam temperature is low and the specific volume of the secondary steam is small, resulting in a low vapor content at the inlet of the rising film heat exchanger 1 after heat-shock flash evaporation.

[0078] It should be noted that the above detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0079] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments described in this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0080] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0081] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0082] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.

[0083] In the detailed description above, reference has been made to the accompanying drawings, which form part of this document. In the drawings, similar symbols typically identify similar parts unless the context otherwise indicates otherwise. The illustrated embodiments described in the detailed specification, drawings, and claims are not intended to be limiting. Other embodiments may be used and other changes may be made without departing from the spirit or scope of the subject matter presented herein.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An MVR system based on thermal flash evaporation circulating rising film heat transfer, characterized in that: It includes a rising film heat exchanger (1), a vapor-liquid separator (3), a preheater (8), a thermal shock heater (10), and a throttling component (12). The material outlet of the preheater (8) is connected to the material inlet of the heat shock heater (10) so that the preheated liquid enters the heat shock heater (10) after being pressurized. The condensate inlet of the preheater (8) is connected to the condensate outlet of the rising film heat exchanger (1) so that the steam condensate in the shell side of the rising film heat exchanger (1) flows into the preheater (8) and the residual heat of the steam condensate is used to preheat the liquid. The material outlet of the heat-induced heater (10) is connected to the feed inlet of the rising film heat exchanger (1) through the throttling component (12). The heat-induced heater (10) is used to heat the liquid with high-temperature live steam. After the liquid is heated, it is throttled and depressurized by the throttling component (12) and undergoes isenthalpic flash evaporation. The liquid after flash evaporation is converted into a vapor-liquid two-phase flow and then enters the heat exchange tube of the rising film heat exchanger (1). Driven by the expansion kinetic energy of the vapor phase, the liquid rises along the inner wall of the heat exchange tube to form a stable liquid film. The secondary steam outlet at the top of the rising film heat exchanger (1) is connected to the secondary steam inlet of the vapor-liquid separator (3) so that the secondary steam in the rising film heat exchanger (1) enters the vapor-liquid separator (3). The separated vapor phase is compressed and then fed into the rising film heat exchanger (1) through the heating steam inlet of the rising film heat exchanger (1) to be used as a heat source for the rising film heat exchanger (1). The concentrated liquid flowing out of the vapor-liquid separator (3) and the rising film heat exchanger (1) is collected when the concentration is qualified. If it is not qualified, it is pressurized and injected back into the heat shock heater (10) through the material inlet of the heat shock heater (10) for reuse.

2. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: A booster pump (9) is provided between the material outlet of the preheater (8) and the material inlet of the heat shock heater (10). The booster pump (9) is used to pressurize the liquid material from the preheater (8) and send it into the heat shock heater (10).

3. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: It also includes a compressor (2), the inlet of which is connected to the secondary steam outlet of the vapor-liquid separator (3), and the outlet of the compressor (2) is connected to the heating steam inlet of the rising film heat exchanger (1).

4. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 3, characterized in that: The outlet of the compressor (2) is connected to the inlet of the rising film heat exchanger (1), and a flow regulating valve (14) and a check valve are provided between the outlet of the compressor (2) and the inlet of the rising film heat exchanger (1).

5. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: It also includes a concentrate tank (4), the concentrate inlet of which is connected to the concentrate outlet of the rising film heat exchanger (1) and the separation liquid outlet of the vapor-liquid separator (3), respectively, and the concentrate outlet of the concentrate tank (4) is connected to the material inlet of the heat-induced heater (10).

6. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: It also includes a condensate tank (6), the condensate inlet of which is connected to the steam condensate outlet of the rising film heat exchanger (1), and the condensate outlet of which is connected to the condensate inlet of the preheater (8).

7. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: It also includes a measurement and control system, which includes a temperature sensor, a pressure sensor, a flow sensor, a level gauge, and a PLC controller.

8. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: The lower end cap of the rising film heat exchanger (1) is provided with a vapor-liquid distributor (13).

9. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: After the liquid is heated in the heat-stimulating heater (10), the temperature of the liquid needs to be 5~20℃ higher than the evaporation temperature of the rising film heat exchanger (1).

10. The MVR system based on thermal flash evaporation circulating rising film heat exchange according to claim 1, characterized in that: The temperature difference between the vapor phase separated by the vapor-liquid separator (3) and the liquid in the heat exchange tube of the rising film heat exchanger (1) and the liquid in the rising film heat exchanger (1) is 4~10℃.

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