A dual-effect heat pump distillation system
By using a screw compressor in a dual-effect heat pump distillation system to achieve thermal coupling between the first-effect and second-effect distillation columns, the problems of large compressor gas flow and high equipment investment are solved, resulting in reduced energy consumption and improved system stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- XIAN RUISHENGHUA ENERGY SAVING & ENVIRONMENTAL PROTECTION TECH CO LTD
- Filing Date
- 2025-09-04
- Publication Date
- 2026-07-31
AI Technical Summary
Conventional heat pump distillation systems and double-effect distillation systems suffer from problems such as large compressor gas flow, numerous compressors, and high equipment investment. Furthermore, conventional double-effect distillation systems require an external heat source and cannot fundamentally reduce steam usage.
A dual-effect heat pump distillation system is adopted, which uses a screw compressor to achieve thermal coupling between the first-effect distillation column and the second-effect distillation column. The top steam of the first-effect distillation column is pressurized to heat the second-effect distillation column, and the top steam of the second-effect distillation column is used to heat the first-effect distillation column. This reduces the number of compressors and the amount of gas passing through, and realizes the cascade utilization of heat.
It achieves a 50% reduction in compressor air volume, a 30-40% reduction in energy consumption, lower equipment investment, a more stable system, a reduced number of compressors, reduced operating costs, full heat recovery, strong compressor load regulation capability, and adaptability to fluctuations in operating conditions.
Smart Images
Figure CN224573250U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of heat pump distillation technology, specifically relating to a dual-effect heat pump distillation system. Background Technology
[0002] Heat pump distillation is a technology that recovers waste heat from the distillation process by integrating a heat pump system, aiming to significantly reduce energy consumption and operating costs. Its core principle is to use a compressor to pressurize and heat the top vapor or intermediate heat of the column, and then reintroduce it into the distillation column as a heat source, thereby reducing the consumption of external steam or electric heating.
[0003] Double-effect distillation is a technology that significantly improves the energy efficiency of a distillation system through energy integration and thermal coupling. Its core lies in utilizing the coordinated operation of two or more distillation columns to achieve cascade utilization of heat and reduce external energy consumption.
[0004] Double-effect distillation does not have the energy-saving advantages of heat pump distillation. In conventional heat pump distillation processes, single-tower heat pump distillation suffers from problems such as large compressor gas flow, high compressor operating costs, and high equipment investment. Heat pump distillation using two compressors in two effects also suffers from problems such as large compressor gas flow, a large number of compressors, and high equipment investment. Utility Model Content
[0005] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a dual-effect heat pump distillation system.
[0006] A dual-effect heat pump distillation system is characterized by comprising a first-effect distillation column feed pump, which delivers raw materials into a preheater. The preheater is connected to the first-effect distillation column. The first-effect distillation column is connected to a gas-liquid separator via a screw compressor. The gas-liquid separator is connected to a tail gas condenser via a second-effect falling film reboiler. The second-effect falling film reboiler is connected to a first-effect reflux discharge pump via a first-effect reflux tank. The first-effect reflux discharge pump is connected to the preheater. The first-effect distillation column is connected to the first-effect falling film reboiler and the first-effect falling film circulation pump, and the first-effect falling film circulation pump is connected to the first-effect falling film reboiler; the first-effect distillation column is connected to the second-effect distillation column through the first-effect column bottom discharge pump, and the second-effect distillation column is connected to the tail gas condenser through the first-effect falling film reboiler; the first-effect falling film reboiler is connected to the second-effect reflux discharge pump through the second-effect reflux tank. The second-effect falling film reboiler is connected to the second-effect falling film circulation pump, which is connected to the second-effect distillation column. The second-effect falling film reboiler is connected to the second-effect distillation column bottom discharge pump through the second-effect distillation column, which is connected to the first-effect falling film reboiler.
[0007] It should be noted that, compared to conventional heat pump distillation systems with two compressors operating in two effects, this invention only requires a single compressor (screw compressor) to achieve better energy-saving results.
[0008] Preferably, the first-effect reflux tank is connected to the hot-side inlet of the preheater via a first-effect reflux discharge pump, and the hot-side outlet of the preheater is connected to the reflux port of the first-effect distillation column for reflux.
[0009] Preferably, the preheater is connected to the product cooler for cooling and product production.
[0010] Preferably, the double-effect reflux discharge pump is connected to the double-effect distillation column for reflux.
[0011] Preferably, the double-effect reflux discharge pump is connected to the product cooler for cooling and product production.
[0012] Preferably, the bottom discharge pump of the double-effect distillation column is connected to a reboiler cooler for wastewater treatment.
[0013] Preferably, the single-effect distillation column is connected to the start-up reboiler.
[0014] Preferably, the start-up reboiler is connected to external low-pressure steam, the low pressure being >0.2 MPaG, and the start-up reboiler discharges steam condensate.
[0015] Preferably, the raw materials or products include at least one of methanol, ethanol, chloroform, acetone, and ethyl acetate.
[0016] It should be noted that, by adopting the aforementioned technical solution, the top gas of the two-effect distillation column of this utility model is coupled to the first-effect falling film reboiler of the one-effect distillation column, and the top gas of the one-effect distillation column is pressurized by the screw compressor and then coupled to the second-effect falling film reboiler of the two-effect distillation column, thus successfully realizing a dual-effect thermal coupling system combining distillation column and heat pump technology.
[0017] Preferably, taking methanol distillation as an example, with 96% methanol feed, 99% methanol product, and 1% methanol content in wastewater, the bottom temperature of the first-effect distillation column is 70℃, the top temperature of the first-effect distillation column is 65.5℃, and the reflux ratio of the first-effect distillation column is 0.27; the bottom temperature of the second-effect distillation column is 109℃, the top temperature of the second-effect distillation column is 80℃, and the reflux ratio of the second-effect distillation column is 0.81; the top operating pressure of the first-effect distillation column is 103 kPa, and the top operating pressure of the second-effect distillation column is 180 kPa.
[0018] It should be noted that, by adopting the above technical solution, this utility model utilizes the characteristic that the boiling point of the column bottom is low in the first stage of concentration of high-concentration light components and the temperature of the column bottom is high in the second stage of concentration. The distillation column is split into two effects, using two columns (a first-effect distillation column and a second-effect distillation column). The boiling point of the column bottom of the first-effect distillation column is close to the boiling point of the column top, and the difficulty of heating the top of the second-effect distillation column for the first-effect distillation column is relatively low. The waste heat of the product at the top of the first-effect distillation column is compressed by the compressor, which overcomes the sum of the temperature rise of the two columns and directly heats the column bottom of the second-effect distillation column. Then the top of the second-effect distillation column heats the first-effect distillation column. In this process, the different reflux ratios of the two columns must also be considered.
[0019] The design of the technical solution faces many technical challenges. For example, when considering the ratio of the first-effect distillation column and the second-effect distillation column, it is necessary to ensure that the compressor's gas flow rate (including the overhead gas from both the discharge and reflux sections) and temperature rise (the boiling point difference between the top and bottom of the distillation column) meet the total requirements of the two-effect distillation column, and that there is basically no surplus in the tail gas section. Under such circumstances, the technical solution of this application is fundamentally different from the conventional double-effect distillation technology with an external heat source.
[0020] Furthermore, conventional double-effect processes require an external heat source, and the top of the second-effect tower needs to be cooled by an external cold source, which cannot fundamentally reduce the use of steam.
[0021] The system of this application combines the thermal coupling function of the operating temperature of the two columns with the heat recovery function of the two columns. The reboilers of both columns are thermally coupled. The first-effect distillation column is double-effect thermally coupled, and the second-effect distillation column is heat pump thermally coupled. The excess steam from the two columns is combined and sent to the tail gas condenser, which reduces the amount of steam used and the amount of cooling water used. It is a significant improvement compared with conventional heat pump distillation systems and double-effect distillation systems.
[0022] The beneficial effects of this utility model are: This utility model's dual-effect heat pump distillation system combines the energy-saving advantages of heat pump distillation with the thermal coupling advantages of dual-effect distillation columns. The top steam of the first-effect distillation column is pressurized by a compressor to heat the bottom of the second-effect distillation column, and the top steam of the second-effect distillation column is pressurized to heat the bottom of the first-effect distillation column. This reduces the number of compressors and the amount of gas passing through, saving both operating costs and equipment investment costs. At the same time, the system's core compressor equipment avoids multiple units connected in series, resulting in greater stability.
[0023] The dual-effect heat pump distillation system of this invention can achieve: 1. Sufficient heat recovery: feed preheating, heat recovery at the top of the first-effect distillation column, and heat recovery at the top of the second-effect distillation column.
[0024] 2. Low compressor gas volume: The double-effect process of the double-effect distillation column significantly reduces the gas volume because the screw compressor only processes the top steam of the first-effect distillation column, and the heat generated by this part of the steam is efficiently reused to heat the reboiler of the second-effect distillation column, thereby reducing the compressor gas volume by about half.
[0025] 3. Lower Energy Consumption: The dual-effect process of the double-effect distillation column reduces compressor power, is technologically mature, highly automated, and features reasonable equipment selection. More specifically, in a double-effect distillation column, the first-effect distillation column has a high feed concentration, and the boiling point of the bottom product is close to that of the top product. Under the premise of halving the gas flow rate, the compressor pressure ratio increases from 5 to 5.8 (taking methanol as an example). The energy consumption of this system is also lower. Compared with single-effect heat pump distillation, the double-effect heat pump distillation system can save approximately 30-40% of energy.
[0026] 4. Low investment or low cost: The cost of a compressor is related to its gas flow rate and motor power. The larger the gas flow rate, the higher the investment. The more compressors there are, the higher the investment. This system has a small compressor gas flow rate, and the gas flow rate of the compressor only needs to be half that of conventional single-effect heat pump distillation. The number of compressors is only 1, which greatly reduces the cost.
[0027] 5. High controllability: The reboiler auxiliary heating can cope with fluctuations in operating conditions during startup, the screw compressor has strong load adjustment capabilities, and the exhaust gas condenser ensures the outlet temperature.
[0028] 6. More stable system: The dual-effect heat pump distillation system of this utility model relies on only one compressor (screw compressor), with fewer core components, a lower failure rate, and a more stable system.
[0029] 7. Reasonable thermal coupling design: The top gas of the double-effect distillation column is coupled to the bottom of the first-effect distillation column, and the top gas of the first-effect distillation column is coupled to the bottom of the double-effect distillation column by a heat pump pressurization.
[0030] 8. Subsequent processing: The destination of the bottom product from the double-effect distillation column can be divided into several situations. Generally, the bottom product pump of the double-effect distillation column is connected to the reboiler cooler, which sends the reboiled material out of the distillation system. Alternatively, the bottom product pump of the double-effect distillation column can be connected to the next external distillation column for further distillation and separation of materials.
[0031] In summary, this invention successfully improves the heat pump distillation system and combines it with double-effect distillation to form a unique heat pump double-effect distillation system that requires only one compressor. Attached Figure Description
[0032] The accompanying drawings are provided to further understand the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation thereof.
[0033] In the attached diagram: Figure 1 This is a schematic diagram of the preparation process of this utility model.
[0034] The diagram is marked as follows: 1. Product cooler; 2. Feed pump for first-effect distillation column; 3. Start-up reboiler; 4. First-effect distillation column; 5. First-effect falling film reboiler; 6. Preheater; 7. First-effect falling film circulation pump; 8. Second-effect reflux tank; 9. Second-effect reflux discharge pump; 10. First-effect column bottom discharge pump; 11. First-effect reflux discharge pump; 12. Screw compressor; 13. Gas-liquid separator; 14. First-effect reflux tank; 15. Second-effect falling film circulation pump; 16. Second-effect falling film reboiler; 17. Second-effect distillation column; 18. Tail gas condenser; 19. Reboiler cooler; 20. Second-effect distillation column bottom discharge pump. Detailed Implementation
[0035] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.
[0036] Example 1 A dual-effect heat pump distillation system includes a first-effect distillation feed unit, a first-effect distillation column distillation unit, a first-effect distillation column stripping unit, a second-effect distillation column feed unit, a second-effect distillation column distillation unit, and a second-effect distillation column stripping unit. To more clearly describe the function of each component or device, their connections are depicted as separate units.
[0037] The feed unit of the single-effect distillation column is as follows: the outlet of the raw material tank is connected to the inlet of the feed pump 2 of the single-effect distillation column, the outlet of the feed pump 2 of the single-effect distillation column is connected to the inlet of the cold side of the preheater 6, and the outlet of the cold side of the preheater 6 is connected to the inlet of the single-effect distillation column 4.
[0038] The single-effect distillation column unit: The steam outlet at the top of the single-effect distillation column 4 is connected to the inlet of the screw compressor 12. The outlet of the screw compressor 12 is connected to the inlet of the gas-liquid separator 13. The outlet of the gas-liquid separator 13 is connected to the shell-side inlet of the second-effect falling film reboiler 16. The tail gas outlet of the shell-side of the second-effect falling film reboiler 16 is connected to the tail gas condenser 18. The condensate outlet of the shell-side of the second-effect falling film reboiler 16 is connected to the inlet of the first-effect reflux tank 14. A gas phase balance pipeline is also installed between the second-effect falling film reboiler 16 and the first-effect reflux tank 14 to avoid pressure differences between the two devices affecting liquid feed. The outlet of the first-effect reflux tank 14 is connected to the inlet of the first-effect reflux discharge pump 11. The outlet of the first-effect reflux discharge pump 11 is connected to the hot-side inlet of the preheater 6. The hot side outlet of preheater 6 is divided into two connection routes. One route is: the hot side outlet of preheater 6 is connected to the top reflux port of the first-effect distillation column 4 to complete the reflux of the distillation unit of the first-effect distillation column. The other route is: the hot side outlet of preheater 6 is connected to the hot side inlet of product cooler 1. The outlet of product cooler 1 is connected to the external product storage unit to store methanol product.
[0039] Single-Effect Distillation Column Stripping Unit: In the stripping stage of the single-effect distillation column 4, the liquid material supplied by reflux and feed flows from top to bottom through each stage of the trays, undergoing gas-liquid mass transfer with the rising steam. During this process, the low-boiling-point components in the liquid phase are continuously stripped, and their concentration gradually decreases, ultimately yielding a product rich in high-boiling-point components in the bottom of the column, thus completing the stripping of low-boiling-point components.
[0040] The reflux and feed of the first-effect distillation column 4 are gradually reduced to the bottom of the column via gas-liquid mass transfer through each tray, where low-boiling-point substances are extracted. Specifically, the liquid outlet at the bottom of the first-effect distillation column 4 is connected to the inlet of the tube side of the start-up reboiler 3, and the outlet of the tube side of the start-up reboiler 3 is connected to the gas-liquid inlet of the bottom of the first-effect distillation column 4. Externally supplied low-pressure steam is connected to the shell side inlet of the start-up reboiler 3, and the condensate from the shell side outlet of the start-up reboiler 3 is discharged to the outside via a steam trap. The liquid outlet at the bottom of the first-effect distillation column 4 is connected to the inlet of the first-effect falling film circulation pump 7, the outlet of the first-effect falling film circulation pump 7 is connected to the feed inlet of the tube side at the top of the first-effect falling film reboiler 5, and the discharge outlet of the tube side of the first-effect falling film reboiler 5 is connected to the gas-liquid inlet of the bottom of the first-effect distillation column 4. The liquid outlet of the first-effect distillation column 4 is connected to the inlet of the first-effect distillation column bottom discharge pump 10 to complete the distillation unit of the first-effect distillation column.
[0041] The double-effect distillation column feed unit connects the outlet of the first-effect column bottom discharge pump 10 to the inlet in the middle of the double-effect distillation column 17 to complete the double-effect distillation feed.
[0042] The double-effect distillation column unit consists of two paths: the top vapor outlet of the double-effect distillation column 17 is connected to the shell-side inlet of the first-effect falling film reboiler 5; the shell-side tail gas outlet of the first-effect falling film reboiler 5 is connected to the tail gas condenser 18; and the shell-side condensate outlet of the first-effect falling film reboiler 5 is connected to the inlet of the second-effect reflux tank 8. A vapor phase balance pipeline is also installed between the first-effect falling film reboiler 5 and the second-effect reflux tank 8 to prevent pressure differences between the two devices from affecting liquid feed. The outlet of the second-effect reflux tank 8 is connected to the inlet of the second-effect reflux discharge pump 9. The outlet of the second-effect reflux discharge pump 9 has two connection routes: one route connects the second-effect reflux discharge pump 9 to the top reflux port of the double-effect distillation column 17 to complete the reflux of the double-effect distillation column unit; the other route connects the second-effect reflux discharge pump 9 to the hot-side inlet of the product cooler 1. The outlet of the product cooler 1 is connected to an external product storage unit to store methanol product.
[0043] The double-effect distillation column stripping unit: In the stripping stage of the double-effect distillation column 17, the liquid material supplied by reflux and feed flows from top to bottom through each stage of the trays, undergoing gas-liquid mass transfer with the rising vapor. During this process, low-boiling-point components in the liquid phase are continuously stripped, and their concentration gradually decreases, ultimately yielding a product rich in high-boiling-point components at the bottom of the column, thus completing the stripping of low-boiling-point components. Specifically: the bottom outlet of the double-effect distillation column 17 is connected to the inlet of the double-effect falling film circulation pump 15; the outlet of the double-effect falling film circulation pump 15 is connected to the top tube inlet of the double-effect falling film reboiler 16; the tube-side outlet of the double-effect falling film reboiler 16 is connected to the gas-liquid inlet of the bottom of the double-effect distillation column 17, completing the reboiler process. The liquid outlet of the bottom of the double-effect distillation column 17 is connected to the inlet of the bottom discharge pump 20, completing the double-effect distillation column stripping unit.
[0044] Double-Effect Distillation Column Bottom Discharge and Subsequent Processing: The destination of the bottom discharge from the double-effect distillation column 17 can be divided into several cases. Generally, the outlet of the bottom discharge pump 20 of the double-effect distillation column is connected to the hot side inlet of the reboiler 19, and the reboiled material from the hot side outlet of the reboiler 19 is sent out of the distillation system. In other cases, the outlet of the bottom discharge pump 20 of the double-effect distillation column is connected to the feed inlet of the next stage distillation column for continued distillation and separation of materials.
[0045] The working process of a double-effect heat pump distillation system is as follows: The feed material is preheated and enters the first-effect distillation column 4. The top vapor of the first-effect distillation column 4 is pressurized by the screw compressor 12 to heat the bottom of the second-effect distillation column 17. The bottom product of the first-effect distillation column 4 enters the second-effect distillation column 17. The operating pressure at the top of the second-effect distillation column 17 is increased, and the top vapor of the second-effect distillation column 17 heats the bottom of the first-effect distillation column 4. The bottom product of the second-effect distillation column 17 is cooled by the product cooler 1 and then sent out of the system. The condensate from the top vapor of each column is metered and returned to the top of its respective column. The top products are combined and sent to the product cooler 1.
[0046] Example 2 Unlike Example 1, this example provides a more detailed working process, as follows: The working process of a double-effect heat pump distillation system is as follows: The material is stored in a feed tank. The material is fed from the feed tank through a feed pump 2 to the cold side of a preheater 6. In the preheater 6, the relatively low-temperature material exchanges heat with the high-temperature reflux liquid or product liquid flowing from the hot side of the preheater 6 and originating from the top of the first-effect distillation column 4. The material is preheated to near the temperature of the feed plate of the first-effect distillation column 4, thus completing the preheating process. The preheated material enters the middle feed inlet of the first-effect distillation column 4 from the cold side outlet of the preheater 6.
[0047] 1. Treatment of the first-effect distillation column 4 Distillation: The preheated material flows downwards in the first-effect distillation column 4, where it undergoes countercurrent gas-liquid contact and mass transfer with the rising vapor at the bottom of the column on the trays. Volatile components (such as methanol) continuously vaporize and enter the rising vapor, while less volatile components (such as water) continuously condense and enter the downward-flowing liquid. The rising vapor reaches the top of the first-effect distillation column 4, becoming superheated or saturated vapor rich in volatile components (the target product).
[0048] Distillation: The concentration of non-volatile components in the downward-flowing liquid increases. The liquid reaches the bottom of the first-effect distillation column 4, is drawn out by the first-effect falling film circulation pump 7, pressurized, and sent to the top of the tube side of the first-effect falling film reboiler 5. In the first-effect falling film reboiler 5, the bottom liquid in the tube side flows down the tube wall in the form of a falling film.
[0049] The vapor rich in volatile components at the top of the first-effect distillation column 4 exits and enters the screw compressor 12. The screw compressor 12 compresses and pressurizes the vapor, increasing its pressure and saturation temperature. The compressed, high-temperature, high-pressure vapor then enters the gas-liquid separator 13. Here, a small amount of entrained droplets or condensate that may have formed during compression is separated, primarily to prevent liquid from entering downstream equipment and affecting the equipment and process.
[0050] The high-temperature, high-pressure steam, still primarily in the gas phase and separated, enters the shell side of the double-effect falling film reboiler 16. Inside the shell side of the double-effect falling film reboiler 16, the high-temperature, high-pressure steam condenses, releasing a large amount of latent heat of condensation. This heat is used to heat the bottom liquid of the double-effect distillation column 17 flowing within the tube side of the double-effect falling film reboiler 16.
[0051] The condensed liquid (mainly the top product components of the first-effect distillation column 4) flows out from the shell-side condensate outlet of the second-effect falling film reboiler 16 and enters the first-effect reflux tank 14.
[0052] The first-effect distillation column 4 produces and refluxes the following liquid: the liquid flowing from the shell-side condensate outlet of the second-effect falling film reboiler 16 into the first-effect reflux tank 14 is the condensate of the compressed overhead vapor from the first-effect distillation column 4, which is of very high purity. This liquid is buffered and stored in the first-effect reflux tank 14. The first-effect reflux discharge pump 11 draws liquid from the first-effect reflux tank 14, pressurizes it, and sends it to the hot side of the preheater 6.
[0053] On the hot side of preheater 6, the high-temperature reflux liquid / product liquid transfers heat to the raw material liquid on the cold side for preheating, while being cooled itself. The cooled liquid then splits into two streams from the hot side outlet of preheater 6: Reflux liquid: Returned to the top reflux port of the first-effect distillation column 4 to provide internal reflux and control the purity of the top product and the liquid-to-gas ratio of the rectification section.
[0054] Product liquid: fed into the hot side of product cooler 1, further cooled to storage temperature, and then sent out of the system for storage as the product of first-effect distillation column 4, such as methanol product.
[0055] The liquid in the bottom of the first-effect distillation column 4 is heated by the steam from the top of the second-effect distillation column 17 in the shell side of the first-effect falling film reboiler 5, causing partial vaporization and forming a gas-liquid mixture. More details will be described later.
[0056] The gas-liquid mixture returns from the outlet of the first-effect falling film reboiler 5 to the bottom gas-liquid inlet of the first-effect distillation column 4, providing rising steam for the first-effect distillation column 4.
[0057] A portion of the bottom liquid (enriched with non-volatile components) in the first-effect distillation column 4 is extracted by the first-effect column bottom discharge pump 10 and used as the feed for the second-effect distillation column 17.
[0058] The liquid delivered by the first-effect distillation column bottom discharge pump 10 enters the feed inlet in the middle of the second-effect distillation column 17.
[0059] 2. Treatment of the second-effect distillation column 17 Distillation: The feed liquid flows downwards in the second-effect distillation column 17, where it undergoes countercurrent gas-liquid contact and mass transfer with the rising vapor from the bottom of the column on the trays. The remaining volatile components in the feed are further purified and fed into the rising vapor. The rising vapor reaches the top of the column, becoming vapor rich in volatile components (the target product). Its pressure is typically higher than the top pressure of the first-effect distillation column 4, and the top temperature of the second-effect distillation column 17 is higher than the bottom temperature of the first-effect distillation column 4.
[0060] Distillation: The concentration of non-volatile components in the downward-flowing liquid continues to increase. The liquid reaches the bottom of the double-effect distillation column 17, is drawn out by the double-effect falling film circulation pump 15, pressurized, and sent to the top of the tube side of the double-effect falling film reboiler 16. In the double-effect falling film reboiler 16, the bottom liquid in the tube side flows down the tube wall in the form of a falling film.
[0061] The aforementioned text states that "the high-temperature, high-pressure steam, still predominantly in the gas phase, enters the shell side of the double-effect falling film reboiler 16. Within the shell side of the double-effect falling film reboiler 16, the high-temperature, high-pressure steam condenses, releasing a large amount of latent heat of condensation. This heat is used to heat the bottom liquid of the double-effect distillation column 17 flowing within the tube side of the double-effect falling film reboiler 16." More specifically, this high-temperature, high-pressure steam from the top of the first-effect distillation column 4, originating from the gas-liquid separator 13, condenses and releases heat in the shell side of the double-effect falling film reboiler 16. This heat is absorbed by the bottom liquid of the double-effect distillation column 17 flowing through the falling film in the tube side, partially vaporizing to form a gas-liquid mixture.
[0062] The gas-liquid mixture returns from the outlet of the tube side of the double-effect falling film reboiler 16 to the gas-liquid inlet of the bottom of the double-effect distillation column 17, providing rising steam for the column. The final residue (rich in the least volatile components) in the bottom of the double-effect distillation column 17 is extracted and processed by the bottom discharge pump 20.
[0063] The aforementioned text states that "the liquid in the bottom of the first-effect distillation column 4 is heated by the overhead vapor from the second-effect column in the shell side of the first-effect falling film reboiler 5, partially vaporizing to form a gas-liquid mixture." More specifically, the overhead vapor from the second-effect distillation column 17 exits the top and enters the shell side of the first-effect falling film reboiler 5. Within the shell side of the first-effect falling film reboiler 5, the overhead vapor from the second-effect distillation column 17 condenses, releasing its latent heat of condensation. This heat is used to heat the liquid in the bottom of the first-effect distillation column 4 flowing within the tube side of the first-effect falling film reboiler 5, providing it with reboiling heat.
[0064] The liquid condensed from the second-effect distillation column 17 (mainly the product components at the top of the second-effect distillation column 17) flows out from the condensate outlet of the shell side of the first-effect falling film reboiler 5 and enters the second-effect reflux tank 8. The tail gas (non-condensable gas) from the shell side of the first-effect falling film reboiler 5 enters the tail gas condenser 18 for further processing.
[0065] Product and Reflux of Second-Effect Distillation Column 17: The shell-side condensate from the first-effect reboiler 5 enters the second-effect reflux tank 8, which is the condensate of the overhead vapor from the second-effect distillation column 17. This liquid is buffered and stored in the second-effect reflux tank 8.
[0066] The double-effect reflux discharge pump 9 draws liquid from the double-effect reflux tank 8 and pressurizes it. The pressurized liquid then splits into two streams: Reflux liquid: Returned to the top reflux port of the double-effect distillation column 17 to provide internal reflux.
[0067] Product liquid: fed into the hot side of product cooler 1, it can be combined with or connected in parallel with the product liquid of first-effect distillation column 4. After being cooled to the storage temperature, it is sent out of the system as the product of second-effect distillation column 17 for storage, such as methanol product.
[0068] Residual liquid treatment of double-effect distillation column 17: The final residual liquid in the bottom of double-effect distillation column 17 (mainly non-volatile components, such as water, heavy component impurities, etc.) is extracted by the bottom discharge pump 20 of double-effect distillation column.
[0069] After the residual liquid is extracted, it enters the hot side of the reboiler 19 for cooling. Once it reaches the discharge or storage temperature, it is sent out of the system or into subsequent distillation equipment.
[0070] 3. Processing of other auxiliary systems Start-up reboiler 3: Used during system startup or when the heat from the first-effect falling film reboiler 5 (heated by the top of the second-effect distillation column 17) is insufficient. External low-pressure steam enters the shell side of start-up reboiler 3, heating the liquid from the reboiler of the first-effect distillation column 4 in the tube side, providing a startup heat source or supplementary heat for the first-effect distillation column 4. It is usually shut down or used as a standby after normal operation. The steam condensate is discharged through the drain valve of start-up reboiler 3.
[0071] Tail gas condenser 18: Receives tail gas (non-condensable gas) from the shell side of the first-effect falling film reboiler 5 and the shell side of the second-effect falling film reboiler 16, condenses and cools it, separates out any small amount of liquid components that may be entrained, and discharges the non-condensable gas from the system into the tail gas treatment unit.
[0072] Example 3 Unlike Example 2, this example provides specific parameters for the working process, as follows: When the material is methanol, a methanol solution at 30℃, atmospheric pressure, 96% concentration, and a flow rate of 21t / h is selected and fed from the raw material tank through the feed pump 2 of the first-effect distillation column. After preheating by the preheater 6, it is heated to 68℃ and enters the feed inlet of the first-effect distillation column 4. The bottom temperature of the first-effect distillation column 4 is 70℃, the top temperature is 65.5℃, the reflux ratio of the first-effect distillation column 4 is 0.27, and the methanol concentration at the outlet of the first-effect distillation column 4 is 92%. The bottom temperature of the first-effect distillation column 4 is 70℃ and enters the feed inlet of the second-effect distillation column 17. The bottom temperature of the second-effect distillation column 17 is 109℃, the top temperature is 80℃, the reflux ratio of the second-effect distillation column 17 is 0.81, and the methanol concentration at the outlet of the second-effect distillation column 17 is 1%. The methanol purity of the product from the first-effect distillation column 4 is 99.54%, and the methanol purity of the top product from the second-effect distillation column 17 is 99.56%. The operating pressure at the top of the first-effect distillation column 4 is 103 kPa, and the temperature is increased to 51°C by the screw compressor 12, serving as the heat source for the second-effect falling film reboiler 16. The operating pressure at the top of the second-effect distillation column 17 is 180 kPa, serving as the heat source for the first-effect falling film reboiler 5.
[0073] Temperature gradient requirement: To ensure heat transfer efficiency, the operating pressure of the first column must maintain its steam temperature 8-10°C higher than the boiling point of the liquid at the bottom of the second column. This temperature difference is the key to thermal coupling.
[0074] The compressor has an inlet pressure of 105 kPaA, corresponding to a saturation temperature of 66°C, and an outlet pressure of 600 kPaA, corresponding to a saturation temperature of 117°C.
[0075] It should be noted that, in addition to methanol, the materials can also include ethanol, chloroform, acetone and ethyl acetate. The dual-effect heat pump distillation system of this invention can be widely used in the distillation and purification processes of various materials such as methanol, ethanol, chloroform, acetone and ethyl acetate.
[0076] It should be further noted that the meanings and principles of the terms used in this application are understandable and well-known to those skilled in the art.
[0077] Among them, reflux ratio is the ratio of reflux liquid flow rate to the product flow rate at the top of the column.
[0078] Screw compressor 12: Based on the twin-screw positive displacement compression principle, it realizes the intake, compression and discharge of gas through a pair of meshing helical male and female rotors.
[0079] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. A double-effect heat pump rectification system, characterized by, It includes a first-effect distillation column feed pump, which delivers raw materials into a preheater. The preheater is connected to the first-effect distillation column. The first-effect distillation column is connected to a gas-liquid separator via a screw compressor. The gas-liquid separator is connected to a tail gas condenser via a second-effect falling film reboiler. The second-effect falling film reboiler is connected to a first-effect reflux discharge pump via a first-effect reflux tank. The first-effect reflux discharge pump is connected to the preheater. The first-effect distillation column is connected to the first-effect falling film reboiler and the first-effect falling film circulation pump, and the first-effect falling film circulation pump is connected to the first-effect falling film reboiler; the first-effect distillation column is connected to the second-effect distillation column through the first-effect column bottom discharge pump, and the second-effect distillation column is connected to the tail gas condenser through the first-effect falling film reboiler; the first-effect falling film reboiler is connected to the second-effect reflux discharge pump through the second-effect reflux tank. The second-effect falling film reboiler is connected to the second-effect falling film circulation pump, which is connected to the second-effect distillation column. The second-effect falling film reboiler is connected to the second-effect distillation column bottom discharge pump through the second-effect distillation column, which is connected to the first-effect falling film reboiler.
2. A double-effect heat pump rectifying system according to claim 1, characterized in that, The first-effect reflux tank is connected to the hot-side inlet of the preheater via a first-effect reflux discharge pump, and the hot-side outlet of the preheater is connected to the reflux port of the first-effect distillation column for reflux.
3. The double-effect heat pump rectifying system of claim 1, wherein, The preheater is connected to the product cooler for cooling and product production.
4. The double-effect heat pump rectifying system of claim 1, wherein, The double-effect reflux discharge pump is connected to the double-effect distillation column for reflux.
5. The double-effect heat pump rectifying system of claim 1, wherein, The double-effect reflux discharge pump is connected to the product cooler for cooling and product production.
6. The double-effect heat pump rectifying system of claim 1, wherein, The bottom feed pump of the double-effect distillation column is connected to a reboiler cooler for wastewater treatment.
7. The double-effect heat pump rectifying system of claim 1, wherein, The single-effect distillation column is connected to the start-up reboiler.
8. A double-effect heat pump rectifying system according to claim 7, wherein, The start-up reboiler is connected to external low-pressure steam, which is >0.2MPaG, and the start-up reboiler discharges steam condensate.
9. A dual-effect heat pump distillation system according to claim 3 or 5, characterized in that, The raw materials or products include at least one of methanol, ethanol, chloroform, acetone, and ethyl acetate.
10. A double-effect heat pump distillation system according to any one of claims 1-8, characterized in that, With 96% methanol feed and 99% methanol output, and wastewater containing 1% methanol, the bottom temperature of the first-effect distillation column is 70℃, the top temperature is 65.5℃, and the reflux ratio is 0.
27. The bottom temperature of the second-effect distillation column is 109℃, the top temperature is 80℃, and the reflux ratio is 0.
81. The operating pressure at the top of the first-effect distillation column is 103 kPa, and the operating pressure at the top of the second-effect distillation column is 180 kPa.