Self-driven heat pump rectification system and energy-saving method thereof
Patent Information
- Application Number
- CN202611230061.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-13
- Publication Date
- 2026-09-29
AI Technical Summary
（1）外部能量依赖问题：传统热泵精馏需要通过外部能量（通常为电能）驱动压缩机，以对塔顶气体加压后向塔釜供热
（1）无需外部能量输入：本发明实施例利用精馏塔顶气体自身压力能驱动膨胀机做功进而带动压缩机工作，实现了热泵精馏系统的自驱动运行，无需外部电能或其他能量输入，特别适用于外部能量供应受限的场合；
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Figure CN122828401A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical separation and energy-saving technology, and particularly relates to heat pump distillation technology. Background Technology
[0002] Distillation is the most widely used method for component separation in petrochemical, coal chemical, and fine chemical industries, but it is also a unit operation with extremely high energy consumption. In conventional distillation processes, the reboiler in the column usually consumes a large amount of high-grade heat energy to provide the heat of vaporization required for separation, while the heat of the vapor at the top of the column is often discharged into the environment through the condenser, resulting in a large amount of energy waste.
[0003] Heat pump distillation technology uses a compressor to pressurize and heat the overhead vapor before sending it to the reboiler as a heat source, effectively recovering the latent heat of condensation of the overhead vapor and thus significantly reducing external steam consumption, resulting in substantial energy savings. However, traditional heat pump distillation systems have the following technical problems: (1) External energy dependence problem: Traditional heat pump distillation requires external energy (usually electricity) to drive the compressor to pressurize the gas at the top of the column and then supply heat to the bottom of the column. For some devices, due to insufficient external energy supply (such as limited power capacity or unstable power grid), the energy cycle of heat pump distillation cannot be realized, which limits the promotion and application of this technology; (2) Explosion-proof safety and investment issues: In flammable and explosive environments such as petroleum and chemical industries, explosion-proof requirements are high. Using an electric motor to drive the compressor requires the configuration of an explosion-proof motor and related electrical facilities, which will significantly increase the investment and floor space of the unit, raising the economic threshold of the project; (3) Waste of steam pressure energy: In conventional distillation systems, the heating steam supplied to the reboiler is usually at a high pressure and needs to be reduced to the required pressure by a pressure reducing valve before heating. During this process, the pressure energy of the steam is converted into heat energy and lost, resulting in a decrease in steam quality and ineffective utilization of pressure energy. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a self-driven heat pump distillation system and its energy-saving method, which can drive the heat pump compressor without external energy input.
[0005] According to a first aspect of the present invention, a self-driven heat pump distillation system is provided, comprising a distillation column, a steam reboiler, a heat pump reboiler, a compressor, an expander, a flash reflux tank, a condenser, and a separator; the steam reboiler and the heat pump reboiler are respectively disposed in the reboiler of the distillation column; the vapor phase outlet at the top of the distillation column is divided into two paths, one connected to the inlet of the compressor and the other connected to the inlet of the expander; the liquid phase outlet in the reboiler is divided into three paths, the first path connected to the cold-side inlet of the steam reboiler, the second path connected to the cold-side inlet of the heat pump reboiler, and the third path used for product collection from the reboiler; the cold-side outlet of the steam reboiler and the cold-side outlet of the heat pump reboiler... The inlet is connected to the first reflux port and the second reflux port located in the column bottom, respectively; the compressor is driven by the expander; the outlet of the compressor is connected to the hot side inlet of the heat pump reboiler, and the hot side outlet of the heat pump reboiler is connected to the inlet of the flash chamber of the flash reflux tank; the liquid phase outlet of the storage chamber of the flash reflux tank is divided into two paths, one path is connected to the top reflux port of the distillation column, and the other path serves as the top product outlet; the vapor phase outlet of the flash chamber of the flash reflux tank is connected to the inlet of the compressor; the outlet of the expander is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the separator, and the liquid phase outlet of the separator is connected to the inlet of the storage chamber of the flash reflux tank.
[0006] According to a second aspect of the present invention, a self-driven heat pump distillation energy-saving method is provided, comprising the following steps: Increase the operating pressure of the distillation column so that the pressure and temperature of the overhead gas in the distillation column meet the requirements for the expander to perform its work. The overhead gas extracted from the top of the distillation column is divided into two paths. One path is sent to an expander for expansion and depressurization, and the other path is sent to a compressor. The shaft power output by the expander directly drives the compressor. The compressed gas is used as the heat source of the heat pump reboiler in the bottom of the distillation column. The condensate obtained after condensation and heat release is sent to the flash chamber of the flash reflux tank for flash evaporation and gas-liquid separation. The separated gas phase is sent to the inlet of the compressor, and the separated liquid phase enters the storage chamber of the flash reflux tank. The outlet gas of the expander is condensed by the condenser and then enters the separator for separation. The separated liquid phase enters the storage chamber of the flash reflux tank. A portion of the liquid in the storage chamber is returned to the top of the distillation column as reflux liquid, and the other portion of the liquid in the storage chamber is collected as the top product of the column.
[0007] Compared with the prior art, the present invention has at least the following beneficial effects: (1) No external energy input required: The embodiments of the present invention utilize the pressure energy of the gas at the top of the distillation column to drive the expander to do work and thus drive the compressor to work, realizing the self-driven operation of the heat pump distillation system without the need for external electrical energy or other energy input, which is particularly suitable for occasions where the external energy supply is limited; (2) Reduced investment and floor space: The embodiments of the present invention eliminate the motor, frequency converter and supporting electrical facilities in the traditional heat pump distillation system, which greatly reduces the investment in the unit and the floor space. At the same time, there is no need to configure an explosion-proof motor, which significantly reduces the equipment investment and safety requirements in explosion-proof environments; (3) Recovering steam pressure energy: In this embodiment of the invention, by increasing the operating pressure of the distillation column, the steam pressure energy that would otherwise be lost through the pressure reducing valve is indirectly utilized and converted into mechanical work to drive the compressor, thereby improving the overall energy efficiency of the system; (4) Stable and reliable operation: The embodiments of the present invention adopt a mechanically directly connected expander-compressor combination, which has a simple system structure, stable and reliable operation, low maintenance workload, and strong adaptability; (5) Significant energy saving effect: Taking 50% (wt) methanol dehydration as an example, the self-driven heat pump distillation system of this invention can reduce the heating steam consumption from 13.3 t / h to about 8.2 t / h (equivalent to 0.6 MPaG saturated steam), and the energy saving rate can reach 38.5%. Attached Figure Description
[0008] Figure 1 A schematic diagram of a self-driven heat pump distillation system according to an embodiment of the present invention is shown. Detailed Implementation
[0009] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0010] Figure 1 A schematic diagram of a self-driven heat pump distillation system according to an embodiment of the present invention is shown. Please refer to... Figure 1 The self-driven heat pump distillation system according to an embodiment of the present invention includes a distillation column 1, a steam reboiler 21, a heat pump reboiler 22, a compressor 3, an expander 4, a flash reflux tank 5, a condenser 6, and a separator 7.
[0011] The steam reboiler 21 and the heat pump reboiler 22 are respectively installed in the bottom of the distillation column 1. The vapor outlet 12 at the top of the distillation column 1 is divided into two paths: one path is connected to the inlet of the compressor 3, and the other path is connected to the inlet of the expander 4. Specifically, the vapor outlet 12 at the top of the distillation column 1 is connected to a gas distribution pipeline, which divides the high-pressure gas generated at the top of the column into two streams. The first gas stream is connected to the inlet of the compressor 3, and the second gas stream is connected to the inlet of the expander 4.
[0012] The liquid phase outlet of the reboiler of distillation column 1 is divided into three paths: the first path is connected to the cold side inlet of steam reboiler 21, the second path is connected to the cold side inlet of heat pump reboiler 22, and the third path is used for product collection from the reboiler. The cold side outlet of steam reboiler 21 and the cold side outlet of heat pump reboiler 22 are respectively connected to the first reflux port and the second reflux port located in the reboiler of distillation column.
[0013] The compressor 3 is driven by the expander 4. Specifically, the expander 4 and the compressor 3 are an integrated structure, or the rotor of the expander 4 is directly mechanically connected to the rotor of the compressor 3 through a coupling or gearbox, so that the shaft power output by the expander 4 during expansion directly drives the compressor 3, realizing the self-driving of the system.
[0014] The outlet of compressor 3 is connected to the hot-side inlet of heat pump reboiler 22, and the hot-side outlet of heat pump reboiler 22 is connected to the inlet of the flash chamber of flash reflux tank 5. The liquid phase outlet of the storage chamber of flash reflux tank 5 is divided into two paths: one path is connected to the top reflux port of distillation column 1 via reflux pump P1, and the other path serves as the top product outlet. The vapor phase outlet of the flash chamber of flash reflux tank 5 is connected to the inlet of compressor 3.
[0015] The outlet of expander 4 is connected to the inlet of condenser 6, the outlet of condenser 6 is connected to the inlet of separator 7, the liquid phase outlet of separator 7 is connected to the inlet of the storage chamber of flash reflux tank 5, and the gas phase outlet of separator 7 is connected to vacuum pump P2. The separated non-condensable gas is discharged out of the system through vacuum pump P2.
[0016] The types of compressor 3 and expander 4 can be selected according to the processing scale and process conditions, and their specific forms include, but are not limited to, centrifugal, axial flow, Roots, or screw types. The heat transfer area and configuration ratio of heat pump reboiler 22 and steam reboiler 21 can be rationally designed according to the heat load distribution.
[0017] The working process of a self-driven heat pump distillation system according to an embodiment of the present invention is as follows.
[0018] (S1) Pressure boosting operation: The feed liquid in the bottom of the distillation column 1 is heated by the steam reboiler 21, and the operating pressure of the distillation column 1 is increased to the set value, so that the pressure and temperature of the gas at the top of the column increase accordingly, and pressure energy that can be used for expansion and work is obtained; In some specific embodiments, the operating pressure of the distillation column can be optimized and adjusted in the range of 0.3 to 0.6 MPaG according to the properties of the specific system. (S2) Gas splitting: The high-pressure gas generated at the top of the distillation column is split into two streams according to a set ratio. The splitting ratio is determined by optimizing the system energy balance based on the work demand of the expander and the compression ratio of the compressor. (S3) Expansion work: The first high-pressure gas is sent into the expander 4 to expand and reduce pressure, and the output shaft of the expander 4 drives the compressor 3; (S4) Compression heating: The second high-pressure gas is sent into the compressor 3, and the shaft work output by the expander 4 is used to compress and pressurize the gas, so that the gas temperature and pressure are further increased to meet the heat transfer temperature difference requirements of the heat pump reboiler 22. (S5) Heat pump heating: The compressed high-temperature gas is sent into the heat pump reboiler 22, and the condensation heat release provides the vaporization heat of the material in the bottom of the tower, realizing the transfer of heat from the top of the tower to the bottom of the tower. (S6) Condensation Reflux: The high-temperature and high-pressure condensate from the hot side outlet of the heat pump reboiler 22 enters the flash chamber of the flash reflux tank 5 for flash evaporation and gas-liquid separation. After the high-temperature and high-pressure liquid flashes in the flash chamber of the flash reflux tank 5, the separated gas enters the inlet of the compressor 3, and the separated cooled liquid flows into the storage chamber of the flash reflux tank 5. The low-pressure gas from the outlet of the expander 4 is condensed by the condenser 6, and after the non-condensable gas is separated by the separator 7, the liquid phase enters the storage chamber of the flash reflux tank 5. Part of the liquid in the storage chamber of the reflux tank is returned to the top of the distillation column as reflux liquid, and the other part of the liquid is collected as the top product.
[0019] During the above-described operation, heat adjustment can be performed. During the start-up phase of distillation column 1, all heat is supplied through the steam reboiler 21. The heat pump reboiler 22 is used for heating distillation column 1 during normal operation. During the heat pump heating phase, the steam supply is reduced accordingly to ensure stable column bottom temperature.
[0020] As can be seen from the above description, the heat pump distillation process of the self-driven heat pump distillation system of the present invention does not require external power input.
[0021] According to another embodiment of the present invention, a self-driven heat pump distillation energy-saving method includes the following steps: Increase the operating pressure of the distillation column to a level higher than the conventional atmospheric or low-pressure operation, so that the pressure and temperature of the overhead gas in the distillation column meet the requirements for the expander to perform its work. The overhead gas extracted from the top of the distillation column is divided into two paths. One path is sent to an expander for expansion and depressurization, and the other path is sent to a compressor. The shaft power output by the expander directly drives the compressor. The compressed gas is used as the heat source of the heat pump reboiler in the bottom of the distillation column. The condensate obtained after condensation and heat release is sent to the flash chamber of the flash reflux tank for flash evaporation and gas-liquid separation. The separated gas phase is sent to the inlet of the compressor, and the separated liquid phase enters the storage chamber of the flash reflux tank. The outlet gas of the expander is condensed by the condenser and then enters the separator for separation. The separated liquid phase enters the storage chamber of the flash reflux tank. A portion of the liquid in the storage chamber is returned to the top of the distillation column as reflux liquid, and the other portion of the liquid in the storage chamber is collected as the top product of the column.
[0022] Preferably, the temperature of the gas compressed by the compressor is more than 5°C higher than the temperature of the distillation column bottom to ensure that the heat pump reboiler has a sufficient heat transfer temperature difference.
[0023] In some specific embodiments, the self-driven heat pump distillation energy-saving method according to another embodiment of the present invention employs the aforementioned self-driven heat pump distillation system.
[0024] The following specific application example further illustrates the technical solution of the present invention, and the superiority of the embodiments of the present invention is demonstrated by comparing the energy consumption with that of traditional distillation processes.
[0025] Application Example 1 Application Example 1 uses the dehydration distillation of a 50% (wt) methanol aqueous solution as an example to illustrate the specific application and energy-saving effect of the self-driven heat pump distillation system of this invention.
[0026] (1) Conventional distillation scheme (comparative example) A conventional distillation process is employed, with the distillation column operating at atmospheric pressure, and the top operating pressure approximately 0.1 MPaG. The feed is a 50% (wt) methanol-water solution, requiring the top methanol product to have a water content of 10 ppm (by mass). The distillation column is equipped with 50 theoretical plates, a reflux temperature of 40°C, and an operating reflux ratio of 1.01.
[0027] Under these conditions, process simulation calculations indicate that the heat load required in the column bottom is approximately 7.64 MW. This heat is provided by 0.6 MPaG saturated steam, equivalent to a steam consumption of approximately 13.3 t / h. The steam at the top of the column releases heat upon condensation in the condenser, and this heat is discharged to the cooling water system without being recovered or utilized.
[0028] (2) Self-driven heat pump distillation scheme (this invention) Using the self-driven heat pump distillation system of this invention, the operating pressure of the distillation column is increased to 0.4 MPaG. Under the same separation requirements (10 ppm water content in the methanol product at the top of the column) and the same number of theoretical plates (50 plates), due to the increase in operating pressure, the temperature inside the column increases accordingly, the reflux temperature rises to 90°C, and the operating reflux ratio is adjusted to 2.0.
[0029] Under these conditions, process simulation calculations indicate that the heat load required in the reboiler is approximately 11.15 MW. This heat demand is met by two parts: Heating via heat pump reboiler: The gas at the top of the tower (temperature approximately 115℃, pressure 0.4MPaG) is split into two streams. One stream enters the expander to expand and do work, driving the compressor to compress and pressurize the other stream. After compression, the gas temperature rises to approximately 145℃ and is sent to the heat pump reboiler for condensation and heat release. The recoverable heat is approximately 6.45MW (equivalent to approximately 11.2t / h of 0.6MPaG saturated steam). Steam reboiler supplementary heating: The difference between the heat supply of the heat pump reboiler and the total heat load of the tower bottom is supplemented by the steam reboiler, and the supplementary heat is equivalent to about 8.2t / h of 0.6MPaG saturated steam.
[0030] (3) Comparison of energy-saving effects The steam consumption of the two schemes was compared, and the results are shown in Table 1.
[0031]
[0032] As shown in Table 1, although the total heat load of the distillation column increases due to the increase in operating pressure, the actual external steam consumption is reduced from 13.3 t / h to 8.2 t / h, achieving an energy saving rate of 38.5%, because the heat pump reboiler recovers the latent heat of condensation of the top steam. Furthermore, the system does not require external electrical energy to drive the compressor, achieving fully self-driven operation.
[0033] This invention increases the operating pressure of the distillation column, dividing the higher-pressure gas generated at the top of the column into two streams. One stream drives the compressor through an expander, while the other stream is pressurized by the compressor to heat the column bottom. This achieves a self-driven heat pump distillation cycle that requires no external energy input, resulting in a comprehensive effect of reducing energy consumption, reducing investment, and improving safety.
[0034] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A self-driven heat pump distillation system, characterized in that, It includes distillation columns, steam reboilers, heat pump reboilers, compressors, expanders, flash reflux tanks, condensers, and separators; The steam reboiler and the heat pump reboiler are respectively installed in the bottom of the distillation column. The vapor phase outlet at the top of the distillation column is divided into two paths: one path is connected to the inlet of the compressor, and the other path is connected to the inlet of the expander. The liquid phase outlet in the bottom of the column is divided into three paths: the first path is connected to the cold side inlet of the steam reboiler, the second path is connected to the cold side inlet of the heat pump reboiler, and the third path is used for product collection from the bottom of the column. The cold side outlets of the steam reboiler and the heat pump reboiler are respectively connected to the first reflux port and the second reflux port located in the bottom of the column. The compressor is driven by the expander; the compressor outlet is connected to the hot-side inlet of the heat pump reboiler, and the hot-side outlet of the heat pump reboiler is connected to the inlet of the flash chamber of the flash reflux tank; the liquid phase outlet of the storage chamber of the flash reflux tank is divided into two paths, one path is connected to the top reflux port of the distillation column, and the other path serves as the top product outlet; the gas phase outlet of the flash chamber of the flash reflux tank is connected to the compressor inlet. The outlet of the expander is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the separator, and the liquid phase outlet of the separator is connected to the inlet of the storage chamber of the flash reflux tank.
2. The self-driven heat pump distillation system according to claim 1, characterized in that, The gas phase outlet of the separator is connected to a vacuum pump.
3. The self-driven heat pump distillation system according to claim 1, characterized in that, One of the liquid phase outlets of the flash reflux tank is connected to the top reflux port of the distillation column via a reflux pump.
4. The self-driven heat pump distillation system according to claim 1, characterized in that, The expander and the compressor are an integral structure; or, the rotor of the expander is connected to the rotor of the compressor via a coupling or gearbox.
5. The self-driven heat pump distillation system according to claim 1, characterized in that, The compressor and the expander are of the following types: centrifugal, axial, Roots, or screw.
6. A self-driven heat pump distillation energy-saving method, characterized in that, Includes the following steps: Increase the operating pressure of the distillation column so that the pressure and temperature of the overhead gas in the distillation column meet the requirements for the expander to perform its work. The overhead gas extracted from the top of the distillation column is divided into two paths. One path is sent to an expander for expansion and depressurization, and the other path is sent to a compressor. The shaft power output by the expander directly drives the compressor. The compressed gas is used as the heat source of the heat pump reboiler in the bottom of the distillation column. The condensate obtained after condensation and heat release is sent to the flash chamber of the flash reflux tank for flash evaporation and gas-liquid separation. The separated gas phase is sent to the inlet of the compressor, and the separated liquid phase enters the storage chamber of the flash reflux tank. The outlet gas of the expander is condensed by the condenser and then enters the separator for separation. The separated liquid phase enters the storage chamber of the flash reflux tank. A portion of the liquid in the storage chamber is returned to the top of the distillation column as reflux liquid, and the other portion of the liquid in the storage chamber is collected as the top product of the column.
7. The energy-saving method for self-driven heat pump distillation according to claim 6, characterized in that, The non-condensable vapor obtained from the separator is sent to a vacuum pump.
8. The energy-saving method for self-driven heat pump distillation according to claim 6, characterized in that, The distillation column is equipped with a steam reboiler, which is used for heating and supplementing heating during the start-up phase of the distillation column.
9. The energy-saving method for self-driven heat pump distillation according to claim 6, characterized in that, The temperature of the gas compressed by the compressor is more than 5°C higher than the temperature of the bottom of the distillation column to ensure that the heat pump reboiler has a sufficient heat transfer temperature difference.
10. The energy-saving method for self-driven heat pump distillation according to claim 6, characterized in that, The expander and the compressor are an integral structure; or, the rotor of the expander is connected to the rotor of the compressor via a coupling or gearbox.