Heat pump rectification device and polyvinyl alcohol waste liquid recovery device

Abstract

The invention relates to chemical equipment, and provides a heat pump rectification device and a polyvinyl alcohol waste liquid recovery device.The heat pump rectification device comprises a rectification tower (1), a compressor (2) and a tower kettle reboiler (3), a tower top gas phase outlet of the rectification tower (1) is connected with a gas inlet of the compressor (2), a gas outlet of the compressor (2) is connected with a heat source inlet of the tower kettle reboiler (3), and the heat source inlet of the tower kettle reboiler (3) is connected with a gas outlet of the compressor (2). A kettle liquid outlet of the rectifying tower (1) is connected with the tower kettle reboiler (3) through a circulating pump (5), and kettle liquid of the tower kettle reboiler (3) flows back to the rectifying tower (1). The system can effectively improve the utilization rate of steam at the top of the rectifying tower, reduces the consumption of cooling capacity at the top of the tower while reducing heat supply at the bottom of the tower, and is obvious in energy-saving effect.

Description

Technical Field

[0001] This invention relates to chemical equipment, specifically to a heat pump distillation unit and a polyvinyl alcohol waste liquid recovery unit. Background Technology

[0002] Distillation is a separation process that uses the different volatility of components in a mixture to separate the components.

[0003] Distillation typically takes place in a distillation column, where the gas and liquid phases come into countercurrent contact, resulting in interphase heat and mass transfer. Volatile components in the liquid phase enter the gas phase, while less volatile components in the gas phase transfer to the liquid phase. Thus, high-purity volatile components are obtained at the top of the column, and high-purity less volatile components at the bottom. The feed liquid is added from the middle of the column. The section above the feed inlet further concentrates the volatile components in the rising vapor; this is called the rectification section. The section below the feed inlet extracts the volatile components from the descending liquid; this is called the stripping section. The vapor drawn from the top of the column is condensed; a portion of the condensate is returned to the distillation column as reflux, and the remaining distillate is the top product. The liquid drawn from the bottom of the column is partially vaporized in a reboiler; the vapor rises along the column, and the remaining liquid is the bottom product. Therefore, distillation requires both refrigeration and heating. By rationally designing heat recovery processes, energy consumption during production can be effectively reduced.

[0004] See Chinese Patent CN219636938U, which provides a polyvinyl alcohol (PVA) waste liquid recovery device. In the overall energy consumption of a PVA production unit, steam consumption accounts for approximately 71%. To reduce the production cost of PVA production units, it is necessary to consider reducing steam consumption. To this end, the recovery device is equipped with multiple recovery processes for energy saving. For example, high-temperature hot water from the methanol purification tower bottom heats the material in the acetaldehyde crude fractionation tower reboiler, and the distillate vapor from the acetic acid crude fractionation tower is directly transported to the methyl acetate purification tower. The distillate vapor from the acetic acid purification tower serves as a heat source for the methyl acetate crude fractionation tower reboiler. Although the recovery process reduces the proportion of steam consumption, there is still room for energy saving as energy conservation and carbon reduction targets continue to increase, thereby reducing energy consumption and improving market competitiveness. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a heat pump distillation device and a polyvinyl alcohol waste liquid recovery device, so as to further improve the utilization rate of the top steam of the distillation column, reduce the heat supply at the bottom of the column and reduce the consumption of the cold energy at the top of the column, resulting in significant energy saving effect.

[0006] To address the aforementioned technical problems, the present invention provides a heat pump distillation apparatus, comprising a distillation column, a compressor, and a reboiler. The vapor outlet at the top of the distillation column is connected to the inlet of the compressor, the outlet of the compressor is connected to the heat source inlet of the reboiler, the liquid outlet of the distillation column is connected to the reboiler via a circulation pump, and the liquid in the reboiler is returned to the distillation column.

[0007] In some specific embodiments, a liquid seal tank and a flash tank are also included. The inlet of the liquid seal tank is connected to the reboiler in the column bottom so that the condensate from the reboiler enters the liquid seal tank. The outlet of the liquid seal tank is connected to the flash tank, and the gas phase outlet of the flash tank is connected to the inlet of the compressor.

[0008] In some specific embodiments, the top vapor outlet of the distillation column is also connected to a distillation condenser. The uncondensed vapor phase of the distillation condenser is output to the tail gas condenser. The condensate outlet of the distillation condenser and the condensate outlet of the tail gas condenser are connected to a distillation tank. The distillation tank is connected to the compressor through a spray pipeline to spray the condensate onto the compressor for cooling. The spray liquid is suitable for being collected and transported to the flash tank.

[0009] In some specific embodiments, the condensate outlet of the flash tank is connected to the inlet of the distillation condenser.

[0010] In some specific embodiments, the outlet of the reboiler and / or the outlet of the liquid seal tank are connected to the inlet of the tail gas condenser.

[0011] In some specific embodiments, a silencer is also included, which is disposed between the compressor and the reboiler in the tower bottom. The bottom condensate outlet of the silencer is connected to the flash tank, and the silencer is configured to collect the spray liquid and deliver it to the flash tank.

[0012] In some specific embodiments, a first regulating switch is provided on the pipeline connecting the top vapor outlet of the distillation column to the inlet of the compressor, and a second regulating switch is provided on the pipeline connecting the top vapor outlet of the distillation column to the distillation condenser.

[0013] In some specific embodiments, the bottom of the distillation column is connected to a distillation column reboiler, and the heat source inlet of the distillation column reboiler is connected to an external heat source.

[0014] The present invention also provides a device for recycling polyvinyl alcohol waste liquid, including the above-mentioned heat pump distillation device.

[0015] The beneficial effects of the present invention through the above solution are as follows: In the technical solution of this invention, the low-temperature steam distilled from the top of the distillation column is input into a compressor, which compresses the steam to increase its temperature and improve its heat grade. The compressed high-temperature steam is then transported to the reboiler at the bottom of the column. The bottom liquid of the distillation column is then pumped to the reboiler to exchange heat with the compressed high-temperature steam. The heated bottom liquid is then returned to the bottom of the distillation column, thereby efficiently recovering the latent heat of vaporization of the top steam, reducing the heat supply to the bottom of the column and lowering the consumption of cooling capacity at the top, thus achieving a good energy-saving effect.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a specific embodiment of the heat pump distillation device of the present invention.

[0018] Explanation of reference numerals in the attached figures 1. Distillation column; 2. Compressor; 3. Reboiler; 4. Reboiler; 5. Circulating pump; 6. Liquid seal tank; 7. Flash tank; 8. Distillation condenser; 9. Tail gas condenser; 10. Distillation tank; 11. Silencer; 12. First regulating switch; 13. Second regulating switch. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention, and the scope of protection of the present invention is not limited to the specific embodiments described below.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "forming," "having," "setting," and "connecting," etc., should be interpreted broadly. For example, a connection can be a direct connection or an indirect connection through an intermediate medium; it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate connector; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] In this invention, unless otherwise specified, the directional terms "upper" and "lower" used to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. The directional terms of this invention should be understood in conjunction with the actual installation state.

[0022] This invention provides a heat pump distillation apparatus, see [link to relevant documentation]. Figure 1 As a specific embodiment of the heat pump distillation device of the present invention, it includes a distillation column 1, a compressor 2, and a reboiler 3. The gas phase outlet at the top of the distillation column 1 is connected to the inlet of the compressor 2, the outlet of the compressor 2 is connected to the heat source inlet of the reboiler 3, the liquid outlet of the distillation column 1 is connected to the reboiler 3 through a circulating pump 5, and the liquid in the reboiler 3 is returned to the distillation column 1.

[0023] In the above basic embodiment, the low-temperature steam distilled from the top of the distillation column 1 is input into the compressor 2. The compressor 2 compresses the low-temperature steam, thereby increasing its pressure and temperature and improving its heat grade. The compressed high-temperature steam is then transported to the reboiler 3. The bottom liquid of the distillation column 1 is transported to the top of the reboiler 3 by the circulating pump 5. After entering the reboiler 3, it exchanges heat with the compressed high-temperature steam. The heated bottom liquid can flow back from the bottom of the reboiler 3 to the bottom of the distillation column 1. This efficiently recovers the latent heat of vaporization of the steam at the top of the distillation column 1, reduces the heat supply to the bottom of the distillation column 1, and reduces the consumption of cold energy at the top of the column, thus achieving a good energy-saving effect.

[0024] In some specific implementations, see Figure 1 The heat pump distillation apparatus of the present invention further includes a liquid seal tank 6 and a flash tank 7. The inlet of the liquid seal tank 6 is connected to the reboiler 3 at the bottom of the column, so that the condensed liquid phase of the reboiler 3 enters the liquid seal tank 6. Specifically, the liquid outlet of the reboiler 3 is set to correspond to the liquid level of the reboiler 3, so that the liquid outlet is close to the liquid surface at the bottom of the reboiler 3. This allows the compressed high-temperature steam to exchange heat in the reboiler 3, and the condensed liquid phase to enter the liquid seal tank 6 by means of the pressure difference. The outlet of the liquid seal tank 6 is connected to the flash tank 7. The condensate is transported from the liquid seal tank 6 to the flash tank 7 by means of the pressure difference. In the flash tank 7, the high-temperature condensate flashes and depressurizes to cool down. The gas phase outlet of the flash tank 7 is connected to the inlet of the compressor 2. The flashed vapor phase goes to the compressor 2 and is recompressed together with the low-temperature steam distilled from the top of the distillation column 1, which can further reduce steam consumption and improve energy saving.

[0025] In some specific implementations, see Figure 1The top vapor outlet of distillation column 1 is also connected to a distillation condenser 8. The distillate vapor from distillation column 1 enters the distillation condenser 8 for condensation. To increase the throughput, two distillation condensers 8 can be connected in parallel. The uncondensed vapor from distillation condenser 8 is output to tail gas condenser 9. The condensate outlets of distillation condenser 8 and tail gas condenser 9 are connected to distillation tank 10. Distillation tank 10 is connected to compressor 2 through a spray pipeline to spray the condensate onto compressor 2 for cooling. At the same time, the spray liquid heats up after exchanging heat with compressor 2. The spray liquid is collected and sent to flash tank 7. In flash tank 7, the high-temperature condensate is flashed, depressurized, and cooled, thereby forming low-temperature steam that is sent back to compressor 2 for compression. This utilizes the heat generated during the operation of compressor 2, further improving the energy-saving effect.

[0026] Preferably, the condensate outlet of the flash tank 7 is connected to the inlet of the distillation condenser 8, so that the flash condensate at the bottom of the flash tank 7 can be transported to the distillation condenser 8 and finally to the distillation tank 10, so that the compressor 2 can be sprayed and cooled again after cooling.

[0027] See Figure 1 The outlet of the reboiler 3 and / or the outlet of the liquid seal tank 6 are connected to the inlet of the tail gas condenser 9. A small amount of gas phase that is not completely condensed after heat exchange with the high-temperature steam compressed in the reboiler 3 can enter the tail gas condenser 9 for further recycling. Specifically, the outlet of the reboiler 3 is set according to the liquid level of the reboiler 3, so that the outlet is close to the liquid surface at the bottom of the reboiler 3. The inlet of the high-temperature steam compressed by the compressor 2 is set near the top of the reboiler 3, so that the gas phase that is not completely condensed after sufficient heat exchange with the liquid in the distillation column 1 is transported to the tail gas condenser 9.

[0028] In some specific embodiments, the heat pump distillation apparatus of the present invention further includes a silencer 11, which is disposed between the compressor 2 and the reboiler 3. The silencer 11 effectively reduces the noise of the high-temperature and high-pressure steam after compression by the compressor 2, reduces noise pollution, protects the environment and the health of the staff, and can also optimize the steam flow field, reduce energy consumption and structural vibration. Furthermore, the condensate outlet at the bottom of the silencer 11 is connected to the flash tank 7, and the spray liquid that is transported from the distillation tank 10 to the compressor 2 for spray cooling can be collected in the silencer 11. The collected spray liquid can be transported to the flash tank 7 through the bottom of the silencer 11.

[0029] In some specific implementations, see Figure 1A first regulating switch 12 is installed on the pipeline connecting the top vapor outlet of distillation column 1 to the inlet of compressor 2, and a second regulating switch 13 is installed on the pipeline connecting the top vapor outlet of distillation column 1 to distillation condenser 8. The first regulating switch 12 and the second regulating switch 13 can adjust the amount of gas delivered to compressor 2 and directly to distillation condenser 8 respectively according to actual conditions. This allows the heat pump distillation device of the present invention to be directly improved on the original distillation column equipment, while retaining the original equipment. In case of an emergency, the first regulating switch 12 can be directly shut off, and the heat pump distillation device can be disconnected at any time, ensuring that the normal operation of distillation column 1 is not affected. Specifically, the first regulating switch 12 and the second regulating switch 13 are preferably regulating valves; more preferably, the regulating valves can be electromagnetic regulating valves, facilitating automatic opening and closing control.

[0030] In some specific embodiments, the compressor 2 is a screw compressor, centrifugal compressor, or reciprocating compressor, etc., preferably a screw compressor, which operates smoothly, has low vibration, can effectively reduce the risk of liquid slugging, and is safe and reliable; the reboiler 3 is a vertical thermosiphon reboiler, a horizontal thermosiphon reboiler, or a falling film reboiler, etc., preferably a falling film reboiler, which has high heat transfer efficiency and short residence time; in cases where reboiler blockage may occur, a thermosiphon tubular reboiler is preferred. To ensure heat exchange effect, the thermosiphon tubular reboiler needs to be equipped with a centrifugal pump, and the material flow is consistent with that of the falling film reboiler.

[0031] In some specific implementations, see Figure 1 The bottom of the distillation column 1 is connected to the distillation column reboiler 4. The heat source inlet of the distillation column reboiler 4 is connected to an external heat source. The part of the heat that is insufficient can be supplemented by external steam through the distillation column reboiler 4. The amount of steam is preferably automatically regulated. Specifically, the temperature of the distillation column 1 can be monitored. The controller can automatically switch on and off and adjust the amount of external steam supplementation according to the temperature, so as to effectively reduce the amount of steam consumption while meeting the heat demand in the production process.

[0032] To better understand the technical solution of this invention, the following is combined with... Figure 1 The specific embodiments shown illustrate its workflow: See Figure 1The heat pump distillation apparatus of this invention includes a distillation column 1, a compressor 2, a reboiler 3, a circulating pump 5, a liquid seal tank 6, a flash tank 7, a distillation condenser 8, a tail gas condenser 9, and a silencer 11. The low-temperature vapor distilled from the top of the distillation column 1 is transported to the distillation condenser 8 for condensation via a second regulating switch 13, and to the inlet of the compressor 2 via a first regulating switch 12. The high-temperature, high-pressure vapor compressed by the compressor 2 is then reduced in noise by the silencer 11 and enters the reboiler 3. The liquid in the reboiler of the distillation column 1 is sent to the reboiler 3 via the circulating pump 5 and exchanges heat with the compressed gas, thus heating and evaporating the liquid. The liquid at the bottom of the reboiler 3 is then transported to the distillation column. The bottom of column 1 is used to improve heat exchange efficiency. A small amount of gas phase that is not completely condensed after heat exchange enters the tail gas condenser 9. After condensation, the liquid phase enters the liquid seal tank 6 by means of the pressure difference. The condensate enters the flash tank 7 from the liquid seal tank 6 by means of the pressure difference. In the flash tank 7, the high temperature condensate flashes and depressurizes to cool down. The flash vapor phase is sent to the inlet of compressor 2 and is recompressed together with the low temperature vapor distilled from the top of distillation column 1. The flash condensate is sent to the distillation condenser 8. The condensate from distillation condenser 8 and tail gas condenser 9 enters the distillation tank 10 and is then sent to compressor 2. It is used as the spray liquid for compressor 2 to cool compressor 2. Excess spray liquid is collected in silencer 11 and discharged from the bottom of silencer 11 to flash tank 7.

[0033] Through the above technical solution, the heat pump distillation device of the present invention compresses the low-temperature steam that was originally condensed by circulating water at the top of the column using a steam compressor, increases its temperature, and then condenses it in the reboiler 3 to transfer heat to the bottom material of the distillation column 1. That is, the compressor 2 improves the quality of the previously wasted energy and reuses it. The energy balance of the distillation system is maintained only by the compressor 2. A small amount of electricity is used to improve the heat grade of the steam at the top of the column, which efficiently recovers the latent heat of vaporization of the steam at the top of the column. This reduces the supply of heat to the bottom of the column and reduces the consumption of cold energy at the top of the column, thereby achieving the purpose of energy saving. In addition, the heat pump distillation device of the present invention also has the following advantages: 1. The operating conditions and process parameters of the existing distillation columns will remain unchanged, and the operation of each column will not be affected; 2. The steam heat from the material at the top of the tower is effectively recovered and used for heating the bottom of the tower, resulting in significant heat savings and a more pronounced energy-saving effect; 3. While saving a large amount of steam, the circulating water consumption of the original distillation column's material condenser can be greatly reduced; 4. The original distillation tower equipment can be improved and the original equipment can be retained. In the event of an emergency, the heat pump distillation device of this invention can be cut off at any time to ensure that the normal operation of the distillation tower is not affected.

[0034] This invention also provides a polyvinyl alcohol waste liquid recovery device, which includes the heat pump distillation device of this invention. Regarding the polyvinyl alcohol waste liquid recovery device provided by Chinese Patent CN219636938U in the background art, the catalytic decomposition tower can be improved by applying the heat pump distillation device of this invention to the catalytic decomposition tower. After energy-saving modification, the steam consumption of a single tower is reduced by approximately 10% of the steam consumption in the recovery process, and the circulating water consumption is reduced by 750-850 t / h, resulting in an annual saving of 8000-11000 tons of standard coal.

[0035] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0036] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0037] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A heat pump distillation apparatus, characterized in that, The distillation column (1), compressor (2), and reboiler (3) are included. The gas phase outlet of the top of the distillation column (1) is connected to the inlet of the compressor (2), the outlet of the compressor (2) is connected to the heat source inlet of the reboiler (3), the liquid outlet of the distillation column (1) is connected to the reboiler (3) through a circulating pump (5), and the liquid in the reboiler (3) is returned to the distillation column (1).

2. The heat pump distillation apparatus according to claim 1, characterized in that, It also includes a liquid seal tank (6) and a flash tank (7). The inlet of the liquid seal tank (6) is connected to the reboiler (3) of the tower bottom so that the condensate phase of the reboiler (3) enters the liquid seal tank (6). The outlet of the liquid seal tank (6) is connected to the flash tank (7). The gas phase outlet of the flash tank (7) is connected to the inlet of the compressor (2).

3. The heat pump distillation apparatus according to claim 2, characterized in that, The top gas outlet of the distillation column (1) is also connected to a distillation condenser (8). The uncondensed gas phase of the distillation condenser (8) is output to the tail gas condenser (9). The condensate outlet of the distillation condenser (8) and the condensate outlet of the tail gas condenser (9) are connected to a distillation tank (10). The distillation tank (10) is connected to the compressor (2) through a spray pipeline to spray the condensate onto the compressor (2) for cooling. The spray liquid is suitable for being collected and transported to the flash tank (7).

4. The heat pump distillation apparatus according to claim 3, characterized in that, The condensate outlet of the flash tank (7) is connected to the inlet of the distillation condenser (8).

5. The heat pump distillation apparatus according to claim 3, characterized in that, The outlet of the reboiler (3) and / or the outlet of the liquid seal tank (6) are connected to the inlet of the tail gas condenser (9).

6. The heat pump distillation apparatus according to claim 3, characterized in that, It also includes a silencer (11) which is disposed between the compressor (2) and the reboiler (3) of the tower. The bottom condensate outlet of the silencer (11) is connected to the flash tank (7). The silencer (11) is configured to collect the spray liquid and deliver it to the flash tank (7).

7. The heat pump distillation apparatus according to claim 3, characterized in that, A first regulating switch (12) is provided on the pipeline connecting the top vapor outlet of the distillation column (1) to the inlet of the compressor (2), and a second regulating switch (13) is provided on the pipeline connecting the top vapor outlet of the distillation column (1) to the distillation condenser (8).

8. The heat pump distillation apparatus according to any one of claims 1 to 7, characterized in that, The bottom of the distillation column (1) is connected to a distillation column reboiler (4), and the heat source inlet of the distillation column reboiler (4) is connected to an external heat source.

9. A device for recovering polyvinyl alcohol waste liquid, characterized in that, The heat pump distillation apparatus includes any one of claims 1 to 8.

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