High-water-content low-carbon alcohol separation system and process method thereof

Abstract

The invention belongs to the field of chemical engineering, and relates to a high-water-content low-carbon alcohol separation system and a process method thereof, the system comprises a first crude separation tower, a second crude separation tower, a stripping tower, a regeneration tower, a methanol tower, an ethanol tower, an isopropanol tower, an n-propanol tower and an n-butanol tower, each tower is provided with a condenser and a reboiler, and a mixed alcohol raw material is subjected to a crude dehydration and extractive distillation dehydration mode. Coarse dehydration, namely dehydration by a coarse separation tower and a stripping tower, can remove about two thirds of water with lower energy consumption; compared with an azeotropic distillation dehydration process, the extractive distillation dehydration process is lower in energy consumption and higher in efficiency, a heat exchange network of the separation process is optimized, and energy consumption is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering and relates to a separation system and process method for high water content low carbon alcohols. Background Technology

[0002] Low-carbon mixed alcohols mainly originate from byproducts of coal-to-oil plants, large amounts of fusel alcohols found in methanol plants, and mixed alcohols in the brewing industry. These low-carbon mixed alcohols typically have a high water content, exceeding 20%. Their composition includes water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, pentanol, and other polyols. These low-carbon alcohols are crucial industrial solvents and raw materials in the chemical and pharmaceutical industries. Separating these low-carbon mixed alcohols to obtain high-purity monoalcohols would benefit the economic efficiency of the coal-to-oil and methanol industries, address environmental issues, and improve the quality of brewing products. However, the high water content and azeotropic interaction between water and various components in the low-carbon mixed alcohols make it difficult to obtain high-purity monoalcohols without removing the water.

[0003] Chinese patent CN105669377A discloses a process for separating mixed alcohols. This method employs a combination of conventional distillation and azeotropic dehydration. The raw material is separated in a light component removal tower. The top of the tower, after removing light components and methanol, is sent to a methanol pressurization tower. After separation in the methanol pressurization tower, the light components are collected at the top, and methanol is obtained at the bottom. The bottom material from the light component removal tower is sent to an azeotropic tower, where it undergoes azeotropic dehydration with cyclohexane as an azeotropic agent. The aqueous solution containing the azeotropic agent and alcohol enters a pressurized stripping tower. After separation in the pressurized stripping tower, wastewater is discharged from the bottom, and the top material is returned to the azeotropic tower for further distillation. The anhydrous mixed alcohol at the bottom of the azeotropic tower is then passed sequentially through an ethanol tower, a propanol tower, and a butanol tower to obtain ethanol, propanol, butanol, and heavy alcohol. In terms of energy saving, the top gas phase of the butanol tower is used as the heat source for the reboiler of the light alcohol removal tower, the top gas phase of the propanol tower is used as the heat source for the reboiler of the methanol pressurized tower, the pressurized stripping tower is used as the heat source for the reboiler of the azeotropic tower, and the top gas phase of the light alcohol removal tower and the bottom wastewater of the pressurized stripping tower are used to preheat the raw materials in sequence. This process has the following disadvantages: (1) All the water in this process needs to be removed by azeotropic agent in an azeotropic manner. The circulation volume of azeotropic agent is very large. Although the coupled heat exchange method is used to save energy, the energy consumption is still very high, especially when the water content of the raw materials is high. (2) This process has relatively strict requirements for raw materials. The mixed alcohols after dehydration are all distilled in a single tower to obtain the corresponding products. If there are impurities between ethanol and propanol, or between propanol and butanol, the purity of the ethanol, propanol and butanol products will decrease accordingly.

[0004] Therefore, it is necessary to develop a new system and method for separating mixed alcohols. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a separation system and process method for high water content low carbon alcohols. The system separates mixed alcohols by crude dehydration, extractive distillation dehydration and conventional distillation, and saves energy by optimizing the heat exchange network and making full use of waste heat recovery technology.

[0006] The technical solution adopted by this invention to solve the technical problem is:

[0007] The first aspect of this invention provides a separation system for high-water-content low-carbon alcohols, comprising a primary crude separator, a primary crude separator heat exchanger / cooler, a primary crude separator circulating water cooler, a primary crude separator phase separation tank, a stripping tower, a stripping tower feed preheater, an extraction tower, a regeneration tower, a methanol tower, an ethanol tower, an isopropanol tower, a n-propanol tower, and a n-butanol tower. Each tower is equipped with a corresponding reboiler and condenser. The primary crude separator has a feed inlet, and a feed preheater is installed on the inlet pipeline. The primary crude separator has a side line at the top, which is connected to the inlet of the extraction tower via a pipeline. The bottom outlet of the extraction tower is connected to the inlet of the regeneration tower via a pipeline. The top vapor sampling outlet of the regeneration tower is connected to the regeneration tower condenser via a pipeline. The inlet of the regeneration tower and the outlet pipeline of the condenser are split into two lines: one connects to the reflux port of the regeneration tower, and the other connects to the first inlet of the stripping tower. The bottom outlet of the regeneration tower passes through the heat exchanger and reboiler of the ethanol tower and the feed preheater in sequence before entering the extractant inlet of the extraction tower. The top outlet of the extraction tower passes through the condenser of the extraction tower and splits into two lines: one connects to the reflux port of the extraction tower, and the other connects to the inlet of the methanol tower. The methanol tower is equipped with a methanol tower steam reboiler, a methanol tower heat exchanger reboiler I, and a methanol tower heat exchanger reboiler II. The bottom outlet of the methanol tower is connected to the inlet of the ethanol tower, and the bottom outlet of the ethanol tower is connected to the inlet of the isopropanol tower. The bottom outlet of the n-propanol column is connected to the inlet of the n-propanol column via a pipeline. The bottom of the n-propanol column is the isobutanol product outlet pipeline. The top vapor phase pipeline of the n-propanol column is split into two paths after passing through the second heat exchanger and reboiler of the methanol column. One path is connected to the reflux port of the n-propanol column, and the other path serves as the n-propanol product outlet pipeline. The lower part of the crude fractionation column has a second side stream. The second side stream passes through the heat exchanger and circulating water cooler of the crude fractionation column and then enters the phase separation tank of the crude fractionation column. The organic phase outlet of the phase separation tank is connected to the inlet of the crude fractionation column via a pipeline through the heat exchanger and cooler of the crude fractionation column. The aqueous phase outlet of the phase separation tank is connected to the first stripping column via a pipeline through the feed preheater of the stripping column. The two inlets are as follows: The bottom outlet of the stripping tower enters the feed preheater of the stripping tower via a pipeline and is then discharged as wastewater. The top vapor outlet of the stripping tower is connected to the inlet of the stripping tower condenser via a pipeline. The outlet pipeline of the stripping tower condenser is split into two paths: one path connects to the reflux port, and the other path passes through the circulating water cooler of the crude fractionation tower and then connects to the inlet of the phase separation tank of the crude fractionation tower. The bottom outlet of the crude fractionation tower is connected to the inlet of the n-butanol tower via a pipeline. The top vapor outlet pipeline of the n-butanol tower passes through the heat exchanger and reboiler of the methanol tower and is then split into two paths: one path connects to the reflux port of the n-butanol tower, and the other path serves as the n-butanol product outlet pipeline. The bottom outlet pipeline of the n-butanol tower is the heavy alcohol outlet pipeline.

[0008] Furthermore, it also includes a second crude fractionation tower, a second crude fractionation tower steam reboiler, a second crude fractionation tower condenser, and a second crude fractionation tower reflux phase separation tank. The first crude fractionation tower is equipped with a first crude fractionation tower heat exchange reboiler and a first crude fractionation tower steam reboiler. The first crude fractionation tower phase separation tank is installed at the bottom of the first crude fractionation tower. The bottom outlet pipeline of the first crude fractionation tower is divided into two paths: one path is directly connected to the inlet of the second crude fractionation tower, and the other path is connected to the inlet of the second crude fractionation tower after passing through the first crude fractionation tower phase separation tank and the first crude fractionation tower phase separation heat exchange cooler. The bottom outlet of the second crude fractionation tower is connected to the inlet of the n-butanol tower via a pipeline. The top gas phase outlet pipeline of the second crude fractionation tower passes through the crude fractionation tower in sequence. The heat exchanger and reboiler of the first separation tower and the condenser of the second roughing tower are connected to the inlet of the reflux phase separator of the second roughing tower. The organic phase outlet of the reflux phase separator of the second roughing tower is connected to the top reflux port of the second roughing tower via a pipeline. The aqueous phase outlets of the phase separators of the first and second roughing towers are connected to the first inlet of the stripping tower via pipelines through the feed preheater of the stripping tower. The top outlet of the stripping tower is connected to the inlet of the stripping tower condenser via a pipeline. The outlet pipeline of the stripping tower condenser is divided into two paths: one path connects to the reflux port of the stripping tower, and the other path connects to the inlet of the reflux phase separator of the second roughing tower after passing through the condenser of the second roughing tower.

[0009] Furthermore, the top of the coarse fractionation tower is connected to the coarse fractionation tower condenser. The gas phase outlet of the coarse fractionation tower condenser is used for the discharge of non-condensable gas. The liquid phase outlet pipeline of the coarse fractionation tower condenser is divided into two paths: one path is connected to the reflux inlet of the coarse fractionation tower, and the other path serves as the methanol product outlet pipeline.

[0010] Furthermore, the outlet pipelines of the methanol tower condenser, ethanol tower condenser, and isopropanol tower condenser respectively equipped at the top of the methanol tower, ethanol tower, and isopropanol tower are all divided into two paths. One path is connected to the reflux port of the methanol tower, ethanol tower, and isopropanol tower respectively, and the other path serves as the methanol product collection pipeline, ethanol product collection pipeline, and isopropanol product collection pipeline respectively.

[0011] The second aspect of the present invention provides a process method for the separation system of high water content low carbon alcohol described in the first aspect. The coarse separation tower includes only a coarse separation tower 1. The mixed alcohol feedstock is preheated by the feedstock preheater and then sent to the coarse separation tower 1. The gas phase at the top of the coarse separation tower 1 enters the coarse separation tower 1 condenser for condensation. The non-condensable gas is discharged. Part of the condensed liquid is returned to the coarse separation tower 1 as reflux, and part of it is collected as methanol product.

[0012] The crude fractionation column is an atmospheric pressure column with a top pressure of -10 to 50 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 110 to 150°C. A mixed solution of methanol, ethanol, propanol, a small amount of butanol, and water collected from the upper side stream of the crude fractionation column is sent to the middle of the extraction column. The extractant is added from the upper middle part of the extraction column. The extractant and water at the bottom of the extraction column are sent to the regeneration column. The vapor phase at the top of the regeneration column enters the condenser of the regeneration column for condensation. Part of the condensed liquid is returned to the regeneration column as reflux, and the other part is collected as wastewater and stripped in the stripping column. The extractant at the bottom of the regeneration column passes through the heat exchanger and reboiler of the ethanol column and the feed preheater of the crude fractionation column before returning to the extraction column for recycling. The vapor phase at the top of the extraction column enters the condenser of the extraction column for condensation. Part of the condensed liquid is returned to the extraction column as reflux, and the other part is collected in the methanol column. The vapor phase at the top of the methanol column enters... The methanol tower condenser condenses the liquid, and part of the condensed liquid is returned to the methanol tower as reflux, while the other part is collected as methanol product. The bottom mixture of ethanol, n-propanol, and a small amount of isopropanol and butanol from the methanol tower is sent to the ethanol tower. The top vapor phase of the ethanol tower enters the ethanol tower condenser for condensation, and part of the condensed liquid is returned to the ethanol tower as reflux, while the other part is collected as ethanol product. The bottom material of the ethanol tower is sent to the isopropanol tower, and the top vapor phase of the isopropanol tower enters the isopropanol tower condenser for condensation. Part of the condensed liquid is returned to the isopropanol tower as reflux, while the other part is collected as isopropanol product. The bottom material of the isopropanol tower is sent to the n-propanol tower, and the top vapor phase of the n-propanol tower enters the methanol tower heat exchanger reboiler for secondary condensation. Part of the condensed liquid is returned to the n-propanol tower as reflux, while the other part is collected as n-propanol product. Isobutanol product is collected from the bottom of the n-propanol tower.

[0013] The bottom of the crude fractionation column, containing heavy alcohols such as butanol and pentanol, is sent to the n-butanol column. The vapor phase from the top of the n-butanol column enters the reboiler of the methanol column for condensation. Part of the condensed liquid is returned to the n-butanol column as reflux, and the other part is collected as n-butanol product. The bottom of the n-butanol column contains heavy alcohol products. The butanol and water from the lower side stream of the crude fractionation column are cooled and then enter the phase separation tank of the crude fractionation column for phase separation. The organic phase is returned to the crude fractionation column after heat exchange in the crude fractionation column cooler. The aqueous phase is preheated in the stripping column feed preheater and then sent to the stripping column. The vapor phase from the top of the stripping column enters the stripping column condenser for condensation. Part of the condensed liquid is returned to the stripping column as reflux, and the other part is collected and separated in the phase separation tank of the crude fractionation column. The wastewater from the bottom of the stripping column is collected, cooled in the stripping column feed preheater, and then discharged.

[0014] The third aspect of the present invention provides a process method for the separation system of high water content low carbon alcohols described in the first aspect. The coarse separation tower includes a coarse separation tower 1 and a coarse separation tower 2. The mixed alcohol feedstock is preheated by the feedstock preheater and then fed into the coarse separation tower 1. The gas phase at the top of the coarse separation tower 1 enters the coarse separation tower 1 condenser for condensation. The non-condensable gas is discharged. Part of the condensed liquid is returned to the coarse separation tower 1 as reflux, and part of it is collected as methanol product.

[0015] The crude fractionation column is an atmospheric pressure column with a top pressure of -10 to 50 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 70 to 120°C. A mixed solution of methanol, ethanol, propanol, a small amount of butanol, and water collected from the upper side stream of the crude fractionation column is sent to the middle of the extraction column. The extractant is added from the upper part of the extraction column. The extractant and water at the bottom of the extraction column are sent to the regeneration column. The vapor phase at the top of the regeneration column enters the condenser of the regeneration column for condensation. Part of the condensed liquid is returned to the regeneration column as reflux, and the other part is collected as wastewater and stripped in the stripping column. The extractant at the bottom of the regeneration column passes through the heat exchanger and reboiler of the ethanol column and the feed preheater of the crude fractionation column before returning to the extraction column for recycling. The vapor phase at the top of the extraction column enters the condenser of the extraction column for condensation. Part of the condensed liquid is returned to the extraction column as reflux, and the other part is collected to the methanol column. The vapor phase at the top of the methanol column enters the methanol column... The methanol tower condenses the liquid, and a portion of the condensed liquid is returned to the methanol tower as reflux, while the remainder is collected as methanol product. A mixed solution of ethanol, n-propanol, and small amounts of isopropanol and butanol from the bottom of the methanol tower is sent to the ethanol tower. The vapor phase from the top of the ethanol tower enters the ethanol tower condenser for further condensation. A portion of the condensed liquid is returned to the ethanol tower as reflux, while the remainder is collected as ethanol product. The bottom material from the ethanol tower is sent to the isopropanol tower. The vapor phase from the top of the isopropanol tower enters the isopropanol tower condenser for further condensation. A portion of the condensed liquid is returned to the isopropanol tower as reflux, while the remainder is collected as isopropanol product. The bottom material from the isopropanol tower is sent to the n-propanol tower. The vapor phase from the top of the n-propanol tower enters the methanol tower's heat exchanger reboiler for secondary condensation. A portion of the condensed liquid is returned to the n-propanol tower as reflux, while the remainder is collected as n-propanol product. Isobutanol product is collected from the bottom of the n-propanol tower.

[0016] The butanol, pentanol, and other heavy alcohols collected from the bottom of the first crude fractionation tower are cooled and then sent to the first crude fractionation tower phase separation tank for phase separation. The organic phase is sent to the second crude fractionation tower after heat exchange in the phase separation cooler of the first crude fractionation tower. The second crude fractionation tower (37) is a pressurized tower with a top pressure of 100-300 kPa and a top temperature of 100-150℃. The bottom temperature of the tower is 120-170℃. The gas phase at the top of the second crude fractionation tower is sent to the heat exchange reboiler of the first crude fractionation tower for condensation. The condensed liquid enters the reflux phase separation tank of the second crude fractionation tower. The organic phase in the reflux phase separation tank of the second crude fractionation tower enters the second crude fractionation tower. The water in the phase separation tanks of the first crude fractionation tower and the reflux phase separation tank of the second crude fractionation tower... The vapor phase is preheated by the feed preheater of the stripping tower and then enters the stripping tower. The vapor phase at the top of the stripping tower enters the stripping tower condenser for condensation. Part of the condensed liquid is returned to the stripping tower as reflux, and part is collected and sent to the reflux phase separator of the coarse fractionation tower for phase separation. The wastewater at the bottom of the stripping tower is collected, cooled by the feed preheater of the stripping tower, and then discharged. The material from the bottom of the coarse fractionation tower is sent to the n-butanol tower. The vapor phase at the top of the n-butanol tower enters the heat exchanger reboiler of the methanol tower for condensation. Part of the condensed liquid is returned to the n-butanol tower as reflux, and part is collected as the n-butanol product. The heavy alcohol product is collected from the bottom of the n-butanol tower.

[0017] Furthermore, the stripping tower is an atmospheric pressure tower with a top pressure of -10 to 50 kPa, a top temperature of 60 to 95°C, and a bottom temperature of 80 to 120°C; the extraction tower is a vacuum tower with a top pressure of -90 kPa to atmospheric pressure, a top temperature of 40 to 90°C, and a bottom temperature of 100 to 160°C; the regeneration tower is a vacuum tower with a top pressure of -95 to 20 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 120 to 170°C; and the methanol tower is an atmospheric pressure tower with a top pressure of -20 to 100 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 60 to 110°C. The ethanol column is a negative pressure column, with a top pressure of -80 kPa to atmospheric pressure, a top temperature of 40-80℃, and a bottom temperature of 60-110℃; the isopropanol column is an atmospheric pressure column, with a top pressure of -20-100 kPa, a top temperature of 60-100℃, and a bottom temperature of 80-130℃; the n-propanol column is an atmospheric pressure column, with a top pressure of -20-100 kPa, a top temperature of 60-100℃, and a bottom temperature of 80-130℃; the n-butanol column is an atmospheric pressure column, with a top pressure of -20-100 kPa, a top temperature of 100-140℃, and a bottom temperature of 120-170℃.

[0018] Furthermore, the coarse fractionation tower heat exchange cooler uses the organic phase from the coarse fractionation tower phase separation tank as the coolant; the coarse fractionation tower circulating water cooler uses circulating water as the coolant, with a cooling temperature of 30-80℃; the stripping tower feed preheater uses the wastewater collected from the bottom of the stripping tower as the heat source; and the stripping tower steam reboiler, extraction tower steam reboiler, and regeneration tower steam reboiler all use steam as the heat source.

[0019] Furthermore, the methanol tower is equipped with three reboilers: one is a methanol tower steam reboiler with steam as the heat source; one is a methanol tower heat exchange reboiler one with the overhead gas phase of the n-butanol tower as the heat source; and one is a methanol tower heat exchange reboiler two with the overhead gas phase of the n-propanol tower as the heat source.

[0020] Furthermore, the ethanol tower is equipped with three reboilers: one is an ethanol tower steam reboiler, which uses steam as a heat source; one is an ethanol tower hot water reboiler, which uses steam condensate as a heat source; and the other is an ethanol tower heat exchange reboiler, which uses the extractant at the bottom of the extraction tower as a heat source.

[0021] Further, the extractant is one or more of ethylene glycol, 1,3-propylene glycol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), N-formylmorpholine (NFM), and dimethyl sulfoxide (DMSO).

[0022] The advantages and positive effects of this invention are:

[0023] 1. The present invention provides a separation system and method for high-water-content low-carbon alcohols, which reduces the energy consumption of mixed alcohol separation. It replaces the original azeotropic distillation process with a crude dehydration + extractive distillation dehydration method. The crude dehydration, i.e., dehydration by a crude separator + stripping tower, can remove about two-thirds of the water with lower energy consumption. The remaining one-third of the water is dehydrated by extractive distillation. The extractive distillation dehydration process has lower energy consumption and higher efficiency than the azeotropic distillation dehydration process.

[0024] 2. The separation system and method for high-water-content low-carbon alcohols of this invention optimizes the heat exchange network of the separation process, greatly reducing energy consumption. Specifically, the side stream from the coarse separation tower is used as a preheating source for the organic phase in the phase separation tank of the coarse separation tower (single-tower coarse separation process); the top gas phase of the second coarse separation tower is used as a heat source for the steam reboiler of the first coarse separation tower (double-tower coarse separation process); the bottom wastewater of the stripping tower is used as a preheating source for the feed to the stripping tower; the extractant at the bottom of the regeneration tower is used as a heat source for the heat exchanger and reboiler of the ethanol tower, and then as a heat source for the feed preheater of the coarse separation tower; the top gas phase of the propanol tower is used as a heat source for the heat exchanger and reboiler of the methanol tower; the top gas phase of the n-butanol tower is used as a heat source for the heat exchanger and reboiler of the methanol tower; the steam condensate is used as a heat source for the steam reboiler of the isopropanol tower; and the steam condensate is used as a heat source for the steam reboiler of the ethanol tower. Attached Figure Description

[0025] Figure 1 Here is a process system diagram for Example 1:

[0026] Figure 2 Here is a process system diagram for Example 3:

[0027] 1-Crude Separator 1; 2-Crude Separator 1 Steam Reboiler; 3-Crude Separator 1 Condenser; 4-Feed Preheater; 5-Crude Separator 1 Heat Exchanger Cooler; 6-Crude Separator 1 Circulating Water Cooler; 7-Crude Separator 1 Phase Separation Tank; 8-Stripping Tower; 9-Stripping Tower Steam Reboiler; 10-Stripping Tower Condenser; 11-Stripping Tower Feed Preheater; 12-Extraction Tower; 13-Extraction Tower Steam Reboiler; 14-Extraction Tower Condenser; 15-Regeneration Tower; 16-Regeneration Tower Steam Reboiler; 17-Regeneration Tower Condenser; 18-Methanol Tower; 19-Methanol Tower Steam Reboiler; 20-Methanol Tower Heat Exchanger Reboiler 1; 21-Methanol Tower Heat Exchanger Reboiler 2 Hot reboiler II; 22-Methanol tower condenser; 23-Ethanol tower; 24-Ethanol tower steam reboiler; 25-Ethanol tower hot water reboiler; 26-Ethanol tower heat exchange reboiler; 27-Ethanol tower condenser; 28-Isopropanol tower; 29-Isopropanol tower steam reboiler; 30-Isopropanol tower hot water reboiler; 31-Isopropanol tower condenser; 32-n-Propanol tower; 33-n-Propanol tower reboiler; 34-n-Butanol tower; 35-n-Butanol tower reboiler; 36-Crude fraction 1 tower heat exchange reboiler; 37-Crude fraction 2 tower; 38-Crude fraction 2 tower reboiler; 39-Crude fraction 2 tower condenser; 40-Crude fraction 2 tower reflux phase separator. Detailed Implementation

[0028] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0029] Example 1 (Single Tower System)

[0030] A separation system for high-water-content low-carbon alcohols includes a crude separation tower 1, a crude separation tower phase-separation heat exchange cooler 5, a crude separation tower circulating water cooler 6, a crude separation tower phase-separation tank 7, a stripping tower 8, a stripping tower feed preheater 11, an extraction tower 12, a regeneration tower 15, a methanol tower 18, an ethanol tower 23, an isopropanol tower 28, a n-propanol tower 32, and a n-butanol tower 34, each tower being equipped with a corresponding reboiler and condenser.

[0031] The crude fractionation tower 1 has a raw material inlet. The bottom of the crude fractionation tower 1 is equipped with a crude fractionation tower steam reboiler 2. A raw material preheater 4 is installed on the inlet pipeline. The top outlet pipeline of the crude fractionation tower 1 is connected to the crude fractionation tower condenser 3. The gas phase outlet of the crude fractionation tower condenser 3 is used for the discharge of non-condensable gas. The liquid phase outlet pipeline of the crude fractionation tower condenser 3 is divided into two paths: one path is connected to the reflux inlet of the crude fractionation tower 1, and the other path is used as the methanol product outlet pipeline. The coarse separator 1 has a side line at the top, which is connected to the inlet of the extraction tower 12 via a pipeline. The bottom outlet of the extraction tower 12 is connected to the inlet of the regeneration tower 15 via a pipeline. The top gas phase outlet of the regeneration tower 15 is connected to the inlet of the regeneration tower condenser 17 via a pipeline. The outlet pipeline of the regeneration tower condenser 17 is split into two branches: one connected to the reflux port of the regeneration tower 15, and the other connected to the first inlet of the stripping tower 8. The bottom outlet of the regeneration tower 15 is connected via a pipeline through the shell side of the ethanol tower heat exchanger reboiler 26 (which also serves as an extractant cooler) and the shell side of the feed preheater 4 before entering the extractant inlet of the extraction tower 12. The top outlet of the extraction tower 12 is connected to the extraction tower condenser 1 via a pipeline. The inlet of extraction tower condenser 14 is split into two lines: one line connects to the reflux port of extraction tower 12, and the other line connects to the inlet of methanol tower 18. The top gas phase outlet of methanol tower 18 is connected to the inlet of methanol tower condenser 22 via a pipeline. The outlet of methanol tower condenser 22 is also split into two lines: one line connects to the reflux port of methanol tower 18, and the other line connects to an external outlet. The bottom outlet of methanol tower 18 is connected to the inlet of ethanol tower 23 via a pipeline. The bottom outlet of ethanol tower 23 is connected to the inlet of isopropanol tower 28 via a pipeline. The bottom outlet of isopropanol tower 28 is connected to the inlet of n-propanol tower 32 via a pipeline. The bottom of n-propanol tower 32 is the isobutanol product outlet pipeline. The outlet pipelines of the methanol tower 18, ethanol tower 23, and isopropanol tower 28, respectively equipped with methanol tower condenser 22, ethanol tower condenser 27, and isopropanol tower condenser 31, are each divided into two paths. One path connects to the reflux port of methanol tower 18, ethanol tower 23, and isopropanol tower 28, respectively, and the other path serves as the methanol product outlet pipeline, ethanol product outlet pipeline, and isopropanol product outlet pipeline, respectively. The overhead gas phase of n-propanol tower 32 is connected to the shell-side inlet of methanol tower heat exchanger reboiler 21 (which also serves as the n-propanol tower condenser) via a pipeline. The shell-side outlet of methanol tower heat exchanger reboiler 21 (which also serves as the n-propanol tower condenser) is divided into two paths via a pipeline. One path connects to the reflux port of n-propanol tower 32, and the other path serves as the n-propanol product outlet pipeline.

[0032] Stripping tower 8 is equipped with stripping tower steam reboiler 9; extraction tower 12 is equipped with extraction tower steam reboiler 13; regeneration tower 15 is equipped with regeneration tower steam reboiler 16; methanol tower 18 is equipped with methanol tower steam reboiler 19, methanol tower heat exchange reboiler 1 20 (which also serves as a butanol tower condenser), and methanol tower heat exchange reboiler 21 (which also serves as a n-propanol tower condenser); ethanol tower 23 is equipped with ethanol tower steam reboiler 24, ethanol tower hot water reboiler 25, and ethanol tower heat exchange reboiler 26 (which also serves as an extractant cooler); isopropanol tower 28 is equipped with isopropanol tower steam reboiler 29 and isopropanol tower hot water reboiler 30; n-propanol tower 32 is equipped with n-propanol tower reboiler 33, n-butanol tower 34, and n-butanol tower reboiler 35.

[0033] The lower part of the coarse separator 1 has a second side line. The outlet pipeline of the second side line enters the heat medium inlet of the phase-separated heat exchanger 5 of the coarse separator 1, passes through the tube side of the circulating water cooler 6 of the coarse separator 1, and then enters the inlet of the phase-separated tank 7 of the coarse separator 1. The organic phase outlet of the phase-separated tank 7 is connected to the refrigerant inlet of the phase-separated heat exchanger 5 of the coarse separator 1 through a pipeline. The refrigerant outlet of the phase-separated heat exchanger 5 of the coarse separator 1 is connected to the coarse separator 1 through a pipeline. The water phase outlet of the phase-separated tank 7 is connected to the second inlet of the stripper 8 through the tube side of the feed preheater 11 of the stripper 1 through a pipeline. The bottom outlet of the stripper 8 enters the shell side of the feed preheater 11 of the stripper 1 through a pipeline and then is discharged as wastewater. The top vapor phase outlet of the stripper 8 is connected to the steam... The inlet and outlet pipelines of stripping tower condenser 10 are split into two paths: one path connects to the reflux port of stripping tower 8, and the other path connects to the inlet of phase separation tank 7 of crude fractionation tower after passing through the circulating water cooler 6 of crude fractionation tower 1. The bottom outlet of crude fractionation tower 1 is connected to the inlet of n-butanol tower 34 via a pipeline. The top vapor outlet of n-butanol tower 34 is connected to the shell-side inlet of methanol tower heat exchanger reboiler-20 (which also serves as n-butanol tower condenser) via a pipeline. The shell-side outlet pipeline of methanol tower heat exchanger reboiler-20 (which also serves as butanol tower condenser) is split into two paths: one path connects to the reflux port of n-butanol tower 34 via a pipeline, and the other path serves as the n-butanol product outlet pipeline. The bottom outlet pipeline of n-butanol tower 34 is the heavy alcohol outlet pipeline.

[0034] Example 2

[0035] A process method for the separation system of high-water-content low-carbon alcohols described in Example 1: The mixed alcohol feedstock is preheated by a feedstock preheater 4 and then fed into the primary separation column 1. The feedstock preheater 4 uses the extractant from the bottom of the regeneration column as a heat source. The extractant is selected from one or more mixtures of ethylene glycol, 1,3-propylene glycol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), N-formylmorpholine (NFM), and dimethyl sulfoxide (DMSO). The primary separation column 1 is equipped with a reboiler 2, using steam as a heat source. The primary separation column is an atmospheric pressure column with an atmospheric pressure at the top, a top temperature of 58°C, and a bottom temperature of 130°C. The vapor phase at the top of the primary separation column 1 enters the primary separation column condenser 3 for condensation. Non-condensable gases are discharged. Part of the condensed liquid is returned to the primary separation column 1 as reflux, and part is collected as methanol product.

[0036] A mixed solution of methanol, ethanol, propanol, a small amount of butanol and water collected from the upper side stream of coarse fractionation column 1 is sent to extraction column 12.

[0037] Two coolers are installed at the lower side stream 2 of the coarse fractionation tower 1. One is a coarse fractionation tower heat exchange and phase separation heat exchange cooler 5, using the organic phase of the coarse fractionation tower phase separation tank 7 as the coolant; the other is a coarse fractionation tower circulating water cooler 6, using circulating water as the coolant. The material collected from side stream 2 is cooled and then enters the coarse fractionation tower phase separation tank 7 for phase separation. The cooling temperature is 50℃. The organic phase is returned to coarse fractionation tower 1 after heat exchange in the coarse fractionation tower phase separation heat exchange cooler 5; the aqueous phase is preheated and then sent to the stripping tower 8.

[0038] The heavy alcohols such as butanol and pentanol collected from the bottom of the crude fractionation column 1 are sent to the n-butanol column 34.

[0039] The material from the crude fractionation tank 7 is preheated by the stripper feed preheater 11 and then sent to the stripper 8. The stripper feed preheater 11 uses the wastewater collected from the bottom of the stripper 8 as a heat source. Wastewater from the top of the regeneration tower 15 is also sent to the stripper 8. The stripper 8 is equipped with a reboiler 9, which uses steam as a heat source. The stripper is an atmospheric pressure tower with an atmospheric pressure at the top, a top temperature of 92°C, and a bottom temperature of 100°C. The vapor phase at the top of the stripper 8 enters the stripper condenser 10 for condensation. Part of the condensed liquid is returned to the stripper 8 as reflux, and part is collected and sent to the crude fractionation tank 7 for phase separation. The wastewater collected from the bottom of the stripper 8 is cooled by the stripper feed preheater 11 before being discharged.

[0040] The material from the side stream of the coarse fractionation tower 1 is fed to the middle of the extraction tower 12. The extractant is added from the upper part of the extraction tower 12. The extraction tower 12 is equipped with a reboiler 13, which uses steam as a heat source. The extraction tower 12 is a vacuum tower with a top pressure of -55 kPa and a top temperature of 58°C. The bottom temperature of the tower is 146°C. The vapor phase at the top of the extraction tower 12 enters the extraction tower condenser 14 for condensation. Part of the condensed liquid is returned to the extraction tower 12 as reflux, and part is collected and sent to the methanol tower 18.

[0041] The material at the bottom of extraction tower 12 is sent to regeneration tower 15. Regeneration tower 15 is equipped with a regeneration tower steam reboiler 16, which uses steam as a heat source. Regeneration tower 15 is a vacuum tower with a top pressure of -85 kPa, a top temperature of 54℃, and a bottom temperature of 154℃. The vapor phase at the top of regeneration tower 15 enters regeneration tower condenser 17 for condensation. Part of the condensed liquid is returned to regeneration tower 15 as reflux, and part is collected as wastewater and stripped to stripping tower 8. The extractant at the bottom of regeneration tower 15 passes through ethanol tower heat exchange reboiler 26 (extractant cooler) and raw material preheater 4 for heat exchange before returning to extraction tower 12 for recycling.

[0042] The material from the top of extraction column 12 is sent to methanol column 18. Methanol column 18 is equipped with three reboilers: one is a methanol column steam reboiler 19, using steam as a heat source; one is a methanol column heat exchange reboiler 20 (butanol column condenser), using the vapor phase from the top of n-butanol column 34 as a heat source; and the other is a methanol column heat exchange reboiler 21 (also serving as a n-propanol column condenser), using the vapor phase from the top of n-propanol column 32 as a heat source. Methanol column 18 is an atmospheric pressure column, with an atmospheric pressure at the top, a top temperature of 63°C, and a bottom temperature of 85°C. The vapor phase from the top of methanol column 18 enters methanol column condenser 22 for condensation. Part of the condensed liquid is returned to methanol column 18 as reflux, and the other part is collected as methanol product.

[0043] The bottom material from methanol tower 18 is sent to ethanol tower 23. Ethanol tower 23 is equipped with three reboilers: one is an ethanol tower steam reboiler 24, using steam as a heat source; one is an ethanol tower hot water reboiler 25, using steam condensate as a heat source; and the third is an ethanol tower heat exchange reboiler 26 (which also serves as an extractant cooler), using the extractant from the bottom of extraction tower 12 as a heat source. Ethanol tower 23 is a negative pressure tower, with a top pressure of -60 kPa, a top temperature of 56°C, and a bottom temperature of 81°C. The vapor phase from the top of ethanol tower 23 enters ethanol tower condenser 27 for condensation. Part of the condensed liquid is returned to ethanol tower 23 as reflux, and the other part is collected as ethanol product.

[0044] The bottom material from ethanol column 23 is sent to isopropanol column 28. Isopropanol column 28 is equipped with two reboilers: a steam reboiler 29 using steam as a heat source, and a hot water reboiler 30 using steam condensate as a heat source. Isopropanol column 28 is an atmospheric pressure column with an atmospheric pressure at the top, a top temperature of 83°C, and a bottom temperature of 103°C. The vapor phase from the top of isopropanol column 28 enters isopropanol condenser 31 for condensation. Part of the condensed liquid is returned to isopropanol column 28 as reflux, and the remainder is collected as isopropanol product.

[0045] The bottom material from isopropanol column 28 is sent to n-propanol column 32, which is equipped with a reboiler 33 using steam as a heat source. n-Propanol column 32 is an atmospheric pressure column, with an atmospheric pressure at the top, a top temperature of 99°C, and a bottom temperature of 117°C. The vapor phase from the top of n-propanol column 32 enters the methanol column's heat exchanger reboiler 21 (which also serves as a condenser for the n-propanol column) for condensation. Part of the condensed liquid is returned to n-propanol column 32 as reflux, and the remainder is collected as n-propanol product. Isobutanol product is collected from the bottom of n-propanol column 32.

[0046] The material from the bottom of the crude fractionation column 1 is sent to the n-butanol column 34, which is equipped with a reboiler 35 using steam as a heat source. The n-butanol column 34 is an atmospheric pressure column, with an atmospheric pressure at the top, a top temperature of 120℃, and a bottom temperature of 141℃. The vapor phase from the top of the n-butanol column 34 enters the methanol column's heat exchanger reboiler 20 (which also serves as the n-butanol column condenser) for condensation. Part of the condensed liquid is returned to the n-butanol column 34 as reflux, and the remainder is collected as the n-butanol product. The heavy alcohol product is collected from the bottom of the n-butanol column 34.

[0047] Example 3 (Dual Tower System)

[0048] The only difference from Example 1 is that it also includes a second crude fractionation tower 37, a second crude fractionation tower steam reboiler 38, a second crude fractionation tower condenser 39, and a second crude fractionation tower reflux phase separator 40. The first crude fractionation tower 1 is equipped with two reboilers: a first crude fractionation tower heat exchange reboiler 36 (which also serves as a second crude fractionation tower condenser) and a first crude fractionation tower steam reboiler 2. The first crude fractionation tower phase separator 7 is installed at the bottom of the tower. The bottom outlet pipeline of the first crude fractionation tower 1 is divided into two paths, one of which is connected to the inlet of the second crude fractionation tower 37. Another path passes sequentially through the heat medium inlet and outlet of the phase-separating heat exchanger 5 in the first coarse separator, then enters the tube side of the circulating water cooler 6 in the first coarse separator, and is connected to the inlet of the phase-separating tank 7 in the first coarse separator via a pipeline. The organic phase extraction pipeline of the phase-separating tank 7 in the first coarse separator passes through the coolant inlet and outlet of the phase-separating heat exchanger 5 in the first coarse separator, and is connected to the inlet of the second coarse separator 37. The aqueous phase is connected to the first inlet of the stripping tower 8 via an extraction pipeline. The bottom of the second coarse separator 37 is sampled... The outlet is connected to the inlet of n-butanol column 34 via a pipeline. The top gas phase sampling outlet of crude fractionation column 37 is connected to the shell-side inlet of the heat exchanger reboiler 36 of crude fractionation column 1 (which also serves as the condenser of crude fractionation column 2) via a pipeline. The shell-side outlet of the heat exchanger reboiler 36 of crude fractionation column 1 is connected to the inlet of the reflux phase separator 40 of crude fractionation column 2 via a pipeline through the condenser 39 of crude fractionation column 2. The organic phase sampling outlet of the reflux phase separator 40 of crude fractionation column 2 is connected to the top reflux of crude fractionation column 37 via a pipeline. The water phase outlets of the coarse fractionation tower phase separation tank 7 and the coarse fractionation tower reflux phase separation tank 40 are connected to the first inlet of the stripping tower 8 via pipelines through the feed preheater 11 of the stripping tower. The top outlet of the stripping tower 8 is connected to the inlet of the stripping tower condenser 10 via pipelines. The outlet pipeline of the stripping tower condenser 10 is divided into two paths: one path connects to the reflux port of the stripping tower 8, and the other path passes through the coarse fractionation tower condenser 39 and is connected to the inlet of the coarse fractionation tower reflux phase separation tank 40 via pipelines.

[0049] Example 4

[0050] A process method for the separation system of high-water-content low-carbon alcohols described in Example 3: The mixed alcohol feedstock is preheated by a feedstock preheater 4 and then fed into the primary fractionation column 1. The feedstock preheater 4 uses the extractant from the bottom of the regeneration column 15 as a heat source. The primary fractionation column 1 is equipped with two reboilers: one is a primary fractionation column steam reboiler 2, using steam as a heat source; the other is a primary fractionation column heat exchange reboiler 36, using the vapor phase from the top of the secondary fractionation column 37 as a heat source. The primary fractionation column 1 is an atmospheric pressure column with an atmospheric pressure at the top, a top temperature of 58°C, and a bottom temperature of 96°C. The vapor phase from the top of the primary fractionation column 1 enters the primary fractionation column condenser 3 for condensation. Non-condensable gases are discharged, and part of the condensed liquid is returned to the primary fractionation column 1 as reflux, while the other part is collected as methanol product.

[0051] A mixed solution of methanol, ethanol, propanol, a small amount of butanol and water collected from the side stream of the coarse fractionation tower 1 is sent to the extraction tower 12.

[0052] Two coolers are installed on the bottom material outlet pipeline of the first coarse fractionation tower. One is the bottom phase-separation heat exchange cooler 5, which uses the organic phase of the phase separation tank 7 as the coolant; the other is the bottom phase-separation circulating water cooler 6, which uses circulating water as the coolant. The material exiting the bottom of the first coarse fractionation tower is cooled and then enters the phase separation tank 7 for phase separation. The cooling temperature is 50℃. The organic phase is sent to the inlet of the second coarse fractionation tower 37 after heat exchange in the bottom phase-separation heat exchange cooler 5.

[0053] The material at the bottom of the first coarse fractionation column 1 can be directly sent to the second coarse fractionation column 37 without passing through the bottom phase separation tank 8. The second coarse fractionation column 37 is equipped with a steam reboiler 38, using steam as a heat source. The second coarse fractionation column 37 is a pressurized column with a top pressure of 150 kPa, a top temperature of 118°C, and a bottom temperature of 152°C. The vapor phase at the top of the second coarse fractionation column 37 enters the heat exchange reboiler 36 of the first coarse fractionation column for condensation. The condensed liquid is cooled by the condenser 39 of the second coarse fractionation column and then enters the reflux phase separation tank 40 for phase separation, with the organic phase returning to the top of the second coarse fractionation column 37. The butanol, pentanol, and other heavy alcohols collected from the bottom of the second coarse fractionation column 37 are sent to the n-butanol column 34.

[0054] The material from the first roughing column phase separation tank 7 and the aqueous phase from the second roughing column reflux phase separation tank 40 are preheated by the stripping column feed preheater 11 and then sent to the stripping column 8. The stripping column feed preheater 11 uses the wastewater collected from the bottom of the stripping column 8 as a heat source. Wastewater from the top of the regeneration column 15 is also sent to the stripping column 8. The stripping column 8 is equipped with a stripping column steam reboiler 9, which uses steam as a heat source. The stripping column 8 is an atmospheric pressure column with an atmospheric pressure at the top, a top temperature of 91°C, and a bottom temperature of 100°C. The vapor phase at the top of the stripping column 8 enters the stripping column condenser 10 for condensation. Part of the condensed liquid is returned to the stripping column 8 as reflux, and part is collected and sent to the second roughing column reflux phase separation tank 40 for phase separation. The wastewater collected from the bottom of the stripping column 8 is cooled by the stripping column feed preheater 11 and then discharged.

[0055] The material from the side stream of the coarse fractionation tower 1 is fed to the middle of the extraction tower 12. The extractant is added from the upper part of the extraction tower 12. The extraction tower 12 is equipped with an extraction tower steam reboiler 13, which uses steam as a heat source. The extraction tower 12 is a vacuum tower with a top pressure of -55 kPa and a top temperature of 58°C and a bottom temperature of 146°C. The vapor phase at the top of the extraction tower 12 enters the extraction tower condenser 14 for condensation. Part of the condensed liquid is returned to the extraction tower 12 as reflux, and part is collected and sent to the methanol tower 18.

[0056] The material at the bottom of extraction tower 12 is sent to regeneration tower 15. Regeneration tower 15 is equipped with a regeneration tower steam reboiler 16, which uses steam as a heat source. Regeneration tower 15 is a vacuum tower with a top pressure of -85 kPa, a top temperature of 54℃, and a bottom temperature of 154℃. The vapor phase at the top of regeneration tower 15 enters regeneration tower condenser 17 for condensation. Part of the condensed liquid is returned to regeneration tower 15 as reflux, and part is collected as wastewater and stripped to stripping tower 8. The extractant at the bottom of regeneration tower 15 passes through ethanol tower heat exchange reboiler 26 (which also serves as extractant cooler) and raw material preheater 4 for heat exchange before returning to extraction tower 12 for recycling.

[0057] The material from the top of extraction column 12 is sent to methanol column 18. Methanol column 18 is equipped with three reboilers: one is a methanol column steam reboiler 19, using steam as a heat source; one is a methanol column heat exchange reboiler 20 (which also serves as a butanol column condenser), using the vapor phase from the top of n-butanol column 34 as a heat source; and the other is a methanol column heat exchange reboiler 21 (which also serves as a n-propanol column condenser), using the vapor phase from the top of n-propanol column 32 as a heat source. Methanol column 18 is an atmospheric pressure column, with an atmospheric pressure at the top, a top temperature of 63°C, and a bottom temperature of 85°C. The vapor phase from the top of methanol column 18 enters methanol column condenser 22 for condensation. Part of the condensed liquid is returned to methanol column 18 as reflux, and the other part is collected as methanol product.

[0058] The bottom material from methanol tower 18 is sent to ethanol tower 23. Ethanol tower 23 is equipped with three reboilers: one is an ethanol tower steam reboiler 24, using steam as a heat source; one is an ethanol tower hot water reboiler 25, using steam condensate as a heat source; and the third is an ethanol tower heat exchange reboiler 26 (which also serves as an extractant cooler), using the extractant from the bottom of extraction tower 12 as a heat source. Ethanol tower 23 is a negative pressure tower, with a top pressure of -60 kPa, a top temperature of 56°C, and a bottom temperature of 81°C. The vapor phase from the top of ethanol tower 23 enters ethanol tower condenser 27 for condensation. Part of the condensed liquid is returned to ethanol tower 23 as reflux, and the other part is collected as ethanol product.

[0059] The bottom material from ethanol column 23 is sent to isopropanol column 28. Isopropanol column 28 is equipped with two reboilers: a steam reboiler 29 using steam as a heat source, and a hot water reboiler 30 using steam condensate as a heat source. Isopropanol column 28 is an atmospheric pressure column with an atmospheric pressure at the top, a top temperature of 83°C, and a bottom temperature of 103°C. The vapor phase from the top of isopropanol column 28 enters isopropanol condenser 31 for condensation. Part of the condensed liquid is returned to isopropanol column 28 as reflux, and the remainder is collected as isopropanol product.

[0060] The bottom material from isopropanol column 28 is sent to n-propanol column 32. n-Propanol column 32 is equipped with a n-propanol column reboiler 33, using steam as a heat source. n-Propanol column 32 is an atmospheric pressure column, with an atmospheric pressure at the top, a top temperature of 99℃, and a bottom temperature of 117℃. The vapor phase from the top of n-propanol column 32 enters the methanol column heat exchanger reboiler 21 (which also serves as a condenser for the n-propanol column) for condensation. Part of the condensed liquid is returned to n-propanol column 32 as reflux, and the remainder is collected as n-propanol product. Isobutanol product is collected from the bottom of n-propanol column 32.

[0061] The material from the bottom of the crude fractionation column 37 is sent to the n-butanol column 34, which is equipped with a n-butanol reboiler 35 using steam as a heat source. The n-butanol column 34 is an atmospheric pressure column with an atmospheric pressure at the top, a top temperature of 120°C, and a bottom temperature of 141°C. The vapor phase from the top of the n-butanol column 34 enters the methanol column heat exchanger reboiler 20 (which also serves as a butanol column condenser) for condensation. Part of the condensed liquid is returned to the n-butanol column 34 as reflux, and the remainder is collected as the n-butanol product. The heavy alcohol product is collected from the bottom of the n-butanol column 34.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A separation system for high-water-content low-carbon alcohols, characterized in that, The system includes a primary fractionation tower (1), a primary fractionation tower heat exchanger and cooler (5), a primary fractionation tower circulating water cooler (6), a primary fractionation tower phase separation tank (7), a stripping tower (8), a stripping tower feed preheater (11), an extraction tower (12), a regeneration tower (15), a methanol tower (18), an ethanol tower (23), an isopropanol tower (28), a n-propanol tower (32), and a n-butanol tower (34). Each tower is equipped with a corresponding reboiler and condenser. The primary fractionation tower (1) has a raw material inlet, and a raw material preheater (4) is installed on the inlet pipeline. The primary fractionation tower (1) has a side line at the top, which is connected to the inlet of the extraction tower (12) through a pipeline. The bottom outlet of the extraction tower (12) is connected to the inlet of the regeneration tower (15) through a pipeline. The regeneration tower (15) is connected to the regeneration tower (16). The top vapor sampling outlet of the 5) tower is connected to the inlet of the regeneration tower condenser (17) via a pipeline. The outlet pipeline of the regeneration tower condenser (17) is divided into two paths, one of which is connected to the reflux port of the regeneration tower (15), and the other is connected to the first inlet of the stripping tower (8). The bottom outlet of the regeneration tower (15) passes through the ethanol tower heat exchanger reboiler (26) and the raw material preheater (4) via a pipeline and then enters the extractant inlet of the extraction tower (12). The top sampling outlet of the extraction tower (12) passes through the extraction tower condenser (14) via a pipeline and then is divided into two paths, one of which is connected to the reflux port of the extraction tower (12), and the other is connected to the inlet of the methanol tower (18). The methanol tower (18) is equipped with a methanol tower steam reboiler (19), a methanol tower heat exchanger reboiler (20), and a methanol tower... The bottom outlet of the methanol tower (18) is connected to the inlet of the ethanol tower (23) via a pipeline. The bottom outlet of the ethanol tower (23) is connected to the inlet of the isopropanol tower (28) via a pipeline. The bottom outlet of the isopropanol tower (28) is connected to the inlet of the n-propanol tower (32) via a pipeline. The bottom of the n-propanol tower (32) is the isobutanol product outlet pipeline. The gas phase pipeline at the top of the n-propanol tower (32) is split into two paths after passing through the methanol tower heat exchanger reboiler (21). One path is connected to the reflux port of the n-propanol tower (32), and the other path serves as the n-propanol product outlet pipeline. The lower part of the coarse fraction tower (1) has a second side line. The second side line passes through the coarse fraction tower heat exchanger cooler (5) and the coarse fraction tower circulating water cooler (6) via a pipeline. The organic phase outlet of the crude fractionation tower phase separation tank (7) is connected to the inlet of the crude fractionation tower (1) via a pipeline through the crude fractionation tower heat exchanger (5). The water phase outlet of the crude fractionation tower phase separation tank (7) is connected to the second inlet of the stripping tower (8) via a pipeline through the stripping tower feed preheater (11). The bottom outlet of the stripping tower (8) is connected to the stripping tower feed preheater (11) via a pipeline and then discharged as wastewater. The top gas phase outlet of the stripping tower (8) is connected to the inlet of the stripping tower condenser (10) via a pipeline. The outlet pipeline of the stripping tower condenser (10) is divided into two paths: one path is connected to the reflux port, and the other path is connected to the inlet of the crude fractionation tower phase separation tank (7) via the crude fractionation tower circulating water cooler (6).The bottom outlet of the coarse fractionation column (1) is connected to the inlet of the n-butanol column (34) via a pipeline. The top gas phase outlet pipeline of the n-butanol column (34) splits into two paths after passing through the methanol column heat exchanger reboiler (20). One path is connected to the reflux port of the n-butanol column (34) via a pipeline, and the other path serves as the n-butanol product outlet pipeline. The bottom outlet pipeline of the n-butanol column (34) is the heavy alcohol outlet pipeline.

2. The separation system for high-water-content low-carbon alcohols according to claim 1, characterized in that, It also includes a second crude fractionation tower (37), a second crude fractionation tower steam reboiler (38), a second crude fractionation tower condenser (39), and a second crude fractionation tower reflux phase separation tank (40). The first crude fractionation tower (1) is equipped with a first crude fractionation tower heat exchange reboiler (36) and a first crude fractionation tower steam reboiler (2). The first crude fractionation tower phase separation tank (7) is installed at the bottom of the first crude fractionation tower (1). The bottom outlet pipeline of the first crude fractionation tower (1) is divided into two paths. One path is directly connected to the inlet of the second crude fractionation tower (37), and the other path is connected to the inlet of the second crude fractionation tower (37) after passing through the first crude fractionation tower phase separation tank (7) and the first crude fractionation tower phase separation heat exchange cooler (5). The bottom outlet of the second crude fractionation tower (37) is connected to the inlet of the n-butanol tower (34) through a pipeline. The top gas phase outlet pipeline of the second crude fractionation tower (37) passes through the crude fractionation tower in sequence. The heat exchanger reboiler (36) of the first separation tower and the condenser (39) of the second rough separation tower are connected to the inlet of the reflux phase separator (40) of the second rough separation tower. The organic phase outlet of the reflux phase separator (40) of the second rough separation tower is connected to the top reflux port of the second rough separation tower (37) through a pipeline. The water phase outlets of the phase separator (7) of the first rough separation tower and the reflux phase separator (40) of the second rough separation tower are connected to the first inlet of the stripping tower (8) through the feed preheater (11) of the stripping tower through a pipeline. The top outlet of the stripping tower (8) is connected to the inlet of the stripping tower condenser (10) through a pipeline. The outlet pipeline of the stripping tower condenser (10) is divided into two paths: one path is connected to the reflux port of the stripping tower (8), and the other path is connected to the inlet of the reflux phase separator (40) of the second rough separation tower after passing through the condenser (39) of the second rough separation tower.

3. The separation system for high-water-content low-carbon alcohols according to claim 1 or 2, characterized in that, The top of the coarse fractionation tower (1) is connected to the coarse fractionation tower condenser (3). The gas phase outlet of the coarse fractionation tower condenser (3) is used for the discharge of non-condensable gas. The liquid phase outlet pipeline of the coarse fractionation tower condenser (3) is divided into two paths: one path is connected to the reflux inlet of the coarse fractionation tower (1), and the other path is used as the methanol product outlet pipeline.

4. The separation system for high-water-content low-carbon alcohols according to claim 1 or 2, characterized in that, The outlet pipelines of the methanol tower condenser (22), ethanol tower condenser (27), and isopropanol tower condenser (31) equipped at the top of the methanol tower (18), ethanol tower (23), and isopropanol tower (28) are all divided into two paths. One path is connected to the reflux port of the methanol tower (18), ethanol tower (23), and isopropanol tower (28) respectively, and the other path is used as the methanol product collection pipeline, ethanol product collection pipeline, and isopropanol product collection pipeline respectively.

5. A process method for separating high-water-content low-carbon alcohols according to claim 1, characterized in that, After the mixed alcohol feedstock is preheated by the feedstock preheater (4), it is sent to the crude fractionation tower (1). The gas phase at the top of the crude fractionation tower (1) enters the crude fractionation tower condenser (3) for condensation. The non-condensable gas is discharged. Part of the condensed liquid is returned to the crude fractionation tower (1) as reflux, and part of it is collected as methanol product. The coarse fractionation column is an atmospheric pressure column with a top pressure of -10 to 50 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 110 to 150°C. A mixed solution of methanol, ethanol, propanol, a small amount of butanol, and water collected from the upper side stream of the coarse fractionation column (1) is sent to the middle of the extraction column (12). The extractant is added from the upper part of the extraction column (12). The extractant and water at the bottom of the extraction column (12) are sent to the regeneration column (15). The gas phase at the top of the regeneration column (15) enters the condenser (17) of the regeneration column for condensation. The condensed liquid is partially condensed. A portion of the extractant is returned to the regeneration tower (15) as reflux, and another portion is treated as wastewater and stripped to the stripping tower (8). The extractant at the bottom of the regeneration tower (15) is then passed through the ethanol tower reboiler (26) and the raw material preheater (4) of the coarse fractionation tower before being returned to the extraction tower (12) for recycling. The vapor phase at the top of the extraction tower (12) enters the extraction tower condenser (14) for condensation. A portion of the condensed liquid is returned to the extraction tower (12) as reflux, and the other portion is collected and sent to the methanol tower (18). The vapor phase at the top of the methanol tower (18) enters the methanol tower. The condenser (22) condenses the liquid, and part of the condensed liquid is returned to the methanol tower (18) as reflux, while the rest is collected as methanol product. The bottom mixture of ethanol, n-propanol, and a small amount of isopropanol and butanol from the methanol tower (18) is sent to the ethanol tower (23). The top vapor phase of the ethanol tower (23) enters the ethanol tower condenser (27) for condensation. Part of the condensed liquid is returned to the ethanol tower (23) as reflux, while the rest is collected as ethanol product. The bottom material of the ethanol tower (23) is sent to the isopropanol tower (28). The vapor phase at the top of column (28) enters the isopropanol column condenser (31) for condensation. Part of the condensed liquid is returned to the isopropanol column (28) as reflux, and part is collected as isopropanol product. The bottom material of the isopropanol column (28) is sent to the n-propanol column (32). The vapor phase at the top of the n-propanol column (32) enters the methanol column heat exchanger reboiler II (21) for condensation. Part of the condensed liquid is returned to the n-propanol column (32) as reflux, and part is collected as n-propanol product. Isobutanol product is collected from the bottom of the n-propanol column (32). The bottom of the crude fractionation column (1) contains butanol, pentanol, and other heavy alcohols, which are sent to the n-butanol column (34). The vapor phase from the top of the n-butanol column (34) enters the heat exchanger reboiler (20) of the methanol column for condensation. Part of the condensed liquid is returned to the n-butanol column (34) as reflux, and part is collected as n-butanol product. The bottom of the n-butanol column (34) contains heavy alcohol products. The butanol and water collected from the lower side stream of the crude fractionation column (1) are cooled and then enter the phase separation tank (7) of the crude fractionation column for phase separation. The organic phase is separated into two phases. After heat exchange in the coarse fractionation tower cooler (5), the liquid returns to the coarse fractionation tower (1); the aqueous phase is preheated by the feed preheater (11) of the stripping tower (8) and then sent to the stripping tower (8). The vapor phase at the top of the stripping tower (8) enters the stripping tower condenser (10) for condensation. Part of the condensed liquid is returned to the stripping tower (8) as reflux, and part is collected to the coarse fractionation tower phase separation tank (7) for phase separation. The wastewater at the bottom of the stripping tower (8) is collected and discharged after being cooled by the feed preheater (11) of the stripping tower.

6. A process method for separating high-water-content low-carbon alcohols according to claim 2, characterized in that, After the mixed alcohol feedstock is preheated by the feedstock preheater (4), it is sent to the crude fractionation tower (1). The gas phase at the top of the crude fractionation tower (1) enters the crude fractionation tower condenser (3) for condensation. The non-condensable gas is discharged. Part of the condensed liquid is returned to the crude fractionation tower (1) as reflux, and part of it is collected as methanol product. The coarse fractionation column is an atmospheric pressure column with a top pressure of -10 to 50 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 70 to 120°C. A mixed solution of methanol, ethanol, propanol, a small amount of butanol, and water collected from the upper side stream of the coarse fractionation column (1) is sent to the middle of the extraction column (12). The extractant is added from the upper part of the extraction column (12). The extractant and water at the bottom of the extraction column (12) are sent to the regeneration column (15). The gas phase at the top of the regeneration column (15) enters the condenser (17) of the regeneration column for condensation. The condensed liquid is partially condensed. A portion of the extractant is returned to the regeneration tower (15) as reflux, and another portion is treated as wastewater and stripped to the stripping tower (8). The extractant at the bottom of the regeneration tower (15) is then passed through the ethanol tower reboiler (26) and the raw material preheater (4) of the coarse fractionation tower before being returned to the extraction tower (12) for recycling. The vapor phase at the top of the extraction tower (12) enters the extraction tower condenser (14) for condensation. A portion of the condensed liquid is returned to the extraction tower (12) as reflux, and the other portion is collected and sent to the methanol tower (18). The vapor phase at the top of the methanol tower (18) enters the methanol tower. The condenser (22) condenses the liquid, and part of the condensed liquid is returned to the methanol tower (18) as reflux, while the rest is collected as methanol product. The bottom mixture of ethanol, n-propanol, and a small amount of isopropanol and butanol from the methanol tower (18) is sent to the ethanol tower (23). The top vapor phase of the ethanol tower (23) enters the ethanol tower condenser (27) for condensation. Part of the condensed liquid is returned to the ethanol tower (23) as reflux, while the rest is collected as ethanol product. The bottom material of the ethanol tower (23) is sent to the isopropanol tower (28). The vapor phase at the top of column (28) enters the isopropanol column condenser (31) for condensation. Part of the condensed liquid is returned to the isopropanol column (28) as reflux, and part is collected as isopropanol product. The bottom material of the isopropanol column (28) is sent to the n-propanol column (32). The vapor phase at the top of the n-propanol column (32) enters the methanol column heat exchanger reboiler II (21) for condensation. Part of the condensed liquid is returned to the n-propanol column (32) as reflux, and part is collected as n-propanol product. Isobutanol product is collected from the bottom of the n-propanol column (32). The heavy alcohols such as butanol and pentanol collected from the bottom of the first crude fractionation tower (1) are cooled and then enter the phase separation tank (7) of the first crude fractionation tower for phase separation. The organic phase is sent to the second crude fractionation tower (37) after heat exchange in the phase separation cooler (5) of the first crude fractionation tower. The second crude fractionation tower (37) is a pressurized tower with a top pressure of 100-300 kPa, a top temperature of 100-150℃, and a bottom temperature of 120-170℃. The gas phase from the top of the second crude fractionation tower (37) is sent to the heat exchange reboiler (30) of the first crude fractionation tower for condensation. The condensed liquid enters the reflux phase separation tank (40) of the second crude fractionation tower. The organic phase from the reflux phase separation tank (40) of the second crude fractionation tower enters the second crude fractionation tower (37). The aqueous phases from the phase separation tank (7) of the first crude fractionation tower and the reflux phase separation tank (40) of the second crude fractionation tower are stripped by a stripping tower. After being preheated by the feed preheater (11), the gas phase from the top of the stripper (8) enters the stripper condenser (10) for condensation. Part of the condensed liquid is returned to the stripper (8) as reflux, and part is collected to the reflux phase separator (40) of the coarse fractionation tower for phase separation. The wastewater from the bottom of the stripper (8) is collected and discharged after being cooled by the feed preheater (11). The material from the bottom of the coarse fractionation tower (37) is sent to the n-butanol tower (34). The gas phase from the top of the n-butanol tower (34) enters the methanol tower heat exchanger reboiler (20) for condensation. Part of the condensed liquid is returned to the n-butanol tower (34) as reflux, and part is collected as n-butanol product. The heavy alcohol product is collected from the bottom of the n-butanol tower (34).

7. The process method according to claim 5 or 6, characterized in that, The stripping tower (8) is an atmospheric pressure tower with a top pressure of -10 to 50 kPa, a top temperature of 60 to 95°C, and a bottom temperature of 80 to 120°C; the extraction tower (12) is a vacuum tower with a top pressure of -90 kPa to atmospheric pressure, a top temperature of 40 to 90°C, and a bottom temperature of 100 to 160°C; the regeneration tower (15) is a vacuum tower with a top pressure of -95 to 20 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 120 to 170°C; the methanol tower (18) is an atmospheric pressure tower with a top pressure of -20 to 100 kPa, a top temperature of 40 to 90°C, and a bottom temperature of 60 to 110°C; the ethanol tower... (23) is a negative pressure tower with a top pressure of -80 kPa to atmospheric pressure, a top temperature of 40-80℃, and a bottom temperature of 60-110℃; (28) is an isopropanol tower with a top pressure of -20-100 kPa, a top temperature of 60-100℃, and a bottom temperature of 80-130℃; (32) is an n-propanol tower with a top pressure of -20-100 kPa, a top temperature of 60-100℃, and a bottom temperature of 80-130℃; (34) is an n-butanol tower with a top pressure of -20-100 kPa, a top temperature of 100-140℃, and a bottom temperature of 120-170℃.

8. The process method according to claim 5 or 6, characterized in that, The coarse fractionation tower heat exchanger (5) uses the organic phase of the coarse fractionation tower phase separation tank (7) as the coolant; the coarse fractionation tower circulating water cooler (6) uses circulating water as the coolant, with a cooling temperature of 30-80℃; the stripping tower feed preheater (11) uses the wastewater collected from the bottom of the stripping tower (8) as the heat source; the stripping tower steam reboiler (9), the extraction tower steam reboiler (13), and the regeneration tower steam reboiler (16) all use steam as the heat source.

9. The process method according to claim 5 or 6, characterized in that, The methanol tower (18) is equipped with three reboilers: one is a methanol tower steam reboiler (19) which uses steam as a heat source; one is a methanol tower heat exchange reboiler one (20) which uses the gas phase at the top of the n-butanol tower (34) as a heat source; and one is a methanol tower heat exchange reboiler two (21) which uses the gas phase at the top of the n-propanol tower (32) as a heat source.

10. The process method according to claim 5 or 6, characterized in that, The ethanol tower (23) is equipped with three reboilers: one is an ethanol tower steam reboiler (24) with water vapor as the heat source; one is an ethanol tower hot water reboiler (25) with steam condensate as the heat source; and the other is an ethanol tower heat exchange reboiler (26) with the extractant at the bottom of the extraction tower (12) as the heat source.

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