Method for recovering methanol and acetone in oxide waste liquid and method for treating methanol-to-ethylene waste liquid

Abstract

The invention relates to a method for recovering methanol and acetone in oxide waste liquid and a method for treating methanol-to-ethylene waste liquid, which comprises the following steps of: feeding the oxide-containing waste liquid into a light component removal tower, obtaining acetaldehyde and light components at the tower top, feeding a material discharged from the tower bottom into a methanol-acetone azeotrope tower, and feeding methanol-acetone azeotrope obtained at the tower top into an acetone extractive distillation tower, performing extraction separation by taking water as an extracting agent to obtain an acetone product at the tower top and a methanol-water mixture at the tower bottom; the methanol-water mixture enters a methanol recovery tower to be separated to obtain a methanol product; part of the acetone product or the methanol product is circulated back to the methanol-acetone azeotrope tower, so that the ratio of materials in the methanol-acetone azeotrope tower is close to that of methanol and acetone azeotrope under the operation pressure. The content of organic oxides in the wastewater treated by the method provided by the invention is reduced to below 1wt%, various high-purity organic matter products are obtained while the oxide waste liquid is effectively treated, and the economic benefit is good.

Description

Technical Field

[0001] The invention relates to a method for recovering and treating high-concentration oxide waste liquid from methanol to olefins, and belongs to the fields of environmental protection and chemical industry. Background Art

[0002] The state has proposed to take "clean, low-carbon, safe and efficient" as the basic principle to be followed in the development of modern coal chemical industry. This requires coal chemical enterprises to vigorously develop new technologies in wastewater treatment to solve the dual problems of environmental protection and water conservation in the production process. For methanol to olefins technology, in addition to producing ethylene and propylene, methanol will also produce a small amount of alcohol, aldehyde, ketone and other oxides during the reaction process. After these oxides enter the water scrubber and stripper with the process gas, part of them enter the water to form oxide waste liquid, which is usually used as fuel for combustion treatment. However, since the water content of this part of oxide waste liquid is very high (about 60-80wt%) and the output is large, it is difficult to burn and difficult to handle. The oxygen-containing organic matter in the oxide waste liquid, alcohol, aldehyde, ketone and other substances, can be used as industrial solvents and organic raw materials in industries such as chemical and pharmaceutical industries. If they are separated and recycled, the cost of coal liquefaction to olefins can be further reduced and its biodegradability can be improved.

[0003] The oxides contained in the oxide waste liquid of methanol to olefins are mainly acetaldehyde (boiling point 20.99°C), methanol (boiling point 64.53°C), acetone (boiling point 56.14°C), and also contain small amounts of ethanol, n-propanol, isopropanol, butanol, butanone, pentanone, hexanone, pentenone, etc. Except for acetaldehyde, these oxides can form a variety of azeotropes with each other, which are difficult to separate.

[0004] CN102040303A discloses a method for recovering organic matter in wastewater from a methanol-to-olefins process. The method uses a pervaporation membrane or a steam permeation membrane that preferentially permeates organic matter to separate organic matter from water in the wastewater, and then the organic matter containing methanol is subjected to steam stripping treatment. The stripping product is then dehydrated through a pervaporation membrane or a steam permeation membrane that preferentially permeates water to obtain methanol and derivative products. The recovery method ultimately obtains a mixture of multiple aldehydes, ketones, and alcohols, and does not perform deep separation of the mixture to obtain a high-purity single-component organic product.

[0005] CN103044217A discloses a method for treating non-acidic oxygen-containing organic matter. The invention first uses distillation to extract all the light components of non-acidic organic matter such as acetaldehyde, ethanol, propionaldehyde, acetone, and n-propanol in wastewater, and then cuts, separates, and refines them in sequence. The process is complicated. In addition, to extract all the organic matter together, the tower bottom needs to be heated to a higher temperature first. This temperature is higher than the tower bottom temperature of most subsequent product refining towers, and it needs to be repeatedly heated and cooled, which consumes a lot of energy.

[0006] CN111499495A discloses a method for recovering various alcohols from troxtrostatic synthesis wastewater. In the invention, the recovered alcohols are dehydrated and refined by distillation to obtain high-purity products. The heating temperature is high and the energy consumption is large. In addition, the invention does not involve the recovery of ketone substances.

[0007] CN103467257A and CN103483148A disclose methods for recovering aldehydes, ketones and alcohols in trotropsch synthesis water using multiple distillation units. The invention ultimately obtains a mixed alcohol product that can only be burned as fuel without deep separation of the mixture. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for recovering methanol and acetone from oxide waste liquid.

[0009] In a first aspect, the present invention provides a method for recovering methanol and acetone in oxide waste liquid, comprising: sending the oxide waste liquid to a light component removal tower, obtaining acetaldehyde and light components at the top of the tower, discharging from the bottom of the tower into a methanol-acetone azeotrope tower, sending the methanol-acetone azeotrope obtained at the top of the tower to an acetone extraction and distillation tower, extracting and separating with water as an extractant, obtaining an acetone product at the top of the tower, and discharging from the bottom of the tower as a methanol-water mixture; the methanol-water mixture enters a methanol recovery tower for separation to obtain a methanol product; and recycling part of the acetone product or the methanol product back to the methanol-acetone azeotrope tower, so that the material in the methanol-acetone azeotrope tower is close to the ratio of methanol and acetone azeotrope under the operating pressure.

[0010] In a second aspect, the present invention provides a method for treating waste liquid from methanol to ethylene, wherein the reaction product of the methanol to olefin process enters a water washing tower, and the obtained waste water containing organic oxides is sent to a stripping tower, and the gas phase after stripping is cooled by heat exchange at the top of the tower to obtain a waste liquid containing oxides; the above-mentioned method for recovering methanol and acetone in the waste liquid containing oxides is used to treat the waste liquid containing oxides to obtain acetone products and methanol products.

[0011] Compared with the prior art, the method for recovering methanol and acetone from oxide waste liquid provided by the present invention has the following beneficial effects:

[0012] (1) The method provided by the present invention recovers high-value methanol, acetone and acetaldehyde products, as well as oxide fuel, from oxide waste liquid. The oxide content in the treated wastewater is reduced to less than 1wt%, and the discharge can meet the discharge standards. The wastewater discharge can be reduced, while improving the economic benefits of the enterprise.

[0013] (2) The acetone product and the methanol product are recycled back to the acetone-methanol azeotrope tower to improve the recovery rate of methanol and acetone and achieve efficient recovery of important components. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a schematic flow diagram of the method for recovering methanol and acetone from oxide waste liquid.

[0015] in:

[0016] 1- oxide waste liquid 2- light removal tower 3- light components

[0017] 4-Bottom discharge of light removal tower 5-Methanol-acetone azeotrope tower 6-Methanol-acetone azeotrope

[0018] 7-Methanol-acetone azeotropic tower bottom discharge 8-Acetone extraction tower

[0019] 9-acetone product 10-circulating acetone 11-bottom discharge of acetone extraction tower

[0020] 12-Methanol recovery tower 13-Methanol product 14-Circulating methanol

[0021] 15-extraction solvent 16-dehydration tower 17-dehydration tower top discharge

[0022] 18- Treated wastewater DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are described in detail below:

[0024] In the present application, unless otherwise specified, the pressure referred to refers to the apparent pressure.

[0025] In this application, the descriptions such as "top", "middle", and "bottom" are all based on the relative position of the container. The "bottom" refers to the position of 0-10% from the bottom to the top of the container, the "middle" refers to the position of 40-60% from the bottom to the top of the container, and the "top" refers to the position of 90-100% from the bottom to the top of the container.

[0026] In a first aspect, the present invention provides a method for recovering methanol and acetone in oxide waste liquid, comprising: sending the oxide waste liquid to a light component removal tower, obtaining acetaldehyde and light components at the top of the tower, discharging from the bottom of the tower into a methanol-acetone azeotrope tower, sending the methanol-acetone azeotrope obtained at the top of the tower to an acetone extraction and distillation tower, extracting and separating with water as an extractant, obtaining an acetone product at the top of the tower, and discharging from the bottom of the tower as a methanol-water mixture; the methanol-water mixture enters a methanol recovery tower for separation to obtain a methanol product; and recycling part of the acetone product or the methanol product back to the methanol-acetone azeotrope tower, so that the material in the methanol-acetone azeotrope tower is close to the ratio of methanol and acetone azeotrope under the operating pressure.

[0027] Optionally, in the oxide-containing waste liquid, the content of organic oxides is 10wt%-60wt%, the content of water is 40wt%-90wt%, and the organic oxides are C1-C6 organic oxygen-containing compounds. The organic oxides include methanol and acetone.

[0028] Optionally, the oxygen-containing waste liquid contains 5wt%-20wt% methanol, 3wt%-30wt% acetone, 1wt%-10wt% acetaldehyde, and 1wt%-5wt% other organic oxides.

[0029] In the method provided by the present invention, the oxide waste liquid can be an oxide waste liquid in a methanol to olefin process, wherein the organic oxides contained therein are mainly acetaldehyde, methanol, acetone, and ethanol, n-propanol, isopropanol, butanol, butanone, pentanone, hexanone, and pentenone. Except for acetaldehyde, these oxides can form a variety of azeotropes with each other, which are difficult to separate. Among all azeotropes, the boiling point of methanol-acetone azeotrope is the lowest at 55.8°C, and acetone accounts for about 88wt% in the atmospheric pressure azeotropic composition.

[0030] In the method provided by the present invention, the oxide-containing waste liquid is sent to a light-removal tower, and acetaldehyde and light components are obtained at the top of the tower. The acetaldehyde and light components refer to acetaldehyde and / or other organic oxide-containing components with a boiling point of less than 50°C at normal pressure.

[0031] Optionally, the bottom discharge of the methanol-acetone azeotrope tower enters a dehydration tower, a concentrated oxide-water mixture is obtained at the top of the tower, and the bottom discharge of the tower is water.

[0032] Optionally, the top discharge of the dehydration tower contains 70-90wt% of an oxide mixture and the remainder of water, wherein the oxide mixture includes methanol, ethanol, n-propanol, isopropanol, butanol, butanone, pentanone, hexanone and pentenone; and the water content in the bottom discharge is >99w%, and the oxide content is <1w%.

[0033] In the method provided by the present invention, the operating conditions of the lightness removal tower are: pressure of 0-0.15MPa, tower top temperature of 20-50°C, tower bottom temperature of 70-120°C, and reflux ratio of 2-10.

[0034] The operating conditions of the methanol-acetone azeotrope tower are: pressure of 0-1.0 MPa, reflux ratio of 5-10, tower top temperature of 55-140°C, and tower bottom temperature of 75-180°C.

[0035] The operating conditions of the acetone extractive distillation tower are as follows: pressure of 0-0.15 MPa, reflux ratio of 2-20, tower top temperature of 55-85°C, tower bottom temperature of 90-120°C, and feed mass ratio of extractant to methanol-acetone azeotrope of 1.0-10.0. In the method provided by the present invention, the extractant is water and is recycled. According to different needs, the extractant can also be selected from one or more mixtures of toluene, isopropanol, ethanol and monoethanolamine, or selected from a mixture of water and the above extractants.

[0036] The operating conditions of the methanol recovery tower are: pressure 0-0.5MPa, reflux ratio 2-8, tower top temperature 65-120°C, tower bottom temperature 80-160°C;

[0037] Optionally, the operating conditions of the dehydration tower are: absolute pressure of 30-200 kPa, reflux ratio of 0.5-5, top temperature of 40-90°C, and bottom temperature of 70-120°C.

[0038] Preferably, the operating conditions of the methanol-acetone azeotrope tower are: pressure of 0-0.5 MPa, tower top temperature of 55-115°C, and tower bottom temperature of 75-155°C.

[0039] In the method provided by the present invention, a preferred embodiment is that when the methanol-acetone mass ratio in the oxide-containing waste liquid is greater than 0.4, the operating conditions of the methanol-acetone azeotrope tower are: the pressure is 0.1-0.3MPa, preferably 0.2-0.3MPa, for example, it is operated under a pressure of 0.2MPa, 0.25MPa or 0.3MPa, and part of the acetone product is recycled back to the methanol-acetone azeotrope tower, and the ratio of the circulation amount to the production amount is 0.1-1.0.

[0040] In the method provided by the present invention, a preferred embodiment is that when the methanol-acetone mass ratio in the oxide-containing waste liquid is not more than 0.4, the operating conditions of the methanol-acetone azeotrope tower are: the pressure is 0.1-0.3MPa, preferably 0.2-0.3MPa, for example, it is operated under a pressure of 0.2MPa, 0.25MPa or 0.3MPa, and part of the methanol product is recycled back to the methanol-acetone azeotrope tower, and the ratio of the circulation amount to the production amount is 0.1-1.0.

[0041] In a second aspect, the present invention provides a method for treating waste liquid from methanol to ethylene, wherein the reaction product of the methanol to olefin process enters a water washing tower, and the obtained waste water containing organic oxides is sent to a stripping tower, and the gas phase after stripping is cooled by heat exchange at the top of the tower to obtain a waste liquid containing oxides; the above-mentioned method for recovering methanol and acetone in the waste liquid containing oxides is used to treat the waste liquid containing oxides to obtain acetone products and methanol products.

[0042] In one embodiment of the method provided by the present invention, the oxide-containing wastewater is fed into a light-removal tower, and an acetaldehyde product (boiling point at normal pressure is 20.99°C) is obtained at the top of the tower, and the acetaldehyde purity is >98%, and other low-boiling organic oxygen-containing compounds, such as ether and dimethyl ether, may also be contained therein. The bottom discharge is fed into a methanol-acetone azeotrope tower for distillation separation, and a methanol-acetone azeotrope (boiling point at normal pressure is 55.8°C) is obtained at the top of the tower. The bottom discharge is fed into a dehydration tower for further separation, and a mixture of oxides and water is obtained at the top of the dehydration tower, preferably the top discharge contains 70wt%-90wt% of the oxide mixture and 10wt%-30wt% of water; the oxide mixture includes methanol, ethanol, n-propanol, isopropanol, butanol, butanone, pentanone, hexanone and pentenone; the bottom discharge is mainly water, and preferably the water content is >99wt%.

[0043] The methanol-acetone azeotrope is transported to an acetone extraction distillation tower, preferably using water as an extractant to separate them, obtaining an acetone product with a purity of >96% at the top of the tower, and a methanol-water mixture at the bottom of the tower. The methanol-water mixture enters a methanol recovery tower for separation to obtain a methanol product.

[0044] The content ratio of methanol and acetone in the material entering the methanol-acetone azeotrope tower is related to the treated oxygenate-containing waste liquid. In order to recover the maximum amount of methanol and acetone, when the mass ratio of methanol to acetone is lower than or higher than the ratio of methanol and acetone azeotrope at the operating pressure, part of the methanol product or part of the acetone product is recycled back to the methanol-acetone azeotrope tower, and the material in the methanol-acetone azeotrope tower is adjusted to be close to the ratio of methanol and acetone azeotrope at the operating pressure.

[0045] The separation system used in the method provided by the present invention is used for the above-mentioned method of recovering methanol and acetone in high-concentration oxide waste liquid, comprising a light removal tower, a methanol-acetone azeotrope tower, a dehydration tower, an acetone extraction distillation tower and a methanol recovery tower connected in sequence, wherein the light removal tower is used to separate low-boiling organic oxygen-containing substances, and the bottom discharge of the tower is connected to the raw material inlet of the methanol-acetone azeotrope tower;

[0046] The methanol-acetone azeotrope tower is used to separate the methanol-acetone azeotrope, the bottom discharge of the tower is connected to the raw material inlet of the dehydration tower, and the top discharge of the methanol-acetone azeotrope tower is connected to the raw material inlet of the extraction distillation tower;

[0047] The dehydration tower is used to separate the remaining oxide mixture in the wastewater, and the top discharge material is a concentrated oxide mixture, and the bottom discharge material is discharged externally;

[0048] The acetone extraction distillation tower is used to separate methanol and acetone, the top discharge is discharged externally, and the bottom discharge is connected to the methanol recovery tower;

[0049] The top discharge of the acetone extraction distillation tower and the top discharge of the methanol recovery tower are respectively connected to the raw material inlet of the methanol-acetone azeotrope tower.

[0050] The method for recovering methanol and acetone in oxide waste liquid provided by the present invention is to respectively obtain high-purity acetaldehyde, acetone and methanol products, and oxide-water mixture by setting a lightness removal tower, a methanol-acetone azeotrope tower, an acetone extraction distillation tower and a dehydration tower, and partially recycle the obtained methanol product and acetone product back to the methanol-acetone azeotrope tower to adjust the mass ratio of methanol and acetone of the material to increase the amount of methanol recovered from the oxide waste liquid. Methanol and acetone are pulled out from the oxide waste liquid by means of an azeotrope, and the oxide waste liquid can be treated at a lower temperature to reduce the content of the oxide therein. The methanol-acetone azeotrope is further separated to obtain high-purity methanol and acetone products, creating new income for the enterprise.

[0051] The oxide-water mixture can be burned as fuel after dehydration and concentration. The oxide content in the oxide waste liquid can be reduced to less than 1wt%, meeting the emission standards. While effectively treating the oxide waste liquid, a variety of high-purity organic products are obtained, creating new revenue.

[0052] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0053] Attached Figure 1 The schematic diagram of the process for recovering methanol and acetone from waste liquid containing oxygenates is shown in FIG. Figure 1As shown in the figure, the oxide-containing waste liquid 1 enters the light component removal tower 2. The light components 3 are discharged from the top of the tower and collected and treated separately. The bottom discharge 4 enters the methanol-acetone azeotrope tower 5. The methanol and acetone contents in the feed material to the tower are analyzed, and the methanol-acetone composition ratio in the feed material to the tower is X1. It is compared with the methanol-acetone composition ratio X of the theoretical azeotrope under the actual operating pressure. If X1 < X, that is, the methanol content in the feed material to the tower is low, then the recycled methanol 14 is introduced. If X1 > X, that is, the acetone content is low, then the recycled acetone 10 is introduced to adjust the methanol and acetone contents in the feed of the methanol-acetone azeotrope tower to be close to the theoretical azeotrope composition. The methanol-acetone azeotrope 6 is taken from the top of the methanol-acetone azeotrope tower 5 and introduced into the acetone extractive distillation tower 8. The extraction solvent 15 is introduced from the middle upper part of the tower. The top discharge of the acetone extractive distillation tower is the acetone product 9. Part of the acetone product is recycled to the azeotrope tower 5 through the pipeline 10 as needed. The bottom discharge of the acetone extractive distillation tower 8 is introduced into the methanol recovery tower 12 for separating the extraction solvent and methanol, and the methanol product 13 is obtained from the top. Part of the methanol product is returned to the inlet of the methanol-acetone azeotrope tower 5 through the pipeline 14 as needed. The bottom discharge 7 of the methanol-acetone azeotrope tower, the mixture of oxides and water, enters the dehydration tower 16. The high-concentration oxide mixture 17 is taken from the top of the tower, and the treated wastewater 18 is discharged from the bottom of the tower and can also be subjected to subsequent wastewater treatment.

[0054] The following further describes the present invention in detail with specific embodiments, but the present invention is not limited to the following embodiments.

[0055] In the embodiments: The purity analysis of the acetaldehyde product, methanol product, and acetone product is carried out by gas chromatography. The calculation method of the recovery rate of each component is as follows:

[0056]

[0057] In the formula, Q is the mass flow rate of the material flow, with the unit of kg / h, and wt is the mass fraction of the target component in the material flow.

[0058] Two kinds of oxide-containing waste liquids to be treated are taken from the bottom condensate liquid of the high-pressure separator at the top of the stripping tower after the methanol-to-olefins reactor in the refinery. The compositions of the oxide waste liquid A and oxide waste liquid B are shown in Table 1.

[0059] Example 1

[0060] The process flow is as Figure 1As shown, the mass ratio of methanol to acetone in the oxide waste liquid A is 0.69. The oxide waste liquid A first enters the light removal tower, which operates under a slightly positive pressure, and the acetaldehyde product is extracted from the top of the tower. The bottom discharge enters the methanol-acetone azeotrope tower, and the operating pressure of the methanol-acetone azeotrope tower is 0.3MPa. The methanol-acetone azeotrope is extracted from the top of the methanol-acetone azeotrope tower and introduced into the acetone extraction distillation tower, and water enters from the top of the tower as the extraction solvent. The top discharge of the acetone extraction distillation tower is the acetone product; the bottom discharge of the acetone extraction distillation tower is introduced into the methanol recovery tower to separate water and methanol, and the methanol product is obtained from the top of the tower. The water extracted from the bottom of the tower is recycled back to the acetone extraction distillation tower. The bottom discharge of the methanol-acetone azeotrope tower enters the dehydration tower, and the high-concentration oxide is extracted from the top of the tower, and the treated wastewater is obtained at the bottom of the tower. There is no methanol product and acetone product circulation in the methanol-acetone azeotrope tower.

[0061] In the acetone extraction distillation column, the mass ratio of extractant water to feed is 2.0. The operating conditions of each distillation column are shown in Table 2, and the composition and purity of each product are analyzed. The yield of each product is shown in Table 3.

[0062] Example 2

[0063] The mass ratio of methanol to acetone in the oxide waste liquid A to be treated is 0.69. The method for recovering methanol and acetone is the same as in Example 1, except that part of the acetone product is recycled back to the methanol-acetone azeotrope column, and the mass ratio of methanol to acetone in the azeotrope column feed is adjusted from 0.69 to 0.45. The operating conditions of each distillation column are shown in Table 2, and the composition and purity of each product are analyzed. The purity and yield of each product are shown in Table 3.

[0064] Example 3

[0065] The mass ratio of methanol to acetone in the oxide waste liquid B to be treated is 0.28. The method for recovering methanol and acetone is the same as in Example 1, except that the operating pressure of the methanol-acetone azeotrope tower is 0.2MPa, part of the methanol product is recycled back to the methanol-acetone azeotrope tower, and the mass ratio of methanol to acetone in the azeotrope tower feed is adjusted from 0.28 to 0.32. The operating conditions of each distillation tower are shown in Table 2, and the composition and purity of each product are analyzed. The purity and yield of each product are shown in Table 3.

[0066] Table 1

[0067] Components, wt% Oxide waste liquid A Oxide waste liquid B Acetaldehyde 4.5 1.1 Methanol 11.4 5.4 Ethanol 1.5 0.3 acetone 16.6 19.1 Other C2-C6 oxides 4.3 4.2 water 61.7 69.9

[0068] Table 2

[0069]

[0070]

[0071] Table 3

[0072]

[0073]

[0074] It can be seen from the data in Table 3 that the method provided by the present invention is used to treat the oxide-containing waste liquid, and the content of oxide-containing waste water after treatment is reduced to below 0.5%. When treating oxide waste liquid A, the method of reflux of part of the acetone product can increase the methanol recovery rate by 9 percentage points and the acetone recovery rate by 3.3 percentage points. When treating oxide waste liquid B by the method provided by the present invention, the methanol recovery rate is 88.5% and the acetone recovery rate is 89.5%.

Claims

1. A method for recovering methanol and acetone from oxide waste liquid, characterized in that: include: The waste liquid containing oxides is sent to a light component removal tower, acetaldehyde and light components are obtained at the top of the tower, the bottom discharge enters a methanol-acetone azeotrope tower, the methanol-acetone azeotrope obtained at the top of the tower is sent to an acetone extraction and distillation tower, water is used as an extractant for extraction and separation, the top discharge obtains an acetone product, and the bottom discharge is a methanol-water mixture; the methanol-water mixture enters a methanol recovery tower for separation to obtain a methanol product; part of the acetone product or the methanol product is recycled back to the methanol-acetone azeotrope tower, so that the material in the methanol-acetone azeotrope tower is close to the ratio of methanol and acetone azeotrope under the operating pressure.

2. The method for recovering methanol and acetone in oxide waste liquid according to claim 1, characterized in that: In the oxide-containing waste liquid, the content of organic oxides is 10wt%-60wt%, the content of water is 40wt%-90wt%, and the organic oxides are C1-C6 organic oxygen-containing compounds.

3. The method for recovering methanol and acetone in oxide waste liquid according to claim 2, characterized in that: The methanol content in the oxide-containing waste liquid is 5wt%-20wt%, the acetone content is 3wt%-30wt%, the acetaldehyde content is 1wt%-10wt%, and the content of other organic oxides is 1wt%-5wt%.

4. The method for recovering methanol and acetone from oxide waste liquid according to any one of claims 1 to 3, characterized in that: The bottom discharge of the methanol-acetone azeotrope tower enters a dehydration tower, a concentrated oxide-water mixture is obtained at the top of the tower, and the bottom discharge of the tower is water.

5. The method for recovering methanol and acetone in oxide waste liquid according to claim 4, characterized in that: The top discharge of the dehydration tower contains 70wt%-90wt% of an oxide mixture, wherein the oxide mixture includes methanol, ethanol, n-propanol, isopropanol, butanol, butanone, pentanone, hexanone and pentenone; and the water content of the bottom discharge is greater than 99wt%.

6. The method for recovering methanol and acetone from oxide waste liquid according to any one of claims 1 to 3, characterized in that: The operating conditions of the lightness removal tower are: pressure of 0-0.15MPa, tower top temperature of 20-50°C, tower bottom temperature of 70-120°C, and reflux ratio of 2-10; The operating conditions of the methanol-acetone azeotrope tower are: pressure of 0-1.0 MPa, tower top temperature of 55-140°C, tower bottom temperature of 75-180°C, and reflux ratio of 5-20; The operating conditions of the acetone extraction distillation tower are: pressure of 0-0.15 MPa, tower top temperature of 55-85°C, tower bottom temperature of 90-120°C, reflux ratio of 2-20, and mass ratio of extractant to feed of 1.0-10.0; The operating conditions of the methanol recovery tower are: pressure of 0-0.5MPa, tower top temperature of 65-120°C, tower bottom temperature of 80-160°C, and reflux ratio of 2-8; The operating conditions of the dehydration tower are: absolute pressure of 30-200 kPa, tower top temperature of 40-90° C., tower bottom temperature of 70-120° C., and reflux ratio of 0.5-5.

7. The method for recovering methanol and acetone from oxide waste liquid according to any one of claims 1 to 3, characterized in that: The operating conditions of the methanol-acetone azeotrope tower are: pressure of 0-0.5 MPa, tower top temperature of 55-115°C, and tower bottom temperature of 75-155°C.

8. The method for recovering methanol and acetone in oxide waste liquid according to claim 7, characterized in that: When the methanol-acetone mass ratio in the oxide-containing waste liquid is greater than 0.4, the operating conditions of the methanol-acetone azeotrope tower are: the pressure is 0.1-0.3 MPa, part of the acetone product is recycled back to the methanol-acetone azeotrope tower, and the ratio of the circulation amount to the production amount is 0.1-1.

0.

9. The method for recovering methanol and acetone in oxide waste liquid according to claim 7, characterized in that: When the mass ratio of methanol to acetone in the oxide-containing waste liquid is not greater than 0.4, the operating conditions of the methanol-acetone azeotrope tower are: the pressure is 0.1-0.3 MPa, part of the methanol product is recycled back to the methanol-acetone azeotrope tower, and the ratio of the circulation amount to the production amount is 0.1-1.

0.

10. A method for treating waste liquid from methanol to ethylene, characterized in that: The reaction product of the methanol to olefins process enters a water washing tower, and the obtained wastewater containing organic oxides is sent to a stripping tower. The gas phase after stripping is cooled by heat exchange at the top of the tower to obtain an oxide-containing waste liquid; the method for recovering methanol and acetone in the oxide waste liquid according to any one of claims 1 to 9 is used to treat the oxide-containing waste liquid to obtain an acetone product and a methanol product.

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