Method and system for recovering methanol and acetone in oxide waste liquid, and methanol-to-ethylene waste liquid treatment method

Abstract

The invention relates to a method for recovering methanol and acetone in an oxide waste liquid, a separation system and a methanol-to-ethylene waste liquid treatment method, and the method comprises the following steps: sending the oxide-containing waste liquid to a light component removal tower to obtain acetaldehyde and light components at the tower top, and sending a material discharged from the tower bottom to a methanol-acetone azeotrope tower, sending a methanol-acetone azeotrope obtained at the tower top to a methanol-acetone separation system, and separating to obtain an acetone product and a methanol product; a material discharged from the bottom of the methanol-acetone azeotrope tower enters a dehydrating tower, a concentrated oxide-water mixture is obtained from the top of the tower, and a material discharged from the bottom of the tower is treated wastewater; wherein in the oxide-containing waste liquid, the mass ratio of acetone to methanol is 0.5 to 3.0, and the operation pressure of the methanol-acetone azeotrope tower is 0.1 to 1.5 MPa. The content of organic oxides in the wastewater treated by the method provided by the invention is less than 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 and a separation system 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-containing waste liquid to a light-removing tower, obtaining acetaldehyde and light components at the top of the tower, the bottom discharge of the tower entering a methanol-acetone azeotrope tower, and the methanol-acetone azeotrope obtained at the top of the tower being sent to a methanol-acetone separation system to separate and obtain an acetone product and a methanol product; the bottom discharge of the methanol-acetone azeotrope tower entering a dehydration tower, obtaining a concentrated oxide-water mixture at the top of the tower, and the bottom discharge of the tower being treated waste water; wherein, in the oxide-containing waste liquid, the mass ratio of acetone to methanol is 0.5-3.0, and the operating pressure of the methanol-acetone azeotrope tower is 0.1-1.5 MPa.

[0010] In a second aspect, the present invention provides a separation system for recovering methanol and acetone in oxide waste liquid, which is used in the above-mentioned method for recovering methanol and acetone in oxide waste liquid, comprising a light removal tower, a methanol-acetone azeotrope tower, a dehydration tower, a methanol tower and an acetone tower connected in sequence;

[0011] The light removal tower is used to separate low-boiling-point organic oxygen-containing substances, the top discharge of which is the acetaldehyde product outlet, and the bottom discharge is connected to the raw material inlet of the methanol-acetone azeotrope tower;

[0012] The methanol-acetone azeotrope tower is used to separate the methanol-acetone azeotrope, and the top discharge of the methanol-acetone azeotrope tower is connected to the raw material inlet of the methanol tower; the bottom discharge is connected to the raw material inlet of the dehydration tower;

[0013] The methanol tower and the acetone tower are used for separating methanol-acetone azeotrope, the bottom discharge of the methanol tower is the methanol product outlet, and the top discharge is connected to the acetone tower, the bottom discharge of the acetone tower is the acetone product outlet, and the top discharge of the acetone tower is connected to the methanol tower;

[0014] The dehydration tower is used to concentrate the oxide mixture, the top discharge of the dehydration tower is the mixed oxide outlet, and the bottom discharge of the tower is the waste water outlet.

[0015] In a third 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 an oxide-containing waste liquid; the above-mentioned method for recovering methanol and acetone in the oxide waste liquid is used to treat the oxide-containing waste liquid to obtain an acetone product and a methanol product.

[0016] 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:

[0017] (1) The method provided by the present invention recovers high-value components such as methanol and acetone, as well as oxide fuel from oxide waste liquid. The oxide content in the treated wastewater is reduced to less than 1wt%, which can meet the discharge standards. The wastewater discharge can be reduced, while improving the economic benefits of the enterprise.

[0018] (2) The pressure swing azeotropic distillation method is used to improve the recovery rate of methanol and acetone and achieve efficient recovery of important components.

[0019] (3) A methanol-acetone pressure swing combined separation tower is used to separate the azeotropic mixture of methanol and acetone, without the need to introduce a third extractant, thereby reducing system interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic flow diagram of the method for recovering methanol and acetone from oxide waste liquid.

[0021] in:

[0022] 1-Oxide waste liquid 2-Light removal tower 3-Light removal tower top discharge

[0023] 4- Light removal tower bottom discharge 5, 11- Liquid booster pump 6- Methanol-acetone azeotropic tower

[0024] 7- Azeotropic tower top discharge | 8- Azeotropic tower bottom discharge 9- Methanol tower

[0025] 10-Methanol tower top discharge 12-Methanol tower bottom discharge 13-Acetone tower

[0026] 14-Acetone tower top discharge 15-Acetone product 16-Dehydration tower

[0027] 17- Dehydration tower top discharge 18- Treated wastewater DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in detail below:

[0029] In the present application, unless otherwise specified, the pressure referred to refers to the apparent pressure.

[0030] 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.

[0031] In a first aspect, the present invention provides a method for recovering methanol and acetone in oxide waste liquid, comprising: sending the oxide-containing waste liquid to a light-removing tower, obtaining acetaldehyde and light components at the top of the tower, the bottom discharge of the tower entering a methanol-acetone azeotrope tower, and the methanol-acetone azeotrope obtained at the top of the tower being sent to a methanol-acetone separation system to separate and obtain an acetone product and a methanol product; the bottom discharge of the methanol-acetone azeotrope tower entering a dehydration tower, obtaining a concentrated oxide-water mixture at the top of the tower, and the bottom discharge of the tower being treated waste water; wherein, in the oxide-containing waste liquid, the mass ratio of acetone to methanol is 0.5-3.0, and the operating pressure of the methanol-acetone azeotrope tower is 0.1-1.5 MPa.

[0032] 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.

[0033] Optionally, 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 oxides is 1wt%-5wt%.

[0034] Optionally, the top discharge of the dehydration tower contains 70-90wt% of an oxide mixture and 10-30wt% of water, and the oxide mixture includes methanol, ethanol, n-propanol, isopropanol, butanol, butanone, pentanone, hexanone and pentenone; the water content in the bottom discharge is >99wt%, and the oxide content is <1wt%.

[0035] In the method provided by the present invention, the acetaldehyde and light components refer to acetaldehyde and / or other organic oxide-containing components having a boiling point less than 50° C. under normal pressure.

[0036] Optionally, the operating conditions of the methanol-acetone azeotrope tower are: tower top temperature is 85-155°C, tower bottom temperature is 115-185°C, and reflux ratio is 5-20.

[0037] In the method provided by the present invention, the mass ratio of acetone to methanol in the oxygenate waste liquid to be treated is 0.5-3.0, the contents of acetone and methanol in the oxygenate waste liquid are analyzed and monitored, the mass ratio of acetone to methanol is calculated, and as the mass ratio of acetone to methanol decreases, the operating pressure of the methanol-acetone azeotrope tower is increased accordingly. In a preferred embodiment, the mass ratio of acetone to methanol is 2-3, the operating pressure of the methanol-acetone azeotrope tower is 0.20-0.35MPa, the top temperature of the methanol-acetone azeotrope tower is 85-100°C, and the bottom temperature is 115-130°C.

[0038] In a preferred embodiment, the mass ratio of acetone to methanol is 1-2, the operating pressure of the methanol-acetone azeotrope tower is 0.35-1.0 MPa, the top temperature of the methanol-acetone azeotrope tower is 100-135°C, and the bottom temperature is 130-165°C.

[0039] In a preferred embodiment, the mass ratio of acetone to methanol is 0.5-1, the operating pressure of the methanol-acetone azeotrope tower is 1.0-1.5 MPa, the top temperature of the methanol-acetone azeotrope tower is 135-155°C, and the bottom temperature is 165-185°C.

[0040] In the method provided by the present invention, the operating conditions of the lightness removal tower are: pressure of 0-0.15 MPa, tower top temperature of 20-50°C, tower bottom temperature of 70-120°C, and reflux ratio of 2-10;

[0041] The operating conditions of the dehydration tower are: absolute pressure of 30-200 kPa, reflux ratio of 0.5-5, tower top temperature of 40-90°C, and tower bottom temperature of 70-120°C.

[0042] Optionally, the methanol-acetone separation system adopts an acetone extraction tower and a methanol recovery tower connected in series, and the methanol-acetone azeotrope is sent to the acetone extraction tower, and water is used as the extractant for extraction and separation, and an acetone product is obtained at the top of the tower, and a methanol-water mixture is obtained at the bottom of the tower; the methanol-water mixture enters the methanol recovery tower for separation to obtain a methanol product.

[0043] Preferably, the operating conditions of the acetone extraction tower are: pressure of 0.5-2.0 MPa, reflux ratio of 1-5, tower top temperature of 110-165°C, tower bottom temperature of 120-185°C, and mass ratio of extractant to feed of 1.0-10.0;

[0044] The operating conditions of the methanol recovery tower are: pressure of 0-1.0MPa, tower top temperature of 55-135°C, tower bottom temperature of 65-145°C, and reflux ratio of 1-5.

[0045] Optionally, the methanol-acetone separation system adopts a pressure swing azeotropic distillation method to send the methanol-acetone azeotrope to a methanol tower, the bottom discharge of the methanol tower is a methanol product, the top discharge enters an acetone tower, the acetone product is obtained at the bottom of the acetone tower, and the top discharge is returned to the methanol tower; wherein the operating pressure of the acetone tower is 0.5-1.5 MPa higher than the operating pressure of the methanol tower.

[0046] Preferably, the operating conditions of the methanol tower are: pressure 0-1.0 MPa, tower top temperature 55-135°C, tower bottom temperature 65-145°C, and reflux ratio 1-5; the operating conditions of the acetone tower are: pressure 0.5-2.0 MPa, tower top temperature 110-165°C, tower bottom temperature 120-185°C, and reflux ratio 1-5.

[0047] In the method provided by the present invention, the oxide waste liquid may 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, pentenone, etc. Except for acetaldehyde, these oxides can form a variety of azeotropes with each other, which are difficult to separate.

[0048] In a second aspect, the present invention provides a separation system for recovering methanol and acetone in oxide waste liquid, which is used in the above-mentioned method for recovering methanol and acetone in oxide waste liquid, comprising a light removal tower, a methanol-acetone azeotrope tower, a dehydration tower, a methanol tower and an acetone tower connected in sequence;

[0049] The light removal tower is used to separate low-boiling-point organic oxygen-containing substances, the top discharge of which is the acetaldehyde product outlet, and the bottom discharge is connected to the raw material inlet of the methanol-acetone azeotrope tower;

[0050] The methanol-acetone azeotrope tower is used to separate the methanol-acetone azeotrope, and the top discharge of the methanol-acetone azeotrope tower is connected to the raw material inlet of the methanol tower; the bottom discharge is connected to the raw material inlet of the dehydration tower;

[0051] The methanol tower and the acetone tower are used for separating methanol-acetone azeotrope, the bottom discharge of the methanol tower is the methanol product outlet, and the top discharge is connected to the acetone tower, the bottom discharge of the acetone tower is the acetone product outlet, and the top discharge of the acetone tower is connected to the methanol tower;

[0052] The dehydration tower is used to concentrate the oxide mixture, the top discharge of the dehydration tower is the mixed oxide outlet, and the bottom discharge of the tower is the waste water outlet.

[0053] In a third 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 wastewater 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; and any of the above methods for recovering methanol and acetone in the waste liquid containing oxides is used to treat the waste liquid containing oxides to obtain an acetone product and a methanol product.

[0054] 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 is obtained at the top of the tower, wherein the acetaldehyde purity is >98%, and other low-boiling organic oxygen-containing compounds, such as ether and dimethyl ether, may also be contained. The bottom discharge is fed into a methanol-acetone azeotrope tower for distillation separation, and a methanol-acetone azeotrope 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%.

[0055] A preferred embodiment of the method provided by the present invention is to transport the methanol-acetone azeotrope to an acetone extraction distillation tower, separate them using water as an extractant, obtain an acetone product with a purity of >96% at the top of the tower, and obtain 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.

[0056] The method for recovering methanol and acetone from oxide waste liquid provided by the present invention extracts methanol and acetone from the oxide waste liquid in the form of an azeotrope, and can treat the oxide waste liquid at a lower temperature to reduce the content of oxides therein. Further separation of the methanol-acetone azeotrope can obtain high-purity methanol and acetone products, creating new revenue for the enterprise.

[0057] 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.

[0058] 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.

[0059] 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, the mass ratio of acetone to methanol in the oxide waste liquid to be treated is 0.5-3.0, the oxide waste liquid 1 first enters the light removal tower 2, the light component 3 is extracted from the top of the tower for separate collection and treatment, the bottom of the tower extract 4 is pressurized by the liquid phase booster pump 5 and then enters the methanol-acetone azeotrope tower 6, and the operating pressure of the methanol-acetone azeotrope tower 6 is 0.1-1.0MPa. The methanol-acetone azeotrope 7 is extracted from the top of the methanol-acetone azeotrope tower 6 and introduced into the methanol tower 9 in the methanol-acetone pressure swing combination separation tower, the methanol product 12 is obtained at the bottom of the methanol tower, the mixed material 10 is extracted from the top of the tower, and enters the acetone tower 13 after the boost pressure is adjusted, the acetone product 15 is obtained at the bottom of the acetone tower, and the mixed material 14 is extracted from the top of the tower and returned to the methanol tower 9. The remaining material 8 is taken out from the bottom of the methanol-acetone pressure swing azeotropic tower and enters the dehydration tower 16, and the high-concentration oxide 17 is taken out from the top of the tower. The waste water 18 after the treatment of the bottom material is discharged from the device and subjected to subsequent wastewater treatment.

[0060] The present invention is further described in detail below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0061] The oxide-containing waste liquid used in the embodiment comes from the condensed liquid at the bottom of the high fraction tank at the top of the stripping tower after the methanol to olefins reactor. The composition of the oxide waste liquid is shown in Table 1.

[0062] In the embodiment, the purity of the acetaldehyde product, the methanol product and the acetone product was analyzed by gas chromatography, and the yield of each component was calculated as follows:

[0063]

[0064] Where Q is the mass flow rate of the logistics, unit is kg / h, and wt is the mass fraction of the target component in the logistics.

[0065] Example 1

[0066] The mass ratio of acetone to methanol in the oxide waste liquid is 1.45. Figure 1 In the process shown, the oxide waste liquid first enters the light removal tower, which operates at normal pressure, and the acetaldehyde product is extracted from the top of the tower. The bottom discharge of the tower is pressurized by the liquid phase booster pump and then enters the methanol-acetone azeotrope tower. The operating pressure of the methanol-acetone azeotrope tower is 0.5MPa. The methanol-acetone azeotrope is extracted from the top of the methanol-acetone azeotrope tower and introduced into the methanol tower. The operating pressure of the methanol tower is normal pressure. The methanol product is obtained at the bottom of the methanol tower. The top discharge pressure is adjusted and enters the acetone tower. The operating pressure of the acetone tower is 1.0MPa. The acetone product is obtained at the bottom of the acetone tower, and the top discharge returns to the methanol tower. The bottom discharge of the methanol-acetone azeotrope tower enters the dehydration tower, which operates at normal pressure. The high-concentration oxide is extracted from the top of the dehydration tower, and the wastewater at the bottom of the tower is discharged from the device. Other operating conditions of each distillation tower are shown in Table 2, and the purity and yield of each product are shown in Table 3.

[0067] Example 2

[0068] The process flow is the same as that of Example 1, the oxide waste liquid to be treated is the same as that of Example 1, and the operating conditions of the lightness removal tower, methanol tower, and dehydration tower are the same as those of Example 1. The difference is that the operating pressure of the methanol-acetone azeotrope tower is 0.3 MPa. Other operating conditions of each distillation tower are shown in Table 2, and the purity and yield of each product are shown in Table 3.

[0069] Table 1

[0070]

[0071]

[0072] Table 2

[0073]

[0074]

[0075] Table 3

[0076] Instance Number Example 1 Example 2 Acetaldehyde purity, wt% 99.9 99.9 Acetaldehyde recovery rate, % 99.6 99.6 Methanol purity, wt% 97.3 97.4 Methanol recovery rate, % 88.4 49.2 Acetone purity, wt% 99.4 99.3 Acetone recovery, % 82.7 84.9 Mixed oxide purity, wt% 83.6 88.8 Water purity, wt% 99.5 99.2 Water recovery rate, % 93.4 97.5

[0077] It can be seen from the data in Table 2-3 that, when other operating conditions are basically the same, the operating pressure of the methanol-acetone azeotrope tower is increased from 0.3MPa to 0.5MPa, and the methanol recovery rate can be increased from 49.2% to 88.4%. Other separation effects are basically the same, and the system efficiency is significantly improved.

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, and the bottom discharge enters a methanol-acetone azeotrope tower, and the methanol-acetone azeotrope obtained at the top of the tower is sent to a methanol-acetone separation system to separate and obtain acetone products and methanol products; 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 is treated wastewater; wherein, in the waste liquid containing oxides, the mass ratio of acetone to methanol is 0.5-3.0, and the operating pressure of the methanol-acetone azeotrope tower is 0.1-1.5MPa.

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 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 top discharge of the dehydration tower contains 70-90wt% of an oxide mixture and 10-30wt% of water, wherein the oxide mixture includes methanol, ethanol, n-propanol, isopropanol, butanol, butanone, pentanone, hexanone and pentenone; the water content of the bottom discharge is greater than 99wt%, and the oxide content is less than 1wt%.

5. 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: the tower top temperature is 70-160°C, the tower bottom temperature is 100-200°C, and the reflux ratio is 5-20.

6. The method for recovering methanol and acetone in oxide waste liquid according to claim 5, characterized in that: The operating conditions of the methanol-acetone azeotrope tower are: the tower top temperature is 85-155°C, and the tower bottom temperature is 115-185°C.

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 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 dehydration tower are: absolute pressure of 30-200 kPa, reflux ratio of 0.5-5, tower top temperature of 40-90°C, and tower bottom temperature of 70-120°C.

8. The method for recovering methanol and acetone from oxide waste liquid according to any one of claims 1 to 3, characterized in that: The methanol-acetone separation system adopts an acetone extraction tower and a methanol recovery tower connected in series, and the methanol-acetone azeotrope is sent to the acetone extraction tower, and water is used as an extractant for extraction and separation, and an acetone product is obtained at the top of the tower, and a methanol-water mixture is obtained at the bottom of the tower; the methanol-water mixture enters the methanol recovery tower for separation to obtain a methanol product.

9. The method for recovering methanol and acetone in oxide waste liquid according to claim 8, characterized in that: The operating conditions of the acetone extraction tower are: pressure of 0.5-2.0 MPa, reflux ratio of 1-5, tower top temperature of 110-165°C, tower bottom temperature of 120-185°C, and mass ratio of extractant to feed of 1.0-10.0; The operating conditions of the methanol recovery tower are: pressure of 0-1.0MPa, reflux ratio of 1-5, tower top temperature of 55-135°C, and tower bottom temperature of 65-145°C.

10. The method for recovering methanol and acetone from oxide waste liquid according to any one of claims 1 to 3, characterized in that: The methanol-acetone separation system adopts a pressure swing azeotropic distillation method to send the methanol-acetone azeotrope to a methanol tower. The bottom discharge of the methanol tower is a methanol product, and the top discharge enters an acetone tower. The acetone product is obtained at the bottom of the acetone tower, and the top discharge returns to the methanol tower; wherein the operating pressure of the acetone tower is 0.5-1.5 MPa higher than the operating pressure of the methanol tower.

11. The method for recovering methanol and acetone in oxide waste liquid according to claim 10, characterized in that: The operating conditions of the acetone tower are: pressure 0.5-2.0MPa, reflux ratio 1-5, tower top temperature 110-165℃, tower bottom temperature 120-185℃; The operating conditions of the methanol tower are: pressure 0-1.0MPa, reflux ratio 1-5, tower top temperature 55-135°C, and tower bottom temperature 65-145°C.

12. A separation system for recovering methanol and acetone from oxide waste liquid, used in the method for recovering methanol and acetone from oxide waste liquid according to claim 10 or 11, characterized in that: It comprises a light removal tower, a methanol-acetone azeotrope tower, a dehydration tower, a methanol tower and an acetone tower which are connected in sequence; The light removal tower is used to separate low-boiling-point organic oxygen-containing substances, the top discharge of which is the acetaldehyde product outlet, and the bottom discharge is connected to the raw material inlet of the methanol-acetone azeotrope tower; The methanol-acetone azeotrope tower is used to separate the methanol-acetone azeotrope, and the top discharge of the methanol-acetone azeotrope tower is connected to the raw material inlet of the methanol tower; the bottom discharge is connected to the raw material inlet of the dehydration tower; The methanol tower and the acetone tower are used for separating methanol-acetone azeotrope, the bottom discharge of the methanol tower is the methanol product outlet, and the top discharge is connected to the acetone tower, the bottom discharge of the acetone tower is the acetone product outlet, and the top discharge of the acetone tower is connected to the methanol tower; The dehydration tower is used to concentrate the oxide mixture, the top discharge of the dehydration tower is the mixed oxide outlet, and the bottom discharge of the tower is the waste water outlet.

13. 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 11 is used to treat the oxide-containing waste liquid to obtain an acetone product and a methanol product.

Images