A methanol recovery system for ethylene glycol rectification

Abstract

This invention discloses an ethylene glycol distillation methanol recovery system, comprising: a first methanol recovery tower, a second methanol recovery tower, a dehydration tower, an ethanol recovery tower, a mixed alcohol-ester tank, and a flow divider assembly; the second methanol recovery tower is connected to the first methanol recovery tower; the dehydration tower is connected to the second methanol recovery tower; the ethanol recovery tower is connected to the dehydration tower; the mixed alcohol-ester tank is connected to the ethanol recovery tower; one end of the flow divider assembly is connected to the first methanol recovery tower, and the other end is connected to the ethanol recovery tower. In this invention, when the catalyst deteriorates, the bottom liquid of the first methanol recovery tower is directly introduced into the ethanol recovery tower through the flow divider assembly. The methanol and ethanol in the bottom liquid of the first methanol recovery tower are separated by the distillation process of the ethanol recovery tower. This avoids the waste caused by directly sending the bottom liquid containing large amounts of ethylene glycol, methanol, and ethanol components into the mixed alcohol-ester tank, thus improving resource utilization.

Description

Technical Field

[0001] This utility model relates to the field of ethylene glycol refining technology in coal chemical industry, specifically to an ethylene glycol distillation methanol recovery system.

[0002] The coal-to-ethylene glycol process uses coal as raw material. After gasification, conversion, purification, and separation, CO and H2 are obtained. CO is synthesized and refined through catalytic coupling to produce dimethyl oxalate, which is then hydrogenated with H2 in the presence of a copper catalyst to produce crude ethylene glycol. After condensation, separation, and flash evaporation, liquid-phase crude ethylene glycol and crude methanol are obtained and sent to the ethylene glycol refining and separation unit for distillation to finally obtain polyester-grade ethylene glycol.

[0003] In an ethylene glycol distillation methanol recovery system, a first methanol recovery tower and a second methanol recovery tower are typically installed. In normal operation: the bottom liquid from the first methanol recovery tower is sent to the second methanol recovery tower for further distillation, with recovered methanol collected at the top; the bottom liquid from the second methanol recovery tower is sent to a dehydration tower for dehydration. The top liquid from the dehydration tower contains lighter components such as water, methanol, and methyl glycolate, while the bottom liquid is sent to a subsequent distillation tower for purification to produce qualified ethylene glycol. The components collected at the top of the dehydration tower are sent to an ethanol recovery tower. In the ethanol recovery tower, recovered ethanol is collected via a side stream, recovered methanol is collected via reflux at the top, and the bottom liquid is sent to a mixed alcohol-ester tank for sale as a byproduct.

[0004] However, when the ethylene glycol synthesis hydrogenation catalyst deteriorates at the end of its lifespan, it is often accompanied by dimethyl oxalate breakthrough and an increase in unknown components, leading to a severe deterioration in the quality of the crude alcohol entering the distillation system. In order to ensure the quality of the final ethylene glycol product, the bottom liquid of the first methanol recovery tower is directly sent to the mixed alcohol ester tank for sale as mixed alcohol esters. However, the bottom liquid of the first methanol recovery tower contains a high concentration of valuable ethylene glycol, methanol, and ethanol components, ultimately resulting in serious waste of resources. Utility Model Content

[0005] To address the technical problem in the prior art where the methanol distillation recovery tower bottom liquid is entirely sent to a mixed alcohol ester tank for sale when the ethylene glycol synthesis hydrogenation catalyst deteriorates, resulting in the waste of a large amount of valuable ethylene glycol, methanol, and ethanol components, this invention provides an ethylene glycol distillation methanol recovery system.

[0006] This utility model discloses an ethylene glycol distillation methanol recovery system. When catalyst deterioration leads to a decline in the quality of the bottom liquid in the first methanol recovery tower, rendering it unsuitable for subsequent distillation systems to produce qualified ethylene glycol, the system uses a splitter assembly to directly introduce the bottom liquid from the first methanol recovery tower into an ethanol recovery tower. The ethanol recovery tower then utilizes its distillation properties to separate methanol and ethanol from the bottom liquid of the first methanol recovery tower. This avoids the waste caused by directly sending the bottom liquid containing large amounts of ethylene glycol, methanol, and ethanol to a mixed alcohol-ester tank, thus improving resource utilization.

[0007] An ethylene glycol distillation methanol recovery system includes: a first methanol recovery tower, a second methanol recovery tower, a dehydration tower, an ethanol recovery tower, a mixed alcohol-ester tank, and a flow divider assembly; the second methanol recovery tower is connected to the bottom of the first methanol recovery tower; the dehydration tower is connected to the bottom of the second methanol recovery tower; the ethanol recovery tower is connected to the top of the dehydration tower; the mixed alcohol-ester tank is connected to the bottom of the ethanol recovery tower; the flow divider assembly has one end connected to the bottom of the first methanol recovery tower and the other end connected to the ethanol recovery tower, and the flow divider assembly is used to adjust the flow of liquid from the bottom of the first methanol recovery tower to the ethanol recovery tower.

[0008] Optionally, the diversion assembly includes: a diversion pipeline and a first switching valve; one end of the diversion pipeline is connected to the bottom of the first methanol recovery tower, and the other end is connected to the ethanol recovery tower; the first switching valve is installed on the diversion pipeline.

[0009] Optionally, the bottom of the first methanol recovery tower is connected to the second methanol recovery tower via a first connecting pipeline.

[0010] Optionally, the top of the dehydration tower is connected to the ethanol recovery tower via a second connecting pipeline.

[0011] Optionally, one end of the diversion pipeline is connected to the first connecting pipeline, and the other end is connected to the second connecting pipeline; a second switching valve is installed on the first connecting pipeline, and the second switching valve is located between the diversion pipeline and the second methanol recovery tower.

[0012] Optionally, a first condenser is provided at the top of the first methanol recovery tower.

[0013] Optionally, a second condenser is provided at the top of the second methanol recovery tower.

[0014] Optionally, a third condenser is provided at the top of the ethanol recovery tower.

[0015] Optionally, the ethylene glycol distillation methanol recovery system further includes: a dehydration tower reflux tank, one end of which is connected to the top of the dehydration tower, and the other end of which is connected to the ethanol recovery tower.

[0016] This utility model has the following beneficial effects:

[0017] This utility model discloses an ethylene glycol distillation methanol recovery system. When catalyst deterioration leads to a decline in the quality of the bottom liquid in the first methanol recovery tower, rendering it unsuitable for subsequent distillation systems to produce qualified ethylene glycol, the system uses a splitter assembly to directly introduce the bottom liquid from the first methanol recovery tower into an ethanol recovery tower. The ethanol recovery tower then utilizes its distillation properties to separate methanol and ethanol from the bottom liquid of the first methanol recovery tower. This avoids the waste caused by directly sending the bottom liquid containing large amounts of ethylene glycol, methanol, and ethanol to a mixed alcohol-ester tank, thus improving resource utilization. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the ethylene glycol distillation methanol recovery system of this utility model.

[0019] In the diagram: 1. First methanol recovery tower; 2. Second methanol recovery tower; 3. Dehydration tower; 4. Ethanol recovery tower; 5. Mixed alcohol-ester tank; 6. Diversion pipeline; 7. First connecting pipeline; 8. Second connecting pipeline; 9. First condenser; 10. Second condenser; 11. Third condenser; 12. Dehydration tower reflux tank. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0021] Example 1:

[0022] Reference Figure 1 This embodiment discloses an ethylene glycol distillation methanol recovery system, including: a first methanol recovery tower 1, a second methanol recovery tower 2, a dehydration tower 3, a dehydration tower reflux tank 12, an ethanol recovery tower 4, a mixed alcohol ester tank 5, and a diversion component.

[0023] The first methanol recovery tower 1 is used for the preliminary separation of methanol from crude alcohol. A first condenser 9 is installed at the top of the first methanol recovery tower 1. The first condenser 9 is used to condense the top vapor of the tower; part of the condensate is refluxed, and part is collected as methanol product. The bottom liquid of the first methanol recovery tower 1 contains ethylene glycol, methanol, ethanol, water, and dimethyl oxalate, etc.

[0024] The second methanol recovery tower 2 is connected to the bottom of the first methanol recovery tower 1 and is used for further distillation of the bottom liquid of the first methanol recovery tower 1 to recover methanol. A second condenser 10 is installed at the top of the second methanol recovery tower 2. The recovered methanol is collected from the top of the second methanol recovery tower 2, and the bottom liquid of the second methanol recovery tower 2 mainly contains ethylene glycol, water, and heavy components.

[0025] Dehydration tower 3 is connected to the bottom of the second methanol recovery tower 2. Dehydration tower 3 receives the liquid from the bottom of the second methanol recovery tower 2 and performs dehydration. Vapor containing light components (water, methanol, methyl glycolate, etc.) is collected from the top of dehydration tower 3.

[0026] One end of the dehydration tower reflux tank 12 is connected to the top of the dehydration tower 3 to receive the vapor containing light components from the top of the dehydration tower 3, and the other end is connected to the ethanol recovery tower 4. Non-condensable gas is discharged from the top of the dehydration tower reflux tank 12, and part of the liquid at the bottom of the dehydration tower reflux tank 12 is returned to the top of the dehydration tower 3, while the other part is collected and sent to the ethanol recovery tower 4.

[0027] The feed inlet of the ethanol recovery tower 4 is connected to the outlet of the dehydration tower reflux tank 12 via a second connecting pipeline 8, receiving steam containing light components from the top of the dehydration tower 3. A third condenser 11 is installed at the top of the ethanol recovery tower 4. Methanol is recovered from the top of the ethanol recovery tower 4, and a side outlet is provided in the tower body of the ethanol recovery tower 4 to recover ethanol. The bottom liquid of the ethanol recovery tower 4 mainly consists of heavy components (mixed alcohol esters).

[0028] The mixed alcohol ester tank 5 is connected to the bottom of the ethanol recovery tower 4. The mixed alcohol ester tank 5 collects and stores the bottom liquid of the ethanol recovery tower 4 as a by-product for sale.

[0029] One end of the diversion component is connected to the bottom of the first methanol recovery tower 1, and the other end is connected to the ethanol recovery tower 4. The diversion component is used to adjust the flow of the liquid from the bottom of the first methanol recovery tower 1 to the ethanol recovery tower 4.

[0030] Reference Figure 1 The diversion assembly includes a diversion line 6 and a first switching valve. One end of the diversion line 6 is connected to the bottom of the first methanol recovery tower 1, and the other end is connected to the ethanol recovery tower 4; the diversion line 6 is made of DN25 stainless steel. The first switching valve is installed on the diversion line 6 and is used to control the on / off state of the diversion line 6.

[0031] Reference Figure 1 The bottom of the first methanol recovery tower 1 is connected to the second methanol recovery tower 2 via a first connecting pipeline 7. The top of the dehydration tower 3 is connected to the ethanol recovery tower 4 via a second connecting pipeline 8. One end of the diversion pipeline 6 is connected to the first connecting pipeline 7, and the other end is connected to the second connecting pipeline 8. A second switching valve is installed on the first connecting pipeline 7, and the second switching valve is located between the diversion pipeline 6 and the second methanol recovery tower 2. This arrangement allows for flexible adjustment of the bottom liquid entering the second methanol recovery tower 2 via the second switching valve to adapt to different operating conditions.

[0032] The working principle of the ethylene glycol distillation methanol recovery system of this utility model is as follows: Under normal operating conditions: the first switching valve on the diversion pipeline 6 is closed, and the second switching valve on the first connecting pipeline 7 is opened; the bottom liquid of the first methanol recovery tower 1 enters the second methanol recovery tower 2 for distillation through the first connecting pipeline 7. Methanol is recovered from the top of the second methanol recovery tower 2, and the bottom liquid of the second methanol recovery tower 2 enters the dehydration tower 3 for dehydration; the top vapor of the dehydration tower 3 enters the dehydration tower reflux tank 12, and the bottom liquid enters the ethanol recovery tower 4 through the second connecting pipeline 8; in the ethanol recovery tower 4, methanol is recovered from the top, ethanol is collected from the side stream, and the bottom liquid is sent to the mixed alcohol ester tank 5.

[0033] Under catalyst deterioration conditions: Close the second switching valve on the first connecting pipeline 7 and open the first switching valve on the diversion pipeline 6. The bottom liquid of the first methanol recovery tower 1 no longer enters the second methanol recovery tower 2. The bottom liquid flows directly into the second connecting pipeline 8 through the diversion pipeline 6, mixes with the material from the dehydration tower reflux tank 12, and then enters the ethanol recovery tower 4 together. In the ethanol recovery tower 4, the mixed feed is distilled, methanol is recovered from the top of the tower, ethanol is recovered from the side stream, and the mixed alcohol esters from the bottom of the tower are sent to the mixed alcohol ester tank 5.

[0034] Obviously, the embodiments described above are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0037] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A methanol recovery system for rectifying ethylene glycol, characterized by, include: First methanol recovery tower (1); The second methanol recovery tower (2) is connected to the bottom of the first methanol recovery tower (1); The dehydration tower (3) is connected to the bottom of the second methanol recovery tower (2); The ethanol recovery tower (4) is connected to the top of the dehydration tower (3); The mixing alcohol ester tank (5) is connected to the bottom of the ethanol recovery tower (4); The diversion component has one end connected to the bottom of the first methanol recovery tower (1) and the other end connected to the ethanol recovery tower (4). The diversion component is used to adjust the flow of the bottom liquid of the first methanol recovery tower (1) to the ethanol recovery tower (4).

2. The ethylene glycol rectification methanol recovery system of claim 1, wherein, The splitter component includes: The diversion pipeline (6) is connected at one end to the bottom of the first methanol recovery tower (1) and at the other end to the ethanol recovery tower (4). The first switching valve is installed on the diversion line (6).

3. The methanol recovery system for rectifying ethylene glycol according to claim 2, characterized in that: The bottom of the first methanol recovery tower (1) is connected to the second methanol recovery tower (2) through the first connecting pipeline (7).

4. The methanol recovery system of claim 3, wherein, The top of the dehydration tower (3) is connected to the ethanol recovery tower (4) via a second connecting pipeline (8).

5. The methanol recovery system of claim 4, wherein, One end of the diversion pipeline (6) is connected to the first connecting pipeline (7), and the other end is connected to the second connecting pipeline (8); A second switching valve is installed on the first connecting pipeline (7), and the second switching valve is located between the diversion pipeline (6) and the second methanol recovery tower (2).

6. The ethylene glycol rectification methanol recovery system of claim 1, wherein: A first condenser (9) is provided at the top of the first methanol recovery tower (1).

7. The methanol recovery system of claim 1, wherein: A second condenser (10) is provided at the top of the second methanol recovery tower (2).

8. The ethylene glycol rectification methanol recovery system of claim 1, wherein: A third condenser (11) is provided at the top of the ethanol recovery tower (4).

9. The methanol recovery system from glycol rectification according to any one of claims 1 to 8, characterized in that, The ethylene glycol distillation methanol recovery system also includes: The dehydration tower reflux tank (12) is connected at one end to the top of the dehydration tower (3) and at the other end to the ethanol recovery tower (4).

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