阅读说明：本技术 一种乙二醇水溶液的蒸馏方法和蒸馏装置 (Method and device for distilling ethylene glycol aqueous solution ) 是由 杨建春 汪帆 朱荣欣 于 2020-05-18 设计创作，主要内容包括：本发明公开一种乙二醇水溶液的蒸馏方法和蒸馏装置。所述蒸馏方法包括如下步骤：乙二醇水溶液粗品在进行多效蒸发之前,先经过预浓缩,得到含水量降低的乙二醇水溶液；所述预浓缩的热源由乙烯氧化制备环氧乙烷/乙二醇过程中的低品质热源提供。在负压下操作,脱除乙二醇水溶液中的部分水,降低了乙二醇水溶液脱水操作的能耗。(The invention discloses a distillation method and a distillation device for an ethylene glycol aqueous solution. The distillation method comprises the following steps: pre-concentrating the crude product of the ethylene glycol aqueous solution before multi-effect evaporation to obtain the ethylene glycol aqueous solution with reduced water content; the pre-concentrated heat source is provided by a low-quality heat source in the process of preparing ethylene oxide/glycol by oxidizing ethylene. And the operation is carried out under negative pressure, part of water in the glycol aqueous solution is removed, and the energy consumption of the glycol aqueous solution dehydration operation is reduced.)

1. A method for distilling an aqueous ethylene glycol solution, comprising the steps of: pre-concentrating the crude product of the ethylene glycol aqueous solution before multi-effect evaporation to obtain the ethylene glycol aqueous solution with reduced water content;

the pre-concentrated heat source is provided by a low-quality heat source in the process of preparing ethylene oxide/glycol by oxidizing ethylene.

2. Distillation method according to claim 1, characterized in that it comprises the following steps: preparing ethylene glycol from ethylene oxide to obtain a crude product, namely a crude product of ethylene glycol aqueous solution; pre-concentrating the crude product of the ethylene glycol aqueous solution to obtain the ethylene glycol aqueous solution with reduced water content; the glycol aqueous solution with the reduced water content is subjected to multi-effect evaporation to obtain a glycol concentrated solution;

wherein the pre-concentrated heat source is provided by a low-quality heat source in the process of preparing ethylene oxide/glycol by ethylene oxidation.

3. The distillation method of claim 1 or 2, wherein the low quality heat source comprises at least one of ethylene oxide reaction product, ethylene oxide absorption lean liquor, ethylene oxide stripper overhead vapor, carbon dioxide stripper overhead vapor, ethylene oxide rectifier overhead vapor, ethylene glycol aqueous solution multi-effect evaporation last-effect obtained overhead vapor, and ethylene glycol dehydration tower overhead vapor.

4. Distillation method according to any one of claims 1 to 3, characterised in that the preconcentration is a concentration by distillation under negative pressure.

5. Method for distilling an aqueous ethylene glycol solution according to any one of claims 1 to 4, characterized in that it comprises the following steps:

(1) preparing a crude product of ethylene glycol aqueous solution by hydration reaction of a mixture of ethylene oxide and water;

(2) pre-concentrating the crude product of the ethylene glycol aqueous solution to obtain the ethylene glycol aqueous solution with reduced water content;

(3) the glycol aqueous solution with the reduced water content is subjected to multi-effect evaporation to obtain a glycol concentrated solution;

(4) dehydrating and rectifying the ethylene glycol concentrated solution to obtain pure ethylene glycol;

the pre-concentrated heat source comprises at least one of ethylene oxide reaction products, ethylene oxide absorption barren liquor, gas phase at the top of an ethylene oxide stripping tower, gas phase at the top of a carbon dioxide stripping tower, gas phase at the top of an ethylene oxide rectifying tower, tower top steam obtained by multi-effect evaporation of an ethylene glycol aqueous solution and tower top steam of an ethylene glycol dehydrating tower.

6. An ethylene glycol aqueous solution distillation apparatus, characterized in that the distillation apparatus comprises: a pre-concentration tower and a multi-effect evaporator;

the material inlet of the pre-concentration tower is connected with the material outlet of the ethylene glycol reaction device, and the material inlet of the multi-effect evaporator is connected with the material outlet of the pre-concentration tower;

at least one reboiler is arranged at the bottom of the pre-concentration tower, and a heat exchange medium inlet of the reboiler is connected with at least one of an ethylene oxide reaction product pipeline, an ethylene oxide absorption lean solution pipeline, an ethylene oxide stripping tower top gas phase pipeline, an ethylene oxide rectification tower top gas phase pipeline, a carbon dioxide stripping tower top gas phase pipeline, a multi-effect evaporator last effect tower top steam pipeline and an ethylene glycol dehydration tower top gas phase pipeline.

7. A system for producing ethylene glycol from ethylene oxide, the system comprising an ethylene oxide production unit, an ethylene glycol production unit, and an ethylene glycol purification unit;

the ethylene oxide preparation unit comprises an ethylene oxide reactor, an ethylene oxide absorption tower, an ethylene oxide stripping tower, an ethylene oxide rectifying tower and a carbon dioxide stripping tower;

the ethylene glycol preparation unit comprises an ethylene glycol reaction device;

the ethylene glycol purification unit comprises a distillation device, an ethylene glycol dehydration tower and an ethylene glycol rectification tower;

the distillation apparatus comprises: a pre-concentration tower and a multi-effect evaporator;

the material inlet of the pre-concentration tower is connected with the material outlet of the ethylene glycol reaction device, and the material inlet of the multi-effect evaporator is connected with the material outlet of the pre-concentration tower;

at least one reboiler is arranged at the bottom of the pre-concentration tower, and a heat exchange medium inlet of the reboiler is connected with at least one of an ethylene oxide reaction product pipeline, an ethylene oxide absorption lean solution pipeline, an ethylene oxide stripping tower top gas phase pipeline, an ethylene oxide rectification tower top gas phase pipeline, a carbon dioxide stripping tower top gas phase pipeline, a multi-effect evaporator last-effect tower top steam pipeline and an ethylene glycol dehydration tower top steam pipeline.

8. The apparatus of claim 6 or the system of claim 7, wherein the number of reboilers is two, three, four, or more.

9. The apparatus of claim 6 or any of the systems of claims 7-8, wherein a condenser is disposed at the top of the pre-concentration column.

10. The apparatus or system according to claim 9, wherein the feed inlet of the condenser is connected to the top gas phase outlet of the pre-concentration column, and the feed outlet of the condenser is connected to the upper part of the pre-concentration column and/or to an external pipeline.

Technical Field

The invention belongs to the field of ethylene glycol preparation, and particularly relates to a distillation method and a distillation device for an ethylene glycol aqueous solution.

Background

Ethylene Oxide (EO) is an important organic compound, and is mainly used as a raw material for preparing Ethylene Glycol (EG). The dominant process for ethylene oxide/ethylene glycol production is the ethylene oxidation process, which includes an oxidation reaction unit and separation units for ethylene oxide absorption/stripping, carbon dioxide absorption/stripping, ethylene oxide rectification, etc. The mixture of ethylene, oxygen and auxiliary gas (nitrogen or methane) enters an ethylene oxidation reactor and reacts under the catalysis of a silver-based catalyst to obtain a reaction gas product; the reaction gas product passes through an ethylene oxide absorption tower, an EO absorbent absorbs ethylene oxide in the reaction gas product to obtain a recovered gas without ethylene oxide and an EO absorption rich solution, the EO absorption rich solution enters an ethylene oxide stripping tower, and ethylene oxide and EO absorption lean solution are obtained through stripping separation; the recovered gas without ethylene oxide contains carbon dioxide as a reaction by-product, and the recovered gas is introduced into a carbon dioxide absorption tower and is treated with CO₂Absorbing with absorbent to obtain recovered gas with reduced carbon dioxide content and CO₂Absorbing rich liquid, CO₂The absorption rich solution enters a carbon dioxide stripping tower for stripping and separating CO₂Absorbing carbon dioxide absorbed in the rich liquid and obtaining CO₂And absorbing the barren solution. The preparation of ethylene glycol from ethylene oxide comprises the preparation units: ethylene oxide enters an ethylene glycol preparation reactor, and a crude ethylene glycol aqueous solution is prepared through hydration reaction; an ethylene glycol purification unit: and (3) distilling and dehydrating the ethylene glycol aqueous solution crude product to obtain an ethylene glycol crude product, separating the ethylene glycol crude product by an ethylene glycol rectifying tower and optionally by a diethylene glycol rectifying tower to obtain pure ethylene glycol, wherein the ethylene glycol rectifying tower is provided with a side line for extraction.

A large amount of heat is released in the ethylene oxidation reaction process, the reaction heat is led out by water or heat conducting oil and is used for generating high-pressure steam and medium-pressure steam required by the operation of the device, and nevertheless, a large amount of external steam is still required for providing energy for the separation unit, so that a large energy-saving and consumption-reducing space exists in the ethylene oxide/ethylene glycol device.

Disclosure of Invention

The invention provides a distillation method of an ethylene glycol aqueous solution, which comprises the following steps: pre-concentrating the crude product of the ethylene glycol aqueous solution before multi-effect evaporation to obtain the ethylene glycol aqueous solution with reduced water content;

the pre-concentrated heat source is provided by a low-quality heat source in the process of preparing ethylene glycol from ethylene oxide.

Specifically, the distillation method comprises the following steps: preparing ethylene glycol from ethylene oxide to obtain a crude product, namely a crude product of ethylene glycol aqueous solution; pre-concentrating the crude product of the ethylene glycol aqueous solution to obtain the ethylene glycol aqueous solution with reduced water content; the glycol aqueous solution with the reduced water content is subjected to multi-effect evaporation to obtain a glycol concentrated solution;

wherein the pre-concentrated heat source is provided by a low-quality heat source in the process of preparing ethylene glycol from ethylene oxide.

For example, the low quality heat source includes at least one of ethylene oxide reaction product, ethylene oxide absorption lean solution, ethylene oxide stripper overhead vapor, carbon dioxide stripper overhead vapor, ethylene oxide rectifier overhead vapor, overhead vapor from the last effect of multi-effect evaporation of aqueous ethylene glycol, and ethylene glycol dehydration column overhead vapor.

According to an embodiment of the invention, the pre-concentration is a concentration by distillation under negative pressure.

According to an embodiment of the invention, the pre-concentrated heat source comprises at least one of ethylene oxide reaction products, ethylene oxide absorption lean liquor, ethylene oxide stripper overhead vapor, carbon dioxide stripper overhead vapor, ethylene oxide rectifier overhead vapor, overhead vapor from multi-effect evaporation of aqueous ethylene glycol, and ethylene glycol dehydration column overhead vapor.

According to an embodiment of the present invention, the method for distilling an aqueous ethylene glycol solution comprises the steps of:

(1) preparing a crude product of ethylene glycol aqueous solution by hydration reaction of a mixture of ethylene oxide and water;

(2) pre-concentrating the crude product of the ethylene glycol aqueous solution to obtain the ethylene glycol aqueous solution with reduced water content;

(3) the glycol aqueous solution with the reduced water content is subjected to multi-effect evaporation to obtain a glycol concentrated solution;

(4) dehydrating and rectifying the ethylene glycol concentrated solution to obtain pure ethylene glycol;

the pre-concentrated heat source comprises at least one of ethylene oxide reaction products, ethylene oxide absorption barren liquor, gas phase at the top of an ethylene oxide stripping tower, gas phase at the top of a carbon dioxide stripping tower, gas phase at the top of an ethylene oxide rectifying tower, tower top steam obtained by multi-effect evaporation of an ethylene glycol aqueous solution and tower top steam of an ethylene glycol dehydrating tower.

Preferably, the ethylene oxide reaction product is used as a heat source for heat exchange and then sent to an ethylene oxide absorption tower.

Preferably, the ethylene oxide absorption barren solution is taken as a heat source for heat exchange, and then is removed from the ethylene oxide absorption tower.

Preferably, the overhead ethylene oxide gas phase from the ethylene oxide stripping unit and the overhead ethylene oxide gas phase from the ethylene oxide rectifying unit are used as heat sources for heat exchange and then used as reaction raw materials or produced for preparing ethylene glycol.

Preferably, the overhead carbon dioxide gas phase from the carbon dioxide stripping unit is discharged or further treated for recovering carbon dioxide after heat exchange as a heat source.

Preferably, the water vapor from the top of the ethylene glycol dehydration unit is used as a heat source for heat exchange to obtain condensed liquid water, and the condensed liquid water is discharged or used as process water for reuse.

Preferably, the tower top steam obtained in the last effect of the multi-effect evaporation is used as a heat source for heat exchange to obtain condensed liquid water, and the condensed liquid water is discharged or used as process water for reuse.

The present invention also provides a distillation apparatus for ethylene glycol aqueous solution distillation, the distillation apparatus comprising: a pre-concentration tower and a multi-effect evaporator;

the material inlet of the pre-concentration tower is connected with the material outlet of the ethylene glycol reaction device, and the material inlet of the multi-effect evaporator is connected with the material outlet of the pre-concentration tower;

at least one reboiler is arranged at the bottom of the pre-concentration tower, and a heat exchange medium inlet of the reboiler is connected with at least one of an ethylene oxide reaction product pipeline, an ethylene oxide absorption lean solution pipeline, an ethylene oxide stripping tower top gas phase pipeline, an ethylene oxide rectification tower top gas phase pipeline, a carbon dioxide stripping tower top gas phase pipeline, a multi-effect evaporator last effect tower top steam pipeline and an ethylene glycol dehydration tower top gas phase pipeline.

The invention also provides a system for preparing ethylene glycol from ethylene oxide, which comprises an ethylene oxide preparation unit, an ethylene glycol preparation unit and an ethylene glycol purification unit;

the ethylene oxide preparation unit comprises an ethylene oxide reactor, an ethylene oxide absorption tower, an ethylene oxide stripping tower, an ethylene oxide rectifying tower and a carbon dioxide stripping tower;

the ethylene glycol preparation unit comprises an ethylene glycol reaction device;

the ethylene glycol purification unit comprises a distillation device, an ethylene glycol dehydration tower and an ethylene glycol rectification tower;

the distillation apparatus comprises: a pre-concentration tower and a multi-effect evaporator;

the material inlet of the pre-concentration tower is connected with the material outlet of the ethylene glycol reaction device, and the material inlet of the multi-effect evaporator is connected with the material outlet of the pre-concentration tower;

the tower bottom of the pre-concentration tower is provided with at least one reboiler, and a heat exchange medium inlet of the reboiler is connected with at least one of an ethylene oxide reaction product pipeline, an ethylene oxide absorption lean solution pipeline, an overhead gas phase pipeline of an ethylene oxide stripping tower, an overhead gas phase pipeline of an ethylene oxide rectifying tower, an overhead gas phase pipeline of a carbon dioxide stripping tower, an overhead gas phase pipeline of an ethylene glycol dehydrating tower and an overhead steam pipeline of a last-effect tower of a multi-effect evaporator.

According to embodiments of the invention, the number of reboilers may be two, three, four or more.

According to an embodiment of the invention, the top of the pre-concentration column is provided with a condenser. Preferably, a material inlet of the condenser is connected with a gas phase outlet at the top of the pre-concentration tower, and a material outlet of the condenser is connected with the upper part of the pre-concentration tower and/or is connected with an external pipeline.

According to an embodiment of the present invention, the number of the pre-concentration columns may be one, two or more, and may for example comprise two pre-concentration columns, three pre-concentration columns, or more pre-concentration columns in series.

According to an embodiment of the invention, the pre-concentration column comprises two pre-concentration columns in series, the bottom of the first pre-concentration column is provided with four reboilers, and the bottom of the second pre-concentration column is provided with three reboilers. Preferably, the heat exchange medium inlets of the four reboilers of the first preconcentration tower are respectively connected with an ethylene oxide reaction product pipeline, an ethylene oxide absorption lean solution pipeline, an ethylene oxide stripping tower top gas phase pipeline and a carbon dioxide stripping tower top gas phase pipeline. Preferably, the heat exchange medium inlets of the three reboilers of the second preconcentration tower are respectively connected with an ethylene oxide rectification tower top gas phase pipeline, an ethylene glycol dehydration tower top gas phase pipeline and a multi-effect evaporator last-effect tower top steam pipeline.

According to an embodiment of the invention, the ethylene oxide reaction product line is connected to the product outlet of the ethylene oxide reactor.

According to an embodiment of the present invention, the ethylene oxide absorption lean liquid line is connected to a take-off of the absorption lean liquid of the ethylene oxide stripper.

According to an embodiment of the invention, the ethylene oxide stripper overhead gas phase line is connected to an ethylene oxide stripper overhead gas phase take-off.

According to an embodiment of the invention, the carbon dioxide stripper overhead gas phase line is connected to a carbon dioxide stripper overhead gas phase take-off.

According to an embodiment of the invention, the ethylene oxide rectification column top gas phase pipeline is connected with an ethylene oxide rectification column top gas phase extraction outlet.

According to an embodiment of the present invention, the ethylene glycol dehydration column overhead gas phase line is connected to an ethylene glycol dehydration column overhead gas phase take-off port.

According to the embodiment of the invention, the last-effect overhead steam pipeline of the multi-effect evaporator is connected with a last-effect overhead steam extraction port of the multi-effect evaporator.

The invention has the beneficial effects that:

research shows that a system for preparing ethylene oxide/ethylene glycol by oxidizing ethylene has more low-temperature heat sources, although the heat load of the part of energy is large, because the grade of the part of energy is low, a heat sink matched with the part of energy is difficult to find, and an industrially common method is cooling by an air cooling or water cooling mode, so that great energy waste exists. The application provides a distillation method and a device of an ethylene glycol aqueous solution based on the above, wherein a pre-distillation step is added before the multi-effect evaporation and water removal of the ethylene glycol aqueous solution, low-quality heat sources such as tower top steam from an ethylene oxide reaction product, absorption barren liquor from an ethylene oxide absorption tower, ethylene oxide gas phase from the top of an ethylene oxide rectifying tower, carbon dioxide gas phase from the top of a carbon dioxide stripping tower, tower top steam from the last effect of a multi-effect evaporator and/or water steam from the top of an ethylene glycol dehydration tower are used for providing heat for the pre-distillation, and the device and the method operate under negative pressure to remove part of water in the ethylene glycol aqueous solution, thereby reducing the energy consumption of an ethylene glycol production device.

Drawings

Fig. 1 is a distillation apparatus of an ethylene glycol aqueous solution provided in example 1.

Reference numerals: t1, an EG preconcentration first tower, T2, an EG preconcentration second tower, B11, a reboiler I, B12, a reboiler II, B13, a reboiler III, B14, a reboiler IV, B15, a reboiler V, B16, a reboiler VI, B17, a reboiler VII, C11, a condenser I, C21, a condenser II, 101, an EG reaction liquid feeding pipeline, 102, a preconcentration first tower top gas phase pipeline, 103, a preconcentration first tower bottom liquid phase pipeline, 104, a preconcentration first tower top fraction pipeline, 202, a preconcentration second tower top gas phase pipeline, 203, a preconcentration second tower bottom liquid phase pipeline, 204 and a preconcentration second tower top fraction pipeline.

1. Epoxidation reaction product inlet line, 2 epoxidation reaction product outlet line, 3 EO absorption lean liquid inlet line, 4 EO absorption lean liquid outlet line, 5 EO stripper overhead ethylene oxide gas phase inlet line, 6 EO stripper overhead ethylene oxide gas phase condensation outlet line, 7, CO₂StrippingGas phase inlet line at the top of the column, 8, CO₂A gas phase condensation outlet line at the top of the stripping tower, a gas phase inlet line at the top of the EO rectifying tower, a gas phase condensation outlet line at the top of the EO rectifying tower, a water vapor inlet line at the top of the EG dehydrating tower, a water vapor condensation outlet line at the top of the EG dehydrating tower, a multi-effect evaporation last-effect tower top vapor inlet line, a multi-effect evaporation last-effect tower top vapor condensation outlet line and a multi-effect evaporation last-effect tower top vapor condensation outlet line, wherein the gas phase condensation outlet line is 9, the gas phase inlet line at the top of the EO rectifying tower, the gas phase condensation outlet line at the top of the EO rectifying tower, the water vapor inlet line at the top of the EG dehydrating tower, the water vapor condensation outlet line at the top of the EG dehydrating tower, 12, the water vapor condensation outlet line at the top of the EG dehydrating tower, the multi-effect evaporation last effect tower top.

Detailed Description

As mentioned above, the method for distilling the ethylene glycol aqueous solution comprises the steps of: pre-concentrating the crude product of the ethylene glycol aqueous solution before the crude product of the ethylene glycol aqueous solution enters multiple-effect evaporation to obtain the ethylene glycol aqueous solution with reduced water content;

the pre-concentrated heat source is provided by a low-quality heat source in the process of preparing ethylene glycol from ethylene oxide. For example, the low quality heat source includes at least one of ethylene oxide reaction product, ethylene oxide absorption lean solution, ethylene oxide stripper overhead vapor, carbon dioxide stripper overhead vapor, ethylene oxide rectifier overhead vapor, overhead vapor from the last effect of multi-effect evaporation of aqueous ethylene glycol, and ethylene glycol dehydration column overhead vapor.

According to an embodiment of the invention, the ethylene oxide reaction product comprises unreacted ethylene, oxygen, a stabilizing gas (nitrogen and/or methane), ethylene oxide, and by-product carbon dioxide.

According to an embodiment of the invention, the temperature of the ethylene oxide reaction product is 78-88 ℃, preferably 80-85 ℃, such as 80 ℃, 81 ℃, 82 ℃, 83 ℃, 84 ℃ or 85 ℃.

According to an embodiment of the present invention, the ethylene oxide reaction product is sent to an ethylene oxide absorber after heat exchange as a heat source.

According to an embodiment of the invention, the temperature of the ethylene oxide absorption lean solution is 78-85 ℃, preferably 80-82 ℃, such as 80 ℃, 81 ℃, 82 ℃.

According to the embodiment of the invention, the ethylene oxide absorption barren solution is returned to the ethylene oxide absorption tower after being used as a heat source for heat exchange.

According to an embodiment of the invention, the ethylene oxide stripper overhead vapour is ethylene oxide and has a temperature in the range of from 75 to 80 ℃, preferably from 77 to 78 ℃, e.g. 76 ℃, 77 ℃, 78 ℃.

According to the embodiment of the invention, the gas phase at the top of the ethylene oxide stripping tower and/or the gas phase at the top of the ethylene oxide rectifying tower are taken out or used as reaction raw materials for preparing the ethylene glycol after heat exchange by using the gas phase at the top of the ethylene oxide stripping tower and/or the gas phase at the top of the ethylene oxide rectifying tower as a heat source.

According to an embodiment of the present invention, the gas phase at the top of the carbon dioxide stripping column is carbon dioxide, and the temperature thereof is 105-115 ℃, preferably 109-111 ℃, such as 109 ℃, 110 ℃, 112 ℃, 114 ℃.

According to the embodiment of the invention, the gas phase at the top of the carbon dioxide stripping tower is used as a heat source for further treatment after heat exchange.

According to an embodiment of the invention, the gas phase at the top of the ethylene oxide rectification column is ethylene oxide and has a temperature of 48 to 53 ℃, preferably 50 to 51 ℃, for example 48 ℃, 49 ℃, 50 ℃, 51 ℃, 53 ℃.

According to an embodiment of the present invention, the ethylene glycol dehydration column overhead vapor is water vapor having a temperature of 48 to 53 ℃, preferably 50 to 51 ℃, for example, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 53 ℃.

According to an embodiment of the present invention, the crude ethylene glycol aqueous solution is prepared by hydration of a mixture of ethylene oxide and water. Wherein the crude ethylene glycol solution contains 85-91 wt% of water, such as 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt% or 91 wt% of water.

According to an embodiment of the invention, the temperature of the crude ethylene glycol aqueous solution is in the range of 40 to 150 ℃, such as 50 to 100 ℃, exemplary 40 ℃, 50 ℃, 60 ℃, 70 ℃, 90 ℃, 100 ℃, 120 ℃, 150 ℃.

According to an embodiment of the invention, the water content of the reduced water content aqueous ethylene glycol solution is in the range of 70 to 80 wt. -%, such as 70 wt. -%, 72 wt. -%, 74 wt. -%, 76 wt. -%, 78 wt. -% or 80 wt. -%.

According to an embodiment of the invention, the multi-effect evaporation is at least three-effect evaporation, such as four-effect evaporation, five-effect evaporation or more, preferably five-effect evaporation.

According to an embodiment of the invention, the temperature of the steam obtained in the last stage of the multi-effect evaporation is 55-65 ℃, preferably 56-58 ℃, such as 56 ℃, 57 ℃, 58 ℃, 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃, 65 ℃.

According to an embodiment of the present invention, the glycol aqueous solution with reduced water content is subjected to multiple-effect evaporation to obtain a glycol concentrate; and dehydrating and rectifying the ethylene glycol concentrated solution to obtain pure ethylene glycol.

According to an embodiment of the invention, the ethylene glycol concentrate contains 10 to 30 wt% water, such as 15 to 25 wt% water, exemplary 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt% water.

The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

Example 1

As shown in fig. 1, the ethylene glycol aqueous solution distillation apparatus includes: EG preconcentration one column T1, EG preconcentration two column T2 and multiple effect evaporators (not shown in fig. 1);

the material inlet of the first EG pre-concentration tower T1 is connected with an EG reaction liquid feeding pipeline 101, the material outlet at the bottom of the first EG pre-concentration tower T1 is connected with the middle part of the second EG pre-concentration tower T2 through a liquid phase pipeline 103 at the bottom of the first EG pre-concentration tower, and the material inlet of the multi-effect evaporator is connected with the material outlet of the second EG pre-concentration tower T2.

The bottom of the EG preconcentration column T1 was provided with four reboilers: the reboiler I B11, the reboiler II B12, the reboiler III B13 and the reboiler IV B14, and the bottom of the second-stage pre-concentration tower is provided with three reboilers: a reboiler five B15, a reboiler six B16 and a reboiler seven B17.

The inlet of the heat exchange medium of the first reboiler B11 is connected to an ethylene oxide reaction product inlet line 1, and the outlet of the heat exchange medium is connected to an ethylene oxide reaction product outlet line 2.

The reboiler B12 has its heat exchange medium inlet connected to EO absorption lean liquid inlet line 3 and its heat exchange medium outlet connected to EO absorption lean liquid outlet line 4.

The inlet of the heat exchange medium of the reboiler III B13 is connected with an EO stripping overhead ethylene oxide gas phase inlet line 5, and the outlet of the heat exchange medium is connected with an EO stripping overhead ethylene oxide gas phase condensation outlet line 6.

The heat exchange medium inlet of the reboiler IV B14 and CO₂The gas phase inlet line 7 at the top of the stripping tower is connected, and the outlet of the heat exchange medium is connected with CO₂The stripper overhead gas phase condensation outlet line 8 is connected.

The top of the first EG pre-concentration tower T1 is provided with a first condenser C11, the material inlet of the first condenser C11 is connected with a first pre-concentration tower top gas phase pipeline 102, after the material is condensed, a part of the condensed material flows back to the upper part of the first EG pre-concentration tower T1, and a part of the condensed material is extracted through a first pre-concentration tower top fraction pipeline 104.

The inlet of the heat exchange medium of the reboiler penta B15 is connected with the gas phase inlet line 9 at the top of the EO rectification tower, and the outlet of the heat exchange medium is connected with the condensation outlet line 10 at the top of the EO rectification tower.

The inlet of the heat exchange medium of the reboiler VI B16 is connected with a water vapor inlet line 11 at the top of the EG dehydrating tower, and the outlet of the heat exchange medium is connected with a water vapor condensation outlet line 12 at the top of the EG dehydrating tower.

The inlet of the heat exchange medium of the reboiler seven B17 is connected with the multi-effect evaporation last-effect overhead steam inlet 13, and the outlet of the heat exchange medium is connected with the multi-effect evaporation last-effect overhead steam condensation outlet line 14.

The epoxidation reaction product inlet line 1 is connected to the product outlet of the ethylene oxide reactor. The EO absorption lean liquid inlet line 3 is connected to the absorption lean liquid outlet of the ethylene oxide stripping tower. An ethylene oxide gas phase inlet line 5 at the top of the EO stripping tower is connected with a gas phase extraction port at the top of the ethylene oxide stripping tower. CO 2₂The gas phase inlet line 7 at the top of the stripping tower is connected with the gas phase extraction port at the top of the carbon dioxide stripping tower. EO rectification tower top gas phase inlet line 9 and ethylene oxide rectification tower topThe gas phase extraction outlet is connected. The water vapor inlet line 11 at the top of the EG dehydration tower is connected with the gas phase extraction outlet at the top of the ethylene glycol dehydration tower. The steam inlet line 13 at the last effect tower top of the multi-effect evaporation is connected with the steam outlet at the last effect tower top of the multi-effect evaporator.

The top of the EG pre-concentration second tower T2 is provided with a second condenser C21, the material inlet of the second condenser C21 is connected with a gas phase pipeline 202 at the top of the pre-concentration second tower, after the material is condensed, a part of the condensed material flows back to the upper part of the EG pre-concentration second tower T2, and a part of the condensed material is extracted through a fraction pipeline 204 at the top of the pre-concentration second tower.

The bottom of the EG preconcentration secondary column T2 is provided with a preconcentration secondary column bottom liquid phase line 203.

Example 2

For a 28 ten thousand ton/year ethylene glycol plant, 295t/h of an aqueous EG solution at a temperature of 50 ℃ contains 12 wt% EG, 86% water, 2% MEG and TEG by weight.

With the apparatus shown in FIG. 1, the EG aqueous solution was first passed through two columns: EG preconcentrate one column T1 and EG preconcentrate two columns T2 were preconcentrated. The bottom of the first EG preconcentration column T1 is connected with the middle part of the first EG preconcentration column T2 through a liquid phase preconcentration column bottom pipeline 103, and the first preconcentration column overhead pipeline 104 and the second preconcentration column overhead pipeline 204 are both connected with a vacuum system. The overhead gas phase of the first condenser C11 and the second condenser C21 is condensed by the condensers and then is partially extracted by reflux.

TABLE 1

Reboiler device	Heat source	Temperature of	Flow rate kg/h
				B11	Epoxidation reaction product	80-85	911682
B12	EO absorption barren liquor	80-82	1135590
				B13	EO stripper overhead gas phase	77-78	181886
B14	CO2Stripper overhead gas phase	109-111	17384
				B15	Top gas phase of EO rectifying tower	50-51	31000
B16	Water vapor at top of EG dehydration tower	50-51	14139
				B17	Last effect overhead steam of five effect evaporation	56-58	19200

The bottom of the EG preconcentration tower is supplied with heat by four reboilers B11-14, and the heat source is listed in Table 1; the bottom of the EG pre-concentration diethyl acetal was supplied with heat from three reboilers B15-17, the heat source being given in Table 1.

The operation pressure of the EG preconcentration tower is 9.6kPa, the tower top temperature is 45 ℃, the tower bottom temperature is 47 ℃, and the reflux ratio is 0.12; the operating pressure of the EG pre-concentration secondary tower is 5.6kPa, the temperature of the top of the tower is 36 ℃, the temperature of the bottom of the tower is 38 ℃, and the reflux ratio is 0.12. An ethylene glycol aqueous solution with improved concentration is extracted from an EG preconcentration secondary tower T2, the EG content is 21.2 wt%, and dehydration is continued by a multi-effect evaporation system.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.