Energy-saving and efficiency-increasing method for comprehensive utilization of high-temperature lean solution

Abstract

The application discloses an energy-saving and efficiency-increasing method for comprehensively utilizing high-temperature lean liquid, wherein the high-temperature lean liquid is generated in the production process of an ethylene glycol device. The energy-saving and efficiency-increasing method for comprehensively utilizing high-temperature lean liquid introduces the high-temperature lean liquid into a desalted water section and a refining section for heat exchange in a manner of increasing a side line extraction of a high-temperature lean liquid pipeline and parallel connection of a heat exchanger, so that the high-temperature lean liquid can be cooled to a certain extent and the heat energy of the high-temperature lean liquid can be used for heating materials in a tower kettle of the desalted water and the refining tower, thereby reducing energy waste and heat exchanger load and achieving the energy-saving and environmental protection effects.

Description

Technical Field

[0001] This invention relates to the field of energy-saving technology in the production process of ethylene glycol plants, and in particular to an energy-saving and efficiency-enhancing method that comprehensively utilizes high-temperature lean liquor. Background Technology

[0002] In ethylene glycol plants in the petrochemical industry, lean liquor acts as an absorbent, absorbing the reaction product ethylene oxide from the circulating gas and transforming it into rich liquor. The rich liquor then enters a stripping tower via heating and depressurization, where ethylene oxide is released.

[0003] After desorption, the rich solution becomes lean solution. The high-temperature lean solution needs to be cooled by a large amount of circulating water to become a low-temperature lean solution for reuse as an absorbent in the ethylene oxide gas absorption process. The cooling process of the lean solution generates a large amount of circulating water consumption. Meanwhile, the rich solution from the bottom of the absorption tower requires a large amount of steam heating before entering the desorption tower to separate the reaction product ethylene oxide. In the same unit, the demineralized water heating and the reboiler of the purification tower both require external heat sources. These stages all require a large supply of heat energy, but the abundant heat energy in the high-temperature lean solution is not fully utilized, resulting in significant energy waste. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing an energy-saving and efficiency-enhancing method that comprehensively utilizes high-temperature lean liquor, which is generated during the production process of an ethylene glycol unit.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides an energy-saving and efficiency-enhancing method for comprehensively utilizing high-temperature lean liquor, which is generated during the production process of an ethylene glycol unit, and includes the following steps:

[0007] Step 1: The high-temperature lean liquor from the bottom of the analytical column enters the lean liquor chiller and the reboiler of the refining column respectively, and participates in heat exchange as a hot-side medium. After being cooled by the lean liquor chiller, the high-temperature lean liquor enters the lean-rich liquor heat exchanger to exchange heat with the low-temperature rich liquor. The cooled lean liquor and the lean liquor at the outlet of the reboiler of the refining column are combined into a single stream to participate in the next stage of heat exchange.

[0008] Step two: In the next stage, the lean solution enters the lean solution cooler and the demineralized water heat exchanger respectively. This process can reduce the external heat source consumption for heating the demineralized water. At the same time, the above process can reduce the heat load of the lean solution cooler and reduce the consumption of circulating cooling water.

[0009] Step three, the lean liquid after heat exchange in step two enters the lean liquid after-cooler and is cooled again by circulating water, the cooled lean liquid is divided into two routes, one route is sent to the lean liquid refrigerator by the side line added at the outlet of the lean liquid after-cooler as the cold side medium of the lean liquid refrigerator, and the other route is used for other sections of the device.

[0010] Further, in step one, the high-temperature lean liquid from the bottom of the analysis tower enters the lean liquid refrigerator and the refined tower reboiler respectively according to the flow ratio (2-5):1.

[0011] Further, in step two, the next stage lean liquid enters the lean liquid cooler and the desalted water heat exchanger respectively according to the flow ratio (1-3):1.

[0012] Further, in step three, the cooled lean liquid is divided into two routes and enters the cold side medium of the lean liquid refrigerator and other sections according to the flow ratio (20-25):1.

[0013] Compared with the prior art, the present application has the following advantages:

[0014] The present application is an energy-saving and efficiency-increasing method for comprehensive utilization of high-temperature lean liquid, which introduces the high-temperature lean liquid into the desalted water section and the refining section for heat exchange by increasing the side line extraction of the high-temperature lean liquid pipeline and parallel heat exchangers, cools the high-temperature lean liquid to a certain extent, and uses the heat energy of the high-temperature lean liquid for heating the materials in the desalted water section and the refined tower, reduces energy waste and heat exchanger load, and achieves the effects of energy saving and environmental protection. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Figure 1 is a schematic diagram of the energy-saving and efficiency-increasing system for high-temperature lean liquid of the present application. DETAILED DESCRIPTION

[0016] The present application will be described in detail and specifically below with specific examples and drawings, so that it can be better understood.

[0017] Example 1

[0018] Reference Figure 1The high-temperature lean liquid flow from the analysis tower bottom is 886 t / h, and the temperature is 132.5℃, which is divided into two paths to enter the lean liquid refrigerator 1 and the refined tower reboiler 3. Among them, 730 t / h is cooled by the lean liquid refrigerator 1, and the temperature is 119℃, which enters the lean and rich liquid heat exchanger 2 for further cooling. Another 156 t / h enters the refined tower reboiler 3 as a reboiler heat source to participate in heat exchange, and the temperature of the cooled lean liquid is 50℃. The high-temperature lean liquid after heat exchange in the above two paths is combined and participates in the next stage of heat exchange, and the temperature of the combined lean liquid stream is 60.2℃. The combined lean liquid stream is divided into two paths to enter the newly added desalted water heat exchanger 6 and the lean liquid cooler 4 for the next heat exchange. 250 t / h of high-temperature lean liquid is used as a heat source to enter the newly added desalted water heat exchanger 6, and 210 t / h of desalted water at a temperature of 45℃ is heated to 55℃. The remaining lean liquid enters the lean liquid cooler 4 and is cooled by circulating cooling water. The cooled lean liquid enters the lean liquid post-cooler 5 and is cooled again to 37℃ by circulating cooling water. The cooled lean liquid is divided into two paths, of which 850 t / h is used as a cooling medium for the lean liquid refrigerator 1 and is cooled to 29℃, and the remaining 36 t / h is used for other sections of the device.

[0019] In the prior art (before rectification), the high-temperature lean liquid is not utilized, and is directly cooled by circulating water. The heat load of the heat exchanger for cooling the high-temperature lean liquid is 20MW. In the present application, the energy consumption in Example 1 (after rectification) is greatly reduced to 17.5MV, and the heat load of the newly added desalted water heat exchanger is 2.6MW. At the same time, the cooling load is reduced by the same proportion, from 7.5MW to 5.5MW, saving 1.9MW of energy, and the annual energy saving benefit is 8,208,000 yuan.

[0020] Example 2

[0021] Reference Figure 1The high-temperature lean liquid flow from the analysis tower bottom is 532 t / h, and the temperature is 135 DEG C, which is divided into two paths to enter the lean liquid refrigerator 1 and the refined tower reboiler 3. Among them, 438 t / h is cooled by the lean liquid refrigerator 1, and the temperature is 121 DEG C, which enters the lean-liquid heat exchanger 2 for further cooling. Another 94 t / h enters the refined tower reboiler 3 as a reboiler heat source to participate in heat exchange, and the temperature of the cooled lean liquid is 52 DEG C. The high-temperature lean liquid after heat exchange in the above two paths is combined to participate in the next heat exchange, and the temperature of the combined lean liquid stream is 63 DEG C. The combined lean liquid stream is divided into two paths to enter the newly added desalted water heat exchanger 6 and the lean liquid cooler 4 for the next heat exchange. The 150 t / h high-temperature lean liquid is used as a heat source to enter the newly added desalted water heat exchanger 6, and the 126 t / h desalted water at 45 DEG C is heated to 58 DEG C. The remaining lean liquid enters the lean liquid cooler 4 and is cooled by circulating cooling water. The cooled lean liquid enters the lean liquid post-cooler 5 and is cooled again to 39 DEG C by circulating cooling water. The cooled lean liquid is divided into two paths, of which 510 t / h is used as the cooling medium of the lean liquid refrigerator 1 to be cooled to 31 DEG C, and the remaining 22 t / h is used in other sections of the device.

[0022] In the prior art (before modification), the high-temperature lean liquid is not utilized, and is directly cooled by circulating water. The heat load of the heat exchanger for cooling the high-temperature lean liquid is 12 MW. In the embodiment 2 of the present application (after modification), the energy consumption is greatly reduced to 10.5 MW, and the heat load of the newly added desalted water heat exchanger is 1.6 MW. At the same time, the cooling capacity load is also reduced in the same proportion, from the original 4.5 MW to 3.3 MW, saving 1.2 MW of energy, and the annual energy saving benefit is 4,925,000 yuan.

[0023] The above only describes the preferred embodiments of the present application, and does not limit the implementation and protection scope of the present application. For those skilled in the art, it should be realized that any equivalent replacement and obvious changes made according to the content of the present application and the drawings should be included in the protection scope of the present application.

Claims

1. A method for energy conservation and efficiency improvement through comprehensive utilization of high-temperature lean liquor, wherein the high-temperature lean liquor is generated during the production process of an ethylene glycol unit, characterized in that... Includes the following steps: Step 1: The high-temperature lean liquor from the bottom of the analytical column enters the lean liquor chiller and the reboiler of the refining column respectively, and participates in heat exchange as a hot-side medium. After being cooled by the lean liquor chiller, the high-temperature lean liquor enters the lean-rich liquor heat exchanger to exchange heat with the low-temperature rich liquor. The cooled lean liquor and the lean liquor at the outlet of the reboiler of the refining column are combined into a single stream to participate in the next stage of heat exchange. Step two: In the next stage, the lean solution enters the lean solution cooler and the demineralized water heat exchanger respectively. This process can reduce the external heat source consumption for heating the demineralized water. At the same time, the above process can reduce the heat load of the lean solution cooler and reduce the consumption of circulating cooling water. Step 3: After heat exchange in Step 2, the lean liquor enters the lean liquor aftercooler and is cooled again by circulating water. The cooled lean liquor is divided into two paths. One path is sent to the lean liquor chiller via a side line added to the outlet of the lean liquor aftercooler, serving as the cold side medium of the lean liquor chiller. The other path is used for other sections of the equipment.

2. The energy-saving and efficiency-enhancing method for comprehensive utilization of high-temperature lean liquor according to claim 1, characterized in that, In step one, the high-temperature lean liquor from the bottom of the analytical column enters the lean liquor chiller and the reboiler of the refining column at a flow ratio of (2-5):

1.

3. The energy-saving and efficiency-enhancing method for comprehensive utilization of high-temperature lean liquor according to claim 1, characterized in that, In step two, the lean liquor in the next stage enters the lean liquor cooler and the demineralized water heat exchanger at a flow rate ratio of (1-3):

1.

4. The energy-saving and efficiency-enhancing method for comprehensive utilization of high-temperature lean liquor according to claim 1, characterized in that, In step three, the cooled lean liquor is divided into two streams, which enter the cold side medium and other sections of the lean liquor chiller at a flow ratio of (20-25):1.

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