Refining tower energy-saving system for preparing ethylene glycol (EG) through hydrolysis
By introducing a side-stream reboiler and flow control into the hydrolysis to ethylene glycol unit, the high energy consumption problem when the load exceeds the refining tower was solved, achieving efficient and energy-saving separation and recovery, reducing equipment and operating costs, and improving the economic benefits of the unit.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- 连云港石化有限公司
- Filing Date
- 2025-06-10
- Publication Date
- 2026-05-15
AI Technical Summary
Existing hydrolysis-to-ethylene glycol units experience a decrease in separation and recovery efficiency when the load exceeds 100% of the refining tower. This necessitates the addition of an ethylene glycol recycling tower and steam usage, resulting in high energy consumption and costs, making long-term efficient operation difficult.
By introducing a side-stream reboiler into the refining tower system, a heat source is provided by the side-stream reboiler to replace the ethylene glycol circulation tower. Combined with a vacuum system and flow control, this achieves efficient separation of ethylene glycol aqueous solution, reducing steam usage and equipment requirements.
Maintaining efficient separation and recovery of ethylene glycol under load changes reduces equipment investment and operating costs, improves the economic benefits of the unit, and achieves long-term efficient and energy-saving operation.
Smart Images
Figure CN224236101U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of chemical production technology, specifically to an energy-saving system for a hydrolysis-to-ethylene glycol (EG) refining tower. Background Technology
[0002] In the current chemical industry, the hydrolysis-to-ethylene glycol process is widely used due to its unique advantages. These plants offer operational flexibility ranging from 60% to 130%. The ethylene glycol side-stream reboiler, in particular, has the capability to replace the ethylene glycol circulation tower under specific operating conditions, especially during overload production, maximizing ethylene glycol recovery and significantly improving plant efficiency. Developing an energy-saving device for the hydrolysis-to-ethylene glycol plant can not only reduce construction investment and steam energy costs but also decrease the equipment footprint, comprehensively lowering operating and investment costs and helping the plant achieve higher production and revenue. Therefore, the more energy-efficient the device, the more beneficial it is to the overall economic benefits of the plant.
[0003] In existing hydrolysis-to-ethylene glycol (EG) plants, load variations in the EG section have a critical impact on production. When the load in the EG section increases, exceeding 100% of the refining tower's capacity, the separation and recovery efficiency reaches its maximum. However, at this point, to recover the ethylene glycol solution to the ethylene glycol dehydration tower, it is necessary to utilize an ethylene glycol circulation tower. This process not only requires new tower equipment but also significantly increases steam consumption, contradicting energy-saving goals. Therefore, existing technologies cannot guarantee long-term high-efficiency operation.
[0004] In response to this common phenomenon in the industry, this utility model has specially developed an energy-saving solution for a hydrolysis-to-ethylene glycol production unit, aiming to enable the hydrolysis-to-ethylene glycol production unit to achieve high-efficiency, energy-saving, and long-cycle operation, thereby significantly increasing the economic benefits of the unit. Utility Model Content
[0005] The purpose of this invention is to provide an energy-saving system for a hydrolysis-to-ethylene glycol (EG) refining tower, in order to solve the problem mentioned in the background art that the existing technology cannot ensure that the EG refining tower maintains high-efficiency operation for a long time.
[0006] The technical solution is as follows:
[0007] An energy-saving system for a hydrolysis-to-ethylene glycol (EG) refining tower includes a refining tower, a top cooler, a reflux tank, a reflux pump, a reboiler circulation pump, a reboiler, a side-stream reboiler, and a side-stream circulation pump. The system is characterized in that the top section of the refining tower is connected to a vacuum system via a pipeline; the top of the refining tower is connected to the top cooler; the top cooler is connected to the reflux tank; the reflux tank is connected to the reflux pump; the reflux pump is connected to the refining tower; and the reflux pump is connected to a qualified ethylene glycol tank via a pipeline. Line 2 connects the purification tower to the reboiler circulation pump, the reboiler circulation pump to the reboiler via a three-phase pipeline, the reboiler to the purification tower via a pipeline, the upper part of the side-line reboiler to the side-line circulation pump via a four-phase pipeline, the lower part of the side-line reboiler to the purification tower, the lower part of the side-line reboiler to the external mixed alcohol via a five-phase pipeline, the bottom of the purification tower to the dehydration tower inlet pipeline, and the bottom of the purification tower to the reaction feed tank via a six-phase pipeline.
[0008] Furthermore, pipeline 1 is equipped with gate valve 1 and pressure gauge; pipeline 2 is equipped with online analyzer, flow meter 1 and flow control valve 1; pipeline 3 is equipped with flow meter 2 and flow control valve 2; pipeline 4 is equipped with flow meter 3 and flow control valve 3; pipeline 5 is equipped with gate valve 2; gate valve 3 is installed on the dehydration tower inlet pipeline; and pipeline 6 is equipped with tower bottom pump and gate valve 4.
[0009] This invention has the following advantages: Ethylene glycol aqueous solution is separated under negative pressure (8 kPaA) and 155°C. The operating load of the hydrolysis to ethylene glycol unit is 60%~130%. When the load of the ethylene glycol section exceeds 100% of the refining tower, our recovery efficiency reaches its maximum. However, more than 85% of the ethylene glycol in the tower bottom cannot be recovered, requiring additional ethylene glycol circulation towers and reboilers, among other supporting facilities. Furthermore, the recovered ethylene glycol aqueous solution is returned to the dehydration tower, increasing steam usage. This results in inefficient long-cycle production and high steam energy consumption. We can increase efficiency by adding a side-stream reboiler. This not only replaces the ethylene glycol circulation tower and other related equipment but also reduces operating costs, increases the output of qualified ethylene glycol products, reduces waste of ethylene glycol aqueous solution in the tower bottom and steam usage, increases the economic benefits of the unit, and is conducive to the long-term development of the hydrolysis to ethylene glycol unit. Attached Figure Description
[0010] Figure 1 This is the system flowchart for this device. Detailed Implementation
[0011] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0012] In one embodiment, see Figure 1 An energy-saving system for a hydrolysis-to-ethylene glycol (EG) refining tower includes a refining tower 10, a top cooler 24, a reflux tank 23, a reflux pump 22, a reboiler circulation pump 7, a reboiler 5, a side-stream reboiler 25, and a side-stream circulation pump 19. The system is characterized in that the top section of the refining tower 10 is connected to the vacuum system via a pipeline 1, which is equipped with a gate valve 1 and a pressure gauge 11. The top of the refining tower 10 is connected to the top cooler 24, which is connected to the reflux tank 23. The reflux tank 23 is connected to the reflux pump 22, which is connected to the refining tower 10. The reflux pump 22 is connected to the qualified ethylene glycol tank via a pipeline 2, which is equipped with an online analyzer 21, a flow meter 26, and a flow control valve 20. The refining tower 10 is connected to the reboiler... The reboiler circulation pump 7 is connected to the reboiler 5 via a three-phase pipeline. Flow meter 26 and flow control valve 24 are installed on pipeline 3. The reboiler 5 is connected to the purification tower 10 via a pipeline. The upper part of the side-line reboiler 25 is connected to the side-line circulation pump 19 via a four-phase pipeline. Flow meter 318 and flow control valve 317 are installed on pipeline 4. The lower part of the side-line reboiler 25 is connected to the purification tower 10. The lower part of the side-line reboiler 25 is connected to the external mixed alcohol via a five-phase pipeline. Gate valve 214 is installed on pipeline 5. The bottom of the purification tower 10 is connected to the dehydration tower inlet pipeline. The bottom of the purification tower 10 is also connected to the reaction feed tank via a six-phase pipeline. Tower bottom pump 12 and gate valve 413 are installed on pipeline 6. Gate valve 38 is installed on the dehydration tower inlet pipeline.
[0013] In one embodiment, see Figure 1The working principle of this utility model is as follows: The purification tower 10 purifies the 98% ethylene glycol aqueous solution at 155℃ and a negative pressure of 8 kPa. The reboiler 5 provides a heat source to the purification tower 10 through heat exchange with 1.4 MPa steam. A vacuum is maintained under the action of the vacuum system. The pressure gauge 11 is precisely adjusted by gate valve 1. When the load of the ethylene glycol section exceeds 100% of the purification tower 10, the ethylene glycol aqueous solution content in the bottom of the purification tower 10 is above 85%. This necessitates the use of a series of equipment, such as a MEG circulation tower, for recovery. To reduce equipment and operating costs, a side-stream reboiler 25 was put into operation. The side-stream reboiler 25 provides a heat source through heat exchange with 0.6 MPa steam and is precisely controlled by flow meter 3 18 and flow control valve 3 17. It is powered by a side-stream circulation pump 29, and the forced circulation volume is precisely controlled by flow meter 3 18 and flow control valve 3 17. After running for a period of time, we found that the content of by-products such as heavy alcohols is the highest at the side-stream reboiler 25, which needs to be sent to the outside for treatment periodically. We can simply open the gate valve 2 14 periodically to achieve efficient operation and energy saving.
[0014] This utility model is simple to operate, convenient to use, and suitable for widespread promotion and application. Although embodiments of this utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of this utility model, the scope of which is defined by the appended claims and their equivalents.
Claims
1. An energy-saving system for a hydrolysis-to-ethylene glycol (EG) refining tower, comprising a refining tower (10), a tower top cooler (24), a reflux tank (23), a reflux pump (22), a reboiler circulation pump (7), a reboiler (5), a side-stream reboiler (25), and a side-stream circulation pump (19), characterized in that, The top section of the refining column (10) and the vacuum system are connected via pipeline one. The top of the refining column (10) is connected to the top cooler (24). The top cooler (24) is connected to the reflux tank (23). The reflux tank (23) is connected to the reflux pump (22). The reflux pump (22) is connected to the refining column (10). The reflux pump (22) is connected to the qualified ethylene glycol tank via pipeline two. The refining column (10) is connected to the reboiler circulation pump (7). The reboiler circulation pump (7) is connected to the re- The reboiler (5) is connected to the purification tower (10) via a pipeline. The upper part of the side-stream reboiler (25) is connected to the side-stream circulating pump (19) via a pipeline. The lower part of the side-stream reboiler (25) is connected to the purification tower (10). The lower part of the side-stream reboiler (25) is connected to the external mixed alcohol via a pipeline. The bottom of the purification tower (10) is connected to the inlet pipeline of the dehydration tower. The bottom of the purification tower (10) is also connected to the reaction feed tank via a pipeline.
2. The energy-saving system for a hydrolysis-to-ethylene glycol (EG) refining tower according to claim 1, characterized in that, Pipeline 1 is equipped with gate valve 1 (1) and pressure gauge (11), pipeline 2 is equipped with online analyzer (21), flow meter 1 (26) and flow control valve 1 (20), pipeline 3 is equipped with flow meter 2 (6) and flow control valve 2 (4), pipeline 4 is equipped with flow meter 3 (18) and flow control valve 3 (17), pipeline 5 is equipped with gate valve 2 (14), the dewatering tower inlet pipeline is equipped with gate valve 3 (8), and pipeline 6 is equipped with tower bottom pump (12) and gate valve 4 (13).