Ethylene glycol-water energy-saving separation system based on liquid phase atomization spraying

Abstract

The invention relates to the technical field of chemical separation, in particular to an ethylene glycol-water energy-saving separation system based on liquid phase atomization spraying, and the system comprises a tower kettle liquid phase feed atomizer which is arranged at the upper part of a tower kettle and is used for atomizing filtered tower kettle liquid phase feed into micron-sized liquid drops; the multi-layer tower tray is arranged above the tower kettle liquid phase feeding atomizer, is used for carrying out vapor-liquid two-phase mass transfer and separation on the tower kettle reboiler, is arranged at the bottom of the tower kettle, and is used for heating tower kettle liquid and generating ethylene glycol-water mixed steam. Sensible heat and latent heat of esterified mixed steam are efficiently utilized through an atomization spraying technology, preheating and steam stripping are carried out on spraying liquid, the heat load of a tower kettle reboiler is greatly reduced, and a novel separation technology system is constructed. Actual measurement data shows that under the same productivity, compared with a traditional process, the system saves energy by about 41.4%, can save heat energy by about 860,000 kilocalories per hour, equivalently reduces carbon emission by about 319kg CO2 per hour, and reduces carbon emission by about 2679.6 TCO2 per year.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical separation, in particular to an energy-saving and consumption-reducing equipment in a polyester production process, and more particularly to an energy-saving process column system for efficiently separating ethylene glycol and water by means of liquid-phase atomization and spraying technology. BACKGROUND

[0002] The polyester industry is an important pillar industry of the national economy. According to industry reports, the scale of China's polyester industry has ranked first in the world. Under the background of current capacity expansion and intensified competition, energy saving and consumption reduction has become the core strategy for enterprises to enhance competitiveness and realize green and low-carbon transformation.

[0003] In the polyester production process, a large amount of ethylene glycol-water mixture is generated by esterification reaction and needs to be effectively separated and recovered. The traditional ethylene glycol-water separation process column usually adopts conventional rectification technology, which has a significant energy consumption problem: (1) Low heat utilization rate: The latent heat of the mixed steam generated by esterification reaction cannot be fully utilized, and a large amount of energy (usually heat transfer oil) needs to be consumed for cooling and heating in the overhead condenser and the column reboiler, resulting in a large amount of repeated heating energy consumption.

[0004] (2) Limited process optimization space: The traditional column feed method (usually liquid phase directly into the column) has low heat exchange efficiency with the rising steam, and the mass transfer and heat transfer process is not sufficient, so the energy consumption optimization space is limited, and the energy consumption is high.

[0005] Therefore, it is urgent to develop a new type of high-efficiency and energy-saving separation system to recover and utilize the waste heat in the process and significantly reduce the overall energy consumption of the system. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art and provide an ethylene glycol-water energy-saving separation system based on liquid-phase atomization and spraying, which organically couples rectification technology with stripping technology and innovatively adopts liquid-phase atomization feeding method to significantly improve the column heat exchange efficiency and thus significantly reduce the system energy consumption.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solution: an ethylene glycol-water energy-saving separation system based on liquid-phase atomization and spraying, the system comprising: a column liquid-phase feed atomizer arranged at the upper part of the column for atomizing the filtered column liquid-phase feed into micron-sized droplets; a multi-layer tray arranged above the column liquid-phase feed atomizer for mass transfer and separation of vapor-liquid two-phase; a column reboiler arranged at the bottom of the column for heating the column liquid and generating ethylene glycol-water mixed steam; a tower top condenser arranged at the top of the tower for condensing the vapor distilled from the top of the tower; a sub-tank arranged at the top of the tower and connected with the tower top condenser; a tower top distillate overflow extraction pump connected with the sub-tank a tower top reflux conveying pump connected with the sub-tank for refluxing part of the condensed liquid to the top of the tower; a tower kettle liquid phase feed precision filter arranged above the tower kettle liquid phase feed pipeline and before the tower kettle liquid phase feed atomizer for filtering the feed liquid; The system is configured to pass the ethylene glycol-water mixed vapor generated by the esterification system into the tower kettle to directly contact and exchange heat with the atomized droplets from the tower kettle liquid phase feed atomizer and to realize the cooperative operation of the rectification process and the stripping process.

[0008] Preferably, the tower kettle liquid phase feed atomizer adopts a spiral nozzle structure, preferably a DN40 spiral nozzle, to atomize the liquid phase material into liquid droplets with a particle size of 30-50 μm to form a stable saturated vapor-droplet two-phase flow system.

[0009] Preferably, the installation position of the tower kettle liquid phase feed atomizer is located within a space 1 m-2 m below the lowermost tray, and the installation height is higher than the inlet of the tower kettle ethylene glycol-water mixed vapor feed.

[0010] Preferably, the filtering precision of the tower kettle liquid phase feed precision filter is 20 μm-80 μm, and the material is 304, 316L stainless steel. Two groups of the tower kettle liquid phase feed precision filter are arranged in parallel, one for standby and one for use, and are isolated and switched by a ball valve.

[0011] Preferably, the tower kettle liquid phase feed is divided into two routes: the first route enters the tower kettle via the tower kettle liquid phase feed precision filter and the tower kettle liquid phase feed atomizer; and the second route is directly conveyed to the middle and upper layers of the multi-layer tray as reflux feed.

[0012] Preferably, the feed pressure of the tower kettle liquid phase feed is in the range of 0.1-0.8 MPa. A pneumatic regulating valve and a mass flow meter are arranged on the feed pipeline for accurate control of the feed flow.

[0013] Preferably, the multi-layer tray is a guided float valve tray or a bubble cap tray. A multi-point temperature detection device is arranged on the multi-layer tray for monitoring the temperature gradient in the tower and transmitting data to the DCS system.

[0014] Preferably, the tower kettle reboiler adopts a coil type structure with heat conducting oil as the heating medium.

[0015] A process for separation in an energy-saving ethylene glycol-water separation system based on liquid-phase atomization spraying, the process comprising the following steps: S1: The ethylene glycol-water mixed steam generated by the esterification reaction is fed into the system from the bottom of the column; S2: The ethylene glycol-water tower bottom liquid feed to be separated is filtered through the tower bottom liquid feed precision filter and divided into two streams; the first stream is atomized by the tower bottom liquid feed atomizer and sprayed into the tower bottom, where it comes into countercurrent contact with the rising mixed steam feed and the steam generated by the reboiler to complete heat exchange and flash evaporation. S3: The second feed stream is directly fed to the upper and middle trays of the column to participate in the distillation mass transfer process as reflux. S4: The rising vapor undergoes mass transfer separation with the downstream reflux liquid on the multi-layer trays. Light components such as water and a small amount of light components are distilled from the top of the column, and after condensation in the top condenser, part of it is collected and part is refluxed. S5: The heavy component ethylene glycol in the bottom of the column is partially vaporized by heating in the bottom reboiler, and partially extracted by the extraction pump to the downstream section.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. Significant Energy Saving: By utilizing the sensible and latent heat of the esterification mixed steam through atomized spraying technology, the spray liquid is preheated and stripped, significantly reducing the heat load on the reboiler and establishing a novel separation technology system. Actual test data shows that, at the same production capacity, the system of this invention saves approximately 41.4% more energy than traditional processes, saving approximately 860,000 kcal of heat energy per hour.

[0017] 2. High separation efficiency: Micron-level atomization creates a huge specific surface area, making the vapor-liquid mass and heat transfer process more rapid and thorough. The optimized feeding method (bottom atomization + upper and middle reflux) makes the temperature and concentration field distribution within the column more reasonable, improving separation accuracy and efficiency.

[0018] 3. Outstanding emission reduction benefits: The significant energy-saving effect directly translates into a reduction in carbon emissions. According to the provided example, a 300,000-ton / year capacity unit can reduce carbon emissions by approximately 2,679.6 tons annually, demonstrating substantial environmental benefits.

[0019] 4. Stable and reliable operation: The system has a reasonable structural design and adopts measures such as precision filtration and DCS automatic monitoring (such as flow rate, temperature and pressure) to ensure the long-term stable operation of the device. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Fig. 1 This is an overall structural view of the present invention; Fig. 2 This is a schematic diagram of the atomizer structure and operation of the present invention.

[0022] Explanation of reference numerals in the attached figures: 1. Ethylene glycol-water mixed steam feed; 2. Bottom liquid feed; 3. Bottom reboiler; 4. Outlet pump; 5. Bottom liquid feed atomizer; 6. Multi-layer trays; 7. Top condenser; 8. Separate storage tank; 9. Top distillate overflow pump; 10. Top reflux transfer pump; 11. Bottom liquid feed precision filter. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figs. 1-2 The present invention provides a technical solution: An energy-saving ethylene glycol-water separation system based on liquid-phase atomized spraying, the system comprising: The column bottom liquid phase feed atomizer 5 is located at the top of the column bottom and is used to atomize the filtered column bottom liquid phase feed 2 into micron-sized droplets; Multi-layer tray 6 is disposed above the liquid phase feed atomizer 5 in the bottom of the tower and is used for mass transfer and separation of the vapor and liquid phases. The reboiler 3 is located at the bottom of the column bottom and is used to heat the liquid in the column bottom and generate ethylene glycol-water mixed vapor; The top condenser 7 is located at the top of the column and is used to condense the vapor distilled from the top of the column. The storage tank 8 is located at the top of the tower and is connected to the top condenser 7. The top distillate overflow pump 9 is connected to the distribution tank 8. The top reflux pump 10 is connected to the storage tank 8 and is used to return part of the condensate to the top of the tower. A precision filter 11 for the liquid phase feed of the tower bottom is installed above the liquid phase feed pipeline of the tower bottom and before the liquid phase feed atomizer 5 of the tower bottom, and is used to filter the feed liquid. The system is configured to feed 1, a mixture of ethylene glycol and water vapor generated by the esterification system, into the bottom of the column, so that it comes into direct contact with the atomized droplets from the liquid feed atomizer 5 in the bottom of the column and undergoes heat exchange and stripping, thereby achieving coordinated operation of the distillation process and the stripping process.

[0025] Specifically, the tower bottom liquid phase feed atomizer 5 adopts a spiral nozzle structure, preferably a DN40 spiral nozzle, to atomize the liquid phase material into droplets with a particle size of 30-50μm, so as to form a stable saturated steam-droplet two-phase flow system.

[0026] Specifically, the installation position of the liquid phase feed atomizer 5 in the tower bottom is located in the space 1m-2m below the lowest tray, and its installation height is higher than the inlet of the ethylene glycol-water mixed steam feed 1 in the tower bottom.

[0027] Specifically, the filtration accuracy of the precision filter 11 for the liquid phase feed in the tower bottom is 20μm-80μm, and the material is 304 or 316L stainless steel. Two sets of the precision filter 11 for the liquid phase feed in the tower bottom are set in parallel, one for standby and one for use, and are isolated and switched by ball valves.

[0028] Specifically, the liquid feed 2 in the bottom of the tower is divided into two paths: the first path enters the bottom of the tower via the precision filter 11 and the atomizer 5; the second path is used as a reflux feed and is directly delivered to the middle and upper layers of the multi-layer tray 6.

[0029] Specifically, the feed pressure range of the liquid phase feed 2 in the tower bottom is 0.1-0.8 MPa; a pneumatic regulating valve and a mass flow meter are installed on the feed pipeline to accurately control the feed flow rate.

[0030] Specifically, the multi-layer tray 6 is a guided floating valve tray or a bubble cap tray; the multi-layer tray 6 is equipped with a multi-point temperature detection device to monitor the temperature gradient inside the tower and transmit the data to the DCS system.

[0031] Specifically, the reboiler 3 of the tower adopts a coil structure and uses heat transfer oil as the heating medium.

[0032] A process for separation in an energy-saving ethylene glycol-water separation system based on liquid-phase atomization spraying, the process comprising the following steps: S1: The ethylene glycol-water mixed steam generated by the esterification reaction is fed into the system from the bottom of the column; S2: The ethylene glycol-water tower bottom liquid feed 2 to be separated is filtered by the tower bottom liquid feed precision filter 11 and divided into two streams; the first stream is atomized by the tower bottom liquid feed atomizer 5 and sprayed into the tower bottom, where it comes into countercurrent contact with the rising mixed steam feed 1 and the steam generated by the reboiler 3 to complete heat exchange and flash evaporation. S3: The second feed stream is directly fed to the upper and middle trays of the column to participate in the distillation mass transfer process as reflux. S4: The rising vapor undergoes mass transfer separation with the downstream reflux liquid on the multi-layer tray 6. The light component water and a small amount of light components are distilled from the top of the column, and after being condensed by the top condenser 7, part of it is collected and part of it is refluxed. S5: The heavy component ethylene glycol in the bottom of the tower is partially heated and vaporized by the reboiler 3, and partially extracted by the extraction pump 4 to the downstream section.

[0033] This technology innovatively couples traditional distillation and stripping processes to construct a novel separation technology system. While retaining the main structure of a traditional polyester distillation column, this system creatively integrates conventional bottom liquid feeding with atomizer feeding, forming micron-level atomized droplets at the bottom of the trays; another portion is refluxed from the upper trays, achieving synergistic efficiency between distillation and stripping processes. It exhibits significant energy-saving benefits. The working principle of the technical solution is as follows: An ethylene glycol-water separation technology combining a distillation column and a stripping column. It includes a conventional multi-layer tray, a reboiler, a liquid feed to the reboiler, a mixed steam feed, an atomizer, and a precision filter. The multi-layer trays are either floating valve trays or bubble cap trays; the atomizer is a spiral type, located 1-2 meters below the first tray, higher than the reflux nozzle and the mixing steam inlet. The atomizer is welded, with three supports welded to the reactor wall as fixed support points; the liquid feed point in the reactor is above the 12th tray, with the same feed source as the atomizer, and the feed line is made of 304 stainless steel; the reactor reboiler is coil-heated, with heat transfer oil as the heating medium; the precision filter is made of 304 / 316L stainless steel, with a vent and control ball valve at the top and an outlet at the bottom. The filter is connected to the feed line by a flange, and the flange connection is sealed with a PTFE gasket or a metal graphite gasket; the precision filters are in a set, one for standby, and ball valves are used for isolation and switching before and after the filter.

[0034] Furthermore, a mass flow meter is installed in the feed pipeline, and a pneumatic regulating valve is installed before the mass flow meter to control the feed flow rate.

[0035] Furthermore, the multi-layer tray is equipped with multiple thermometers, each equipped with a transmitter, which collects data and transmits it to the DCS for monitoring in real time.

[0036] Furthermore, a pressure gauge is designed at the inlet of the precision filter to monitor the filtration of the liquid phase feed into the tower bottom via liquid phase spraying → countercurrent heat exchange of mixed steam → mass transfer through the guide float valve tray, ensuring the atomizer's atomization effect at an operating pressure of 0.2-0.5 MPa and a temperature gradient of 110-125℃.

[0037] Invention Effects Compared with existing technologies, under the same production capacity, the atomized spray effectively utilizes the heat of esterification steam, effectively stripping moisture from the spray while preheating the material falling into the reboiler. Compared with the traditional process of heating and evaporating at the bottom, this effectively reduces energy consumption. Another portion of the material flows in from the upper and middle trays; due to its higher density, it effectively carries away heavy components as it flows downwards through multiple trays. Data comparison with similar devices shows that the expected results have been achieved.

[0038]

[0039] This technology has been running continuously for 3 months in a 300,000-ton / year capacity plant. The data above was collected after stable operation. Based on the comparison of the above data, compared with the traditional process, it saves approximately 860,000 kcal of heat per hour, equivalent to 122.86 kg of standard coal. According to recommended values, this is equivalent to reducing carbon emissions by approximately 319 kg CO2 per hour, and reducing carbon emissions by approximately 2679.6 TCO2 per year. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An energy-saving ethylene glycol-water separation system based on liquid-phase atomized spraying, characterized in that, The system includes: The column bottom liquid phase feed atomizer (5) is located at the top of the column bottom and is used to atomize the filtered column bottom liquid phase feed (2) into micron-sized droplets; Multi-layer tray (6) is set above the liquid phase feed atomizer (5) in the bottom of the tower and is used for mass transfer and separation of the vapor and liquid phases; The reboiler (3) is located at the bottom of the column and is used to heat the liquid in the column and generate ethylene glycol-water mixed vapor; A column top condenser (7) is installed at the top of the column to condense the vapor distilled from the top of the column. The sub-storage tank (8) is located at the top of the tower and connected to the top condenser (7); The top distillate component overflow pump (9) is connected to the sub-storage tank (8); A top reflux pump (10) is connected to the storage tank (8) and is used to return part of the condensate to the top of the tower. A precision filter (11) for the liquid phase feed of the tower bottom is installed above the liquid phase feed pipeline of the tower bottom and before the liquid phase feed atomizer (5) of the tower bottom, and is used to filter the feed liquid; The system is configured to feed the ethylene glycol-water mixed steam (1) generated by the esterification system into the bottom of the column, so that it comes into direct contact with the atomized droplets from the liquid phase feed atomizer (5) in the bottom of the column and performs heat exchange and stripping, thereby realizing the coordinated operation of the distillation process and the stripping process.

2. The ethylene glycol-water energy-saving separation system based on liquid-phase atomized spraying according to claim 1, characterized in that, The liquid phase feed atomizer (5) in the tower bottom adopts a spiral nozzle structure, preferably a DN40 spiral nozzle, to atomize the liquid phase material into droplets with a particle size of 30-50μm, so as to form a stable saturated steam-droplet two-phase flow system.

3. The ethylene glycol-water energy-saving separation system based on liquid-phase atomized spraying according to claim 1, characterized in that, The installation position of the liquid phase feed atomizer (5) in the tower bottom is located in the space 1m-2m below the lowest tray, and its installation height is higher than the inlet of the ethylene glycol-water mixed steam feed (1) in the tower bottom.

4. The ethylene glycol-water energy-saving separation system based on liquid-phase atomized spraying according to claim 1, characterized in that, The filtration accuracy of the precision filter (11) for the liquid phase feed in the tower bottom is 20μm-80μm, and the material is 304 or 316L stainless steel. Two sets of the precision filter (11) for the liquid phase feed in the tower bottom are set in parallel, one for standby and one for use, and are isolated and switched by ball valve.

5. The ethylene glycol-water energy-saving separation system based on liquid-phase atomized spraying according to claim 1, characterized in that, The liquid feed (2) in the tower bottom is divided into two paths: the first path enters the tower bottom through the precision filter (11) and the atomizer (5); the second path is used as a reflux feed and is directly delivered to the middle and upper layers of the multi-layer tray (6).

6. The ethylene glycol-water energy-saving separation system based on liquid-phase atomized spraying according to claim 1, characterized in that, The feed pressure range of the liquid phase feed (2) in the tower bottom is 0.1-0.8MPa; the feed pipeline is equipped with a pneumatic regulating valve and a mass flow meter for precise control of the feed flow rate.

7. The ethylene glycol-water energy-saving separation system based on liquid-phase atomized spraying according to claim 1, characterized in that, The multi-layer tray (6) is a guide valve tray or a bubble cap tray; the multi-layer tray (6) is equipped with a multi-point temperature detection device to monitor the temperature gradient inside the tower and transmit the data to the DCS system.

8. The ethylene glycol-water energy-saving separation system based on liquid-phase atomized spraying according to claim 1, characterized in that, The reboiler (3) of the tower adopts a coil structure and uses heat transfer oil as the heating medium.

9. A process for energy-saving separation of ethylene glycol and water using the system described in any one of claims 1-8, characterized in that, The process includes the following steps: S1: The ethylene glycol-water mixed steam generated by the esterification reaction is fed into the system from the bottom of the tower; S2: The ethylene glycol-water tower bottom liquid feed (2) to be separated is filtered through the tower bottom liquid feed precision filter (11) and divided into two streams; the first stream is atomized by the tower bottom liquid feed atomizer (5) and sprayed into the tower bottom, where it comes into countercurrent contact with the rising mixed steam feed (1) and the steam generated by the reboiler (3) to complete heat exchange and flash evaporation; S3: The second feed stream is directly fed to the upper and middle trays of the column to participate in the distillation mass transfer process as reflux. S4: The rising vapor undergoes mass transfer separation with the downstream reflux liquid on the multi-layer tray (6). The light component water and a small amount of light components are distilled from the top of the column, condensed by the top condenser (7), and part of them are collected and part of them are refluxed. S5: The heavy component ethylene glycol in the bottom of the tower is partially heated and vaporized by the reboiler (3), and partially extracted by the extraction pump (4) to the downstream section.

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