Ethylene glycol pre-dehydrating tower device and use method thereof

Abstract

The invention discloses an ethylene glycol pre-dehydration tower device and a use method thereof, and belongs to the technical field of ethylene glycol dehydration. The ethylene glycol pre-dehydration tower is characterized in that a fog pad, a spraying device, a first elastic tower tray, a second elastic tower tray, a third elastic tower tray and a fourth elastic tower tray are mounted in the ethylene glycol pre-dehydration tower from top to bottom, and the first elastic tower tray, the second elastic tower tray, the third elastic tower tray and the fourth elastic tower tray are the same in structure; the elastic tray is provided with a float valve as a vapor-liquid outlet channel, the float valve automatically adjusts the opening degree according to the change of vapor-liquid flow, the elastic tray is also provided with a downcomer used for draining liquid of the upper tray to the lower tray, and condensate of the upper tray is drained to the lower tray to be contacted and mixed with a gas phase; the technical problems that an ethylene glycol pre-dehydration tower is low in operation flexibility and poor in pre-dehydration effect are solved, and the method is mainly applied to ethylene glycol pre-dehydration.

Description

Technical Field

[0001] The invention belongs to the technical field of ethylene glycol dehydration, and particularly relates to an ethylene glycol pre-dehydration tower device and a use method thereof. Background Art

[0002] With the continuous growth of China's economy and the acceleration of urbanization, the demand for ethylene glycol in the chemical industry continues to increase. The use of ethylene oxide hydration to produce ethylene glycol is currently the most commonly used method for industrial production of ethylene glycol. The hydration reaction is to add ethylene oxide and water in an appropriate proportion to a reactor and react to generate ethylene glycol under high temperature and high pressure. In the ethylene glycol production process, in order to facilitate further vacuum dehydration of ethylene glycol, ethylene glycol needs to be pre-dehydrated. In this process, the dehydration efficiency and operating flexibility of the operating tower are particularly important. The lower the dehydration efficiency, the greater the material loss of the device. A small operating flexibility range will increase the load of the device and greatly increase the energy consumption cost, which is not conducive to the development of the enterprise. At present, the optimization process of energy consumption and material consumption of chemical production devices is accelerating. In order to maximize the benefits to the greatest extent, the applicant has found through research that through certain technical improvements, the operating flexibility of the pre-dehydration tower can be expanded, the chemical oxygen demand of the wastewater can be effectively reduced, and the amount of reflux condensate can be greatly reduced, thereby reducing the use of steam and promoting cost savings.

[0003] 202311476493.1 discloses a method for dehydrating an ethylene glycol aqueous solution, which comprises the following steps: firstly, modifying a cationic resin with metal ions to obtain a modified cationic resin; secondly, passing an ethylene glycol aqueous solution and excess butyraldehyde through a packing tower filled with the modified cationic resin to react for a period of time; wherein the butyraldehyde is used as both a reactant and an extractant; finally, after reacting for a period of time, standing and separating the solution, using the modified cationic resin as a catalyst, allowing the extract phase to hydrolyze at a certain temperature, and then distilling and recovering the butyraldehyde to obtain a concentrated ethylene glycol aqueous solution;

[0004] The above equipment requires a large amount of butyraldehyde and has low dehydration efficiency and operating flexibility. Based on this, how to improve the pre-dehydration effect and operating flexibility of the ethylene glycol device is an urgent task. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide an ethylene glycol pre-dehydration tower device and a method of using the same, so as to solve the technical problems of low operating flexibility and poor pre-dehydration effect of the ethylene glycol pre-dehydration tower.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: an ethylene glycol pre-dehydration tower device and a method of using the same, comprising an ethylene glycol pre-dehydration tower for pre-dehydrating an ethylene glycol aqueous solution, characterized in that a mist pad, a spray device, a first elastic tower plate, a second elastic tower plate, a third elastic tower plate and a fourth elastic tower plate are installed from top to bottom in the ethylene glycol pre-dehydration tower, wherein the first elastic tower plate, the second elastic tower plate, the third elastic tower plate and the fourth elastic tower plate have the same structure, the elastic tower plate has a float valve as a channel for gas-liquid connection, the float valve automatically adjusts the opening according to the change of gas-liquid flow rate, and also has a downcomer for draining the liquid from the upper tower plate to the lower tower plate, and the condensate from the upper tower plate is drained to the lower tower plate to contact and mix with the gas phase;

[0007] The process condensate water pipeline and the clean condensate water pipeline are connected to supply liquid to the spray device. The process condensate water pipeline and the clean condensate water pipeline are arranged in the same manner and are both provided with a first delivery pump, a first flow meter and a first flow valve. A first gate valve is installed on the converging pipeline of the clean condensate water pipeline and the process condensate water pipeline. The feed pipeline introduces ethylene glycol aqueous solution from outside the boundary and adds it from the middle of the ethylene glycol pre-dehydration tower. The process condensate water pipeline and the clean condensate water pipeline use the first delivery pump to deliver the condensed water in the process condensate water pipeline and the clean condensate water pipeline to the spray device, wherein the first delivery pumps of the process condensate water pipeline and the process condensate water pipeline can be started at the same time, and the flow rate and delivery volume of each pipeline are respectively measured by the first flow meter and the first flow valve, and the multiple condensate sources are used to meet the replenishment volume of the ethylene glycol pre-dehydration tower;

[0008] An ethylene glycol aqueous solution is drawn out from the bottom of the ethylene glycol pre-dehydration tower, heated in a tower kettle reboiler, and then refluxed into the ethylene glycol pre-dehydration tower. The tower kettle reboiler is connected to steam heating from a steam pipeline. The steam pipeline is connected to 0.5Mpa steam to heat the tower kettle reboiler. A second gate valve, a second flow meter, and a second flow valve are arranged on the steam pipeline. A pressure relief pipeline is connected to the upper part of the ethylene glycol pre-dehydration tower. A second pressure gauge and a flow rate controller are arranged on the pressure relief pipeline. The pressure relief pipeline is used to take out the low-pressure steam generated by ethylene glycol dehydration. The discharge speed of the low-pressure steam is controlled by the second pressure gauge and the flow rate controller. The generated low-pressure steam is used for heating the tower kettle reboiler to maintain the temperature of the tower kettle reboiler and reduce the steam consumption of the tower kettle reboiler. At the same time, the low-pressure steam can be used for pipeline heating in the plant area, and the condensed water generated by the heating is returned for utilization;

[0009] The bottom of the glycol pre-dehydration tower is connected to the first drainage funnel through a drainage pipeline, a branch pipeline is connected to the second delivery pump from the drainage pipeline, and the second delivery pump is connected to the second drainage funnel through a pipeline.

[0010] Furthermore: the pressure difference between the upper part of the first elastic tower tray and the lower part of the fourth elastic tower tray is greater than 10 kPa.

[0011] Furthermore: the ethylene glycol pre-dehydration tower is provided with a first thermometer and a second thermometer, the first thermometer displays the gas phase temperature, and the second thermometer displays the liquid phase temperature.

[0012] Further: the second delivery pump is also connected to a delivery pipeline connected to the ethylene glycol pre-dehydration tower kettle filter, the delivery pipeline is provided with a first pressure gauge, a third gate valve and a fourth gate valve in sequence, the upper part of the ethylene glycol pre-dehydration tower kettle filter is connected to the third drainage funnel through a tower top pipeline, the tower top pipeline is provided with a fifth gate valve, a part of the liquid after being filtered by the ethylene glycol pre-dehydration tower kettle filter is sent to the dehydration tower for vacuum complete dehydration, and the other part enters the ethylene glycol downstream through the third drainage funnel;

[0013] The lower parts of the first drainage funnel, the second drainage funnel and the third drainage funnel converge and are sent to the downstream of ethylene glycol.

[0014] Furthermore: taking the ethylene glycol feed amount as the base, the total water intake of clean condensed water and process condensed water is 15% to 30% of the ethylene glycol feed amount, and the steam with a ratio of 20% to 35% of the ethylene glycol feed amount as the base is used to heat the tower bottom reboiler, so that the temperature of the tower bottom liquid is above 140°C, and the low-pressure steam flow rate taken out from the top of the ethylene glycol pre-dehydration tower is 40% to 60% of the sum of the total water intake and the feed amount, and the pressure difference between the upper part of the first elastic tower plate and the lower part of the fourth elastic tower plate is maintained at 10-11 MPa.

[0015] Compared with the prior art, the present invention has the following advantages: on the one hand, the operational flexibility of the ethylene glycol pre-dehydration tower is expanded by combining a plurality of elastic tower plates; on the other hand, the discharge speed and discharge amount of the tower top steam of the pressure relief pipeline are adjusted according to the flow rate of the ethylene glycol aqueous solution and the amount of condensed water used, the pressure difference between the upper part of the first elastic tower plate and the lower part of the fourth elastic tower plate is maintained, the pre-dehydration capacity of ethylene glycol is improved, and the organic matter content at the tower top is made lower than 0.02wt%. Since the structure of the present application is more reasonable, the production cost is lower, and it is suitable for comprehensive promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] In the description of the invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0019] Embodiment 1:

[0020] In one technical solution of the present invention, Figure 1 As shown, an ethylene glycol pre-dehydration tower device and a method of using the same include an ethylene glycol pre-dehydration tower 9 for pre-dehydrating an ethylene glycol aqueous solution, characterized in that a mist pad 8, a spray device 10, a first elastic tower plate 11, a second elastic tower plate 13, a third elastic tower plate 14 and a fourth elastic tower plate 16 are installed from top to bottom in the ethylene glycol pre-dehydration tower 9, the elastic tower plate has a float valve as a channel for vapor and liquid to be connected, the float valve automatically adjusts the opening according to the change of vapor and liquid flow, and also has a downcomer for draining the liquid from the upper tower plate to the lower tower plate, and the condensate from the upper tower plate is drained to the lower tower plate to contact and mix with the gas phase;

[0021] After the process condensate water pipeline 2 and the clean condensate water pipeline 3 are merged, the liquid is supplied to the spray device 10. The process condensate water pipeline 2 and the clean condensate water pipeline 3 are arranged in the same manner and are both provided with a first delivery pump 5, a first flow meter 6 and a first flow valve 7. A first gate valve 4 is installed on the converging pipeline of the clean condensate water pipeline 3 and the process condensate water pipeline 2. The feed pipeline 40 introduces ethylene glycol aqueous solution from outside the boundary and adds it from the middle of the ethylene glycol pre-dehydration tower 9. The process condensate water pipeline and the clean condensate water pipeline use the first delivery pump to deliver the condensed water in the process condensate water pipeline and the clean condensate water pipeline to the spray device, wherein the first delivery pumps of the process condensate water pipeline and the process condensate water pipeline can be started at the same time, and the flow rate and delivery volume of each pipeline are respectively measured by the first flow meter and the first flow valve, and the multi-condensate source is used to meet the replenishment volume of the ethylene glycol pre-dehydration tower;

[0022] An ethylene glycol aqueous solution is drawn out from the bottom of the ethylene glycol pre-dehydration tower 9, heated in the tower kettle reboiler 20, and then refluxed into the ethylene glycol pre-dehydration tower 9. The tower kettle reboiler 20 is connected to steam heating from a steam pipeline 41. A second gate valve 17, a second flow meter 18, and a second flow valve 19 are arranged on the steam pipeline 41. A pressure relief pipeline 44 is connected to the upper part of the ethylene glycol pre-dehydration tower 9. A second pressure gauge 32 and a flow rate controller 33 are arranged on the pressure relief pipeline 44. The pressure relief pipeline is used to take out the low-pressure steam generated by ethylene glycol dehydration. The discharge speed of the low-pressure steam is controlled by the second pressure gauge and the flow rate controller. The generated low-pressure steam is used for heating the tower kettle reboiler to maintain the temperature of the tower kettle reboiler and reduce the steam consumption of the tower kettle reboiler. At the same time, the low-pressure steam can be used for pipeline heating in the plant area, and the condensed water generated by the heating is returned for utilization;

[0023] The bottom of the glycol pre-dehydration tower 9 is connected to the first drainage funnel 21 through a drainage pipeline 45, a branch pipeline 46 is connected to the drainage pipeline 45 and connected to the second delivery pump 23, and the second delivery pump 23 is connected to the second drainage funnel 22 through a pipeline;

[0024] The glycol pre-dehydration tower 9 is provided with a first thermometer 12 and a second thermometer 15, wherein the first thermometer 12 displays the gas phase temperature and the second thermometer 15 displays the liquid phase temperature;

[0025] The second delivery pump 23 is also connected to a delivery pipeline 47 connected to the ethylene glycol pre-dehydration tower kettle filter 28. The delivery pipeline 47 is provided with a first pressure gauge 24, a third gate valve 25 and a fourth gate valve 26 in sequence. The upper part of the ethylene glycol pre-dehydration tower kettle filter 28 is connected to the third drainage funnel 29 through a tower top pipeline 48. The tower top pipeline 48 is provided with a fifth gate valve 27. After being filtered by the ethylene glycol pre-dehydration tower kettle filter 28, part of the liquid is sent to the dehydration tower for vacuum complete dehydration, and the other part enters the ethylene glycol downstream through the third drainage funnel 29;

[0026] The first drainage funnel 21, the second drainage funnel 22 and the third drainage funnel 29 converge at the bottom and are sent to the downstream of ethylene glycol.

[0027] By adopting the above technical scheme, the embodiment of the present invention is as follows: the feed pipeline 40 is connected to the raw material from the upstream and sent into the ethylene glycol pre-dehydration tower 9, a part of the ethylene glycol aqueous solution entering the ethylene glycol pre-dehydration tower 9 enters the tower bottom reboiler 20, the tower bottom reboiler 20 heats the ethylene glycol aqueous solution and then sends it back from the lower part of the ethylene glycol pre-dehydration tower 9, and the ethylene glycol aqueous solution is heated and vaporized;

[0028] The process condensate pipeline 2 and the clean condensate pipeline 3 are connected to the condensate from outside the boundary and sent to the spray device 10 through the first delivery pump 5. The spray device 10 sprays the condensate in the ethylene glycol pre-dehydration tower 9. During the descent of the condensate, the liquid phase and the vapor phase of the evaporation of the ethylene glycol aqueous solution are fully in two-phase contact. When the gaseous ethylene glycol is cooled, the thermal motion of the molecules gradually weakens, the distance between the molecules decreases, and the force between the molecules increases. The gaseous ethylene glycol gradually turns into a liquid state, while the condensed water, the ethylene glycol in the high-temperature gas phase is condensed and releases heat. The molecules of the condensed water absorb the heat when the gaseous ethylene glycol condenses and releases heat, the average kinetic energy of the molecules increases, the movement rate accelerates, the distance between the molecules gradually increases, and the condensed water gradually turns into a gaseous state;

[0029] The water in the liquid condensed water descending from the lower part of the first tray 11, the second tray 13, the third tray 14 and the fourth tray 16 is heated by the ascending gaseous ethylene glycol, the water vaporizes and rises, the propylene glycol liquefies and descends, the gaseous heavy components are condensed and removed multiple times, the liquid light components are continuously vaporized, and the pre-dehydration of the ethylene glycol aqueous solution is achieved. The dehydrated ethylene glycol solution is sent to the downstream of the ethylene glycol from the drainage line 45 through the first drainage funnel 21. The first drainage funnel, the second drainage funnel and the third drainage funnel are used to collect and separate the water phase. In the operation of the pre-dehydration tower, the mixture of ethylene glycol and water will produce dust. The drainage funnel is used to collect the separated water phase to prevent the water phase from re-contacting the ethylene glycol mixture. By controlling the discharge of the water phase, the drainage funnel helps maintain the liquid level in the tower to ensure the stability of the dehydration process. At the same time, the drainage funnel reduces the potential ethylene glycol in the water flowing out of the tower to maintain the purity of the ethylene glycol. The other route is sent to the second drainage funnel through the branch pipeline 36. The ethylene glycol solution in the branch pipeline 36 can also be sent to the ethylene glycol pre-dehydration tower kettle filter 28 through the second delivery pump 23. After being filtered by the ethylene glycol pre-dehydration tower kettle filter 28 to remove possible solid impurities, it is sent to the dehydration tower for vacuum drying.

[0030] Embodiment 2:

[0031] A glycol pre-dehydration tower device and a method for using the same. The device takes the glycol feed amount as a base, the total water intake of clean condensed water and process condensed water is 15% to 30% of the glycol feed amount, and the tower bottom reboiler 20 is heated by steam with a ratio of 20% to 35% of the glycol feed amount as a base, so that the temperature of the tower bottom liquid is above 140°C, the flow rate of low-pressure steam taken out from the top of the glycol pre-dehydration tower 9 is 40% to 60% of the sum of the total water intake and the feed amount, and the pressure difference between the upper part of the first elastic tower plate 11 and the lower part of the fourth elastic tower plate 16 is maintained at 10-11 MPa.

[0032] By adopting the above technical scheme, an implementation method of this scheme is as follows: taking the ethylene glycol feed amount as the base, the total water intake of clean condensed water and process condensed water is 25% of the ethylene glycol feed amount, and the steam with the ethylene glycol feed amount as the base ratio of 30% is used to heat the tower bottom reboiler 20, so that the temperature of the tower bottom liquid is above 140°C, the flow rate of low-pressure steam taken out from the top of the ethylene glycol pre-dehydration tower 9 is 50% of the sum of the total water intake and the feed amount, and the pressure difference between the upper part of the first elastic tower tray 11 and the lower part of the fourth elastic tower tray 16 is maintained at 10.3 MPa;

[0033] A further statement of the above technical scheme is as follows: the feed rate of ethylene glycol aqueous solution raw material is 184 t / h, the total water inflow of clean condensed water and process condensed water is 7 t / h, the flow rate of the tower bottom reboiler 20 is 1660 t / h, the steam pressure for heating the tower bottom reboiler 20 is 0.5 MPa, and its flow rate is 65.3 t / h. The pressure difference between the upper part of the first tower tray 11 and the lower part of the fourth tower tray 16 is controlled to be 10.3 Kpa, the tower bottom liquid temperature at the bottom of the ethylene glycol pre-dehydration tower is 142°C, and the steam discharge capacity of the pressure relief pipeline is 97 t / h.

[0034] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention. These improvements should also be regarded as within the scope of protection of the present invention.

Claims

1. An ethylene glycol pre-dehydration tower device and a method for using the same, comprising an ethylene glycol pre-dehydration tower (9) for pre-dehydrating an ethylene glycol aqueous solution, characterized in that: A mist pad (8), a spray device (10), a first elastic tray (11), a second elastic tray (13), a third elastic tray (14) and a fourth elastic tray (16) are installed from top to bottom in the ethylene glycol pre-dehydration tower (9); The process condensate pipeline (2) and the clean condensate pipeline (3) are connected to supply liquid to the spray device (10). The process condensate pipeline (2) and the clean condensate pipeline (3) are arranged in the same manner and are both provided with a first delivery pump (5), a first flow meter (6) and a first flow valve (7). A first gate valve (4) is installed on the converging pipeline of the clean condensate pipeline (3) and the process condensate pipeline (2). The feed pipeline (40) introduces ethylene glycol aqueous solution from outside the boundary and adds it from the middle of the ethylene glycol pre-dehydration tower (9); An ethylene glycol aqueous solution is drawn out from the bottom of the ethylene glycol pre-dehydration tower (9), heated in a tower kettle reboiler (20), and then refluxed into the ethylene glycol pre-dehydration tower (9); the tower kettle reboiler (20) is connected to steam heating from a steam pipeline (41); a second gate valve (17), a second flow meter (18), and a second flow valve (19) are arranged on the steam pipeline (41); a pressure relief pipeline (44) is connected to the upper part of the ethylene glycol pre-dehydration tower (9); a second pressure gauge (32) and a flow rate controller (33) are arranged on the pressure relief pipeline (44); The bottom of the ethylene glycol pre-dehydration tower (9) is connected to the first drainage funnel (21) via a drainage pipeline (45), a branch pipeline (46) is connected to the drainage pipeline (45) and connected to the second delivery pump (23), and the second delivery pump (23) is connected to the second drainage funnel (22) via a pipeline.

2. The ethylene glycol pre-dehydration tower device and the method for using the same according to claim 1, characterized in that: The pressure difference between the upper part of the first elastic tray (11) and the lower part of the fourth elastic tray (16) is greater than 10 kPa.

3. The ethylene glycol pre-dehydration tower device and the use method thereof according to claim 2, characterized in that: The ethylene glycol pre-dehydration tower (9) is provided with a first thermometer (12) and a second thermometer (15), wherein the first thermometer (12) displays the gas phase temperature and the second thermometer (15) displays the liquid phase temperature.

4. The ethylene glycol pre-dehydration tower device and the use method thereof according to claim 3, characterized in that: The second delivery pump (23) is also connected to a delivery pipeline (47) and communicated with a glycol pre-dehydration tower kettle filter (28). The delivery pipeline (47) is provided with a first pressure gauge (24), a third gate valve (25) and a fourth gate valve (26) in sequence. The upper part of the glycol pre-dehydration tower kettle filter (28) is connected to a third drainage funnel (29) through a tower top pipeline (48). A fifth gate valve (27) is provided on the tower top pipeline (48). After being filtered by the glycol pre-dehydration tower kettle filter (28), a part of the liquid is sent to a dehydration tower for complete vacuum dehydration, and the other part enters the glycol downstream through the third drainage funnel (29); The first drainage funnel (21), the second drainage funnel (22) and the third drainage funnel (29) converge at their lower parts and are sent to the downstream of ethylene glycol.

5. The ethylene glycol pre-dehydration tower device and the use method thereof according to claim 1, characterized in that: Taking the ethylene glycol feed amount as the base, the total water intake of clean condensed water and process condensed water is 15% to 30% of the ethylene glycol feed amount. Steam with a ratio of 20% to 35% of the ethylene glycol feed amount is used to heat the bottom reboiler (20), so that the temperature of the bottom liquid is above 140°C. The flow rate of low-pressure steam taken out from the top of the ethylene glycol pre-dehydration tower (9) is 40% to 60% of the sum of the total water intake and the feed amount, and the pressure difference between the upper part of the first elastic tower plate (11) and the lower part of the fourth elastic tower plate (16) is maintained at 10-11 MPa.

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