Steam heat source control system of distillation tower reboiler

Abstract

The utility model discloses a steam heat source control system of a reboiler of a distillation tower. The steam heat source control system comprises the reboiler connected with the distillation tower, the reboiler is respectively connected with a steam inlet reboiler pipeline and a reboiler outlet condensed water pipeline; the device further comprises a condensed water tank; a condensed water tank top gas phase pipeline and a condensed water tank bottom outlet pipeline are respectively arranged at the upper end and the lower end of the condensed water tank; the tail end of the condensed water tank top gas phase pipeline is connected to the steam inlet reboiler pipeline; the tail end of the reboiler outlet condensation water pipeline is connected to the condensation water tank bottom outlet pipeline; a liquid level meter is arranged on the condensed water tank; a steam flow meter is arranged on the steam inlet reboiler pipeline; a thermometer is arranged on the distillation tower; the liquid level meter and the steam flow meter are electrically connected with an over-relaxation selection control unit; and the override selection control unit is electrically connected with a flow regulating valve preset on a bottom outlet pipeline of the condensed water tank. Condensed water at the outlet of the reboiler does not directly enter the condensing tank and is connected with the outlet pipeline of the condensing water tank, so that the height of the skirt of the tower body is reduced, the investment is saved, the working efficiency is high, and the device is safe and reliable.

Description

Technical Field

[0001] The utility model belongs to the technical field of distillation tower reboilers, in particular to a steam heat source control system for a distillation tower reboiler. Background Art

[0002] The reboiler is a special heat exchanger that can exchange heat and has a vaporization space. It is an important part of the distillation tower system. Steam is the most common and typical heat source for the reboiler. There are two control systems for the conventional reboiler at the bottom of the distillation tower with steam as the heat source: 1) A control valve is set on the steam pipe at the inlet of the reboiler, and the condensation temperature of the steam is changed by adjusting the pressure of the steam after the control valve, thereby adjusting the heat transfer temperature difference of the reboiler to achieve the purpose of controlling the heat transfer rate of the reboiler. This control method has a simple control loop and low investment, but because the sensitive plate temperature or product quality of the distillation tower has a strong hysteresis, the control quality is not ideal, so this control scheme is only suitable for simple distillation processes. 2) A control valve is set on the condensate pipe at the outlet of the reboiler, and the liquid level of the condensate in the reboiler is adjusted to change the heat transfer area of ​​the reboiler to achieve the purpose of controlling the heat transfer rate of the reboiler. At present, due to the flow rate of the steam trap, a condensate tank is usually set at the outlet of the steam condensate. A gas phase balance is set at the top of the condensate tank and connected to the steam pipeline at the inlet of the reboiler. A control valve is set on the outlet pipeline of the condensate tank. The liquid level of the condensate tank is controlled by the control valve on the outlet pipeline. Under this control mode, the flow of steam is stable, the vaporization amount of the reboiler is stable, and the operation of the fractionation tower is relatively stable. However, since the balance line connects the reboiler heating steam inlet with the condensate tank, the pressure of the condensate tank is equal to the pressure of the reboiler steam side inlet. If the condensate is to flow from the reboiler to the condensate tank, there must be a certain height difference between the two to overcome the resistance of the condensate from the reboiler steam side inlet to the condensate tank. In this way, the height of the skirt of the fractionation tower has to be increased, which increases industrial investment. Moreover, if the liquid level of the condensate tank is set too high, the condensate will accumulate in the reboiler, affecting the heat exchange. If the liquid level of the condensate tank is set too low, the steam will break through the liquid seal, forming a passage, causing the reboiler to fail. Summary of the invention

[0003] The technical problem to be solved by the utility model is to overcome the existing defects and provide a steam heat source control system for a distillation tower reboiler. The condensed water at the outlet of the reboiler at the bottom of the fractionation tower does not directly enter the condensation tank, but is connected to the outlet pipeline of the condensation tank. The heat exchange area of ​​the reboiler is regulated by a flow regulating valve arranged on the outlet pipeline of the condensation tank; the regulating valve is controlled by the temperature at the bottom of the fractionation tower and the steam flow in cascade with the liquid level of the condensation tank to form an override selection control unit, which, on the one hand, matches the fractionation temperature of the material in the fractionation tower, and on the other hand, prevents the steam from breaking through the liquid seal and forming a passage, thereby avoiding failure of the reboiler and improving the reliability of the reboiler.

[0004] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a steam heat source control system for a distillation tower reboiler, comprising a reboiler connected to the distillation tower; the reboiler is respectively connected to a steam inlet reboiler pipeline and a reboiler outlet condensate pipeline, which are respectively used to provide a steam heat source for the reboiler and discharge condensate after the steam is cooled; it also comprises a condensate tank; the upper and lower ends of the condensate tank are respectively provided with a condensate tank top gas phase pipeline and a condensate tank bottom outlet pipeline; the end of the condensate tank top gas phase pipeline is connected to the steam inlet reboiler pipeline; the reboiler outlet condensate ... The end of the condensation pipeline is connected to the bottom outlet pipeline of the condensate tank; a liquid level meter is arranged on the condensate tank; a steam flow meter is arranged on the steam inlet reboiler pipeline; a thermometer is arranged on the distillation tower; the liquid level meter and the steam flow meter are electrically connected to the over-relaxation selection control unit; the over-relaxation selection control unit is electrically connected to the flow regulating valve preset on the bottom outlet pipeline of the condensate tank, and is used to control the flow regulating valve in cascade through the steam flow and the temperature of the fractionation tower, and is used to control the flow regulating valve by the liquid level of the condensate tank when the liquid level of the condensate tank is lower than the preset value. The cascade control refers to the control of the opening of the flow regulating valve by taking the temperature of the fractionation tower as the main variable and the steam flow as the secondary variable; the steam flow is positively correlated with the opening of the flow regulating valve; the temperature of the fractionation tower is negatively correlated with the opening of the flow regulating valve.

[0005] As a further optimization, a safety valve mechanism is provided at the top of the condensate tank.

[0006] As a further optimization, the liquid level meter and steam flow meter have a wireless communication module for establishing communication with the override selection control unit via wireless transmission.

[0007] As a further optimization, the bottom end of the distillation tower is connected to the bottom of the reboiler through a reboiler pipeline from the bottom of the fractionation tower; the top of the reboiler is connected to the side wall of the distillation tower through a reboiler return pipeline.

[0008] As a further optimization, the static pressure head h between the reboiler outlet flange and the flow regulating valve needs to be greater than 1.5 times the height difference converted from the pressure head loss between the reboiler condensate outlet and the flow regulating valve, and must not be less than 800mm.

[0009] As a further optimization, the flow regulating valve is 500-800 mm above the ground.

[0010] Compared with the prior art, the beneficial effects of the utility model are:

[0011] (1) The reboiler and condensate tank of this system are not arranged in series up and down. Instead, the condensate at the outlet of the reboiler does not directly enter the condensate tank, but is connected to the condensate pipeline at the outlet of the condensate tank. This greatly reduces the height of the equipment. In this way, the height of the skirt of the distillation tower does not need to be raised, saving industrial investment.

[0012] (2) The steam heating power of this system can be adapted to the operating temperature of the distillation tower, and it is sensitive to adjustment and quick to respond.

[0013] (3) The system has a water-sealing function, which prevents high-pressure steam from breaking through the water-sealing barrier, ensures that the reboiler 2 is in working condition, and prevents high-pressure steam from damaging the condensate pipeline by impact.

[0014] In short, the condensate at the reboiler outlet of this system does not directly enter the condensate tank, but is connected to the condensate tank outlet pipeline, which reduces the equipment height, saves investment, and has high working efficiency, safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of an embodiment of the utility model;

[0016] Figure 2 The figure is a schematic diagram of the height relationship between the reboiler outlet flange and the flow regulating valve in an embodiment of the utility model.

[0017] In the figure: 1. distillation tower; 2. reboiler; 3. condensate tank; 4. safety valve mechanism; 5. thermometer; 6. steam flow meter; 7. liquid level gauge; 8. low value selector; 9. flow control valve; 10. pipeline from the bottom of the distillation tower to the reboiler; 11. pipeline from the reboiler back to the tower; 12. condensate pipeline at the reboiler outlet; 13. pipeline for steam to enter the reboiler; 14. gas phase pipeline at the top of the condensate tank; 15. outlet pipeline from the bottom of the condensate tank; 16. water outlet of the reboiler; 17. outlet flange of the reboiler. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely 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 of the embodiments.

[0019] Example 1, please refer to Figure 1-2. The utility model provides a technical solution: a steam heat source control system for a distillation tower reboiler, comprising a reboiler 2 connected to the distillation tower; the reboiler 2 is respectively connected to a steam inlet reboiler pipeline 13 and a reboiler outlet condensate pipeline 12, which are respectively used to provide a steam heat source for the reboiler 2 and discharge condensate after steam cooling; it also comprises a condensate tank 3; the upper and lower ends of the condensate tank 3 are respectively provided with a condensate tank top gas phase pipeline 14 and a condensate tank bottom outlet pipeline 15; the end of the condensate tank top gas phase pipeline 14 is connected to the steam inlet reboiler pipeline 13; the end of the reboiler outlet condensate pipeline 12 is connected to the reboiler bottom outlet pipeline 15; the reboiler top gas phase pipeline 14 is connected to the reboiler bottom outlet pipeline 15; the reboiler bottom outlet pipeline 12 is connected to the reboiler top outlet pipeline 13; the reboiler bottom outlet pipeline 12 is connected to the reboiler bottom outlet pipeline 15; the reboiler top gas phase pipeline 14 is connected to the reboiler top outlet pipeline 12; the reboiler bottom outlet pipeline 12 is connected to the reboiler bottom outlet pipeline 15; the reboiler bottom outlet pipeline 12 is connected to the reboiler bottom outlet pipeline 15; the reboiler bottom outlet pipeline 12 is connected to the reboiler bottom outlet pipeline 15; the reboiler bottom outlet pipeline 12 is connected to the reboiler bottom outlet pipeline 12 ... It is connected to the bottom outlet pipeline 15 of the condensate tank; a liquid level meter 7 is arranged on the condensate tank 3; a steam flow meter 6 is arranged on the steam inlet reboiler pipeline 13; a thermometer 5 is arranged on the distillation tower; the liquid level meter 7, the steam flow meter 6 and the thermometer 5 are all electrically connected to the override selection control unit; the override selection control unit is electrically connected to the flow regulating valve 9 preset on the bottom outlet pipeline 15 of the condensate tank, and is used to control the flow regulating valve 9 in cascade through the steam flow and the temperature of the distillation tower 1, and is used to control the flow regulating valve 9 by the liquid level of the condensate tank 3 when the liquid level of the condensate tank 3 is lower than the preset value.

[0020] When in use, the condensate at the outlet of the reboiler 2 at the bottom of the fractionation tower 1 does not directly enter the condensation tank, but is connected to the condensate pipeline at the outlet of the condensate tank 3. A remote thermometer 5 is set at the bottom of the fractionation tower 1, a flow meter is set on the steam pipeline at the inlet of the reboiler 2, a remote level gauge 7 is set on the condensate tank 3, and a flow regulating valve 9 is set on the outlet pipeline of the condensate tank 3. The temperature at the bottom of the fractionation tower 1 and the steam flow are cascaded with the liquid level of the condensate tank 3 to form an override selection to control the regulating valve at the outlet of the condensate tank 3. Under normal circumstances, the steam flow and the temperature at the bottom of the fractionation tower 1 are cascaded to control the regulating valve at the outlet of the condensate tank. When the liquid level of the condensate tank 3 is low to a certain extent, the liquid level of the condensate tank 3 is used to control the regulating valve at the outlet of the condensate tank 3. The cascade control means that the temperature of the fractionation tower 1 is used as the main variable, and the steam flow rate is used as the secondary variable to jointly control the opening of the flow control valve 9; the steam flow rate is positively correlated with the opening of the flow control valve 9; the temperature of the fractionation tower 1 is negatively correlated with the opening of the flow control valve 9. First, the condensate at the outlet of the reboiler 2 at the bottom of the fractionation tower 1 does not directly enter the condensation tank, but flows back through the condensation tank bottom outlet pipeline 15 to replenish the condensation tank 3; when the bottom of the condensation tank 3 is filled with water, a water seal is formed to prevent high-pressure steam from entering the low-pressure condensation tank bottom outlet pipeline 15. When the water level in the condensation tank 3 rises, a communicating vessel is formed with the reboiler 2 through the reboiler outlet condensation pipeline 12, submerging part of the heat exchange tubes, thereby controlling the heat exchange area of ​​the reboiler 2, thereby achieving the effect of regulating the heat exchange efficiency. Secondly, the over-relaxation selection control unit including the low value selector 8 first takes the temperature of the fractionation tower 1 as the main variable and the steam flow rate as the secondary variable. When the temperature of the fractionation tower 1 is low, the preset value of the flow meter on the steam pipeline will increase. At this time, the flow control valve 9 is controlled to increase the opening to speed up drainage, lower the water level, and expand the heat exchange area of ​​the reboiler 2, thereby increasing the heating amount. When the temperature of the fractionation tower 1 is high, the preset value of the flow meter on the steam pipeline will decrease. At this time, the flow control valve 9 is controlled to decrease the opening to slow down drainage, increase the water level, and reduce the heat exchange area of ​​the reboiler 2, thereby reducing the heating amount.

[0021] However, when the liquid level of the condensate tank 3 is lower than the preset value, the water sealing effect must be maintained to prevent high-pressure steam from breaking through the water layer, so that the reboiler 2 is "short-circuited" and fails. It can be seen that the preset minimum water level still maintains the high pressure in the condensate tank 3. When the water level drops to the preset value, the flow regulating valve 9 is controlled by the liquid level of the condensate tank 3. At this time, the lower the water level, the lower the opening of the flow regulating valve 9, and the accumulated condensed water is added to the condensate tank 3 to maintain the water sealing state. It can be seen that during normal operation, the equipment does not need to be installed too high, and the condensed water at the outlet of the reboiler can also be discharged normally. Therefore, the present invention can reduce the installation height of the equipment, optimize the pipe diameter of the condensate and reduce the investment in the condensate pipe network. The heating sensitivity of the reboiler 2 is improved by cascade control of the steam flow and the bottom temperature of the fractionating tower 1, so that the heating amount can be automatically adjusted according to the feeding situation of the fractionating tower 1.

[0022] In order to improve safety, a safety valve mechanism 4 is provided at the top of the condensate tank 3 .

[0023] In order to facilitate signal transmission and reduce wiring, the liquid level meter 7, steam flow meter 6 and thermometer 5 all have wireless communication modules for establishing communication with the over-relaxation selection control unit through wireless transmission. Secondly, the over-relaxation selection control unit can also communicate with the flow control valve 9 through wireless transmission to reduce wiring costs.

[0024] In order to establish a circulating heating system between the distillation tower and the reboiler 2, the bottom end of the distillation tower is connected to the bottom of the reboiler 2 through a reboiler pipeline 10 from the bottom of the fractionation tower; the top of the reboiler 2 is connected to the bottom of the side wall of the distillation tower through a reboiler return pipeline 11.

[0025] It should be noted that there needs to be a sufficient static pressure difference from the water outlet 16 of the reboiler to the flow regulating valve 9 to drive the condensed water to flow in one direction. Preferably, the static pressure head h between the reboiler outlet flange 17 and the flow regulating valve 9 needs to be greater than 1.5 times the height difference converted from the pressure head loss between the water outlet 16 of the reboiler and the flow regulating valve 9, and shall not be less than 800mm. At this time, the difference between the reboiler outlet flange 17 and the water outlet 16 of the reboiler is one nozzle length.

[0026] In order to facilitate the installation and maintenance of the outlet control valve of the condensate tank 3, the flow regulating valve 9 is 500-800 mm above the ground.

[0027] The advantages of the utility model are as follows.

[0028] (1) The reboiler 2 and the condensate tank of the system are not arranged in series up and down, but the condensate at the outlet of the reboiler 2 does not directly enter the condensate tank, but is connected to the condensate pipeline at the outlet of the condensate tank 3; the height of the equipment is greatly reduced, so that the height of the skirt of the distillation tower 1 does not need to be raised, saving industrial investment.

[0029] (2) The steam heating power of this system can be adapted to the operating temperature of the distillation tower, and it is sensitive to adjustment and quick to respond.

[0030] (3) The system has a water-sealing function, which prevents high-pressure steam from breaking through the water-sealing barrier, ensures that the reboiler 2 is in working condition, and prevents high-pressure steam from damaging the condensate pipeline by impact.

[0031] In summary, the condensed water at the outlet of the reboiler 2 of this embodiment does not directly enter the condensation tank, but is connected to the outlet pipeline of the condensed water tank 3, which reduces the height of the equipment, saves investment, and has high working efficiency, safety and reliability.

[0032] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A steam heat source control system for a distillation tower reboiler, comprising a reboiler (2) connected to a distillation tower; the reboiler (2) is respectively connected to a steam inlet reboiler pipeline (13) and a reboiler outlet condensate pipeline (12), which are respectively used to provide a steam heat source for the reboiler (2) and discharge condensate after steam cooling; characterized in that: Also includes a condensate tank (3); The condensate tank (3) is provided with a condensate tank top gas phase pipeline (14) and a condensate tank bottom outlet pipeline (15) at the upper and lower ends thereof respectively; the end of the condensate tank top gas phase pipeline (14) is connected to the steam inlet reboiler pipeline (13); the end of the reboiler outlet condensate pipeline (12) is connected to the condensate tank bottom outlet pipeline (15); A liquid level meter (7) is provided on the condensate tank (3); a steam flow meter (6) is provided on the steam inlet reboiler pipeline (13); and a thermometer (5) is provided on the distillation tower; The liquid level meter (7) and the steam flow meter (6) are electrically connected to an over-relaxation selection control unit; the over-relaxation selection control unit is electrically connected to a flow control valve (9) provided on the bottom outlet pipeline (15) of the condensate tank.

2. The steam heat source control system of a distillation tower reboiler according to claim 1, characterized in that: A safety valve mechanism (4) is provided at the top of the condensate tank (3).

3. The steam heat source control system of a distillation tower reboiler according to claim 1, characterized in that: The liquid level meter (7), steam flow meter (6) and thermometer (5) all have a wireless communication module for establishing communication with the override selection control unit via wireless transmission.

4. The steam heat source control system of a distillation tower reboiler according to claim 1, characterized in that: The bottom end of the distillation tower is connected to the bottom of the reboiler (2) through a fractionation tower bottom inlet reboiler pipeline (10); the top end of the reboiler (2) is connected to the side wall of the distillation tower through a reboiler return pipeline (11).

5. The steam heat source control system of a distillation tower reboiler according to claim 1, characterized in that: The static pressure head h between the reboiler outlet flange (17) and the flow regulating valve (9) must be greater than 1.5 times the height difference converted from the pressure head loss between the reboiler outlet (16) and the flow regulating valve (9), and must not be less than 800 mm.

6. The steam heat source control system of a distillation tower reboiler according to claim 5, characterized in that: The flow regulating valve (9) is 500-800 mm above the ground.

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