Vacuum breaker and fire arrester blocking structure for maleic anhydride plant

Abstract

The utility model relates to the technical field of maleic anhydride production chemical equipment, especially to a maleic anhydride device prevents broken vacuum and fire arrestor block structure. The structure analytic tower bottom intercommunication outlet liquid pipe is connected respectively and inserts two reboilers, and the reboiler export is equipped with small bore first anti -vacuum -breaking pipe A, second anti -vacuum -breaking pipe A, first anti -vacuum -breaking pipe B, second anti -vacuum -breaking pipe B and matched control valve group, and the anti -vacuum -breaking pipe pipe diameter is less than reboiling reflux pipe, and the corresponding control valve is respectively installed on each pipeline. Two tail gas steam ejectors are communicated with analytic tower top, and are respectively connected with waste water tank through condensate tank. The device balances pressure difference through small bore anti -vacuum -breaking pipe, avoids the analytic tower instantaneous broken vacuum caused by the opening and close of large pipe diameter reboiling reflux pipe, and stabilizes the analytic working condition in the tower, simultaneously adopts double condensate tank independent drainage structure, avoids the condensate mutual stringing and backflow caused by the uneven pressure of two tail gas steam ejectors, and prevents the crystallization blockage of fire arrestor caused by the water in tail gas.

Description

Technical Field

[0001] This utility model relates to the field of chemical equipment technology for maleic anhydride production, and in particular to a structure for preventing vacuum breakage and flame arrestor blockage in a maleic anhydride device. Background Technology

[0002] The maleic anhydride unit extracts tail gas through a tail gas steam ejector. A vacuum is created using 1.5 MPa steam to draw in the tail gas from the absorption tower and other components. The resulting mixed solution is then cooled by circulating water and discharged into a wastewater tank (vacuum wastewater) for wastewater treatment. Because the condensate from the two ejectors merges into a single stream entering a sealed tank, the pressure difference between the two condensate tanks restricts drainage, causing unstable ejector operating pressure and even water carryover at the exhaust gas end. This water reacts with maleic anhydride to form maleic acid, which then converts to fumaric acid. Fumaric acid precipitates at low temperatures, clogging the flame arrester.

[0003] Because the condensate enters the wastewater tank by gravity, the downward flow of the condensate is obstructed after the water level in the wastewater tank fluctuates and the water seal is broken, causing fluctuations in the vacuum system. In addition, the tail gas steam ejectors need to be switched during the cleaning process. The two tail gas steam ejectors collect non-condensable steam through steam condensers and then discharge it into the wastewater tank. The outlets of the two steam condensers are combined. The two tail gas steam ejectors are of different models, and the gravity of the condensate water is different, causing cross-contamination during the discharge into the wastewater tank. The condensate enters the tail gas system through the tail gas steam ejectors, and the increased water content in the tail gas causes material precipitation and blockage of the flame arrester.

[0004] Because the reboiler at the bottom of the column may precipitate substances such as tar and fumaric acid during operation, causing blockage, the heat exchanger needs to be switched. The valve pipe diameter between the reboiler at the bottom of the column and the stripping column is DN1700. During the switching of the reboiler at the bottom of the column, the vacuum level will be instantly destroyed due to the large pipe diameter.

[0005] Sudden changes in vacuum can cause significant fluctuations in temperature, pressure, liquid level, and flow rate, leading to a sharp drop in the separation efficiency of units such as distillation, evaporation, and drying. Sudden changes in the pressure of the reaction system may result in uncontrolled reaction rates, increased side reactions, and decreased product purity and yield. Utility Model Content

[0006] To address the vacuum breakage caused by the reboiler switching at the bottom of the desorption column and prevent negative pressure fluctuations from affecting the desorption process, while also eliminating operational fluctuations in the exhaust gas injection system at the top of the absorption column and preventing water carryover in the exhaust gas and crystallization blockage of the flame arrester, this utility model provides a structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device.

[0007] Therefore, the present invention provides the following technical solution:

[0008] A structure for preventing vacuum breaking and flame arrester blockage in a maleic anhydride apparatus includes a stripping column. The bottom liquid outlet of the stripping column is connected to a liquid outlet pipe, which is connected to the inlets of a first reboiler and a second reboiler. The outlet of the first reboiler is connected to the first heating reflux port of the stripping column via a first reboiler reflux pipe, and the outlet of the second reboiler is connected to the second heating reflux port of the stripping column via a second reboiler reflux pipe (to achieve circulating heating of the bottom material of the stripping column and ensure stable distillation stripping conditions). A first reboiler reflux valve and a second reboiler reflux valve are respectively installed on the first and second reboiler reflux pipes (for main circuit on / off control, realizing one-to-one switching of reboilers). The outlet of the first reboiler is connected to the first anti-vacuum tube A. The first anti-vacuum tube A is connected to the first drain tube and the first anti-vacuum tube B. The first drain tube is connected to the first drain valve. The first anti-vacuum tube B is connected to the first steam inlet of the stripping tower (a small-diameter balance bypass is added for pre-balancing pressure difference before switching). The outlet of the second reboiler is connected to the second anti-vacuum tube A, the second anti-vacuum tube A is connected to the second anti-vacuum tube B, and the second anti-vacuum tube B is connected to the second steam inlet of the stripping column (the two bypasses are set independently and are adapted to the switching operation of the two reboilers respectively). First vacuum rupture prevention valve A and second vacuum rupture prevention valve A are respectively installed on the first vacuum rupture prevention tube A and the second vacuum rupture prevention tube A; first vacuum rupture prevention valve B and second vacuum rupture prevention valve B are respectively installed on the first vacuum rupture prevention tube B and the second vacuum rupture prevention tube B (by precisely controlling the opening and closing of the bypass through grouped valves, slow pressure relief and stabilization are achieved). The top of the analytical tower is connected to a tail gas steam ejector via a tail gas pipe. The outlet of the tail gas steam ejector is connected to a condensate tank, and the condensate outlet of the condensate tank is connected to a wastewater tank via a condensate pipe.

[0009] Furthermore, the first anti-rupture vacuum tube A is connected to the first drain pipe, and the first drain pipe is connected to the first drain valve; the second anti-rupture vacuum tube A is connected to the second drain pipe, and the second drain pipe is connected to the second drain valve.

[0010] Furthermore, a first drain valve and a second drain valve are respectively installed on the first drain pipe and the second drain pipe (when the pipeline is blocked, the drain valve is opened to clear the pipeline).

[0011] Furthermore, the top of the analytical tower is connected to two tail gas steam ejectors via a tail gas pipe (one for operation and one for standby, both are three-stage ejectors; in cases of insufficient vacuum, both tail gas steam ejectors will be used simultaneously). The outlet of the first tail gas steam ejector is connected to the first condensate tank, and the outlet of the second tail gas steam ejector is connected to the second condensate tank. The condensate outlet of the first condensate tank is connected to the first condensate pipe, and the condensate outlet of the second condensate tank is connected to the second condensate pipe. Both the first and second condensate pipes are connected to a wastewater tank (when one condensate tank is in operation, the other condensate tank serves as a standby). A first drain valve and a second drain valve are respectively installed on the first and second condensate pipes (to independently regulate the condensate discharge of each branch and maintain a stable water seal level).

[0012] Furthermore, the diameters of the first anti-vacuum tube A and the second anti-vacuum tube A, as well as the first anti-vacuum tube B and the second anti-vacuum tube B, are all smaller than the diameters of the first reboiler reflux tube and the second reboiler reflux tube (using small-diameter flow limiting buffers to prevent instantaneous pressure relief during the opening and closing of large valves and to prevent sudden vacuum break in the analytical column).

[0013] Furthermore, the wastewater tank is equipped with a remote level gauge and a local level gauge.

[0014] Advantages and positive effects of this utility model: This structure is equipped with a first vacuum rupture prevention tube A, a second vacuum rupture prevention tube A, a first vacuum rupture prevention tube B, a second vacuum rupture prevention tube B, and matching first vacuum rupture prevention valve A, second vacuum rupture prevention valve A, first vacuum rupture prevention valve B, and second vacuum rupture prevention valve B. During the switching from the first reboiler to the second reboiler, the second vacuum rupture prevention valve B is slightly opened first, followed by the second vacuum rupture prevention valve A. After stable steam discharge, the first vacuum rupture prevention valve B and the first vacuum rupture prevention valve A are closed. This effectively avoids the instantaneous vacuum rupture problem caused by the opening and closing of the large-diameter reboiler reflux pipeline, stabilizes the vacuum level inside the stripping column, the bottom temperature of the column, and the steam consumption, ensures the material stripping and distillation separation effect of the stripping column, and avoids the impact of operating condition fluctuations on production continuity.

[0015] Two exhaust gas steam ejectors are connected to the top of the analytical tower. The outlets of the exhaust gas steam ejectors are connected to the corresponding condensate tanks. Each condensate tank is then connected to the wastewater tank through a corresponding condensate pipe. At the same time, the liquid level is monitored in real time by a liquid level gauge to ensure that the liquid level in the wastewater tank does not exceed 60% and is lower than the condensate drain pipe outlet. This completely eliminates the possibility of condensate cross-contamination and backflow caused by the convergence of the outlets of the two exhaust gas steam ejectors due to differences in specifications. It stabilizes the steam supply conditions of the first and second condensate pipes, ensures the negative pressure suction effect of the exhaust gas steam ejectors, and allows one to be used and the other to be on standby, so that they can work independently.

[0016] This structure effectively prevents condensate from mixing into the exhaust gas system, eliminates the formation of crystals from maleic anhydride upon contact with water, solves the problem of flame arrester blockage, reduces equipment cleaning frequency, lowers operation and maintenance costs, and at the same time avoids damage to the desorption tower and exhaust gas steam ejector caused by condensate backflow and water in the exhaust gas, thus extending the service life of the equipment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device provided by this utility model.

[0019] Figure 2 This is a schematic diagram of the condensate structure of a maleic anhydride device for preventing vacuum breakage and flame arrestor blockage, provided by this utility model.

[0020] In the diagram: 1. Desorption tower; 2. Discharge pipe; 3. First reboiler; 4. Second reboiler; 5. First reboiler reflux pipe; 6. Second reboiler reflux pipe; 7. First vacuum protection pipe A; 8. First drain pipe; 9. First vacuum protection pipe B; 10. Second vacuum protection pipe A; 11. Second drain pipe; 12. Second vacuum protection pipe B; 13. First condensate tank; 14. Second condensate tank; 15. First condensate pipe; 16. Second condensate pipe; 17. Wastewater tank; 18. First reboiler reflux valve; 19. Second reboiler reflux valve; 20. First vacuum protection valve A; 21. Second vacuum protection valve A; 22. First vacuum protection valve B; 23. Second vacuum protection valve B; 24. First drain valve; 25. Second drain valve; 26. First drain valve; 27. Second drain valve. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention 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 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 should fall within the protection scope of the present invention.

[0022] This utility model provides a structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device, such as... Figure 1As shown, the system includes a stripping column 1. The bottom liquid outlet of the stripping column 1 is connected to a liquid outlet pipe 2, which is connected to the inlets of a first reboiler 3 and a second reboiler 4. The outlet of the first reboiler 3 is connected to the first heating reflux port of the stripping column 1 via a first reboiler reflux pipe 5, and the outlet of the second reboiler 4 is connected to the second heating reflux port of the stripping column 1 via a second reboiler reflux pipe 6. A first reboiler reflux valve 18 and a second reboiler reflux valve 19 are respectively installed on the first reboiler reflux pipe 5 and the second reboiler reflux pipe 6.

[0023] The diameters of the first anti-rupture vacuum tube A7, the second anti-rupture vacuum tube A10, the first anti-rupture vacuum tube B9, and the second anti-rupture vacuum tube B12 are all smaller than the diameters of the first reboiler reflux tube 5 and the second reboiler reflux tube 6.

[0024] The outlet of the first reboiler 3 is connected to the first anti-vacuum tube A7, which is connected to the first drain tube 8 and the first anti-vacuum tube B9. The first drain tube 8 is connected to the first drain valve 24, and the first anti-vacuum tube B9 is connected to the first steam inlet of the stripping column 1. The outlet of the second reboiler 4 is connected to the second anti-vacuum tube A10, which is connected to the second drain tube 11 and the second anti-vacuum tube B12. The second drain tube 11 is connected to the second drain valve 25, and the second anti-vacuum tube B12 is connected to the second steam inlet of the stripping column 1.

[0025] A first vacuum rupture prevention valve A20 and a second vacuum rupture prevention valve A21 are respectively installed on the first vacuum rupture prevention tube A7 and the second vacuum rupture prevention tube A10; a first vacuum rupture prevention valve B22 and a second vacuum rupture prevention valve B23 are respectively installed on the first vacuum rupture prevention tube B9 and the second vacuum rupture prevention tube B12. A first drain valve 24 and a second drain valve 25 are respectively installed on the first drain pipe 8 and the second drain pipe 11.

[0026] like Figure 2 As shown, the top of the analytical tower is connected to two tail gas steam ejectors. The outlet of the first tail gas steam ejector is connected to the first condensate tank 13, and the outlet of the second tail gas steam ejector is connected to the second condensate tank 14. The condensate outlet of the first condensate tank 13 is connected to the first condensate pipe 15, and the condensate outlet of the second condensate tank 14 is connected to the second condensate pipe 16. Both the first condensate pipe 15 and the second condensate pipe 16 are connected to the wastewater tank 17.

[0027] A first drain valve 26 and a second drain valve 27 are respectively installed on the first condensate pipe 15 and the second condensate pipe 16. The wastewater tank 17 is equipped with a remote level gauge and a local level gauge to monitor the liquid level in the wastewater tank 17 in real time. With the help of the drain valves, the liquid level in the wastewater tank 17 is stably controlled below 60% of the tank volume.

[0028] Working principle: The material at the bottom of the stripping column 1 is sent to the first reboiler 3 and the second reboiler 4 through the liquid outlet pipe 2. During normal production, one reboiler is in use and the other is on standby. The heated medium is returned to the stripping column 1 through the first reboiler reflux pipe 5 and the second reboiler reflux pipe 6 to provide a heat source for the stripping distillation in the column. The first reboiler reflux valve 18 and the second reboiler reflux valve 19 control the on / off of the main pipeline. The overall diameter of the first vacuum rupture prevention pipe A7, the second vacuum rupture prevention pipe A10, the first vacuum rupture prevention pipe B9, and the second vacuum rupture prevention pipe B12 is much smaller than that of the main reboiler reflux pipeline. The small-diameter vacuum rupture prevention pipeline restricts and buffers the flow to achieve a smooth pressure difference transition.

[0029] Taking the switching from the first reboiler 3 to the second reboiler 4 as an example: First, slightly open the second vacuum rupture prevention valve B23, then open the second vacuum rupture prevention valve A21. After the steam in the second reboiler 4 enters the stripping column through the second vacuum rupture prevention tube A10 and the second vacuum rupture prevention tube B12, and the system pressure is balanced, close the first vacuum rupture prevention valve B22 and the first vacuum rupture prevention valve A20 to maintain system pressure balance. Then, gradually open the second vacuum rupture prevention valve B23 to 80% to 100%. After the vacuum system stabilizes, open the second reboiler reflux valve 19, close the first vacuum rupture prevention valve B22 and the first vacuum rupture prevention valve A20, and finally completely close the first reboiler reflux valve 18 to complete the switch from the first reboiler 3 to the second reboiler 4. The vacuum degree, the bottom temperature of the stripping column 1, and the steam consumption parameters are monitored and recorded in real time throughout the process. Because high-pressure steam exists in the reboiler, directly switching between the first reboiler 3 and the second reboiler 4 would cause the high-pressure steam in the second reboiler 4 to directly enter the desorption column, disrupting the pressure balance within the desorption column. By first opening the small-diameter anti-vacuum-break pipeline, slowly equalizing the pressure, and then closing the large-diameter reboiler reflux main pipeline, the sudden drop in negative pressure in the desorption column 1 caused by the instantaneous opening and closing of the large-diameter pipeline is avoided, thus preventing the vacuum-break problem during the switching process, stabilizing the desorption conditions within the column, and preventing large fluctuations in process parameters.

[0030] Meanwhile, the first tail gas steam ejector and the second tail gas steam ejector are each independently equipped with a first condensate tank 13 and a second condensate tank 14, and the condensate collection systems of the two ejectors are completely separate; the condensate generated by the ejectors is collected separately without crosstalk, and then discharged into the wastewater tank 17 independently through the first condensate pipe 15, the second condensate pipe 16, the first drain valve 26, and the second drain valve 27. The original condensate confluence structure was abandoned. At the same time, the liquid level in the wastewater tank 17 was monitored in real time by remote and local level gauges. The operator adjusted the opening of the first drain valve 26 and the second drain valve 27 according to the liquid level reading to control the inlet flow rate and ensure that the liquid level in the wastewater tank does not exceed 60% and is lower than the condensate drain pipe opening, so as to maintain a continuous and effective water seal and completely avoid vacuum fluctuations caused by water seal failure. The defects of condensate cross-contamination and backflow caused by the different specifications and operating pressures of the two ejectors were eliminated, and the condensate was prevented from mixing into the tail gas system. This prevented maleic anhydride from hydrolyzing in water to form fumaric acid crystals, and prevented the tail gas back flame arrester from clogging from the root, stabilized the overall operating conditions of the tail gas absorption and vacuum system, and ensured the continuous and stable production of the maleic anhydride unit.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model 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 therein. Such 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 this utility model.

Claims

1. A structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device, characterized in that, The system includes a desorption tower (1), the bottom liquid outlet of which is connected to a liquid outlet pipe (2), and the liquid outlet pipe (2) is connected to the inlets of the first reboiler (3) and the second reboiler (4) respectively; the outlet of the first reboiler (3) is connected to the first heating reflux port of the desorption tower (1) through the first reboiler reflux pipe (5), and the outlet of the second reboiler (4) is connected to the second heating reflux port of the desorption tower (1) through the second reboiler reflux pipe (6); a first reboiler reflux valve (18) and a second reboiler reflux valve (19) are respectively installed on the first reboiler reflux pipe (5) and the second reboiler reflux pipe (6). The outlet of the first reboiler (3) is connected to the first anti-vacuum tube A (7), the first anti-vacuum tube A (7) is connected to the first anti-vacuum tube B (9), and the first anti-vacuum tube B (9) is connected to the first steam inlet of the stripping tower (1); The outlet of the second reboiler (4) is connected to the second anti-vacuum tube A (10), the second anti-vacuum tube A (10) is connected to the second anti-vacuum tube B (12), and the second anti-vacuum tube B (12) is connected to the second steam inlet of the stripping tower (1); First vacuum rupture valve A (20) and second vacuum rupture valve A (21) are installed on the first vacuum rupture prevention tube A (7) and the second vacuum rupture prevention tube A (10), respectively; first vacuum rupture valve B (22) and second vacuum rupture valve B (23) are installed on the first vacuum rupture prevention tube B (9) and the second vacuum rupture prevention tube B (12), respectively. The top of the analytical tower (1) is connected to the tail gas steam ejector through the tail gas pipe. The outlet of the tail gas steam ejector is connected to the condensate tank. The condensate outlet of the condensate tank is connected to the wastewater tank (17) through the condensate pipe.

2. The structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device according to claim 1, characterized in that, The first anti-break vacuum tube A (7) is connected to the first drain tube (8), and the first drain tube (8) is connected to the first drain valve (24); the second anti-break vacuum tube A (10) is connected to the second drain tube (11), and the second drain tube (11) is connected to the second drain valve (25).

3. The structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device according to claim 1, characterized in that, The top of the analytical tower (1) is connected to two tail gas steam ejectors via tail gas pipes. The outlet of the first tail gas steam ejector is connected to the first condensate tank (13), and the outlet of the second tail gas steam ejector is connected to the second condensate tank (14). The condensate outlet of the first condensate tank (13) is connected to the first condensate pipe (15), and the condensate outlet of the second condensate tank (14) is connected to the second condensate pipe (16). Both the first condensate pipe (15) and the second condensate pipe (16) are connected to the wastewater tank (17). A first drain valve (26) and a second drain valve (27) are respectively installed on the first condensate pipe (15) and the second condensate pipe (16).

4. The structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device according to claim 1, characterized in that, The diameters of the first anti-rupture vacuum tube A (7) and the second anti-rupture vacuum tube A (10), as well as the first anti-rupture vacuum tube B (9) and the second anti-rupture vacuum tube B (12), are all smaller than the diameters of the first reboiler reflux tube (5) and the second reboiler reflux tube (6).

5. The structure for preventing vacuum breakage and flame arrester blockage in a maleic anhydride device according to claim 1, characterized in that, The wastewater tank (17) is equipped with a remote level gauge and a local level gauge.

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