Leakage detection system for lining of urea high-pressure equipment

Abstract

The utility model relates to a leakage detection system for a lining of urea high-pressure equipment, which comprises an air inlet header pipe, the air inlet header pipe distributes air into a plurality of leakage detection loops of the urea high-pressure equipment through an air source distributor, and an electromagnetic stop valve is arranged between the air inlet header pipe and the air source distributor. A filtering pressure reducing valve is further arranged between the electromagnetic stop valve and the air source distributor, each leakage detecting loop at least comprises a leakage detecting air inlet pipe and a leakage detecting air outlet pipe which are correspondingly arranged, the leakage detecting air inlet pipe and the leakage detecting air outlet pipe are connected to leakage detecting holes in the two ends of the same channel of the urea high-pressure equipment respectively, and each leakage detecting air inlet pipe is provided with a switch valve. The leakage detection air outlet pipes of the same leakage detection loop are converged and then introduced into the same online analyzer, and the signal output end of the online analyzer is connected to a DCS system. According to the leakage detection system, the leakage detection points are divided into a plurality of leakage detection loops, each leakage detection loop is independently detected, the leakage points can be accurately positioned in time, and convenience is brought to defect elimination and maintenance of the leakage points.

Description

Technical Field

[0001] The utility model relates to the technical field of urea production, in particular to a urea high-pressure equipment lining leak detection system. Background Art

[0002] Urea high-pressure equipment mainly includes four major equipments: urea synthesis tower, stripping tower, high-pressure methylammonium condenser, high-pressure methylammonium scrubber, etc. In normal production, these high-pressure equipments are in a high-temperature, high-pressure and highly corrosive working environment of ammonium carbamate solution. In addition, it is inevitable that over-temperature and over-pressure will occur in normal production, and slight imbalances of materials such as ammonia carbon ratio, water carbon ratio, anti-corrosion oxygen content, and defects left during maintenance will cause the corrosion of the equipment lining to intensify, and leakage will occur in severe cases. If the leakage is not discovered and handled in time, the leakage will continue to expand, and the leaked medium will corrode and penetrate the carbon steel layer of the equipment shell, and even cause explosions, causing vicious safety and environmental accidents.

[0003] Therefore, it is necessary to set up a leak detection system for such equipment. The leak detection methods currently used are steam leak detection and ammonia infrared detection. The steam leak detection method is to pass steam into the various leak detection holes of the high-pressure equipment, and the steam passing through the leak detection channel is led out of the equipment from the leak detection pipe. Once the lining of the equipment leaks, the leaked ammonia-containing medium will be taken out with the steam, and then the ammonia content in the steam is sampled and analyzed to determine whether the lining of the high-pressure equipment leaks. Since urea steam sometimes contains trace amounts of ammonia, it is not possible to determine the presence of a leak based solely on the presence of ammonia in the steam. Multiple analyses are required to improve the accuracy rate. This analysis cannot be done in real time online, which is not conducive to timely detection of equipment leaks. In addition, trace amounts of ammonia will form ammonia water after condensation in the leak detection channel. Ammonia water can easily enter the carbon steel layer of the equipment shell, causing stress corrosion to it, and it is also easy to cause rust in carbon steel equipment or pipelines. The generated rust and other impurities enter the leak detection channel with the steam, causing the leak detection channel to be blocked, so that the leak detection system cannot operate effectively.

[0004] The ammonia infrared detection method is to pass nitrogen into each leak detection hole of the high-pressure equipment, and the nitrogen that passes through the leak detection channel is led out of the equipment from the leak detection main pipe, and then the ammonia content in the nitrogen is detected by instrument analysis to determine whether there is a leak. Although this method realizes online real-time leak detection, since the nitrogen is collected and led out of the leak detection nitrogen main pipe, it is necessary to ensure that each leak detection pipe is unobstructed in order to accurately detect whether the equipment has a leak. Moreover, such a setting can only determine whether the entire equipment has a leak, but cannot locate the specific leak point. Utility Model Content

[0005] In view of the problems existing in the above-mentioned leak detection method, the utility model provides a urea high-pressure equipment lining leak detection system, which can monitor the leakage of the urea high-pressure equipment online in real time and accurately locate the leakage point.

[0006] The specific technical scheme of the utility model is: a urea high-pressure equipment lining leak detection system, including an air intake main pipe, the air intake main pipe diverts the gas into several leak detection circuits of the urea high-pressure equipment through an air source distributor, an electromagnetic shut-off valve is also arranged between the air intake main pipe and the air source distributor, and a filter pressure reducing valve is also arranged between the electromagnetic shut-off valve and the air source distributor, each of the leak detection circuits includes at least one group of correspondingly arranged leak detection air intake pipes and leak detection air outlet pipes, the leak detection air intake pipes and leak detection air outlet pipes are respectively connected to the leak detection holes at both ends of the same channel of the urea high-pressure equipment, each of the leak detection air intake pipes is provided with a switch valve, the leak detection air outlet pipes of the same leak detection circuit are collected and introduced into the same online analyzer, and the signal output end of the online analyzer is connected to the DCS system.

[0007] Further, preferably, nitrogen or non-corrosive inert gas is introduced into the intake manifold.

[0008] Furthermore, preferably, the online analyzer is connected to the DCS system by hard wiring.

[0009] Furthermore, preferably, the online analyzer has an alarm function.

[0010] Further, preferably, the online analyzer has a measurement range of 0 to 1000 ppm, a measurement accuracy of 1 ppm, an indication error of ±5% FS, a response time T90 < 30S, and an energized remote transmission function outputting a standard 4 to 20 mA signal.

[0011] Furthermore, preferably, a flow meter is also provided on the leak detection circuit.

[0012] The beneficial effects of the utility model are as follows: the leak detection system divides the leak detection points into multiple leak detection loops according to the structural characteristics of the urea high-pressure equipment, and detects each leak detection loop separately, which can accurately locate the leak point in time, bringing convenience to the repair and elimination of the leak point of the equipment. At the same time, the DCS system realizes remote real-time monitoring of the entire leak detection system. Compared with the existing leak detection methods, the accuracy and timeliness of leak detection have been improved, and the operator can also analyze and predict the leakage situation according to the historical trend chart of each leak point, which provides a strong guarantee for the long-term safe operation of the urea high-pressure equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of equipment connection of a urea high-pressure equipment lining leak detection system according to an embodiment;

[0014] Figure 2 Display screen for DCS system;

[0015] In the figure: 1-air intake main pipe, 2-electromagnetic shut-off valve, 3-filter pressure reducing valve, 4-gas source distributor, 5-leak detection circuit, 501-leak detection air intake pipe, 502-leak detection air outlet pipe, 6-flow meter, 7-switch valve, 8-online analyzer, 9-DCS system, 10-urea high-pressure equipment. DETAILED DESCRIPTION

[0016] In order to make the technical problems and technical solutions solved by the utility model more clearly understood, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0017] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0018] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] like Figure 1 Figure 2 As shown, a urea high-pressure equipment lining leak detection system includes an air intake main pipe 1, which diverts gas into several leak detection circuits 5 of the urea high-pressure equipment 10 through an air source distributor 4. An electromagnetic shut-off valve 2 is also provided between the air intake main pipe 1 and the air source distributor 4, and a filter pressure reducing valve 3 is also provided between the electromagnetic shut-off valve 2 and the air source distributor 4. Each leak detection circuit 5 includes at least one set of correspondingly arranged leak detection air intake pipes 501 and leak detection air outlet pipes 502. The leak detection air intake pipes 501 and the leak detection air outlet pipes 502 are respectively connected to the leak detection holes at both ends of the same channel of the urea high-pressure equipment 10. A flow meter 6 is provided on the leak detection circuit 5, and a switch valve 7 is provided on each leak detection air intake pipe 501. The leak detection air outlet pipes 502 of the same leak detection circuit are collected and introduced into the same online analyzer 8, and the signal output end of the online analyzer 8 is connected to the DCS system 9.

[0020] The gas introduced into the air intake main pipe is nitrogen or non-corrosive inert gas to avoid corrosion of the blind layer plate and shell of the urea synthesis tower.

[0021] The leak detection hole is set when the urea high-pressure equipment is manufactured. It is an existing structure. The specific structure can refer to Liaohe Fertilizer Plant, Liu Ziliang, Current status and maintenance of the leak detection system of urea high-pressure equipment; Zhao Jianguo, Comparison of the leak detection hole structure of multi-layer wrapped thick-walled cylinder sections of urea synthesis tower, Chemical Safety and Environment 2005, 50(812): 14-16.

[0022] The electromagnetic cut-off valve 2 is interlocked with the urea high-pressure device 10. When the urea high-pressure device 10 is running, the electromagnetic cut-off valve 2 is opened to connect the leak detection gas source; when the urea high-pressure device 10 is shut down for maintenance, the electromagnetic cut-off valve 2 is closed to cut off the leak detection gas source.

[0023] The flow meter 6 can use a glass flow meter, and the air intake can be flexibly adjusted according to the displayed value of the flow meter to ensure that the air intake of each leak detection circuit is sufficient, thereby avoiding the leak detection channel being blocked due to too low air intake.

[0024] The switch valve 7 can use an electric stop valve to facilitate remote control.

[0025] The online analyzer 8 uses a fixed electrochemical online analyzer with a measurement range of 0-1000ppm, a measurement accuracy of 1ppm, an indication error of ±5% FS, a response time of T90 <30S, and a live remote transmission function that outputs a standard 4-20mA signal. It can also be equipped with an alarm (such as an audible and visual alarm) to give an alarm when the detected ammonia content exceeds the alarm threshold. The online analyzer is made of 304 stainless steel and has good corrosion resistance.

[0026] In order to ensure the reliability of the leak detection system, the online analyzer 8 and the DCS system 9 are connected by hard wiring.

[0027] The DCS system realizes the display, monitoring, analysis and alarm of the leak detection system. The leak detection system is connected to the process flow monitoring screen, and the real-time control of the leak detection system can be completed by operating the DCS system; the first-level alarm threshold of 5ppm and the second-level alarm threshold of 10ppm are set in the DCS system, and real-time alarm prompts can be given; trend charts can also be prepared for each leak detection point to record the trend changes of each leak detection point.

[0028] Working principle: When the urea high-pressure equipment is in operation, open the electromagnetic shut-off valve 2, and introduce nitrogen into the intake manifold 1. The nitrogen is decompressed to 0.1MPa by the filter pressure reducing valve 3 and then sent to the gas source distributor 4. The gas source distributor 4 diverts the nitrogen into several leak detection circuits 5 of the urea high-pressure equipment 10. The nitrogen flows from the leak detection inlet pipe 501 into the leak detection channel inside the urea high-pressure equipment 10, and flows out from the leak detection outlet pipe 502 after passing through the leak detection channel. In this process, the nitrogen will bring out the leaking medium, and the leak detection outlet pipe 502 of each leak detection circuit 5 will collect it and introduce it into the online analyzer 8 for analysis, and transmit the analysis result signal to the DCS system for display and alarm. When an alarm occurs at the leak detection point, the possible leak point is found through the corresponding alarm instrument, and then the specific leak point is accurately determined by controlling the switch valve 7 on the leak detection inlet pipe 501.

[0029] The company's ammonia processing center has two urea production units: the B urea production unit is a urea production unit that uses the ammonia self-stripping process from SNAMPROGETTI, Italy, with an annual output of 130,000 tons of urea; the C urea production unit uses the carbon dioxide stripping process, with an annual output of 300,000 tons of urea. The leak detection system of this application is applied to the B urea production unit and the C urea production unit, and the specific situation is as follows:

[0030] 1. B urea production unit has a total of 10 detection circuits

[0031] Synthetic tower: 13 groups of leak detection holes. The top three groups and the bottom three groups each use one detection loop; the middle eight groups, every two groups use one detection loop; a total of 6 detection loops.

[0032] Stripping tower: According to the distribution of leak detection holes on site, it is divided into two groups, upper and lower. Each group uses one leak detection circuit, for a total of 2 detection circuits.

[0033] Methylamine condenser: 1 set of leak detection holes, using 1 detection loop.

[0034] Methylamine separator: 1 set of leak detection holes, using 1 detection loop.

[0035] 2. C urea production unit has 9 detection circuits

[0036] Synthesis tower: 8 groups of leak detection holes, every two groups use one detection loop, a total of 4 detection loops.

[0037] High-pressure methylammonium scrubber: two sets of leak detection holes, upper and lower, and the two sets share one detection circuit.

[0038] High-pressure methylammonium cold condenser: 2 groups of leak detection holes, each group uses 1 detection loop, a total of 2 detection loops.

[0039] Stripping tower: There are two groups of leak detection holes, one in the upper and lower parts, and each group uses one detection loop, for a total of two detection loops.

[0040] Since the leak detection system of this application was put into use in the B and C urea production units in October 2022, it has been operating well, with a leakage alarm accuracy of 100%. The entire leak detection system can be monitored in real time in the main control room without on-site operation. According to the position number of the DCS monitoring alarm point, the leakage point can be accurately located in time, which brings convenience to the elimination and maintenance of the equipment leakage point. In addition, the operator can also analyze and predict the leakage situation according to the historical trend chart of each leakage point, which is conducive to taking timely measures. Compared with traditional manual regular inspections, it not only saves manpower investment, but also improves the accuracy and timeliness of leak detection, providing a strong guarantee for the long-term safe operation of urea high-pressure equipment.

[0041] The present invention is described in detail above through specific and preferred embodiments, but those skilled in the art should understand that the present invention is not limited to the embodiments described above, and any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A urea high pressure equipment lining leak detection system, characterized in that: The invention comprises an air intake main pipe (1), wherein the air intake main pipe (1) distributes gas through an air source distributor (4) and flows into a plurality of leak detection circuits (5) of a urea high-pressure device (10); an electromagnetic shut-off valve (2) is further provided between the air intake main pipe (1) and the air source distributor (4); a filter pressure reducing valve (3) is further provided between the electromagnetic shut-off valve (2) and the air source distributor (4); each of the leak detection circuits (5) comprises at least one set of correspondingly provided leak detection air intake pipes (501) and leak detection air outlet pipes (502); the leak detection air intake pipes (501) and the leak detection air outlet pipes (502) are respectively connected to leak detection holes at both ends of the same channel of the urea high-pressure device (10); a switch valve (7) is provided on each of the leak detection air intake pipes (501); the leak detection air outlet pipes (502) of the same leak detection circuit (5) are collected and introduced into the same online analyzer (8); the signal output end of the online analyzer (8) is connected to a DCS system (9).

2. The urea high pressure equipment lining leak detection system according to claim 1, characterized in that: Introduce nitrogen or non-corrosive inert gas into the intake manifold (1).

3. The urea high pressure equipment lining leak detection system according to claim 1, characterized in that: The online analyzer (8) is connected to the DCS system (9) by hard wiring.

4. The urea high pressure equipment lining leak detection system according to claim 1, characterized in that: The online analyzer (8) is equipped with an alarm.

5. The urea high pressure equipment lining leak detection system according to claim 4, characterized in that: The online analyzer (8) has a measurement range of 0 to 1000 ppm, a measurement accuracy of 1 ppm, an indication error of ±5% FS, a response time T90 < 30 s, and an energized remote transmission function that outputs a standard 4 to 20 mA signal.

6. The urea high pressure equipment lining leak detection system according to claim 1, characterized in that: The leak detection circuit (5) is also provided with a flow meter (6).

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