An anti-reflux system

Abstract

The application discloses a backflow prevention system, which comprises a flow regulating valve, a cut-off valve, a check valve, a differential pressure low interlock and a signal processing unit. A feed pump is communicated with the flow regulating valve, the check valve, the cut-off valve and a high-pressure reactor in sequence. The differential pressure low interlock is communicated with an inlet pipeline connecting the feed pump and the flow regulating valve at one end and with an outlet pipeline connecting the cut-off valve and the high-pressure reactor at the other end. The output end of the differential pressure low interlock is connected with the input end of the signal processing unit in communication. The output end of the signal processing unit is connected with the control end of the flow regulating valve and the control end of the cut-off valve in communication. The signal processing unit controls the on-off of the flow regulating valve and the cut-off valve according to the differential pressure between the two ends of the differential pressure low interlock. The application realizes multi-stage protection of the high-pressure channeling low-pressure working condition by constructing a highly integrated backflow prevention system, and improves the safety of the high-pressure reaction system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-pressure reaction systems, and in particular to a backflow prevention system. BACKGROUND

[0002] High-pressure leakage into low-pressure systems is one of the common safety risks in chemical plants, which can cause contamination of low-pressure system materials, equipment overpressure rupture, and even explosion, fire, and personnel injury.

[0003] In a high-pressure reaction system, the operating pressure is often much higher than the design pressure of the low-pressure raw material tank. Once a high-pressure leakage into low-pressure backflow condition occurs, the risk is higher. Therefore, it is very important for high-pressure reactions to adopt a safety protection strategy to prevent backflow and overpressure.

[0004] The cause of a previous accident was that the circulating hydrogen compressor was interlocked to stop due to low lubricating oil pressure, which in turn interlocked the high-pressure pump to stop. However, the high-pressure pump outlet hand valve was not closed in time and the check valve failed. The high-pressure reaction liquid with a pressure of 5.7 MPaG in the reactor flowed backward into the hydrogenation raw material buffer tank through the inlet of the feed pump, causing the buffer tank to overpressure and explode and catch fire. This is a typical high-pressure reaction system pump stop backflow overpressure accident.

[0005] The existing safety technical measures to prevent backflow and overpressure generally include increasing the design pressure of the low-pressure system, adding check valves to the feed line, and equipping the low-pressure system with safety valves. Increasing the design pressure as an intrinsic safety measure greatly increases equipment investment while ensuring safety, and is not economically feasible in many high-pressure reaction systems. Adding check valves to the feed line only alleviates the occurrence of backflow conditions to a certain extent. According to the description in API 521, even if double check valves are used in series, there may still be 10% backflow, which cannot prevent low-pressure equipment overpressure from the source. While equipping the low-pressure equipment with safety valves can effectively relieve pressure, in cases where the upstream and downstream pressure difference is very large, the backflow is often large, and the relief capacity and discharge diameter of the safety valve on the low-pressure equipment increase, making it difficult to select and install, and increasing the investment in relief equipment. SUMMARY

[0006] Therefore, it is necessary to provide a backflow prevention system to solve the technical problem of insufficient safety of the existing backflow prevention system.

[0007] This invention provides an anti-backflow system, comprising: a flow regulating valve, a shut-off valve, a check valve, a low differential pressure interlock, and a signal processing unit. A feed pump is sequentially connected to the flow regulating valve, the check valve, and the shut-off valve, and then connected to a high-pressure reactor. One end of the low differential pressure interlock is connected to the inlet pipeline connecting the feed pump and the flow regulating valve, and the other end is connected to the outlet pipeline connecting the shut-off valve and the high-pressure reactor. The output end of the low differential pressure interlock is communicatively connected to the input end of the signal processing unit. The output end of the signal processing unit is communicatively connected to the control end of the flow regulating valve and the control end of the shut-off valve. The signal processing unit controls the on / off state of the flow regulating valve and the shut-off valve based on the pressure difference across the low differential pressure interlock.

[0008] Furthermore, it also includes a flow low interlock for detecting the flow rate of the outlet pipeline, the output of which is communicatively connected to the input of the signal processing unit.

[0009] Furthermore, the signal processing unit includes: a first AND gate, the first input terminal of the first AND gate being communicatively connected to the output terminal of the low flow rate interlock, the second input terminal of the first AND gate being communicatively connected to the input terminal of the low differential pressure interlock, and the output terminal of the first AND gate being communicatively connected to the control terminal of the flow regulating valve and the control terminal of the shut-off valve, respectively.

[0010] Furthermore, the input terminal of the signal processing unit is also communicatively connected to the operating signal terminal of the feed pump and / or the external interlock signal terminal. The signal processing unit also includes a second AND gate and an OR gate. The operating signal of the feed pump is communicatively connected to the first input terminal of the OR gate. The output terminal of the low flow interlock is communicatively connected to the second input terminal of the OR gate. The output terminal of the OR gate is communicatively connected to the first input terminal of the first AND gate and the second input terminal of the second AND gate, respectively. The first input terminal of the second AND gate is communicatively connected to the external interlock signal. The output terminal of the second AND gate is communicatively connected to the third input terminal of the first AND gate.

[0011] Furthermore:

[0012] The operating signal terminal of the feed pump is communicatively connected to the first input terminal of the OR gate via a first pulse element. When the first pulse element receives a signal transition, it outputs a first pulse signal; and / or

[0013] The output of the OR gate is communicatively connected to the second input of the AND gate through a second pulse element. When the second pulse element receives a signal transition, it outputs a second pulse signal.

[0014] Furthermore, the output of the OR gate is communicatively connected to the first input of the first AND gate via a delay element.

[0015] Further, the output end of the second AND gate is also connected with the control end of the feed pump, to control the opening or closing of the feed pump.

[0016] Further, a first flow controller for detecting the pipeline flow of the outlet pipeline is further included, the first flow controller controls the valve opening of the flow regulating valve according to the pipeline flow of the outlet pipeline, and the output end of the first AND gate is also connected with the control end of the first flow controller, to control the opening or closing of the first flow controller.

[0017] Further, a feed regulating valve connected with the inlet pipeline and a second flow controller for detecting the pipeline flow of the inlet pipeline are further included, the feed regulating valve is connected with the feed buffer tank, and the second flow controller controls the valve opening of the feed regulating valve according to the pipeline flow of the inlet pipeline.

[0018] Further, a safety valve connected with the pipeline connected with the flow regulating valve and the check valve is further included, the safety valve is connected with the flare and / or the feed buffer tank.

[0019] The present application adds differential pressure low interlock, check valve and cut-off valve at the outlet of the feed pump of the high-pressure reactor, the flow regulating valve can be cut off, the differential pressure low interlock signal is introduced into the signal processing unit, and the cut-off valve and the flow regulating valve are closed at the same time, to prevent high-pressure from flowing into low-pressure. If the interlock fails and the valve is not cut off in time, the low-pressure equipment can still rely on the check valve and the safety valve to release pressure, to avoid the low-pressure equipment from being broken due to overpressure. By constructing a highly integrated anti-backflow system, multi-stage protection for the condition of high-pressure flowing into low-pressure is realized, and the safety of the high-pressure reaction system is improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The system principle diagram of an anti-backflow system according to an embodiment of the present application;

[0021] Figure 2 The principle diagram of the signal processing unit of an anti-backflow system according to an embodiment of the present application.

[0022] Legend

[0023] 1 - flow regulating valve; 2 - shut-off valve; 3 - check valve; 31 - first check valve; 32 - second check valve; 4 - differential pressure low interlock; 5 - signal processing unit; 51 - first AND gate; 52 - second AND gate; 53 - OR gate; 54 - first pulse element; 55 - second pulse element; 56 - delay element; 57 - first warning light; 58 - second warning light; 6 - feed pump; 61 - running signal terminal; 7 - flow low interlock; 8 - first flow controller; 9 - feed regulating valve; 10 - second flow controller; 11 - safety valve; 12 - first solenoid valve; 13 - second solenoid valve; 14 - inlet line; 15 - outlet line. DETAILED DESCRIPTION

[0024] The specific embodiments of the present application will be further described with reference to the drawings. Like components are denoted by like reference numerals throughout the drawings. It is noted that the words "front", "rear", "left", "right", "upper" and "lower" as used in the following description refer to directions in the drawings, and the words "inner" and "outer" refer to directions toward or away from the geometric center of the particular component.

[0025] As Figure 1 shown is a backflow prevention system according to an embodiment of the present application, comprising: a flow regulating valve 1, a shut-off valve 2, a check valve 3, a differential pressure low interlock 4, and a signal processing unit 5. A feed pump 6 is connected in sequence with the flow regulating valve 1, the check valve 3, the shut-off valve 2, and then connected with a high-pressure reactor. One end of the differential pressure low interlock 4 is connected with an inlet line 14 connecting the feed pump 6 and the flow regulating valve 1, and the other end is connected with an outlet line 15 connecting the shut-off valve 2 and the high-pressure reactor. The output terminal of the differential pressure low interlock 4 is connected in communication with the input terminal of the signal processing unit 5. The output terminal of the signal processing unit 5 is connected in communication with the control terminal of the flow regulating valve 1 and the control terminal of the shut-off valve 2. The signal processing unit 5 controls the on-off of the flow regulating valve 1 and the shut-off valve 2 according to the differential pressure between the two ends of the differential pressure low interlock 4.

[0026] Specifically, the backflow prevention system according to the embodiment is applied in a high-pressure reaction system, and the flow regulating valve 1, the shut-off valve 2, the check valve 3, the differential pressure low interlock 4, and the signal processing unit 5 are arranged between the feed pump 6 of the high-pressure reactor and the high-pressure reactor. The differential pressure low interlock 4 detects the differential pressure between the two ends of the inlet line 14 and the outlet line 15, and controls the on-off of the flow regulating valve 1 and the shut-off valve 2 according to the differential pressure.

[0027] Specifically, the differential pressure low interlock 4 detects the pressure difference between the inlet pipeline 14 pressure and the outlet pipeline 15 pressure, when the pressure difference is greater than the preset pressure difference threshold, the outlet pipeline 15 pressure is normal, at this time the differential pressure low interlock 4 outputs a logic signal 1 to the signal processing unit 5, the signal processing unit 5 opens the flow regulating valve 1 and the shut-off valve 2, and keeps the feed pump 6 connected to the high-pressure reactor. When the outlet pipeline 15 pressure rises or the inlet pipeline 14 pressure decreases, resulting in a pressure difference less than or equal to the preset pressure difference threshold, the differential pressure low interlock 4 outputs a logic signal 0 to the signal processing unit 5, triggering the signal processing unit 5 to close the flow regulating valve 1 and the shut-off valve 2. Wherein, the flow regulating valve 1 and the shut-off valve 2 can be controlled by electromagnetic valves to open and close.

[0028] The present application adds a differential pressure low interlock, a check valve and a shut-off valve at the outlet of the high-pressure reactor feed pump, the flow regulating valve can be shut off, the differential pressure low interlock signal is introduced into the signal processing unit, and the shut-off valve and the flow regulating valve are closed at the same time, so as to prevent high-pressure from flowing into low-pressure. If the interlock fails and the valve is not shut off in time, the low-pressure equipment can still rely on the check valve and its own safety valve to release pressure, avoiding the rupture of the low-pressure equipment due to overpressure. By constructing a highly integrated anti-backflow system, multi-level protection is realized for the condition of high-pressure flowing into low-pressure, and the safety of the high-pressure reaction system is improved.

[0029] As shown in Figure 1 and Figure 2 , another embodiment of the anti-backflow system of the present application comprises a flow regulating valve 1, a shut-off valve 2, a check valve 3, a differential pressure low interlock 4, and a signal processing unit 5. The feed pump 6 is connected in sequence with the flow regulating valve 1, the check valve 3, and the shut-off valve 2, and then connected with the high-pressure reactor. One end of the differential pressure low interlock 4 is connected with the inlet pipeline 14 connecting the feed pump 6 and the flow regulating valve 1, and the other end is connected with the outlet pipeline 15 connecting the shut-off valve 2 and the high-pressure reactor. The output end of the differential pressure low interlock 4 is in communication connection with the input end of the signal processing unit 5. The output end of the signal processing unit 5 is in communication connection with the control end of the flow regulating valve 1 and the control end of the shut-off valve 2. The signal processing unit 5 controls the opening and closing of the flow regulating valve 1 and the shut-off valve 2 according to the pressure difference between the two ends of the differential pressure low interlock 4.

[0030] It also comprises a flow low interlock 7 for detecting the pipeline flow of the outlet pipeline 15. The output end of the flow low interlock 7 is in communication connection with the input end of the signal processing unit 5.

[0031] The signal processing unit 5 comprises a first AND gate 51, a first input end of the first AND gate 51 being in communication connection with an output end of the flow low interlock 7, a second input end of the first AND gate 51 being in communication connection with an input end of the differential pressure low interlock 4, and an output end of the first AND gate 51 being in communication connection with a control end of the flow regulating valve 1 and a control end of the shut-off valve 2 respectively, an input end of the signal processing unit 5 further being in communication connection with a running signal end 61 of the feed pump 6 and / or an external interlock signal end, the signal processing unit 5 further comprising a second AND gate 52 and an OR gate 53, the running signal of the feed pump 6 being in communication connection with a first input end of the OR gate 53, and an output end of the flow low interlock 7 being in communication connection with a second input end of the OR gate 53, an output end of the OR gate 53 being in communication connection with the first input end of the first AND gate 51 and a second input end of the second AND gate 52 respectively, a first input end of the second AND gate 52 being in communication connection with the external interlock signal, and an output end of the second AND gate 52 being in communication connection with a third input end of the first AND gate 51;

[0032] The running signal end 61 of the feed pump 6 is in communication connection with the first input end of the OR gate 53 through a first pulse element 54, the first pulse element 54 outputting a first pulse signal upon receiving a signal jump; and / or

[0033] The output end of the OR gate 53 is in communication connection with the second input end of the second AND gate 52 through a second pulse element 55, the second pulse element 55 outputting a second pulse signal upon receiving a signal jump;

[0034] The output end of the OR gate 53 is in communication connection with the first input end of the first AND gate 51 through a delay element 56;

[0035] Further comprising a first flow controller 8 detecting a pipeline flow of the outlet pipeline 15, the first flow controller 8 controlling a valve opening degree of the flow regulating valve 1 according to the pipeline flow of the outlet pipeline 15, and the output end of the first AND gate 51 being further in communication connection with a control end of the first flow controller 8 to control opening or closing of the first flow controller 8, and the output end of the second AND gate 52 being further in communication connection with a control end of the feed pump 6 to control opening or closing of the feed pump 6;

[0036] Further comprising a feed regulating valve 9 in communication with the inlet pipeline 14, a second flow controller 10 detecting a pipeline flow of the inlet pipeline 14, and a safety valve 11 in communication with a pipeline in communication with the flow regulating valve 1 and the check valve 3, the feed regulating valve 9 being in communication with a feed buffer tank, the second flow controller 10 controlling a valve opening degree of the feed regulating valve 9 according to the pipeline flow of the inlet pipeline 14, and the safety valve 11 being in communication with a flare and / or a feed buffer tank.

[0037] Specifically, the embodiment is between the high-pressure reactor feed pump 6 and the high-pressure reactor flow regulating valve 1, shut-off valve 2, check valve 3, differential pressure low interlock 4, and signal processing unit 5. The signals of the differential pressure low interlock 4 and flow low interlock 7 are introduced into the signal processing unit 5. The differential pressure low interlock 4 detects the differential pressure between the inlet pipeline 14 and the outlet pipeline 15, and the flow low interlock 7 detects the pipeline flow of the outlet pipeline 15, and controls the on-off of the flow regulating valve 1 and the shut-off valve 2 according to the differential pressure and the pipeline flow of the outlet pipeline. By simultaneously closing the shut-off valve 2 and the flow regulating valve 1, the purpose of preventing high-pressure from leaking into low-pressure is achieved. If the interlock fails and the valve does not cut off in time, the low-pressure equipment, such as the buffer tank, can still rely on the check valve 3 and its own safety valve to release pressure, avoiding the rupture of the low-pressure equipment due to overpressure. Preferably, the check valve 3 includes a first check valve 31 and a second check valve 32. Figure 1 In the table, L is the low alarm value, LL is the low-low interlock value, and IA is the abbreviation of Instrument Air.

[0038] Specifically, the embodiment is composed of the following parts:

[0039] The flow regulating valve 1 is a control valve that adjusts the valve opening degree according to the output of the first flow controller 8. The flow regulating valve 1 is closed by the first solenoid valve 12. The first solenoid valve 12 is controlled by the signal processing unit 5 to be powered on and powered off.

[0040] The shut-off valve 2 is closed by the second solenoid valve 13. The second solenoid valve 13 is controlled by the signal processing unit 5 to be powered on and powered off.

[0041] The check valve 3 includes a first check valve 31 and a second check valve 32. The first check valve 31 and the second check valve 32 are two different types and manufacturers of check valves, which are arranged between the flow regulating valve 1 and the shut-off valve 2. This prevents the reverse flow of high-temperature liquid / gas through the safety valve 11 when the shut-off valve 2 fails and the safety valve 11 trips at the same time.

[0042] The differential pressure low interlock 4 is a pressure difference detector. When the pressure drop (or pressure difference) between the two ends, i.e., the pressure drop of the flow regulating valve 1, the shut-off valve 2, the first check valve 31, and the second check valve 32, is lower than the preset interlock value, the differential pressure low interlock 4 outputs a signal to start the anti-backflow protection logic of the signal processing unit 5.

[0043] The signal processing unit 5 executes the anti-backflow protection logic according to various interlock signals.

[0044] The running signal end 61 of the feed pump 6 is used to input the signal processing unit 5 to execute the anti-backflow protection logic.

[0045] Flow low interlock 7, a flow detector, outputs a signal when the detected flow is lower than a preset interlock value, and the interlock triggers the action of the signal processing unit 5.

[0046] First flow controller 8, usually used to control the flow of the stream.

[0047] Feed regulating valve 9 communicates the inlet line 14 with the feed buffer tank, and adjusts the valve opening according to the output of the second flow controller 10.

[0048] Second flow controller 10 provides minimum flow protection for the feed pump 6, and controls the valve opening of the feed regulating valve 9 to be larger when the detected flow is low, to avoid pump choking.

[0049] Safety valve 11 communicates with the flare / feed buffer tank, and protects the reactor from overpressure due to high outlet pressure of the feed pump.

[0050] First solenoid valve 12, interlocks to close the flow regulating valve 1.

[0051] Second solenoid valve 13, interlocks to close the shut-off valve 2.

[0052] The system will initiate interlocked closing of the feed valve flow regulating valve 1 and shut-off valve 2 when the following conditions are met:

[0053] Pressure differential low interlock 4, the pressure differential is lower than the interlock value, flow low interlock 7, the flow is lower than the interlock value, or other process interlocks (set as needed) trigger. When the feed line shut-off interlock fails, the first check valve 31 and the second check valve 32 on the line can cooperate with the safety valve on the low pressure equipment, such as the safety valve on the buffer tank, to achieve multi-stage protection in the reverse flow overpressure working condition.

[0054] The following describes the preferred relative positions of the instruments and valves in the anti-reverse flow overpressure protection system:

[0055] Flow low interlock 7, the measuring instrument thereof must be located downstream of the shut-off valve 2, because if it is located upstream of the safety valve 11, the interlock cannot protect against reverse flow caused by false tripping of the safety valve 11.

[0056] First flow controller 8, the same measuring device as the flow low interlock 7 can be used.

[0057] The differential pressure low interlock 4 requires measuring the total differential pressure of shut-off valve 2, first check valve 31, second check valve 32, and flow control valve 1. This ensures a certain positive differential pressure is maintained during normal feeding. If the differential pressure low interlock 4 does not include shut-off valve 2, the flow low interlock 4 will be released within time P1 after pump start-up, and the first flow controller 8 will be in automatic mode. Since there is no flow in the pipeline after flow control valve 1, the first flow controller 8 will open flow control valve 1 to its maximum, but shut-off valve 2 will remain closed. At this time, the differential pressure gauge will only detect the static pressure of the pump, and the differential pressure will be zero. This fails to achieve the effect of releasing the differential pressure low interlock after the pump starts and builds pressure during startup. Since the two pressure taps of the differential pressure low interlock 4 include the shut-off valve 2, and the shut-off valve 2 is in the closed state during startup and is located between the two pressure detection points of the differential pressure low interlock 4, after the feed pump 6 is started, the pipeline pressure between the feed pump 6 and the flow regulating valve 1 increases, while the pipeline pressure after the shut-off valve 2 remains unchanged. This results in the differential pressure low interlock 4 reading being positive, allowing the flow regulating valve 1 and the shut-off valve 2 to open normally. This will not trigger the interlock of the signal processing unit 5, preventing the flow regulating valve 1 and the shut-off valve 2 from opening. Therefore, there is no need to design a startup bypass for the differential pressure low interlock.

[0058] Safety valve 11 is located downstream of flow regulating valve 1 to prevent false tripping of safety valve 11 due to high pressure head of feed pump 6. At the same time, because it is located upstream of first check valve 31, second check valve 32 and shut-off valve 2, it prevents backflow of high-pressure reaction liquid caused by false tripping of safety valve 11.

[0059] Check valve 3 includes a first check valve 31 and a second check valve 32. Check valve 3 is located between flow regulating valve 1 and shut-off valve 2 to prevent backflow of high-pressure reaction liquid caused by false tripping of safety valve and failure of shut-off valve 2.

[0060] Shut-off valve 2 is a tight-shutoff (TSO) valve, which requires a high degree of sealing performance to ensure a tight shut-off. Therefore, shut-off valve 2 is located closest to the reaction section, which is the high-pressure reaction system.

[0061] like Figure 2 The diagram shown is a system logic diagram of signal processing unit 5.

[0062] The feed pump running signal of the feed pump running signal terminal 61 is sent to the first pulse element 54, and the output value is connected to the feed flow low interlock signal output by the flow low interlock 7 through the OR gate 53. The voting result of the OR gate 53 is divided into two paths: one path is sent to the second pulse element 55 and connected to other process interlock signals (set as needed) through the second AND gate 52, and the voting result of the second AND gate 52 is one of the inputs of the first AND gate 51; the other path of the voting result of the OR gate 53 is sent to the delay element 56, and the voting result is also one of the inputs of the first AND gate 51. The differential pressure low interlock signal of the differential pressure low interlock 4 is the last input of the first AND gate 51. According to the voting result of the first AND gate 51, the flow regulating valve 1, the shut-off valve 2 and the first flow controller 8 are closed. Alternatively, the voting result of the second AND gate 52 interlocks the feed pump 6 to stop.

[0063] When the differential pressure low interlock 4 triggers, the output of the first AND gate 51 becomes 0, the output of the second AND gate 52 becomes 0, the feed pump 6 stops, and the flow regulating valve 1, the shut-off valve 2 and the first flow controller 8 are closed.

[0064] Specifically, the differential pressure low interlock 4 detects the differential pressure of the inlet pipeline 14 pressure minus the outlet pipeline 15 pressure. If the differential pressure is greater than or equal to the preset interlock value, the differential pressure low interlock 4 outputs a logic signal 1, and if the differential pressure is less than the preset interlock value, the differential pressure low interlock 4 outputs a logic signal 0.

[0065] The flow low interlock 7 detects the pipeline flow of the outlet pipeline 15, and if the detected flow is greater than or equal to the preset interlock value, the flow low interlock 7 outputs a logic signal 1, and if the detected flow is less than the preset interlock value, the flow low interlock 7 outputs a logic signal 0. Other process interlocks output a logic signal 1 or a logic signal 0 as needed.

[0066] If no other interlock is triggered or the interlock condition is removed, the feed pump 6 can be started by clicking the "start pump" button. The first pulse element 54 outputs a logic signal 1 to bypass the logic signal 0 output by the low flow interlock 7 for a time P1, and the or gate 53 outputs a logic signal 1, while the delay element 56 starts to count. After the pump is started, the pressure is re-established, and once the pressure difference between the inlet line 14 and the outlet line 15 exceeds the interlock value of the low pressure difference interlock 4, the output value of the low pressure difference interlock 4 returns to signal 1, and after the delay element 56 reaches the delay response time T1, the first and gate 51 outputs a recoverable 1, at which time the flow regulating valve 1 and the shut-off valve 2 are opened. Subsequently, the line flow of the outlet line 14 will be higher than the interlock value set by the low flow interlock 7, and the output value of the low flow interlock 7 returns to 1. Therefore, although the first pulse element 54 outputs a signal 0 after the time P1, the signal 1 output by the low flow interlock 7 will bypass the signal 0 output by the first pulse element 54, and the or gate 53 outputs a signal 1 that can be maintained, ensuring that the flow regulating valve 1 and the shut-off valve 2 are in an open state.

[0067] The settings of each element and parameter are as follows:

[0068] The first and gate 51 outputs a logic signal 1 when all inputs are logic signal 1, and outputs a logic signal 0 when any input is a logic signal 0.

[0069] The second and gate 52 outputs a logic signal 1 when all inputs are logic signal 1, and outputs a logic signal 0 when any input is a logic signal 0.

[0070] The or gate 53 outputs a logic signal 1 when any input is a logic signal 1, and outputs a logic signal 0 when all inputs are logic signal 0.

[0071] The first pulse element 54 outputs a logic signal 1 when a logic signal 0 is detected to change to a logic signal 1 for a time P1, and then outputs a logic signal 0. The default value of the time P1 is 20s. The maximum set value is determined according to the start-stop time allowed by the pump. The time must ensure that the flow regulating valve 1 and the shut-off valve 2 are opened to make the flow value higher than the interlock value of the low flow interlock 7.

[0072] The second pulse element 55 outputs a logic signal 0 for a time P2 when a logic signal 1 is detected to change to a logic signal 0, and then outputs a logic signal 1. The default value of the time P2 is 20s. The function is to generate a signal 0 to interlock the pump when the flow is lower than the interlock value of the low flow interlock 7. After the interlock, the signal returns to 1 after the time P2 to ensure that the pump is started subsequently.

[0073] The time delay element 56 outputs the signal after a time delay of Tl. The default value of Tl is 5s. The time must be greater than the time for the pump pressure to balance.

[0074] The alarm value L of the first flow controller 8 is determined according to the process, but must be higher than the interlock value of the low flow interlock 7. The alarm value L higher than the low flow interlock value can alarm first and then interlock when the process is abnormal, and if the operator receives the low alarm signal, there is enough process safety time to intervene, which can avoid triggering the interlock. This setting conforms to the general rule that the interlock is not triggered first if it can be solved by alarm.

[0075] The interlock value of the low flow interlock 7 is determined according to the working condition. The default interlock value is 10% lower than the minimum process flow.

[0076] The default interlock value of the differential pressure low interlock 4 is 50% of the pressure drop when the control flow regulating valve 1 and the shut-off valve 2 are fully open.

[0077] The first warning light 57 is turned on or off according to the output signal of the differential pressure low interlock 4 or the low flow interlock 7. When the output signal is signal 1, it is turned off, and when the output signal is signal 0, it is turned on.

[0078] The second warning light 58 is turned on or off according to the output signal of the feed pump running signal end 61. When the output signal is signal 0, it is turned off, and when the output signal is signal 1, it is turned on.

[0079] The embodiment realizes multi-level protection of the reverse flow overpressure condition of the high-pressure reaction system by constructing an anti-reverse flow system, and improves the safety of the high-pressure reaction system. The embodiment reasonably arranges the relative positions of the instruments and valves, increases the logical operation block, and does not need to set the start-up bypass, thereby reducing the burden of bypass management. The interlock shutdown and the re-starting of the system basically do not need manual operation, avoiding the complexity and danger of operation.

[0080] Embodiment 1

[0081] A certain hydroformylation device reactor operating pressure is 18 MPaG, and the liquid phase in the raw material tank is continuously pumped to the reactor during the reaction process. The design pressure of the raw material tank is 0.35 MPaG. In the HAZOP analysis, the reverse flow overpressure condition caused by the stop of the feed pump 6 is identified, the overpressure ratio is much larger than 3, the potential overpressure rupture of the raw material tank causes personnel casualties, and the scenario acceptable risk frequency is 1.0e-5. After adopting the "safety protection strategy to prevent reverse flow overpressure", double check valves, shut-off valves and electromagnetic valves are added to the raw material feeding pipeline, interlocking is set for closing the flow regulating valve and the shut-off valve when the pump outlet flow or the raw material feeding pipeline pressure difference is low, and the safety valve discharge amount of the raw material tank is calculated to meet 10% of the reverse flow of high-pressure materials. At this time, the reverse flow overpressure condition has increased two independent protection layers, one is the low-low interlocking of the pump outlet flow or the pipeline pressure difference to close the flow regulating valve and the shut-off valve, and the other is the double check valve combined with the safety valve on the raw material tank. The failure probability can reach 0.01, considering the frequency of pump stop condition is 0.1 times / year, the event occurrence frequency is reduced to 1.0e-5, and the risk is reduced to the acceptable range.

[0082] Example 2

[0083] The operating pressure of the hydrogenation reactor of a certain citral hydrogenation device is 5 MPaG, and the feed valve is closed to increase the pressure before the reaction. The design pressure of the raw material tank is 0.35 MPaG. In the HAZOP analysis, the reverse flow overpressure condition caused by the misoperation of the raw material feed valve is identified, the overpressure ratio is greater than 3, the potential overpressure rupture of the raw material tank causes personnel casualties, and the scenario acceptable risk frequency is 1.0e-5. After adopting the "safety protection strategy to prevent reverse flow overpressure", double check valves and shut-off valves are added to the raw material feeding pipeline, electromagnetic valves are added to the flow regulating valves, interlocking is set for closing the flow regulating valve and the shut-off valve when the reactor pressure is higher than 20 kPaG or the raw material feeding pipeline pressure difference is low, and the safety valve discharge amount of the raw material tank is calculated to meet 10% of the reverse flow of high-pressure materials. At this time, the reverse flow overpressure condition has increased two independent protection layers, one is the low-low interlocking of the reactor pressure or the raw material feeding pipeline pressure difference to close the flow regulating valve and the shut-off valve, and the other is the double check valve combined with the safety valve on the raw material tank. The failure probability can reach 0.01, considering the frequency of personnel misoperation of the raw material feed valve is 0.1 times / year, the event occurrence frequency is reduced to 1.0e-5, and the risk is reduced to the acceptable range.

[0084] The above examples combine Hazard and Operability Analysis (HAZOP) and Layer of Protection Analysis (LOPA) analysis methods, and through semi-quantitative calculation, it is shown that after the high-pressure reaction adopts the "safety protection strategy of preventing reverse flow overpressure", the risk of high-pressure channeling low-pressure condition is reduced to an acceptable range, and the safety is obviously improved.

[0085] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An anti-reflux system, characterized in that The application relates to a feed pump (6) which is connected in sequence with a flow regulating valve (1), a shut-off valve (2), a check valve (3), a differential pressure low interlock (4) and a signal processing unit (5), wherein the feed pump (6) is connected with a high-pressure reactor after being connected with the flow regulating valve (1), the check valve (3) and the shut-off valve (2) in sequence, one end of the differential pressure low interlock (4) is connected with an inlet pipeline (14) connecting the feed pump (6) and the flow regulating valve (1), the other end of the differential pressure low interlock (4) is connected with an outlet pipeline (15) connecting the shut-off valve (2) and the high-pressure reactor, the output end of the differential pressure low interlock (4) is connected with the input end of the signal processing unit (5), the output end of the signal processing unit (5) is connected with the control end of the flow regulating valve (1) and the control end of the shut-off valve (2), and the signal processing unit (5) controls the on-off of the flow regulating valve (1) and the shut-off valve (2) according to the differential pressure between the two ends of the differential pressure low interlock (4). The application further comprises a flow low interlock (7) for detecting the pipeline flow of the outlet pipeline (15), and the output end of the flow low interlock (7) is connected with the input end of the signal processing unit (5). The signal processing unit (5) comprises a first AND gate (51), the first input end of the first AND gate (51) is connected with the output end of the flow low interlock (7), the second input end of the first AND gate (51) is connected with the input end of the differential pressure low interlock (4), and the output end of the first AND gate (51) is connected with the control end of the flow regulating valve (1) and the control end of the shut-off valve (2) respectively. The input end of the signal processing unit (5) is further connected with the running signal end (61) of the feed pump (6) and / or an external interlock signal end, the signal processing unit (5) further comprises a second AND gate (52) and an OR gate (53), the running signal of the feed pump (6) is connected with the first input end of the OR gate (53), the output end of the flow low interlock (7) is connected with the second input end of the OR gate (53), the output end of the OR gate (53) is connected with the first input end of the first AND gate (51) and the second input end of the second AND gate (52) respectively, the first input end of the second AND gate (52) is connected with the external interlock signal, and the output end of the second AND gate (52) is connected with the third input end of the first AND gate (51). The running signal end (61) of the feed pump (6) is connected with the first input end of the OR gate (53) through a first pulse element (54), and the first pulse element (54) outputs a first pulse signal when receiving a signal jump. The output end of the OR gate (53) is connected with the second input end of the second AND gate (52) through a second pulse element (55), and the second pulse element (55) outputs a second pulse signal when receiving a signal jump. The output end of the OR gate (53) is connected with the first input end of the first AND gate (51) through a delay element (56). ​ 2. The anti-reflux system of claim 1, wherein, ​ 3. The anti-reflux system of claim 1, wherein, The output end of the second AND gate (52) is also in communication connection with the control end of the feed pump (6), to control the opening or closing of the feed pump (6).

4. The anti-reflux system of claim 1, wherein, A first flow controller (8) for detecting the pipeline flow of the outlet pipeline (15) is further included, which controls the valve opening degree of the flow regulating valve (1) according to the pipeline flow of the outlet pipeline (15), and the output end of the first AND gate (51) is also in communication connection with the control end of the first flow controller (8), to control the opening or closing of the first flow controller (8).

5. The anti-reflux system of claim 1, wherein, A feed regulating valve (9) in communication with the inlet pipeline (14) and a second flow controller (10) for detecting the pipeline flow of the inlet pipeline (14) are further included, the feed regulating valve (9) is in communication with a feed buffer tank, and the second flow controller (10) controls the valve opening degree of the feed regulating valve (9) according to the pipeline flow of the inlet pipeline (14).

6. The anti-reflux system of claim 1, wherein, A safety valve (11) in communication with the pipeline in communication with the flow regulating valve (1) and the check valve (3) is further included, which is in communication with a flare and / or a feed buffer tank.

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