Emergency nitrogen filling system for a mixer in a vinyl chloride production process

Abstract

The utility model relates to the technical field of vinyl chloride production safety, concretely is a kind of mixer emergency nitrogen charging system in vinyl chloride production process, including fire arrester, acetylene cooler, demister and mixer that pass through pipeline communication in proper order, second acetylene cut-off valve being located on acetylene inlet pipeline, still include the emergency nitrogen charging unit for the emergency nitrogen charging of mixer, automatic control unit, the nitrogen charging replacement unit for replacing residual acetylene in acetylene inlet pipeline, and the emergency bypass for emergency gas supply when emergency nitrogen charging unit failure;The gas outlet of emergency nitrogen charging unit is communicated with the pipeline between mixer and demister, and the connecting point is located in the side of first acetylene cut-off valve close to mixer;The system can replace residual acetylene in associated equipment during overhaul, reduce concentration, eliminate safety risk;When nitrogen cut-off valve fails, emergency bypass can guarantee continuous nitrogen charging, avoid accident expansion, improve system reliability and accident disposal effectiveness.

Description

Technical Field

[0001] This utility model relates to the field of vinyl chloride production safety technology, specifically an emergency nitrogen charging system for a mixer during vinyl chloride production. Background Technology

[0002] In the vinyl chloride production process, acetylene gas passes sequentially through a flame arrester, acetylene cooler, and demister before being combined with hydrogen chloride gas in a mixer. After further cooling and dehydration, the mixture enters the converter to react and produce vinyl chloride. However, during production, the presence of superchlorination risks associated with hydrogen chloride means that free chlorine readily reacts with acetylene to form chloroacetylene, which can easily lead to excessive temperature and pressure in the mixer, potentially causing explosions and fires, resulting in serious safety accidents.

[0003] The Chinese patent publication CN110252163A, which discloses a mixer protection system and method for vinyl chloride production, can predict explosion risks by monitoring parameters such as temperature change rate, pressure, and temperature, and take valve-linked nitrogen purging measures. However, it has the following problems: First, the system's purging is not targeted enough during maintenance. Nitrogen is only delivered to the mixer and acetylene inlet pipe through a single pipeline, which cannot replace residual acetylene in the acetylene inlet pipe and related equipment such as flame arresters and coolers. This makes it difficult to reduce the acetylene concentration in the pipeline, leading to the potential safety risk of residual acetylene leaking or entering the mixer during maintenance. Second, the nitrogen purging system lacks emergency protection for failures. If the core component, the nitrogen shut-off valve, fails, it will directly interrupt the nitrogen purging path, making it impossible to deliver nitrogen to the mixer in time during an accident, which may cause the accident to escalate. Utility Model Content

[0004] The purpose of this invention is to provide an emergency nitrogen purging system for mixers in the vinyl chloride production process. This system addresses the problems of existing protection systems, such as poor targeting of nitrogen purging during maintenance, inability of a single pipeline to remove residual acetylene from equipment such as acetylene inlet pipes, flame arresters, and coolers, difficulty in reducing pipeline concentration, leakage risks, and lack of emergency backup for the nitrogen purging system. A malfunction of the nitrogen shut-off valve will interrupt the nitrogen purging path, making it impossible to supply nitrogen in a timely manner during an accident.

[0005] To achieve the above objectives, this utility model provides the following technical solution: an emergency nitrogen charging system for a mixer in vinyl chloride production, comprising a flame arrester, an acetylene cooler, a demister, and a mixer connected sequentially by pipelines; a first acetylene shut-off valve located on the pipeline between the mixer and the demister; an acetylene inlet pipe connected to the inlet port of the flame arrester; a second acetylene shut-off valve located on the acetylene inlet pipe; and an emergency nitrogen charging unit for emergency nitrogen charging and fire extinguishing of the mixer; an automatic control unit; a nitrogen purging and replacement unit for replacing residual acetylene in the acetylene inlet pipe; and a system for handling malfunctions of the emergency nitrogen charging unit. An emergency bypass for emergency gas supply is provided; the outlet port of the emergency nitrogen charging unit is connected to the pipeline between the mixer and the demister, and the connection point is located on the side of the first acetylene shut-off valve near the mixer; the inlet port of the nitrogen purging and replacement unit is connected to the emergency nitrogen charging unit, and the connection point is located on the side of the outlet port of the emergency bypass; the outlet port of the nitrogen purging and replacement unit is connected to the acetylene inlet pipeline, and the connection point is located on the side of the second acetylene shut-off valve near the flame arrester; the emergency nitrogen charging unit, the emergency bypass, the nitrogen purging and replacement unit, the first acetylene shut-off valve, and the second acetylene shut-off valve are all electrically connected to the automatic control unit.

[0006] Furthermore, the emergency nitrogen charging unit includes a nitrogen gas source pipe for supplying nitrogen, a pressure reducing valve and a nitrogen shut-off valve sequentially disposed on the nitrogen gas source pipe, and the outlet port of the nitrogen gas source pipe is connected to the pipeline between the mixer and the demister.

[0007] Furthermore, the emergency bypass includes a nitrogen branch, a second electric valve on the nitrogen branch for controlling the opening and closing of the branch, and a first electric valve on the nitrogen source pipe located at both ends of the nitrogen shut-off valve; both ends of the nitrogen branch are connected to the nitrogen source pipe, its inlet port is located at the inlet end of the first electric valve near the pressure reducing valve, and its outlet port is located at the outlet end of the first electric valve near the mixer.

[0008] Furthermore, the emergency nitrogen charging unit also includes a first pressure sensor, an electromagnetic flow regulating valve, a one-way check valve, a flow sensor, and a manual valve, all installed on the nitrogen gas source pipe; the first pressure sensor is located upstream of the nitrogen branch inlet port; the electromagnetic flow regulating valve is located between the first pressure sensor and the pressure reducing valve; the one-way check valve is located downstream of the nitrogen branch outlet port; and the flow sensor and manual valve are sequentially installed downstream of the one-way check valve along the nitrogen flow direction.

[0009] Furthermore, the nitrogen purging and replacement unit includes a replacement pipeline connected to the nitrogen gas source pipe and two third electric valves installed on the replacement pipeline. The connection point between the inlet port of the replacement pipeline and the nitrogen gas source pipe is located between the flow sensor and the manual valve. The connection point between the outlet port of the replacement pipeline and the acetylene inlet pipe is located on the side of the second acetylene shut-off valve near the flame arrester.

[0010] Furthermore, the automatic control unit includes a DCS control system, an alarm module built into the DCS control system, and a second pressure sensor and a temperature sensor located on the mixer; the first pressure sensor, the pressure reducing valve, the nitrogen shut-off valve, the second electric valve, two first electric valves, the electromagnetic flow regulating valve, the flow sensor, two third electric valves, the alarm module, the first acetylene shut-off valve, and the second acetylene shut-off valve are all electrically connected to the DCS control system.

[0011] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model discloses an emergency nitrogen charging system for a mixer in the vinyl chloride production process. Through a nitrogen replacement unit, the inlet port of which is connected to the emergency nitrogen charging unit, and the outlet port connected to the side of the acetylene inlet pipe near the flame arrester, it can replace residual acetylene in the acetylene inlet pipe and related equipment such as the flame arrester and cooler during system maintenance. This reduces the acetylene concentration in the pipeline and eliminates the safety risks caused by residual acetylene leakage or entry into the mixer during maintenance. Furthermore, with the aid of an emergency bypass, nitrogen charging can continue even if the nitrogen shut-off valve of the emergency nitrogen charging unit malfunctions, preventing the interruption of nitrogen charging from escalating into an unmanageable accident and improving the reliability of the nitrogen charging system and the effectiveness of accident handling. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the emergency nitrogen charging system for the mixer in the vinyl chloride production process of this utility model.

[0013] In the diagram: 1. Mixer; 2. Demister; 3. Acetylene cooler; 4. Flame arrester; 5. First acetylene shut-off valve; 6. Nitrogen supply line; 7. Nitrogen branch line; 8. Pressure reducing valve; 9. First pressure sensor; 10. First electric valve; 11. Nitrogen shut-off valve; 12. Second electric valve; 13. One-way check valve; 14. Flow sensor; 15. Manual valve; 16. Temperature sensor; 17. Second pressure sensor; 18. DCS control system; 19. Second acetylene shut-off valve; 20. Replacement pipeline; 21. Electromagnetic flow regulating valve. Detailed Implementation

[0014] Please see Figure 1An emergency nitrogen charging system for a mixer in vinyl chloride production includes a flame arrester 4, an acetylene cooler 3, a demister 2, and a mixer 1 connected sequentially by pipelines; a first acetylene shut-off valve 5 located on the pipeline between the mixer 1 and the demister 2; an acetylene inlet pipe connected to the inlet port of the flame arrester 4; a second acetylene shut-off valve 19 located on the acetylene inlet pipe; an emergency nitrogen charging unit for emergency nitrogen charging of the mixer 1 for fire extinguishing; an automatic control unit; a nitrogen purging and replacement unit for replacing residual acetylene in the acetylene inlet pipe; and an emergency nitrogen supply unit for emergency nitrogen supply in case of failure of the emergency nitrogen charging unit. Emergency bypass; the outlet port of the emergency nitrogen charging unit is connected to the pipeline between the mixer 1 and the demister 2, and the connection point is located on the side of the first acetylene shut-off valve 5 near the mixer 1; the inlet port of the nitrogen charging and replacement unit is connected to the emergency nitrogen charging unit, and the connection point is located on the side of the outlet port of the emergency bypass; the outlet port of the nitrogen charging and replacement unit is connected to the acetylene inlet pipeline, and the connection point is located on the side of the second acetylene shut-off valve 19 near the flame arrester 4; the emergency nitrogen charging unit, emergency bypass, nitrogen charging and replacement unit, first acetylene shut-off valve 5 and second acetylene shut-off valve 19 are all electrically connected to the automatic control unit.

[0015] This application further proposes that the emergency nitrogen charging unit includes a nitrogen gas source pipe 6 for supplying nitrogen, a pressure reducing valve 8 and a nitrogen shut-off valve 11 arranged sequentially on the nitrogen gas source pipe 6, and the outlet port of the nitrogen gas source pipe 6 is connected to the pipeline between the mixer 1 and the demister 2.

[0016] Specifically, the nitrogen source pipe 6 is directly connected to the pipeline where the mixer 1 is located, ensuring that nitrogen can quickly reach the mixer 1 in an emergency, thereby improving the efficiency of fire extinguishing and emergency response; the pressure reducing valve 8 can adjust the high-pressure nitrogen to a stable pressure suitable for the working conditions, avoiding damage to the equipment due to excessive pressure or affecting the nitrogen filling effect due to excessively low pressure; the nitrogen shut-off valve 11 can quickly respond to control commands, realizing the timely opening and closing of the nitrogen filling passage.

[0017] This application further proposes that the emergency bypass includes a nitrogen branch 7, a second electric valve 12 installed on the nitrogen branch 7 for controlling the opening and closing of the branch, and a first electric valve 10 installed on the nitrogen source pipe 6 and located at both ends of the nitrogen shut-off valve 11; both ends of the nitrogen branch 7 are connected to the nitrogen source pipe 6, its inlet port is located at the inlet end of the first electric valve 10 near the pressure reducing valve 8, and its outlet port is located at the outlet end of the first electric valve 10 near the mixer 1.

[0018] Specifically, nitrogen branch 7 and nitrogen shut-off valve 11 are connected in parallel. When nitrogen shut-off valve 11 fails to open, it can quickly switch to emergency branch gas supply to avoid nitrogen charging interruption leading to accident expansion. The two first electric valves 10 can cut off the faulty main line to prevent the fault from spreading. At the same time, they work with the second electric valve 12 to control the start and stop of emergency branch to ensure orderly emergency nitrogen charging.

[0019] This application further proposes that the emergency nitrogen charging unit also includes a first pressure sensor 9, an electromagnetic flow regulating valve 21, a one-way check valve 13, a flow sensor 14, and a manual valve 15, all located on the nitrogen source pipe 6. The first pressure sensor 9 is located upstream of the inlet port of the nitrogen branch 7. The electromagnetic flow regulating valve 21 is located between the first pressure sensor 9 and the pressure reducing valve 8. The one-way check valve 13 is located downstream of the outlet port of the nitrogen branch 7. The flow sensor 14 and the manual valve 15 are sequentially located downstream of the one-way check valve 13 along the nitrogen flow direction.

[0020] Specifically, the first pressure sensor 9 and the flow sensor 14 monitor the nitrogen source pressure and nitrogen charging flow rate in real time, respectively, to provide data support for the DCS control system 18 and ensure that the nitrogen charging parameters can be dynamically adjusted; the electromagnetic flow regulating valve 21 works in conjunction with the pressure reducing valve 8 to flexibly adjust the nitrogen charging flow rate and pressure according to the working conditions, adapting to the nitrogen charging requirements of different accident levels; the one-way check valve 13 effectively blocks the reverse flow of gas in the mixer 1 into the nitrogen pipeline, avoiding secondary safety hazards; the manual valve 15 serves as a manual emergency control component, which can be manually operated in case of failure of the automatic DCS control system.

[0021] This application further proposes that the nitrogen replacement unit includes a replacement pipeline 20 connected to the nitrogen source pipe 6, and two third electric valves 22 provided on the replacement pipeline 20. The connection point between the inlet port of the replacement pipeline 20 and the nitrogen source pipe 6 is located between the flow sensor 14 and the manual valve 15. The connection point between the outlet port of the replacement pipeline 20 and the acetylene inlet pipe is located on the side of the second acetylene shut-off valve 19 near the flame arrester 4.

[0022] Specifically, the inlet end of the replacement pipeline 20 is connected between the flow sensor 14 and the manual valve 15. The flow sensor 14 can monitor the nitrogen flow rate in real time to ensure a stable nitrogen supply during the replacement process.

[0023] This application further proposes that the automatic control unit includes a DCS control system 18, an alarm module built into the DCS control system 18, and a second pressure sensor 17 and a temperature sensor 16 disposed on the mixer 1; the first pressure sensor 9, the pressure reducing valve 8, the nitrogen shut-off valve 11, the second electric valve 12, two first electric valves 10, the electromagnetic flow regulating valve 21, the flow sensor 14, two third electric valves 22, the alarm module, the first acetylene shut-off valve 5 and the second acetylene shut-off valve 19 are all electrically connected to the DCS control system 18.

[0024] Among them, the second pressure sensor 17 and temperature sensor 16 are respectively connected to the signal input terminal of the DCS control system 18, transmitting the pressure and temperature data inside the mixer 1 to the DCS control system 18 in real time; the first pressure sensor 9 and flow sensor 14 on the nitrogen source pipe 6 are also connected to the signal input terminal of the DCS control system 18, continuously feeding back nitrogen source pressure and nitrogen charging flow information; pressure reducing valve 8, nitrogen shut-off valve 11, second electric valve 12, two first electric valves 10, electromagnetic flow regulating valve 21, two third electric valves 22, and first acetylene shut-off valve 14 are also connected to the DCS control system 18. Both the shut-off valve 5 and the second acetylene shut-off valve 19 are connected to the signal output terminal of the DCS control system 18 through control lines, and receive start / stop and adjustment commands issued by the DCS control system 18; the alarm module built into the DCS control system 18 is integrated with the DCS control system 18, and can receive alarm trigger signals issued by the DCS control system 18 and activate the audible and visual alarm function; the one-way check valve 13 is a mechanical component and does not form an electrical connection with the DCS control system 18, but is installed in the nitrogen gas source pipe 6 through a pipeline to play a role in preventing backflow.

[0025] Specifically, the second pressure sensor 17, temperature sensor 16, and the first pressure sensor 9 and flow sensor 14 transmit key parameters to the DCS control system 18 in real time, enabling operators to fully grasp the operating status of mixer 1 and nitrogen pipeline, providing data support for fault prediction. The DCS control system 18 can automatically issue control commands to each actuator based on the detection data, realizing the automated execution of actions such as acetylene cut-off, nitrogen charging start-up, and flow regulation, improving the speed of accident response and avoiding delays caused by human operation. The alarm module is integrated with the DCS control system 18 and can trigger alarms in a timely manner when parameters are abnormal or components fail, reminding operators to take quick action.

[0026] Working process and principle: When the emergency nitrogen charging system of the mixer is operating normally, the first acetylene shut-off valve 5, the second acetylene shut-off valve 19, the two first electric valves 10 and the manual valve 15 are all in the open state. Acetylene enters the flame arrester 4 through the acetylene inlet pipe, and then flows through the acetylene cooler 3 and the demister 2 before entering the mixer 1. The nitrogen shut-off valve 11 of the emergency nitrogen charging unit, the second electric valve 12 of the emergency bypass and the two third electric valves 22 of the nitrogen charging and replacement unit are all in the closed state, and the nitrogen source pipe 6 remains on standby. When the second pressure sensor 17 and temperature sensor 16 of the automatic control unit detect over-temperature and over-pressure inside the mixer 1, the DCS control system 18 immediately issues a command to close the first acetylene shut-off valve 5 and the second acetylene shut-off valve 19, while simultaneously opening the nitrogen shut-off valve 11. Nitrogen gas flows through the nitrogen source pipe 6, sequentially through the electromagnetic flow regulating valve 21 (the DCS control system 18 dynamically adjusts the nitrogen charging flow rate according to the temperature and pressure data inside the mixer), the pressure reducing valve 8 (to stabilize the nitrogen pressure within the suitable operating range), the one-way check valve 13 (to prevent gas inside the mixer from flowing back into the nitrogen pipeline), and the flow sensor 14 (to collect nitrogen charging flow data in real time and feed it back to the DCS control system 18), finally quickly charging the mixer 1 to extinguish the fire. If the nitrogen shut-off valve 11 malfunctions, causing the nitrogen charging flow rate to be 0, the flow sensor 14 will transmit the abnormal data to the DCS control system 18. The DCS control system 18 will immediately trigger an audible and visual alarm. The operator can remotely close the first electric valve 10 at both ends of the nitrogen shut-off valve 11 through the DCS control system 18, while simultaneously opening the second electric valve 12, to achieve emergency nitrogen charging through the nitrogen branch line 7. During system maintenance, the first acetylene shut-off valve 5 and the second acetylene shut-off valve 19 must first be closed via the DCS control system 18 to cut off the acetylene supply. Subsequently, the DCS control system 18 opens the two third electric valves 22 of the nitrogen purging unit, allowing nitrogen to enter the acetylene inlet pipe via the purging pipeline 20. This replaces residual acetylene in the acetylene inlet pipe, flame arrester 4, acetylene cooler 3, demister 2, and related connecting pipes, reducing the acetylene concentration in the pipes and preventing leakage or entry of residual acetylene into the mixer 1 during maintenance, thus avoiding safety risks. Throughout operation, the first pressure sensor 9 monitors the nitrogen source pressure in real time. If abnormal nitrogen source pressure or nitrogen flow occurs, the alarm module in the DCS control system 18 will immediately trigger an alarm, allowing operators to respond promptly and ensuring the safe and stable operation of the unit.

[0027] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An emergency nitrogen charging system for a mixer in a vinyl chloride production process, comprising a flame arrester (4), an acetylene cooler (3), a demister (2), and a mixer (1) connected sequentially by pipelines, a first acetylene shut-off valve (5) located on a pipeline between the mixer (1) and the demister (2), an acetylene inlet pipe connected to the inlet port of the flame arrester (4), and a second acetylene shut-off valve (19) located on the acetylene inlet pipe, characterized in that, It also includes an emergency nitrogen charging unit for emergency nitrogen charging to the mixer (1) for fire extinguishing, an automatic control unit, a nitrogen charging and replacement unit for replacing residual acetylene in the acetylene inlet pipe, and an emergency bypass for emergency gas supply when the emergency nitrogen charging unit fails; the outlet port of the emergency nitrogen charging unit is connected to the pipeline between the mixer (1) and the demister (2), and the connection point is located on the side of the first acetylene shut-off valve (5) near the mixer (1); the inlet port of the nitrogen charging and replacement unit is connected to the emergency nitrogen charging unit, and the connection point is located on the side of the outlet port of the emergency bypass; the outlet port of the nitrogen charging and replacement unit is connected to the acetylene inlet pipe, and the connection point is located on the side of the second acetylene shut-off valve (19) near the flame arrester (4); the emergency nitrogen charging unit, the emergency bypass, the nitrogen charging and replacement unit, the first acetylene shut-off valve (5) and the second acetylene shut-off valve (19) are all electrically connected to the automatic control unit.

2. The mixer emergency nitrogen charging system according to claim 1, characterized in that, The emergency nitrogen charging unit includes a nitrogen gas source pipe (6) for supplying nitrogen, a pressure reducing valve (8) and a nitrogen shut-off valve (11) sequentially disposed on the nitrogen gas source pipe (6), and the outlet port of the nitrogen gas source pipe (6) is connected to the pipeline between the mixer (1) and the demister (2).

3. The mixer emergency nitrogen charging system according to claim 2, characterized in that, The emergency bypass includes a nitrogen branch (7), a second electric valve (12) installed on the nitrogen branch (7) for controlling the opening and closing of the branch, and a first electric valve (10) installed on the nitrogen source pipe (6) and located at both ends of the nitrogen shut-off valve (11); both ends of the nitrogen branch (7) are connected to the nitrogen source pipe (6), its inlet port is located at the inlet end of the first electric valve (10) near the pressure reducing valve (8), and its outlet port is located at the outlet end of the first electric valve (10) near the mixer (1).

4. The mixer emergency nitrogen charging system according to claim 3, characterized in that, The emergency nitrogen charging unit also includes a first pressure sensor (9), an electromagnetic flow regulating valve (21), a one-way check valve (13), a flow sensor (14), and a manual valve (15) installed on the nitrogen source pipe (6); the first pressure sensor (9) is located upstream of the inlet port of the nitrogen branch (7); the electromagnetic flow regulating valve (21) is located between the first pressure sensor (9) and the pressure reducing valve (8); the one-way check valve (13) is located downstream of the outlet port of the nitrogen branch (7); the flow sensor (14) and the manual valve (15) are sequentially installed downstream of the one-way check valve (13) along the nitrogen flow direction.

5. The mixer emergency nitrogen charging system according to claim 4, characterized in that, The nitrogen replacement unit includes a replacement pipeline (20) connected to the nitrogen source pipe (6) and two third electric valves (22) installed on the replacement pipeline (20). The connection point between the inlet port of the replacement pipeline (20) and the nitrogen source pipe (6) is located between the flow sensor (14) and the manual valve (15). The connection point between the outlet port of the replacement pipeline (20) and the acetylene inlet pipe is located on the side of the second acetylene shut-off valve (19) near the flame arrester (4).

6. The mixer emergency nitrogen charging system according to claim 5, characterized in that, The automatic control unit includes a DCS control system (18), an alarm module built into the DCS control system (18), and a second pressure sensor (17) and a temperature sensor (16) located on the mixer (1). The first pressure sensor (9), pressure reducing valve (8), nitrogen shut-off valve (11), second electric valve (12), two first electric valves (10), electromagnetic flow regulating valve (21), flow sensor (14), two third electric valves (22), alarm module, first acetylene shut-off valve (5) and second acetylene shut-off valve (19) are all electrically connected to the DCS control system (18).

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