Improved system for absorbing hydrogen chloride tail gas in chlor-alkali production

Abstract

The utility model discloses an improved system for hydrogen chloride tail gas absorption in chlor-alkali production, which is characterized in that a top gas outlet of a hydrogen chloride tail gas absorption tower is connected with a middle-lower side gas inlet pipeline of a hydraulic ejector, a bottom water outlet pipeline of the hydraulic ejector is connected with a gas-liquid separator, and a liquid seal overflow water outlet of the gas-liquid separator is connected with a tail gas water absorption tank; a lower side water outlet of the tail gas absorption water tank is connected with an inlet pipeline of an absorption water pump; according to the utility model, the problems of poor hydrogen chloride absorption effect, high consumption of raw materials and auxiliary materials and low automatic control level in the prior art are solved, the process index stability is ensured to be optimal, the tail gas emission is lower than the emission standard, and the safety and the stability of the system are enhanced.

Description

Technical Field

[0001] This utility model relates to the field of chlor-alkali production technology, specifically to an improved system for absorbing hydrogen chloride tail gas in chlor-alkali production. Background Technology

[0002] Hydrogen chloride tail gas is highly acidic, irritating, toxic, and corrosive. When released into the atmosphere, it reacts with water vapor to form acid rain, harming the environment and ecosystems. The hydrogen chloride tail gas absorption process typically includes four main steps: tail gas introduction, absorption process, purified gas emission, and absorbent treatment. It usually involves countercurrent contact of water or alkaline solution within the absorption tower. The hydrogen chloride gas is absorbed by the absorbent, and the treated gas is discharged from the top of the tower. The emission limit for hydrogen chloride in the chlor-alkali industry is required to be below 5 mg / m³, making process control during the hydrogen chloride tail gas absorption process particularly important.

[0003] In the existing system process, considering that equipment and control systems increase initial investment and maintenance costs, the absorption system has a simple design and short process flow, only completing the most basic absorption process and control level. For the treatment of high-concentration or large-volume hydrogen chloride tail gas, emergency response is often delayed, tail gas intermittently exceeds emission limits, process control deviates, and high furnace pressure in the synthesis furnace can easily cause the explosion-proof membrane to rupture, resulting in environmental pollution and corrosion of surrounding equipment. Adopting a better automated control and remote monitoring system can greatly improve production efficiency, improve the on-site production environment, enhance intrinsic safety, and make full use of the alkaline solution in chlor-alkali production to absorb tail gas. The frequency converter pump transports the absorbent liquid back to the salt water distribution tank for recycling, greatly reducing energy consumption. Utility Model Content

[0004] This invention addresses the aforementioned problems by providing an improved system for absorbing hydrogen chloride tail gas in chlor-alkali production. It achieves full-process online monitoring, remote automatic control, and emergency response of the tail gas absorption system without manual intervention, while significantly improving the on-site production environment and enhancing inherent safety.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an improved system for absorbing hydrogen chloride tail gas in chlor-alkali production, comprising connecting the upper outlet of the hydrogen chloride tail gas absorption tower of the synthesis furnace to the lower inlet pipeline of the hydraulic jet, connecting the upper inlet of the hydraulic jet to the outlet pipeline of the absorption water pump, and connecting the lower outlet pipeline of the hydraulic jet to the hydraulic jet.

[0006] The liquid seal overflow outlet of the gas-liquid separator is connected to the tail gas absorption tank; the lower outlet of the tail gas absorption tank is connected to the inlet pipeline of the absorption water pump, and the outlet pipe of the absorption water pump is connected to three independent pipelines: one pipeline is connected to the salt distribution tank, the second pipeline is connected to the top of the hydraulic jet, and the third pipeline is connected to the upper part of the waste gas absorption tower.

[0007] The top of the tail gas absorption tank is connected to seven pipelines that enter the tail gas absorption tank, namely nitrogen, production water, sodium hydroxide, condensate from the hydrogen scrubbing tower, condensate from the hydrogen system dehydration device, overflow water from the gas-liquid separator, and overflow water from the waste gas absorption tower. The gas outlet at the top of the tail gas absorption tank is connected to the pipeline in the middle and lower part of the waste gas absorption tower.

[0008] The exhaust gas absorption tower has its top outlet connected to the flame arrester inlet pipeline, the flame arrester outlet pipeline connected to the atmosphere, and nitrogen and steam pipelines connected to the atmosphere pipeline after the flame arrester.

[0009] The sodium hydroxide pipeline is equipped with a flow meter and a regulating valve, the tail gas absorption water tank is equipped with a level gauge, the absorption water pump inlet pipeline is equipped with an absorption water thermometer and the absorption water pump outlet pipeline is equipped with an absorption water pump outlet pressure gauge, the absorption water inlet jet nozzle connection pipeline is equipped with an online pH meter, the top of the gas-liquid separator is equipped with a pressure gauge, and the absorption water pump outlet to the salt distribution tank pipeline is equipped with a regulating valve.

[0010] The outlet of the waste gas absorption tower is equipped with a hydrogen chloride tail gas analyzer, the outlet pipeline of the flame arrester is equipped with a thermometer, the nitrogen pipeline is equipped with a switch valve, and the steam pipeline is equipped with a switch valve; the control terminals of the regulating valves and switch valves on the pipelines are connected to the output terminal of the controller, and the input terminal of the controller is connected to the flow meter, thermometer, level gauge, and pH meter respectively.

[0011] This invention ensures optimal stability of process parameters, reduces energy consumption, lowers exhaust emissions below emission limits, and enhances system safety and stability.

[0012] Preferably, the absorption pump is a variable frequency pump, and there are two of them connected in parallel.

[0013] Preferably, a liquid delivery pipeline is provided between the absorption water pump and the hydraulic jet, and an absorption water pH meter and a pump outlet pressure gauge are installed on the liquid delivery pipeline.

[0014] Preferably, a connecting pipeline is provided between the sodium hydroxide main pipe branch line and the tail gas absorption water tank, and a sodium hydroxide flow meter and regulating valve are installed on the connecting pipeline.

[0015] Preferably, a nitrogen pipeline is installed on the flame arrester outlet pipeline of the waste gas absorption tower as a gas inerting protection pipeline, and a nitrogen switch valve is installed on the pipeline.

[0016] Preferably, a steam pipeline is installed on the flame arrester outlet pipeline of the waste gas absorption tower as a cooling and diluting combustible gas pipeline, and a steam switch valve is installed on the pipeline.

[0017] Preferably, the outlet of the absorption water pump and the salt dispensing tank are equipped with a liquid delivery pipeline, and a liquid level regulating valve for the tail gas absorption water tank is installed on the liquid delivery pipeline.

[0018] More preferably, a pressure gauge is installed on the gas-liquid separator; a level gauge and a thermometer are installed on the tail gas absorption water tank; and a thermometer and a hydrogen chloride tail gas analyzer are installed at the outlet of the flame arrester.

[0019] Preferably, the outlet of the condensate pump from the hydrogen scrubbing tower and the condensate from the dewatering device in the chlor-alkali hydrogen treatment unit are connected to the tail gas absorption water tank by separate pipelines. The hydrogen condensate from the hydrogen scrubbing tower and the dewatering device has a temperature ≤35℃ and a pH greater than 10.

[0020] The beneficial effects of this utility model are as follows:

[0021] 1. The condensate from the hydrogen scrubbing tower and the condensate from the hydrogen system dehydration device are connected to the tail gas absorption water tank, reducing the raw material consumption of sodium hydroxide and improving efficiency and reducing costs. The entire tail gas absorption process does not require cooling treatment, and the tail gas absorption water is continuously replaced before being transported to the salt distribution tank.

[0022] 2. Automatic control valves are installed on the material conveying pipeline and gas purging pipeline, which can automatically control the liquid level and pH in the system and remotely and automatically handle accidents such as fires in the venting pipe, avoiding the problems of deviation of indicators and untimely emergency response caused by manual operation, and greatly improving production efficiency and safety.

[0023] 3. The online instruments set in the system can realize the safety monitoring of the exhaust gas system. The pressure gauge of the gas-liquid separator can detect whether the system pipeline and tower are blocked; the pressure gauge of the pump outlet can detect whether the pump equipment is delivering liquid normally; and the hydrogen chloride exhaust gas analyzer can detect whether the treated exhaust gas is less than the emission limit. Attached Figure Description

[0024] Figure 1 A process flow diagram of an improved system for absorbing hydrogen chloride tail gas in chlor-alkali production. Detailed Implementation

[0025] Figure 1 The system includes: 1. Tail gas absorption water tank level gauge; 2. Absorption water thermometer; 3. Absorption water frequency conversion pump; 4. Absorption water pump outlet pressure gauge; 5. Tail gas absorption water tank level regulating valve; 6. Gas-liquid separator pressure gauge; 7. Absorption water pH meter; 8. Sodium hydroxide regulating valve; 9. Sodium hydroxide flow meter; 10. Hydraulic ejector; 11. Gas-liquid separator; 12. Waste gas absorption tower; 13. Hydrogen chloride tail gas absorption tower; 14. Tail gas absorption water tank; 15. Hydrogen scrubbing tower condensate; 16. Hydrogen system dehydration device condensate; 17. Absorption water inlet hydraulic ejector connecting pipeline; 18. Absorption water inlet waste gas absorption tower connecting pipeline; 19. Hydrogen chloride tail gas inlet hydraulic ejector connecting pipeline; 20. Nitrogen switch valve; 21. Waste gas vent pipe thermometer; 22. Steam switch valve; 23. Flame arrester; 24. Hydrogen chloride tail gas analyzer.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 An improved system for absorbing hydrogen chloride tail gas in chlor-alkali production is provided, wherein the hydrogen chloride tail gas pipeline of the synthesis furnace is connected to the lower part of the hydrogen chloride tail gas absorption tower 13, and the pure water pipeline is connected to the upper part of the hydrogen chloride tail gas absorption tower 13.

[0028] The top outlet of the hydrogen chloride tail gas absorption tower 13 is connected to the lower air inlet pipeline of the hydraulic jet 10.

[0029] The water outlet pipe at the bottom of the hydraulic jet 10 is connected to the gas-liquid separator 11.

[0030] The liquid seal overflow outlet of the gas-liquid separator 11 is connected to the tail gas absorption water tank 14.

[0031] The lower outlet of the exhaust gas absorption water tank 14 is connected to the inlet pipeline of the absorption water pump 3.

[0032] The outlet water connection pipeline of the absorption water pump 3 leads to the brine dispensing tank.

[0033] The outlet connection pipeline of the absorption water pump 3 is connected to the top inlet of the hydraulic jet 10 via the absorption water inlet hydraulic jet 17.

[0034] The water outlet connection pipeline of the absorption water pump 3 is connected to the upper part of the waste gas absorption tower 12 via the absorption water inlet connection pipeline 18.

[0035] The top outlet of the exhaust gas absorption tower 12 is connected to the inlet pipeline of the flame arrester 23, the outlet pipeline of the flame arrester 23 is connected to the atmosphere, and the nitrogen pipeline and the steam pipeline are connected to the atmospheric pipeline after the flame arrester.

[0036] The top of the exhaust gas absorption tank 14 is connected to 7 independent inlet pipelines, which are from the nitrogen pipeline, the production water pipeline, the sodium hydroxide solution pipeline, the hydrogen scrubbing tower condensate pipeline, the hydrogen system dehydration device condensate pipeline, the gas-liquid separator overflow water pipeline, and the exhaust gas absorption tower overflow water pipeline.

[0037] A flow meter 9 and a sodium hydroxide regulating valve 8 are installed on the sodium hydroxide pipeline. A level gauge 1 is installed on the tail gas absorption water tank. An absorption water thermometer 2 is installed on the inlet pipeline of the absorption water pump and an absorption water pump outlet pressure gauge 4 is installed on the outlet pipeline.

[0038] The absorber inlet hydraulic ejector is connected to the absorber inlet hydraulic ejector connecting pipeline 17, which is equipped with an absorber pH meter 7. The gas-liquid separator 11 is equipped with a pressure gauge 6 at the top. The absorber pump outlet to the salt distribution tank pipeline is equipped with a tail gas absorber level regulating valve 5. The exhaust gas absorption tower outlet is equipped with a hydrogen chloride tail gas analyzer 24. The flame arrester outlet pipeline is equipped with a thermometer 21. The nitrogen pipeline is equipped with a nitrogen switch valve 20. The steam pipeline is equipped with a steam switch valve 22. The online instruments, valves, absorber pump operating variables or controlled variables are connected to the controller. The controller automatically outputs control commands according to the input data or status.

[0039] The sodium hydroxide regulating valve 8 on the sodium hydroxide pipeline and the pH meter 7 of the absorption water form a PID self-control loop.

[0040] The tail gas absorption water tank level regulating valve 5 on the outlet salt distribution tank pipeline of the absorption water pump and the tail gas absorption water tank level gauge 1 form a PID self-control loop.

[0041] The top outlet of the exhaust gas absorption tank 14 is connected to the lower pipeline of the exhaust gas absorption tower 12, and the top outlet of the gas-liquid separator 11 is connected to the lower pipeline of the exhaust gas absorption tower 12.

[0042] Preferably, the absorption water variable frequency pump is a variable frequency pump, there are two of them, connected in parallel, namely pump A and pump B. An outlet pressure gauge 4 is installed at the pump outlet. The two pumps can be started and stopped remotely. When the running pump trips, malfunctions, or the pump outlet pressure is low, the standby pump is interlocked to start, reducing the impact of pump failure on the production process.

[0043] Preferably, a liquid delivery pipeline is provided between the absorption water pump and the hydraulic jet, and an absorption water pH meter is installed on the liquid delivery pipeline. The sodium hydroxide regulating valve and the absorption water pH meter form a PID self-control loop with a pH setting of 10. When the exhaust gas volume suddenly increases and the condensate of the hydrogen system cannot neutralize the pH of the absorption water to a strongly alkaline state, the sodium hydroxide PID self-control loop automatically adjusts according to the pH value to ensure that the pH value is not low during the absorption process, so that the exhaust gas can be effectively absorbed and safety is improved.

[0044] Preferably, the outlet of the condensate pump of the hydrogen scrubbing tower and the condensate of the dewatering device in the chlor-alkali hydrogen treatment unit are connected to the tail gas absorption tank by separate pipelines. The condensate temperature of the hydrogen scrubbing tower and the dewatering device is ≤35℃, and the condensate with a pH greater than 10 is used as the tail gas absorption liquid. The laboratory analysis data are as follows: pH of the condensate from the hydrogen scrubbing tower: 11.5, 11.2, 10.9, 11.8, 10.8; pH of the condensate from the dewatering device: 10.7, 11.7, 11.4, 11.9, 10.6.

[0045] Preferably, a nitrogen pipeline and a steam pipeline are installed on the flame arrester outlet pipeline of the waste gas absorption tower, and a switch valve is installed on each pipeline. When the flame arrester outlet temperature is detected to be high, the nitrogen and steam switch valves are automatically opened by interlocking to dilute the hydrogen concentration, reduce the temperature, and isolate oxygen, thereby effectively controlling the fire and preventing an explosion.

[0046] Preferably, a pressure gauge is installed on the gas-liquid separator to detect in real time whether the system operating pressure is normal and whether there is any blockage. At the same time, an alarm value is set for the online value. When the monitored data approaches the preset threshold, the system automatically triggers an alarm to identify potential risks in advance.

[0047] Preferably, a pressure gauge is installed at the outlet of the absorption pump to detect in real time whether the pump is malfunctioning, has excessive pressure, leaks, or is blocked. When the monitoring data reaches the preset low value or the pump stops due to a malfunction, the interlock is automatically triggered, and the standby pump is started to ensure that the absorption liquid continues to flow and the exhaust gas continues to meet the emission standards.

[0048] Preferably, a hydrogen chloride tail gas analyzer is installed at the outlet of the waste gas absorption tower to monitor the emission concentration in real time, avoid exceeding emission standards, and evaluate the treatment effect of the absorption tower based on the data, ensuring the normal operation of the tail gas system and reducing the risk of shutdown.

[0049] Specifically, a remote automatic control scheme for an improved hydrogen chloride tail gas absorption system in chlor-alkali production is as follows:

[0050] (1) The sodium hydroxide regulating valve 8 and the absorbent water pH meter 7 form a PID self-control loop, and the set value is set to 10.

[0051] (2) The tail gas absorption water tank level regulating valve 5 and the tail gas absorption water tank level gauge 1 form a PID self-control loop, and the tail gas absorption tank level setting value is set to 60%.

[0052] (3) The online value of the exhaust gas vent pipe thermometer 21 is interlocked with the nitrogen switch valve 20 and the steam switch valve 22. When the online value of 21 is ≥50℃, the timer starts and counts for 30 seconds, and the interlock opens the switch valves 20 and 22.

[0053] (4) When the online value of the pressure gauge 6 of the gas-liquid separator reaches the high alarm set value, the DCS will pop up an alarm and an audible and visual alarm.

[0054] (5) The two absorption pumps are mutually controlled for emergency operation. If pump A fails and stops, pump B will start interlocked; conversely, if pump B fails and stops, pump A will start interlocked. If a single pump is running and the outlet pressure gauge 4 is below 0.1 MPa, the standby pump will start interlocked. If the outlet pressure returns to normal, the original running pump will stop.

[0055] (6) When the online value of the hydrogen chloride tail gas analyzer reaches the high alarm set value, the DCS will pop up an alarm and an audible and visual alarm.

Claims

1. An improved system for absorbing hydrogen chloride tail gas in chlor-alkali production, characterized in that: The top outlet of the hydrogen chloride tail gas absorption tower (13) is connected to the lower air inlet pipeline of the hydraulic jet (10). The water outlet pipeline at the bottom of the hydraulic jet (10) is connected to the gas-liquid separator (11). The liquid seal overflow outlet of the gas-liquid separator (11) is connected to the tail gas absorption water tank (14). The lower outlet of the exhaust gas absorption water tank (14) is connected to the inlet pipeline of the absorption water pump (3). The outlet water connection pipeline of the absorption water pump (3) leads to the salt dissolving water tank.

2. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 1, characterized in that: The outlet connection line of the absorption water pump (3) is connected to the top inlet of the hydraulic jet (10) via the absorption water inlet hydraulic jet (17) connection line. The water outlet connection line of the absorption water pump (3) is connected to the upper part of the waste gas absorption tower (12) via the absorption water inlet connection line (18).

3. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 2, characterized in that: The top outlet of the exhaust gas absorption tower (12) is connected to the inlet pipeline of the flame arrester (23), the outlet pipeline of the flame arrester (23) is connected to the atmosphere, and the nitrogen pipeline and the steam pipeline are connected to the atmospheric pipeline after the flame arrester.

4. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 1, characterized in that: The top of the tail gas absorption water tank (14) is connected to 7 independent inlet pipelines, namely the nitrogen pipeline, the production water pipeline, the sodium hydroxide solution pipeline, the hydrogen scrubbing tower condensate pipeline, the hydrogen system dehydration device condensate pipeline, the gas-liquid separator overflow water pipeline, and the waste gas absorption tower overflow water pipeline.

5. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 4, characterized in that: A flow meter (9) and a sodium hydroxide regulating valve (8) are installed on the sodium hydroxide pipeline. A level gauge (1) is installed on the tail gas absorption water tank. An absorption water thermometer (2) is installed on the inlet pipeline of the absorption water pump and an absorption water pump outlet pressure gauge (4) is installed on the outlet pipeline.

6. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 5, characterized in that: A pH meter (7) for the absorber is installed on the water inlet jet connector (17), a pressure gauge (6) is installed on the top of the gas-liquid separator (11), a tail gas absorber level regulating valve (5) is installed on the absorber pump outlet to the salt distribution tank, a hydrogen chloride tail gas analyzer (24) is installed at the outlet of the waste gas absorption tower, a thermometer (21) is installed on the flame arrester outlet pipeline, a nitrogen switch valve (20) is installed on the nitrogen pipeline, and a steam switch valve (22) is installed on the steam pipeline.

7. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 6, characterized in that: The sodium hydroxide regulating valve (8) on the sodium hydroxide pipeline and the absorbent water pH meter (7) form a PID self-control loop.

8. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 6, characterized in that: The tail gas absorption water tank level regulating valve (5) on the outlet desalination water distribution tank pipeline of the absorption water pump and the tail gas absorption water tank level gauge (1) form a PID self-control loop.

9. The improved system for absorbing hydrogen chloride tail gas in chlor-alkali production according to claim 2, characterized in that: The top outlet of the exhaust gas absorption tank (14) is connected to the lower pipeline of the exhaust gas absorption tower (12), and the top outlet of the gas-liquid separator (11) is connected to the lower pipeline of the exhaust gas absorption tower (12).

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