1. Core equipment safety design: full protection from materials to monitoring
2. Process safety control: prevent risks from the source
3. Full chain management of hazardous chemicals
4. Personnel safety and behavior control
5. Emergency management: rapid response and full scenario coverage
1. Core equipment safety design: full protection from materials to monitoring
1.1. Selection of corrosion-resistant and explosion-proof materials
Parts in contact with chlorine: titanium alloy (TA2) and Hastelloy C-276 (wet chlorine corrosion resistance life> 10 years) are used to replace ordinary stainless steel (316L can only be used for 2-3 years in wet chlorine), eliminating equipment perforation and leakage from the source.
Hydrogen area: electrical equipment is Ex IIB T3 explosion-proof grade, and the junction box adopts a cast-in design to prevent electric sparks from igniting hydrogen (explosion concentration range 4%-75%).
Electrolyzer structure: double-chamber vacuum tank design, the isolation valve is automatically triggered when the diaphragm ruptures to avoid mixing Cl₂ and H₂ (explosion limit 5%-95% mixed concentration).
1.2. Intelligent monitoring and dual redundant system
Leak detection:
Laser gas detector (accuracy 0.1ppm) is installed on the chlorine pipeline, and 1 monitoring point is set every 10 meters. The sound and light alarm is triggered within 0.5 seconds when leaking.
Thermal conductivity sensors are deployed in the hydrogen compressor room, and the diffusion range is calculated in real time in combination with anemometers, and the explosion-proof fans on the roof are linked (ventilation frequency ≥ 12 times/hour).
Pressure/temperature monitoring:
The electrolyzer is equipped with a triple pressure transmitter (median algorithm). When the set value (such as 1.2bar) is exceeded, the SIS safety instrument system (SIL3 level) automatically cuts off the power supply, and the response time is <50ms.
The storage tank is equipped with an infrared thermal imager. When the temperature is abnormal (such as liquid chlorine storage tank exceeds -35℃), liquid nitrogen spray cooling is started, and the error is controlled within ±0.5℃.
1.3. Regular maintenance and preventive maintenance
Non-destructive testing: Ultrasonic wall thickness testing of pipelines is carried out every year (replacement is mandatory when the remaining thickness is <80% of the design value), and the coating of the electrolyzer electrode is tested by X-ray fluorescence spectrometer (recoating when the ruthenium content is <90% of the design value).
Membrane performance test: Extract membranes every quarter for ion mobility test, and replace them as a whole when the attenuation exceeds 15% (to avoid Cl₂ mixing into caustic soda due to membrane damage, causing downstream reactions to get out of control).
2. Process safety control: prevent risks from the source
2.1. Automation and interlock protection
DCS distributed control system: real-time monitoring of 300+ process parameters (such as brine flow, current density), key parameters set ±5% fluctuation threshold, automatically switch to manual mode and alarm when exceeding the limit.
Emergency shutdown system (ESD):
10 emergency shutdown buttons are set in the whole plant. After pressing, the electrolysis power supply will be cut off within 3 seconds, all material valves will be closed within 10 seconds, and the alkali solution spray system will be started at the same time (neutralization chlorine efficiency> 99%).
The hydrogen compressor and the electrolyzer adopt "current-flow" interlocking. When the electrolyzer is powered off, the hydrogen compressor will be shut down synchronously to prevent the negative pressure from sucking in air to form an explosive mixture.
2.2. Strict control of hazardous process parameters
Brine purity: Control calcium and magnesium ions <1ppm (through chelating resin tower + ceramic membrane filtration). Excessive impurities will cause electrode scaling, and local overheating will cause chlorine decomposition (decomposed into O₂ and ClO₂ above 200°C, increasing the risk of explosion).
Current density: The upper limit is controlled at 4.5kA/m² (membrane process safety range). Ultra-high current will cause a sudden increase in membrane resistance and temperature exceeding 85°C, increasing the probability of membrane rupture.
2.3. Material flow safety design
Check valve and flame arrester: The hydrogen pipeline is installed with a stainless steel explosion-proof flame arrester (flame arrester core pore <0.01mm) to prevent backfire to the electrolytic cell; chlorine delivery uses a double-seat check valve to automatically cut off the backflow when the pressure fluctuates.
Nitrogen protection: High-purity nitrogen (purity ≥99.99%) is used for purging storage tanks and pipelines. Production can only be started when the oxygen content is <0.5% after replacement to avoid oxygen-carrying operation of the hydrogen system.
3. Full-chain management of hazardous chemicals
3.1. Storage safety
Liquid chlorine storage tank:
Use "above-ground double-wall tank" (stainless steel inner tank + concrete outer tank), with leak detection sensors in the interlayer space, and the maximum storage capacity does not exceed 85% of the design capacity (in compliance with OSHA 1910.119 standard).
A 3-meter-high explosion-proof wall is set up in the storage tank area, open flames are prohibited within 50 meters around it, and a fixed water curtain system (cooling rate ≥5℃/minute) is equipped to prevent direct sunlight from heating.
Hydrogen storage:
Use high-pressure pipe bundles (20MPa) or low-temperature storage tanks (-253℃), ≥100 meters away from the office area, and set up a real-time monitoring screen for hydrogen concentration (data is synchronized to the local emergency management department).
3.2. Loading and unloading and transportation safety
Crane pipe interlocking: Liquid chlorine loading and unloading uses universal joint crane pipe + RFID vehicle number recognition. Loading and unloading cannot be started when it is not grounded or the sealing ring is aged, and the whole process is monitored by video (storage time ≥90 days).
Transport vehicles: equipped with GPS tracking + emergency cut-off remote control (in case of a car accident, the platform can remotely close the tank valve). Drivers must hold a "Dangerous Chemical Transport Qualification Certificate" and stop every 2 hours to check the status of the goods.
3.3. Dynamic inventory monitoring
Use the MES system to track the inventory of chlorine and hydrogen in real time, set safety thresholds (such as triggering an early warning when the chlorine inventory is greater than 50 tons, starting priority delivery or deep processing into sodium hypochlorite), and avoid the risk of excessive storage.
4. Personnel safety and behavior control
4.1. Gradual training and certification
Pre-job training: New employees must pass 80 hours of safety training (including chlorine leakage simulation and hydrogen explosion VR drills), and can work with two certificates (special operation certificate + factory-level safety certificate) after passing the assessment.
Regular refresher training: Conduct "accident review meetings" every quarter (such as the Minamata disease incident in Japan and the case analysis of the chlorine leakage accident of Chongqing Tianyuan Chemical), and conduct cardiopulmonary resuscitation (CPR) + positive pressure air respirator (SCBA) practical assessment every year (pass rate must be 100%).
4.2. Personal protective equipment (PPE)
Core area: Entering the electrolysis workshop must wear chemical protective clothing (Cl₂ penetration time ＞60 minutes), built-in SCBA (gas supply time ≥60 minutes), and high temperature resistant puncture boots (insulation level ≥10kV).
Smart PPE: equipped with a helmet with sensors (to monitor falls and collisions) and a wristband (real-time heart rate, body temperature, and gas concentration alarms), and abnormal data is automatically synchronized to the safety management platform.
4.3. Work permit and restricted area management
Confined space work: A "three-level permit" (jointly signed by the workshop director + safety engineer + process engineer) is required to enter the electrolytic cell for maintenance. Ventilation and replacement for 4 hours are required before entry. O₂≥19.5% and Cl₂＜1ppm are detected before entry. A dedicated person is assigned to monitor the outside (confirmed by phone every 15 minutes).
AI behavior monitoring: The camera identifies behaviors such as not wearing a protective mask and illegal fire, and gives real-time voice warnings and captures and archives them. Those who violate the rules more than 3 times a month will be suspended for retraining.
5. Emergency Management: Rapid Response and Full Scenario Coverage
5.1. Emergency Plan and Drills
Classification Plan: Formulate the "Special Plan for Chlorine Leakage" and "Comprehensive Plan for Hydrogen Explosion", clarify 13 types of emergency roles (such as leak plugging team, medical rescue team, public opinion team), and conduct cross-regional practical drills with fire and environmental protection departments every six months (such as simulating the evacuation of communities within 3 kilometers, and the response time requirement is <15 minutes).
Emergency Materials: Reserve 50 tons of caustic soda flakes (used to neutralize leaked chlorine, 1 ton of caustic soda flakes can neutralize 0.85 tons of Cl₂), 20 mobile explosion-proof fans, 100 sets of positive pressure respirators, and all material positioning systems update the location in real time.
5.2. Leakage Disposal Technology
Chlorine Leakage:
Small range (<10kg): Use a portable alkali solution spray gun (NaOH concentration 30%) to neutralize and form a sodium chloride solution for collection and treatment.
Large-scale leakage: Start the fixed spray system (alkali concentration 20%, coverage area ≥ 50 meters around the leakage source), and use a negative pressure fan to introduce the gas into the neutralization tank (the NaOH storage in the tank is configured at 1.5 times the maximum tank capacity).
Hydrogen leakage: Immediately cut off all power supplies, turn on the exhaust fan on the top of the plant (to prevent hydrogen from depositing on the ground), and use nitrogen to purge and dilute to below the explosion concentration (<4%).
5.3. Firefighting system
The entire plant is equipped with a water spray fire extinguishing system (atomization particle size <300μm, cooling efficiency increased by 30%), and a heptafluoropropane gas fire extinguishing device is added to the hydrogen area (spraying time <10 seconds), and the fire water pool capacity is designed according to the maximum fire duration of 6 hours (in accordance with GB 50160 standard).
