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Chlorine is a yellow-green, irritating gas at room temperature and pressure. At room temperature and pressures above 709 kPa, it is in a liquid state; liquid chlorine is golden yellow in color. According to the Catalog of Hazardous Chemicals (2015 edition), chlorine is a highly hazardous substance; it is a strong irritant gas. When inhaled through the respiratory tract, it comes into contact with the moisture on the surface of the respiratory mucosa, resulting in the formation of hydrochloric acid and hypochlorous acid. Hypochlorous acid further decomposes into hydrochloric acid and atomic oxygen, causing local irritation and corrosion. Occupational exposure limit: MAC (Maximum Allowable Concentration) (mg/m3): 1. Therefore, there are strict requirements for the storage of liquid chlorine. Here is a brief summary of the safety technical requirements for chlorine liquid storage, to help everyone learn and understand them. Image Image Image I. Relevant regulations, standards, and specification requirements There are numerous regulations, standards, and specifications related to the safety requirements for liquid chlorine storage; the main ones are as follows: 1. \"Guidelines for Identifying Safety Risks and Hazards in Enterprises Producing Liquid Chlorine (Chlorine Gas), Vinyl Chloride, and Peroxides (Trial Version)\". 2. “Safety Regulations for Chlorine” (GB 11984-2008). 3. \"Technical Requirements for Safe Use of Liquid Chlorine\" (AQ 3014-2008). 4. \"Technical Requirements for Automated Control Systems for Filling Liquid Chlorine Cylinders\" (AQ 3051-2015). 5. \"Methods for Handling and Disposing of Liquid Chlorine Leaks\" (HG/T 4684-2014). 6. “General Technical Requirements for Safety Facilities for Chlorine Production in Chlor-alkali Industry” (T/CCASC1003-2021). 7. “Guiding Opinions of the China Chlor-Alkali Association on Carrying Out Rectifications for Phasing Out Outdated Process Technologies: Liquid chlorine storage warehouses without enclosed and automatic absorption systems” (No. 2021 Xie Zi 001). 8. Notice on the “Guidelines for the Safe Renovation of Liquid Chlorine Storage Facilities and Related Equipment in Shandong Province, as Well as Emergency Response to Liquid Chlorine Leaks (Trial)” (Lu Jing Ji Han [2020] No. 56). 9. \"Technical Specifications for Safe Production of Chlor-alkali Products\" (DB37T 1933-2022). 10. “Technical Specifications for Safe Production of Liquid Chlorine” (HG/T30025-2018). 11. “Specifications for the Treatment and Disposal of Waste Chlorine Gas” (GB/T 31856-2015). 12. “Guidelines for the Protection against Occupational Hazards of Chlorine” (GBZT275-2016). Image Image Image Image II. Main safety technical requirements 1. Requirements for liquid chlorine storage tanks (vessels) (1) The design and manufacture of liquid chlorine storage tanks (vessels) shall comply with the relevant regulations for pressure vessels. (2) Chlorine pipeline flange gaskets should be chlorine-resistant gaskets. (3) For large-capacity liquid chlorine storage tanks, flexible connections or spring suspension brackets should be installed on the liquid chlorine inlet and outlet pipes to prevent installation stresses caused by foundation settlement. (4) Liquid chlorine storage tanks and liquid chlorine pipelines should be insulated using polyurethane spray foam with an oxygen index 30 higher. (5) Depending on the volume of the liquid chlorine storage tanks, at least one tank with the largest volume should be designated as an emergency backup tank for liquid chlorine in case of accidents. The standby tank should be empty, the pipelines connected to various storage tanks should allow for switching operations, and it should be equipped with the capability to switch using remote control. 2. Requirements for the liquid chlorine storage tank building: (1) The structural design and fire resistance rating of the liquid chlorine storage building must comply with the relevant provisions specified in the \"Code for Fire Protection Design of Buildings\" GB50016. (2) It is recommended that the liquid chlorine storage tank building adopt a sealed structure, and corrosion and leakage prevention measures should be implemented in the design or renovation of such buildings and structures. (3) The liquid chlorine storage tank area should be 0.3m to 0.5m below the surrounding ground, or an accident bund 0.3m to 0.5m high should be installed around the storage area to prevent the expansion of the area where liquid chlorine vaporizes in the event of a leakage. A liquid chlorine collection tank should be installed in a low-lying corner on the ground, with a fixed suction hood placed above it. 3. Requirements for control instrument installation in liquid chlorine storage tanks: (1) Liquid chlorine storage areas that constitute level 1 or level 2 major hazard sources shall have an emergency shutdown function and be equipped with an independent safety instrument system. (2) The switching of liquid chlorine storage tanks should be carried out through remote automated operation. (3) Manual valves and two isolation valves shall be installed on the inlet and outlet pipelines. The manual valve should be installed near the storage tank; one isolation valve should be connected to the DCS system, while another isolation valve should be connected to the SIS system. (4) The storage tank shall be equipped with a safety valve; a burst disc shall be installed in front of the safety valve, and a pressure monitoring device shall be placed between the burst disc and the safety valve. The vent line of the safety valve shall lead to the absorption unit. (5) The storage tank shall be equipped with local and remote pressure monitoring. (6) The liquid level should be monitored both locally and remotely, using liquid level sensors based on different measurement principles. The remote liquid level meters should be leak-proof types that do not come into contact with the medium, and they should provide digital display of the liquid level as well as audible and visual alarms for extremely high liquid levels. For on-site level indication, glass plate level gauges should not be used. On-site, the liquid chlorine level should be indicated by distinct color bands for low level, normal level, and high level (yellow, green, red). 4. Requirements for capturing chlorine in the event of an accident: (1) The facility should be equipped with devices for handling chlorine in emergency situations. In enclosed structures, not only fixed air intake units should be installed, but also movable non-metallic hose-based air intake systems; the radius of these hoses should cover the equipment and pipelines located within the enclosed structure ； In enclosed structure workshops, accidental chlorine should be routed to absorption units. (2) Ditches and spill ponds shall be installed on the ground surrounding the liquid chlorine storage tank; these ditches and spill ponds shall be connected to each other and covered with grating, and the capacity of the spill ponds shall be sufficient. (3) When a liquid chlorine storage tank leaks, it is prohibited to spray water directly onto the tank; instead, mist-type water spraying devices can be installed around the factory building and the perimeter of the tank area to minimize the contamination of the air by chlorine gas. (4) The accident chlorine treatment unit shall have the capability to operate continuously for 24 hours, and the alkali solution circulation tanks shall be arranged in a ‘one in use, one in standby’ configuration. (5) The absorption unit of the accident chlorine treatment system is equipped with manual and automatic start functions; the automatic start is interlocked with the chlorine leak detection alarm, and the number of alarms as well as their parameters can be set according to actual conditions. (6) The concentration of the alkaline solution should be capable of online monitoring to meet the requirements for handling chlorine in case of accidents under any conditions (the mass fraction of the newly prepared alkaline solution should be around 15%, while that of the replaced alkaline solution should not be lower than 5%). (7) New, modified, and expanded projects should have separate installations (the waste gas generated from liquid chlorine filling can be combined with it); they should not share the same facilities as those used for handling chlorine from electrolysis accidents, turbine seal gas treatment systems, and sodium hypochlorite production units. (8) Electrical equipment such as backflow pumps, alkali circulation pumps, and emergency chlorine fans should meet the requirements for particularly important loads in category I loads. 5. Leakage alarm settings: Chlorine leak detection alarms should be installed in areas where liquid chlorine is stored. The maximum allowable concentration of chlorine in the air of working areas and chlorine storage areas is 1 mg/m3. Chlorine leak detection and alarm devices should be installed in the liquid chlorine plant, and their installation on-site shall meet the requirements of the \"Design Code for Detection and Alarm of Flammable and Toxic Gases in Petrochemical Industries\" (GB/T 50493-2019). For chlorine detectors, an electrochemical type is recommended; the measurement range should be 0 ppm to 10 ppm, with a first-level alarm set at 1 ppm and a second-level alarm set at 3 ppm.