Key Design Points for Anhydrous Hydrogen Fluoride Storage Areas —— Personal Summary 15753301851

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Key Design Points for Anhydrous Hydrogen Fluoride Storage Areas – Personal Summary 1. Basic Information on Anhydrous Hydrogen Fluoride 1.1 Anhydrous hydrogen fluoride (also known as AHF) is a toxic gas that is colorless and has an irritating odor at normal temperature and pressure. It is highly hygroscopic; when exposed to air, it reacts with water vapor to form white acid mist (commonly referred to as the “fuming” phenomenon). It is also highly soluble in water, capable of mixing with water in any proportion. The saturated vapor pressure of anhydrous hydrogen fluoride is shown in the table below: Temperature/C, Saturated vapor pressure/kPa. 20: 1.35178; 36.74: 4.8378. 22: 8.84715; 38.6413: 6.4613. 24: 16.78344; 98.7053: 26. 25: 25.18124; 111.596: 28. 34: 34.06124; 125.159: 30. 43: 43.44454; 139.422: 32. 53: 53.353148; 154.413: 34. 63: 63.809750; 170.162: 1.2 The fire hazard associated with anhydrous hydrogen fluoride is classified as Category V according to the \"Code for Fire Protection Design of Buildings\" GB50016. It is also considered a hazardous chemical according to the \"Catalogue of Hazardous Chemicals\" (2015). According to the Classification Information Table of Hazardous Chemicals, the acute toxicity of anhydrous hydrogen fluoride via oral exposure is classified as Category 2* ； Acute toxicity – dermal, Category 1 ； Acute toxicity – inhalation, Category 2*. According to the \"List of Hazardous Chemicals Subject to Priority Supervision\" issued in Document No. An Jian Zong Guan San [2011] 95, anhydrous hydrogen fluoride is classified as a hazardous chemical subject to priority supervision. According to GB18218-2009 \"Identification of Major Hazard Sources for Hazardous Chemicals\", the critical amount for hydrogen fluoride is 1 T. 2. General layout design 2.1 The storage capacity of anhydrous hydrogen fluoride storage areas is generally greater than 1 ton, and such areas are often classified as major hazard sources, falling under the category of \"two key points and one major hazard\" facilities. The external safety protection distance shall meet the **standard requirements; the assessment and calculation of this distance should be carried out in accordance with GB/T37243. It must also satisfy the requirements of the individual risk criteria established in GB36894. New constructions and renovations should be avoided in densely populated areas, and should be located on the upwind side of the direction from which winds blow most rarely throughout the year in densely populated zones and ordinary industrial areas; they should not be situated in areas where winds are trapped. The site selection should meet the requirements of GB50489. According to the \"Criteria for Identifying Major Hidden Dangers in Chemical and Hazardous Chemicals Production and Operation Units\", production units and storage facilities that fall under the category of \"two key aspects and one major issue\" and whose external safety protection distances do not meet the **standard requirements are deemed to have major hidden dangers. 2.2 The roads in the AHF tank farm can be divided into main roads, secondary roads, and side roads. The road surface width for main roads should be 7.0–9.0 m, that for secondary roads should be 6.0–7.0 m, and that for side roads should be 4.0–6.0 m. Fire lanes should be provided along the two long sides of the tank area, and the width of these fire lanes should not be less than 4.0 m ； The turning radius at the inner edge of the road surface for fire trucks should not be less than 9.0 m, and the clear height above the road surface should not be lower than 5.0 m. 3. PID Design 3.1 In accordance with the \"Three-Year Action Plan for the Special Rectification of Hazardous Chemicals Safety\", the automation systems for the production units and storage facilities involved in fluorination processes must be deployed at 100% ； The upstream and downstream supporting equipment of the fluorination process unit must be under automated control. In accordance with the Interim Provisions on the Supervision and Management of Major Hazard Sources of Hazardous Chemicals and the Standards for Identifying Major Hidden Dangers in Chemical and Hazardous Chemical Production and Operation Units, hydrogen fluoride storage units must monitor parameters such as the temperature, pressure, and liquid level of the storage tanks, and integrate these measurements into the DCS system. For Class 1 or Class 2 major hazard sources, an emergency shutdown system is required ； The tank areas that constitute level 1 and level 2 major hazard sources are equipped with emergency shutdown functionality ； Tank areas that are classified as major hazard sources of level 1 or 2 and involve toxic gases, liquefied gases, or highly toxic liquids are equipped with independent safety instrument systems. The storage level in the hydrogen fluoride storage tanks (vessels) shall not exceed 80% of their capacity, and each tank should be equipped with two types of measurement methods. Anhydrous hydrogen fluoride storage tanks should be equipped with two different types of measuring instruments: weight and level, or two different types of level gauges. (There is controversy here: if weight is a factor, hoses must be used, but it is best not to use hoses with AHF.) The tank level should be interlocked with the high-level switch of the shut-off valve; the SIS shut-off valve shall be activated by an interlock based on either the level or weight, in the event of a high level. The inlet and outlet operation valves of the storage tank can both be operated without human intervention. 3.2. Hydrogen fluoride storage tanks (vessels) must be equipped with emergency tanks, and their effective volume shall not be less than that of the largest storage tank. The emergency tank should be kept as an empty tank, and in emergency situations it can be automatically emptied through DCS control. The corresponding transfer pumps and valves can all be remotely controlled. 3.3 Storage tanks (vessels) shall be equipped with emergency relief facilities, and the fluid released as a result of such relief shall be discharged into the exhaust gas treatment system. Design a safety valve or a combination of a safety valve and a burst disc based on the design pressure of the tank. The spray pump of the exhaust gas absorption system can be activated remotely. 3.4 In accordance with the Safety Technical Specifications for Hydrogen Fluoride Production, a spray water curtain should be installed around the storage tank area; it should have remote control functionality or employ an entirely enclosed absorption process. The \"Notice from the Zhejiang Provincial Emergency Management Department on Carrying Out Special Rectification Actions for the Safety of Enterprises Involved in Toxic Gases\" (Zhe Emergency Hazardous Chemicals 2021 No. 1) requires closed management to be implemented in the areas where hydrogen fluoride is loaded and unloaded from tankers, as well as in the areas where hydrogen fluoride storage tanks are located, as these areas represent major hazards. Weihai City in Shandong Province has issued guidelines for the enclosed renovation of hydrogen fluoride and liquid ammonia systems. Based on the actual conditions of work safety in local hydrogen fluoride and liquid ammonia-related enterprises, the special task force in Weihai City formulated guidelines for the closed-system renovation of hydrogen fluoride and liquid ammonia storage facilities. These guidelines specify concrete measures for managing safety risks associated with the closed storage of hydrogen fluoride and liquid ammonia. They also provide guidance on ensuring that hydrogen fluoride storage areas are completely sealed and that fixed water spray systems are installed in liquid ammonia storage areas, thereby effectively minimizing the impact of any leaks and preventing safety hazards related to the storage of these substances. To date, Weihai Hengbang Chemical Co., Ltd. has completed the preliminary design of the sprinkler system for the liquid ammonia storage tank area, and it is currently undergoing an internal review ； Weihai Xinyuan New Materials Co., Ltd. is carrying out civil engineering work for the sealing renovation of the hydrogen fluoride storage tank area. The above are local requirements. 3.5 The hydrogen fluoride packaging, unloading, and storage systems shall be equipped with negative pressure absorption devices required for fault repair. 3.6 Hydrogen fluoride filling should be carried out using a universal piping filling system. 3.7 The flow velocity of liquid hydrogen fluoride in carbon steel pipes should not exceed 1.8 m/s. 3.8 Anhydrous hydrogen fluoride storage tanks are generally equipped with chilled water (-5°C) for cooling. 4. Equipment Selection 4.1 Anhydrous hydrogen fluoride storage tanks are generally designed as horizontal tanks with double heads or as spherical tanks, with a design pressure of not less than 0.2 MPa.g. The flange design for anhydrous hydrogen fluoride piping is rated at no less than 2.0 MPa, typically PN25 with male and female faces. The tank outlet is equipped with a feed inlet, an exhaust outlet, a level gauge port, a temperature port, a pressure gauge port, a pump mounting port, an access hatch, a relief outlet, and some also require a cooling water interface. The material used for anhydrous hydrogen fluoride storage tanks is generally Q345R, with a corrosion allowance of at least 3.0 mm; a sediment collection tray is designed at the bottom of the tank. 4.2 Submersible pumps are generally used for the liquid feeding pump and tank transfer pump of anhydrous hydrogen fluoride, and they are installed directly in the storage tank. 4.3 Exhaust gas absorption systems generally use PPH absorption towers, variable-frequency fans, etc. 5. Design of equipment layout 5.1 The equipment layout should be divided into the following functional areas: storage area, loading/unloading area, and exhaust gas absorption area. 5.2 Storage area: The number of storage tanks within a tank group should not exceed 4 rows. The tank group should be equipped with a protective dike, and the effective volume within this dike should not be less than the volume of the largest tank in the group (refer to the practices for fire dikes). The distance from a horizontal storage tank to the line at the foot of the inner embankment of the protective dike should not be less than 3 m, while the distance from a vertical storage tank to that line should not be less than half of the tank’s wall height. Levees and dikes should be able to withstand the hydrostatic pressure of the liquid they contain, and shall not leak ； The height of the protective dike for vertical storage tanks should be the calculated height plus 0.2 m. When the height of the dike exceeds 3.6 m (based on the design floor level inside the dike), safety measures must be implemented to ensure that operators can operate the valves properly and can escape quickly in emergency situations. Note: When the height of the protective dike is greater than 3.6 m (measured from the ground level inside the dike), the safety measures taken include the use of remotely controlled shut-off valves on the inlet and outlet pipelines of the storage tank, high-level interlocks, as well as the installation of elevated walkways inside the dike to connect the tank ladders with the dike stepping stones. The height of the protective dike for horizontal storage tanks should not be less than 0.5 m (based on the designed floor level inside the dike) ； The areas where pipes pass through the embankment should be tightly sealed using corrosion-resistant materials ； A sump is generally designed within the tank farm enclosure; this sump collects rainwater from the initial period, fire water in case of leaks, as well as clean rainwater. The sump should be equipped with measures to separate rainwater from wastewater. 5.3 Loading and unloading area: The layout of the loading arms in the loading and unloading area should take into account the height of the tank trucks. For domestic anhydrous hydrogen fluoride tank trucks, a dumping nozzle is usually installed at the top; the height of this dumping nozzle, as well as that of the loading arm platform, must match the height of the tank truck’s connection ports. The floor of the loading and unloading area is usually hardened with concrete; some manufacturers require flow meters for measurement and also install load cells in the tank truck parking area. Platforms are generally equipped with emergency escape slides. An emergency absorption air intake hood is designed near the flexible hose. 5.4 Exhaust gas absorption area: The exhaust gas absorption area typically includes a water scrubber tower, an alkali scrubber tower, a spray pump, and an exhaust fan. The power supply for pumps and fans is generally considered a relatively important load among primary loads. The exhaust gas absorption area is generally isolated by a cofferdam, and an anti-corrosion floor is installed inside the cofferdam. 6. Pipeline design: The pipelines involved in the anhydrous hydrogen fluoride tank area generally include AHF pipelines connected to the storage tanks, as well as aqueous acid pipelines connected to the absorption towers. If the pressure and diameter of AHF pipes meet the requirements for pressure pipes, they are classified as GC1. Pipelines are mostly made of carbon steel; generally, steel grade 20# specified in GB6479-2013 or the standard GB 9948-2013 for seamless steel tubes used in petroleum cracking can be chosen. The material of the fittings can be the same as that of the pipeline. The design pressure of the pipe flange should be no less than 2.0 MPa; generally, butt-welded flanges of type PN25 WN FM/M are used, and the standards can be European or American flange standards as specified in HG/T20592-2009. Gaskets can be metal wound gaskets made of carbon steel and PTFE. For fasteners, high-strength bolts and nuts are required; fully threaded studs made of 35CrMo can be used, along with Type II hex head nuts made of 30CrMo. If hydroxyl groups are present, lined pipes can be used, or FRPP polypropylene pipes can also be an option. We don’t just design chemicals – we design dreams too! !