I have a question regarding the design of a styrene storage tank; I hope experts can help answer it.
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For the company’s second-phase plan, which involves projects related to styrene, a storage tank with a capacity of 40 m3 is required. We would appreciate your help in determining what type of storage tank should be chosen, as well as guidance on matters related to loading and unloading pipelines and issues related to temperature reduction during summer.
Styrene is classified as a Class B fire hazard; it is a flammable and explosive substance that gradually undergoes polymerization and oxidation when exposed to air； For a 40m3 storage tank, either a vertical fixed-roof tank or a horizontal tank can be used; what’s important is to implement a nitrogen purge to prevent it from coming into contact with air, thereby avoiding polymerization ； For the loading, unloading, and transportation of pipes, conventional metal hoses can be used for loading/unloading, as well as seamless steel pipes for transportation. It is important to ensure that the pipes are thoroughly cleaned before loading and unloading to prevent blockages due to polymer accumulation ； Insulation measures are applied to the tank body to address the issue of high temperatures caused by sunlight.
Interpretation of Petrochemical Regulations 6.2.2 Fixed-roof nitrogen sealing
The flexible metal hose can no longer be used; a flexible conduit should be used instead
It’s very easy. For this, use a fixed top with nitrogen sealing; the nitrogen sealing system should be designed for proportional control. It’s also a good idea to add a vent valve, one that includes a flame arrester as well. All of these components aren’t expensive at all. A flexible hose can be used for connection at the bottom
There are no documents or regulations that mandate the use of flexible hoses; I’ve only heard that this requirement applies to liquefied hydrocarbons. Additionally, flexible hoses are not very suitable for styrene, as it tends to self-polymerize.
Styrene is a colorless oily liquid at temperatures ranging from -30.6°C to 146°C; it has a flash point of 31°C and is classified as a Flammable Liquid of Category A. Styrene is carcinogenic and must be stored in a sealed manner to prevent leaks. It has very reactive chemical properties; it oxidizes easily in air and can also polymerize at room temperature to form pale yellow polystyrene, which is viscous (and thus prone to clogging pipes). Therefore, nitrogen purging is used for these pipes, and blind ends should be avoided as much as possible. The polymerization reaction is exothermic, so storage tanks must be equipped with safety devices to prevent overpressure. As the temperature rises, the polymerization reaction speeds up; hence, styrene storage tanks and pipelines should be insulated with polyurethane, and the tops of the tanks should be sealed with nitrogen to prevent oxidation. Styrene should be stored with a polymerization inhibitor to prevent polymerization over long periods of time
To be honest, the tank I saw was vertical, with a capacity of 100 cubic meters, a fixed roof, no nitrogen seal, and a circulating water spray system; in summer, the temperature reached 25 degrees Celsius
Paragraph 4.2.5 of the explanatory notes for the \"Design Code for Tank Areas in Petrochemical Storage and Transportation Systems\" (SH/T 3007-2014) states, \"......for substances such as styrene, which require contact with oxygen in order to prevent polymerization......\", meaning that for tanks containing styrene of high purity, the anti-polymerization agents added must be able to exert their effect in the presence of oxygen. Therefore, nitrogen sealing is generally not used, and only a small amount of air is introduced. The storage temperature for styrene should be between 5 and 20°C.
Original poster, we have also been working on the design of a styrene storage tank area recently; we are using horizontal tanks with a capacity of 50 cubic meters. We plan to use nitrogen sealing along with internal coils through which cold water will flow to achieve cooling. I’m not sure if this internal coil cooling method will work – most designs I’ve seen use external coolers for cooling. Perhaps it’s because the tank volume is relatively large, which makes internal coil cooling less effective. But I’m not sure if this approach will work for tanks with a capacity of 50 cubic meters. How did you guys handle it in the end?