Problems with the benzene tank design
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I am designing a 500-cubic-meter benzene storage tank using an internal floating roof design, with the floating disk made of stainless steel. However, benzene is highly toxic; according to GB50341-2014, the Design Code for Vertical Cylindrical Steel Storage Tanks, this code does not apply to substances that are highly toxic. I would like to ask experts: what type of storage tank should be used for benzene, and which design code should be applied?
Benzene is classified as highly hazardous.
HG20660 \"Classification Standards for Toxicity Hazards and Explosion Risks of Chemical Media in Pressure Vessels\" specifies that benzene is classified as extremely hazardous
Firstly, as the original poster said, 50341 is not suitable for storing substances with extremely high or high toxicity; benzene is highly toxic (as listed in the catalog of highly toxic substances), and its hazard level is extreme (as specified in HG50660). Apart from its high toxicity, benzene can be designed as a Class A B flammable liquid; therefore, it is sufficient to install a nitrogen blanket and an oil vapor recovery system on the internal floating roof tank. The benzene tanks I have encountered so far are designed and installed in this way. I welcome you to share your design processes and results in the future – good luck!
This post was last edited by sdswypf on 2020-4-19 at 15:50. For non-pressure storage tanks containing extremely hazardous substances with high toxicity, such situations arise from time to time in design work, and choosing the appropriate design standards is indeed a challenging task! According to HG 20660-2000, benzene is classified as highly toxic when used to determine the technical requirements for the sealing and integrity of containers ； According to HG/T 20660-2017, benzene is an extremely hazardous medium ； According to GBZ 230-2010, substances that are clearly classified as human carcinogens are designated as having extreme hazards; since benzene is a carcinogen to humans, it is classified as an extremely hazardous substance ； At the same time, benzene is also an explosive substance. Section 1.0.2 of GB 50341-2014 stipulates that this code is applicable to the design of vertical cylindrical welded steel tanks under normal or near-normal pressure for storing petroleum, petrochemical products, and other similar liquids; it is not applicable to the design of buried tanks, tanks for storing highly toxic or extremely hazardous substances, or tanks for storing artificially refrigerated liquids ； Therefore, whether the toxicity of benzene is classified according to HG 20660-2000, HG/T 20660-2017, or GBZ 230-2010, GB 50341-2014 is not applicable to benzene storage tanks. SH/T 3007-2014, 1 (Scope): This standard specifies the selection of storage tanks in petrochemical storage and transportation systems, as well as the design principles and technical requirements for atmospheric, low-pressure, and high-pressure storage areas. These specifications apply to the engineering design of tank farms for the storage and transportation systems of liquid materials (including raw materials, intermediate materials, finished products, and auxiliary production materials) in petrochemical and coal chemical enterprises, and are not applicable to the design of low-temperature and atmospheric-pressure tank farms for liquefied hydrocarbons and liquid ammonia, nor to natural gas liquefaction tank farms. 4.2.5 It stipulates that for storing Class A B and Class A C liquids with a boiling point of 45°C or higher, or those with a saturated vapor pressure of not more than 88 kPa at 37.8°C, floating roof tanks or internal floating roof tanks should be used. ” Furthermore, clause 4.2.9 b) stipulates that \"inner floating roof tanks used for storing liquids of toxicity grades I and II, as well as inner floating roof tanks for Class A B and Class B A liquids with a diameter greater than 40 m, shall not use fusible materials for their inner floating roofs.\" Taking all of the above into account, the boiling point of benzene is 80.1°C; under normal operating conditions, it is more appropriate to use an internal floating roof tank for the 500-liter benzene storage tank in question. Then, based on the operating conditions and design parameters, it is determined whether to follow GB50341-2014 or other standards such as SY/T 0608-2014 for the design.
Use internal floating roof storage tanks with nitrogen sealing protection. Basis: Article 6.2.2 of the \"Code for Fire Protection Design of Petrochemical Enterprises (2018 Edition)\” (GB 50160-2008): For storing Class A B and Class B A liquids, floating roof tanks or internal floating roof tanks with metal floating decks should be used. For materials with special requirements or for tanks with a volume of 200 m3 or less, other types of tanks can be employed provided that appropriate safety measures are taken.