Pipeline material selection issue after concentrated sulfuric acid is classified as a highly hazardous substance

FRP is the scientific name for fiberglass reinforced plastic. It is made using synthetic resin as a binder and glass fiber reinforced plastic, following a specific molding process. The most widely used applications at present include fiberglass tanks, fiberglass pipes, fiberglass cooling towers, fiberglass grilles, etc. The properties of fiberglass-reinforced plastic vary greatly depending on the resin used. Currently used for chemical industry corrosion protection include: epoxy fiberglass, phenolic fiberglass (good acid resistance), furan fiberglass (good corrosion resistance), and polyester fiberglass (easy to install, etc.). The following is a corrosion resistance table for epoxy fiberglass, phenolic fiberglass, and furan fiberglass against common media (sulfuric acid, hydrochloric acid, hypochlorous acid, sodium hydroxide):

FRP pipes are definitely not suitable for use with concentrated sulfuric acid, right? Won’t they get oxidized? Furthermore, non-metallic pipes shall not be used for the transportation of extremely hazardous fluids, as specified in SHT3161 4.1.7

Concentrated sulfuric acid has been classified as a \"human carcinogen,\" and its toxicity level has been upgraded to \"extremely hazardous.\" According to GB50316-2000, such pipelines should be designed in accordance with Class A1 fluid piping standards. Clause 13.1.3.6 of GB50316-2000 stipulates the following requirements for flanges: 1) Flat-welded {plate-type} flanges shall not be used; 2) In addition to using gasketed flanges, the nominal pressure of the flanges should be selected such that there is a margin of 25% or more, and it should not be lower than 2.0 MPa; 3) When soft gaskets are used, flanges with male-female surfaces or rod-and-groove surfaces should be chosen. Based on these regulations, for pipelines carrying concentrated sulfuric acid, 1) flat-welded {plate-type} flanges shall not be used, and 2) the nominal pressure of the flanges must be at least 2.0 MPa. In my opinion, the use of non-metallic materials such as fiber-reinforced glass fiber reinforced plastic (FRP) or non-metallic lining materials for such pipelines does not comply with the requirements of the \"Code for Design of Industrial Metal Pipelines\" GB50316-2000

Concentrated sulfuric acid is commonly used for the dehydration and drying of materials. In previous project designs, sulfuric acid was classified as a medium-hazardous medium; therefore, aside from 98% concentrated sulfuric acid which is handled through carbon steel pipes, sulfuric acids with concentrations of 75–95% are generally processed using non-metallic pipes such as PVC. It seems that their use will no longer be allowed in the future. So, what should be done with the sulfuric acid non-metallic pipes in existing installations? Is it necessary to upgrade to GC1 level through renovation and replacement? I checked industry standards for non-metallic equipment such as \"Plastic Equipment\" (HG 20640), and it is indeed specified since quite some time ago that they are not suitable for storing highly hazardous media; even moderately hazardous media are not permitted to be stored using such equipment.

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Yes, how can this problem be solved?

A new conclusion has finally been reached: According to the \"Announcement by the State Administration for Market Regulation on Matters Related to Administrative Licenses for Special Equipment (No. 3, 2019)\", the degree of hazard posed by the substances contained in pressure vessels and pressure pipelines is determined in accordance with the \"Catalogue of Hazardous Chemicals\" (2015 version). Sulfuric acid is classified as a Category 1A corrosive substance, and it does not belong to the category of highly hazardous substances.

Use carbon steel at lower temperatures; use glass lining when the temperature exceeds 25°C

I would like to ask: I checked the list of hazardous chemicals, and it doesn’t state that \"sulfuric acid belongs to Category 1A of corrosive substances and is not considered a highly hazardous substance.\" Could you please tell me where this regulation can be found?

The note field in the row for the product name “sulfuric acid” does not indicate it as “highly toxic”; thus, the toxicity of the medium in pressure pipelines is classified according to standard MSDS guidelines, rather than in accordance with standards such as the \"Classification of Hazards from Occupational Exposure to Toxic Substances\" (GBZ 230-2010) and the \"Classification Standards for Toxicity and Explosion Hazards of Chemical Media in Pressure Vessels\" (HG/T 20660-2017).