Is hydrogen explosion considered in the production, use, and storage of concentrated sulfuric acid?
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In the production and storage of concentrated sulfuric acid, carbon steel equipment is inevitably used. When concentrated sulfuric acid comes into contact with water and becomes diluted, it reacts with carbon steel equipment and pipelines to produce hydrogen gas. In China, there have been accidents involving explosions of concentrated sulfuric acid storage tanks during maintenance work. Therefore, in facilities involved in the handling of concentrated sulfuric acid or where such acid is stored, is it necessary to designate areas prone to hydrogen gas explosions and install hydrogen gas detectors?
This should not be necessary. For safety facilities, considerations such as protection against rain and leaks are necessary. The hazard level of general substances and the installation of safety facilities are determined based on the inherent hazards of the substances and their hazard classification. For reference only.
It is not required for normal production; however, safety measures such as nitrogen purging must be observed during hot work.
Production and storage locations need not be considered; if consideration is given to reactions, there is no way to proceed. (The reaction products may vary depending on the different metals used in the reaction.) Of course, no one will object if you do that
There are now regulations requiring the installation of breather valves on the vent pipes of storage tanks used for storing concentrated sulfuric acid, and the reason for this is the generation of hydrogen gas. In addition, it is stipulated that before carrying out hot work on equipment or pipelines in contact with sulfuric acid, enterprises must conduct flammable gas analysis and follow the relevant procedures outlined in AQ 3022 before proceeding with such work.
Under normal operation, there is no need to worry about the hazards of hydrogen, but remember to be especially careful when welding the equipment, as an explosion is possible.
For continuous production facilities, there is no risk of hydrogen explosions. However, for equipment and pipelines containing concentrated sulfuric acid that have not been in use for a long time, the concentration of the acid decreases as it absorbs moisture from the air; this diluted sulfuric acid then reacts chemically with carbon steel to produce hydrogen, posing an explosion risk if heating is applied carelessly. Additionally, when diluting 98% sulfuric acid to 93% concentration during winter, improper addition of water can also lead to localized corrosion of equipment and pipelines due to the diluted acid. Therefore, it is important to minimize the duration of shutdowns in sulfuric acid processing facilities. If shutdowns are unavoidable, storage tanks and pipelines used for holding and transporting concentrated acid should be circulated regularly to prevent the acid from being diluted and its passivation layer damaged. It is also necessary to ensure proper sealing of the system to keep it dry. The liquid level in sulfuric acid storage tanks should not be left unchanged; when diluting concentrated acid with water in winter, it is strictly prohibited to add water directly to the tank – instead, a dilution tank should be used to gradually add water in small amounts. Previously, an explosion caused by hydrogen occurred in a sulfuric acid tank that had not been used for a long time at one facility. The reason was that hydrogen was generated as concentrated acid mixed with dilute acid; there was no gas displacement, no hot work analysis was conducted, and training was insufficient (both management personnel and workers believed that sulfuric acid could not burn or explode, so they skipped the necessary pre-operation procedures and checks). The lid of the sulfuric acid tank was blown off, and one person was thrown away by the explosion – it was a very sobering lesson.