Design of nitrogen and water seals for large acid water tanks in refineries

Washed, desulfurized, and sent to the flare line

The core of this issue is actually finding a balance between safety and environmental protection. The washing, desulfurization, and flare utilization methods mentioned in the comments are all common approaches. I would like to add some practical experience from field applications: For the flare system, if there is an existing low-pressure flare network on site, connecting to it is the most reliable option – it’s simple to operate and ensures thorough treatment. However, it’s important to be aware of the impact of pressure fluctuations in large tanks on the backpressure of the flare system, as well as the corrosion issue caused by sulfur-containing gases on the flare pipelines (heating or upgrading the material is necessary in such cases). Alkali/amine desulfurization: Suitable for intermittent low-flow emissions. A small alkaline scrubber can be installed to absorb hydrogen sulfide using circulating alkaline solution; the resulting waste liquid is then sent to a wastewater treatment plant or desulfurization facility for processing. The capital investment for such equipment is low, but alkali needs to be added regularly and waste must be disposed of periodically. Desulfurization after water washing (quenching): If the exhaust volume resulting from the breakdown of the water seal is not high, water is first used for spraying to cool down and partially dissolve hydrogen sulfide, after which it is sent to a small desulfurization tank (such as an iron oxide dry desulfurization system). This approach is suitable for storage areas with limited space; however, the desulfurizing agent needs to be replaced regularly, and solid waste is generated as a result. As a further reminder: acidic gases contain hydrogen sulfide, so leak monitoring and the designation of explosion-proof areas must also be taken into account. The specific measures to be adopted should be determined based on the actual conditions of your facility (such as the flow rate of waste gas, the concentration of hydrogen sulfide, and whether there is any excess), as well as local environmental emission standards. It is recommended to conduct a pilot test first or have a design institute do the calculations; don’t apply the methods directly