Safety issues related to the use of negative pressure systems in tank areas to prevent uncontrolled emissions of waste gases
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Acidic substances stored in tanks, such as hydrochloric acid and phosphorous acid, can produce significant gas emissions when exposed to moisture during rainy weather. When negative pressure devices are used to absorb these exhaust gases, a vacuum is created inside the tank, which can cause damage to the tank. What measures can be taken or what devices can be installed to prevent the formation of this vacuum and ensure safe operation?
It is not connected to the vent port and kept at a certain distance. It is best to design the vacuum port in a trumpet shape, with the tank’s vent extending slightly into this trumpet shape. It can absorb mist without creating excessive negative pressure inside the tank.
It’s not that we are very familiar with your actual situation, but we have a storage tank for concentrated sulfuric acid (98%), along with a drainage pipeline that leads to a ditch. There is a drying device installed on this pipeline, filled with a large amount of desiccant; the desiccant is replaced regularly. Additionally, I wonder if it would be possible to install a gas seal device on your tank to maintain a slight positive pressure, so that air can be introduced into it when the pressure drops. (Example: N2 envelope)
A breathing valve can be used. For better performance, a nitrogen seal valve combined with a single exhaust valve can be used.
Regarding the items that come after this air respirator, I consulted the Safety Supervision Bureau and received a reply stating that a refrigerated dryer can be added
On the top of our storage tank, there is only one negative pressure port and one feed port. Yesterday, employees created negative pressure, which resulted in a vacuum inside the tank and damaged the tank’s roof. Fortunately, the tank was empty, so the tank body was not damaged
Is it possible to install a pressure detection device that automatically stops the vacuuming equipment when the pressure reaches a certain level?
1. A liquid seal is used, with an alkaline substance as the liquid in this seal to absorb acid mist. A vent valve is installed on the liquid seal tube; it should be closed when feeding material into the tank, and opened when discharging material, in order to prevent a vacuum from forming inside the tank. 2. If the diameter of the negative pressure port mentioned by the poster is large, two pipes can be welded to the flange of that port: one connected to the fan and the other used for evacuation.