How to clean a concentrated sulfuric acid tank?
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Our facility has a 2.5-cubic-meter carbon steel tank (horizontal type) used for storing 98% concentrated sulfuric acid. A hole has been found at the bottom of the tank, and repairs are planned. I would like to ask the experts: 1. Can the tank be repaired by welding? 2. How to clean and replace the residual concentrated sulfuric acid in the tank? Can it be directly diluted with water and then discharged, or can a weak base be added for neutralization? 3. Can repair welding be carried out directly without cleaning?
1. First, the wall thickness should be measured; if it is within the allowable range, patch welding can be carried out. 2. It should first be neutralized with a weak base, followed by rinsing and displacement with water. 3. Direct patch welding is not allowed.
1. Repair can be carried out by patch welding when the wall thickness is not severely corroded. 2. The residual concentrated sulfuric acid in the tank cannot be diluted with water and then discharged directly; lime can be added to neutralize it. 3. Weld repairs should be carried out after cleaning. 4. Air must be continuously replaced before and during welding; leaks can be sealed by using a thick-walled steel pipe whose diameter is twice that of the leaking area, with the pipe ends welded shut, and corner welds applied at the joint points. This is a method commonly used in sulfuric acid plants. Last edited by rgsmdqy on 2007-8-22 06:59.]
No cleaning is required; welding can be carried out directly in an outdoor area with good ventilation (of course, the welding surface needs to be prepared first). There is usually acid accumulation inside the sulfuric acid flue gas pipelines, and the situation is similar to that in horizontal acid tanks. No sulfuric acid plant cleans these pipelines when dealing with flue gas, as doing so would increase downtime! 98% concentrated sulfuric acid has oxidizing properties and does not produce hydrogen; however, if it is used for cleaning, diluting the concentrated sulfuric acid to make it weak sulfuric acid can easily result in the production of hydrogen! Welding without cleaning requires certain skills; if not done properly, cracks can easily form in the weld. This post was last edited by in the blink of an eye on 2007-8-23 09:52]
When our company carried out repair welding on the concentrated sulfuric acid tanks, it didn’t clean them either, but ventilation was provided. If welding is performed directly at the crack, the entire weld will break, similar to undercutting. So later on, we added a steel plate.
Although 98% concentrated sulfuric acid has oxidizing properties, it can also produce hydrogen gas. Our company’s 5,000 m3 large tank experienced a hydrogen explosion during operation; the lid was torn open by a gap of over 10 meters, and the tank’s shell was deformed... yet the liquid level was still at 64%. This post was last edited by zxg.wylton on 2007-11-13 09:06.]
It is best not to let water enter the tank, as this accelerates corrosion of the tank walls and shortens its service life. Ventilation must not stop at any point. {:2_36:}
1. Cleaning will accelerate corrosion; lime can be added. Pay attention to ventilation during welding... otherwise, hydrogen poses a risk of explosion... 2. Generally, if the storage tank is not under pressure, it is possible to consider performing weld repairs. You can think of it as reinforcement for openings. However, the thickness of the welded patch plate should be equal to the thickness of the bottom plate as designed, and the diameter should be twice that of the opening. Pay attention when selecting welding electrodes····