The sulfuric acid circulation tank designed by Nanhua has a leak – everyone, please analyze the reasons. Those who come up with the correct analysis, or those who contribute to it, will be rewarded
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The sulfuric acid circulation tank designed by Nanhua has a leak – let’s analyze the reasons. Many years ago I encountered a strange situation: in a 20,000-ton sulfuric acid production plant, the sulfuric acid circulation tank for the absorption tower was located on the first floor, inside a rectangular building; there were two circulation pumps installed there. The circulation tank was 5 meters wide, 8 meters long, and 3 meters high. The interior was constructed using traditional methods: a steel shell lined with granite, sealed together with acid-resistant cement and water glass. Half a year later, it was discovered that the bottom of the steel shell had corroded through; therefore, the structure had to be rebuilt. Yet several months later, leaks still occurred. The anti-corrosion techniques used were all correct, leaving all the engineering technicians at a loss: L :L. Please analyze the real reason. :lol Last edited by rgsmdqy on 2008-3-24 18:01 ]
Occupied first: lol It’s probably a material issue – the materials used do not meet the required standards. It might also be that a little water got in, or the purity of the sulfuric acid is not sufficient! Sulfuric acid generally requires an acid-resistant lining; as far as I remember, granite has not been used for this purpose, but acid-resistant mesh fabric has been employed as a lining. This post was last edited by Xinchan on 2008-3-24 17:02.]
All the materials are fine; just keep going with it. Using cloth won’t work :lol The last edit to this post was made by rgsmdqy on 2008-3-24 at 17:06.]
There are probably four reasons: First, there is an issue with the materials – it’s not clear whether the cement or water glass has been tested (it seems to be the main problem based on your description). Second, there could be problems with the construction process; if you’re sure there are no issues, then this can be ignored. Cracks are likely to form inside, which leads to corrosion. Fourth, there’s the issue of thermal expansion and contraction – if the material is placed outdoors without any protective measures, cracks are likely to form inside, resulting in corrosion. This post was last edited by rgsmdqy on 2008-3-24 at 17:18
There is a leak in the sulfuric acid circulation tank, and it’s difficult to make a judgment based solely on what the poster has described. In my opinion, the issue should be analyzed from the following aspects: 1. Design aspect: Whether the materials chosen for the design meet the required standards. The strength and stiffness of the steel casing also need to be taken into consideration. 2. Construction aspect: Whether the construction quality meets the requirements. 3. Operation aspect: Whether there are any conditions during equipment operation (such as large temperature differences between the media, or frequent switching between empty and full tanks) that could cause cracks at the joints where the acid-resistant cement meets water glass.
The steel shell is lined with granite, and the joints between the lining and the steel shell are sealed using acid-resistant cement and water glass; as a result, the bonding between them is not good. Once filled with sulfuric acid, the lining tends to be damaged first and corrode (in my opinion)
1. The problems with granite: in the chemical and light industry, granite is used to manufacture various corrosion-resistant pipes, tanks, and containers； It is indeed appropriate to use it in the field of environmental protection for equipment used in the treatment of waste gases and liquids. However, the physicochemical properties of granite vary depending on its type, and even ores of the same type from different deposits can differ as well. The chemical composition of granite has an impact on its utilization; in particular, when it is used for acid- or alkali-resistant applications, attention must be paid to the differences in chemical properties resulting from its lithological characteristics. As an acid-resistant lining, if granite with a high content of alkaline feldspar is used, it is very likely to be corroded. . . 2. Another possibility is: what is the concentration of sulfuric acid? Perhaps the level of acidic gases indoors is too high, and corrosion occurs as a result of factors coming from both the outside and inside
It is recommended to start the inspection and analysis from the following aspects: 1. Examine the granite lining; it is best to take samples from cross-sections for testing in order to determine the degree of acid erosion. It is advisable to take samples from multiple locations, paying special attention to the joints between layers of the lining as well as areas where there are sudden changes in shape, and compare these with control samples. 2. Also check the granite lining for any cracks or similar issues. Could it be that issues such as expansion or vibration are causing the lining to delaminate or crack? 3. Remove the steel casing and inspect the back side of the lining at the area where the casing has been corroded to identify signs of corrosion; based on these signs, determine the source of leakage in the lining. 4. Check whether there is a difference in expansion rate between acid-resistant cement and granite. 5. Check the bottom support of the circulation tank, assess the stress conditions on it, and determine whether there are excessive periodic bending moments; such moments can cause cracking or delamination of the lining layer. Suggestions: 1. Improve the lining construction process: Consider whether expansion joints have been taken into account during lining installation, what the properties of the materials used to fill these joints are, and whether they can compensate for the expansion and contraction resulting from thermal changes. I’m not familiar with the construction methods used for this type of lining in your factory. If possible, it would be better to minimize the size of each individual lining piece and offset the seams between the upper and lower layers. 2. According to the lining construction specifications, it is not allowed to add an anti-corrosion layer inside the steel shell; if this is permitted, an acid-resistant anti-corrosion layer could be considered for use inside the steel shell.
Maybe use lead lining or PTFE lining; I think there’s an issue with the lining installation process
Continuing the analysis: lol Since the materials and manufacturing process are fine, we can consider some aspects related to construction, but they’re not crucial. Since several instances of corrosion occurred at the bottom, an analysis can be conducted based on the characteristics of the bottom of the circulation tank. The circulation tank is located indoors; a circulation pump is installed on the acid tank, and there must be an opening through which acidic gases can evaporate, resulting in sulfuric acid vapor in the air. The bottom of the acid tank should be the point with the lowest temperature (it is made of steel); steam condenses at the bottom of the tank, causing corrosion there. This corrosion then spreads rapidly. Due to the pressure exerted on the bottom, corrosion can lead to leaks quite quickly. When a leak occurs, it is possible to verify the shape of the leak site, which is smaller at the top and larger at the bottom; the reason for this is as mentioned above. If the lower part is small and the upper part is large, it is a problem with the materials used for corrosion prevention. Consider applying anti-corrosion treatment to the outside of the tank, such as spraying polytetrafluoroethylene coating (which can be applied both on the inside and outside).