Issues related to sulfuric acid materials at moderate temperatures for medium-grade sulfuric acid
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It is a constant-pressure reactor with stirring, equipped with a jacket; the maximum temperature during reaction is 110 degrees, while the solubility is around 70-80. The material currently used is enamel, and after the reaction, cooling is achieved using saline at -10 degrees. At present, perforations in this kettle occur quite frequently. I would like to ask everyone: is there any material suitable for these conditions, or are there any new manufacturing processes that can solve this problem?
The last edit to this post was made by Litaotao1314 on 2011-12-20 at 17:38. Reply to 1# lizhicn2002: Based on what you’ve described, applying PTFE coating should be able to solve your problem
This post was last edited by realben on 2011-12-20 at 16:04. There are many reasons for the damage to enamel coatings; generally, they include the following: (1) Mechanical damage – Enamel coatings have very poor impact resistance, and any impact from metal or hard objects can cause damage to them. Therefore, during the use of enamel reactors, it is essential to prevent any metals or hard objects from falling into the reactor. In case of blockages, a plastic rod must be used to clear them. When performing maintenance, the lid must be properly closed to avoid weld slag melting the enamel surface and causing small pits or cracks in it. (II) Thermal stress damage: After being baked at a high temperature of 900°C, the enamel-lined tank cools down, causing the enamel to bond to the steel plate. Since the linear expansion coefficient and elongation of enamel are lower than those of steel plates, the deformation of the enamel after cooling is less than that of the steel plate; as a result, the enamel is subjected to compressive stress due to the restraint exerted by the steel plate. After the enamel kettle is manufactured, its enamel has pre-compression stress, while the steel plate has pre-tension stress. Since prestress is related to the linear expansion coefficient and elongation, and the linear expansion coefficient and elongation are closely tied to temperature, the operating temperature of the enamel kettle has a significant impact on its use. If the stress generated in the enamel due to large temperature changes exceeds its allowable stress, the enamel will be damaged. Therefore, the enamel layer of an enamel-lined reactor is extremely prone to cracking when exposed to sudden changes in temperature. Therefore, enamel reactors have temperature limits: 200°C, and they cannot withstand sudden temperature changes: cold shock
Reply 3# realben: The 20# alloy can indeed be suitable for this environment, but it’s really expensive and difficult to use. Thank you!
Reply to 2# zhouxuelei: Is the cost of spraying high? The key is whether it can be used in situations with such thermal shock
This post was last edited by yuchenchf on 2011-12-22 08:02. Reply to 5# lizhicn2002: The cost per square meter for the spraying services provided by our company is around 3000, excluding taxes. These services can be used in areas with alternating hot and cold conditions; if you’re interested, we can discuss the details further
The poster is asking whether the perforation occurred inside the reaction vessel or in the jacket. If it’s a perforation in the enamel lining of the reaction vessel, then according to the poster’s description, there’s an issue with the way you operated it. The reaction takes place at 110 degrees Celsius; if you introduce saltwater at -10 degrees Celsius into the jacket after heating, the enamel lining is very likely to crack. It is recommended that you not rush to use saltwater right after using steam – instead, use cooling water first, and wait until the temperature drops to around 30 degrees before introducing saltwater. This way, the problem mentioned by the poster should basically not occur. The third floor explained it in great detail
Enameled reaction vessels are used at 110 degrees in a sulfuric acid environment, and given the occurrence of sudden temperature changes, it is not surprising that enamel cracking often occurs; using a vessel with a graphite lining can solve this problem of enamel cracking.
Reply to 6# zhouxuelei: What I want to say is that there’s no need to use enamel as the coating directly
The adhesive used for lining your graphite block is likely to corrode first
Have you seen phenolic graphite mortar? Let’s take a look at others’ insightful opinions together! ! Phenolic graphite mortar is used for bonding structural components of chemical equipment made of graphite; it can be used at the boiling point of 75% sulfuric acid without any corrosion occurring.