Selection of materials
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There is a heat exchanger with an operating pressure of 1.6 MPa and an operating temperature of 80 degrees. The solution contains 14.4% sulfuric acid, 0.04% chloride ions, and 0.0072% fluoride ions. What material would be suitable for use in this application?
A shell-and-tube heat exchanger with a carbon steel outer tube and N inner tetrafluoroethylene thin tubes. It has good anti-corrosion and heat exchange performance, which is worth considering.
Thank you for your reply. What I mean is, what metal material would be more suitable for such operating conditions?
20# steel, used for heat exchangers in the aluminum immersion process.
Thank you for your reply. Then how should the tube sheets and tube banks be handled?
Is it feasible to use super duplex steel S25073 (ASTM A240 S32750) for such operating conditions?
You can check on this material with the code 1.4529.
Thank you for your reply. 1.4529 is a super stainless steel material, equivalent to N08926 in the United States. Main components: 20Cr-25Ni-6Mo-1Cu-0.2N. Mechanical properties: Tensile strength: σb » 650 Mpa; Elongation: δ » 35%. The equivalent German designation is X1NiCrMoCuN25-20-7, with the digital grade being 1.4529 and UNS N08926. It exhibits very high resistance to pitting and crevice corrosion in halide-containing media as well as in acidic environments containing hydrogen sulfides; it can effectively resist chloride-induced stress corrosion. It also shows good corrosion resistance in both oxidizing and reducing media, possesses good stability, and its mechanical properties are slightly superior to those of 904L. It can be used in the manufacture of pressure vessels operating at temperatures ranging from -196 to 400°C.
If existing heat exchange equipment requires anti-corrosion protection, then there is no issue regarding the type of steel to be used; what remains is the choice of anti-corrosion coating. This is a typical high-temperature acid corrosion environment, and what’s most problematic is the presence of F ions as well. The top priority is to address the F-ion corrosion issue. There are hydrofluoric acid-resistant coatings available on the market, and some manufacturers produce coatings that are also resistant to high temperatures of up to 150°C.
This post was last edited by Wang Genrong on 2016-12-13 at 16:12. Silicon carbide shell-and-tube heat exchangers manufactured using pressureless sintering can meet your requirements. Or a tetrafluoro tube (or coil) heat exchanger is also possible. What is your heat exchange type, gas-liquid, or?
We heat the waste electrolyte with steam; the electrolyte contains the components mentioned above