How to choose the evaporator material with fluorochlorine?
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The current project produces nickel sulfate, involving the evaporation and concentration of nickel sulfate solutions with a concentration of 100–120 g/L, followed by crystallization. The solution is based on a sulfuric acid system; before evaporation, its pH is between 3 and 4, with F contents of 30–50 ppm and Cl contents of 40–50 ppm. Four-effect evaporation is used, with the temperature of the solution during evaporation ranging from 70 to 90 degrees Celsius. After evaporation and concentration, the F and Cl concentrations increase to 150–200 ppm, at which point the solution temperature is 90 degrees Celsius. Under such conditions, TA2 was initially considered as a suitable material, but it has poor corrosion resistance, and there have been cases of corrosion and perforation after two years of use. Are there any other suitable materials recommended?
There must be something wrong with your approach. Firstly, using TA2 material for chloride ions is definitely no problem. However, due to the presence of fluoride ions, TA2 material cannot be used, so this approach you mentioned certainly cannot take advantage of both options at the same time. Since the concentration of chloride ions on your side is not high, I recommend choosing materials from the duplex steel series. I am also only considering this from a theoretical perspective; for more specific information, one can consult the relevant heat exchanger manufacturers or industry experts.
It is recommended to use a graphite concentration device.
This post was last edited by Wang Genrong on 2019-11-12 at 14:48. A concentration device made of graphite can be used.
Graphite or silicon carbide: graphite is cheaper than silicon carbide, but it’s larger in size and more prone to damage; silicon carbide, on the other hand, is too expensive. Choose graphite – it’s cheaper! We also have metal products with coatings; we can send you some samples for you to try and see if they work.
Impervious graphite; phenolic impregnation is generally sufficient for this material. Its heat transfer performance is similar to that of carbon steel, and it is better than stainless steel