What material should be used for the evaporation and concentration of dilute alkalis containing chloride ions?
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A 7% dilute alkali solution containing about 0.5% chloride ions needs to be evaporated and concentrated to a 15–20% alkali solution; this is achieved by using negative pressure to heat and evaporate the water vapor, with a heating temperature of around 80 degrees. What material should be used for the heating section?
For reference: at 100°C, with 6000 ppm of chloride ions and a pH of 9, 2205 is required at the very least
Can I provide you with a polyaniline hanging slice?
This post was last edited by Wang Wei2 on 2021-1-30 at 11:49. When choosing metal materials, it is necessary to consider not only the chloride issue associated with stainless steel but also the alkali embrittlement problem in the weld seams. For such problems, corrosion prevention using paint coatings can be considered.
Enameled 2205 titanium; our company uses 2205 for handling sodium chloride, 2205 for pipes and valves, and titanium for the main equipment
Polymer ceramic coatings can be chosen.
Double-phase stainless steel 2205 should work; the chloride content is fine and there’s no issue with titanium
The estimate for enamel is uncertain; if it’s for pipes, at least double-phase steel should be used. If high purity isn’t a requirement, then carbon steel can be used directly. For the equipment, it is still recommended to use at least titanium.
2205 has failed; it may be resistant to chlorine corrosion, but not to high-temperature alkalis； Later, trying to use tetrafluoroethylene failed as well; it peeled off under high-temperature alkaline conditions and could not adhere properly to the stainless steel surface.