Crystallization treatment method for purification filter plates.
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Our factory produces electrolytic zinc from zinc monoxide, and the various parameters of the traditional acid process are satisfactory! But there is one problem that has been plaguing production: the filter plates crystallize very quickly. Experiments were conducted using oxalic acid, sodium hydroxide, hydrofluoric acid, hydrochloric acid, and other substances to remove these crystals, but none of these methods proved effective. The only option left is manual cleaning, which is time-consuming and labor-intensive. I earnestly ask those with experience whether there are any good methods that can help reduce the time and effort required for this task.
First, it is necessary to determine what causes crystallization on the filter press plates. Heating is generally an effective method to address this issue, while acids and bases usually have no effect on crystallization. Try raising the temperature
As mentioned above, it depends on what kind of solution is involved in the crystallization – whether it’s impurities that crystallize or the solution itself. A laboratory analysis should be conducted to determine the cause and apply the appropriate solution. The most common method is to put it in water, pass steam over it, and test it by tapping on it
This situation also occurs during the pressure filtration process for producing polyaluminum chloride; the crystals are aluminum hydroxide, and they are difficult to remove. Method 1: Improve the previous reaction conversion rate to reduce crystallites. 2. Slightly increase the pressure filtration temperature (but consider the temperature tolerance of the filter plates, as excessively high temperatures can cause them to deform). 3. The crystals are cleaned using a high-pressure water gun.
None of the crystals are easy to deal with; I’ve suffered a lot because of them, and now I avoid them. You’d better figure out what crystal it is first
I once soaked it in oxalic acid solution and heated it for a week with no reaction; the crystallines are likely calcium sulfate and sodium sulfate (the zinc oxide powder was treated with an alkali before leaching)
The best approach is to find a way to prevent crystallization on the surface of the filter cloth; merely treating the symptoms rather than addressing the root cause isn’t a solution. Washing and blowing air during the filtration process are steps that cannot be skipped. . .
First, soak the plate in hot water, then clean it with high-pressure water and a wire brush; it’s quite difficult
It’s still necessary to analyze the components further, as well as the reasons for their formation, control issues, raw material problems, and so on. If it’s an insoluble substance, the solubility product rule can be used to facilitate the corresponding precipitation transformation, after which it can be removed by soaking in acids or similar substances
Passing hot, low-concentration crystallized filtrate through should allow the crystals to be washed away