How to replace the sulfate lost during the zinc smelting process in the later stage?
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Generally speaking, when using roasted ore to wet zinc, the temperature of the roasting process must be strictly controlled during the roasting process so that the roasted ore itself contains sulfate radicals, which is commonly known as sulfation roasting! But if we increase the roasting temperature due to changes in the process, the part of the sulfate radicals that can be supplemented by the subsequent leaching process will no longer exist, or will be reduced! In the process of hydrosmelting, how should we replenish the sulfate radicals that are constantly lost during the smelting process? And while replenishing this part of sulfate radicals, it will not cause the volume expansion of the solution during the leaching process! Please discuss it with the brothers and sisters who are engaged in work and research in this area, thank you!
Acid balance, leaching with sulfuric acid.
2# che123 Adding sulfuric acid is straightforward and simple. The key is that after adding sulfuric acid, the volume of the leachate expands greatly. How to solve this problem?
Is your process conventional wet method or jarosite method?
4# che123 My process is a conventional wet process, so it is a bit troublesome.
First, control the electrolytic acid-zinc ratio. After the acid is reduced, add concentrated sulfuric acid during leaching, so that the leaching volume will not be large. Are you saying that the zinc content in the supernatant is too low, making it difficult to supplement acid? Pay attention to the water points for leaching to prevent water from entering the system. Open more cooling towers for electrolysis to reduce the system volume.
This post was last edited by atkqn0030 on 2009-7-8 11:31 1. The idea of adding acid radicals by roasting has been cited repeatedly in many books, but this view is wrong. It is completely possible to add acid radicals during leaching, but the acid consumption increases in the wet method, and the leaching intensity increases. It is still beneficial from the perspective of leaching rate, but impurity leaching increases the amount of zinc powder and the difficulty of controlling solution electrolysis. If you use a leaching residue volatilization kiln for treatment, you do not need to consider the zinc leaching rate. The main considerations are production cost and solution quality. 2. If zinc sulfate is not generated during the roasting process, zinc ferrite and zinc oxide will be generated. About 70% of zinc ferrite is leached during high-temperature and high-acid leaching. Zinc oxide leaching can also bring in acid ions. Anyway, no matter what kind of zinc, one zinc needs an acid ion to enter the solution, which is the same as bringing in zinc sulfate during roasting. For example, the zinc roasting sand produced by Longcheng Chemical Plant and other plants using oxidation roasting is also directly used for wet zinc smelting. The acid balance problem does not exist. 3. As for the problem of solution volume balance, it is even more nonsense. Nowadays, electrolytic zinc uses the conversion method (Otokumbu method) to produce about 80Kg of sulfuric acid per ton of zinc. The roasted sand of acidification roasting contains about 5% sulfur (calculated as all entering the solution) and 55% zinc. The dosage of gold per ton of electrolytic zinc roasting is 1.0638, which is 296Kg when converted into sulfuric acid. How much volume is this? 4. Furthermore, if the production of electrolytic zinc requires about 3.8-5T/T of steam per ton of zinc (depending on the leaching method), indirect heat exchange can save the volume of 3.8-5 cubic meters/ton of zinc, so this volume is not a problem. I would like to correct the original wrong statement (we are in Zhongnan, and the above data is calculated based on our company's experience). The conditions for the existence of the original statement: (1) Differences in climate across regions ； (2) New technology - indirect heat exchange had not yet appeared, so it is a mistake now.
7# atkqn0030 Brother, I am studying chemical engineering, and my job is roasting. I read the book on zinc metallurgy every day. You have taught me a lot today. You directly said that the book I read was wrong. However, I still want to believe that you are right. It is impossible to rely solely on books for process operation. I believe in practice. Thank you for your valuable opinions. I hope you can give me more advice in the future!
7# atkqn0030 However, in our factory, after leaching and adding acid, the volume is really scary, so I came to ask for advice! Is there something wrong in some link that causes the volume to expand?
7# atkqn0030 I strongly support the original poster’s point of view. I have been engaged in electrolytic zinc for many years. We now generally use low-temperature roasting in boiling furnaces. The acid is added during the leaching process. There is no need to add acid during the leaching process. The acid in the electrolytic waste liquid is enough. Our data has been stable at 220-250 kg acid/ton of zinc. So I firmly support the original poster’s point of view
The key depends on what kind of process you use. I am doing leaching. Basically, there is no need to consider this issue with the vitriol method. However, you don’t seem to be very knowledgeable about the question you asked. If you need to supplement acid, why will the volume increase? If you want to increase the leaching of initial acid, it is reasonable to add too much acid to cause acid swelling.