Why don't sodium sulfate crystals grow?
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Hello, fellow Haiyou friends. What we do is the extraction of sodium sulfate from wastewater, mainly to consider the impact of sodium sulfate on sewage. Now the operation of the device is quite stable. We are using a spiral propeller centrifuge. During operation, we found that the sodium sulfate crystals no longer grow. And almost every time, after running for half a month, it can no longer run because the crystals do not grow and cannot be separated from the centrifuge. I wonder if you friends can help analyze the reason? It is said that crystals should grow infinitely. I took samples and kept them at constant temperature for 24 hours, but they still did not grow. If it cools, it will become one big piece.
The sodium sulfate crystal mentioned by the poster should be sodium sulfate with 10 crystal waters. After the crystal nucleus is formed, it slowly crystallizes in a supersaturated solution to grow. At this time, external disturbance must be applied to prevent the formation of a large cake. It is recommended that during cooling, the clear liquid should be continuously cooled and circulated, the solid-liquid mixture should be extracted from the bottom of the cone in the settling tank, and a hydrocyclone separator should be set up. The clear liquid should be returned to the settling tank, and the concentrated liquid should be separated in the centrifuge. This problem should be solved. This method is similar to the design of chlor-alkali freezing denitration.
I am talking about anhydrous sodium sulfate. During the evaporation and crystallization process, the sodium sulfate crystals no longer grow and appear suspended in the supersaturated solution, making it impossible to centrifuge. So I would like to ask what the specific reason is. We are using a propeller centrifuge. I wonder if it has something to do with the structure of the centrifuge?
Haven't you ever encountered such a problem?
I heard an expert say today that impurities have a great impact on the crystallization of sodium sulfate. Because our process is to extract sodium sulfate from wastewater, I wonder if the organic impurities in the wastewater will affect the crystallization? Do you have any other opinions?