How can the mother liquor after MVR treatment be better reintroduced into the evaporation system?
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After MVR concentration and crystallization, the mixture is separated using a centrifuge. The liquid resulting from centrifugation is a saturated salt solution; it is usually allowed to flow back into the initial feed tank, thereby returning to the system. However, this liquid is at high temperature and has a high solubility, so when it comes into contact with the feed wastewater at normal temperature in the feed tank, a large amount of salt crystals are formed there. Later, a heating strip was added to the raw material tank to maintain the temperature; as a result, less salt was produced. However, even with the condensate water generated by the MVR being used to feed the heating strips, the heat generated was not sufficient to keep the temperature in the raw material tank high enough, and salt continued to form inside the tank, leading to blockages in the pipelines. How can this problem be solved? I seek advice from experts.
Is it possible to add another storage tank and a transfer pump to send the material directly back to the \"crystallizer\"?”
I’ve thought about it too; it’s necessary to insulate this storage tank, and the residence time cannot be too long, as otherwise the temperature will drop and crystallization will occur. The main concern is whether the pipeline through which the material is pumped back to the tank will frequently experience blockages due to the material itself. It’s very troublesome to clog it once – there’s water and steam being blown at it. I haven’t tried it, so I don’t know how effective it is.
What is the ratio of this mother liquor volume to the raw material liquid volume? Will it crystallize inside the raw water tank? There can’t be that much mother liquor, right?
Not all of it will crystallize; only part of it will. The liquid in your feed tank is at room temperature, and once the mother liquor comes out of it, its temperature drops, resulting in a decrease in solubility. This causes salts to precipitate, which in turn blocks the bottom of the tank as well as the level gauge. I have worked on several projects; taking sodium sulfate with a production rate of 3 tons per hour as an example, the raw material is stored in a tank for 2 hours – the tank has a capacity of 6 cubic meters. The mother liquor that comes out is concentrated by half, meaning that approximately 1 ton of mother liquor per hour needs to be fed back into the system.
Sodium sulfate is thermocrystalline. . . . . It is discharged after being concentrated to a multiple
Depending on the situation, high temperatures are sent directly back into the vaporization process, while low temperatures are returned to the system
Then why is it said that \"raw material wastewater at room temperature will result in a large amount of salt crystals forming in the raw material tank\"? Isn’t that contradictory?
Add a heat exchanger to exchange heat between the incoming and outgoing materials, or use steam through the heat exchanger to raise the temperature of the material in the feed tank