I had a question about the large scale brine to salt manufacturing process. (It’s for a piece I’m writing.)
Does this process generate a lot of waste water?
I don’t mean the water that’s evaporated off to make the salt. The descriptions I’ve read of this process speak of washing the salt repeatedly. This is the water I’m referring to. Does anyone know if this water reused or does it go down the sewer?
Habeed
July 14, 2015, 6:18pm
2
What would you do with the water instead? The water has contaminates in it. You either (a) wash it down the drain or (b) boil off the water, leaving the contaminates as salt, and then throw away the contaminants.
Which is the most widely used method in the salt industry?
Looks like the water is reused, to an extent.
Processing brine
4 The simplest method of evaporating brine is solar evaporation, but it can only
5 The salt is scooped up by machines running on temporary railroad tracks laid on top of the layer of salt. It is then washed with highly concentrated salt water. This water contains so much salt that it cannot hold any more, so the salt is washed free of any trace impurities without dissolving. The washed salt is removed from the salt water, rinsed with a small amount of fresh water, and piled into huge stacks to drain for two or three months. At this point the salt is about 99.4% pure and can be used for many industrial purposes. If purer salt is needed, it is rewashed in salt water and fresh water, allowed to drain for one or two days, then dried in a hot air oven at about 365°F (185°C). This salt is about 99.8% pure and can be used for food processing.
6 Most brine is processed by a multiple-effect vacuum evaporator. This device consists of three or more closed metal cylinders with conical bottoms. Brine is first treated chemically to remove calcium and magnesium compounds. It then fills the bottom of the cylinders. The brine in the first cylinder passes through tubes heated by steam. The brine boils and its steam enters the next cylinder, where it heats the brine there. The steam from this brine heats the brine in the next cylinder, and so on. In each cylinder the condensation of steam causes the pressure inside to drop, allowing the brine to boil at a lower temperature. Salt is removed from the bottom of the cylinders as a thick slurry. It is filtered to remove excess brine, dried, and passed through screens to sort the particles by size. Salt made this way is known as vacuum pan salt and consists of small cubic crystals.
7 Brine may also be processed in a grainer. The brine is chemically purified and pumped into a long open pan heated by steam running through pipes immersed in the brine. The brine is heated to a temperature slightly below the boiling point and flakes of salt form on its surface as it evaporates. Usually a temperature of about 194°F (90°C) is used. Lower temperatures produce larger flakes and higher temperatures produce smaller flakes. The flakes grow until they sink to the bottom of the pan, where they are collected and dried. Grainer salt consists of small flakes rather than cubes and is preferred for certain uses in food processing. Sometimes the Alberger process is used, in which the brine is first partially evaporated in a vacuum evaporator then moved to a grainer. This process produces a mixture of flakes and cubes.
8 At this point salt used for most purposes is ready to be packaged in bags or boxes and shipped to consumers. To make iodized table salt, however, potassium iodide is added, then magnesium carbonate, calcium silicate, calcium phosphate, magnesium silicate, or calcium carbonate is added to make it free-flowing. The salt is then packaged and shipped to restaurants and grocery stores.How salt is made - material, used, processing, procedure, industry, machine, Raw Materials
More information at the link, including mining salt domes.
jimbuff314:
Looks like the water is reused, to an extent.
More information at the link, including mining salt domes.
Thanks. But I had found that site. It really doesn’t make clear what happens with the wash water.
I ended up emailing a salt manufacturer. Hopefully, they’ll answer.
Habeed:
What would you do with the water instead? The water has contaminates in it. You either (a) wash it down the drain or (b) boil off the water, leaving the contaminates as salt, and then throw away the contaminants.
Instead of reusing it or putting it down the sewer?? As far as I know those are the only two options for wash water.
With many plants trying for a reduce waste (zero emissions is the term, but no one really gets it to zero), it’s possibly they’re reusing it.
But as no one here knows , I’ve emailed a salt manufacturer.