Patent ID: 9593023
Date: 2017-03-14
CPC Classifications: C01D,C22B

Claim:
1. A method for treating a purge stream derived from an anhydrous sodium carbonate crystallizer, or a sodium carbonate monohydrate crystallizer, or a sodium carbonate decahydrate crystallizer, or a sodium sesquicarbonate crystallizer, or a wegsheiderite crystallizer, or a sodium bicarbonate crystallizer, said purge stream comprising sodium carbonate and/or sodium bicarbonate and at least 1% by weight of a sodium salt selected among sodium chloride, sodium sulfate and mixtures thereof, the method comprising the following steps: f) adding lime to the purge stream, in presence of water, g) separating the calcium carbonate mud from the aqueous sodium hydroxide solution; h) concentrating the aqueous sodium hydroxide solution by removing part of the water to obtain: i) separating the crystallized solid comprising sodium carbonate and sodium chloride and/or sodium sulfate from the concentrated aqueous sodium hydroxide solution, said crystallized solid to be disposed of or to be further valorized, j) valorizing the concentrated aqueous sodium hydroxide solution as a salable sodium hydroxide solution or recycling at least one part of the concentrated aqueous sodium hydroxide solution to the anhydrous sodium carbonate crystallizer, or to the sodium carbonate monohydrate crystallizer, or to the sodium carbonate decahydrate crystallizer, or to the sodium sesquicarbonate crystallizer, or to the bicarbonate crystallizer, or to processes upstream of the anhydrous sodium carbonate crystallizer, or of the sodium carbonate monohydrate crystallizer, or of the sodium carbonate decahydrate crystallizer, or of the sodium sesquicarbonate crystallizer, or of the bicarbonate crystallizer.