US 12,434,976 B1
Process for treating a sodium carbonate purge
Alain Vandendoren, Wezembeek-Oppem (BE)
Assigned to Solvay SA, Brussels (BE)
Filed by Solvay SA, Brussels (BE)
Filed on Oct. 3, 2022, as Appl. No. 17/937,623.
Application 17/937,623 is a continuation of application No. 16/953,404, filed on Nov. 20, 2020, granted, now 11,465,907.
Application 16/953,404 is a continuation of application No. 15/456,008, filed on Mar. 10, 2017, abandoned.
Application 15/456,008 is a continuation of application No. 14/537,974, filed on Nov. 11, 2014, granted, now 9,593,023.
Claims priority of application No. 13192428 (EP), filed on Nov. 12, 2013.
This patent is subject to a terminal disclaimer.
Int. Cl. C01D 1/42 (2006.01); C01D 1/22 (2006.01); C01D 7/12 (2006.01); C01D 7/14 (2006.01); C01D 7/24 (2006.01); C22B 26/10 (2006.01)
CPC C01D 1/42 (2013.01) [C01D 1/22 (2013.01); C01D 7/126 (2013.01); C01D 7/14 (2013.01); C01D 7/24 (2013.01); C22B 26/10 (2013.01)] 18 Claims
OG exemplary drawing
 
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 from a group of sodium chloride, sodium sulfate and mixtures thereof, the method comprising the following steps:
f) causticizing at least 50 mol. % of the sodium from sodium carbonate and/or sodium bicarbonate into an aqueous sodium hydroxide solution and into a calcium carbonate mud by reaction of the purge stream by adding lime, 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:
a concentrated aqueous sodium hydroxide solution comprising at least 25 wt % NaOH, and
a crystallized solid comprising sodium carbonate and comprising sodium chloride and/or sodium sulfate,
wherein the lime added at step f) and water removed at step h) are controlled so that the weight ratio of sodium carbonate to the sum of the sodium chloride and/or sodium sulfate in crystallized solid is at most 2, recovering the water removed at step h) as condensates from an evaporator, and recycling the condensates to a calcined carbonate or bicarbonate ore leaching or to a carbonate or a bicarbonate ore solution mining;
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; and
j) 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 sodium 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 sodium bicarbonate crystallizer.