Sodium chloride production process
View Patent ↗The present invention pertains to a process for producing sodium chloride comprising the steps of (i) preparing a brine comprising at least 150 g/l of sodium chloride by dissolving a sodium chloride source in water, (ii) subjecting the resulting brine to a eutectic freeze crystallization step by indirect cooling of said brine, resulting in the formation of ice, sodium chloride dihydrate, and a mother liquor, (iii) separating the sodium chloride dihydrate formed in step (ii) from the ice and optionally mother liquor at the eutectic temperature, such that a sodium chloride dihydrate-rich stream is formed, and (iv) feeding said sodium chloride dihydrate-rich stream to a recrystallizer to form sodium chloride and a mother liquor.
1. A process for producing sodium chloride comprising the steps of
(i) preparing a brine comprising at least 150 g/l of sodium chloride by dissolving a sodium chloride source in water,
(ii) subjecting the resulting brine to a eutectic freeze crystallization step by indirect cooling of said brine, resulting in the formation of ice, sodium chloride dihydrate, and a mother liquor,
(iii) separating the sodium chloride dihydrate formed in step (ii) from the ice at the eutectic temperature, such that a sodium chloride dihydrate-rich stream is formed, and
(iv) feeding said sodium chloride dihydrate-rich stream to a recrystallizer to form sodium chloride and a mother liquor.
2. The process according to claim 1 wherein the brine prepared in step (i) has a NaCl concentration of at least 300 g/l.
3. The process according to claim 1 wherein mother liquor obtained in step (ii) and step (iv) is recycled to step (i).
4. The process according to claim 1 wherein step (ii) is carried out in a fluidized bed heat exchanger/crystallizer.
5. The process according to claim 1 wherein step (iii) takes place during the eutectic freeze crystallization step.
6. The process according to claim 1 wherein in step (iii) the ice, sodium dihydrate, and mother liquor are separated so that a dihydrate-rich stream and an ice-rich stream are formed.
7. The process according to claim 6 wherein the ice in the ice-rich stream is separated from the mother liquor, washed, melted, and at least in part used as wash liquid.
8. The process according to claim 6 wherein the ice in the ice-rich stream is not separated from the mother liquor but melted at sub-zero temperatures, and the cold generated is used to cool the brine prepared in step (i) and/or to condensate refrigerants to/at sub-zero temperatures.
9. The process according to claim 1 wherein brine prepared in step (i) is cooled to a temperature of between 0° C. and −15° C. and subsequently subjected to a separation step to remove any crystallized Glauber salt prior to step (ii).
10. The process according to claim 1 wherein the sodium chloride dihydrate formed in step (ii) is separated from the ice and mother liquor.
11. The process according to claim 1 wherein mother liquor obtained in step (ii) is recycled to step (i).
12. The process according to claim 1 wherein mother liquor obtained in step (iv) is recycled to step (i).
13. The process according to claim 1 wherein step (iii) takes place during and after the eutectic freeze crystallization step.
14. The process according to claim 1 wherein step (iii) takes place after the eutectic freeze crystallization step.