IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0992533
(2005-12-09)
|
등록번호 |
US-8282690
(2012-10-09)
|
우선권정보 |
IN-2630/DEL/2005 (2005-09-30) |
국제출원번호 |
PCT/IN2005/000404
(2005-12-09)
|
§371/§102 date |
20090720
(20090720)
|
국제공개번호 |
WO2007/036949
(2007-04-05)
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발명자
/ 주소 |
- Mukhopadhyay, Indrajit
- Ghosh, Pushpito Kumar
- Vadakke, Puthoor Mohandas
- Hamidani, Abdulhamid Usmanbhai
- Susarla, Venkata Rama Krishna Sarma
- Sanghavi, Rahul Jasvantrai
|
출원인 / 주소 |
- Council of Scientific and Industrial Research
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
0 인용 특허 :
4 |
초록
▼
The process of the invention deals with significant improvements in salt purity and whiteness brought about through treatment of brine with alum prior to charging into crystallizers for solar salt production. The improvements realized are partly on account of elimination of suspended impurities like
The process of the invention deals with significant improvements in salt purity and whiteness brought about through treatment of brine with alum prior to charging into crystallizers for solar salt production. The improvements realized are partly on account of elimination of suspended impurities like gypsum and clayey matter in the brine, which may otherwise be carried along with the brine in the crystallizer and finally end up in the salt, and partly due to the improved crystal size and morphology that minimizes embedded impurities in the salt. Rain washing of the heaped salt has resulted in a salt with greatly reduced calcium and sulphate impurity levels hitherto not achieved in solar salt production. Alum treatment by the process of the invention requires no additional time or infrastructure and the cost of the treatment works out to 3 U.S. cents per ton of salt. The process can be implemented in any solar salt works.
대표청구항
▼
1. A process for obtaining salt from brine, the said process comprising the steps of: (i) subjecting brine to solar evaporation to crystallize out carbonate salts and gypsum to obtain concentrated brine,(ii) mixing an alum solution with the above said concentrated brine,(iii) settling of suspended p
1. A process for obtaining salt from brine, the said process comprising the steps of: (i) subjecting brine to solar evaporation to crystallize out carbonate salts and gypsum to obtain concentrated brine,(ii) mixing an alum solution with the above said concentrated brine,(iii) settling of suspended particles under gravity and subsequent clarification of brine in a pre-crystallizer,(iv) feeding the above said clarified brine into a crystallizer and while inhibiting flocs from entering into the crystallizer by maintaining adequate dead volume in the pre-crystallizer and also minimizing re-contamination of the clarified brine with clay/soil, and continuing solar evaporation to crystallize out salt,(v) repeating the steps of (ii) to (iv) to build up a salt layer in the crystallizer,(vi) draining out bittern from the crystallizer followed by charging fresh brine into the crystallizer,(vii) harvesting and washing of salt to obtain salt. 2. A process as claimed in claim 1, wherein the purity of salt obtained is ≧99.5% (on dry basis). 3. A process as claimed in claim 1, wherein the salt obtained has specifications as Ca≦0.03%, Mg≦0.06% and SO4≦0.15% and a composition of Ca≦0.005%, Mg≦0.03% and SO4≦0.10% after further natural rain washing. 4. A process as claimed in claim 1, wherein the Al content of salt obtained is ≦0.3 ppm after the conventional purification process. 5. A process as claimed in claim 1, wherein the whiteness of the solar salt obtained is in the range of 82-88 with respect to MgO taken as the primary reference with the whiteness index of 99. 6. A process as claimed in claim 1, wherein optical microscopic evidence shows measurable changes in the morphology of salt crystals, obtained, with lower degree of agglomeration wherein impurities can reside at the interface and larger crystal size as compared to the morphology of salt crystals obtained from concentrated brine without any alum solution treatment. 7. A process as claimed in claim 1, wherein the brine used in step (i) of claim 1, is natural brine. 8. A process as claimed in claim 1, wherein the concentrated brine used in step (i) of claim 1, is obtained in solar salt works by the conventional method of solar evaporation in shallow pans. 9. A process as claimed in claim 1, wherein the concentrated brine used in step (ii) of claim 1 has a density in the range of 20-24° Be′. 10. A process as claimed in claim 1, wherein the concentrated brine is treated, in step (ii) of claim 1, with an alum solution having alum selected from the group consisting of hydrated aluminum sulphate, ferric alum, non-ferric alum, potash alum and poly aluminum chloride and mixtures of two or more thereof. 11. A process as claimed in claim 1, wherein the dosage of alum solution given to concentrated brine, in step (ii) of claim 1, is in the concentration range of 10-75 ppm. 12. A process as claimed in claim 1, wherein the alum is mixed with the brine, in step (ii), in the pre-crystallizer as alum solution. 13. A process as claimed in claim 1, wherein the alum solution dosage in step (ii) of claim 1, is given to the concentrated brine under ambient conditions. 14. A process as claimed in claim 1, wherein the suspended particles settle along with the floc under gravity in step (iii) of claim 1 within the normal residence time of the concentrated brine in the precrystallizer. 15. A process as claimed in claim 1, wherein complete settling of floc along with suspended impurities and clarification of brine in step (iii) of claim 1 is achieved within a time period of 12-96 hours. 16. A process as claimed in claim 1, wherein the turbidity of brine in step (iii) of claim 1 is reduced from 7-11 NTU to the level of 1-4 NTU. 17. A process as claimed in claim 1, wherein the clarified brine in step (iii) of claim 1 does not undergo any measurable change in composition or pH after alum solution treatment. 18. A process as claimed in claim 1, wherein the clarified brine is fed into the crystallizer, in step (iv) of claim 1, maintaining a height of 2-2.5″ of residual brine in the precrystallizer to eliminate the possibility of carry over of flocs to the crystallizer. 19. A process as claimed in claim 1, wherein a dirt free channel, for the flow of clarified brine from precrystallizer to crystallizer is ensured in step (iv) of claim 1 to minimize the possibility of recontamination of clarified brine with clayey matter. 20. A process as claimed in claim 1, wherein clarified brine is charged into the crystallizer in step (v) of claim 1 either once up to a depth of 13-15″ or up to a depth of 11″ repeatedly as mentioned in step of claim 1 to build up the salt layer of 3″ thickness. 21. A process as claimed in claim 1, wherein solar evaporation of clarified brine in step (iv) of claim 1 was carried out till 27° Be″ to produce salt of highest purity. 22. A process as claimed claim 1, wherein the precrystallizer is used for the treatment of concentrated brine with alum solution repeatedly in step (ii) of claim 1 without affecting the clarity of brine. 23. A process as claimed in claim 1, wherein the bittern is drained out from the crystallizer in step (vi) of claim 1 on attaining about 27° Be′ density. 24. A process as claimed in claim 1, wherein the fresh brine charged into the crystallizer for raking the salt in step (vi) of claim 1 is of about 25° Be′ density. 25. A process as claimed in claim 1, wherein clarification of brine eliminates carryover of precrystallized gypsum and clayey matter into the crystallizer in step (iv) of claim 1 thereby minimizing the physical contamination of salt with gypsum and clay resulting in greatly reduced levels of Ca and SO4 in the solar salt obtained. 26. A process as claimed in claim 1, wherein the improved clarity of brine minimizes the possibility of impure particles acting as nucleation sites for salt crystals and thereby reduces the possibility of embedded impurities in the solar salt obtained. 27. A process as claimed in claim 1, wherein the bittern obtained after the harvesting of salt from the clarified brine in step (vii) of claim 1 is utilized to produce bittern based products like low sodium salt, potassium and magnesium chemicals of improved quality and whiteness. 28. A process as claimed in claim 7, wherein said brine is selected from sea brine, sub soil brine or lake brine. 29. A process as claimed in claim 10, wherein the concentrated brine is treated, in step (ii) of claim 1, with aluminum sulphate (alum solution). 30. A process as claimed in claim 15, wherein complete settling of floc along with suspended impurities and clarification of brine in step (iii) of claim 1 is achieved within a time period of 24-48 hours. 31. A process as claimed in claim 16, wherein the turbidity of brine in step (iii) of claim 1 is reduced from 7 to 11 NTU to the level of 2.5 to 3.5 NTU due to clarification. 32. A process as claimed in claim 19, wherein said channel is a lined channel.
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