Chemistry of inorganic compounds – Carbon or compound thereof – Oxygen containing
Reexamination Certificate
1999-10-25
2002-11-05
Silverman, Stanley (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Oxygen containing
C423S184000, C423S186000, C423S206100, C423SDIG001, C023S30200R
Reexamination Certificate
active
06475458
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for formulating food grade sodium bicarbonate and more particularly, the present invention relates to a method for formulating food grade sodium bicarbonate by ion exchange purification of sodium bicarbonate.
BACKGROUND OF THE INVENTION
In the synthesis of food grade sodium bicarbonate, soda ash is typically treated with carbon dioxide or purified from product formed in the Solvay process. In order to formulate food grade sodium bicarbonate, the compound must be purified to leave a product having less than 100 ppm impurities. The prior art has addressed this need in many ways, however, the methods include the use of several unit operations, expensive equipment, high energy input among other factors all contributing to the cost of processing.
It would be desirable if a method existed, where the product could be prepared without the limitations of the prior art. The present methodology proposes a solution to the existing methods.
SUMMARY OF THE INVENTION
One object of the present invention is to provide an improved method for formulating food grade sodium bicarbonate.
A further object of one embodiment of the present invention is to provide a method for formulating food grade sodium bicarbonate by purification, comprising the steps of:
a) providing a saturated feedstock of sodium bicarbonate, the sodium bicarbonate containing at least sodium sulfate as an impurity;
b) filtering the saturated feedstock to remove impurities to form a first filtrate;
c) passing the filtrate through an ion exchanger containing a chelating cationic resin to reduce calcium and magnesium ion concentration present in the filtrate;
d) cooling the filtrate while introducing a source of ammonia or ammonium ions and carbon dioxide to retain ammonium sulfate in the filtrate and precipitating sodium bicarbonate; and
e) filtering precipitated sodium bicarbonate.
The processes as discussed herein offer a straightforward method of purifying sodium bicarbonate to the food grade standard using ion exchange solubility shifting with reduced levels of energy.
As a further object of one embodiment of the present invention, there is provided a method for formulating food grade sodium bicarbonate by purification, comprising the steps of:
a) providing a saturated feedstock of sodium bicarbonate, the sodium bicarbonate containing at least sodium sulfate, calcium and magnesium as an impurities;
b) filtering the saturated feedstock to remove impurities to form a first filtrate;
c) passing the filtrate through an ion exchanger containing a chelating cationic resin to reduce calcium and magnesium ion concentration present in the filtrate to less than 10 parts per million;
d) cooling the filtrate while introducing a source of ammonia or ammonium ions and carbon dioxide to retain ammonium sulfate in the filtrate and precipitating sodium bicarbonate; and
e) filtering precipitated sodium bicarbonate.
By making use of the ion exchangers and solubility shifting, the liquor is progressively purified without risking the introduction of additional impurities to the liquor. Further, since the processes do not require high temperatures, there is no concern with the sodium bicarbonate being converted to sodium carbonate. This typically occurs at approximately 100° C. With the use of the ion exchangers and the recognition of solubility shifting, high temperature unit operations are avoided, product yield is high and impurity concentration is reduced to an acceptable level.
Having thus described the invention, reference will now be made to the accompanying drawing illustrating preferred embodiments.
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Airborne Industrial Minerals Inc.
Renault Ogilvy
Sharpe Paul
Silverman Stanley
Vanoy Timothy C.
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