Citric acid from corn calcium salt extraction process
1, Brief introduction of citric acid extraction process
The composition of citric acid fermentation liquid is rather complex, which contains a variety of nutrient substances that have not been metabolized and a small amount of non-citric acid substances produced in the metabolic process.If it is required to obtain high-quality crystalline citric acid, then it is still required to conduct extraction process. At present, the calcium salt extraction process is mainly used to extract citric acid in industrial production.
2,Principle of calcium salt process:the method uses two principles to achieve the extraction of citric acid from the citric acid fermentation liquid with more complex composition.
(1) The characteristic is utilized that calcium citrate has small solubility in hot water , and through reaction of citric acid and calcium carbonate (or calcium oxide, calcium hydroxide) , so as to achieve the result of separating citric acid from other composition of the fermentation solution ;
(2) The principle which strong acid is used to produce weak acid is utilized. The sulfuric acid is used to decompose calcium citrate salt, then citric acid is obtained again;
3,Advantages and disadvantages of calcium salt extraction process
Advantages: The process is mature, the product quality is good and stable,and the comprehensive production cost is low;
Disadvantages: Calcium sulfate is the by-product. If there is no complete industrial support, it is more troublesome to deal with this by-product;
4,Classification of calcium salt extraction process
(1)One-step calcium salt method (referred to as citro-calcium method) : Calcium citrate is obtained by neutralization reaction between citric acid and calcium carbonate (or calcium oxide, calcium hydroxide) , and thencalcium citrate is obtained by reaction between calcium citrate and concentrated sulfuric acid. Because there is only one-step of neutralization reaction, calcium citrate is obtained, so it is called one- step calcium salt method (citro-calcium method).
(2)Two-step calcium salt method (referred to as hydrogen calcium method) : Calcium hydrogen citrate is obtained by the two-step neutralization reaction of citric acid and calcium carbonate (or calcium oxide, calcium hydroxide), and then citric acid is obtained by reaction between calcium hydrogen citrate and sulfuric acid. Because there is two-step neutralization reaction, the reaction leads to the result of obtaining calcium hydrogen citrate, it is called two-step calcium salt method (hydrogen calcium method).
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