CS243258B1 - Method of calcium hydrgenphosphate production - Google Patents

Abstract

Bred lime or / and / or lime hydrate with the appropriate acid, using excess calcium salt, the solid phase is separated and the resulting solution is water-soluble calcium salts with a reaction, for example with phosphoric acid a converts the ammonia to a precipitate that is formed from the resulting slurry and worked up to the desired product. Part of ammonium solution salts can be returned to production. The product is suitable for cosmetic use, food industry, pharmaceutical industry and as a feed additive mixtures in animal production.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for the manufacture of calcium dihydrate or anhydrous dicalcium phosphate or a mixture thereof.

For convenience, precipitation methods are widespread methods of manufacturing the above products. Limestone is the most commonly used starting calcium raw material, which is converted into a water-soluble calcium salt by reaction with the appropriate acid, with high purity requirements for the starting calcium raw material being generally required. The water-soluble calcium salt thus obtained is further precipitated to the desired product.

Thus, as is evident, the drawback of the precipitation processes used hitherto is primarily that the quality of the product depends on the quality of the starting limestone.

According to the invention, these disadvantages are overcome by the process for producing calcium dihydrate or anhydrous calcium phosphate or mixtures thereof from quicklime and / or lime hydrate.

The process consists in reacting quicklime and / or lime hydrate and / or lime milk with an appropriate acid, using an excess of calcium raw material, separating the solid phase and the resulting water-soluble calcium salt solution by reaction with trihydrogenphosphoric acid, and with ammonium and / or ammonium hydroxide and / or ammonium hydrogen phosphate and / or ammonium and / or ammonium hydroxide and / or ammonium hydrogen phosphate and / or with a mixture of dihydrogen phosphate and ammonium hydrogen phosphate and / or with a mixture of dihydrogen phosphate and ammonium and hydrogen phosphate a precipitate which is separated from the resulting suspension and processed into a product, with some of the ammonium salt solution being optionally recycled.

Preferably, stabilizers are added to retard the dehydration of the hydrate and / or the hydrolysis of the anhydrous dicalcium phosphate.

The basic effect of the process according to the invention is that the quality of the product does not depend on the purity of the starting calcium raw material. As a result, the production method according to the invention becomes significantly more advantageous than the prior art precipitation processes.

The manufacture may be continuous, discontinuous or a combination of both. For example, quicklime and / or lime hydrate is reacted with an appropriate acid, e.g. hydrochloric acid, using an excess of calcium raw material. After separation of the solid phase, the resulting solution of water-soluble calcium salt at a concentration of 1 wt. % to a saturated solution at a given temperature, 1% wt. up to 90 wt. and the ammonia is mixed simultaneously or sequentially, in one or more stages, or alternatively dilution or mixing with recycle of the ammonium salt solution. The precipitation temperature depends on the desired product composition and ranges from 0 ° C to the boiling point. The resulting precipitate is collected, for example by filtration or centrifugation, washed and dried, optionally partially or completely dehydrated by heat treatment to obtain the product of the desired composition. Part of the remaining solution can be returned to production. The wash water can be incorporated into the production cycle. Additives, for example sodium pyrophosphate, are advantageously metered into the solutions to be precipitated and / or directly into the precipitation apparatus and / or into the wet or dry product and / or in the eventual adjustment of the particle size by grinding.

The production method of the invention is described in more detail below with reference to specific embodiments.

Example 1

The lime hydrate in an amount corresponding to a 5% excess over stoichiometry was dissolved at 60 ° C in hydrochloric acid to form a 10% by weight solution. After separation of the solid phase, this was mixed in an batch stirred reactor with an equimolar amount of 8% by weight of trihydrogenphosphoric acid containing 1% by weight of sodium pyrophosphate. The pH was adjusted to 7 with ammonia gas. The precipitation temperature did not exceed 30 ° C. The resulting precipitate was filtered off, washed and dried at 40 ° C. The resulting product was dibasic calcium phosphate dihydrate.

Example 2

The process was conducted as in Example 1 except that ammonium chloride was added to the stirred batch reactor at a molar ratio of 1:10 to phosphoric acid.

Example 3

The process was conducted as in Example 1 except that the precipitation temperature was maintained at 80 ° C. The dried precipitate was dehydrated by indirect heating with steam at 95 ° C. The resulting product was anhydrous dibasic calcium phosphate.

Example 4

The process was conducted as in Example 1 except that the precipitation temperature was maintained at 60 ° C. The dried precipitate was dehydrated by indirect heating with steam at 70 ° C. The resulting product was a mixture containing 60% by weight of dihydrate and 40% by weight of anhydrous dibasic calcium phosphate.

The products obtained are suitable for use in the cosmetics, food, pharmaceutical industries and as an enriching additive in animal feed.

Claims (2)

A process for the preparation of dihydrate and / or anhydrous dibasic calcium phosphate, optionally in admixture with hydroxylapatite and / or calcium phosphate, characterized in that quicklime and / or lime hydrate and / or lime milk with an appropriate acid are reacted excess solid calcium, separating the solid phase and the resulting water-soluble calcium salt solution by reaction with phosphoric acid and ammonia and / or ammonium hydroxide and / or with ammonium dihydrogen phosphate and ammonia and / or with ammonium hydroxide and / or with ammonium phosphate and / or a mixture of ammonium phosphate and ammonium phosphate and ammonium hydrogen phosphate and / or with a mixture of dihydrogen phosphate and ammonium hydrogen phosphate and ammonia and / or ammonium hydroxide are converted to a precipitate which is separated from the resulting suspension and processed to a product, with some of the ammonium salt solution optionally being recycled. 2. The process according to claim 1, wherein stabilizers retarding dehydration of the dihydrate and / or hydrolysis of anhydrous dicalcium phosphate are added.