GB2332426A

GB2332426A - Preparing monocalcium phosphate monohydrate for use as feedstuff component

Info

Publication number: GB2332426A
Application number: GB9726680A
Authority: GB
Inventors: Axel Bruckert; Burkhard Jochemzyk; Klaus Butchereit
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-06-10
Filing date: 1997-12-17
Publication date: 1999-06-23
Also published as: FR2771601A1; GB9726680D0; DE19623082C1

Abstract

Monocalcium phosphate monohydrate with improved characteristics for use as a feedstuff component is produced by reacting calcium carbonate of organic origin, preferably eggshells, and/or a calcium phosphate of organic origin eg bones with orthophosphoric acid. A highly pure product is produced with a Ca- and P-Water solubility of at least 90% which is almost free of dicalcium phosphate and contains only water soluble calcium hydrogen carbonate as a slight impurity.

Description

1 2332426 IMPROVED MONOCALCIUM PHOSPHATE MONOHYDRATE FOR USE AS A

FEEDSTUFF COMPONENT AND A METHOD OF PRODUCING IT The invention relates to a monocalcium phosphate monohydrate with improved characteristics, which is used as a feedstuff component, and to a method of producing it from an organic calcium carrier and/or calcium phosphate carrier.

Monocalcium phosphate monohydrates are gaining ever more importance in the feedstuff industry due to their high biological efficiency and the bone mineralisation associated therewith. Monocalcium phosphate monohydrate is a suitable feedstuff component for growing animals, particularly for high output commercial animals, such as milk cows, since both the calcium and also the phosphorous is required by the animals in a large amount as a nutritional supplement.

High demands are made of monocalcium phosphate monohydrate constituting a feedstuff component. The phosphorous and the calcium must be present in an intestinally assimilable form so that both components can be readily digested by the animals. These two components in the monocalcium phosphate monohydrate must consequently have a high water solubility so that they can be optimally, absorbed by the animals. Furthermore, it is highly advantageous if the monocalcium phosphate monohydrate has a long storage life and a high mechanical load bearing ability.

Previously, only mineral apatites or other mineral calcium carriers or calcium phosphate carriers have been used for producing monocalcium phosphate 2 monohydrate. Their use for producing monocalcium phosphate monohydrate has, however, considerable disadvantages. Thus, for instance, the treatment of the apatite is expensive and time consuming since the apatite contains various impurities, such as fluorides, iron and aluminium, which must be removed from the monocalcium phosphate monohydrate which is then obtained by means of various purif,,lng processes. Only after carrying out these necessary purifying processes can a monocalcium phosphate monohydrate, which is suitable for the feedstuff industry, be obtained from the crude apatite.

There are several known treatment methods in which different acids are used in order to produce monocalcium phosphate monohydrate. Thus the treatment can be performed -,s-ith sulphuric acid, however, this results in a mixture of monocalcium phosphate monohydrate with calcium sulphate (gy psum). which substantially impairs the quality of the end product. Furthermore, the product also contains the various impurities (fluorides. heavy metals) mentioned above, which originate from the apatite. This product is therefore not suitable in this c unpurified form for use as a feedstuff.

In order to produce feedstuff quality, it is necessary that the calcium sulphate and the other impurities be removed as completely as possible from the treated crude apatite. The fluorides are removed, for instance, by the addition of sodium and silica in the form of sodium silico fluoride. The gypsum which is produced must also be removed by time consuming stirring.

When treating with sulphuric acid, the acid which is used must be added in excess so that all the phosphate is decomposed and no undecomposed apatite remains. However, iron and aluminium, which are both contained in crude 3 apatite, can also substantially disrupt the treatment since they form water insoluble phosphates and thus impede the formation of the desired monocalcium phosphate monohydrate. These impurities must therefore also be removed.

It is also possible to treat apatite with hydrochloric acid. This does produce monocalcium phosphate but it is contaminated with calcium chloride and is consequently only suitable for the feedstuff industry if the calcium chloride is removed in further purification steps.

The products produced from the apatite must in turn be dried, ground and aranulated in additional method steps. The granulate which is obtained is then again dried, sieved and cooled. Numerous time-consuming and expensive method steps are thus necessary in order to reach the desired end product, monocalcium phosphate monohydrate, starting from mineral apatite.

A further substantial disadvantage of the monocalcium phosphate monoh-, lldrate obtained from apatite by traditional methods is that the monocalcium phosphate monohydrate is contaminated with dicalcium phosphate, which is also formed in the treatment process. The dicalcium phosphate contained in a monocalcium phosphate monohydrate considerably reduces the water solubility of the monocalclum phosphate monohydrate.

It is thus the object of the present invention to provide a method that overcomes the disadvantages known in the prior art and by means of which a monocalcium phosphate monohydrate with improved characteristics can be produced, which is suitable for use in the food industry.

4 According to the present invention, there is provided a method of manufacturing monocalcium phosphate monohydrate with a Ca- and P solubility of at least 90%, for use as a feedstuff component- the method comprising reacting orthophosphoric acid with calcium carbonate of organic origin and/or calcium orthophosphate of organic origin.

The invention also extends to a method in which the heated reaction mixture is further agitated so that sufficient water is vaporised from it in order to produce a granulated product.

A monocalcium phosphate monohydrate mith improved characteristics can be produced with the method in accordance with the invention which is suitable for the feedstuff industry'. The monocalcium phosphate monohydrate in accordance with the invention has a Ca- and P- water solubility which is improved by comparison with the prior art and also has a higher biOI02cal availability. Furthermore, the monocalcium phosphate monohydrate produced by means of the method in accordance with the invention is in a highly- pure form.

The method in accordance with the invention is performed by reacting an organic calcium carrier and/or an organic calcium phosphate carrier with phosphoric acid. CaC03 of organic origin is advantageously used as the calcium carrier. Eggshells, mussels, limestone, corals etc. are suitable for this purpose. The use of chicken eggshells is particularly preferred. Calcium orthophosphate from bone processing is advantageously used as the calcium phosphate carrier.

The reaction of a mixture comprising calcium carbonate and calcium orthophosphate with orthophosphoric acid occurs stoichiometrically in accordance with the following reaction pattern 1:

CaCO3 + 2 H3P04 + H,0 --o.. Ca (H2P04)21-1-,0 + H2C03 &-F H- + HCO3- Ca3 (P04)2 + 5 H2C03 + 14,0 --o., Ca(H2P04)2H_.)0 + 2 Ca(HCO3)2 2Ca (HC03)2 + 4 H3P04 -->. 2 Ca (142P04)2H,0 + 2 HC03&-.F H- + HCO3- Ca3 (P04)2 + 4 H3P04 + 3 1-1,0 --0.. 3 Ca (H2P04)2H20 Ca (HC03)2 --, H3P04 + 2 11,0 -O'CaHP042H,0 + 2 1121C03 --. Ca (1-1, P04)2H70 + Ca (11C03)2 + HC03 CaC03 + H3P04, 2 H_.,0 --. CalAP0427H.)0 --> Ca (14,P04)2H,0 + Ca (HC03)2 The reaction of calcium orthophosphate of organic origin with orthophosphoric acid occurs in accordance with reaction pattern 2:

Ca3 (P04)2 + 4 H3P04 + 3 H20 -.> 3 Ca (H2P04)2H20 CaHP04211,0 + H3P04 -1" Ca (112P04)2H20 + H20 6 The reaction of calcium carbonate from eggshells with orthophosphoric acid occurs in accordance with reaction pattern 3:

CaC03 + 2 H3P04 + H,0 Ca fflP04)2H,0 + H,0 + C02 - H2C03 CaCO3 + H- + HCO3- + H,0 -.> Ca (HCo,)2--4- 11,0 Ca(FIC03)2+ 2 H3P04 + H,0 --. Ca(11,P04)211-,0 - H,C0-, - H- + HCO-,- In the method in accordance with the invention, the phosphate is added directly to a calcium-carbonate an&'or calcium phosphate- carrier of organic origin. The monocalcium phosphate monohydrate in accordance with the present invention surprisingly exhibits a substantially higher P- and Ca-solubility than the products known from the prior art. The solubilities may be at least 90%.

These increased Ca- and P-solubilities can be attributed, in addition to the age and the purity of the calcium- and/or calcium phosphate- c arri er, to the complex reactions of the calcium carbonate of organic origin, constituting a single component or in a mixture with calcium orthophosphate or organic origin. with orthophosphoric acid. The calcium carbonate content of the eggshell, for instance, forms water soluble calcium hydrogen carbonate in the C02-water vapour phase which in turn reacts with the orthophosphoric acid to form monocalcium phosphate monohydrate with the liberation Of C02 and water.

C02 and water are present in the reversible reaction in the form of H+ and 7 HC03-. This "carbon dioxide" reacts with the free calcium carbonate to form calcium hydrogen carbonate, which then reacts in turn with orthophosphoric acid to form monocalcium phosphate monohydrate (pattern 3). An analogous reaction occurs also in the mixture of calcium carbonate and calcium orthophosphate (pattern 1).

The---carbondioxide" thus acts as an additional acid and as a reaction catalyst in the method in accordance with the invention. It results in the starting materials being almost completely converted into the end product. Furthermore, the formation of undesired byproducts, such as the formation of dicalcium phosphate, is also substantially suppressed.

When usin the method in accordance with the invention, no additional 9 purification steps, for instance defluoridisation or the removal of gypsum, calcium fluoride etc. are also necessary. The raw materials used are present in pure form so that the very good Ca- and P-water solubility of the product which is produced is not impaired by impurities in the starting products.

The method is preferably performed by calcium carbonate from eg.,gshells and/or calcium orthophosphate from bone processing being reacted in a stoichiometric ratio with technically pure phosphoric acid, which contains I to 72%. preferably 50 to 56%. P,05. The addition of the calcium carbonate and/or calcium orthophosphate is effected by means of a quantity dosing device. It has proved to be advantageous to add the calciumand/or calcium phosphate- carrier to the reaction system in a particle size of < 0.2 mm. Water can be added in dependence on the residual water content of the organic calcium carbonate.

The reaction is preferably performed at a temperature of 150C to 1300C, 8 preferably of WC to 105'C. The reaction duration is dependent on the temperature and preferably lies in a range of 1 second to 10 minutes. Pure monocalcium phosphate monohydrate is produced with a Ca- and P-water solubility of at least 90%.

It was further determined that a highly pure product is obtained if the reaction is performed in a closed reaction system, preferably with the starting components being added continuously.

An additional comminution or granulation step is also not necessan. in the method in accordance with the invention since a granulate can be produced depending on the speed of the stirring device in the reaction mixer and the addition of a certain amount of orthophosphoric acid. The heated mixture can be further agitated so that sufficient water can spontaneously vaporise in order thus to obtain a granulated product. The size of the granulate is set by a predetermined residence time of the reaction mixture in the reaction mixer. At the same time, the product is aerated in this reaction mixer so that the surface dries immediately and sticking together and agglomeration of the reaction product can be prevented. The subsequent drying of the product can be effected in a continuously operating drier. The preheated drying air can be mixed with the carbon dioxide produced during the reaction and the aeration air.

The method in accordance with the invention has considerable advantages by comparison with the method known from the prior art since additional purification steps and finishing processes are not necessary. The production of the monocalcium phosphate monohydrate in accordance with the invention is performed in one or at most two method steps. Monocalcium phosphate 9 monohydrate with excellent Ca- and P-water solubility is produced by the direct reaction of highly concentrated phosphoric acid with the organic calciumand/or calcium phosphate-carriers.

The following Table 1 shows that the monocalcium phosphate monohydrate of the present invention is considerably improved by comparison with a conventional product since it has a Ca- and P-solubility of at least 90%. f Furthermore, it is also present in a purer form since it is practically ree of dicalcium phosphate and contains only water-soluble calcium hydrogen carbonate as a slight impurity.

Table 1

Monocalcium phosphate monohydrate Product in accordance Comparative with the invention product Legal Requirement Physiologically 1 1 1 1 1 100 70 i utilisable calcium compound DirectIv absorbable phosphate 100 - i No anion burdening 1 100 - 1 the metabolism P-water solubility > 80 % 118 104 Ca-water solubility > 80 % ill 100 P content at least 22 % 100 100 Ca content at least 16 % at most 17 % 100 100 Ratio Ca: P < 0.80: 1 100 100 Free of dicalcium at most 8 % phosphate 112 100 F content < 2000 mg/kg 100 1 90 Free of heavy metals (impurities) 95 60 Point rating 1 1136 Ratio of product in accordance with the 1.38 invention to the comparative product Point rating: Achieving the legal specification = 100 Points.

1 824 1 The invention will be explained in more detail with reference to the following exemplary embodiments, though the invention is not limited thereby.

Exemplary Embodiment 1 Monocalcium phosphate monohydrate was produced by continuously reacting a mixture of 567.5g calcium orthophosphate (bone meal) and 492g calcium carbonate (eggshells) with 1945g orthophosphoric acid. The reaction, which occurred in a foaming C02-water vapour phase, lasted 12 seconds. The reaction temperature was 8 1 'C and was made use of after termination of the reaction for product granulation and drying. The dried granulate was cooled. The yield was 86.7%.

Exemplary Embodiment 2 Monocalcium phosphate monohydrate was produced by reacting a mixture of 20.3 wl.% calcium orthophosphate (bone meal) and 20.3 "1.% calcium carbonate (eggshells) with 73.3 wt.% orthophosphoric acid (containing 54 ni.% P205 75% concentration). The reaction was performed at a temperature of 8 PC within 12 sec. The yield was 86.7%.

11 Exemplary Embodiment 3 Monocalcium phosphate monohydrate was produced by reacting 44 wt.% calcium orthophosphate (bone meal) with 59 wt.% orthophosphoric acid (containing 54 Wt-% P205, 75% concentration). The reaction was performed at a temperature of 79'C within 12 sec. The yield was 96.8%.

Exemplary Embodiment 4 Monocalcium phosphate monohydrate was produced by reacting 41.5 wt.% calcium carbonate (eggshells) with 91.1 wL% orthophosphoric acid (containing 54 "-t.% P205 75% concentration). The reaction was performed at a temperature of WC within 13 sec. The yield was 75.5%.

12

Claims

1. A method of manufacturing monocalciurn phosphate monohydrate with a Caand P-solubility of at least 90% for use as a feedstuff component, the method comprising reacting orthophosphoric acid with calcium carbonate of organic origin and/or calcium orthophosphate of organic origin.

2. A method as claimed in Claim 1, in which the calcium carbonate is obtained from eggshells and/or the calcium orthophosphate is obtained from bones.

3. A method as claimed in Claim I or Claim 2. in which the organic calcium carrier and/or the organic calcium phosphate carrier is or are reacted with orthophosphoric acid which contains 1% to 72% P'22 05- A method as claimed in Claim 3), inv,-hich the orthophosphoric acid contains 50% to 56% P-,0;.

5. A method as claimed in any preceding Claim, in which the starting components are continuously added to the reaction mixture in a closed reaction system.

6. A method as claimed in any preceding Claims, in which the reaction of the components is conducted at a temperature in the range of 15'C to 1-1)0<>c.

13 A method as claimed in Claim 6, in which the reaction is conducted at a temperature in the range of 60T to 105T.

8. A method as claimed in any preceding Claim. in which the heated reaction mixture is further agitated so that sufficient water is vaporised from it in order to produce a granulated product.

9. Monocalcium phosphate monohydrate with a Ca- and P-solubility of at least 90% for use as a feedstuff component, obtained by reacting orthophosphoric acid with calcium carbonate of organic origin and/or calcium orthophosphate of organic origin.

10. Monocalcium phosphate monohydrate as claimed in Claim 9, in which the calcium carbonate is obtained from eggshells and/or the calcium orthophosphate is obtained from bones.

11. A method of manufacturing monocalcium phosphate monohydrate substantially as herein specifically described with reference to the accompanying examples.