FI106712B - Improved Ca-N-P solution fertilizer - Google Patents

Description

1 106712

This invention relates to a calcium, phosphorus and nitrogen-containing acidic stock solution used to prepare a solution fertilizer. More particularly, the invention relates to a stock solution prepared from one pure compound, urea calcium phosphate nitrate, Ca (H2PO4) (NO3) 'CO (NH2) 2, by dissolving it in water.

10 Solution fertilizers have been used and manufactured industrially for decades and global growth is expected. Adding fertilizers directly to the irrigation system has proven to be a very effective and environmentally friendly way to increase the yield. Because the nutrients are in liquid, dissolved form, a precise and uniform distribution of the nutrients to the desired target is achieved. Solution fertilizers, especially in hot and dry cultivation areas as well as in greenhouses and gardens, provide the plants with the exact nutrients they need and have a good nutrient efficiency, for example 80-90% for nitrogen. At the same time, the efficiency of water use is improved. Handling of liquid fertilizers is also easier for the farmer than solids.

Compounds used in solution fertilization are typically sold as solids. These are what the farmer makes powerful: · ··; Dissolve the compounds in water according to the instructions given in .1! 1 ·. The required dose of the stock solution is then taken and diluted to the final desired lightness by adding it directly to the water of the irrigation system using a dispenser or injector.

When using irrigation fertilizers, it is important that the compounds to be dissolved are sufficiently soluble in water and that they do not re-precipitate from the solution during prolonged storage.

«· ·

Potential precipitates easily clog the nozzles of the nozzles used in the irrigation water system and also the nozzles of the dispenser.

When solubilizing typical granules of P raw materials used in field fertilizers, large amounts of large particle size solids often remain, causing clogging. Additionally, if it is desired to include calcium and trace elements in the fertilizer, such as Mg, Fe, Cu, Zn, jaη, B, and Mo, solutions are particularly susceptible to precipitation, depending on which compounds are used as N and P starting materials. Inorganic compounds formed in solutions, such as dicalcium phosphate in particular, are sparingly soluble and tend to precipitate even at low concentrations if the pH of the solution increases. When the pH is suitably low, nutrients and trace elements remain better in solution.

The solution fertilizer should be completely soluble in water. However, in practice, small amounts of water-insoluble solid particles may be allowed, provided that the particle size of these particles is sufficiently small to prevent clogging in irrigation systems. In addition, the amount of these particles in the solution must be sufficiently low. Very small particles (<50 pm) travel easily with the water · ··· and do not cause problems in practice. According to Finnish Patent Publication FI 98518, a concentrated aqueous suspension fertilizer containing * * ί ** · at least one plant-insoluble plant nutrient containing water-insoluble solids may be used. These particles had a particle size of less than 50 µm with a pH of less than 2.

30

It is known that, for example, ammonium, phosphate, potassium or sodium phosphate, phosphoric acid or urea phosphate and nitrates can be used as sources of phosphorus and nitrogen in calcium fertilizer fertilizers. However, the problem is that, for example, the use of diammonium phosphate (DAP) raises the pH of the solution, whereupon calcium phosphate precipitates easily. Mono- | »» *. *. ammonium phosphate solutions (MAP) have a pH in the range of 4-5, whereas iron and aluminum phosphates have a low solubility. Nitrate compounds are good sources of nitrogen because the roots of plants are able to utilize this type of nitrogen more efficiently and faster than nitrogen derived from urea, for example. Nitrates, chlorides or phosphates can be used as the source of calcium-5. The trace elements can either be chelated, for example EDTA complexes, or are more easily precipitated, simple inorganic salts.

In order to avoid the precipitation of calcium and trace elements in concentrated stock solutions, Vetanovetz and Peters (EP 569513) have developed a solid compound fertilizer with phosphorus source as urea phosphate and calcium source as an inorganic salt such as nitrate. When this starting compound mixture of solids is dissolved in water, a non-precipitated, water-soluble, acidic and stable stock solution is formed. The proportion of urea phosphate in the mixture of compounds may be between 5 and 95% by weight, and the calcium salt may also be between 5 and 95% by weight. The total concentration of the stock solution can range from 2 to 40%. However, in practice, stock solutions with a concentration greater than 10% are generally not used, since making such a solution would already require agitation to effectively dissolve the solid starting mixture in the amount of water used to form a homogeneous solution. In addition, the solid starting blend according to the patent of Vetanovets and Peters may contain from 0.1 to 50% by weight of an inorganic trace element such as Fe, Cu, Mn, Zn or Mg salt.

m · · · 1 · 1: The acidic stock solution thus obtained with urea phosphate is completely soluble, even though the Ca content is high, which is a considerable advantage over the preparation of a similar solution, for example, from monoammonium phosphate. However, the starting material mixture contains both urea phosphate and calcium nitrate as individual compounds. The compounds have different dissolution rates, and obtaining a uniform, concentrated stock solution of 1:11 to 1:35 would require mixing upon dissolution. Solid urea phosphate has good physical properties but the problem with solid calcium nitrate is its hygroscopicity, which makes it difficult to store material. The entire fertilizer mixture may clump under the influence of moisture and heat in the air and segregate due to handling and vibration, thereby compromising material consistency during storage. 5 The critical relative humidity (CRH) of urea phosphate is 81.9% and that of anhydrous calcium nitrate is only 49.9%. The CRH of the mixture is lower than the CRH of its components, depending on the composition. The melting point of calcium nitrate, Ca (NO 3) 2 · 4H 2 O, is very low, 42.7 ° C. The use of the compound in warm countries, where · 10 relative humidity is also often high, may be a problem. In the urophosphate-calcium nitrate system, the close relationship between nutrients limits the simultaneous presence of calcium and phosphorus. It is often the case to add other nutrient components, such as ka-15 lithium, which further reduce the amount of calcium in the solution.

The hygroscopicity of the calcium compounds has been successfully reduced by forming urea adducts with nitrate or phosphate (Patent Publication FR 1182058).

Sullivan et al. (U.S. Pat. No. 4,507,139) prepared a solid field fertilizer wherein urea was added to nitric acid-treated calcium-containing phosphate ore, hydroxyapatite, 1 to 25, and a slurry was obtained which was granulated, dried and screened. With this fixed N-P field fertilizer - *: **! Tea has a low pH (1.0-4.0) and excellent shelf life: * · *: Femininity. In further X-ray diffraction studies, * j 'was observed. it was found that the favorable stability and moisture properties of the fertilizer in question were due to the novel crystalline compound, urea-calcium phosphate nitrate, Ca (Η2Ρ04) (NO3) CO CO (NH2) 2 · polysalt salts as described above have better physical properties than corresponding compound mixtures.

j * 35 This is due to the fact that all components are evenly (»«. *. t in one crystal lattice, so that the surface of the crystal also has fewer ions that are easily absorbed, solvated, 1 * · «<» * · 5 106712 compared to the more hygroscopic component of the mixture Another important consideration is the even dissolution of the components The more soluble component of the mixture is first solubilized. evenly and in a certain proportion, which also results in a uniform fertilizer solution.

10

The solubility of calcium phosphate has been improved by the simultaneous addition of urea nitrate (Kochemba et al., Zhurnal Prikladnoi Khimii, 1982 vol. 55 no. 4, pp. 914-915). The amount of dissolved calcium and phosphorus was increased by addition of calcium phosphate and urea nitrate relative to each other, thereby achieving greater solubility than directly mixing the corresponding amounts of urea phosphate and calcium nitrate and dissolving the mixture in water. However, the method is of no practical importance, due to the explosivity of urea nitrate.

The use of starting materials to keep the pH of solution fertilizers sufficiently low may effectively reduce the risk of precipitation by low soluble salts i * 25, but it should be possible to further improve the physical properties of the individual components of the starting compounds. so they are consistent and user-friendly.

The process of the present invention can prepare ... 30 acidic stock solution and the crystalline compound used to prepare the solution has excellent physical properties.

It is an object of the present invention to use one pure compound urea-calcium phosphate-, nitrate, Ca (H2PO4) (NO3) 'CO (NH2) 2 to make a stock solution. which is easy for the farmer to maintain a consistent quality for a long time and is simple to prepare the desired stock fertilizer stock solution.

In addition, it was surprisingly found that this crystalline double salt used as a field fertilizer has better properties in the use of a solution fertilizer than, for example, a mixture of urea phosphate and calcium nitrate. This double salt provides a higher solubility of calcium in water.

The main features of the invention are apparent from the appended claims.

According to the invention, it has surprisingly been found that it is possible to prepare a stock solution 15 for a fertilizer solution using only one pure compound which already contains the required nutrients in appropriate proportions and has an exceptionally high calcium content compared to similar compound fertilizers.

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The invention thus relates to the use of a crystalline calcium, nitrogen and phosphorus-containing double urea-added double salt, urea-calcium phosphate nitrate, Ca (H2PO4) (NO3) 'CO (NH2) 2r for the preparation of a stock fertilizer solution having % and Ca / N molar ratio 1/3, urea ··· «· an / nitrate molar ratio 1 and Ca / P molar ratio 1. This ratio is best for the simultaneous solubility of calcium and phosphate« · · -1 and this ratio is not achieved by mixing calcium - 1 · · rate and urea phosphate because if the Ca / P molar ratio is 1 ... 30 then the urea / nitrate molar ratio is 1/2.

The inventive compound provides a stock solution having: an exceptionally high Ca content and at the same time a CO (NH2) 2: Ca: NO3: P is 1: 1: 1: 1, which is not possible «1 ·. ·. This can be achieved by using, for example, urea phosphate as the starting material and calcium nitrate in which the ratios are fixed to each other according to CO (NH 2) 2: P = 1 and Ca: NO 3 = 1: 2.

7 106712

The urea-calcium phosphate nitrate salt used to prepare the solution fertilizer of the invention may be prepared by a known process (U.S. Pat. No. 4,507,139). Other ways of preparing this crystalline salt include, for example, using pure phosphoric acid and urea or urea phosphate as sources of phosphorus and nitrogen, and calcium carbonate or calcium nitrate as the calcium source and, if necessary, nitric acid.

The salt required for preparing the stock solution of the invention must be sufficiently soluble and the solids content must not cause problems in irrigation systems. When the compound prepared in the above manner is dissolved in water, less than 2.5% solids remain, based on the compound to be dissolved. Thus, the compound has a solubility in water of at least 97.5%. The water-insoluble solid has an average particle size of 5 µm and more than 95% less than 50 µm. By changing the solution conditions, the amount of solids can be reduced.

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For a solution for irrigation fertilization, the stock solution of this invention is typically diluted to less than 1% to 2%, whereby no precipitation occurs.

«T i * <<•« <·; The salt has a critical relative humidity (CRH) of 68.9% and a melting point above 360 ° C used to prepare the stock solution of the invention. However, the compound begins to decompose at 150 ° C.

The stock solution of the invention may also contain one or more trace elements such as magnesium, iron, manganese, copper, boron, zinc or molybdenum. These trace elements • ·. can be added either as inorganic salts or as metal cups.

The advantage of the above process of the invention is that the resulting stock solution is sufficiently acidic so that the sparse soluble Ca salts remain at these concentrations in solution. Further, for example, phosphorus does not precipitate as sparingly soluble salts with water impurities such as magnesium and iron to form NH 4 MgPCV 6 H 2 O and NH 4 Fe (HPO 4) 2'1 / 2H 2 O.

5

Further, using the urea-calcium phosphate nitrate salt of the invention, Ca (H2PO4) (NO3) " CO (NH2) 2, stock solution provides an exceptionally high calcium content compared to the phosphorus to nitrogen ratio. The solubility properties of the salt are good enough to it can be used as a solution fertilizer.

The salt used has very good physical properties and the material retains even quality for long periods of storage. The user-friendliness of the material is a considerable commercial advantage.

The invention will now be described in more detail by way of exemplary embodiments, without, however, limiting the invention to these.

20

Example 1.

The solubility of calcium is limited by the phosphorus content of the solution and vice versa. What matters is how much calcium and phosphorus are present in the solution at the same time. This can be illustrated by plotting the solubility product of these two components ····· Ca * H3PO4. Figure 1 shows the product of calcium and phosphate calculated for two different cases.

• · · • · · · ·

When calcium source is used as the Ca source and urea phosphate as the source of phosphorus, the amount of calcium nitrate in the soluble mixture varies between 5-95% and the amount of urea phosphate # · · • * * *] * between 95 and 5% gives the curve a of Fig. 1. Here: the solubility product of calcium phosphate is shown, expressed by different ratios of luminescence / phosphorus. Calcium and phosphate content. Even with the most favorable case, with a low calcium nitrate content of 1 · · ') * · * less than 300, the yield of the mouths remains. Using urea-calcium 9106712 phosphate nitrate salt as a source of calcium and phosphate provides a significantly better yield of about 600 (point b).

Correspondingly, the calcium / phosphate inputs can be viewed using the 5 calcium / nitrogen ratio (Figure 2 curve a). This differs from Figure 1 because nitrogen comes not only from nitrate but also from urea. When using calcium nitrate and urea phosphate, the maximum yield of calcium and phosphate is less than 300 at a urea phosphate content of 50% by weight.

According to this example, dissolving urea-calcium phosphate nitrate in water results in a significantly higher solubility of calcium phosphate in water than using a mixture of calcium nitrate and urea phosphate.

15

Example 2.

The synthesis product, which consisted mainly of urea-calcium-phosphate-nitrate, was made into a 10% aqueous solution at 24 ° C. This solution was analyzed for ions in solution. The pH of the solution was 2.4. The results obtained were compared with the corresponding solution obtained by mixing calcium nitrate and urea phosphate and dissolving the mixture in water. In this 4 (&lt; 1 &gt; 1 control experiment, the concentration of calcium nitrate ranged from 25-75 wt.% And urea phosphate from 75-25 wt.%.

I I I

·; 1 25 presented the results of the analyzes.

• ♦ ♦ ·· · ♦ • 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

IM

«• · • ♦ 1 ♦ 1 1 ♦ · • 1 1 1 1 ♦ 10 10 106712

Table 1. Analyzes of 10% solutions of the salt and reference mixtures of the invention. Analyzes of the mixtures are calculated from the composition of the components.

salt 25% CN + 50% CN + 75% CN +

10% solution 75% UP 50 S UP 25% UP

___ 10% -liuos__10% -liuos__10% solution

Urea - N% __ 1.56__1.22__0.89__0.44_

Nitrate - N% __ 0, 73__0.41__0.59__0.89_

Total nitrogen, N% __ 2.29__1, 63__1.48__1.33_

Ca -% __ 1, 60__0, 42__0, 85__1,28_ P205 -% __ 2,44__3, 37__2,25__1,12_

Ca% * P205% __ 3; _9__1 ^ 4__1 ^ 9__1 ^ 4_ N% / P205% | 0.94 I 0.48 1 0.66 1.19 5

The conversion factor for the conversion of phosphorus pentoxide to phosphoric acid content is H3PO4% = 1.38 to P205%.

The concentration of dissolved calcium is lower in all cases where a mixture of calcium nitrate and urea phosphate was used than when using the salt of the invention. Similarly, the solubility yield of Ca% * P2Os%, which describes the solubility of calcium phosphate, is highest with the compound of the invention.

«· T | «| «•« «. . ·. According to this example, the dissolution of urea-calcium phosphate nitrate in water results in a significantly higher solubility and concentration of calcium phosphate in water than using mixtures of calcium nitrate and urea phosphate.

• · · i · i 20

Example 3.

A 2% solution of urea calcium phosphate nitrate prepared according to Example 3 was made by adding 4.82 g of product 236, 7 g of water. After the solution was filtered and insoluble

4 I I

!!! The residue was weighed to give 0.11 g (2.3 wt%).

In the assays, the substance turned out to be the unreacted starting material, · · * · · Ca 3 (PO 4) 2. Particle size distribution analysis showed a residual 106712 of very fine particle size with an average particle size of 5 µm and a slow descent.

Example 4.

The crystalline urea adducted double salt was prepared from calcium phosphate, Ca 3 (PO 4) 2 23.1 g, calcium hydroxide,

Ca (OH) 2 1.73 g, nitric acid, 27.4 ml 65% and urea 14 g by mixing the compounds in the above order and adding 2.8 g water. The mixture was stirred for 10 min, after which 500 ml of acetone was added. The resulting precipitate was filtered and washed twice with acetone.

The double salt had a purity of 85% and, based on an X-ray diffraction pattern, contained as its main impurity the urea adduct of calcium 15 nitrate, the solubility of the Ca (NO 3) 2 4 CO (NH 2) 2 · salt in water was 11.5% and 2.3%.

The thermal stability and moisture resistance of the salt were compared with those of calcium nitrate. Based on its analysis by thermogravimetry-20, the salt was completely stable in air up to 150 ° C, while calcium nitrate melts as early as 42 ° C and forms a solution with its own crystalline waters. According to fridge measurements at 25 ° C and 80% relative humidity: 6 the weight change of salt after 6 h was 3.9%. The side component of the synthesis, with <25 components, Ca (NO3) 2'4CO (NH2) 2 'Ha had the same critical critical humidity <* t c as the actual product salt.

Ca (H 2 PO 4) (NO 3) 'CO (NH 2) 2 67-69% at 25 ° C, while calcium nitrate it is clearly lower 50-47% at 25-30 ° C.

30 «1 ·. * · '* This example demonstrates that the physical properties of the salt produced by this method are significantly better; than with calcium nitrate and the salt can be used as a solution «-«. ·· *. wax stock solution as starting material. 1 • »« · · • «· * • • • • • • • • •

Claims (9)

12 106712 Chlorine-free stock solution containing at least calcium, phosphorus and nitrogen for preparing a fertilizer solution, characterized in that said stock solution is prepared by dissolving a crystalline salt which is predominantly urea-calcium phosphate nitrate, Ca (H2PO4) (NO3) 'CO. (NH 2) 2, in water to form an acidic solution of up to 12%. 10 Stock solution according to claim 1, characterized in that it has a calcium content of 1.5% or more while its phosphorus content, P2O5, is 2.4% or more. 15 Stock solution according to claim 1 or 2, characterized in that said stock solution preferably has a concentration of urea-calcium phosphate nitrate salt of up to 10%. 20 Stock solution according to one of claims 1 to 3, characterized in that it contains insoluble compounds: less than 2.5%. . 25 Stock solution according to claim 4, characterized in that the insoluble compounds have a particle size of more than 95% smaller than 50 µm. A stock solution according to any one of claims 1 to 5, characterized in that said solution is made into a 0.01% dilution for use in irrigation fertilization. Ml • · • · · · · Stock solution according to any one of claims 1 to 6, characterized by «1. ··«. said solution containing one or more * T 35 trace elements. «· ·« · 1 • · · ♦ M 13 106712 Stock solution according to claim 1, characterized in that the salt used for its preparation has a critical relative humidity (CRH) of 65% or more, a water solubility of 10% or more and that the salt is thermally stable at temperatures below 150 ° C. Stock solution according to claim 1, characterized in that the salt used for its preparation has a concentration of urea-calcium phosphate nitrate, Ca (H2PO4) (NO3) 'CO (NH2) urea adduct, Ca (NO 3) 2 4 CO (NH 2) 2, and calcium phosphate, insoluble component, Ca 3 (PO 4) 2. • «« «« «« «i« i «i« i «i« i «i« i «i« i «. · * · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 106712