CS251775B2 - Process for producing feed phosphates - Google Patents

Abstract

The solution relates to a method for producing feed phosphates from raw phosphates, trivalent superphosphates or products containing both of these components, in which these are ground together with sodium carbonate or sodium chloride or a mixture consisting of sodium carbonate and quartz sand or sodium carbonate, sodium chloride and quartz sand, to a grain size of maximum 100 >um and briquetted, the mixture obtained is thermally treated at a temperature of 1,450 °C, traces of fluorine are removed using nitrogen or gaseous carbon dioxide, the melt is cooled with water and compressed air and granulated and the granulate is dried to a residual moisture of maximum 5% by weight, the essence of which consists in the granulate being ground wet to a grain size of maximum 200 /um and simultaneously decomposed with phosphoric acid or a mixture of phosphoric acid and sulfuric acid, in an amount of 4 to 35% wt., calculated per product.

Description

The invention relates to a process for producing feed phosphates from crude phosphates or trivalent superphosphates or a mixture of crude phosphates and trivalent superphosphates. The invention makes it possible to produce phosphate compounds which have a low fluorine content and which can be easily recovered by the animals.

The starting material for the feed phosphates produced by the chemical industry and used on the farm is raw phosphate or apatite, which can be decomposed and de-fluorinated. Phosphate compounds used as feed are produced synthetically. After decomposition, phosphoric acid is formed which is freed from fluorine and neutralized.

The decomposition of the crude phosphate can be carried out by heating, wherein the starting material is treated with sodium carbonate Na ₂ CO ₂ or sodium sulfate Na 2 SO 4 or other alkaline decomposition agents. The alkali phosphates obtained are basic compounds, well soluble in water and citric acid, which are not suitable for direct use as feed phosphate.

Thermal decomposition of the crude phosphate is described in Hungarian patent 157,735. The decomposition is carried out with aqueous alkali metal hydroxide and solid alkali metal carbonate at a temperature of 1000 to 1300 ° C. The end product has a high fluorine content and is therefore harmful to animals. The phosphate compounds present in the final product cannot be recovered by the animals and can therefore only be used as fertilizer.

Improvement of the thermal decomposition of the raw phosphates is described in Hungarian patent specification 175 314. Here, after thermal decomposition, it is cooled by compressed air and water and granulated to obtain a fine-grained product of consistent quality. The final product has a high fluorine content and contains a silicon compound of the formula 3 CaO.P ₂ O ₅ .2Mg0.SiO ₂ · This product also cannot be used by animals and can only be used as fertilizer.

Hungarian patent 170 710 describes a process for decomposing crude phosphate for the production of feed additives. According to this method, the starting material is chemically fluorinated by means of additives such as sodium carbonate and is simultaneously converted to calcium orthophosphate by a one-stage chemical and thermal decomposition.

The end product contains a fluorine fraction below 0.3% by weight, on average 0.2% by weight. For this purpose, a pre-product with a SiO ₂ content below 2 wt. and thermal decomposition is carried out at a high temperature, practically at a temperature between 1420 to 1550 ° C. However, the defluorisation efficiency of the end product is still not sufficient and the proportion of fluorine in the end product varies depending on the composition of the starting material in the range of 0.15 to 0.25% by weight. In order to improve the quality of the final product, this range should be reduced.

The decomposition producing phosphoric acid and thermal decomposition have the drawback that, although the end product is to be used as feed, the usable fraction of P ₂ O 5 is not sufficiently high and the quality of the end product is not sufficiently stable.

The object of the invention is to provide an improved process for producing phosphate compound, wherein the content kysličníku'fosforečného P ₂ ° 5 ^{°, and} t ^the hexafluorophosphate is present in a form that animals could utilize well, the proportion of fluorine would remain below 0.35 4 wt. , and for which the requirement of potassium and calcium could also be met.

Accordingly, the present invention relates to a process for the manufacture of feed phosphates from crude phosphates, trivalent superphosphates or a product comprising both of said components, wherein these together with sodium carbonate, sodium chloride or a mixture consisting of sodium carbonate and quartz sand or sodium carbonate, sodium chloride and quartz sand is ground to a maximum of 100 µm and briquetted, the resulting mixture is heat treated at 1450 ° C, de-fluorinated with nitrogen or carbon dioxide, cooled with water and compressed air, and granulated and dried to a residual granulate Moisture maximum 5 4 wt., whose essence consists in the fact that the granulate is wet grinded up to grain maximum

200 .mu.m and at the same time decomposes 4 to. 35 wt. phosphoric acid or mixtures of phosphoric acid and sulfuric acid, calculated on the product.

To carry out the process according to the invention, the crude phosphates, such as Moroccan black or white phosphate and / or trivalent superphosphates, used as starting material, are ground with co-additives which are devoid of fluorine, after which the mixture obtained is homogenized.

Sodium carbonate or sodium chloride or a mixture of sodium carbonate with sodium chloride or mixtures thereof with quartz sand may be used as additives. The grinding is carried out up to a grain size of at least 100 µm. The ratio of additive to phosphorus-containing substances in the grinding fluid is between 0.1 to 0.25: 1 to 1.1.

The grinding agent can optionally be briquetted in a known manner with 0.3 to 1 wt. methyl silicate as a binder. The moisture content of the briquette is adjusted to 2 to 3% by weight. Briquetting serves to reduce dustiness.

The next step is to melt, for example in an arc furnace at a temperature of between 1000 to 1450 ° C. Nitrogen or carbon dioxide gas is blown into the liquid mixture to remove fluorine-containing gases.

The liquid melt is cooled in a granulator with water and compressed air at a rate of 350 ° C / sec and granulated. The granulate, which has an average grain size of 1 to 6 mm, is wet-ground while being decomposed with phosphoric acid or a mixture of phosphoric acid and sulfuric acid.

The amount of phosphoric acid or a mixture of phosphoric acid and sulfuric acid is 4 to 35% by weight, based on the amount of product. The grain of the product is a maximum of 200 / l. The addition of acid reduces the pH of the granulate from 8 to 9 to a pH of 5 to 6.

The product is air dried at a maximum temperature of 100 ° C to a residual moisture content of less than 5% by weight.

The final product obtained has a fluorine content of less than 0.15% by weight. The proportion of the total phosphorus pentoxide content (P2 O5) soluble in citric acid is 94 to 99.8% by weight. The final product is fine-grained and of consistent quality.

The process according to the invention makes it possible to produce feed phosphates which can be better utilized by the animals and which, in addition to constant quality, also have a low fluorine content, since the co-milling and homogenization of the starting material and the additives greatly increase the defluorisation efficiency.

The fluorine-containing gases are removed during thermal decomposition by blowing nitrogen or carbon dioxide gas.

The advantages of this method, compared to the known method using water vapor, consist in eliminating the risk of explosion and hydration of the fluorine compounds, which makes it easy to purify mixtures containing fluorine compounds.

After thermal decomposition, chemical decomposition is carried out concomitantly with wet grinding, which leads to an increase in decomposition efficiency and thus to a usable fraction of phosphorus pentoxide. The coupling of the chemical decomposition to wet grinding ensures a consistent quality.

The process according to the invention is further illustrated by the following examples.

Example 1

Production of feed phosphates from trivalent superphosphates (TSP)

The mill is charged with 75 kg of trivalent superphosphate, 10 kg of sodium carbonate and 15 kg of sodium chloride. This mixture is ground to a particle size of 80-100 µm and homogenized.

The homogeneous mixture is melted at 1450 ° C in a low-voltage three-phase arc furnace, and nitrogen (3 x 10 1 / min) is injected through the electrodes to remove fluorine-containing gases. The liquid melt is cooled in the granulator with water and compressed air at a rate of 350 ° C / sec. The granulate, which has a grain size of 1 to 4 mm, is ground in a ball mill up to a grain size below 200 µm.

and

To reduce the pH of the grinder from 8 to 9 to a pH of 5 to 6, phosphoric acid and sulfuric acid are added to the water used for grinding. This requires, by weight of the product,% by weight. % phosphoric acid H 2 PO 4 and 1 wt. sulfuric acid H 2 SO 4.

The product obtained is air-dried at a temperature below 100 ° C to a residual moisture content of 5% by weight.

Composition of superphosphate (TSP) used as starting material:

CaO: 20.5%, P ₂ O ₅ : 48.5 4, SiC> ₂ : 3.3 4, Fe ₂ O ₃ : 2.4 4, MgO: 0.38 4, Na ₂ O: 0.53 4,

F: 1.2 4, humidity: 3.5 i

Composition of the final product (weight 93 kg):

CaO: 15.1 4, P ₂ O ₅ : 39.7%, SiO ₂ : 3.2 4, Fe ₂ O ₃ : 2.2 4, MgO: 0.32%, Na ₂ 0: 13.7 4 ,

F: 0.12%, Pb: 50 ppm, Cu: 10 ppm, As: 1 ppm.

The contained P ₂ O ₅ is 99.2 4 soluble in citric acid.

Example 2

Production of feed phosphates from trivalent superphosphates

75 kg of trivalent superphosphate, 25 kg of sodium carbonate and 2 kg of quartz sand are injected into the mill. This mixture is ground to a particle size of 70-100 µm and homogenized.

The powder obtained is briquetted with 24 methyl methyl silicate as a binding agent. It is then melted at 1450 ° C in a low-voltage three-phase arc furnace, gaseous carbon dioxide being blown over the electrodes to remove the fluorine fraction.

The melt is cooled in the granulator with water and compressed air at a rate of 350 ° C / sec. Granules having an average grain size of 100 to 200 .mu.m and ground. Phosphoric acid is added to the water used for grinding to reduce the pH from 8-9 to a pH of 5-6.

This requires 8% by weight, based on the product. phosphoric acid H 2 PO 4.

The product obtained is pounded with air at a temperature of less than 100 ° C to a residual moisture content of 44 wt.

Composition of superphosphate used as starting material:

CaO: 20.5 4, P ₂ O ₅ : 48.5 4, SiO ₂ : 3.3 4, Fe ₂ O ₃ : 2.4 4, MgO: 0.38 4, Na ₂ O: 0.53 4 ,

F: 1.2 4, humidity: 3.7 4.

Composition of the final product (weight 92 kg):

CaO: 15.3 4, P ₂ O ₅ : 39.7 4, SiO ₂ : 3.1 4, Fe ₂ O ₃ : 2.0 4, MgO: 0.29 4, Na ₂ 0: 14.9 4 ,

Ft 0.14 4, Pb: 50 ppm, Cu: 10 ppm. As: 1 ppm

The phosphorus p ₂ O ₃ contained is 98% soluble in citric acid.

Example 3

Comparative example

The procedure is analogous to Example 2, except that the starting material is mixed with phosphoric acid only at thermal decomposition, nitrogen is not forced into the melt and no wet grinding is performed after thermal decomposition.

The product contained 0.28% fluorine contained phosphorus oxide P ₂ ° 5 L ^ev soluble citric acid of only 90%.

Example 4

Production of superphosphates from a mixture of Moroccan white phosphates and superphosphate (TSP)

65 kg of superphosphate and 15 kg of Moroccan white phosphate, 10 kg of sodium carbonate Na ₂ CO ₃ and 10 kg of sodium chloride are introduced into the mill. This mixture is ground up to a grain size of 80 to 100 µm and homogenized.

The resulting pulverulent mixture is briquetted and then melted in a three-phase arc furnace at low voltage at 1450 ° C, while nitrogen (3 x 10 1 / min) is blown over the electrodes to remove the fluorine fraction.

The liquid melt is cooled in the granulator with water and compressed air at a rate of 350 ° C / sec. The granulate, whose grain diameter is 1 to 4 mm, is ground in a ball mill up to a grain size of 170 to 200 µm. Phosphoric acid and sulfuric acid are added to the water used for grinding to reduce the pH of the grinder from 8 to 9 to a pH of 5 to 6. This requires 5% by weight of the product. % phosphoric acid and 1 wt. of sulfuric acid.

The product obtained is air-dried at a temperature below 100 ° C to a residual moisture content of 3% by weight.

Composition of starting materials:

superphosphate (TSP): CaO 20.5%, P-48.5%, SiO _2: 3.3% Fe. ^: 2.4%, MgO: 0.38%, Na ₂ 0: 0 , 53%, F: 1.2%, humidity: 3.7% Moroccan white phosphate:

CaO: 53.5 i, P ₂ ° 5 ^{! 32.6} * ' ^si0 2 ^{: 4} ' ° ^Fe 2 ° 3 ^{: 0.38 Mg0: 0.3} * ' ^Na 2 ° ^! ° ^'61 *'

F: 2.87%

Composition of the final product (weight: 91 kg):

CaO: 20.9 », P ₂ O ₅ : 39.6%, SiO ₂ : 3.4%, Fe ₂ O ₃ : 2.05%, MgO: 0.3%, Na ₂ 0: 11.8% ,

F: 0.14%, Pb: 50 ppm, Cu: 10 ppm. As: 1 ppm.

Example 5

Production of feed phosphates from a mixture of Moroccan black phosphates and superphosphate (TSP)

The mill was charged with 65 kg of superphosphate and 20 kg of black Moroccan phosphate, 5 kg of sodium carbonate Na ₂ CO _3, 10 kg of NaCl and 0.1 kg of silica sand. These are homogenized except for a grain size of 80 to 100a.

The homogeneous mixture is melted in a three-phase low-voltage arc furnace at 1450 ° C, nitrogen being injected three times, 10 l / min, to remove the fluorine fraction. The liquid melt is cooled in the granulator with water and compressed air at a rate of 350 ° C / sec. The granulate whose particle size has a diameter of 1-4 mm was ground in a ball mill to a particle size of 100 to 200 _/ "m.

9% by weight, based on the product, are added to the water used for the grinding. phosphoric acid, whereby the pH of the grist falls from 8 to 9 to a pH of 5 to 6.

The product obtained is air-dried at a temperature below 100 ° C to a residual moisture content of 5% by weight.

Composition of starting materials:

superphosphate (TSP): CaO: 20.5 4, P ₂ ° 5 ^{! 48.5} * ' ^si0 2 ^{: 3.3} *' ^Fe 2 ° 3 ^{! 2.4} * ^{MgO 3 0.38} Na ₂ 0: 0.53 4, F: 1.2 4, humidity: 3.7 4.

moroccan black phosphate:

CaO: 50.5 4, P ₂ ° 5 ^{: 31.2 SiO} 2 ^{! 4.0 Fe} 2 ° 3 ^{! 0.94 MgO 3 0.33} * ^Na 2 ^O 1 ^1.11

C0 ₂ : 5.9 4, SO ₃ : 4.5%

Composition of the finished product (weight 90 kg):

CaO: 25.9 4, P ₂ O ₃ : 42.3 4, SiO ₂ : 3.0 4, Fe ₂ O ₃ : 1.9%, MgO: 0.28 4, Na ₂ O: 9.8 4,

F: 0.14 P, Pb: 50 ppm, Cu: 10 ppm, As: 1 ppm.

The phosphorus p ₂ O 5 contained is 98% soluble in citric acid.

Example 6

Production of feed phosphates from Moroccan black phosphate

The mill is charged with 80 kg of Moroccan black phosphate, 5 kg of Na ₂ CO ₃ -carbonate, kg of NaCl and 4 kg of silica. This mixture is ground up to a grain size of 80-100 µm and homogenized.

The homogeneous mixture was melted in a low-voltage three-phase arc furnace at 1450 ° C, dry carbon dioxide gas (12 L / min) was blown three times to remove the fluorine fraction. The liquid melt is cooled in the granulator with water and compressed air at a rate of 350 ° C / sec. The granulate having a grain diameter of 1 to 4 mm is ground in a ball mill up to a grain size of 170 to 200 µm.

28% by weight, based on the product, are added to the water used for grinding. phosphoric acid, wherein the pH of the grinder is reduced from 8 to 9 to a pH of 5 to 6.

The product obtained is air-dried at a temperature below 100 ° C to a residual moisture content of 4% by weight.

Composition of Moroccan black phosphate:

CaO: 50.5 4, P ₂ O ₅ : 31.2 4, SiO 2: 4.0 4, Fe ₂ O ₃ : 0.94 4, MgO: 0.33 4, Na ₂ 0: 1.11 4, CO ₂ : 5.9 4, SO ₃ : 4.5 4

Composition of the final product (weight: 104 kg):

CaO: 36.7 4, P ₂ O ₅ : 41.8 4, SiO ₂ : 6.1.1, Fe ₂ O ₃ : 0.8 4, MgO: 0.25 4, Na ₂ O: 7.5 4 F: F: 0.14 4, Pb: 50 ppm, Cu: 10 ppm, As: 1 ppm.

and

The phosphorus pentoxide contained is 99.2% soluble in citric acid.

Claims (1)

Process for the manufacture of feed phosphates from crude phosphates, trivalent superphosphates or a product containing both components, which is ground together with sodium carbonate, sodium chloride or a mixture consisting of sodium carbonate and quartz sand or sodium carbonate, sodium chloride and quartz sand up to 100 µm and briquetting, the mixture is heat treated at 1450 ° C, de-fluorine is removed with nitrogen or carbon dioxide gas, the melt is cooled with water and compressed air and granulated and the granulate dried to a maximum residual moisture content Characterized in that the granulate is wet milled to a maximum grain size of 200 .mu.m and simultaneously decomposed with phosphoric acid or a mixture of phosphoric acid and sulfuric acid in an amount of 4 to 35% by weight, calculated per product.