CS251521B1 - A method of preparing granulated NPK nitrophosphate type fertilizers with enhanced sinter resistance - Google Patents

Abstract

The solution relates to a method of preparing a granulated NPK fertilizer of the nitrophosphate type with increased resistance of the sorted granulate to sintering. Increased resistance to sintering and at the same time increased point strength of the granules is achieved as a result of the appropriate distribution of H3PO4 into individual neutralization stages, whereby before entering the first neutralization stage, such an amount of acid is added that adjusts the molar ratio of CaO: P2O5 to 2.1 to 2.25 and subsequent ammoniating increases the pH above 3. The remaining acid is added in the second neutralization stage, where the pH is adjusted to 5 to 5.8.

Description

The invention relates to a process for preparing a granular NPK fertilizer of the nitrophosphate type with increased sintering resistance of the sorted granulate.

It is well known that most commercially produced granular fertilizers, if not suitably treated, exhibit an undesirable tendency to sinter during storage. In order to reduce, respectively. To suppress this negative effect, the granulate needs to be treated by the addition of finely ground materials with separating effects (materials such as kaolin, bentonite, dolomite, limestone and others) or substances of a hydrophobic nature (mineral and peat oils, aliphatic amines and others).

The resulting surface treatment effect is also dependent on the tendency of the untreated granulate to sinter, reflecting the jelm of the internal physico-chemical structure. The higher this slope, the greater the amount of separation and / or separation. a hydrophobic substance should be used to obtain the desired anti-caking effect. Even the most efficient coating systems cannot reduce the sintering of the fertilizer to an acceptable extent if the untreated granulate has too high a tendency to sinter during storage.

Accordingly, it is desirable that the untreated granulate has a sintering below a defined limit value, which will be different for each fertilizer type and type as well as for each coating system.

When evaluating the sintering of the nitrophosphate NPK containing 10-14 wt. % nitrogen, 18 to 22 wt. % total phosphorus pentoxide, 10 to 14 wt. % water-soluble phosphorus pentoxide and 18 to 22 wt. Potassium oxide, in the production of which the content of water-soluble phosphorus pentoxide in fertilizers is regulated by changing the ratio of phosphoric acid: phosphate. fractions 1 to 4 mm.

With a granulate of this quality, one of the most efficient fatty amine-based coatings (3 kg of 10% fatty amine solution in mineral oil per tonne of fertilizer) can reduce the crease rate of ipod 150 N, which corresponds to an approximate granular flow rate after three months storage according to CSN 65 4925 at the first level of quality. Such a level cannot be reached if the sinter value of the untreated granulate exceeds the above-mentioned limit of 320 N.

In the nitrophosphate process, for the preparation of NPK, ground phosphate is decomposed in excess of 50 to 60% nitric acid). PhosphateOm provides only a minor portion of phosphorus pentoxide in fertilizer. The main source is phosphoric acid, which is added to the process most often at the point of entry into the neutralization node, where it is mixed with the acid decomposition product of phosphate. In several stage neutralization systems, phosphoric acid is separated into. individual reactor linkages for optimal ammonia utilization (U.S. Pat. No. 3,130,039). In order to achieve at least 50% of the water-soluble phosphorus pentoxide in the product, it is necessary that the amount of phosphorus pentoxide from phosphoric acid be min. 2.3 times the same phosphate component. In the next step, the gavage-neutralized NP of the buckskin is adjusted to the desired fertilizer composition by adding potassium salt. After granulation, drying, sorting and surface treatment, a granular NPK fertilizer is obtained.

A disadvantage of the known processes for the preparation of nitrophosphate NPK fertilizers with a content of 10 to 14 wt. % nitrogen, 18 to 22 wt. % Phosphorus pentoxide, 10 to 14 wt. % water-soluble phosphorus pentoxide and 18 to 22 perfcent wt. potassium oxide is that the untreated surface granulate has a high tendency to sinter (up to 700 N).

For the purposes of the present invention, it was golden that in the case of aik, only an amount of phosphoric acid was added to the decomposition mixture prior to non-centralization to adjust the molar ratio of calcium oxide: phosphorus pentoxide in the mixture after decomposition of apatite to 2.15 to 2.25. by addition to a pH greater than 3, and the remaining amount of acid is added to the mixture in the next neutralization step with a final addition to a pH of 5 to 5.8. After addition of the potassium salt, granulation and drying, a granulate is obtained which, after tracing to at least 95% of the 1 to 4 mm fraction, achieves a sintering according to ISO 120 to 280 N, which is significantly lower than the granulates obtained according to known processes.

A further advantage of this process is that a granulate with a higher point strength (30-40 N vs. 20-30 N) is obtained and the mixture during ammonia has a better tclk due to the complete and irreversible transition of calcium in the first neutralization step to dicalcium phosphate and salt system in the product.

The essence of the proposed solution of the process for the preparation of granular NPK fertilizers of nitrophosphate type with increased resistance to sintering, containing 10 to 14 wt. 18 to 22 wt. % phosphorus pentoxide, 10 to 14 wt. % water-soluble phosphorus pentoxide and 18 to 22 wt. is to add to the mixture after apatite decomposition with 50 to 60% nitric acid before neutralization, an amount of 50 to 55% phosphoric acid which adjusts the molar ratio of calcium oxide: phosphorus pentoxide to 2.1 to 2.25 followed by the addition of the mixture to a pH greater than 3 and the remaining phosphoric acid added in the next neutralization step, the resulting mixture being adjusted to a pH of 5 to 5.8 with gaseous ammonia.

Examples:

Example 1 The example corresponds to the poodle process of the present invention. While stirring in a glass vessel, 1,320 grams of finely ground Apatite Wheel containing 39.5 wt. phosphorus pentoxide by adding 3,375 g of 60% nitric acid at 70 ° C for 60 minutes. 500 g of phosphoric acid with a content of 52.5% by weight were added to the obtained mixture. % phosphorus pentoxide, 3.5 wt. % sulfuric acid, 1.1 wt. % fluorine and 3.6 wt. iron, aluminum and magnesium.

The mixture with a molar ratio of calcium oxide: phosphorus pentoxide - 2.24 was treated with gaseous ammonia at 110 to 120 ° C to pH 3.7 and thus treated contained 8.3% by weight. % ammoniacal nitrogen, 14.6 wt. % phosphorus pentoxide and 12.8 wt. calcium oxide.

To the partially neutralized mixture was added 2,264 g of phosphoric acid of the above-mentioned quartz, while ammonia was added at 120-130 ° C to pH 5.7. The resulting m-molar calcium oxide: phosphorus pentoxide = 0.88 mixture contained 12.3 wt. % water, 10.6 wt. nitrogen ammonia, 15.2 wt. % water-soluble phosphorus pentoxide and 0.2 wt. water-soluble calcium oxide. To this NP of slurry was added, with stirring and heating at 130 degrees C, 3,340 g of a drastic room containing 59 wt. potassium oxide.

A portion of the formed NPK slurry after drying in a thin layer and after coarse crushing was dried to a water content of 1.2% by weight. The obtained pulp was used as granulation bed for granulation of the remaining NPK slurry in a 1-aborafore screw granulator at a rate of 2.5 µg pulp per 1 kg of anhydrous slurry.

The granulation at 90 ° C yielded a wet granulate with a content of 3.4% by weight. water, which was reduced to 1.2 wt. The dried granulate yielded a product containing 98.1 wt. fraction 1 to 4 mm, 12 wt. nitrogen, 20.1% w / w; % phosphorus pentoxide, 11.05 wt. % water-soluble phosphorus pentoxide and 19.90 wt. potassium oxide.

From 6 reproduction experiments, the sintering of the sieved granulate according to the ISO method was determined. These fluctuated in the range 126 to 231 N. The point strength of the granules was 29.5 to 41.8 N at an average of 34.3 N. Example 2

The procedure of Example 1 except that the ammonia in the first stage was led to an ipH of 2.3. The average sinter of the dried and screened granulate (1.15% water, 98.4% fractions 1 to 4 mmj) reached 393 N, the average point strength of the granules was 28.3 N.

Example 3

The procedure as in Example 1, but the entire volume of phosphoric acid was added to the basic mixture before the first stage of ammonia and at this stage the mixture was ammonia to pH 2.3. The average sintering of the sorted and dried granulate reached 436 N and the average point strength of the granules was 26.1 N.

Claims (3)

EXAMPLES Example 1 'Example corresponding to the method of the present invention. 320 grams of finely divided apatite round, containing 39.5 wt%, was continuously disintegrated under continuous stirring in a glass vessel. phosphorus pentoxide by the addition of 3,375 g of 60% acidic acid at 70 ° C for 60 minutes. To the resulting mixture was added 500 g of phosphoric acid extraction acid containing 52.5% by weight. phosphorus pentoxide, 3.5% by weight. % sulfuric acid, 1.1 wt. % fluorine and 3.6 wt. iron oxide, aluminum oxide and magnesium oxide. The mixture with the molar ratio of calcium oxide: phosphorus pentoxide - 2.24 was adjusted to a pH of 3.7 by gasification of ammonia at 110-120 ° C and thus treated with 8.3% by weight. % of ammonia nitrogen, 14.6% phosphorous oxide and 12.8% w / w. of calcium oxide. To the time of the neutralized mixture, 2 264 g of phosphoric acid of the aforementioned quality was added, with simultaneous ammonia addition at 120 to 130 ° C to pH 5.7. The resulting calcium oxide / phosphorus pentoxide molar ratio = 0.88 contained 12.3 wt. % water, 10.6 wt. nitrogen ammonia, 15.2 wt. water soluble phosphorus oxide and 0.2 wt. calcium sulphate oxide. To this NP slurry was added, with stirring and heating at 130 degrees C, 3,340 g of a drastic salt containing 59% by weight. of potassium oxide. The resulting NPK slurries after drying the coating layer and after coarse crushing were reached to a water content of 1.2% by weight. The pulp obtained was used as a granulation bed for the granulation of the remaining NPK slurry in a screw la-boron granulator at a ratio of 2.5 kg / liter to 1 kg of anhydrous slurry. Granulation at 90 ° C gave a wet granulate containing 3.4% by weight. % of water, which was dried to 1.2 wt. From the dried granulate, a product with a content of 98.1% by weight was obtained. fractions of 1 to 4 mm, 12 wt. % nitrogen, 20.1% wt. phosphorus oxide, 11.05 wt. water-soluble phosphorus pentoxide and 19.90 wt. oxidase. From 6 reproduction experiments, the sizing of the sorted granulate was determined according to the ISO method. These varied between 126 and 231 N. The point strength of the granules reached 29.5 to 41.8 N at a diameter of 34.3 N. Example 2 A procedure similar to Example 1, only the ammonia in the first stage was fed to ipH 2.3. The average dried and sorted granulate (1.15% water, 98.4% fraction 1 to 4 mm) reached 393 N , average point strength of granules 28.3 N. Example 3 The procedure of the alcohol in Example 1, but the entire phosphoric acid volume) was added to the decomposition mixture before the first stage of ammonia and in this step the mixture was saponified to pH2.3. The average particle size of the dried and dried granules reached 436 N and the average point strength of the granules was 26.1 N. The process for preparing granular NPK nitro-phosphate-type fertilizers with increased sintering strength when stored at 10-14% by weight. % nitrogen, 18-2.2 wt. % total phosphorus pentoxide, 10 to 14 wt. % water-soluble oxidophosphorus and 18-22 wt. characterized in that 50 to 55% by weight of phosphoric acid is added to the mixture after the apatite 50 to 60% by weight of the acid of the invention is neutralized to a molar ratio of lime: oxide phosphorous 2.1 to 2.25, followed by addition of the mixture to pH 3, and the remaining phosphoric acid is added to the next neutralization step, with the resulting mixture being adjusted to a pH of 5 to 5.8 with ammonia gas.