DE2263334C3 - Process for the production of granulated PK-Dfingmittel from Thomas phosphate and potash salt - Google Patents

Description

^30th

PK fertilizers are increasingly used to supply the soil and plants with phosphoric acid and potash. Thomas phosphate has proven to be a particularly suitable P ₂ O ₅ form, since this is easily absorbed by the plant roots _{as citric acid-soluble P 2} O _5.

According to Gicke (Analytical Chemistry of Fertilizers, Enke-Verlag, 1949, p. 28), Thomas phosphate contains 15 to 20% citric acid-soluble P ₂ O ₅ . At these P ₂ O ₅ contents, products containing 10% citric acid soluble in P ₂ O ₅ and 20% K ₂ O, e.g. B. from chloride potash fertilizer salt. A granulate of the brand 10/20 has the following composition according to DT-PS 973396:

5.75 t Thomas phosphate (15.6% P ₂ O ₅ ) 3.31 t potassium chloride (54.4% K ₂ O)

with a grain size of 0.5 to 4 mm.

These granules were produced by built-up granulation after moistening with 8 to 12% water. If the soil has a good P ₂ O ₅ supply, a narrowing of the P ₂ O ₅ : K ₂ O ratio is important in practice.

This ratio of z. B. P ₂ O ₅ : K ₂ O = 12:18 cannot be adjusted to up to 60% K _{2 O by increasing the K 2 O content.} So z. B. a mixture of 35 parts by weight of potash fertilizer salt and 65 parts by weight of Thomas phosphate with 17% citric acid soluble in P ₂ O ₅ only the mark 11/20.

The German patent specification 12 42 644 teaches Preßgranulicrung with 2 to 4% moisture using water-soluble P ₂ O ₅ from superphosphate or triple phosphate. According to this process, water-soluble P ₂ O ₅ cannot react with Thomas phosphate because a moisture content of "2 to 4%" is set. Such fertilizers thus contain water-soluble P ₂ O ₅ , which is precisely not contained in the PK mixed fertilizer according to the invention.

The proposal of the German Auslegeschrift 17 92 for the production of a PK fertilizer with a graduated nutrient ratio P ₂ O ₅ : K ₂ O of about 12 to 18:20 relates to Thomas phosphate with triple superphosphate or with phosphoric acid in the presence

, To convert K-ilidiinscsalz and with water or from Kaliduny-su * _{D bd} " _{bci one end} .

Saline solution ^^ ^X ^ f ^ _Kh implementation of P ₃ O, temperature of P ₁ O which is _{soluble in water above VU,}

Kon.ponen en e, n Re geh _rrejchi ^^ _q

¹⁰¹ Se call also with a stepped rlriltnis P ₁ O ₅ -K, 0 of about 12 to 16:22 ffÄÄ, in such a PK-Düngemi, - ^ n ie the content of free lime with wasserö loan phosphates or phosphoric acid is abgesattigt. In this process, precise technological conditions must be adhered to in order to achieve the low residual content of water-soluble P ₂ O ₅ . On the other hand, according to the worship of the invention, a PK fertilizer egg is produced which does not contain any water-soluble PO ₅ . .

The method of the invention takes a different approach to setting graded nutrient behavior. POKO in PK fertilizers with Thomas phosphate, changing dicalcium phosphate with Thomas phosphate "with ntf-r 16% ctrsl P, 0 ₅ " is combined. The prejudice of technology against dicalcium phosphate H ₈ in the uptake of water including the rehabilitated return material. It is surprising that the return material is practically not hydrated and therefore this water does not have to be evaporated as well.

A process has now been developed for the production of granulated PK fertilizers from Thomas phosphate and kale fertilizer salt with a citric acid-free P ₂ O ₅ content of more than 10% with a K ₂ O content of more than Ϊ5 to 24% while setting a nutrient ratio between 12: 24 to 18:18 found, which is characterized in that the Thomas phosphate with a citric acid soluble P ^ content of less than 16% with dicalcium phosphate anhydrate up to dicalcium phosphate dihydrate and the Kal.dungesalz miί a Κ, Ο content of 50 to 60% with the addition of return material in the form of Fe.ngut or crushed material mixed with moistening, briefly subjected to pre-granulation, then further granulated, calcined and dried at such a temperature that the content of water of hydration _{in the} Gutlinmnrnktisch goes to zero.
^k0 Se ^P Be £ uchui of the return material with content of completely or partially calcined dihydrate can be separated from the moistening of the feed and this can only then be mixed with the moistened feed. The Vorgranulat.on can be carried out in 3 to 5 minutes. Thomas phosphate with a content of between about 12 to 16 Å citric acid-soluble P ₂ O ₅ can be used and dicalcium phosphate with a statistical content of 0.5 to 1.5% water of crystallization can be used. Chloride or sulfate kahdungesalz with about 50 to 55% K ₂ O can be used and dilute to practically cold-saturated solutions of inorganic salts, in particular solutions of MgCl ₂ , MgSO ₄ , Ca (NO _{3 I 2} or solid inorganic salts, such as finely ground gravel ent (MgSO ₄ · H ₂ O) or calcined gravel (MgSO ₄ ) can be used.

In addition, granulating screws or granulating plates can be used to pre-granulate the material to be mixed. The good grain can be sieved to a grain size of about 0.5 to 3.5 mm, and hydroxylapatitic rock phosphate with ame.sensaurelöslicher P ₂ O ₅ as P ₂ O ₅ component can be used instead of a partial amount of Thomas phosphate.

⁴⁵

The method of the invention is, for example described as follows:

example 1

Type P ₂ O ₅ : K, O = 12:18 Thomas phosphate (1
1 3.2 % citric acid soluble (ells.) P ₂ O ₅ ,

Diculcium phosphute monohydrate (2) (CaI IPO ₄
with 45% citric acid soluble (ctls.) P ₂ O ₅ ,

Chloride potash fertilizer salt (3) with 58% K ₁ O

Starting product

With

I ₂ O)

2
3
Return goods

610

88

310

30Ü

1308

The starting products (1-3) are mixed with the fine and the comminuted return material with moistening in a compulsory mixer (Lödige) and pregranulated about 6mir in a twin-screw mixer, then further granulated, calcined and dried in a rotary kiln with direct heating. The granules at the outlet of the dryer, a Gutstemperatur of 150 ⁰ C. It is evaporated 8 kg water of hydration in addition to the granulating water. The granulate is sieved to a grain size of 0.5-3.5 mm, the fine material is combined with the comminuted oversize grain and returned to the feed material.

Example 2

Type P ₂ O ₅ : K, O = 12.5: 20 Thomas phosphate (1) with 13.2% CtSLP ₂ O ₅ ,

CaHPO ₄ -H ₂ O (2) with 45% ctsl. P ₂ O ₅ ,
Chloride potash fertilizer salt (3) with 58% K ₁ O

Starting product

kg

1 550 2 117 3 345 Return goods 340

1352

Abandonment gul kg 1 530 2 178 3 310

1018

The moistened mixture (1-3) is the separately ίο illuminated return goods of 470 kg according to the Weight ratio 1: 0.47 admixed. The further processing takes place according to Example 2. In the calcination 18 kg of water of hydration are evaporated in addition to the granules.

To increase the yield of good grain from 0.8 to 3.5 mm, a MgSO ₄ solution which is cold-saturated at room temperature is used as the granulating liquid in an amount of 2 percent by weight of MgSO ₄ , calculated on the granulating material.

Example 4

Type P, Os: K ₁ O = 16:18 Thomas phosphate (1) with 15.5% ctsl.>, 0 ₅ ,
CaHPO ₄ -H ₁ O (2) with 45% ctsl. P ₂ O ₅ ,

Chloride potash fertilizer salt (3) with 60% K ₁ O

Output

552

166

300

1018

The moistening and pre-granulation takes place according to Example 2, then further granulation is carried out on a plate granulator using a Ca (NO ₃ ) ₂ solution with about 1% Ca (NOj) ₂ , calculated on the granulated material, in about 4 minutes. The moist granulate is then further granulated in a roller drum to increase the yield and then calcined and dried in a drying drum with evaporation of 18 kg of the water of hydration and the water of granulation. The outlet temperature is about 108 ° C. Finished granules of 1: 3.5 mm are sieved off. The fine and the comminuted return material is mixed with the feed material after the separate moistening.

The dry starting product (1 -3) and the calcined return material are moistened separately in the compulsory mixer, thereby shortening the pre-granulation time to about 3 minutes, then the combined feed material is further granulated and calcined in the rotary kiln, with 12 kg of water of hydration in addition to the granulating water evaporated, dried and the expiring at 110 ⁰ C to the granulate grain size of 1 - 3.5 mm sieved product particles. 340 kg of returned goods are mixed with the input goods as fine goods in accordance with the ratio of input goods: return goods such as 1: 0.34.

Example 3

Type P ₂ O ₅ : K ₂ O = 15:18 Thomas phosphate (1) with _{13.2% CtSLP 2} O ₅ ,

CaHPO ₄ -H ₂ O (2) with 45% ctsl.P ₂ O ₅ , sulphatic potassium salt with 58% K ₂ O (3)

Example 5

Type PiO ₅ : K ₂ O = 18:18 Thomas phosphate (1)
15.5% CIsLP ₂ O ,,

CaHPO ₄ -H ₂ O with 45% ctsl. P ₂ O ₅ ,
Chloride potash fertilizer salt (3) with 60% K ₂ O

Feed kg 1 494 2 230 3 300 1024 Return goods 780

1804
Ratio of feed material: return material = 1: 0.78

The process of the invention is carried out according to Example 2.

During calcination ,? A kg of water of hydration from the Ca! I PO., 11.0 evaporates on 1000 kg of granulated material.

As a binding agent, 1% finely ground, calcined kieserite (MgSO ₄ ) is added to the mix when it is moistened with water to increase the granulate yield.

The method of the invention offers the possibility with Thomas phosphate with a content below 16% ctsl. PIOs and optionally hydroxyiapatitisches with a subset of rock phosphate with ameisensäurelöslichem P ₂ O ₅ instead of slag with dicalcium phosphate Anhydril with a statistical content of hydrate water up to dihydrate without Absiittigung the content of free CaO of Thomas phosphate in conjunction with Kalidüngesalzen an approaching Nährsloffverhältnis P ₂ O ₅ : K ₂ O to be set between about 12:24 and 18:18, e.g. B.

12:18 (example 1) or from 18:18 (example S).

The technological driving conditions are in not limited to the nutrient forms.

According to the method of the invention takes place with the calcined return material when mixed with the In the case of moistened feed material, surprisingly, practically no hydration with dci granulating liquid took place. Through this technical effect makes it possible to carry out the method of the invention without any significant Quantities of dampening water are bound as water of hydration before granulating the mixture the substances takes place that would have to be removed again during drying.

The method of the invention thus offers the possibility for the production of PK fertilizers with Thomas phosphate _{to be able to process batches with low contents of Ctsl.P 2} Os, which up to now could not be used for such PK fertilizers.

Claims (1)

Claim: Process for the production of granulated PK fertilizers from Thomas phosphate and potash fertilizer _{salt with a citric acid-soluble P 2} O content of over 10% with a K ₂ O content of over 12 to 24% while setting a nutrient ratio between 12:24 and 18:18, thereby characterized that the Thomas phosphate with a citric acid-soluble Ρ, Ο, -Gehali of less than 16% with dicalcium phosphate anhydrite to dicalcium phosphate dihydrate and the _{potassium fertilizer salt with a K 2} O-GeIwIt of 50 to 607n with the addition of return material in the form of fine material or The comminuted material is mixed with moistening, briefly subjected to the pre-granulation ion, then further granulated, calcined and dried at such a temperature that the content of water of hydration in the material grain is practically zero.