PL73598B2 - - Google Patents

Description

Priority: Application announced: May 10, 1973 Patent description was published: April 15, 1975 73598 KI. 16b, 1/02 MKP C05c 1/02 READING ROOM [I PateflfOwe Office "Inventor: Jan Turlej Entitled to the provisional patent: Zakłady Azotowe named after F. Dzierzynski, Tarnów (Poland) Method of preventing caking of mineral fertilizers The subject of the invention is a method preventing caking of fertilizers, especially those containing ammonium nitrate, by coating their granules. The tendency to caking manifests itself initially in the disappearance of the first granular flowability of the fertilizer, and then in the spontaneous agglomeration of the granules into hard-to-crush lumps, which consolidates with time. This tendency results from the ease of dissolution of ammonium nitrate in water adsorbed from the air. Low mechanical strength of the granules and the transformation of the crystalline form of ammonium nitrate occurring when the temperature exceeds 32.2 ° C, combined with a change in the volume of the granules, causing their disintegration to grains and dust, which is equal to the development of the surface. As a result, the amount of adsorption the desired moisture and the amount of ammonium nitrate solution covering and joining the adjacent grains of the fertilizer. These connections, as a result of the crystallization of a saturated solution, are then fixed. To reduce caking of fertilizers, stabilizing additives are used, whose task is to increase the mechanical strength of the granules and reduce the susceptibility to the transfer of ammonium nitrate from one crystalline form to another, and agents for coating the granules of the counterpart The known methods of preventing caking include the addition of aluminum, calcium, ammonium sulfates, potassium and magnesium nitrates, mixtures of boron compounds with ammonium phosphate and ammonium sulfate to the ammonium nitrate solution, and sprinkling the cooled granules with detergents and powdering limestone, dolomite, gypsum, bentonite, diatomaceous earth, etc. Powdering with these agents only slightly prevents agglomeration. This applies in particular to limestone, dolomite and gypsum due to the reactivity of these substances with ammonium nitrate and a low adhesion to the granules, as well as the ease of segregation during transport of the fertilizer, especially when the flour used contained less than 90% of particles with a smaller diameter The aim of the invention is to provide a more effective method than the above-mentioned methods of preventing the caking of fertilizers. This aim is achieved by the use of powdering the granules or grains of the fertilizer with dried and ground phosphogypsum. Usable phosphogypsum is a waste resulting from the decomposition of phosphorites with sulfuric acid in the production of extractive phosphoric acid. It is a mixture of the sparingly soluble sulphates, phosphates and fluorosilicates of calcium, aluminum, iron, magnesium, sodium, rare earths and silica, predominantly calcium sulphate. The amount of phosphorus used according to the invention is 2 to 7% by weight. In order to increase the degree of adhesion of gypsum phosphorus flour, it is preferable to sprinkle the fertilizer granules with a detergent in the form of a solution of lignin sulphonates (sulphite lug) with the addition of sodium kerylbenzene sulphonate (sulphapol) in the amount of 0.27o, or with sulfite lug alone or water. Phosphogypsum consists in the production of permanent shells around granules, which prevent the formation of crystal bridges between them. A test was carried out for the caking tendency of calcium ammonium nitrate coated with various anti-caking substances by subjecting specially prepared fertilizer briquettes to the effect of crushing crushing. The effectiveness of the anti-caking agent can be concluded from the amount of force used to crush the briquette. The results of the test are illustrated by the following table: - uncoated calcium ammonium nitrate 12-17 kg / cm2 - dewy ammonium nitrate, a mixture of sulphite sulphite and cerylbenzene sulphonate sodium calcium monosulfonate. 7-10 kg / cm2 - calcium ammonium nitrate, a mixture of sulphite and sodium kerylbenzene sulphonate and powdered with phosphogypsum 2--4 kg / cm2 - ammonium nitrate sprinkled with sulphite silt and phosphogypsum powdered 3-5 kg / cm2 - ammonium nitrate sprinkled with water and phosphogypsum - 6 kg / cm 2 - calcium ammonium nitrate powdered with phosphogypsum without sprinkling 4 - 7 kg / cm 2. These properties do not have, for example, gypsum - mineral with a crystalline structure. Due to the enormous surface area of the colloidal system, the phosphogypsum granule shells are particularly durable and effectively prevent the agglomeration of fertilizers during transport and storage. EXAMPLE 1 118 kg of dried dolomite flour are introduced into 820 kg of an alloy containing 98% by weight of NH4NO3 and 2% by weight of H20. After mixing, the magma is granulated in a granulation tower. After cooling to 40 ° C., granule fractions with a diameter of 0.75-6 mm are separated on a vibrating sieve and mixed in a powder box with 70 kg of dry phosphogypsum flour. The powdered calcium ammonium nitrate contains 28% N, 6.6% CaO, 4.9% SO4, 2.6% MgO and 0.28% P2O5. 2 kg of a solution containing 39 parts of dry liquor (6% dry matter) and 1 part of sodium kerylbenzenesulfonate and immediately powdered 50 kg of flour from dried phosphogypsum. The obtained ammonium nitrate contains 33% N, 3.5% SO4, 2% CaO and 0.2% P2Q5. PL PL

Claims (3)

1. Claims 1. A method of preventing caking of mineral fertilizers containing nitrogen and other nutrients such as magnesium, calcium, phosphorus, potassium, sulfur, boron and micronutrients by coating their granules, characterized in that the granules or grains of the fertilizer are powdered dried and ground phosphogypsum being a mixture of calcium, aluminum, iron, magnesium, sodium, rare earth and silica sulfates, phosphates and fluorosilicates. 2. The method according to claim The method of claim 1, wherein phosphogypsum is used in an amount of 2 to 7% by weight. 3. The method according to p. The method of claim 1, wherein prior to powdering with phosphogypsum the fertilizer granules are sprinkled with sulphite slug containing ligninsulphonates, or a mixture of sulphite and sodium kerylbenzene sulphcinate or water. Bltk 2656/75 r. 100 copies A4 Price PLN 10 PL PL