SU1114669A1 - Method for producing slow-release fertilizer - Google Patents

Abstract

A method for producing a honeycomb fertilizer by reacting urea and a gypsum-containing component with subsequent granulation and drying of the finished product, characterized in that, in order to increase the concentration of nutrients and simplify the process by lowering the temperature, the urea is preliminarily mixed with a formalin solution at a molar ratio of urea, and a urea, and the urea will regain the temperature by urea. -3: 1, phosphogypsum is used as a gypsum-containing component, and the reaction is carried out at a molar ratio of urea: Ca2O2H2O pa Mr 1: 0.230, 65. (L

Description

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. The invention relates to the chemical industry and can be used in the production of mineral fertilizers, in particular controlled fertilizers; solubility-nutrients. Of these, there is a known method for producing capsulated slow-acting fertilizers, which consists in applying to the surface of granules heated to 70-90 ° C, a suspension of phosphogypsum in a 50% aqueous solution of urea resin for 2-3 minutes. According to the example, for 200 g of fertilizer (nitroamm phosphate), 6 g of a 10% phosphogypsum suspension in a 20% urea resin solution is used, which is 0.3 wt.% Of the weight of fertilizer l. The disadvantages of this method are low utilization of phosphogypsum (0.3 wt.% Of the weight of the fertilizer), complexity of the fertilizer coating technology with a uniform film, as well as the impossibility of obtaining slow-moving fertilizer in the whole mass. The method of obtaining slow-moving fertilizer is the closest to the proposed method. on the basis of urea and gypsum, according to which calcium sulfate dihydrate CaSO "ZHjO is added in an amount of 4 mol per 1 mol of urea to the molten urea at 140 ° C. The temperature of the mixture decreases to 110 ° C. The mixture is then cooled, ground and scattered on a sieve 2. The disadvantages of this method are the low concentration of nitrogen in the fertilizer, the possibility of biuret formation in the urea melt at 140 ° C, the high process temperature, requiring significant energy consumption during the industrial scale, and the use of skilled calcium sulfate dihydrate as a feedstock. The purpose of the invention is to increase the concentration of nutrients and simplify the process by lowering the temperature. The goal is achieved by the fact that urea is preliminarily introduced into the solution formally with a molar ratio of urea formaldehyde of 1-3: 1 at 70-80 ° C, the resulting solution is mixed with phosphogypsum and the interaction is carried out at a molar ratio of urea: Ca 50 and 2HjO equal to 1: n, .73 -0.65. The fertilizer is then milled and dispersed to form a granulated product. Phosphogypsum composition, wt.%: CaS042H20 93-95, 1 1, 4, F 0.15-0.4, other impurities, including trace elements, are used as the gypsum-containing co-component. The use of a freshly prepared urea-formaldehyde resin instead of a melt of urea reduces the process temperature to 70-80 ° C compared with the prototype, which significantly reduces energy consumption and prevents the formation of biuret. The use of phosphogypsum instead of natural gypsum reduces the cost of the process and improves the properties of the fertilizer due to the addition of micro elements contained in the fo1: dog gips. In addition, the use of phosphogypsum production waste makes a significant contribution to solving the problem of protecting the environment from chemical wastes. With a molar ratio of urea: CaSO {-2} {0, greater than 1: 0.65, a product is obtained which is low in nitrogen (5-10 wt.%, Example 7), and has a low rate of leaching. At a molar ratio of urea: CaSO f2H20 less than 1: 0.23, the degree of utilization of phosphogypsum is low (less than 25 wt.% in the mixture), and part of the urea is not in a slowly digestible form (Example 8). Example 1. 19.02 g of urea is dissolved at 70 ° C in 17.54 g of 28.5% formalin, which corresponds to a molar ratio of urea and formaldehyde of 2: 1. The resulting solution is mixed in 44.36 g of phosphogypsum, the humidity of which is 20%. The molar ratio of urea and CaSO / - 2H20 is 1: 0.65. The resulting mass is dried and analyzed. The nitrogen concentration in the product is 15%. The degree of nitrogen leaching in 5 days is 87.47%. The remaining examples are made analogous to Example 1, but differ in the ratio of the reactants. A comparative analysis of the proposed and known (which is taken as the basic object) methods for obtaining a slow-acting fertilizer is given in the table (data for

311

known method obtained in identical conditions).

From the data of the table it follows that the proposed method of obtaining a slow-acting fertilizer as compared with the prototype allows reducing the process temperature by 25-70 ° C (70-80 as compared to 95-140 ° C) to avoid the formation of biuret, increase the urea nitrogen concentration by 2.72 -3.93 times (15% nitrogen in example 1, 21.65% in example 6, compared with the prototype, where nitrogen contains 5.51%), while maintaining a slow nitrogen release, and using CaSOx- instead of quafi-saturated salt 2HjO phosphogypsum - waste production of phosphoric acid than the street the quality of the utility is improved6698 / 16 Circulation 425 Subscription VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Branch gash Patent, Uzhgorod, st. Project, 4

9 - 4

This is due to the introduction of PjOj and trace elements contained in phosphogypsum, and environmental pollution is prevented. The resulting compositions contain high amounts of assimilable nitrogen and CaO.

In addition, the cost of transporting and storing phosphogypsum is 3-5 p. per 1 ton excluding the cost of storage space.

The implementation of the proposed slow-acting fertilizers will bring in agricultural products and will allow to utilize the tonnage production waste - phosphogypsum, as well as to obtain a social and health-improving effect due to the ingress of phosphogypsum into the surrounding environment.

Claims (1)

METHOD FOR PRODUCING SLOW-ACTING FERTILIZER by reacting urea and a gypsum-containing component with subsequent granulation and drying of the finished product, characterized in that, in order to increase the concentration of nutrients and simplify the process by lowering the temperature, the urea is pre-mixed with formalin solution at a molar ratio of urea: formaldehyde of 1 3: 1, phosphogypsum is used as the gypsum-containing component and the interaction is carried out at a molar ratio of urea: CaBCO · 2H ₂ 0 equal to 1: 0 , 230.65.