Procedure for the preparation of nitrogen fertilizers and complexes in highly homogenized spherical granulated form from liquid urea-formaldehyde resins and the fertilizer prepared in this way

摘要

A process for the preparation of nitrogen and complex fertilizers, to slowly release nitrogen, in granular form, characterized in that said process comprises the steps of a) preparing an aqueous urea / formaldehyde dispersion, adding a first aqueous catalyst solution to said dispersion, the molar ratio of urea / formaldehyde being in the aqueous urea / formaldehyde dispersions and the weight ratio of the first aqueous catalyst added to said urea / formaldehyde dispersions equal to Dispersions Molar ratio U / F Proportion by weight of solution of first aqueous catalyst pH Final molar ratio of U / F of the corresponding liquid mixtures 1 0.40 0.104% 5-5.5 1.33 0.50 0.100% 4.5-4.8 1.54 7 0.40 0.068% 5- 5.4 1.25 11 0.31 0.037% 4-4.4 1.11 13 0.33 0.135% 5-5.5 1.33 to start the condensation, control the pH of said dispersion to keep said pH inside of the intervals indicated above of 4 , 0 to 7.0, stop the condensation by increasing the pH, add additional urea to obtain a mixture having the final molar ratio of urea / formaldehyde indicated above and b) supply the mixtures to a granulation device, while adding and adding mix a second aqueous catalyst in the amount indicated below and decrease the pH of the mixture to the values indicated below, Mixtures (of dispersions) Proportion by weight of solution of second aqueous catalyst pH 2 (obtained from dispersion 1) 1, 66% 5.6-5.8 6 (obtained from dispersion 5) 1.5% 5.8-6.0 8 (obtained from dispersion 7) 1.33% 5.6-5.8 12 (obtained of dispersion 11) 1.66% 5.6-5.8 14 (obtained from dispersion 13) 1.0% 6.2-6.4 and carry out a condensation / drying reaction, including said device for granulation recycling media to recycle the product as a growth initiator; c) providing a granulated product comprising spherical shaped urea / formaldehyde fertilizer granules having a diameter of 2.0 to 3.0 mm, having a high particle size homogeneity and having a density in the range of 0.5 at 1 g / cm3, and a total nitrogen content of 36 to 42%.