Concentrated NP- and NPK-Fertilizers based on Kyzylkum Evaporated Phosphoric Acid, Carbamide and Potassium Chloride: Advanced Study

In the paper the processes of carboammophos and carboammophos potassium preparation based on
the ammonization of the samples by evaporated wet phosphoric acid (WPA) (35.92; 40.85; 46.41;
51.07% P2O5) to pH = 5.3 (to obtain ammophos pulp) and pH = 7.0 (to obtain diammophos pulp) with
subsequent addition of 70% solution of urea and crystalline potassium chloride (60% K2O) were
studied. Moreover, for urea-phosphate, weight ratio of the N: P2O5: K2O ranged from 1: 0.5 to 1: 1: 1
for the N: P2O5: K2O urea-phosphate-potassium from 1: 0.7: 0.3 to 1: 1: 1. To avoid loss of ammonia,
the drying of NP- and NPK slurry based on diammonium phosphate (DAP) were produced not higher
than 60°C, and monoammonium phosphate (MAP) - first at 60°C, then at 100°C to constant weight
(less than 1% H2O). It is shown that on the basis of both MAP and DAP slurry are obtaining, samples
of urea-phosphate similar in composition and properties. And all brands of urea-phosphate-potassium
contain a high concentration of nutrients (up to 19.7% N. 19.7% P2O5 and 19.7% K2O). Phosphorus in
them is in a form digestible for plants. The strength of both NPK and NPK fertilizer granules satisfies
the requirements of agriculture. Such fertilizers in agriculture are in great demand.
Experimental Design: Determination of total,l digestible, and water soluble forms of phosphorus
(P2O5total, P2O5deg. P2O5water) were performed on KFK-3 (λ= 440 nm) as phosphorus-vanadiummolybdenum
complex. This method is based on measuring the light transmission of yellow
phosphorus-vanadium-molybdenum complex relative to the reference solution containing a certain
amount of phosphates. Slurry pH was adjusted and determined by potentiometric method on
ionometer I-130M (Russia). The mass was cooled, and then scattered by the size of the particles.
Granules with a size of 2-3 mm were subjected to strength testing. The static strength of the granules
was determined according to State standard 21560.2-82. This method based on crushing the
granules using for that specified weights on scale called MIP 10-1 (Russia), which indicate kgf/cm2 per
granule. Further dried granules of the fertilizer were performed chemical analysis. Digestible forms of
P2O5 were determined by solubility in both 2% citric acid and 0.2 M solution of Trilon B (EDTA). The
nitrogen content in the products was determined by Kjeldahl — distillation of ammonia in an alkaline
medium with Devard alloy followed by titration of 0.1N NaOH.