Concentrated Np- and Npk-Fertilizers Based on Kyzylkum Evaporated Phosphoric Acid, Carbamide and Potassium Chloride

Abstract

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) was performed on KFK-3 (λ= 440 nm) as phosphorus-vanadium-molybdenum 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.   Findings: Preparation process consists of as follow: First slurry of  ammophos and diammophos were prepared by neutralization  of evaporated WPA containing 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; Second to obtain NP fertilizer 70% solution of carbamide was added to MAP and DAP slurry at 60° C followed by stirring thorough. Then NP slurry was dried not higher than 100 °C for MAP and not higher than 60 °C for DAP, respectively; Third to prepare NPK fertilizer 70% solution of urea and crystalline potassium chloride (60% K2O) were added to MAP and DAP slurries. Next NPK slurry was dried not higher than 100 °C for MAP and not higher than 60 °C for DAP, respectively; Fourth NP and NPK fertilizer were tested on static strength accordingly above mentioned study design using State standard 21560.2-82; Fifth dried granules NP and NPK fertilizers were analyzed on various form of P2O5 including N and K2O.  The latter was evaluated by calculation from difference N and P2O5 accordingly weight ratio N:K and N:P2O5:K2O equal to 1:0.5; 1:0.7; 1:1 and 1:0.3:1; 1:0.5:1; 1:1:1 respectively.