Concentrated Np- and Npk-Fertilizers Based on Kyzylkum Evaporated Phosphoric Acid, Carbamide and Potassium Chloride
Authors: Shahzoda Turdialieva , Kadyrbergenovich Alimov Umarbek , Sattarovich Namazov Shafoat , Reypnazarovich Seytnazarov Atanazar , Mikhaylovich Beglov Boris 
Published: March 2019

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.