Сomposition and Rheological Properties of Decomposition Products of Low Grade Phosphorite with Phosphoric Acid

The investigations’ results of composition and rheological properties (density and viscosity) of reaction mass – calcium-phosphate and acid monobasic calcium phosphate’s slurries which were obtained at temperature 30-100°С have been given in this study. Chemical composition of calcium-phosphate and acid monocalcium phosphate slurries were found out. It was established that the decomposition products of low grade phosphorite from the Central Kyzyl kum deposit with phosphoric acid (35.69, 41.2 and 44.98% Р2О5) have successful flowing in the determined temperatures. Density and viscosity of slurry were studied depending on the concentration and the norm of the phosphoric acid and the temperature from 30 to 100°С. It was shown that in investigation have ranges of parameters the rheological characteristics of slurries will successfully flow with exciting installations in the industrial conditions.

Aims: The investigations of composition and rheological properties (density and viscosity) of reaction mass, calcium-phosphate and acid monobasic calcium phosphate’s slurries.

Study Design: Determination of total and water soluble forms of phosphorus (P2O5tot., P2O5wat.) was performed on KFK-3 (l = 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. The concentration of the free form of phosphorus (P2O5tot.) was determined by potentiometric method on ionomer I-130M (Russia). Determination of CaO and MgO carried out by volume of complexometric titration of 0.05 N solution of EDTA in the presence of calcein indicators and chrome navy. The content of the total form SO3 (SO3tot.) was by gravimetric, precipitation as barium sulphate. The concentration of free of SO3 (SO3free.) was determined by back titration alkaline solution (0.1N NaOH solution) in the presence of phenolphthalein indicator methyl red. Analysis on Al2O3 and Fe2O3 were carried out by complexometric method. The density was determined by pycnometric technique, and its viscosity –using viscometer grade of VPJ-2 with a capillary diameter of 1.47 and 2.37 mm. The density and viscosity were determined at temperatures from 30 to 100 ° C in a thermostat filled with glycerol.

Place and Duration of Study: Laboratory of phosphate fertilizers of the Institute of General and Inorganic Chemistry under Academy Science of the Republic of Uzbekistan, in July 2015.

Methodology: Decomposition of phosphate Central Kyzylkum with evaporated wet-processing phosphoric (WPA) was carried out in a thermostated glass reactor (500 ml) which is equipped with screw stirrer for 60 min. at 95°C. Norm of WPA was 200, 250, 300; 300, 400, 450, 500 and 400, 450, 500, 550, 600% for CaO in the raw material. After decomposition process of phosphorite the resulting slurry consists of the liquid and the solid part of the complex dispersed system which are the structured and unstructured suspensions of the dispersed phases. The content in the reactor was divided into two parts: the first part of the pulp suspension was left the calcium phosphate for further the study, while the second part is separated into solid and liquid phase by filtration. The filtered liquid phase was subjected to cooling at 40°C for 2 hours to isolate crystals of a monobasic calcium phosphate (MCP) by a laboratory centrifuge mark OPN-8 (Russia).

Results: The rheological properties (the density and the viscosity) of the calcium phosphate and acid MCP slurry were high when lower norm, and higher concentration of WPA. However, with increasing temperature, the density and the viscosity markedly decreased. It can be seen that on the rheological properties significantly affect the concentration of WPA and temperature. However, the increase of the norm at the same temperature and the concentration of WPA, there viscosity and the density are significantly reduced. Thickening of the acidic MCP was observed at certain temperatures during the experiment, indicating that the crystallization of the components of the metal-phosphate in one. Also, the higher the norm and lower the concentration of WPA, the lower the figures.

Conclusion: In all cases, the increase of temperature, higher norm of acid, lower concentration of acid lead to decrease of the rheological properties.