No abstract

Continuous reaction crystallization of struvite from water solutions containing phosphate(V) (1.0 mass%) and calcium ions (from 0.01 to 0.20 mass%) was investigated. Process was carried out in temperature 298 K in continuous DT MSMPR type crystallizer with internal circulation of suspension. Influence of pH (from 9 to 11) and mean residence time of suspension in crystallizer (from 900 to 3600 s) on product crystal size distribution, mean size, population homogeneity and shape of crystals, as well as chemical composition of solid phase was tested. Within the investigated process parameter ranges struvite crystals of mean size from 18 to ca. 50 μm were produced. With the increase in calcium ions concentration in a feed mean crystal size decreased from 34.2 to 18.4 μm (pH 9, τ 900 s). Coexistence of struvite and hydroxyapatite crystals in the solid product was confirmed analytically (Ca content in solid product from 0.3 to 8.4 mass%). Presence of calcium ions favoured crystallization of struvite in a form of tubular crystals, characterized by lengthwise cracks and irregular edges. Co-precipitated hydroxyapatite particles showed relatively small sizes, even below 1 μm, forming agglomerates on the surface of larger struvite crystals and individual agglomerates.

Crystal Growth & Design ARTICLEF sat , density of saturated solution, kg/m 3 τ, mean residence time of suspension in a crystallizer working volume, defined as V w /q v , s

No abstract

No abstract

No abstract

The research results and kinetic studies on the barium ions precipitation process by means of crystalline ammonium sulfate addition are presented. The influence of: barium, sodium, potassium and calcium chlorides concentration in the feeding solution and also the process temperature on barium sulfate mass crystallization kinetics are investigated. Experiments were carried out in the MSMPR crystallizer with internal circulation of suspension. The barium sulfate nucleation and crystal growth rates were estimated from crystal size distribution taking into account a size dependent growth (SDG). Research results may be utilized in the used quenching salts processing technology.

No abstract