Mixing and Crystallization Kinetics in Gas‐liquid Reactive Crystallization

Abstract

A study of gas-liquid reactive crystallization for CO 2 -BaCl 2 -H 2 O system was performed in a continuous flow crystallizer. The influences of mixing on the crystallization kinetics of barium carbonate crystals were investigated. The mixing parameters are stirrer speed, feed concentration, gas-flow rate, pH of solution, addition rate of NaOH solution, and mean residence time. Under pH-stat operation, the crystallization mechanism can be assessed by the addition rate of NaOH solution, which acts as an indicator for the absorption rate of carbon dioxide. Assuming a size-independent agglomeration mechanism, the nucleation rate, growth rate and agglomeration kernel can be obtained, simultaneously, at steady state, by the method of moments. Evidence shows that feed concentration, feed rate, gas-flow rate, and stirrer speed have a significant influence on the nucleation rates and mean particle sizes. This shows the effect of micromixing. The crystallization mechanism tends to be reaction limited when the feed concentration of barium chloride solution is higher than 5 mM, while at lower stirrer speeds and feed concentrations, the mechanism tends to be both mixing and reaction controlled. The growth rate depends on the mean supersaturation value and the pH of the solution and the mass-transfer resistance cannot be completely eliminated in this work. For a monodispersal collision model, in the viscous sub-range of turbulence, the agglomeration kernel can be expressed as, showing a low efficiency of collision. The result is also demonstrated by the agglomeration kernel expression. Comparison with a liquid-liquid-mixing reactive crystallization system is also discussed.

Recovery of metals and complexant in wastewater by shear induced dissociation coupling with ultrafiltration

“…Nevertheless, the shear rate of the rotating disk aggrandizes with the increase of the radius at a fixed speed, and the larger the radius is, the higher the shear rate is. Thus, the membrane surface can be divided into complexation region and dissociation region when the rotating speed exceeds the critical one . Under the action of the shear field, the complexes located far from the central axis of the membrane dissociate firstly due to the greater shear force.…”

“…SID‐UF is especially suitable for the treatment of low concentrations of heavy metals and is considered as a promising and actionable alternative due to its high selectivity, low cost, and without the consumption of acid and alkali . In previous work, the shear stabilities of single ion as Cu (II), Zn (II), Cd (II), and Ni (II) have been studied, which is helpful to promote the industrial removal of these ions . However, the real wastewater is usually multi‐ion coexisting system.…”

Aggregation of growing crystals in suspension: I. Mumtaz revisited

“…Mumtaz's work has found applications in industrial crystallisation (Braun et al, 2004;Brunsteiner et al, 2005;Chen et al, 2004;Chen et al, 2003;Chew et al, 2004;Falk et al, 2011;Hollander et al, 2003;Ilievski, 2001;Ilievski and Livk, 2006;Kramer and Jansens, 2003;Li et al, 2001;Livk and Ilievski, 2007;Rielly and Marquis, 2001;Wang et al, 2006;Yokota et al, 1999;Zauner and Jones, 2000), precipitation (Lakshminarayanan and Valiyaveettil, 2003;Lewis and Mangere, 2011;Lindenberg et al, 2008;Lawler, 2008, 2010;Wagterveld et al, 2012;Wan et al, 2011), nanoprecipitation (Jia et al, 2008;Pujol et al, 2004;Schwarzer and Peukert, 2005;Schwarzer et al, 2006), population balance modelling (Balakin et al, 2012;Briesen, 2006;Briesen, 2007;Derksen, 2002;Hollander et al, 2001a;Hollander et al, 2002;Hollander et al, 2001b;Mersmann et al, 2002;Reinhold and Briesen, 2012;Sgraja et al, 2010) and colloid science (Gruy, 2012;Kind, 2002).…”

CO2 Absorption and Magnesium Carbonate Precipitation in MgCl2–NH3–NH4Cl Solutions: Implications for Carbon Capture and Storage

“…Only a few studies have focused on testing the reactive absorption and precipitation using materials extracted from natural minerals. Soluble barium salt was used to absorb CO 2 via reactive crystallization [28][29][30], but was limited by the low natural abundance and toxicity. Ca(OH) 2 was also a possible absorbent [31,32], but Ca(OH) 2 solid is usually produced from CaCO 3 with CO 2 as a byproduct, negating its sequestering function.…”