CaCO₃ Precipitation Kinetics in the System CaCl₂–CO₂–Mg(OH)₂–H₂O for Comprehensive Utilization of Soda Production Wastes

Abstract

The precipitation of CaCO3 and its kinetics for the CaCl2–CO2–Mg­(OH)2–H2O system were systematically studied to develop a novel process for eliminating solid and liquid waste from the Solvay soda process. The effects of operating conditions including temperature, CaCl2 concentration, flow rate of CO2, and stirring speed on the reaction kinetics were experimentally determined. The results revealed that low temperature, high CO2 flow rate, and fast stirring speed can accelerate the reaction rate, and the mass transfer of CO2 is the controlling step. An MSMPR crystallizer was used to obtain the experimental crystal size distribution (CSD). A simplified population balance equation (PBE) was used to correlate the parameters on the basis of supersaturation. The soda solid and liquid wastes discharged from the Solvay industry were used as raw material to test the new process and validate the methodology. The precipitated CaCO3 consists of calcite or aragonite with high purity and uniform CSD. A double-effect evaporative-cooling crystallization process to recover MgCl2·6H2O and NaCl was simulated with help of Aspen plus and the electrolyte-NRTL (ELENRTL) model, suggesting economic benefits.

Transparent Flexible Moisture-Absorbing Film as Ca2+ Pump Dispenser Mimic

“…Before rinsing, free Ca 2+ was distributed on the surface and interior of the Ca@SA/PAAS film, which can be directly observed by using calconcarboxylic acid (CCA) indicator coloring. CCA is blue under the condition of no free Ca 2+ , while CCA shows a distinct purple color when CCA encounters free Ca 2+ . − The OM images of the CCA-colored Ca@SA/PAAS film sections before rinsing (Figure b 1 ) showed a uniform purple color, indicating the storage of free Ca 2+ on the surface and interior of the Ca@SA/PAAS film. After the film surface was rinsed (I), it turned blue (Figure b 2 ), showing that the free Ca 2+ on the surface was completely removed during rinsing.…”

A New Process for Peracetic Acid Production from Acetic Acid and Hydrogen Peroxide Based on Kinetic Modeling and Distillation Simulation

“…In this paper, the activity of the proton, a H + = m H + γ H + , in the equilibrium mixture is calculated using the ELECNRTL equations 30,31 with the help of Aspen Plus, while the activity coefficient γ H + can be expressed by the following three terms:…”

“…The equilibrium constants for reactions –, designated as K 1 , K 2 , K 3 , and K w , are expressed on the basis of molality by the following equations, respectively. In this paper, the activity of the proton, a H + = m H + γ H + , in the equilibrium mixture is calculated using the ELECNRTL equations , with the help of Aspen Plus, while the activity coefficient γ H + can be expressed by the following three terms: The natural logarithm of the activity coefficient of and can be described as follows: where Q e is the electron charge; ε and ε w are the dielectric constants of the solvent and water; z i and r i are the charge number of segment-based species i and the Born radius of segment species i ; M B , A φ , ρ, and I x symbolize the molecular weight of the solvent, the Debye–Hückel parameter, the closest approach parameter, and the ionic strength, respectively. lnγ c NRTL , lnγ a NRTL , and lnγ B NRTL are the local composition activity coefficients for the cation, the anion, and the solvent, which can be expressed as the following expressions: where X j is the effective mole fraction of species j and can be calculated by x j Z j ; τ is the energy parameter, and α is the nonrandomness factor; T ° is the reference temperature of 298.15 K; the subscripts w and ca denote the solvent (water) and the electrolyte (cation–anion), respectively.…”