cg9b00941_si_001.pdf (3.84 MB)
Estimation of the Growth and the Dissolution Kinetics of Ammonium Bicarbonate in Aqueous Ammonia Solutions from Batch Crystallization Experiments
journal contribution
posted on 2019-09-13, 20:29 authored by Federico Milella, Marco MazzottiIn
this work, we estimate the macroscopic crystal growth and dissolution
rates of ammonium bicarbonate in aqueous ammonia solutions as a function
of the solution supersaturation in a range of process conditions of
industrial relevance. The electrolytic and reactive nature of the
mixtures requires the computation of the driving force for crystallization
using an activity-based speciation model. The model parameters have
been estimated based on experimental speciation data obtained by applying
tailored multivariate data analyses on the measured ATR-FTIR spectra
of the solutions. Moreover, the volatility of CO2(aq) and
NH3(aq) requires operating the system under its vapor pressure
in order to avoid depletion of the solute in the liquid phase. For
this reason, a sealed crystallizer equipped with custom-made connections
for the online monitoring tools, such as FBRM and ATR-FTIR probes,
has been used during the experiments. In addition to estimating the
crystallization kinetics, it has been found that the speciation in
solution and the supersaturation can affect the relative growth of
the ammonium bicarbonate crystal facets, thus leading to different
crystal habits. Finally, this work provides a sound thermodynamic
framework in which the kinetics models for crystal growth and dissolution
of ammonium bicarbonate can be applied to the design and optimization
of ammonia-based CO2 capture absorption processes that
exploit solid formation.