Results of Adipic Acid Crystallization Experiments
The solubility of Adipic Acid is given in Figure I.1. Here we see
that as a saturated solution is cooled crystals will be produced.
The Adipic Acid crystallizes as an aggregate of platelet particles
as shown in Figure I.2. The particle size distribution of the
particles shown in Figure I.2 is given in Figure I.3. The
aggregates are on the order of several hundred microns in
diameter and consist of crystallites approximately 50 microns in
size. Other experiments using other operating conditions
including rpm, final temperature and mean residence time show
similar aggregated particles. A logarithmic plot of the particle
size distribution (a Randolph and Larson plot) of data from
Figure I.3 is given in Figure I.4. The plot should be linear from
zero size to the largest sizes if only nucleation and growth are
responsible for the particle size distribution. We see no
particles of very small size because all these particles have been
aggregated into the large aggregates. As a result, we can
conclude that the OLI model predicts the solubility reasonably
well and to model this system, a model that includes nucleation
(secondary), growth, aggregation and breakage is needed.
Figure I.1 Solubility of Adipic Acid in water as a function of
temperature.
Figure I.2 Adipic Acid particles crystallized in a baffled 1.3 liter
stirred tank with a Ruston Impeller operating at 400 rpm. A
saturated solution at 28 C was fed to the tank and cooled to 15 C
in the tank to induce crystallization.
7
01
02
03
Differential Volume (%)
6
5
4
3
2
1
0
0.01
0.1
1
10
100
1000
10000
Particle Diameter (micro-meter)
Figure I.3 Particle size distribution of Adipic Acid particles
crystallized in a baffled 1.3 liter stirred tank with a Ruston
Impeller operating at 400 rpm. A saturated solution at 28 C was
fed to the tank and cooled to 15 C in the tank to induce
crystallization. Curves 01,02 and 03 are repeat measurements to
see if the sampling and analytical procedures are reproducible.
100
Differential Number %
10
01
02
03
1
0.1
0.01
0.001
0
100
200
300
400
500
Particle Diameter (micro-meter0
Figure 1.4 Logrithmic plot of the particle size distribution of
Adipic Acid particles crystallized in a baffled 1.3 liter stirred tank
with a Ruston Impeller operating at 400 rpm. A saturated
solution at 28 C was fed to the tank and cooled to 15 C in the
tank to induce crystallization. Curves 01, 02 and 03 are repeat
measurements to see if the sampling and analytical procedures
are reproducible.
600