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C. Neugebauer et al.
particle flows not only between adjacent process chambers but also between different functional compartments within each chamber. This is followed in Sect. 3 by
experimental and simulation results on the particle exchange rates between chambers
under the influence of weir design. Section 4 collects the experimental results with
respect to the influence of thermal conditions on particle properties. This is followed
in Sect. 5 by the presentation of a model extension, to allow predictive simulation
of property development for different thermal conditions in each chamber. Using
the extended model, the dynamic and steady-state behavior can be studied in detail.
Section 6 presents results of the system theoretic analysis using the process model,
identifying different process regimes (stable, unstable) depending on the operation
and process conditions. This presentation is followed in Sect. 7 by results on control of the overall process, to stabilize operation and to guarantee desired product
properties. The chapter closes with Sect. 8, a summary and outlook.
2 Basic Population Balance Model for Spray Granulation
in A Multi-chamber Setup
In this section a multi-chamber and multi-compartment model of a horizontal fluidized bed apparatus for layering granulation is presented. Each chamber is designed
individually and process conditions, such as spray rate, particle feed or gas temperature, can be adjusted for each chamber separately. Particle growth is described
by population balance modeling. The particle exchange rates between the process
chambers are determined individually to account for different weir configurations.
The growth of particles by layering is described within the population balance
equation (PBE) framework as introduced for particulate processes by Ramkrishna
[2].
The main idea of population balance modeling is the description of the temporal
evolution of the number density function (or other density functions derived from
it). For this, all relevant sub-processes that yield a change in the density have to be
modelled. The density function characterizes the distribution of particle properties,
for example the particle size, moisture content or temperature. Solving for the density
function thereby gives information on the change of these particle properties. Population balance modeling has been used successfully to describe fluidized bed drying,
agglomeration and layering granulation processes, for instance by Refs. [3–7].
To account for the fact that the sprayed solution or suspension can only reach
a fraction of the particle bed it is necessary to divide the process chamber into
compartments of different functionalities. For this purpose [8–10] introduced multicompartment models for fluidized bed coating and layering granulation. Particularly,
two-compartment models have been applied by Refs. [11–14] for fluidized bed layering granulation and coating processes.
C. Neugebauer et al.
particle flows not only between adjacent process chambers but also between different functional compartments within each chamber. This is followed in Sect. 3 by
experimental and simulation results on the particle exchange rates between chambers
under the influence of weir design. Section 4 collects the experimental results with
respect to the influence of thermal conditions on particle properties. This is followed
in Sect. 5 by the presentation of a model extension, to allow predictive simulation
of property development for different thermal conditions in each chamber. Using
the extended model, the dynamic and steady-state behavior can be studied in detail.
Section 6 presents results of the system theoretic analysis using the process model,
identifying different process regimes (stable, unstable) depending on the operation
and process conditions. This presentation is followed in Sect. 7 by results on control of the overall process, to stabilize operation and to guarantee desired product
properties. The chapter closes with Sect. 8, a summary and outlook.
2 Basic Population Balance Model for Spray Granulation
in A Multi-chamber Setup
In this section a multi-chamber and multi-compartment model of a horizontal fluidized bed apparatus for layering granulation is presented. Each chamber is designed
individually and process conditions, such as spray rate, particle feed or gas temperature, can be adjusted for each chamber separately. Particle growth is described
by population balance modeling. The particle exchange rates between the process
chambers are determined individually to account for different weir configurations.
The growth of particles by layering is described within the population balance
equation (PBE) framework as introduced for particulate processes by Ramkrishna
[2].
The main idea of population balance modeling is the description of the temporal
evolution of the number density function (or other density functions derived from
it). For this, all relevant sub-processes that yield a change in the density have to be
modelled. The density function characterizes the distribution of particle properties,
for example the particle size, moisture content or temperature. Solving for the density
function thereby gives information on the change of these particle properties. Population balance modeling has been used successfully to describe fluidized bed drying,
agglomeration and layering granulation processes, for instance by Refs. [3–7].
To account for the fact that the sprayed solution or suspension can only reach
a fraction of the particle bed it is necessary to divide the process chamber into
compartments of different functionalities. For this purpose [8–10] introduced multicompartment models for fluidized bed coating and layering granulation. Particularly,
two-compartment models have been applied by Refs. [11–14] for fluidized bed layering granulation and coating processes.