Abstract nr. F8


Oct 27, 2013 (4 years and 6 months ago)


Abstract nr. F8


Crilles Casper Larsen

Institut for



1. maj 1999


Jørn Møller Sonnergaard, Poul Bertelsen og Per Holm

Titel på forskningsprojekt

Process control method and evaluation of aqueous film coating

A thermodynamic process control method for aqueous film coating

Crilles C. Larsen
, Jørn M. Sonnergaard
, Poul Bertelsen
, Per Holm

PharoTech A/S,
Carl Jacobsensvej 22
, DK
2500 Valby, Denmark.


Department of Pharmaceutics, The Royal Danish S
chool of Pharmacy, Universitetsparken 2, DK
2100 Copenhagen, Denmark


Pharmaceutical Development, Nycomed Denmark A/S, DK
4000 Roskilde, Denmark

Corresponding author. Tel.: +45
36130300, Fax: +45
36130319, e
mail: ccl@pharotech.org

A process control m
ethod for aqueous film coating of pellets, utilising the mass and energy balance of the
coating process, was developed. The method was based on a comparison of the thermodynamics of the actual
coating process with the thermodynamics of the optimal adiabati
c coating process. By measuring the actual
coating conditions and calculating the optimal adiabatic coating conditions followed by determining the
percentage evaporation capacity used of the optimal adiabatic coating conditions critical process conditions
during coating was avoided.

The thermodynamic method was developed on a standard lab size fluidised bed (Aeromatic Fielder MP1)
modified with high precision temperature and flow sensors enabling monitoring and logging of the coating
process. A sorption de
humidifier was connected by a special set up to the inlet side of the fluidised bed to
control the inlet air humidity.

Several different process and equipment variables including inlet air humidity, film formulation and coating
insert were varied to test

the robustness of the thermodynamic model. The maximum critical

spray rate and
outlet air humidity were identified for the employed film formulations and inlet air humidities. The
thermodynamic model could register even small changes in the mass and ener
gy balance as the spray rate
was increased. This was indicated by an utilisation of the potential evaporation capacity of more than 100%.
By regulating the inlet air temperature the process was controlled and the balance was re
established. If the
ed increase in spray rate was too high the mass and energy balance could not be re
established and
the process went uncontrollable. The presented thermodynamic process control method was not influenced
by the employed inlet air humidities, film formulation
s or coating inserts. Thereby making the method ideal
as a general analytical technique for process monitoring and control in aqueous film coating of pellets.