Abstract
PurposeThe aim of this paper is the development of a process control concept for a hot melt extrusion (HME) and pelletization process. The new concept should improve the particle size distribution of the pellets produced.MethodsProduction of pellets containing an active pharmaceutical ingredient (API) can be achieved by means of HME, followed by a pelletization process step. The quality of pellets produced depends on the strand temperature at the pelletizer’s inlet and the pelletizer’s intake speed. This paper presents a strategy for the strand diameter and temperature control based on adjusting the cooling intensity on the cooling track between the HME and the pelletization step and altering the pelletizer’s intake speed. Two concepts are presented and compared to the open-loop operation of the system: the first one is model predictive control (MPC) in combination with a model based on the local linear model tree (LOLIMOT) algorithm, and the second one is PID control. The quality of the pellets produced was analyzed in terms of particle size distribution (PSD).ResultsBy implementation of the two control concepts, strand temperature and diameter could be kept close to the desired set points. Consequently, the presented concepts yielded pellets with a narrower particle size distribution than the open-loop operation of the plant.ConclusionsThe application of the presented control strategies can improve the quality of the pellets produced by an HME and pelletization system in terms of their particle size distribution.
Highlights
This paper presents a model-based control system for the strand temperature and strand diameter in a pharmaceutical hot melt extrusion (HME) process
HME processes are used in pharmaceutical manufacturing to produce advanced dosage forms, e.g., amorphous solid dispersions (ASDs) for improving solubility [1] and for producing oral dosage forms containing poorly soluble active pharmaceutical ingredients (APIs) [2] or for sustained-release
This study proposes two different control strategies that automatically adjust both of the above-mentioned parameters to increase the pellet quality
Summary
This paper presents a model-based control system for the strand temperature and strand diameter in a pharmaceutical hot melt extrusion (HME) process. Strand pelletization was used, which typically requires a cooling track between the extruder outlet and the pelletizer inlet to achieve suitable strand temperature. As is the case with many other continuous pharmaceutical manufacturing processes [7,8,9,10,11,12], appropriate control strategies must be defined. Model-based approaches for control strategy development were successfully demonstrated in the pharmaceutical industry already [8, 10, 11, 13, 14]. This study focuses on the cooling and pelletization step after the HME process itself. In [16], a study of a process control approach in a
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