20
th
European Symposium on Computer Aided Process Engineering – ESCAPE20
S. Pierucci and G. Buzzi Ferraris (Editors)
© 2010 Elsevier B.V. All rights reserved.
Control of Process Operations and Monitoring of
Product Qualities through Generic Model-based in
Batch Cooling Crystallization
Noor Asma Fazli Abdul Samad, Ravendra Singh, Gürkan Sin, Krist V. Gernaey,
Rafiqul Gani
Department of Chemical and Biochemical Engineering, Søltofts Plads, Building 229,
Technical University of Denmark, DK-2800 Lyngby, Denmark, rag@kt.dtu.dk
Abstract
A generic model-based framework has been developed for crystallization processes,
with applications aiming at the control of process operations and the monitoring of
product quality. This generic model-based framework allows the systematic
development of a wide range of crystallization models for different operational
scenarios. This enables the design and control engineers to analyze various
crystallization operations and conditions, thus facilitating the development of process
control and monitoring systems (PAT systems) for crystallization processes. The
generic framework has been implemented in the ICAS-PAT software which allows the
user to design and validate PAT systems through a systematic computer-aided
framework. The application of the framework is highlighted for batch cooling
crystallization of paracetamol where the framework was applied for design of a process
monitoring and control system to obtain a desired crystal size distribution (CSD).
Keywords: crystal size distribution (CSD), PAT, process monitoring and control,
crystallization, paracetamol
1. Introduction
Crystallization is an important operation when manufacturing fine chemicals or
pharmaceuticals. It is a widely used technique in solid-liquid separation processes to
obtain solid products of high purity at relatively low costs. Requirements for crystal
products are usually high purity, a specific crystal size distribution and a desired crystal
shape [1]. Consequently many efforts have been made to model the crystallization
process to support the development of appropriate process operations and control
scenarios to meet specific end product demands. So far, the published crystallization
process models have been problem specific, meaning that the models were developed
with a certain crystal product in mind. Hence it is not surprising to notice that research
on crystallization modeling emphasizes different issues such as crystal size distribution
(CSD) or crystallization kinetics, depending on the aim of the specific modeling study.
Furthermore, specific models employ numerous underlying assumptions, for example,
on agglomeration and crystal breakage factors. As a consequence, there are many
specific models available in the literature with different degrees of complexity, which
makes their selection and use for a specific problem difficult if not confusing. There is
therefore a need for the development of a generic crystallization model to assist the
systematic and efficient development of appropriate models for specific crystallization
processes.