ISBN 9783843956116

978-3-8439-5611-6, Reihe Ingenieurwissenschaften

Anne Cathrine Kufner
Towards Robust Operation of a Small-Scale Continuous Slug Flow Cooling Crystallizer

223 Seiten, Dissertation Technische Universität Dortmund (2024), Softcover, A5

Zusammenfassung / Abstract

In the context of industrial crystallization, a paradigm shift occured in recent years, with continuous crystallization gaining increasing prominence over batch processes, especially in small-scale applications (Q < 100 mL/min) involving fine chemicals or active pharmaceutical ingredients. This shift is driven by the ability of continuous processes to overcome typical batch challenges such as limited capacity and batch-to-batch-variability.

However, continuous crystallization als presents challenges, particularly at low flow rates, where settling, fouling, encrustation, and blockage may occur. This highlights the need for innovative concepts like the Slug Flow Crystallizer (SFC). The SFC employs segmented flow using an immiscible fluid - here a gaseous phase - to divide the mother liquor into characteristic slugs, enabling plug-flow-like profiles even under laminar conditions. The gaseous phase enhances heat transfer, simplifies phase separation, and reduces the liquid wall film, thereby stabilizing slug flow, maintaining consistent slug length, and narrowing residence time distribution, contributing to a narrow particle size distribution.

This study aims to enable robust and reproducible crystallization in the SFC for small-scale production by identifying operation windows and focusing on a sweet-spot for producing high-quality crystals. Experimental and model-based strategies were combined. Experiments identified viable operating ranges and suitable substance systems. Integration with downstream processes demonstrated a stable operation and high-quality products. The model-based approach, developed from experimental results, includes a suspension correlation within a population balance model to describe the crystallization behavior. Additionally, various substance systems were tested to demonstrate the SFC's potential for API crystallization.