Continuous Crystallisation

Abstract

Mixing 2) Nucleation 3) Growth 4) Filter/wash/dry Required to:  Produce consistent composition  Control crystallisation driving force  Influence flow rate, shear-kinetic effects  Consistent suspension of seed and product Controlled via:  Supersaturation  High shear  External fields, e.g. ultrasound, nonphotochemical laser induced nucleation  Seed. Seeds produced via dry milling, wet media milling, precipitation, recycle, dissolution, spray drying or secondary nucleation Controlled to avoid:  Fouling  Agglomeration  Dissolution  Crystalline form transformation(s) Controlled via:  Supersaturation (typically low) via cooling, anti-solvent, evaporation  Effective heat/mass transfer Ensures:  Efficient desupersaturation Controlled to avoid:  Fouling  Agglomeration  Attrition (particle breakage)  Dissolution  Crystalline form transformation(s) Required to:  Create filter cake  Remove mother liquor and impurities  Maintain particle attributes Controlled to avoid:  Agglomeration  Attrition (particle breakage)Continuous crystallisation has been implemented for many decades in other manufacturing sectors, typically for large volume commodity chemicals, and offers a range of potential advantages [16,17] including lower operating and capital costs, reduced down time and more efficient use of energy and materials. Cooling and anti-solvent crystallisation are commonly used in industrial applications and can be readily implemented in continuous. The aim is to follow a controlled trajectory through the solubility phase diagram (section 1.2).

Direct Processing of a Flow Reaction Mixture Using Continuous Mixed Suspension Mixed Product Removal Crystallizer

“…The most common type of continuous tank crystallizer is the mixed suspension mixed product removal (MSMPR) reactor system, , which could be operated in a single stage or in multiple stages. If the crystallization kinetics is fast, then plug flow crystallizers can be preferred ensuring efficient mixing and short residence time. ,, MSMPR, a key device in the continuous crystallization studies, is practically the same instrument that is utilized in batch processes. ,, In parallel, it performs the difficulties attached to batch equipment as well. Previous studies have reported simplicity, lower investment, and maintenance costs , as the main advantages of MSMPR crystallizers.…”

“…If the crystallization kinetics is fast, then plug flow crystallizers 11 efficient mixing and short residence time. 7,12,13 MSMPR, a key device in the continuous crystallization studies, is practically the same instrument that is utilized in batch processes. 4,14,15 In parallel, it performs the difficulties attached to batch equipment as well.…”

Enhanced Product Quality Control through Separation of Crystallization Phenomena in a Four-Stage MSMPR Cascade

“…Although continuous crystallization is already well established to manufacture large-volume commodity products such as sugar and inorganic salts, batch processing remains the method of choice in the pharmaceutical and fine chemical sector. In order to satisfy the high demands placed on the products resulting from these industry branches, continuous plant and equipment concepts are required that guarantee an enhanced control of the product quality attributes mentioned above. , …”

“…One possibility to realize a continuous process is the use of a cascade of multistage mixed suspension mixed product removal (MSMPR) crystallizers. These stirred vessels currently dominate in industrial crystallization processes and are preferably used when high residence times are needed, which may be the case if the desired crystalline product shows slow nucleation and low growth rates . Furthermore, this continuous crystallizer type is characterized by a highly efficient mixing, which has a positive effect on solid–liquid mass transfer, preventing fouling and blockage issues .…”

“…In order to satisfy the high demands placed on the products resulting from these industry branches, continuous plant and equipment concepts are required that guarantee an enhanced control of the product quality attributes mentioned above. 1,2 1.1. Continuous Crystallization Using a Cascade of MSMPR Vessels.…”