SFTR: Development of the new segmented flow tubular reactor (SFTR) for powder synthesis in an industrial pilot plant

• Research unit: EU RFP
• Project number: 99.0449-1

Key words (English)

Tubular reactor; micro-volumes; mixing problems

Alternative project number (English)

EU project number: G5RD-1999-00123

Research programs (English)

EU-programme: 5. Frame Research Programme - 1.3.1 Innovative products, processes and organization

Short description (English)

See abstract

Further information (English)

Full name of research-institution/enterprise:
EPF Lausanne
Institut des Matériaux
Laboratoire de Technologie des Poudres

Partners and International Organizations (English)

Coordinator: Kemgas ltd (F)

Abstract (English)

The current approach of scaling-up batch precipitation processes first elaborated at the laboratory scale in small vessels is time consuming, risky and, often leads to high development costs. A new tubular reactor, the Segmented Flow Tubular Reactor (SFTR), has been developed to overcome the problems often encountered when using batch reactors. The SFTR is composed of a mixer-segmenter and a tubular reactor. A supersaturation is created in the mixing chamber inducing the precipitation of particles. The precipitating suspension is then segmented into identical small volumes by a non-miscible fluid. This succession of micro-volumes is fed into a tube of small diameter, the residence time being determined by the tube length and the immiscible fluid flow rate. The SFTR achieves a quasi-plug flow and avoids the mixing problems encountered in batch reactors leading to inhomogeneous reaction conditions and resulting in broad particle size distributions. Narrower particle size distributions, enhanced control of particle morphology, polymorph selectivity and better stoichiometry control are the advantages of the SFTR process. The goal of this project is to build a pilot scale multi-channel Segmented Flow Tubular Reactor where each individual reactor is run in exactly the same way as those at the laboratory-scale, eliminating the scale-up process. The goal of our laboratory in this project is to explore the calcium carbonate precipitation system to prove the ability of the SFTR to adapt to change while two other partners have to explore the barium titanate and mixed manganese-nickel oxalate systems. We have improved a lot the understanding of the calcium carbonate precipitation mechanism. The presence of calcite seeds and of a polymer additive allows the formation of well defined particles with a narrow particles size distribution. The shape of the particles is controlled by the amount of additive: small amounts of polymer induces the formation of rhombohedral particles while increasing the polymer concentration leads to rice-shaped particles which are agglomerates made up of nanocrystals. The production of calcium carbonate powder was carried out in a 25-hour continuous run in the SFTR. About 47 g of powder were recovered showing a 35 m2/g specific area, a median diameter of 390 nm and a span of 1.06. This powder is of better quality than the 10 g produced a year ago to reach the first milestone. The next milestone is to produce one kilo of such quality calcium carbonate in the pilot scale multi-channel Segmented Flow Tubular Reactor by the end of the project.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 99.0449-1