Production of Nano-particles on the SDR

The Process Intensification and Innovation Centre (PIIC) at Newcastle University has pioneered a process for continuous production of nano particles using thin highly sheared films which can be generated on a rotating surface. Unsteady film surface waves coupled with the shearing action of the rotating surface ensure that micro mixing is achieved on the disc. These films are less than 100 microns thick and so offer a short diffusion path length resulting in excellent heat and mass transfer performance. Residence times on the Spinning Disc Reactor (SDR) range from a few seconds down to fractions of a second. Therefore the SDR is well suited to fast processes where the inherent reaction kinetics are of the same order or faster than the mixing kinetics.

Several reactive crystallisation pathways have been studied to exploit the intense mixing conditions on the disc. Highly supersaturated homogeneous solutions can been created on the disc, leading to homogeneously nucleated nanoparticles. Among others, the precipitation of barium sulphate from barium chloride and sodium sulphate has been investigated. It was found that uniformly distributed nanoparticles could be produced an order of magnitude smaller than those crystals formed in an agitated batch vessel as is shown in the graph below. These particles have applications in many industry sectors such as paints/pigments, electronics and pharmaceuticals.

As well as liquid/liquid reactions, gas/liquid reactions can also be carried out on the SDR. An atmosphere of carbon dioxide diffusing into a thin film of calcium hydroxide enabled nanoparticles of calcium carbonate to be precipitated. Titanium dioxide nanoparticles have also been precipitated on the disc.

Extended projects have included the use of ultrasound to influence precipitation's, and the use of surfactants to arrest crystal growth.

The graph below shows crystal size distributions for barium sulphate produced on a modified SDR. The two SDR curves representing two reactant feed rates compare favourably with the equivalent batch result. The crystals formed from the SDR are an order of magnitude smaller than those formed in the batch reactor and are held within a tighter size band. These results are reproducible and work is underway to tailor crystal size and distribution using several operating parameters.