Spinning discs Mixing

The use of a rotating reactor to provide efficient mixing has been proposed and tested for viscous polymerizations and acid-catalysed rearrangement reactions [6], The principle of these spinning disc reactors is that the centrifugal force... 

Impact nozzles Spinning discs Internal mixing... 

Another variation of the PTA process is the Higee aeration system. To achieve the necessary air and water mix, water pumped into the center of a spinning disc of packing material and air is pumped countercurrently toward the center from the outside of... 

Chapter 5 gives an overview of novel green reactors and the application of the CFD technique in modelling of green reactors. This chapter presents detailed discussions on a number of novel reactors, namely, the microreactor, microwave reactor and spinning disc reactor. A brief introduction on CFD and the application of CFD in modelling laminar mixing in a stirred tank reactor is presented. 

Spinning disc as High gravity forces Mixing prior to 7... 

One of the attractive features of the SDR is that its high fluid dynamic intensity favours the rapid transmission of heat, mass and momentum, thereby making it an ideal vehicle for performing fast endothermic reactions which usually also benefit from an intense mixing environment. It must be noted, however, that heat transfer from the process liquid to any cooling/heating fluid behind the disc involves a second film coefficient which may severely limit the overall heat transfer rate (this is discussed later). Some of the more relevant recent experimental studies of spinning disc performance may now be considered. 

The stirred tank, of course, uses the stirrer for mixing, but the performance, even with modem designs of paddles, does little to ensure highly uniform reactions - the main point of stirring (or mixing) the fluid(s) within the pot . The most common types of mixers are in-line units and rotor stator mixers. Other mixer types considered below include variants based upon ejectors, fluidics, types using venturi aeration and ideas based upon spinning discs. 

The chapter on mixers is comparatively short - not because mixers are unimportant, but because mixing is such an integral part of other intensive processes (heat exchange, reactions and crystallisation/precipitation as examples), that the topic is addressed continuously through other equipment and application chapters. The point is well made by Wu et al. (2(X)7) who stresses in their recent review that PI needs to be implemented via increased mixing, as well as heat and mass transfer - hence the success in this area of the spinning disc and the oscillatory baffle reactors. 

Within the sector there is a mix of batch and continuous processes, the former offering flexibihty (possibly overcome in continuous mode using the spinning disc reactor (SDR)), and low-volume production. Where continuous processes can be improved using PI, and where batch operations can become continuous by using PI technology, the following benefits were seen for the company ... 

Spinning disc technology, as used in the SDR, has been tested on foodstuffs. In particular, it has been used for dehydration of food, and has been proposed for rapid pasteurisation of heat-sensitive liquid foods, fii Figure 10.5 the SDR is illustrated heating treacle. The good mixing characteristics and excellent heat transfer are evident in the highly uniform temperature distribution across the disc. 

Research at Leeds University in the UK (Dunn, 2007) that studied the pouring of liquids onto heated or cooled spinning discs and collection of them at the periphery suggested that the phenomenon could provide the food industry with more efficient and shorter mixing and processing times. It was demonstrated that mixing and... 

Blends, e.g. 80 20, of poly (methyl methacrylate) (PMMA, weight average molar mass, Mw, of 15,000 g/mol) and polybutadiene (PB, with Mw 420,000 g/mol) (e.g. from Aldrich) are prepared by mixing solutions of a mass fraction of PMMA of 0.02 in toluene and mass fraction of PB of 0.02 in toluene in a ratio of 8 2 followed by spin-coating onto pre-cleaned silicon wafers. Following the spinning, the samples are treated for 24 h at ambient temperatures under vacuum to remove residual solvent. Pieces of the blend-covered silicon wafer are glued to the sample holder disc and inserted into the AFM. 

In the external gradient method, the spin fluid density gradient is formed external to the disc and injected into the disc while the disc is spiiming. The externally formed spin fluid contains at least two miscible or partially miscible liquids of different densities in an incompletely mixed condition. 

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