Reactor, with impinging streams

Figure 7.23 Combined multifunctional impinging stream gas-liquid reactor with the screen foam remover (2) in Fig. 7.21 replaced by the internal cyclone (9) in this figure.

Chen [16] studied experimentally the preparation of ultrafine white carbon black by the common (one-step) precipitation process with the submerged circulative impinging stream reactor (SCISR) developed by Wu [15] as the reaction-precipitation equipment and obtained satisfactory results. 

The experimental equipment system for the preparation of nano copper powder by reduction-precipitation is shown in Fig. I4.l, where the submerged circulative impinging stream reactor (SCISR) has the same structure as was used in the investigations described in the previous chapters in Part II of this book, with the same effective volume of 3.6x10 3 m it is also operated without the top cover but is made of titanium for anti-corrosion of Cl-. 

An investigation on the preparation of nano Titania by TiCl4-hydrorization-precipitation was carried out with the submerged circulative impinging stream reactor (SCISR) as the reaction device and the results compared with those obtained with the traditional stirred tank reactor (STR). The following can be concluded ... 

Experimental Apparatus and Procedures. The amorphous alloys of about 15 microns thick and 3 mm wide ribbons were prepared by the disk method (8), the details of which have been described elsewhere (5). The important step of the method is the impinging of the molten mother alloy, held in a quartz tube with a small nozzle, onto the surface of a rotating disk of stainless steel. A flow type of a reactor apparatus, previously described (5), was used for the catalytic reaction. The reaction was carried out under atmospheric pressure and at temperatures from 220 to 370°C. The catalysts were pretreated with a stream of hydrogen in advance of a run. A gas chromatography was used for analyzing the hydrocarbons methane, ethylene, ethane, propylene, propane, butenes, butanes, total C5 hydrocarbons, and higher hydrocarbons (C6 to Cj0, not separated), as well as carbon monoxide, carbon dioxide and water. Alcohols and aldehydes could be detected by the gas chro-motography but were not found to be produced in sizable amounts. 

Fig.4.5-2. An impinging-stream reactor with two pairs of tangentiai...

The major characteristic of impinging streams is the penetration of particles from one stream into the opposite one through the impingement plane (Fig.4.5), thus, increasing their mean residence time in the reactor as well as their relative velocity with respect to the air. The scheme in Fig.4.5-4 demonstrates this effect in the following way. Reactors 1 to 10 simulate the impingement zone of the particles and in each reactor particles reside for some time. A pulse of particles introduced in reactor 1 may be divided into three streams. One stream occupies reactors 3 to 5, the other, reactors 6 to 8, and the third one will occupy reactors 9 and 10. Eventually, the pulse accumulates in reactor 12 while passing reactor 11. 

Impinging streams were thoroughly treated in chapter 4.5 when studying the RTD of such systems. The flow system below comprises of four reactors three of which are equipped with heat exchangers. 

T.Bar and A.Tamir, An Impinging-stream Reactor with Two Pairs of Air Feed, The Canadian Journal of Chemical Engineering, 68(1990)541-552. 

The CFD model described above has been used by Liu and Fox (2006) to simulate the experiments of Johnson and Prud homme (2003a) in a confined impinging-jets reactor. In these experiments, two coaxial impinging jets with equal flow rates are used to introduce the two reactant-streams. The jet Reynolds number Re, determines the fluid dynamics in the reactor. Typical CFD results are shown in Fig. 6 9 for a jet Reynolds number of Re, = 400 and a reaction time of tr — 4.8 msec. The latter is controlled by fixing the inlet concentrations of the reactants. Further, details on the reactor geometry and the CFD model can be found in Liu and Fox (2006). 

As can be expected, the intensive fluctuation region is symmetrical with respect to the impingement plane, provided the two streams leaving the drawing tubes are at the same velocity. This is simply because the two sides of the reactor have the same structure. In addition, the figures also show that the region is essentially symmetrical about the flow axis, suggesting that the above assumption is reasonable. 

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