Reactor spin rate

Figure 3 shows a composite result from several simulations and considers the relationship between disk temperature and spin rate for a helium carrier in a fixed reactor geometry (fo/f[Pg.338]

Figure 2. Radial-axial velocity field and temperature contours for a rotating-disk reactor at an operating condition where a buoyancy-driven recirculation vortex has developed. The disk temperature is HOOK, the Reynolds number is 1000, Gr/Re / = 6.2, fo/f = 1.28, and L/f = 2.16. The disk radius is 4.9 cm, the spin rate is 495 rpm. The maximum axial velocity is 55.3 cm/sec. The gas is helium.

Figure 3. Relationship of susceptor temperature to spin rate that is required to operate a particular reactor geometry in the one-dimensional regime.

The other boundary conditions are relatively simple. The temperature and species composition far from the disk (the reactor inlet) are specified. The radial and circumferential velocities are zero far from the disk a boundary condition is not required for the axial velocity at large x. The radial velocity on the disk is zero, the circumferential velocity is determined from the spinning rate W = Q, and the disk temperature is specified. 

Figure 6. Species profiles in a rotating disk CVD reactor. Inlet gas is 0.1 percent silane in a carrier of 99.9 percent helium. The disk temperature is 1000 K and the spin rate is 1000 rpm.

Figure 8. Species profiles in a rotating-disk CVD reactor. Inlet gas is 0.1% silane in carrier of 99.9% helium. The disk temperature is 1000 K and the spin rate is 1000 rpm. Reprinted with permission from R. J. Kee, G. H. Evans, and M. E. Coltrin in Supercomputer Research in Chemistry and Chemical Engineering (K. F. Jensen and D. G. Truhlar, eds.), p. 334. ACS Symposium Series 353, American Chemical Society, Washington, D.C., 1987 [31]. Copyright 1987 American Chemical Society.

Various experimental methods to evaluate the kinetics of flow processes existed even in the last centuty. They developed gradually with the expansion of the petrochemical industry. In the 1940s, conversion versus residence time measurement in tubular reactors was the basic tool for rate evaluations. In the 1950s, differential reactor experiments became popular. Only in the 1960s did the use of Continuous-flow Stirred Tank Reactors (CSTRs) start to spread for kinetic studies. A large variety of CSTRs was used to study heterogeneous (contact) catalytic reactions. These included spinning basket CSTRs as well as many kinds of fixed bed reactors with external or internal recycle pumps (Jankowski 1978, Berty 1984.)... 

The key to obtaining pore size information from the NMR response is to have the response dominated by the surface relaxation rate [19-26]. Two steps are involved in surface relaxation. The first is the relaxation of the spin while in the proximity of the pore wall and the other is the diffusional exchange of molecules between the pore wall and the interior of the pore. These two processes are in series and when the latter dominates, the kinetics of the relaxation process is analogous to that of a stirred-tank reactor with first-order surface and bulk reactions. This condition is called the fast-diffusion limit [19] and the kinetics of relaxation are described by Eq. (3.6.3) ... 

The results have shown that spinning/falling basket autoclaves can be used effectively for gathering data on coal hydroliquefaction, a single contact being representative of steady state conditions. As with other types of reactors for coal liquefaction, the catalysts were deactivated to a constant activity but the rate of deactivation was much more rapid in tiie autoclaves. 

A second method of local planarization involves spinning photoresist onto the SiOj ILD to obtain local planarity. The resist is then hard baked and etched with an RIE etch tailored to remove SiOz (or ILD) at the same rate as the photoresist. Because the etch rate of the two materials is equal, the planarity of the resist film transfers into the SiOz film. However, a precise match in SiOj and photoresist etch rates is difficult to maintain because the relative ratio of SiOj to photoresist exposed increases as the etch back proceeds. Loading effects then result in a decrease in the Si02 etch rate and increase in the photoresist etch rate. Furthermore, polymer deposits build up on the etch reactor chamber walls over time etching of this polymer depletes the chemicals used to etch the photoresist, which slows the photoresist etch rate. If the etch rates are not matched, the planarity of the photoresist layer will not transfer well to the SiOz. 

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