Chum-turbulent flow regime

Figure 5.3-8. Details of the chum-turbulent flow regime of BSCR according to Inga [1], (db)0-gas bubble size at atmospheric conditions in the absence of solid particles, (d, )ps- bubble size at the operating pressure and catalyst concentration. Column height = 2.8 m, internal diameter = 0.316 m. P < 8 bars. Organic media, catalyst diameter < 100 pm.

Bubble columns Loop reactors Stirred tanks Hydrocyclones Reasonable Reasonable Reasonable Reasonable Modeling of chum-turbulent flow regime Modeling of chum-turbulent flow regime Improved geometrical representation of impeller and baffles Improved geometrical representation of system... 

Methods are given for the bubbly and chum-turbulent flow regimes within the vessel. The criterion for safe use to take account of disengagement is, GAh vJ Vv,(l-a,) - However, when disengagement is not accounted for, then = 1.0, and the above equation is not required. 

Recommendations for p range from 1 to 1.5 and for q from 0 to 2. Rice et al. [62] concluded that this was due to the different regimes and recommended q values of 2, 1, 1/3 and 0 for chain bubbling, bubbling flow, chum-turbulent flow and slug flow, respectively. 

Three-phase fluidized beds and slurry reactors (see Figs. 30g-l) in which the solid catalyst is suspended in the liquid usually operate under conditions of homogeneous bubbly flow or chum turbulent flow (see regime map in Fig. 33). The presence of solids alters the bubble hydrodynamics to a significant extent. In recent years there has been considerable research effort on the study of the hydrodynamics of such systems (see, e.g., Fan, 1989). However, the scale-up aspects of such reactors are still a mater of some uncertainty, especially for systems with high solids concentration and operations at increased pressures it is for this reason that the Shell Middle Distillate Synthesis process adopts the multi-tubular trickle bed reactor concept (cf. Fig. 30e). The even distribution of liquid to thousands of tubes packed with catalyst, however poses problems of a different engineering nature. 

Of interest is a recent theoretical relation for eg in gas-liquid bubble columns based on liquid circulation and claimed to be valid both in the homogeneous bubble flow regime and in the chum-turbulent regime, also for non-Newtonian fluids. For power law fluids with... 

CFD approach. This model has too many unknown parameters when applied to multiphase flow. The kind of model used by Dudukovic group (72) computed the Reynolds stresses in agreement with measurements done in L.S. Fan s laboratory. In the Matonis et al (75) paper we show our capability to compute turbulence in a slurry bubble column in the chum-turbulent regime in agreement with our measurements. 

The CARPT—CT techniques have been introduced at CREL to provide cold flow modeling information on slurry bubble column flows operated in chum turbulent regime needed for gas-to-Hquid conversion processes (Degaleesan, 1997 Degaleesan and Dudukovic, 1998 Degaleesan et al.. 

The other two flow types are both of great practical importance. There is one important difference between these two flow types. In the homogeneous regime, some coalescence may occur when it does, the bubble size will increase with the height above the gas distributor. In the chum-turbulent regime, coalescence and... 

This relation has been checked for a wide range of gas flow rates and vessels sizes (0.15 - 2.6 m in diameter), and appeared to be independent of scale. It covered both flow regimes (homogeneous and chum-turbulent). 

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