Liquid mixing performance

This study investigates the hydrodynamic behaviour of an aimular bubble column reactor with continuous liquid and gas flow using an Eulerian-Eulerian computational fluid dynamics approach. The residence time distribution is completed using a numerical scalar technique which compares favourably to the corresponding experimental data. It is shown that liquid mixing performance and residence time are strong functions of flowrate and direction. 

Three basic fluid contacting patterns describe the majority of gas-liquid mixing operations. These are (1) mixed gas/mixed liquid - a stirred tank with continuous in and out gas and liquid flow (2) mixed gas/batch mixed liquid - a stirred tank with continuous in and out gas flow only (3) concurrent plug flow of gas and liquid - an inline mixer with continuous in and out flow. For these cases the material balance/rate expressions and resulting performance equations can be formalized as ... 

Mixing performance, 306 Blending, 324 Emulsions, 324 Extraction, 324 Gas-liquid contacting, 324 Gas-liquid dispersion, 325 Liquid-liquid dispersion, 325, 326 Mixing vortex, 311 Motionless mixing, see static mixing National Fire Protection Association, 399 Net positive suction head, 160-194 Available from system, 160, 188, 189,... 

Mechanically stirred gas-liquid reactor performances are affected by the degree of mixing, apparatus geometry, stirring power, flow rate, discharge and feed locations for the gas and liquid. For a correct design, the following requirements must be satisfied ... 

As might be expected, the vapour phase may offer the controlling resistance to mass transfer in high pressure distillations. Values for tray efficiencies at elevated pressure are scarce [23, 24]. The prediction of tray efficiency may be approached in several ways. One way is to utilize field performance data taken for the same system in very similar equipment. Unfortunately such data are seldom available. When they are available, and can be judged as accurate and representative, they should be used as a basis for efficiency specification [25], Another way is to utilize laboratory-or pilot-plant efficiency data. For example a small laboratory-Oldershaw tray-column can be used with the same system. Of course, the results must be corrected for vapour-and liquid mixing effects to obtain overall tray efficiencies for large-scale design [26], Another approach is the use of empirical or fundamental mass-transfer models [27-30],... 

Example 10.2 compares data of Table 10.4 with calculations based on Figures 10.6 and 10.7 for all-liquid mixing. Power and rpm requirements at a given superficial liquid velocity are seen to be very sensitive to impeller diameter. When alternate combinations of HP/rpm are shown in the table for a particular performance, the design of the agitator shaft may be a discriminant between them. The shaft must allow for the torque and bending moment caused by the hydraulic forces acting on the impeller and shaft. Also, the... 

Estimation of liquid mixing in a fluidized bed may be performed by a variety of correlations provided in literature. The problem in using the proposed correlations is, that they were obtained under many different operating... 

P 12] The mixing performance was analyzed by a dilution-type experiment. Here, water and the fluorescent dye uranine, sodium fluorescein [22], The latter is water-soluble. External pressure was applied to the liquids using a fluid dispenser. The flow rates of both water and the aqueous uranine solution were 5 pi min-1. A fluorescent microscope with a digital CCD camera with a 1.25x objective was used for optical mixing analysis. Fluorescent filters at 460-490 and 515-550 nm... 

Many operations treat particle-liquid mixing in chemical industry. The first aim of solid-liquid mixing is to make a solid particle float. However, mixing performance of operations/equipment is not clear. Additionally, when many kinds of particles are involved, it is not known whether there is any difference in the mixedness between the following two cases the case where all particles are treated as a particle (two-phase mixing—particle and continuous liquid phase) and the case where every particle is treated individually (multiple-phase mixing—each particle and continuous liquid phase). Therefore, a solution to this unsolved problem is not imperative. 

From the mass transfer point of view, airlift fermenters should be designed and operated in such a way that carryover of air from the riser into the downcomer is kept as low as possible. Gas in the downcomer liquid contributes little to oxygen transfer. It reduces the effective density difference between the contents of the riser and downcomer, however, which reduces the liquid circulation rate and also impairs the mixing performance of the fermenter. In fermentations where even a momentary lack of oxygen can very seriously affect productivity, some air is essential to maintain aerobic conditions and sustain fermentation in the downcomer. 

One of the primary reasons that the spray dryer-scrubber is able to achieve excellent sulfur dioxide removal with such low liquid-to-gas ratios is the small size of the droplets produced by the high speed centrifugal atomizer. This type of atomizer also has an easily controlled turndown capability which is a desirable feature that has been demonstrated in the pilot tests. As gas flow decreases, the amount of sodium carbonate solution can be decreased in direct proportion without interfering with sulfur dioxide removal efliciency. The atomizer actually produces finer droplets at the lower liquid flow rates. This appears to compensate for any gas-liquid mixing problems that could impair performance. 

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