Mixing liquid-gas

The proposed technique will be used here to illustrate the case of interfacial heat and multicomponent mass transfer in a perfectly mixed gas-liquid disperser. Since in this case the holding time is also the average residence time, the gas and liquid phases spend the same time on the average. If xc = zd = f, then for small values of t, the local residence times tc and td of adjacent elements of the continuous and dispersed phases are nearly of the same order of magnitude, and hence these two elements remain in the disperser for nearly equal times. One may conclude from this that the local relative velocity between them is negligibly small, at least for small average residence times. Gal-Or and Walatka (G9) have recently shown that this is justified especially in dispersions of high <6 values and relatively small bubbles in actual practice where surfactants are present. Under this domain, Eqs. (66), (68), (69) show that as the bubble size decreases, the quantity of surfactants necessary to make a bubble behave like a solid particle becomes smaller. Under these circumstances (pd + y) - oo and Eq. (69) reduces to... 

In this example, a fluidised biofilm sand bed reactor for nitrification, as investigated by Tanaka et al. (1981), is modelled as three tanks-in-series with a recycle loop (Fig. 1). With continuous operation, ammonium ion is fed to the reactor, and the products nitrite and nitrate exit in the effluent. The bed expands in volume because of the constant circulation flow of liquid upwards through the bed. Oxygen is supplied external to the bed in a well-mixed gas-liquid absorber. 

Reference Material Material or substance whose property values are sufficiently homogeneous and well-established so as to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials. (Note A reference material may be in the form of a pure or mixed gas, liquid, or solid. Examples include synthetic mixtures such as calibration solutions used in chemical analysis as well as materials based on natural environmental samples such as sediments.)... 

A reference material may be in the form of a pure or mixed gas, liquid or solid... 

Due to the approximate uniformity of the intensively mixed gas/liquid system and, therefore, the intensity character of the target quantity kLa, the influencing process quantities (stirrer power P, air throughput q) have to be formulated in an intensive manner as well. Now, the question arises whether, in addition to the volume-related stirrer power, P/V, the gas throughput also has be formulated as a volume-related one (q/V), or if its inclusion as the so-called superficial velocity vG = q/S (as accurate... 

In the fixed-film reactor, the organisms grow on an inert surface that is maintained in the reactor. The inert surface can be granular material, proprietary plastic packing, rotating discs, wood slats, mass-transfer packing, or even a sponge-type material. The reactor can be flooded or nave a mixed gas-liquid space (Fig. 25-52). The biomass level on the... 

Figure 3.49. Well-mixed gas-liquid contacting stage.

A schematic illustration of a typical inlet apparatus for separating volatile hydrides from the analyte solution, in which they are generated upon reduction with sodium tetrahydroborate. When the mixed analyte solution containing volatile hydrides enters the main part of the gas/liquid separator, the volatiles are released and mix with argon sweep and makeup gas, with which they are transported to the center of the plasma. The unwanted analyte solution drains from the end of the gas/liquid separator. The actual construction details of these gas/liquid separators can vary considerably, but all serve the same purpose. In some of them, there can be an intermediate stage for removal of air and hydrogen from the hydrides before the latter are sent to the plasma. 

Gas-liquid mixing Gassliquid transfer Gas mantles Gas, manufactured... 

Increased gas rate increases turbulence and the degree of back mixing of liquid. 

Topics that acquire special importance on the industrial scale are the quality of mixing in tanks and the residence time distribution in vessels where plug flow may be the goal. The information about agitation in tanks described for gas/liquid and slurry reactions is largely apphcable here. The relation between heat transfer and agitation also is discussed elsewhere in this Handbook. Residence time distribution is covered at length under Reactor Efficiency. A special case is that of laminar and related flow distributions characteristic of non-Newtonian fluids, which often occiu s in polymerization reactors. 

Device kia, s V, m kioV, mVs (duty) a, m Liquid mixing Gas mixing Power per unit volume, kW/m ... 

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 ... 

The power consumed by an agitator depends on its dimensions and the physical properties of the fluids being mixed (i.e., density and viscosity). Since there is a possibility of a gas-liquid surface being... 

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