Experimental liquid/solid system

A turbine type agitator is commonly used for liquid-solid systems. Mixing rates depend on the forces required to suspend all solid particles. Minimum levels can be determined for (1) lifting the particles, and (2) for suspending them in an homogeneous manner [200]. Similar requirements apply to liquid-liquid systems. For cases where two poorly miscible fluids of about equal volume are used in the reaction, the mixer is placed at the interface. For a bench-scale experimental system of about 2 liters capacity, the minimum rotational speed to obtain well-dispersed system is 300 to 400 rpm [201], depending on the type of mixer. This rotational value decreases as the vessel volume increases. 

In practice, the contact angle can be experimentally determined in a rather routine manner, as can the liquid surface tension and even the solid surface energy. The interfacial energy for the liquid-solid system of interest, ysi, can then be calculated using Young s equation. Alternatively, if ysL, Yl, and ys are known as a function of temperature, the contact angle can be predicted at a specified temperature. 

Agitated tank reactors Batch agitated reactor This is a batch stirred tank reactor. For liquid-solid systems, the liquid is agitated by a mechanical apparatus (impeller) and the reactor is of tank shape. For gas-solid systems, the gas is agitated and rapidly circulated through a fixed-bed of solids. This reactor is basically an experimental one used for adsorption, ion exchange, and catalysis studies. 

The analysis of this type of reactor requires a uniform composition of fluid phase throughout the volume. While this is easily achieved by standard agitation devices for liquid-solid systems, i.e. impellers, it requites special design to be achieved for gas-solid systems. This type of reactor is basically used for laboratory experimentation. 

Volume-fraction effects on particle coarsening rates have been observed experimentally. For comparisons between theory and experiment, data from liquid+solid systems are far superior to those from solid+solid systems, as the latter are potentially strongly influenced by coherency stresses. Hardy and Voorhees studied Sn-rich and Pb-rich solid phases in Pb-Sn eutectic liquid over the range

presented data in support of the volume-fraction effect, as shown in Fig. 15.9 [7],... 

In the case of a stationary basket-type reactor, kLaL correlations proposed for conventional agitated slurry reactors by Ramachandran and Choudhari (1983) can be used. No experimental data for liquid-solid systems are, however, available. 

This chapter presents a quantitative method to determine the photoadsorption capacity of a polycrystalline semiconductor oxide irradiated in liquid-solid system. The determination is performed imder reaction conditions so that it is really indicative of the photoadsorption capacity. The method uses the experimental results obtained in typical batch photoreactivity runs on this ground it has been applied to the following photocatalytic processes carried out in aqueous suspensions (i) oxidation of phenol in the presence of a commercial Ti02 catalyst (Degussa P25) and... 

Experimental checking. Figure 4.29 compares the theoretical calculations and experimental results for the evolution of g/(l — with Wg/v for a MFPB. The bed height has been fixed at 0.25 m. Two liquid-solid systems with solid fractions of 0.1 and 0.3 m3/m3 have been chosen. A 0.0275 m diameter spheres of density 980-1030 kg/m3 were selected as mobile packing. Air and water are the working fluids. The gas fraction results from bed expansion when gas flows through the liquid-solid system. 

Experimental gas-solid mass transfer data are presented for the well defined supercritical CO 2-naphthalene system at 10-200 atm and 35 C. These data are compared with low pressure gas-solid and liquid-solid systems. It has been found that both natural and forced convection are important under these conditions and that mass transfer rates at near-critical conditions are higher than at lower or higher pressure. 

The purpose of probe calibration in liquid—solid systems is to ascertain if the responding curves of the probe and the measuring system are linear for the test materials. Since in liquid-solid systems particles are distributed uniformly, the reproducibility would be perfect. If the calibration results of the whole system are linear, for gas-solid systems the only parameter which needs to be changed is the index of refraction of the continuous phase. Experiments showed that in the case of a gas-solid system, under the same experimental conditions the output signals of concentration were larger that those for the liquid—solid systems. 

Application of artificial neural networks (ANN) for modelling of the kinetics of a catalytic hydrogenation reaction in a gas-liquid-solid system has been studied and discussed. The kinetics of the hydrogenation of 2,4-DNT over a palladium on alumina catalyst has been described with feedforward neural networks of dififerent architectures. A simple experimental procedure to supply learning data has been proposed. The accuracy and flexibility of the hybrid first principles-neural network model have been tested and compared with those of the classical model. 

The first experimental confirmation that gravity plays a role in spin modes in a liquid/solid system came in the study of descending fronts in which the viscosity was significantly increased with silica gel (55). Masere et al. found... 

B.9.1.6 Mixing Time in Three-Phase (Gas-Liquid-Solid) System There are no reported experimental data on gas-liquid-solid systems that are relevant to animal cell culture using microcarrier beads as support for the cells. As mentioned earlier in the case of gas-liquid and solid-liquid systems, because of (i) the low density difference (Ap 30-50 kg/m ) and (ii) low aeration rates, there is insignificant impact of introduction of the solid and gas phases. Further, if an upflow impeller is used, the power drop due to aeration is less than 10% at low aeration rates (Fig. 7A.6). Therefore, Equation 7B.11 can be used in this case also. 

In this article we have discussed the problems associated with the experimentally measured contact angle. The observations are the presence of a significant contact angle hysteresis with most liquid-solid systems, the relaxation of contact angle to lower values for advancing... 

Cini et al. (1991b) proposed the use of a tubular Pd/AljOj mesoporous membrane for the hydrogenation of a-methylstyrene to cumene. A comparison between the tubular catalyst and a fully-wetted pellet revealed a rate increase by up to a factor of 20. From that study, several other theoretical (Torres et al, 1994) and experimental ones confirmed that a three-phase membrane reactor can improve the mass transfer rate of gas-liquid-solid systems. 

If experimental liquid-solid adsorption equiiibrium data are available for each solute species i at a given temperature, then, to obtain the equilibria in a muitisolute system, employ relation (4.1.62) for each soiute species to obtain a relation between iti and/j(C ). For exampie, for a system of two solutes being present (i = 1,2), obtain... 

The first experimental confirmation that gravity plays a role in spin modes in a liquid-solid system came in the study of descending fronts in which the viscosity was significantly increased with silica gel. Masere et al. found that silica gd significantly altered the spin behavior, as predicted by Garbey et Pojman et al. made a similar observation in square reartors. Pojman et al. studied the dependence of spin modes on viscosity with the FP of HDDA with persulfate initiator. They found that the number of spins was independent of the viscosity until a critical viscosity was reached, when the spins vanished. 

These scaling laws have been examined experimentally and shown to agree fairly well with experimental data for many liquid/solid systems (de Gennes 1985 Brochard-Wyart et al. 1991 Marmur 1997 Tanner 1979 Ca2abat and Cohen Stuart 1986). 

There is a great interest in the nature of the interface between water and silicate minerals (see for example Davis and Hayes (1986)). Much of the chemical activity in soils, sediments and porous rocks occurs at such an interface. Experimentally, it is very difficult to examine this interface because it is such a small part of the liquid-solid system. Hydrated smectites and vermiculites have water between all of the silicate layers and therefore the percentage of the sample which is interface is enormously larger than the interface between, for example, a grsin of quartz in contact with liquid water. Another way to look at this is that the surface are of a quartz sand is probably much less than 1 m gram while a typical smectite has a surface area of as much as 800 m /gram. For these, and other reasons, intercalated clays have been extensively studied. 

One goal of our experimental program with the bench-scale unit was to develop the necessary correlations for use in the ultimate design of large commercial plants. Because of the complexity inherent in the three-phase gas-liquid-solid reaction systems, many models can be postulated. In order to provide a background for the final selection of the reaction model, we shall first review briefly the three-phase system. 

The ability to predict liquid-liquid and liquid-solid equilibria in complex systems is still rather undeveloped, in part because of the lack of systematic and molecularly interpreted experimental iirformatiom Considerable research has... 

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