Gas-liquid interactions

In general, silicate melts are unstable under the conditions that prevailed in the solar nebula. However, chondrules and some CAIs crystallized from partially molten to completely molten droplets. The melting events that produced chondrules and CAIs thus present an ideal situation for chemical and isotopic fractionations to occur. 

Element and isotopic abundances of Si and Mg in CAIs suggest evaporation, (a) Correlated isotopic fractionations in Type CAIs. (b) Si02 versus MgO for CAIs, relative to the calculated condensation sequence abundances (heavy line). Unmelted Type A inclusions (open circles) follow the condensation path, whereas partly melted Type inclusions (filled circles) deviate, because of loss of both Mg and Si, as illustrated by the arrow. Modified from Davis and Richter (2004). 

In an open system, where the gas is removed and not permitted to back-react with the liquid, the tendency for the light isotope to preferentially go into the gas phase results in an isotopically light gas and the liquid composition becomes increasingly isotopically heavy. This 

In a system undergoing Rayleigh distillation, an isotopic ratio in the liquid will evolve according to 

In this equation, ,/ and mi/2 are the masses of the two isotopes making up RZ1, and the terms are condensation coefficients for the two isotopes, which are determined experimentally and are typically close to 1. Equation (7.2.1) is valid if a is independent of the evolving composition of the evaporating liquid, and the diffusive transport rate is fast enough to keep the liquid homogeneous. The last condition is violated in solids, where diffusion is very slow relative to the evaporation rate, so solids do not undergo Rayleigh distillation. 

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The liquid mean residence time, tm, in counter-current mode was significantly lower than in co-current mode. Statistical analysis (Yates method of ANOVA) indicates that along with the liquid flowrate, the direction of liquid travel is the most significant factor in the liquid mean residence time. This variation in the liquid phase mean residence time, suggests an increase in short-circuiting or channeling in the counter-current mode as a result of the gas-liquid interactions. 

Mirabel, P., George, C., Magi, E., and Ponche, J.E. Gas-liquid interactions, in Heterogeneous and Liquid-Phase Processes, Warneck, P., Ed. (Berlin Springer-Verlag, 1996), pp. 175-181. 

The ability of the centrifugal extractor to solve difficult liquid-liquid separation problems, as illustrated in the previous examples, has allowed its use in a wide range of extraction applications. The long history of use has given it a general acceptance in chemical manufacturing—an acceptance not shared by the broader application of gas-liquid interactions. 

The following developments will be restricted to laminar liquid flow with weak gas-liquid interactions. However, this is not a limitation of the proposed methodology which could be easily applied to any other flow regime. Applications will be presented for the modelling of the irrigation rate, the dynamic liquid holdup and the apparent reaction rate in the absence of external mass transfer limitations and in the case of non volatile liquid reactants (i.e. approximatively the operating conditions of petroleum hydrotreatment). 

This equation is reproduced in Figure 5 for different values of Lj-. The experimental system considered in this figure consists of water flowing through a bed of 3 mm diam. spheres with a porosity equal to 0.35. The pressure drop is assumed to be negligible (6. pjE). Comparison of Eq.16 with the correlation proposed by Specchia et al. (18), for the low gas-liquid interaction regime,... 

For a given liquid flow rate the pressure gradient increases with increasing gas flow. This is expected due to the increased energy loss associated with the increased gas-liquid interactions. 

To sum up, the particle external mass-transfer coefficients for particle diameters larger than 3 mm may be determined with the relationships proposed by Satoet al. or Ruether et al. for G > 0.01 kg/m sec that is, when the gas-liquid interaction is significant. For trickle flow, Eq. (115) with a constant of 0.8 will give reasonable values. For particle diameters smaller than 3 mm, the specific relations proposed by Goto (G13) should be used. 

Fig. 5 shows the bubble plume in front view (y-z plane) and profile (z-x plane). In both cases the photo is accompanied by a drawing schematizing the observed flows. For a constant gas input, the total gas/liquid contact surface is greater for small bubbles than for larger bubbles and the gas-liquid interactions are also greater. It was observed that the smaller the bubbles, the greater the liquid velocity, the more agitated and more turbulent the bubble plume, and the more spread out the plume at the air/liquid interface. 

Sulfur dioxide containment by gas-liquid interactions can be as simple as flue, or process gas scrubbing with dilute ammonium hydroxide (Eqs. 3.23 and 3.24). 

A further gas-liquid interaction process to a useful product is the sodium carbonate-potassium carbonate eutectic melt process. This operates at a temperature of about 425°C, well above the melting point of the eutectic [43]. Sulfur dioxide absorption takes place with loss of carbon dioxide (Eq. 3.32). 

The hydrogen sulfide initial product can be subsequently converted to more useful sulfur via the Claus process. In return for the high operating temperatures required for this process, it gives a substantially dry plume, unlike the other gas-liquid interaction processes mentioned. This may be an important consideration if the process is to be operated in a fog susceptible area. 

A special reactor for gas-liquid interaction is described by the authors in patent [18]. Due to the holes in the stirrer, C02 is involved intensively in the epoxy compound. 

By increasing the gas velocity, the shear stress at the interface is augmented consequently breakup is accelerated and the frequency is increased. By increasing the liquid velocity, the liquid momentum is increased which accelerates the rush of the liquid toward the axis of the nozzle, hence increasing the gas-liquid interaction and accelerating the liquid breakup and increasing the fi-equency. This self-induced pulsation is one of the major sources of noise in twin-fluid nozzles. 

Also, changing the entrance angle increases pulsation. However, the amplitude of the pulsation is substantially decreased. The reason for this behavior lies in the gas-liquid interaction. As the entrance angle is reduced, liquid surface exposed to steam and consequently shear stresses at the interface are increased. Therefore, an increase in pulsation is observed. However, as the liquid direction is more aligned with the gas flow, the effect of liquid momentum opposing gas flow is reduced and as a result the amplitude of the pulsation is noticeably reduced. When the entrance dent is removed this effect becomes so pronounced that pulsation virtually disappears. 

Phases Gas, liquid, gas-liquid interacting with solid catalyst or inert solid. Use if the order of the reaction is positive and > 95 % conversion is the target, and for consecutive reactions with an intermediate as the target product. Caution use for highly exothermic reactions. Not suitable for Arr (ATad ) > 10 or > 100 °C usually keep AT j < 50 °C. Provides large gas throughput. Related topics for GL, trickle reactor. Section 6.17, or bubble reactor. Section 6.13. 

Instead of using the Larkins et al s two phase parameter 6] q proportional to the resultant of the friction forces, Charpentier et al. (54, 62) have suggested for the high gas-liquid interaction systems to use the two phase parameters and proportio-... 

The following developments will be restricted to the laminar liquid flow with weak gas-liquid interactions. However, this is not a limitation of the proposed methodology which could be easily applied to any other flow regime. 

It is also to note that the two-phase pressure drop and the liquid phase holdup necessary for the use of this correlation may be estimated from equations (7) and (8) respectively. This representation is only suitable for weak gas-liquid interaction flow in which the eventual anticoalescent characteristics of solutions do not intervene. Besides it may be noticed that the results obtained with ionic solution for glass beads do not fit with this correlation, and this occurs all the more as the anticoalescent characteristics are more pronounced (NaOH then Na2S0 ). 

Dynamic QM/MM A Hybrid Approach to Simulating Gas-Liquid Interactions... 

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