Liquid-phase distribution

In practice, granular beds comprising a very large number of catalyst pellets are used. It is well known that the efficiency of a catalytic reactor depends crucially on the liquid phase distribution within the catalyst bed [14]. It is likely that the development of hot spots in a catalyst bed is also related to the character of liquid phase distribution. Therefore, it is very important to map the spatial distribution of the liquid phase in a catalytic reactor for various operation regimes. This eventually should lead to the formulation of the mechanisms responsible for the development of critical phenomena on both a micro- and macroscale. 

This can explain why hydrogen flow rate has little effect on liquid phase distribution in the catalyst bed and on conversion. At the same time, higher flow rates of warm hydrogen intensify evaporation of liquid in the inert layer and remove the resulting vapor out of the reactor, leading to the decrease in liquid content in the inert layer. 

Fig. 22. Spatial maps of the liquid-phase distribution within a catalyst pellet under reactive conditions. For each image, the temperature and time of detection are indicated. The intensity scale is shown on the left-hand side. Reprinted from reference 68), with permission from American Chemical Society, Copyright (2002).

The authors studied the dominant monomeric species in 0.5 to 4 M HCIO4 solutions. The total Zr concentration was not reported but since the authors have used radioactive Zr, it can be safely assumed that the Zr concentration was sufficiently low to allow investigations of monomer behaviour. This is confirmed by the statement of the authors that the Zr concentrations were always much lower than the concentration of P-isopropyltropolone, which was always smaller than 4 x 10 M. The acid dependency of liquid/liquid phase distribution ratios of Zr was used to deduce the stoichiometry of the monomeric species. Two independent extraction equilibria were tested to account for uncertainties in the chemistry of the exchange equilibria (a) extraction from 3 M (Na, H)C104 solutions of perchlorates of Zr by methylisobutylketone and (b) extraction of P-isopropyltropolonates of Zr in chloroform. 

The quality of separation of gas-liquid mixture in separators depends on the velocity (flow rate) of gas, thermobaric conditions, physical and chemical properties of the phases, geometrical parameters and, most importantly, dispersiveness of the liquid phase (distribution of drops over sizes and the parameters of this distribution) that goes into the separator together with the gas flow from the delivery pipeline. The key parameter of this distribution is the average size of drops that are formed in the gas flow in the delivery pipeline. Therefore, it depends on the parameters of the pipeline and also on the parameters of the device of preliminary condensation (DPC), which, as a rule, is placed at some distance from the separator (see technological schemes in Chapter 1). Therefore, the efficiency of gas-liquid mixture separation is influenced not only by the parameters of the separator, but also by the particular details of the technological circuit before the separator. 

In liquid elution chromatography, separation is based on adsorption on the solid or on partition to a stationary or bonded liquid phase. Distribution coefficients are modest so that solutes migrate through the column as shown in Figs. 14.1-2 and 14.1-3. Gradients can be used but usually are not since the column has to be reequilibrated afterward. Two somewhat different approaches have bMn taken ... 

Figure 1. Cumulative liquid phase distribution as a function of carbon number. Circles correspond to the composition of mixture F, triangles to the eomposition of mixture G and squares to the...

Figure 10.9 Idealized liquid-phase distribution (in three dimensions) for selected values of the dihedral angle. (From Ref. 9.)...

From the liquid phase distribution, the capillary forces Fc on the individual gel particles are accessible, with one contribution from the bulk liquid and a second from the three-phase contact line. By use of the discrete element method (DEM), capillary forces can be loaded on the primary partides, which are connected by bonds as a result, micro-cracks - and also shrinkage -can be simulated (Kharaghani et al., 2011). The cracking criterion is, hence, set by the strength of the necks interlinking the primary partides. 

Stationary Phase. Synonymous with liquid phase, distributed on a solid, in gas-liquid chromatography or the granular solid adsorbent in gas-solid chromatography. The liquid may be chemically bonded to the solid. 

Besides LPD (liquid-phase distribution) techniques, SPD (solid-phase distribution) methods by means of cartridges can also be used, which reduces the time of extraction. Comparing both techniques, SPD seems to be sUghtly less effective than LPD, although the recoverable capabUities are similar [76]. Recendy, also diol-phase cartridges (diol-SPE) have been described with optimistic published results [187]. 

Estimation of the Intergranular-Liquid-Phase Distribution Using Local Impedance Technique... 

The liquid phase distribution over time obtained from the numerical simulation is shown in Fig. 11 At the onset of evaporation, a curved meniscus develops inside the cylinder and recedes. Upon further evaporation, capillary effects become clearly visible large pores dry out earlier, while small pores stay saturated for a longer time. In order to study the effect of wettability, another simulation with the same particle packing but with a different value of the equilibrium contact angle has been performed, see Fig. 12. By comparing these two figures, one can see that the capillary effects are clearly more pronounced for smaller equilibrium contact angle. 

The effect of foe liquid flow rate on foe liquid phase distribution is approximately foe same in all parts of foe column. 

Calculation of the liquid phase distribution in packed columns in the presence of wall effect... 

The quantitative description of the radial spreading in case of wall flow is carried out using different models [58, 8-13, 59, 73] based on the differential equation of Cihla and Schmidt, Eq. (3). The difference between them is in the boundary conditions at which the differential equation is solved. All these methods describe well Ihe liquid phase distribution over the cross-section of the column using two experimental constants, dqjending on the type of the packing and the dimensions of frie column. 

In the first investigation of this series [21], the liquid phase distribution in the packing in case of initial uniform distribution and a single deflecting ring installed over the packing bed is calculate and ejq erimentally proved. 

I.e. in this case the solution of Cihia and Schmidt [6] fi r a cylindrical column with a reflecting wall, Eq. (6), can be used for calculatitm of L. Because the distance between the mints C or plane F is smaller than the radius R of the circumscribed cylinder, the liquid phase distribution in the jmsm is sli tly better than in the cylinder, i.e. wh using Eq. (34) instead of Eq. (33), the calculated height of the (tacking is big r than tW necessary fcxr the distribution of the liquid phase to a given depee of uniformity. 

Fortunately, the modem good constmctions of liquid phase distributors, due to the good design, can ensure quite better degree of initial uniformil, for example 2-5% nonuniformity. That is why more investigations on the of nonuniformity of the liquid phase distribution are not necessary. 

The distance between the drip points of the distributor I is chosen 130 mm. For determination of the height of the redistribution layer, ho.95, ensuring 95% uniformity of the liquid phase distribution over the column cross-section, Eq. (38) (Chapter 8)... 

He has published about 128 papers and has 51 patented inventions, most of them in the area of packed bed columns. On the basis of his patented inventions about uniform liquid phase distribution over the whole cross-section of the apparatus, and by using his own mathematical model, he succeeded to introduce in industry new own packings and new processes without any pilot plant investigations for a given system. 

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