Distribution of liquid

Packed columns must be provided with good initial distribution of liquid across the column cross section and redistribution of liquid at various height intei vals that decrease with increasing column diameter. A wide variety of distributors and redistributors are available. Packed columns should be considered when ... 

Typically the plate is half-moon in shape and is sloped slightly in the direction of liquid flow. Gas contacts the liquid as it showers from the plate, and a serrated lip or weir at the edge of the plate can be used to improve the distribution of liquid in the shower. 

Liquid Holdup The major factor influencing this property is the liquia flow rate, but the shape, size, and wetting characteristics of the particles and the gas rate and the initial distribution of liquid also enter in. One of the simpler correlations is that of Midoux et al. (J. 

A heterogeneous tubular reaetor that ineorporates three phases where gas and liquid reaetants are eontaeted with the solid eatalyst partieles, is elassified as a triekle-bed reaetor. The liquid is usually allowed to flow down over the bed of eatalyst, while the gas flows either up or down through the void spaees between the wetted pellets. Co-eurrent downflow of the gas is generally preferred beeause it allows for better distribution of liquid over the eatalyst bed and higher liquid flow rates are possible without flooding. 

These contribute to the uniform distribution of liquid as it enters the tray from the downcomer. There are about as many tray designs without weirs as with them. The downcomer without inlet weir tends to maintain uniform liquid distribution itself. The tray design with recessed seal pan ensures against vapor backflow into the downcomer, but this is seldom necessary. It is not recommended for fluids that are dirty or tend to foul surfaces. The inlet weir is objectionable for the same reason. 

Tests by FRI and Nutter [132] emphasize that distribution of liquid must be uniform and at minimum values to achieve good HETP values over a range of system pressures for hydrocarbons distillation. 

When considering environment it generally becomes difficult since actual service conditions are most of the time unpredictable. As an example, there is a systematic difference in the frequency distributions of liquid water content in rain. It appears that the areas most likely to have high values of liquid water are where there is a plentiful supply of moisture and a high instability in the atmosphere. The lowest values of liquid water are obtained from the climatic areas of light continuous rains such as that found along the northwest coast of the United States. 

Holdup and Residence-Time Distribution of Liquid Phase... 

Eulerian two-fluid model coupled with dispersed itequations was applied to predict gas-liquid two-phase flow in cyclohexane oxidation airlift loop reactor. Simulation results have presented typical hydrodynamic characteristics, distribution of liquid velocity and gas hold-up in the riser and downcomer were presented. The draft-tube geometry not only affects the magnitude of liquid superficial velocity and gas hold-up, but also the detailed liquid velocity and gas hold-up distribution in the reactor, the final construction of the reactor lies on the industrial technical requirement. The investigation indicates that CFD of airlift reactors can be used to model, design and scale up airlift loop reactors efficiently. 

Inlet weirs, or recessed pans, are sometimes used to improve the distribution of liquid across the plate but are seldom needed with segmental downcomers. 

Such spatial variations in, e.g., mixing rate, bubble size, drop size, or crystal size usually are the direct or indirect result of spatial variations in the turbulence parameters across the flow domain. Stirred vessels are notorious indeed, due to the wide spread in turbulence intensity as a result of the action of the revolving impeller. Scale-up is still an important issue in the field of mixing, for at least two good reasons first, usually it is not just a single nondimensional number that should be kept constant, and, secondly, average values for specific parameters such as the specific power input do not reflect the wide spread in turbulent conditions within the vessel and the nonlinear interactions between flow and process. Colenbrander (2000) reported experimental data on the steady drop size distributions of liquid-liquid dispersions in stirred vessels of different sizes and on the response of the drop size distribution to a sudden change in stirred speed. 

Colenbrander, G. W., Experimental Findings on the Scale-Up Behaviour of the Drop Size Distribution of Liquid-Liquid Dispersions in Stirred Vessels . Proceedings of the 10th European Conference on Mixing, Delft, Netherlands, 173-180 (2000). 

Another important application of plain-orifice atomizers is jet engine afterburner injectors. The fuel injection system typically consists of one or more circular manifolds supported by struts in a jet pipe. The fuel is supplied to the manifold by feed pipes in the support struts and sprayed into the combustion zone through the orifices in the manifold. Increasing the number of orifices and/or using a ringlike manifold may promote uniform distribution of liquid. To reduce the risk of blockage of orifices, a minimum orifice size of 0.5 mm is usually regarded as practical for kerosene-type fuels. 

Figure 9.9 A scheme of distribution of liquid phase (black at the successive stages of slow drying (a), (b), (c), and (d). The insert shows the corresponding points at the desorption branch of isotherm, where U is the degree of pore filling and P/P the partical pressure of solvent vapor [3],...

The distribution of liquid over packings has been studied experimentally by many workers and, for instance, Tour and Lerman164 65 showed that for a single point feed the distribution is given by ... 

Koido, Furusawa, and Moriyama [206] used a technique based on the steady-state test method for reservoir rock, sandstone, and other porous media. In this method, a DL is sandwiched between similar DLs on the inlet and outlet sides. The material on the inlet is used to guarantee homogeneous distribution of liquid water in the planar direction, while the material at the outlet minimizes the flow in the outlet. Liquid water is introduced first and then a constant flow rate of air is injected. Once it is at steady state, the pressure difference between the inlet and outlet is measured. The sample is then weighed and the permeability is calculated in a way similar to that of Nguyen and colleagues [205]. 

Such in situ coated columns with an equilibrium distribution of liquid phase have long operational lifetimes because the amount of liquid stationary phase remains constant in the column as long as its concentration in the mobile phase and the temperature remain constant. The column can be coated successively with different liquid phases after removing the stationary liquid phase with a suitable solvent and reactivating by treatment with dry eluent before recoating. 

Figure 6.1 illustrates such an example (Abbott et al. 1992). Here, a gold surface is first coated with a hydrophilic SAM of alkanethiolate. The desired geometric pattern is then formed on the surface through micromachining (in this case, using a surgical scalpel), and the resulting features are covered with a hydrophobic SAM (of dialkyl disulfide) (see Fig. 6.1a). This procedure can be used to construct micrometer-scale hydrophobic lines on the surface so that the resulting shapes and distribution of liquid drops can be controlled (see Fig. 6.1b).

Cream is pasteurized at 71° to 77 °C for 30 min, cooled to 5°-10°C, and held for several hours to provide the required distribution of liquid and crystalline milk fat. For continuous butter making, pasteurized cream, containing about 40% milk fat, is processed by one of the fol-... 

Set the edge of the dried gel, with the gel surface downwards, into the rehydration solution and slowly lower it. Lift gel at the edges with forceps and slowly lower it down again to ensure an even distribution of liquid and to remove air bubbles. 

The trickle bed reactors that operate in the downflow configuration and have a number of operational problems, including poor distribution of liquid and pulsing operation at high liquid and gas loading. Scaleup of these liquid-gas-solid reactors is much more difficult than a gas-solid or gas-liquid reactor. Nevertheless, the downflow system is convenient when the bed is filled with small catalyst particles. And, because the catalyst particles are small, these reactors are quite effective as filters of the incoming feed. Any suspended fine solids, such as fine clays from production operations, accumulate at the front end of the bed. Eventually, this will lead to high pressure differentials between the inlet and outlet end of the reactor. 

A wide variety of process options can be used with the H-Oil process depending on the specific operation. In all cases, a catalytic ebullated-bed reactor system is used to provide an efficient hydroconversion. The system insures uniform distribution of liquid, hydrogen-rich gas, and catalyst across the reactor. The ebullated-bed system operates under essentially isothermal conditions, exhibiting... 

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