Vapor-liquid mixtures

Figure 3.1a shows a flash drum used to separate by gravity a vapor-liquid mixture. The velocity of the vapor through the flash drum must be less than the settling velocity of the liquid drops. Figure 3.11) shows a simple gravity settler for removing a... 

Some small amount of byproduct formation occurs. The principal byproduct is di-isopropyl ether. The reactor product is cooled, and a phase separation of the resulting vapor-liquid mixture produces a vapor containing predominantly propylene and propane and a liquid containing predominantly the other components. Unreacted propylene is recycled to the reactor, and a purge prevents the buildup of propane. The first distillation in Fig. 10.3a (column Cl) removes... 

The reactants dissolve and immediately begin to react to form further dichloroethane. The reaction is essentially complete at a point only two-thirds up the rising leg. As the liquid continues to rise, boiling begins, and finally, the vapor-liquid mixture enters the disengagement drum. A very slight excess of ethylene ensures essentially 100 percent conversion of chlorine. 

In most applieations, the reaetion oeeurs between a dissolved gas and a liquid-phase reaetant in the presenee of a solid eatalyst. In some eases, the liquid is an inert medium and the reaetion takes plaee between the dissolved gases at the solid surfaee. These reaetors have many diverse applieations in eatalytie proeesses and are used extensively in the ehemieal industry. Triekle-bed reaetors have been developed by the petroleum industry for hydrodesulfurization, hydroeraeking, and hydrotreating of various petroleum fraetions of relatively high boiling point. Under reaetion eonditions, the hydroearbon feed is frequently a vapor-liquid mixture that reaets at liquid hourly spaee veloeities (LHSV in volume of fresh feed, as liquid/volume of bed, hr) in the... 

Steps used to model flow from the reaotor, assuming relief is homogeneous vapor/liquid mixture. (Source Reproduced with 1996 AlChE. All rights reserved.)... 

Effects of Two-Phase Vapor-Liquid Mixture on Relief Valve Capacity... 

These units normally do not have a disengaging space but allow the vapor-liquid mixture to enter the distillation unit or other similar item of equipment. Feed is from the bottom with a split flow on the shell side by means of a shell-side baffle in the center being open at each end. 

Calculate mean specific gravity in tube as average of inlet liquid and outlet vapor-liquid mixture. 

The temperature difference between the exiting vapor-liquid mixture and the inlet shell-side steam or hot fluid should not exceed 75-82°F, primarily due to fouling problems and possible conversion in the tube to inefficient film boiling in the upper section of the tubes. 

Note that due to flashing and formation of a vapor-liquid mixture, the control valve is always placed as close to the inlet of the evaporator as possible. 

Thermodynamic equilibrium in a vapor-liquid mixture is given by the condition that the vapor and liquid fugacities for each component are equal2 ... 

Some general guidelines for vapor-liquid mixtures in terms of their nonideality are ... 

The separation of gas-liquid (or vapor-liquid) mixtures can be enhanced by installing a mesh pad at the top of the disengagement zone to coalesce the smaller droplets to larger ones. If this is done, then the KT in Equation 8.3 is normally specified to be 0.11 m s-1, although this can take lower values down to 0.06 m-s-1 for vacuum systems8. 

The three reboilers in Figure 15.13 are shown under natural circulation. The flow of liquid from the column to the reboiler is created by the difference in hydrostatic head between the column of liquid feeding the reboiler and the vapor-liquid mixture created by the reboiler. 

The heat transfer mechanism of a vapor-liquid mixture in which the critical heat flux has been exceeded can be classified as partial or stable film boiling. The differ-... 

Grolmes, M. A., and H. K. Fauske, 1969, Propagation Characteristics of Compression and Rarefaction Pressure Pulses in One-Component Vapor-Liquid Mixtures, Nuclear Eng. Design 77 137-142. (3) Grolmes, M. A., and H. K. Fauske, 1970, Modeling of Sodium Expulsion of Freon-11, ASME Paper 70-HT-24, Fluids Engineering Heat Transfer and Lubrication Conf., Detroit, MI. (4)... 

Horizontal blowdown drum/catch tank This type of drum, shown in Fig. 23-49, combines both the vapor-liquid separation and holdup functions in one vessel. Horizontal arums are commonly used where space is plentiful. The two-phase mixture usually enters at one end, and the vapor exits at the other end. To overcome reentrainment of liquid droplets, due to high inlet velocities, various devices and piping arrangements are used to provide a more uniform distribution of vapor-liquid mixtures into the separator, as shown in Fig. 23-50. For two-phase streams with very high vapor flow rates, inlets may be provided at each end, with the vapor outlet at the center of the drum, thus minimizing vapor velocities at the inlet and aiding vapor-liquid separation. 

In order to achieve the isothermal heat addition and isothermal heat rejection processes, the Carnot simple vapor cycle must operate inside the vapor dome. The T-S diagram of a Carnot cycle operating inside the vapor dome is shown in Fig. 2.2. Saturated water at state 2 is evaporated isothermally to state 3, where it is saturated vapor. The steam enters a turbine at state 3 and expands isentropically, producing work, until state 4 is reached. The vapor-liquid mixture would then be partially condensed isothermally until state 1 is reached. At state 1, a pump would isentropically compress the vapor-liquid mixture to state 2. 

At low pressures the following equations are valid for a binary vapor—liquid mixture ... 

Calculation of tube-side pressure drop is straightforward, even of vapor-liquid mixtures when their proportions can be estimated. Example 8.7 employs the methods of Chapter 6 for pressure drop in a thermosiphon reboiler. 

The most widely used is ammonia absorption in water. A flowsketch of the process is in Figure 8.27. Liquid ammonia at a high pressure is obtained overhead in a stripper, and then is expanded through a valve and becomes the low temperature vapor-liquid mixture that functions as the refrigerant. The low pressure vapor is absorbed in weak liquor from the bottom of the stripper. Energy input to the refrigeration system is primarily that of the steam to the stripper reboiler and a minor amount of power to the pump and the cooling water circulation. 

Individuals of multicomponent mixtures compete for the limited space on the adsorbent. Equilibrium curves of binary mixtures, when plotted as x vs. y diagrams, resemble those of vapor-liquid mixtures, either for gases (Fig. 15.5) or liquids (Fig. 15.6). The shapes of adsorption curves of binary mixtures, Figure 15.7, are varied the total adsorptions of the components of the pairs of Figure 15.7 would be more nearly constant over the whole range of compositions in terms of liquid volume fractions rather than the mol fractions shown. 

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