Gravity settling vapor

IV.2.1 a Sizing vertical gravity settling vapor/liquid separator... 

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... 

Heterogeneous hydrogenation catalysts can be used in either a supported or an unsupported form. The most common supports are based on alurnina, carbon, and siUca. Supports are usually used with the more expensive metals and serve several purposes. Most importandy, they increase the efficiency of the catalyst based on the weight of metal used and they aid in the recovery of the catalyst, both of which help to keep costs low. When supported catalysts are employed, they can be used as a fixed bed or as a slurry (Uquid phase) or a fluidized bed (vapor phase). In a fixed-bed process, the amine or amine solution flows over the immobile catalyst. This eliminates the need for an elaborate catalyst recovery system and minimizes catalyst loss. When a slurry or fluidized bed is used, the catalyst must be separated from the amine by gravity (settling), filtration, or other means. 

Horizontal separators normally are more efficient at handling large volumes of gas than vertical types since liquid droplets fall perpendicular to the gas flow in the gravity settling section, and are more easily settled out of the gas continuous phase. Also, since interface area is larger in a horizontal separator, it is easier for gas bubbles, which come out of solution as liquid approaches equilibrium, to reach the vapor space. 

The mechanism of vapor-phase separation is illustrated in Fig. 1. Both stages—coalescence and disengagement followed by gravity settling—must be considered in sizing the drum and selecting the wire-mesh pad. 

The reflux drum separates liquid and wet gas by gravity settling. A horizontal vapor-liquid separator works in much the same way as the vertical KO drum. 

FIGURE 8.3 Columns for water removal used for enzymatic reactions conducted in refluxing solvent. Portions of this figure were adapted from Reference 239. Key to letters (a) exit from reaction vessel (e.g., round-bottom flask) (b) arm for vapor transport (c) entrance to condenser (d) packed bed of molecular sieves (or other drying agent) (e) arm to return dehydrated solvent to reactor and (f) gravity-settling or phase separation column. 

Entrainment reduction takes place in the vapor space. Here the velocity of the vapor stream is reduced to a velocity at which gravity settling of droplets of size Dp and larger can take place. These liquid droplets settle from the vapor stream when the vapor residence time in the vessel is equal to or greater than the time of droplet fall. For this condition,... 

We work in a stagnant industry. It s true that vapor-liquid separation can be greatly improved by the use of vertical vortex tubes, which are a relatively new development. Yet most vapor-liquid separators are still empty vessels that depend on gravity settling and are sized in accordance with Stokes Law. 

IV.2.1 Sizing vapor/liqutd separator by gravity settling method... 

Vessel sized for liquid surge drum and vapor/liquid separation by gravity settling method can be used for final design. Vessel siz for vapor/liquid separation by mist eliminator method should be checked by the mist eliminator vendor to confirm its size. Vessel sized for Hquid/liquid separation by surge volume method or with coalescer pad is a rough preliminary sizing. Its size should be checked by vendor or an expert. 

FIGURE 14.5 A small drop of liquid suspended in a vapor of the same chemical species. We ignore the very slow gravity settling of... 

Vapor-Liquid Gravity Separator Design Fundamentals The critical factors in the performance of a horizontal separator are the vapor residence time and the settling rate of the liquid droplets. However, two other factors enter into the design—the vapor velocity must be limited to avoid liquid entrainment, and there must be sufficient freeboard within the vessel to allow for a feed distributor. For vertical separators, the design is based on a vapor velocity that must be less than the settling velocity of the smallest droplet that is to be collected, with due allowance for turbulence and maldistribution of the feed. The vapor residence time is a function of the vapor flow rate (mass), vapor density, and volume of vapor space in the separator, based on the following ... 

The majority of the process vessels you see in your plant are gravity, vapor-liquid separators. Their main purpose is to settle out droplets of entrained liquid from the upflowing gas. Factors that affect the settling rate of these droplets are... 

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