Vane type separators

Eng. J., 1, 549 (1955)]. Chevron (hook-and-vane) type separators are also used because of their higher-allowable velocities or because of their reduced tendency to foiil with solids suspended in the entrained liquid. 

Depending on the number of stages, the gas that flashes in the lowci pressure separators can be compres.sed and then recombined with the gas from the high-pressure separator. Both reciprocating and centrifugal compressors are commonly used. In low-horsepower installations, especially lor compressing gas from stock tanks (vapor recovery), rotary aiuf vane type compressors are common. 

FIG. 14-110 Typical impingement separators, (a) Jet impactor. (b) Wave plate, (c) Staggered channels. (Blaw-Knox Food 6- Chemical Equipment, Inc.) (d) Vane-type mist extractor. (Maloney-Crawford Tank and Mfg. Co.) (e) Peerless line separator. (Peerless Mfg. Co.) (/) Strong separator. (Strong Carlisle and Hammond.) (g) Karbate line separator. (Union Catbide Corporation) (h) Type E horizontal separator. (Wright-Austin Co.) (0 PL separator. (Ingersoll Rand.) (/) Wire-mesh demister. (Otto H. York Co.)... 

Q In a gas compressor train, moisture must be removed from the gas before the latter goes on to the next stage, d his is done either by scrubbing in a knitted-wire-mesh separator, or with a vane-type separator that takes advantage of impingement, centrifugal force and surface tension. 

We thus make the distinction between vane-type axial inlets and tangential inlets. By tangential inlets, we mean both slot and wra >around inlets, unless we explicitly distinguish between the two. Pipe type inlets are also a type of tangential inlet, which compromises some degree of separation performance for the sake of construction simplicity. 

The second cyclone body shown in Figure 13.3.4 illustrate a vane-type inlet design that we refer to herein as a swirl tube separator. Vane inlets are the most symmetrical of all inlet designs but are somewhat more comphcated to design and fabricate or, in some cases, to cast. Both the twin inlet and vane inlet cyclone designs described thus far are of the conventional reverse-flow variety. 

The design criteria for vane-type gas separators are discussed in the following paragraphs. 

Definition Vertical vane-type separator with liquid removal efficiency of 100 percent for removal of particles 10 microns and larger. 

Primary separator section. The inlet section has been designed to utilize the forces of gravity and centrifugal force through the use of small diameter cyclones to remove liquid and solid particles. In some applications the vane-type mist extractor will be used. 

Design features. Replacement of the final separation elements can be made with a minimum of time and effort through the use of a full opening O-ring or float ring closure. The primary separation elements (vane-type mist extractor or cyclone section) are completely maintenance-free and self-cleaning, with no replacement or moving parts to cause shutdown. 

FIG. S-25 Vane-type separator performance curves. (Source Peerless.)... 

The vane-type line separator offers efficient separation of entrained liquids from a gas or vapor stream. This separator design has been used successfully for over 25 years in diemical plants, refineries, natural gas pipelines, and all types of industrial processing plants where efficient Uquid-gas separation has been required. See Figs. S-30 and S-31. 

It is significant to note that the liquid drainage in the vane-type mist extractor differs from the drainage in other impingement-type mist extractors, in that vane drainage occurs with the liquid out of the gas flow and at a ri t an e to the direction of flow through the separator. 

The individual vane corrugations, depth and size of the liquid pockets, and the vane spacing are critical features of the vane-type mist extractor. Many years of testing and operating experience eventually arrive at optimum dimensions and spacing. The slightest variation in any one of these three features will materially decrease the capacity and performance of this type of separator. 

Efficiency and capacities. The vane-type line separator (see Fig. S-33) will remove all of the entrained liquid droplets that are 8-10 microns and larger. The efficienty of the unit decreases on droplet sizes less than 8 microns as shown on the chart. In order to separate these smaller droplets, the separator must be preceded by an ag omerating or coalescing device to increase the size of the droplets so that they can be removed by the mist extractor. Several types of ag omerating devices are available. Some of these are capable of achieving efficiencies as high as 99 /2 percent removal of 1 micron size droplets. 

Low-pressure drop. Since the vane-type mist extractor is self-cleaning and contains no small openings that can fill up and restrict the flow—such as are present in wire mesh pads or filter screens— the pressure drop across the separator is very low. The drop is as small as 2-3 in of water in the larger sizes. 

In case of a horizontal separator, significantly higher gas flow can be achieved in comparison to vertical gas flow, simply because, in the horizontal mode the liquid can easily drain downwards due to gravity. This is the reason the vane type mist eliminator is very popular in horizontal separators. 

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