Eliminators, entrainment

Reynolds, S.C. Entrainment Eliminators Save Money. Petroleum Refiner, July 1953, p. 138. 

Spray chambers These are essentially horizontal spray towers and may be arranged as in Fig. 7.19. They are frequently used for adiabatic humidfication-cooling operations with recirculating liquid. With large liquid drops, gas rates up to roughly 0.8 to 1.2 kg/m - s (600 to 900 Ib/ft h) are possible, but in any case entrainment eliminators are necessary. 

Drift is entrained water in the tower discharge vapors. Drift loss is a function of the drift-eliminator design, which typically varies between 0.1 and 0.2 percent of the water supphed to the tower. New developments in eliminator design make it possible to reduce drift loss well below 0.1 percent. 

In general, this equipment offers an economical heat-transfer area for first cost as well as operating cost. Capacity is hmited primarily by the air velocity which can be used without excessive dust entrainment. Table 12-32 shows hmiting air velocities suitable for various sohds particles. Usually, the equipment is satisfactory for particles larger than 100 mesh in size. [The use of indirect-heated conveyors eliminates the problem of dust entrainment, but capacity is limited by the heat-transfer coefficients obtainable on the deck (see Sec. 11)]. 

The amount of material released to the atmosphere will be further reduced because liquid entrainment from the two-phase flashing jet resulting from a leak will be reduced or eliminated. 

Entrainment of fine particulate matter such as sand and silt in cooling water can contribute significantly to erosion-corrosion. In these cases it is important to eliminate or reduce the amount of particulate by settling or filtration. It may also be necessary to reduce or eliminate entrained gas bubbles. 

Figure 1 is based upon 5% of the liquid entrained in the vapor. This is adequate for normal design. A mist eliminator can get entrainment down to 1%. 

The scrubbing liquid is fed into the pool at the bottom of the scrubber and later recirculated from the entrainment separator baffles by gravity instead of being circulated by a pump as in venturi scrubbers. Many devices using contactor ducts of various shapes are offered commercially. The principal advantage of this scrubber is the elimination of a pump for recirculation of the scrubbing liquid. 

Drift Eliminator Baffling that causes discharging hot air containing entraining water droplets to change direction a number of times. Droplets hit the eliminator surface and fail back into the tower. 

Commonly, amine absorbers include an integral gas. scrubber section in the bottom of the tower. This scrubber would be the same diameter as required for the tower. The gas entering the tower would have to pass through a mist eliminator and then a chimney tray. The purpose of this scrubber is to remove entrained water and hydrocarbon liquids from the gas to protect the amine solution from contamination. 

Turndovn is usually limited to 0.5 1, and liquid distribution can be poor if the sprays are not carefully laid out and the system flow tested for uniformity. Another problem is misting of the liquid from the sprays and the resulting entrainment out of the tower or up to overhead mist eliminators. 

Catalysts developed in the titanium-aluminum alkyl family are highly reactive and stereoselective. Very small amounts of the catalyst are needed to achieve polymerization (one gram catalyst/300,000 grams polymer). Consequently, the catalyst entrained in the polymer is very small, and the catalyst removal step is eliminated in many new processes. Amoco has introduced a new gas-phase process called absolute gas-phase in which polymerization of olefins (ethylene, propylene) occurs in the total absence of inert solvents such as liquefied propylene in the reactor. Titanium residues resulting from the catalyst are less than 1 ppm, and aluminum residues are less than those from previous catalysts used in this application. 

Liquid vortexing in suction vessel, thus creating gas entrainment into suction piping. Figure 3-43 suggests a common method to eliminate suction vor-... 

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