Separator Venturi scrubber

A considerable reduction in particle size separation can be achieved at the expense of increased pressure drop using a Venturi scrubber (see Fig. 11.2c). 

Current designs for venturi scrubbers generally use the vertical downflow of gas through the venturi contactor and incorporate three features (I) a wet-approach or flooded-waU entry sec tion, to avoid dust buildup at a wet-dry pmction (2) an adjustable throat for the venturi (or orifice), to provide for adjustment of the pressure drop and (3) a flooded elbow located below the venturi and ahead of the entrainment separator, to reduce wear by abrasive particles. The venturi throat is sometimes fitted with a refractoiy fining to resist abrasion by dust particles. The entrainment separator is commonly, but not invariably, of the cyclone type. An example of the standard form of venturi scrubber is shown in Fig. 17-48. The wet-approach entiy section has made practical the recirculation of slurries. Various forms of adjustable throats, which may be under manual or automatic control. 

Wet scrubber for formaldehyde and methanol only afterburner for organic vent gases Venturi scrubber followed by cyclone separator and packed countercurrent scrubber... 

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. 

Figure 1.69 shows a venturi scrubber in which water is injected at the throat and the separation is then carried out in a cyclone separator. 

Of the seven plants where the control device was known, three controlled emissions with venturi scrubbers, three controlled emissions using ESP s, and one controlled emissions with one scrubber and one new ESP on two separate boilers. In total, 13 boilers were located at these seven plants. Four of the individual boilers were known to be controlled by venturi scrubbers, and nine were known to be controlled by ESP. 

Almost all particle-separating devices can be converted into wet scrubbers by adding liquid spraying systems. Three types of commonly used scrubbers are the spray chamber, cyclonic scrubber, and venturi scrubber. Figure 7.18 shows a simple spray chamber in which water is sprayed through a series of nozzles into a settling chamber. The dust-laden gas is fed from the bottom of the chamber and exits from the upper portion of the chamber. 

Venturi scrubbers. In a venturi scmbber, a liquid jet issues from a nozzle. The jet induces cocurrent gas flow into the throat of the jet. Mass transfer takes place between the gas and the atomized liquid downstream of the nozzle. Mass transfer is usually poor and depends on the throat velocity or pressure drop, the liquid/gas ratio, and the liquid atomization pattern. Because of the cocurrent nature of contacting, the maximum solute removal does not exceed a single theoretical stage. Venturi scmbbers are used primarily for separation of fine particulate matter or... 

The steam may be purified by Droplet Separation techniques such as knitted wire mesh demister pads, wave plate separators and fiber pad separators using PTFE fibers. It can also be purified by scrubbing devices such as packed columns, venturi scrubbers, and irrigated sieve plates. Sometimes a combination of Droplet Separators and Scrubbers are used because AN emissions from neutralizers are very difficult to remove due to the very fine particles103. 

A review of Table 8 and Fig. 3-2 indicates that large-diameter particles can be removed with low-energy devices such as settling chambers, cyclones, and spray chambers. Submicron particles must be removed with high-energy units such as bag filters, electrostatic precipitators, and venturi scrubbers. Intermediate particles can be removed with impingement separators or low-energy wet collectors. Obviously, other equipment performance characteristics as noted in Table 8 will also have their influence on the final equipment... 

Venturi Scrubbers. Venturi scrubbers are used to separate air streams from solids that are noxious, hazardous, or explosive. The exiting liquid stream, usually a solid-water suspension or a slurry, may be returned to the process for recovery. 

A schematic flowsheet of the WCF is shown in Figure 3. Solidiflca-tion takes place in the 4-ft-diameter by 13-ft-high fluidized-bed calciner. Most of the plant equipment is devoted to cleaning up the entrained radioactive particles in the calciner off-gas. The off-gas passes into a cyclone to remove most of the solids, a quench tank to cool the gas, a venturi scrubber-separator-demister, a silica gel adsorber for the removal of voltaile ruthenium, another cyclone, and Anally a high-efficiency HEPA filter to remove submicron particles before discharging to the 250-ft plant stack. 

Venturi scrubbers have lower capital cost than other types of scrubber because they are mechanically simple but they have a high energy consumption because of the need for pressurizing the gas to force it through the venturi. They also double as a fly-ash collection device, and so there is no need for separate scrubbers and fly-ash collectors when these units are used. " Because venturi scrubbers are cocurrent devices, with both the flue gas and absorbent traveling in the same direction, they cannot remove sulfur dioxide as completely as countercurrent devices, such as wet-scrubber towers, They also produce a wet mixture of... 

Process design and operation, which are the central and important areas in chemical engineering, have attracted many applications of MOO since the year 2000. In all, there are 35 applications of MOO for process design and operation (Table 2.1). These cover fluidized bed dryer, cyclone separator, a pilot scale venturi scrubber, hydrogen cyanide production, heat exchanger network, grinding, froth floatation circuits, simulated moving bed (SMB) and related separation systems, thermal... 

Forced oxidation is achieved by air sparging of the slurry in an oxidation tank, either on the bleed stream to the solids dewatering system or on the recirculated slurry within the scrubber slurry loop. For a one-scrubber-loop forced oxidation system, the slurry effluent from all scrubbers in the system (e.g., the venturi scrubber and spray tower at Shawnee constitute a two-scrubber system, and the spray tower alone or TCA, a one-scrubber system) are sent to a single effluent hold tank, which is the oxidation tank. For a two-loop forced oxidation system, there are two scrubbers in series (e.g., venturi and spray tower at Shawnee) with effluent from each scrubber going to a separate tank the effluent hold tank for the upstream scrubber (with respect to gas flow) is the oxidation tank. For either one-loop or two-loop forced oxidation systems, the oxidation tank may be followed by a second tank, in series, to provide further limestone dissolution and gypsum desupersaturation time prior to recycle to the scrubber. 

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