Spray chamber scrubbers

Spray chambers, 26 688, 715 Spray chamber scrubbers, 26 713-714 Spray chilling, 11 550-551, 555 flavor encapsulation by, 11 540 Spray chilling encapsulation processes, 16 448... 

Spray Dryers A spray diyer consists of a large cyhndrical and usu ly vertical chamber into which material to be dried is sprayed in the form of small droplets and into which is fed a large volume of hot gas sufficient to supply the heat necessary to complete evaporation of the liquid. Heat transfer and mass transfer are accomphshed by direct contact of the hot gas with the dispersed droplets. After completion of diying, the cooled gas and solids are separated. This may be accomplished partially at the bottom of the diying chamber by classification and separation of the coarse dried particles. Fine particles are separated from the gas in external cyclones or bag collectors. When only the coarse-particle fraction is desired for fini ed product, fines may be recovered in wet scrubbers the scrubber liquid is concentrated and returned as feed to the diyer. Horizontal spray chambers are manufactured with a longitudinal screw conveyor in the bottom of the diying chamber for continuous removal of settled coarse particles. 

In Venturi scrubbers the gas is the motive fluid. This equipment is of simple design and is able to handle slurries and large volumes of gas, but the gas pressure drop may be high. When the reaction is slow, further holdup in a spray chamber is necessary. 

When the pollutant loading is exeeptionally high or consists of relatively large particles (> 2 /tm), venturi scrubbers or spray chambers may be used to reduce the load on the ESP. Much larger particles (> 10 /tm) are controlled with mechanical collectors such as cyclones. Gas conditioning equipment to reduce both inlet concentration and gas temperature is occasionally used as part of the original design of wet ESPs (AWMA, 1992 Flynn, 1999). 

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. 

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... 

Spray chambers are frequently used for scrubbing sulfur dioxide and solid particulates from stack gases. The nozzles can be designed to handle slurries, e.g., lime slurry fed to the stack gas scrubber. 

Venturi scrubber, turbulent contact absorber, marble bed absorber, horizontal spray chamber, cocurrent rotator. Based on data qf Frank, 1977... 

Spray contactors can be categorized into two basic types (1) preformed sprty, which includes countercurrent, cocunoit, and crosscurrent spray chambers spray dryers cyclcmic spray devices and injector venturis, and (2) gas atomized spray, which consists primarily of venturi scrubbers. Many cotmneirnal spray systems use mne than one type of spray contactor and often combine sprays with trays or packing. 

Hansen and Danos (1982) report on experience with a large (18 ft X 8H ft X 46 ft) cross-flow scrubber in a phosphoric acid plant. The scrubber consisted of a spray chamber followed by multiple packed beds of plastic woven mesh. With regard to the spray chamber section of the scrubber, they conclude that a spray nozzle pressure over 60 psig is required to attain 80% fluoride removal efficiency (1.5 transfer units) the amount of spray chamber water should be about 20 to 30 gpm/1,000 acfin and full cone spray nozzles directed countercurrent to the gas flow are preferred. The plastic woven mesh may be irrigated with low-pressure co-current sprays however, the nozzles should be mounted so that they are equidis-... 

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