Vertical dry scrubbers

FIG. F-25 Position of vertical dry scrubber upstream of gas turbine. (Source Peerless.)... 

FIG. F-32 System installed in Saudi Arabia includes one vertical dry scrubber followed by two pressure regulating valves and a line separator. A condensate drain tank is mounted alongside. (Source Peerless.)... 

Semi-dry scrubbers involve a chemical reaction with a wet slurry, and a dry scrubbing of the gases with dry collection of co-products. Typically the process is used to treat acid gases in a spray dryer, coupled with a pulse-jet fabric filter. In the scheme shown in Figure 7.16, with a vertical downflow spray dryer, an alkahne slurry is injected to neutralize the adds present in the flue gas. The gas temperature is controlled by the flow rate of the dilution water. 

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. 

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. 

Current designs for Venturi scrubbers generally use the vertical downflow of gas through the Venturi throat and incorporate three features (1) a wet-approach or flooded-wall entry section to avoid a dust buildup at a wet-dry junction ... 

The process is conducted in a vertical steel apparatus filled with the catalyst suspended in liquid ethylchloride. This mixture is treated by hydrogen chloride and ethylene, while the contents of the reactor are intensively agitated. With the formation of ethylchloride, the volume of the liquid in the apparatus grows therefore, the surplus of ethylchloride is constantly withdrawn from the reaction zone. Liquid ethylchloride, leaking from the reactor with catalyst particles, as well as dissolved hydrogen chloride, is vapourised, washed in a scrubber with a 10% alkaline solution, dried with sulfuric acid and condensed. The reaction gases, laden with ethylchloride vapours, are washed with water from hydrogen chloride, dried with concentrated sulfuric acid and sent into an absorber, where ethylchloride is extracted with kerosene. By distillation and subsequent condensation, ethylchloride is extracted from the obtained solution. 

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