Rotary atomizers

Thermal decomposition of spent acids, eg, sulfuric acid, is required as an intermediate step at temperatures sufficientiy high to completely consume the organic contaminants by combustion temperatures above 1000°C are required. Concentrated acid can be made from the sulfur oxides. Spent acid is sprayed into a vertical combustion chamber, where the energy required to heat and vaporize the feed and support these endothermic reactions is suppHed by complete combustion of fuel oil plus added sulfur, if further acid production is desired. High feed rates of up to 30 t/d of uniform spent acid droplets are attained with a single rotary atomizer and decomposition rates of ca 400 t/d are possible (98). 

Recent developments in rotary atomization include the use of semiconductive composites (qv) for the rotary cup permitting the constmction of a unit that does not produce an ignition spark when brought close to a grounded workpiece yet has the transfer efficiencies associated with a rotary atomizer. In addition, the use of the semiconductive material softens the electrostatic field and results in less edge buildup and better penetration into recess areas. Other systems use electronic means to effectively prevent arcing to grounded surfaces. 

Fig. 9. (a) Pressure atomizers (b) rotary atomizer and (c) twin-fluid atomizers (89,90). 

Figure 30-2 illustrates a wet SO2 desulfurization system using a spray tower absorber. Figure 30-3 illustrates a rotary atomizer injecting an alk ine slurry into a spray dryer for SO2 control. 

Rotary Atomization Spinning Disk 10-200 Spray drying. Aerial distribution of pesticides. Chemical processing Good mono-dispersity of droplets. Independent control of atomization quality and liquid flow rate Satellite droplets, 360° spray pattern... 

Rotary atomization processes in spray drying have been studied extensively by many researchers, for example, Kayano and Kamiya,[1101 Tanasawa et al.,11111 Hinze and Milbom "21 Christensen and Steely, 1131 and Kitamura and Takahashi 114] Details of the processes have been described and reviewed by Masters,[2] Dombrowski and Munday 941 Matsumoto et al.,[I0y Christensen and Steely, 113] Eisenklam, 115] and Fraser et al., 116] among others. 

An attractive feature of rotary atomization is the nearly uniform droplets produced with small disks at high rotational speeds and low liquid flow rates. Therefore, rotary atomization is probably the most generally successful method for producing moderately monodisperse sprays over a wide range of droplet sizes. The mean... 

One of the special rotary atomizers worth mentioning is the windmill type atomizer. In this atomizer, radial cuts are made at the periphery of a disk and the tips of segments are twisted, so that the disk is actually converted into a windmill that can rotate rapidly when exposed to an air flow at aircraft flight speed. The windmill type atomizer has been demonstrated 1171 to be an ideal rotary atomizer for generating a narrow spectrum of droplet sizes in the range most suitable for aerial applications of pesticides at relatively high liquid flow rates. 

A spray-dryer eonsists of a feed tank, a rotary or nozzle atomizer, an air heater, a drying ehamber, and a eyelone to separate the powder from the air. A rotary atomizer uses eentrifugal energy to form the droplet. Pressure-nozzle atomizers feed solution to a nozzle under pressure, whieh forms the droplet. Two-fluid nozzles feed solutions separately into a nozzle head, whieh produces high-speed atomizing air that breaks the solution into tiny droplets. Both the feed solution and the drying air are fed into the drying ehamber in a standard eoeurrent flow [27]. 

Rotating Nozzle (rotary atomizer) fluid is fed at low pressure to the center of a rapidly rotating disk and centrifugal force breaks up the fluid. These types of nozzles are used mainly in a spray drying application. 

Aerosols (qv) are very finely divided sprays having droplet diameters of l ndash 30 Jim. They are used almost entirely as space sprays for application to enclosures, particularly against flying insects. Aerosols are most conveniendy applied by the familiar liquefied gas dispersion or bomb but can be generated on a larger scale by rotary atomizers or twin fluid atomizers. 

FIGURE 8 Impact of rotary atomizer rotation rate and feed rate on droplet size. 

Varga CM. Snyder HE. High-magnification shadowgraphy characterization of rotary atomizer dn lci production for pharmaceutical aj lications. Institute for liquid atomization and spraying systems conference. Toronto, Ontario. Canada 2006. 

Spray. Direct type, continuous operation. Rotary atomizer, pressure nozzle, or two-fluid nozzle. Includes combined spray-fluid bed and spray-belt dryers Suited for large capacities. Product is usually powdery, spherical, and free-flowing. High temperatures can sometimes be used with heat-sensitive materials. Products generally have low bulk density. See comments under Liquids. Pressure-nozzle atomizers subject to erosion Requires special pumping equipment to feed the atomizer. See comments under Liquids. Not applicable unless feed is pumpable Not applicable Not applicable Not applicable Not applicable... 

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