Dual-fluid nozzle

Atomization of granulation liquid is mostly achieved by using a set of dual fluid nozzles. The main advantages of dual fluid nozzles include ... 

It is very important to use the same type of nozzle and operate the nozzles under the same operating conditions during scale-up. When dual fluid nozzles are used, the spray rate and atomization airflow should be kept the same so that spray properties such as spray angle, droplet size, and its distribution stay the same. If superficial air velocity remains the same during scale-up, the relative position of nozzle to bed and nozzle-to-nozzle positions should be kept the same. The number of spray nozzles used should correlate with the bed surface area. 

Annular jet. This technology was developed by the Southwest Research Institute and has not been extensively used in the food industry (10). It relies upon two concentric jets. The inner jet contains the liquid core material. The outer jet contains the liquid wall material, generally molten, that solidifies upon exiting the jet. This dual fluid stream breaks into droplets much as water does upon exiting a spray nozzle ... 

The atomizing nozzle may be one of four basic types 1) dual-fluid 2) single-fluid pressurized 3) singlefluid disk or rotary and 4) single-fluid ultrasonic. 

Aqueous wastes contain oxidizable compounds within a liquid water stream and may be endothermic or exothermic depending on the concentration of oxidizable compounds. Proper atomization of fhe liquid stream is probably the most critical aspect of handling aqueous wastes. This is because the droplet must be small enough to be capable of completely evaporating within the thermal oxidizer chamber and still allow for sufficient residence time to oxidize the combustible compounds. The fluid nozzle, pressure drop, and atomization fluid (e.g., air or steam) demand (if dual fluid atomization is used) should be matched to what is used in the field to obtain a meaningful simulation. 

The co-extrusion process was developed by Southwest Research Institute in the United States, and has found a number of commercial applications. A dual fluid stream of liquid core and shell materials is pumped through concentric tubes and forms droplets under the influence of vibration (Fig. 1.14). The shell is then hardened by chemical crosslinkings, cooling, or solvent evaporation. Different types of extrusion nozzles have been developed in order to optimize the process [103]. 

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