Gas atomization process

Figure 5.5. (a) Calculated trajectories of liquid metal sheet and droplets near a close-coupled atomizer (Atomization gas Ar, Ma = 1 at nozzle exit, Metal Ni, 7° = 1877 K, rii(JmL = 3.74). (Reprinted with permission from Ref. 325.) (b) High-speed video imaging of actual gas atomization process with a close-coupled atomizer. (Courtesy of Mr. Paul Martiniano and Dr. Paul Follansbee, General Electric Corporate R D, Schenectady, NY, USA.)... 

Fig. 36.4 Mechanism of disintegration of a liquid sheet into droplets with three basic stages during the gas atomization process [12]. (From N. Dombrowski, W. R. Johns Chem. Eng. Sd. 18, 1963)...

Gas atomization process (GAP) Atomization of molten titanium by a jet of inert gas Sumitomo Titanium Corp. n.a. Near-spherical Porosities... 

Gas-atomization process. In this process, the atomization of molten titanium is performed by a jet of inert gas, usually hehum or argon. The particles exhibit a spherical shape. 

The production of micron-sized polymer powders fi om molten polymers is an attractive, facile, low energy, and economic process. Polymer powders with tailored characteristics such as particle shape, size distribution, and purity can be directly prepared from the molten state of polymers such as polyethylene-based waxes that can not be ground using conventional methods [10-12,46,83-84]. The Gas Atomization Process (GAP) for mass-producing high quality spherical... 

Li, X.-G. (2014). Modeling and simulation of the gas-atomization process of metal melts for metal-matrix-composite production. Dissertation, University of Bremen, Shaker Verlag. ISBN 978-3-8440-3209-3. 

The analysis of the influence of particle clustering on the heat and mass transfer within the spray has been investigated. Especially in the hot gas atomization process, the preferential concentration of particles is an important mechanism that increases the inhomogeneity in the spray. The cluster structures strongly depend on the local Stokes number and their formation is induced by coherent flow structures of the continuous gas phase. 

The setup and the performance of the hot gas atomization process will be assessed in detail by means of experimental and numerical investigations. The sprayed polymer solutions, that represent the input to the process, greatly influence the outcome of the hot gas atomization and drying process. In the materials section, the properties of PVP K30 and K90 solutions will be characterized. To point out the differences between hot gas atomization and conventional concurrent spray drying processes, the atomizer performance on different scales is analyzed. The atomizer gas temperature influences the atomization and the drying process and the spray flow may be influenced by changing the spray chamber design. 

The powder product, which results from the hot gas atomization process, is probed at the conical part of the spray tower. The product is deposited onto a glass fiber filter with the application of a vacuum. In order to measure the total gas temperature distribution inside the spray tower, thermocouples inside the pilot plant are installed (Fig. 19.3 right). 

Due to the entrainment of the colder gas from the bottom of the spray tower, the temperature level is strongly decreased in the axial and radial direction. That means that in the hot gas atomization process, the high temperatures zones are located only close to the atomizer. The consequence is that the thermal energy is concentrated on the spray jet, which is desired to improve the atomizer performance. The temperature profiles on the spray axis and at the wall, measured at different operation times (until 40 min), are illustrated in Fig. 19.6. 

The variant A shows a flow pattern that is related to concurrent spray drying processes with pneumatic nozzle systems. The flow from the air dispenser is centered and pointing downward to adapt the direction of the heat flow to the low expansion angle of the spray flow. In some applications, the air stream has a swirl component to avoid the uncmitrolled deflection of the spray onto the spray chamber walls. In the hot gas atomization process swirl is not necessary because of the strong axial momentum flux from the nozzle. 

---