Spinning cup atomization

This process, also termed rapid spinning cup (RSC) process, was invented in the early 1980 s contemporarily by Osaka University in Japan[191] and Battelle s Columbus Division in the US)192 Unlike water atomization where water streams or droplets are used to disintegrate a molten metal, a coherent fast-moving liquid layer is used in the RSC process. Liquid quenchants include water, oil, glycerine, and other commercial quenching liquids. The materials atomized with the spinning cup method include a wide variety of metals and alloys such as tin, lead, aluminum alloys, copper alloys, iron alloys (stainless steels and high speed tool steels), zinc alloys and superalloys.[192] 

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Spinning basket reactor, 21 352, 353 Spinning-cup atomizers, 23 659 Spinning-cup sulfur burner, 23 660 Spinning machines, 19 749 Spinning processes, hollow-fiber, 16 7-12 Spinning pump, for olefin fiber extrusion, 11 231... 

Spinning Cup Atomization (RSC) <10-300 Standard deviation 1.5-1.7 Sn, Pb, Al, Cu, Zn alloys, Stainless and High speed tool steels, Superalloys 105-106 — 0.5-1.4x 10 3 Fine, clean, spherical particles, Narrow size distribution Small facility Relatively low volume productivity... 

Figure 2.23. Schematic of single-stage spinning cup atomization of melt.

Spinning-cup atomizers are used in some plants to provide finer atomization, allowing smaller burner chambers and easier turndown, but with the burden of added rotating equipment. Rotary kiln burners were once popular to bum lower quality sulfur, but few are still in operation. Spray burners can be operated intermittently and used at higher rates than rotary burners. 

The stationary spray nozzle has the advantage of simplicity and no moving parts. The spinning cup atomizer has the advantage of lower input pressure, smaller droplets, more flexible downturn and a shorter furnace. 

Spent acid is sprayed into a decomposition furnace in the form of 500-1000 pm droplets (Dafft and White, 2002). The droplets present a large acid surface to the hot combustion gas, promoting rapid evaporation and decomposition. The droplets are most commonly produced by forcing the acid into the furnace through fine nozzles (Rohm and Haas, 2003 Bete, 2005). Spinning cup atomizers are also used. 

Spent Acid or Burning. Burners for spent acid or hydrogen sulfide are generally similar to those used for elemental sulfur. There are, however, a few critical differences. Special types of nozzles are required both for H2S, a gaseous fuel, and for the corrosive and viscous spent acids. In a few cases, spent acids maybe so viscous that only a spinning cup can satisfactorily atomize them. Because combustion of H2S is highly exothermic, carehil design is necessary to avoid excessive temperatures. 

In the atomizing process, a stream of molten zinc is broken into tiny droplets by the force of a pressurized fluid impinging on the stream. The fluid can be any convenient material, although air is normally used. The atomized drops cool and soHdify rapidly in a coUection chamber. The powder is screened to specified sizes. Particulate zinc is also produced by other methods such as electrolytic deposition and spinning-cup techniques, but these are not of commercial importance. 

Sulfur dioxide is manufactured mostly by combustion of sulfur or its iron sulfide mineral, pyrite, FeS2, in air. The flame temperatures for such combustion of sulfur in the air are usually in the range 1,200 to 1,600°C. Many types of sulfur burners are available and are used to produce sulfur dioxide. They include rotary-kiln, spray, spinning-cup and air-atomizing sulfur burners. Selection and design of burners depend on quality of sulfur to be burned, and rate and concentration of sulfur dioxide to be generated. Pyrites or other metal sulfides may be burned in air in fluid-bed roasters to form sulfur dioxide. 

The sulfur is preheated and delivered to a burner as a liquid at a temperature of about 145 °C. The degree of atomization and mixing are key factors for an efficient combustion. Atomization is accomplished by spray nozzles or by a mechanically driven spinning cup (Figure 6.3.2). Some burners also contain secondary air inlets to promote mixing. The atomizer breaks the liquid sulfur into microscopic droplets that burn in suspension in a refractory-lined furnace. Sulfur combustion in air is self-supporting and no supplementary fuel is required. 

Figure 8.7. Mechanisms and location of drop formation in spinning disk or cup atomizers (a) direct formation at the disk edge (b) formation from strings of liquid leaving the disk edge (c) formation from liquid sheets leaving the disk edge.

A spinning disk device—also called a rotary atomizer—is a device that forms on a rotary flat disk a liquid film that breaks up when leaving the disk into droplets (see Figure 10.8). A number of different physical shapes are common, as flat or vaned disk and cup or slotted wheel. The diameter of the rotary part vary between 25 and 450 mm with rotating speeds of 12,000-60,000 rpm . ° The droplet format can be assisted by vibration or without vibration. 

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