Prilling size distribution

Product diameter is small and bulk density is low in most cases, except prilling. Feed hquids must be pumpable and capable of atomization or dispersion. Attrition is usually high, requiring fines recycle or recoveiy. Given the importance of the droplet-size distribution, nozzle design and an understanding of the fluid mechanics of drop formation are critical. In addition, heat and mass-transfer rates during... 

Particle size distribution/physical form, e.g. fine powder, flakes, granules, pellets, prills, lumps Porosity... 

The density of the prills is reduced substantially when much evaporation occurs with 0.2-0.5% water in the feed, ammonium nitrate prills have a specific gravity of 0.95, but with 3-5% water it falls to 0.75. Prilled granules usually are less dense than those made by layering growth in drum or fluidized bed granulators. The latter processes also can make larger prills economically. To make large prills, a tall tower is needed to ensure solidification before the bottom is reached. The size distribution depends very much on the character of the atomization but can be made moderately uniform. Some commercial data of cumulative % less than size are ... 

Power supply, 9 from a not gas stream, 12 generation with steam, 11 Pressure control, 42,44,51,52,59,60 Pressure drop cyclone separators, 617 gas-solid flow, 119-120 granular beds, 117 heat exchanger example, 193, 194 heat exchangers, 188 non-Newtonian flow, 106-109 wire mesh pads, 616 Pressure drop, piplines, 92 chart method, 96 two-phase flow, 116 typical values, 95 Ptaskie vessel code, ASME, 625 Prilling, 361,362 equipment size, 367 flowsketch, 366 operating, data. 367 products of, 367 size distribution, 362 Prism membrane separation process, 633 643... 

Three microscopic pictures of the DE emulsion structure treated with the EXMIX nozzle are inserted in Fig. 23.13 (bottom). To keep the microstructure of such DE unchanged, an INMIX nozzle is obviously the better choice for a GLR up to ca. 0.5. On the other hand, the GLR also determines the spray drop/spray particle size distributions of the end-use prilled or spray-dried powders, which is an additional criterion for the choice of the spray nozzle. The comparison of, r5o,3 Nozzle and. 90,3 Nozzle with 50,3 Initial and 3 903 Initial for the same emulsion at GLR = 0 (Fig. 23.12 (top) and Fig. 23.13) indicates the dispersing capacity of the velocity field (and related to locally acting shear and elongation stresses) of the pure liquid phase flow in the nozzle which was explored further in detail (section Impact of Pure Liquid-Cap Nozzle Flow on Secondary Droplet Size of SE, DE ). 

For the tertiary droplets and related prill powder particle size of SE and DE small size and a narrow size distribution are desirable for most of the industrial apphca-tions. As discussed in the previous sections, the criteria for keeping the microstructure of an emulsion unchanged, is equally important for applications where functional components shall be preserved within such microstructure. To obtain the small spray droplet and still keeping the emulsion microstmcture unchanged is technologically enormously challenging. 

Sasol in South Africa produces a porous, prilled ammonium nitrate (PPAN) that finds its widest application in a mix with fuel oil. This mixture is used as an explosive and is commonly known as ANFO (Ammonium Nitrate Fuel Oil). Standard PPAN contains randomly distributed closed pores of an uncontrolled variable size and quantity. Sasol also makes EXPAN by using a patented process where polymeric microspheres are entrained uniformly in individual prills. Surfactants are added prior to the prilling process to ensure that the microspheres are evenly distributed in the prill. The addition of these microspheres (or encapsulated gas bubbles) reduces and controls prill density to desired levels. This improves the sensitivity and performance of the explosive while retaining the desirable properties of the standard prills (mechanical strength, oil absorption and free-flowability)106. 

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