Spraying, fluidized-bed granulators

This specific example refers to the encapsulation of aromatic oils with different volatUity (namely orange, mint or pergamot oil) by spray fluidized bed granulation. 

Figure 13.3 A schematic diagram of agitation fluidized bed granulator (NQ-i60, Fuji Paudal). i Agitation fluidized bed. 2 Bag filter. 3 Spray nozzle. 4 Blower. 5 Heater. 6 Motor. 7 Agitator blade. 8 Slit plate. 9 Image probe. 10 Image processing system. II Host computer. 12 Controller. 13 Pump. 14 Binder. Reprinted from Watano et al. (2001) with permission from Elsevier Science.

Kovacova (1990) describes a method for the batch drying of fruit and vegetable pulp in a fluidized bed in which carrier particles (variously crystalline and caster sugar, dried skim milk, potato and wheat starch, apple powder, semolina or oat flakes), pre-moistened to a solids content of between 55% and 76%, are fed to a preheated fluidized bed and sprayed with the pulp to be dried. A product with a narrow particle size distribution and a uniform pulp content is claimed. Specific foods for which fluidized bed granulation has been used include potato puree (Zelenskaya and Filipenko, 1989) and granulated dried apple (Haida et al, 1994). 

Kurita, Y. and Sekiguchi, L, Effect of vortex orifice air distributor on granule growth in conical fluidized bed granulation with bottom entry spray, /. Ghent. Eng. Japan, 33 (2000) 57-66. 

Rumpf H. Agglomeration. Krepper W, ed. NY (Publ.) Interscience, 1962 374. Schaefer T, Worts O. Control of fluidized bed granulation I effects of spray angle, nozzle height and starting materials on granule size and size distribution. Arch Pharm Chem Sci Ed 1977 5 51-60. 

Fluidized Bed Granulation The next evolution was to position a nozzle in the expansion chamber, to spray a water or binding medium downward into the dry fluidizing powders (figure 2). By... 

Schaefer, T. and O. Worts, Control of Fluidized Bed Granulation, I. Effects of Spray Angle, Nozzle Height and Starting Materials on Granule Size and Size Distribution, Arch. Pharm. Chemi. Sci., Ed. 5, 1977, pp.51-60. 

Figure 12.17. Fluidized bed and spouted bed granulators, (a) A batch fluidized bed granulator used in the pharmaceutical industry performance data in Table 12.19(a). (b) Part of a fluidized bed incineration process for paper mill waste recovering sodium sulfate pellets performance data in Table 12.19(b). (c) A three-stage fluidized bed granulator for more complete control of process conditions and more nearly uniform size distribution, (d) Two modes of injection of spray to spouted beds, into the body on the left and at the top on the right performance data in Table 12.19(c).

In summary, the second option, which is to perform a dry blend in a fluidized bed granulator in a very short time followed by spraying the granulation liquid onto the mixed dry powders, is recommended as the first choice for the manufacture of low-dose products. 

Table 4.4 summarizes the main important parameters for the fluidized bed granulation process and their impact. Granule properties can be affected by several parameters. Granule size, for example, can be affected by starting material properties, atomization, spray liquid properties, and attrition. It is very important to take a comprehensive review of all the process parameters for process development. 

The average particle diameter which is growing during granulation and agglomeration has no effect on the conversion of sulfur dioxide. An increase in particle diameter leads to higher Re-numbers, and thus to an enhanced mass transfer of sulfur dioxide. However, the opposite phenomenon is that the increased mass transfer of the evaporation reduces the mass transfer surface. In addition, these experimental studies illustrate that the liquid-sprayed fluidized bed can be used as a reactive absorber. 

Spray onto dispersed powder (cf. powder clustering, agitation methods above) Atomized liquid feed is sprayed into circulating dispersion of already-dried particles. Hot gases maintain dispersion. Spray granulation, spouted and fluidized bed granulation Fluidized and spouted beds, Wurster apparatus... 

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