Spray drier

Spray Drying and Agglomeration. Most instant coffee products are spray-dried. Stainless steel towers with a concurrent flow of hot ak and atomized extract droplets are utilized for this purpose. Atomization, through pressure nozzles, is controUed based on selection of the nozzles, properties of the extract, pressures used, bulk density, and capacity requkements. Low inlet ak temperatures (200—280°C) are preferred for best flavor quaHty. The spray towers must be provided with adequate dust coUection systems such as cyclones or bag filters. The dried particles are coUected from the conical bottom of the spray drier through a rotary valve and conveyed to bulk storage bins or packaging lines. Processors may screen the dry product to... 

Most spray-dried instant coffees have been marketed in a granular form, rather than the small spherical spray-dried form, since the mid-1960s. The granular appearance is achieved by steam fusing the spray-dried material in towers similar to the spray drier. Belt agglomerators are also common. 

For processing under aseptic conditions, the spray drier must be connected to a filling hne that allows aseptic handling of the product. 

Zerstaubuogs-apparat, m. spray apparatus, atomizer. -mittel, n. atomizing agent, -trockner, m. atomizing (or spraying) drier. 

For the preparation of spray-dried polyelectrolyte complexes, the polyanion was dissolved in dilute NH4HCO3 solution and mixed with the chitosan carbamate solution just before spray-drying. The excess NH4HCO3 decomposed thermally between 60 and 107 °C on the other hand, the carbamate function released carbon dioxide under the effect of the temperature at which the spray-drier was operated, thus regenerating chitosan at the moment of the polyelectrolyte microsphere formation (Fig. 5). 

All the driers discussed above are unsuitable for mixtures with a high liquid proportion (slurries). For such mixtures spray driers (see Fig. 7.2-11) or cyclone driers (see Fig. 7.2-12) are effective. In the former the sluri-y is injected into the drier by a nozzle that atomizes the suspension. Small droplets fall down countercurrently to the hot gas that rises in the conical drier zone. In cyclone driers the sluriy and the hot gas flow cocurrently. Driers of both kinds are characterized by short residence times. Therefore, they are particularly suitable for temperature sensitive products. A significant proportion of driers of all kinds, appropriately modified, can also be operated as solids mixers and/or granulators. 

Figure 7.2-11. Spray drier with heat recovery system 1. Spray tower and drying system 2. Air heater 3. Air fan 4. Cyclone dust separator 5. Wet dust separator and entrainment separator 6. Exhaust air fan 7. Pneumatic product conveyer 8. Intermediate product storage 9. Product sieving and packing 10. Wet product pumping system (by courtesy of BMA, TAG-Division). 

DRYPAC A flue-gas desulfurization process in which an aqueous lime suspension is injected into a spray drier. Developed by Flakt Industri, Sweden. In 1986 it was in use in 17 plants in Sweden, Denmark, Finland, Germany, and the United States. 

E-SOX A flue-gas desulfurization process. The gas is contacted with calcium hydroxide or sodium hydroxide solution in a spray drier, and the resulting particles are trapped in an elec-tostatic precipitator. Developed and piloted by the U.S. Environmental Protection Agency. 

Liquid and solids Coating Spray drier, fluidized bed coater... 

Spray drying requires formulahon of a relatively stable, usually aqueous dispersion of zeolite and colloidal binder particles, which are then fed to the spray drier [88, 89], Organic dispersing agents may be added to the spray drier feed slurry to stabilize the dispersion while the slurry is fed to the drier. 

An aqueous solution (30 wt % concentration) of commercially available KF was introduced into a stainless steel spray-drier as a spray at the rate of 3 kg h and dried by a stream of air (300-500 nC). Instantly dried KF was produced at the rate of 820 g h-1 as a bulky mass d 0.41 yield 91 %. 

The dispersed droplet size, referred to as emulsion or particle size, can be reduced in the spray drier infeed matrix by more vigorous mixing or homogenization. There is also a new technique for creating small emulsions termed microfluidization which will be discussed later. This research was designed to determine whether the size of emulsion in the infeed solution will affect the characteristics of the final spray dried powder. Materials and Methods... 

In practice, the excess activated sludge is conditioned with 3-6% pcClj and tillered on vacuum filters. This reduces the moisture to about 80% and produces a filter cake which is dried in rotary or spray driers to a moisture content of less than 5%. It is bagged and sold direct as a fertilizer, or to fertilizer manufacturers who use it in mixed fertilizer. 

Little is known, at present, about the formation mechanism of hollow microspheres, and of the influence of the composition or process parameters on their quality and properties. It is extremely difficult to study the formation mechanism in a spray drier, as for this purpose individual droplets should be followed as they are treated. 

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