Spray drying operation

Impurities such as solvents and a variety of reactants can be removed from a polymer product to a very low (10 - 50 ppm) level via Supercritical Extraction (See chapter 9.6.) or Rapid Expansion Technology (See chapter 6.5.). In both methods, a compressed gas is used to extract undesired impurities out of the solid polymer (SCE), or as a compressed solvent for the polymer in a spray-drying operation. Several successes have been reported [48,49] and patented. 

Particle size of the primary emulsion particles was unaffected by the spray drying operation. 

Fig. 7.1. Droplet and particle sizes obtained in spray drying operations [1].

Sodium Chloride. Sodium chloride (NaCl) is used by some detergent manufacturers, its main function being as an inert filler or diluent. In spray-drying operations, NaCl is used to control Crutcher slurry viscosity and the density of the spray-dried bead or granules. In liquid formulations, NaCl is used to control product viscosity through the salt effect. Although salt is used to some extent in autodish formulations, it is not recommended because of potential machine and dishware corrosion. 

Atomization is the popular name given to the first step in a spray-drying operation, viz. the division of a liquid, suspension or emulsion into fine narrow-sized droplets or particles which can quickly lose the liquid phase under appropriate physical conditions. Liquids, suspensions and emulsions are usually atomized by forcing them at high velocity through... 

Choice of atomizer system The choice of atomizer system for a specific spray drying operation depends upon the particle size distribution required in the final dried product. It also depends upon the physical and chemical properties of the feed liquid. 

Theoretical prediction of mean particle sizes is difficult and of little practical importance, since the selection of spray drying operational parameters is based on ejq)erience and pilot-scale test work. The scientific literature, however, contains numerous estimation formulas to help predict the droplet sizes in sprays. Table 12-42 provides nomenclature for these estimation formulas. 

Aqueous solutions of these peaked materials show lower toxicides, lower viscosities, lower gel temperatures, and remain fluid over a wider concentration range. In spray-drying operations, there is less evolution of volatile material, since they contain less unreacted hydrophobe than conventional materials. They wet cotton more efficiently, show higher initial foam heights (but lower foam stability), reduce interfacial tension against mineral oil more efficiently and effectively than the corresponding conventional types. When sulfated to produce AES, the product has less non-POE alkyl sulfate and, consequently, less skin irritation and a greater tendency to thicken upon salt addition. 

Epstein J, Davis GT, Eng L et al. (1977). Potential hazards associated with spray drying operations. Environ Sci Technol, 11, 70-75. 

Because of the high selectivity of the extractant for the sulfuric acid, the only outlet for salts is the crystallizer. As the salt does not interfere with the extraction, complete removal in the crystallizer is not required. Thus, whereas the thermal processes described above (direct evaporation or spray drying) operate at a high acid concentration (low water partial vapor pressure, difficulties in controlling crystallization), the ABC extract-... 

The most important factors in this spray-drying operation are (a) the fineness of the spray droplets, which in turn will control the size of the silica aggregates in the... 

Fernandes, R. V. B., Borges, S. V., and Botrel, D. A. (2013a). Influence of spray drying operating conditions on microencapsulated rosemary essential oil properties. Ciincia e Tecnologia de Alimentos, 33(Suppl. 1), 171-178. 

The efficiency of the spray drying operation is defined as the ratio of the heat used in evaporation to the total heat input. Thus... 

In spray drying operations a potential danger of explosion and fire can exist under certain conditions [7],... 

When the spray-drying operation is cocurrent, i.e., hot air introduced into the dryer close to the atomizing device, there is less danger of overheating as the evaporation rates are high (34-160 kg/h/m of particle area) [3], Thus, cocurrent drying chambers are preferred to minimize heat deactivation of enzymes during the process. 

Silicate agglomerates of relatively high bulk density and large particle size can be prepared by recycling the fine particles that are normally produced in spray drying operations back into the spray dryer. As these particles fall through the dryer, they encounter droplets of sodium silicate solution that have been atomized into the dryer. The particles may adhere to one another and agglomerate as they dry [67]. 

Fig. 8.3 Typical problems associated with spray drying operations a condensation in the bag filter, b nozzle bearding, c dripping, and d stringing...

The product purity profile is a very important attribute for any product. During spray drying operation, chenfical degradation may occur ... 

The way in which spray contacts the drying air is a critical factor in spray-drying operations. Spray air contact is determined by the position of the atomizer in relation to the air inlet. 

There are several other methods that a flavor house may use to determine moisture content. They include microwave or infrared ovens (may be used in a spray drying operation for rapid analysis for process control) and refractive index (liquid... 

A major concern in spray drying of enzymes is the retention of their activities, whereas this complication is not seen in the case of purely chemical systems. Therefore, the enzyme activity retention must be close to 100% in the spray-drying operation and moreover, the shelf life of the dried enzyme products must be excellent, i.e., enzyme activity must be retained for long-time storage. 

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