Drying single-particle

Each spray-dried droplet forms a single particle whose size is determined by the droplet size, the dissolved solids of the feed solution, and the density of the resulting solid particle. For a given formulation and process, both the solid content and density of the powder remain constant within a batch and from batch to batch therefore, the distribution of the primary particle size is determined by the droplet size distribution. A narrowly distributed particle size can be achieved with a well-designed atomizer and controlled process parameters. 

ABSTRACT Experimental results frombirchwood and pinewood pyrolysis in a new single particle reactor are presented. Apparent kinetic parameters for the mass-loss of wood particles (5-800 mg) at tenyeratures from 300 to 860 C are determined. Kinetic parameters for the evolution of CO, COj, H O, Hj and CH4 are also established. The drying process was examined and it was found that drying and pyrolysis increasingly overlap in time as temperature rises and that the overlap is substantial above 4S0 C. 

Bunker MJ, Davies MC, Chen XY, et al. Single particle friction on blister packaging materials used in dry powder inhalers. Eur J Pharm Sci 2006 29(5) 405-413. 

Area for drying, m or ft A, surface area of a single particle Surface area per unit volume, m m or ft ft also slope of drying-rate curve [Eq. (24.22)]... 

The calculation of the forces is the calculation of the derivative of E of Eq. (3) with respect to some nuclear coordinate, R/s, where s equals x, y, or z. The derivative of the second term of the right-hand side of Eq. (3) with respect to Ru is straightforward, but this is not the case for dEe/dRis. Independent of whether a Hartree-Fock or a density-functional method is applied, one may at first assume that the single-particle equations are solved exactly. In that case, the... 

Spray drying is a one-step continuous processing operation that can transform feed from a fluid state into a dried form by spraying the feed into a hot drying medium. The product can be a single particle or agglomerates. The feed can be a solution, a paste, or a suspension. This process has become one of the most important methods for drying liquid foods to powder form. 

This model assumes that the drying of single particles in a fluidized bed is totally controlled by diffusion of moisture inside the particle. For the analysis of particulate drying, diffusion equation for spheres of an equivalent diameter can be used. Zahed and Epstein [33] developed a diffusion model for spout bed drying and later Martinez-Vera et al. [34] applied the same model for fluidized bed drying. 

C. Fyhr, I.C. Kemp, Comparison of different drying kinetics models for single particles. Drying Technology, 16 (1998) 1339-1369. 

Similar results are reported from the drying of bark and peat in superheated steam in a pilot-plant pneumatic conveying dryer [22], The results are presented as a convective apparent heat-transfer coefficient, defined with the assumption that the temperature of the particle surface coincides with the saturation temperature of the transport steam. This transfer coefficient shows a clear dependence on the moisture content of the particles and the particle sizes. Fyhr [23] presented a model for a pneumatic conveying steam dryer. The dryer model consists of two submodels, one for the single particle and the other for the hydrodynamics of gas and particles in the dryer. 

Since only analytes attached to or close to metal surface are enhanced, the need for effective surface attachment is crucial if reproducible results are to be obtained. In many early experiments this was widely ignored. Commercial dyes were simply added to colloid or placed on surfaces and the results, where favourable, have been reported in many studies. The problem with this approach is that the surface chemistry of an element such as silver is complex. Little is understood about the surfaces on which the analyte is adsorbed, particularly in aqueous solution or, as is often done, with particles prepared in aqueous solutions and dried out on a surface for investigation. Further, where colloidal suspensions are used, it is common practice to aggregate the colloid in order to shift the frequency of the plasmon to a value that would place it in resonance with the laser. In fact, it is clear from ultraviolet-visible absorption that a range of clusters are made in most conditions and only a few are likely to be in resonance with the laser. However, this gives a bigger SERS enhancement than for single particles. 

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