Supercritical assisted atomization

SAA, supercritical assisted atomization This process is based on the solubilization of a fixed amount of supercritical carbon dioxide in the liquid solution then the ternary mixture is sprayed through a nozzle, and as a consequence of atomization, solid particles are formed ]. 

Reverchon E. and Della Porta G. 2003. Micronization of antibiotics by supercritical assisted atomization, J. Supercritical Fluids, 26, 243-252. 

Besides the supercritical fluid extraction (SFE) for preparation of medicines and materials processing, supercritical fluid technology involves processes such as supercritical anti-solvent (SAS), rapid expansion supercritical solutions (RESS), rapid expansion of a supercritical solution into a liquid solvent (RESOLV), supercritical assisted atomization (SAA), impregnation and solution enhanced dispersion by supercritical CO2 (SEDS) that involves the supercritical fluid in drug processing to drug delivery systems. 

Renata Adami, Ernesto Reverehon, Composite polymer-Fe304 microparticles for biomedical applications, produced by Supercritical Assisted Atomization, Powder Technology 2 % (2012), p. 102-108. 

An approach to VOC reduction is use of supercritical carbon dioxide as a component in a solvent mixture (216). The critical temperatin-e and pressure of CO2 are 31.3°C and 7.4 MPa (72.9 atm), respectively. Below that temperatin-e and above that pressure, CO2 is a supercritical fluid. Under these conditions, solvency properties of CO2 are similar to aromatic hydrocarbons. A very high solids coating and supercritical CO2 are metered into a proportioning spray gim in such a ratio as to reduce the viscosity to the level needed for proper atomization. Airless spray guns are used it has been found that the rapid evaporation of the CO2 as the coating leaves the orifice of the spray gun assists atomization. VOC emission reductions of 50% or more have been reported. 

Very recently, atomization processes assisted by supercritical COj have been proposed by various authors. They are based on the mixing and/or solubilization of SC-CO2 in a liquid solution and the subsequent atomization of the mixture. " ... 

Various alternative precursor delivery processes have been designed specifically to circumvent the low volatility and low thermal stability problems associated with (Ba(dpm)2 (see Sect. 2.4.1.2). The first method involves the dissolution of Y(dpm)j, Ba(dpm)2 and Cu(dpm)2 precursors in solvents such as butylacetate [188], THF [153, 156], toluene [189], decane [190] and supercritical carbon dioxide [191]. According to this process, termed aerosol-assisted CVD (AACVD), the multicomponent precursor solution is atomized or vaporized into a carrier gas stream or directly into the reaction chamber, with deposition occurring on a heated substrate. Some attractive features of AACVD include deposition at atmospheric pressure, the ability to use thermally sensitive precursors, and a high precursor transport rate [189]. Figure 2-30 shows a sum-... 

Salmaso, S., Elvassore, N., Bertucco, A., and Caliceti, P Production of solid lipid submicron particles for protein delivery using a novel supercritical gas-assisted melting atomization process. Journal of... 

The basic idea of the gas-assisted spray process consists of an enrichment of the polymer with supercritical carbon dioxide (scCOa) which leads to a decrease in viscosity and surface tension. The eiuichment of the polymer with SCCO2 in the spray process occurs upstream the nozzle in a static mixer under high pressure conditions. Downstream the nozzle ambient conditions exist, thus the prior phase equilibrium is disturbed. Therefore, the amount of CO2 that is dissolved in the polymer decreases dramatically. This is followed by a spontaneous gas emission in the polymer. Hence, the atomization of the polymer is assisted by the expanding gas which also leads to a decline of the temperamre based on the Joule Thompson Effect. However, to date there is no detailed knowledge of the fundamental mechanisms to form sprays and particles by this gas-assisted high-pressure spray process. 

The decompressive release of supercritical carbon dioxide during spray application produces a new type of spray that can have superior atomization characteristics compared to conventional air-less and air-assisted application methods (41). Supercritical carbon dioxide has good solvent properties in a variety of polymers. Solubility of the polymer is influenced by polymer molecular weight, polydispersity, solubility parameter, functionality, and structure (42). Significantly increased solubility has been demonstrated by including fluorine, silicon, and bulky substituent groups in the polymer structure. 

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