An experimental and modeling investigation of particle production by spray pyrolysis using a laminar flow aerosol reacto
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Melissa M. Lunden Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720
Kikuo Okuyamaa) Department of Chemical Engineering, Hiroshima University, Kagamiyama 1-4-1, Higashi-Hiroshima 739-8527 Japan (Received 21 July 1999; accepted 28 December 1999)
The influence of operating parameters on the morphology of particles prepared by spray pyrolysis was investigated using a temperature-graded laminar flow aerosol reactor. Experimentally, zirconia particles were prepared by spray pyrolysis using an aqueous solution of zirconyl hydroxide chloride. Hollow particles were formed if the reactor temperature was high, the temperature gradient was too large, the flow rate of carrier gas was high, and the initial solute concentration was low. A numerical simulation of the pyrolysis process was developed using a combination of two previous models. The simulation results compared well with the experimental results.
I. INTRODUCTION
Small particles with sizes of submicron up to several micrometers have important applications in the areas of electronic materials, catalysis, and analytical chemistry. It is important to develop a process which can produce the particles having controlled characteristics such as size, morphology, composition, and others. To be industrially relevant, the process needs to be low cost with both a continuous operation and a high production rate. Spray pyrolysis, a method for producing particulate materials that combines both liquid and gas phase aerosol processes, may be such a process.1 Particle synthesis by spray pyrolysis involves the atomization of a precursor solution into discrete droplets. These droplets are subsequently transported through a furnace where the solvent is evaporated from the droplets and the dissolved species react to form the product particulate. Spray pyrolysis has a number of advantges including the following: (i) the particles produced are spherical; (ii) the distribution of their diameters is uniform and controllable from micrometer to submicron; (iii) the purity of the product is high; (iv) the process is a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 15, No. 3, Mar 2000
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continuous. These advantages are realized because the precursor salts are mixed in solution at the molecular level; after atomization, all particle formation processes are integrated inside the droplet. Each droplet has the same composition; thus multicomponent and composite particles can be easily synthesized by controlling the chemistry of the precursor solution. The application of the spray pryrolysis process to industry is very promising because the equipment is simple with short processing times on the order of a few seconds. By comparison, the use of conventional solid-phase or liquid-phase methods requires the repetition of some operations, such as calcination and milling, to obtain the desired particle size. Moreover,
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