The production of ultrafine powder by mixing cooling gas (oxygen) and hot gas (plasma gas and silica vapour) in a flow reactor is considered. A simple one-dimensional model is developed to study the influence of the mixing on the particle growth mechanism. Two functions, one for the variation of the cooling gas concentration along the reactor length, and another for the mean mass temperature variation, are suggested for description of the mixing. The times for mixing (cooling) are estimated with the assumption that the mixing of the flows takes place at lengths in the range of d to 3d (where d is the reactor diameter), and that during the mixing the flow is cooled. The evolution of the particle size distribution function (PSDF) is calculated for different values of mixing (cooling) time. The results obtained show that the mixing process leads to delays in monomer generation on the one hand, and to the impossibility of establishing self-preservation of the PSDF on the other.
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