Accession Number:

ADA196656

Title:

Reaction of Microparticles by the Diffusion of Reactive Gases through Porous Shells

Descriptive Note:

Technical rept. Sep 1986-May 1987

Corporate Author:

CHEMICAL RESEARCH AND DEVELOPMENT CENTER ABERDEEN PROVING GROUND MD

Personal Author(s):

Report Date:

1988-04-01

Pagination or Media Count:

26.0

Abstract:

A new experimental technique, single particle electrodynamic balance SPEB, was used to study the heterogeneous reaction between single acid droplets and basic gases. Experiments with phosphoric acid droplets and ammonia gas show that the droplet reaction dynamics are sequentially controlled by surface phase, gas phase diffusion-controlled, and porous shell diffusion- controlled reactions. Gas phase diffusion-controlled reactions terminate when ammonium phosphate crystallizes at the droplet surface, and porous shell diffusion-controlled reactions become rate limiting. We derive a semiempirical model to describe the porous shell diffusion-controlled reactions of acid droplets with surface layers of crystallized solids. The model is parameterized with an effective porous shell diffusion coefficient to describe the transport of reactive gases through the porous shell. Keywords Heterogeneous reaction, Gas phase diffusion, Porous shell diffusion, Surface phase, Crystallization. mjm

Subject Categories:

  • Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE