Reaction of microparticles by the diffusion of reactive gases through porous shells
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 reaction of acid droplets with surface layers of crystallized solids. The model is parametrized with an effective porous-shell diffusion coefficient to describe the transport of reactive gases through the porous shell. The model is compared to reaction data obtained from the SPEB for the reaction of phosphoric acid droplets layered with shells of ammonium phosphate. The characteristic pore radius of the porous shell is determined as a function of reaction condition.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 15, 1987
- Source ID
- 10.1063/1.338050
Entities
People
- Glenn O. Rubel