PNEUMATIC DISSEMINATION OF DRY POWDERS
Abstract
The object of this study was to obtain basic data on the dissemination of bulk powder into airborne primary particles 1 micron to 10 microns in diameter. Results indicated that discrete particles are obtained when initially suspended agglomerates are shattered by wall or target impact. Significant reagglomeration can occur later because of triboelectrification and insufficient dilution with primary air. Modification by powder additives proves to be selective in weakening contact forces between particles and changing electrification. Seventeen powders and sixteen additives were selected for study. These had a wide range of properties different sizes, smooth and rough surfaces, spherical and irregular shapes, crystalline and amorphous structures, organic and inorganic compositions, and different dielectric constants. Flowability, angle of repose, adhesive force, viscosity of a fluidized bed, and evidences of electric charge separation were measured for various powders and powder-additive combinations. Certain combinations, with the additive at about 1% concentration, showed marked changes in bulk properties and improved dissemination. Aerodynamic disseminating methods, which permitted control of breakup forces over a wide range of values, were used to test for ability to achieve aerosol form. Several assessment methods were evaluated, and a laminar flow settling chamber in which aerosol particles, deposit on long horizontal plates, was considered to be most applicable for this type of research. Effects of air velocity, powder to air ratio, and flow geometry, were studied.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1967
- Accession Number
- AD0822654
Entities
People
- Don Pon
- Paul L. Magill
Organizations
- SRI International