Spinning wheel powder feeding device — fundamentals and applications

A spinning wheel powder feeding system has been developed as a conveying mechanism to feed fine particle aggregates on a laboratory scale. An example of a use of this conveying mechanism is with a transport tube reactor, since the reactor only provides a few seconds residence time to react the powder. Methods to shear the powder mechanically, as opposed to using a high gas velocity, are developed as to not reduce the available residence time in the reactor. The objective is to feed a powder at the smallest particle aggregate size possible rather than a large particle aggregate size generated by an upstream feeding device, and to achieve such dispersion using minimized gas flow. Statistical results show that the spinning wheel alone is able to reduce the mean aggregate size of the Particle Size Distribution (PSD) and when a minimal amount of gas is added to the system the PSD is reduced further. In addition, a fundamental model employing a discrete particle aggregate breakage equation combined with a Monte Carlo method has shown that the spinning wheel feeding system is able to consistently reduce particle aggregate size.

Graphical abstractFig. 1. Spinning wheel feeder design and spinning wheel feeder housing.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 2. Experimental design and locations where PSDs were taken.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 3. Volume PSDs for ZnO taken from three locations in the spinning wheel feeder.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 4. VisiSizer observations of particles: a) No spinning wheel or gas shear b) Spinning wheel shear only, c) Spinning wheel and gas shear.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 5. Rosin-Rammler parameter D¯ vs. wheel spinning rates.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 6. Rosin-Rammler parameter D¯ vs. gas flow rate at 2200 rpm.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 7. Rosin-Rammler parameter n vs. gas flow rate at 3300 rpm.Figure optionsDownload full-size imageDownload as PowerPoint slideequation(7)Sj=# of breakage events# of possible breakage eventsequation(8)b(i,j)=# of particles of size i in j# of particles of size in jFig. 8. Experimental (data points) vs. Model (solid lines) for different wheel settings.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 9. Model PSD prediction for different wheel settings and a Hamaker constant of 40 × 10− 20 J.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. 10. Model PSD prediction for different Hamaker constants and a wheel setting of 2200 rpm.Figure optionsDownload full-size imageDownload as PowerPoint slide