Abstract: Dense phase pneumatic conveying is the tendency of clean and efficient transport technology of granular materials. Coarse particles are difficult to be driven by stable dense phase pneumatic conveying because of their properties. The light medium mixed flow pneumatic conveying is proposed and designed to realize coarse particles stable dense phase transport. Compared to traditional pneumatic conveying technology, the light medium mixed flow pneumatic conveying has theoretical advantages. Conveying characteristics, including flow regime, particle self-organization, and the relationship between inlet pressure fluctuation and particle slug formation, are studied by computational fluid dynamics-discrete element method(CFD-DEM) coupling numerical simulation method. Results indicated that particle density and size are the main factors of flow regime in the light medium mixed flow pneumatic conveying, and the particle density has remarkable effect. By analysis of slug collapse and building process, quasi-periodicity and dynamic stability slug flow could been found in the new proposed method. Meanwhile, particle segregation self-organization (coarse particles on the top, and fine particles on the bottom) and self-lubrication phenomenon of fine particle could be also found. There are strong correlations among the inlet pressure fluctuation, mass flow rate of mixed particles, and the flow regime. The move velocity and the solid slug length could be estimated by conveying energy efficiency and mixed particles mass flow rate. This work is beneficial to broaden the application field of pneumatic conveying, and provides a new approach for coarse particle dense phase pneumatic conveying.

Key words: coarse particle, pneumatic conveying, computational fluid dynamics-discrete element method(CFD-DEM) coupling simulation, conveying characteristics, light medium mixed flow