Study on the effect of nanoparticles on the bulk and flow properties of granular systems

In the process of coal combustion and gasification, the evaporation of inorganic substances forms submicron particles, which are very cohesive and play an important role in the adhesion of gasification fine ash. These particles attach to the surface of larger particles and form self-agglomerates that participate in the flow. In order to study the effect of nanoparticles on the bulk and flow properties of the granular system, different contents of nano-silica particles were added to the ideal spherical granular systems (glass beads) and the actual gasification fine ash granular systems, respectively. The bulk properties and the initial flow properties of powders were examined by the compressibility test and the shear cell test. It was found that the nanoparticles formed the very loose and highly compressible packing structures. With the increase of nanoparticle volume fraction in the granular system, the bulk density showed the approximately linear monotonous decreasing. However, effects of nanoparticles on the flow properties of particles with different sizes were different. When the content of nanoparticles in the system increased to a certain extent, the cohesion of the granular system composed of smaller host particles reduced and the flowability would be improved. But the increase of nanoparticles made the cohesion of the system composed of larger host particles increase first and then decrease. However, a few number of nanoparticles could minimize the internal friction angles of the larger particle systems. •The bulk and flow properties of nanoparticles were studied.•The bulk density of the powder mixtures decreased approximately linearly with the increase of nanoparticles.•The effect of nanoparticles on the flowability of host particles with different sizes was different.•A few nanoparticles could make the internal friction angle of larger host particles reach the minimum.