In an embodiment, a method of operating at least one pressure vessel to inject a particulate slurry into a high-pressure line, comprises a first operating cycle comprising: isolating the at least one pressure vessel from the high-pressure line; introducing particulate solids into the pressure vessel through a particulate solids inlet aperture; a second operating cycle comprising: providing high-pressure flow into the pressure vessel; and providing a high-pressure slurry flow from the pressure vessel into the high-pressure line. The method further comprises operating the at least one pressure vessel in the second operating cycle to create a heterogeneous flow of slurry into the high-pressure line.