US Patent 7794133 Dust-reducing mixing device and process

Mixing devices and processes that make it possible to mix flowable finely divided solid particles with liquids (and/or slurries of solids in liquids) contained in an open top container outdoors under windy conditions, with reduced or eliminated dusting from entrainment of the flowable finely divided solids by the wind, utilize a mixing device with a dust-tight housing open at its bottom and partially immersed below the surface of the liquid, an inlet port on the housing for the finely divided solids, an outlet port on the housing for escape of air displaced by liquids flowing through an opening into the immersed portion of the housing, and, inside the housing, a driven impeller that causes the actual mixing.