Radial flow electrostatic filter

A filter for the separation of finely divided solid particles from a liquid of low electrical conductivity comprising a cylindrical casing, a particulate filter bed resting on the lower end of the casing comprising glass beads having a size in the range of approximately 1/8 inch to approximately 1/4 inch and a depth of approximately 75 percent of the length of the casing, a tubular central perforated electrode extending from one end of the casing vertically through at least a portion of the filter bed, said central electrode being perforated over an interval within the filter bed, a perforated cylindrical outer electrode concentric with the central electrode, a perforated cylindrical liner within the casing and joined at its upper and lower ends to the casing, conductors extending through the casing and supporting the outer electrode at a midpoint between the central electrode and the liner in the filter bed with its upper end below the top of the filter bed and its lower end above the bottom of the filter bed, bushings supporting the conductors and insulating said conductors from the casing, inlet means constructed and arranged to deliver liquid to be filtered into the central electrode, an outlet through the wall of the casing between the upper and lower ends of the liner, means for grounding the central electrode, means for connecting the conductors to an electric power source for applying a voltage gradient of 5 to 20 kv per inch between the electrodes, a backflush inlet opening through the lower end of the casing, a backflush outlet at the upper end of the casing, and valve means to control flow of liquid through the filter during backflushing and filtering.

A filter for the separation of finely divided solid particles from a liquid of low electrical conductivity comprising a vertical cylindrical casing, a particulate filter bed within the casing comprising substantially spherical, smooth-surfaced, nondeformable particles of high electrical resistivity having a size in the range of approximately 3 mesh to 6 mesh, a tubular central electrode extending vertically through at least a portion of the filter bed, said central electrode being perforated only in the interval within the filter bed, a vertical cylindrical perforated liner within the casing adjacent but spaced from the wall of the casing to provide an annular passage adjacent the wall of the casing, means closing the upper and lower ends of the annular passage, the perforations in the liner being of a size to prohibit passage of particles of the filter bed therethrough, said liner defining the outer boundary of the filter bed, a perforated cylindrical outer electrode concentric with the central electrode supported vertically at a midpoint between the central electrode and the liner with its upper end below the top of the filter bed and its lower end above the bottom of the filter bed, liquid inlet means constructed and arranged to deliver liquid to be filtered into the central electrode, an outlet through the casing communicating with the annular passage, means for grounding the central electrode, the casing and the liner, means connecting the outer electrode to an electric power source adapted to apply a voltage gradient of 5 to 20 kv per inch between the central electrode and the outer electrode and between the outer electrode and the liner, a backflush inlet constructed and arranged to deliver backflush liquid into the lower end of the filter bed, a backflush outlet at the upper end of the casing above the filter bed, and valve means to control flow of liquid through the filter during backflushing and filtering.