Centrifugal jig

A centrifugal jig for separating a heavy fraction from a lightweight fraction of a slurry, comprising:

• a rotor movably mounted for rotation about a central axis, the rotor including an annular jig screen and a surrounding hollow hutch, the hutch having an interior normally filled with fluid during operation of the centrifugal jig and leading to at least one hutch outlet;
• a pulsator to direct fluid pulsations into the rotating hutch and radially inward against the circumference of the jig screen as it rotates about the central axis;
• the jig screen having a recovery zone extending along the central axis between a first annular end where slurry enters the recovery zone and a second annular end where a lightweight fraction of the slurry is discharged;
• the jig screen further having a stratification zone contiguous to said recovery zone extending along the central axis and leading to the first annular end of the recovery zone;
• feed means for introducing slurry onto the stratification zone of the jig screen;
• the stratification zone comprising a layer of material constructed so as to prohibit outward radial passage of particles in the slurry through said layer during rotation of the jig screen while permitting fluid pulsations to be imparted inwardly through said layer to the slurry by operation of the pulsator to pre-stratify the slurry prior to it reaching the recovery zone;
• the recovery zone comprising a layer of material having openings formed therethrough of a size permitting passage of particles in the slurry in response to rotation of the jig screen and through which fluid pulsations are directed to the slurry by operation of the pulsator;
• a stationary shroud surrounding the rotor;
• the stationary shroud including a first annular partition for collecting the lightweight fraction of the slurry discharged from the rotating jig screen, and a second annular partition for collecting a heavy fraction of the slurry passed radially outward through the openings along the recovery zone of the rotating jig screen.

An annular jig screen formed about a central axis for use within a centrifugal jig that separates a heavy fraction from a lightweight fraction of a slurry, the jig screen comprising:

• a recovery zone extending along the central axis between a first annular end where slurry enters the recovery zone and a second annular end where a lightweight fraction of the slurry is discharged;
• a stratification zone contiguous to said recovery zone extending along the central axis and leading to the first annular end of the recovery zone;
• the stratification zone comprising a layer of material constructed so as to prohibit outward radial passage of particles in the slurry through said layer while permitting fluid pulsations to be imparted inwardly through said layer to the slurry during rotation of the jig screen to prestratify the slurry prior to it reaching the recovery zone;
• the recovery zone comprising a layer of material having openings formed therethrough of a size permitting passage of particles in the slurry and through which fluid pulsations are directed to the slurry during rotation of the jig screen.

A method of separating a heavy fraction from a lightweight fraction of a slurry on a centrifugal jig having a rotor including an annular jig screen rotatably mounted about a central axis;

• comprising the following steps:
• forming the jig screen with an axial stratification zone and an adjacent axial recovery zone;
• rotating the jig screen;
• introducing slurry onto the stratification zone of the rotating jig screen;
• and causing it to flow across the stratification zone to and across the recovery zone;
• prohibiting outward radial passage of particles in the slurry through the stratification zone of the rotating jig screen while imparting fluid pulsations inwardly through the stratification zone to the slurry as it flows across the stratification zone of the rotating jig screen to pre-stratify the slurry prior to it reaching the recovery zone;
• directing fluid pulsations radially inward against the circumference of the rotating jig screen through openings formed through the recovery zone of the jig screen, said openings being of a size permitting passage of particles in the slurry as it flows across the recovery zone of the rotating jig screen;
• discharging the slurry from one end of the recovery zone while collecting a lightweight fraction of the slurry so discharged;
• and
• passing a heavy fraction of the slurry radially outward through the openings along the recovery zone of the rotating jig screen and collecting the fraction so passed.