Autogenous heavy medium process and apparatus for separating coal from refuse

A process for separating coal from raw input which includes coal and refuse, comprising the steps of:

• screening the raw input to produce feed solids having a size range of about 2".times.0;
• admixing said feed solids with a non-magnetic heavy medium having a specific gravity in a range of about 1.10 to about 1.40 to form a feedstock slurry;
• subjecting said feedstock slurry sequentially both to substantially constant acceleration for a predetermined time and then to increasing acceleration in at least one cyclonic separator to produce a coal-rich slurry and a refuse-rich slurry, said feedstock accelerating step including the steps of confining said feedstock slurry in a chamber having a substantially cylindrical shape with a predetermined axial dimension and a conical end wall having an axial extent corresponding to about one-half said predetermined axial dimension to provide said substantially constant acceleration followed by said increasing acceleration, and including the step of exhausting through a vortex finder terminating above the median of said cylindrical chamber said coal-rich slurry and discharging from the apex of said conical end wall the refuse-rich slurry;
• dewatering said coal-rich slurry to produce a coal product and a coal-rich underflow slurry;
• dewatering said refuse-rich slurry to produce a refuse product and a refuse-rich underflow slurry;
• conflowing said coal and refuse slurries to produce a heavy medium;
• periodically sampling said heavy medium to determine its specific gravity;
• bleeding said heavy medium and adding water to said feedstock slurry as indicated by said sampled specific gravity to adjust the specific gravity of the medium in said range;
• whereby coal is separated from refuse in a continuous process.

A process for separating coal from raw input which includes coal and refuse, comprising the steps of:

• screening the raw input to produce feed solids having a size range of about 2".times.0;
• admixing said feed solids with a non-magnetic heavy medium to form a feedstock slurry having a solids content of at least about 10%;
• maintaining the specific gravity of said heavy medium prior to introduction of said raw input below the specific gravity of the coal to be separated;
• cyclonically separating said feedstock slurry to produce a coal-rich overflow slurry having middlings contained therein and a refuse-rich underflow slurry;
• said cyclonic separating step including the steps of:
• admitting said feedstock slurry tangentially into a substantially cylindrical chamber for subjecting said feedstock to substantially constant acceleration through a first axial extent,
• immediately thereafter admitting said feedstock slurry into a tapered chamber in fluid communication with said cylindrical chamber to subject said feedstock slurry to increasing acceleration through a second axial extent corresponding to about one-half said first axial extent,
• exhausting said coal-rich middlings-containing slurry in one direction from said cylindrical chamber through a vortex finder depending centrally into said cylindrical chamber a distance less than about one-half said first axial extent, and
• discharging said refuse-rich slurry in the opposite direction through an orifice in said tapered chamber aligned axially with said vortex finder,
• dewatering the coal-rich slurry to produce a coal product and a fine coal slurry;
• dewatering said refuse-rich slurry to produce a refuse product and a fine refuse slurry;
• admitting said middlings-containing coal-rich overflow into a secondary cyclonic separator to produce a low ash middlings-free overflow and a high ash middlings rich underflow;
• crushing said high ash middlings-rich underflow solids to a size range smaller than said screened raw input;
• admixing said high ash crushed underflow solids with said feed solids and with said fine coal and fine refuse slurries to form said feedstock slurry;
• and
• recirculating said feedstock slurry to said cyclonic separating step.

Apparatus for separating coal from raw input which includes coal and refuse, comprising:

• means for screening the raw input to produce solids having a size range of about 2".times.0;
• means for mixing said solids with a non-magnetic heavy medium to form a feedstock slurry;
• means for cyclonically separating said feedstock slurry to produce a coal-rich slurry and a refuse-rich slurry, said cyclonic separating means including a wall forming a substantially cylindrical chamber and a bottom wall forming a tapered chamber adjacent an underflow orifice, said cylindrical chamber having an axial length slightly greater than its inside diameter, said tapered chamber having an axial length corresponding to about one-half the axial length of said cylindrical chamber, and including a vortex finder depending centrally into said cylindrical chamber and terminating above the median thereof and an outlet orifice in said tapered chamber in axial alignment with said vortex finder;
• means for dewatering the coal-rich slurry to produce a coal product and a fine coal slurry;
• means for dewatering said refuse-rich slurry to produce a refuse product and a fine refuse slurry;
• means for mixing said fine coal and fine refuse slurries together to form said non-magnetic heavy medium;
• and
• means for feeding said heavy medium to said first-mentioned mixing means to form said feedstock slurry;
• whereby coal can be separated from refuse on a continuous basis utilizing an autogenous non-magnetic heavy medium.

A process for separating coal and refuse from raw input comprising the steps of:

• screening said raw input to a size range of about 2".times.0;
• entraining said screened raw input in a heavy medium slurry having a specific gravity lower than the specific gravity of the coal to be separated;
• admitting said raw input and heavy medium tangentially under pressure through an inlet into a substantially cylindrical chamber having an axial length slightly greater than its diameter to subject said input to a substantially constant acceleration for a predetermined time interval;
• causing said raw input to enter a tapered chamber having an included cone angle of about 90.degree. to about 120.degree. at one end of said substantially cylindrical chamber for increasing the acceleration on the raw input;
• discharging a refuse-rich slurry through an orifice at the apex of said tapered chamber;
• and
• exhausting coal-rich slurry from about the middle of said cylindrical chamber through a vortex finder of a predetermined inside diameter.

For use in a process of separating coal and refuse from raw input having a size range of about 2".times.0 entrained in a heavy medium slurry having a predetermined specific gravity, a cyclonic separator, comprising:

• a wall defining a substantially cylindrical chamber having a predetermined inside diameter;
• means providing a transverse end wall at one end of said chamber;
• means providing at least one tangential inlet into said chamber adjacent said end wall;
• a tapered end wall at the other end of said cylindrical chamber having an included cone angle in a range of about 90.degree. to about 140.degree.;
• means providing an orifice in said tapered wall adjacent the apex thereof;
• a vortex finder depending into said cylindrical chamber and terminating at about the median thereof;
• and
• the inside diameter of said cylindrical chamber being slightly less than its axial length.