Method and apparatus for concentrating a slurry

A method for dewatering a slurry of titanium dioxide having an initial specific gravity of about 1.01 or greater using a filtration system comprising a filter stack, a means for oscillating said filter stack, a feed tank, a permeate holding tank, a concentrate removal line and a water source wherein the method comprises the steps of:

• removing slurry from said feed tank;
• when said slurry in said feed tank initially has a specific gravity of about 1.2 or greater, adding sufficient water or permeate to said feed tank to reduce the specific gravity of the slurry stored in said feed tank to a range of about 1.01 to about 1.1;
• passing permeate fluid from said permeate holding tank through said filter stack for period of time ranging from about 20 minutes to about 16 hours;
• initiating fluid flow from said feed tank while directing concentrate flow from said filter stack to said feed tank;
• adding slurry to said feed tank thereby increasing the specific gravity of the slurry in said feed tank to a range of about 1.2 to about 1.8 whereby the rate of increase of the specific gravity of the slurry in said feed tank is about 0.1 per hour;
• initiating oscillation of said filter stack;
• increasing the oscillation amplitude of said filter stack;
• setting the oscillation amplitude of said filter stack to a distance between about 0.6 cm and about 3.8 cm;
• increasing the specific gravity of the slurry in said feed tank;
• and,
• removing concentrate and permeate from said filter stack, said concentrate removed from said filter stack has a specific gravity ranging from about 2.0 to about 2.3 and said permeate removed from said filter stack has a specific gravity ranging from about 1.0 to about 1.

A method for dewatering a slurry of titanium dioxide having an initial specific gravity of from about 1.01 to about 1.8 using a filtration system comprising a filter stack, a means for oscillating said filter stack, a feed tank containing a slurry, a permeate holding tank, a concentrate removal line and a water source wherein the method comprises the steps of:

• when said slurry in said feed tank initially has a specific gravity of about 1.2 or greater, lowering the specific gravity of said slurry stored in said feed tank to a range of about 1.0 to about 1.1;
• passing permeate fluid from said permeate holding tank through said filter stack for period of time ranging from about 20 minutes to about 16 hours, said permeate fluid having a specific gravity between about 1.0 and about 1.1;
• initiating fluid flow from said feed tank while directing concentrate flow from said filter stack to said feed tank;
• adding slurry having a specific gravity of from about 1.2 to about 1.8 to said feed tank;
• initiating oscillation of said filter stack at an amplitude between about 0.32 cm and about 0.6 cm;
• increasing oscillation of said filter stack to an am plitude between about 0.6 cm and about 1.3 cm;
• subsequently setting the oscillation of said filter stack to an amplitude between about 0.6 cm and about 3.8 cm;
• increasing the specific gravity of the slurry in said feed tank to a range of about 1.2 to about 1.8;
• removing concentrate and permeate from said filter stack, said concentrating having a specific gravity ranging from about 2.0 to about 2.2 when processing a slurry containing the rutile form of titanium dioxide, said concentrate having a specific gravity ranging from about 2.0 to about 2.3 when processing a slurry containing the anatase form of titanium dioxide and said permeate having a specific gravity ranging from about 1.0 to about 1.1;
• monitoring concentrate flow rate and specific gravity;
• flushing said filter stack by replacing the slurry flow from said feed tank with permeate flow obtained from said permeate holding tank for a period of time sufficient to lower the concentrate specific gravity to a range of about 1.0 to about 1.2 upon detection of a concentrate specific gravity of greater than 2.2 when processing a slurry containing the rutile form of titanium dioxide and greater than 2.3 when processing a slurry containing the anatase form of titanium dioxide;
• and,
• restoring slurry flow from said feed tank while continuing to monitor concentrate flow rate and specific gravity.