Extracting soluble substances from subdivided solids with a water-base liquid extraction medium

A method for extracting soluble substances from subdivided solids containing small particles and fines with water base liquid extraction medium, said process employing at least one tank having first and second portions, at least one discharge outlet for the withdrawal of enriched extraction liquid from the at least one tank, at least one milli-screen, said at least one milli-screen having an upstream face and a downstream face with respect to the flow of liquid medium when the liquid medium is withdrawn through said at least one discharge outlet, a plurality of discrete milli-openings extending from the upstream side to the downstream side of said at least one milli-screen, said milli-openings comprising sizes less than about 0.095 inches across on the upstream side of the said at least one milli-screen, said process comprising the steps of:

• introducing subdivided solids into a first portion of the at least one tank;
• said subdivided solids containing small particles and fines;
• said small particles and fines containing substances that can be extracted with a water base liquid medium;
• introducing water base liquid extraction medium into a second portion of the at least one tank;
• contacting at least some of the subdivided solids with the upstream face of said at least one milli-screen;
• pushing the at least some of subdivided solids including small particles and fines toward the second portion of the tank with said at least one milli-screen countercurrent to the flow of the water base liquid extraction medium;
• and
• separating at least some of said small particles and fines from the liquid extraction medium with said at least one milli-screen;
• withdrawing the enriched extraction liquid from the first portion of the at least one tank;
• and
• withdrawing the spent subdivided solids from said second portion of the at least one tank.