Coal gasification ash residue carbon residue separation device, water flow grading device and grading process

The coal gasification ash residue carbon residue separation device comprises a material barrel and a fine selection groove arranged on the peripheral side of the material barrel in a sleeving mode, an impeller cavity communicated with the bottom of the fine selection groove is fixed in the material barrel, and the bottom of the impeller cavity is communicated with a centrifugal impeller. A driving shaft for driving the centrifugal impeller to rotate is rotationally inserted into the impeller cavity, upwards extends out of the material barrel and is connected with a driving mechanism for driving the driving shaft to rotate, the bottom of the material barrel is communicated with a water inlet pipe, and the top end of the water inlet pipe extends into the material barrel and is provided with a water inlet coaxial with the centrifugal impeller; the top end of the material barrel upwards extends out of the concentration groove and is provided with an overflow opening, an overflow interval of an annular structure i