Patent ID: 8404121

Claim:
A separation process comprising: (a) providing a separation vessel comprising (i) a fluid inlet, (ii) a solids outlet comprising an overflow conduit having a height h w measured from a base portion of the separation vessel, and (iii) a fluid outlet at a first position between the base portion and h w ; (b) feeding an aerated inlet mixture to the separation vessel via the fluid inlet at a flowrate Q i , the aerated inlet mixture comprising (i) a fluid, (ii) a solid contaminant, and (iii) an aerating gas; (c) separating the inlet mixture in the separation vessel into (i) an upper float layer comprising aerated solids and being located at a second position, and (ii) a lower clarified layer comprising a clarified fluid and being located at a third position, the second position being relatively further away from the base portion of the separation vessel than the third position; (d) withdrawing the upper float layer from the separation vessel via the overflow conduit; (e) withdrawing the lower clarified layer from the separation vessel via the fluid outlet at a selected flowrate Q o ; and (f) performing (a)-(e) as a continuous separation process with a control process comprising: (i) selecting an operating height h o that is larger than h w ; (ii) measuring an instantaneous height h(t) of the separation vessel contents; (iii) adjusting the flowrate Q o based on a first error function h(t)-h 0 to minimize the first error function; and (iv) repeating (i)-(iii) of the control process.