Patent ID: 8678200

Claim:
A duct for use in an apparatus for separating suspended solids from a liquid, the duct comprising: an inlet for receiving an input flow of slurry comprising the suspended solids suspended in the liquid; an inlet portion for receiving the input flow of slurry from the inlet to produce an internal flow of slurry; an outlet portion for receiving the internal flow of slurry from the inlet portion to produce an output flow of slurry, wherein the maximum width of the outlet portion is greater than the maximum width of the inlet portion, both maximum widths determined in a direction normal to the internal flow of slurry; a duct section that connects the inlet and outlet portions, wherein the duct section comprises: an upper portion having a length to width aspect ratio of at least 40:1 in a plane normal to the internal flow of slurry; and at least one gas feed configured to introduce gas into the internal flow of slurry, wherein: the at least one gas feed comprises a gas-feed conduit having a plurality of apertures, wherein at least the plurality of apertures and a portion of the gas feed conduit are located in the duct section, the gas-feed conduit is connected to a gas-pressure control configured to increase a gas flow rate in order to purge the duct section of previously suspended solids that settle in the duct section, and the at least one gas feed is configured to produce gas bubbles that break the surface at the outlet portion resulting in the output flow of slurry comprising the suspended solids suspended in the liquid.