Self-cleaning slurry metering valve

A slurry metering system for directing a slurry from a feed source to a processing unit comprising:

• a slurry feed source, a circulation loop which directs said slurry from said feed source to a location closer to said processing unit and back to said feed source, a slurry metering valve placed in-line with said circulation loop, said slurry metering valve comprising a valve body having a primary fluid flow path therethrough from an inlet end to an outlet end, said primary flow path comprising a portion of said circulation loop, a valve stem connected to said valve body and movable through said primary flow path, a valve seat located adjacent said primary flow path and containing a passage therethrough communicating with said primary flow path at a valve seat passage inlet and with a downstream outlet passage in said valve body separate from said primary flow path at a valve seat passage outlet, said downstream outlet passage directing a metered slurry outside said valve body, means to direct said metered slurry from said separate outlet passage to said processing unit, said valve stem comprising and upper valving portion for movement away and against said valve seat for controlling fluid flow through said outlet passage, said valve stem further comprising a lower portion which is movable through said primary flow path and said valve seat passage, said lower portion of said valve stem including a metering component and a cleaning component, said metering component including a gradual downward taper to allow control of fluid flow volume through said valve seat passage when said metering component is placed at said valve seat passage inlet, said cleaning component being below said metering component and having a cut-away portion substantially narrower than said metering component to allow greater fluid flow from said primary flow path to effectively flush and remove accumulated solids from said valve seat passage when said cleaning component is placed at said valve seat passage inlet, at least part of said cleaning component of said valve stem being contained within said valve seat passage when said cleaning component is placed at said valve seat passage inlet.

A process for directing a metered flow of slurry from a continuous feed of slurry comprises:

• passing said continuous feed of slurry through a primary flow path in a slurry metering valve from the inlet of said primary flow path to the outlet end thereof, said metering valve including a valve stem movable through said primary flow path, a valve seat located adjacent said primary flow path, said valve seat containing a passage therethrough communicating with said primary flow path at a valve seat passage inlet and with a downstream outlet passage in said metering valve separate from said primary flow path at a valve seat passage outlet, said valve stem comprising an upper valving portion for movement away and against said valve seat for controlling fluid flow through said outlet passage, said valve stem further comprising a lower portion which is movable through said primary flow path and said valve seat passage, said lower portion of said valve stem containing a metering component and a cleaning component, said metering component including a gradual downward taper to allow control of fluid flow volume through said valve seat passage when said metering component is placed at said valve seat passage inlet, said cleaning component being below said metering component and having a cut-away portion substantially narrower than said metering component to allow greater fluid flow from said primary flow path to effectively flush and remove accumulated solids from said valve seat passage when said cleaning component is placed at said valve seat passage inlet, at least part of said cleaning component of said valve stem being contained within said valve seat passage when said cleaning component is placed at said valve seat passage inlet, metering in said valve a portion of said continuous flow of slurry in said primary flow path through said valve seat passage by placing said metering component at said valve seat passage inlet and directing said metered slurry to said outlet passage, periodically placing said cleaning component of said lower portion of said valve stem at said valve seat passage inlet to flush accumulated solids through said valve seat passage.