Controlled feeding of powders to conveying systems and process

A method of feeding finely divided powdered material into a conveying conduit through which a stream of powder-transporting gas is flowing, the powder being maintained in a closed vessel having at its bottom a feed device which mechanically urges a stream of the powder downwardly through a feed aperture at a controlled rate into the conveying conduit, said method comprising providing a shroud within the powder in the vessel, disposing a horizontal annular plate below the shroud with powder in the form of an annular mass thereof residing on the upper surface of the plate, introducing gas from the conveying conduit at a location upstream of the entry of powder thereinto to the interior of said vessel at a first location above the annular plate and at a second location above the level of the powder in the vessel whereby pressure fluctuations in the conveyor conduit are equalized throughout essentially the entire mass of powder in the vessel and whereby a smaller mass of stable powder resides at the annular plate and orbiting the plate in horizontal plane thereby urging powder only from the stable mass thereof inwardly toward and through the aperture in the plate along a path which moves in a horizontal plane around the periphery of the aperture in the plate.

Apparatus for feeding finely divided powdered material into a conveying conduit through which a stream of powder-transporting gas is flowing, said apparatus comprising a closed vessel containing a mass of the powder to be fed;

• a feed device at the bottom of the vessel for mechanically urging a stream of the powder downwardly through a feed aperture at a controlled rate into the conveying conduit;
• said feed device including a fixed shroud disposed within the powder in the vessel, a horizontal annular feed plate having an aperture therethrough located directly below the lower end of the shroud and means for orbiting said plate about the vertical axis of the fixed shroud so that powder is urged inwardly from the mass of powder and over the edge of the aperture in said annular plate along a path which continuously moves around the periphery of the aperture pressure equalization lines connecting the conveying conduit at a location upstream of the entry of powder thereinto to the interior of the vessel at a first location at said feed device and above the feed aperture and at a second location above the level of the powder in the vessel.

Apparatus for controllably feeding powder from a mass thereof held in a container downwardly into a lower zone comprising:

• a shroud within the mass of powder;
• a controllable powder feeding device disposed directly below the shroud, said device including a horizontal annular plate having a central aperture supported on a bottom wall of the container, said bottom wall having an aperture in register with the aperture in said annular plate for passing agitated powder into said lower zone;
• and means located above the lower end of the shroud for injecting a gas stream upwardly into and through the mass of powder to agitate the powder above the lower end of the shroud thereby rendering it more flowable while maintaining a stable mass of powder at the location of said powderfeeding device, whereby as said feed device feeds powder to said lower zone additional powder flows from gas-agitated mass of powder into said stable mass of powder.