Apparatus and process for pneumatically conveying particulate material

DETAILED DESCRIPTION I claim: 1.
Apparatus for conveying material by fluid under pressure comprising: a vessel having an inlet for material; a material conveying conduit for discharging material from the vessel having a material inlet flow connected to the inside of the vessel; means for supplying gaseous fluid under pressure to the vessel for pressurizing the vessel and entraining material through the material inlet of the conveying conduit and conveying it through the conduit; means for controlling the rate at which material is conveyed through the material conveying conduit including means responsive to a condition for selectively supplying fluid under pressure directly from the vessel to a fluid inlet in the material conveying conduit downstream of the material inlet while maintaining the supply of gaseous fluid under pressure to the vessel; said conveying conduit being substantially free of material flow control means between the material inlet and the downstream fluid inlet of the material conveying conduit when material is being conveyed through the material conveying conduit; said means responsive to a condition including differential pressure means responsive to the difference between the pressure inside the vessel and a predetermined pressure; said means for selectively supplying fluid under pressure directly from the vessel to the fluid inlet in the material conveying conduit downstream of the material inlet further includes a by-pass conduit flow connected at one end to the downstream fluid inlet and selectively flow connected at its other end to the inside of the vessel and said differential pressure means is a by-pass valve means for controlling the flow of fluid under pressure from said vessel into said by-pass conduit; said by-pass valve means being responsive to the difference between the pressure inside the vessel and a predetermined pressure so that when the pressure inside the vessel exceeds said predetermined pressure, said by-pass valve means opens to supply fluid under pressure from the vessel directly to the conveying conduit so that less material enters the material inlet to increase the ratio of conveying fluid to material in the conveying conduit and thereby control the rate at which material is conveyed; first sensing means for sensing when the quantity of material in the vessel reaches a predetermined minimum; valve means responsive to said sensing means for changing the predetermined pressure at which said by-pass valve means is responsive