Process and device for pneumatically conveying powdery substances and their use

A process for the pneumatic conveyance of pulverulent substances having a specific gravity of 0.1 to 15.0 g/cm3 and a particle size range of between 0.1 and 300 μm comprising the steps of providing a device comprising a container having an inner diameter (d) and a length (a) wherein the ratio between (a) and (d) is between 0.5 to 10.0, the container defines a pump chamber, the pump chamber having a pulverulent substance supply line and a pulverulent substance discharge line, a source of negative pressure connected to the pump chamber via a vacuum line for drawing into the pump chamber via the supply line the material to be conveyed, a source of conveying gas connected to the pump chamber via a conveying gas line for discharging from the pump chamber via the discharge line the material to be conveyed, shut-off members in the vacuum line and the conveying gas line, a flat filter element disposed on the container between both the source of the negative pressure and the source of conveying gas and the pump chamber and has a diameter which is ≦d, and means for vibrating the filter element, carrying out an intake phase with the shut-off member of the vacuum line opened and at a negative pressure of between 1 and 25 mbar applied and with the discharge line closed and a shut-off member of the supply line open, closing the shut-off member of the supply line after an interval predetermining the level in the pump chamber, thereafter opening a shut-off member of the discharge line and a shut-off member of the conveying-gas line to form an emptying cycle during which the material to be conveyed is ejected by means of a pressure flow consisting of compressed gas wherein the filter element is vibrated and simultaneously purified.