Bayer Aktiengesellschaft

Mathias Benz

Benno Franz Ulfik

Heiko Herold

Jorg Rainer Schmitz

For the metered feed of coarse granular material into an air jet mill an injector 3 operated by propellent air is used, the coarse material being fed continuously to a closed injector hopper 6 provided on the injector 3. In the injector hopper 6, the pressure is measured at a product-free point and, by resetting the propellent air mass flow at the injector 3 is held constant at a preselected setpoint partial vacuum value. Said setpoint value is preferably set so low that at said pressure there is only just no return flow from the injector 3 into the injector hopper 6. The apparatus for effecting said method comprises a control loop having a pressure sensor 16 for measuring the flow in the closed injector hopper 6, a motor-adjustable valve 4, 5 as an actuator for varying the supplied propellent air mass flow and a loop controller, which compares the actual pressure value with a preselected setpoint value and supplies a control signal for operating the actuator 4, 5.

Method and apparatus for the metered feed of coarse granular material

In the process for the continuous collection of pulverulent or dusty samples from a particle-laden stream, a sample stream is drawn off from a particle-laden main stream in a pneumatic conveying line 17 and passed via a collection line 9 to a particle size measurement device 10. In order to reduce spin, the main stream in the conveying line 17 is passed through a venturi-like cross-sectional constriction 3, 4, 5, the cross-sectional area of which is 10 to 60% of the free cross-sectional area of the conveying line 17. Samples are then collected downstream from the cross-sectional constriction through one or more probe tubes 7, wherein a partial stream is collected from the main stream parallel to the direction of flow thereof. In conjunction with a jet mill 14, into which the product to be ground and the propellant air are continuously introduced, the particle size distribution measured in the continuously collected sample stream may be used as a control parameter in order to adjust a parameter which determines particle size distribution of the jet mill 14 in such a manner that the particle size distribution in the product stream remains constant.

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Bergisch Gladbach, Germany

Mathias Benz