| 摘要 |
A metering method and apparatus is provided for the controlled discharge of powder from a fluidized-bed blender to a material container, which gives accurate material weights while separating powder from fluidizing gas. In this method the material container is filled with a series of short duration discharges at a reduced powder flow rate. This method enables the apparatus to more precisely measure the weight of the container and maintain homogeneity of the blended material in both the bed and the container. The apparatus for carrying out this method includes a flexible pressure-tight sleeve connecting the fluidized bed to the container. When a ball valve located at the bottom of the fluidized bed opens to discharge powder, the sleeve retains the high pressure fluidizing gas inside the sleeve and the container. This causes the pressure to build at the outlet of the valve thus preventing the gas from rapidly exhausting and forcing powder through the outlet. The short duration discharges are terminated when a load cell, provided to electronically weigh the container, measures a predetermined material weight. To improve accuracy, the load cell measurement is monitored only during the relatively quiescent period between discharges, and the measured weight of the material in the container is continuously corrected to eliminate the effects of fluidizing gas pressure forces. Finally, an off-gas hose extending from the container lid exhausts the fluidizing gas at a controlled rate of flow and separates the gas from the powder.
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