Fluidized bed powder discharge and metering method and apparatus
First Claim
1. An apparatus to discharge and meter powder from a fluidizing vessel into a container positioned below the vessel comprising:
- (a) a valve mounted below said vessel to control the discharge of powder from said vessel;
(b) a conduit assembly disposed between said valve and said container;
(c) said vessel, valve, conduit assembly and container forming a substantially pressure-tight system for minimizing pressure differential across said valve caused by fluidizing gas;
(d) means to alternately open and close said valve to cause short duration discharges of powder;
(e) means to measure the weight of powder discharged into said container; and
(f) means to discontinue opening of said valve when a predetermined weight of powder has been discharged into said container.
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Accused Products
Abstract
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.
55 Citations
13 Claims
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1. An apparatus to discharge and meter powder from a fluidizing vessel into a container positioned below the vessel comprising:
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(a) a valve mounted below said vessel to control the discharge of powder from said vessel; (b) a conduit assembly disposed between said valve and said container; (c) said vessel, valve, conduit assembly and container forming a substantially pressure-tight system for minimizing pressure differential across said valve caused by fluidizing gas; (d) means to alternately open and close said valve to cause short duration discharges of powder; (e) means to measure the weight of powder discharged into said container; and (f) means to discontinue opening of said valve when a predetermined weight of powder has been discharged into said container. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of discharging and metering powder from a fluidizing vessel into a material-receiving container comprising the steps of:
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(a) alternately opening and closing a valve mounted below said fluidizing vessel to cause discharge of powder and gas from said vessel in short duration discharge periods; (b) increasing the duration of said discharges in inverse proportion to the amount of powder remaining in said fluidizing vessel whereby substantially equal amounts of powder are discharged in each discharge period; (c) weighing the container and powder therein; and (d) terminating the discharge of powder from the fluidizing vessel when the weight of the container and powder therein reaches a predetermined amount. - View Dependent Claims (10, 11)
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12. A method of discharging and metering powder from a fluidizing vessel into a material-receiving container comprising the steps of:
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(a) alternately opening and closing a valve mounted below said fluidizing vessel to cause discharge of powder and gas from said vessel in short duration discharge periods; (b) retaining substantially all of the discharged gas in the container to cause the pressure in the fluidizing vessel and the container to equalize, thereby decreasing the rate of discharge of powder and gas through said valve; (c) weighing the container and the powder therein; and (d) terminating the discharge of powder from said fluidizing vessel when the weight of the container and powder therein reaches a predetermined amount. - View Dependent Claims (13)
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Specification