| 摘要 |
<p>The drying takes place in several successive zones, each zone after the first has its bed support palte through which the drying air passes at a shallower angle than the preceding one. The first zone may be at 40 degrees to the horizontal and the fourth zone at 20 degrees, with the slope of intermediate zones reducing gradually. Each zone is also supplied with its own supply of heated drying air independently controlled. For drying at high temps., above 250 degrees C, an alternative design of equipment is preferred which uses steps in each zone instead of sloping plates. The steps in successive zones are shallower and independently controlled heating air is still supplied to each zone. The different zones allow for control of the flow and depth of material. It is also possible to vary the fluidisation air flow and press, to each zone. The result is bed depths not exceeding 10 cm. compared with 20-80 cm using other fluid bed driers. The separate control of drying air-press. and flow for each zone helps to control the flow of dry material as a function of its moisture content.</p> |
