| A fluid bed dryer for processing a particulate material | | | | dryer and having a common wall one end of which is |
| includes a housing providing a series of chambers with | | | | open to the entrance end of the first chamber of the |
| adjacent chambers separated by a longitudinally | | | | fluid bed dryer, the base of the pre-drying chamber |
| extending common wall and connected by a | | | | extends into a connecting turn around section without |
| turn-around section to provide a serpentine path | | | | termination comprising a bottom plate having a pair of |
| leading from an entrance end of a first chamber to an | | | | edges one of which intersects the bottom plate of the |
| exit end of a last chamber. Each turn-around section is | | | | non-plug flow dryer at the common wall and the other |
| open at one end of one of the common walls to the | | | | of which intersects the bottom plate of the plug flow |
| adjacent chambers separated by the common wall | | | | dryer at the common wall. |
| and serves to receive and turn particulate material | | | | Fluid bed dryer used for drying thermally sensitive |
| distributed across the width of one of the chambers | | | | materials are generally of the plug flow type operated |
| through an arcuate path of 180° and deliver the | | | | at relatively low temperatures and requiring relatively |
| material to the other chamber. Each of the chambers | | | | long material residence times in the equipment to |
| and turn-around sections have a base including at least | | | | satisfactorily dry the material. Such dryers are usually |
| one bottom plate with a number of gas introduction | | | | provided in a folded design providing a serpentine flow |
| openings distributed across each plate and oriented to | | | | path for the material whereby economies of space, |
| introduce gas into said chamber in a specific direction | | | | gas ducting and thermal energy can be obtained. In a |
| to fluidize and move a particulate material in that | | | | folded or serpentine flow path dryer design the |
| direction. The gas introduction openings in each of the | | | | material being processed loops back and forth as it |
| chambers are oriented to uniformly fluidize and move | | | | passes through the equipment. Although this design |
| the particulate material in a direction parallel to the | | | | minimizes the space and distances required in |
| common wall and the gas introduction openings in each | | | | operating the equipment, in folded fluid bed dryers using |
| turn-around section are oriented to successively | | | | a conventional bottom plate design as shown in FIG. 6, |
| receive and turn incremental vertical columns of the | | | | there is a tendency for some materials being |
| particulate material with each incremental vertical | | | | processed to stop fluidizing and pile up at the turn |
| column of the particulate material received and turned | | | | around sections between the adjacent chambers |
| successively in accordance with the distance each | | | | thereby requiring the process to be shut down due to |
| incremental vertical column is spaced from the | | | | malfunction of the equipment. That is, conventional plug |
| common wall. A plenum chamber provides pressurized | | | | flow fluid beds are fitted with bottom plates rectilinear |
| gas beneath each bottom plate and a source of | | | | in form and are placed with no particular consideration |
| pressurized gas is connected to each plenum | | | | as to the energy required to maintain the desired |
| chamber. | | | | fluidization and directional transport of the material |
| In a still further preferred embodiment, the base of | | | | being processed in the turn around sections of a |
| each of the chambers extends into a connecting | | | | folded, plug flow fluid bed. |
| turn-around section and terminates in an edge that | | | | This invention teaches an improved fluid bed dryer |
| extends from the one end of the common wall at an | | | | design and more specifically, an improved fluid bed |
| oblique angle relative to the common wall, and a | | | | base or bottom plate design wherein each incremental |
| bottom plate having a pair of edges that intersect at | | | | volume of the material being processed adjacent an |
| an angle and a plurality of gas introduction openings | | | | incremental area of the gas distribution bottom plate is |
| oriented to fluidize and move the particulate material in | | | | provided with that energy required to maintain the bed |
| a direction substantially perpendicular to the direction of | | | | in a fluid condition and to transport the material |
| movement of the particulate material in said chambers, | | | | adjacent the plate in a specific desired direction away |
| is inset with the pair of intersecting edges abutting the | | | | from that incremental area of the plate and to an area |
| edges of the base of each chamber in the connecting | | | | from which additional material is being removed in a |
| turn-around section. In this embodiment vertical columns | | | | specific direction with a minimum loss of fines. |
| of the particulate material delivered from one of the | | | | The object of the present invention is to provide an |
| chambers to the turn-around section are successively | | | | improved fluid bed dryer particularly suited for drying a |
| and incrementally turned after each vertical column | | | | readily decrepitateable, feed material of broad particle |
| transverses each of the intersecting edges of the | | | | size distribution which is capable of sustained operation |
| bottom plate. | | | | without process interruption because of fluidization or |
| In a still further preferred embodiment, in a non-plug | | | | material transport failure while continuously producing a |
| flow pre-drying chamber adjacent a plug flow fluid bed | | | | product having a minimum of fines. |