Split plenum

The alternative to using a single plenum and adjusting the gas flow with the distributor plate is the use of a split plenum. Here, the gas flow is regulated separately through a central and annular plenum. The air can be supplied by a single blower but separate controls are necessary for each plenum. If independent control of the gas flow to each plenum is required, then two blowers are necessary. 

Figure 11. Alternative gas distribution systems in fluidized bed coaters, (a) single plenum and (b) split plenum.

The primary coolant is collected into six larger channels in the lower portion of the bottom reflector blocks, and then splits and merges with the coolant flow from the neighboring fuel elements in the core support block layer prior to exiting to the lower plenum. This coolant flows to the cross duct, located at one side of the lower plenum. 

One commercially available system comprising a parallel arrangement of cyclones, called swirl tubes , is the multicyclone unit illustrated in Fig. 16.2.2. The solids-bearing feed stream enters the separator vessel via a centrally located pipe at the top of the vessel. The feed exits this inlet pipe near its bottom end from where it flows radially outwards - between two tube sheets - and into the feed chamber or plenum. The solids-bearing gas then enters the individual swirl tubes wherein it is split into a solids-laden underflow stream and a clean-gas overflow stream. 

---