Fluid-Bed Zone

1) Sufficient particle residence times at high temperatures must be provided for steady agglomeration. 

2) The reactor wall should be protected from direct flame radiation by the dense particle cloud that is formed by the downward flow. 

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The mixing points of the standard and advanced E-Gas systems between the respective first stages and the slurry point on the H20-coal axis are located in the comparatively broad fluid-bed zone C. 

If agglomeration takes place, the particle size will increase. Figure 9.5 indicates that a minimum particle size of dp = 1 mm is necessary to form a stable moving bed below the fluidization line (f-fine) at 0.15 m/s superficial gas velocity in the bed. For bed gas velocities up to 0.3 m/s, agglomerates of 4 mm are necessary. The maximum fuel particle size for entrainment into the fluid-bed zone can be also read off the diagram at the e-fine for the ex-bed gas velocities. The values of dp,e = 125-200 pm lead to the conclusion that the fuel particle size must be <0.2 mm. 

Figure 20-87 shows a typical production-size batch fluid-bed granulator. The air-handling unit dehumidifies and heats the inlet air. Heated fluidization air enters the processing zone through a distribu-... 

Fluid beds can be fired with gas and oil across the top of the slumped bed since sufficient freeboard exists with coal firing to prevent particle elutriation. Oil, gas or dual-fuel burners so arranged could also provide the means for bed preheating, especially if the flame is redirected down to the fluidization zone. 

The Model II plants were of a greatly improved design, incorporating two basic major developments—the downflow or bottom withdrawal Fluid bed and the direct liquid injection of oil feed into the reaction zone. The downflow development permitted withdrawal of catalyst for circulation from the bottom of the bed. 

The fixed-bed reactor consisted of a 4mm i.d, 40cm long quartz tube, with the catalyst section held by a small plug of calcined glass wool Preheat zone was 15cm of the inlet zone. The fluid-bed reactor used for the chlorinated feed (B) was a 1cm quartz tube fused onto an Q.flcn quartz tube. The lcm tube contained a fritted disc on which the catalyst was supported at a location in the middle of the heated zone. The fluid-bed used for other feeds was slightly smaller, but similar in configuration [2]. 

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