Group B materials

Kapoor, 1976 Kai and Furusaki, 1985 Yoshida et al., 1976). Although less information exists for larger particle sizes, bubble size appears to not change with temperature for Group B materials (Sishtla et al., 1986 Wittman et al., 1981), and to increase with temperature for Group D materials (Sittiphong et al. 1981). 

Group B materials fluidize readily and tend to form bubbles, which grow rapidly by coalescence. However, bed expansion is small. That is, the minimum bubbling velocity, Vmb, usually is approximately equal to (or only slightly greater than) the minimum fluidizing velocity Vmj, The fluidized bed does not retain its aeration and collapses quickly when the gas supply is removed. 

Classes 3 and 4 correspond roughly to group B materials on Geldart s diagram, 5 and 6 to group A and 7 to group C. 

Increases in above do not lead to further increases in PjLg. For Geldart group B materials, nearly all of any gas flow in excess of that required mf goes into the formation of bubbles. Therefore, as Uf increases beyond Un,f, AP/ig remains almost constant and then begins to decrease as the bubble volume in the bed increases. 

Although the automatic L-valve is geometrically simpler and less expensive to install than the loop seal, for the reason given above, the automatic L-valve can be more difficult to operate when using group B materials. Loop seal operation requires fewer adjustments, and is often preferred over the L-valve for automatic operation with group B materials. For group A materials, either automatic device can be used. 

Use of electrical equipment that did not meet National Electrical Code (NEC) requirements. Ethylene oxide is a NEC Class 1, Division 1, Group B material. The Gas House did not meet the NEC requirement for working with ethylene oxide. The electrical equipment in the Gas House could have predicted initiation for the explosion (EPA 2000). 

---