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Momentum and mass transfer in packed beds subject to gas flow in high-temperature reactors and shaft furnaces. Dependable design of fixed and traveling bed reactors operating at high temperatures requires a detailed knowledge of heat and mass transfer at the solid surface and precise information about the pressure and gas velocity distribution inside the fixed bed. Special interest is focussed on the mixing of different component streams in some packed beds. The mixing depends on several parameters, such as particle size, bed length and diameter, configuration of junction points, and mass flow ratio of the individual gas streams. A general view summarizes our present knowledge of physical models of momentum and mass transfer and of mathematical descriptions of processes occurring in packed beds in terms of technical geometry (three-dimensional array). In particular, possibilities of calculating the dispersion in complex packed beds through which flow take place are displayed. In this connection it is shown there are still some unsolved problems. |
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