For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, when the _______________ is the controlling resistance?
Correct answer: B. Diffusion through ash layer
- A. Film diffusion
- B. Diffusion through ash layer
- C. Chemical reaction
- D. Either A., B. or C.
Explanation
For the shrinking-core model, resistance through the ash layer gives a characteristic time proportional to the square of particle diameter. Film diffusion and surface reaction resistances instead give a linear diameter dependence for fixed fractional conversion.
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