The development of pulsed flow air classification theory and design for municipal solid waste processing

The development of pulsed flow air classification theory and design for municipal solid waste (MSW) processing is described. The results of previous theoretical and empirical work is summarized and the results of recent experimental studies are presented in greater detail. Pulse flow air classification using smaller scale (air flow regimes of approximately 161 cm²) air classifiers is found to process MSW into combustible and noncombustible fractions more efficiently than zig-zag and straight air classifiers. In recent studies with larger air classifiers (air flow regimes of 929 cm² and greater), this result has been confirmed. Furthermore, with active pulsed air classifiers, the pulse frequency was found to have little effect on the efficiency in the 1 to 2.5 Hz range, while symmetric and quick-rise pulse shapes appeared to outperform slow-rise pulse shapes. Active pulsed air classifier performance improved as the percentage of the air flow pulsed increased. In direct comparisons using simulated and actual MSW feeds the passive pulsed stacked-triangle outperformed the active pulsed which in turn outperformed the zig-zag non-pulsing air classifier.