RP-531 -- Recirculation of Air from Dust Collectors in Industrial Operations ✓ Most Recent

The fractional penetrations of three types of industrial dust collectors (pulsed cartridge units, pulsed fabric bag units and electrostatic precipitators) as functions of loading time and particle size are presented. The fractional penetrations were measured with an optical particle counter for particle sizes between 0.442 um and 8.50 urn. The readings were taken over time intervals of 2 to 5 minutes to average any downstream particle concentration fluctuations due to pulsing. It was found that the fractional penetrations for the cartridge units were generally an order of magnitude below those of the fabric bag units. The electrostatic precipitators were seen to have considerably higher downstream mass concentrations than the nitration type units. A collector quality factor, "the figure of merit", is a collector performance parameter that takes into account both the penetration and pressure drop of a given unit. For the cartridge units the figure of merit was found to be approximately five times higher than for the fabric bag units. A field test method was developed that uses a real time light scattering instrument, the MIE RAM-1, and gravimetric analysis to determine upstream and downstream total mass concentrations. The respirable downstream mass concentration was determined by placing a Dor-Oliver cyclone upstream of the MIE RAM-1. Field test data reveal that there is a great deal of variation in the performance of dust collectors in the field due to differences in operating parameters, dust types and maintenance. A computer model was developed which uses the fractional filter efficiencies obtained for the dust collectors to predict the respirable dust concentration in the working zone of an industrial environment. Parametric studies were performed on the recirculated air system. From these parametric studies, it was found that the hood capture efficiency is the most important factor in the system when a high quality dust collector is used. A 10% change in the hood capture efficiency may change the respirable dust concentration by as much as 50%.