Effect of gas relative humidity on reactor wall fouling generated due to bed electrification in gas-solid fluidized beds

By having a thorough understanding of the methods involved in reducing electrification within gas-solid fluidized beds, additional techniques for reduction or prevention can be developed. In this study, the effect of fluidizing gas relative humidity was investigated with the focus on its influence on charge distribution within a fluidized bed, and the amount of particle wall fouling within the bubbling and slugging fluidization flow regimes. Gas relative humidities of 0%, 20%, 40%, 60% and 80% were evaluated with polyethylene resin received from a commercial reactor. The effect on charging was examined for particles in three regions of the bed: elutriated fines, bulk particles and those particles that adhered to the fluidization column wall. Particle charge, mass, and size distributions were measured for all regions. It was found that the effect of relative humidity on wall fouling was only apparent in the bubbling flow regime where the particle layer on the wall reduced at 60% and 80% relative humidity. A similar trend was also observed for these particle charges while their charge-to-mass ratio remained constant. In the slugging flow regime for those particles that adhered to the column wall a decline in particle net charge-to-mass ratio was obtained for only at high humidity of 80%. Other variations in charge and charge-to-mass ratio were observed in both flow regimes but did not follow any trends with respect to the gas relative humidity. (C) 2012 Elsevier B.V. All rights reserved.