Plume Rise from Stacks with Scrubbers: A State-of-the-Art Review

Abstract

The state of the art of predicting plume rise from stacks with scrubbers is evaluated critically. The significant moisture content of the scrubbed plume upon exit leads to important thermodynamic effects during plume rise that are unaccounted for in the usual dry plume rise theories. For example, under conditionally unstable atmospheres, a wet scrubbed plume treated as completely dry acts as if the atmosphere were stable, whereas in reality the scrubbed plume behaves instead as if the atmosphere were unstable. Even the use of moist plume models developed for application to cooling tower plume rise is not valid since these models 1) employ the Boussinesq approximation. 2) use a number of additional simplifying approximations that require small exit temperature differences between tower exit and ambient temperatures, and 3) are not calibrated to stack data. Although both dry and moist plume theories often are used to predict plume rise from stacks with scrubbers, both theories contain unacceptable assumptions. The invalid approximations made in each theory are detailed in this paper, and the direction and magnitude of the important errors are estimated for these models when applied to scrubber stack plumes.