Evolution of particles in the plumes of coal-fired power plants—II. A numerical model and comparisons with field measurements

Abstract

A three-dimensional numerical model is described which considers the effects of advection, diffusion, coagulation, gravitational settling, gas-to-particle (g-to-p) conversion and interactions with the ambient air on the evolution with time of particle size distributions in power plant plumes. From inputs of an atmospheric temperature, humidity and wind sounding, and the concentrations of particles and trace gases emitted from a power plant and in the ambient air, the model provides predictions of the particle size distributions, total particle concentrations, concentrations of trace gases, g-to-p conversion rates and the light-scattering coefficient of the particles at points in the plume downwind of the stack. Comparisons of the model predictions with airborne measurements obtained in the plumes from two coal-fired power plants show that the model is capable of predicting many of the principal features of the evolution of the particle size distributions and related parameters for transit distances up to at least 30 km. The model predicts maximum g-to-p conversion rates at the edges of the plumes where the predicted g-to-p conversion rates are comparable to values derived from field measurements. Elsewhere in the plumes the predicted g-to-p conversion rates are about an order of magnitude lower than the average values deduced from field measurements.