A predictive model of synergetic particulate-SO3 removal in ultralow cold-side electrostatic precipitators

Abstract

In this paper, a comprehensive predictive model is established for the synergetic removal of fine particulate matter (PM) and SO3 in the ultralow cold-side electrostatic precipitator (ESP). Based on the population balance model framework, the current model incorporates SO3 condensation and coagulation in the low temperature economizer (LTE), as well as the quasi-1D dynamics of particle charging, migration, resuspension and deposition in the multi-staged ESP. Simplifications are made so that the resulting model can serve as a convenient software tool aiding the design and operation evaluation of the ultralow cold-side ESP. The model is validated against measurements of two coal-fired units with varied LTE outlet temperatures. In all cases, the predicted PM and SO3 emissions escaping the ESP agree well with the test data, and the relative errors are less than 17%. Quantitatively, running LTE removes ~60% of ultrafine PM0.1, and 80–95% of SO3 condense onto the preexisting fly ash in the LTE, resulting in a dp−2 -dependence of sulfur content in the size-segregated ash particles. Notably, the emitted PM1, PM10 and SO3 concentrations are largely reduced with lower LTE outlet temperatures; however, this promoting effect becomes marginal if further reducing the LTE outlet temperature under 100 °C. Finally, we conclude from a parametric analysis that the most important factor in the ultralow cold-side ESP is the flow residence time in the ESP, followed by the effects of intensified coagulation and elevated ash permittivity.