The impact of chlorine and sulfur on alkali metal migration and submicron particle formation during solid fuel combustion

Abstract

Submicron particles (PM1) emission from the incineration of solid fuels rich in chlorine, sulfur, or alkali metal elements pose environmental and health concerns for humans. The current understanding of the interactions between these elements and PM1 formation is extensive, but it still lacks a systematic approach. This paper establishes a comprehensive model to predict the migration process of Cl, S, and alkali metals during solid fuel combustion by adding Cl, S, and K additives. The model is divided into combustion, vaporization, nucleation and condensation, and coagulation sub-models. The model predicts that K, Cl, and S additives will not cause changes in fuel's burnout time and temperature. While these additives each promotes the vaporization rate of sodium to varying degrees, for example, the vaporization rate with +K + S is much lower than with +K + Cl. Also, the model calculates that the addition of SO2 significantly inhibits the formation of KCl. In the Sufco + K condition, introducing SO2 reduces the concentration of KCl by about 80%, but if Cl is added, the concentration increases by approximately four times. Predictions were also made for the changes in K2SO4, NaCl, and Na2SO4 under different conditions. After adding K, Cl, and S, the production of PM1 significantly increased, and the peak shifted towards larger size with +K + Cl producing more PM1. Overall, the predicted results align well with the experimental findings. The model's systematic construction of the interactions between chlorine, sulfur, and alkali metal elements and the formation mechanism of PM1 provides a more complete picture of solid fuel combustion emissions.