In Situ Measurements of the Release Characteristics and Catalytic Effects of Different Chemical Forms of Sodium during Combustion of Zhundong Coal

Abstract

This work studies the temporal release characteristics of different chemical forms of sodium during the combustion of Zhundong coal and the catalytic effects of sodium on the combustion process via target-sodium removal and enrichment approaches. The target-sodium removal approach extracts specific forms of sodium from the raw coal via a chemical method to produce coal samples with designated characteristics. In the target-sodium enrichment approach, three kinds of H2O-soluble sodium compounds, including NaCl, NaOH and Na2SO4, are manually added into the raw coal. The experimental measurement is conducted using a multi-point Laser-Induced Breakdown Spectroscopy (LIBS) system. The system quantitatively measures the temporal release flux of sodium during the combustion process, and performs the in-situ measurement of surface temperature and diameter of a burning coal pellet. It is found that H2O-soluble sodium is the major chemical form of sodium released during the combustion and exhibits the highest volatility. All the three forms of enriched H2O-soluble sodium compounds show a catalytic effect on the coal combustion (burnout time decreased by more than 5.7%) and the catalytic activity of NaOH is found to be the strongest (burnout time decreased by 36.8%).