高碱煤燃烧过程中灰中主要元素的迁移规律

To study the fouling and slagging properties of fly ash from combustion of Xinjiang high alkali coal, XRF and SEM-EDX analysis were carried out to ash samples taken from various heating surfaces in a 300 MW subcritical boiler burning high alkali coal. Results show that in the gas temperature range of 800-1100°C, mass fractions of CaO, MgO and SO₃ in ash samples are relatively high; whereas for in temperature range of 600-800°C, mass fractions of Na₂O, Fe₂O₃ and SO₃ are relatively high, in which case serious fouling on high-temperature convection heating surfaces is caused by Na₂SO₄, CaSO₄ and NaFeSO₄ during combustion of high alkali coal. For locations where the gas temperature is in the range of 669-915°C, both the initial melting temperature of ash samples and corresponding liquid slag ratio are higher than those in other places. Na₂SO₄ particles with sizes of 2-4 μm rich in Na and S are found to stick on surface of ash sample C, which at high temperatures have high sticky properties and low melting temperatures, and therefore may lead to serious fouling problems.