Experimental research on fully burning high-alkali coal in a 300 MW boiler with slag-tap furnace

Safety issues such as contamination and slagging restrict the use of high-alkali coal. To explore the possibility of fully burning high-alkali coal in a boiler with slag-tap furnace, Na2CO3-blended burning tests and a fully burning high-alkali coal test were carried out in a 300 MW boiler with slag-tap furnace. The results showed that fully burning high-alkali coal had little effect on the steam parameters and the boiler could operate safely. The Na content in the flue gas tended to decrease from SH5 to RH2 and increased from RH2 to ECON. The increase of Na content in the fuel would significantly raise Na content in the flue gas, slightly increase the K content, and increase the ability of liquid slag to capture Na. Before the Na content in SH coal ash was increased by 150%, the capture ability of liquid slag to Na had reached saturation. The added Na2CO3 made the Al and Ca elements migrate to the liquid slag to form a high melting point Na-Al-Ca compound. The microstructure analysis showed that liquid slag has a rich pore structure inside and outside and the Na content in the pore was higher than that out. Mineralogy analysis found that deposition samples mainly included Quartz, Magnesioferrite, Anhydrite, Lime, and CaSiO4 and the addition of Na2CO3 hardly affected the mineral composition.