Study on Alkali Metal Migration Characteristics in the Pyrolysis of Naomaohu Coal in CO Atmosphere

The four-step chemical extraction method was used for stepwise extraction to compare the occurrence of alkali metals in Naomaohu coal and the other four types of high alkali coal. The coal sample was placed in a vertical furnace with CO gas atmosphere to study the migration and release law of alkali metal with temperature changing at 400–800 °C. The results show that sodium in the Naomaohu coal is mainly in the form of water-soluble sodium, while potassium is mainly composed of insoluble potassium and organic potassium. The increase of pyrolysis temperature promotes the release of sodium and potassium, and the water-soluble sodium changes to insoluble sodium, and a substitution reaction occurs between sodium and potassium. At 700 °C, the amount of sodium and potassium released from the coal char is relatively reduced, resulting in enrichment.