Release and transformation behaviors of sodium species with different occurrence modes during pyrolysis of Zhundong coal

A series of pyrolysis experiments on Zhundong coal were conducted by using a pressurized tube reactor. Under different pyrolysis temperature, residence time and pressure, the release and transformation behaviors of sodium species with different occurrence modes were investigated by the method of sequential chemical extraction. The results indicate that sodium species are mainly in the form of hydrated ion and albite, and organic forms are quite less. At 500-700℃, water-soluble sodium would be combined with char matrix, forming hydrochloric acid-soluble but water-insoluble sodium. At 700-900℃, soluble sodium could react with minerals such as kaolin, forming insoluble aluminosilicate. At 1 000℃, release of sodium became intense; part of kaolin might be involved into reactions with lime, which inhibited its reactions with soluble sodium. Besides, it is found that release and transformation behaviors of sodium mainly take place at the initial stage of pyrolysis along with release of volatiles and raising pressure has negligible influence on those behaviors. © 2017, Science Press. All right reserved.