Abstract: The high content of alkali metals in Zhundong coal induces serious slagging and fouling problems during combustion,however,the migration and transformation rules of alkali metals under pressurized condition in Zhundong coal gasification are still ambiguous.In order to obtain the migration and transformation mechanism of Na Cl in Zhundong coal under pressurized condition,according to the thermodynamic calculation method of Gibbs free energy minimum principle of the system,the thermodynamic equilibrium calculation module of HSC Chemistry was adopted to calculate the molar mass of sodium-based compounds in the pressurized gasification process of pure Na Cl and Zhundong coal.The results show that pressure impacts the gasification temperature of pure Na Cl significantly.At ordinary pressure,the start and finish temperatures of gasification are 800 ℃ and 1 400 ℃ respectively.When the reaction pressure up to 4 MPa,the start and finish temperatures of gasification increase to 1 500 ℃ and 2 200 ℃ respectively.When the Si,Al,H,O of Zhundong coal participate in the reaction under the condition of 0.1 MPa,300 ℃,the Na Cl will react with SiO_2,Al_2O_3 and H_2O in the coal ash to form a large number of sodium-based compounds,such as NaAlSi_3O_8,NaAlSiO_4,etc.In 1 500 ℃,the generated gaseous Na Cl accounts for only about 25% of the molar mass of Na.The higher the reaction pressure of the system is,the more NaAlSi_3O_8,NaAlSiO_4 and Na_2SiO_3 with low melting point and fluxing action will be generated,and the higher risk of slagging in the furnace will be.