Study On The Influence Of Alkali Metal Loading Method On The Metallurgical Properties Of Coke

The skeleton role of the coke in blast furnace cannot be substituted by any other substance.Intensified smelting also requires higher quality of coke.Alkali metals which exist in blast furnace and coking coal would influence the quality of coke,reducing its strength,weakening the skeleton role and hence affect the process of blast furnace.Therefore,alkali gas adsorption method and alkali powder coking method were used to systematically explore the influence of external and internal（adding alkali carbonates for coking）alkali metals on the metallurgical properties of coke.The XRD analysis,SEM characterization and other means were occupied to characterize the coke.The following conclusions can be drawn according to the experiment results:Firstly,in the alkali gas adsorption method,the potassium elements were mainly adsorbed on the surface of coke and pore walls in the form of free metal,silicate and carbide.The sodium elements mainly existed on the surface of the coke in a free state.In the alkali powder coking method,the endogenous potassium and sodium were continuously combined with silicon and aluminum in the ash during the coking process.Most of the alkali metals existed in the form of insoluble aluminosilicate in these coke samples.Secondly,according to the adsorption experiments,it was found that potassium easily formed interlayer compounds with the coke,resulting in the degradation of coke and the decrease of particle size.Therefore,the potassium showed a certain erosion effect on coke.Sodium is difficult to form an interlayer compound with the carbon layer,so sodium has no obvious erosion effect on coke.The coke samples that adsorbed different contents of alkali metals were tested according to the national standard of reactivity index（CRI）and post-reaction strength（CSR）.The results showed that as the alkali metal concentration increased,within a certain range,although the CRI increased significantly,the CSR did not decrease significantly.Thirdly,under CO₂ conditions,the thermal compressive strength tests were carried out on the coke samples that were made by the alkali powder coking method.The results showed that under the same potassium adsorption content,as the test temperature increased,the thermal compressive strength decreased.When the temperature exceeded1100°C,the decrease became more obvious.At the same temperature,as the potassium content increased,the thermal compressive strength decreased.But when it was above1100°C,the strength decrease caused by the alkali was not as great as that caused by the temperature.Subsequently,the thermal compressive strength tests of coke with different endogenous alkali metal sodium content were performed at 1100°C.It was found that as the content of sodium in the coke increased,the thermal compressive strength of coke decreased.But the decrease content of thermal compressive strength that caused by sodium was far less than that caused by potassium.