The Effects Of Molten Slag/ash And Mineral Matter Behaviors On Coal Gasification Reaction Characteristics At Elevated Temperature

The effects of molten slag/ash and mineral matter behaviors on gasification reaction characteristics of coal at elevated temperature were investigated by using STA449F3 thermo-balance. And the differences in coal gasification characteristics between high and low ash fusion temperature coals were studied. CO2/H2O gasification reactivity of high ash fusion temperature coal(HN coal) and low ash fusion temperature coal (BS,SF coal) were compared in the temperature range from 900℃to 1380℃, and kinetic models of coal gasification at elevated temperature were analyzed. The CO2 gasification reactivity of coal chars with adding different proportions of coarse slag were investigated by an isothermal thermo-gravimetric analysis at temperatures from 900℃to 1380℃, the thermal behaviors of the samples were studied by thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC), the effects of proportions of coarse slag and gasification temperatures on the gasification reactivity of coal chars were compared. For the purpose of understanding the effects of mineral matter behaviors during char-CO2 gasification at elevated temperature, the minerals in char/ash samples with different conversion (0,50%,75%) of coal gasification in a temperature range 1000～1300℃were analyzed by means of XRD and FactSage modeling. The main achievements were summarized as following:(1) The characteristics of gasification reaction rate of coal chars were separated into reaction control zone with low temperature (900～1100℃) and gas diffusion zone with high temperature (1100～1380℃). At high temperature (1100～1380℃), for chars with high ash fusion temperature (HN coal), the carbon conversion and reaction rate would continue increasing as temperature increase while for chars with low ash fusion temperature (BS,SF coal) the carbon conversion and reaction rate leveled off or even decreased a little.(2) The gasification reactivity and carbon conversion of BS coal chars were separated into low and high temperature regions according to flow temperature of coal ash fusion. The gasification reactivity and carbon conversion of coal chars with adding coarse slag were improved in low temperature region; the loading of coarse slag decreased carbon conversion and the gasification reactivity of coal chars with adding more than a certain proportion of coarse slag leveled off in high temperature region. (3) The minerals melt completely at 1300℃in the ash fusion temperature range 1100～1300℃, which hindered coal gasification. The carbon conversion decreased, and the gasification reactivity leveled off.