Abstract: Based on the original modified model for calculating theoretical combustion temperature (T_○f)， the calculation methods for the combustion efficiency of pulverized coal， the decomposition heat of pulverized coal and the heat consumption of SiO₂ in ash which was reduced at high temperature， were modified and improved in order to propose a more comprehensive model for calculating T_○f. The effects of oxygen enrichment rate， blast temperature， blast humidity and coal rate on T_○f were analyzed and compared among the traditional model， the original modified model and the present parameters model under different blast respectively. The results showed that compared with the traditional model and original modified model， the calculation value of T_○f using the present model under different blast parameters tends to be flatter and the thermal state of hearth is relatively stable. Actually， according to two kinds of smooth operation conditions existing in the practical production which are “high oxygen enrichment rate， low coal injection rate” and “low oxygen enrichment rate， high coal injection rate” with suitable T_f， it was verified that this model could appropriately reflect the actual thermal state of hearth in blast furnace(BF).

Key words: theoretical combustion temperature in BF, hearth, calculation model, combustion ratio of PCI, PCI decomposition