Abstract: In order to further explore the smelting law under the oxygen-enriched blast furnace operation， a previous blast furnace oxygen-enriched comprehensive model was revised to study the thermal state of the blast furnace under different operating conditions. The results showed that furnace cylinder injection of circulating gas can effectively offset the increase of fuel ratio caused by oxygen enrichment operation， and in the low-oxygen enrichment operation， the blast furnace can meet the upper and lower heat balance without spraying the circulating gas. Increasing the amount of coal injection needs to correspond to increasing the oxygen enrichment rate， and different coal injections have different oxygen-enrichment operating intervals. From the model， the limit value of humidification under oxygen-enriched operation can be obtained， where the blast humidity should not exceed 21.2g/m³， and the corresponding oxygen enrichment rate maximum is about 4.6%.

Key words: blast furnace, oxygen-enrichment extreme, fuel ratio, coal injection, blast humidity