Abstract: According to the theory of carbon balance, it is shown that the cha-racteristic parameters of the grid coke in B. F are deteriorated with the increase of coal injection rate. lnvestigations into the effect of coke quality, solution loss, insititu-reduction and coke-melt reactions on the coke beat strength as well as increasing the ore preneduction degree and using new charging technic to restrain the coke degradtion are intraduced. With the above aim, the optimum of B. F operation under an ultra coal injection rate is discussed.

Key words: Coal injection, Grid coke, Coke degradation