Abstract: Disclosed herein is a self-fluxing pellet to be charged into blast furnace, the pellets containing open pores of diameters larger than 5 .mu.m in an amount greater than 0.045 cm.sup.3 /g. Calcium.ferrite structures with a thickness of 100 .mu.m or greater exist around pores of diameters larger than 5 .mu.m including the open pores. The self-fluxing pellets as a whole has a CaO/SiO.sub.2 value higher than 0.8. For forming the self-fluxing pellets, at least one of coarse dolomite and limestone having a particle size of 44 .mu.m-1 mm is added as a pellet material to powdery iron ore. The green pellet formed from the resulting powdery mixture are sintered at a temperature of 1220.degree. C.-1300.degree. C. to have a CaO/SiO.sub.2 value higher than 0.8 after sintering.

Abstract: A method for diagnosing the interior of a rotary kiln, which method permits one to make a correct determination as to the state of deposit of ash on the inner wall of the rotary kiln. According to the method, a detector is inserted into a gas stream from the rotary kiln and kept there for a certain period of time so as to allow ash to deposit thereon. Then, the weight, density and composition of the thus-formed deposit of ash are determined. The weight is corrected in view of the ash present in pulverized coal which was used as a fuel for burners, thereby obtaining corrected ash deposit weight (Wa). The weight is also corrected in accordance with the percentage of fine iron ores present in prefired pellets and the percentage of fine iron ores present in the deposit of ash and determined by the composition of the deposit and that of the fine iron ores, thereby obtaining corrected weight (Wd) of the deposited fine iron ores.