having a diameter of 113 mm and a length of 205 mm and has two barrels which rotate at a rotation speed of 30 rpm table 2 lists the ratio of a powder having a particle diameter of 1 mm or less to the mass of the sieved powders an increase in the percentage of the powder having a particle diameter of 1 mm or less indicates that the residue can be easily pulverized is not adhered on a hearth and has good removability in the present invention removability is considered to be excellent when the percentage of the powder having a particle diameter of 1 mm or less is 29 or more working examples and poor when the percentage is less than 29 comparative examples the following are discussions based on table 2 with respect to nos 1 2 3 and 5 the carbon content of the residue is 5 or more rcs redc u00d7 100 is 22 or more and the carbon content of the agglomerate is 122 or more of the carbon content required to reduce iron oxide contained in the agglomerate with respect to nos 1 2 and 3 of these among the compositions of the agglomerate cao sio 2 is in the range of 0 25 to 1 20 and al 2 o 3 sio 2 is in the range of 0 2 to 0 7 which satisfy the formulae 1.