| 摘要 |
Clay roofing tiles formed e.g. from a composition comprising: i) 60 to 100 parts by wt. of clay; and ii) 0 to 40 parts of rock flour, are fired by a process effected in three stages in a one-high counterflow continuous kiln. In the first stage the green tiles are raised to their peak firing temperature in 6 to 20 minutes, in the second stage the partly fired tiles are maintained at said temperature for 2 to 10 minutes and in the third stage the fired tiles are subjected to a diminishing temperature gradient over not more than 25 minutes. The three stages are carried out in the first, second and third zones, (20, 22 and 26, Fig. 1) of said kiln, which is a sliding ball kiln in which the balls 5 are transported on guide rails 44, 46 and the kiln has an underflow channel comprising gaps 52 and 54. <IMAGE> |
