Tunnel kiln adapted for firing frost-resistant bricks in a reducing atmosphere

A method of cooling, in a reducing atmosphere, fired ceramic materials in a tunnel kiln having a cooling zone, said method comprising the steps of:

• (a) extracting heated gases from within said tunnel kiln;
• (b) cooling said extracted gases;
• and
• (c) returning at least a portion of said extracted and cooled gases to said cooling zone.

A method of firing architectural face-bricks in a reducing atmosphere;

• (a) firing uncured bricks in a reducing atmosphere within a firing zone of a tunnel kiln;
• (b) preliminarily cooling said fired bricks in an indirect cooling zone downstream of said firing zone while yet maintaining said reducing atmosphere therein by a closed-loop cooling path which (i) extracts heated gases from the indirect cooling zone, (ii) cools said extracted gases, and then (iii) reintroduces said cooled gases into said indirect cooling zone;
• (c) finally cooling said fired bricks in a direct cooling zone downstream of said indirect cooling zone by extracting heated gases therefrom and introducing cooling air thereinto, whereby to create an atmosphere within said direct cooling zone which is enriched with oxygen as compared to the atmosphere within said firing and indirect cooling zones;
• and
• (d) preventing said oxygen-enriched atmosphere of said direct cooling zone from entering said indirect cooling zone, whereby said reducing atmosphere is maintained within said firing and indirect cooling zones.

A tunnel kiln system having a cooling zone adapted to continuously cool fired ceramic materials in a reducing atmosphere, said kiln system comprising:

• (a) means for extracting heated gases from within said tunnel kiln;
• (b) means for cooling said extracted gases;
• and
• (c) means for returning at least a portion of said extracted and cooled gases to said cooling zone.

In a tunnel kiln of the type having kiln cars which are capable of passing through the kiln in a train formation from an entrance end to an exit end of the kiln, the improvement comprising:

• means for firing uncured ceramic material in a firing zone of the kiln;
• means for indirectly cooling kiln gases in an indirect cooling zone arranged downstream of said firing zone, thereby to preliminarily cool said fired ceramic material;
• means for directly cooling said ceramic material in a direct cooling zone arranged downstream of said indirect cooling zone;
• and
• partition means for partitioning said indirect and direct cooling zones, thereby to substantially preclude an atmosphere established in said direct cooling zone from contaminating an atmosphere established in said indirect cooling zone.