twyer-box

from The Century Dictionary.

• noun A chamber or duct from which the separate twyer-pipes are led into the walls of the furnace proper.
• noun In the Bessemer converting vessel, the chamber below the refractory bottom from which air passes into the molded twyer-blocks and so up into and through the molten metal. Air is supplied to the box from a pipe leading down from the hollow trunnion of the converter.