Stack apparatus to control furnace gas exit velocity

Abstract

An exhaust stack for a combustion zone of a furnace includes a main stack having a first chamber therein in communication with the combustion zone, and a main damper disposed for movement within the first chamber to be positioned to provide a cross-section of the first chamber through which combustion products from the combustion zone may flow, and a secondary stack having a second chamber therein in communication with the first chamber and being disposed within the first chamber, the secondary stack having a second damper disposed for movement within the second chamber to be positioned to provide a cross-section of the second chamber through which the combustion products from the combustion zone may flow.

Dependencies are inferred from the claim text.