During the re-configuration of their grate-kiln induration system for the firing of iron ore pellets at the Whyalla Steelworks, caused by a change from an earthy hematite to a magnetite ore with considerably less flux, OneSteel commissioned a detailed thermal flow analysis of the design options on the existing cooler in support of the process change. A key objective of this investigation was to decide if and where one might locate baffle walls within the cooler to improve the process and to control the off-gas flows to earlier stages within the process. The thermo-fluid analysis comprised the development of comprehensive three dimensional computational models of gas flow through the cooler coupled with the heat transport and exchange with the cooling pellet bed. The models were implemented within the context of an open source - object based computational fluid dynamics (CFD) simulation software framework. This paper describes the development of the CFD model, its verification and application to evaluating design options to improve the flow control within the cooler. In particular, the analysis considers the role and potential location of above bed baffle walls, cooler stack butterfly lid opening and its exhaust pressure on the flow distribution to the exit flow ducts from the cooler. (C) 2009 Elsevier Ltd. All rights reserved.