Pinch technology can be considered as a methodology allowing process integration in a scientific and systematic manner and enabling an energy/capital trade-off even before design. However, if optimum systems are to be achieved, the processes of plant design and utility system need to be conducted simultaneously. The present paper provides a new methodology whereby furnaces may be integrated into such processes. A simple mathematical model of a furnace allows a simplified flue gas representation to be employed. The suggested approach for furnace integration which is based on pinch technology incorporates the optimization of air preheating and stack temperature using a standard targeting procedure.