Insightful Analysis and Targeting of the Optimal Hot Feed toward Energy Saving

Feed of hot material from the upstream process is a strategy to improve energy efficiency, but the energy saving contributed by hot feed depends on the characteristics of the feed stream and receiving process. In this work, we present an insightful analysis of introducing hot feed into a process based on pinch technology. The changes of the grand composite curve, pinch temperature, and utility demands with an increase in the hot feed temperature are presented, and the reasons for such changes are explored. A graphical method is then developed to target the optimal hot feed temperature that minimizes the hot utility consumption. In addition, for a heat exchanger network design that does not match the grand composite curve, an improved graphical method employing the actual cold composite curve is proposed to target the optimal hot feed temperature. A wax oil hydrogenation process is analyzed to illustrate the proposed targeting methods.