Waste heat integration between processes

Energy integration between several processes has been applied giving more economical and profitable operation. The method for waste heat integration of several processes was analysed to reduce energy usage in three possible steps: 1. retrofit of the individual processes, 2. analysis of efficient transfer of waste heat between: ◦ existing non-retrofitted processes ◦ existing non-retrofitted and efficiently retrofitted processes ◦ efficient retrofits and 3. simultaneous integration between some non-retrofitted and some retrofitted existing processes using mixed integer non-linear programming (MINLP). The integration between the processes can be carried out by all the steps, or by the first and the third steps or only by the last step depending on the complexity of the problems. All the steps can be carried out simultaneously and the MINLP algorithm applied with or without the first and the second step. The approach has been illustrated by four complex processes using pinch analysis and MINLP. The optimal solution of pinch analysis and MINLP yields the same additional savings of 526 000 USD/a and selects the same structure and parameters as the MINLP one.