This thesis discusses topics in the field of process engineering that have received much attention over the past twenty years, process integration and optimization of energy and environmental systems. It emphasizes the applications of three commercial software tools for process integration, ADVENT, HEXTRAN and SlTPERTARGET, that are readily available to academic users at low costs. Specifically, Chapter 1 presents an overview of the basic concepts used in process integration of energy systems. Chapter 2 compares the use of single and dual temperature-of-approach methods to synthesize energy-optimum and minimum-cost, heat-exchanger networks (HENs), and shows how to implement them using three software tools. Chapters 3 and 4 demonstrate how to optimize the energy recovery in petroleum refinery distillation systems via process integration. Chapter 3 presents an extension to a case study of heat integration of a vacuum distillation system. Chapter 4 describes the detailed synthesis, retrofit and optimization of HENs for a system of atmospheric and vacuum distillation towers, and it represents the first process integration and optimization study of a complex process in petroleum refineries using all three commercial software tools. Chapter 5 presents, through four progressive tutorial examples, a recent conceptual method developed in the field of process integration of environmental systems applied to wastewater minimization and to the design of distributed effluent treatment systems. / Master of Science