The process industry is an integral part of modern society, manufacturing a vast array of low-margin, high-volume, bulk chemicals such as refinery fuels and petrochemicals. These are typically produced in chemical plants that continuously process appropriate feedstocks to the respective value-added chemicals. For economic reasons of material/energy efficiency, material/energy recycle, also referred to as process integration, has traditionally been employed in the chemical process industry. In more recent decades, long-term sustainability concerns reflected in increasingly stringent product quality and environment discharge norms as well as carbon emissions/energy efficiency targets have pushed the industry toward higher levels of process integration. The objective of the integration is to eliminate waste/side product discharge and minimize energy consumption per kg product. Material/energy integration (recycle) is thus the bedrock of designing sustainable, zero waste discharge, and highly energy-efficient continuous chemical processes.