Investigating operability issues of heat integration for implementation in the oil refining industry

Paper in proceeding, 2016

Heat integration is important for increasing the energy efficiency of industrial processes. However, the increased interdependencies caused by heat integration can result in process operability issues. Depending on which operability and implementation issues that are considered in retrofit of heat exchanger networks (HENs), the savings potential varies significantly. It is important to know what operability issues to consider in order to estimate reliable heat savings potentials while at the same time maximize the possibilities for implementation of heat recovery through heat integrated HENs. Although operability has been studied previously, the literature is not consistent in categorizations and definitions of the concept. No systematic and complete survey of operability perspectives of heat integration has been presented. This paper aims to map and categorize the relations between heat integration retrofit measures and potential effects on process operability in order to better understand which operability issues that are likely to have a large effect on heat savings potential and/or likeliness of implementation. A literature survey of operability research in process industry is presented to clarify the definition of operability. Previous studies define operability in different ways; in this paper these variations of definitions are compared and evaluated. One definition is proposed for the purpose of heat integration, which combines previous definitions in literature. Following this definition, operability is divided into the subcategories; Flexibility, Controllability, Startup/Shutdown and Reliability/Availability. These subcategories, and other practical implementation issues, are matched with different implications of heat integration measures commonly used for retrofit of HENs in chemical processes. The results are then presented in a schematic view and conclusions are drawn about operability aspects to consider for the retrofit of HENs.