Direct and indirect integration of organic rankine cycle in total site

Abstract

Industrial sector is one of the major energy consumers in the world. Energy inefficiency in industry due to energy losses and wastages, which contributes to unnecessary carbon emission and global warming. Various initiatives have been taken for enhancing the energy efficiency in the industrial sector. Pinch Analysis is one of the important systematic tools for improving energy supply and demand in a process plant. Total Site Heat Integration for multiple processes (industrial cluster) has been introduced, as an extension to Pinch Analysis, to debottleneck the limitation of energy recovery in a single process plant. The availability of low temperature waste heat could be found, after considering the maximum heat recovery within the industrial cluster through TSHI. Organic Rankine Cycle (ORC) has been widely used for power recovery from low temperature heat sources. ORC integration is frequently being considered for direct heat transfer from a waste heat stream. In this study, integrating ORC via indirect heat transfer for a site utility system is studied, together with the direct integration of ORC to a waste heat stream. The indirect integration provides more opportunity of energy recovery through cumulating the low temperature waste heat from various stream, which has the potential of generating more power than depending on an individual waste heat stream. Economic comparison between direct and indirect ORC integration has been done in this work through a case study. A simple case study shows direct integration has better energy saving opportunity. Indirect ORC integration could be more efficient when the waste heat sources are distributed in different processes and stream.