OVERALL SITE OPTIMIZATION BY PINCH TECHNOLOGY

The importance of integration in process plant design has long been re cognised. This is evidenced for example, by the existence of complex h eat and power networks in modern production sites. These networks repr esent site-wide integration. They usually allow process heating duties in several processes to be effected at low cost by using turbine pass -out steam after obtaining a credit for power generated in a central t urbine. When looking for energy saving in retrofit projects, an instal led heat and power network of this type usually introduces a counter-p roductive element. a reduction in steam heating duties leads to a redu ction in turbine pass-out steam which, In turn, leads to a reduction i n power generation. This makes optimisation of the process slow and op timisation of the process in the site context two rather different tas ks. More complications are given through other more general reflectors across a site. A modern processing plant such as ethylene, for instan ce, is usually linked into the overall site and interacts with other p lants through several utilities, not just back pressure steam. This ma kes it necessary to not only understand the fundamental process demand s but also to analyse these demands in the site context. Process licen sors will usually prefer to consider standard designs for individual p rocesses. The best project, on the other hand, will almost invariably be site dependent. This article highlights the distinction between the application of process integration techniques-in particular pinch tec hnology-within an individual process and their wider application in th e overall site context The ''counter productive'' aspect of heat savin gs in the context of isntalled heat and power networks Is given attent ion. In addition to energy, the article discusses yields, flexibility and capital cost savings.