Hot Discharges/Feeds between Plants To Combine Utility Streams for Heat Integration

Abstract

A sharp increase in worldwide energy requirements has forced people to exploit novel energy conservation technologies and new alternative energies. Heat integration, as a method of saving energy, is proposed in this paper in the form of integrating multiple hot discharges/feeds between plants and utility streams to reduce utility requirements and increase steam production for the total site. T–Q graphic methods are proposed to coordinate the temperatures of multiple hot discharges/feeds between plants and the steam production. The grand composite curve (GCC), the composite curve of the streams employed for hot discharges/feeds, and the curve of steam generation are combined into the T–Q diagram to obtain an insight into the interrelationship between these streams. A bilevel mixed integer linear programming (MILP) framework is presented to minimize the total hot and cold utilities of the up and down plants and to maximize the steam generation in the total site. The first level of the programming framework is formulated to target the utility requirements, and the second level of the programming framework is formulated to maximize the steam production. Two examples are investigated to demonstrate the performance of the proposed method, and the results show a decrease in the total hot and cold utilities of the up and down plants and also indicate an increase in steam production.