Simultaneous Designing of a Heat Exchangers Network with least Cost and Emissions

Energy conservation and clean environment are important topics for search. Heat Exchangers Network (HEN) is an effective way of achieving energy recovery and minimizing operation cost for chemical plants. Reduction of greenhouse gasses (GHG) emission is a direct result of energy integration while gathering it with clean fuel switching minimizes emissions. In this work, we formulated a simultaneous methodology with a multiobjective function of minimizing cost and maximizing emission reduction through designing a [HEN] constrained by fuel type and minimum temperature difference approach (ΔTmin). Application of this methodology with a mathematical solver (GAMS) on an existing naphtha treating unit resulted excellent results. Energy recovery technique through HENs at several values of (ΔTmin) reduced energy consumption from 27% to 18% and reduced emissions of gasses from 21% to 12% comparing to actual data of the treating unit. While the application of fuel switching technique; increased emission reduction percentage to 34%. Combination of both techniques improved results; where HEN at optimum (ΔTmin = 18°C) with natural gas switching achieved reduction of energy and GHG by 24% and 44% respectively, so it is the candidate design for the unit revamping. Another revamping technique was fuel switching to coke, where adding Post Combustion Carbon Capture (PCC) is an emission reduction solution by 85%.