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

Abstract Energy conservation, clean environment are important topics for search. Heat Exchangers Network [HEN] is an effective way for achieving energy recovery and so on minimizing operating 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 by 27% to 18% and reduced gasses emissions by 21% to 12% comparing to actual data of the treating unit. While application of fuel switching technique; increased emission reduction percentage to 34%. Combination both techniques improved results; where HEN at optimum (ΔTmin=18ᵒC) 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%.