OICC Press International Journal of Industrial Chemistry 2228-5547 9 4 2023 11 17 Thermodynamic optimization of steady-flow industrial chemical processes https://doi.org/10.1007/s40090-018-0164-1 EN Leslie Glasser Department of Chemistry, Curtin Computational Group, Curtin University, GPO Box U1987, Perth, WA, 6845, Australia 0000-0002-8883-0564 James Alistair Fox Materials and Process Synthesis (MaPS), College of Civil and Chemical Engineering, University of South Africa, Florida Science Campus, Pretoria, South Africa 0000-0002-2075-3638 Diane Hildebrandt Institute for the Development of Energy for African Sustainability (IDEAS) Research Unit, University of South Africa (UNISA), Florida Science Campus, Private Bag X6, Johannesburg, 1710, South Africa D. Glasser University of South Africa, 5th Floor, Pha-Pha Building, Cnr. Pioneer and Christian De Wet Road, Private Bag X6, Florida, Johannesburg, 1710, South Africa Journal Article 2023 11 17 Industrial steady-flow chemical processes are generally organised as a sequence of individually optimised operations. However, this may not achieve overall optimization since material (as recycle), heat and work transfers overall may not be well balanced. We introduce the idea of a preliminary overall thermodynamic balance to produce a reversible process, with the objective of minimising, for both economic and environmental reasons, the quality and quantity of energy used. This balance may later require adjustment to account for the realities of available materials and equipment. For this purpose, we introduce (i) a Carnot temperature, TCarnot, by which a Carnot machine (an engine which can operate as either a heat pump or a turbine) can supply the required heat at the correct temperature for a process to operate reversibly, that is with least energy, and (ii) the GH Diagram on which Carnot temperature-based processes are plotted in ∆G–∆H space. We demonstrate the utility of this analysis by simple application to the Haber–Bosch process for ammonia synthesis and by a sequence of operations for the synthesis of methanol. We also briefly introduce the state function exergy, which uses the natural environment as the reference base for energy in place of pure elements under standard conditions.