(99a) Connecting Chemical Process Design Economics and Entropy Generation

Systematic analysis of chemical process systems with the two steady-state balance equations from the First and Second Laws of Thermodynamics provides insights about both energy efficiency and property models when entropy generation is the indicator of irreversibilities^1-4. Consistent evaluations of overall processes and of subsections yield reliable comparisons for energy requirements of process alternatives, indicate the impacts of potential changes, and check property model and calculational consistencies.

TEPET is a standardized methodology specifically developed for techno-economic evaluation of alternative fuels manufacture⁵. This approach enables qualitative and quantitative statements regarding the technical and economic feasibility of fuel synthesis concepts, including identification of appropriate fuel production concepts within predefined framework conditions. Specifically, it avoids uncertainties in results of previous studies for assessing and comparing feasibilities of alternatives for fuel manufacturing that would arise from significant differences in applied methodology, level of detail, and key assumptions for economic factors and market prices. The inputs to the software are output files from AspenPlus® simulations, which are heat integrated to minimize utility costs by designing an optimized heat exchanger network based on results from pinch-point analysis.

This presentation describes results from a case study to relate entropy generation to process design economics. AspenPlus® has available process simulation files for the manufacture of fuel grade methanol from syngas feed. Entropy generation and economic analyses have been done for different processes with the same feed and product bases to reveal their differences in irreversibilities and costs. A relationship between entropy generations and cost has been established for these systems. Changes in cost from process improvements suggested by reducing entropy generation have also been obtained.

References:

1. J.P. O’Connell, “Chemical process systems analysis using thermodynamic balance equations with entropy generation”, Comp. & Chem. Eng. 2017, 107, 3-15.
2. J.P. O’Connell, “Chemical process systems analysis using thermodynamic balance equations with entropy generation. Revaluation and extension”, Comp. & Chem. Eng. 2018, 111, 37-42.
3. J. P. O’Connell, “Detailed Examination of Energy Flows and Entropy Generation in Low Pressure Binary Distillation Columns”, Ind. Eng. Chem. Res., 2018, 57 (32), 11186–11194
4. J. P. O’Connell, “Analysis of Chemical Process Systems with Entropy Generation”, AIChE Annual Meeting, Pittsburgh, PA, paper 421d.
5. F. G. Albrecht, D. H. König, N. Baucks, R-U. Dietrich, “A standardized methodology for the techno-economic evaluation of alternative fuels – A case study”, Fuel, 2017, 194, 511–526.