Mass and energy balances are typically used in the analysis of flow-sheets and equipment. They however can also be used to understand the impact of the choice of feedstock and chemistry on processes and in particular the effect on carbon efficiency in appropriate processes. This can be done at a high level, that is before the flow-sheet is even synthesized. In addition, another powerful tool that is rather underutilized in the chemical engineer's toolbox is the concept of entropy or exergy. Combining overall entropy or exergy balances with the overall process mass and energy balances allows one to look at integrating a process at the highest level. In addition it allows one to calculate targets of performance. We call this approach, ComPS, or Complete Process Synthesis. The approach has been formulated as a matrix based method (Patel et. al.).

CompS, allows one to scan all different chemistries and in effect flow-sheets at a very high level. We are therefore able to quickly scan different options before the flow-sheet even exists, and to set and compare performance targets. Previous research has then (Mukoma et. al.) allowed us to develop the flow-sheet once the chemistry had been chosen, and in effect find the target for a real process.

ComPS is used to identify opportunities in a liquids production plant. In particular we identified the opportunity for the co-feeding of coal and natural gas and looked at the various optimal ways of integrating the process. Because of the number of degrees of freedom, we can set different targets, for example a zero CO2 emissions plant or a net zero work process. We get different answers depending on the target but all show that there are large opportunities and the optimum relative amounts of the two feeds in the process are different depending on the objective chosen.

References:

Patel, Bilal, Hildebrandt, Diane, Glasser, David, and Hausberger, Brendon. (2005) Thermodynamics Analysis of Processes. 1. Implications of Work Integration. Ind. Eng. Chem. Res. Vol. 44, 3529-3537

Patel, B., Hildebrandt, D., Glasser, D. and Hausberger, B. Matrix based methods for Complete Process Synthesis, Manuscript in preparation.

Mukoma, P., Hildebrandt, D., Glasser, D. and Hausberger, B. Fischer-Tropsch Results and their Analysis for Process Synthesis. Submitted to Ind. Eng. Chem. Res.