Synthesis and Integration of Chemical Processes from a Mass, Energy, and Entropy Perspective

Abstract

A method for setting performance targets for a chemical process, based on mass, energy, and entropy, is presented. These targets can be determined in the early stages of the design process to aid in the synthesis of a suitable flowsheet. These targets are “global” targets, because the overall process is considered and does not consider the individual processing units. A method of determining the minimum amount of inputs (mass, energy, and work) is illustrated by setting various targets (for example, no CO2 emissions, no energy emitted from the process, or ΔH = 0 and ΔG = 0). The approach allows one to screen the various options easily and thus determine processes that are efficient and environmentally friendly. This approach also allows opportunities of mass, heat, and work integration to be determined and applied at the earliest stages of the design process. Initially, a graphical solution is illustrated, and thereafter, the approach is generalized using a linear programming formulation. The approach is demonstrated by identifying opportunities in a methanol production plant.

Assessing the environmental potential of carbon dioxide utilization

“…After a short description of methanol production, the graphical design framework by Patel et al [3] is briefly summarized and then extended for environmental analysis.…”

“…Patel et al [3] use these balance equations as constraints for a linear program (LP). We adopt the approach for the production of any compound of the form C x H y O z at standard conditions (298K, 1 bar).…”

“…Systematic methods to identify promising candidate reactions are therefore desirable. Patel et al [3] recently introduced a thermodynamic process design framework. The framework can directly be employed to identify promising CO 2 -based reactions from a thermodynamic perspective.…”

“…But the utilization of CCU is most often motivated environmentally. Therefore, we extend the framework from Patel et al [3] by an optimization step based on ecological criteria such as the GWP. This extension enables the identification of the ecologically optimal composition of reactants and products.…”

Making processes work

“…There are three fundamental tools that can be used to synthesise and analyse processes (Patel et al, 2007):…”