Classification of Chemical Processes: A Graphical Approach to Process Synthesis To Improve Reactive Process Work Efficiency

Abstract

To reduce carbon dioxide emissions for chemical processes, one should make them as reversible as possible. Patel et al. [Ind. Eng. Chem. Res. 2005, 44, 3529−3537] showed that, in some cases, one can analyze processes in terms of their work and heat requirements. In particular, for processes, there exists a temperature that is called “the Carnot temperature”, at which one can satisfy the work requirement for the process, using the heat that must be added or removed. The analogy of a heat engine and Carnot temperature is applied to chemical processes, particularly on reactive processes, using a graphical approach. This approach looks at chemical processes holistically, where only the inlet and outlet streams are considered. The process is represented in a ΔH−ΔG space. Chemical processes are classified in different thermodynamics regions as defined in the ΔH−ΔG space, and their feasibility in terms of heat and work requirement is discussed. This approach allows one to determine whether heat at an appropriate temperature is sufficient to meet the work requirement of a chemical process, or if other means should be considered. The approach is used to investigate and discuss the possibility of combining reactive chemical processes classified in different thermodynamic regions in the ΔH−ΔG space, with the purpose of making infeasible processes possible, or to minimize, or even eliminate, the work requirement of the combined process.

Making processes work

“…In other works (Sempuga et al, 2010;Fox et al, 2013) it has been shown how once one has this target material balance one can synthesise a process flow-sheet using what has been termed the "gh-diagram". As this is just a two dimensional plot no matter how complex the process this is a relatively simple procedure.…”

Preparation and Characterization of Lanthanum-Promoted Copper-based Oxygen Carriers for Chemical Looping Combustion Process

“…Similar evaluations concluded that the cost was 18-37 Euro for a pre-combustion technology using IGCC, and 13-30 Euro for an oxy-fuel process (Petrakopoulou et al, 2010;Adanez et al, 2012). Chemical looping combustion significantly improves the energy conversion efficiency, in terms of electricity generation (Ekstrom et al, 2008), because it improves the reversibility of the fuel combustion process through two linked parallel processes (Anheden and Svedberg, 1998;McGlashan, 2008;Sempuga et al, 2010Sempuga et al, , 2011.…”

Process flow sheet synthesis: Systems‐level design applied to synthetic crude production

“…From the enthalpy and Gibbs free energy values for the methane steam reforming it is possible to calculate the “Carnot Temperature” for this material balance. The Carnot Temperature is the temperature at which an independent material balance, process or reaction could be operated reversibly as a heat engine. The Carnot Temperature for Methane Steam Reforming is …”