Exergy as a tool for measuring process intensification in chemical engineering

Abstract

Exergy is defined as the maximum shaft work that can be done in a process to bring the system into equilibrium with the environment. Thus, exergy analyses are the first step to understand where the weak points of processes are. It considers intrinsically the quality of energy: when energy loses its quality, exergy is destroyed. In addition, optimization of processes aiming at the minimization of exergy destruction can be done as a function of the topology and physical characteristics of the system, such as finite dimensions, shapes, materials, finite speeds, and finite‐time intervals of operation, establishing a direct relationship between exergy and process intensification. However, the emphasis on exergy in chemical engineering is still very poor compared with other fields, in spite of being one of the areas in which more exergy is destroyed due to reaction and separation. This paper gives an overview of the current application of exergy analyses in chemical engineering, showing the main fields in which exergy studies are performed and focusing the attention on two critical points of action: separation technologies (distillation and membrane technology) and CO2 capture. New research trends in chemical engineering using exergy as a tool for process intensification are highlighted. © 2013 Society of Chemical Industry

Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review

“…However, using energy alone in the efficiency analysis of processes is bound to lead to misconceptions, misevaluations and poor decisions [8]: it only embraces information of the inputs and outputs of the energy in the process and excludes its quality [9]. The use of second law analysis allows the quality of the energy to be determined, and the irreversibilities quantified, as a result of the entropy that is generated and which causes inefficiency in the process [1].…”

Exergy efficiency of light conversion into biomass in the macroalga Ulva sp. (Chlorophyta) cultivated under the pulsed light in a photobioreactor

“…The goal of the optimization of energy conversion system, including macroalgae cultivation, is to maximize the exergy produced by the system per invested exergy (Szargut, Morris, & Steward, ). The exergy efficiency (Dewulf, Van Langenhove, & Van De Velde, ; Golberg, ; Luis, ; Sciubba, ) of light conversion to biomass was calculated using Equation : where η is the exergy conversion efficiency, E g (J · m −2 ) is the energy accumulated in the biomass during N days per illuminated area of the reactor and E i (J · m −2 ) is the light energy invested during N days . The accumulated energy in the biomass during N days was calculated using Equation : where c p (kJ · g −1 ) is the energy density of the biomass, DW/FW is the ratio of dry weight to wet weight and A (m 2 ) is the illuminated area of the reactor with thalli.…”

“…The goal of the optimization of energy conversion system, including macroalgae cultivation, is to maximize the exergy produced by the system per invested exergy (Szargut, Morris, & Steward, 1988). The exergy efficiency (Dewulf, Van Langenhove, & Van De Velde, 2005;Golberg, 2015;Luis, 2013;Sciubba, 2003) of light conversion to biomass was calculated using…”

The use of exergetic indicators in the food industry – A review

“…BoroumandJazi et al (2013) reviewed the applications of ExA in various industrial sectors in different countries. Luis (2013) focused on the chemical industry and showed that most of the ExA publications relate to the energy-and thermodynamicsrelated fields. According to Dincer and Rosen (2013c), ExA seems to be applied mainly by European companies, and one of the reasons could be their longer-term viewpoints on sustainability.…”

“…2(a)). However, the number of publications of the food industry in relation to the total number of publications, as shown by Luis (2013), is still small, indicating a need for identifying relevant research questions that can better couple ExA to food science and technology ( Fig. 2(b)).…”