CHEMICAL ENGINEERING TRANSACTIONS VOL. 70, 2018 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Timothy G. Walmsley, Petar S. Varbanov, Rongxin Su, Jiří J. Klemeš Copyright © 2018, AIDIC Servizi S.r.l. ISBN 978-88-95608-67-9; ISSN 2283-9216 Exergetic Analysis of Combustion Processes of Variable Mixtures of Refinery Residual Gas: Effect of Propane Daniel Barragan-Noriega*, Sergio A. Morales, Viatcheslav Kafarov Universidad Industrial de Santander, Escuela de Ingeniería Química, Centro de Investigación para el Desarrollo Sostenible en Industria y Energía – CIDES, Cra 27 calle 9, Bucaramanga -Santander, Colombia engineer.barragan@gmail.com Due to the depletion of non-renewable natural resources, the increase in the emission of pollutants and the growing global energy demand, it is increasingly important to implement strategies that lead to a sustainable use of available resources and to improve the efficiency of the processes currently employed; A tool widely used for this purpose is the exergy analysis. Currently, refining processes use refinery gases as the main source of energy, which consist of mixtures of natural gas and residual gases; these are obtained as by-products in different processing units, so their composition varies according to the process they come from, highlighting their content of gases such as ethylene, hydrogen, propane and propylene. In this order of ideas, in this work we evaluated the effect of the variation of the proportion of residual gas (propane) with respect to natural gas, on the thermodynamic behaviour of combustion in a refinery furnace; through the methodology of exergy analysis. The process was simulated using the software Aspen-Plus®-v.8.8, obtaining thermodynamic properties of the flows involved in the combustion for each of the propane-natural gas mixtures analysed. Then, the exergy analysis was performed, obtaining profiles of irreversibility and exergetic efficiency, finding that the variation of the residual gas at the entrance of the furnace does not greatly affect the exergetic efficiency (variations less than 1 %); however, the irreversibilities of the process increase up to 70 % as the proportion of residual gas increases. 1. Introduction One of the processes necessary for the use of current energy resources is the refining of oil; in this, between 4 % and 8 % of the extracted oil is used for the generation of energy consumed in the process (Elías et al., 2015). Energy consumption represents around 40 % of the total operating cost (Zargarzadeh et al., 2007), with thermal processes being the largest energy consumers with around 70 % (Campos Avella et al., 2007). The processes of separation and transformation are those that require more energy consumption (Wauquier, 2004). In order to obtain the necessary energy for these processes, furnaces are generally used, in which combustion of refinery gases takes place. In addition, the increase in demand and the cost of energy have led this industry to develop more efficient energy consumption strategies (Mehdizadeh Fard et al., 2017). Some of these initiatives include energy conservation, processes intensification, quality and quantity of products and an adequate disposal of energy waste for its later use (Hey, 2017). Environmental regulations are also a factor that encourages industries to consider energy efficiency in their processes as a key aspect to reduce greenhouse gas emissions (Mehdizadeh Fard et al., 2017). At present, refining processes use refinery gases as a main source of energy, consisting of a mixture of natural gas and residual gases; which are obtained as by-products in the different units of processes and are used as partial or total substitutes for natural gas. The composition of these gases varies according to the process from which they come, highlighting in their content compounds such as ethylene, hydrogen, propane and propylene (Cala et al., 2013). To evaluate the use of these gases as fuel, the concept of "interchangeability" is used, referring to the ability to substitute a gaseous fuel for another without affecting the performance of the equipment used for combustion (Natural Gas Council Plus, 2005). From its study, different indexes have emerged that allow the evaluation of the quality of the resulting fuel based on its physicochemical and thermodynamic properties, highlighting the DOI: 10.3303/CET1870198 Please cite this article as: Barragan-Noriega D., Morales S.A., Kafarov V., 2018, Exergetic analysis of combustion processes of variable mixtures of refinery residual gas: effect of propane , Chemical Engineering Transactions, 70, 1183-1188 DOI:10.3303/CET1870198 1183