Proposta de substituição do etilenoglicol em bombas de unidades recuperadoras de vapor: estudo de caso em uma base de distribuição de combustíveis

Abstract

This study proposes a comparative analysis of fluids with the potential to replace ethylene glycol in cooling systems for liquid ring vacuum pumps used in Vapor Recovery Units (VRUs), aiming to reduce operational risks, logistical constraints, and impacts associated with the use of this fluid. Initially, an overview of the operating principles of VRUs at fuel distribution terminals was presented, highlighting their importance in controlling volatile organic compound (VOC) emissions and the role of the operating fluid in the performance of the vacuum pump. Subsequently, the main physicochemical properties of ethylene glycol relevant to this application were examined, as well as its limitations related to toxicity, regulatory restrictions, and procurement difficulties. Based on this assessment, technical criteria were established for selecting potential substitutes, considering thermophysical properties, thermal performance, operational stability, chemical compatibility with hydrocarbons, and behavior under vacuum system conditions. According to these criteria, propylene glycol and glycerol, both belonging to the class of organic alcohols, were selected for comparison with ethylene glycol. The properties of aqueous solutions of these compounds at different concentrations were obtained using the SecCool software, allowing a comparative evaluation of parameters such as density, specific heat capacity, thermal conductivity, and freezing and boiling points. The results indicated that propylene glycol exhibits behavior similar to that of ethylene glycol for most of the properties evaluated, standing out due to its higher specific heat capacity values, low toxicity, and high level of operational safety. Glycerol, in turn, presented limitations associated with higher density, lower thermal conductivity, and a reduced ability to lower the freezing point of solutions, characteristics that restrict its application as a heat-transfer fluid under the conditions studied. Additionally, a comparative assessment of the environmental, economic, and safety aspects of ethylene glycol and propylene glycol was conducted. Although ethylene glycol has a lower acquisition cost and a smaller environmental impact during its production, propylene glycol is distinguished by its lower toxicity, greater operational safety, and easier availability. Considering the set of properties evaluated and the operating conditions of the VRUs, it is concluded that propylene glycol represents a technically viable alternative for replacing ethylene glycol in the cooling system of liquid ring vacuum pumps, provided that its application is experimentally validated. Therefore, bench-scale and pilot-scale tests are recommended to assess the fluid’s performance under real operating conditions, enabling an integrated evaluation of the system’s technical, economic, and safety aspects.