Bosting an Oil Refinery into a Biorefinery

Abstract

The use of biofuels is increasingly important in order to mitigate the consumption of petroleum and increase the energy use of renewable sources. The estimative is that in 2040 the demand for oil will intensificate by 26% and part of it will have to be supplied by renewable energy. Biofuels offer a reliable alternative and among the process associated to biofuels production, thermal cracking results on a liquid product (bio-oil) with similar characteristics to the fossil fuels, particularly when performed with triglyceride sources (TG). In this sense, the main goal of this work is to propose an alternative sequence of chemical processes aiming to boost an oil refinery chain into a green refinery by producing, co-processing and improving bio-oil characteristics obtained from triglyceride source. Some bio-oil characteristics like density, acidity (AI), iodine index (II), oxygen content (OC), carbon number distribution and chemical compositions are presented. The properties of bio-oil obtained from the thermal cracking of triglycerides might be compared to petroleum and its derivate. Although the characteristics are similar between them, the bio-oil requires upgrading to reduce its high acid index, until achieve levels acceptable for its processing at a refinery. The content of olefins and oxygen might be reduced through hydrotreatment process. The hydrotreatment can promote the saturation of the double bonds and remove the oxygen atoms. The hydrotreatment unit is present in most of the refineries and further investigations are required to evaluate the hydrogen consumption. The proposal of this work is divided in four steps: the first is to produce bio-oil through triglyceride’s thermal cracking in a continuous and steady state regime; the second process is to promote the esterification of bio-oil to reduce its acid index; the third stage is co-processing bio-oil in a distillation unit being fractionated into desired fractions; the fourth step involves hydrotreatment to reduce both iodine index and oxygen content. Thus, the co-processing of bio-oil appears to be a promising approach to increasing the biofuels content in an oil refinery, to reduce sulfur and to maintain the quality parameters of commercial fuels.