Reducing Costs and CO2 Emissions on the Production of Biodiesel by the Supercritical Methanol Method

摘要

Over the past decade, significant research efforts have focused on finding alternative non-fossil energy sources as an attempt to reduce the effects of global wanning and the dependence on petroleum fuels. Biodiesel has emerged as an interesting alternative. Biodiesel is generally produced by a catalytic reaction, which may lead to high energy consumptions to separate the catalyst and to undesirable side reactions. A recently proposed process involves the use of short-chain alcohols (methanol) at supercritical conditions, avoiding the use of a catalyst and the occurrence of side reactions. Such a process, known as the Saka-Dadan process, allows the use of low-quality oils as reactants and requires fewer pieces of equipment than conventional catalytic processes;;however, its high energy requirements and the reaction conditions make the main product, biodiesel fuel, still more expensive than petroleum diesel. This paper proposes an intensification-based alternative to the Saka-Dadan process for biodiesel production. As an attempt to reduce equipment costs, a reactive distillation system is proposed to achieve the tasks of esterification reaction and the biodiesel purification in a single shell. Then, to reduce energy consumptions, two thermally coupled reactive distillation systems are analyzed. In particular, a reactive Petlyuk system and a reactive thermally coupled direct sequence have been studied. Simulations have been carried out by using the AspenOne~(TM) process simulator to demonstrate the feasibility of such alternatives to produce biodiesel with methanol at high pressure and temperature. Results indicate that thermally coupled reactive systems present favorable energy performance and higher thermodynamic efficiency when compared to the conventional scheme, allowing high conversions of the fatty acid. CO2 emissions and costs calculations were also computed, finding an important reduction on both parameters by using the thermally coupled reactive systems when compared to both the conventional process and the reactive distillation process (without thermal coupling).