Exergetic analysis of the production technology of biodiesel from rapeseed oil

Abstract

Analysis of the efficiency reserves of the most promising technologies for biodiesel production showed the feasibility of implementing the technological cycle in the following sequence: first, the transesterification of vegetable oil with supercritical alcohol, then the fluid supercritical СО2 extraction of the cooled reaction mixture; its separation in the field of centrifugal forces to separate glycerol from the target product, and then the separation of carbon dioxide by gas-liquid separation to obtain purified biodiesel and return carbon dioxide to the extraction stage. In accordance with the methodology of exergetic analysis, the influence of internal and external energy losses on the system is considered. The total number of internal exergetic losses associated with the irreversibility of any real processes included losses from the final temperature difference as a result of recuperative heat exchange between material and heat flows, as well as hydraulic losses caused by a sudden increase in the specific volume of the coolant when it enters the operating volumes of the devices from the pipeline. External losses are related to the conditions of the system interface with the environment. They are caused by the difference between the temperature of heat carriers and the ambient temperature, imperfect thermal insulation of equipment and condensate discharge. Exergetic analysis has shown that the exergetic efficiency for the technology of biodiesel production in supercritical conditions using steam-ejection refrigerating machine is 52.62%, which is 15–20% higher than that of known technologies. This characterizes the proposed technology as a heat-technological system with a high degree of thermodynamic perfection, which was achieved by organizing work in closed thermodynamic cycles and using exhausted heat carriers.