The use of renewable energy carriers in the mobility sector can happen by replacing fossil fuels. One option is biodiesel, which is obtained from vegetable oils. It is produced by adding methanol and potassium hydroxide (as catalyst) and is a transesterification, a chemical equilibrium reaction. On a large industrial scale, production is carried out continuously in stirred tank reactors. This process is demonstrated on a small scale by the CE 650 experimental plant.
The chemical reaction takes place at temperatures of around 60°C. The products leave the reactor after a predefined dwell time. The products are a two-phase mixture: A biodiesel-rich phase and a phase with by-products. The by-products are pumped out of the following phase separator. The options for the biodiesel-rich phase are: Return to the reactor, second transesterification stage, methanol recovery (distillation) and biodiesel washing (absorption).
The biodiesel-rich phase contains residual amounts of methanol, potassium hydroxide and vegetable oil, in addition to the biodiesel. The remaining vegetable oil is reacted in the second transesterification stage. The methanol is distilled off in the methanol recovery stage. Residual amounts of the catalyst are removed in the biodiesel washing stage. Then the products are stored.
The rate of transesterification is dependent on the reaction time and the temperature. The chemical equilibrium is shifted by the separation of the by-products. The biodiesel produced is analysed in the laboratory. The process parameters can be varied to investigate the dependencies. The experimental plant is controlled by a PLC, which is operated by means of a touch panel. The GUNT software takes care of data acquisition.