Consumption of primary energy has risen substantially in recent years, and greenhouse gases (GHG) emissions have increased by a substantial amount. To counter this trend, there is a global strong emphasis on regenerative energy such as biofuels to effectively reduce or avoid such emissions.
The Lurgi biodiesel process is centered on the transesterification of different raw materials to methyl ester using methanol in the presence of a catalyst. In principle, most edible oils and fats — both vegetable and animal sources— can be transesterified if suitably prepared.
Transesterification is based on the chemical reaction of triglycerides with methanol to methyl ester and glycerine in the presence of an alkaline catalyst. The reaction occurs in two mixer-settler units. The actual conversion occurs in the mixers. The separation of methyl ester as the light phase and glycerine water as the heavy phase occurs in the settlers due to the insolubility of both products and the difference in density. Byproduct components are removed from the methyl ester in the downstream washing stage, which operates in a counter-current mode. After a final drying step under vacuum, the biodiesel is ready for use.
Any residual methanol contained in the glycerine water is removed in a rectification column. In this unit operation, the methanol has a purity, which is suitable for recycling back to process. For further refinement of the glycerine water, optional steps are available such as chemical treatment, evaporation, distillation and bleaching to either deliver crude glycerine at approximately 80% concentration or pharmaceutical-grade glycerine at >99.7% purity.
Licensors: Lurgi GmbH.
