The methylester coming from the upstream methylester washing (unit 6163W) still contains unacceptable quantity of water and methanol which cannot be removed by centrifugation. The methylester is therefore subject to a final drying step: the volatile methanol and water are evaporated from the top of the column, condensed and sent to recovery in the downstream methanol rectification (unit 6160), while biodiesel product is drawn from the bottom, cooled and sent to storage.
The Desmet Methylester Drying Unit is designed to meet the restrictive biodiesel standard requirement, in terms of water and methanol specification, thanks to the specifically designed two-step drying accomplished first in the packing drying column and completed in the relevant post flasher.