Mineral Oil High Vacuum Stripper
The purpose of a mineral oil system in a solvent extraction plant is to remove as much of the solvent vapor as possible from the air before it exits the solvent extraction process.
Most of the air enters the extraction system together with the meal at the entrance of the extractor.
For a safe operation, the hexane content of the vapours coming out of the mineral oil system should be less then 20% of the lower explosion limit (LEL) of the air mixture (about 10 gr/m3 vapour). However, as legislation becomes more and more stringent for hexane emissions of the plant the content of hexane in the outgoing air should be as low as possible.
In this respect, Desmet has studied and re-engineered the whole section to obtain optimum results. The solvent vapour absorber, the mineral oil stripper and heat exchangers have been redesigned for optimal absorption and stripping. This leads to the safe levels of 10 g/m3.
However, by some further improvements, Desmet has developed a patented new system ‘the mineral oil high vacuum stripper’ that allows to further reduce the hexane load in the outgoing vapour to about 1 gr/m3. Also, in the optimized design, special attention has been given to avoid any contamination of the crude oil with mineral oil (MOSH/MOAH) of the system, to guarantee an optimal crude edible oil quality.
How does it work
In the optimized system, an extra mineral oil stripper working under deep vacuum is added after the main mineral oil stripping column. This allows a deeper and better stripping of the last traces of hexane from the mineral oil, and this in turn allows better absorption of hexane in the hexane absorption column.
Combined with some other smaller improvements in the heat exchange set-up, this can lead to the very low hexane contents of about 1 gr/m3 vapour at the air outlet of the mineral oil system.
As mentioned above, also a dedicated vacuum condenser has been added to condense the vapours coming out of the mineral oil stripper, to avoid any contamination possibilities of the crude vegetable oil with mineral oil (potential MOSH/MOAH) contamination.
The optimized mineral oil system is integrated in new plants, but viewing the compact design and the much better performance, upgrades or replacements of older mineral oil systems can be considered in existing plants to increase the sustainability of your operations.
Key advantages
Re-engineered design
Optimized for maximum hexane absorption
Vertical & compact
Space-saving layout
Low residual hexane
Cleaner exhaust air
No MOSH/MOAH contamination
Pure crude edible oil
Energy efficient
Optimized heat exchange reduces power use