Division 10.4 Hexane losses
United Kingdom
BAT 32. In order to reduce the hexane losses from oilseed processing and refining, BAT is to use all of the techniques given below.
| Technique | Description | |
|---|---|---|
| (a) | Countercurrent flow of meal and steam in the desolventiser-toaster | Hexane is removed from the hexane-laden meal in a desolventiser-toaster, involving a countercurrent flow of steam and meal. |
| (b) | Evaporation from the oil/hexane mixture | Hexane is removed from the oil/hexane mixture using evaporators. The vapours from the desolventiser-toaster (steam/hexane mixture) are used to provide thermal energy in the first stage of the evaporation. |
| (c) | Condensation in combination with a mineral oil wet scrubber | Hexane vapours are cooled to below their dew point so that they condense. Uncondensed hexane is absorbed in a scrubber using mineral oil as a scrubbing liquid for subsequent recovery. |
| (d) | Gravitational phase separation in combination with distillation | Undissolved hexane is separated from the aqueous phase by means of a gravitational phase separator. Any residual hexane is distilled off by heating the aqueous phase to approximately 80-95 °C. |
Table 22
BAT-associated emission levels (BAT-AELs) for hexane losses from oilseed processing and refining
| Parameter | Type of seeds or beans processed | Unit | BAT-AEL(yearly average) |
|---|---|---|---|
| Hexane losses | Soybeans | kg/tonne of seeds or beans processed | 0,3-0,55 |
| Rapeseeds and sunflower seeds | 0,2-0,7 |