While in the simple semi continuous extraction the system is equipped with two extraction vessels, for semi-continuous serial extraction the system is equipped with three extraction vessels. Taking advantage of the typical flowers and leaves extraction kinetic, the intelligent automation of the system will apply a different extraction strategy.
As we see, most of the extract comes out in the first half of the extraction (120 minutes of a 240-minute total, or 60 minutes of a 120-minute total time). Starting from this data, the process program will apply a different approach, compared to other kind of extractor:
- After the first half of the extraction, we collected solute from extraction vessel E1, and for this reason, the CO2 isn’t more saturated by compounds like before.
- This means that CO2 can solubilize more compounds than what are available in extractor E1.
- So the system will put in series, from extractor E1 to extractor E2. Iin this way the CO2 from E1 (poor in solute and with high solvent power) can solubilize chemical compounds in E2, breaking down the time of extraction.
- Connecting E2 in series with E1, after the first half of the process, will give to the production manager the ability to recover the last 15% to 30% left in E1.
- After another 120 min, the solvent will extract the most of the compounds from E2, and so the system will put E2 and E3 in series, and then again E3 and E1, in an endless loop.
The serial semi-continuous automation program is completely different if it is compared with the simple semi-continuous. The advantage is clear: in the same amount of processing time we have results almost comparable to a double-sized system.