The cleaning procedure is an important practice: it is just as important as the extraction process.
Any extraction system needs to be cleaned periodically: this period depends on many factors. The following issues all have an impact on the cleaning period:
- Type of the raw material
- Quality of the raw material
- Any pre-treatment of the raw material
- Number of extractions between cleanings
- Use of a co-solvent in the extraction process
Throughout the process the bacteria contamination is very low: during the extraction we have a hostile environment inside the system for bacteria: no oxygen, high pressure and saturation of CO2. If you use a small amount of ethanol or oil as a co-solvent, the viscosity of the extract is decreased and the deposit of solid parts in the system is reduced dramatically. This condition will change immediately when you stop the system and open the lid of the extractor. Ambient air goes inside the extractor/circuit along with any bacteria in the air. The cleanliness of the ambient air is therefore an important factor.
So it is important to reduce the time that the extractor is open, and the more time the flow of CO2 is arrested, then the higher the probability of precipitation of solids in the piping with negative pressure.
How to Clean the Machine
To clean the piping and exchanger effectively we need a mix of supercritical CO2 and another co-solvent. If apolar or medium polar compounds were extracted, then we use ethanol. If polar compounds were extracted we use water. It is important to remember that ethanol is a flammable fluid, therefore the quantity of ethanol used in the process is very important.
There are two methods you can use to clean the frites:
- Use the canister during cleaning. Fill the canister with glass marbles, from 8 to 12 mm diameter. If not available, use stainless steel balls, same diameter.
- Use an ultrasound bath. If the frites are not perfectly cleaned, remove them from the canister and put the discs in the bath.
The small balls will help the ethanol to go from the bottom to the top of the extractor. Use the valve installed on the bottom flange of the extractor to purge ethanol if present at the bottom of the extractor into a safety container. Typical parameters are: pressure at 300 bar and temperature about 60° C/140° F.
The process is fully automatic, there is a sequence written in the program recipe to clean the extraction vessels in the same cleaning process. Separators are only partially cleaned by these procedures. Depending on the quality of the raw material, you may need to open and manually clean the inner wall of the vessels with ethanol and a brush. Check the inner wall of the separators after the automatic cleaning in order to check the status of each separator. If they appear yellow and sticky, they will need to be cleaned manually.