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Which Vacuum Pumps Control Pressure & Temperature Reliably?
Busch Vacuum Solutions are used for distillation processes in the extraction of high quality essential oils from fruits to control pressure and temperature reliably.
May 21, 2021
Vacuum technology from Busch Vacuum Solutions is used for distillation processes in the extraction of high quality essential oils from citrus fruits to control pressure and temperature reliably. Essential oils are used in the production of perfumes, where they are used as top notes, or in flavoring foods.
After the oil/water emulsion has been extracted from the fruit skins, the separated raw oils are refined in distillation processes. Either thin-film evaporators or short-path distillers are used depending on the fruit. This produces extremely pure oils that have a precisely defined scent and are not influenced by other ingredients in terms of fragrance or color.
Distillers can use COBRA screw vacuum pumps that are free of operating fluids. The frequency-controlled vacuum pumps precisely guarantee the required vacuum level which, together with the temperature, ensures the desired product quality.
Oils are extracted from bergamot, lemons, oranges, blood oranges and mandarins. The extraction of the oil is similar for all citrus fruits. The essential oils containing water are extracted mechanically from the fruit skins on 12 production lines. The remaining solids and water are separated from this emulsion in the downstream multistage centrifugal separators. The raw oils extracted in this way are custom mixed for individual customer recipes in order to produce the same fragrance. Precision quality control ensures that the essential oils produce the same fragrance or flavor each and every time.
Distillation Process - Before (Liquid Ring)
The raw oils extracted in the first stage are refined on a total of five distillation lines and then temporarily stored in a controlled atmosphere. Distillation of the essential raw oils must be carried out as carefully as possible so that the scents are not influenced. The liquid ring vacuum pumps previously used only achieved a vacuum of 40 to 60 millibar. A higher temperature was therefore required for evaporation. This was 80 to 90 degrees Celsius for thin-film evaporators, depending on the type of fruit.
Distillation Process - After (Screw)
All thin-film evaporators are now equipped with COBRA screw vacuum pumps, which maintain a much higher permanent vacuum. The advantage in this case is that the distillation processes can be carried out at ambient temperature. Varying ambient temperatures or different oils can mean that fine adjustments of the operating vacuum and the pumping speed of the vacuum pump are required. This is possible simply by regulating the frequency-controlled motor of the vacuum pump.
Short-path distillers operate at even lower pressures. This is why vacuum boosters are installed upstream of the COBRA screw vacuum pumps installed there. These vacuum boosters are also driven by frequency-controlled motors and can therefore be regulated as required.
In short-path distillation, the exact operating pressures also depend on the oils to be distilled. The operating temperatures are usually slightly higher than the ambient temperature but significantly lower than when liquid ring vacuum pumps were still used.
COBRA screw vacuum pumps are used as backing pumps in thin-film evaporators and short-path distillers.
COBRA screw vacuum pumps from Busch have been specially developed for applications in which low pressures and the compression of extracted gases and vapors without operating fluids are necessary, for example to prevent contamination between the gas or vapor with an operating fluid. The major difference to the previously used liquid ring vacuum pumps is that COBRA screw vacuum pumps do not require any operating fluid to compress the process gas. This is why it is called a "dry" screw vacuum pump.
In COBRA screw vacuum pumps, two screw-shaped rotors rotate in opposite directions. The extracted vapors are trapped between the cylinder and screw chambers, compressed, and transported to the gas outlet. During the compression process the screw rotors do not come in contact with each other or the cylinder. Precise manufacturing and minimal clearance between the moving parts enable this operating principle and, in addition, guarantee a low ultimate pressure of <0.1 mbar.
COBRA screw vacuum pumps operate using water cooling, which ensures an even temperature distribution throughout the pump body and thus thermal stability in the entire process. Due to the variable pitch in the screw coils, the process gas is pre-compressed. The advantage of this is that both gas temperatures and the power consumption of the vacuum pump are reduced significantly.
Generally, dry screw vacuum pumps operate at higher temperatures than liquid ring vacuum pumps. This prevents condensation of the vapors in the vacuum pump, eliminating the possibility of contamination with an operating fluid.
Benefits of Dry Screw vs. Liquid Ring
The switch from liquid ring to dry screw vacuum technology has tremendous benefits.
The quality assurance of the essential oils produced has been considerably simplified.
Quality impairments caused by higher temperatures during the distillation process can be eliminated completely.
Distillation at low pressures, precisely adjusted to the product, allows the process to run under optimum conditions and guarantees the best results for the fragrance.
This also produces a completely clear, colorless oil.
Eliminating the liquid ring vacuum technology means that the operating fluid water and thus the costs for it and the additional expenditure for maintenance work were also eliminated. Maintenance consists only of a Busch service technician inspecting and servicing the COBRA vacuum pumps and vacuum systems once a year.
Contact Rogers Machinery for assistance with selecting vacuum systems for oil extraction processes.