Hemp biomass separator is the primary equipment in the solvent extraction process for CBD oil production. Increasing separation efficiency at this stage leads to significantly higher production efficiency of the CBD oil extraction process.
Conventional centrifugal separators (basket centrifuge) are often used to separate the biomass from the solvent. Dried hemp plant stock which is pulverized or shredded is packed in a mesh bag. This ‘soak bag’ is then placed in the ‘spinner’ basket of the centrifuge, immersed in solvent of choice. The solvent ‘extracts’ the CBD oil from the hemp biomass. The soak bag is then spun at about 1000 RPM (< 2000 g’s) to separate the solvent from the biomass. The solvent is drained from the centrifuge vessel after a predetermined mixing time. Absorption time again depends on the solvent used.
Hemp biomass separator outlined above is sufficient for small scale (< 1000 Lbs/Day) producers. This is due to the following advantages of this technology:
- Relatively lower capital expense.
- Extraction & separation stages combined.
However, when production volumes are higher the disadvantages of the ‘basket centrifuge’ become evident. Some of the inherent drawbacks are listed below.
- Batch process not easily adaptable for higher volume, continuous production.
- Incomplete mixing of solvent due to insufficient movement of solvent through the biomass.
- Low separation efficiency (hemp biomass from solvent) due to relatively low g-force.
- High levels of residual biomass particles in separated solvent (depends on bag mesh size*).
- Need for down-stream filtration to remove remaining biomass particles*.
* The trade-off is between mesh size (to maximize particle separation) and extraction efficiency. In other words, finer mesh bags leads to lower extraction efficiency and longer process time. Finer mesh bags also limit bag reuse. Coarser mesh bags allow more particles in the separated solvent which leads to more filter resources downstream with associated cost and labor.
An industrial scale hemp biomass separation and purification process using high-g industrial centrifuges addresses most of drawbacks (listed above) and is suitable for processing hemp biomass on a larger scale. The typical flow-diagram below shows the primary components and their functions.
An industrial scale hemp biomass separation and solvent purification process is shown above. The 2 primary components and their function are described below.
#1. Decanter centrifuge for hemp biomass separation
A decanter centrifuge for hemp biomass separation is highly efficient at extracting maximum solvent. Exerting ~ 3000 g’s of centrifugal force, the hemp decanter can separate up-to 95% of dry hemp biomass from the solvent on a continuous basis. Details on the operation of hemp decanter are available on our decanter centrifuge page.
The operation can be briefly described as follows. The slurry of hemp biomass mixed with solvent is pumped from the agitated reactor tank to the decanter. The centrifugal force within the decanter bowl slings out the hemp solids towards the bowl shell wall. A stainless steel auger, rotating at a speed differential to the bowl, scrubs the solids towards the solids discharge ports to be slung out. The separated solvent flows towards the liquid discharge end and exits the decanter bowl.
#2. Disc stack centrifuge for hemp solvent dewaxing
Separated solvent from step #1 above carries over suspended plant matter (chlorophyll, waxes, lipids etc.) which are separated with through a high-g, vertical disc stack centrifuge in step #2. An Alfa Laval, self-cleaning disc centrifuge exerts up-to 10,000 g’s of centrifugal force on the solvent. Particles down to 0.5µ level can be separated at this level of centrifugal separator force. The relatively heavier suspended hemp particles are pushed towards the bowl periphery and the lighter solvent flows towards the bowl center. The accumulated solids are automatically ejected during the self-cleaning cycle of the centrifuge while the clean solvent continuously flows out of the centrifuge under pressure.
The main drawback of disc stack centrifuges is their inability to operate below 32F. This restriction is primarily due to the use of water to hydraulically operate the sludge ejection mechanism. But the substantially higher g-force makes up for this deficiency.
Industrial hemp centrifuge application offers efficient biomass separation for large scale hemp CBD oil extraction processing. Contact Dolphin Centrifuge for more details.