Dolphin Centrifuge

Hemp Solvent Biomass Separator | Alfa Laval Decanter Centrifuge

Table of Contents

What is a Hemp Biomass Solvent Separator?

A hemp biomass separator is a piece of primary equipment in the solvent extraction process for CBD oil production. Its purpose is to separate the solvent liquid from the hemp biomass. This separation step is after the absorption of CBD oil into the solvent.

Different Types of Hemp Biomass Separators

There are 2 types of hemp biomass and solvent separators. Read our detailed article explaining the technical differences between ethanol extraction centrifuges.

Basket Centrifuge

Basket Centrifuge for Ethanol Extraction
Basket Centrifuge for Ethanol Extraction

This centrifuge is like an industrial washing machine. The ‘basket’ refers to a perforated container that spins inside a stationary vessel.

Decanter Centrifuge

Decanter Centrifuge for Ethanol Extraction
Decanter Centrifuge for Ethanol Extraction

A decanter is an industrial bowl centrifuge. In a decanter centrifuge, the rotating bowl has a built-in scroll. This scroll rotates at a differential speed compared to the bowl. The scroll scrapes the solids collected at the bowl wall and ejects them.

Large Volume Hemp Centrifuge - Explosion Proof
Large Volume Hemp Centrifuge - Explosion Proof - 40 GPM

Petroleum, wastewater, chemical, and other industries use decanter centrifuges. Their primary application is large-scale continuous solid/liquid separation.

How do Centrifugal Biomass Solvent Separators Work?

Centrifugal biomass separators separate biomass and solvent using centrifugal force. The high centrifugal force generated by the centrifuge separates the 2 phases.

The 2 types of solvent biomass separators work in different ways. The description below delves into their respective operations. It also highlights the pros and cons of each centrifuge.

Operation of a ‘basket type’ centrifuge in hemp biomass separation

Ethanol Extraction Basket Centrifuge Cross Section
Ethanol Extraction Basket Centrifuge Cross Section

The producer packs pulverized dried hemp plant stock in a mesh bag. This ‘soak bag’ is then placed in the ‘spinner’ basket of the centrifuge.

Next, the user adds their solvent of choice into the centrifuge. Rotation of the basket stirs the solvent and hemp biomass. The solvent extracts CBD oil from the hemp biomass in a predetermined mixing time. Absorption time depends on the solvent used.

The soak bag is then spun at about 1000 RPM (< 1000 g’s) to separate the solvent from the biomass. The operator then drains the solvent from the centrifuge vessel.

Operation of a decanter centrifuge in hemp biomass separation

Alfa Laval Decanter NX-416 Stainless Steel Class 1 Div 2
Alfa Laval Decanter NX-416 Stainless Steel Class 1 Div 2

A decanter centrifuge uses the centrifugal force differently for hemp biomass separation.

In this process, the producer mixes hemp biomass and solvent in a reactor. The reactor vessel has mechanical agitation. During a predetermined reaction time, the solvent extracts the CBD Oil from the hemp.

The operator then pumps this biomass and solvent slurry into the decanter centrifuge.

A decanter centrifuge generates over 3,000 g’s of centrifugal force. This force slings the heavier hemp biomass towards the bowl wall. The biomass collects at the rotating bowl wall.

An auger rotates at a differential speed inside the bowl. It pushes the solids towards the solids' discharge end. The lighter solvent stays above the separated biomass. This liquid phase flows towards the liquid end. The solvent then comes out of the other end of the centrifuge.

Comparison of Centrifugal Biomass Separators

Biomass Dryness Vs Ethanol Residence Time
Biomass Dryness Vs Ethanol Residence Time

A ‘Basket type’ or 'Washing Machine' type 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.

  • The batch process is not easily adaptable for higher volume, continuous production.
  • Incomplete mixing of solvent due to the insufficient movement of a 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 downstream 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 long process time.  Finer mesh bags also limit bag reuse. Coarser mesh bags allow more particles in the separated solvent, leading to more filter resources downstream with associated costs and labor.

An industrial-scale hemp biomass separation and purification process using high-g industrial centrifuges addresses most of the drawbacks (listed above) and is suitable for processing hemp biomass on a larger scale. 

Read about our "Comparison of Biomass Ethanol Centrifuges - Technical Comparison"

Where does a Centrifugal Biomass Solvent Separator Fit into Hemp CBD Oil Processing?

The typical flow diagram below shows a recommended hemp CBD Oil recovery system setup. This system uses industrial centrifuges as the main separation equipment.

Hemp Biomass Solvent Separation System  – Flow Diagram

Hemp Biomass Separation Flow Diagram

Technical Considerations in Biomass Solvent Separation Equipment

Working with solvents required special considerations. This includes:

  • Electrical Classification (C1D2 etc.)
  • Material of Construction (Food-Grade, Stainless Steel)
  • Elastomers in Fluid Contact Areas (Viton, EPDM, etc.)
  • Equipment Adaptation (No Heat or Sparks)
  • Additional Safety Devices

Dolphin Centrifuge has the experience and technical expertise to execute engineered systems for such classified equipment.

Capabilities of Decanter Biomass Separator

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 continuously. Details on the operation of the hemp decanter are available on our decanter centrifuge page.

For more information, please visit  Centrifuge applications in hemp CBD oil extraction.

To know more about us - visit our About Us page.

by Sanjay Prabhu MSME
Engineering Manager, Dolphin Centrifuge


To get more details email us or call us at (248) 522-2573

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