Understanding Solvent Recovery Performance Metrics

Solvent Recovery Performance Terminology

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"Percent Solvent Recovered" vs "Percent Residual Solvent"​

When comparing solvent recovery equipment, it is critical for both client and manufacturer to be using the same terminology. Differences in terminology can be disastrous. One example of potentially confusing terminology is (%) Solvent Recovered, which is a commonly advertised specification among Falling Film Evaporator manufacturers.

(%) Solvent Recovered refers to the percentage of the total solvent that is recovered from the total ethanol in the starting solution. It is easy for equipment manufacturers to claim greater than 99% solvent recovered by using this metric, but it really doesn’t tell you anything about the solvent content of the extract after it goes through the recovery process. The metric looks outstanding at first glance, but potentially cause you to misunderstand your next processing step.

It is easy for equipment manufacturers to claim greater than 99% solvent recovered by using this metric, but it really doesn’t tell you anything about the solvent content of the extract after it goes through the recovery process.

An arguably more important metric is the (%) Residual Solvent that remains in the extract following recovery. The (%) Residual solvent really determines what your next processing step is.

Please see the example below. It shows how a falling film recovery system can simultaneously achieve the 99% Solvent Recovered metric, while still leaving 20% residual solvent behind in your extract. Ask potential manufacturer’s to state their systems performance in both terms to you.

**Please note that the term “miscella” refers to a mixture of extract and ethanol.

For Example

Solvent Recovered vs Residual Solvent Example

Example (Text)

Starting Miscella: 3% CBD, 97% ethanol, 1000 Lbs total miscella

Ending Miscella: 80% extract, 20% ethanol. 30 Lbs. of CBD, and 7.5 Lbs. of ethanol.

(%) Solvent Recovered: (962.5 Lbs / 970 Lbs) x 100% = 99.2%

(%) Residual Solvent: (7.5 Lbs / 37.5 Lbs) x 100% = 20%

Takeaway (Text)

20% Residual Solvent means that secondary processing in a rotary evaporator or Aptia VCO is required before wiped film distillation can occur.

99% Solvent Recovered does not accurately tell you what your next processing step needs to be.

At Aptia, we focus on providing our clients straightforward information that they need to make the best choices for their businesses.

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Published by Aptia Engineering on January 30, 2020

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