The origin of the first alcohol produced still is a matter of debate. Whether the first apparatus considered a still was the tribikos of Ancient Greece (a kind of alembic with three arms that was used to obtain substances purified by distillation), or Abu Musa Jabir ibn Hayyan’s alembic, they sought the same end-product.
Alcohol refinement that started as a niche branch of alchemy would readily become commonplace across almost all cultures. The process used is relatively simple in nature and involves the heating of a mixture containing Ethanol (EtOH) to the point that it vaporizes and then condensing it on a cooler section of an apparatus for the purpose of purifying it. This purified alcohol could be used for a myriad of purposes, namely botanical extraction or in our case, flower or hemp extraction.
Within the industry, a step common to all solvent extractions on their way to a fully refined distillate is one in which the crude oil is dissolved in ethanol. Whether this tincture be the direct result of an extraction or the product of a winterization methodology, the task of removing the solvent and re-concentrating the crude oil is ubiquitous.
Ethanol is liquid at room temperature and boils at a temperature of 78°C. The dipole moment exhibited by the stereochemistry of Ethanol also makes it relatively difficult to squeeze out of a tincture unless considerable heat and agitation are used. Unless, that is, the pressure within the system is decreased enough so that the boiling point of ethanol is lowered to the point that it was more readily evaporated.
A tool synonymous with the biomass lab space is the rotary evaporator, and it was designed as a rudimentary evaporating solution that took advantage of these concepts to efficiently distill off solvents.
In operation, the tincture is heated and agitated along the inner surface area of a glass vessel at it rotates on an angled axis at vacuum. This vessel sits in a heat-controlled water bath that is dialled in to the temperature at which the target compound boils at a specified pressure. Along the vapor path is placed a hollow condensing coil through which chilling fluid is run at a subfreezing temperature that liquefies the solvent as it is pulled toward the vapor path to the pump.
At the base of this condenser is a collection flask that can be isolated and emptied periodically to obtain the reclaimed solvent. This technology proved effective while it was used to reclaim solvent from smaller batches of tincture. However, the extraction technology quickly caught up to the limitations of this system as the volume of tincture capable of being extracted at once rose dramatically. Between emptying each vessel after each batch as well as the cleaning of the glassware for the purposes of compliance, rotary evaporation falls short of what is needed in a production setting.
It was only a matter of time before industrial falling film evaporators started showing up in the labs of processors who were “in the know”. This is arrangement is a semi-continuous, very rugged, and reliable solvent recovery platform. In its operation, the tincture is syphoned into a closed system at low pressure. A flowmeter regulates the rate at which the tincture is shotgun fed onto a heated evaporator column down which it flows in a laminar fashion. This thin film distribution of the tincture allows for very efficient exposure of the solvent to the heat from the column. Gravity pulls the concentrated oil down the column and into a collection column below.
As the solvent and some residual crude oil are turned to vapor, they travel along the vapor path to another shorter column and must travel against gravity toward the heat exchangers.
Any residual moisture or crude oil that managed to make it through to the secondary column is separated there due to their having greater molecular weights than Ethanol. The distilled Ethanol is then re-condensed along the heat exchanges before being delivered back as reproofed solvent.
It remains to be noted that when a throughput capacity calls for this volume of solvent to be on a manufacturing floor at one time, safety in the lab must be called into question.
Falling film evaporators are capable of processing upwards of 60 gallons per hour of tincture, requiring quantities of solvent on hand that any fire marshal would want to have a word about. As such, a facility must be equipped to allow for safe operation of the machinery in compliance with Class 1 Division 2 certification as per NEC article 500 through 503/CEC section 18.
This is simply a classification system indicating a hazardous work environment as Ethanol vapor is flammable and long-term exposure can be neurotoxic. There is no end to the safety measures that can be taken, but there are some that key features that will make happy your governing agencies and operators alike.
Most notably, explosion proof fittings must be adopted throughout the workspace in which solvent above a certain quantity will be present. Sniffers to detect the levels of ethanol in the air, and fire suppression are also givens in a compliant facility. With all the proper precautions having been taken, a safe, high throughput is an achievable feat.