Peggy on Reflux Columns Distillation

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Reflux Operations

How a Reflux Still Produces Optimum Alcohol

Peggy Korth

 

Column: Column height and diameter are determined by the amount of anticipated vapor and desired flow to maximize the distillation process for a specified quantity of beer.  Beer is the fluid result of microbial and enzyme action on five and six carbon sugars that contains alcohol produced during the fermentation of sugars.

 

The distillation process is designed to separate water from alcohol within beer.  The percent of alcohol within any liquid is measured as ‘proof’.  Pure alcohol is measured as ‘200 Proof’ alcohol.  Therefore percent and proof are a multiple of 2. 

 

Achieving the desired alcohol ‘proof’ or percent-of-alcohol also influences column parameters.  When the beer is heated, hot vapors enter into the bottom of a distillation column passing through a selected condenser.  The selection of condensing materials depends on the amount of flow, desired alcohol proof, and cost containment for the project.  Condensing materials can be either packing material or a plate system.  Packing with marbles or copper scrubbers is common in small stills.  Larger stills use staggered plates which maximize surface area that comes in contact with the rising hot beer.  The beer vapor condenses when it comes in contact with the physical impediment causing a separation of the alcohol and water.  The heavier water rains back down into the bottom of the still. Packing in the lower section of the still is referred to as ‘a stripper’ because it strips water from the alcohol.

 

Heat re-evaporates the condensate leaving beer with a greater amount of water in the heated beer container.  Rising vapors continue to make a higher percentage of alcohol. Packing and plates allow the separated condensate to be redistilled.  Alcohol from a pot still does not use packing or plates.  In a reflux still the packing or plate portion of the still is referred to as a rectifier.

 

Reflux: Reflux in a physical action on the hot alcohol to cool the vapor and allow it to drip back into the lower level of beer.  Because the rectifier (scrubbers or plates) concentrates the alcohol or raises the proof as it travels up the column, the action of reflux ‘concentrates’ or raises the ‘proof’ of the alcohol.  Two conditions elevate alcohol proof:

  • Introducing cooling to the highest level of alcohol vapor
  • Allowing the vapor to fall back into the heated beer thereby creating reflux.

Achieving the highest level or desired level of condensation is known as ‘equilibrium’.

 

As the condensate within the column falls, the physical presence of the droplets removes water from the rising vapor due to the hydrophilic nature of the alcohol molecule.  However, heat allows the properties of the lighter alcohol to continue to rise above the water-laden droplets thereby concentrating the proof or percent-of-alcohol at the top of the still.

 

Temperature Control: Proper heating and valving control alcohol vapor.  To keep the alcohol at its highest percentage and lower the risk of water passing through the alcohol outlet at the top of the still, the heat is adjusted for ideal alcohol vapor production.  Proper valving controls temperature.  A valve adjusts the flow of rising vapor thereby controlling physical parameters of a still for size, construction materials, or internal design factors.  Using the exact boiling point of pure alcohol prevents water from passing or rising above the condensation point because water requires a higher boiling temperature.  A mixture of a lower-proof of alcohol has a greater water content.  The boiling point is related to the percent of alcohol and water.  Therefore, having the ideal temperature allows the highest concentration of alcohol to rise higher within the still.  The liquid with ‘higher water content’ will condense at a lower part of the still and fall down back into the beer. 

 

Temperature and flooding: Temperature is most critical at the highest point in the still.  Cooling causes alcohol vapor to condense first.  If a large quantity alcohol condenses due to a rapid lowering of temperature, the condensate overwhelms the system in mass and is referred to as flooding.   It is possible for the entire vapor content to condense with a temperature drop and will empty all the vapor within the column.  When this happens, distilling must start again.  Proper insulation assists in controlling temperature change.  Ideally, the temperature is kept constant when equilibrium is achieved.

 

Vocabulary

Column

Vapor

Proof

Flow

Beer

Microbe

Enzyme

Sugar

Alcohol

Condensation

Packing

Plates

Stripping

Reflux

Rectifier

Hydrophilic

Equilibrium

Valving

Boiling Point

2007 All Rights Reserved Peggy G. Korth