There are three ways of controlling reflux within a column still. These include Vapor Management Design (VM) , Liquid Management Design (LM) or Cooling Management Design (CM). You will conmanly see these as VM, LM, and CM which are abbreviations used to describe the type of management system used within the still. I’ve explained each system below and included an illustration to help you understand the difference between VM, LM and CM designs.
Liquid Management Reflux Still Design (LM)
This type of still design returns a portion of the condensate back to the column via a needle valve. By adjusting the valve you change reflux ratio’s within the column. An example of a still that use this design is the Bokakob shown below.
In the Bokakob design the vapor travels through the column past the copper plates (A) and hits the condenser (B). The distilled product falls onto the plates (A) at which point it either exits the reflux still via the needle valve (D) or drips back down over the packing in the column. By Adjusting the valve you can control the amount of reflux in the column. Hence why it is called a liquid management reflux still.
Vapor Management Reflux Still Design (VM)
A reflux still using vapor management uses a large gate valve (C) to control the vapor going to the reflux condenser (B) and the final product condenser (E) . The VP design allows for very fine adjustments of reflux within the still. An example of a Reflux still designed using the VM system is shown in the picture below.
Cooling Management Reflux Still Design ( CM)
A Still using cooling management design has a reflux condenser (A) before the take off port (B). This condenser is usually in the column of the still and reflux is controlled by a water valve (D) hence the “cooling management design”. (see illustration below) This type of design is difficult to fine tune reflux within the column . An example of this design is this CM reflux still plan.
If you’ve got any questions about the difference between the CM, VM and LM designs or are still confused drop me a line and I’ll do my best to help you.