Distillation as it is practised in industry today has many variations. Within its playbook is a powerful technique called “Multiple Effect Distillation” (MED) that greatly reduces the amount of thermal energy expended per unit of product. It may also be conducted at very low absolute pressure (or, if you prefer, high vacuum) enabling the evaporator to operate at room temperature. Unfortunately, distillation as practised in industry today cannot employ both techniques simultaneously. The two are mutually exclusive. MED involves high temperatures in at least one evaporator. High vacuum distillation incurs extra energy costs to chill the condenser. Using conventional technology then, you may have EITHER low temperature OR low energy consumption but not both.
By contrast, pass-through distillation (PTD) uses the proven techniques of MED and high vacuum to provide BOTH room temperature evaporation and low energy consumption simultaneously.
What is the distinction between PTD and conventional distillation that enables this feat? In a word, decoupling. In conventional distillation equipment, the evaporator and the condenser are “coupled”. They are connected in a way that forces them to operate at or near the same pressure. They cannot be controlled or operated in an independent manner. In PTD however, the evaporator and the condenser are decoupled, providing an extra degree of freedom that permits independent operation.
Please watch this 5 minute explanatory video.
Pass-through Distillation (PTD) is useful because it delivers reduced energy use and lower operating temperatures when compared to conventional distillation.
The low energy consumption is due to the use of multiple effects, which is a well-established technique in playbook of conventional distillation. The low operating temperature is due to aggressive vacuum (low absolute pressure); once again, a well-known and often-used technique in conventional distillation.