Welcome to the Emerging World of Pass-through Distillation

Thank you for taking the time to visit this site. Its purpose is to make you aware of an energy-saving approach to distillation that may never have occurred to you. Although it is a fairly obvious combination of existing processes, it has not yet been put to widespread use. Its time has arrived.

WHAT IS IT GOOD FOR?

*Distillation at room temperature or below
*Low energy requirement

HOW DOES IT WORK?

Reduced to its essentials, distillation is a two-step process, evaporation and condensation. These two steps are “coupled” because they are carried out at the same pressure. The practical consequence is that low evaporator temperature requires an even lower condenser temperature, and that generally involves expensive refrigeration.

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Pass-through distillation is a four step process, similar to simple distillation in that it begins by evaporating some feed liquid and ends by condensing it. These steps however are decoupled by an absorption step (step 2) and a desorption step (step 3) which involve a recirculating inventory of absorbent fluid. In step 2 this fluid absorbs the gases evaporated in the first step. In step 3 the absorbed material is boiled out of the absorbent fluid.

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Decoupling permits the evaporator to operate at very low pressure (and a consequent low temperature) while the condenser operates at higher pressure (with consequent low cost cooling).

The four steps lend themselves to interesting heat economies. The absorption step runs at a higher temperature than the evaporator. This means that the heat released in the absorber may be used in the evaporator, permitting the first step to operate without an external energy source. The material absorbed by the absorption fluid must be boiled out in step 3 (desorption) through externally supplied heat. However if all the temperature sensitive material was left behind in step 1, step 3 may safely involve high temperatures, making it possible the use of low-energy multiple effect distillation (MED).

Please click here to play a 3 minute video that will acquaint you with the term “Pass-through distillation”. Then go to PTD 101 (a selection on the menu bar) to see companion videos that explain how PTD reduces energy costs and imparts other benefits, both direct and indirect.

Please visit the “About” tab to learn where the term and the concept originated, and the motivation behind the creation of this site.

Check out the “Commercialization” tab to meet the companies bringing PTD to the marketplace.

Some visitors to this site may have insights of their own they wish to share. If you happen to be one, please click the “Contact” tab and freely make your remark.