Climate Change Techno-Activist

Life on earth is threatened by greenhouse gas accumulation in the atmosphere. Climate scientists have been sounding this alarm for many years. In 2015, representatives of  196 countries met in Paris and pledged to take abatement measures. But the targets set are not close to being met.  Environmental groups are urging people to become activists to save the planet. Generally, what is meant by that term is a person who strives to achieve a certain outcome by attempting to influence governments to do this and ban that. There is no doubt that that kind of activism is needed.

I invite you to become a different kind of activist; one that actively promotes technologies that can help solve the problem. Be a Climate Change Techno-Activist. There is no better place to start than by promoting Pass-through Distillation (PTD).

Industrial processes use one-third of all the world’s energy. Distillation accounts for one third of that or roughly 10% of all the energy used for any purpose. It all comes from steam generated in boilers burning fossil fuels. In many applications, PTD can replace conventional distillation using much less energy. This by itself is sufficient reason to to promote it.

But PTD has an even more powerful GHG reduction lever.

The International Energy Agency (IEA) has modelling software that can predict global temperature rise under various assumptions. They have discovered a few scenarios under which disaster is averted. All of these scenarios include liquid transportation fuel made from biomass. This elevates cellulosic ethanol from the status of “failed commercial experiment”  to “existential imperative”.

But cellulosic ethanol needs an economic breakthrough if it is to proliferate. That breakthrough could be a production technique known in some quarters as “CARAF”, which stands for Concurrent Alcohol Removal And Fermentation. Since the 1970′s this technique has been shown in laboratories to bring about remarkable benefits which, if implemented at plant scale, would bring about large improvements both in capital costs and operating costs. But removal of ethanol from a fermentation broth demands a low temperature separation technique. Conventional distillation is a hot process that kills the microbes that carry out fermentation. The removal techniques used in the lab are not feasible at commercial scale. And so despite its promise, CARAF has not yet been implemented in a commercial ethanol plant.

Pass-through distillation is a scalable separation technology that operates at low enough temperatures to keep yeast alive and well. This fact has recently been demonstrated experimentally at Lambton College in Sarnia Canada.

So Cellulosic Ethanol saves the world, CARAF saves the cellulosic ethanol industry and PTD enables CARAF to work. That’s the essence of the story. Explore this website to learn the details. Hopefully you will become a techno-activist and do what you can to promote the dissemination of knowledge about PTD.


Aspen Plus Modelling for PTD

Process modelling tools such as Aspen Plus are indispensable in developing new unit operations like PTD and predicting how they will perform in the context of a chemical plant.

In 2016 Hayley Hayden Smestad wrote her Chemical Engineering Master’s thesis at Worcester Polytechnic Institute on the topic of applying PTD to ethanol/water separation.

She concluded  “Aspen Plus V8.8 was used for the determination of parameters to use with the eNRTL­RK property method to accurately model the mixed solvent electrolyte system of ethanol, water and lithium bromide. These parameters can be implemented for a variety of applications especially the pass­through distillation application considered here. The accurate modeling of the ternary system was critical to the development of a foundation for the modeling of pass­through distillation with the specific application of separating bioethanol from a fermentation broth using a combination of evaporation, absorption, stripping and condensing to provide a low pressure, low temperature separation that does not damage temperature sensitive components present in a fermentation broth while at the same time minimizing energy required to achieve the separation. The simulation developed in Aspen Plus V8.8 to model this system will prove useful for future studies, as a teaching tool for how the process works, as well as a platform to test out variations in the system quickly with little associated risk”

There are presently efforts underway at two Universities to extend PTD Aspen modelling.


Institution: McMaster University,   Hamilton, Ontario Canada

Title:  Aspen Plus Modelling of Generation 1 and 2 Biofuel Plants Equipped with Pass-through Distillation

The Team:  Danilo Salas Ramirez, Zicong Zou, ViVek Patel, and Salim Kairulla.

Supervisor:  Professor Amin Rajabzadeh


Manchester U logo

Institution: The University of Manchester, Manchester UK

Title:   Modelling of the In Situ Separation of Ethanol from a Fermentation Broth Using     Pass-Through Distillation

Student: Scott Bromley

Supervisor: Prof. Anton Kiss



Pass-through Distillation Pilot Plant

In 2014 two Canadian Companies collaborated to test Pass-through distillation experimentally.

One of the companies,Fielding Chemical Technologies Inc., is Canada’s foremost chemical recycler. Fielding wanted to learn through the pilot plant whether or not PTD could offer advanced treatment of hazardous industrial waste.

The other company, Drystill Holdings Inc., is a start-up technology company that has invented and patented equipment specifically for PTD, including the Stripper/Absorber Module (SAM) described in the fifth and sixth lectures of PTD 101. The pilot plant featured a mid-sized SAM capable of boiling 50 Kg of water per hour.

The pilot plant operated successfully for many months before being dismantled to make way for another project. For Drystill it furnished proof of concept for their proprietary technology. Fielding learned that the technology may be applied to the processing of industrial wastes, but has decided not to implement it for the time being.

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This is a picture of Drystill’s prototype SAM. It contains 100 heat pipes 25 mm in diameter and 550 mm in length.


Here is the same SAM installed on Fielding’s pilot plant framework.

Click here to see a video of SAM at work.

Click on the logos below to learn more about Fielding and Drystill.



About PTD

There are only so many unit operations known to chemical engineers, so it seems safe to say that every conceivable pair of them has been considered and, where appropriate, tested out in lab or plant. Some pairs exhibit such useful synergies that the combination becomes a unit operation in its own right, and it acquires a name of its own; witness evaporation + condensation = distillation.

I have searched the literature for references to current and previous attempts to combine evaporation and absorption. So far I have come up almost empty-handed. Yet this combination can provide low temperature distillations with half the energy used by current industrial practice. Has something been overlooked? As a community of professionals serving the world’s chemical engineering needs, we ought to talk.

To facilitate discussion, I have given combination of evaporation and gas absorption a name: “Pass-through distillation” and created this web site to serve as a clearing house for information on the topic. It is intended for the benefit of engineers and scientists in academia and industry world-wide.

If this field of enquiry ultimately generates wealth, some of it may rub off on Drystill and I will openly accept my share. In the meantime my activities relative to this web site will be directed toward shedding light on a topic that may benefit our planet.

Ian McGregor P. Eng.


Pass-through Distillation voted Project of the Year

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Keynote Address for PEO Gala

Good evening Ladies and Gentlemen. It is a great honour to address you tonight on behalf of Drystill, this year’s project of the year winner in the small company category. I would like to tell you our story. It is a story of how a very small Canadian company is making a big impact on world-scale problems. Removal of ethanol from watery mixtures, like fermentation broth, is an important industrial activity. Drystill has invented a device it claims can do a better job than conventional equipment. With funding assistance from NSERC, Drystill teamed up with Sheridan College to build and test a bench scale prototype under rigorous academic supervision. The testing validated Drystill’s claims. That is the project in a nutshell. Although it may not sound remarkable, I think you will be astonished by its significance to the world in general – and to Canada in particular. The removal of ethanol from watery mixtures is only one of thousands of tasks carried out every day by the process known as distillation. Although many people associate the term mainly with whiskey and other alcoholic beverages, distillation is in fact an industrial workhorse, touching almost everything we eat, wear and use. It is also a very old technology, used by the early Egyptians to prepare fragrances and medicines. Simplicity is its main virtue: You simply boil a liquid then cool the vapours to turn them back into a liquid.  Although mankind has become a lot smarter about the science behind distillation, the same ancient process is still in extensive use all over the world. Distillation, however, it has two serious drawbacks: Its enormous use of energy is costly both in financial and environmental terms, and its hot operating temperature is troublesome in some important applications. Drystill, in contrast, champions an alternative process called Pass-through Distillation. It enables economical low temperature distillation, reducing boiling temperatures down to 30 degrees Celsius while simultaneously reducing energy use by 50%. The Pass-through distillation process is in the public domain. It is not patentable because it is an obvious combination of well-known scientific principles. But it has never been implemented industrially for want of a suitable heat and mass transfer device with which to carry it out. Drystill has met that need with its invention of the SAM: an acronym for Stripper/Absorption Module. The SAM has patents granted or pending internationally. In industrial settings, distillation is not powered by renewable sources like wind or solar energy. It is powered by steam, generated by burning fossil fuels in a steam boiler. This means that where pass-through distillation displaces conventional distillation, the same results are achieved by burning half the fuel. The signing of the Paris Agreement last April marks the beginning of world-wide deliberate action against Global Warming. Each signatory country, including Canada, has pledged to cut back on the combustion of fuels to halt the progressive build-up of carbon dioxide in the atmosphere. No single measure will accomplish it. Some measures will be easy to bear – but others will be very painful. It will be painful to curtail our vacation travelling. It will be painful to have to cut back the thermostats of our domestic furnaces. But if manufacturers were to replace their conventional distillation equipment with Drystill equipment, the only pain would be its capital cost. That pain however would be offset by a fast payback due to reduced fuel costs. Government incentives could make that payback very rapid indeed. Once the investment has paid for itself, it will continue to save fuel costs for years to come. As countries around the world get serious about living up to their commitment to burn less fuel, this is the kind of measure that is going to be sought. It doesn’t affect anyone in a negative way. It is low hanging fruit in the quest for greenhouse gas reduction. But can Pass-through distillation be applied widely enough to make a significant impact on the global warming problem? Many people are surprised to learn just how much of our global energy budget is devoted to distillation. This pie chart, representing data from the US Energy Information Administration shows that 32% of all energy is used by industry. A third of that goes in to distillation! This is a whopping 9% of all energy used in the United States for any purpose. Pass-through distillation can cut that down significantly. It is applicable in many industries including food and beverage, pharmaceuticals, pulp and paper, specialty chemicals, wastewater treatment and others. It is reasonable therefore to say that Drystill’s technology is an attractive greenhouse gas control measure in the context of the current industrial environment. But industry itself is undergoing enormous changes. While coal, crude oil, and natural gas remain the dominant source of both energy and chemical feedstocks, there is a movement toward renewable sources such as agricultural crops and harvested biomass. Already in North America 10% of the fuel we burn in our cars is corn ethanol. Efforts have been underway for at least two decades to make ethanol economically from straw, wood chips, corn cobs and other waste biomass. When that effort finally succeeds, the world’s dependency on fossil fuels for transportation will be broken, and we will be well on our way to defeating the global warming menace permanently. Unfortunately there remain serious economic problems with the production of cellulosic ethanol. Many studies have shown that low temperature distillation enhances economics by keeping microorganisms alive and preventing destruction of expensive enzymes. Researchers have demonstrated this at lab scale but low temperature distillation through conventional means is not feasible at plant scale. A breakthrough technology is needed, and Drystill believes that pass-through distillation is the answer. The success of the cellulosic ethanol industry and victory over global warming may hinge on one question: Can pass-through distillation remove ethanol from a fermentation broth at a temperature of 30 degrees C? Here’s a news flash for you: Drystill and Sheridan College just tested it using a Drystill SAM. IT WORKED . For the good of our planet, this technology needs to be tested at demonstration plant scale as soon as possible. Since it is a Canadian invention, I am hopeful that a way will be found to do this testing in Canada, and that Canada will reap economic benefits by becoming the purveyor of pass-through distillation technology to biorefineries all over the world.

Akzo Nobel Announces Finalists in Imagine Chemistry Competition


Akzo Nobel logo


Developed in conjunction with KPMG, Imagine Chemistry was launched to help solve real-life chemistry-related challenges and uncover sustainable opportunities for AkzoNobel’s Specialty Chemicals businesses.

From January to March 2017, participants could submit solutions through a dedicated online challenge platform (The platform is now closed for submissions for 2017). Special challenge teams comprised of subject matter experts worked with participants through the platform to enrich and validate their solutions and determine if they are a good fit for AkzoNobel’s business.

An enthusiastic response resulted in more than 200 innovative ideas being submitted by chemistry start-ups, scientists, research groups and students around the world.

A jury made up of AkzoNobel business and R&D leaders and prominent international experts then selected the most promising ideas as finalists. This year’s finals will take place at AkzoNobel’s RD&I Center in Deventer, the Netherlands, from June 1-3, 2017.

Drystill is one of 20 finalists that will be participating at the event. Here is an excerpt from Akzo’s website, in which they describe Drystill’s submission:

“Pass-through distillation for wastewater

Steve Furlong, Drystill, Mississauga, Ontario, Canada

Challenge area: Wastewater-free chemical sites


Drystill is innovating thermal evaporation technology with its Stripping Absorption Module (SAM), a pioneering heat and mass transfer device.SAM can remove water from almost any stream or water source without heating it or putting it in contact with a drying material.


Conventional thermal evaporation of industrial waste has a high carbon footprint and costs. SAM offers a practical, low cost, low carbon solution that leads to wastewater-free chemical sites. This is achieved by dewatering effluent to produce clean, reusable water and high caloric-value/low-volume liquid residue.


Water vapor is transported to a compartment containing hygroscopic salt solution, which is then dewatered using conventional methods. SAM consumes no external heat or power: evaporation is caused by the exothermic absorption of the effluent vapors into a flow of concentrated brine (such as LiBr).

Pass-through Distillation, Drystill Chosen by Akzo Nobel

This year Akzo Nobel launched the first global innovation challenge for startups in chemistry. Through a competition called “Imagine Chemistry” Akzo is trying to accelerate the commercialization of important new ideas from around the world. On April 5, 2017 Program Manager Rinske van Heiningen announced that Drystill has been selected as one of ten finalists. She wrote:“We received over 200 submissions for more sustainable chemistry, which we have carefully reviewed with our team of researchers. We believe your solution ‘Drystill & Pass-through distillation: Improving the operating costs and carbon footprint of waste water concentration’ holds great potential and we are honoured to invite you to the finals, taking place in Deventer, The Netherlands from 1-3 June 2017. At the event, we will work together to further build on your idea during the workshops.

During the three-day event you will get personal feedback from our experts and AkzoNobel decision makers. The team will consist of senior level management, such as chief procurement officers, finance directors, operations managers, sales & marketing directors, R&D directors, etc. The composition of the team may vary depending on the phase and specifics of your startup. With this feedback, as well as the challenges/hurdles you perceive yourself, you will work in small teams over several rounds to further develop your concept.

Pass-through Distillation testing at Sheridan College

Sheridan College and Drystill Technologies are collaborating on a project to test pass-through distillation at lab scale, assisted by funding from NSERC.

The project formally commenced on May 30, 2016 and will operate until the end of the year. Many important industrial separations will be tested using room temperature pass-through distillation, including:

*separation of ethanol from fermentation broth

*separation of essential oils from aqueous slurry

*removal of water from corn ethanol plant syrup

*separation of butanol from fermentation broth

The SAM comprises 20 heat pipes 28 cm in length by12mm  in diameter, arranged vertically in a single column. It is capable of boiling 2.3 kg/hr of water. Drystill has built other SAMs in the past, but this one breaks new ground in that it includes an external stripping column between the evaporation and absorption chambers. Another new feature is mechanical distribution devices that permit even distribution of liquids over the heat pipes at extremely low flow rates.

The video below was taken on Aug 12, 2016 when the assembly of the apparatus was nearly complete and was being tested for leak tightness.


Drystill explains its version of Pass-through Distillation

Pass-through Distillation (PTD) is a powerful public domain concept, but to date its only commercial champion is the Canadian company Drystill.  Drystill’s contribution to the field is a proprietary piece of equipment called a SAM, which combines the first two process steps into a compact and efficient unit. When PTD is carried out using a SAM, the process is given a Drystill tradename,  TIEGA. This video is something of a Drystill infomercial,

Definition of Pass-through Distillation

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.



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.


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.