chemical engineering

Medical Oxygen

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Emergency hospital during 1918 influenza epidemic, Camp Funston, Kansas. (CC-BY-2.5)

There are some questions about whether the SARS-CoV-2 virus is more or less deadly than the 1918 influenza virus. It’s not really possible to accurately compare the two pandemics’ case and fatality data, for one very big reason. Oxygen!

Today, when someone has any sort of respiratory problem the first likely action is to provide supplementary oxygen. The air we breathe contains about 21% oxygen, which for a healthy person is obviously quite adequate. But for sick people, raising the concentration to near 100% can take the load off their heart and lungs and help prevent other problems like organ failure.

In the 1918 pandemic, the use of supplemental oxygen was not widely known or accepted (as illustrated in the picture, where no one is getting oxygen). There had been some experimentation and use in prior decades (and in treating some chemical weapons victims of the First World War), but it was not yet widespread. Even if it had been enthusiastically embraced, the supplies of oxygen were very limited and it was not readily available on an industrial scale. Therefore we read stories of even young and previously healthy people succumbing to the influenza virus within hours, turning blue due to lack of oxygen in their bloodstream. If oxygen had been available, many of them may have had a reasonable chance to survive and recover. Of course, today we have many other pharmaceutical interventions like steroids and monoclonal antibodies, none of which were available in 1918. But the oxygen is still needed to keep the patient alive long enough so that the pharmaceuticals can have a chance at working.

Where do we get the medical oxygen? There are smaller scale purifying units that take air and concentrate the oxygen in it using membranes to separate the oxygen from nitrogen. These are fine for portable use, smaller scales, or lower flows, but they are not readily scalable to the huge volumes required in a hospital and high-flow oxygen therapy. Likewise, oxygen cylinders are not very practical in hospitals due to their limited capacity. For example, the large “T” size cylinders (about 24 cm diameter by 130 cm tall) only contain about 9,000 L of oxygen once it is depressurized. For patients needing high flow oxygen therapy at up to 60 L per minute, the cylinder would only last about 3 hours or less. If there are a lot of patients, it would take a small army of people constantly moving cylinders in and out of rooms and the hospital. Unfortunately, in poorer and less industrialized parts of the world these options are often the only ones available.

The big industrial oxygen supplies are typically provided in the form of liquid oxygen, shipped and stored in specialized trucks and tanks. The liquid oxygen stored at the hospital is then vapourized into its gaseous form and piped to the patient rooms as required. This is a much more compact and efficient delivery system, since one hundred litres of liquid oxygen expands into about 85,000 L of gaseous oxygen for breathing purposes.

The large scale production and supply of liquid oxygen is a chemical and mechanical engineering accomplishment dating back to the early 1900’s. It took several decades for many plants to be built, with continuous improvements over the years to improve the process and reduce energy requirements. The industrial process uses distillation to separate oxygen from nitrogen (and argon and other trace gases) in air. Since oxygen and nitrogen have quite different boiling points (-183oC for oxygen, and -195.8oC for nitrogen), separation by distillation is a reasonably straightforward approach. However, distillation requires that air be liquified through a combination of pressure and low temperature, and this presents some significant engineering challenges.

Modern plants, often called “Air Separation Units” or ASUs, operate at pressures up to about 6 atmospheres and temperatures in the -170 to -190 range. Clearly it takes some significant compression and refrigeration equipment to carry this out, and the plants are carefully designed to be as energy efficient as possible. The video below, from one major manufacturer, gives a simple overview of the ASU process. Of course, ASUs are built not only for medical oxygen, but also for the many other industrial uses of oxygen such as in steel production, metal cutting, water treatment and chemicals manufacturing.

Bibliography:
Graninge, C. Breath of life: the evolution of oxygen therapy. J.R. Soc. Med. 97: 489-493 (2004).
Heffner, J.E. The Story of Oxygen. Respiratory Care, 58: 18-31 (2013).
Tellier, N. Air Separation and Liquifaction. (https://cryogenicsociety.org/resources/cryo_central/air_separation_and_liquefaction/)

These companies are sucking carbon from the atmosphere

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Carbon capture is becoming increasingly popular among investors, and these companies are at the forefront.

Source: These companies are sucking carbon from the atmosphere

I’m currently not completely convinced that these “direct air capture” systems that remove carbon dioxide from the atmosphere are very practical. Technically they can certainly work, but the capital and operating costs are probably substantial, compared to the amount of CO2 you recover. However, if they do become widespread (as the linked article suggests), that will keep a lot of chemical engineers busy. And mechanical and electrical engineers too! And civil engineers during the construction phase.

We Don’t Teach Much

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“In this way you must understand how laughable it is to say, ‘Tell me what to do!’ What advice could I possibly give? No, a far better request is, ‘Train my mind to adapt to any circumstance’….In this way, if circumstances take you off script…you won’t be desperate for a new prompting.”

Epictetus, Discourses

I ran across this quote from the early 2nd century Stoic philosopher Epictetus the other day (“The Daily Stoic” by Ryan Holiday). It reminded me that in engineering education we can’t possibly teach all the information and facts that one might need after graduation. In chemical engineering, for example, there are thousands of different chemicals, types of equipment, different processes for making so many different products. There are different methods for various pharmaceuticals, papers, metals, solvents, plastics, toothpaste, and the list goes on without end. There is a 27 volume Encyclopedia of Chemical Technology that covers many topics in chemical engineering, but even that has its limitations, even if some superhuman could actually learn everything in it. Forty-five years after starting a chemical engineering program in university and I’m still learning new things every week.

So no, we can’t teach everything an engineer might eventually need to know. We probably can’t even teach a small fraction of what people will eventually know or need to use. So we have to focus on training the engineer’s mind. How to approach problems, how to break them down into logical and manageable pieces. How to understand the science behind new situations. How to recognize the limitations of their skills and knowledge, and how they can address those knowledge gaps (it’s important to know what you don’t know!).

So when students of all sorts ask “why do we have to learn this, when are we ever going to use it?”, the answer may well be “possibly never”. But it’s part of the training of the mind, which definitely will get used eventually.

mRNA Vaccine Production

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There aren’t very many positive things to say about a pandemic, but perhaps one positive outcome has been the successful advancement of mRNA vaccine technology. Although some people have the impression that this was very rapidly developed over the past year or so, the mRNA idea dates back to the late 1980s. It’s actually been undergoing development for 20+ years, although obviously the target wasn’t always the coronavirus. As a chemical engineer, I’m interested in the scale-up and production aspects, since that’s what we do best.

As a vaccine production method, the mRNA platform is exciting because it is so fast. Traditional vaccine production methods required the growth of batches of cells to produce the vaccine components. This cell growth is done in big tanks, sort of like beer brewing, but is typically slow. It may take many days or weeks to get one batch done. Some vaccines are still produced in chicken eggs (influenza) or cells grown in small “roller bottles” (measles). All of these are slow and difficult to scale-up to produce billions of doses.

The mRNA production method is not cell-growth based, it just uses a biochemical synthesis method. Here, you just mix a bunch of ingredients, add some enzymes to assemble the mRNA molecules, then enclose them in some nanoparticles. These nanoparticles are a key part of the product, and they serve a couple of key roles: 1) they protect the mRNA from degradation, since RNA is fairly unstable especially once injected into your arm; and 2) they provide the mechanism for the mRNA to get into your muscle cells where your body uses it to produce the “antigen” (the piece of virus protein that your body learns to recognize and fight, if you’re ever infected with the virus in the future).

This biochemical synthesis method can be done in a few hours, versus the days or weeks for the traditional vaccine manufacturing methods. There are still some purification and packaging steps involved which take some more time, but the overall process is still very fast in comparison to the older ones. The mRNA platform is very adaptable too, so the vaccine can be quickly modified if necessary, as the virus mutates, just by changing the “manufacturing template” (DNA plasmid) that assembles the mRNA molecules.

The Sartorius company (a science materials & equipment supplier) has produced a short video giving some information about mRNA vaccines and production, which is pretty good and not too technical.

Largest helium facility in Canada opens in Saskatchewan

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After writing a recent post about helium supply and demand, this news article came up about a new helium production facility in Canada. I wasn’t aware that it was under construction, but it’s nice to see some Canadian progress in securing supplies of this important resource. The photo shows some typical chemical engineering design elements like piperacks, process vessels, separators, compressors, etc. How to put together a process like this, in a safe, sustainable, and economical way, is one aspect of chemical engineering education.

Saskatchewan is now officially home to the largest helium purification facility in Canada after opening in Battle Creek on Tuesday.

Source: Largest helium facility in Canada opens in Saskatchewan | Globalnews.ca

Chemical Engineering 2021 Student Design Projects

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Photo by fauxels on Pexels.com

Each year, final-year students in Canadian engineering programs pursue open-ended group design projects (“capstone design projects”). This gives them the opportunity to combine the knowledge and skills obtained over the previous 3 academic years (plus work term experience for Waterloo students), and to tackle a problem that is a bit more challenging and wide-ranging than what a typical course assignment can cover.

Our Chemical Engineering class of 2021 has finished up their projects, and some short introductory videos are available for viewing. As usual, the projects are student-selected and they cover a wide range of topics from food processing to low carbon energy systems, reusable plastics to automotive parts manufacturing, and biotechnology to metallurgical processes. Allowing students to pick their own project topic let’s them tailor their experience to an area of interest, that perhaps they want to pursue after graduation.

Anyone interested in chemical engineering, or learning about the wide variety of things that chemical engineers can do, should have a look at some of the videos. They are each only about 1 minute long, give a brief high level overview, and can be found at this link.

What I’ve Learned About He

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Aside from being an English pronoun, He is the symbol for Helium, element #2 on the periodic table. The New York Times article discusses the uses and limitations around He supply, and is an interesting read. Over the last year, I’ve been on a PhD advisory committee for a student in Prof. Steven Young‘s group in the School of Environment, Enterprise and Development (SEED). His student is researching the “industrial ecology” of He, looking into where it comes from, how it’s used, and where the losses occur in the production, transportation and use. It’s quite an interesting issue, and I’ve learned a few things that might be of general interest.

  • We typically think of Helium use in balloons, or perhaps deep sea diving, but the major worldwide uses are in hospitals (for MRIs), specialized welding and manufacturing, and laboratories (for cryogenics or analytical equipment).
  • He is collected and purified from natural gas. It is produced during the radioactive decay of uranium in the earth, and collects in pockets of natural gas.
  • He is one of the few elements on earth that doesn’t have a “cycle”, like the carbon cycle or nitrogen cycle. That means, once it’s released into the air there is no natural way to get it back because it is so light and inert. It simply drifts away into the atmosphere and eventually leaves the planet.
  • He is so “light” (a small atom) that it is notoriously difficult to contain. It easily leaks and diffuses through materials, even solid metals. That’s why your balloon deflates after a couple of days, and why there are a lot of losses of He during transportation and use.

Since He is so important for some specialized applications, like MRIs, there are concerns that we need to conserve it. Also, since it is associated with natural gas, which we’re trying to scale back because of climate change, it may become more difficult to obtain. It occurs in the air at a concentration of about 5 ppm, so someday we may have to extract it from the air, like we already do with another related element, argon (Ar).

So Helium is kind of an interesting and important material. It involves chemical and mechanical engineering (for extraction, purification, and transportation), physics (for cryogenics, MRI and other applications), and industrial ecology (for understanding how it flows through our global economy, and what might happen in the future).

Microbiome Engineering

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A recent edition of “Chemical Engineering Progress” (a magazine from the American Institute for Chemical Engineers), has an interesting section on “Microbiome Engineering”, as illustrated on the cover. This subject nicely illustrates the diversity of directions that chemical engineers might find in a career path.

A microbiome is essentially a community of various types of microbes that live in an environment. Most of this section discusses the human gut microbiome, those trillions of bacteria that live in our bodies in the digestive tract. Apparently, of all the cells in a human body, about 57% of them are microbial (i.e. bacteria, yeast, etc.), and the rest are human cells.

The microbiome in the gut contains about 3,000 different microbial species. In recent years evidence has been mounting that these microbes play key roles in human nutrition, metabolic diseases (like diabetes), mood disorders, and immune system regulation and disorders. Recent information suggests that people with a poor gut microbiome may be more susceptible to COVID-19 infection and severe complications, for example. There is a lot still to be learned about what constitutes a “good” gut microbiome, and how to manipulate it to improve health.

Of particular interest to chemical engineers is the question of how to manufacture so-called “living biotherapeutic products” (LBPs) that could be implanted or swallowed to modify the gut microbiome and cure diseases. Most pharmaceuticals are either chemicals (single or mixtures) or inactivated (dead) parts of microbes or viruses (as used in vaccines). Producing a living product that can grow and thrive in the gut is a somewhat new challenge, especially if it needs to be a complex mixture of microbes.

Some of these engineering/manufacturing challenges would include issues like:

  • How to shield the manufacturing process and product from oxygen, since many of these gut microbes may be negatively affected by exposure to oxygen (so-called obligate anaerobes).
  • How to get the multiple species of microbes assembled into the LBP. Grow them all separately then mix? Some may grow better in the presence of other species, due to their complex nutritional requirements and symbiotic effects. Growing mixtures of microbes is much more difficult to control if they grow at different rates.
  • How to ensure the final LBP product is consistently the same every time it’s produced. The growth history of microbes can affect their final performance and capabilities, even if they are genetically the same. What we call “process control” in chemical engineering will be crucial to consistency of products.

This area of Living Biotherapeutic Products of quite a new one, although it has certain similarities to existing industrial processes like the production of baker’s yeast or Bifidobacteria for dairy starter cultures. As the medical science evolves and promising new therapeutics are identified, chemical engineers will definitely be involved in translating these developments into manufacturing processes that meet future needs.