Carbon Capture: Taking a Walk In the Wrong Direction

Aryana p -

For the beginning of my lab experience, I have unexpectedly found myself skipping to the last steps of the scientific method. Because I am traveling, I originally planned to simply perform calculations to prepare myself for experimentation and the creation of Carbon Capture membranes. However, I discovered that your environment truly does influence your work. Walking through Ahmedabad, India, diesel fumes pound all of my senses. I can see clouds shroud the night, feel and taste thick air in my lungs, and hear the fumes spilling from car engines. Surrounded by the problem my experiment aims to mitigate, I could not think about the geometry of filtration membranes. Instead, I set aside experimentation, and pondered the question: How will I imitate this heavy polluted air in our sterile labs, so that I can test the membranes?

My onsite advisor introduced me to a diagram making platform called Miro to answer this question.This is the platform where I conceptualized my originally vague notions of how membranes were tested in the laboratory. What was at first a blur of wires are winding tubes, became a clear, easy understandable diagram. In the process of making this diagram that is usually meant for readers like you to understand, I actually gained a deeper understanding myself, and I will now explain to you how membranes are filtered in the lab. 

From one gas tank, 20% carbon dioxide in N2 is pumped into the system to mimic the composition of air. This is the feed gas. Feed gases pump through one side of the membrane while sweep gases ‘sweep’ the permeated feed gas on the other side of the membrane, easing the flow through. In this case the sweep gas is pure N2. To mimic outside conditions, it is necessary to consider the humidity outside. Therefore, if testing humidity, the sweep gas will be moisturized with water by flowing through a chamber with water and vapor. The sweep gas(which may or may not be humidified depending on whether we are testing with humidity) will then flow to the rectangular prism-shaped membrane chamber. The feed gas goes through the top of the membrane chamber, while the sweep runs through the other side. The retentate—the bad stuff—flows from one side while the permeate the—good stuff—flows through the other. Both of these are tested in machines called IRGAs which are connected to a computer that can show the scientist the concentration of CO2 in their respective gases. 

What I have introduced is not the complete complexity of this system, but the rest will have to wait until the next blog when I learn more about the importance of vacuums to this system. As I contemplate these complex topics, I will also always remember to step outside of the lab, because maybe I will confront a new problem or an unexpected solution. Apparently, taking a walk really does have its benefits!

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    lydia_felice
    Interesting start! You make a great point about how explaining a difficult concept to a non-specialist audience can help us understand it better ourselves. I’ve used Miro as a teaching tool before, so I’m really interested to see the diagram that you created. I am also curious to learn more about how you will mimic pollution in the sterile lab environment. Keep up the good work!
    faiza_s
    Sounds fascinating! I'm curious on how you plan on taking into account variables like particulate matter or other pollutants in your lab simulations, given that real-world air pollution is more complex than just CO₂ and humidity?
    aryana_p
    Yes! I am so glad my on-site advisor introduced me to Miro. It really helped me understand what was originally just a mess of wires and pipes in this system. I'll be sure to include it in the future when I start membrane testing.
    aryana_p
    Thats a great question. Upon further research I discovered that the membrane polymers used in DAC can filter up to 40 other different air substances. However, this will not be a central part of my research. I plan on solely focusing on carbon dioxide, considering it is the largest pollutant as of now. I did briefly consider whether other large particulate matter could clog these filters, but I remembered a term called fouling. This is a build up of excess matter that clogs most membranes, so it is standard to replace these membranes after this happens. It could be interesting to see if I can research at which points in time the membranes begin to foul and become unusable.

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