Week 5: Desiccant Experiments

Taara S -

Hello all, welcome back.

This week I was able to experiment with desiccant materials and graph their results. On Wednesday, I ran a 30-minute adsorption experiment with powdered zeolite once my vertical setup was done being modified. The moisture capacity of the powder, which is found by taking (the final weight – the initial weight / the initial weight) x 100, was only around 5%, while the capacity of the beaded zeolite using the master’s student setup was around 30-40%. I assumed this was due to the little time I was running the experiment, so for my next desiccant, I made sure the humidities of both chambers were in range of each other and that adsorption had actually been completed. 

Then, I tested moisture absorber beads I had purchased on Amazon. I kept them in the beaded form instead of crushing them. While running the adsorption experiment, all was going well in terms of the sensor readings, but once I opened the desiccant chamber to weigh the beads, there was fluid everywhere and the beads were all sticking together (pictured below). I decided to continue with desorption to see if the liquid could be removed, but after a little while, I noticed the setup looked like it was about to fall over and the fan sounded like it was about to die. I disassembled the two chambers and noticed that the plastic had shrunk/been melted by the heater.  

On Thursday, I then tested the same moisture absorber beads in the horizontal setup this time to see if it was my setup or the desiccant itself that was causing liquid to form. But after adsorption, the same thing occurred with the beads turning into liquid. I also discussed with my Professor what modifications needed to be made to the vertical setup. We purchased a new fan that could reach higher speeds and decided to only do adsorption experiments until we could integrate a better heater.

On Friday, after doing calibrating tests with the new fan in the vertical setup, I tested powdered zeolite at moderate humidity, and it worked really well! The sensors were still not super accurate, but I was able to complete adsorption and the capacity ended up being ~12%. 

On Monday, I then tested the powdered zeolite in the horizontal setup in order to make a comparison between the two setups. The adsorption capacity was 28% and the desorption capacity was 9%. Unfortunately, I tested moderate humidity (around 60%) in the vertical setup but tested high humidity (around 90%) in the horizontal setup, so the experiments were not scientifically comparable. 

On Tuesday, I wanted to test powdered silica gel in the vertical setup so I began by crushing the beads. This process was very laborious and many of the beads stayed intact. Once I finally got 10 grams, I began the experiment. But throughout, the bottom chamber humidity fluctuated significantly, possibly due to the humidifier tube, and my professor believed the powder particle size was too big/10 grams was too heavy and therefore could not properly fluidize.

Today, my plan is to retest the silica gel as well as test activated-alumina, so by tomorrow I will be able to compare the three desiccants against each other and determine which is most efficient in the vertical setup at moderate humidity.

Thanks for reading and stay tuned for next week!

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    Great problem solving, Taara! I know one of you research questions is about accessibility of materials and tools to perform AWC. Do you feel that you have had to augment the tools out there significantly to achieve your goals?
    Nice work! What is the duration of each experiment?
    Thank you, Ms. Bennett! Since the two setups were built from scratch by my professor, he used accessible materials that were around the lab or purchased off the internet. There's a lot of rubber, pipes, and plastic tubing used which are easy to find if someone were to build their own setup. But, when running calibration tests, I did find myself finding issues with parts of the setup so we did make changes such as buying a new fan off Amazon or adding more tubing to the humidifier. But overall the materials and tools used for the dehumidifiers are accessible and adaptable.
    Thank you! In the vertical setup, each experiment's duration really depends on how long adsorption takes, but because the sensors are not the most accurate, I usually run each experiment for a 110 minutes (20 minutes for the base condition and 90 minutes for adsorption).

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