A close look at supercritical carbon dioxide CO2
TLDRIn this video, the creator showcases a homemade plastic chamber for holding liquid CO2 and explains its construction and function. Using an aluminum base with acrylic sides and a flexible fiberglass heater, the chamber can heat CO2 to a supercritical state, blending liquid and gas phases. The creator details the process, including pressure readings and design challenges, and demonstrates reversing the supercritical state using dry ice. Potential applications for supercritical CO2, such as decaffeinating coffee beans and dry cleaning, are also discussed. Suggestions for future experiments are welcomed.
Takeaways
- 🛠️ The presenter has built a plastic chamber from aluminum and acrylic to hold liquid CO2.
- 🔥 The chamber is designed to be heated slowly using a strip heater, typically used for bending acrylic or heating pipes.
- 📈 A pressure gauge is used to monitor the pressure inside the chamber, which initially reads about 700 PSI.
- 🔩 A thermacouple is inserted through a tiny drilled hole for more accurate temperature readings.
- 🌡️ The CO2 inside the chamber begins to boil when the heater is turned on, indicating a phase change.
- 🔁 After the boiling stops and the chamber is shaken, the liquid and gas phases of CO2 blend together, creating a supercritical state.
- ❄️ To transition back to two phases, dry ice is used to cool the chamber rapidly, separating the liquid and gas phases again.
- 🔧 The chamber was constructed by machining an aluminum disc, cutting an O-ring groove, and assembling it with acrylic parts and O-rings.
- 💡 The presenter encountered a problem with pressure building before the chamber could be sealed, which deformed the O-rings.
- 🧪 The chamber was designed to withstand much higher pressures, up to 2,000 to 4,000 PSI, even though supercritical CO2 occurs around 1,100 PSI.
- 🚀 The presenter plans to experiment with supercritical CO2 for applications such as decaffeinating green coffee beans and dry cleaning.
Q & A
What is the main purpose of the plastic chamber project described in the script?
-The main purpose of the plastic chamber project is to demonstrate the process of transitioning liquid CO2 to a supercritical state and then back to two distinct phases, using heating and cooling methods.
What materials were used to construct the chamber?
-The chamber is constructed from an aluminum piece with acrylic on the front and back.
What type of heater is used to heat the chamber?
-A strip heater, typically used for bending acrylic or heating pipes, is used to heat the chamber.
How is the liquid CO2 heated inside the chamber?
-The liquid CO2 is heated by wrapping the strip heater around the chamber.
What is the initial pressure reading on the pressure gauge before heating the CO2?
-The initial pressure reading on the pressure gauge is about 700 PSI.
What method was used to measure the temperature inside the chamber?
-A thermocouple was inserted through a tiny drilled hole to measure the temperature inside the chamber.
What happens when the CO2 reaches a supercritical state?
-When the CO2 reaches a supercritical state, the density between the liquid and gas phase becomes so similar that they blend together, forming one continuous phase.
How is the chamber cooled down to transition back from a supercritical state to two distinct phases?
-The chamber is cooled down by holding a piece of dry ice against the aluminum exterior to rapidly decrease the temperature.
What was the issue encountered when filling the chamber with liquid CO2?
-The issue encountered was the pressure build-up before the chamber could be sealed properly, which deformed the O-ring due to the high pressure during the sealing process.
What design considerations were made for the acrylic thickness in the chamber?
-Engineering formulas were used to determine the thickness of the acrylic, anticipating higher pressures up to 2,000 to 4,000 PSI.
What are some potential applications of supercritical CO2 mentioned in the script?
-Some potential applications of supercritical CO2 include extracting caffeine from green coffee beans and dry cleaning to remove oily substances without using water or hydrocarbon solvents.
Outlines
🔧 Building a Liquid CO2 Chamber
The video script introduces a DIY project involving the construction of a plastic chamber designed to hold liquid CO2. The creator uses aluminum and acrylic for the chamber's construction, incorporating a flexible fiberglass strip heater typically used for bending acrylic to heat the chamber slowly. The purpose of the heater is to increase the temperature, causing the liquid CO2 to boil and eventually reach a supercritical state where the distinction between liquid and gas phases disappears. The creator also mentions the use of a pressure gauge and a thermacouple for monitoring, and the process of transitioning the CO2 back to a two-phase state using dry ice. The video provides a step-by-step explanation of the chamber's assembly, including the challenges faced during the construction process.
🌡 Experimenting with Supercritical CO2
In the second paragraph, the script discusses the issues encountered with the CO2 chamber, specifically the absence of a valve which complicates the filling process and leads to high pressure before the chamber is sealed. The creator had to use engineering formulas to determine the necessary thickness of the acrylic to withstand anticipated pressures, but the actual pressure remained under 2,000 PSI, much lower than expected. The script also outlines safety precautions taken during the initial testing phase, such as setting up the chamber in a shop corner with remote monitoring. The creator expresses interest in using supercritical CO2 for extracting caffeine from green coffee beans and for dry cleaning purposes, highlighting the commercial potential of this technology. The video concludes with an invitation for viewers to suggest other applications for supercritical CO2.
Mindmap
Keywords
💡Plastic Chamber
💡Liquid CO2
💡Strip Heater
💡Thermocouple
💡Pressure Gauge
💡Supercritical Fluid
💡Dry Ice
💡Acrylic
💡O-Ring
💡Decaffeination
💡Dry Cleaning
Highlights
Introduction of a homemade plastic chamber designed to hold liquid CO2.
Demonstration of the chamber's functionality with a strip heater for controlled heating.
Use of a flexible fiberglass covered heater typically used for bending acrylic.
The chamber is made from aluminum with acrylic front and back, designed for slow heating.
Installation of a pressure gauge to monitor the CO2 inside the chamber.
Drilling a hole for a thermacouple to get more accurate temperature readings.
Observation of CO2 boiling within the chamber as heat is applied.
Transition of CO2 from liquid to gas phase and the disappearance of the dividing line between the two.
Shaking the chamber results in a uniform phase of supercritical CO2.
Unplugging the heater to allow the cloudiness within the chamber to subside.
Using dry ice to rapidly decrease the temperature and revert CO2 back to two phases.
Description of the chamber's construction process, including machining aluminum and acrylic parts.
Challenge of filling the chamber without a valve, leading to high pressure deformation of the O-ring.
Design considerations for the thickness of acrylic based on engineering formulas and anticipated pressures.
Safety measures taken by setting up the chamber in a shop corner with a camera for remote monitoring.
Experimentation with supercritical CO2 to potentially extract caffeine from green coffee beans.
Discussion of commercial uses of supercritical CO2, such as decaffeination and dry cleaning.
Invitation for suggestions on other potential uses for supercritical CO2.
Closing remarks and sign-off for the video.
Transcripts
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