Welcome to the hompage of Project NTP, a Senior Design project at Stevens Institute of Technology. The members of this group are all New York University/Stevens Institute of Technology Dual Degree students in the Chemical Engineering program, completing their degrees this year at Stevens. Our project's name is short for 'Non-Thermal Plasma', but that barely begins to describe what we are doing here in our Senior Design project.
Plasma is the fourth and least common material phase; while liquids, solids and gases all are easy to find in our everyday lives, plasma is quite rare indeed. Plasma is a high-energy gaseous phase where some outer shell electrons have escaped from their atoms and the two are present as gaseous positive ions and negative free electrons. Also present in plasma, though to a lesser degree, are gaseous free radicals with their dissociated electrons, and it is these free radical particles that are our interest in this project. Free radicals react quickly and easily with other atoms and molecules, meaning that the free radicals in plasma allow for some interesting reaction pathways.
Just because you've never seen plasma, per se, doesn't mean it isn't around you if you wish to go looking. When lightning strikes, you see a thin, spidery flash of light, but it is actually plasma: superheated gases present due to a strong electrical field. There's even an old They Might Be Giants ditty that everyone knows: "The sun is a mass of incandescent gas, a gigantic nuclear furnace... where hydrogen is turned into helium at a temperature of millions of degrees". And that, too, is plasma. It's the hardest of the material phases to find, and in many ways the most fleeting, but it is nonetheless all around us, from lightning strikes and the stars in the heavens, down to the neon sign on the Chinese take-out place around the corner.
Our project focuses on non-thermal plasma, which means quite simply 'plasma generated without heat'. Thermal plasma reaches its excited state due to high temperatures, at which point outer shell electrons have sufficient energy to escape, and plasma is formed. Non-thermal plasma simply means the excitation energy comes from some other source, be it an electrical field, bombardment with energetic photons, magnetic field pulses, or anything else that can creatively strip electrons from an atom or molecule. It's not exactly 'cold', because there is still a lot of energy to plasma generation and the plasma itself at least will be hotter than the temperature of its surroundings, usually by a margin of a few hundred degrees. But it's still 'non-thermal', since the energy for excitation isn't derived from heat, despite the fact that in both cases the temperatures involved will be quite a bit higher than room temperature. So we've talked about what we're using: low-temperature plasma with an external excitation source, most likely an electrical field (due to its simplicity compared to other options). And we've talked about why it's important: plasma is a powerfully reactive phase of matter, and specifically free radicals can lead to strong reactions.
What we haven't talked about is what we plan on doing with it, which is basically the rest of the project. To put it simply, we want to use plasma to generate hydrogen. A simple decomposition reaction, removing one or more hydrogen atoms from a methane molecule, was selected as our chosen reaction, and our expectation is that the hydrogen generated by our plasma decomposition reactor will be used to power hydrogen fuel cells. The project, then, is dedicated to making a functional plasma reactor to break down methane and other hydrogen-rich gases into their components, and harvest the hydrogen generated by the reactor for later use.
We've tried several different approaches to designing this reactor, and if you are really interested in our progress from one idea to another, feel free to look at our presentations from the first semester of Project NTP. These presentations show in some detail how we learned about plasma and designed our reactor from our growing knowledge both of how plasma works and how to construct a safe reactor vessel for the temperatures we expect to be working at. In chronological order, these presentations are:
Our final design for the project was a very interesting cylindrical reactor, making good use of both a thin electically-charged reaction volume and a constricted reactor volume. A thin reaction volume will lead to good plasma generation thanks to strong electrostatic effects working at all points in the reactor, which will help to strip or just excite electrons in the gases present. We also found that having a constriction before our reactor chamber increased the likelihood of plasma ignition, as turbulent effects led to a relatively high level of random motion and energetic molecular interactions... so our gas feeds into a large volume, which then constricts down across the separated plates for the reaction as the gas is pushed across the plates.
This chamber fits in very nicely with the rest of Professor Woo Y. Lee's CVD Labs at Stevens Institute of Technology, where we are partnered up with Prof. Lee's graduate students, who are working on much the same project as we are. The graduate students have beenresearching this plasma reactor problem for a good deal longer than we have and were an invaluable resource as we got up to our elbows in the project, either to pick their brains mercilessly or to help us in assembling a key component. The graduate students have been working on decomposing ammonia to harvest its hydrogen, with significant success. With a reactor design similar to our inital hourglass approach, the graduate students have found that a thin-walled glass reaction chamber with one of the two electrodes run through it works well at igniting plasma with their gas composition, and at several points around the thin reaction volume the second electrode is wound around the vessel, providing intense electrical stimulus at several points in the reactor. Our approach differs from theirs strictly because we wished to maintain an equal field for plasma generation during throughout the reactor volume, which makes it a good deal easier to calculate what should happen in the reactor.
Another key aspect of our project is verification: making sure that the nice pretty-looking gases in the reaction chamber are actually doing something. After the reaction chamber,we collect the gases for analysis, running the exiting gases through an automated sampler attached to a small gas chromatograph. With the use of the gas chromatograph we can either look for the products (hydrogen and decomposed methane by-products) or the reactant (methane) to see what level of reaction conversion we have obtained. There is a bit of difficulty involved in this, as the GS releases the gas at atmospheric pressure, and the reaction vessel may be working below atmospheric pressure depending on the initial conditions. After all, nothing is ever easy. With a bit of clever engineering it was suggested to us that we allow the product gases to build up in the containment loop of the GC, approaching atmospheric pressure, before we will be able to run the samples through the GC for analysis.
And no project would be complete without a sense of why we are doing it. This means that we need to have a full understanding of why we are doing this project, what its existence will accomplish, and what the ramifications of such a project will be. Firstly, we have a SEED model of a theoretical product, in-home plasma reformers to generate hydrogen as fuel for PEM-based hydrogen fuel cells, which are expected to enter the automotive market in significant numbers in the next three years. Click here to look at the economic analysis for this theoretical product, which suggests that even with a small market share of future automotive users there is potential for a niche market based on existing natural gas utilities.
Similarly, our environmental and economic analysis of the ramification of fuel cell technologies can be found here, in a paper we submitted to the Stevens Institute of Technology Technogenesis competition. All of this information combined nicely for our posterboard presentation at Stevens Institute's Design Day, the final presentation of our year's work on the problem on non-thermal plasma breakdown reactions. You may also find our final paper for this project here, which summarizes and presents our work over the past year far more thoroughly than this website would be able to do in a reasonable fashion.
To see our Links page, please click here.
