The Process and Technologies behind Plasma Gasification
March 29, 2010
thinkgreen.com
If you follow news about alternative fuels or green energy, you've probably run across the term "gasification" a time or two. For most of us, it's kind of a fuzzy, foreign concept that involves taking waste material and converting it into a fuel known as synthesis gas, or "syngas" for short. This fuel or syngas can be used to power generators, vehicles, or even power plants.
In the past, gasification focused on converting one particular waste stream, be it coal or corn, into a usable fuel. Now, this exciting new technology is reaching a point where possibly everything in your trashcan could be converted into clean energy or other environmentally beneficial products.
It's called plasma gasification, and this breaking development in the field of waste-to-energy technology could really help put a dent in society's sustainability problem.
Experts like Waste Management's Managing Director for Organic Growth Joe Vaillancourt and InEnTec's CEO Jeff Surma are currently working to get the word out about plasma gasification and bring this next generation technology into the mainstream. Without a doubt, the most promising form of this technology is InEnTec's Plasma Enhanced Melter, or PEM for short.
Why is Plasma Gasification a Game Changer?
In short, PEM technology takes gasification to the next level, because it holds promise to process a diverse range of materials, like municipal waste, into clean syngas and do it rather efficiently.
Older gasification methods have focused on "feedstocks" like coal and biomass to produce an alternative fuel, yet they failed to address the bigger question of 'what do we do with society's trash?' Often, activists slammed these gasifiers as "incinerators in disguise," on account of their limited feedstocks and more primitive thermal gasification methods (often not carbon-conscious).
With the development of the PEM, however, gasification technology has progressed to the point of being considered a source of green energy. Because of its ability to process heterogeneous waste streams, some enthusiasts go so far as to call plasma-assisted gasification 'the ultimate form of recycling.' Though, as Joe Vaillancourt points out, "Gasification is not a technology that replaces or is better than existing recycling programs… it can process many waste streams that today are not able to be recycled."
There are a number of forms of waste gasification being actively marketed including plasma arc gasification; plasma torch gasification; pyrolysis; and combined pyrolysis-gasification systems. Gasification systems incorporating plasma torches have been under development for many years and there are a number of these systems being marketed as waste gasification alternatives, but according to Surma, "there aren't really any similar technologies in use." The PEM is changing the game, because it's allowing waste companies to effectively harvest the energy potential that's hidden in your trashcan.
How Does it Work?
InEntec's Plasma Enhanced Melter takes some of the best points of previous waste to energy methods and combines them with the power of a super-heated plasma arc. This process makes it possible to expand the kinds of waste streams that can be converted into energy and other useful materials.
In a nutshell, the process works like this: waste is loaded into the PEM, where it first goes through a process of partial oxidation. This process gasifies a portion of the waste, which is siphoned to make syngas. The remaining solids are then lowered into a molten glass bath, heated by – you guessed it – an intense plasma arc. As the garbage reaches temperatures between 10,000 and 20,000 degrees Fahrenheit the heat breaks down the chemical bonds, releasing the atoms and molecules to be reused in the form of syngas, or other materials. "When it hits the PEM it will gasify completely, you can treat radioactive waste, hazardous waste, anything," says Vaillancourt.
Perhaps the most impressive part of the process is what happens next. The PEM system not only captures the resulting gases to produce a super-clean syngas, it also collects the other inorganic compounds as well. Metals are drained through the bottom of the melter and are combined to make a recyclable alloy, while the rest are combined and formed into a glass-like substance that can be reused as building materials.
The final stage in the process has to do with refining the hydrogen-rich syngas released throughout the PEM's process. As you might expect, the hot burning plasma arc produces a very clean product. Still, it must undergo a multi-stage scrubbing process in order to reach a rating of ultra-pure. "All particulate is routed back to the plasma chamber and ultimately is incorporated into the glass," says Surma. Once it reaches the ultra pure state, syngas can be converted into liquid fuels like ethanol or hydrogen, or it can be burned for electricity generation similar to natural gas.
Where is Plasma Gasification Technology in Use?
While it's a pretty safe bet that almost every business across the nation would like to convert its trash into something useful, plasma gasification technology is only now getting a chance to prove itself. Currently, there is only one test plant in operation, and it's located in Richland, WA. There are a number of projects in the pipeline for InEnTec though.
"We have a plant under construction in Midland, Michigan that will process hazardous waste. It's for the Dow Chemical Company and we expect it to be on line by the end of the year," says Surma. When it comes to PEM systems that process municipal waste, there are plans to build a plant in Texas, and contracts have been signed to build a PEM facility in Reno, Nevada.
One strategy for deploying the PEM will be to tailor systems to work on site at certain types of chemical and industrial plants. Since the PEM can produce hydrogen, diesel, etc., the melter could be geared to produce specific fuel products serving that particular plant. Ideally, a PEM would allow companies to lower their footprint by processing their waste onsite, while harvesting energy in a closed loop.
According to Surma, "The biggest hurdle at this point is to get the first plant deployed and prove that the system works at scale." Once that milestone is achieved, Surma believes that the barriers to getting plasma gasification into mainstream use will be removed, and hopefully widespread adoption will follow.
What Are the Environmental Benefits of Plasma Gasification?
Aside from some of the more general ways in which plasma gasification could benefit America's hazardous waste and landfill footprint, plasma gasification could also help lower greenhouse gas emissions substantially.
The most obvious method would be offsetting the use of other dirtier fuels. Since the syngas that a PEM produces is exceptionally clean, it could cut emissions by replacing coal or oil in electricity production. It can also be used to produce a variety of clean transportation fuels like dimethyl ether, hydrogen, or even synthetic gasoline, all of which produce less carbon per unit of energy than fossil fuels.
Finally, there's the fact that the PEM taps into a whole new source of energy-waste, which opens up huge possibilities for sustainability and greenhouse gas reductions. Since this source has already been extracted, processed, and transported, processing it for use as fuel has a lighter carbon footprint compared to something like oil.
Is it carbon neutral? "International bodies are currently at work on a standardized way to calculate trash to fuel emissions," says Surma, but because PEM technology is advancing so rapidly, the standards haven't yet been created.
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