Oct122008
Trash To Treasure: Creating Energy
We talked about trash to treasure a long time ago, then I just stumbled over this interview. It’s a quick overview of what can and is being done now. What do you think about that this one, Pickens?
NOTE: I removed the “plasma gasification” as I was just informed that these folks are not using plasma gasification. My bad.
Covanta does NOT use plasma gasification! They use incineration to burn garbage and trash, run the heat through a boiler creating steam and use the steam to run turbines and generators.
Plasma gasification is another technology altogether, which uses an ultra high heat electric arc or torch to convert organic feedstock to synthetic gas or “syngas”, consisting mainly of Carbon Monoxide and Hydrogen. These gases have a relatively low heat content (about 125 to 250 BTU’s per standard cubic foot.
In addition, plasma technology is very expensive and it uses significant amounts of energy to sustain itself, which reduces the amount of power it can sell. My preference would be to use pyrolysis (heating in the absence of oxygen) to create a high BTU syngas, which would be supplied to an internal combustion engine to run a generator. We’ve already done this with manure, sewage sludge, waste plastics and other wastes and will be commercializing the process in the next 90 days.
Joel Keller
R&A Energy Solutions
440/377-2387
Joel –
Very interesting – we’d love to hear more. What I know of the plasma gasification is that once the plant is running, it sustains itself – running on its own energy. So while it is technically using more energy in the process, it’s using more of its own energy. Am I off-base here? I’m no scientific expert.
Thanks for stopping by and commenting.
-Jason
Jason,
There is only so much energy available in any fuel. For instance, if coal is the fuel choice, it has about 10,000 BTU’s per pound of heat energy.
Taking into account system efficiencies, plasma torch will liberate all 10,000 of those BTU’s, but only 50% of them will likely be available for making power, heating water, making steam or to whatever other use they are put. Of the 50% of the liberated energy that can be captured, significant amounts will be wasted as radiant heat or by transfer to thermal conductors or to the air.
So, if plasma torch is going to effectively need to use 25% of the power it generates in order to maintain its temperature, only 37.5% of the intrinsic energy will be available to make power. This is called “energy balance” and although I’m not an electrical engineer, I can understand this fairly well.
With the pyrolysis process we are using, heat that would otherwise be lost, will be harvested to keep the reactor vessel hot so that the process won’t stop for lack of energy. We will use the exhaust heat from the Internal Combustion engine/generator sets to heat the reactor vessel. This will give us a much better energy balance and near 50% efficiency in making power. We will only lose about 12% of the total power production for internal use, instead of the 25% or so with plasma.