I finally swapped out the gas generator on my '88 Colman two-burner for a dual-fuel one. (It was time, too: it was putting out a yellow, sooty flame that no amount of cleaning fixed.)
Anyhow, I noticed that the soot buildup on the burner “cooked off” almost totally after the first use…and it made sense to me, too, given that carbon is a fuel in and of itself (“coke” being carbon black derived from coal, used for melting iron ore to make steel.)
Which has me thinking: of all the “typical” auto emissions (soot, CO, HC, NOx), the first three are “burnable.”
As for NOx, I’m not sure: I always thought that N2 was the “lowest energy” state, where nitrogen always wanted to be (and in the case of TNT, wanted to be real bad.)
Given that, wouldn’t a flame burning in an Oxygen-rich environment serve as an inexpensive emissions control device? I wasn’t thinking so much re: new gasoline passenger vehciles, but these three cases:
1. Small-engine (lawnmower and the like), particulalry 2-strokers.
2. As an alternative to “Clean diesel,” which seems to skewer efficiency and cause drivablitiy problems.
3. For that older car that “just can’t quite” pass emissions.
That’s pretty much what a cat does, it ‘burns’ the remaining unburnt CO and HC. NOx is a problem, though, it has to be ‘unburnt’ (‘reduced’ in chemical terms). That’s what the urea’s used for in the larger ‘clean diesels’. As for a flame, you’d need a big one, given the volume of exhaust gas.
Not only that, but given the by product emissions of this device, it would need to be in an enclosed environment and or scrubbed. Now you’re back to square one. The alternative would be to tightly control the fuel going in; another expensive proposition. Two strokes are making a comeback, but on the back of tightly controlling the lubricant and more complete combustion. Still, nothing like an electric from batteries charged by an energy recovery plant.
Perfect combustion of a hydrocarbon yields CO2 and H20. In simple terms – CH4 + 2 O2 = CO2 + 2 H2O. Unfortuntately perfect combustion does not occur in the real world. Soot and HC are unburned hydrocarbons. NOx is NO, NO2, etc. In an engine the mix of fuel and air varies in the cylinder, so some areas are lean and all the fuel burns, some are rich so some of the fuel burns incompletely. The imcomplete burning is where you get the soot, unburned hydrocarbons and other stuff. Texases and Dagosa are right, there are things you can do to make engines have less emmissions and be more effecient but there is a cost to accomplish this. Running an engine lean does not provide enough power and is ineffecient.
Auto companies, EPA and a lot of other folks are working on ways to improve fuel effeciency and reduce emmissions. A lot of progress has been made over the years. A real nice 60’s/70’s era Baracudda was in front of me yesterday, it was in great shape and the engine had a nice rumble to it, but I could smell the unburned fuel coming out of the exhaust. This does not happen with newer cars.