It takes quite a bit of energy to make ozone, which then turns back into O2 rather quickly.
Another idea for getting rid of methane is to find a wavelength it absorbs and the other stuff in air doesn't, then have a laser beam at that wavelength bounce back and forth between mirrors in the open air. The excited state would have to be one that reacts readily with O2, or with N2 to form an intermediate that reacts with O2. I don't know whether those criteria can be met effectively and affordably. -- Back on my earlier suggestion of a catalytic converter -- Any time you heat air to combustion temperature you form NOx, so even without fuel you would need a catalytic converter to avoid creating pollution. But the real reason for the catalytic converter in my suggestion is to get rid of the methane. An internal combustion engine doesn't completely burn the fuel; wasted fuel is part of the pollution that the converter is there to remove. So I suspect it would work better on methane than the compressor would. On Jan 28, 8:31 pm, "Hawkins, Dave" <[email protected]> wrote: > Ozone is itself a greenhouse gas > > -----Original Message----- > From: [email protected] > > [mailto:[email protected]] On Behalf Of Andrew Lockley > Sent: Wednesday, January 28, 2009 8:11 PM > To: Alvia Gaskill > Cc: David Schnare; [email protected]; geoengineering > Subject: [geo] Re: methane air capture > > Thanks. > Is there any technical reason why a diesel engine couldn't be developed > that would reach the compression ratios needed? I don't quite see why > it needs to be 500:1 when you only need to get it to c1800C to burn > methane. That suggests 40:1 approx, which is doable I think. I also > don't see why compression adjusts the ppm - surely it stays the same and > is squished. Is that to do with supercritical fluids? > > I don't think we can just throw our hands up an admit defeat if methane > outgasses on a large scale. We have to solve the problem! > > What about enhancing ozone levels to promote photchemical degradation, > or using CSP for atmospheric-pressure oxidation? > > A > > 2009/1/29 Alvia Gaskill <[email protected]>: > > I don't think methane at ambient levels (2 ppm) can be combusted in a > > diesel engine. A typical diesel engine has a compression ratio of > > around 20, meaning that the air drawn in is compressed by a factor of > 20. > >http://en.wikipedia.org/wiki/Diesel_engine#How_diesel_engines_work As > > > a result, the temperature of the compressed air is raised to around > > 1000 degrees F, high enough for the diesel fuel to autoignite. Thus, > > no need for spark plugs for a diesel engine. Unfortunately, the > > ambient concentration for autoignition of methane is about 5% or > > around 50,000 ppm and at 1000 degrees F. In the diesel combustion > > chamber, it will be around 40 ppm, ambient nominally 2 ppm. So while > > a 5% methane in air fuel would probably burn in a diesel engine, lower > levels would not. > > > This issue has been addressed in studies conducted for the USEPA as > > part of the Coalbed Methane Outreach Program, run out of EPA's Climate > > > Protection Division. > > >http://www.irgltd.com/Resources/Publications/US/Technical%20and%20Econ > > omic%20Assessment%20-%20Mitigation%20of%20Methane%20Emissions%20Coal%2 > > 0Mine%20Ventilation%20Air.pdf > > > The goal of this study was to determine ways to use methane from coal > > mine ventilation air as fuel at levels above 3000 ppm. One of the > > units tested was able to combust methane at levels as low as 800 ppm. > > > As noted on page 3, "Below 4.5%, methane will not ignite or sustain > > combustion on its own without a constant ignition source, unless it > > can remain in an environment where temperatures exceed 1832 degrees F. > > > Therefore, any conventional method proposed to use ventilation air as > > a fuel or even to destroy it, would require a net energy input in > > addition to the fuel value of the methane contained in the ventilation > air." > > > Internal combustion engines and solar gas turbines can burn low levels > > > of methane as ancillary fuel, but won't operate on ventilation gas > > alone as the temperatures don't get high enough to combust the > > methane. To burn ventilation air containing methane as a primary > > fuel, a thermal flow and a catalytic reactor were evaluated. Both > > require an external source of electricity to provide the initial heat > > for combustion, with the catalytic system operating at lower > > temperatures of around 700-1500 degrees F vs. 1832 for the other one > (page 19). > > > So, it doesn't appear that it is possible to combust ambient levels of > > > methane using a diesel engine or any other source using the methane as > > > the primary fuel. Compressing the low levels of methane in ambient > > air to 1000 ppm, about the lower limit of the catalytic system, would > > require a compression ratio of 500. Even if this could be overcome, > > in my opinion, the extremely large volumes of air required would > > preclude the use of such a system to mitigate ambient methane. The > > better approach would be to limit the sources of methane emissions > > including feedbacks to prevent a runaway outcome for which there is > also no mitigation technology. > > > ----- Original Message ----- From: "Andrew Lockley" > > <[email protected]> > > To: "David Schnare" <[email protected]> > > Cc: <[email protected]>; "geoengineering" > > <[email protected]> > > Sent: Wednesday, January 28, 2009 9:56 AM > > Subject: [geo] Re: methane air capture > > >> You don't need a licence to squash air. I'm not proposing a fuel - > >> I'm proposing to drive the diesel engine with windpower. > > >> A > > >> 2009/1/28 David Schnare <[email protected]>: > > >>> In the U.S., use of a compresion ignition engine requires > >>> certification of both the fuel and the engine (by EPA), and limits > >>> the amounts of priority pollutants that may be emitted from such an > >>> engine. These include NOx, SOx and particulates, all of which will > >>> emerge from the scheme you are discussing. > > >>> In a regulatory state, nothing is as easy as it seems. > > >>> David Schnare > > >>> On Tue, Jan 27, 2009 at 8:33 PM, Andrew Lockley > >>> <[email protected]> > >>> wrote: > > >>>> You don't need a combustible fuel-air ratio provided that the > >>>> combustion doesn't need to be self-sustaining. Once the correct > >>>> temperature is reached, any methane present will oxidise. The > >>>> advantage of using a diesel engine is that it runs with minimal > >>>> energy input as the temperature can be changed without > >>>> irrecoverable energy input - the mix cools as it expands. I > >>>> thought about using a jet engine - essentially an adapted turboprop > > >>>> or high-bypass turbofan, but I think it would be more lossy. > > >>>> I don't agree that you'd be processing 'a few hundred cc'. I > >>>> envisage building vast arrays of wind turbines, all connected to > >>>> huge marine diesel engines. > > >>>> Why would you need a catalytic convertor? The CH4 just oxidises to > > >>>> H20 and Co2. I can see the benefit of a heat exchanger, and I > >>>> already thought of that. > > >>>> I covered the issue of hydroxl radical - it's created by ozone > >>>> photochemistry, so the best way to manipulate it seems to be by > >>>> delivering ozone to the stratosphere. > > >>>> A > > >>>> 2009/1/28 dsw_s <[email protected]>: > > >>>> > Compression ignition requires a suitable ratio of fuel to air. > >>>> > Even if compression in a diesel engine perfectly removed methane > >>>> > from the air, you're not going to process the atmosphere a few > >>>> > hundred cc at a time. To remove methane from the air, I see two > >>>> > options: increase the amount of hydroxyl radical if there's > >>>> > enough methane to deplete it, or as you say build air-cooled CSP > >>>> > plants. For the CSP option you would want a counter-flow heat > >>>> > exchanger and a catalytic converter on the outgoing air. > > >>>> > On Jan 27, 2:03 pm, Andrew Lockley <[email protected]> > wrote: > >>>> >> If you fixed up diesel engine to a wind turbine, you'd get >> > >>>> >> compression ignition of any methane residue in the atmosphere, > >>>> >> even without injecting any fuel. This would be expensive, but I > > >>>> >> think it would work. > > >>>> >> An alternative would be to pump air through concentrated solar > >>>> >> power plants > > >>>> >> Any thoughts? We appear to need some bright ideas on methane > >>>> >> remediation pretty soon. > > >>>> >> A > > >>> -- > >>> David W. Schnare > >>> Center for Environmental Stewardship --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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