Can someone who understands atmospheric chemistry pls calculate whether the ozone cure would be worse than the methane disease?
The laser idea exists already for CFCs, and I will add it to the 'ghg remediation' wiki A 2009/1/29 dsw_s <[email protected]>: > > 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. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
