Re: [math-fun] A modest proposal for carbon sequestration in space
True, but I'm not saying that you don't have to pump. Furthermore, in order to "sequester" the CO2, we only have to get it into orbit, so we don't have to send it any further than geosynchronous orbit. The pressure in the pipe goes down exponentially with height, and the molecules at the top are going extremely fast. If they bounce off the inside of the pipe without losing energy (not a good assumption), then they should come flying out the end. The failure mode is probably that the temperature gets so hot above the "atmosphere", that it melts the carbon tube. Even if the tube doesn't melt, it may radiate away an enormous amount of the energy which we would rather be used to propel the molecules _up_ the tube. So the pressure & density at high altitudes inside the tube would be much higher than the pressure & density outside the tube, so my assumptions about the density inside & outside would no longer hold. So, ideally, we might rather have a true "nanotube" in which the CO2 molecule travels as if in a waveguide, rather than ballistically. Then we would need an enormous number of them in parallel to carry a substantial amount of gas. Launching the molecules into such a waveguide might then be problematic. BTW, I understand that we actually _do_ lose H2 into space all the time, but probably not at an appreciable rate. At 12:00 PM 8/1/2006, Eugene Salamin wrote:
--- Henry Baker <hbaker1@pipeline.com> wrote:
Eugene:
My intuition is that CO2 is only modestly heavier than N2+O2, so you only have to lift the _difference_ between the weight of the CO2 and the atmospheric pressure due to N2+O2.
Then it should take no energy to dispose of the atmosphere into space.
Gene
The earth absorbs sunlight with a cross section of 2*pi*R^2, and reradiates it as a sphere, with area 4*pi*R^2. This gives an area advantage of a factor of 2. A cylinder, side-on to the sun, would absorb as 2*r*length, and reradiate as 2*pi*r*length, giving an area advantage of a factor of pi/2. Since the radiation goes like T^4, I don't see why the temperature of a cylinder would be much higher than that of the earth, about 300 K. Although the theoretical temperature of the atmosphere (gas) near the "top" is quite high, the density is so low that little heat is available, is my understanding. Bill C. -----Original Message----- From: math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com [mailto:math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com] On Behalf Of Henry Baker Sent: Tuesday, August 01, 2006 1:30 PM To: Eugene Salamin Cc: math-fun Subject: Re: [math-fun] A modest proposal for carbon sequestration in space True, but I'm not saying that you don't have to pump. Furthermore, in order to "sequester" the CO2, we only have to get it into orbit, so we don't have to send it any further than geosynchronous orbit. The pressure in the pipe goes down exponentially with height, and the molecules at the top are going extremely fast. If they bounce off the inside of the pipe without losing energy (not a good assumption), then they should come flying out the end. The failure mode is probably that the temperature gets so hot above the "atmosphere", that it melts the carbon tube. Even if the tube doesn't melt, it may radiate away an enormous amount of the energy which we would rather be used to propel the molecules _up_ the tube. So the pressure & density at high altitudes inside the tube would be much higher than the pressure & density outside the tube, so my assumptions about the density inside & outside would no longer hold. So, ideally, we might rather have a true "nanotube" in which the CO2 molecule travels as if in a waveguide, rather than ballistically. Then we would need an enormous number of them in parallel to carry a substantial amount of gas. Launching the molecules into such a waveguide might then be problematic. BTW, I understand that we actually _do_ lose H2 into space all the time, but probably not at an appreciable rate. At 12:00 PM 8/1/2006, Eugene Salamin wrote:
--- Henry Baker <hbaker1@pipeline.com> wrote:
Eugene:
My intuition is that CO2 is only modestly heavier than N2+O2, so you only have to lift the _difference_ between the weight of the CO2 and the atmospheric pressure due to N2+O2.
Then it should take no energy to dispose of the atmosphere into space.
Gene
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--- Henry Baker <hbaker1@pipeline.com> wrote:
True, but I'm not saying that you don't have to pump. Furthermore, in order to "sequester" the CO2, we only have to get it into orbit, so we don't have to send it any further than geosynchronous orbit.
What I said in my original reply could be restated as: The diesel engines that pump CO2 into the space tube at ground level will generate about (4/e) times the amount of CO2 that they can pump up to geosynchronous, where e is the efficiency of the sequestration system. Gene __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
If I remember my physics correctly, air pressure is approx. 14.7#/sq in, which is the weight of the entire column of air 1 inch square sitting on the square inch. According to a source on the internet, standard air has an average molecular weight of ~29, while CO2 has a molecular weight of ~44. So I would estimate that the same column of pure CO2 would produce a pressure of approx 22.3#/sq in. This would mean that to pump pure CO2 into the "stack", it should take a head pressure of 7.6#/sq in. I suspect that this kind of pressure is easily available from the tailpipe of a 4-stroke internal combustion engine. If you diluted the CO2 with air in the ratio 1:1, then the molecular weight would be 36.5 and the head pressure would be only 3.8#/sq in. Diesel engines can be run very, very leanly, thus producing a relatively small % of CO2 in the output; this is not the most efficient way to run such an engine, however, but it does allow one to match the exhaust pressure with the required head pressure. At 01:39 PM 8/1/2006, Eugene Salamin wrote:
--- Henry Baker <hbaker1@pipeline.com> wrote:
True, but I'm not saying that you don't have to pump. Furthermore, in order to "sequester" the CO2, we only have to get it into orbit, so we don't have to send it any further than geosynchronous orbit.
What I said in my original reply could be restated as: The diesel engines that pump CO2 into the space tube at ground level will generate about (4/e) times the amount of CO2 that they can pump up to geosynchronous, where e is the efficiency of the sequestration system.
Gene
That would be the initial condition. However, the internal pressure will increase, up to the point where the amount of CO_2 being blown out the other end matches the input. That will require a _lot_ of CO_2 to be pumped in, and hence a large increase in the pressure. Franklin T. Adams-Watters -----Original Message----- From: Henry Baker <hbaker1@pipeline.com> If I remember my physics correctly, air pressure is approx. 14.7#/sq in, which is the weight of the entire column of air 1 inch square sitting on the square inch. According to a source on the internet, standard air has an average molecular weight of ~29, while CO2 has a molecular weight of ~44. So I would estimate that the same column of pure CO2 would produce a pressure of approx 22.3#/sq in. This would mean that to pump pure CO2 into the "stack", it should take a head pressure of 7.6#/sq in. ...
No, the pressure won't increase over time, unless the model itself breaks (i.e., by radiating away too much energy, melting the column, or destroying the column with high-speed CO2 molecules, etc.). To get some idea about how this might actually work, see the following web page re stacks of superballs: http://www.physics.gla.ac.uk/~kskeldon/PubSci/exhibits/D12/ I seem to recall a video of this type of demonstration somewhere on the internet, but haven't been able to find it. Needless to say, one model for the CO2 column (or any air column) is a stack of superballs. At 02:49 PM 8/1/2006, franktaw@netscape.net wrote:
That would be the initial condition. However, the internal pressure will increase, up to the point where the amount of CO_2 being blown out the other end matches the input. That will require a _lot_ of CO_2 to be pumped in, and hence a large increase in the pressure.
Franklin T. Adams-Watters
-----Original Message----- From: Henry Baker <hbaker1@pipeline.com>
If I remember my physics correctly, air pressure is approx. 14.7#/sq in, which is the weight of the entire column of air 1 inch square sitting on the square inch.
According to a source on the internet, standard air has an average molecular weight of ~29, while CO2 has a molecular weight of ~44.
So I would estimate that the same column of pure CO2 would produce a pressure of approx 22.3#/sq in.
This would mean that to pump pure CO2 into the "stack", it should take a head pressure of 7.6#/sq in. ...
This works well for a marble on top of a superball (you might need to duck!). If the balls are of the same size, one would expect, I think, a Boltzmann distribution in the energies. That's why a few molecules might escape. Of course, that (evaporation)cools off the remaining gas, so even fewer molecules would have the necessary escape velocity. You still need to provide the energy to the gas molecules to get any substantial amount of gas to orbit, I think. Bill -----Original Message----- From: math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com [mailto:math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com] On Behalf Of Henry Baker Sent: Tuesday, August 01, 2006 4:10 PM To: franktaw@netscape.net Cc: math-fun@mailman.xmission.com; gene_salamin@yahoo.com Subject: Re: [math-fun] A modest proposal for carbon sequestration in space No, the pressure won't increase over time, unless the model itself breaks (i.e., by radiating away too much energy, melting the column, or destroying the column with high-speed CO2 molecules, etc.). To get some idea about how this might actually work, see the following web page re stacks of superballs: http://www.physics.gla.ac.uk/~kskeldon/PubSci/exhibits/D12/ I seem to recall a video of this type of demonstration somewhere on the internet, but haven't been able to find it. Needless to say, one model for the CO2 column (or any air column) is a stack of superballs.
If you keep pumping carbon dioxide into the column, the pressure will increase. If you don't, you won't get a measurable amount of carbon dioxide escaping. Franklin T. Adams-Watters -----Original Message----- From: Henry Baker <hbaker1@pipeline.com> No, the pressure won't increase over time, unless the model itself breaks (i.e., by radiating away too much energy, melting the column, or destroying the column with high-speed CO2 molecules, etc.). To get some idea about how this might actually work, see the following web page re stacks of superballs: http://www.physics.gla.ac.uk/~kskeldon/PubSci/exhibits/D12/ I seem to recall a video of this type of demonstration somewhere on the internet, but haven't been able to find it. Needless to say, one model for the CO2 column (or any air column) is a stack of superballs. At 02:49 PM 8/1/2006, franktaw@netscape.net wrote:
That would be the initial condition. However, the internal pressure will increase, up to the point where the amount of CO_2 being blown out the other end matches the input. That will require a _lot_ of CO_2 to be pumped in, and hence a large increase in the pressure.
Franklin T. Adams-Watters
-----Original Message----- From: Henry Baker <hbaker1@pipeline.com>
If I remember my physics correctly, air pressure is approx. 14.7#/sq in, which is the weight of the entire column of air 1 inch square sitting on the square inch.
According to a source on the internet, standard air has an average molecular weight of ~29, while CO2 has a molecular weight of ~44.
So I would estimate that the same column of pure CO2 would produce a pressure of approx 22.3#/sq in.
This would mean that to pump pure CO2 into the "stack", it should take a head pressure of 7.6#/sq in. ...
Frank, Gene & others were correct, and I was grossly mistaken. If the density for air is at the 50% point at 4-5 miles, then a geosynchronous orbit at 22,200 miles is ~5000 doublings. This means that the density of the air in geosynchronous orbit is ~10^(-1500) of what it is at sea level. This number is 65 orders of magnitude smaller than Avagadro's number. So the chances of finding an air molecule at this height are zero. The number of orders of magnitude may change with the type of molecule, but the answer is the same. This means that no reasonable (or even unreasonable) amount of pumping will cause any amount of gas to be emitted at this height. Yes, some vanishingly small fraction of the molecules may achieve escape velocity, but those velocity distributions involve exponentials, as well. Now that I understand this a little better, I now think we have a much bigger problem: where, when and how did we lose the rest of the Earth's atmosphere ? Even 5 billion years can't put a dent in the numbers above, so how come the Earth's atmosphere isn't a lot bigger, so that the rate of loss today would still be measurable ? This tells me that something fairly dramatic must have happened early in the Solar system's history to pull and/or blast away most of the early atmosphere. At 08:20 PM 8/1/2006, franktaw@netscape.net wrote:
If you keep pumping carbon dioxide into the column, the pressure will increase. If you don't, you won't get a measurable amount of carbon dioxide escaping.
Franklin T. Adams-Watters
Your absolutely right. In the early history of the solar, a very strong solar wind blew away most of the atmospheres of the inner planets. A further decrease, for the Earth, was due to ... carbon sequestration. Franklin T. Adams-Watters -----Original Message----- From: Henry Baker <hbaker1@pipeline.com> ... Now that I understand this a little better, I now think we have a much bigger problem: where, when and how did we lose the rest of the Earth's atmosphere ? Even 5 billion years can't put a dent in the numbers above, so how come the Earth's atmosphere isn't a lot bigger, so that the rate of loss today would still be measurable ? This tells me that something fairly dramatic must have happened early in the Solar system's history to pull and/or blast away most of the early atmosphere. At 08:20 PM 8/1/2006, franktaw@netscape.net wrote:
If you keep pumping carbon dioxide into the column, the pressure will increase. If you don't, you won't get a measurable amount of carbon dioxide escaping.
Franklin T. Adams-Watters
So, is it enough to pressurize the column at the bottom of the stack, and wait/hope that a few molecules at the top of the column of gas are energetic enough to fly out the hole at synch. orbit? I think (but I don't know) that one might need to exert a lot of pressure to make this work, probably with as much energy as what Gene suggested, to pump out the gas. Can we assume that the pipe is not heated (is insulated), so that any energy for the molecules comes from the gas itself or the from pump? In that case, it would seem that the energy required to overcome the gravitational potential energy (up to geosynch) is a good way to look at it. Bill -----Original Message----- From: math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com [mailto:math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com] On Behalf Of Henry Baker Sent: Tuesday, August 01, 2006 3:34 PM To: Eugene Salamin Cc: math-fun Subject: Re: [math-fun] A modest proposal for carbon sequestration in space If I remember my physics correctly, air pressure is approx. 14.7#/sq in, which is the weight of the entire column of air 1 inch square sitting on the square inch. According to a source on the internet, standard air has an average molecular weight of ~29, while CO2 has a molecular weight of ~44. So I would estimate that the same column of pure CO2 would produce a pressure of approx 22.3#/sq in. This would mean that to pump pure CO2 into the "stack", it should take a head pressure of 7.6#/sq in. I suspect that this kind of pressure is easily available from the tailpipe of a 4-stroke internal combustion engine. If you diluted the CO2 with air in the ratio 1:1, then the molecular weight would be 36.5 and the head pressure would be only 3.8#/sq in. Diesel engines can be run very, very leanly, thus producing a relatively small % of CO2 in the output; this is not the most efficient way to run such an engine, however, but it does allow one to match the exhaust pressure with the required head pressure. At 01:39 PM 8/1/2006, Eugene Salamin wrote:
--- Henry Baker <hbaker1@pipeline.com> wrote:
True, but I'm not saying that you don't have to pump. Furthermore, in order to "sequester" the CO2, we only have to get it into orbit, so we don't have to send it any further than geosynchronous orbit.
What I said in my original reply could be restated as: The diesel engines that pump CO2 into the space tube at ground level will generate
about (4/e) times the amount of CO2 that they can pump up to geosynchronous, where e is the efficiency of the sequestration system.
Gene
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participants (4)
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Cordwell, William R -
Eugene Salamin -
franktaw＠netscape.net -
Henry Baker