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PostPosted: Jul 29, 2018 7:38 pm 
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Suppose that we wish to poduce less carbon dioxide. Increasing nuclear power could help us to achieve this. Also carbon neutral synthetic fuels would help, especially because airliners, road vehicles and ships consume liquid fuels. Relatively inexpensive hydrogen could be produced with high temperature reactors. That would help very much to make synthetic fuels competitive. But hydrogen production is not good enough because plain hydrogen is quite impractical compared to more conventional liquid fuels, such as gasoline, Diesel oil, methanol, etc. Carbon is needed for synthesizing such fuels. There is a problem. Where to get that carbon from? Carbon dioxide could be extracted from sea water, Arctic Sea for example. The desired carbon neutrality could be achieved that way. But, although the extraction process could be developed quite inexpensive, that kind of carbon dioxide production could not compete with similar carbon dioxide that was originally a byproduct of a coal burning plant, selling that byproduct carbon dioxide with zero or negative price.

If you offer a product with a bargain price, and a competitor offers similar product with negative price, you lose.

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PostPosted: Jul 30, 2018 6:30 am 
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The easiest way to capture carbon dioxide is to dig up limestone, fire it in an electrical furnace and then dump the lime on fields or in the sea.

As regards HTRs, I think recent strides in high temperature alkaline electrolysis have started to erode the rationale of the sulfur-iodine or copper-chlorine processes.


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PostPosted: Jul 31, 2018 1:12 am 
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Carbon is most economically captured by plants or new laboratory substitutes. These products can be converted to fuels for direct carbon fuel cells. Fuel is produced by first capturing CO2 from atmosphere. Fuels can achieve better than IC engines.


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PostPosted: Jul 31, 2018 8:49 am 
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If we look at different fuels from the carbon circulation viewpoint, hydrogen is the extreme choice because no carbon is needed at all. But, as I already said, it is not as practical as common liquid fuels are.

The next choice would be methane, but storage of methane requires also pressurization. Following choices would be ethane and propane. Anyone who has used propane gas knows that a propane bottle is quite simple and light. At room temperature the pressure inside a propane bottle is only 10 bar. Now, that reduction of pressure is significant. Compare that to ethane (over 40 bar) or hydrogen (over 700 bar, still not liquid). It is also true that dimethyl ether can be stored in even lower pressure and methanol would not require pressurization at all, but those two otherwise fine fuel chemicals have much lower energy density than propane.

Add more carbon atoms to the molecule, you get an easier liquid fuel, such as Diesel oil or gasoline. But more carbon is something we would like to avoid. The point here is that if you wish to minimize the carbon circulation, then use fuels with minimized carbon content. So, propane may be quite good, but it really is not so much better than gasoline or diesel oil.

Getting carbon in carbon neutral way is the difficult task. Grabbing carbon from biomass is certainly one option, and vegetation takes all the needed carbon dioxide from air. Biomass converted into fuel is an already used option of forest industry, and Brazil produces sugar canes for fuel production. We could calculate what is the upper limit for using biomass as a carbon source, but the limit is there, and unfortunately it is not very high.

If we really wish to reach carbon neutrality, we should stop mining coal and pumping oil out of ground. But there is another option: Capture excess carbon and pump all of it in into underground storage.

This is a system that does not work with the normal free market logic. If we wish to use carbon in a carbon neutral cycle, we must extract carbon dioxide from sea water or from air. If we wish to use all coal and oil reserves, we must pump the excess carbon dioxide into underground storages. So there is one process that tries to bury existing above ground reserves of carbon dioxide, and another process that tries to add to that reserve by extracting carbon dioxide from sea water or air. It looks ridiculous, and free market economy would reject such arrangement, because it does not look economically sound and there is no mathematical solution. That's why politics must step in.

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PostPosted: Jul 31, 2018 6:26 pm 
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As we know, steam boats did not replace sailships because sails stopped working, but because steam engines required less labour on board, so going steam was economically sound and competitive. Later Diesel engines replaced steam engines because Diesel required even less labour. Again that was economically sound.

What could potentially stop coal burning plants and how? We know that they may continue working until coal reserves get depleted. If nuclear power becomes superior enough, nuclear power plants will replace coal burning plants simply because that is economically sound. If nuclear energy presses energy prices down, coal burning and mining stops. After that we don't have to worry about how to make carbon capture and storage (CCS) really working. Because CCS won't be needed anymore.

We just need more advanced nuclear power than we already have.

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PostPosted: Jul 31, 2018 10:35 pm 
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For carbon neutral synthetic fuels, it is necessary to extract CO2 from air. For this you have to
A. Increase the utilisation of carbon from air by hothouse or more advanced technology.
B. Improve conversion of agriculture or forest waste to short carbon chain fuels.
C. Develop better energy production technology such as direct carbon fuel cells.
It will still be low scale distributed generation which has its own niche.


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PostPosted: Aug 01, 2018 3:28 am 
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jagdish wrote:

For carbon neutral synthetic fuels, it is necessary to extract CO2 from air.

Or from seawater. The ocean contains about sixty times more carbon in the form of dissolved inorganic carbon than in the pre-anthropogenic atmosphere. The average concentration of inorganic carbon in the ocean is 2.3 mmol / kg. Dissolved carbon dioxide in the ocean occurs mainly in three inorganic forms: free aqueous carbon dioxide, bicarbonate, and carbonate ion. So, there is plenty of carbon dioxide in seawater to be extracted. The horizontal distribution of total dissolved inorganic carbon in the surface ocean is mainly governed by the temperature-dependent solubility of carbon dioxide on interannual timescales. Warm low-latitude surface water generally holds less carbon dioxide than cold high-latitude surface water because of the enhanced solubility at low temperature. It seems that Arctic sea would be most abundant source of free carbon dioxide, but also other oceans are rich of carbon.

https://www.soest.hawaii.edu/oceanograp ... nclp07.pdf

To extract one ton of carbon from seawater, the facility must pump through at least 36,232 ton seawater, or much more, because the extraction efficiency is less than 100 %.

Also good to know: Solubility of carbon dioxide in water is much greater than solubility of oxygen and nitrogen. That means, once you extract gases from sea water, you get a gas mix that is rich of carbon dioxide.

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PostPosted: Aug 01, 2018 6:07 am 
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If you fire calcium carbonate in an electrical furnace you produce a nice concentrated stream of near pure carbon dioxide.

You can then spread the lime produced out on the ground or into the sea where it will react with atmospheric or oceanic carbon dioxide.
No need for enormous collection infrastructure.


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PostPosted: Aug 02, 2018 1:53 am 
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nipo wrote:

If nuclear energy presses energy prices down, coal burning and mining stops.



Except that ridiculously inexpensive nuclear power would not stop coal mining. Because a coal mine is a superior carbon source compared to carbon dioxide extraction either from air or seawater. But, on the other hand, if coal, oil and natural gas were no more used to electric power production, that alone would be a huge achievement.

The goal of carbon neutral synthetic fuel production seems extremely difficult. Hydrogen is impractical and hydrazine is toxic. Most other fuels contain carbon.

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PostPosted: Aug 06, 2018 2:28 am 
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You would have to look at the economics of CO2 production to see if running a cryogenic ASU and selling the unused product streams (LOx, LN2, maybe argon), versus say seawater extraction. In particular, if you are using deep ocean water via a long pipe, you gain both a colder heatsink, higher CO2 extraction, a high mineral content seawater brine, and perhaps some more desirable gases. It also highly resembles an open cycle OTEC plant, where you get both the brine, desalinated water, and dissolved gases at higher concentration than air. You can sell off the brine to mineral processing facilities (and if not too salty, seawater using aquaculture hydroponics), and heat rejection water output to (seawater) cooled agriculture systems.


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PostPosted: Aug 08, 2018 2:34 am 
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E Ireland wrote:
If you fire calcium carbonate in an electrical furnace you produce a nice concentrated stream of near pure carbon dioxide.

You can then spread the lime produced out on the ground or into the sea where it will react with atmospheric or oceanic carbon dioxide.
No need for enormous collection infrastructure.


You could not pay me enough money to go handling calcium oxide and spreading it.


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PostPosted: Aug 08, 2018 3:03 am 
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If the main product was carbon dioxide, the volumetric flow rate of seawater would be huge, and production of valuable byproducts would also be quite high. But actually there are many products, and probably there is no need to label main products and byproducts. Nitrogen, oxygen and noble gases could be those products that may be sold with good price. Otherwise carbon dioxide and distilled water would be byproducts that would be sold with very low price, but they become intermediate products for the fuel synthesis. If synthetic fuel production was located on the same site, then produced carbon dioxide would be competitive in synthetic fuel production, compared to carbon dioxide that had to be brought from a distant coal power plant. Also hydrogen could be produced from distilled water which would be otherwise unimportant byproduct. In this case distilled water becomes important intermediate product. A very high temperature nuclear reactor would be useful in hydrogen production, so I think it would be economically sound to build the seawater extraction plant, hydrogen production and nuclear power plant on the same site, just to minimize distances.


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PostPosted: Aug 08, 2018 4:30 am 
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modifiedgenes wrote:
E Ireland wrote:
If you fire calcium carbonate in an electrical furnace you produce a nice concentrated stream of near pure carbon dioxide.

You can then spread the lime produced out on the ground or into the sea where it will react with atmospheric or oceanic carbon dioxide.
No need for enormous collection infrastructure.


You could not pay me enough money to go handling calcium oxide and spreading it.


Luckily farmers already spread quick and slaked line in enormous quantities!


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PostPosted: Aug 11, 2018 9:02 pm 
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Two issues are involved, carbon and energy. Nature gives us biomass which was the source of fire and is still a source of food and many other things. Fossils of biomass are currently the major source of fuel and organic chemicals.
For increased carbon neutral fuels, we have to increase the efficiency of processes. This could be done by
Improved agriculture including hothouse or other controlled farming.
Improved crop varietie.
Indoor photosynthesis.
Conversion of biomass to smokeless fuels like short chain hydrocarbons, alcohols, ethers, ketonees.
High efficiency fuel cells.
The work will doubtless continue.


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PostPosted: Aug 12, 2018 7:47 am 
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Also im hoping to investigate the idea of growing water hyacinth inside giant ponds reclaimed from the sea, using the exhaust heat of the reactor to keep thep lants warm and growing at the optimum rate for as much of the year as possible.
(Using the technology of concrete breakwaters)

There are no extra heat exchangers as the giant lake of water transfers the heat, and in good conditions water hyacinth is apparently capable of approaching 200t of dry matter per hectare per year.

Animal feed and a carbon source potentially, without consuming any land.

And at its ~12%w/w protein content, it is one of the most efficient protein crops per unit area in the world.


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