CO2 Removal

This is interesting as it provides a viable option not presently available. Not necessarily wonderful but not so problematic either. You have a present day coal plant and a retrofit reduces your output but puts the CO2 in a form that can be dealt with. It may still be expensive but it has leveled the playing field between you and a Greenfield power plant.

All that matters because financing new plants will absorb most available capital for the next few years and total rebuilds are typically a lousy financial option.

Of course, we expect most capital to flow into alternative systems and simply prolonging the life of these plants may be the only option. This certainly makes it possible to manage the problem.

Of course CO2 disposal is still the real problem, but I assume this process naturally separates out the nitrogen so it is now as efficient as is possible making geological storage much more attractive. Also modest compression reduces the volume hugely and there are plenty of natural geological traps to exploit. Just keep drilling deeper.

I do not know if it will be much utilized, but well funded facilities will certainly look at this option, just for political reasons. Now if we could only get them to use the chlorine quench method to strip out the Sox and NOx and particulates we would have power plant and metal smelters all running completely clean. It is actually possible, since efficient CO2 removal was the remaining difficulty.

In short, I now think it is possible to operate a thermal metal smelter or steel mill while efficiently capturing all the output gases and particulate and the heat energy while dumping only the nitrogen gas back into the atmosphere and perhaps minor residuals if that. It took about thirty tears to establish proper solutions and will now take just as long for commercial acceptance now that it can be done.

June 23, 2009

CO2 Removal from the Atmosphere

http://nextbigfuture.com/2009/06/co2-removal-from-atmosphere.html


Professor Klaus Lackner, Ewing-Worzel Professor of Geophysics in the Department of Earth and Environmental Engineering at Columbia University have developed a sorbent that is "close to the ideal," in that it uses a relatively small amount of energy to release the CO2 and is not prohibitively expensive.

"By the time we make liquid CO2 we have spent approximately 50 kilojoules [of electricity] per mole of CO2." Compare that, Lackner said, to the average power plant in the U.S. which produces one mole of CO2 with every 230 kilojoules of electricity.

"In other words, if we simply plugged our device in to the power grid to satisfy its energy needs, for every roughly 1000 kilograms [of carbon dioxide] we collected we would re-emit 200, so 800 we can chalk up as having been successful," he said.

The biggest cost was at the "back-end" of the collector, primarily the technology used to release the CO2 from the sorbent. He said for that reason, on a cost-basis, the "synthetic tree" could not compete with modern coal-fired power plants that are designed to release fewer carbon emissions than their older predecessors. But he said when compared to the cost of retro-fitting an existing coal plant, the "synthetic tree" becomes more viable.

"Each unit would take out a ton of CO2 a day -- which would be the amount of CO2 produced by 20 average automobiles in the U.S.A. And the cost of each unit would be about the cost of a Toyota. So that would mean if you added a five percent surcharge on automobile purchases that money could go to building units to remove the CO2 those vehicles are going to create."

The technology is not being developed as an alternative to the carbon capture and storage methods currently being tested for large-scale use on coal-fired power stations. He's targeting carbon that's already in the air

Acid Rain in a Pipe

One of my frustrations watching the so called march of technology is that the whole problem of smoke stack pollution is readily solvable. Yet we have stayed with old systems, if any are used at all, that only partially ameliorate the problem. We have even exported our smelters offshore and wink at the horrific and noxious pollution thrown into the atmosphere.

Our coal burners currently use a fluidized bed that is charged with limestone. The limestone reacts with the sulphur to produce gypsum while absorbing some heat. This is good for about 60% of the sulphur and little else. Most such gypsum ends as waste. Not a great solution.

In the late seventies I met a technologist who had the simple insight that since natural ozone produces acid rain in the first place, it may be possible to achieve the same result in the stack using the best and fastest oxidizer possible. That is chlorine gas. He patented the idea and became its champion.

He met me and I persuaded him to run proper bench tests under the auspicious of the University of British Columbia. This ensured that the results would be credible. After that he continued to champion the protocol with little additional progress, in part due to his own business perspective.

What we developed was a very promising protocol.

The flue gas, whether from a smelter or a coal burner is well over 600 degrees when it exits the combustion chamber. It is also traveling fast. At this point water is sprayed into the gas stream along with chlorine gas. This produces hydrochloric acid in the gas stream. This acid reacts preferentially with the SOx first and secondly the NOx converting them into first sulphuric acid and then nitric acid. And the surplus hydrochloric acid is sponged up by the CO2 to produce some carbonic acid. These acids continue to additionally react with any metals in the flue stream converting them into salts that are usually soluble.

Our bench tests confirmed the implied stoichemistry of the reactions and showed a complete reduction of the SOx and NOx in the flue gas.

The spent flue gas was then sent through a water quench to sponge up any excess chlorine and to strip the heat, acids and salts out of the stream. This also would collect most of the particulate. The end result is a clean stack gas that is primarily CO2 and nitrogen.

In the heyday of the Acid Rain scare, a literature search search isolated over 150 separate strategies been explored, all stuck with slower reaction speeds than we could easily achieve with chlorine gas.

What I have just described is an aggressive reaction protocol that can be tuned nicely to be fast and efficient. The capital cost to implement this procedure is minor for a new plant and likely very doable as a retrofit for older facilities. We are only engineering a reaction chamber for the flue gas.

The waste is in the form of a hot solution of acids and salts in addition to the particulate already handled. The solution mix would be run through a small acid plant that would recover the chlorine, and produce both sulphuric acid and nitric acids as salable products. The salts would also presumably be recovered at least as a blend for later processing off site.

The total consumables for a typical power plant would be around one carload of chlorine gas per year.

Of course, even the scientifically literate shy away from the word chlorine, making this protocol a hard sell. But it is the real solution to our second major source of atmospheric pollution.

As an aside. Ozone is likely as good. The problem is producing pure ozone. The plasma arc produces mostly nitrous oxide rather than ozone which is very counter productive. Other methods of producing ozone are costly compared to chlorine.