Showing posts with label NOx. Show all posts
Showing posts with label NOx. Show all posts

Monday, November 17, 2008

Australian Low CO2 Coal Burner

We have here an interesting project from Australia. We start with compressing air in order to separate out the nitrogen. This does not have to be a perfect separation and yields of 98% are likely and much less would do.

The oxygen is then blended with exhaust gases to give the same ratios associated air. This will ensure that a more complete burn is achieved as this gas blend is fed into the powdered coal burner. The carbon monoxide could be sharply reduced.

A portion of the exhaust gas is taken off and also compressed in order to liquefy the carbon dioxide.

Of course, this is all doable. The main trick is to get the nitrogen out of system before it gets to the burner itself to hugely reduce the amount of exhaust gases needing compression. Something like this is able to remove most produced carbon dioxide in a transportable form for disposal.

Much is made of geological disposal and my question is it possible to get deep enough to use liquid pressures to keep the co2 liquid in the ground facilitating easy disposal.

This is a coal thermal plant so the heat of compression should be put back into the various heating processes employed by the plant.

I would like to see the reverse Rankin cycle engine integrated with this.

Then we get to the real problem that has made ideas like this fail for decades. It is the problem of compressor efficiency. It has never been good enough to avoid large systemic losses and we are asking here for high volume compressors. It sounds like an engineering nightmare from this distant remove.

I got a solid introduction to the technology thirty years ago and not to be too picky, I see minimal evidence of real improvement. I think that the industry has just never been sexy enough and besides, folks are prepared to make do with designs lifted straight of engine design in particular.

I really would like to find evidence of major improvement, but the only evidence that I note is emphasizes by the organizations on their own reliability. Somehow I suspect that the equipment itself continues to be maintenance demanding.

A lot of energy is currently lost by compressors and we are sticking them on both front and back. Marrying this up with the reverse Rankin cycle could help a bit, but developing a new super efficient compressor for industrial applications was grossly overdue decades ago and is even more compelling today.

Maybe someone has done it?

One other reason I would like something like this to actually work is that grabbing the flue gas gives you an opportunity to collect the heavy metals. That would eliminate the primary source of mercury entering the environment. This is not a minor problem. It is impacting us through our consumption of fish and is endemic in high fish diets although that knowledge is at best suppressed.

I posted last year on the utility of stripping the flue gas stream of SOx and NOx and heavy metal using a chlorine cycle.

The resulting gas was CO2 stripped of its heat and compressor ready.

In the event, these folks are taking a run at using a lot of compression and it will be worth following to see if it has a happy outcome.

Xstrata, J-Power in low-emission coal tech first

SYDNEY (Bloomberg) J-Power and Xstrata PLC have started a 206 million Australian dollar, or $137 million, project in Australia that will be the first in the world to use a low-emission coal-fired generating technology.

The technology may cut typical
carbon dioxide emissions from coal-fired generation by about 90 percent.

Schlumberger Ltd., Mitsui & Co. and IHI Corp. are also in the group funding the venture in Queensland state, the Callide Oxyfuel Project said Friday in a statement. The 30-megawatt plant is due to start operating in 2011.

The federal and state governments are contributing A$85 million to the Callide project. The Japanese government and the Australian Coal Association are also providing money for the plant.

"This project will lay the foundation for the widespread deployment of low-emission coal technology so essential for Australian power generation and for the millions of people across the world relying on Australian coal," Australian Resources and Energy Minister Martin Ferguson said Friday in a separate statement.

The venture's oxyfuel technology involves burning coal in a mix of oxygen and recirculated waste gases, instead of air, resulting in higher concentrations of
carbon dioxide that can be more easily captured from the exhaust gases.

The carbon waste is then liquefied and buried underground. The technology may cut carbon dioxide emissions from coal-fired generators by about 90 percent, the venture said.

The technology can be fitted at existing coal-fired generators instead of building a new low-emissions plant.

Australia, which plans to introduce
emissions trading in 2010 to fight global warming, depends on coal for more than 80 percent of its power supplies

Thursday, August 16, 2007

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.