MORE ON BLACK ENERGY
Continuing some non-negatives of black energy from SIMPLE SOLUTIONS for Planet Earth (http://simplesolutionsbook1.com/), let me provide some info about clean coal.
IS THERE SUCH A THING AS CLEAN COAL?
…yes, there is such a thing as cleaner coal. Not really clean, mind you, but cleaner than really dirty. Coal, when burned, produces heat, carbon dioxide and oxides of sulfur and nitrogen, which, in the atmosphere, can get converted into acid rain—sulfuric acid and nitric acid. The Federal Government and industry have invested $4 billion over the past two decades to develop technology to remove 99% of particulates and 95% of acid rain pollutants.
Some sulfur can be removed before burning by washing the coal, but most of it is captured, subsequently, but before leaving the factory, by using flue gas desulphurization units, or scrubbers. The scrubbing agent is usually simple limestone or lime, which, like a sponge, absorbs sulfur compounds.
Nitrogen oxides are formed by any fuel that burns hot enough. This is because 80% of our atmosphere is nitrogen, a gas that does not cause any harm, but at high temperatures, combines with the other almost 20% part, oxygen, and NOx is bad. It causes smog, helps form ground level ozone and makes acid rain. The best way around these nitrogen oxides is to prevent forming it. Staged combustion processes work, but scrubbers can also be used. Ninety percent of NOx can be removed by catalysts.
The latest coal burning technology uses a fluidized bed boiler, which is fed pulverized coal and limestone, and operates at 1400 °F (760 °C) instead of the more traditional 3000 °F (1650 °C). In goes the fuel, lime sponge and air, out comes heat, carbon dioxide and calcium sulfate—which can be used to make wallboards—plus 10% of the sulfur and nitrogen compounds. It’s not perfect. The next step will be a pressurized fluidized bed boiler, which should be able to generate 50% more electricity and take out more pollutants. However, the more complicated the technology gets, the finer you need to crush the coal, and the more energy inefficient and expensive it will be.
Ah, but there is an even cleaner coal technology: coal gasification. Basically, you burn coal under controlled conditions, produce mostly methane, carbon monoxide and hydrogen, all which burn well, and use this hot gaseous mixture to spin a gas turbine to generate electricity and boil water with the exhaust gases to generate more electricity. 99.9% of sulfur and small particles can be removed. If the economics make sense, the carbon monoxide and hydrogen can be pre-removed and converted into plastics and other fuels. A plant in Kingsport, Tennessee is using this system to make photographic film and methanol.90
With great fanfare, in 2002, Australia announced ZeroGen, integrating coal-based gasification and carbon capture and storage in deep saline aquifers to produce low emission base load electricity. In mid-2007, the project collapsed, for no commercial backing could be found.
Nevertheless, there is yet an even cleaner coal option. Thirty years ago, I spent time at the Lawrence Livermore National Laboratory, assisting on a project called “In Situ Coal Gasification.” We also looked at in situ (meaning in place) oil shale retorting and tar sands production. The process started as a Plowshare Experiment to utilize controlled nuclear reactions underground to break apart coal beds. Then, the coal (or oil shale) was burned in place (in situ), and methane, carbon monoxide and hydrogen were tapped, with the carbon dioxide separated and geologically stored. This was mostly a laboratory model and planning project. Then, the use of nuclear energy became unpopular, so conventional explosives were suggested.
The really worrisome factor was the cost. When oil sold for $2/barrel in the early seventies, the economics of in-situ coal gasification were such that if petroleum only sold for $2.50/barrel, the concept would be profitable. Then, oil went up to $10/barrel in the later seventies, and, gosh, if it only went up to $12/barrel, billions could be made with this new coal technology. Well, oil is now more than $120/barrel, and, while there is no sign of in-situ coal gasification, yet, I can predict we will see some significant movement, first in Congress, then in Go-Co (government-company) partnerships.
This is one of the lessons I learned about next generation technologies. You can always rig the economics to look promisingly attractive, or, to be fair, honestly calculated to be favorable because there are so many unknowns. The reality, though, is generally lacking.
On the plus side, global warming should not be a dampener with regards to this option because any carbon dioxide produced can conveniently be stored back underground for later utilization as feedstock to produce methanol. Yes, the end result will still be more carbon dioxide into the atmosphere, but, at least you’ll be able to use this resource twice. A case can then be made about coal meeting any post-Kyoto Protocol.
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