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Coal Gasification

Coal Gasification

Could coal gasification provide a solution to the energy crunch?

Whatever next century, non-carbon based fuels might also be in our future, the prospect of cost effectively getting a non-polluting fuel from coal is also being given serious interest at the U.S. Department of Energy(DOE), and in universities and research and development labs all over the world. The reasons are fairly simple.

The pros of using gasoline from coal:

  • We have more coal in reserves than we do oil.
  • These reserves are spread more evenly around the world.
  • The fuel that could be obtained from turning solid coal to a liquid energy source could be used to power vehicles, heat homes and run factories with very mild modification to existing systems.
  • Road trials in over-congested European capitals have found that coal-powered vehicles also result in a better air quality, because coal/gas produces less tailpipe emissions. U.S. studies have shown that particulate emissions can actually be reduced up to 75 percent (as opposed to traditional diesel) and nitrogen oxide emissions can be reduced by as much as 60 percent (source: U.S. Department of Energy research).
  • Coal gasification can be used as a way to reclaim decades of old coal waste piles and secondary sources that are not really profitable for conventional uses.
  • While the fuel source and the means to create it are still carbon-base and do still produce greenhouse gases and other polluting emissions, we do know how to take them out of the process before they do any damage.

Scientists figured out the technology behind coal gasification as early as World War II. The Nazis actually had a process and had been experimenting with getting gas from coal as early as the 1940s, but cheap oil and gasoline kept the technology from being brought to the commercial market in the post war world. Today, as oil becomes increasingly expensive and seems to be pretty much bottoming at around $3 a gallon in the United States, the idea of getting usable petroleum from a still relatively abundant source – coal – is becoming economically interesting again.

Although the diesel fuel that comes out of the process is carbon-based, the DOE research seems to point the way towards a product that is bio-degradable, non-toxic and whose use can – overall – actually reduce greenhouse gas emission by an estimated 20 percent. This figure is reached, however, by including the calculations for the CO2 emissions resulting from the long distance transport and refining of crude oil into fuel products – not because coal emissions are any lower in CO2 than gasoline or diesel.

The cons of using gasoline from oil:

How Coal Gasification Power Plants Work

A coal to oil (referred to in the trade as ‘syngas’) refinery revolves around its “gasifier.” This is basically a big compartment where feedstock (coal, in this case) is fed in and is then converted to into syngas by applying heat and steam in a high pressure environment. The amount of oxygen allowed into the gasifier is very carefully controlled so that only a small amount of the feedstock burns completely. This partial oxidation process provides the heat necessary to break the feedstock down chemically into syngas. (source: U.S. Department of Energy).

Syngas is primarily hydrogen, carbon monoxide and other constituents in smaller percentages – the composition varies, according to what feedstock is actually used. Mineral impurities in the coal drop out and area collected at the bottom of the gasifier. Typically, these also have industrial value in the marketplace, providing another source of profit to the refinery. Sulfur impurities in the coal are converted into hydrogen sulfide and carbonyl sulfide – which can be converted in another process to sulfur – also marketable. Ammonia is also created, which can also be stripped out pretty easily and sold.

Department of Energy’s Plans

According to the DOE, coal gasification is already in its first stages of commercially viable application. The DOE is now studying the future gasification concepts and looking at the ways the process can be improved, in terms of costs, technology, emissions- capture, efficiencies and fuel flexibility. The DOE’s research, for example, is now suggesting that the same gasification process being used for coal could also be used – with a few modifications – to produce usable fuels from other feedstocks, like biomass, municipal waste, solid waste – or a combination of feedstocks.

  • The actual liquefaction process of taking coal to gasoline us actually more CO2 intensive and can produce more sulfides (ie. “acid rain”) than conventional oil refining. According to the U.S. Department of Energy, the basic technology for better CO2 capture and scrubbing the sulfides out of the plant emissions does exist, but it would have to be widely utilized on a global scale to reduce this very negative impact.
  • The process is still expensive vis a vis conventional oil refining – although as the price for a gallon of gasoline continues to rise, coal gasification becomes more and more cost-effective.
  • Coal, like oil, is a non-renewable resource. While there are still vast reserves of coal in the world, like oil, someday those reserves will also dwindle.
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