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Even More Natural Gas on the Way

Sometimes you have to wonder, how did so much energy get packed away in the earth’s crust?  Even with tens of millions of years, moving continents, a series of biological eras, and uncountable tons of materials piled, laid out and compressed, the reservoir numbers coming in since horizontal drilling and reservoir fracturing grew out of the formative stage are stunning on top of stunning.  If that’s not enough, then lots of natural gas has been over looked because the reservoirs also hold contaminating chemicals – that has lured intense and successful research to bring these resources on line, too.

Algeria, already a major exporter of oil and natural gas is sitting on huge undeveloped reserves of shale gas that the country now intends to develop with the help of international partners. The estimate is that Algeria could come up with 1,000 trillion cubic feet of natural gas trapped in shale rock only 3,280 feet below the surface.

The drilling and fracturing transformation that started decades ago in the United States has companies and countries across the globe scrambling to replicate the success and develop shale gas reserves of their own.

Here is graphical list of the very biggest reserves within the borders of the short list of countries.  With the U.S thought to be set for decades if not centuries, the countries with higher reserves represent a huge resource.

Top 2010 World National Natural Gas Reserves
Top 2010 World National Natural Gas Reserves.

When we last looked at natural gas the interest was on another technology to recover gas that was not economical due to the costs of cleaning up the other chemicals that come out with the natural gas.  It seems that there is another technology on its way to clean up natural gas at a much lower cost.

A team of Battelle researchers at the Department of Energy’s Pacific Northwest National Laboratory has discovered a method that could dramatically cut the amount of heat needed during natural gas processing, reducing the amount of energy needed during a key-processing step.  The first blush is a savings of 10%.  That might turn out to be low.

Even now some raw natural gas is purified in a process called “sweetening” before it can be used as a fuel. The gas industry currently uses a process called Thermal Swing Regeneration for sweetening natural gas. In that process, chemical sponges called ‘sorbents’ remove toxic and flammable gases, such as rotten-egg smelling hydrogen sulfide from natural gas.

The chemical sorbents are dissolved in water with the gas set up to flow through. Then solution must then be heated up and boiled to remove the hydrogen sulfide, in order to prepare the sorbent for recycled future use. Once the hydrogen sulfide is boiled off, the sorbent is then cooled and ready for use again. This repeated heating and cooling requires a lot of energy and reduces the efficiency of the process.

The new, Battelle-PNNL created process is called Antisolvent Swing Regeneration, that takes advantage of hydrogen sulfide’s ability to dissolve better in some liquids than others at room temperatures. In the new process, the hydrogen sulfide “swings” between different liquids during the processing at nearly room temperature, resulting in its removal, in just a few steps, from the liquids that can be recycled again and again.

Phillip Koech, lead author and senior research scientist explains, “Because hydrogen sulfide is such a common contaminant in methane, natural gas processors could potentially use this method in the sweetening process, reducing their energy use and saving money on the cost of sorbent materials.”

In the lab the team dissolved hydrogen sulfide in several different recyclable binding organic liquids and found that nearly all of them could hold the chemical without added water. They found one – DMEA – that could hold the most hydrogen sulfide. A chemical analysis suggested that hydrogen sulfide forms a salt with DMEA, turning the DMEA from an oily liquid into something more like salty water, but not water at all.

Based on the chemical characteristics of the salty DMEA, the team thought the salt could be easily disrupted and turned back into the gas hydrogen sulfide by adding a liquid hydrocarbon called an alkane. They mixed the hydrogen sulfide-containing DMEA with the alkane known as hexane and shook it like a bottle of salad dressing. Most of the hydrogen sulfide returned to its gaseous nature and bubbled out of the mix, leaving a soup of DMEA and hexane.

Having successfully removed the hydrogen sulfide from the DMEA, the team needed to find an alkane that would separate out the hexane and the DMEA, and found one in hexadecane, which separates from DMEA in the same way that oil and vinegar drift apart in salad dressing. The team suspects the components separated due to a bit of salt remaining in the DMEA.

But unlike hexane’s ability to perform at room temperature, the team had to warm the DMEA-hexadecane solution just a little – to about 40º C (104º F), the temperature of a hot summer day or a hot tub – to get the liquids to release the hydrogen sulfide. After the gas bubbled off and the two liquids separated, the team could pour off the hexadecane and re-use the left over DMEA.

Lastly, the team tested how well the chemicals could be re-used by recycling the hydrogen sulfide through the DMEA and hexadecane five times. The liquids retained their ability to remove the hydrogen sulfide and recover the DMEA in its initial form. The team expects DMEA will be able to pull hydrogen sulfide from natural gas using this process and they expect to scale up the process with future research.

The active chemical process is called a polarity swing that occurs naturally at nearly room temperature, drastically reducing the need for heat during natural gas sweetening. Scientists estimate this method could cut the amount of energy needed to complete the sweetening process by at least 10 percent.

Here is the part beyond saving natural gas for process heating from David Heldebrant, corresponding author and project manager, “Applying ASSR to natural gas sweetening could result in a more environmentally friendly process because hexadecane is non-toxic.”  That’s very good news, aside from not wanting a lot of hydrogen sulfide getting out of control.  “We also anticipate chemical sorbents could last longer because they are not subjected to repeated heating and cooling, which degrade the sorbent,” Heldebrant adds.

The paper is published in the March 11 online issue of the journal Energy and Environmental Science and patents are pending on this technology. The technology is already available for licensing worldwide.

That just leaves recycling the hydrogen sulfide back deep into the earth’s crust, unless someone figures out a way to made worthwhile use of it as well.  Which would come as no great surprise . . .

By. Brian Westenhaus of New Energy and Fuel

Source: Here comes Even More Natural Gas

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Leave a comment
  • Anonymous on March 16 2011 said:
    I didnt believe in shale gas in the US, but I was wrong - though not as wrong as some people think. As for some of the advertisement in this article, I definitely dont believe in it, although in the long run - the very long run - it might be OK.

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