Will Atomised Refined Coal become a viable alternative for gas and oil? Consulting engineer BRYAN LEYLAND explains why this process being developed across the Tasman has him so intrigued as a future source of energy.
by Brian Leyland, InterTech
Earlier this year, I was one of about 70 people invited to be present at a “show and tell” seminar put on by InterTech Systems at its premises, just north of Sydney, to demonstrate a revolutionary Atomised Refined Coal (ARC) process for refining coal and other minerals.
If InterTech can deliver what it has promised – and I believe they can – it will have a world-wide effect on energy supply and geopolitics. ARC promises to be a viable substitute for gas for power generation and for oil for transport. Not only that, but the by-products from the coal refining process could supply much of the alumina the world needs, plus large quantities of other minerals and elements that may soon be in short supply.
ARC goes back to the 1980s with Bob Lloyd, a brilliant electrical engineer with chemical engineering skills. His idea was to get rid of the ash in coal before it was burned, rather than separating it out after it had gone through the furnace. Realizing mechanical methods would not work, he then met someone with experience in using hydrogen fluoride (HF) for mineral processing. In the late 1980s he become involved with a 50,000 tonne per anum coal refinery that was built in Japan. Then a drop in oil prices led to this work being abandoned and the refinery dismantled.
Some years ago, Lloyd met up with the people who founded InterTech and they spent a lot of time and effort together assessing his previous work and making sure that they alone had access to his intellectual property – particularly the ability to recover and recycle the hydrogen fluoride. This is the key to the ARC economic viability.
At the seminar Lloyd told me he had operated the coal refining plant for eight months and produced 30,000 tonnes of refined coal. The coal refining process starts off with crushed coal that is dumped into a bath of HF. The process works best with coal with an ash content of at least 10 percent. The HF dissolves the silica (given off as a gas and recovered) and other impurities. Subsequent processes recover alumina, sulfur, titania, water, rare earths and metal fluorides and the value of these byproducts is likely to exceed the cost of mining the coal.
The refining part of the ARC process operates at relatively low temperatures and pressures, and uses reasonably established technology for mineral separation using hydrofluoric acid. As an example, I was told in 2003 the New South Wales power generation industry used 28 million tons of coal that produced about seven million tonnes of ash. If they converted to using refined coal, the ash would yield 4.2 millions of silica, 1.75 million tonnes of alumina, and 70,000 tonnes of titanium – with a total value of $760 million.
The refined coal from the refinery is about rice grain size and can be transported and handled quite safely. Ash content is less than 0.3 percent. The only problem is that it has a <0.2 percent water content and it must be kept dry during transport and storage.
If the refined coal is ground up in a conventional pulverized coal mill it can be fired into conventional boiler without any great problems, and without any sulfur or other pollutants in the stack gas. This means that high sulfur coal can be refined and burned in existing coal fired stations without a stack gas cleanup system. If the ash in the coal has useful quantities of valuable byproducts they will offset some, or all, of the cost of refining the coal. Further economies will arise from reduced boiler maintenance and eliminating the cost of ash disposal. Using refined coal may well reduce rather than increase the cost of generation.
Substitute for natural gas or oil
The major use for the refined coal is found by passing it through a patented device called a “dynamist”. This device produces coal dust so fine that when somebody at the seminar got a handful of it and blew on it, it floated upwards into the air. (Afterwards, someone explained to me that it was fortunate that nobody nearby was smoking!) This Atomized coal can substitute for natural gas or oil in many applications.
If, as expected, ARC can be burned successfully in a large modern gas turbine, then the obvious thing to do is to abandon inefficient conventional coal fired power station technology and also the expensive and complex “integrated gasification combined cycle” (IGCC) and Ultra Clean Coal” (UCC, which is not the same as ARC) in favor of feeding ARC into a more or less conventional combined cycle station. Because combined cycle stations are about 30 percent more efficient than steam stations, this would reduce fuel consumption and CO2 emissions by 30 percent. It is expected that IGCC will reduce CO2 by only 15 percent.
Mitsubishi are known to have done extensive testing with various versions of UCC and refined coal. Both are understood to have been burned successfully in a large gas turbine. If ARC can be used to fire existing large gas turbines, there is a huge potential market because, since 1990 in the United States alone, 150,000 MW of gas fired combined cycle stations have been built. Recent large increases in gas price means that many of them are now uneconomic compared to conventional coal.
Car engines on atomized coal
InterTech plans to build an advanced version of the original 50,000 tpa refinery very soon. Once it has proved itself, they plan to move on to a ‘standardized’ 500,000 tpa refinery. Four of these plants could supply a 1000 MW CCGT power station.
Further down the track, there is the potential for using ARC with conventional petrol engines and in diesel engines. I was told General Motors has successfully used this fuel in a pair of prototype gas turbine driven cars. I understand GM assessed the refined coal against other coal fuel options, such as solvent refined coal and coal to liquid fuels, and concluded that refined coal was the most cost effective by far.
One significant advantage of ARC is that the granular fuel is difficult to ignite making it much safer in the event of a car accident.
At the seminar we saw a Mercedes car engine running on atomized coal. This coal came from a local coal mine and had not been refined. I was impressed that the engine ran on this and I am confident that it would run even better on atomized refined coal because the refining process makes it more reactive.
If ARC is adopted worldwide the influence that OPEC has on world oil supplies and Europe’s dependency on Russian gas will be reduced. ARC would postpone the advent of “peak oil”, substantially reduce air pollution from sulfur dioxide, etc, from burning coal for power generation and for other uses. Finally, the by-products available from processing the ash in the coal could make a big difference to the cost and availability of many scarce and important minerals.
Governments, environmentalists and others who believe that carbon dioxide causes dangerous man-made global warming should hail this process as a major breakthrough because of the reduced carbon dioxide emissions. More that 50 percent of the world’s electricity is generated from coal. If half of these stations were CCGTs burning ARC, they would be cost competitive with conventional stations and the reduction in CO2 emissions would exceed what could be achieved by heavily subsidized windfarms and other renewables.
If you are interested in participating in the development of ARC technology in America, you may contact Dr. Ed Berry for more information.