Syngas underground coal gasification
Underground coal gasification produces syngas. A product rich in hydrogen (H2), methane (CH4) and carbon monoxide (CO), without the need for a mine.
The Syngas industry is expanding in Australia as a result of a continuing and growing demand for energy and the introduction of new technology such as directional drilling that is making it possible.
Australia is fortunate to be host to very large quantities of stranded coal beds that are neither economical to mine by conventional means nor able to be sold into conventional markets. This is why the production of syngas (synthesis gas), produced by means of underground coal gasification in such stranded deep deposits, is important. By using this technology these coal beds can be made available to produce much needed transport fuels, power for electricity generation, synthetic natural gas and fertiliser.
The syngas underground coal gasification process is a means whereby Australia will be able to avoid any future shortages of gas that could force the gas price to rise dramatically, thereby adversely effecting our future industrial prospects and standard of living.
Coal gasification is not a new process. It was used as early as the 1800's for the provision of heating gas to cities and towns. Electricity has been generated from the use of coal gas turbines and coal gas has been used for many years for the production of synthetic liquid fuels. However, gas extracted from coal for these purposes has been produced from above ground gasification. It is only now that syngas underground coal gasification is being adopted in many countries as the new clean energy of choice, because of its efficiency and its ability to make use of otherwise redundant coal sources.
A primary benefit of syngas underground coal gasification, besides that of suppling the market with low cost energy, is that it can be fed into existing coal seam gas pipelines, therefore adding to the overall national gas supply.
Syngas underground coal gasification eliminates the need, and therefore the cost, of mining the coal and bringing it to the surface before gasification can begin. The cheaper and more efficient in-situ process takes place with the following procedure:
1. Wells are drilled vertically into the coal seam and linked together horizontally
2. Either air or oxygen is pumped into one of the wells, called the injection well, and ignited to cause the combustion of the coal seam.
3. The resulting partial combustion of the coal produces heat, carbon dioxide and some syngas
4. A series of chemical reactions then takes place that involves a combination of pressure, carbon and heat, steam is also produced from water existing in the heated coal, as well as carbon. This results in the production of more syngas.
5. The syngas that is produced flows through the horizontal connections in the coal seam and finds its way to the surface through another vertical well, called a production well.
The composition of the gas that arrives at the surface, where it is collected, depends on many factors such as whether air or oxygen was used to create combustion, the amount of water in the coal, the temperature and pressure created, as well as the type of coal involved.
As an example of what could be Australia's future as far as the production of syngas through underground coal gasification is concerned, we only have to take into account the 7.8 billion tonne coal resource in the Arckaringa Basin in South Australia that has the potential to supply 330,000 barrels a day for more than 70 years.
