Gasification begins with combustion of the coal between endpoints. As a cavity forms and the coal is emptied out, the gasification front is pulled progressively back toward the vertical wells. Friedmann says that the technique made UCG a more reliable process... _TechnologyReview
Engineering safer and cleaner methods for gasifying coal underground, in situ, is taking a higher priority in Australia, China, and South Africa. Underground coal gasification, UGC, is a promising source of syngas -- particularly for nations that are less endowed with natural gas than the US.
UCG got started in the former Soviet Union and reached commercial scale by the 1950s. One such plant in Angren, Uzbekistan, continues to generate up to 18 billion cubic feet of syngas per year. But Soviet production peaked in the 1960s as production of cheaper natural gas ramped up. The U.S. conducted 33 UCG pilot projects in the 15 years following the first Arab oil embargo.
The U.S. work demonstrated an improved method that enhanced the quality of the syngas developed by Lawrence Livermore in the 1980s. Whereas earlier UCG efforts used one horizontal well to connect distant air injection and syngas removal wells, the improved method uses parallel injection and syngas removal wells 20 to 30 meters apart that descend vertically to the seam and then horizontally through the seam for several hundred meters to several kilometers.
...Following a 100-day run this spring at Bloodwood Creek test site in Queensland, Australian UCG developer Carbon Energy estimated that it could generate syngas for A$1.25 (US$1.10) per gigajoule of energy, at a time when Australian natural gas was fetching A$3.50 to A$7 per gigajoule. Those economics enabled Carbon Energy to raise A$32 million in June, which the firm is using to install a small five-megawatt generator this winter and engineer a 20-megawatt power plant for late 2010. Ultimately it plans to build a 300-megawatt power plant at the site. _TechnologyReview
Similar approaches to harvesting energy from inaccessible oil sands deposits and oil shale deposits may well turn modern Peak Oil Doomers to more productive pursuits.
Labels: coal, syngas