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The coal to gas technology which Solid Energy and L&M Energy are investigating, owes a lot for its development to Lenin and Soviet Union engineers. By Lindsay Clark.
The coal is ignited through wells drilled from the surface into the targeted coal seam and as much as 75 percent of the energy from coal in an underground coalfield can be extracted. Other wells will pump air or oxygen to keep the coal burning at the right temperature to generate the maximum amount of gas. Other wells are sunk along the coal seam with the coal fractured using the ‘fraccing’ technology common in petroleum exploration. Having a sealed underground chamber for manufacturing gas will be similar in some ways to the way ‘town gas’ used to be made in many New Zealand cities before the advent of natural gas where coal was heated in city gas company retorts to generate gas for domestic gas consumption. The gas produced from underground coal gasification is called syngas because it can be used for making synthetic transport fuels, fertilisers, chemicals or other synthetic products. The gas can also be used to generate electricity. Judging by the trials and tribulations which underground coal gasification has undergone over the past 100 years, the process will not necessarily be easy to implement in New Zealand. A lot of knowledge will have to be built up about what works best in different ranked coal grades, individual coal seams and which produces the most valuable gas. Britain started to look seriously at coal gasification about 100 years ago, when Vladimir Lenin, the Russian Bolshevik leader then in exile in Europe, read about experimental work in the UK in 1913 and wrote an article for Pravda newspaper about underground gasification entitled, “A Great Victory for Technology”. He saw gasification as a way of liberating workers from the dangerous work of mining coal underground. Although the British concept of UCG had not been proven in practice, Soviet engineers, backed by enthusiasm from both Lenin and later Stalin, pushed the development of underground gasification at great cost while the idea lapsed in the rest of the world. Interrupted by World War II, UGC plants began to be built in earnest in the 1950s and by the 1960s the Soviet Union had about 14 industrial scale plants operating. While we can thank Lenin for the initial development of underground gasification, but it was also the discovery of huge natural gas reserves in the USSR (and elsewhere around the world) that provided easy cheap energy that made UGC redundant and plants were closed. For many years only one commercial UGC plant operated in the world, in the former central Asian Soviet republic, and now independent, Uzbekistan. The Uzbekistan plant in Angren is still happily producing about 1,000,000 cubic metres of syngas a day to drive a local power station. Oddly, the Uzbekistan UGC plant is now 91 percent owned by an Australian company, Linc Energy and Australia is now a country where interest in UGC is amongst the strongest. Linc Energy’s plant is particularly interesting. It has successfully developed a pilot UGC at Chinchilla on the Queensland coalfields at a relatively cheap cost. Also Linc has combined syngas from the underground gasification to supply a pilot Gas to Liquids (GTL) technology plant that made a clean liquid fuel. Linc Energy says it has enough coal resources to run a full-scale plant producing 20,000 barrels per day of high quality diesel and jet fuels for 60 years. Ergo Exergy, the Montreal-based UGC technology supplier which is working with Solid Energy on its Waikato project, says its principals have been responsible for the Uzbekistan UGC plant’s success over almost 50 years, and Ergo is still providing technical assistance there. It has also helped start new plants in Canada and South Africa and is working with some big companies in other parts of the world. Ergo Exergy says it operated the Chinchilla site and provided its trademarked εUCG™ technology to Linc. The Canadian company also says it terminated the arrangements with inc in 2006 so Ergo could concentrate on worldwide commercial UCG projects. A number of other Australian companies including Carbon Energy, Cougar Energy and Clean Global Energy are also developing underground coal gasification projects. From a New Zealand perspective it is notable that a number of these companies as well as Linc Energy are looking at the large lignite fields of southern Australia to further develop gasification. Both Solid Energy and the L&M Group have often stated their ambition to develop the Southland lignite fields, the country’s biggest coal resource, as a source of liquid fuel, fertilisers, chemicals or power generation. The two companies both have current permits over the main Southland and Otago lignite fields. Solid Energy has been the most active recently in pressing forward with prospective new developments including a possible fertiliser plant with Ravensdown based on the Mataura lignite field – the largest coal field in the country. The big question is whether Solid Energy, or L&M, will eventually try to use UGC technology for their Southland lignite resources? This would mean the envisaged big opencast mine and above ground plant to turn lignite into the first stage syngas, would be replaced by an out-of-sight chamber underground making syngas. Just the final products processing from the raw syngas would be done above ground. Or will the companies move their big plant ambitions north to continue work on the Waikato coalfields where they plan to start experimenting with UGC? Waikato holds a number of deeper, never-mined coalfields that might be more suitable for gasification. The answer to where these modern coal miners will focus in future will depend first on whether they can make underground gasification economically work.
Energy NZ Vol.4 No.4 July-August 2010 |
The idea behind underground coal gasification (UCG) is a simple one. Instead of mining coal by traditional methods from the surface, why not bring up all the energy from the coal as a gas by controlled burning of the coal seams deep underground?