Abstract
In this study, the composition of tars collected during a six-day underground coal gasification (UCG) test at the experimental mine ‘Barbara’ in Poland in 2013 was examined. During the test, tar samples were taken every day from the liquid product separator and analysed by the methods used for testing properties of typical coke oven (coal) tar. The obtained results were compared with each other and with the data for coal tar. As gasification progressed, a decreasing trend in the water content and an increasing trend in the ash content were observed. The tars tested were characterized by large changes in the residue after coking and content of parts insoluble in toluene and by smaller fluctuations in the content of parts insoluble in quinoline. All tested samples were characterized by very high distillation losses, while for samples starting from the third day of gasification, a clear decrease in losses was visible. A chromatographic analysis showed that there were no major differences in composition between the tested tars and that none of the tar had a dominant component such as naphthalene in coal tar. The content of polycyclic aromatic hydrocarbons (PAHs) in UCG tars is several times lower than that in coal tar. No light monoaromatic hydrocarbons (benzene, toluene, ethylbenzene and xylenes—BTEX) were found in the analysed tars, which results from the fact that these compounds, due to their high volatility, did not separate from the process gas in the liquid product separator.
Highlights
The process of underground coal gasification (UCG) is considered to be one of the forms of clean coal technologies for obtaining gaseous fuel and synthesis gas from hard coal (Burton et al 2006; Bhutto et al 2013; Cough 2009)
Starting with a relatively low content at the beginning of the test, we note an increase to 15.3% on the 3rd day and stabilization at 14% at the end of the test
Based on the research carried out, the following conclusions can be drawn: (1) The conditions of the gasification process have a significant influence on the quality of the gas obtained and on the properties of liquid tar products, which are a by-product of the UCG process
Summary
The process of underground coal gasification (UCG) is considered to be one of the forms of clean coal technologies for obtaining gaseous fuel and synthesis gas from hard coal (Burton et al 2006; Bhutto et al 2013; Cough 2009). After many years of research and trials on an industrial scale conducted around the world (mainly in the USA, China, Australia, South Africa, Russia, Canada and Poland), the technology of underground coal gasification is still not fully mature for its widespread use on an industrial scale (Greg 2018). The only active installation in which underground coal gasification is carried out on an industrial scale is located in Angren (Uzbekistan), located on the territory of the former Soviet Union (Olness 1982). This installation has been operating since 1961, supplying low-calorific gas to a nearby power plant. Further research is needed to make these technologies applicable on a mass scale
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