Abstract
The main goal of the study was the analysis of the parameters of wastewater generated during the ex situ underground coal gasification (UCG) experiments on lignite from Belchatow, and hard coal from Ziemowit and Bobrek coal mines, simulated in the ex situ reactor. The UCG wastewater may pose a potential threat to the groundwater since it contains high concentrations of inorganic (i.e., ammonia nitrogen, nitrites, chlorides, free and bound cyanides, sulfates and trace elements: As, B, Cr, Zn, Al, Cd, Co, Mn, Cu, Mo, Ni, Pb, Hg, Se, Ti, Fe) and organic (i.e., phenolics, benzene and their alkyl derivatives, and polycyclic aromatic hydrocarbons) contaminants. The principal component analysis and hierarchical clustering analysis enabled to effectively explore the similarities and dissimilarities between the samples generated in lignite and hard coal oxygen gasification process in terms of the amounts and concentrations of particular components. The total amount of wastewater produced in lignite gasification process was higher than the amount generated in hard coal gasification experiments. The lignite gasification wastewater was also characterized by the highest contents of acenaphthene, phenanthrene, anthracene, fluoranthene, and pyrene, whereas hard coal gasification wastewater was characterized by relatively higher concentrations of nitrites, As, Cr, Cu, benzene, toluene, xylene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene.
Highlights
The underground coal gasification (UCG) is considered to be a prospective technique of coal utilization for the purposes of energy generation and chemical synthesis substrates production
The studied experimental data included measurements of physical and chemical parameters in wastewater generated in the UCG process on lignite and hard coal simulated in the ex situ reactor
The wastewater generated in the UCG poses the potential threat to the environment if treated inappropriately, since it contains high concentrations of benzo(a)anthracene benzo(b)fluoranthene chrysene
Summary
The underground coal gasification (UCG) is considered to be a prospective technique of coal utilization for the purposes of energy generation and chemical synthesis substrates production. Its advantages over a traditional coal gasification process results from the utilization of coal in situ and includes avoidance of cost and/or risk generating operational steps, like involvement of manpower underground, coal transport and pre-processing at the surface, as well as surface gasification infrastructure. A few dozen large-scale experiments and commercial applications of the UCG process have been accomplished (Gregg and Edgar 1978; Burton et al 2006). The environmental aspects have been paid much attention in Chinchilla project (Australia) (Blinderman 2005). The latest news on Kingaroy project (Queensland, Australia) proves that the environmental aspects of the UCG process should not be neglected (Burgess 2011; Sollars 2011)
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