Tar related issues in underground coal gasification

Technology UCG is worldwide presented as the technology with the lower adverse effect on the environment in comparison to all until now applied techniques of the underground and surface coal mining. The present paper deals with the pollution from the underground coal gasification in situ taking into the consideration the amounts of the gasified coal based on the samples from the simulated gasification and chemical analysis of tar. Pollution of rock surrounding can be caused by evasive gas, aromatic hydrocarbon, extractable non-polar substances and solid residues. During individual gasification, there are raising polluting gases as hydrocarbon, hydrosulphide, carbon disulfide, oxide nitrogen, mercaptans. Such gas compounds have high toxicity and significant stink. Some of the less qualitative sorts of coal obtain till 6 % of sulphur, that is oxidised during gasification and burning to the sulphur dioxide, and hydrosulfide is also rising. By not perfect coal burning, there are also raising polyaromatic hydrocarbons (PAH), many of them are toxic, or they have mutagenic effects. The question is how these tars will affect the underground and surface water in the area which has been encumbered with the mining and chemical industry for a longer period.