(534c) Gasification of Residue from the Sovlent Extraction of Powder River Basin Coal

Coal can be solvent extracted to produce an ash-free extract, which can be used as a fuel or further processed. This leaves behind a solid residue. Gasification is a means of converting this residue into a valuable intermediate, syngas.

We solvent extracted Powder River Basin coal with tetralin, a hydrogen donor solvent, at about 360 C. The weight of the residue from this extraction was about half of the original dry coal weight. We then measured gasification rates for this residue in both steam and carbon dioxide using a modified drop tube reactor.

The residue gasification kinetics were compared to prior measurements of gasification rates for un-extracted Powder River Basin coal. We observed higher rates with the residue. Activation energies for both the residue and the un-extracted coal were nearly the same, suggesting the same rate-limiting mechanism. The higher rates for the residue may be due to higher particle porosity created by the removal of the extract. Alternatively, the residue, which contains essentially the entire inorganic fraction of the coal, is expected to have a higher concentration of naturally-occurring gasification catalysts, such as calcium.

Some types of commercial gasifiers, such as fluidized bed gasifiers, require highly reactive feedstocks in order to achieve high conversion rates. Our results show that gasifiers that are suitable for Powder River Basin coal should also be suitable for the extraction residue.