Key words: lignin, sludge-lignin, supercritical water, oxidation, corrosion
Oxidation of sulfate lignin and sludge-lignin (waste of the Baikal Pulp and Paper
Mill) in the stream of water-oxygen mixture and in air in the programmed heating
regime is studied. Based on the temporal dependences of the power of resistive heaters
and the reactor wall temperature, it was revealed that the maximum rates of lignin and
sludge-lignin oxidation in the H2O/O2 mixture are reached at 613—643 K. Oxidation of
both substances in the H2O/O2 mixture is completed at lower temperatures than in air.
The temperature dependences of compositions of volatile and liquid products, including
the content of phenols, are obtained. Using the mass-spectrometric analysis it is shown
that during oxidation in the H2O/O2 stream 90.3 and 79.5 % of carbon is removed from
lignin and sludge-lignin, respectively, in the form of carbon oxides. The mechanisms of
transformation of heteroatomic components are discussed. Formation of hydrochloric
and sulfuric acids in the course of sludge-lignin oxidation in the H2O/O2 stream
causes the corrosion of stainless steel.
doi:10.1134/S1990793120070076