Сверхкритические флюиды. Теория и практика
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2019, N3, pp. 77-96

O.N. Fedyaeva, A.A. Vostrikov

Comparative Analysis of Lignin and Sludge-Lignin Oxidation in the Stream of Air and Water-Oxygen Mixture

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.

Key words: lignin, sludge-lignin, supercritical water, oxidation, corrosion

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