Supercritical water gasification of chicken manure continuously supplied into the reactor

The article presents the research results of the chicken manure gasification in supercritical water. The experiments were carried out using a tubular flow reactor at a pressure of 25 MPa, a temperature gradient along its vertical axis (390-600 degrees C from top to bottom), and a chicken manure flow rate of 6.9-9.6 g/min, including experiments with the addition of NaOH (2.4 wt%). Data were obtained on the yield and composition of carbonized residues, volatile and liquid products, as well as the content of toxic substances (phenols, N-containing aromatics, and polyaromatic hydrocarbons (PAHs)) and mineral components in effluent collected at the reactor outlet. It is shown that an increase in the residence time of reagents in the high-temperature region of the reactor (HTR) improves the gasification efficiency. Using gas chromatography - mass spectrometry, it was revealed that phenol, pyridine, pyrazine, pyrrole, aniline, indole, quinoline, and their alkyl derivatives predominate in the composition of water-soluble products. The total content of phenols in effluent decreases from 1.3 to 1.1 g/dm3 when increasing the residence time of reagents in HTR, and does not depend on adding NaOH while the total content of N-containing aromatics decreases from 1.0 to 0.7 g/dm3 when adding NaOH. The content of PAHs, which is dominated by naphthalene, increases from 0.5 to 2.1 mg/dm3 in effluent when increasing the residence time of reagents in HTR. According to capillary electrophoresis data, increasing the residence time in HTR and adding NaOH result in increase of the content of NH4+ ions in effluent from 9.8 to 10.9 g/dm3.