Supercritical Water Cooxidation of Poultry Manure and Brown Coal in the Flow Mode

Abstract

The results of joint supercritical water oxidation (SCWO) on poultry manure (PM) and brown coal (BC) mixtures continuously fed as an NaOH stabilized (0.8 wt %) slurry into a tubular reactor at 25 MPa, temperature gradient along its vertical axis of 390–600°C, varied reactant flow rate, and concentrations of PM and BC in the slurry are presented. The addition of BC leads to a reduction of the total energy consumption by ohmic heaters by factors of 1.5–1.8, depending on the content of combustible matter in the slurry. The forming gas mixture contains CO₂, N₂, and a trace amount of N₂O. Calcium and sodium carbonates, phosphates, and aluminosilicates are predominant in the composition of ash residues. The total content of phenols (17–32 μg/dm³) and polycyclic aromatic hydrocarbons (2–4 μg/dm³) in the effluent depends on the PM concentration in the slurry and does not exceed the level of their maximum permissible concentration in wastewater. The formation of HNO₃ and H₂SO₄ during the SCWO process results in the corrosion of construction materials and increases the content of chromium, copper, and nickel in the aqueous effluent. The mechanisms of the transformation of the organic and mineral components of PM and BC are discussed.