Experimental Study on the Oxygen-Enriched Combustion Characteristics of CO in Flue Gas from an Anode Furnace

The flue gas of a copper smelting plant contains high-concentration SO2, which could be used for sulfuric acid production via a catalytic oxidation approach. Coal as a reducing agent during pyrometallurgical copper refinement in an anode furnace leads to high-concentration CO in the flue gas. High concentrations of CO not only compete for oxygen consumption but also reduce the activity of oxidation catalysts, thereby severely hindering the resource recovery of SO2 from flue gas. This problem may be resolved via installing a combustion chamber downstream, which introduces air to assist with CO oxidation. However, the complex composition of anode furnace flue gas affects CO combustion reactions, and the flue gas temperature may decrease from 1150 °C to 600 °C during flow to the combustion chamber, making CO combustion difficult. Additionally, significant air leakage could account for more than 60% of the total flue gas volume, which makes it difficult to determine the flue gas volume and severely hinders the calculation of the required oxygen dosage for the combustion chamber. In this study, an anode furnace with single production copper output of the 160-ton class was selected, and its flue gas volume as well as the required air supply for complete CO combustion were calculated based on the CO concentration via adopting the elements conservation law. When CO accounts for 3–10% of the total flue gas volume, the total flue gas flow volume ranges from 6800.3 to 7637.3 Nm3/h during reduction in an anode furnace, and the required air supply for CO burn-off ranges from 545.1 Nm3/h to 1617.9 Nm3/h. Based on the flue gas composition and conditions in the combustion chamber, the influences of the temperature and CO2 and H2O concentrations on CO oxidation were systematically investigated via using a tube reactor experimental system. CO oxidation initiated at 500 °C and reached near-complete conversion (99.9%) at 800 °C. The addition of 5% H2O notably enhanced the reaction, reducing the T50 (50% conversion temperature) from 675 °C to 650 °C. Conversely, a marked suppression was observed with 6.09% CO2 at 650 °C, where the oxidation rate dropped sharply from 50.27% to 27.75%. A dedicated examination of O2 then confirmed that increasing its concentration effectively enhanced combustion completeness under the optimized conditions. At 650 °C, the CO oxidation rate increased from 24% to 56% as the O2 concentration rose from 17.58% to 41%, whereas a further increase in O2 to 51% suppressed the rate to 39%.