Characteristics of N/S transformation during combustion of oil sludge pyrolysis

The evolvement characteristics of nitrogen-containing and sulfur-containing gas, as well as the transformation characteristics of N/S during oil sludge pyrolysis combustion were studied by TG-MS and XPS. It is found that nitrogen in OS char mainly exists as N-Q and N-5, while sulfur in OS char exists as S2-, S4+, and S6+. The content of N-Q is 75.79%, which is higher than N-5. Meanwhile, the content of S2- is much higher than that of the sum of S4+ and S6+. This indicates that sulfur in OS char is mainly pyrite or sulfide. The formation of porous structure in pyrolysis char is accelerated with the increase of pyrolysis temperature, and thus the oxygen adsorption capacity is improved. When the combustion temperature increases from 900 to 1 000 ℃, S4+ content increases and S6+ content decreases, meaning this temperature rage is favor for the SO2 emission. When the temperature reaches 1 100 ℃, more S4+ is converted into S6+ and S2-. This is because the excessive temperature could promote SO2 to convert into SO3 and other sulfur-containing gas, which could reacte with inorganic minerals in OS char to increase the content of S6+ and S2-. © 2021, Editorial Office of Journal of China University of Petroleum(Edition of Natural Science). All right reserved.