Evolution mechanism of C/N-containing gas-solid groups during pulverized coal pressurized O₂/CO₂/N₂ devolatilization

Pressurized oxyfuel combustion technology is an advanced coal-fired power generation technology for effective carbon capture. The evolution characteristics of pressurized devolatilization in the O₂ and CO₂ reactive atmospheres have a decisive influence on its pressurized oxyfuel combustion. The effects of devolatilization time, O₂ concentration, and CO₂ concentration on the evolution mechanism of products characteristics at high temperatures and high pressures in O₂/CO₂/N₂ atmosphere are investigated by a pressurized devolatilization experimental system. The conversion mechanism of C and N during the pressurized devolatilization is obtained by quantitatively on-line measuring the emission characteristics of the gas-phase products and semi-quantitatively off-line characterizing the solid-phase products of the pore structures, the carbon skeleton structures, and oxygen/nitrogen-containing functional groups structures. The experimental results show that the extension of the devolatilization time can reduce the CO and NO_x emissions, and a volume ratio of O₂ to CO₂ greater than 0.5 significantly inhibits the CO emissions, and the volume ratio greater than 1 significantly increases the conversion of Fuel-N to Gas-N. In addition, the increasing devolatilization time promotes the development of pore structures. The O₂ atmosphere has a dominant effect on both gas products and solid products, while the CO₂ atmosphere mainly affects the gas products characteristics during the pressurized devolatilization process.