Effects of Reaction Condition on the Emission Characteristics of Fuel-N during the O₂/H₂O Combustion Process of Demineralized Coal

Abstract

This research investigated the emission and evolution characteristics of fuel-N during the O2/H2O combustion process of a typical bituminous coal (Shenhua). To avoid the catalytic interference of alkali metal salts, the demineralized coal obtained from the raw coal sample was employed for the investigation in this research. The effects of reaction temperature (T r) and H2O concentration, which were two vital factors affecting coal combustion characteristics, on the emission characteristics of fuel-N during the combustion process were also taken into consideration. Isothermal combustion tests performed under different O2/H2O conditions (T r: 1073 and 1473 K; O2: 30%; H2O: 0, 3.5, 8.5, 15, 20, and 30 vol %) indicated that relatively high concentrations of N2O, HCN, and NH3 were measured in the O2/H2O combustion of the coal sample. With the increase of T r and H2O concentration, more fuel-N would be released in the devolatilization/volatile oxidation stage of the reaction. The X-ray photoelectron spectroscopy results of chars after devolatilization indicated that most of the N-5 decomposed into HCN or converted to N-6 or N-Q in the early reaction stage at high temperatures and that N-Q was the dominated form of a nitrogen-containing functional group (C­(N)) existing on the char particle surface. The reducibility of the chars after O2/H2O devolatilization played vital roles in reducing the emission of NO during the whole O2/H2O combustion process.

Effects of Torrefaction Pretreatment on the Structural Features and Combustion Characteristics of Biomass-Based Fuel

“…Due to the rapid thermal degradation of hemicellulose content in the oxidizing upgradation processes, the destruction of thick-walled fibers in the particles tended to be promoted, which accelerates the rapid desorption of abundant inclusions as well as the drastic formation of tube-like pore structures. Due to the reduction in fragmentation intensity and enhancement in homogeneity resulting from increasing torrefaction severity, the average pore diameter decreased, accompanied by significant enhancement in pore volume [ 39 ]. When the torrefaction temperature remained identical, the upgraded samples obtained from raw flue gas normally had the largest surface area and pore volume, and the smallest average diameter.…”