Investigation of the NO Reduction Characteristics of Coal Char at Different Conversion Degrees under an NO Atmosphere

Abstract

The effect of preoxidative treatments on the reducing characteristics of ShenHua (SH) coal char and the evolution of surface nitrogen-containing complexes during the reducing process under different temperature conditions were investigated using temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The SH samples were oxidized to different conversion degrees (0.15, 0.22, 0.32, 0.42, 0.52, 0.73, and 0.89) under an O2 atmosphere, and the reductivity of each char sample was considerably enhanced after the preoxidative treatment. This phenomenon could be attributed to the generation of active sites and oxygen-containing complexes on the SH particle surface during the oxidation process. The preoxidized samples were obviously more reactive than the raw char, and per unit mass almost all the preoxidized samples could consume more NO than SH raw char under the same experimental conditions. The entire TPR process could be divided into the following four sections: (a) the reversible physical adsorption stage, (b) the heterogeneous reaction stage, (c) the multireaction stage, and (d) the equilibrium reaction stage. The primary reaction path at each stage could be summarized using the TPR and XPS results. The evolution of the C­(N) and the variation in the elemental distribution (C, O, and N) during the TPR process were investigated by XPS. The results showed that N-Q was the most stable organic structure of the nitrogen-containing complexes on the particle, and the decomposition of N-6, N-5, and N-Q occurred when the reaction temperature reached 1173 K. The total amounts of N-Q, N-6, and N-5 decreased when the reaction temperature exceeded 1173 K, indicating interaction between the nitrogen-containing complexes occurred. Meanwhile, prior to the attachment of NO molecules to the char particle surface and forming C­(N), more NO molecules were consumed by CO at this temperature. The results in this research clarified the effect of the conversion degree on the char reductivity and the primary reduction reaction path under different temperature conditions, providing a technical framework for the reducing process of air-staged combustion technology.

Experimental study Char‐NO reduction characteristics at elevated pressure

“…The Char‐NO reaction was inhibited, resulting in a reduction in NO consumption, CO production, and N reduction rate during the experiment. It was consistent with the experimental conclusion that Wang 31 obtained a good correlation between the amounts of char samples surface active sites and the ability to reduce NO.…”

Physicochemical Properties and AAEM Retention of Copyrolysis Char from Coal Blended with Corn Stalks

“…A horizontal fixed bed furnace was used to rapidly pyrolyze the blends and obtain char samples; the flowchart of the furnace can be found elsewhere. 11 Before each test, the furnace was heated to the set temperature (from 400 to 1000 °C at intervals of 100 °C) under a continuous argon (>99.99%) flow of 1 L•min −1 . Subsequently, the quartz boat with the blend sample (1 ± 0.05 g) was rapidly placed in the middle of the furnace and held for 20 min.…”

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

“…Both HCN and NH 3 could react with NO, generating N 2 under high-temperature conditions . Additionally, massive oxygen-containing functional groups (C­(O)) were generated on the particle surface, and a large amount of NO molecules would be reduced by the functionalities rapidly . The results in this research also demonstrated that the addition of H 2 O tended to promote the formation of N 2 O in the reaction zone.…”