Effects of reaction condition on NO emission characteristic, surface behavior and microstructure of demineralized char during O2/H2O combustion process. (1st October 2019)

• Record Type: Journal Article
• Authors: Wang, Zhuozhi; Zhao, Yaying; Sun, Rui; Li, Yupeng; Ren, Xiaohan; Xu, Jie
• Is Part Of: Fuel. Volume 253(2019)
• Page Start: 1424
• Page End: 1435
• Publication Date: 2019-10-01
• Subjects: Coal char -- O2/H2O combustion -- Surface active site -- Microstructure -- NO; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2019.05.119
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Fuel-N mainly released in the form of NO in O2 /H2 O combustion of demineralized char. Increase of Tr and O2 concentration could inhibit NO emission in O2 /H2 O combustion. C(O) amount reflected demineralized char reactivity and NO emission characteristics in combustion. There was linear correlation between I(Gr+VL+Vr) /ID and demineralized char reactivity. Abstract: Surface behavior and structural characteristics of char particles generally play a vital role in affecting char NO emission characteristics during combustion process. A typical bituminous Shenhua from northwest China was employed for demineralization in this research. The demineralized coal without catalytic interference of alkali metal salts was employed as the experimental sample. Moreover, by means of the utilization of isothermal combustion test, Temperature Programmed Desorption (TPD) and Raman spectrometer, the conversion ratio of nitrogen content in char to NO, as well as the evolution of char surface behavior and micro-structure in the process of O2 /H2 O combustion under different conditions were determined. With the increase of reaction temperature (Tr ) and O2 concentration, more surface active sites (Cf ), oxygen containing functional groups (C(O)) and small aromatic ring structures generated on char particle surface inhibiting the emission of NO during O2 /H2 O combustion process. Under identical reaction conditions (Tr, O2 and H2 O concentration), the partially oxidized chars with moderate burnout degree (Xc ≈ 0.3) had the largest amount of Cf on particle surface. On the other hand, the amount of Cf and small aromatic ring structures first increased and then decreased as the H2 O concentration enhanced. When the Cf amount and the value of I(Gr+VL+Vr) /ID reached the maximum at the H2 O concentration of approximately 8.5 vol%, the conversion ratio of char-N to NO reached the minimum value. Meanwhile, the increase of H2 O concentration initially accelerated the NO reduction rate and this positive effects gradually diminished when the H2 O concentration exceeded the critical value (8.5 vol%). Thus, the optimal combustion condition for char combustion with the lowest NO conversion ratio in this study was: 1473 K, 30% O2 and 8.5 vol% H2 O.