Char-nitrogen oxidation under fluidised bed combustion conditions: single particle studies

Combustion studies in a fluidised bed—The link between temperature, NOx and N2O formation, char morphology and coal type

“…Crelling et al (1993) concluded that variations both in lithotype and maceral composition gave rise to large variations in nitrogen content, char morphology and reactivity, i.e., that although the nitrogen content decreased in the order: vitrinite N semifusinite N inertinite, the conversion of the coal and char nitrogen to NO showed the reverse order: fusinite N semifusinite N vitrinite. Other authors also concluded that there could be other factors related to the structure and properties of the coal, in addition to the combustion conditions, such as rank and the degree of surface oxidation (Shimizu et al, 1992;Gavin and Dorrington, 1993;Pels et al, 1993), maceral composition (Gonzáles de Andrés and Wang et al, 1994), mineral matter (Zhao et al, 2003), char reactivity, and surface area (Kilpinen et al, 2002;Shen et al, 2003;Zhao et al, 2003).…”

Si̇rkülasyonlu Bi̇r Akişkan Yatakli Yakicida İşletme Parametreleri̇ni̇n So2 Emi̇syonu Üzeri̇ndeki̇ Etki̇leri̇

“…The oxidation of this char-nitrogen gives an important contribution to the total nitrogen oxide emissions from the combustor. The mechanism of char-nitrogen oxidation to the products is very complex, and includes not only several homogeneous and heterogeneous reactions but also mass transfer effects inside the pore system of the char and in the boundary layer surrounding the particle [21]. In the present study, fuel-NO x can be formed through: Combustion of the nitrogenous species released with volatile matter (such as HCN, NH 3 ), and oxidation of the nitrogen retained in the char.…”

Analysis of environmental benefits of CFB combustors via one-dimensional model

“…There are great differences in the hydrodynamics between the dense bed and the dilute region. However, most of the models in the literature do not completely take account of the performance of the dense bed, consider the dense bed as well-mixed distributed flow with constant voidage, and use generally lumped formulation [1][2][3][4][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Experimental evidence has been reported by Svensson et al [29], and Werther and Wein [30] that, the fluid-dynamical behavior of the dense bed is similar to that of bubbling fluidized beds.…”

“…The reactions of nitric oxide with carbons or chars are of current interest with regard to their possible role in reducing NO emissions from combustion systems. As mentioned above, large literature concerning these reactions has developed, as evidenced in three reviews [14][15][16] and by the recent publication of many papers in the area [17][18][19][20][21][22][23][24][25]. These works have suggested considerable complexity in the mechanisms of NO reduction and a large variability in reported kinetics.…”

“…The emission of NO depends on temperature because the NO oxidation changes significantly with temperatures [19]. It must also be noted that together with this, at the operating temperature of the CFB combustor (between the temperatures 800 and 950 • C), nitrogen in air does not take part in an oxidation reaction to form NO.…”