NO_x Reduction by Potassium-Containing Coal Briquettes. Effect of NO₂ Concentration

Abstract

The reactions of a potassium-containing bituminous coal briquette and the corresponding catalyst-free char with different NO/O2 mixtures have been investigated at temperatures between 300 and 325 °C. The isothermal reactions have been followed by two techniques: thermogravimetry and gas chromatography + chemiluminescence analysis. A NO/NO2 mixture rich in NO2 results in a high carbon loss compared to that corresponding to the mixture poor in NO2. Despite that, NO x conversion is similar for both mixtures. The extra weight loss in the presence of a high concentration of NO2 is a consequence of NO2 reduction by carbon, producing NO and CO2 evolution.

Formation and Reduction of NO2 in Fixed Bed Combustion of Coal Char under Oxy–Fuel Conditions: Experimental and Density Functional Theory Analysis

“…Taking products (P) for example, the Δ G values are −2.127, −2.095, −2.063, and −2.033 eV at 1073, 1273, 1273, and 1673 K, respectively. In addition, NO 2 has a lower bond order, lower bond energy, and higher thermal energy change with increasing temperature in comparison with NO, as reported by García-García et al That is, NO has better thermal stability than NO 2 , and the bond of N–O in the NO 2 molecule is more likely to break. In the presence of CO, NO 2 is more likely to react with CO in the gaseous phase, especially at high temperature.…”

“…However, the physicochemical properties of NO 2 are significantly different from those of NO. For instance, NO 2 molecules have a lower bond order and bond energy, higher dipolar moment, as well as more stable and toxic in contrast to NO . Therefore, the formation and reduction behaviors of NO and NO 2 greatly differ, which makes it essential to further explore the formation and reduction behaviors of NO 2 during O 2 /CO 2 combustion.…”

Minimization of No Emissions From Multi-Burner Coal-Fired Boilers

“…The non-catalytic and catalytic reduction of nitrogen oxides on char surfaces has been extensively investigated and can be classified into three main groups: 1) those, carried out at low temperatures (< 573 K), that pursue a better understanding of the NO reduction phenomenon in order to develop materials suitable for the destruction of NO at post-combustion conditions (Rubel et al, 1995, Lizzio et al, 1997García-García et al, 1997, Illán-Gómez et al, 1998, García-García et al, 1999, Xia et al, 1999, Ciambelli et al, 1999 2) those focused on the mechanism of nitrogen oxides reduction on char surface (Madley and Strickland-Constable, 1953, Smith et al, 1959,Teng et al, 1992, Illán-Gómez et al, 1993, Chu and Schmidt, 1993, Teng and Suuberg, 1993a, 1993b, Rodríguez-Mirasol et al, 1994, Suzuki et al, 1994, Illán-Gómez et al, 1995a, 1995b, 1995c, 1996a, 1996b, Orikasa, H. et al, 1995, Chambrion et al, 1996, 1997a, 1997b., 1998a., 1998b., Guo and Hecker, 1996, Suuberg et al, 1996, Teng et al, 1997, Carabineiro et al, 1997, Aarna and Suuberg, 1998, Zhonghua et al, 1999, Noda et al, 1999, Tomita, 2001; and those that search for a kinetic expression for this reaction suitable for modeling and design purposes (Furusawa et al, 1980…”

Minimization of No Emissions From Multi-Burner Coal-Fired Boilers

“…Recent work by Linares-Solano and coworkers, 31 Ciambelli et al 32 and Lizzio et al 33 stressed the importance of oxygen in the reduction of NO on char surface, when carbonaceous materials loaded with catalyst were considered and at relatively low temperatures (<900 K). Tomita and coworkers, 13 have also studied the influence of O 2 on the NO -char reaction, and at temperatures closer to pulverized coal combustion (1123 K).…”