The rapid industrialization brought severe air pollution problems (SOx, NOx) caused by combustion processes from industry and transportation means (car, train, aircraft). Also, domestic energy consumption have increased according to the industrial development. Because of this air pollution problems,...
The rapid industrialization brought severe air pollution problems (SOx, NOx) caused by combustion processes from industry and transportation means (car, train, aircraft). Also, domestic energy consumption have increased according to the industrial development. Because of this air pollution problems, air quality became worse and worse for last 20 years so that the air pollution control regulations of Korea became stringent accordingly. Therefore, new technologies should be developed to reduce the pollutants within the regulation limit from combustion processes. The Selective Non-Catalytic Reduction (SNCR) process is a useful method for NOx reduction by injecting amines or cyanides containing selective reducing agents such as ammonia, urea, cyanuric acid and ammonium sulfate into the flue gases. This process reduces nitric oxides to nitrogen and water rapidly and effectively at rather higher temperatures (1073~1373K). Therefore, it has been studied for improving NO removal efficiency by using additives such as CO, methane, methanol, ethanol, sodium species and surfactants to reduce the optimum NO_(x) reduction temperature. The maximum NO removal efficiency by NH_(3) exhibits at 950℃ and increases with increasing Normalized Stoichiometric Ratio (NSR) up to 1.8. The optimum reaction temperature is lowered and the reaction temperature window is widened with increasing the concentration of gas additives (CO, CH_(4)). In the case of CH_(4) additive, the optimum reduction temperature is about 50℃ lower than that of CO injection. The optimum reaction temperature is lowered and the maximum NO removal efficiency decreases with increasing the concentration of alcohol additives (CH_(3)OH, C_(2)H_(5)OH). The higher NO removal efficiency can be obtained by the simultaneous injection of gas/liquid additives compared to the injection of single additive at lower temperatures due to the synergic effect. The addition of phenol lowers the optimum reaction temperature similar with that of the toluene addition. Compared to the toluene addition with the same molar ratio, the higher NO removal efficiency can be obtained by the phenol addition since the OH radicals in phenol converts NH_(3) to NH_(2) radicals. Therefore, the VOCs pollutant can be utilized in the SNCR process for promoting NO reduction and removing the VOCs at the same time. An Arrhenius plot of the calculated rate constants (k_(f) and k_(r)) was drawn on the basis of the reduction rate and concentrations of NO and CN_(3) based on the proposed simple kinetic model of Lee and Kim (1996). From the Arrhenius plot, the temperature dependence of reaction rate coefficient can be expressed as: k_(f) = k_(f0) exp [-(E_(f)-E_(fa))/RT] k_(r) = k_(r0) exp [-(E_(r)-E_(ra))/RT] The values of k)(f0), E_(f), k_(r0) and E_(r) are 6.81×10^(12), -270 (kJ/mol), 3.17×10^(12), and -234 (kJ/mol), respectively. The lowered activation energies (E_(fa)) of CO, CH_(4), CH_(3)OH, C_(2)H_(5)OH are found to be 11.04, 22.07, 4.42, 6.62 respectively. The lowered activation energy (E_(ra)) of CO, CH_(4), CH_(3)OH, C_(2)H_(5)OH are 9.57, 19.13, 3.83, 5.74 respectively. Without the additives, E_(Fa) and E_(Ra) are equal to zero. The proposed simple kinetic model can successfully predict the NO reduction by NH_(3) and additives.
The rapid industrialization brought severe air pollution problems (SOx, NOx) caused by combustion processes from industry and transportation means (car, train, aircraft). Also, domestic energy consumption have increased according to the industrial development. Because of this air pollution problems, air quality became worse and worse for last 20 years so that the air pollution control regulations of Korea became stringent accordingly. Therefore, new technologies should be developed to reduce the pollutants within the regulation limit from combustion processes. The Selective Non-Catalytic Reduction (SNCR) process is a useful method for NOx reduction by injecting amines or cyanides containing selective reducing agents such as ammonia, urea, cyanuric acid and ammonium sulfate into the flue gases. This process reduces nitric oxides to nitrogen and water rapidly and effectively at rather higher temperatures (1073~1373K). Therefore, it has been studied for improving NO removal efficiency by using additives such as CO, methane, methanol, ethanol, sodium species and surfactants to reduce the optimum NO_(x) reduction temperature. The maximum NO removal efficiency by NH_(3) exhibits at 950℃ and increases with increasing Normalized Stoichiometric Ratio (NSR) up to 1.8. The optimum reaction temperature is lowered and the reaction temperature window is widened with increasing the concentration of gas additives (CO, CH_(4)). In the case of CH_(4) additive, the optimum reduction temperature is about 50℃ lower than that of CO injection. The optimum reaction temperature is lowered and the maximum NO removal efficiency decreases with increasing the concentration of alcohol additives (CH_(3)OH, C_(2)H_(5)OH). The higher NO removal efficiency can be obtained by the simultaneous injection of gas/liquid additives compared to the injection of single additive at lower temperatures due to the synergic effect. The addition of phenol lowers the optimum reaction temperature similar with that of the toluene addition. Compared to the toluene addition with the same molar ratio, the higher NO removal efficiency can be obtained by the phenol addition since the OH radicals in phenol converts NH_(3) to NH_(2) radicals. Therefore, the VOCs pollutant can be utilized in the SNCR process for promoting NO reduction and removing the VOCs at the same time. An Arrhenius plot of the calculated rate constants (k_(f) and k_(r)) was drawn on the basis of the reduction rate and concentrations of NO and CN_(3) based on the proposed simple kinetic model of Lee and Kim (1996). From the Arrhenius plot, the temperature dependence of reaction rate coefficient can be expressed as: k_(f) = k_(f0) exp [-(E_(f)-E_(fa))/RT] k_(r) = k_(r0) exp [-(E_(r)-E_(ra))/RT] The values of k)(f0), E_(f), k_(r0) and E_(r) are 6.81×10^(12), -270 (kJ/mol), 3.17×10^(12), and -234 (kJ/mol), respectively. The lowered activation energies (E_(fa)) of CO, CH_(4), CH_(3)OH, C_(2)H_(5)OH are found to be 11.04, 22.07, 4.42, 6.62 respectively. The lowered activation energy (E_(ra)) of CO, CH_(4), CH_(3)OH, C_(2)H_(5)OH are 9.57, 19.13, 3.83, 5.74 respectively. Without the additives, E_(Fa) and E_(Ra) are equal to zero. The proposed simple kinetic model can successfully predict the NO reduction by NH_(3) and additives.
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#환원제 첨가제 촉매 환원 공정 질소산화물 SNCR Nitric Oxide
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