In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) st...In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.展开更多
The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600?MWe coal-fired boiler are retrofitted in which methane ...The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600?MWe coal-fired boiler are retrofitted in which methane gas is selected as a secondary fuel for re-combustion. The CFD models of combustion process are built to investigate?effects of the methane gasratio on combustion process and NOx emissions. A total of 4 cases are numerically studied, including the pure coal combustion case, the coal combustion with 7.5%, 10%, 12.5% of methane gas re-combustion cases respectively. The results show that the re-combustion of methane can reduce the temperature at primary combustion zone, but increase the temperatures at the re-combustion area and the furnace outlet. The NOx concentration at the furnace outlet reduces with the increasing methane gas ratio.?Methane re-combustion can greatly benefit to the NOx emissions reduction.展开更多
This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess...This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650 ppm C2H4, 5.8% O2 in N2 and GHSV = 12000 h-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma- catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.展开更多
Selective Catalytic Reduction (SCR) catalysts respond slowly to transient inputs, which is troublesome when designing ammonia feed controllers. An experimental SCR test apparatus installed on a slipstream of a Coo-per...Selective Catalytic Reduction (SCR) catalysts respond slowly to transient inputs, which is troublesome when designing ammonia feed controllers. An experimental SCR test apparatus installed on a slipstream of a Coo-per-Bessemer GMV-4, 2-stroke cycle natural gas engine is utilized. Ammonia (NH3) feed rate control algo-rithm development is carried out. Two control algorithms are evaluated: a feed forward control algorithm, using a pre ammonia injection ceramic NOx sensor and a feed forward plus feedback control algorithm, us-ing a pre ammonia injection ceramic NOx sensor and post catalyst ceramic NOx sensor to generate feedback signals. The feed forward algorithm controls to constant user input NH3/NOx molar ratio. The data show the lack of pressure compensation on the ceramic NOx sensors cause errors in feed forward NOx readings, re-sulting in sub optimal ammonia feed. The feedback system minimizes the post catalyst ceramic NOx sensor signal by adjusting the NH3/NOx molar ratio. The NOx sensors respond to ammonia + NOx;therefore, the feed forward plus feedback algorithm minimizes the sum of NOx emissions and ammonia slip. Successful application of the feedback control minimization technique is demonstrated with feedback periods of 15 and 5 minutes with molar ratio step sizes of 5 and 2.5%, respectively.展开更多
In order to alleviate the pressure of environmental protection and further strengthen the monitoring and control of NOx emission of thermal power units, combining with the transformation of boiler low-nitrogen burner,...In order to alleviate the pressure of environmental protection and further strengthen the monitoring and control of NOx emission of thermal power units, combining with the transformation of boiler low-nitrogen burner, combustion optimization, static and dynamic ratio of air and coal, and SCR denitration system process, third-order NOx online control technology was designed and applied, which takes the combustion security, boiler efficiency and environmental evaluation into account and provide reference for thermal power units to deepen energy conservation and emission reduction.展开更多
基金the National Natural Science Foundation of China (51676090)the Natural Science Foundation of Jiangsu Province (BK20150513), and the Six Talent Peaks Project in Jiangsu Province.
文摘In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.
文摘The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600?MWe coal-fired boiler are retrofitted in which methane gas is selected as a secondary fuel for re-combustion. The CFD models of combustion process are built to investigate?effects of the methane gasratio on combustion process and NOx emissions. A total of 4 cases are numerically studied, including the pure coal combustion case, the coal combustion with 7.5%, 10%, 12.5% of methane gas re-combustion cases respectively. The results show that the re-combustion of methane can reduce the temperature at primary combustion zone, but increase the temperatures at the re-combustion area and the furnace outlet. The NOx concentration at the furnace outlet reduces with the increasing methane gas ratio.?Methane re-combustion can greatly benefit to the NOx emissions reduction.
基金supported by the National Natural Science Foundation of China(Grant No.20077005)the National High Technology Research and Development Program("863 Programm”)of China(Grant No.2002AA649140)the Provincial Grants of Science and Technology of Liaoning,China(No.20022112).
文摘This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650 ppm C2H4, 5.8% O2 in N2 and GHSV = 12000 h-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma- catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.
文摘Selective Catalytic Reduction (SCR) catalysts respond slowly to transient inputs, which is troublesome when designing ammonia feed controllers. An experimental SCR test apparatus installed on a slipstream of a Coo-per-Bessemer GMV-4, 2-stroke cycle natural gas engine is utilized. Ammonia (NH3) feed rate control algo-rithm development is carried out. Two control algorithms are evaluated: a feed forward control algorithm, using a pre ammonia injection ceramic NOx sensor and a feed forward plus feedback control algorithm, us-ing a pre ammonia injection ceramic NOx sensor and post catalyst ceramic NOx sensor to generate feedback signals. The feed forward algorithm controls to constant user input NH3/NOx molar ratio. The data show the lack of pressure compensation on the ceramic NOx sensors cause errors in feed forward NOx readings, re-sulting in sub optimal ammonia feed. The feedback system minimizes the post catalyst ceramic NOx sensor signal by adjusting the NH3/NOx molar ratio. The NOx sensors respond to ammonia + NOx;therefore, the feed forward plus feedback algorithm minimizes the sum of NOx emissions and ammonia slip. Successful application of the feedback control minimization technique is demonstrated with feedback periods of 15 and 5 minutes with molar ratio step sizes of 5 and 2.5%, respectively.
文摘In order to alleviate the pressure of environmental protection and further strengthen the monitoring and control of NOx emission of thermal power units, combining with the transformation of boiler low-nitrogen burner, combustion optimization, static and dynamic ratio of air and coal, and SCR denitration system process, third-order NOx online control technology was designed and applied, which takes the combustion security, boiler efficiency and environmental evaluation into account and provide reference for thermal power units to deepen energy conservation and emission reduction.
