Papers by Keyword: Selective Catalytic Reduction (SCR)

Abstract: To explore NOx mitigation strategies in Chinese cement industry systematically, a material flow analysis was developed. The realistic output of cement production in China were identified and quantified. The inventory data of Chinese cement production were selected without denitration technology applications at that time. Then the life cycle impact assessment (LCIA) results were calculated with the principal of ISO 14040 and ISO 14044 of Life Cycle Assessment. The impact categories of global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), photochemical oxidant formation potential (POCP), and human toxicity potential (HTP) were used to calculate environmental impact. The results showed that the NOx emission was the major environmental damages and the following was CO₂ emission. This argument disagreed with the view that CO₂ emission was the major contributor of environmental load. The reason is that the NOx emission is far over the international level due to few denitration technology applications. In the assumption of selective non-catalytic reduction (SNCR) technology applications, there is still large emission mitigation potential according to the target scenario analysis. The application of selective catalytic reduction (SCR) technology with higher deNOx efficiency and the roadmap of deNOx of Chinese cement industry were also discussed. The SNCR technology with the auxiliary of SCR development over the coming decades will be decisive for the roadmaps of Chinese cement industry to reach deeper NOx emission cuts.

Abstract: The V₂O₅-WO₃/TiO₂ honeycomb catalysts with cordierite modified were prepared by solid-liquid mixing method. Its thermal stability, crystal structure, abrasion resistance and activity were studied by XRD, abrasion equipment and simulated flue gas analyzer,respectively. The results indicated that V₂O₅-WO₃/Cordierite-TiO₂ honeycomb catalyst possessed a better thermal stability, mechanical property and activity at the higher temperature comparing to commercial catalyst. There was no rutile phase present after the catalysts were calcined at 700°C, and the vanadia and tungsten trioxide phases could be apparently visible on TiO₂. Key word:V₂O₅-WO₃/ TiO₂; Cordierite; flue gas denitrification; NO_x; selective catalytic reduction (SCR)

Abstract: A Ce-Zr-Ti composite oxide catalyst was prepared by the sol-gel method and its NH₃-SCR activities were investigated. The Ce-Zr-Ti oxide catalyst exhibited high activity and 92.7-98.8% NO conversion was obtained in the temperature range 250-450 °C at the high gas hourly space velocity of 50,000 h^-1. In comparison with Ce-Ti oxide catalyst, the Ce-Zr-Ti oxide catalyst showed strong resistance to H₂O and SO₂. The excellent performance of the Ce-Zr-Ti oxide catalyst might be attributed to the large surface area and strong interaction among the three elements of Ce, Zr and Ti.

Abstract: The efficiency and problem of SNCR in cement are explained by case study .Catalyst also is discussed by the research. And this paper presents and discusses the technical feasibility issues related to implementing SCR technology at cement plant. Some pilot plant trial and scale-full plant are also discussed and the result show that SCR can reduce NOx emissions from cement kilns by greater than 90% and achieve less than 100 mg/Nm3 NOx emissions. The fact suggests that it is a more effective and proven technology to reduce nitrogen oxide emissions from cement kilns.

Abstract: NOx is the main air pollutant of coal-fired power plants, which is one of the important reasons to cause pollution such as acid rain, photochemical smog and so on. Selective catalytic reduction process is the major technology for reducing NOx emissions from coal-fired power plants. However, the commercial vanaidia-based catalyst is active within a narrow temperature window of 300-400°C, easily to be deacticed by SO₂ in the flue gas. And the formation of N₂O and toxicity of vanaidia cause secondary pollution. Therefore, it is of more importance to develop a new environmental-friendly catalyst for low temperature SCR with high activity.

Abstract: A Ce-Zr-Mn-O_x (CZM) catalyst has been discovered for selective catalytic reduction of NO_x with NH₃ in the presence of O₂. In this paper, The catalysts of CZM with 10~50 wt% MnO₂ content and Ce-Zr-O₂ (CZ) catalyst are prepared by hydrothermal synthesis method. The catalytic activity of CZM catalysts at different temperatures, different space velocities and different ratios of NH₃/NO are studied. The results show that the catalyst of CZM with 40 wt% MnO₂ content yields higher NO conversion at low temperature than others. This catalyst shows nearly 90% NO_x conversion in a temperature range of 150°C~250 °C at a space velocity of 53000 h^-1 .

Abstract: Life cycle analysis combined with technical economic evaluation method in the paper to control the cost of denitration. A simple model for denitration cost is developed. The influence of different flue gas concentration of NOx to the cost of unit denitration is analysed by life cycle analysis, includes construction, operation and decommissioning, which based on 600 MW coal-fired units. Preliminary calculations reveal that comparing with directly using the denitration technology of selective catalytic reduction (SCR), after using Air staged Low NOx Combustion Technology reduced NOx below 400mg/m³, using SCR denitration further decreased the concentration of NOx in flue gas to 100mg/m3 can save more than 44% of the general denitration cost. This can improve effectively the environmental protection and economy of the coal-fired unit.

Abstract: By SCR test device to study the main factors affecting the SCR DeNOx efficiency of flue gas for glass furnace,and analyzes the relationship between the main parameters and DeNOx efficiency, such as the reaction temperature, NH₃/NO_x, initial concentration of NOx, and space velocity.In the actual flue gas conditions of glass furnace,there was an optimum working range for the SCR test device. The reaction temperature is 340~400°C,NH₃/NO_x is 0.9~1.0,space velocity is 4000~5000 h^-1. In this condition, the DeNOx efficiency can reach 80%.

Abstract: The mixing degree of ammonia and exhaust gas has significant effect on the NO_x conversion efficiency of SCR (selective catalytic reduction) system. It is essential to investigate the structure of urea nozzle since it considerably impacts the atomization of urea water solution. This paper simulated the process of urea spray by the software FIRE and analyzed the influence of spray characteristics such as nozzle hole number, nozzle hole chamfering as well as the spray angle on the atomization of urea water solution. Simulation results can indicate the optimal nozzle for a certain circumstance which is beneficial to the engineering design.

Abstract: Software FLUENT is used to carry out the numerical simulation of SCR reactor for studying the influence of the guide plates.The results show that the flowing conditions of the flue gas in the SCR system have a significant influence upon the actual effect of the denitration reaction based on a 330MW coal-fired power plant.In order to improve the performance of the device, choosing the solution that can satisfy the requirement of design which σ (uneven speed value of the first section upon the catalyst) is less than 15%. In the optimal decision,σ is 14.4% and the system pressure drop is 134.43Pa. The appropriate arrangement of the guide plates has a positive impact on the denitration reaction and the workinglife of the catalyst.