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851.
Characterization and reactivity of natural manganese ore catalysts in the selective catalytic oxidation of ammonia to nitrogen 总被引:3,自引:0,他引:3
Natural manganese ore (NMO) catalysts were characterized and tested in the selective catalytic oxidation of ammonia to nitrogen oxides under dilute conditions. Also, the oxidation of ammonia (NH(3)) was carried out using pure MnO(2), Mn(2)O(3) for comparing with the activity. It is found that the activity of NMO was similar to that of MnO(2) at low temperature below 150 degrees C but above this temperature, the activity of these catalysts showed the difference. In the course of NH(3) oxidation, N(2), NO, N(2)O and H(2)O were produced. But the quantity of NO(2) produced in this experiment was negligible. At temperature below 250 degrees C, selectivity into N(2) from NH(3) oxidation was in the order, NMO > MnO(2) > Mn(2)O(3). This is the reverse of activity of these manganese oxides. Also the characterization of NH(3) oxidation was proposed and supported by the effect of space velocity, inlet O(2) and NH(3) concentration. The increase of space velocity remarkably influenced not only the conversion but also selectivity into N(2). The higher the reaction temperature was, the higher the effect of inlet O(2) and NH(3) concentration on the reaction rate was. By introducing NO during NH(3) oxidation reaction, the possibility of NMO as selective catalytic reduction catalyst at low temperature was studied and showed positive results. 相似文献
852.
Jian-guo Jiang Xue-juan Du Mao-zhe Chen Chang Zhang 《Environmental pollution (Barking, Essex : 1987)》2009,157(11):2933-2938
Novel dynamic equipment with gas in and out continuously was developed to study the capture capacity of CO2. Municipal solid waste incineration (MSWI) fly ash has a high capture rate of CO2 in CO2-rich gas. Fly ash can sequester pure CO2 rapidly, and its capacity is 16.3 g CO2/100 g fly ash with no water added and 21.4 g CO2/100 g fly ash with 20% water added. For simulated incineration gas containing 12% CO2, the capture rate decreased and the capacity was 13.2 g CO2/100 g fly ash with no water added and 18.5 g CO2/100 g fly ash with 20% water added. After accelerated carbonation, the C and O contents increased, indicating CO2 capture in the fly ash; CO2 combines with Ca(OH)2 to form CaCO3, which increased the CaCO3 content from 12.5 to 54.3%. The leaching of Pb markedly decreased from 24.48 to 0.111 mg/L. 相似文献
853.
854.
855.
Evaluation of PCDD/F congener distributions in MWI flue gas treated with SCR catalysts 总被引:1,自引:0,他引:1
Partitioning of PCDD/F congeners between gaseous and particulate phases and removal efficiencies of the air pollution control devices (APCDs) for PCDD/Fs at an existing municipal waste incinerator (MWI) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP), wet scrubbers (WS) and selective catalytic reduction system (SCR) as APCDs. The average PCDD/F concentration of stack gas is 1.49 ng/N m3, and the International Toxic Equivalent Quantity (I-TEQ) is 0.043 ng-I-TEQ/N m3. The EP increases PCDD/F concentration by 174.0% while the average removal efficiency of WS + SCR system for PCDD/Fs reaches 99.1%. In addition, the PCDF removal efficiency achieved with WS + SCR system (97.1–99.8%) is higher than that for PCDDs (96.5–99.3%). The results obtained on gas/particulate partitioning in flue gas indicate that the particulate-phase PCDD/Fs accounted for 65% at the inlet of EP, 20% at the outlet of EP and 50% at the stack, respectively, of the total PCDD/F concentrations. This study also indicates that as the chlorination level of PCDD/F congeners increases, the percentage of PCDD/Fs existing in gas phase decreases in all flue gas samples. 相似文献
856.
Background, Aims and Scope This research attempted to identify the dominant factors simultaneously affecting the airborne concentrations of five air
pollutants with principal component analysis and to determine the meteorologically related parameters that cause severe air-pollution
events. According to the definition of subPSI and PSI values through the U.S. EPA, the historical raw data of five criteria
air pollutants, SO2, CO, O3, PM10 and NO2, were calculated as daily subPSI values. In addition to the airborne concentrations,
this study simultaneous collected the surface meteorological parameters of the Taipei meteorological station, established
by the Central Weather Bureau.
Methods Principal component analysis was conducted to screen severe air pollution scenarios for five air pollutants: SO2, CO, O3,
PM10 and NO2. The concentrations of various air pollutants measured at 17 air-quality stations in northern Taiwan from 1995
to 2001 were transformed into daily subPSI values. The correlation analysis of the five air pollutants and four meteorological
parameters (wind speed, temperature, mixing height and ventilation rate) were included in this research. After screening severe
air pollution scenarios, this study recognized the synoptic patterns easily causing the severe air-pollution events.
Results and Discussion Analytical results showed that the eigenvalues of the first two principal components for SO2, CO, O3, PM10 and NO2 were greater
than 1. The first component of five air pollutants explained 64, 64, 67, 76 and 63% of subPSI variance for SO2, CO, O3, PM10
and NO2, respectively. Only the correlation coefficient of NO2 and CO had statistically significant positive values (0.82);
other pollutant pairs presented medium (0.4 to 0.7) or low (0 to 0.4) positive values. The correlation coefficients for air
pollutants and three meteorological parameters (wind speed, mixing height and ventilation index) were medium or low negative
values. In northern Taiwan, spring was most likely induced high concentrations and the component scores of the first component
for SO2, CO, PM10 and NO2; summer was the worst season that caused high O3 episodes. Consequently, the analytical results
of factor loadings for the first principal component and emission inventory of various sources revealed that mobile sources
were dominant factors affecting ambient air quality in northern Taiwan.
Conclusion According to the results of principal component analysis for the five air pollutants, the first two of 17 components were
cited as major factors and explained 71% of subPSI variance. Based on the inventory of NOx emissions and the isopleth diagram
of factor loading for the first component, mobile sources in the southwest Taipei City accounted for the highest factor loading
values and emission inventory values. Synoptic analysis and principal component analysis demonstrated that three types of
weather patterns (high-pressure recirculation, prefrontal warm sector and the southwesterly wind system) easily caused the
severe air-pollution scenarios. In summary, if severe air-pollution days occurred, the average meteorological parameters experienced
adverse conditions for diffusing air pollutants; that is, the average values of wind speed, mixing height and ventilation
index were lower than 2.1 ms-1, 360 m and 800 m2s-1, respectively. If one of the three synoptic patterns were to occur in
combination with adverse meteorological conditions, severe air-pollution events would be developed.
Recommendation and Outlook By utilizing synoptic patterns, this work found three weather systems easily caused severe air-pollution events over northern
Taiwan. Analytical results showed, respectively, the wind speed and mixing height were less than 2.1 m/s and 360 m during
severe air-pollution events. 相似文献
857.
858.
Mass transfer plays a significant role in the ozonation process. The prediction models associated with the volumetric overall mass transfer coefficient (KLa) and initial fractional ozone absorption (FOA0) during the ozonation process were developed through the use of dimensional analysis. It was found that the volumetric overall mass transfer coefficient is the function of diffusivity, agitation speed, and gas flow rate, and the parameters in the KLa equation are determined. Application of the prediction models for KLa and FOA0 would yield information to choose the most practically feasible operating parameters. The removability of total organic carbon (TOC) can be estimated based on the mass balance relationship and kinetic expression of TOC oxidation, during continuous laboratory ozonation of humic acid solution. The reaction rate constant averaged 0.0291 L/mg·min. The developed model in combination with the mass transfer and reaction kinetics can be used successfully in forecasting the most efficient agitation speed to control the formation of organic compounds. Also, the critical value of ozone partial pressure to achieve the highest TOC removability can be determined through the use of the above developed model. 相似文献
859.
气候变化对涟水流域蓝水绿水资源的影响 总被引:1,自引:0,他引:1
利用SWAT分布式水文模型模拟分析1996~2015年过去20 a及2020~2079年未来60 a长期气候变化背景下涟水流域蓝水绿水资源的时空分布变化特征。将气候变化划分为1996~2015年、2020~2049年、2050~2079年三段气象背景时期,选用Had GEM2-AO大气模式的RCP2.6、RCP4.5、RCP6、RCP8.5四种典型浓度路径作为未来时期的气象输入条件,并细分为9种气候变化情景。运用PSO粒子群优化算法,以KGE克林效率系数为目标函数,采用湘乡站实测径流量及MOD16蒸散发数据并行校准模型参数,通过p-factor、r-factor、R2、NSE和PBIAS评价模型模拟效果和不确定性,评价结果表明校准期及验证期蓝水绿水模拟均达到可信程度。情景分析结果表明,对比1996~2015年、2020~2049年、2050~2079年三段气候背景时期,在各RCP浓度路径下蓝水均呈现了不同程度的下降趋势,大约降低了1.4%~17.3%,绿水流均表现出一定的上升趋势,约增长3.5%~12.4%,绿水蓄量则在持续降低,大致下降了7.8%~19.7%,即使将95PPU模拟不确定性范围考虑进来,绿水流的增长趋势也较为明显。因此,将绿水资源纳入涟水流域未来水资源评价体系,实现蓝水绿水综合规划管理具有实际意义。 相似文献
860.
城市矿产是工业化和城市化过程的产物,它是蕴藏于城市中有较高经济价值并可回收利用的二次资源,具有载能性、循环性、战略性。随着工业化、城镇化和消费持续升级,"垃圾围城"已然成为中国许多大中城市亟需解决的环境问题,严重阻碍中国的可持续发展。城市矿产变废为宝,能有效化解资源与环境双重约束。为此,中国政府先后出台一系列城市矿产产业政策以推动其快速发展。本文收集1987—2015年国家层面颁布的相关政策文件,在运用内容分析法对政策文本梳理、编码并统计计量的基础上,首先从颁布部门、数量、力度等方面对政策体系进行总体分析,然后构建并运用政策工具-政策作用环节两维度分析框架,探讨中国城市矿产政策体系的演化过程及发展特征。研究发现:(1)从政策发展历程分析,中国城市矿产政策体系经历了依附环境保护政策的孕育期、体系初建的形成期和效力深化的发展期。(2)从政策颁布维度分析,中国城市矿产政策颁布速度逐渐加快,力度逐渐增强,参与机构数量不断增多。(3)从政策工具维度分析,中国城市矿产政策体系以环境型政策为主,逐渐呈现出强化供给型政策的演化趋势。(4)从政策作用环节分析,中国城市矿产政策体系由重点关注回收、深加工环节向关注全产业链环节演变。最后,针对中国城市矿产政策体系演变特征与存在的不足,本文从以下三个方面提出了促进中国城市矿产产业发展的政策建议:一是加强部际联系,完善顶层设计;二是加强消费引导,完善需求型政策;三是立足产品全生命周期,健全产业政策体系。 相似文献