Synergistic effect of transition metal oxides and ozone on PCDD/F destruction

Catalytic oxidations of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) with ozone on the transition metal oxides (iron oxide or manganese oxide) at the temperature range of 120-180 degrees C were investigated. These two catalysts were prepared by precipitation methods. Iron oxide has a higher surface area (330 m(2)/g) than manganese oxide (53 m(2)/g). In the absence of ozone, the removal efficiencies of PCDD/Fs achieved with iron oxide or manganese oxide were between 83% and 85%, while the destruction efficiencies were only between 20% and 25% at 180 degrees C. It indicates that adsorption was the main removal mechanism of PCDD/Fs over these two catalysts. On the other hand, ozone addition greatly enhanced the catalytic activity of iron oxide or manganese oxide catalysts on the oxidation of gaseous PCDD/Fs. At 180 degrees C, the destruction efficiencies of gaseous PCDD/Fs achieved with iron oxide or manganese oxide with 100 ppm O(3) exceeded 90%. It indicates that catalytic ozonation achieved with iron oxide or manganese oxide is effective in decomposing PCDD/Fs and the application of ozone lowers the reaction temperature of PCDD/F oxidation below 200 degrees C. Furthermore, the synergistic effect of iron oxide and ozone is superior to that of manganese oxide due to the fact that the surface of iron oxide has more hydroxyl groups, which easily form hydrogen bonds with ozone and decompose to form atomic oxygen for the further reaction with dioxin molecules.     

Influence of leaks in surface filters on particulate emissions

Compliance with severe limit values of dust emissions is a main characteristic of surface filters. This characteristic is due to the high particle collection efficiency of surface filters. Beside regular operation it is necessary to consider phenomena such as a "pinhole" bypass through leaks in surface filters to ensure the above mentioned compliance with the limit values at all times. Experimental research has been carried out to observe and understand the "pinhole" bypass through leaks and the behaviour of pinholes over filtration time. To work out the influence of different filtration conditions the parameters pinhole diameter, filter face velocity and dust cake thickness were varied. The results can be explained by formulas usually used to calculate volumetric flow rates of orifice gauges. The experiments and the calculations lead to the conclusions that bigger pinholes decrease the collection efficiency and higher filter face velocities increase the collection efficiency of pinholed filter media.     

Approaches adopted to assess environmental impacts of PCDD/F emissions from a municipal solid waste incinerator

Different approaches were carried out in this work to assess environmental impacts of a municipal solid waste incinerator. A total of seven sites in the vicinity of the facility were chosen to collect air, banyan leaf and soil samples for analyses of PCDD/Fs by high-resolution gas chromatography/high-resolution mass spectrometry. Based on the PCDD/F concentrations of the three matrices determined at sites upwind, downwind and area of maximum ground concentration, it was found that the environmental impact of the MSWI was not obvious. PCDD/F concentration isopleths of the three environmental compartments coupled with wind rose of the region proved that the influence of the MSWI on the environment was also rather limited. It clarified emission sources by confirming that the PCDD/F concentrations originated mostly from the existing stationary emission sources in the vicinity. Through principal component and cluster analyses on congener profiles, the influence of metallurgical facilities and medical waste incinerators on the ambient air was assessed. Moreover, the modeling of ISCST3 demonstrated also that the contribution of the MSWI to ambient atmospheric PCDD/Fs was minimal. The approaches studied have led to identical conclusions, and thus are useful to cross-evaluate the environmental impact of an MSWI.     

Removal characteristics of PCDD/Fs by the dual bag filter system of a fly ash treatment plant

In this study, a dual bag filter system was established to decrease the concentration of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in the stack flue gases of a fly ash treatment plant, which retained zinc from the fly ash of electric arc furnaces. Compared to the original single bag filter system with activated carbon injection (ACI) of 40 kg h(-1), the PCDD/F concentrations in the stack flue gas after the plant was equipped with the dual bag filter system dropped enormously from 3.38-7.73 ng I-TEQNm(-3) to 0.03 ng I-TEQNm(-3), and the total PCDD/F I-TEQ removal efficiency increased from 97.6% to 99.3% with ACI of 16 kg h(-1), that is, about 40% of the original AC usage. The AC utilization efficiency (0.560 mg I-TEQ absorbed kg ACI(-1)) of the dual bag filter system (AC: 16 kg h(-1)) was estimated about three times higher than that (0.192 mg I-TEQ absorbed kg ACI(-1)) of single bag filter system with ACI (40 kg h(-1)). The reason is that the particulate phase PCDD/Fs and some gas phase PCDD/Fs (captured by the recycled AC/ash mixture) were removed first by the first bag filter, and the rest of the gas phase PCDD/Fs were able to be adsorbed more completely by the AC/ash mixture due to a lower fly ash load, and then were removed by the second bag filter.     

Inhibition of PCDD/F and PCB formation in co-combustion

Co-combustion of coal-solid waste mixtures in pilot and laboratory-scale combustors with emphasis on monitoring of toxic chlorinated hydrocarbon emissions such as polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) and polychlorinated biphenyls (PCB) is elaborated. The objective of the work is to investigate the so-called primary measures technique. Twenty different thermally resistant inorganic compounds were added directly to the fuel as inhibitors of PCDD/F formation. The fuel-types used in this study included lignite coal, pre-treated municipal solid waste and polyvinyl chloride (PVC). Principle component analysis (PCA) provides the basis for a feasible discussion about the efficiency of 20 inhibitors on PCDD/F and PCB formation. The study showed that the metal oxides group investigated had no inhibitory effect. Although the single N- and S-containing compounds, used as additives for the type of lignite coal, solid waste and PVC fuel, are not very effective as inhibitors, all other N- and S-containing substances are capable to strongly reduce PCDD/F and PCB flue gas emission. The most effective inhibitors are (NH(4))(2)SO(4) and (NH(4))(2)S(2)O(3). (NH(4))(2)SO(4) present at 3% of the fuel can reduce the PCDD/F emissions to 90%. Its low cost and high efficiency favour them as useful for full-scale combustion units.     

Effects of calcium-based sorbents on PCDD/F formation from pentachlorophenol combustion process

Calcium-based sorbents are widely employed to reduce the acidic gases emission from combustion processes, and also have effects on trace organic pollutants formation and emission. Batch experiments were conducted to investigate the effects of calcium-based sorbents on pentachlorophenol (PCP) forming PCDDs/Fs during high temperature combustion processes. The results indicated that highly chlorinated PCDD/F homologues were the predominant dioxin products from PCP thermo decomposition, and only minor increasing of PCDDs happened when Ca/Cl ratio was lower than 1, while a major jump occurred when Ca/Cl ratio increased from 1 to 2. The CaO addition clearly promoted the production of all chlorinated dibenzo-p-dioxins homologue and 4-7DFs homologue. Comparison of total PCDD/F emission and its I-TEQ for three different calcium-based sorbents addition (CaO, CaCO3, basic fly ash) indicated that CaO and fly ash containing CaO had almost the same promotion effects on PCDDs/Fs originated from PCP, while CaCO3 inhibit PCDD/F formation greatly with inhibition efficiency up to 70%. Such effects may be partly proved by the observed clearly different micro-surface structures of their reaction residues. The mechanism of CaO on condensation and dechlorination reactions for PCP forming PCDDs and acid-base interaction were proposed to speculate the promotion effects of CaO, and the reaction precedence was used to speculate the inhibition effects of CaCO3 on PCDDs/Fs originated from PCP. The results of the present paper might be useful for the industrial application of calcium-based sorbents to control PCDD/F emission.     

Solubility enhancement of PCDD/F in the presence of dissolved humic matter

From previous studies, we, the authors collected and arranged the octanol-water partition coefficients (K(ow)), water solubility (S0), and dissolved humic matter (DHM)-water partition coefficients (K(oc)) for 95 organic compounds, and presented the correlations between each physical property. The K(oc) and K(ow) of dioxins estimated were significantly increased while S0 was decreased on increasing the chlorine number. In the presence of DHM, solubility enhancement (Sw/S0, Sw is the actual solubility in the presence of DHM) in highly chlorinated PCDD/F such as HpCDDs and OCDD is higher than that in low chlorinated ones. It means that dioxins abundant wastes (fly ash) should not be codisposed with organic abundant wastes (sewage sludge, food waste or bottom ash, etc.) to minimize the leachability of dioxins.     

环境介质对形状记忆合金弹簧记忆回复效应的影响*

针对SAM电火花加工机器人加工时常用的3种工作介质水、煤油和乳化液，研究了SMA弹簧的记忆恢复变形特性和变形规律。结果表明，对应不同的环境介质，SMA弹簧的记忆回复变形量与驱动电流间存在一一对应关系，通过控制驱动电流可控制记忆回复变形量。在不同环境介质中SMA弹簧的记忆回复变形速度的变化趋势是一致的，都是先随着回复位移的增加而增加，在接近中间段时达到最大，然后随着位移的增加而减小。驱动电流是对SMA弹簧动态变形速度影响最 明显的参数，通过选择合适的驱动电流可有效地控制SMA弹簧的回复变形速度。     

Influence of stack geometry on the performance of thermoacoustic refrigerator

The work reported in this paper is focused on the performance of a thermoacoustic refrigerator under various operating conditions. The experiments were conducted with various stack geometries fabricated with epoxy glass and Mylar material. Four stacks with different pore sizes are used to evaluate the performance of the refrigerator. Stack 1 has parallel plates of Mylar material 0.12 mm thick spaced 0.36 mm apart. Stacks 2, 3 and 4 are made of epoxy glass with pores of circular cross-section having 1, 2 and 3 mm diameter, respectively. The entire resonator system was constructed from aluminium material coated with polyurethane material from inside to reduce conduction heat losses. Helium gas was used as a working fluid. The experiments were conducted with different drive ratios ranging from 1.6% to 2% with varying cooling load from 2 to 10 W. For the experiments, operating frequencies from 200 to 600 Hz with mean pressure varying from 2 to 10 bar in steps of 2 bar each were considered. The temperatures of the hot end and cold end of the heat exchangers were recorded using RTDs and a data acquisition system under various operating conditions. The coefficient of performance (COP) and relative COP (COPR) are evaluated. Results show that COP of the refrigerator rises with increase of cooling load and decreases at higher drive ratio. It was also observed that the temperature difference between the hot end and cold end of the stack is higher at 2 W cooling load for 400 Hz operating frequency. The temperature difference between the hot end and cold end of the stack was observed to be 19.4, 17.2, 14 and 12.4°C for stacks 1, 2, 3 and 4, respectively, for 10 bar mean pressure and 2 W cooling load. The temperature difference and COP of the parallel plate stack are better compared with other stack geometries.     

舒适性空调用袋式过滤器过滤性能的试验研究

根据国家标准GB12218-89，并参照欧洲EN779：2002标准，对各类舒适性空调用袋式过滤器的过滤性能进行试验研究，为各类公共场所选择合理的空气滤器使空气中可吸入颗粒物（PM10）的浓度达到国家规范中的要求提供技术参考。     

Characteristics of PCDD/F content in fly ash discharged from municipal solid waste incinerators

Different from most previous studies with quantity-limited data, this paper presents PCDD/F content characterization in the fly ash discharged from sixteen large-scale commercial MSWIs. From the results with over hundreds of data using periodically sampling and analysis, it was found that the PCDD/F contents in the fly ash were from 9.07 to 46.68 ng/g, d.w., and if based on international toxicity equivalent quantity, they were from 0.78 to 2.86 ng I-TEQ/g, d.w. The higher chlorinated PCDDs likely dominated more than lower chlorinated PCDDs, but this tendency was not for PCDFs. The OCDD had the highest contribution to the total PCDD/F content, but if based on I-TEQ content, 2,3,4,7,8-PeCDF is the PCDD/F congener with the highest toxicity contribution. Moreover, the PCDD/F characteristic index (DCI) is suggested using the representative congener content of 2,3,4,7,8-PeCDF to characterize the fly ash. The DCI is 0.875 ± 7.6% for the fly ash discharged from the MSWI with the APCD assembly of SD, AC and BF. The findings obtained in this work provide overview information on the PCDD/F content characterization in fly ash. They will provide PCDD/F fingerprint information to distinguish from other PCDD/F sources, like steel refinery industry, hazardous waste incinerators, or cement kilns, and thus be applied to fly ash management in the environment.     

Excellent passivation effect of Cat-CVD SiNx/i-a-Si stack films on Si substrates

We have demonstrated that the surface recombination velocity can be lowered to as low as 1.3 cm/s for n-type c-Si wafers and to 9.0 cm/s for p-type wafers by using amorphous Si (a-Si) and Si nitride (SiN_x) stacked films prepared by catalytic chemical vapor deposition (Cat-CVD). These values are much lower than those of c-Si wafers passivated by same stacked structures formed by low-damage remote plasma-enhanced CVD (PECVD). It is revealed that Cat-CVD a-Si insertion layers play an important role to improve interface quality, and also SiN_x films are also essential for reducing the surface recombination velocity down to such low levels.     

时效Ti49Ni51合金的显微组织与双程形状记忆效应

采用弯曲试验和透射电镜分析研究了时效Ｔi49Ni51合金的显微组织与双程形状记忆应用,结果表明,５００６℃,１h时效处理试样中,相呈透镜片状,周围有较强的应变场初度,而５００℃,３０h时效试样中,ＴiNi4相已聚集长大成粗片状,与基体失去共格,５００℃,１h时效处理试样在训练后可获得较好的双程形记忆效应,时效Ｔi49Ni51合金中ＴiNi4相粒子周围的共格应变场和主地位错交互作用可以产生有效内应力场,从而诱发双程形状记忆效应。     

变形对 Cu-Al-Mn记忆合金相变滞后的影响

为了研究CuAlMn形状记忆合金的相变滞后效应,以Cu-Al10.61-Mn6.95(ω（B）/%）合金（A合金）与Cu-Al11.05-Mn6.81-Zn0.21(ω（B）/%）合金（B合金）为研究对象,应用电阻法测定其相变点,并利用X射线衍射谱标定其结构。结果表明,A合金主要由18R马氏体构成,B合金主要由9R马氏体构成,而9R马氏体结构的合金相变滞后温度远大于18R马氏体结构的合金。为了进一步研究变形对相变滞后温度的影响,对B合金进行了拉伸变形试验。研究发现,通过增大预变形量可以有效地提高滞后宽度。     

Validation of the CALUX bioassay as a screening and semi-quantitative method for PCDD/F levels in cow's milk

The objectives of this study were first to set up and validate the quality criteria of the Xenobiotic Detection Systems-chemical activated luciferase gene expression (CALUX) bioassay for the analysis of cow's milk samples spiked with polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The application of this bioassay was then tested by analyzing 28 commercially available pasteurized milk samples and comparing the data with the reference method for PCDD/F analysis. The CALUX criteria from the U.S. EPA and the European Union (EU) were calculated from 16 replaced spiked milk (SM) samples and 8 performance evaluation (PE) samples to validate the CALUX bioassay system. The CALUX bioassay criteria included control chart for quality control (QC) standards, recovery efficiency, and data comparability. The control chart for QC standards were both within the micro+/-2sigma range. The recovery efficiencies ranged from 60.4% to 106% with an average of 79.9% (relative standard deviation (RSD): 20.7%). The mean of data comparability (i.e., relative percent difference, RPD) between CALUX bioassay and high-resolution gas chromatography and high-resolution mass spectrometry (HRGC/HRMS) was 19.0% for SM samples. For the PE samples, Pearson's correlation coefficient between CALUX and the HRGC/HRMS method was 0.953. The high correlation shows that the CALUX system is suitable as a screening method and a semi-quantitative method to analyze the PCDD/F concentration in milk samples. Next, the validated CALUX bioassay was applied to measure 28 commercially available pasteurized milk samples. These milk samples were also analyzed with the HRGC/HRMS method to compare the analysis data from two different methods. There is no false negative sample when applying the bioassay to pasteurized milk and PE samples as a screening method and a semi-quantitative method. The present study indicates that CALUX is a powerful bioassay method for screening a large number of milk samples.     

预变量与时效温度对Fe—Mn—Si合金记忆效应的影响

研究了预变形量和时效温度对Fe-28Mn-5．7Si-5Cr-0．82Ni-0．045Nb合金形状记忆效应的影响。结果表明，合金形状回复率随预变量的增大而减小，在2％左右合金回复率可以达到80％。合金经1023K时效处理时形状记忆效应最好，比固溶态提高了90％，这主要是时效处理有效提高了奥氏体基体的强度，而奥氏体基体的强度的提高可以抑制塑性变形的产生。     

Mechanical behavior and shape memory effect of an aged NiAl–Fe alloy

The mechanical behavior and shape memory effect of an aged NiAl–Fe alloy has been investigated. It was found that the first yielding stress of NiAl–Fe alloy in a compression test was decreased with the precipitation of a Ni₅Al₃ phase after aging at 473–673 K, and increased as the aging temperature increased higher. The one-way shape recovery of NiAl–Fe alloy increased as the aging temperature increased from 473 to 673 K, and decreased as the aging temperature increased higher than 673 K. The morphology of precipitates in the NiAl–Fe alloy aged at 473–873 K was investigated, and the mechanism of its effect on the mechanical properties is discussed.     

Evaluating the environmental impact of an old municipal waste incinerator: PCDD/F levels in soil and vegetation samples

In order to determine the temporal variation in the levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the vicinity of an old municipal solid waste incinerator (MSWI) (S. Adrià del Besòs, Barcelona, Spain), 24 soil and vegetation samples were collected at the same sampling points in which samples had been taken 1 year before. Each sample was analyzed for PCDDs and PCDFs by high-resolution gas chromatography/high-resolution mass spectrometry. While in the previous study PCDD/F concentrations in soil ranged from 1.22 to 34. 28 ng I-TEQ/kg (median and mean values: 9.06 and 12.24 ng I-TEQ/kg), in the present study, PCDD/F levels ranged from 1.33 to 54.23 ng I-TEQ/kg (median and mean values: 11.85 and 14.41 ng I-TEQ/kg). On the other hand, in the previous study, PCDD/F levels in vegetation ranged from 0.33 to 1.98 ng I-TEQ/kg (median and mean values: 0.58 and 0.70 ng I-TEQ/kg), whereas in the present study, PCDD/F levels ranged from 0.32 to 2.52 ng I-TEQ/kg (median and mean values: 0.82 and 0.97 ng I-TEQ/kg). During the last 12 months, PCDD/F levels increased in 16 of the 24 soil samples and in 17 of the 24 vegetation samples analyzed. However, no significant differences in the median I-TEQ concentrations of both studies were found either in soil or vegetation samples.     

Influence of multiple reflections on transmission through a stack of plates

We examine the problem of light transmission along the normal through a stack of flat plates whose thicknesses and separations vary. For a modest number of plates, an exact calculation is straightforward, but then one must address how to average over both the disorder in the stack and the distribution of incident wavelengths. Model calculations are used to show that an average over the light's distribution can suppress most of the fluctuations due to disorder. Our results are in qualitative agreement with experimental data and imply that multiple reflections do contribute significantly to the measurements. Finally we explore the effect of multiple reflections on photometry.