Characteristics of a nuclides distribution during a melt decontamination of radioactive aluminum wastes

The characteristics of an aluminum melting and the distribution of surrogate nuclide have been investigated in a muffle furnace and a lab-scale arc furnace as part of the fundamental research for a melting of the metallic wastes generated by dismantling research reactors. The melting of aluminum was carried out with the use of surrogate nuclides such as cobalt, cesium, and strontium, and fluxes such as NaCl-KCl-Na₃AlF₆ (flux A), NaCl-NaF-KF (flux B), CaF₂ (flux C), and LiF-KCl-BaCl₂ (flux D). The effects of the melting temperature and the type of flux on the melting of the aluminum and the surrogate nuclide distribution in the ingot, slag, and dust phase were investigated in a muffle furnace. The addition of the flux increased the fluidity of the aluminum melt, which has a slight difference according to the type of fluxes, and the amounts of the slag generated during the melting with the flux types B and C were larger than those with flux types A and D. The results of the XRD analysis showed that the surrogate nuclides move into the slag, which can be easily separated from the melt, and then they combine with the aluminum oxide to form a more stable compound. The remaining cobalt in the ingot phase was less than 20% and the others were transferred into the slag and dust. A removal efficiency of more than 99.5% for cesium and strontium from the ingot phase could be achieved. Similar results for the slag formation and the distribution of the surrogate nuclides were obtained in a DC graphite arc melting system. Therefore, it is expected that a greater part of the aluminum wastes generated from the retired research reactors can be recycled or their volume reduced to be disposed of by melting.     

Non-steady-state catalytic decontamination of waste gases

The non-steady-state behaviour of a fixed bed reactor controlled by periodical direction reversal of reactant feed, applied in catalytic oxidation of industrial waste gases, containing organic compounds and carbon monoxide, has been investigated. The effects of the type of oxidized compound, its initial feed concentration, linear gas velocity, inerts-to-catalyst ratio and inerts thermophysical characteristics on the formation of reactor concentration and temperature fields were elucidated. It was shown that autothermal reactor behaviour is guaranteed by concentrations of the oxidized component which ensure an adiabatic temperature increase in excess of 20 °C. Deviations of either flow rate or initial concentration of the oxidized compound do not disturb the operational stability.     

Regeneration methods of decontamination of phenol-containing waste waters

Regeneration methods of phenol extraction from waste waters using evaporation, liquid extraction, adsorption, ion exchange and membrane techniques have been reviewed based on the data found in Khimiya (Russian Journal of Chemistry) issued after 1993.     

Interaction of a high-temperature two-phase melt with a metal substrate

Different stages of the formation of a cast self-propagating high-temperature fusion coating are analyzed in the presence of an intense convective flow in the reacting melt. A model is proposed for the melt-substrate thermal interaction assuming that by the time the combustion wave exits at the substrate combustion and phase separation processes are complete. This model is analyzed numerically and the results agree adequately with the actual process.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 4, pp. 28–37, July–August, 1993.     

含氮氧化物(NOx)废气的处理方法

本文介绍了氮氧化物废气的产生原理,处理方法,并结合某厂硝化废气处理装置的改造过程的实例,对加压水吸收处理氮氧化物废气的方法进行了详细介绍,同时将该法与其他处理方法进行了比较.     

Estimation of the melt rheology of polymer waste from melt flow index

The need for recycling of polymeric waste has been well recogmized as a result of the escalating prices of the petrochemical feedstocks and the growing awareness to curtail solid waste that causes environmental pollution. During processing, the molecular weight of the polymer is reduced due to thermal and shear degradation. Since the melt rheology of the processed material is sensitive to the changes in molecular structure, knowledge of the complete flow curve depicting the variation of melt viscosity with shear rate at processing temperatures is a useful tool for assessing the reprocessibility of waste material and for specifying the conditions of reprocessing. In the present paper, an effective method is proposed to generate the melt flow curves of polymer waste from knowledge of its melt flow index. The method makes use of a master curve that can be obtained by plotting the available viscosity data in terms of modified functions based on the melt flow index. The master curves characteristic of the particular generic resin type are presented for low-density polyethylene, polypropylene and polystyrene.     

Partition characteristics of close-boiling components in a chromatographic column

Partition characteristics of three close-boiling components (dichloromethane, diethylether, and dimethoxymethane) were investigated with dinonylphthaiate-coated Chromosorb A and helium as the carrier. The outlet stream from the Chromatographic column was monitored continuously. Partition coefficients were experimentally determined at various column temperatures for the three components. With the assumption of uniform film thickness, two parameters were estimated by Fourier analysis of the response curves. The Peclet number for particle was expressed in terms of the Reynolds number and the Schmidt number as: $$\frac{1}{{Pe,p}} = \frac{{0.87}}{{\operatorname{Re} \cdot Sc}} + 0.5$$ Intraparticle diffusion coefficient of each component was also determined in the form of the dimensionless group. P_i. The theoretical response curve in time domain was in good agreement with the observed one. From the sensitivity analysis, it is concluded that the liquid film resistance was small and the diffusion in the liquid phase was not a rate-determining step.     

Quasi-unidimensional model of formation of a flat glass strip on metal melt

Glass and Ceramics -     

Removal of metal ions from electrochemical decontamination solution using organic acids

Applicability of the organic acids and cyclodextrin (CD) for the removal of Fe, Co and Ni from the spent electro-decontamination solution was investigated. Oxalic acid showed the highest removal efficiency: 90% for 0.89 M Fe and 95% for 0.0089 M Co and Ni, respectively. The metal–oxalate precipitates were characterized by differential scanning calorimetry/thermogravimetry analysis (DSC/TGA), Fourier transform infrared (FTIR) and X-ray fluorescence (XRF). After thermal decomposition at >300°C, the metal–oxalate precipitates were transformed into metal oxides (Fe₂O₃, FeO, CoO and NiO) and pure metals (Co and Ni). The results imply that organic acids have a high potential for the removal of heavy metals from electro-decontamination solutions.     

Selective solid‐phase extraction of metal for water decontamination

Metal‐contaminated industrial effluent is a major concern for human health. Therefore, the removal of metal is of primary importance. In this study, metals were selectively extracted from water. Selective metal recovery was studied with a crown‐ether‐based polymer, wherein the selectivity was observed for strontium over lead. Parameters influencing the metal recovery, such as the contact time, adsorbent dosage, and metal‐ion concentration, were evaluated. Interestingly, the adsorption rate of strontium was exponentially increased for the initial 4 h, and lead was adsorbed exponentially after 6 h. Notably, 98% strontium adsorption and 64% lead adsorption were obtained in 24 h. The Langmuir adsorption isotherm was in good agreement and demonstrated that the reactive sites of the adsorbent were homogeneous with monolayer metal adsorption with an adsorbent. The Freundlich adsorption isotherm was not obeyed by both metals. The pseudo‐first‐order and pseudo‐second‐order kinetics indicated that strontium was adsorbed by chemisorption and lead was adsorbed by physisorption. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42849.     

医疗废物焚烧炉启炉过程二噁英排放特性

选择了位于华东地区的某医疗废物焚烧处置设施开展启炉过程与正常工况下烟气和飞灰的二噁英排放特性对比研究。数据显示, 启炉后期烟气中二噁英的浓度达到1.68 ng I-TEQ·m^-3, 在焚烧炉温度稳定以后12 h, 达到2.77 ng I-TEQ·m^-3, 飞灰中二噁英毒性当量水平也达到4.5 ng I-TEQ·g^-1。启炉过程中烟气中气相二噁英所占比例逐渐增加, 从平均占到50%增加到超过90%。启炉过程中烟气二噁英排放速率高于其正常达标时的排放水平, 最高值为58.1 mg I-TEQ·h^-1, 超过正常排放的40倍。一个启炉周期二噁英的排放总量达到0.785 mg I-TEQ, 达标正常工况下二噁英的年排放总量为8.4 mg I-TEQ, 按照平均每年3次启炉来计算, 启炉过程二噁英的排放量占到全年正常排放的28%。     

电动力强化植物修复土壤重金属的研究进展

由植物修复优缺点出发,介绍了电动强化技术及其作用机理,总结了影响强化效率的各个参数,并指出了该技术存在的问题及研究方向。随着不断地完善和发展,电动力强化技术将会在植物修复领域发挥重要作用。     

电动力强化植物修复土壤重金属的研究进展

由植物修复优缺点出发,介绍了电动强化技术及其作用机理,总结了影响强化效率的各个参数,并指出了该技术存在的问题及研究方向。随着不断地完善和发展,电动力强化技术将会在植物修复领域发挥重要作用。     

Chemical and thermal characteristics of milk-fat fractions isolated by a melt crystallization

Anhydrous milk fat (AMF) was fractionated by a two-stage dry fractionation process to produce three fractions: high melting (HMF), middle melting (MMF), and low melting (LMF). The HMF (m.p. 42°C) exhibited a broad melting range similar to a plastic fat. The MMF (m.p. 33°C) resembled the original AMF (m.p. 31°C), but with slightly higher solid fat content. The LMF (m.p. 16°C) was liquid at ambient temperature. Differences in the thermal properties of these fractions were attributed to the triacylglycerols (TAG) and their fatty acid composition. Saturated TAG with carbon numbers of 36–54 were concentrated in the HMF; whereas unsaturated TAG of carbon number 36–54 predominated in the LMF. Likewise, the long-chain saturated fatty acids were significantly higher and the long-chain unsaturated fatty acids were significantly lower in the HMF fraction. Binary blends of milk-fat fractions with a range of melting profiles were produced by mixing HMF with AMF, MMF, or LMF. Laboratory-prepared fractions were similar to commercially available fractions.     

Modelling of the reversed flow fixed bed reactor for catalytic decontamination of waste gases

Catalytic decontamination of waste gases in a fixed bed reactor, operating at non-steady state conditions achieved by periodic gas flow reversal, is simulated on the basis of a mathematical model. The opportunity to utilize a significant part of the reaction heat is discussed and the effect of catalyst inactivation upon reactor performance is analyzed. Stable temperature regime and conversion exceeding 99.5% could be ensured by a more than eightfold reduction of catalyst activity.     

Void content of a viscoelastic composite melt: Reduction during mixing

Mica and polystyrene in four ratios were sheared for three different times, each at three speeds, and at two temperatures in the viscoelastic region, in a screw mixer. From precise density measurements on the resulting composites, void volume fractions were calculated and found to be proportional to mica concentration and independent of total screw rotations. Experimental void/mica ratios were represented by a kinetic model; they decreased from a single value common to all conditions to a steady-state value proportional to the square root of the screw speed. Void formation and elimination occur simultaneously. The goodness of the fit to the data is insensitive to the details of the kinetic model. The characteristic rate constant depends only on temperature, increasing at the same rate as the reciprocal of the low-frequency dynamic viscosity. Cavitation in regions of diverging flow of the mixer may inhibit void elimination.