Applied Mechanics and Materials Vol. 768

Abstract: Composite insulator was widely used in the power grid because its excellent performance. Aging issue of composite insulators was appeared with the long-term operating. The internal structure of silicone rubber may be changed with the broken of macromolecular chains of silicone rubber, because long-term operating in the environments of surface discharge, ultraviolet, pollution and other harsh conditions. In order to study the aging characteristics of composite insulator at the different operating life, the components and thermal stability were analyzed using fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA) respectively. The results of FTIR showed that silicon rubber composition in composite insulator changed slightly with different operating life, especially in the internal surface. However, the absorption peaks of Si-CH₃ and Si-O-Si on external surface of the insulator were decreased obviously with operating life longer. The thermal gravimetric analysis results showed that the thermostability of composite insulator was almost not changed with different operating life. The temperature of 5% weightlessness was between 320°C to 335°C. It illustrated that the composite insulator had a good thermostability at room temperature and qualitative change wouldn't occur for a long time laying aside. The study of the aging characteristics of composite insulators will provided the reference for performance evaluation of running composite insulators.

Abstract: Polymer resin and glass fiber are the main wastes during the production process of glass-fiber reinforced plastics (GRP). With GRP products used widely in many fields, GRP wastes also got a large increase and the disposal of GRP wastes became a serious environmental problem. In this paper, the combustion characteristic of GRP wastes was tested by the thermal analysis and contrasted to that of powdered coal. In the full-scale test of GRP wastes co-processing in the cement kiln, the efficiency of coal-saving, the influence on chemical components of the product and the CO₂ emission were investigated to evaluate the feasibility of this technology.

Abstract: As the effect of density separation for waste plastic mixtures was poor, this research studied the impacts of wetting agents on the sorting rates of waste plastic mixtures and the mechanisms of wetting agents in density separation. The results showed that the surface activity of plastics could be changed by wetting agents and thus the sorting rates of plastics under the density separation system could be improved. Impacts of wetting agents such as CaLS, NP-7 and MC on density separation of plastics are related not only to the molecular structure of plastic materials but also to the separating media. The density separation system in the presence of different wetting agents established in this research separated the target plastic with a rate of 100%, which applied to a mixture of 9 kinds of common plastics such as PVC, PC, PS and so on.

Abstract: Over the past several decades with significant technological advances there has been continuous increase in plastic manufacturing in China, which has contributed to the production of a great deal of plastics worldwide every year, and at the same time it has resulted in a large amount of plastic solid waste (PSW). It has great potential values for waste plastics to reuse as secondary materials, which may lessen pressure on resource and environment. The paper studies the status of waste plastics in recycling, reusing and reducing on management countering on the increase in the flow of waste plastics in Shanghai. In light of the methodology of life cycle, the study analyzes the environmental impacts associating with the alternatives in a ‘cradle to grave’ approve to PSW technological recycling systems. We will choose regenerating and energy recovery processes based on site investigation and literatures data in Shanghai to analyze recycling options and how various processes affect the environment. Life-cycle methodology was very suitable for evaluating the overall environmental consequences, and could be used for making decisions and planning strategies with the rapid increase of plastic solid waste generation for Shanghai.

Abstract: The semi-dry flue gas desulfurization technology is widely used by coal-fired power plant. Desulfurization ash produced by semi-dry flue gas desulfurization, which consist CaSO₃, CaCO₃, Ca (OH) ₂, CaSO₄ and so on. It will bring new environment pollution if not been disposed properly. Building material industry is the main field in terms of the comprehensive utilization of desulfurization ash. While hazardous elements especial S and Hg may be released in the condition of temperature changes in the process of desulfurization ash utilization, causing second environment pollution. Combined with the research achievement of preparing autoclaved brick before, the content of S and Hg in raw materials and autoclaved brick were studied during the thermal utilization process in this article. The thermal stability of calcium sulfite was analyzed by the chemical reagent calcium sulfite. The results shown that calcium sulfite only lost crystal water whether in oxygen or air when the temperature is below 450°C, calcium sulfite was completely oxidized to calcium sulfate when the temperature is 475 °C in oxygen or 515°C in air. The contents of S and Hg which existed in desulfurization ash were 7.03%wt and 460μg/kg, respectively. The contents of S and Hg in autoclaved brick which made by desulfurization ash mainly were 5.16%wt and 450μg/kg, respectively. The results shown that the content of elements S and Hg in raw materials and autoclaved brick were roughly the same, which indicated that S and Hg no escape in the process of preparing autoclaved brick. The research provided a certain references for the comprehensive utilization of semi-dry flue gas desulfurization ash in the condition of heat and humid.

Abstract: This study evaluates the efficiency of lead (Pb) extraction from spent leaded glass in strongly alkaline solution after mechanical activation in a planetary ball mill as the chemical breakage and defects formed in the inner structures will contribute to the easy dissolution of the activated leaded glass. The influence of rotate speed and time of mechanical activation, NaOH concentrations, leaching temperature, phase ratios (v/w) had been studied. More than 78% of Pb extraction can be achieved after mechanical activation, compared with 3.5% Pb extraction for chemical leaching of non-activated samples. High purity lead powder can be obtained by electrowinning from the leaching solution. The Pb-depleted solution can be recycled into the leaching step. Thus, a novel hydrometallurgical process for recovering Pb from spent leaded glass in alkaline solution is proposed.

Abstract: The feasibility of one strategy of bioaugmentation was assessed to enhance copper extraction from chalcopyrite. Bioaugmentation consisted of the re-addition of one iron/sulfur oxidizing acidophile (Acidithiobacillus caldus, Ferroplasma thermophilum or Leptospirillum ferriphilum) into the early stage (on the 5^th day) of the bioleaching system. The strain selection and inoculum concentration of bioaugmentation were separately investigated by comparing changes in the bioleaching performance and leached solid residues. Results indicated that bioaugmentation with three augmented strains synergistically promoted the total microbial growth and increased the cell numbers, and then accelerated the iron/sulfur oxidation, thereby catalytically regenerated the copper leaching agents of Fe³⁺ and H⁺ compared to the unamended control. Finally, an enhancement in copper extraction was detected and moreover positively correlated with the introducing cell numbers. Particularly, re-addition of L. ferriphilum on the 5^th day showed the best improvement in copper leaching, which remarkably shortened the incubation time (12 days) of almost full copper extraction while only 85.8% of copper was leached after 24 days in the control. Therefore, bioaugmentation could be a useful bio-remedy to improve the bioleaching kinetics and level of copper ore.

Abstract: With the rapid urbanization and economic growth in China especially near 2 decades, the vast amount of municipal solid waste (MSW) were produced annually. Landfills are the predominant disposal sites for MSW in China, receiving more than 75% of the collected MSW every year. While the volume concentration is usually less than 1%, NMOCs are generally considered as the main source of the odorous problem at MSW landfills, because they include many compounds with very low odor thresholds. What’s more, aromatics is vital part of NMOCs for its toxic effect, which contains Benzene. The main objective of this study was to understand the comprehensive behavior of aromatics of landfill gas. In this work we present an integrated evaluation of working surface concentration distribution and emission rate of a municipal solid waste landfill. And in order to understand the transportation of aromatic, a new parameter was introduced to analyze this process. Thus, result shows, the fugitive emission of aromatics in the operating surface may need pay more attention. The highest average concentration for aromatics was found in autumn. Aromatic’s emission rate in winter was larger than autumn, the highest emission rate of aromatics toluene, 0.011g/m²/h. The B:T ratio in winter was significant higher that of other seasons.

Abstract: In this paper, the critical flux was applied to represent the tendency of membrane fouling. The response surface model was used to study different factors, such as sludge concentration, space between membranes and aeration rate, affecting membrane fouling of the upper and lower layer membrane module. It was found that the model is fitting and significant, moreover, the sludge concentration, space between membranes and aeration rate has a significant impact on the upper and lower membrane fouling. Meanwhile, it was also observed that the critical flux of both upper and lower layer membrane module sharply decreased with the increase of sludge concentration. However, the different variation tendency of membrane fouling between upper and lower layer membrane module was detected due to the change of space between membranes and aeration rate, when it was under different sludge concentrations. Finally, optimum operating parameters under different sludge concentration simulated by response surface model were successfully applied to the process of using flat-sheet membrane for four-stage sludge thickening.

Abstract: Phosphorus is a necessary nutrient element to all lives in the world. Distribution and phosphate rock reserves in the world disclose shortage crisis of phosphorus. Thus phosphorus recovery has been a research hot spot in the world. Mr.Ohtake’ group [1] recommended a new method to recover phosphorus from sewage sludge during heating process. It seems that nearly 90% of the poly-phosphate (poly-P) and 87% of total phosphate (T-P) can be released from cultivated sludge by heating at 70 °C for 1 hour. Meanwhile, released poly-P can precipitate with Ca in neutral condition without any pH adjustment. Sewage sludge was used in this research to identify its performance during thermal treatment. With the increase of temperature and heating time, release of poly-P and T-P increased obviously. However, poly-P would be hydrolyzed when temperature was higher than 80 °C. With addition of EDTA, release of poly-P increased nearly 100%. Migration of metal cations during thermal treatment can provide indirect evidence which kinds of metal cations would make impediment on poly-P release. A novel phenomenon was observed poly-P mixed with ortho-phosphate can precipitate with NH₄⁺ and Mg²⁺ as struvite at pH 8.5.