城市垃圾焚烧飞灰处理技术及其在水泥生产中资源化利用

分析了城市垃圾处理技术的现状和发展趋势;介绍了城市垃圾焚烧飞灰处理技术的发展和资源化利用的紧迫性;阐述了水泥生产中资源化利用垃圾焚烧飞灰的可行性和前景;回顾了国内外水泥生产协同处理固体废物技术的发展历程,并提出了目前亟需解决的一些关键技术。在广泛研究的基础上,明确指出了水泥生产中资源化利用垃圾焚烧飞灰是实现焚烧飞灰资源化利用和无害化处理的重要途径。     

热处理对粉煤灰酸渣基二氧化硅气凝胶结构和疏水性的影响

粉煤灰酸渣是粉煤灰经酸溶提铝后的副产品,主要化学成分为无定形二氧化硅,其资源化利用不仅解决了粉煤灰酸渣堆存带来的环境问题,还能获得附加值较高的二氧化硅气凝胶。以粉煤灰酸渣制备的水玻璃为原料,通过溶胶-凝胶—溶剂交换/表面改性—常压干燥工艺成功制备了低密度（0.083 g/cm³）、高比表面积（708 m²/g）、高疏水性（接触角为143°）的多孔二氧化硅气凝胶。通过热重-差热分析、红外光谱分析、接触角测试、扫描电镜分析、氮气吸附-脱附测试等手段对热处理前后二氧化硅气凝胶的结构和疏水性进行了表征。结果表明,随着热处理温度升高,二氧化硅气凝胶的比表面积增大、疏水性逐渐减弱直至消失。300 ℃热处理后,二氧化硅气凝胶仍具有较强的疏水性（接触角约为128°）,密度为0.080 g/cm³。当热处温度为400~600 ℃时,二氧化硅气凝胶仍具有中孔结构,由疏水性变为亲水性,密度从0.073 g/cm³增加到0.078 g/cm³。     

Co‐gasification of woody biomass and sewage sludge in a fixed‐bed downdraft gasifier

Experimental and numerical studies of cogasification of woody biomass and sewage sludge have been carried out. The gasification experiments were performed in a fixed‐bed downdraft gasifier and the experimental results show that 20 wt % dried sewage sludge in the feedstock was effectively gasified to generate producer gas comprising over 30 vol % of syngas with an average lower heating value of 4.5 MJ/Nm³. Further increasing sewage sludge content to 33 wt % leads to the blockage of gasifier, which is resulted from the formation of agglomerated ash. The numerical models were then developed to simulate the reactions taking place in four different zones of the gasifier (i.e., drying, pyrolysis, combustion, and reduction zones) and to predict the producer gas composition and cold gas efficiency. The deviation between the numerical and experimental results obtained was lower than 10%. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2508–2521, 2015     

Thermal,chemical and thermo‐chemical pre‐treatment of waste activated sludge for anaerobic digestion

The influence of different pre‐treatments was studied in order to observe the effects of temperature, pH and treatment time on Waste Activated Sludge (WAS) solubilization, and anaerobic digestion of pre‐treated sludge. Results showed that thermo‐chemical pre‐treatments were the most efficient on Chemical Oxygen Demand (COD) solubilization, which could reach 83% at 170 °C with pH = 12. Yet, increase in COD solubilization in thermo‐chemical pre‐treatment was not linked to an increase in soluble Volatile Solids (VS) as optimal conditions were 170 °C, and 130 °C with pH = 10, for this criterion. So, temperature was found to be the most influential parameter on COD and VS solubilization. Biodegradability batch anaerobic tests confirmed results obtained on WAS solubilization, that is to say that 170 °C and 130 °C with pH = 10 were optimal conditions, with respectively 45% and 21% of anaerobic digestion enhancement. Thus these two conditions were chosen for sludge treatment before continuous anaerobic digestion. Results, after stabilization have shown a better efficiency of 170 °C compared with 130 °C with pH = 10 pre‐treatment, since after anaerobic digestion it led to 71% of COD degradation and 59% of Total Solids (TS) degradation, with an improvement of 54% in biogas production. The main differences between those two pre‐treatments could be due to the pre‐treatments themselves more than to an effect on anaerobic digestion, because the first one led to a partial loss of WAS COD (near 17% of initial COD) and the second one to an increase in TS due to addition of base. Copyright © 2004 Society of Chemical Industry     

Comparison of thermo‐oxidative treatments for the anaerobic digestion of sewage sludge

BACKGROUND: In this study, various thermo‐oxidative treatments were examined and compared with the aim of overcoming the disadvantages of thermal treatment and enhancing the anaerobic digestion of sewage sludge. RESULTS: Oxygen, hydrogen peroxide and ozone were selected as oxidant, accompanied with the addition of either acid (HCl) or alkali (Na₂CO₃) for oxygen. The temperature and duration were fixed at 170 °C and 1 h, respectively. Anaerobically digested sludge was used as the substrate, to see the effects on the refractory part of sewage sludge. A batch methanogenesis test using 120 mL serum bottles was run at 35 °C for 20 days, and methane production, solids reduction, dewaterability and color intensity were measured. As the strength of the oxidants was increased, methane production tended to decrease, whereas solids reduction was increased. The dewaterability of the sludges and the color in the filtrates became worse for thermo‐oxidative treatment with oxygen and alkali. On the other hand, the dewaterability was improved significantly and color generation was restricted the most for the thermo‐oxidative treatment with oxygen and acid. CONCLUSION: Lowering the pH of thermo‐oxidative treatment is advantageous with respect to the dewaterability and color generation of digested sludge. Based on evaluation of the overall performance, thermo‐oxidative treatment with acid is considered the best among the thermo‐oxidative treatments examined. Copyright © 2008 Society of Chemical Industry     

Utilization of bagasse fly ash generated in the sugar industry for the removal and recovery of phenol and p-nitrophenol from wastewater

Bagasse fly ash, a waste generated in local sugar industries, has been converted into a low cost adsorbent. The product so obtained has been characterized and used for the removal of phenol and p-nitrophenol. Investigations include the effect of pH, sorbent dosage, phenol concentration and the effect of surfactants on the uptake of phenol and p-nitrophenol. The adsorption data follow both Langmuir and Freundlich models. Isotherms have also been used to obtain the thermodynamic parameters of the process. Some experiments have also been performed with a view to recover phenols and have in-situ chemical regeneration of the spent carbon column. © 1998 SCI.