Effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria: Soot-ceria contact and interfacial oxygen evolution

Ceria is widely used as a catalyst for soot combustion, but effects of Zr substitution on the reaction mechanism is ambiguous. The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria. The nanostructured CeO₂, Ce_0.92Zr_0.08O₂, and Ce_0.84Zr_0.16O₂ composed of 5–6 nm crystallites display T_m-CO2 (the temperature at maximum CO₂ yield) at 383, 355, and 375°C under 10 vol.% O₂/N₂, respectively. The size of agglomerate decreases from 165.5 to 51.9–57.3 nm, which is beneficial for the soot-ceria contact. Moreover, Zr increases the amount of surface oxygen vacancies, generating more active oxygen (O₂^? and O^?) for soot oxidation. Thus, the activities of Ce_0.92Zr_0.08O₂ and Ce_0.84Zr_0.16O₂ in soot combustion are better than that of CeO₂. Although oxygen vacancies promote the migration of lattice O^2?, the enriched surface Zr also inhibits the mobility of lattice O^2?. Therefore, the T_m-CO2 of Ce_0.84Zr_0.16O₂ is higher than that of Ce_0.92Zr_0.08O₂. Based on reaction kinetic study, soot in direct contact with ceria preferentially decomposes with low activation energy, while the oxidation of isolated soot occurs through diffusion with high activation energy. The obtained findings provide new understanding on the soot combustion over nanoceria.     

利用木薯渣进行纤维素分解菌混合发酵工艺研究

从自然界中筛选出6株相互间无拮抗作用的纤维素分解菌进行混合发酵,研究了该混菌以工业废弃物木薯渣为原料发酵的最佳产酶条件是:培养基配方为木薯渣4 g,黄豆粉0.75 g,KH2PO40.20 g,NaCl 0.02g,MgSO4·7H2O 0.015 g,蒸馏水1 000 mL;发酵工艺为初始pH=7.0,培养温度40℃,每250 mL锥形瓶装培养液140mL,接种量3%,在140 r·min-1转速下发酵72 h.结果表明,混合菌的发酵可大幅度提高纤维素酶活力及对还原糖的耐受力.     

钻井废液的固液分离工艺与设备

影响钻井废液固液分离的因素包括钻井废液的稀释比例、脱稳处理药剂的种类和加量、固液分离设备。文章介绍了钻井废液处理的基本流程,分析了钻井废液pH值对固液分离效果的影响,论述了卧式螺旋卸料沉降离心机的基本结构、设备参数和操作参数对固液分离效果的影响。     

基于固液分离预处理的餐厨垃圾厌氧发酵

研究不同预处理方法所获餐厨垃圾浆料的半连续式厌氧发酵效果,评价该类餐厨垃圾的产甲烷资源化潜能.结果表明,固液油三相分离预处理后的液相餐厨垃圾作为进料较固液混合相餐厨垃圾在厌氧发酵时具有更高的VS去除率,实际产甲烷潜能和甲烷转化率,分别为91.2％,531.5mLCH4/gVS和54.3％,表明液相餐厨垃圾半连续中温湿式...     

Volatilization of heavy metals during incineration of municipal solid wastes

Incineration experiments with MSW, which had been impregnated with heavy metals, were presented to obtain information on the volatilization behavior of the elements cadmium (Cd), lead (Pb), and zinc (Zn) under different conditions. Experiments were carried out in a bubbling fluid bed system connected to a customized inductively coupled plasma optical emission spectroscopy(ICP-OES) for analyzing metals in the flue gas. The results indicated that the combustion temperature, the gas atmosphere, and the chlorine content in the flue gas could affect the volatilization behavior of heavy metals. In the fluidized bed combustion, a large surface area was provided by the bed sand particles, and they may act as absorbents for the gaseous ash-forming compound. Comparer with the metals Cd and Pb, the vaporization of Zn was low. The formation of stable compounds such as ZnO.Al2O3 could greatly decrease the metals volatilization. The presence of chlorine would enhance the volatilization of heavy metals by increasing the formation of metal chlorides. However, when the oxygen content was high, the chlorinating reaction was kinetically hindered, which heavy metals release would be delayed.     

Emission control for precursors causing acid rain (V): Improvement of acid soil with the bio-briquette combustion ash

The bio-briquette technique which mixes coal, biomass and sulfur fixation agent and bio-briquettes under 3-5 t/cm^2 line pressure has aroused people‘s attention in view of controlling the air pollution and the acid rain. In this paper, the physicochemical properties of bio-briquette and its ash were investigated. And the acid soil was improved by the bio-briquette combustion ash, which contained nutritive substances such as P, N, K and had the acid-neutralizing capacity(ANC). The pH, EC, effective nutrient elements(Ca, Mg, K, P and N), heavy metal elements(AI, Cu, Cd, Cr, Zn and Mn) and acid-neutralizing capacity change of ash-added soils within the range of 0-10%, were also studied. Specially, when 5% bio-briquette combustion ash was added to the tested soil, the content of the effective elements such as Ca, Mg and K rose by 100 times, ? times and twice, respectively. The total nitrogen also increased by about twice. The results showed the oxyanions such as that of AI, Cu, Cd, Cr, Zn and Mn were not potentially dangerous, because they were about the same as the averages of them in Chinese soil. It is shown that the ANC became stronger, though the ANC hardly increases in the ash-added soil. On the basis of the evaluation indices, it is concluded that the best mixture ratio is to add 2.5%--8% of the bio-briquette combustion ash to the tested soil.     

Neutron activation analysis of ceramic tiles and its component and radon exhalation rate

IntroductionCeramic,consistofearthymaterialslikeclaykaolin ,limestoneandsandglass .Ceramicmaterialsarenonmetalic ,inorganiccompoundsprimaryoxides ,alsocarbides ,nitridesandsilicides .Twotypesofbondingmechanismsoccurinceramicmaterial ,ionicandcovalent.Theo…     

Application of environmentally conscious manufacturing strategies for an automotive component

Application of appropriate environmentally conscious manufacturing strategies enables the sustainable development of products and processes. Automotive component manufacturers recognise the potential of applying appropriate strategies for attaining Triple Bottom Line benefits. In this context, three strategies such as eco-efficiency, waste minimisation and material efficiency are being applied to minimise environmental impacts associated with the manufacture of automotive products and its associated processes. A case study of an automotive component manufacturing firm has been exemplified. After conducting the study, the potential environmental impact was reduced by 20% and eco-efficiency was improved by 13%. Further, improvements have been observed in terms of overall resource consumption and material efficiency. The overall power consumption was reduced by 18% and weight of the component was reduced by 11%. The study aimed at improving the sustainable performance of product by incorporating green and environmentally friendlier manufacturing practices.

Abbreviations: USEPA: United Nations Environmental Protection Agency; OECD: Organisation for Economic Co-operation and Development; WBCSD: World Business Council for Sustainable Development; Eco-QFD: Environmental Quality Function Deployment; WCED: World Commission on Environment and Development; LCA: Life Cycle Assessment     

固体推进剂老化过程影响因素及化学反应机理研究进展

基于固体推进剂的贮存老化,以NEPE推进剂和以HTPB推进剂为代表,综述了近年来固体推进剂老化进程中所受的各种影响因素、作用机制及化学反应机理研究进展。总结了温湿度、应力和环境气氛为代表的外部环境因素,配方性质、组分变化和添加剂等内部影响因素对推进剂老化及贮存失效期限的影响。分别从微观和宏观角度出发,分析了内外部各种影响因素加速或减缓固体推进剂老化进程的作用机制。此外,针对黏合剂、氧化剂、防老剂等化学组分,总结了固体推进剂贮存老化期间发生的氧化交联、分解、降解断链等主要化学反应,并分析了各个反应发生的机理及原因。最后,展望了未来固体推进剂老化影响因素研究的发展趋势,并为今后固体推进剂老化机理及失效模式研究提供了研究思路。     

煤矿巷道瓦斯爆炸传播规律及破坏效应分析

井下瓦斯爆炸的影响因素众多,随机性强,分析和研究瓦斯爆炸的传播规律只有通过巷道模拟实验的方法。通过对爆炸过程中爆炸压力、温度、速度等相关参数随时间、空间的变化规律的分析,进一步研究瓦斯爆炸的机理和破坏效应,在煤矿生产过程中采取合适的阻隔防爆技术措施,减少瓦斯爆炸带来的损失。