Application of human factors evaluation in engineering design and safe operation of dense phase ethylene treaters

Ethylene treaters are widely used in the petrochemical industry to remove impurities from ethylene feedstock imported from pipeline networks or storage caverns. The safety concerns of dense phase ethylene treaters due to the reactive and highly flammable nature of ethylene are well known and studied. Under certain conditions, ethylene may self-polymerize and decompose violently with heat release. Under other conditions, ethylene will auto-refrigerate, generating cold liquids that may cause potential brittle fracture hazards. Therefore, dense phase ethylene treaters present design challenges with the unique combination of high temperature decomposition and cold temperature brittle fracture hazards.Due to these safety concerns, it is important to select the appropriate engineering design options for dense phase ethylene treaters and the associated regeneration facilities. Totally automated treater regeneration systems add complexity and instrument maintenance requirements while manually operated systems rely heavily on operator training and procedures. Unfortunately, little or no information or design guidance is available from published research findings in the literature on the evaluation and risk assessment of current industrial design options and practices for dense phase ethylene treaters.This paper presents a systematic risk assessment method to evaluate the engineering design and safe operation options for dense phase ethylene treaters. The proposed risk assessment method integrates human factors task analysis into the traditional HAZOP, LOPA and fault tree analysis to allow evaluation of automated, manual and hybrid approaches with a goal of selecting and optimizing design options to ensure plant safety. This approach provides a realistic assessment of the operational risk and allows identification of fit-for-purpose risk reduction. Applying this systematic risk assessment approach, a simpler and more cost effective design solution can be justified, thereby avoiding the need for a high integrity protective system.     

Determinants of CO2 emissions in Brazil and Russia between 1992 and 2011: A decomposition analysis

This paper deals with the decomposition analysis of energy-related CO₂ emissions in Brazil and Russia from 1992 to 2011. The refined Laspeyres index (RLI) method applied and both aggregated and sectoral changes in CO₂ emissions decomposed. Brazil’s and Russia’s economies divided into three economic sectors including agriculture, industry and services. Impact of four main factors, such as economic activity, employment, energy intensity, and carbon intensity in CO₂ emissions changes were analyzed. The aggregated decomposition analysis revealed that Brazil is still far from a decoupling between economic growth and carbon dioxide emissions where Russia achieved a substantial decline in carbon emissions mainly due to the improved energy intensity. The empirical findings of sectoral decomposition analysis emphasized that the economic activity was the major CO₂ increasing factor in Brazil’s economic sectors. On the other hand the economic activity effect followed a reducing impact in Russia’s sectoral emissions until 2000. The structural changes between sectors and their impacts on CO₂ emissions were captured by employment effect. Energy intensity and carbon intensity effects underlined that environmental sustainability widely neglected in Brazil and Russia during the study period. The results yield important hints for energy planning and sustainable environment.     

Decomposition of Al13 promoted by salicylic acid under acidic condition: Mechanism study by differential mass spectrometry method and DFT calculation

Decomposition of the polycation Al₁₃O₄(OH)₂₄(H₂O)₁₂⁷⁺ (Al₁₃) promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions, especially in the case of acidic condition that dissolved Al³⁺ species can be released from the Al-bearing substances. However, the microscopic pathway of synchronous proton-promoted and ligand-promoted decomposition process for Al₁₃ is still in the status of ambiguity. Herein, we applied differential mass spectrometry method and DFT calculation to study the initial detailed process of Al₁₃ decomposition under the presence of proton and salicylic acid (H₂Sal). Mass results showed that the mononuclear Al³⁺-H₂Sal complexes dominated the resulting Al species, whereas the monodentate complex Al₁₃HSal⁶⁺ was not observed in the spectra. The difference of decomposition levels between the ligand/Al ratio 0.2 and 0.5 cases revealed that proton and ligand performed synergistic effect in initial Al₁₃ decomposition process, and the proton transfer determined the ring closure efficiency. The ring closure reaction is the prerequisite for the collapse of Al₁₃ structure and detachment of the mononuclear complex. DFT calculations reveal that hydrogen bond plays an important role in inducing the formation of chelated complex accompanying proton transfer. Attachment of protons at the bridging OH⁻ can elongate and weaken the critical bond between targeted Al³⁺ and µ₄-O^2- resulting from delocalization of electron pairs in the oxygen atom. These results demonstrate the detailed mechanism of Al₁₃ composition promoted by ligand and proton, and provide significant understanding for further application and control of Al₁₃.     

Evaluation of thermal properties and process hazard of three ionic liquids through thermodynamic calculations and equilibrium methods

Industrial and new energy applications of ionic liquids (ILs) may have to be used at high temperatures conditions, such as in batteries and fuel applications, which may cause thermal hazards. However, there are few studies on the thermal hazards of ILs. To ensure the thermal safety of ILs processes, three commonly used ILs were selected for analysis: 1-butyl-3-methylimidazolium nitrate ([Bmim]NO₃), 1-butyl-2,3-dimethylimidazolium nitrate ([Bmmim]NO₃), and 1,3-dimethylimidazolium nitrate ([Mmim]NO₃). The process hazards under adiabatic conditions demonstrated that [Bmmim]NO₃ and [Mmim]NO₃ have extensive explosion hazards. The self-reaction characteristics determined by the isothermal test indicated that the ILs are nth reactions, and the thermal decomposition features were also determined by thermogravimetric analysis. The data were obtained with a nonlinear thermodynamic model and used to establish the basic thermal hazards of the three ILs. In addition, based on the thermal equilibrium theory, the critical safety parameters can be inferred. The effects of heat transfer in 25.0 g and 50.0 g containers were discussed. The results show that [Mmim]NO₃ will produce a thermal runaway reaction at a lower temperature (<100 °C) and has the shortest reaction time (<1 day), which means [Mmim]NO₃ is considered to be the most hazardous material among the three ILs studied.     

Decomposition and oxidation of sodium 3,5,6-trichloropyridin-2-ol in sub- and supercritical water

Sodium 3,5,6-trichloropyridin-2-ol (STCP) is a necessary precursor compound for the production of chlorpyrifos and triclopyr, which are extensively used as pesticide and herbicide, respectively. In the process of STCP production, however, large amount of wastewater containing STCP is discharged, which causes increasingly environmental concerns. Therefore, it is of great significance to develop a rapid and effective method for the disposal of containing STCP contaminants. In this work, the thermal decomposition of STCP in sub- and supercritical water was investigated using a continuous tubular reactor. While STCP was stable below 280 °C, it could be effectively decomposed at elevated temperature. FT-IR spectra of the decomposition products indicated that the pyridine ring structure in the STCP molecule was stable even at temperatures up to 400 °C. The decomposition reaction was mainly caused by the substitution of Cl groups in the STCP molecule with OH groups, resulting in polyhydroxylated pyridines as the major decomposition product. Moreover, high pressure favored the substitution reaction. To completely decompose STCP into non-toxic or low toxic compounds, supercritical water oxidation (SCWO) was employed to evaluate the oxidation of STCP using H₂O₂ as an oxidant. It was found that STCP could be completely oxidized to H₂O, CO₂ and corresponding inorganic ammonium salts with an oxidation rate of 99%.     

Decomposition of 2,2',4,4',5,5'-hexachlorobiphenyl with iron supported on an activated carbon from an ion-exchange resin

An activated carbon (AC) containing a high concentration (374 mg g⁻¹) of Fe was prepared by carbonization of an ion-exchange resin. To examine its chemical reactivity as a catalyst to decompose 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153), the decomposition parameters of temperature and time were varied under air or N₂. Decomposition at 350 °C was achieved within 15 min under air and 30 min under N₂, and the efficiency of PCB-153 decomposition was 99.7% and 98.0%, respectively. An analysis of inorganic chloride ions revealed that PCB-153 was mineralized effectively during the decomposition. The Brunauer-Emmett-Teller (BET) surface area and pore volume of the AC were measured to assess the adsorption capacity before and after the decomposition. The differences between decomposition under air and N₂ reflected the differences in the BET surface and pore volume measurements. A decomposition pathway was postulated, and the reactive characteristics of chlorine atoms loaded on the benzene rings followed the order of para > meta > ortho, which agrees with the calculated results from a density functional theory study.     

光合细菌两段流化床处理鸡粪粪水的研究

光合细菌对高浓度有机废水具有较好的适应性和处理能力,特别是作为一个预处理工艺对后续污水处理可以产生重要的影响。鉴于光合细菌生长时间相对较长,为提高光合细菌对高浓度有机污水的处理效率,本研究利用光合细菌两段流化床反应器对鸡粪粪水进行降解。试验结果表明:经过60 d的启动运行后,反应器进入稳定状态,在进水pH值6.0,COD小于10000mg/L范围内,流化床水力停留时间(HRT)为48 h时,对废水COD去除率为88.10%,TN去除率为68.29%,NH3-N去除率为94.42%,NO3-N去除率为65.43%。     

Fine root decomposition and nutrient release in Toona sinensis plantation under the reconstruction mode of low-efficiency cypress forest gaps北大核心CSCD

Fine root decomposition is an important way in which nutrients are returned to plantation soil; thus, further study of this process will be helpful for understanding material cycling in forest ecosystems. We investigated a Toona sinensis plantation in the central Sichuan hilly region using litter bags containing T. sinensis fine roots to evaluate the dynamics of fine root decomposition and nutrient release for one year in forest gaps of 50 m2 (L1), 100 m2 (L2), and 150 m2 (L3). The results showed that T. sinensis fine root decomposition was fastest in the first 90 days. As time passed, the decomposition rate slowed. One year later, the residue rate was 75.44%, 73.92%, and 72.07%, respectively. The fine root decomposition rate of L3 was greater than that of L2, which was greater than that of L1. During fine root decomposition, the dynamics of the fine root nutrient concentrations changed. C, P, and K concentrations of the fine roots declined in forest gaps, while N, Ca, and Mg concentrations increased overall in the fine roots. In conclusion, forest gaps had effects on the fine root decomposition and nutrient release of T. sinensis, and different sized forest gaps produced different results. © 2018 Science Press. All rights reserved.     

水中臭氧分解动力学研究

在磷酸盐缓冲液中研究了臭氧的自分解,根据臭氧分解机理推导出其动力学方程。由不同温度和pH值下的实验结果确定出kT,0,n以及活化能E。      

新能源汽车需求市场培育的政策取向:供给侧抑或需求侧

政策支持是促进新能源汽车消费市场等商业化条件成熟的重要手段。近年来,中央和一些地方政府在新能源汽车需求市场培育的"供给侧"和"需求侧"都先后出台了相应的市场培育政策。"供给侧"和"需求侧"的政策功能与效果不完全相同,地方政府在选择和应用新能源汽车需求培育政策时面临着诸多困惑。论文尝试将基尼系数分解法引入到新能源汽车需求市场"供给侧"和"需求侧"政策实施效果的区域差异分析中,分析了我国培育新能源汽车消费市场培养"供给侧"和"需求侧"政策取向的分布情况以及现阶段政策取向所面临的困惑,应用我国新能源汽车试点推广城市数据开展了实证研究。结果表明,"供给侧"政策着力于改善新能源汽车消费市场供给体系的质量和效率,为需求市场持续发展提供驱动力量;"需求侧"政策着力于激发新能源汽车消费的积极性和购买能力,为需求市场持续发展提供拉动力量。"供给侧"和"需求侧"政策在不同收入水平区域试点城市中的实施效果存在差异,高收入区域试点城市"供给侧"和"需求侧"政策都有着明显效果,但是"供给侧"政策效果更为显著;中等收入区域试点城市"需求侧"政策效果十分显著,"供给侧"政策效果相对较弱;收入稍低区域试点城市则以"供给侧"政策效果更为显著,"需求侧"政策效果相对较弱。我国新能源汽车市场培育在"供给侧"和"需求侧"政策取向上应因地制宜,各有侧重点。