Quantitative risk assessment integrated with dynamic process simulation for reactor section in heavy oil desulfurization process

A new methodology for quantitative risk assessment (QRA) integrated with dynamic simulation and accident simulation is proposed. The objective of this study is to discover inherent risks that are undetectable by conventional risk analysis methods based on steady-state conditions. The target process is the reactor section in the heavy oil desulfurization (HOD) process, which is likely to pose vast potential risks due to the high operating conditions of pressure and temperature. First, a dynamic simulation of a shut-down procedure was performed to observe the behavior of process variables using Aspen HYSYS V10, which is a commercially available process software. Based on the results of the dynamic simulation, several blind spots indicating a higher operating pressure than that in the steady-state simulation were identified. To assess the risks of the detected blind spots, a QRA was performed using the commercial software of SAFETI V8.22, which performs risk calculation based on consequence and frequency data. As a result of applying the proposed method to the HOD process, the risk assessment outcome was identified as intolerably risky unlike that of steady-state conditions, thereby indicating that dynamic simulations can serve as a method to spot inherent risks that are undetectable in steady-state conditions. In addition, mitigation procedures that reduce the risk of the process to a tolerable level are performed, thereby enabling a safer and more reliable process.     

Dynamic Inherently Safer Modifications: Metric development and its validation for fire and explosion prevention

Of the numerous inherent safety assessment tools, a dynamic metric capable of investigating and incorporating the temporal risk evolution when conducting Inherently Safer Modifications (ISMs) is yet to be established. To this end, this work developed a Dynamic Inherent Safety Metric (DISM) and validated its functionality and viability through a case study. Firstly, the Information-Flow-based Accident-causing Model (IFAM) was adapted to construct the topology of Bayesian Networks (BN). Then, Bayesian deductive reasoning was executed to do crucial risk identification by ranking posterior probabilities. Finally, risk-based ISMs were performed to address the relatively contributing risk factors. The case study results show that the fire and explosion risk decreased by approximately a third after implementing ISMs, thus demonstrating that the modified processing scenario could be inherently safer than the original processing scenario. The newly developed inherent safety metric (i.e., DISM) can assist in temporal risk identification and assessment, and it is expected to function as a novel assessment tool for measuring and comparing the inherent safeness before and after implementing ISMs with simultaneous considerations on the time-varying risk factors.     

Biogenic volatile organic compound emission patterns and secondary pollutant formation potentials of dominant greening trees in Chengdu, southwest China

Integral to the urban ecosystem, greening trees provide many ecological benefits, but the active biogenic volatile organic compounds (BVOCs) they release contribute to the production of ozone and secondary organic aerosols, which harm ambient air quality. It is, therefore, necessary to understand the BVOC emission characteristics of dominant greening tree species and their relative contribution to secondary pollutants in various urban contexts. Consequently, this study utilized a dynamic enclosure system to collect BVOC samples of seven dominant greening tree species in urban Chengdu, Southwest China. Gas chromatography/mass spectrometry was used to analyze the BVOC components and standardized BVOC emission rates of each tree species were then calculated to assess their relative potential to form secondary pollutants. We found obvious differences in the composition of BVOCs emitted by each species. Ficus virens displayed a high isoprene emission rate at 31.472 μgC/(gdw (g dry weight)•hr), while Cinnamomum camphora emitted high volumes of D-Limonene at 93.574 μgC/(gdw•hr). In terms of the BVOC emission rates by leaf area, C. camphora had the highest emission rate of total BVOCs at 13,782.59 μgC/(m²•hr), followed by Cedrus deodara with 5466.86 μgC/(m²•hr). Ginkgo biloba and Osmanthus fragrans mainly emitted oxygenated VOCs with lower overall emission rates. The high BVOC emitters like F. virens, C. camphora, and Magnolia grandiflora have high potential for significantly contributing to environmental secondary pollutants, so should be cautiously considered for future planting. This study provides important implications for improving urban greening efforts for subtropical Chinese urban contexts, like Chengdu.     

Analysing economic impact on interdependent infrastructure after flood: Pakistan a case in point

A disaster such as floods can have a drastic impact on interdependent infrastructure and economic sectors. The resilience or the ability of the critical sector to recover quickly from the disruption can also reduce the consequences of the disaster. In this paper, through resilience and recovery time Dynamic Inoperability Input-Output model (DIIM) is applied. Thus, Input-Output (I-O) table is constructed for Pakistan's economic system and a case study is performed on the flooding in Pakistan 2011–12. The purpose of this study is to provide a ballpark estimate of the system-wide impact and ripple effect on the sectors that lasted for several days after the disruption. Furthermore, to analyze the inoperability and economic loss in the sectors caused by the disaster in a developing country. The findings of the research show that most of the critical sectors are associated with agriculture and service sector in terms of inoperability and economic loss respectively. The outcome of the study will be essential for the policy makers, disaster management authorities and health departments to respond accordingly.     

Consequences assessment of explosions in pipes using coupled FEM-SPH method

Explosions often lead to destruction of equipment, which is a difficult problem including complicated fluid-solid interactions. Most traditional CFD methods cannot synchronously solve the movements of fluids and large deformation and fracture of solids because such problem is usually accompanied with constantly moving-and-changing boundary conditions. In this paper, a coupled Finite Element Method-Smoothed Particle Hydrodynamics (FEM-SPH) method was proposed to simulate the dynamic processes of explosions in pipes. The propagation of blast wave and the fracture of pipe were captured in every timestep, where the energy dissipation caused by plastic deformation and crack propagation were fully considered. A rate-dependent failure criterion for high-strain-rate load conditions was employed in the numerical simulation, which was presented in our previous work and has been verified in the dynamic fracture behavior of steels for pressure vessels and pipes. In addition, a simpler formula was proposed to describe the attenuation of blast wave outside the pipe and the consequences caused by the explosions were assessed. Results revealed the interaction between blast wave and pipe, the leakage of detonation products, the attenuations of peak overpressures outside the pipe and the corresponding consequences at different distances. It is found that when considering the energy consumption during plastic deformation and crack propagation in coupled FEM-SPH method, the assessment results are more rational than that without considering such energy consumption.     

Linking energy scenarios with metal demand modeling–The case of indium in CIGS solar cells

Some renewable energy technologies rely on the functionalities provided by geochemically scarce metals. One example are CIGS solar cells, an emerging thin film photovoltaic technology, which contain indium. In this study we model global future indium demand related to the implementation of various energy scenarios and assess implications for the supply system. Influencing parameters of the demand model are either static or dynamic and include technology shares, technological progress and handling in the anthroposphere. Parameters’ levels reflect pessimistic, reference, and optimistic development. The demand from other indium containing products is roughly estimated. For the reference case, the installed capacity of CIGS solar cells ranges from 12 to 387 GW in 2030 (31–1401 GW in 2050), depending on the energy scenario chosen. This translates to between 485 and 15,724 tonnes of primary indium needed from 2000 to 2030 (789–30,556 tonnes through 2050). One scenario exemplifies that optimistic assumptions for technological progress and handling in the anthroposphere can reduce cumulative primary indium demand by 43% until 2050 compared to the reference case, while with pessimistic assumptions the demand increases by about a factor of five. To meet the future indium demand, several options to increase supply are discussed: (1) expansion of zinc metal provision (indium is currently a by-product of zinc mining), (2) improving extraction efficiency, (3) new mining activities where indium is a by-product of other metals and (4) mining of historic residues. Potential future constraints and environmental impacts of these supply options are also briefly discussed.     

红树林原位生态保育系统中叶绿素a的动态变化及其影响因素

根据2012年8月对广西防城港“红树林原位生态保育系统”示范基地8月1日、8月8日、8月15日3天24小时连续水质监测资料,讨论该系统叶绿素含量的周日变化情况与其他环境因子的关系,分析水质的变化情况。     

气相色谱法测定固体废物中丙烯醛、丙烯腈和乙腈的实验研究

采用静态顶空-气相色谱法测定固体废物中丙烯醛、丙烯腈和乙腈的含量。着重讨论了顶空平衡温度、平衡时间等因素对三种物质测定结果的影响,并优化了试验参数。在优化的实验条件下,丙烯醛、丙烯腈、乙腈及溶剂甲醇能完全分离,校准曲线线性范围可达1.00到100 mg/kg,方法检出限分别为0.044、0.034和0.035 mg/kg,实际样品加标回收率在90%～109%之间,相对标准偏差为3.3%～8.6%。     

顶空气相色谱法同时测定空气中甲醇和乙醇实验研究

顶空气相色谱测定空气中甲醇和乙醇含量,方法简单、快速,无需使用有机试剂。本方法以蒸馏水吸收空气中甲醇和乙醇,顶空进样经DB-624毛细管柱分离,氢火焰离子化检测器检测,时间定性,峰面积定量,其甲醇加标回收率为96．7％～104．6％,乙醇加标回收率为94．7％～103．8％,当在采样体积为40L的条件下,甲醇和乙醇最低检出质量浓度均为0．11mg／m^3。实际操作证明,该法能满足工业废气和空气中的甲醇和乙醇的监测。     

Exurban development

Exurbia, the rural area beyond the built-up urban and contiguous suburban area, is being developed rapidly with attendant losses in habitat and ecosystem services. This paper analyzes a spatial dynamic model with two production technologies for residential development—municipal sewer service for suburban development and septic systems for exurban development. In outlying agricultural areas, the additional sewer extension costs can significantly reduce the value of agricultural land in suburban use. Exurban development, while at lower density, can occur immediately and requires only the onsite conversion costs of septic systems. Hence, the willingness to pay for exurban use from households with higher preferences for lot size may exceed the agricultural landowner's reservation price on future suburban use for a range of distances from the city boundary. This results in a “feasible zone” for exurban leapfrog development and another fundamental reason for scattered development in the urban–rural fringe.