Research based on double coverage rate and reliability of gas detector layout optimization

The gas detector layout should be highly attuned to combustible gas leakage and attain a good reliability in avoiding detector malfunction, which is an important guarantee for the normal production of the chemical industry and other related enterprises. Herein, a gas detector layout optimization method based on double coverage and reliability is proposed. The key gas leakage monitoring area is determined through layout scene field investigation. To improve the detection probability and detection system reliability, the dual coverage target and voting mechanism are set, and the gas detector layout is determined with the ray-casting algorithm according to the coverage target. Combined with FLACS software to simulate a variety of typical leakage conditions under different layout scenarios, the relationship between the leaked gas concentration detected by gas detectors in each layout scheme and time is obtained, and the gas leakage detection probability in each layout scheme, number of detectors that can trigger the alarm, shortest time to trigger the alarm and reliability are comprehensively evaluated. The decision-maker selects the final gas detector layout plan according to the evaluation results and actual site needs. The study shows that the detection probability of each layout scheme set according to the double coverage is high, and multiple detectors can trigger the alarm (up to 100%), which ensures that the alarm can be triggered within 10 s under all applicable conditions. According to the evaluation results, the decision-maker can obtain a layout scheme that not only agrees with the actual site conditions but also attains a high detection probability, short detection time and strong reliability.     

脱硝催化剂的失活机理及其再生技术

采用SEM、XRD和XRF对电厂失活脱硝催化剂进行表征,探讨其失活原因和机理。结果表明:电厂脱硝催化剂失活的主要原因是活性组分V的流失及碱金属K、碱土金属Ca和As元素造成的催化剂中毒,烟气中飞灰的沉积也有一定的影响。经吹扫、水洗、酸洗和V负载再生,催化剂的各项物化性质基本恢复,NOx转化率基本达到新鲜催化剂的水平。水洗主要去除催化剂中的碱金属,酸洗主要去除As2O3,负载V补充催化剂活性组分。V再生催化剂在较高温度下的抗硫性能更好。     

Study of the influence of melamine polyphosphate and aluminum hydroxide on the flame propagation and explosion overpressure of aluminum magnesium alloy dust

When aluminum magnesium alloy dust floats in the air, a certain ignition energy can easily cause an accidental explosion. To prevent and control the occurrence of accidental explosions and reduce the severity of accidents, it is necessary to carry out research on the explosion suppression of aluminum magnesium alloy dust. This paper uses a vertical glass tube experimental device and a 20 L spherical explosive experimental device to carry out experimental studies on the suppression of the flame propagation and explosion overpressure of aluminum magnesium alloy dust with melamine polyphosphate (MPP) and Al(OH)₃. With increasing MPP and Al(OH)₃ concentrations, the flame brightness darkened, the flame velocity and propagation distance gradually decreased, and P_max and (dp/dt)_max decreased significantly. When the amount of MPP added reached 60%, the flame propagation distance decreased to 188 mm, which is a decrease of 68%, and the explosion overpressure decreased to 0.014 MPa, effectively suppressing the explosion of aluminum magnesium alloy dust. The experimental results showed that MPP was more effective than Al(OH)₃ in inhibiting the flame propagation and explosion overpressure of the aluminum magnesium alloy dust. Finally, the inhibitory mechanisms of the MPP and Al(OH)₃ were further investigated. The MPP and Al(OH)₃ endothermic decomposition produced an inert gas, diluted the oxygen concentration and trapped active radicals to terminate the combustion chain reaction.     

我国区域空气污染治理效率及其影响机制——基于超效率SBM模型和门槛回归模型

随着人民对美好生活需求的日益增长,政府空气污染治理的效率问题日益得到重视。本文从地方政府空气污染治理效率及其影响因素的视角入手,以全国30个省份为研究对象,运用超效率SBM模型测算2003—2015年各省级区域的空气污染治理效率。在此基础上,运用门槛回归模型分析政府空气污染治理效率的影响机制。研究表明:①地区间空气污染治理效率差异性较为显著。中部、西部空气污染治理效率整体呈下降趋势。东部和东北地区空气污染治理效率则上升比较平稳。②政策规划、碳源、污染物排放和环境治理投入表现出双重门槛特征,其中碳源对空气污染治理效率影响显著,而以碳为首的能源消费结构则主要对中部和西部空气污染治理效率产生影响。落后地区政府应注重产业升级,财政上应对碳税等税目进行征收,产业上应鼓励企业创新,并对落后企业进行倒逼升级。     

基于疲劳累积破坏机制的储罐结构动力可靠度分析

针对随机风载荷作用下储罐结构动力可靠性问题，以300 m3的中小型立式低温储罐为研究对象，利用AR模型进行数值模拟得到风载荷的脉动风速时程与脉动功率谱密度函数。采用ANSYS建立储罐三维有限元模型，并对储罐进行动力学分析，计算出储罐结构的随机响应，进而求出随机风载荷作用下储罐结构动力可靠性所需全部数字特征，最后利用疲劳累积损伤机制计算得到储罐的动力可靠度。结果表明:假设结构强度不随时间退化，前5 a动力可靠度基本保持不变，随着使用年限的延长，动力可靠度下降速度明显增大。研究方法可为储罐的动力可靠性及寿命预测提供一定的理论依据。     

A Bayesian network-based approach for the assessment and management of ageing in major hazard establishments

Currently, there is an increasing attention towards ageing of industrial equipment, as the phenomenon has been recognised as a cause of severe accidents, recorded in the last years in many process establishments. Recent studies described ageing through a number of key-factors affecting the phenomenon by accelerating or slowing it down. The Italian Competent Authority for the prevention of chemical accidents (Seveso III Directive) adopted a short-cut method, accounting for the assessment of these factors, to evaluate the adequateness of ageing management during inspections at Seveso sites. In this paper, a Bayesian Network was developed, by using the data gathered during the first application of the short-cut method, with the aim to verify the robustness of the approach for ageing assessment and the validity of the a priori assumptions used in assessing the key-factors. The structure of the Bayesian network was established by using experts’ knowledge, whereas the Counting Learning algorithm was adopted to execute the parameter learning by means of the software Netica. The results showed that this network could effectively explore the complex logical and uncertain relationships amongst factors affecting equipment ageing. Results of the present study were exploited to improve the short-cut method.     

居民生活用电碳排放交易机制研究

个人排放交易被认为可以促进居民参与碳减排,但是因其减排收益难以覆盖高昂的建立和运行成本,降低了公众接受度。本文提出除了考虑碳减排的收益外,更需要关注个人排放交易机制的教育价值、形成正确的激励以及鼓励创新的价值,并提出可以基于当前国内多地实行的阶梯电价制度,利用电力系统现有的用户网络和账户系统,建立居民生活用电碳排放交易机制,以降低成本并实现上述价值。在此基础上,就居民生活用电碳排放交易机制的配额设定与分配、配额交易以及清缴问题做了细致的分析,并提出绿色电力作为补充电力可以免费获得碳配额以促进绿色消费。同时,比较分析了在居民生活用电交易机制和阶梯电价制度下,不同居民家庭以及电力公司的用电成本(收益),指出了其在形成正确的激励方面的作用。最后指出在条件成熟的情况下,居民生活用电碳排放交易机制可以扩展到居民的其他能源消费领域,以实现更为全面的个人排放交易。     

Transnational environmental collective action facing implementation constraints – the case of nutrient leakage in the Baltic Sea Action Plan

While scholars have showed a long-standing interest for how to design effective environmental treaties and other international agreements, less interest has been paid to implementation phases of these agreements. This article takes the Eutrophication Segment in the Baltic Sea Action Plan as an example of a regional effort to reduce nutrient leakages, where national reporting of adopted strategies has been a key mechanism to improve implementation effectiveness. It is shown that although transnational collective action theory is a powerful tool to analyse underlying drivers and priorities in state implementation policies, a deeper analysis of domestic and external constraints can shed additional light on observed implementation gaps. Varying views among countries on, for example, the role of stakeholder participation, legitimacy and top-down governing versus multi-stakeholder governance approaches may comprise domestic constraints that make effective and efficient implementation problematic. In terms of external constraints, states’ balancing of action plan objectives versus other international commitments, such as other environmental treaties and EU Directives, is shown to potentially reduce implementation efficiency as well.     

城市规划与城镇土地定级相互作用机理研究

城市规划与城镇土地定级之间的相互影响是多方面的。一是城市规划纲要、城市总体规划以及控制性详细规划的编制,分别从宏观和微观两方面影响着城镇土地定级工作;而城市规划的不同实施方式和不同实施程度对具体地块土地级别以及城镇土地级别空间分布格局有着直接和较大的影响。二是城镇土地级别现状和城镇土地级别变化趋势分析,潜在影响着城市规划方案设计、城市规划方案决策、城市规划实施和管理过程,并为其提供依据和指导。在此基础上,如何量化城市规划对城镇土地定级的影响值得进一步具体研究;发挥城镇土地定级工作的作用,更好地为城市规划服务,解决人们的住房问题,更值得深入思考。     

O3氧化结合化学吸收同时脱硫脱硝的动力学及热力学研究

构建了O3氧化多种污染物的反应机制,并对O3氧化SOx、NOx过程进行动力学模拟,然后利用热力学原理计算出Ca(OH)2和CaCO3湿法烟气同时脱硫脱硝吸收反应达到平衡时SOx和NOx的分压力.结果表明,Ca(OH)2作吸收剂湿法烟气同时脱硫脱硝比CaCO3作吸收剂效果好,而且两者几乎100％地去除烟气中的SOx和NO...