Coupling effects of venting and inerting on explosions in interconnected vessels

The coupling effects of venting and CO₂ inerting on stoichiometric methane-air mixture explosions were investigated in an isolated vessel and interconnected vessels. The results indicate that venting mitigates the explosion intensity, especially for small vessels. For vessels connected by pipes, a venting design following EN 14994 (2007) and NFPA 68 (2013) could not meet the venting requirements. For an isolated big vessel and interconnected vessels, increasing the CO₂ volume fraction (Φ) from 0 to 15.0 vol% decreased the maximum explosion overpressure (P_max) and maximum rate of overpressure rise ((dP/dt)_max) and delayed t_max. For closed interconnected vessels, P_max varied approximately linearly with Φ. For both isolated vessel and interconnected vessels, the coupling effects of venting and CO₂ inerting on methane-air explosion were more efficient than those of individual mitigative method (that is, venting alone or CO₂ inerting alone).     

碳达峰碳中和目标下固体废物治理的法律因应

我国在联合国大会上提出了“2030年碳达峰2060年碳中和”的目标。为达成此目标,固体废物治理领域也需要积极作出响应。固体废物治理体系的核心是固体废物的处置。不同的固体废物处置方式有着不同的碳排放结果,填埋或焚烧方式处置所排放的温室气体量都远大于循环利用的方式。应以固体废物领域碳排放统一核算制度为基石,从推进政策实施和立法修改等的多个层面上去因应。立法面向上,《固体废物污染环境防治法》《清洁生产促进法》《循环经济促进法》乃至编纂中的“环境法典”都应当围绕减碳模式的固体废物处置方式改进和制定相关法律规范;制度建设面向上,以固体废物碳排放强制核算法律制度建设为主,通过碳排放强制核算制度规范相关主体及其权利义务关系并深度挖掘固体废物处置的碳减排潜力。     

输气管道高后果区蒸气云爆炸超压预测方法探究

为准确预测输气管道高后果区在发生蒸气云爆炸事故时的超压分布情况,对国内外运用较为广泛的蒸气云爆炸超压预测经验模型和数值模拟方法进行调研,并分别应用其对某输气管道全尺寸泄漏燃爆实验进行超压预测,结合实验数据和输气管道高后果区管理现状进行方法准确性和工程适用性分析。研究结果表明：基于等效TNT假设的Henrych模型、Mills模型和等效TNT当量数值模拟方法均不适合准确预测蒸气云爆炸超压,TNO多能法和混合气体数值模拟方法所预测的结果较为接近实验结果。TNO多能法使用简便且推广性强,但主观性较大,易高估或低估爆炸后果;混合气体数值模拟方法操作繁琐且推广性差,但分析结果精度较高。在对高后果区进行安全管控时,可结合TNO多能法与混合气体数值模拟方法同时对管道工况进行评估,确定TNO多能法的爆源强度等级,继而推广使用TNO多能法。该研究结果可在较大程度上保证评估的准确性并节约成本。     

点火位置对独头巷道中瓦斯爆炸超压的影响

运用AutoReaGas爆炸仿真模拟器研究了独头巷道中点火位置对瓦斯爆炸后果的影响。结果表明,在本计算条件下,爆炸静态超压随着距离的增加而减小,爆炸动压随着距离的增大而增大,点火位置对爆炸后果有重要影响,点火位置离封闭端越近,各个测点上所得到的超压越大。     

ASPEN CLEARCUTTING INCREASES SNOWMELT AND STORM FLOW PEAKS IN NORTH CENTRAL MINNESOTA1

ABSTRACT: Clearcutting aspen from the upland portion of an upland peatland watershed in north central Minnesota caused snowmelt peak discharge to increase 11 to 143 percent. Rainfall peak discharge size increased as much as 250 percent during the first two years after clearcutting, then decreased toward precutting levels in subsequent years. Storm flow volumes from rain during the first two years increased as much as 170 percent but declined to preharvest volumes in the third year. Snowmelt volumes did not significantly change. Snowmelt peak discharge occurred about four to five days earlier after clearcutting, but the timing of storm flow from rainfall was not changed. Snowmelt peaks remained above precut size for nine years after clearcutting on an area undergoing natural regeneration to aspen saplings. Partial cutting - up to approximately one-half of the watershed - reduced peak snowmelt discharge because melt was desynchronized in cleared and forested parts. Clearing more than 2/3 of the watershed caused snowmelt flood peak size to double during years with snow packs in excess of seven inches of water that remained until a day when maximum air temperatures exceeded 60d?F.     

CORRELATION OF ANNUAL PEAK FLOWS FOR PENNSYLVANIA STREAMS1

A common assumption in flood frequency analysis is that annual peak flows are independent events. This study was undertaken to investigate the validity of this assumption with regard to Pennsylvania streams by statistically analyzing the dependence between annual peak flows and to determine if basin carryover effects relate to the degree of dependence. Five tests of dependence, the autocorrelation test, the median crossing test, the turning points test, the rank difference test, and the Spearman rank order serial correlation coefficient test were applied to the series of annual peak flows for 57 streams. Of the 57 streams analyzed, only two exhibited signs of dependence by at least two of the tests performed, and the baseflow component of annual peak flows was found to be unrelated to the degree of dependence exhibited between annual peak flows. It was concluded that the assumption of independence of annual peak flows is valid in flood frequency analysis for Pennsylvania streams.     

LEGAL CHALLENGE OF THE UNGAGED WATERSHED1

The lack of uniform techniques for estimating design discharges in ungaged areas is a source of growing concern in the courts now faced with challenges to floodplain boundaries and culvert design for highway crossings. This paper summarizes a court case in which calculations of the design discharge and the hydraulic backwater effects of a major highway culvert were contested by the plaintiff. Emphasis in the paper is placed on the variation in computed flows and the interpretation of the court in the face of diverse hydrologic methods for the ungaged watershed. The results of a preliminary evaluation of ungaged watershed methods applicable to Pennsylvania are also reported in terms of standard error and bias.     

ANALYZING URBANIZATION IMPACTS ON PENNSYLVANIA FLOOD PEAKS1

ABSTRACT: The impact of man made change on the hydrology of developing watersheds is frequently measured in terms of the ratio: flood peak after development to flood peak before development over a range of return periods. However, the analysis of urbanization effects on flood frequency presents a vexing problem because of a general lack of flood data in urban areas and also because of nonstationarity in the development process. Clearly, the flood peak ratio depends on the impervious fraction and percent of basin sewered and these factors have been taken into account in recent urban flood peak models. In genral, these models are developed either by: (1) split sample analysis of available annual flood data, or (2) by computer simulation using mathematical watershed models capable of representing man made changes. The present paper discusses the results of work in progress to characterize the impact of urbanization on small developing watersheds in Pennsylvania.     

EFFECT OF SURFACE MINING ON STORM FLOW AND PEAK FLOW FROM SIX SMALL BASINS IN EASTERN KENTUCKY1

ABSTRACT: Hydrologic records from six small Eastern Kentucky watersheds were analyzed to determine the effect of surface mining on storm flows and peak flows. Average storm flow volumes were not changed by surface mining, whereas average peak flows were increased 36 percent. Peak flow increases were only in the summer. Smaller peak flows are doubled; moderate ones are increased by about a third; peak flows around 100 csm seem to be largely unaffected; and the larger peak flows may have been reduced by surface mining. The maximum annual storm flows, usually in winter or spring, appeared slightly reduced. No time trend in either storm flows or peak flows could be detected in five years of postmining record. Surface mining is not a serious floodwater discharge problem.     

经济平稳增长下长江经济带碳排放峰值研究——基于全球夜间灯光数据的视角

碳排放达到峰值的时间和水平,将影响各地区的发展空间,对于长江经济带地区协调发展有着深远的影响,这也是应对气候变化和区域管理需要引起高度重视的问题。为此,论文通过1995—2013年的全球夜间灯光数据对长江经济带的GDP进行了估算和校准,进而在经济平稳增长条件下,预测长江经济带地区2014—2050年的GDP,根据碳强度衰减速率,设置了3种模拟情景。研究表明：以“十二五”时期的碳强度下降速率衰减,江苏和江西地区尚未出现碳峰值,其他地区在2050年之前出现碳峰值;其中云南在2025年就率先达到碳峰值。以“十三五”时期的碳强度下降速率衰减,江苏仍未出现碳峰值,安徽和江西地区在2040年之后出现碳峰值,四川、重庆、贵州均在2031年左右达到碳峰值;云南在2023年就率先达到碳峰值。上述两种模拟情景表明,长江上游地区碳排放达峰的时间要早于长江中游地区。进一步以长江经济带实现“2030年达到碳峰值”为目标的模拟情景发现,各地区碳强度衰减速率的差异显著,这从云南碳强度衰减速率2.58%、江西碳强度衰减速率7.53%,便可窥见一斑。由此可以看出,制定碳减排方案的要义,在协调好碳强度和经济增长率之间有效调控的同时,应充分考虑区域发展不平衡,分区域、分阶段推动碳排放达峰的减排政策,这将有利于经济平稳增长下顺利实现碳峰值目标。