穿越城市生活区的天然气管道泄漏连锁爆燃后果评估研究

为评估城市天然气管道泄漏连锁爆燃事故后果,基于计算流体力学(CFD)方法构建穿越城市区域的天然气管道泄漏连锁爆燃后果预测与评估模型,以某城市生活区域为例,在城市生活区域建筑物内风场流动计算的基础上,模拟风场作用下可燃气体在城市建筑物空间内的运移规律,预测可燃气云的积聚区域;考虑意外点火的情况,计算城市生活区域内可燃气云爆燃灾害特征,预测爆燃超压、热辐射和高温的影响。研究结果表明：由于建筑物之间的阻挡与反射作用,建筑物下风向有明显的低风速区域,并在一定时间段后扩散过程趋于稳定;在爆燃火焰作用下,高温和热辐射会造成建筑物部分钢结构发生失效变形。     

Optimization of gas detector placement considering scenario probability and detector reliability in oil refinery installation

Gas detection system is a critical layer of protection in process safety. Leak scenario probability and detector reliability are two key factors in the optimization of gas detector placement. However, they are easily neglected in previous studies, which may lead to an inaccurate evaluation of the optimization solutions. In this study, a stochastic programming (SP) optimization method is proposed considering these two factors. In order to quantitatively represent the probability of leak scenarios, a complete accident scenario set (CASS) is built combining leak sources and wind fields. Then, the computational fluid dynamics (CFD) method is adopted for consequence modeling of gas dispersion. The Markov model is developed to predict the detector reliability. With the objective of minimal cumulative detection time (MCDT), the SP formulation considering scenario probability and detector reliability (MCDT-SPR) is proposed. By introducing the particle swarm optimization (PSO) algorithm, the optimization formulations can be solved. A case study is investigated on a diesel hydrogenation refining unit. Results validate this approach is promising to improve the detection efficiency. This method is more practical and matching with the actual industrial environment, where the leak scenarios and the detector reliability can change dynamically in real process setting.     

Consequence prediction for dust explosions involving interconnected vessels using computational fluid dynamics modeling

Combustible dust explosions continue to present a significant threat toward operating personnel and pneumatic conveyance equipment in a wide variety of processing industries. Following ignition of suspended fuel within a primary enclosure volume, propagation of flame and pressure fronts toward upstream or downstream interconnected enclosures can result in devastating secondary explosions if not impeded through an appropriate isolation mechanism. In such occurrences, an accelerated flame front may result in flame jet ignition within the secondary vessel, greatly increasing the overall explosion severity. Unlike an isolated deflagration event with quantifiable reduced pressures (vent sizing according to NFPA 68 guidance), oscillation of pressure between primary and secondary process vessels leads to uncertain overpressure effects. Dependent on details of the application such as relative enclosure volumes, relief area, fuel type, suspended concentration, duct size, and duct length, the maximum system pressure in both interconnected vessels can be unpredictable. This study proposes the use of FLame ACceleration Simulator (FLACS) computational fluid dynamics (CFD) modeling to provide reliable consequence predictions for specific case scenarios of dust deflagrations involving interconnected equipment. Required minimum supplement to the originally calculated relief area (A_v) was determined through iterative simulation, allowing for reduced explosion pressures (P_red) to be maintained below theoretical enclosure design strengths (P_es).     

初始氧化温度对浸水长焰煤二次氧化特性的影响机制

为揭示不同初始氧化温度下浸水长焰煤的氧化自燃特性,利用红外光谱和热分析实验手段以及MS数值模拟方法研究其氧化自燃规律,并采用线性拟合的方法阐述自由基变化特性。结合分子键能的变化,分析浸水条件下二次氧化的煤氧链式反应过程。研究结果表明:经过120 ℃预氧化后,浸水风干长焰煤的还原性官能团甲基、亚甲基、羟基均高于原煤,而羰基、羧基低于原煤;与原煤相比,浸水风干后的煤预氧化温度在120 ℃时最大升温速率最高（0.036 9 ℃/s）,表现出更强的自燃倾向性;MS模拟优化得出煤中各官能团在预氧化120 ℃时键能变化较大,结合热分析实验,确立预氧化后浸水风干煤体氧化自燃特性机制。     

Hazard analysis on LPG fireball of road tanker BLEVE based on CFD simulation

In order to research the hydrocarbon fireball characteristic of LPG tanker Boiled Liquid Evaporate Vapor Explosion (BLEVE) under different conditions, computational fluid dynamics (CFD) simulations of the hydrocarbon fireballs from the LPG tanker BLEVE accidents were carried out. Several new different factors, such as the mass of fuel, inlet velocity and airflow velocity, were considered to analyze the influence on the evolution of the characteristics of the fireball and the development of the LPG tanker BLEVE accidents. Results indicate that the fireball with a greater mass of fuel radiates more heat but slower. The large longitudinal diameter of the fireball and high radiation heat flux are observed in case of a faster inlet velocity used for the same mass. The airflow was found to shorten the initial phase of the fireball effectively. Some suggestions were proposed to prevent the LPG BLEVE accidents. Analysis performed show that various parameters like fireball diameter, radiative heat flux and lifting speed of fireball can be predicted well using FDS code.     

改性PVDF中空纤维膜处理压裂返排液研究

针对中空纤维膜应用于水力压裂返排液处理时存在的膜污染严重、通量衰减快、影响处理效率等问题,研究了PVDF固含量、凝固浴温度等因素对PVDF膜性能的影响,通过非溶剂致相分离法制备了PVDF中空纤维膜,并采用表面接枝技术,对PVDF中空纤维膜进行了表面亲水化改性。压裂返排液吸附实验结果表明,表面接枝降低了PVDF的接触角,提高了膜的亲水性。与未接枝改性的PVDF膜相比,亲水改性后的PVDF膜表面吸附的压裂返排液更少。将亲水性中空纤维膜用于页岩气水力压裂返排液的过滤处理,应用结果表明其对压裂返排液中的总铁、SS、浊度、细菌去除率达到90%以上,长时间运行后的通量保持率高,有较好的抗膜污染性。     

基于CFD的两种紫外消毒模型的比较研究

为了预测紫外反应器的消毒效率,提高模拟的准确度,对两种紫外光强模型进行了比较分析。利用CFD技术,采用数值模拟的方法,对线源和柱源两种光强模型进行了光强分布以及消毒效率的模拟,并采用生物实验进行了验证。结果表明:与柱源模型相比,线源模型在近灯管处强度高42.3%,在1.2 cm处二者趋于一致;针对同一管式紫外反应器,透光率为95%时,线源模型的模拟结果偏大,柱源结果偏小;透光率为80%时,线源及柱源模型的模拟结果都偏大,流量及模型影响较小,透光率成为主要影响因素。综合比较,柱源模型适用于小型管式紫外灯消毒数值模型的开发。     

旋风分离器内高速旋转流场的数值计算方法选择

数值计算方法已成为研究旋风分离器内部流场的重要途径。利用计算流体力学方法对旋风分离器内部气相流场进行了数值模拟研究。分析了不同湍流模型、离散化方式和压力插值方式对旋风分离器内部计算流场的影响,并将所得数值结果与已知的实验数据进行了对比,以期得到最适合的数值模型。结果表明:对于旋风分离器内部复杂流场的流动,运用雷诺应力模型(Low-Re Stress-Omega)能够较好地预测出强制涡中心涡流的运动情况,同时采用SIMPLEC算法、二阶迎风离散化方式和PRESTO压力梯度插补格式能够获得最好的预报结果。     

基于隐含碳排放的碳减排目标研究

中国政府以2005年为基年提出了碳减排指标,确定各省碳减排基数对于明确各省碳减排责任具有重要意义.本文结合“十一五”期间节能指标分解过程中存在的问题,分析了省际贸易中隐含的碳排放对于确定各省碳减排基数的影响,并分别基于生产者负责原则和消费者负责原则计算了“十二五”期间各省碳减排基数.计算结果表明:①将工业部门拆分为23个部门能够更加充分反映省际贸易结构差异对于隐含碳排放计算的影响;②省际贸易中隐含碳排放不仅在各省间有较大差异而且呈现出从中西部地区调往东部地区的整体转移方向;③不同原则下各省碳减排基数计算结果存在较大差异,消费者负责原则更加真实地反映了各地区实际减排责任,避免了部分省份通过省际调进代替本省生产的方式实现碳减排目标.     

压裂返排液生物处理实验研究

从油田压裂返排液中筛选出EB系列菌种,可高效降解压裂返排液中的高分子和有机污染物。考察了振荡时间、温度、接种量、菌种混合比例等对压裂返排液COD去除率的影响。结果表明:48h振荡、25℃、10%接种量、菌种EB1和EB2按1∶1比例混合是较佳应用条件。EB复合菌种的应用范围较广,其pH值适用范围为6～9,矿化度适用范围为3 000～20 000mg/L。该研究提高了压裂返排液生物处理技术规模化应用的可行性。