Dip-angle influence on areal DNAPL recovery by co-solvent flooding with and without pre-flooding

A two-dimensional (2D) laboratory model was used to study effects of gravity on areal recovery of a representative dense non-aqueous phase liquid (DNAPL) contaminant by an alcohol pre-flood and co-solvent flood in dipping aquifers. Recent studies have demonstrated that injection of alcohol and co-solvent solutions can be used to reduce in-situ the density of DNAPL globules and displace the contaminant from the source zone. However, contact with aqueous alcohol reduces interfacial tension and causes DNAPL swelling, thus facilitating risk of uncontrolled downward DNAPL migration. The 2D laboratory model was operated with constant background gradient flow and a DNAPL spill was simulated using tetrachloroethene (PCE). The spill was dispersed to a trapped, immobile PCE saturation by a water flood. Areal PCE recovery was studied using a double-triangle well pattern to simulate a remediation scheme consisting of an alcohol pre-flood using aqueous isobutanol ( approximately 10% vol.) followed by a co-solvent flood using a solution of ethylene glycol (65%) and 1-propanol (35%). Experiments were conducted with the 2D model oriented in the horizontal plane and compared to experiments at the 15 degrees and 30 degrees dip-angle orientations. Injection was applied either in the downward or upward direction of flow. Experimental results were compared to theoretical predictions for flood front stability and used to evaluate effects of gravity on areal PCE recovery. Sensitivity experiments were performed to evaluate effects of the alcohol pre-flood on PCE areal recovery. For experiments conducted with the alcohol pre-flood and the 2D model oriented in the horizontal plane, results indicate that 89-93% of source zone PCE was recovered. With injection oriented downward, results indicate that areal PCE recovery was 70-77% for a 15 degrees dip angle and 57-59% for a 30 degrees dip angle. With injection oriented upward, results indicate that areal PCE recovery was 57-60% at the 30 degrees dip angle, which was similar to PCE recovery for injection in the downward flow direction. Lower areal PCE recovery at greater dip angles in either direction of flow was attributed to DNAPL swelling and migration, flood front instabilities and bypassing of the displaced fluid past the extraction wells during the alcohol pre-flood. Additional results demonstrate that the use of an alcohol pre-flood can be beneficial in improving DNAPL recovery in the horizontal orientation, but pre-flooding may reduce areal recovery efficiency in dip-angle orientations. This study also demonstrates the use of theoretical perturbation (fingering) analysis in predicting NAPL recovery efficiency for flooding processes in remediating aquifers with dip angles.     

Photochemical oxidation of reduced sulfur compounds in an urban location based on short time monitoring data

This study examines the oxidation of reduced sulfur compounds (RSCs) in urban ambient air. The photochemical conversions of RSC (such as DMS, CS₂, H₂S, DMDS, and CH₃SH) to a further oxidized form (e.g., SO₂, MSA, and H₂SO₄) were assessed using a photochemical box model. For our model simulation of RSC oxidation, measurements were taken at an urban monitoring station in Seoul, Korea (37.6° N, 127° E) during three separate time periods (e.g., Sept. 17–18, Oct. 23, and Oct. 27–28, 2003). The results indicate that DMS and H₂S were the dominant RSCs with concentrations of 370 ± 140 and 110 ± 60 pptv, respectively. The photochemical conversion of DMDS to SO₂ was found to occur more efficiently than other RSCs. The overall results of our study suggest that photochemical conversion of RSCs accounted for less than 15% of the observed SO₂ during the measurement period. The SO₂ production from DMS oxidation (mainly by the reaction with OH) was found to be affected primarily by the abstraction channel due to high NO_x levels during the experimental conditions.     

基于物化生化耦合的污水深度脱氮除磷新工艺

为了解决常规污水处理技术无法进行完整的硝化反硝化过程,污水厂出水中氨氮、总氮、总磷偏高以及运行成本较高的问题,以某污水厂排水为研究对象,通过物化与生化耦合,构建化学催化生物耦合床(CCBF)脱氮系统,研究CCBF系统对污水厂排水中氨氮、总氮、总磷和COD的去除效能。结果表明：当DO为5.5~6.0 mg·L⁻¹、RT为8 h、C/N为1.5∶1时,CCBF可将${\rm{NH}}_4^{+} $-N从48.5 mg·L⁻¹降至4.58 mg·L⁻¹、TN从51.2 mg·L⁻¹降至6.5 mg·L⁻¹、TP从6.6 mg·L⁻¹降至0.48 mg·L⁻¹、COD从78.5 mg·L⁻¹降至33 mg·L⁻¹,去除率分别达到89.5%、85.7%、92.5%和57.9%;污水经处理后,氨氮、总氮、总磷、COD均达到城镇污水处理厂污染物排放标准(GB 18918-2002)一级A排放标准。利用Eckenfelder方程对系统脱氮过程进行模拟,求得${n_{{\rm{NH}}_4^ +{\text{-}} {\rm{N}}}} $=0.314 76,n_TN=0.282 21,${K_{{\rm{NH}}_4^ +{\text{-}} {\rm{N}}}} $=0.128 02,K_TN=0.218 59,与水力负荷为0.000 8~0.007 m³·(m²·min)⁻¹的常规生物处理相比,系统内部生物量充足、活性高,物化与生物耦合强化效果明显。     

基于云模型的高校消防安全标准化评估研究

为评估高校消防安全标准化程度,明确高校消防安全标准化体系,结合高校消防安全标准化体系的模糊性,将高校消防安全标准化等级划分为5个级别,采用黄金分割法将权重云、评价云划分成5个云模型,建立能够反映高校消防安全标准化等级模糊性的云模型。该模型运用于某高校消防安全标准化等级评估中,评估结果客观合理,实用性较强,为后续标准化提升提供了参考依据。     

新型冠状病毒肺炎疫情期间企业生产安全风险管理

本文在分析新型冠状病毒肺炎疫情期间企业安全风险特点的基础上,建立了疫情期间安全风险管理模型,分析了这一特殊时期企业外部变化,以及企业内部人、物、环境、管理变化带来特殊安全风险,提出了针对性的风险管控措施。     

基于Tripod-Beta模型的船舶火灾事故风险分析

为深入分析船舶火灾事故风险因素及其后果产生的影响,通过分析1991-2017年全球船舶火灾事故调查报告,从人员、管理、船舶设备、货物、环境5个方面对船舶火灾影响因素进行识别研究;采用三脚架事故致因模型(Tripod-Beta model),构建考虑安全栅的船舶火灾事故情景演化模型,识别船舶火灾关键影响因素;并在样本量较少的情况下,采用信息扩散理论计算船舶火灾发生率;最后,利用布尔函数和风险矩阵,对船舶火灾事故风险进行评价研究。结果表明:船员不安全行为和船舶设备表面过热、设备短路是船舶火灾事故的关键风险因素;事故后果链中安全栅遭到破坏时,船舶火灾风险处于不希望发生范围内。该方法能有效评估船舶火灾风险的等级,满足海事管理部门的监管工作需求。     

危险化学品火灾爆炸事故不安全动作分布规律研究

以我国210起典型危险化学品火灾爆炸事故为样本,对造成事故的不安全动作进行归类统计,应用云模型云发生器算法计算大类不安全动作的云模型参数值并绘制隶属云图,得出了危险化学品火灾爆炸事故中不安全动作类型和发出者分布规律及特点。结果表明:造成火源型火灾爆炸事故的违规型不安全动作平均发生次数最多,分布不均匀且不稳定,其中现场工作缺乏指导或监护发生次数最多,发出对象为监理;蓄热型火灾爆炸事故中技术型不安全动作分布表现出较大的随机性,其中物料添加不当和隐患排查不彻底发生次数最多,发出对象分别为基层人员和监理。     

基于人体皮肤热模型的热防护服评价方法研究

在热防护服热防护性能测试装置基础上,用自行研制的新型耐高温模拟皮肤传感器代替铜片热流计测量通过应急热防护服装面料的热流量,将热流量作为热波皮肤模型边界条件,得到人体皮肤表层下80μm处的温度值,从而得到一定条件下人体真实皮肤达到二级烧伤所需时间,用其评价热防护服用织物的热防护性能,并将热波皮肤模型(TWMBT)的测试值与Pennes模型以及铜片热流计的测试结果进行分析比较。采用热波皮肤模型分析织物层下的"皮肤"防热时间更接近实际皮肤达到二级烧伤时间值,可较为精确的量化织物热防护性能,为应急救援热防护服装的热设计提供理论依据。     

基于因素重构分析法和主成分分析法的企业安全文化评价模型

针对当前安全文化评价领域存在的评价方法相对简单、主观性较强等问题,基于企业安全文化的人本主体,设计以企业决策层、管理层、执行层为主体的企业安全文化指标体系;充分利用因素重构分析法和主成分分析法在数据处理上的各种优势,建立适应指标体系特征并考虑数据约束条件的企业安全文化评价模型;通过实例分析加以验证。该模型为解决企业安全文化评价中指标体系庞大复杂、样本空间小、缺少可以直接利用的历史数据等难题给出了一条具有可操作性的路径。     

基于社会公共机构的道路交通事故经济损失评价及计量模型研究

根据中国道路交通事故经济损失的研究现状,借鉴国外对道路交通事故经济损失研究的成功经验,提出适用于中国实际情况的交通事故社会公共机构服务损失费用构成;确定了道路交通事故社会公共机构服务损失评价指标体系。基于经济学和统计学理论,主要从警方服务、清障服务、管理部门服务和法律诉讼服务4个方面对道路交通事故社会服务损失进行了深层次理论分析与评价;构建了相应的评价计量模型;提出了我国评价交通事故社会服务损失的一些合理化建议。研究结果对科学、全面、合理地评价道路交通事故社会经济损失具有重要的实际意义。