Analysis of gas dispersion and ventilation within a comprehensive CAD model of an offshore platform via computational fluid dynamics

Maintaining an adequate air flow with a desired air quality that is free from hazardous gases is among the most important actions taken toward the improvement of safety in any process plant. Due to the increased focus on the consequences of existing hazardous material on safety, health, and the environment, air quality and sufficient ventilation within a plant has been increasingly considered in the design stage. This paper investigates and analyzes methane and hydrogen sulfite dispersion and the effect of air ventilation within a CAD model of an offshore platform using computation fluids dynamics (CFD). In addition, this method and its principals could be utilized in any other hazardous environment. Simulations of possible hazardous events along with solutions for preventing or reducing their probability are presented to better assess the data. These investigations are performed by considering hypothetical hazardous scenarios which consist of gas leakages from pipes and process equipment under different conditions. After drafting a precise and highly detailed CAD model of the plant and performing CFD simulations on this model, the results of gas behaviors, dispersion, distribution, accumulation, and its possible hazards are investigated and analyzed. The larger amount of details of the actual plant model in CFD simulation are obtained by using a combination of different methods and software. These include PDMS for 3-D drawing of the plan, Rinoceros for geometrical integration of the process equipment and facilities, and Sharc Harpoon which meshes the model. Moreover, the probability of inducing ignitable or toxic concentration of gases within the atmosphere and air ventilation of the unit is considered by these investigations.     

Experimental data and CFD performance for cloud dispersion analysis: The USP-UPC project

Forecasting the behaviour of a flammable or toxic cloud is a critical challenge in quantitative risk analysis. Recent literature shows that empirical and integral models are unable to model complex dispersion scenarios, like those occurring in semi-confined spaces or with the presence of physical barriers. Although CFD simulators are promising tools in this regard, they still need to be fully validated with comprehensive datasets coming from experimental campaigns designed ad-hoc. In this paper, we present an experimental campaign carried out by a joint venture between University of São Paulo and Universitat Politècnica de Catalunya to investigate CFD tools performance when used to analyse clouds dispersion. The experiments consisted on propane cloud dispersion field tests (unobstructed and with the presence of a fence obstructing the flow) of releases up to 0.5 kg s⁻¹ of 40 s of duration in a discharge area of 700 m². We provide a full 1-s averaged propane concentration evolution dataset of two experiments, extracted from 29 points located at different positions within the cloud, with which we have tested FLACS^® CFD-software performance. FLACS reproduces successfully the presence of complex geometry, showing realistic concentration decreases due to cloud dispersion obstruction by the existence of a fence. However, simulated clouds have not represented the whole complex accumulation dynamics due to wind variation.     

Numerical modeling of water spray suppression of conveyor belt fires in a large-scale tunnel

Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect.     

页岩气开发压裂返排液环境监管及对策建议

水力压裂技术是目前页岩气开发广泛采用的储层改造技术,但该技术的应用产生大量的返排液,返排液如何处置和监管引起了人们的广泛关注。本文收集了国内外压裂液的成分、返排液的水量和水质等资料,从深井灌注、市政污水处理厂处理后外排、现场处理后回用、现场处理后外排四种处理方式上,分析我国返排液环境监管存在的问题,针对实际问题提出对策建议,包括对化学品进行申报登记、制订污水排放的行业标准、对页岩气开发项目进行分段验收、鼓励研发污水处理新技术等。     

An alternative CFD tool for gas dispersion modelling of heavy gas

The numerical simulation of gas dispersion is of great importance in various areas of engineering such as optimisation, synthesis of chemical process, petroleum industry and process safety. The OpenFOAM (Open Field Operation and Manipulation) code is a free and open source computational fluid dynamics (CFD) program. The current research is focused on the development and customisation of a computational tool for handling gas dispersion of heavy gases, such a LNG and CO₂. The novel CFD tool relies on OpenFOAM framework. The core of the work is based on the OpenFOAM solver rhoReactingBuoyantFoam to handle gas dispersion. A series of CFD simulations has been performed for methane and CO₂. The source term of the former is modelled by HSM (Hybrid Switch Model). The model comprises contribution from HEM (Homogeneous Equilibrium Model) approach, frozen model and non-equilibrium model for CO₂ leak. The novel approach switches between equilibrium and non-equilibrium conditions based on the meta-stable parameter on the grounds of thermodynamics and experimental observations. Good agreement with experimental data is observed. Numerical findings for methane leakage from the proposed CFD tool are compared with experimental data and FLACS. Good agreement is observed.     

An optimized airfoil geometry for vertical-axis wind turbine applications

ABSTRACT

In this work, a new airfoil shape optimized for vertical-axis wind turbine applications is proposed. Different airfoil shapes have been analyzed with JavaFoil, a panel method software. Then, the results from the analysis have been used to optimize the performance of the new airfoil shape. Afterward, Computational Fluid Dynamics (CFD) simulations of the proposed airfoil, UO-17-LDA, are run for different angles of attack to provide insight into the flow field and the mechanisms related to this increase in performance. The UO-17-LDA airfoil presents a high lift-to-drag ratio and a delayed stall angle with respect to the original FX-63-137 airfoil, making it suitable for vertical-axis wind turbine applications. This increase in performance has been verified by comparing two VAWT designs with the original and the proposed airfoil using a double-multiple streamtube model. Finally, the practicality of JavaFoil for the comparison of different airfoil geometries has been verified, as it is capable of obtaining results for a wide number of flow conditions in small computational times and with a user-friendly interface. Nevertheless, the results diverge from the actual solution for high angles of attack (beyond stall). Hence, the time and effort required to perform CFD simulations is justified to gain insight into the actual behavior of a particular airfoil, as well as to obtain a richer analysis of the flow field and the mechanisms related to the airfoil performance.     

大庆油田钻井液幼鱼急性毒性试验研究

采用经济合作与发展组织（OECD）推荐的毒性试验鱼种（幼鲤鱼），对大庆油田废钻井液、聚合物体系、三钾聚合物体系钻井液进行急性毒性试验；用概率单位回归法计算出三种钻井液LC50值、钻井液浓度值和95％可信度的浓度范围；采用美国糠虾试验法钻井液毒性分级标准进行评价，并对钻井液中主要化学添加剂毒性作了分析。结果表明大庆油田三种钻井液均属于无毒性水平。     

加压流体萃取-气相色谱质谱法测定土壤和沉积物中27种拟除虫菊酯类农药

建立了加压流体萃取-气相色谱质谱法测定土壤和沉积物中27种拟除虫菊酯类农药的方法。以丙酮/正己烷(V∶V=1∶1)为萃取溶剂,在120℃和10. 3 MPa条件下静态萃取7 min,循环3次,石墨化炭黑串接氨丙基键合硅胶固相萃取柱净化,HP-5MS UI色谱柱分离,优化了提取和分析过程的重要条件。方法检出限为0. 001~0. 012 mg/kg,土壤中低、高浓度的加标回收率范围分别为68. 3%~123%和75. 3%~115%,沉积物中低、高浓度的加标回收率范围分别为67. 1%~120%和78. 6%~110%,单一目标物的相对标准偏差(RSD)均<20%(n=6)。实验结果表明,该方法消耗溶剂少、效率高、检出限低、精密度和准确度好,适用于土壤和沉积物中拟除虫菊酯类农药残留的测定。     

纳米磁流体及其在水资源保护中的应用前景

在简要讨论水体油污染严重,保护水资源重要性的基础上,介绍基于纳米科学技术的新型材料纳米磁流体的制备、性质及其重要应用。重点讨论纳米磁流体在水体油污染治理中急待深入开展的研究内容及其在水资源保护中良好的应用前景。     

利用循环流化床锅炉燃烧技术处理造纸亚铵黑液

循环流化床燃烧技术是一种低温(900℃)流化态燃烧技术,可以燃烧低发热值的生物质燃料.采用循环流化床低温燃烧和分段燃烧技术,通过锅炉尾部凝汽换热设备将黑液加热浓缩,这样既可满足循环流化床锅炉燃烧的条件,又使得脱硫效率提高,SO2的生成量降低,且使各项排放指标均能达到环保排放标准.对比国内外造纸黑液处理办法,我们得出了利用循环流化床锅炉燃烧技术处理亚铵黑液的可行性.对于我国现阶段的小型造纸厂,该技术具有一定的推广应用价值.