基于天然气放空系统的水力计算软件开发

高压天然气放空系统由放空干线管段气体、放空管线及外界大气组成。放空管路属于非稳定流动,其水力计算不能采用一般站场管路的达西公式。以Fano方程为基础,运用流体力学及输气管路流动基础理论进行程序编写,计算软件可实现对各时刻放空所对应的瞬时放空量、累计放空时间、截面压力及温度、储气量的求解。计算结果与图解法进行对比,误差控制在2%以内,弥补了图解法仅可求得瞬时放空量而无法得到其他参数的缺陷,并利用东河伴生气管线下沉工程现场放空数据与本计算软件对比,计算结果吻合度高,符合现场工程实际。     

Analysis of diers venting tests: Validation of a tool for sizing emergency relief systems for runaway chemical reactions

A one-dimensional computer model of multiphase, chemically reacting flow has been used to analyze a number of DIERS Phase III venting tests.     

Disengagement predictions via drift flux correlation vertical,horizontal and spherical vessels

The behavior of an open system is modeled. Thus, for special cases, the void fraction is predicted as a function of location and time. The open system may be an open vessel or a vessel with an open relief device. A single governing equation is derived based on combining the material and energy balances with the churn-turbulent drift flux relationship and assuming no radial gradients. This partial differential equation is not solved. It is, however, bounded by homogeneous and all vapor venting. These special cases are solved. In homogeneous venting the key variable is time. In all vapor venting under pseudo-steady-state conditions the key variable is location. The solution of the partial differential equation is also discussed. Under pseudo-steady-state and churn-turbulent conditions, the open system is modeled. The minimum void fractions (corresponding to a maximum liquid inventory) with all vapor venting, for vertical, horizontal, and spherical vessels are predicted and compared. Analytical expressions for the local and average void fractions in a vertical vessel and non-unity distribution parameters are presented. Void fraction profiles are compared for three cases: 1. vertical cylinders with distribution parameters (Co values) of unity and 1.5, 2. horizontal and vertical cylinders with varying L/D ratios, and 3. spheres with inscribed vertical cylinders having constant gas production to bubble rise ratio (Ψ′ value). The vertical cylinder average void fraction for non-unity distribution parameters can now be calculated analytically. The horizontal cylinder average void fraction predicted by turning it upright results in an over prediction of at most 4%. The sphere average void fraction predicted via an inscribed vertical cylinder, with the same Ψ′ value, is consistenly high by at most 8%.     

The DIERS users group: A forum for development/dissemination of emergency relief system design technology

DIERS was formed in 1976 to develop methods for the design of emergency relief systems capable of handling runaway reactions [1, 2]. Of particular interest at the time were when tow-phase flow venting would occur and the applicability of different methods for sizing emergency relief systems for two-phase, vapor-liquid flashing flow. Approximately $1.6MM was devoted to investigations of two-phase, vapor-liquid onset/disengagement dynamics and the hydrodynamics of emergency relief systems.     

Application of the DIERS methodology to the study of runaway polymerization: Validation of the DIERS methodology using blow-down tests

The Design Institute for Emergency Relief Systems (DIERS) and more recently the DIERS Users Group have been investigating various aspects of emergency relief for more than 12 years. The DIERS programs have given rise to an in-depth understanding of the basic mechanism of how runaway thermal reactions are safely vented. In concert with the development of the understanding of the venting mechanism, DIERS also developed experimental procedures and computational techniques for estimating emergency vent sizes.     

Specification of flame arresting devices for manifolded low pressure storage tanks

The current regulations and accepted recommended practices relating to the use of mechanical flame arresting devices on low pressure, flammable liquid storage tanks will be reviewed. The applicability of these recommendations to typical manifolded tank and closed piping vapor recovery systems, as opposed to the more common “stand alone”, venting to atmosphere storage tanks, will be examined with particular emphasis on the widely varying service conditions that mechanical flame arresting devices may encounter. The limitations placed on the use of commercially available Factory Mutual Approved and Underwriters Laboratories Listed flame arresters will be explained.     

The role of instrumentation and process controls in minimizing accidental releases

Most accidental releases are the result of either mechanical failures or measures taken to prevent such failures, such as, venting through emergency vents, relief valves, or rupture discs. Where the mechanical failure is the result of defective materials, inadequate design, or external factors, little can be done by means of instrumentation to prevent the release. It may be possible, however, to reduce the flow. Many failures are due to process upsets such as overpressure, internal explosions, and runaway reactions. The probability of these failures occurring can be substantially reduced by proper instrumentation.     

Dust explosion venting for dusts pneumatically conveyed into vessels

The size of venting areas of containers in dust explosions has hitherto been calculated by use of nomograms developed from tests in which explosible dust-air mixtures were produced by rapid discharge of combustible dust from storage containers. Such tests did not truly reflect the conditions prevailing when containers are charged with product in industrial practice. There was, therefore, a need to perform dust explosion tests with vented containers and pneumatic product filling. The results of such tests show that there is a considerable reduction in the venting area in comparison with that predicted from results obtained with earlier test procedures.     

The anatomy of an acrylic acid runaway polymerization

The details of an unscheduled polymerization of acrylic acid initiated by indirect heating have been characterized by in-depth analysis of the polymer, kinetic and thermodynamic calculations, and heat and material balances on the system. The data fit together to give a consistent picture of the polymerization scenario. The fact that the acrylic acid polymerization was not violent was primarily due to the presence of about 10 ppm phenothiazine, which delayed the onset of free radical polymerization until about 2 to 3 hours after the monomer had reached its boiling point. Since much of the acrylic acid was converted to dimer during this induction period, the ultimate energy release was greatly limited. Other moderating factors were a relatively slow heatup of the tank contents in the external heat exchange recycle loop, free vapor venting, and the incursion of fire monitor water into the tank.     

Design example: Explosion protection selected for a spray drying installation

A new spray drying installation must withstand a probable dust explosion without endangering personnel. Explosion venting and suppression are considered as well as the reasoning behind the design requirements.     

The use of spreadsheets in modelling accidental releases of toxic chemicals

Many hazardous industrial chemicals are stored as liquidfied compressed gases. To evaluate the possible consequences of a pipeline rupture, hose break, or tank puncture, the safety or process engineer needs a means to estimate the two-phase (liquid and gas) flow rate. Recent technical advances by the American Institute of Chemical Engineers Design Institute of Emergency Relief Systems (DIERS) have produced methods that can be used to compute the two-phase flow rate. These methods are simple and can be completed using a personal computer and a standard spreadsheet program such as Excel (Macintosh) or Lotus (DOS based). This paper presents the two-phase flow rate calculation method and shows how spreadsheets can be used for these calculations.     

男性着装意识及其类型

在对男性衬衫消费行为进行调查的基础上,将调查的数据用SPSS/PC+软件包进行了统计分析。根据着装意识进行了因子分析和聚类分析,男性的着装意识可分为"自我显示"、"互盾"和"舒适"3个因子。在聚类分析中将被调查者划分为"方便舒适型"、"时髦型"、"经济讲究型"、"讲究身份型"和"引人注目型",并分析了各组被调查者的消费行为和个人基本情况。     

对“全投资现金流量表”的修改意见

《建设项目经济评价方法与参数》已使用8年多,其对全投资现金流量表和内部收益率和净现值的现定存在一定问题,建议将全投资现金流量表改称项目现金流量表,并在现金汉出项中增加一项利息支出等。     

Emergency relief considerations under segregation scenarios

Emergency venting and containment requirements are considered for segregation conditions leading to massive accumulation of unreacted materials in process vessels. This study points out the importance of considering off-normal stoichiometry in these upset scenarios.     

超临界流体技术制备中药超细粉体

颗粒细、药效好、用量少已成为现代中药制剂的必然发展趋势。利用近年提出的超临界流体辅助雾化过程成功制备出了中药复方肝炎制剂的超细粉体,系统分析了混合器压力和温度及进液速率对微粒形态、粒径和粒径分布的影响。结果表明:利用超临界辅助雾化过程,以水和乙醇的混合溶液为溶剂,可制备出粒径范围为1.0～5.0μm的复方肝炎超细粉体,且大部分粒子形态呈完整的球形。各影响因素对粒径及粒径分布均有不同程度的影响,其中混合器压力及溶液浓度对粒径及粒径分布的影响最明显,进液速率次之,混合器温度的影响较小。在操作范围内较为理想的工艺条件为混合器压力为14 MPa,温度为60℃,进液速率为4.5 mL/min。     

Pressure venting of dust explosions in large vessels

The validity of the dust explosion venting nomograph D in NFPA 68 was examined in tests with vessels having volumes from 2.4 to 250 cubic meters and with dusts of classes St 1 and St 2.     

Automatic production control applying control theory

A new dynamic production model for the planning level will be presented in this paper. The model is based on methods of control theory, which provide a large variety of appropriate tools for analysing and controlling dynamic systems. With the help of the funnel model and the theory of the logistic operating curve, a continuous flow model of a single work centre has been designed. For the control task a backlog controller and a WIP controller have been developed. The controllers interact to adjust the capacity and the input rate of the work centre so as to eliminate the backlog as soon as possible and to set the WIP to a defined level. By means of envelope curves of capacity flexibility, which are easily applicable to industry, the individual range of capacity adjustments at a single work centre can be modelled. Simulation experiments confirm that this concept ensures the synchronisation of capacity and work. The objective is to develop a closed-loop control for PPC with defined control and reference variables based on the logistical objectives.     

Design charts for two-phase flashing flow in emergency pressure relief systems

The design charts of this paper apply to the high velocity flow of a boiling liquid and its vapor during two-phase emergency pressure relief events. These charts are used to size relief system components to handle a given minimum relief flow requirement. This flow requirement is determined by computer simulation programs such as that described in [1], or by special-case models [2, 3, 4]. Though intended for use in sizing pressure relief systems, the charts are applicable to high-velocity flashing flow problems.     

Espoused drum-buffer-rope flow control in serial lines: A comparative study of simulation models

This paper documents an investigation of drum-buffer-rope (DBR) scheduling and flow control methodology in single-product serial production lines. In particular, DBR flow control is reviewed and the importance of correctly representing this type of flow control mechanism in serial lines is discussed. Departures from valid DBR conceptual and simulation modeling are illustrated. It is shown that the model of a previously published paper is a push system not a DBR system, and that related conclusions regarding protective capacity and constraint location are unsupported. Correct modeling of DBR flow control is shown using discrete simulation experiments that compare the DBR model and a similar push model. Suggestions for additional research are offered.     

气井出砂对涡流工具携液能力的影响

为分析气井出砂对涡流工具携液能力的影响情况,针对气井井底积液以及井筒中存在固体杂质的问题,提出了一种气井中涡流工具携液携砂的三相流模型。通过对气井含砂与不含砂的情况进行模拟,分析了不同条件下涡流工具的携液作用,得到了气井出砂对液相流动规律、体积分数、速度分布的影响情况。结果表明:出砂量为10%的情况下,气井含砂有利于气井携液。气井含砂使运动阻力增加,液相的运动速度减小,轴向速度分布不规律,紊流程度增强,从而使运动更加复杂,气井对液体的携带作用增强;气井含砂使液相的运动速度减小且分布不规律。研究结果对进一步完善涡流工具的排水采气机理、提升气井的携液携砂效果具有参考价值。