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.     

Batch runaway reaction relief: Re-evaluation of “Credible” scenario

Many chemical reactions in the fine chemical and related industries are performed in a semi-batch manner under isothermal conditions. Relief system design evaluation for runaway reactions, using DIERS methodology for example, is frequently studied adiabatically using data derived from batch mode testing. In many cases, however, evaluation of the process isothermally under the realistic semi-batch mode can be extremely useful, often helping to greatly reduce the vent size as a result of a better understanding of the process. In some cases, it is even possible to eliminate runaway reaction as a viable case for relief sizing. Such evaluations of venting are fully consistent with DIERS methodology. This paper presents the arguments for sizing vents for scenarios other than the very worst case, by objective evaluation of trips and interlocks, so that the level of risk is reduced to an acceptable level without the need for extremely large vents.     

The reactive system screening tool (RSST): An easy,inexpensive approach to the DIERS procedure

The RSST DIERS vent sizing methodology is revised to provide realistic design equations for reactive systems consistent with available large-scale experience. Using easy to obtain RSST data such as rate of temperature rise and rate of pressure rise excellent agreement is illustrated for hybrid, vapor and gassy reactive systems.     

Process safety evaluation applying DIERS methodology to existing plant operations

The DIERS methodology can be used to quickly assess the relief capacity envelope for a collection of existing process vessels accounting for both vapor and gassy systems. Easy-to-use vent sizing nomograms and PRESS sheets are proposed that can be completed by the process engineering, the process chemistry and the process safety departments. A vessel volume-vent size diameter relationship is also developed using the source term based on fire exposure to cover a reasonable range of credible upset scenarios. In this way the adequacy of existing relief systems can be quickly surveyed for potential trouble sources—“outliers”—warranting further evaluation and corrective action.     

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.     

Assessing a runaway of a Grignard reaction

The venting and control strategies of a Magnesium Grignard formation reaction were assessed by theoretical predictions of the exotherm and the reaction rate, by simple laboratory measurements of the self heat rate, and by Leung's simplified equations and SAFIRE evaluations, based on DIERS methods. SAFIRE computations showed that the 150 mm dia vent was capable of keeping the reactor pressure below its maximum (MAWP) of 860 kPa for the worst-case exotherm. The response to this evidence was to increase safety protection in the automatic control strategy, following a quantified fault tree analysis of the worst-case runaway scenario.     

Emergency pressure relief discharge control by passive quenching—update

A recent runaway reaction emergency relief system design includes a passive quench tank to collect and contain the two-phase emergency relief discharge. This avoids the release of a large vapor cloud to the atmosphere and the attendant flammability and toxicity hazards. The feasibility of quenching is demonstrated with small scale experiments. A pressure relief simulation model is shown to accurately reproduce the observed temperature and pressure profiles in both the reactor and quench tank during relief. The model is then applied to the design of a full scale system. Quench system design considerations are discussed.     

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 important role of pressure in supercritical fluid process development revealed by reaction calorimetry

The technique of reaction calorimetry adapted for use with reactions in supercritical fluids was used to study some safety aspects of the free-radical dispersion polymerization of methyl methacrylate in scCO₂. The reaction heat rate profile was found to change very little once the dispersion was well formed. Furthermore, it provided valuable information for the calculation of the maximum temperature attainable by the synthesis reaction (MTSR) in the case of a hypothetical cooling system failure. Finally, a series of failure scenarios demonstrated the importance of the pressure as far as the safety of the process is concerned, due to the particularity of the supercritical state of the solvent. It was found that the acceleration phase of the reaction is the most critical period, since a cooling system failure during this phase leaves very little time before the pressure overcomes the operational limit of the equipment and results in an accident. Hence, the utility and the importance of defining the reaction heat rate profile become obvious and several safety features have to be taken into consideration when designing a SCF process. © 2009 American Institute of Chemical Engineers Process Saf Prog 2009     

Laboratory techniques for the quantitative study of thermal decompositions

Two experimental methods are described for studying thermal decomposition reactions in solids and liquids. The first allows early detection of initial exothermicity, calculation of pseudo kinetic parameters describing subsequent decomposition, and estimation of scale effects on the initial temperature for self-sustaining reaction. The second method yields additional data which provides a basis for relief system design.     

理想气体反应不同标准态时热力学函数间关系式的补充

通过理想气体反应等温方程和标准态转换,给出了摩尔反应热力学能、摩尔反应焓、标准摩尔反应亥姆霍兹函数和标准摩尔反应吉布斯函数在等温、等客条件下使用不同标准态时的另一组转换关系式,加上已经给出的在等温、等压条件下使用不同标准态时几个热力学函数间的转换关系式,使这类关系式更全面、完整.对这些关系式的应用条件以及在热化学和基元...     

An overview of emergency relief system design practice

Cost effective loss prevention requires an optimizing strategy to prevent, moderate (relieve) and contain runaway reactions. Ensuring that an emergency relief system design will either avoid or accommodate two-phase vapor-liquid flow is of particular importance. Use of adiabatic runaway reaction test information in combination with digital computer simulation is a powerful method to design an emergency relief system.     

改良单质硅溶解法制备大粒径硅溶胶的研究

在一定的温度和压力条件下,采用单质硅溶解法,用正交试验法研究了反应温度、反应压力、反应时间、氢氧化钠及硅粉用量等对硅溶胶收率及粒径的影响。实验结果表明,硅溶胶制备实验的最佳工艺条件如下:压力为0.5 MPa,在200 mL去离子水中加入15 g硅粉和0.4 g氢氧化钠,并控温度为160℃反应9 h,在此条件下制得的硅溶胶平均粒径为174.4 nm,收率为80.15%。平行实验结果表明,该最佳工艺条件具有良好的重现性。     

The Effect of U.S. Antidumping Law on Firms' Market Power: An Empirical Test

An empirical version of the Lerner index is used to investigate the market power effects of U.S. firms seeking protection under current antidumping law. The market power consequences are examined for each of the three possible resolutions of an antidumping investigation: petition for relief accepted (and duties levied), petition rejected, or petition withdrawn. For each outcome an industry case study is presented and the market power analysis conducted. The results contained herein support the hypothesis that U.S. firms receiving protection enhance their domestic market power, while firms having their petition rejected experience a decrease in market power. The evidence is less clear for plaintiffs who withdraw their antidumping petition prior to its final resolution.     

石家庄市环保产业的现状与对策研究

近年来,石家庄市政府加强了生态环境保护工作的力度,加大了污染治理和生态环境建设的投资规模,为环保产业的发展提供了一个良好的市场契机。综观石家庄环保产业发展的历史,分析当前环保产业的现状可以看出,经过近20年的发展,石家庄市环保产业已经走过了初级阶段的发展历程,完成了量的扩展,但是这种规模是建立在质量不高的发展基础上的。在分析石家庄市环保产业存在问题的基础上,提出了石家庄市环保产业发展对策及努力方向。     

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。     

2008年中国石油和化学工业经济形势分析

受全球金融危机的影响,2008年中国石油和化学工业经济呈现先高后低的态势,全行业景气周期由10年来的高增长转为下行通道.2008年全行业总产值6.58万亿元,比上年增长24.0%,生产增幅先高后低,年底出现负增长;市场疲软,销售率下降;石油和化工产品价格呈现先涨后跌态势;亏损企业增加,全行业利润下降;固定资产投资增势回落;进出口贸易额先增后降.当前面临的主要困难和问题有:1)石油消费需求减少,炼油企业开工率持续走低;2)化肥库存大量积压,企业经营困难;3)劳动密集型产业亏损严重;4)出口严重受阻,国内市场面临进口产品冲击.未来两年石油和化工行业形势不容乐观.但随着国家相关政策的落实,2009年产业结构、产品结构、企业兼并重组以及企业自身结构调整将非常活跃,前两个季度是石油和化工行业最为困难的时期,下半年有望好转.     

入世条件下合理保护我国钢铁工业问题研究

从世界钢铁产能过剩,关国实行“进口钢铁201保障措施调查案”最终救济方案这一背景出发,分析我国加入WTO后,原有的钢铁贸易保护政策受到了很大的限制情况下,适当保护我国钢铁工业的必要性与紧迫性,并对在WTO框架下如何合理保护我国钢铁工业提出建议,对在WTO框架下合理保护我国钢铁工业有现实意义。     

酸化缓蚀剂行业标准在产品质量检验中存在问题剖析及建议

测量油田化学剂中腐蚀速率项目,主要是依据石油天然气行业标准SY／T5405—1996《酸化用缓蚀剂试验方法及评价指标》中规定的方法。在腐蚀速率质量检验过程中发现,同一产品相同条件下加入不同质量分数缓蚀剂得到的测量结果存在明显差别的情况．影响了产品质量判定;标准中的判定指标与实际测量结果存在矛盾;高温高压动态条件无法准确确定反应时间。酸化缓蚀剂行业标准中存在加入质量分数不明确、评价指标错误、高温高压动态腐蚀试验方法操作不严谨及相应测定仪器的不适宜等问题．造成对依据此行业标准进行产品质量检验工作的困扰,影响了对依据该行业标准产品的质量判定结果。根据对存在问题剖析情况提出了系列建议。     

Conflicts and decisions in the search for inherently safer process options

Identification of inherently safer process options is a multi-dimensional problem. Nearly all chemical processes involve a number of processing steps. Associated with each processing step there is usually a number of hazards or hazard types, for example, high pressure, high temperature, acute toxicity, chronic toxicity, fire, explosion. A process which is inherently safer with respect to one of these hazards may be more hazardous with respect to another hazard. Several examples will be discussed, including selection of refrigerants, batch vs. continuous reaction, and solvent selection for a batch exothermic reaction. These examples illustrate the importance of a thorough understanding of all of the potential hazards in the process. Finally, some tools for evaluating process options and selecting among a group of processes with conflicting inherent safety characteristics are discussed.