矿用离心式水泵汽蚀的预防措施及排除方法

排水设备作为煤矿四大固定机械设备之一，承担着排除涌水、预防水灾、保障安全的重要任务。其主体设备一离心式水泵汽蚀的高发态势，对矿井安全构成潜在威胁。本文通过对离心式水泵汽蚀机理的阐释，说明了汽蚀的征兆；分析了影响矿用水泵汽蚀的因素；明确了具体的预防措施和排除方法。     

冶金厂矿废水泵联运增效改造

冶金厂矿输送废水的离心水泵常会在低效区工作。选择一台合适的小离心泵与主泵联运，使主泵工况点移到高效区，增效明显。介绍废水泵联运增效原理方法和实例。     

焦化厂燃煤锅炉废水零排放效益浅析

分析了燃煤锅炉排水现状,采用灰水分离技术和脱硫废碱液调整锅炉废水pH值技术,实现锅炉废水循环利用.分析锅炉废水零排放取得的环境效益、社会效益和经济效益.     

DNTF合成废水污染分析与治理初探

为了解新型高能量密度的含能材料DNTF合成的废水特性,对合成工艺过程中的污染源进行了分析,对合成过程的实际废水COD、BOD、Cl-、SO24-进行了监测。结果表明,DNTF为多步有机合成产物,合成过程中产生的废液、废水可生化性差。可通过超声空化、铁微电解、吸附等预处理提高可生化性。废水的含盐量很高,对生化影响较大。鉴于废水的酸性很强,用其生产絮凝剂,可以实现以废治废。     

废水采样位置对污染源监测结果的影响

近年来,我国经济技术快速发展,但是环保问题也越来越突出。工业生产和人们的日常生活都会产生废水,废水采样是对废水源进行监测和管理的重要环节,废水监测的影响因素较多。本文主要分析了废水采样位置对监测结果的精确性造成的影响,以期为相关技术人员提供一定参考。     

冶金焦化废水治理新技术工业实践

焦化废水是最难处理的高浓度、难降解的有机工业废水之一。经传统方法处理后的废水,各项指标难以达标。以新兴铸管股份有限公司焦化废水工艺改造为例,用烧结带冷高温废气处理焦化废水,降低水中各种污染物的浓度,同时对烧结废气中二氧化硫、氮氧化物、粉尘等也进行了去除,实现“以废治废”。     

改性粉煤灰去除硝基苯废水的研究

粉煤灰经过废硫酸改性处理后吸附能力大大提高,用改性粉煤灰对生化后的硝基苯废水进行了实验研究,实验考察了粉煤灰的投加量、pH值、吸附时间对硝基苯去除率的影响,并对机理进行了分析.粉煤灰改性后应用于硝基苯废水处理中达到以废治废,具有一定的经济意义.     

工人电气操作不慎电火花引燃甲苯仓库爆炸

事故经过： 当事人祝某和郑某携带水泵到仓库提取废乙甲笨。装满一塑料桶后，他们去拔水泵插头准备收工时，插座产生的电火花引燃废乙甲苯，发生燃烧。火灾一发生，祝某和郑某立即逃离现场，没有采取任何自救措施．此时甲笨仓库起火发生剧烈爆炸，上方的火海形成一个巨大蘑菇云。     

活性粉煤灰吸附焦化废水中BaP的研究

利用自制的活性粉煤灰进行了焦化废水中的有机污染物3,4-苯并(a)芘(BaP)的吸附试验。在300 mL焦化废水中,调节pH值为中性或弱碱性,加入3.0 g活性粉煤灰,室温下吸附30 min,对BaP的去除率可达90%以上。试验结果表明,该活性粉煤灰适用于处理焦化废水中有机污染物,达到了"以废治废"的目的。     

大连某港口含酸碱废水处理工程设计方案

采用沉淀 气浮 过滤的废碱处理工艺和采用沉淀 滗水器 过滤的废酸处理工艺处理大连某港口含酸碱类废水,介绍了该工艺的方案、主要构筑物、设备及参数等.实践证明,该工艺对酸碱废水的处理是成功的.该工艺是一种新型高效、经济实用的酸碱废水回用的处理方法,具有很好的推广价值.     

变频调速技术对锅炉给水泵安全运行的影响

分析给水泵变频调速节能原理;针对锅炉给水泵改由变频器控制后存在的汽蚀及平衡盘磨损等问题进行了深入的研究,并提出了解决办法.     

The multi-energy critical separation distance

Devastating vapour cloud explosions can only develop under appropriate (boundary) conditions. The record of vapour cloud explosion incidents from the past demonstrates that these conditions are readily met by the congestion by process equipment at (petro-) chemical plant sites. Therefore, the possibility of an accidental release of a flammable and a subsequent vapour cloud explosion is a major hazardous scenario considered in any risk assessment with regard to the process industries.If an extended flammable vapour cloud at a chemical plant site extends over more than one process unit, which are separated by lanes of sufficient width, the vapour cloud explosion on ignition develops the same number of separate blasts. If, on the other hand, the separation between the units is insufficient, the vapour cloud explosion develops one big blast. The critical separation distance (SD) is the criterion that allows discriminating in this matter for blast modelling purposes.This paper summarises some major results of an experimental research programme with the objective to develop practical guidelines with regard to the critical SD. To this end, a series of small-scale explosion experiments have been performed with vapour clouds containing two separate configurations of obstacles. Blast overpressures at various stations around have been recorded while the SD between the two configurations of obstacles was varied.The experimental programme resulted in some clear indications for the extent of the critical SD between separate areas of congestion. On the basis of safety and conservatism, these indications have been rendered into a concrete guideline. Application of this guideline would allow a greater accuracy in the modelling of blast from vapour cloud explosions.     

Dispersion of the vapour cloud in the Buncefield Incident

Dispersion of the flammable vapour cloud in the 2005 Buncefield Incident is examined. Footage from security cameras around the site is analysed and the results from Computational Fluid Dynamics (CFD) simulations of the vapour dispersion are presented. It is shown that the shape of the terrain and the presence of obstacles significantly affected the dispersion of vapour from the overflowing tank. The CFD model is shown to produce similar qualitative behaviour to that observed in the incident, both in terms of the arrival time of the vapour cloud and its final depth.     

水力侵蚀对路基表面稳定性的影响研究

通过降雨试验和天然降雨水土流失调查 ,笔者首先探讨了风化花岗岩地区路基表面水力侵蚀的表现形式和规律 ,其中 ,基床表层已填筑级配碎石的易于发生级配碎石粗粒化 ,未填筑级配碎石的易于发生沟蚀 ;裸露的路堤边坡水力侵蚀发生发展规律一般为 :沟蚀→边坡滑坍 ;裸露的路堑边坡水力侵蚀发生发展规律一般为 :溅蚀→面蚀→沟蚀→坍塌 ;片石护坡的路堤和路堑边坡易于发生潜蚀。然后分析了水力侵蚀对路基表面稳定性的影响 ,认为溅蚀和面蚀对路基表面稳定性的影响较小 ;沟蚀对路堤边坡表面稳定性的影响程度随侵蚀程度和工程进度具体情况而定。最后 ,提出了施工期路基表面防护的建议     

Factors affecting vapour production in large scale evaporating liquid cascades

This paper presents a computational fluid dynamics (CFD) model of the evaporating liquid cascade produced in a large hydrocarbon storage tank overfilling incident. The model is first validated against the results of a unique series of full-scale experiments, in which liquid hexane was released from a 10 m high tower. Comparisons are presented for the temperature of both the liquid and vapour in the cascade, and the temperature of the vapour current. The validated model is then used to investigate the effects of different tank bund configurations, and the influence of an accumulating vapour layer on the vapour production process.     

Failure of a horizontal pressure vessel containing a high temperature liquid: the velocity of end-cap and rocket missiles

Many process plant installations include cylindrical vessels which contain high temperature liquids with the remaining space above occupied by vapour or a vapour/gas mixture. If such a pressure vessel were to be ruptured, missiles (i.e. fragments) may be generated and equipment in the vicinity put at risk. There is a particular threat from large missiles. Theoretical models have been developed to describe the peak velocity achieved by end-caps and `rocket' missiles generated by the circumferential failure of a vessel. The end-cap missile model assumes that the action of the escaping vapour/liquid on the end-cap is analogous to a missile driven by a gas jet from a constant pressure source. The `rocket' missile velocities are derived via a simple approximation to the impulse applied to the internal face of the closed end of the `rocket'. Experiments have confirmed the validity of these approaches and upper limit values to end-cap and `rocket' velocities have been defined.     

Assessment of an accidental vapour cloud explosion: Lessons from the Indian Oil Corporation Ltd. accident at Jaipur,India

On 29 October 2009, at 19:30 IST, a devastating vapour cloud explosion occurred in a large fuel storage area at the Indian Oil Corporation (IOC) Depot in Jaipur, India, generating significant blast pressure. As a consequence of this explosion, the entire installation was destroyed, buildings in the immediate vicinity were heavily damaged, and windowpane breakages were found up to 2 km from the terminal. The IOC estimated that the total loss from the fire and explosion was approximately INR 2800 million.Ironically, as a storage site, the Jaipur terminal was not highly congested, and thus was not considered to have adequate potential for a vapour cloud explosion (VCE). Nevertheless, the prima facie evidences indicate that this was a case of VCE. Therefore, the main objective of this study is to quantify the potential overpressures due to vapour cloud explosions (VCEs) using the Process Hazard Analysis DNV Norway based PHAST 6.51 Software. The results are validated by the extent of the damage that had occurred. The estimation of the VCE shows that a maximum 1.0 bar overpressure was generated in the surrounding area. The initial assessment of the accident data roughly estimates the release mode, time, and amount of vaporized fuel. A more accurate estimate has been obtained by modelling the dispersion of vapour clouds in the surrounding atmosphere, which reveals trends and relationships for the occurrence of vapour cloud explosions.     

Blast damage to storage tanks and steel clad buildings

The 2005 Buncefield vapour cloud explosion showed the huge cost associated with blast damage to commercial property surrounding a major explosion incident. In most cases there was serious disruption to business activity; in many cases the buildings had to be demolished or abandoned for long periods until extensive repairs were carried out.Another key feature of this and other recent vapour cloud explosions has been the damage done to storage tanks. The blasts almost invariably cause immediate top and bund fires in any tanks surrounded by the vapour – even if they contain relatively high flashpoint materials such as diesel.The first part of this paper describes the patterns of damage observed in buildings in the industrial estates around Buncefield. Methods for assessing the degree of external and internal damage are presented.The second part of the paper deals with failure modes and ignition of various types of liquid storage tank during vapour cloud explosions. Again, the Buncefield data provides excellent examples that illustrate the importance of tank design, fill level, location relative to the cloud, etc.     

A method for simulation of vapour cloud explosions based on computational fluid dynamics (CFD)

The effectiveness of the application of CFD to vapour cloud explosion (VCE) modelling depends on the accuracy with which geometrical details of the obstacles likely to be encountered by the vapour cloud are represented and the correctness with which turbulence is predicted. This is because the severity of a VCE strongly depends on the types of obstacles encountered by the cloud undergoing combustion; the turbulence generated by the obstacles influences flame speed and feeds the process of explosion through enhanced mixing of fuel and oxidant. In this paper a CFD-based method is proposed on the basis of the author’s finding that among the various models available for assessing turbulence, the realizable k-? model yields results closer to experimental findings than the other, more frequently used, turbulence models if used in conjunction with the eddy-dissipation model. The applicability of the method has been demonstrated in simulating the dispersion and ignition of a typical vapour cloud formed as a result of a spill from a liquid petroleum gas (LPG) tank situated in a refinery. The simulation made it possible to assess the overpressures resulting from the combustion of the flammable vapour cloud. The phenomenon of flame acceleration, which is a characteristic of combustion enhanced in the presence of obstacles, was clearly observed. Comparison of the results with an oft-used commercial software reveals that the present CFD-based method achieves a more realistic simulation of the VCE phenomena.     

Revised emergency vacuum relief device sizing for atmospheric distillation systems

Conventional vacuum relief methodologies are usually protective responses; that is, they accomplish their purpose by substitution of an inert gas (usually nitrogen) for the process gases removed by an external vacuum source, or for condensable vapour collapsed by an internal process mechanism (e.g. condensation). While this approach is theoretically possible for all potential vacuum scenarios, it becomes practically impossible to implement for installations where a rapid phase change can impart near-instantaneous system pressure reductions. The procedure outlined in this paper takes a preventive approach: eliminate the source of vacuum generation before the safe lower system pressure limit is reached. For distillation and other refluxing systems, this vacuum source is usually the main overhead condenser, which is designed to collapse large volumes of condensable vapour. To eliminate the vacuum source requires elimination of the system's ability to rapidly condense vapour. This goal is accomplished by introduction of inert gas directly into the condensing system to ‘blanket’ the heat transfer surface and stop condensation. The procedure determines the rate, amount and location for introduction of inert gas. The required design data include: (i) system starting pressure, (ii) maximum allowable system vacuum, (iii) volume of the condensing system, and (iv) normal system condensing rate. By determining the rate at which the condenser removes vapour volume from the system, and designing an inert gas delivery system to meet or exceed this rate, the vacuum generation potential of the system is effectively eliminated using a much smaller quantity of inert gas than with the more traditional volume substitution methods.