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81.
针对瓦斯爆炸事故在矿井开采中的危害及防治,从爆炸发展规律和爆炸防治两大方面对国内外瓦斯爆炸研究状况进行了综合评述.国内外学者通过理论法、实验法、数值模拟法对瓦斯爆炸进行研究,瓦斯爆炸发展规律方面的研究涉及到瓦斯爆炸的机理、瓦斯组分及浓度对爆炸发展规律的影响、爆炸发生的条件及危害、爆炸过程中的燃烧阶段变化及流体流动状态变...  相似文献   
82.
室内火灾中外部燃烧现象的数值模拟   总被引:1,自引:0,他引:1  
外部燃烧是室内火灾中火焰随烟气流出窗户并在窗户外燃烧的现象。外部燃烧会造成火势从初始着火的房间向其他房间或楼层蔓延,具有很大的危害性。本文应用美国国家标准技术局(NIST)开发的FDS程序,对外部燃烧现象进行了研究。首先对Bullen和Thomas的实验进行数值模拟,用以验证FDS对外部燃烧现象的模拟效果。在相近的燃料过量因子的条件下,计算得到的外部燃烧羽流的温度分布结果、外部燃烧火焰的高度和火焰距离窗户所在壁面的水平距离与Bullen和Thomas的实验结果符合得较好。之后,研究了不同窗户大小和不同燃料消耗率对外部燃烧的影响。最后,发现当燃料消耗率足够大致使室内燃料过量因子接近1时,室内火焰将会熄灭,燃料流出窗户形成的外部燃烧火焰会被拉长,火焰肾贴窗户外的壁面向上燃烧。  相似文献   
83.
天然气净化厂放空废气对环境的影响及控制措施   总被引:2,自引:0,他引:2  
天然气净化厂除正常生产有工艺废气排放外,传统装置检修开停产过程、供电或设备异常情况下,会有大量酸气、原料气通过放空火炬燃烧后排放。文章主要分析了天然气净化装置放空废气排放情况及其对周边环境的影响,阐述了异常放空、检修开停产过程原料气和酸气放空的控制措施及其环境效益。  相似文献   
84.
As evidenced by accident statistics, an important factor when considering the safe operation of process plants is the effective mitigation of the effects of gaseous flammable releases, either by a prevention, or a protection approach. A detailed historical analysis was performed considering accidental scenarios associated with the use and management of light gases, starting from raw data selected from FACTS database and analysed by a causal multi-layer method. Results revealed that the major part of the accidental releases involving methane, hydrogen, ethene, ammonia can be attributed to organizational or process/plant immediate causes. As expected, the most frequent scenarios following the release are fire and explosion. We focus our attention on the development of a short-cut method allowing preliminary evaluation of the maximum gaseous build-up under semi-confined conditions, limiting the effects of the fire/explosion scenario to a tolerable level. The limitations of the model that is applied to selected case-studies and require further experimental validation are critically discussed. The results of the application of the model, which can boast of being safe but not disproportionately conservative, can be set as a maximum threshold in proper designing technical measures aiming at limiting the effects to a tolerable level by protection methods, e.g. isolation, venting, suppression and containment.  相似文献   
85.
Experiments using an open space dust explosion apparatus and a standard 20 L explosion apparatus on nano and micron polymethyl methacrylate dust explosions were conducted to reveal the differences in flame and pressure evolutions. Then the effect of combustion and flame propagation regimes on the explosion overpressure characteristics was discussed. The results showed that the flame propagation behavior, flame temperature distribution and ion current distribution all demonstrated the different flame structures for nano and micron dust explosions. The combustion and flame propagation of 100 nm and 30 μm PMMA dust clouds were mainly controlled by the heat transfer efficiency between the particles and external heat sources. Compared with the cluster diffusion dominant combustion of 30 μm dust flame, the premixed-gas dominant combustion of 100 nm dust flame determined a quicker pyrolysis and combustion reaction rate, a faster flame propagation velocity, a stronger combustion reaction intensity, a quicker heat release rate and a higher amount of released reaction heat, which resulted in an earlier pressure rise, a larger maximum overpressure and a higher explosion hazard class. The complex combustion and propagation regime of agglomerated particles strongly influenced the nano flame propagation and explosion pressure evolution characteristics, and limited the maximum overpressure.  相似文献   
86.
To further understand the dynamic mechanism of dust explosion through a vent duct, we designed a small-scale cylindrical vessel connected with a vent duct and performed a dust explosion venting experiment under different opening pressures using corn starch as the explosive medium in this study. The results show that weakening effect of duct on venting is positively correlated with the opening pressure. The explosion pressure in the duct presents a three-peak-structure with time, successively caused by the membrane breaking shock wave, the secondary explosion in the tube, and the continuous combustion, and decreases gradually with the propagation distance. Meanwhile, the three pressure peaks are positively correlated with the opening pressure, while the time interval between them goes to contrary. The increase of opening pressure leads to the increase of secondary explosion intensity and reverse flow in the vessel, further accelerates the reaction rate in the vessel, and then shortens the duration of combustion in the vessel until the phenomenon of flame reignition in the vessel disappears.  相似文献   
87.
Combustible dust explosions continue to present a significant threat toward operating personnel and pneumatic conveyance equipment in a wide variety of processing industries. Following ignition of suspended fuel within a primary enclosure volume, propagation of flame and pressure fronts toward upstream or downstream interconnected enclosures can result in devastating secondary explosions if not impeded through an appropriate isolation mechanism. In such occurrences, an accelerated flame front may result in flame jet ignition within the secondary vessel, greatly increasing the overall explosion severity. Unlike an isolated deflagration event with quantifiable reduced pressures (vent sizing according to NFPA 68 guidance), oscillation of pressure between primary and secondary process vessels leads to uncertain overpressure effects. Dependent on details of the application such as relative enclosure volumes, relief area, fuel type, suspended concentration, duct size, and duct length, the maximum system pressure in both interconnected vessels can be unpredictable. This study proposes the use of FLame ACceleration Simulator (FLACS) computational fluid dynamics (CFD) modeling to provide reliable consequence predictions for specific case scenarios of dust deflagrations involving interconnected equipment. Required minimum supplement to the originally calculated relief area (Av) was determined through iterative simulation, allowing for reduced explosion pressures (Pred) to be maintained below theoretical enclosure design strengths (Pes).  相似文献   
88.
In the event of a BLEVE, the overpressure wave can cause important effects over a certain area. Several thermodynamic assumptions have been proposed as the basis for developing methodologies to predict both the mechanical energy associated to such a wave and the peak overpressure. According to a recent comparative analysis, methods based on real gas behavior and adiabatic irreversible expansion assumptions can give a good estimation of this energy. In this communication, the Artificial Neural Network (ANN) approach has been implemented to predict the BLEVE mechanical energy for the case of propane and butane. Temperature and vessel filling degree at failure have been considered as input parameters (plus vessel volume), and the BLEVE blast energy has been estimated as output data by the ANN model. A Bayesian Regularization algorithm was chosen as the three-layer backpropagation training algorithm. Based on the neurons optimization process, the number of neurons at the hidden layer was five in the case of propane and four in the case of butane. The transfer function applied in this layer was a sigmoid, because it had an easy and straightforward differentiation for using in the backpropagation algorithm. For the output layer, the number of neurons had to be one in both cases, and the transfer function was purelin (linear). The model performance has been compared with experimental values, proving that the mechanical energy of a BLEVE explosion can be adequately predicted with the Artificial Neural Network approach.  相似文献   
89.
90.
The oil industry operates installations and processes with important quantities of flammable substances within a wide range of pressures and temperatures. A particular hazard for this type of installations is an accidental release of a large quantity of flammable material resulting in a devastating vapor cloud explosion.Extensive research was conducted to assess the efficiency of chemicals for inhibition of flames. Especially alkali metal compounds (especially carbonates and bicarbonates of sodium and potassium) have shown to be one of the more efficient flame inhibitor species.In this paper, the principles of flame inhibition by alkali metal compounds are briefly explained. Based on these principles, a practical implementation of an industrial system for chemical inhibition of vapor cloud explosions is discussed. This implementation is based on the use of dry powders of carbonates and bicarbonates of sodium and potassium as flame inhibitor species.The efficiency of the final design of the inhibition system was tested and confirmed on a very large scale in Vapor Cloud Explosion tests in California (US) in September 2016. Several projects in TOTAL were identified in which the VCE inhibition technology is implemented (new cracker units in Daesan (South-Korea) and in Port Arthur (United States)).  相似文献   
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