The influence of the charge-to-mass ratio of the charged water mist on a methane explosion

To study the influence of the charge-to-mass ratio of a charged water mist on a methane explosion, the induction charging method was used to induce charge on a normal water mist; a mesh target method was employed to test the charge-to-mass ratio of its droplets. The propagation images, propagation average velocities, and overpressures of a methane explosion suppressed by charged water mist were analysed. The influence of the charge-to-mass ratio of the suppressant water mist on a methane explosion was studied. Results show that the explosion temperature, propagation average velocity, and peak overpressure deceased more obviously with charged water mist than ordinary water mist. With increasing charge-to-mass ratio, the suppression effect of the charged water mist underwent a significant increase. Under experimental conditions, compared with ordinary water mist, when the charge-to-mass ratio was 0.445 mC/kg and the mist flux was 4 L, the minimum flame propagation average velocity was 3.456 m/s, with a drop of 2.37 m/s (40.68%), and the peak overpressure of the methane explosion was 10.892 kPa, with a drop of 10.798 kPa (49.78%). The suppression effect is considered from the changes of the physico-chemical properties of the water mist as affected by the applied charge-to-mass ratio.     

A methodology to predict shock overpressure decay in a tunnel produced by a premixed methane/air explosion

A methodology for estimating the blast wave overpressure decay in air produced by a gas explosion in a closed-ended tunnel is proposed based on numerical simulations. The influence of the tunnel wall roughness is taken into account in studying a methane/air mixture explosion and the subsequent propagation of the resulting shock wave in air. The pressure time-history is obtained at different axial locations in the tunnel outside the methane/air mixture. If the shock overpressure at two, or more locations, is known, the value at other locations can be determined according to a simple power law. The study demonstrates the accuracy of the proposed methodology to estimate the overpressure change with distance for shock waves in air produced by methane/air mixture explosions. The methodology is applied to experimental data in order to validate the approach.     

The explosion parameters of methanol under variable pressures and 423 K

The high-temperature and high-pressure methanol one-step oxidation has been the primary process for the mass production of dimethoxymethane. However, the risk of explosion for this process is still not properly defined. This paper presents new results from the experimental study on the explosion characteristics, including the explosion pressure and the explosion limits for methanol/air mixtures with a variable oxygen level, under an initial pressure between 0.3 MPa and 0.75 MPa and at the initial temperature of 423 K. The upper explosive limits were found to increase along with the initial pressure. If the limits for normal air are known, the oxygen effect on flammability is predictable from the thermal balance method. With a correlation for the pressure effect and a method for the oxygen effect, we can have the flammable range predictable.     

Industrial accidents in spray dryer plants for dairy products in Europe

Despite the fact that the information about past accidents is an integral part of accident prevention, the information about industrial accidents is not commonly available in food and agricultural sectors. Spray dryer plants for dairy products are not an exception. The aim of this paper is the creation of the representative database for industrial spray drying accidents in order to identify their major causes. The paper is divided into 8 chapters. The first two chapters deal with the general information about technology of spray drying of dairy products. The third chapter provides the outputs from the authors' database containing records of 25 accidents in milk drying facilities in Europe. These accidents took place between 1999 and 2019 in six European countries. Based on the accident database, the most common causes of accidents were identified. Processes that can cause a fire, an explosion, or damage to environment are described in the fourth, fifth and sixth chapter. The seventh chapter deals with process, technical and organizational measures; these were discussed using literature research and the results of the accident database. The eighth chapter is the conclusion with a focus on further improvement of process safety through newly developed protective tools.     

Fire and explosion hazard analysis during surface transport of liquefied petroleum gas (LPG): A case study of LPG truck tanker accident in Kannur,Kerala, India

This paper presents an analysis and simulation of an accident involving a liquefied petroleum gas (LPG) truck tanker in Kannur, Kerala, India. During the accident, a truck tanker hit a divider and overturned. A crack in the bottom pipe caused leakage of LPG for about 20 min forming a large vapor cloud, which got ignited, creating a fireball and a boiling liquid expanding vapor explosion (BLEVE) situation in the LPG tank with subsequent fire and explosion. Many fatalities and injuries were reported along with burning of trees, houses, shops, vehicles, etc. In the present study, ALOHA (Area Locations of Hazardous Atmospheres) and PHAST (Process Hazard Analysis Software Tool) software have been used to model and simulate the accident scenario. Modeling and simulation results of the fireball, jet flame radiation and explosion overpressure agree well with the actual loss reported from the site. The effects of the fireball scenario were more significant in comparison to that of the jet fire scenario.     

Vent burst pressure effects on vented gas explosion reduced pressure

The overpressure generated in a 10 L cylindrical vented vessel with an L/D of 2.8 was investigated, with end ignition opposite the vent, as a function of the vent static burst pressure, P_stat, from 35 to 450 mb. Three different K_v (V^2/3/A_v) of 3.6, 7.2 and 21.7 were investigated for 10% methane–air and 7.5% ethylene–air. It was shown that the dynamic burst pressure, P_burst, was higher than P_stat with a proportionality constant of 1.37. For 10% methane–air P_burst was the controlling peak pressure for K <∼8. This was contrary to the assumption that P_red > P_burst in the literature and in EU and US standards. For higher K_v the overpressure due to flow through the vent, P_fv, was the dominant overpressure and the static burst pressure was not additive to the external overpressure. Literature on the influence of P_stat at low K_v was shown to support the present finding and it is recommended that the influence of P_stat in gas venting standards is revised.     

原油储罐火灾事故环境风险评价分析

通过运用ADMS模型,对2万m3原油储罐发生火灾爆炸事故时有毒有害气体及燃烧次生污染物的环境影响进行预测。结果表明,其产生的废气污染物对环境影响较大;在火灾持续6h的情况下,产生的主要废气污染物在距离事故中心120m范围内的人员将有半数死亡;距120～240m范围内造成组织缺氧;距240～4725m人员不会有生命危险;距离4725m范围内污染物的浓度超出车间最高允许浓度要求。同时提出了相应的环境风险管理措施,为今后类似事故环境影响评价作借鉴,为环保部门环境管理提供参考。     

Experimental investigation on explosion flame propagation of wood dust in a semi-closed tube

In order to explore flame propagation characteristics during wood dust explosions in a semi-closed tube, a high-speed camera, a thermal infrared imaging device and a pressure sensor were used in the study. Poplar dusts with different particle size distributions (0–50, 50–96 and 96–180 μm) were respectively placed in a Hartmann tube to mimic dust cloud explosions, and flame propagation behaviors such as flame propagation velocity, flame temperature and explosion pressure were detected and analyzed. According to the changes of flame shapes, flame propagations in wood dust explosions were divided into three stages including ignition, vertical propagation and free diffusion. Flame propagations for the two smaller particles were dominated by homogeneous combustion, while flame propagation for the largest particles was controlled by heterogeneous combustion, which had been confirmed by individual Damköhler number. All flame propagation velocities for different groups of wood particles in dust explosions were increased at first and then decreased with the augmentation of mass concentration. Flame temperatures and explosion pressures were almost similarly changed. Dust explosions in 50–96 μm wood particles were more intense than in the other two particles, of which the most severe explosion appeared at a mass concentration of 750 g/m³. Meanwhile, flame propagation velocity, flame propagation temperature and explosion pressure reached to the maximum values of 10.45 m/s, 1373 °C and 0.41 MPa. In addition, sensitive concentrations corresponding to the three groups of particles from small to large were 500, 750 and 1000 g/m³, separately, indicating that sensitive concentration in dust explosions of wood particles was elevated with the increase of particle size. Taken together, the finding demonstrated that particle size and mass concentration of wood dusts affected the occurrence and severity of dust explosions, which could provide guidance and reference for the identification, assessment and industrial safety management of wood dust explosions.     

爆炸及其危险性分析与评价

了解爆炸发生的机理,对危险场所进行爆炸危险性评价是预防爆炸事故发生的有效措施。本文对爆炸及典型的爆炸危险性评价方法进行了简略介绍。     

Lower explosion limit of hybrid mixtures of burnable gas and dust

Hybrid mixtures – mixtures of burnable dusts and burnable gases – pose special problems to industries, as their combined Lower Explosion Limit (LEL) can lie below the LEL of the single substances. Different mathematical relations have been proposed by various authors in literature to predict the Lower Explosion Limit of hybrid mixtures (LEL_hybrid). The aim of this work is to prove the validity or limitations of these formulas for various combinations of dusts and gases. The experiments were executed in a standard 20 L vessel apparatus used for dust explosion testing. Permanent spark with an ignition energy of 10 J was used as ignition source. The results obtained so far show that, there are some combinations of dust and gas where the proposed mathematical formulas to predict the lower explosible limits of hybrid mixtures are not safe enough.