粉尘爆炸反应工程学简要综述

１９９３年在波兰召开的第五届国际粉尘爆炸学术会议上，邓煦帆曾在论文中提议建立粉尘爆炸反应工程学，并提出学科的目的意义、性质、主要组成部分和研究方法。本文拟将国内外有关本学科范围内的贡献，加以简要综述，以期能逐渐形成本学科的自身体系和特点。     

爆炸事故及预防

为了促进我国的爆炸安全研究工作更深入发展,本文列出了利用爆炸激波管技术测定氢气、汽油、铝粉等可爆性物质的爆炸特性。研究表明:这些可爆性物质在一定条件都能形成破坏力极大的爆轰现象。实验确定了氢、汽油和氧混合物的可爆(轰)极限、可燃性极限、混合物临界初始压力等爆炸临界条件。控制可爆性物质的初始条件不超过其爆炸临界条件,能够防止爆轰或爆燃现象发生;添加不参加反应的物质(如氩气、氮气、水蒸汽等)能够使已达到爆炸条件的混合物阻爆。本文的数据可供有关部门参考。     

热爆炸理论在粉尘爆炸机理研究中的应用

笔者对粉尘爆炸的几种机理进行了简要分析 ,认为粉尘爆炸是由热爆炸引起的。在对粉尘燃烧过程作了较为合理的假设后 ,将热爆炸理论中均温系统的热爆炸判据 ,应用于粉尘爆炸中 ,得出了爆炸下限与粉尘粒径呈线性关系的结论 ,且与实验符合 ,并推导出粉尘的热爆炸判据。结果表明 :用热爆炸理论来解释粉尘爆炸机理是可行的。     

Fire and explosion risk assessment for large-scale oil export terminal

Now in Russian Federation and other countries large-scale oil terminals (volume of one tank exceeds 100 000 m³, total volume of tanks exceeds 300 000 m³) are designed and constructed. Therefore fire safety of such objects becomes a very important task, solution of which is hardly possible without detail fire risk assessment. This study is aimed to a solution of this problem. Potential, individual and social risks were calculated. The potential risk was defined as a frequency of occurrence of hazardous factors of fires and explosions in a given point of space (the so-called risk contours). The individual risk was defined as a frequency of injuring a given person by hazardous factors of fires and explosions. Time of presence of this person in hazardous zones (near the hazardous installation) is taken into account during calculations of the individual risk. Social risk was defined as a dependence of frequency of injuring a given number of people by hazardous factors of fires and explosions on this number. In practice the social risk is usually determined on injuring not less than 10 people.

The oil terminal under consideration includes the following main parts: crude oil storage consisting of three tanks of volume 100 000 m³ each, input crude oil pipeline of diameter 0.6 m, crude oil pumps, output crude oil pipeline of diameter 0.8 m, auxiliary buildings and facilities. The following main scenarios of tank fires have been considered: rim seal fire, pool fire on a surface of a floating roof, pool fire on a total cross-section surface of the tank, pool fire in a dyke, explosions in closed or semiclosed volumes. Fires and explosions in other parts of the terminal are also taken into account. Effects of escalation of accidents are considered.

Risk contours have been calculated both for the territory of the terminal and for the neighbouring space. The potential risk for the storage zone is near 10⁻⁴–10⁻⁵ year⁻¹, and at a distance 500 m from the terminal the potential risk values do not exceed 10⁻⁶ year⁻¹. The values of the individual risk for various categories of workers are in the range of 10⁻⁵–10⁻⁶ year⁻¹. Because of low number of the workers on the terminal and large distances to towns and villages the social risk value is negligible. These risk values are consistent with practice of the best oil companies, and fire hazard level of the terminal can be accepted as tolerable.     

Post-explosion observations of experimental mine and laboratory coal dust explosions

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRL Lake Lynn Experimental Mine (LLEM), and after laboratory explosions in the PRL 20-L chamber and the Fike 1 m³ chamber. The dusts studied included both high- and low-volatile bituminous coals. Low temperature ashing for 24 h at 515 °C was used to measure the incombustible content of the dust before and after the explosions. The data showed that the post-explosion incombustible content was always as high as, or higher than the initial incombustible content. The MSHA alcohol coking test was used to determine the amount of coked dust in the post-explosion samples. The results showed that almost all coal dust that was suspended within the explosion flame produced significant amounts of coke. Measurements of floor dust concentrations after LLEM explosions were compared with the initial dust loadings to determine the transport distance of dust during an explosion. All these data will be useful in future forensic investigations of accidental dust explosions in coal mines, or elsewhere.     

“Vybuchovy trojuhelnik”: A software tool for evaluation of explosibility of coal mine atmosphere

Rescue operations during mine fires or methane explosions are highly dangerous for rescue workers. The knowledge of the composition of the coal mine atmosphere and the calculations of its explosibility may help to increase the safety of the rescuers. In the Czech Republic, a system called “Mine Gas Laboratory” (DPL) has been used for these purposes. The DPL allows measurement of the composition of the mine atmosphere and transmits the data necessary for evaluation to the surface. Up to now the explosibility evaluation of the coal mine atmosphere has depended either on the rescuers’ experience or on software code calculation. The code called “Vybuchovy trojuhelnik” (explosion triangle) is a graphical computing system intended for fast assessment of explosibility of fuel–air mixture. This article introduces the code and describes two simple methods of explosibility evaluation. The first method is “explosion triangle analysis”—a graphical method based on empirical graphs transformed into equations. The second method uses thermodynamic calculation based on chemical balance dynamics and Gibbs and Helmholtz energy. According to the requirements of the Czech Bureau of Mining (CBU) and Central Mine Rescue Service (HBZS), the code solves the problems of explosion triangle for both standard and non-standard coal mine atmosphere compositions. Unfortunately, the atmosphere composition must be introduced manually due to the unknown format of the data transmitted from the old DPL model. On 1 September 2005, a project started to develop a new system for on-line monitoring and atmosphere explosibility evaluation. The system should be able to measure CO₂, O₂, CH₄, H₂ and CO concentrations as well as the wind speed, temperature and humidity. The “Vybuchovy trojuhelnik” code will be used as a basis for explosibility evaluation, and an on-line connection with the new model of DPL will be established.     

Ignitability characteristics of aluminium and magnesium dusts that are generated during the shredding of post-consumer wastes

The authors investigated the ignitability of aluminium and magnesium dusts that are generated during the shredding of post-consumer waste. The relations between particle size and the minimum explosive concentration, the minimum ignition energy, the ignition temperature of the dust clouds, etc. the relation between of oxygen concentration and dust explosion, the effect of inert substances on dust explosion, etc. were studied experimentally.

The minimum explosive concentration increased exponentially with particle size. The minimum explosive concentrations of the sample dusts were about 170 g/m³ (aluminium: 0–8 μm) and 90 g/m³ (magnesium: 0–20 μm). The minimum ignition energy tended to increase with particle size. It was about 6 mJ for the aluminium samples and 4 mJ for the magnesium samples. The ignition temperature of dust clouds was about 750 °C for aluminium and about 520 °C for magnesium. The lowest concentrations of oxygen to produce a dust explosion were about 10% for aluminium and about 8% for magnesium. A large mixing ratio (more than about 50%) of calcium oxide or calcium carbonate was necessary to decrease the explosibility of magnesium dust. The experimental data obtained in the present investigation will be useful for evaluating the explosibility of aluminium and magnesium dusts generated in metal recycling operations and thus for enhancing the safety of recycling plants.     

焦化苯初馏份蒸馏釜发生爆炸的原因探讨

通过对某企业的一起典型爆炸事故案例进行分析,找出其产生的原因,提出了预防措施。     

Determination of explosion limits – Criterion for ignition under non-atmospheric conditions

Many industrial processes are run at non-atmospheric conditions (elevated temperatures and pressures, other oxidizers than air). To judge whether and if yes to what extent explosive gas(vapor)/air mixtures will occur or may be generated during malfunction it is necessary to know the safety characteristic data at the respective conditions. Safety characteristic data like explosion limits, are depending on pressure, temperature and the oxidizer. Most of the determination methods are standardized for ambient conditions. In order to obtain determination methods for non-atmospheric conditions, particularly for higher initial pressures, reliable ignition criteria were investigated. Ignition tests at the explosion limits were carried out for mixtures of methane, propane, n-butane, n-hexane, hydrogen, ammonia and acetone in air at initial pressures up to 20 bar. The tests have been evaluated according to different ignition criteria: visual flame propagation, temperature and pressure rising. It could be shown that flame propagation and occasionally self-sustained combustion for several seconds occurred together with remarkable temperature rise, although the pressure rise was below 3%. The results showed that the combination of a pressure rise criterion of 2% and a temperature rise criterion of 100 K seems to be a suitable ignition criterion for the determination of explosion limits and limiting oxidizer concentration at higher initial pressures and elevated temperatures. The tests were carried out within the framework of a R&D project founded by the German Ministry of Economics and Technology.     

Simplified model for the evaluation of the effects of explosions on industrial target

The evaluation of vulnerability of process equipment to explosion is a central issue in the analysis of industrial risks. In this work, we have developed a simplified model, however based on fundamental equations, which includes structural and fluid–dynamic parameters for the target (the industrial equipment) and for the impacting pressure wave (shock waves) or object (fragment, debris) produced by different type of chemical explosions.The validity of methodology has been assessed by case histories. Several insights on the dynamic of structural interaction of the explosion with the target have been obtained, with specific reference to escalation effects.The model derives from the well-known Johnson's number, often adopted in impact engineering.