Evaluation of the explosibility of malt grain dust based on static electrification during pneumatic transportation

The possibility of dust explosions by static electricity in a malt grain silo was investigated. Two kinds of experimental equipment were applied. One was to supply electrostatic charge in order to investigate the charge build up characteristics. The other was to transport the malt grain pneumatically in order to investigate the frictional charge accumulation in the transportation system.

The particle charge of the pulverized malt grain was in the order of 10⁻¹⁴ C. The particle charge of the malt grain was in the order of 10⁻⁹ C and the pipe charge in the transport system was also in the order of 10⁻⁹ C. The charge accumulated on both the pulverized particle and the grain particle were small in view of the incendiary potentiality. However, attention must be paid when the particles are dumped into isolated space. There might be a charge accumulation that will lead to the ignition of the dust cloud.     

黄岛石化区消防安全初评估

黄岛石化区是一个集油品储运、原油炼制、芳烃加工为一体的大型石油化工基地。目前,区域内拥有原油炼制能力达到1000多万吨,危险化学品存储能力接近1000万吨,危化品码头吞吐能力接近6000万吨,并且危化品项目的规模还在不断扩大中。鉴于危化品项目的危险性较高,石化区域的消防安全就成了企业生产安全的重要保障,而消防安全是否有保证则与区域内企业的生产存储装置的危险程度、安全设施配置、消防设施的配置以及消防队伍和车辆的配置等有直接的关系。笔者通过对区域内上述各方面信息的详细了解,并在参阅了大量技术文献资料的基础上,分别以生产装置火灾和存储装置火灾为对象进行了消防安全的初步评估,同时对区域内消防方面存在的问题提出改进建议。     

Explosibility of hydrogen–graphite dust hybrid mixtures

To evaluate the hazard of combined hydrogen/dust explosions under severe accident conditions in International Thermonuclear Experimental Reactor (ITER), standard method of 20-L-sphere was used to measure the explosion indices of 4-μm fine graphite dust in lean hydrogen/air mixtures. The mixtures were ignited by a weak electric spark. The tested fuel concentrations were 8–18 vol% H₂ and 25–250 g/m³ dust. If the hydrogen content is higher than 10 vol%, the dust constituent can be induced to explode by the hydrogen explosion initiated by a weak electric spark. Depending on the fuel component concentrations, the explosions proceed in either one or two stages. In two-stage explosions occurring at low hydrogen and dust concentrations, the mixture ignition initiates first a fast hydrogen explosion followed by a slower phase of the dust explosion. With increasing dust concentration, the dust explodes faster and can overlap the hydrogen-explosion stage. At higher hydrogen concentrations, the hybrid mixtures explode in one stage, with hydrogen and dust reacting at the same time scale. Maximum overpressures of hybrid explosions are higher than those observed with hydrogen alone; maximum rates of pressure rise are lower in two-phase explosions and, generally, higher in one-stage explosions, than those characteristic of the corresponding H₂/air mixtures.     

Calorimetric behaviors of hydroxylamine and its salts caused by Fe(III)

The objective of this study is to obtain information on the calorimetric behaviors of aqueous solutions of hydroxylamine (HA), hydroxylamine chloride (HACl), and hydroxylamine nitrate(HAN) caused by different Fe(III) states (free Fe(III) from Fe(NH₄)(SO₄)₂, Fe(CN)₆³⁻, and Fe(EDTA)⁻). The calorimetric data were obtained with a small-scaled reaction calorimeter, Super-CRC.

In the mixing with Fe(III), HA showed the highest reactivity among three substrates. Free Fe(III) and Fe(EDTA)⁻ showed catalytic effects in the reactions. In the overall heat of reactions, Fe(EDTA)⁻ exceeded free Fe(III), which precipitated as Fe(OH)₃ and decreased the chances of interactions with HA. It was suggested that the generation of NH₃ had taken place in the process of reducing HA along with Fe(II) oxidation. Fe(CN)₆³⁻ was less reactive than free Fe(III) and Fe(EDTA)⁻.

The ability of masking Fe(III) was estimated for CyDTA. The HA including CyDTA had no exothermic peak; however, there was an endothermic peak of the heat flow at Fe(III) injection. CyDTA was found to have the ability to inhibit a violent exothermic reaction of HA.     

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.     

新型油氢合建站事故风险评价及应用

油氢合建站作为新型能源基础设施,在实现传统油品加注和氢燃料运营的过程中出现诸多安全新问题。为规避此类问题带来的事故风险,以上海首座油氢合建站为研究对象,通过定性和定量相结合的方法对其建造、运营及维护过程中的事故危险源及有害因素进行风险分析。基于FTA确定引起油氢合建站内危险物质泄漏、火灾及爆炸事故的事件重要度和高风险因素,通过F&EI评价法对油氢合建站危险因素进行定量计算,确定其发生事故的最高危险等级为非常大,暴露危险区域面积为6015.65 m²。基于此,从安全管理、泄漏防控措施、防火防爆技术及事故应急处置等方面提出事故风险管控对策,采用一系列安全管控补偿措施后,油氢合建站事故危险等级降至较轻以下,暴露危险区域被控制在780 m²内。     

Fire and explosion assessment on oil and gas floating production storage offloading (FPSO): An effective screening and comparison tool

Fires and explosions have been identified as major potential hazards for Oil and Gas Floating Production Storage Offloading (FPSO) installations and pose risk to personnel, assets, and the environment. Current fire and explosion assessment (FEA) tools require physical effect modeling software and follows standards from API, ISO, and engineering practices. However, the tools are not specific to any particular system such as an FPSO, and do not provide comprehensive guidance for safety engineers to perform FEA.This paper discusses the development of a screening and comparison tool for FEA on FPSOs and the incorporation of an expert system into the tool. The results are computerized using MS Excel/VBA to provide a structured and comprehensive assessment on each equipment and module handling natural gas, crude oil, methanol and diesel on FPSO topsides.This tool features built-in calculations for jet and pool fire size estimation for gas/liquid releases, and the ability to perform Quantitative Risk Analysis (QRA) to specify the personnel and equipment risk for varying leak sizes and process conditions. Control and recovery measures are incorporated as an expert system based on report findings, engineering practices, and relevant standards. Bowtie analysis is applied in the tool to define detailed control and recovery measures for the FPSO based on the incident scenarios. An explosion assessment is performed by incorporating physical effect modeling software results.Unique features provided in the tool include fire and radiation contour mapping on an FPSO layout to help determine personnel and equipment risk more accurately and fire pump sizing that can be used to verify the amount of water deluge system required to mitigate fires and explosions. In addition, flexibility of data input (process data, failure rate data, etc.) and user interfaces assist safety engineers to screen and compare process alternatives, check design quality, and evaluate design options at any design stage.     

Modelling Thiocyanate Adsorption onto Surfactant-Modified Coir Pith, an Agricultural Solid ‘Waste’

Thiocyanate (SCN⁻) is used in many industrial processes and is found in industrial wastewaters. Adsorptive removal of thiocyanate by surfactant-modified coir pith, an unwanted byproduct of coir fibre industry was studied. Cationic surfactant, hexadecyltrimethylammonium bromide was used as modifier. Optimum pH for maximum adsorption of SCN⁻ was found to be 2.0. Langmuir, Freundlich and Dubinin Radushkevich (D-R) isotherms were used to model the adsorption equilibrium data and the system followed all the three isotherms and the adsorption capacity of the adsorbent was found to be 8.6 mg g⁻¹. Kinetic studies show that the adsorption obeyed second order. Desorption studies showed that upto 90% recovery of SCN⁻ from the spent adsorbent was feasible. Effect of foreign anions on the adsorption of SCN⁻ was also examined.     

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.     

Floating roof storage tank boilover

Storage tanks are important facilities for the major hazard installations (MHIs) to store large quantity of crude oil. There is several fire types can occur with large diameter open top floating roof storage tanks. Boilover is considered one of the most dangerous fires in large-scale oil tank. The world has witnessed many incidents due to boilover in floating roof storage tank. Boilover problem has been studied in experiments and by models to understand how to control the boilover phenomena. An experimental study has been carried out in Jebel Dhanna (JD) terminal area by Abu Dhabi Company for Onshore Oil Operations (ADCO) with support of Resource Protection International (RPI) consultant. 2.4 m diameter and 4.5 m diameters pans have been used to study the characteristics of the large oil-tank fires (i) to gain more knowledge of the boilover phenomenon of crude oil (ii) verify if the crude oil stored by ADCO would boilover (ii) estimation of rate of hot-zone growth and the period needed from ignition to boilover (iii) estimation of radiant heat and consequences of boilover. This paper presents an overview on the floating roof storage tank boilover. The paper also presents briefly boilover experimental research study carried out by ADCO.     

The effect of vent ducts on the reduced explosion pressures of vented dust explosions

An investigation into the effects of vent ducts on reduced explosion pressures is described. Experiments were made using an 18.5m³ explosion vessel and a modified 20 1 sphere, with dusts having K_st values ranging from 144 bar ms⁻¹ to 630 bar ms⁻¹. The vent area/vessel volume ratio bursting pressure of the vent cover, and the length to diameter ratio of the vent duct have been varied. Straight vent ducts, and ducts containing sharp 45° and 90° bends have been used.A simple model to describe the effect of vent ducts on the reduced explosion pressure has been derived and compared with the experimental results. Agreement is shown to be satisfactory in nearly all cases. A comparison between the experimental results and guidance on the effect of vent ducts already available in the literature is discussed.     

Improving Energetic Performance and Water Usage in an Industrial Ethanol Distillery

In this paper, a case study based on an industrial process of ethanol distillation was undertaken. It was aimed to improve the energy and water usage in the process. Pinch Analysis concepts were used to propose a new heat exchanger network and a study was undertaken to the water reuse. The minimization of wastewater is achieved through the exploitation of recycle and reuse opportunities by process modifications. Through these studies, a new streams circuit was obtained, which resulted in a lower consumption of steam and in a reduction in the volume of water collecting of 12 m³ to 1 m³ per tons of crushed sugar cane. Process changes and economical viability were presented. Two kinds of equipment were studied, cooling towers and aspersion tanks.     

Measuring the violence of dust explosions with the “20 l sphere” and with the standard “ISO 1 m vessel”: Systematic comparison and analysis of the discrepancies

On the basis of a systematic testwork with a number of different dusts, the explosion indices as determined within the 20 l sphere and with the ISO-VDI 1 m³ vessel have been compared. The repeatability has been assessed and since some systematic deviations appear a refined physical analysis of the explosion processes is developed. It appears in particular that the cube root law supposed to link both vessels is not verified. A striking illustration of this appears when a dust with a significant explosion severity inside the 20 l sphere is not even explosible in the larger vessel. It is strongly suggested that the ignition energy is forcing very significantly the explosion in the smaller vessel inducing several tens of Celsius degrees of preheating. It is shown also that the inner level of turbulence is decreasing very fast in the 20 l sphere during the flame development so that difficult-to-ignite mixtures would tend to burn at a lower combustion rate. It is further demonstrated that the major bias between the chambers can be explained and quantified with these elements. A correlation with the standard 1 m³ vessel and a grid of interpretation of the data is proposed.     

基于蒙特卡罗模拟的高校室内甲醛暴露健康风险评价

为了量化分析高校新建教学楼室内环境污染引起的健康风险问题,调查了武汉市某高校新建教学楼室内甲醛污染状况,引入美国环保署(EPA)致癌风险模型,运用蒙特卡罗模拟室内甲醛暴露对不同性别的教师和学生受体造成的健康风险,进行不确定性分析,并研究各参数敏感度。结果表明,该教学楼室内的监测点监测得到的甲醛质量浓度数据中有5%超过标准限值(0.10 mg/m³,参照《室内空气质量标准》),存在一定的健康风险。健康风险评估结果显示,男性的癌症风险和超标率略高于女性,教师群体健康风险平均值超过限值(1×10^-6)9倍左右,且高于学生群体3~4倍。对教师造成影响最大的参数为暴露时间,对学生影响最大的参数为甲醛质量浓度,在无致癌风险的室内甲醛质量浓度和在可接受健康风险限值(1×10^-6)下,推荐教师每日平均暴露时间不超过0.31 h/d(男性)和0.35 h/d(女性)。     

Revised fire consequence models for offshore quantitative risk assessment

Offshore oil and gas platforms are well known for their compact geometry, high degree of congestion, limited ventilation and difficult escape routes. A small mishap under such conditions can quickly escalate into a catastrophe. Among all the accidental process-related events occurring offshore, fire is the most frequently reported. It is, therefore, necessary to study the behavior of fires and quantity the hazards posed by them in order to complete a detailed quantitative risk assessment. While there are many consequence models available to predict fire hazards-varying from point source models to highly complex computational fluid dynamic models—only a few have been validated for the unique conditions found offshore.

In this paper, we have considered fire consequence modeling as a suite of sub-models such as individual fire models, radiation model, overpressure model, smoke and toxicity models and human impact models. This comprehensive suite of models was then revised by making the following modifications: (i) fire models: existing fire models have been reviewed and the ones most suitable for offshore conditions were selected; (ii) overpressure impact model: a model has been developed to quantify the overpressure effects from fires to investigate the possible damage from the hot combustion gases released in highly confined compartments; (iii) radiation model: instead of a point/area model, a multipoint grid-based model has been adopted for better modeling and analysis of radiation heat flux consequences. A comparison of the performance of the revised models with the ones used in a commercial software package for offshore risk assessment was also carried out and is discussed in the paper.     

Scaling parameters for vented gas and dust explosions

Results of experiments or calculations for vented explosions are usually presented by expressing a term containing the peak (reduced) pressure as a function of a vent parameter. In gas explosions, the reactivity of the system has been typically characterized through an effective burning velocity, u_f. In the case of dust explosions, a normalized peak rate of pressure rise, K(=V^1/3(dp/dt)_max), has been used instead. Depending on the chosen approach, comparisons between systems with the same “reactivity” take different meanings. In fact, correlation formulas resulting from these two approaches imply different scaling between important system parameters. In the case of a constant-u_f system, and for sufficiently large vent areas, the reduced pressure, Δp_r, is approximately proportional to the square of the peak unvented pressure, Δp_m. On the other hand, correlations developed for constant-K systems imply proportionality of Δp_r with Δp_m raised to a power between −5/3 and −1, with the exact value depending on the assumptions made on the shape of the pressure profile. While the ultimate resolution of the details of the scaling may require recourse to experiments, this theoretical analysis offers a tool for the planning of such experiments and for the interpretation of their results. The paper provides a discussion of these scaling issues with the help of predictions from an isothermal model of vented explosions.     

有机过氧化物生产火灾爆炸危险性分析

针对有机过氧化物自分解温度较低、反应过程易引发火灾爆炸等危险特性,采用危险与可操作分析(HAZOP)方法和事故树(FTA)分析对过氧化物生产过程中存在的火灾爆炸危险性进行分析.结果表明,有机过氧化物生产过程中低温的保证是关键,应对制冷系统进行故障类型及影响分析(FMEA),从而确保制冷系统安全可靠.     

烷基苯联合装置风险及控制研究

烷基苯联合装置含有国家安全监管总局首批重点监管的15种危险化工工艺中的加氢工艺、烷基化工艺两种,装置工艺介质为易燃、易爆、有毒及强腐蚀性物质,生产中潜在危险性较大;开展工艺风险研究,落实控制措施,对于提高装置本质安全性具有极为重要意义.首先探讨了工艺危险和要害部位,确认装置主要风险为火灾、爆炸和毒性危害;然后应用HAZOP方法,以加氢反应进料加热炉、烷基化反应器为分析对象,研究了工艺状态参数温度、压力、物料流量等方面出现偏差的原因、后果及安全措施;还对氢气泄漏发生火灾、爆炸和苯泄漏发生火灾、爆炸、人员中毒进行了事故后果定量分析,提出了相应的安全措施,以消除或降低工艺危险,保障装置安全.     

Fire and explosion disasters occurred due to the Great East Japan Earthquake (March 11, 2011)

The Great East Japan Earthquake (magnitude 9.0 Mw: the moment magnitude scale, based on the seismic moment of the earthquake) occurred at 14:46, March 11, 2011. It triggered huge tsunami waves (seismic sea waves) that reached heights of up to about 20 m. In this paper, the fire and explosion disasters occurred due to the Great East Japan Earthquake are reported shortly. Some fires occurred in seacoast areas after tsunami attacks and some of them were spreading very widely to the tsunami flooded areas. It is important to study the mechanisms of such fires (tsunami fires) for preparing huge tsunami. After the earthquake, a very severe accident happened in the Fukushima Daiichi nuclear power plant. Three reactors experienced full meltdown. During this disaster, hydrogen explosions occurred and made the situation more serious. It has to be realized once again that the countermeasures for hydrogen explosions is indispensable. Also Large scale BLEVEs (Boiling Liquid Expanding Vapor Explosions) happened at LPG storage area in an oil refinery in Chiba Prefecture. This accident started from the falling down of an LPG storage tank by earthquake motions. The tank was heavier than usual, as it was filled with water (1.7 times heavier than LPG) for periodic inspection. Considering these disasters, we have to think about how we prepare the accident of low probability and of very severe consequence. Recently, the risk based approach is widely utilized. However, for such disasters it seems not enough to perform safety management only by risk based approach. Not only probabilistic approach (Risk), but also deterministic approach (Emergency plan, Mitigation technique) should be taken in account.