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.     

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.     

Hazard evaluation of hydrogen–air deflagration with flame propagation velocity measurement by image velocimetry using brightness subtraction

Deflagration phenomena in hydrogen–air mixtures initially filled in 1.4 m³ spherical latex balloons were measured using a high-speed digital video camera and pressure transducers. The image velocimetry using brightness subtraction was introduced to eliminate the background effects for obtaining accurate time evolution records of flame propagation velocity. The maximum flame propagation velocity of about 100 m/s was observed with maximum overpressure 15 kPa at 1 m from ignition point. According to the detailed flame propagation velocity records, there were long deceleration durations. The observed maximum overpressure was smaller than the overpressure estimated by the basis of the observed maximum flame propagation velocity and the pressure wave theories of spherical flames. A new blast curve plot of scaled overpressure vs. distance was tentatively proposed.     

水泥窑用低氮燃烧器燃烧特性的试验研究

基于水泥生产线NO_x排放机理及控制方法,设计、研发了一种新型水泥窑用低氮燃烧器,并分析了天然气、煤制气及混合气的燃烧特性及其污染物的排放特性。结果表明:在过量空气系数α为1.2、二次风占比β为0.6时,新型低氮燃烧器燃烧天然气的效果较好,NO_x排放量为53 mg/m³,CO排放量为22 mg/m³;在相同燃烧条件下,煤制气燃烧温度及NO_x排放量比天然气高,CO排放量低于天然气;在过量空气系数α为1.2、二次风占比β为0.8时,NO_x排放量为57 mg/m³,CO排放量为6 mg/m³;天然气和煤制气掺烧时,其燃烧特性介于两者之间,且掺烧煤制气可提高天然气的燃烧速率。     

家庭厨余垃圾分布式就地厌氧消化工艺及效果研究

针对厨余垃圾收运后集中处理模式的收集难、成本高的问题,设计了分布式就地厌氧消化工艺,用研制的设备进行半连续试验.运行80 d左右趋于稳定,稳定后的VS去除率高于60％;VS进料产气率、VS进料甲烷产率分别为0.444 m3/kg VS、0.245 m3/kg VS,VS去除产气率、VS去除甲烷产率分别为0.737 m3...     

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.     

Determination of the maximum effective burning velocity of dust–air mixtures in constant volume combustion

The reactivity of a combustible dust cloud is traditionally characterized by the so-called K_St value, defined as the maximum rate of pressure rise measured in constant volume explosion vessels, multiplied with the cube root of the vessel volume. The present paper explores the use of an alternative parameter, called the maximum effective burning velocity (u_eff,max), which also is derived from pressure–time histories obtained in constant volume explosion experiments. The proposed parameter describes the reactivity of fuel–air mixtures as a function of the dispersion-induced turbulence intensity. Procedures for estimating u_eff,max from tests in both spherical and cylindrical explosion vessels are outlined, and examples of calculated values for various fuel–air mixtures in closed vessels of different sizes and shapes are presented. Tested fuels include a mixture of 7.5% methane in air, and suspensions of 500 g/m³ cornstarch in air and 500 g/m³ coal dust in air. Three different test vessels have been used: a 20-l spherical vessel and two cylindrical vessels, 7 and 22 l. The results show that the estimated maximum effective burning velocities are less apparatus dependent than the corresponding K_St values.     

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)。     

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.     

避难硐室气体防毒安全性研究

为研究灾变时期井下避难硐室进出口有毒气体CO入侵弥散问题,基于等效原理,利用Gambit软件建立地面钻孔正压通风避难硐室物理模型和开门状态下有毒气体进入避难硐室的流体力学原理及气体弥散数学模型,并利用Fluent软件模拟钻孔压风量与室内CO浓度变化关系,提出在避难硐室的隔离门前加装门衬的办法,使避难人员穿过避难硐室门时...     

海州露天矿采空区地表CO2通量的试验研究

为探究海州露天矿东邦废弃采空区自然发火状态,基于采空区遗煤自燃特性和气体扩散理论,采用智能土壤气体通量监测系统,以月为单位,对东邦自燃采空区上覆地表CO₂通量开展长周期、多测点连续性监测试验;根据试验区域内地表CO₂通量和土壤温度分布特征,探究地下火区释放CO₂的地表涌出范围和变化情况;同时,着眼于温室气体排放的评估,计算试验区域内的CO₂涌出量,并分析其随时间的变化特征。结果表明:地表CO₂通量与土壤温度有明显正相关性;试验区域地表CO₂高通量区域呈逐月扩大和递增的趋势;CO₂涌出量随月份逐渐递增,试验区域年CO₂涌出量约为3.6×10⁶ m³。     

An influence of oxygen content in an oxidizing atmosphere on inhibitive action of fluorinated agents on a hydrogen flame

An experimental investigation of the influence of inhibitors of various chemical natures on flammability limits in mixtures H₂+oxidizer (O₂+N₂)–suppressant (C₂HF₅; CHF₃; C₄F₁₀; inhibitor AKM, which is a mixture of olefins) was carried out. Compositions of N₂ and O₂ with elevated (25 vol%) and reduced (15 vol%) oxygen concentrations and air were used as oxidizing atmospheres. Experiments were done at room temperature and atmospheric pressure. Flammability limits were determined in a closed vessel of volume of 4.2 dm³ (internal diameter 20 cm). Mixtures were prepared immediately in the preliminary evacuated reaction vessel by partial pressures. The mixtures were ignited by an electrical spark of energy near 1 J in the center of the reaction vessel. A flame propagation was detected by a pressure transducer. Twelve flammability curves were measured, which allowed to compare effectiveness of the inhibitors at various oxygen contents in the atmosphere. A qualitative analysis of the obtained results was done, which showed an important role of an inhibitor regeneration.     

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.     

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.     

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.     

掘进巷道停风期间瓦斯超限应急处置技术研究*

为解决掘进巷道停风导致的瓦斯浓度超限问题,提出1种利用瓦斯抽采管路进行局部抽出式通风的应急处置技术措施,并采用理论分析与数值模拟相结合的方法,对比分析掘进巷道停风期间采取应急处置技术前后的掘进巷道瓦斯浓度分布规律和防治效果。结果表明:对掘进巷道内现有的瓦斯抽采管路进行改造,在掘进巷道停风情况下利用瓦斯抽采管路中的负压对掘进巷道进行临时抽出式通风是1种有效的瓦斯超限应急处置技术;负压通风量的大小应依据生产现场的实际状况进行决定,掘进巷道若能在37 s内恢复正常通风,则可选取较小的负压通风量(5 m³/min)进行临时通风;若超过37 s仍不能恢复正常通风,则应选取较大的负压通风量(>5 m³/min)进行临时通风。     

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.     

重庆市“蓝天行动”的历史回顾与新一轮实施发展

通过对2005年以来重庆市“蓝天行动”实施的历史回顾,梳理和总结出重庆市环境空气污染治理监管的成果和经验,并提出了新一轮“蓝天行动”(2018—2022年)以控制细颗粒物PM_2.5污染和减少臭氧污染为重点,以降低氮氧化物浓度为突破点,坚持全民共治、源头防治为目标,制定了“四控两增”针对性的防治工程措施。截止2020年,重庆市优良天数达到333天,PM_2.5年均浓度达到33μg/m³,空气质量评价六项指标首次实现有监测记录以来全部达标,为历史最好水平。     

生物锰氧化物对4种重金属的吸附特性研究

通过培养锰氧化细菌Sphingopyxis sp.4-15,制备生物锰氧化物,研究了生物锰氧化物的结构性质及其在不同影响因素下对4种重金属Cu、Zn、Cr和As的吸附特性。结果表明该生物锰氧化物中含有MnO₂、Mn₃O₄和MnO等晶体锰氧化物,包裹在菌体细胞表面呈现出规则的花球状。其锰主要以高价态的Mn⁴⁺和Mn³⁺形式存在,平均孔径为35.56 nm,比表面积为41.49 m²/g。锰氧化物对重金属的吸附过程受pH值影响,最适pH值为4~6;离子强度对吸附过程干扰较小;升高温度有利于其对Cu和Zn的吸附,而对As的吸附产生抑制;锰氧化物对Cu(Ⅱ)、Zn(Ⅱ)、As(Ⅲ)的吸附在反应360 min时可达到平衡,对Cr(Ⅲ)的吸附在反应5 min内达到平衡;在4种重金属最大初始浓度下,生物锰氧化物对Cu(Ⅱ)、Zn(Ⅱ)、Cr(Ⅲ)、As(Ⅲ)的吸附量依次为:70.184、15.140、9.141、0.089 mg/g,具有较大的重金属吸附容量。