查看更多>>摘要：To investigate the effect of initial temperature, initial vessel pressure and the ratio of hydrogen in the syngas on the spontaneous ignition of high-pressure syngas release, a series of experiments was conducted. The influence law and mechanism of the spontaneous ignition was investigated. The experimental results showed that the pressure in the tube presented an oscillating rise and then a slow decline after high-pressure syngas release. The pressure peak (Pmax) in positions 1 and 2 were 3.215 MPa and 2.620 MPa respectively when the initial vessel pressure was 6.0 MPa. With the increase of the initial temperature and pressure, the syngas shock wave in the tube propagated faster and the pressure peak reached was higher. The Pmax in positions 1 and 2 increased from 1.900 MPa to 1.605 MPa–3.851 MPa and 3.385 MPa respectively with the initial vessel pressure increasing from 3.0 MPa to 7.0 MPa at a temperature of 20 °C. As the initial temperature increased, the critical pressure required for syngas to spontaneous ignition became lower. The numerical simulation results showed that the flow velocity and turbulent kinetic energy of the flow increased with the initial temperature, initial vessel pressure and the ratio of hydrogen in the syngas increased. The maximum temperature rose gradually and spontaneous ignition occurred in a forward direction. In addition, spontaneous ignition was more likely to occur in the tube.
查看更多>>摘要：Pipelines are one of the least expensive means of transporting fluids in long distances and distributing fluids in large areas and cities. Fluids transported and distributed by pipelines are often potentially hazardous, can pollute the environment, and are of high economic value. As such, monitoring these pipelines to predict and detect leakage accurately and promptly, and to determine the location of the leak is of importance. This article reviews and evaluates existing computational methods of pipeline leakage detection and puts recent advances in this area into perspective. The methods are of the following types: mass/volume balance, negative pressure wave, pressure point analysis, statistical methods, and real-time transient modeling. The strengths, weaknesses, and limitations of the five types are discussed in terms of the person-hours that they need to detect a leak, and the certainty and speed of the leakage detection and localization. Future outlook for this field is also provided. To substantiate the evaluation, three of these methods are implemented and tested in a pipeline case study.
查看更多>>摘要：MIKE III apparatus tests were conducted to investigate the minimum ignition energy (MIE) of coal dusts in air and O2/CO2 atmospheres with and without small amount of CH4/H2. The O2 mole fraction (XO2) in the gas mixtures varied from 21% to 50% with the CH4/H2 mole fraction from 0 to 2%. Experimental result showed that MIE of coal dusts significantly decreases even by three orders of magnitude in mJ with increasing XO2 and the addition of CH4/H2. Compared with CH4, H2 had a relatively strong promotion effect on the spark ignition of coal dusts. The inhibiting effect of CO2 was found to be much stronger than N2, but this inhibiting effect of CO2 could be eliminated by 9% increment of XO2. The effect on MIE of coal dusts thus followed by the order: 9% increment of XO2 > CO2 replacing N2 > 2% CH4 or H2 addition. Moreover, two empirical models were used to estimate the MIE of hybrid dust-gas mixture (HMIE), and the results showed that calculated data can well reflect the promoting effect of elevated XO2 and flammable gas addition, and the inhibiting effect of inert gas.
查看更多>>摘要：Autoignition temperature is defined as the minimum temperature at which a fuel will spontaneously combust in air without an ignition source. Although autoignition temperatures are essential information for the safe handling of fuels, reported literature values are widely variable. In the context of process safety, the need for an improved understanding of autoignition phenomenon is made apparent by the continuing occurrence of autoignition incidents in the process industries. This publication seeks to address some shortcomings in the combustion literature with respect to this topic. In this study, the autoignition characteristics of three paraffins and three alcohols were determined using the ASTM E659 method. In particular, each fuel's autoignition temperature was determined in both quartz and borosilicate test flasks. In the case of each fuel, autoignition temperatures were found to be independent of glassware and well within the margins of experimental error and the spread in reported literature values. Although autoignition temperatures for each fuel were consistent between flask types, this study shows that some fuels' overall ignition behavior changed between quartz and borosilicate glassware. To that end, this work presents shortcomings in the ASTM E659 standard and provides suggestions for improvements.
查看更多>>摘要：Battery transportation and storage is an important part in the whole lifespan of batteries. It's significant to make a way to assess the fire risk of batteries during transportation and storage preventing from fire accident. This study presents a novel fire risk assessment method for lithium-ion batteries during transportation and storage. 8 possible failure paths and 9 basic events are deduced by fault tree analysis method. Likehood, severity, and hazard control number are selected as indexes for assessing the hazard risk number (HRN) of each possible failure path and fire accident. To comprehensively assess the value of these indexes, corrosponding sub-indexes are proposed and analyzed by synthesis through fuzzy logic method. To ensure the safety of batteries, four parameters including the synthesis HRN, HRNs of all possible paths, likelihood and severity of all basic events are suggested to set the limitation. The case study of battery transportation by marine verified the proposed method can accurately assess fire risk and locate the possible problems.
查看更多>>摘要：Natural gas pipeline in utility tunnels has been leading to great concern because of potential hazards characterized by flammability and explosives, which could pose a grave threat to the safe operation of utility tunnels and even surrounding facilities. Therefore, revealing the dynamic process of natural gas explosion in utility tunnels is quite important for the consequence analysis and risk assessment, especially in such complex scenarios with various facilities. In this study, a kind of porous material with low cost (porous iron-nickel materials) was selected and crosswise arranged to investigate its explosion-proof effects on the natural gas explosion in utility tunnels. The results demonstrate that porous iron-nickel materials have obvious suppression effects on the gas explosion process. The maximum overpressure decreases from 0.3898 Mpa to 0.2778 Mpa and the maximum flame front velocity decreases from 66.67 m/s to 37.51 m/s. It is also found that the inhibition effect of porous materials on explosion overpressure and fame front velocity increase with the increase of the number of holes in porous materials. This study is helpful to consequence assessment and risk analysis of natural gas explosion accidents in utility tunnels.
查看更多>>摘要：Fuel in aircraft fuel tanks, as well as some industrial processes, are under conditions of reduced pressure. However, few models have been proposed for estimating the influence of the initial pressure on flammability limits at subatmospheric pressures. A model to describe this influence was derived in this study according to the assumption that the heat release rate is equal to the heat loss rate. Several assumptions used in the model simplification process were verified to accord with real situations. The experimental data on seven gaseous fuels, namely methane, ethane, ethylene, propane, propylene, n-butane, and n-butylene, were analysed to validate the proposed model. In general, the simulation results accord well with the data on flammability limits measured at subatmospheric pressures. In its extension to systems functioning at elevated pressures, the proposed model accurately estimated the lower flammability limit data for atmospheric pressures up to 30 MPa and the upper flammability limit (UFL) for atmospheric pressures from 0.1 to 0.9 MPa. However, large deviations were noted between the estimated and actual UFLs for atmospheric pressures from 0.1 to 24.9 MPa. Nevertheless, the proposed model accurately describes the variation trends of flammability limits over a wide pressure range.
查看更多>>摘要：The explosion characteristics of propane-dimethyl ether blends were investigated using a 20-L spherical explosion vessel. The effects of dimethyl ether (DME) addition and equivalence ratio were explored. The results indicated the maximum pressure and maximum pressure rising rate increased with the addition of dimethyl ether and reached maximum value under the equivalence ratio of 1.2. The time to reach maximum explosion pressure showed the opposite effect. The effect of initial temperature and pressure on explosion characteristics of propane with 30% dimethyl ether blending ratio was studied under the equivalence ratio of 1.0. The results indicated that elevated initial pressure increased the maximum explosion pressure and the maximum pressure rising rate, but had little effect on the time to reach maximum explosion pressure. Increasing the initial temperature reduced the maximum explosion pressure and the time to reach maximum explosion pressure. The maximum pressure rising rate was approximately 38 MPa s?1 when the initial temperature was raised from 30 to 120 °C. CHEMKIN software and the theoretical model calculated the maximum explosion pressure to compare with experimental results.
查看更多>>摘要：The risk assessment of chemical clusters faces two challenges. First, the synergistic effects in chemical accidents introduce nonlinearity into the risk. The second challenge is the lack of cooperation and information exchange. A novel method for risk assessment in chemical clusters with the application of a Choquet integral and a multiple linear regression model, is proposed to overcome the challenges in this paper. This method is intended to achieve non-linear risk assessment and determine the distribution of individual risk in chemical clusters without significantly increasing the investment in cooperation and communication between companies. The application of the fuzzy measure and the Choquet integral enables the consideration of the synergistic effects. To evaluate the effectiveness of the method, a cluster of gas stations in Hefei, China, was used as a case study. The risk in chemical clusters was found to increase due to the domino and synergistic effects. The lack of cooperation and information exchange in such clusters leads to the disregard of the domino and synergistic effects and the underestimation of the risk. The new risk assessment method can provide guidance for the process safety, accident prevention, and land-use planning in chemical clusters.
查看更多>>摘要：Long-distance oil and gas pipelines undergo great changes in natural environments and geographical conditions along length. Inadequate communications provided limited and vague information about accidents. Scattered emergency resources need adequate response preparations to reduce recovery time after an accident. Examining historic similar cases in the database in order to propose effectual accident responses is worth studying. In emergency response case-based reasoning (CBR), information on new accidents, such as type, degree, hazard object, etc. need to be as detailed as possible. The anticipated quality and efficiency of traditionally case recommendations might have been directly negatively influenced, by the delayed and ambiguous information available from new pipeline accidents. Thus, to fully extract the required information, and to minimize limitations on reasoning caused by a lack of accident information, this study proposes an accident Case Representation Model. The model contains: (i) an accident features dataset featuring a bipartite graph from hundreds of pipeline cases, and (ii) cases vectorization obtained by applying graph representation learning. As a result, (iii) recommendations of any new accident can be given based on similar case responses. In order to examine the accuracy of the recommended results, a relative similarity concept is proposed, showing that the proposed model's recommendation accuracy is basically maintained at 96.7%. Compared to other case vectorization methods, the accuracy increased by 4%–23%. Taking a block valve failure accident as a case study, this model expands on two related scenarios: overpressure in upstream pipeline and interruption of communication system. The supplementary responses increase the preparation comprehensiveness.
NSTL
Elsevier