Explosibility of cork dust in methane/air mixtures

Explosibility studies of hybrid methane/air/cork dust mixtures were carried out in a near-spherical 22.7 L explosibility test chamber, using 2500 J pyrotechnic ignitors. The suspension dust burned as methane/air/dust clouds and the uniformity of the cork dust dispersion inside the chamber was evaluated through optical dust probes and during the explosion the pressure and the temperature evolution inside the reactor were measured. Tested dust particles had mass median diameter of 71.3 μm and the covered dust cloud concentration was up to 550 g/m³. Measured explosions parameters included minimum explosion concentration, maximum explosion pressures and maximum rate of pressure rise. The cork dust explosion behavior in hybrid methane/air mixtures was studied for atmospheres with 1.98 and 3.5% (v/v) of methane. The effect of methane content on the explosions characteristic parameters was evaluated. The conclusion is that the risk and explosion danger rises with the increase of methane concentration characterized by the reduction of the minimum dust explosion concentration, as methane content increases in the atmosphere. The maximum explosion pressure is not very much sensitive to the methane content and only for the system with 3.5% (v/v) of methane it was observed an increase of maximum rate of pressure rise, when compared with the value obtained for the air/dust system.     

Vented confined explosions in Stramberk experimental mine and AutoReaGas simulation

Research Mining Institute, Inc., Ostrava-Radvanice, in cooperation with Dept. of Theory And Technology of Explosives of University of Pardubice and Klokner Institute of CTU in Prague, has performed three series of experiments examining methane–air mixture explosions and their impact on 14 and 29 cm thick wall. The project was named ‘Modeling Pressure Fields Effects on Engineering Structures During Accidental Explosions of Gases in Buildings’ and was sponsored by Grant Agency of Czech Republic (project No. 103/01/0039). The project is aimed at deeper understanding of pressure field effect upon the structures. Methane-air mixture explosion was used to generate the blast wave. The geometrical configuration of the environment resembled a room of an average size, such as larger kitchen. Preliminary simulations were made by AutoReaGas code (Century Dynamics and TNO). The design phase was followed by tests in an experimental mine in Stramberk. Two masonry dams were build in the mine, with cross-section areas of 10.2 m² and longitudinal distance of 5.7 m, creating an explosion chamber with a volume of 58 m³. Two vent openings with an adjustable free cross-section were used to control the maximum overpressure inside the chamber. The concentration of methane-air mixture was approximately 9.5% (vol.) and the volumes of the clouds were 5.25, 10.2 and 15.3 m³ respectively. The generated blast wave overpressures inside the chamber ranged between 1 and 150 kPa. According to experimental results a calibration of the code was performed. After the calibration it is possible to make relatively accurate simulations in similar geometry and to calculate the pressure loading of the structure at any spot in the simulated space. This paper describes the experiments performed and compares experimental and computational results.     

Experimental simulation of airbag deployment for pipeline closing

Small scale tests were carried out at ISL's shock tube facility STA (100 mm inner diameter) to study the problem of closing a pipeline by means of an airbag in case of explosions or gas leakages. Experiments were carried out to simulate the flow in a pipeline at velocities and gas pressures as present in pipeline flows. In this study the gas used was nitrogen at static pressures of 0.2 up to 5 MPa and at flow velocities of 25 m/s up to 170 m/s. A special Nylon airbag, deployed from the tube wall into the pipe, was used to simulate the airbag inflation in a real pipeline. For this purpose a special gas filling system consisting of a gas generator with a reservoir volume of up to 500 cm³ which permits air pressures up to 17 MPa to be generated inside the airbag was developed at ISL. With a fast pyrotechnically opened valve the reservoir gas was released for airbag filling. The airbag inflation was triggered in such a way that it opened in nearly 3 ms into the pipe flow generated by the shock tube and continued for about 10 ms. For this application a special measuring chamber was designed and constructed with 20 measuring ports. Through two window ports, located one in front of the other, the airbag inflation could be visualized with up to 50 successive flash sparks illuminating a fast rotating film inside a drum camera. Pressure measurements using commercially available PCB pressure gauges at 9 measuring ports placed along the inner tube surface gave some hints on the behaviour of the wall pressure during airbag deployment. As a result from the experiments performed it is to conclude, that, with the Nylon airbag samples available, the pipe flow cannot be blocked by the inflating airbag. The flow forces acting on the airbag during deployment are in the shock tube experiments of the order of about 1000 N, which are not balanced by the airbags' neck, fixing it to the shock tube wall. This outcome suggests that a mechanical support is required to fix the airbag in its place during inflation.     

The effects of Crew Resource Management (CRM) training on flight attendants' safety attitudes

IntroductionA number of well-known incidents and accidents had led the aviation industry to introduce Crew Resource Management (CRM) training designed specifically for flight attendants, and joint (pilot and flight attendant) CRM training as a way to improve teamwork and communication. The development of these new CRM training programs during the 1990s highlighted the growing need for programs to be evaluated using research tools that had been validated for the flight attendant population.MethodThe FSAQ (Flight Safety Attitudes Questionnaire—Flight Attendants) was designed specifically to obtain safety attitude data from flight attendants working for an Asia–Pacific airline. Flight attendants volunteered to participate in a study before receiving CRM training (N = 563) and again (N = 526) after CRM training.ResultsAlmost half (13) of the items from the 36-item FSAQ showed highly significant changes following CRM training. Years of experience, crew position, seniority, leadership roles, flight attendant crew size, and length of route flown were all predictive of safety attitudes.Practical applicationsCRM training for flight attendants is a valuable tool for increasing positive teamwork behaviors between the flight attendant and pilot sub-groups. Joint training sessions, where flight attendants and pilots work together to find solutions to in-flight emergency scenarios, provide a particularly useful strategy in breaking down communication barriers between the two sub-groups.     

国外矿用应急救生舱技术现状

在南非、澳大利亚等矿业发达国家,应急避难室(救生舱)是一种重要的井下应急救援装备,用于在矿井事故发生后保护被困矿工,等待救援。本文对国外现有救生舱产品进行了深入的调研,对救生舱内氧气供应、有害气体去除、空气调节、环境监测、动力供应、附属装备等各主要系统的运行原理和技术指标进行了详细介绍,为分析国外救生舱技术研究现状和研发我国矿井救生舱产品提供参数依据和指导。     

Association between safety leading indicators and safety climate levels

ObjectivesThe aim of this study was to evaluate the association of leading indicators for occupational health and safety, particularly safety inspections and non-compliances, with safety climate levels.MethodsNordic Occupational Safety Climate Assessment Questionnaire was employed to evaluate safety climate in cross-sectional design. The geographically diverse population of the inspection body made it possible to conduct the survey across 10 provinces in Iran. 89 completed questionnaires were obtained with a response rate of 47%. Except for management safety justice, the internal consistency of other six dimensions was found to be acceptable (α ≥ 0.7).ResultsMean scores of dimensions ranged from 3.50 in trust in the efficacy of safety systems (SD = 0.38) to 2.98 in workers' safety priority and risk non-acceptance (SD = 0.47). Tukey HSD tests indicated a statistically significant difference of mean scores among groups undergoing different number of safety inspections and those receiving different number of non-compliances (p < 0.05), with no significant differences based on safety training man-hours and sessions (p > 0.05). Spearman's rank-order correlation showed no relationship between work experience and number of non-compliances (correlation coefficient = − 0.04, p > 0.05) and between safety training man-hours and number of non-compliances (correlation coefficient = − 0.15, p > 0.05).ConclusionsOur results indicate that safety climate levels are influenced by number of safety inspections and the resultant non-compliances.Practical applicationsFindings suggest that safety non-compliances detected as a result of conducting safety inspections could be used to monitor the safety climate state. Establishing plans to conduct scheduled safety inspections and recording findings in the form of safety non-compliance and monitoring their trend could be used to monitor levels of safety climate.     

Influence of the ignition source location on the determination of the explosion pressure at elevated initial pressures

Explosion pressures are determined for rich methane–air mixtures at initial pressures up to 30 bar and at ambient temperature. The experiments are performed in a closed spherical vessel with an internal diameter of 20 cm. Four different igniter positions were used along the vertical axis of the spherical vessel, namely at 1, 6, 11 and 18 cm from the bottom of the vessel. At high initial pressures and central ignition a sharp decrease in explosion pressures is found upon enriching the mixture, leading to a concentration range with seemingly low explosion pressures. It is found that lowering the ignition source substantially increases the explosion pressure for mixtures inside this concentration range, thereby implying that central ignition is unsuitable to determine the explosion pressure for mixtures approaching the flammability limits.     

矿用救生舱内二氧化碳净化特性研究

煤矿救生舱是在矿井下发生事故后保护被困矿工生存、等待救援的密闭舱室设备。在救援过程中,二氧化碳的处理是舱内空气净化系统的一项主要功能。本文对救生舱内二氧化碳净化装置的功率、吸收效率、药剂床层厚度等因素进行了一系列试验,确定了救生舱二氧化碳的最优净化方式,并通过救生舱内真人生存试验对其进行了验证。最终得出救生舱内处理二氧化碳最佳反应条件为:药剂量20kg,最佳功率为100W;间歇式工作的运行时间与停机时间比例为2:3;在救生舱内8人生存模拟实验中,得出8kg药剂可供8人使用6.1h,平均吸收速率为1.34L/min。     

Determination of explosion parameters of methane-air mixtures in the chamber of 40 dm3 at normal and elevated temperature

The experimental results of the measurements of the explosion pressure and rate of explosion pressure rise as a function of molar methane concentration in the mixture with air in the 40 dm³ explosion chamber are presented. The research was aimed at determination of the explosion limits, according to the EU Standard. The influence of initial temperature of the mixture (changing in the range of 293–473 K) on the fundamental explosion parameters was also investigated. The ignition source was an induction electrical spark of the power equal to approximately 10 W. It was stated, that the increase of initial temperature of the methane-air mixture causes a significant increase of the explosion range.     

Application of Modified Carbon Anodes in Microbial Fuel Cells

The effect of different carbon anodes was examined in a new design of single chambered microbial fuel cell (SCMFC). The new cell design used a low-cost hydrophilic membrane to replace costly proton exchange membranes and carbon felt and a range of carbon and modified carbon anodes were investigated. The fuel for the SCMFC was brewery wastewater which was diluted with domestic wastewater and the presented microflora acts as a source of electro-active bacteria. The membrane acts as a separator between the anode chamber and an air cathode and allows the transfer of ions based on the wastewater's natural conductivity. The air cathode was carbon black (Ketjen Black EC 300J) which was deposited (1 mg cm⁻² concentration) directly onto the surface of the separator (one side of the membrane). Steady state polarization demonstrated maximum power densities of up to 30 mW m⁻² and a steady state power density of 20 mW cm⁻² at a current density of 110 mA m⁻² was achieved. The best performing anodes were made from carbon modified with quinone/quinoid groups. With unmodified graphite felt (the control anode material) as anode, the maximal power density obtained was 9.5 mW m⁻².     

The FarmSafe Programme in New Zealand: Process evaluation of year one (2003)

A national programme to raise awareness of safety issues for farmers and farmworkers and reduce farmwork-related injuries (FarmSafe) has been implemented in New Zealand since late 2002. The aims of this paper are to describe the implementation of the first stage of this FarmSafe Programme in 2003, present findings from the process evaluation for the first stage, and place this evaluation in the context of a larger and longer-term evaluation programme. Semi-structured interviews were conducted with key members of the five agencies responsible for the programme, with workshop facilitators (n = 6), and with farmers and farmworkers (n = 29) who had participated in the first stage workshop (FarmSafe Awareness workshop). All workshop evaluation forms were analysed for workshop and facilitator quality. Participant numbers (n = 6341) in the FarmSafe workshop exceeded expectations for 2003. Methods of recruitment, and organisational structure and support were major contributors to high participation in the workshop, as was the ongoing quality of the workshop offered. This process evaluation indicates the programme was successful in achieving widespread participation in a safety training programme within an industry that is predominantly one of self-employment or small businesses, and that is renowned for its independence and geographical isolation.     

新型矿用救生舱空气调节系统研究与设计

救生舱是有效减少井下各种灾害导致人员伤亡的安全设施设备,调节救生舱内的温度是保障矿工生存的重要措施。通过对矿用救生舱热负荷的分析计算和矿用救生舱空气调节系统研究现状的分析,设计了以液态二氧化碳相变制冷为基础的两种空气调节系统,可在无需电力驱动、相对狭小空间配套的情况下,适合作为救生舱的空气调节系统。该系统的研发将会解决矿用救生舱在无电力驱动情况下的温度调节问题。     

Experiments on the influence of pre-ignition turbulence on vented gas and dust explosions

Experiments were performed on the influence of pre-ignition turbulence on the course of vented gas and dust explosions. A vertical cylindrical explosion chamber of approximately 100 l volume and a length-to-diameter ratio (l/d) of 4.7 consisting of a steel bottom segment and three glass sections connected by steel flanges was used to perform the experiments. Sixteen small fans evenly distributed within the chamber produced turbulent fluctuations from 0 to 0.45 m/s. A Laser-Doppler-anemometer (LDA) was used to measure the flow and turbulence fields. During the experiments the pressure and in the case of dust explosions the dust concentration were measured. In addition, the flame propagation was observed by a high-speed video camera. A propane/nitrogen/oxygen mixture was used for the gas explosion experiments, while the dust explosions were produced by a cornstarch/air mixture.It turned out that the reduced explosion pressure increased with increasing turbulence intensity. This effect was most pronounced for small vents with low activation pressures, e.g. for bursting disks made from polyethylene foil. In this case, the overpressure at an initial turbulence of 0.45 m/s was twice that for zero initial turbulence.     

Continuous nitrifying granular sludge bioreactor: Influence of aeration and ammonium loading rate

Granulation of nitrifying bacteria was investigated in a continuous bubble column bioreactor. Then, the combined effect of aeration and ammonium loading rates on dissolved oxygen (DO) concentration as well as nitrification process was evaluated in the system using an experimental design technique. After 120 days, stable nitrifying granules with average diameter of 1.4 mm and settling velocities of 55 m/h were obtained. The influence of increasing ammonium loading rate (ALR) was found to be more significant than decreasing aeration rate on the reduction of DO concentration inside the nitrifying bioreactor. The system could handle the ALR values of 0.48–1.92 gNH₄⁺-N/L d with the ammonium removal efficiency from 65% to nearly 100% at the tested airflow rates of 2.5 and 4.5 L/min. At the low aeration, the complete ammonium conversion to nitrate was replaced with nitrite when the ALR increased to 1.44 gNH₄⁺-N/L d. At the high aeration, however, almost complete nitrification was achieved except the high ALR in which the nitrite accumulation was observed up to 38%. The study demonstrated that the continuous bioreactor had a considerable performance for obtaining stable nitrifying granules to have nitrite accumulation under control with changing the ratio of aeration rate and ALR.     

Dehydration of ethanol with different salts in a packed distillation column

This work aimed the evaluation of a saline extractive distillation for the ethanol production. A thermodynamic model was used to predict the influence of the salts in the liquid–vapor equilibrium of the system water–ethanol and inside the packed column. The experiments were done in a distillation unit, with an internal diameter of 5.9 cm and a packing section with 37 cm of height, packed with raschig rings with 0.73 cm of characteristic inner made of glass. All the bottom and top samples were analyzed by refractive index. Two synthetic charges with the same composition of ethanol that are produced in the refinery (0.02 and 0.25 mol.L^-1) were distilled under atmospheric pressure. Sodium chloride, calcium chloride, potassium acetate, calcium nitrate and a mixture of sodium and potassium acetates were added to the synthetic charges and the results were compared to the experiments already done without the presence of the salts, revealing the ethanol enrichment in the top product of the distillation unit, for all the systems analyzed. Another charge from the refinery, known as load of wine without yeast, was evaluated and the results indicated the same behavior, enriching the ethanol with the application of the saline extractive distillation.     

Flammability envelopes for methanol,ethanol, acetonitrile and toluene

The flammability envelope was experimentally determined up to the point of vapor saturation for four flammable liquids: methanol, ethanol, acetonitrile, and toluene. The experimental apparatus consisted of a 20-L spherical chamber with a centrally located 10 J fuse wire igniter. The liquid was injected and vaporized into the chamber via a septum and a precision syringe. Nitrogen and oxygen were mixed from pure components using a precision pressure gauge. Pressure versus time data were measured for each ignition test. Flammability was defined as any ignition resulting in an increase in pressure of 7% over the initial pressure, as per ASTM E 918–83. All data were obtained at an initial temperature of 298 K and 1 atm. The experimental values of the LFL agreed well with published values. Limiting oxygen concentrations (LOC) were also determined—although these were somewhat lower than published values.The calculated adiabatic flame temperature (CAFT) method was used to model the data using a threshold temperature of 1200 K. A reasonable fit of the flammability envelope was obtained, although this could be improved with a higher threshold temperature.     

Artificial neural network modelling of As(III) removal from water by novel hybrid material

The present study reported a method for removal of As(III) from water solution by a novel hybrid material (Ce-HAHCl). The hybrid material was synthesized by sol–gel method and was characterized by XRD, FTIR, SEM–EDS and TGA–DTA. Batch adsorption experiments were conducted as a function of different variables like adsorbent dose, pH, contact time, agitation speed, initial concentration and temperature. The experimental studies revealed that maximum removal percentage is 98.85 at optimum condition: pH = 5.0, agitation speed = 180 rpm, temperature = 60 °C and contact time = 80 min using 9 g L⁻¹ of adsorbent dose for initial As(III) concentration of 10 mg L⁻¹. Using adsorbent dose of 10 g L⁻¹, the maximum removal percentage remains same with initial As(III) concentration of 25 mg L⁻¹ (or 50 mg L⁻¹). The maximum adsorption capacity of the material is found to be 182.6 mg g⁻¹. Subsequently, the experimental results are used for developing a valid model based on back propagation (BP) learning algorithm with artificial neural networking (BP-ANN) for prediction of removal efficiency. The adequacy of the model (BP-ANN) is checked by value of the absolute relative percentage error (0.293) and correlation coefficient (R² = 0.975). Comparison of experimental and predictive model results show that the model can predict the adsorption efficiency with acceptable accuracy.     

Characterization of heavy metals in fly ash from municipal solid waste incinerators in Shanghai

This study aims to develop a methodology for analysis of characteristics of heavy metals in MSWI fly ash. It performed analysis of composition of heavy metals, leaching toxicity, leaching behavior as a function of pH, specification distribution and corresponding mineral components of residue derived from each step of the sequential extraction. It is found that content of heavy metals follows the sequence of Zn > Pb > Cu > Cr > As > Ni > Cd approximately Hg in both plants, and that total heavy metals account for less than 1% by mass of fly ash. Major hazardous heavy metals in fly ash are As, Cd, Hg, Pb and Zn, whose leaching ratios exceed the limit value described in hazardous waste identification standard. Measured leaching results of Cu, Pb and Zn are essentially consistent with the simulated results at pH between 0 and 13. Content of calcium-silicates, alumino-silicates and glass phases in residue derived from sequential extraction procedure increases steadily from the first step to the fifth step of the sequential extraction procedure. Cu, As, Cr, Hg, Cd, and Ni, relatively stable under strong basic conditions, can be leached out under strong acidic conditions, while Zn and Pb tend to be leached out under both strong acidic and basic conditions.     

Using a cluster randomized controlled trial to determine the effects of intervention of battery and hardwired smoke alarms in New South Wales,Australia: Home fire safety checks pilot program

IntroductionIn 2014, Fire & Rescue New South Wales piloted the delivery of its home fire safety checks program (HFSC) aimed at engaging and educating targeted top “at risk” groups to prevent and prepare for fire. This pilot study aimed to assess the effectiveness of smoke alarms using a cluster randomized controlled trial.MethodsSurvey questionnaires were distributed to the households that had participated in the HFSC program (intervention group). A separate survey questionnaire was distributed to the control group that was identified with similar characteristics to the intervention group in the same suburb. To adjust for potential clustering effects, generalized estimation equations with a log link were used.ResultsMultivariable analyses revealed that battery and hardwired smoking alarm usage increased by 9% and 3% respectively among the intervention group compared to the control group. Females were more likely to install battery smoke alarms than males. Respondents who possessed a certificate or diploma (AOR = 1.31, 95% CI 1.00–1.70, P = 0.047) and those who were educated up to years 8–12 (AOR = 1.32, 95% CI 1.06–1.64, P = 0.012) were significantly more likely to install battery smoke alarms than those who completed bachelor degrees. Conversely, holders of a certificate or diploma and people who were educated up to years 8–12 were 31% (AOR = 0.69, 95% CI 0.52–0.93, P = 0.014) and 24% (AOR = 0.76, 95% CI 0.60–0.95, P = 0.015) significantly less likely to install a hardwired smoke alarm compared to those who completed bachelor degrees.ConclusionsThis pilot study provided evidence of the benefit of the HFSC in New South Wales. Practical Applications: Fire safety intervention programs, like HFSC, need to be targeted to male adults with lower level of schooling even when they are aware of their risks.