Influence of super-absorbent polymer on the growth rate of gas hydrate

The growth rate of hydrate and morphology of methane hydrate formation were studied in a visual pressure cell at 5.5 MPa. The gas hydrate formation was carried out (coal mine methane (CMM) + tetrahydrofuran (THF) + sodium dodecyl sulphate (SDS) + H₂O) with and without SAP. Experimental data on the hydrate growth rate and induction time were obtained for three different CMM samples. The influence of SAP on hydrate growth rate was determined. Results showed that after the addition of SAP, with the methane concentration increased in CMM, the induction time was reduced by 9 min, 10 min and 3 min, and the growth rate was shortened by 0.56 × 10⁻⁶/m³ min⁻¹, 0.53 × 10⁻⁶/m³ min⁻¹ and 1.42 × 10⁻⁶/m³ min⁻¹, respectively. This study could be useful for the recovery of methane from CMM by forming hydrate in the chemical and mining industry.     

Research and practice on fluctuation water injection technology at low permeability coal seam

In order to solve the problem of poor affusion effect on low permeability coal seam, the paper analyzes the micro process of the coal seam water infusion in wetting coal and determines the main factors affecting coal seam water infusion. The permeability of the NO.3 coal seam in east working face of Xingcun coal mine by MTS815.03 servo-controlled rock mechanical test system has been tested. Results show that when the peak stress in coal sample specimens reaches 48.53 MPa, permeability ranges from 0.5158 to 2.9576 × 10⁻⁸ Darcy, and it means that the coal seam is low in permeability and difficult in water injection. Based on the characteristics of low permeability and geostress situation, efficient fluctuation water injection technology with permeable agent and relevant process parameters have been designed. The surface tension of the permeable agent developed here is 31.18 m N/m when mass concentration reaches 0.05%. The permeable agent can permeate into 2 cm thick coal layer completely in 10 s, thus improving the wettability of water effectively and the water injection pressure fluctuates between 7 MPa and 25 MPa. The application of the technique in the 3rd coal seam in east working face of Xingcun coal mine shows not only single-arch injection experienced a significant increase on average, from no more than 10 m³ to 63.3886 m³, but also the effect of dust fall, cooling and rock burst prevention is remarkable.     

Prediction of minimum ignition energy of aerosols using flame kernel modeling combined with flame front propagation theory

Flammable aerosols have created many fire and explosion hazards in the process industry, but the flammability of aerosols has not been fully understood. The minimum ignition energy has been widely used as an indicator for flammability of combustible mixtures, but the amount of experimental data on the minimum ignition energy of aerosols is very limited. In this work, the minimum ignition energy of tetralin aerosols is predicted using an integrated model. The model applies the flame front propagation theory in aerosol systems to the growth of the flame kernel, which was created during the spark discharge in the ignition process. The aerosol minimum ignition energy was defined as the minimum level of energy in the initial flame kernel to maintain the kernel temperature above the minimum ignition temperature of 1073 K specific for tetralin aerosols during the kernel growth. The minimum ignition energy obtained in the model is influenced by the fuel-air equivalence ratio and the size of the aerosol droplets. For tetralin aerosols of 40 μm diameter, E_min decreases significantly from 0.32 mJ to 4.3 × 10 e⁻³ mJ when the equivalence ratio rises from 0.57 to 1.0. For tetralin aerosols of 0.57 equivalence ratio, E_min increases from as 0.09 mJ to 0.32 mJ when the droplet diameter rises from 10 μm to 60 μm. The trends are in agreement with previous experimental observations. The method used in current work has the potential to prediction of the minimum ignition energy of aerosol.     

Experimental study of the evaporation of spreading liquid nitrogen

The investigation of cryogenic liquid pool spreading is an essential procedure to assess the hazard of cryogenic liquid usage. There is a wide range of models used to describe the spreading of a cryogenic liquid pool. Many of these models require the evaporation velocity, which has to be determined experimentally because the heat transfer process between the liquid pool and the surroundings is too complicated to be modeled. In this experimental study, to measure the evaporation velocity when the pool is spreading, liquid nitrogen was continuously released onto unconfined concrete ground. Almost all of the reported results are based on a non-spreading pool in which cryogenic liquid is instantaneously poured onto bounded ground for a very short period of time. For the precise measurement of pool spreading and evaporation weight with time, a cone-type funnel was designed to achieve a nearly constant liquid nitrogen release rate during discharge. Specifically, three nozzles with nominal flow rates of 3.4 × 10⁻² kg/s, 5.6 × 10⁻² kg/s and 9.0 × 10⁻² kg/s were used to investigate the effect of the release rate on the evaporation velocity. It is noted that information about the release rate is not necessary to measure the evaporation velocity in case of the non-spreading pool. A simultaneous measurement of the pool location using thermocouples and of the pool mass using a digital balance was carried out to measure the evaporation velocity and the pool radius. A greater release flow rate was found to result in a greater average evaporation velocity, and the evaporation velocity decreased with the spreading time and the pool radius.     

Anammox in a UASB reactor treating saline wastewater

The feasibility of an anammox (anaerobic ammonium oxidation) UASB (upflow anaerobic sludge blanket) bioreactor to treat ammonium-rich brines was investigated in batch and continuous-flow experiments. The evidence from batch tests indicated that the anammox activity was significantly inhibited under highly saline conditions while the inhibition was reversible. Saline shock loading of 30 g NaCl l⁻¹ caused a 67.5% decrease in specific anammox activity (SAA) compared to reference biomass (not exposed to salt). However, the acclimatized biomass displayed a SAA value just 45.1% lower than that of the reference biomass. When transferred from brine to freshwater, the salt-exposed biomass resumed its activity by 43.1%. Subsequent to appropriate acclimatization, careful manipulation nitrite concentration, nitrogen loading rate (NLR), and other operational parameters for 77 days, the results of continuous-flow experiment revealed that under the salinity of 30 g NaCl l⁻¹ the reactor performed well and the substrate removal capacity (nitrogen removal rate, NRR, of 448 ± 15 mgl⁻¹ d⁻¹) was comparable to the condition of freshwater (NRR of 464 ± 13 mgl⁻¹ d⁻¹). However, the anammox UASB bioreactor was prone to malfunction under transient operating conditions.     

Effects of significant damage of flame gap surfaces in flameproof electrical apparatus on flame gap efficiency

Electrical apparatus for use in the presence of explosive gas atmospheres has to be specially designed to prevent the apparatus from igniting the gas. Flameproof design is one of several options, and one requirement is then that any holes and slits in the enclosure wall be designed to prevent a possible gas explosion inside the enclosure from being transmitted to an explosive gas cloud outside it. Current standards (IEC) require that joint surfaces have a surface roughness of <6.3 μm. Any damaged joint surface has be restored to this quality. The present investigation has demonstrated that flame gap surfaces in flameproof electrical apparatuses can suffer considerable mechanical and corrosive damage before the flame gaps no longer function satisfactorily. In some cases very significant mechanical surface damage in fact improves the gap performance. This indicates that current high costs of repairing and replacing flameproof electrical apparatus in process plants offshore and onshore can be reduced considerably without any increase of the explosion risk.     

The extreme carbon dioxide outburst at the Menzengraben potash mine 7 July 1953

Carbon dioxide is an asphyxiant and an irritant gas. An extreme outburst of carbon dioxide took place 7 July 1953 in a potash mine in the former East Germany. During 25 min, a large amount of CO₂ was blown out of the mine shaft with great force. It was wind still and concentrated CO₂ accumulated in a valley leading to multiple asphyxiation casualties. Based on a review of concentration-response relationships, the location of victims, and other information, it is concluded that concentrations of 10-30% carbon dioxide may have occurred 450 m from the point of release for at least 45 min. It is concluded that 1100-3900 tonnes of CO₂ were blown out of the mine shaft, possibly with intensities around 4 tonnes/s. It is also concluded that the large majority of the gas escaped as a near-vertical high-velocity jet with only little loss of momentum due to impingement. The release was modelled using PHAST. Output from the model is inconsistent with the asphyxiation harm observed. The high-momentum release is predicted to disperse safely and never reach the ground. Carbon dioxide capture and storage (CCS) schemes will involve handling and transportation of unprecedented quantities of CO₂. Case histories to date include sudden releases of CO₂ of up to 50 tonnes only, far too small to provide a suitable empirical perspective on predicted hazard distances for CCS projects. The 1953 outburst contributes to filling this gap.     

Winter storm-related injuries in Oklahoma, January 2007

Introduction

A January 2007 ice storm occurred in Oklahoma, causing power outages and hazardous travel conditions. The objective of this investigation was to describe the nature of winter storm-related injuries among Oklahoma residents, to determine populations at risk, and to inform prevention-planning personnel.

Methods

Winter storm-related injuries were a temporarily reportable condition; all acute-care hospitals and the state medical examiner logged storm-related injuries and deaths during January 12 − 30, 2007. Medical records were retrospectively abstracted.Risk of injury was described by demographic group, injury type, and mechanism.

Results

Among 6,047 persons experiencing winter storm-related injuries, 74% were injured in falls, 13% in motor-vehicle collisions (MVCs), 8% while sledding, 1% by unintentional carbon monoxide poisoning, 1% in cleanup activities, and 3% by other mechanisms. Median age of injured persons was 39 years. Persons aged ≥ 40 years were 1.4 times more likely to experience falls as the cause of injury than those aged < 40 years, and falls were twice as likely as other mechanisms to cause fractures among persons aged ≥ 40 years. Injured persons aged < 40 years were 2.2 times more likely to experience MVC-related injuries, and 19 times more likely to experience sledding-related injuries than persons aged ≥ 40 years.

Conclusions

Younger persons were more likely injured in MVCs and sledding incidents, whereas older persons were more likely to experience falls and fractures.

Impact on industry

Prevention messages for winter storm-related injuries should target winter-driving safety tips to younger adults and precautions regarding falls to older adults.     

Visual performance for trip hazard detection when using incandescent and led miner cap lamps

Introduction

Accident data for 2003-2007 indicate that slip, trip, and falls (STFs) are the second leading accident class (17.8%, n = 2,441) of lost-time injuries in underground mining. Proper lighting plays a critical role in enabling miners to detect STF hazards in this environment. Often, the only lighting available to the miner is from a cap lamp worn on the miner's helmet. The focus of this research was to determine if the spectral content of light from light-emitting diode (LED) cap lamps enabled visual performance improvements for the detection of tripping hazards as compared to incandescent cap lamps that are traditionally used in underground mining. A secondary objective was to determine the effects of aging on visual performance.

Method

The visual performance of 30 subjects was quantified by measuring each subject's speed and accuracy in detecting objects positioned on the floor both in the near field, at 1.83 meters, and far field, at 3.66 meters. Near field objects were positioned at 0 degrees and ± 20 degrees off axis, while far field objects were positioned at 0 degrees and ± 10 degrees off axis. Three age groups were designated: group A consisted of subjects 18 to 25 years old, group B consisted of subjects 40 to 50 years old, and group C consisted of subjects 51 years and older.

Results

Results of the visual performance comparison for a commercially available LED, a prototype LED, and an incandescent cap lamp indicate that the location of objects on the floor, the type of cap lamp used, and subject age all had significant influences on the time required to identify potential trip hazards. The LED-based cap lamps enabled detection times that were an average of 0.96 seconds faster compared to the incandescent cap lamp. Use of the LED cap lamps resulted in average detection times that were about 13.6% faster than those recorded for the incandescent cap lamp. The visual performance differences between the commercially available LED and prototype LED cap lamp were not statistically significant.

Impact on Industry

It can be inferred from this data that the spectral content from LED-based cap lamps could enable significant visual performance improvements for miners in the detection of trip hazards.     

On the development of a new hybrid risk assessment process using occupational accidents’ data: Application on the Greek Public Electric Power Provider

The occupational accidents have a major impact upon human integrity and also bring about high costs for the social health and insurance system of a country. In addition, risk analysis is an essential process for the safety policy of a company, having as main aim the effacement of any potential of damage in a productive procedure, while the quantified risk evaluation is the most crucial part of the whole procedure of assessing hazards in the work. The main goal of this study is double: a) the development and presentation of a new hybrid risk assessment process (HRAP) and b) the application of HRAP in the Greek Public Power Corporation (PPC) (the unique electric power provider and the largest industry in Greece), by using occupational accidents that have been recorded, during the 12-year period of 1993-2004. The new process consists of four distinct phases a) the hazard sources’ identification phase, b) the risk consideration phase, c) the risk-evaluation phase, and d) the phase of the risk assessment and safety-related decision making. The results show that in some cases the risk value has been calculated in PPC to be higher than 500 (in the risk rating of 0-1000), which imposes the taking of suppressive measures for abolishing the danger source, while the fatal accident frequency rate (per 10⁸ man-hrs) is FAFR ≅ 2.4.     

Explorative spatial analysis of traffic accident statistics and road mortality among the provinces of Turkey

Introduction

The aim of the study is to describe the inter-province differences in traffic accidents and mortality on roads of Turkey.

Method

Two different risk indicators were used to evaluate the road safety performance of the provinces in Turkey. These indicators are the ratios between the number of persons killed in road traffic accidents (1) and the number of accidents (2) (nominators) and their exposure to traffic risk (denominator). Population and the number of registered motor vehicles in the provinces were used as denominators individually. Spatial analyses were performed to the mean annual rate of deaths and to the number of fatal accidents that were calculated for the period of 2001-2006. Empirical Bayes smoothing was used to remove background noise from the raw death and accident rates because of the sparsely populated provinces and small number of accident and death rates of provinces. Global and local spatial autocorrelation analyses were performed to show whether the provinces with high rates of deaths-accidents show clustering or are located closer by chance. The spatial distribution of provinces with high rates of deaths and accidents was nonrandom and detected as clustered with significance of P < 0.05 with spatial autocorrelation analyses.

Results

Regions with high concentration of fatal accidents and deaths were located in the provinces that contain the roads connecting the Istanbul, Ankara, and Antalya provinces. Accident and death rates were also modeled with some independent variables such as number of motor vehicles, length of roads, and so forth using geographically weighted regression analysis with forward step-wise elimination. The level of statistical significance was taken as P < 0.05. Large differences were found between the rates of deaths and accidents according to denominators in the provinces. The geographically weighted regression analyses did significantly better predictions for both accident rates and death rates than did ordinary least regressions, as indicated by adjusted R² values. Geographically weighted regression provided values of 0.89-0.99 adjusted R² for death and accident rates, compared with 0.88-0.95, respectively, by ordinary least regressions.

Impact on industry

Geographically weighted regression has the potential to reveal local patterns in the spatial distribution of rates, which would be ignored by the ordinary least regression approach. The application of spatial analysis and modeling of accident statistics and death rates at provincial level in Turkey will help to identification of provinces with outstandingly high accident and death rates. This could help more efficient road safety management in Turkey.     

Predicting safety culture: the roles of employer, operations manager and safety professional

Introduction: This study explores predictive factors in safety culture. Method: In 2008, a sample 939 employees was drawn from 22 departments of a telecoms firm in five regions in central Taiwan. The sample completed a questionnaire containing four scales: the employer safety leadership scale, the operations manager safety leadership scale, the safety professional safety leadership scale, and the safety culture scale. The sample was then randomly split into two subsamples. One subsample was used for measures development, one for the empirical study. Results: A stepwise regression analysis found four factors with a significant impact on safety culture (R² = 0.337): safety informing by operations managers; safety caring by employers; and safety coordination and safety regulation by safety professionals. Safety informing by operations managers (ß = 0.213) was by far the most significant predictive factor. Impact on industry: The findings of this study provide a framework for promoting a positive safety culture at the group level.     

Experimental analysis of the evaporation process for gasoline

This paper presents the findings from a study on the evaporation process of 93 RON (research octane number) unleaded gasoline. The parameters measured in the experiment included the weight, the RVP (Reid vapor pressure) and the viscosity of gasoline, the concentration of NMHC (non-methane total hydrocarbon) in the oil vapor and the concentration of the main vapor constituent. Results showed that the parameters changed significantly as evaporation processed. The weight loss reached 86.36% after 300 days and presented a logarithmic curve with time. The RVP decreased from 38 kPa to 9.6 kPa. The viscosity of gasoline increased from 8.6 × 10^?4 Pa s to 1.51 × 10^?3 Pa s. All the concentrations of NMHC and the main constituent of vapor decreased in varying amounts. Most of the changes might be attributed to the evaporation of volatile hydrocarbons.     

Application of fire suppression materials on suppression of LNG pool fires

An LNG pool fire is considered one of the main hazards of LNG, together with LNG vapor dispersion. Suppression methods are designed to reduce the hazard exclusion zones, distance to reach radiant heat of 5 kW/m², when an LNG pool fire is considered. For LNG vapor dispersion, the hazard exclusion zone is the distance travelled by the LNG vapor to reach a concentration of 2.5% v/v (half of the LNG lower flammability limit).Warming the LNG vapor to reach positive buoyancy faster is one way to suppress LNG vapor dispersion and reduce evaporation rate (thus fire size and its associated radiant heat) and that is the main objective in LNG pool fire suppression. Based on previous research, the use of high expansion foam has been regarded as the primary method in suppressing LNG pool fires. However, in 1980, another method was introduced as an alternative pool fire suppression system, Foamglas^®. The research concluded that 90% of the radiant heat was successfully reduced. Currently-called Foamglas^® pool fire suppression (Foamglas^® PFS) is a passive mitigation system and is deployed after the leak occurs. Foamglas^® PFS is non-flammable, and has a density one-third of the density of LNG, thus floats when an LNG pool is formed.This paper describes the study and confirmation of Foamglas^®PFS effectiveness in suppressing LNG pool fires. In addition, while Foamglas^® PFS is not expected to suppress LNG vapor dispersion, further investigation was conducted to study the effect of Foamglas^®PFS on LNG vapor dispersion. An LNG field experiment was conducted at Brayton Fire Field. The experimental development, procedures, results and findings are detailed in this paper.     

Feasibility study of decomposing methane with hydroxyl radicals

Coal-mine gas disaster is one of the most serious coal-mine disasters in China. The main component of coal-mine gas, methane is chemically stable and very difficult to be degraded by conventional methods. Hydroxyl radical (OH), due to strong oxidizing ability and high electro-negativity, is the primary degradation source of atmospheric methane. In the present study, methane degradation using hydroxyl radicals generated by Fenton’s reagent, Fe²⁺/H₂O₂, has been carried out in the self-designed bubbling reactor. The effects of H₂O₂ concentration, dosage of FeSO₄·7H₂O and initial pH value on methane removal efficiency were investigated respectively. It has been found that the optimal reaction conditions were 100 mM of hydrogen peroxide, 2.00 mM of ferrous ion and initial pH value of 2.5. Under optimal conditions, the removal efficiency of methane reached 25% after 30 min. The preliminary experimental results unambiguously demonstrate that the degradation of methane using hydroxyl radicals generated by Fenton’s reagent is feasible.     

Psychosocial safety climate: Conceptual distinctiveness and effect on job demands and worker psychological health

Psychosocial safety climate is an emerging construct that refers to shared perceptions regarding policies, practices, and procedures for the protection of worker psychological health and safety. The purpose of the research was to: (1) demonstrate that psychosocial safety climate is a construct distinct from related climate measures (i.e., physical safety climate, team psychological safety, and perceived organizational support); and (2) test the proposition that organizational psychosocial safety climate determines work conditions (i.e., job demands) and subsequently worker psychological health. We used samples from two different cultures; an Australian sample (N = 126 workers in 16 teams within a primary health care organization) and a Malaysian sample (N = 180 workers in 31 teams from different organizations and diverse industries). In both samples confirmatory factor analysis verified that psychosocial safety climate is a construct distinct from related climate measures. Using hierarchical linear modeling, psychosocial safety climate was superior to other team level climate measures in its negative relationship to both job demands and psychological health problems. Results supported a mediation process, psychosocial safety climate → job demands → psychological health problems, corroborating psychosocial safety climate as a preeminent stress risk factor, and an efficient target for intervention. We found both physical and psychosocial safety climates were stronger in the Australian, compared with the Malaysian work context. Levels of psychosocial safety climate were significantly lower than those of physical safety climate in both countries indicating a ‘universal’ lack of attention to workplace psychological health.     

MIE determination and thermal degradation study of PA12 polymer powder used for laser sintering

Pulverized materials such as metallic or polymer powders play a considerable role in many industrial processes. Their use requires the introduction of preventive safeguards to control the plant's safety.PA12 polymer powder processing by laser sintering is characteristic of this tendency. The present work concerns PA12 powder (bimodal particle size distribution: 10 μm and 55 μm) and relates to explosion sensitivity and the thermal degradation of this powder, which can occur during laser sintering. Minimum Ignition Energy is determined using a modified Hartmann tube combined with the Langlie method developed in the PRISME Laboratory. This study shows the influence of parameters such as distance between the electrodes, powder concentration and arc power on MIE values. Theses parameters vary in the range of 3–6 A for the current intensity of the spark and the electrode gap in the range of 2.5–4 mm. The MIE is obtained for a spark gap of 3 mm and current intensity of the 4 A spark in our device. It shows that the MIE is less than 40 mJ for concentrations approaching 1000 g/m³. At lower concentrations (under 150 g/m³) the MIE increases but discrepancies in measurements appear, probably because of the static electricity that creates strong irregularities in dust dispersion. The second part of this study concerns the thermal degradation of the PA12 which is performed by thermogravimetric experiments coupled with mass spectrometric (MS) analysis for gas investigation. The mass loss measurement combined with the gas analysis allows the principal stages of degradation to be determined so as to calculate the kinetics parameter PA12. Experiments have been performed for different heating rates between 1 and 30 K min^?1 and the reproducibility of experiments has been verified. The activation energy is determined using two methods: Freidman and KAS. For a reaction rate of between 0.2 and 0.6, the activation energy is nearly constant. The KAS method gives a value of E_a = 250 kJ mol^?1 and the Friedman method gives E_a = 300 kJ mol^?1. The gas analysis by MS shows that oxidation begins at over 350 °C and finishes at under 650 °C with the formation of CO₂ and H₂O. Other major peaks with an m/z ratio of 29, 28 and 30 are noticed in this range of temperature. They show the presence of intermediate species such as C₂H₆, NO or CH₂O. The presence of HCN is also detected (m/z ratio of 27).     

Stability and deformation of surrounding rock in pillarless gob-side entry retaining

We analyzed the stability of the retained gob-side entry in four different Chinese coal mining sites and evaluated the influencing factors of roadway deformation such as mining depth, support strength and area of gob-side hanging roof. It was found that the length of cantilever roof block above roadway has a major impact on the deformation, whereas the impact of mining depth is minor if the depth is less than 500 m. Minimum support resistance of 0.3 MPa is essential to effectively confine the deformation of a retained roadway. We performed physical experiments to further study the features of roof fracturing and their impact on roadway deformation under three typical immediate roof conditions, i.e., thick-immediate roof, thin-immediate roof and non-immediate roof. In addition, equations to calculate desired support resistance of filled gob-side wall were derived based on superimposed continuous laminate model. The results provide valuable theoretical and practical guidance for implementing pillarless gob-side entry retaining in engineering practices.