Safety assessment of potential supercritical solvents for Fischer–Tropsch Synthesis

Fischer–Tropsch Synthesis (FTS) is a primary pathway for gas-to-liquid (GTL) technology. In order to overcome commercial problems associated with reaction and transport phenomena, the use of supercritical solvents has been proposed to enhance conversion, catalyst stability and improve temperature control in fixed-bed reactors. One of the major challenges in designing the supercritical FTS reactor unit is selecting appropriate solvents of critical properties within the required reaction operating conditions. Numerous alternatives exist and should be screened based on relevant criteria. The main aim of this paper is to develop a screening methodology to identify an optimum supercritical solvent or a mixture of solvents that meet the aforementioned criteria while minimizing the cost and more importantly satisfying the safety constraints. A safety metric system was developed in order to compare the risk issues associated with using different solvents. In addition, an economic analysis of using the different solvents was performed. Finally, a case study was solved to illustrate the use of the proposed metrics and the selection of solvents based on safety and techno-economic criteria.     

Testing of dust clouds for the electrostatic-spark ignition hazard in industry. Need for a modified approach?

Current standard test methods for electric-spark minimum ignition energies (MIEs) of dust clouds in air require that a series inductance of at least 1–2 mH be included in the electric-spark discharge circuit. The reason is to prolong the spark discharge duration and thus minimize the spark energy required for ignition. However, when assessing the minimum electrostatic energy ½CU² for dust cloud ignition by accidental electrostatic-spark discharges, current testing standards require that the series inductance of at least 1–2 mH be removed from the spark discharge circuit. No other changes of apparatus and test procedure are required. The present paper questions whether this simple approach is always adequate. The reason is that in practice in industry accidental electrostatic-spark discharge circuits may contain large ohmic resistances due to corrosion, poor electrical grounding connections, poorly electrically conducting construction materials etc. The result is increased spark discharge durations and reduced mechanical disturbance of the dust cloud by the blast wave emitted by the spark. Therefore, testing for minimum ½CU² for ignition by accidental electrostatic spark discharges may not only require removal of the series inductance of 1–2 mH from the standard MIE spark discharge circuit. Additional tests may be needed with one or more quite large series resistances R_s inserted into the spark discharge circuit. The present paper proposes a modified standard test procedure for measurement of the minimum electrostatic-spark ignition energy of dust clouds that accounts for these effects.     

Determination of explosion limits – Criterion for ignition under non-atmospheric conditions

Many industrial processes are run at non-atmospheric conditions (elevated temperatures and pressures, other oxidizers than air). To judge whether and if yes to what extent explosive gas(vapor)/air mixtures will occur or may be generated during malfunction it is necessary to know the safety characteristic data at the respective conditions. Safety characteristic data like explosion limits, are depending on pressure, temperature and the oxidizer. Most of the determination methods are standardized for ambient conditions. In order to obtain determination methods for non-atmospheric conditions, particularly for higher initial pressures, reliable ignition criteria were investigated. Ignition tests at the explosion limits were carried out for mixtures of methane, propane, n-butane, n-hexane, hydrogen, ammonia and acetone in air at initial pressures up to 20 bar. The tests have been evaluated according to different ignition criteria: visual flame propagation, temperature and pressure rising. It could be shown that flame propagation and occasionally self-sustained combustion for several seconds occurred together with remarkable temperature rise, although the pressure rise was below 3%. The results showed that the combination of a pressure rise criterion of 2% and a temperature rise criterion of 100 K seems to be a suitable ignition criterion for the determination of explosion limits and limiting oxidizer concentration at higher initial pressures and elevated temperatures. The tests were carried out within the framework of a R&D project founded by the German Ministry of Economics and Technology.     

Protective clothing for pesticide operators: part I – selection of a reference test chemical for penetration testing

A systematic approach was taken to develop a database for protective clothing for pesticide operators; results are reported as a two-part series. Part I describes the research studies that led to identification of a pesticide formulation that could serve as a reference test chemical for further testing. Measurement of pesticide penetration was conducted using different types of pesticide formulations. Six fabrics were tested using 10 formulations at different concentrations. Three formulations were subsequently selected for further testing. Analysis of the data indicated that, when compared with other formulations, mean percent penetration of 5% Prowl 3.3 EC [emulsifiable concentrate diluted to 5% active ingredient (pendimethalin)] is either similar to or higher than most test chemicals. Those results led to choosing 5% Prowl 3.3 EC as a reference test liquid. Part II of the study, published as a separate paper, includes data on a wide range of textile materials.     

A societal risk study for transportation of class-3 hazmats – A case of Indian state highways

United Nations Class-3 hazardous materials (hazmats) are basically liquid products and transported in road tankers under ambient temperature and atmospheric pressure. They are mostly flammables and some of them are toxic (e.g. benzene) as well. The spillages due to collision related incidents involving the road tankers, carrying such hazmats through highways, pose not only flammability hazards due to pool fire, flash fire and vapor cloud explosion (VCE), but create substantial toxic hazards also. The paper presents the risk-based study of route evaluation of two state highways and one urban city road in western India on account of transportation of class-3 hazmats, namely benzene, toluene, p-xylene, methanol, cyclohexane and acetone. A comparative evaluation of study routes was undertaken based on their societal risks presented in terms of F–N curves and assessed against HSE, UK as well as VROM, The Netherlands risk acceptance criteria. Societal risks contribution of cyclohexane to the overall flammability risk mainly VCE is found to be the highest followed by acetone and benzene compared to other study hazmats. This is due to highly explosive nature of cyclohexane resulting into vapor cloud explosion. While acetone and methanol pool fires are likely to cause larger area of damage compared to others, benzene supersedes others as far as toxicity risk is concerned and larger evacuation area is encountered, as it poses greater Immediately Dangerous to Life or Health (IDLH) distance than others. Besides, study of initial isolation distance following an accident in case of benzene tanker found that benzene spillage requires larger initial isolation distance than others and so are the day and night protective action zone distances.     

Proposal for an Indexical Method of Evaluating Risk of Hand Tool Operators’ Exposure to Mechanical Vibrations

The article presents proposals for an indexical evaluation of exposure of hand tool operators to vibrations. The presented indices have been developed on the basis of the results of laboratory tests. The examinations studied the effect of pressure force and grip force exerted by an operator on a hand tool as well as the amplitudes and frequencies of an exciting signal on vibrations transmitted in the hand-tool handle system.     

Algorithms for Increasing the Efficiency of Precision Production Operator’s Activities

To assess and plan future risk-analysis research projects, 275 documents describing methods and tools for assessing the risks associated with industrial machines or with other sectors such as the military, and the nuclear and aeronautics industries, etc., were collected. These documents were in the format of published books or papers, standards, technical guides and company procedures collected throughout industry. From the collected documents, 112 documents were selected for analysis; 108 methods applied or potentially applicable for assessing the risks associated with industrial machines were analyzed and classified. This paper presents the main quantitative results of the analysis of the methods and tools.     

The Subjective Rating Scales for Measurement of Mental Workload—Thurstonian Scaling

Subjective rating scales for measuring work demands and individual capabilities to cope with work requirements were developed using the Thurstonian procedure. The scales measure six dimensions of mental workload: mental difficulties, feeling of responsibility, awareness of risk, interpersonal conflicts, monotony, and time pressure. Individual scale results make it possible to assess the level of mental workload understood as a relation between the subjective rating of work demands and individual capabilities in each of the six dimensions. Two versions of scales were prepared: classic and modified ones. To assess the level of reliability of the particular scales, 481 participants were examined twice at a 1-month interval. A procedure to prepare scales for the measurement of other dimensions of mental workload is also presented.     

Preparation of Co–MgO mixed oxide nanocatalysts for low temperature CO oxidation: Optimization of preparation conditions

In this study, a series of Co–MgO mixed oxides (30 wt.% Co) were prepared by co-precipitation method and employed as catalyst in low temperature CO oxidation reaction. The preparation conditions were optimized by the Taguchi method of experimental design to synthesize a sample with high catalytic performance toward CO oxidation reaction. The effects of four variables, pH of solution, aging temperature, aging time and molarity of precursor solution at three levels were investigated. The optimized sample was characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of oxygen (O₂-TPD), N₂ adsorption/desorption, thermal gravimetric and differential thermal analysis (TGA/DTA), and transmission electron microscopy (TEM) techniques. The results revealed that the optimized sample showed a mesoporous structure with a narrow pore size distribution centered in the range of 7–17 nm and particle size about 5.5 nm. It was found that the molarity of solution and aging time had the most influence on the CO conversion, respectively. The catalytic results showed that the highest CO conversion obtained from samples synthesized by Taguchi orthogonal array was about 90% at 200 °C, while the CO conversion for optimized sample was 95%. In addition, the effect of operational conditions was studied over optimized sample.     

Suitability of ignition source “exploding wire” for determination of dust explosion characteristics in the 20-L-sphere

Several safety characteristics of dusts are determined in the 20-L-sphere (also known as SIWEK Chamber) according to international standards. Dust cloud ignition is carried out using pyrotechnical igniters. Due to various disadvantages of such igniters the need for alternative ignition sources arises again and again. An alternative could be an ignition source which is known as “exploding wire” or “fuse wire”. The paper presents test results of a comparative study between both ignition sources for the determination of the safety characteristics “Maximum Explosion Pressure” and “Maximum Rate of Explosion Pressure Rise” of five selected dusts in the 20-L-sphere. In addition to that the ignition mechanisms of both ignition sources were analyzed by high speed camera recordings and the ignition energy was determined with electric and calorimetric recordings. The paper shows results of measurements of the ignition energy of both ignition sources as well as sequences of the flame propagation.     

Development and evaluation of a Naïve Bayesian model for coding causation of workers’ compensation claims

IntroductionTracking and trending rates of injuries and illnesses classified as musculoskeletal disorders caused by ergonomic risk factors such as overexertion and repetitive motion (MSDs) and slips, trips, or falls (STFs) in different industry sectors is of high interest to many researchers. Unfortunately, identifying the cause of injuries and illnesses in large datasets such as workers’ compensation systems often requires reading and coding the free form accident text narrative for potentially millions of records.MethodTo alleviate the need for manual coding, this paper describes and evaluates a computer auto-coding algorithm that demonstrated the ability to code millions of claims quickly and accurately by learning from a set of previously manually coded claims.ConclusionsThe auto-coding program was able to code claims as a musculoskeletal disorders, STF or other with approximately 90% accuracy.Impact on industryThe program developed and discussed in this paper provides an accurate and efficient method for identifying the causation of workers' compensation claims as a STF or MSD in a large database based on the unstructured text narrative and resulting injury diagnoses. The program coded thousands of claims in minutes. The method described in this paper can be used by researchers and practitioners to relieve the manual burden of reading and identifying the causation of claims as a STF or MSD. Furthermore, the method can be easily generalized to code/classify other unstructured text narratives.     

Reuse of nickel recovered from spent Ni–Cd batteries for the preparation of C/Ni and C/Ni/Pd layered electrodes for energy sources

Nickel recovered in the recycling process of Ni–Cd batteries was used as a main component of bath for electrodeposition of nickel onto carbon fabric in order to obtain C/Ni composite. A part of the obtained composite was additionally coated with a thin layer of palladium (C/Ni/Pd composite). All the materials were investigated to assess the possibility of their use in the processes of electrochemical storage (sorption/desorption) of hydrogen and electrochemical oxidation of methanol. The obtained results showed the composites to be active electrode materials in these processes. The electrodes exhibited high activity and cyclability, especially in the process of methanol oxidation due to electrocatalytic activity of both nickel deposited onto carbon fabric and the outer layer of porous palladium coating nickel substrate.     

Probabilistic risk assessment for pedestrian–vehicle collision considering uncertainties of pedestrian mobility

Objectives: The uncertainties of pedestrian mobility are important factors affecting the accuracy and robustness of an active pedestrian protection system. This study is to provide the means for probabilistic risk evaluation of pedestrian–vehicle collision by counting the uncertainties in pedestrian motion.

Method: The pedestrian is modeled by a first-order Markov model to characterize the stochastic properties in mobility according to field experiments of pedestrians crossing an uncontrolled road. Based on the assumption of Gaussian distribution, unscented transformation (UT) is employed to predict the collision risk probability with the symmetric σ-set constructed on the basis of discrete trajectory simulation. Simulation experiments were carried out with 10,000 Monte Carlo (MC) simulations as the reference.

Results: The probability density distributions of time-to-collision, minimal distance, and collision probability estimated by UT coincide with the reference ones under various vehicle–pedestrian conflict scenarios, and the maximal deviation of collision probability from the reference is 5.33%. The UT method is about 600 times faster than the MC method (10,000 runs), which means that the proposed method has the potential for online application.

Conclusions: This article presents an effective and efficient algorithm to estimate the collision probability by using a UT method to solve the nonlinear transformation of uncertainties in pedestrian motion. Simulation results show that the UT-based method achieves accurate collision probability estimation and higher computation efficiency than MC and provides more valuable information concerning collision avoidance than the deterministic methods in the design of a pedestrian collision avoidance system.     

Mathematical methods for application of experimental adiabatic data – An update and extension

The paper represents some results of comparative analysis of the methods used for processing and interpreting data of adiabatic calorimetry as well as applying it to practical situations. Specifically two approaches are compared – approximate method based on evaluation of simplified kinetics and a more comprehensive, simulation-based method that utilizes the evaluation of more detailed kinetic models.The analysis is focused on two important types of data processing – correction of experimental results on thermal inertia (phi-factor correction) and estimation of adiabatic time to maximum rate (TMR).The most widely cited method for phi-factor correction is considered and its improvement is proposed to enable more precise prediction of the adiabatic time scale. A procedure for phi-factor correction of pressure response is also proposed. The limitations of this enhanced Fisher's method are discussed by comparison with simulation-based method. All the illustrative materials are based on real examples.As an example of application, the simplified method will be used to predict TMR and its limitations will be discussed.     

Consideration on safety for emerging technology – Case studies of seven service robots

Despite the fact that several manufacturers of service robots launched their innovations into the market, worldwide guidelines or regulations concerning the safety aspects of service robots are not yet available. However the general principles and methodologies of safety of machinery (e.g., ISO/IEC Guide 51, partly ISO14121, ISO12100) could be implemented to a certain degree. The safety of seven service robots as an emerging technology was verified by safety professionals of “NPO – the Safety Engineering Laboratory” a Non Profit Organization. NPO verified the “Critical Hazards” for each service robot mentioned by the respective manufacturers. For those cases, both the “As Low As Reasonably Practicable” principle and the “Reasonable Alternative Design” standard were applied for judging if the risk associated with the Critical Hazards were tolerable or not and if state of the art measures for reducing the risk were applied adequately. These experiences will help to establish guidelines for the safety of service robots as an emerging technology in the future.     

Protective clothing for pesticide operators: part II – data analysis of fabric characteristics

Development of objective measurements is an important requirement for establishing performance-based standards for protective clothing used while handling pesticide. This study, the second in a two-part series, reports on the work completed to evaluate the performance of approximately 100 fabrics that are either used or have the potential to be used for garments worn by operators while applying pesticides. Part I, published separately, provides an overview of these issues and describes research undertaken to select a test chemical for use in subsequent studies. The goals of this study were first to develop a comprehensive approach to evaluate the performance of garments currently being used by pesticide operators, and second, to use the laboratory and field data in the development of performance specifications.     

Structural response for vented methane–air deflagrations: Effects of volumetric blockage ratio

To investigate the effects of cylinders placed parallel to the venting direction on the structural response of the vessel walls to an explosion, 25 batches of vented explosion tests were conducted in a 1 m³ rectangular vessel. Two types of structural response with different amplitudes and frequency distributions were observed and evaluated by comparing the vibration data with both the pressure data and high-speed videos. A low-amplitude structural response of approximately 150–250 m/s², which increased slightly as VBR increased, was triggered by a combination of the initial flame propagation, external explosion, Helmholtz oscillations, and the Taylor instability. A high-amplitude structural response of approximately 9500 m/s² was also observed, which decreased sharply as VBR increased. Additionally, the high amplitude response was never observed when more than two cylinders were present in the vessel. The high amplitude response was triggered due to the coupling between the acoustic wave, the flame, and the resonance of the vessel. The presence of obstacles did not increase the severity of the structural responses under the current experimental conditions. To the contrary, the presence of obstacles in the container attenuated or even inhibited the high-amplitude vibration of the container caused by the explosion.     

Can SVM be used for automatic EEG detection of drowsiness during car driving?

This study aims to develop an automatic method to detect drowsiness onset while driving. Support vector machines (SVM) represents a superior signal classification tool based on pattern recognition. The usefulness of SVM in identifying and differentiating electroencephalographic (EEG) changes that occur between alert and drowsy states was tested. Twenty human subjects underwent driving simulations with EEG monitoring. Alert EEG was marked by dominant beta activity, while drowsy EEG was marked by alpha dropouts. The duration of eye blinks corresponded well with alertness levels associated with fast and slow eye blinks. Samples of EEG data from both states were used to train the SVM program by using a distinguishing criterion of 4 frequency features across 4 principal frequency bands. The trained SVM program was tested on unclassified EEG data and subsequently checked for concordance with manual classification. The classification accuracy reached 99.3%. The SVM program was also able to predict the transition from alertness to drowsiness reliably in over 90% of data samples. This study shows that automatic analysis and detection of EEG changes is possible by SVM and SVM is a good candidate for developing pre-emptive automatic drowsiness detection systems for driving safety.     

Comparison of explosion parameters for Methane–Air mixture in different cylindrical flameproof enclosures

Flameproof enclosures having internal electrical components are generally used in classified hazardous areas such as underground coalmines, refineries and places where explosive gas atmosphere may be formed. Flameproof enclosure can withstand the pressure developed during an internal explosion of an explosive mixture due to electrical arc, spark or hot surface of internal electrical components. The internal electrical component of a flameproof enclosure can form ignition source and also work as an obstacle in the explosion wave propagation. The ignition source position and obstacle in a flameproof enclosure have significant effect on explosion pressure development and rate of explosion pressure rise. To study this effect three cylindrical flameproof enclosures with different diameters and heights are chosen to perform the experiment. The explosive mixture used for the experiment is stoichiometric composition of methane in air at normal atmospheric pressure and temperature.It is observed that the development of maximum explosion pressure (P_max) and maximum rate of explosion pressure rise (dp/dt)_ex in a cylindrical flameproof enclosure are influenced by the position of ignition source, presence of internal metal or non-metal obstacles (component). The severity index, K_G is also calculated for the cylindrical enclosures and found that it is influenced by position of ignition source as well as blockage ratios (BR) of the obstacles in the enclosures.