Methane explosions are among the greatest hazards in the Polish coal mining industry and unfortunately continue to cause many catastrophes. The constant growth of the depth of coal exploitation in the conditions of the high concentration of mining causes the increase of absolute methane content and methane seam pressure from the mined seams. This situation directly affects the increase in the level of methane hazard in the underground work environment. It is therefore obvious to undertake intensive research that will allow for the development of appropriate solutions that help to exclude the risk of mining catastrophes resulting from the ignition and/or methane explosion. In addition to the development of methane hazard prevention methods, an indispensable element of this approach is a very accurate identification of the mechanisms of the combustion and explosion of this gas. The article presents the method of investigation and examples of results of methane explosions carried out in the 400 m experimental gallery of the Experimental Mine “Barbara” of the Central Mining Institute – the only large scale underground experimental facility in Europe. A n analysis has been performed of the influence of the methane release into mining workings on the distribution of the gas concentration and on the course of its explosion or combustion. The data collected characterizes thermodynamic phenomena that form the basis for determining the level of the explosion hazard. Large scale studies have also allowed to assess the risk of conditions that are sufficient for the development of a coal dust explosion initiated by methane explosions. The large scale of the experiments and the system of continuous recording of the course of the experiments allowed the specific characteristics of the methane explosion and burning in underground mining workings to be identified and isolated. For the first time, the course of experiments was recorded via a camera system deployed along the gallery.
The depletion of stocks of fossil fuels and the environment protection requirements increase the significance of hydrogen as a future energy carrier. The present research is focused on the development of new safe methods of production, transport and storage of hydrogen. The paper presents an analysis of problems related to the assessment of the effects of failure of hydrogen transporting pipelines. Scenarios of hazardous events connected with an uncontrollable leakage of hydrogen are discussed. The sizes of heat radiation and pressure wave hazard zones are determined.
From all the detonation parameters of explosives, “strength” – the capability to perform work is the most important for the user. The detonation of explosives in the blast hole is a quick and complicated process: first there is a detonation pressure causing the crushing of the rock in the vicinity of the explosive, then the pressure of the detonation products causes the cracking of the rock. The article presents the methods of determining the capability to perform work by explosives for civil use (dynamite and ANFO) used in the accredited Laboratory of Explosives and Electric Detonators Testing of the Experimental Mine “Barbara” of the Central Mining Institute – the lead block (Trauzl) method and the ballistic pendulum method. The aim of the research was to determine the relationship between the values of the capability to perform the work received in a ballistic pendulum method and a lead block method. As a result of the performed tests and the analysis of the results, the α-Pb coefficient was determined, which can be used to convert the value of the capability to perform work on the ballistic pendulum to the corresponding value of the capability to perform work in the lead block. At present, the Central Mining Institute is the only Notified Body of the European Union in the scope of Directive 2014/28 /EU, which has a station for smelting lead blocks and equipment and for determining the capability to perform work by explosives in lead blocks – this method was abandoned in other research units for testing with a ballistic pendulum and/or underwater test.
Explosions of coal dust are a major safety concern within the coal mining industry. The explosion and subsequent fires caused by coal dust can result in significant property damage, loss of life in underground coal mines and damage to coal processing facilities. The United States Bureau of Mines conducted research on coal dust explosions until 1996 when it was dissolved. In the following years, the American Society for Testing and Materials (ASTM) developed a test standard, ASTM E1226, to provide a standard test method characterizing the “explosibility” of particulate solids of combustible materials suspended in air. The research presented herein investigates the explosive characteristic of Pulverized Pittsburgh Coal dust using the ASTM E1226-12 test standard. The explosibility characteristics include: maximum explosion pressure, (Pmax); maximum rate of pressure rise, (dP/dt)max; and explosibility index, (Kst). Nine Pulverized Pittsburgh Coal dust concentrations, ranging from 30 to 1,500 g/m3, were tested in a 20-Liter Siwek Sphere. The newly recorded dust explosibility characteristics are then compared to explosibility characteristics published by the Bureau of Mines in their 20 liter vessel and procedure predating ASTM E1126-12. The information presented in this paper will allow for structures and devices to be built to protect people from the effects of coal dust explosions.
To investigate the effect of different proximate index on minimum ignition temperature(MIT) of coal dust cloud, 30 types of coal specimens with different characteristics were chosen. A two-furnace automatic coal proximate analyzer was employed to determine the indexes for moisture content, ash content, volatile matter, fixed carbon and MIT of different types of coal specimens. As the calculated results showed that these indexes exhibited high correlation, a principal component analysis (PCA) was adopted to extract principal components for multiple factors affecting MIT of coal dust, and then, the effect of the indexes for each type of coal on MIT of coal dust was analyzed. Based on experimental data, support vector machine (SVM) regression model was constructed to predicate the MIT of coal dust, having a predicating error below 10%. This method can be applied in the predication of the MIT for coal dust, which is beneficial to the assessment of the risk induced by coal dust explosion (CDE).
Based on the example of the development process of the cast suspension of a special-purpose vehicle the application of the integrated engineering design methodology (ICME – Integrated Computational Materials Engineering) and the development of construction has been presented. Identification of the operating and critical loads, which are guidelines for carrying out the structure strength shaping process, material and technological conversion, are due to the needs and requirements of the suspension system and the purpose and objectives of the special mobile platform. The developed cast suspension element construction includes the use of high-strength AlZnMgCu aluminum alloy. The properties of the used alloy and designed shape allows for the transfer of assumed operating loads in normal exploitation conditions and in the dynamic, critical loads to the susceptibility to damage in the assumed casting areas. For the proposed design, conducted numerical analyzes includes the impact of the shock wave pulse on the occurrence of the destructive stress fields. Based on their distribution, the areas of possible decomposition of the structure of the design element were estimated. The results allowed to devise an element with predicted destructions that allow to absorb a significant part of the impact energy of the shock wave front, which is also the buffer zone for the propagation of destruction for the critical kinematic nodes of the system.
In this study, copper nanoparticles and nanofluids were synthesized by electrical explosion of wire (EEW) in liquid media such as water, ethanol, and acetone. The effect of the different conditions on the properties of the as-synthesized Cu powders and nanofluids were investigated. X-ray diffraction (XRD) analysis was employed to measure the phase of the as-synthesized powder. Only pure Cu phase appeared in case of acetone condition, but CuO and CuO2 phases could be observed in the others. The EEWed particle size was broadened from under 50 to 100 nm. The results showed that acetone was the best condition for achieving smaller particles, preventing the oxidation of the Cu particles and good stability of the nanofluids.