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.
Waterproof lime dust used in coal mines is an important element in the system of protection against explosions. This is one of the oldest methods used to prevent coal dust explosions and, according to an expert’s opinion, it will remain so for a long time. T he work is a summary of research on the development of a new method of producing waterproof limestone dust to use it as an anti-explosive powder in coal mines. The typical method of hydrophobic dust production (milling limestone with stearic acid) is no longer profitable due to the restructuring of the mining industry. The main research was conducted on raw materials traditionally used during the production of anti-explosion powder, namely limestone meal with a grain size diameter equal to 80 μm (Czatkowice Limestone Quarry) and stearic acid as a modifier. Silicone preparation and bituminous preparation (Bitumenovoranstrich) were used as additional modifiers. The hydrophobization process was conducted with the use of different techniques: from stearic acid ether solution, from stearic acid vapor, from methyl silicone resin or bituminous preparation solutions. A series of research on modified powders to determine hydrophobization and flow properties was conducted. Depending on method of hydrophobization, the test of “floating on water”, the extraction of stearic acid was carried out, water contact angles on compacted material were determined, the thermal decomposition of powder was made. The increase in moisture after wet storage was indicated. The flow properties of powders were measured with the use of the Powder Characteristics Tester. The evaluation of the suitability of each hydrophobization methods in achieving the intended purpose was valued.
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.
This article shows incidents associated with the use of gas as an energy carrier. It presents selected incidents which have occurred in Poland and around the world in recent decades. Based on this, consequences of gas and air mixture explosions were analysed as well. The article presents the main causes of gas incidents which have taken place, as per instances which are similar worldwide. Incidents associated with the use of gas are not frequent, but at the same time very tragic as they often lead to illness or even death. In Poland, in the last twenty years, construction area disasters caused by gas explosions account for only 5% of all which have occurred, but the number of fatalities resulting from these cases is approximately 14%. The number of individuals injured reached 39% of all construction disaster victims. Considering all these facts, it is necessary to undertake wide preventive measures in order to increase safety in the use of gaseous fuels.
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.
The blasting technique is currently the basic excavation method in Polish underground copper mines. Applied explosives are usually described by parameters determined on the basis of specific standards, in which the manner and conditions of the tests performance were defined. One of the factors that is commonly used to assess the thermodynamic parameters of the explosives is the velocity of detonation. The measurements of the detonation velocity are carried out according to European Standard EN 13631-14:2003 based on a point-to-point method, which determines the average velocity of detonation over a specified distance. The disadvantage of this method is the lack of information on the detonation process along the explosive sample. The other method which provides detailed data on the propagation of the detonation wave within an explosive charge is a continuous method. It allows to analyse the VOD traces over the entire length of the charge. The examination certificates of a given explosive usually presents the average detonation velocities, but not the characteristics of their variations depending on the density or blasthole diameter. Therefore, the average VOD value is not sufficient to assess the efficiency of explosives. Analysis of the abovementioned problem shows, that the local conditions in which explosives are used differ significantly from those in which standard tests are performed. Thus, the actual detonation velocity may be different from that specified by the manufacturer. This article presents the results of VOD measurements of a bulk emulsion explosive depending on the diameter of the blastholes carried out in a selected mining panel of the Rudna copper mine, Poland. The aim of the study was to determine the optimal diameter of the blastholes in terms of detonation velocity. The research consisted of diameters which are currently used in the considered mine.
Cu-Ni composite nanoparticles were successfully synthesized by electrical explosion of wire (EEW) method. Cu-Ni alloy and twisted wires with various Ni contents were used as the feeding material for a 3 kV charging voltage EEW machine in an ethanol ambient chamber. The phase structure and magnetic properties of the as-fabricated samples were studied. It was established that the prepared powders after drying have a spherical form with the particle size is under 100 nm. XRD analysis indicated that the nanopowders consisted of binary Cu-Ni phases. Only pure phases of the intermetallic compound Cu-Ni (Cu0.81Ni0.19 and Cu3.8Ni) were observed in the XRD patterns of the samples. The synthesized intermetallic Cu-Ni alloy nanopowders reveal magnetic behaviors, however, the lower Ni content samples exhibited paramagnetic behaviors, meanwhile, the higher Ni content samples exposed ferromagnetic properties.
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).
Multilayered composites based on light metals are promising materials in many applications. In the present work the 15-layered clad, composed of alternately stacked of Ti(Gr.1) and AA1050-H24 alloy sheets of 1 mm thick has been investigated with respect to determination of the kinetic of the Al3Ti phase growth. The defect-free multilayered composite was successfully formed by explosive welding technology. Then EXW samples were modified via annealing at the temperature of 600oC in closed die under pressure of 44 MPa for various times ranged between 1 and 10 h. Transmission and Scanning Electron Microscopy examinations were conducted in order to study the kinetic of the elements migration across the interfaces between the layers of the Al/Ti composite. The macro-scale observations of samples after EXW revealed that wavy interfaces were always formed in layers near the explosive charge. The increase of the distance from the top surface leads to flattening of the interface with very thin reaction layer between Al and Ti sheets. During annealing the kinetic of the Al3Ti phase growth is similar near all interfaces and coincides with data from other works. It was found that despite the loading after 10 h of annealing still only small part of Al-sheets undergoes dissolution and the width of the reaction layer does not exceed 5-8 µm.
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.