Methane is one of the most common gaseous fuels that also exist in nature as the main part of the natural gas, the flammable part of biogas or as part of the reaction products from biomass pyrolysis. In this respect, the biogas and biomass installations are always subjected to explosion hazards due to methane. Simple methods for evaluating the explosion hazards are of great importance, at least in the preliminary stage. The paper describes such a method based on an elementary analysis of the cubic law of pressure rise during the early stages of flame propagation in a symmetrical cylindrical vessel of small volume (0.17 L). The pressure–time curves for lean, stoichiometric and rich methane–air mixtures were recorded and analyzed. From the early stages of pressure–time history, when the pressure increase is equal to or less than the initial pressure, normal burning velocities were evaluated and discussed. Qualitative experiments were performed in the presence of a radioactive source of 60Co in order to highlight its influence over the explosivity parameters, such as minimum ignition energy, maximum rate of pressure rise, maximum explosion pressure and normal burning velocity. The results are in agreement with the literature data.

Abstract. The dust cloud is the main form of existence of combustible dust in the production area and together with the existence of effective ignition sources are the main causes of dust explosions in production processes. The minimum ignition temperature has an important role in the process of selecting the explosion-protected electrical equipment when performing the explosion risk assessment of combustible dusts. The heated surfaces are able to ignite the dust clouds that can form in process industry. The oil products usually contain hydrogen sulfide and thus on the pipe walls iron sulfides can form, which can be very dangerous from health and safety point of view. In order to study the influence of the pyrophoric sulfide over the minimum ignition temperature of combustible dusts for this work were performed several experiments on a residue collected from the oil pipes contaminated with commercially iron sulfide.

The purpose of this research is to study how the natural gas transported by damaged distribution pipelines can migrate through the soil. If the gas emissions are not detected on time and the air vents are placed on inappropriate sites or are not maintained properly, gas can migrate directly throughout preferential pathways: bed sand pipes, sewer pipes, cable channels, channels for heating, then can enter the confined space and form explosive mixtures. As a proof of these phenomena, a series of events that occurred in industry and accidents suffered by civil citizens have occurred. The equipment used for emissions measurement is provided with 16 sensors to indicate the methane gas concentration. The sensors operate on the thermal conductivity principle being able to measure concentrations between 0% and 100% volume. A field version was adopted for tests to measure concentration of gases migrating through soil. For each location the soil permeability was determined using the running times distance between the source and the release detection heads. Also maps were drawn with time isolines for a particular concentration in order to characterize the dynamics of the natural gas migration, which helps improving the efficiency of solving technical expertise of the events due to natural gas explosions.

In order to investigate the degree of pollution by heavy metals, mining water samples were subjected to analysis, using inductively coupled plasma optical spectrometry method. An experimental module was developed and the water treatment capacity of natural zeolites was studied. The contaminated water was passed through 3 columns filled with zeolites, under static and dynamic mode in order to optimize the ion exchange process. Experiments were performed using different particle sizes of zeolite, and in different pH conditions. In this study, the degree of treatment in static conditions was performed, when a purification degree of 97.04% for zinc and 96.70% for manganese was obtained. In dynamic operation, the purification degree was lower, 81 % for manganese and 93% for zinc.

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