جستجوی مقالات مرتبط با کلیدواژه "hydrogen sulfide" در نشریات گروه "محیط زیست"

Natural gas produced from oil and gas wells often contains hydrogen sulfide and carbon dioxide, which are so-called “sour gasses”. Carbon dioxide (in large quantities) and hydrogen sulfide (even in small quantities) cause many problems during the transmission and consumption of natural gas. In this study, mathematical model for the separation of carbon dioxide and hydrogen sulfide from helium has been investigated with two different membrane species including a ceramic modulus and PEEK-L II and ionic liquids.

The effect of material, diameter, pressure and temperature on separation efficiency has been investigated. The ionic liquid used in this study is [hemim] [BF4]. The ceramic and PEEK-L II was studied. The pressure and concentration during absorption is investigated. The concentration variations of carbon dioxide and hydrogen sulfide in ionic fluid were investigated in time.

For a ceramic modulus, about 50 to 60% of the pressure drop occurs in the first 100 to 120 seconds. For the PEEK-L II modulus, in the first 30 seconds, about 50 to 60% of the pressure drop occurs due to gas absorption. The effect of temperature on the concentration of carbon dioxide and hydrogen sulfide at three temperatures of 25, 50 and 100 °C was investigated. As the temperature rises in the ceramic modulus, the amounts of carbon dioxide and hydrogen sulfide, passing through the membrane, increase.

As the time increases, the concentrations of carbon dioxide and hydrogen sulfide in the ionic fluid are increasing. With increasing temperature from 25 to 100 ° C, the amount of absorbed acidic gases into ionic liquid was increased. The PEEK-L II modules removed more acidic gases than the ceramic modules.

Biofilteration is one of the modern technologies in use for controlling the air pollutants because of its cost-effectiveness, high efficiency, simple operation, and lack of generating waste material. The purpose of the present study was to assess the removal or reduction feasibility of odourous compounds through biofilteration system in order to increase the safety and health of the treatment stuffs. A biological reactor having internal diameter of 14 and length of 95 cm was used for 12 months at ambient temperature in the vicinity of the sludge thickner tank. The concentration of compounds such as hydrogen sulfide, ammonia, orgoanosulforo compounds were measured. In order to maintain the suitable conditions for the growth of biomass at the biofilter bed, nutrients were used. The results showed that the removal efficiency of biofilter at an empty bed retention time of 30 and 15 s was more than 97% for hydrogen sulfide. Almost the same result (96%) was achieved for ammonia. According to the laboratory analysis, it was found that origin of odor was emissions of hydrogen sulfide and ammonia gases in the municipal wastewater treatment plant, where the biofilteration system could remove more than 95% of the odourous compounds. Biofilteration could bring the concentration of H2S and NH3 to less than the permitted level as recommended by the National Department of Environment. Therefore, this method is proposed to clean up contaminants in order to control the health and safety of the stuffs working in such environments.

Encountering hydrogen sulfide gas (H2S) during excavation is one of the important engineering, geological and environmental hazards during the tunnelling. Tackling this hazard and solving its challenges solving are very difficult and costly. During investigation of the situation, one of the main tasks is prediction or evaluation of the risk of H2S gas and selection of the best methods to tackle its engineering and environmental problems. In this study, water conveyance tunnel of Aspar excavated in H2S bearing environment is discussed. This tunnel is excavated in the hydrocarbon formations. In this paper, hazards, characteristics, safety regulations, and geological sources of H2S as well as the methods to decrease the risks and problems in excavation of the tunnel are presented in brief.

In order to determine the source of gas and to select the best methods to mitigate its hazards and problems, in addition to investigation of the same experiences, concentration of various gases was recorded by fixed stations on the machine and by mobile sensors at the beginning, midpoint and end of each working shift. Moreover, sampling of the polluted air and water was implemented. The samples were sent to a specific laboratory for chemical analysis. At the same time, concentration of the gas in the air and water of the tunnel was measured.

Experiments raleted to the tunnel showed that the gas caused an unacceptable condition for workers. For predicting the risk of H2S gas in underground spaces, it is possible to use some evidences such as sulfur springs, organic traces, organic shales, exposure of H2S odor from fresh surface of rock, and smelling of H2S during boreholes drilling. Results of the analysis show that the gas enters the tunnel along with water, dominantly. Also considerable amount of the gas is released to the air at the beginning. According to the investigations, the source of the gas is relevant to hydrocarbon formations inthe area.

Geological formations related to hydrocarbon resources are very important in the formation and reservation of H2S gas. Since the gas is in solution form and is emitted promptly, controlling the inflow of groundwater into the excavation, diluting the concentration of H2S and training the workers are a series of methods used to decrease the risks and problems associated with tunnel excavation in an H2S-bearing environment.

In this study, A mathematical model has been developed for H2S removal in a bio-filter. The model is used for analyzing the bio-filter performance in steady and unsteady state operation conditions. The governing equations including the concentration distribution equations for pollutant component and oxygen in the gas and biofilm phases were derived based on the conservation laws and solved numerically. The change of pollutant concentration through the bio-filter length and bio film thickness was obtained. The model predictions for removal efficiency and elimination capacity in three different gas flow rates (0.03, 0.07 and 0.14 m3/hr) and different inlet concentrations, compared with the experimental data reported by Oyarzun et al., and the accuracy of the model results was obtained. Also the results of the model for unsteady state operation condition were obtained for 1100 ppm of inlet concentration of H2S. These values compared with the existing experimental data too. Finally the effect of some operation parameters such as: specific surface area of the bed, height of the bed, porosity of the bed and gas flow rate, on the removal efficiency of bio-filter was investigated.