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Hydrogen sulfide is one of the main toxic and explosive components of atmospheric air, found in the waters of mineral springs, volcanic gases, and petroleum and natural gas fields. It is used in the production of sulfur, sulfuric acid, mineral fertilizers, sulfides, organosulfur compounds, in analytical chemistry and medicine. Н2S is an active poisonous substance of neuroparalytic action. Upon inhalation of 1.0 mg/l and higher hydrogen sulfide, poisoning with it can develop almost instantly: convulsions and loss of consciousness end in quick death from respiratory and cardiac attack. The maximum permissible concentration of hydrogen sulfide in the air of production zones is 10 mg/m3. The presence of hydrogen sulfide in environmental objects is a serious danger, both from an environmental and technical point of view. Its presence causes chemical and electrochemical corrosion, is easily ignited (at 346°C), and in a mixture with air explodes. Explosive concentrations in the mixture with air are at the level of 4.3-45.5%. With regards above mentioned the control of pre-explosion and fire-hazardous concentrations of hydrogen sulfide is one of the most important tasks of safety and solving various fire-fighting measures. A method for increasing the selectivity and sensitivity of semiconductor methods for determining hydrogen sulfide is proposed, based on the use of optimal values of the sensor temperature and the composition of the gas-sensitive material of catalysts with inadequate activity to different components of the gas mixture. As a result of the conducted experiments, a selective semiconductor hydrogen sulfide sensor was developed, which provides rapid determination of hydrogen sulfide in a wide range of its concentration in atmospheric air and process gases. The main metrological characteristics and operational parameters of the developed selective semiconductor sensors for the determination of hydrogen sulfide are evaluated. Selectivity, measurement range and basic errors, additional sensor errors due to changes in ambient temperature and pressure are studied. The change in the flow rate of the gas mixture in the studied interval (5-50 l/h) does not significantly affect the value of the sensor output signal. Scope of the developed sensors: environmental monitoring of atmospheric air and process gases. The developed semiconductor hydrogen sulfide sensors are not inferior in accuracy and reproducibility to well-known foreign analogues, while retaining the following characteristics: expressiveness, portability, ease of manufacture and operation. The value of the relative standard deviation (Sr) due to immutable components does not exceed 0.05. The output signal of the sensors also does not depend on the location in space and the angles of inclination, which makes it possible to classify the developed sensors (according to GOST-13320-82) as independent. |
