HYDROGEN SULFIDE ENVIRONMENTAL POLLUTION AND METHODS OF ITS DISPOSAL

ABSTRACT

The article discusses issues of protecting the environment from pollution by oil and petroleum products. Hydrogen sulfide pollution of the environment and methods of its disposal. Methods and analyzes of the composition of the initial mixture and exhaust gas are presented. The results of research on the development of technology for the catalytic neutralization of hydrogen sulfide-containing emissions from a gas processing plant are presented. Experimental information are also given.

АННОТАЦИЯ

В статье рассмотрены вопросы о защите окружающей среды, от загрязнения нефти и нефтепродуктами. Сероводородные загрязнения окружающий среды и способы его утилизации. Приведены способы и анализы состава исходных смеси и отходящего газa. Приведены результаты исследований по разработке технологии каталитического обезвреживания сероводородсодержащих выбросов газоперерабатывающего завода. А также приведены экспериментальные данные.

Keywords: environmental protection, hydrogen sulfide pollution, Claus process, reactor.

Ключевые слова: защита окружающей среды, сероводородные загрязнения окружающий среды, процесса Клауса, реактор.

The main sources of anthropogenic pollution are considered to be the extraction and processing of oil and natural gas. A large amount of hydrogen sulfide is emitted during the bacterial decomposition of human and animal waste. Toxic gas is also present in the emissions from sewage treatment plants and landfills. Hydrogen sulfide is also released into the environment from industrial sources, including oil refineries, natural gas producers, pulp and paper mills, manure processing plants, tanneries, and sewage treatment facilities. To design gas purification systems and create safe working conditions, such enterprises commission measurements of hydrogen sulfide in the air. Hydrogen sulfide (H₂S) is a toxic gas with the odor of rotten eggs. H₂S emissions are hazardous to health and the environment. People living in close proximity to farms, manure storage tanks, or pulp and paper mills are most affected by its exposure. However, people suffer much more from the effects of this gas in industrial settings than from such sources. The main technologies currently used and developed for the purification of natural gas from hydrogen sulfide include:

• Chemisorption processes, based on the chemical interaction of H₂S and CO₂ with the active part of the absorbent;

• Physical absorption processes, in which the extraction of acidic components occurs due to their solubility in organic absorbents;

• Combined processes, utilizing both chemical and physical absorbents simultaneously;

• Oxidative processes, based on the irreversible transformation of absorbed hydrogen sulfide into sulfur;

• Natural gas purification from hydrogen sulfide can also be carried out using adsorption processes, based on the extraction of gas components by solid absorbents - adsorbents.

The purification of natural and other gases from hydrogen sulfide can be carried out using various methods.

The choice of natural gas purification process from sulfur compounds in each specific case depends on many factors, the main ones of which are:

• Composition and parameters of the feed gas,

• Required degree of purification and the area of application of the commercial gas,

• Availability and parameters of energy resources, production waste, etc.

Protecting the environment from pollution caused by oil and petroleum products is crucial, considering that over 2.5 billion tons of crude oil are produced annually worldwide. A significant consequence of intensifying oil production is the pollution of the natural environment with oil and its by-products. Vapors emitted from oil and petroleum products are toxic and pose harmful effects on human health, especially those from sulfur oil and sulfur gases, as well as leaded gasoline. Hydrogen sulfide pollution and methods of its disposal are among the most pressing concerns for the global community.

The main industrial process for producing elemental sulfur is the Claus process, which involves the high-temperature combustion of hydrogen sulfide to sulfur dioxide and the subsequent production of elemental sulfur. However, when the gas contains less than 40% hydrogen sulfide, the Claus process becomes economically unviable. Under such circumstances, the direct one-stage oxidation of hydrogen sulfide to elemental sulfur using oxide catalysts proves to be a more appropriate method.

This study focuses on developing a method for the catalytic oxidation of hydrogen sulfide to ensure almost complete conversion into environmentally friendly sulfur. It is known that the oxidation reaction of hydrogen sulfide is exothermic, allowing it to be carried out without heat supply. However, at high concentrations of hydrogen sulfide, the amount of heat released may be so large that when the process is carried out in an adiabatic reactor, the temperature in it will increase above the permissible level. Calculations show that during the oxidation of 1% H₂S into elemental sulfur under adiabatic conditions, the temperature of the gas mixture increases by 60-65°C. Therefore, to maintain the temperature in the reactor within a given range, it is necessary either to ensure heat removal from the reactor or to dilute the gas to an acceptable level of hydrogen sulfide concentration before entering the reactor.

The proposed technology does not require special design; the heat generated and the resulting sulfur are removed from the reaction zone by separately supplying oxygen to each stage. The control diagram for the technological parameters of the installation is shown in Figure 1. This paper presents the results of research on the development of technology for the catalytic neutralization of hydrogen sulfide-containing emissions from a gas processing plant. The product, a gas of the following composition, was subjected to oxidation: [Composition of the gas].

hydrogen sulfide – 28 – 30 vol.%;

carbon dioxide – 5.5 – 6.0 vol.%;

methane – 3 – 7 vol.%;

water – 3 – 4 vol.%.

The composition of the initial mixture and exhaust gas was analyzed by chromatography. The resulting oxidation reactions of H₂S, sulfur and water are condensed and captured in intermediate containers after each stage.

The maximum conversion of hydrogen sulfide into elemental sulfur, with 100% selectivity, is achieved with the following process parameters.

The experiments showed that if the concentration of H₂S in the purified gas is reduced to 4 vol.% by diluting it at the first stage of the installation and oxygen is added to it in an amount ensuring the O₂/H₂S ratio equal to 0.25-0.3 at a space velocity of 3600 hours -1 and the temperature in the first reactor is 300 °C gas, the outlet from the reactor will contain 2.13 vol.%, H₂S.

Figure 1. Scheme for monitoring the technological parameters of the installation

If the mixing of this gas with air is brought to a state at which the concentration of the O₂/H₂S ratio is 0.6-0.7 and it is passed through the second reactor at a volumetric speed of 3000 h-1, at a temperature of 255 ° C, then at least 90% H₂S will turn into elemental sulfur and a small part of it will oxidize to SO₂. If the concentration of H₂S in the purified gas is increased above 6.0% by mass, then an uneven temperature distribution is observed across the catalyst layers, which negatively affects the process.

The experimental data obtained showed that:

– when maintaining the O₂/H₂S molar ratio at the reactor inlet less than 0.35, no sulfur dioxide is formed, and all oxygen is consumed for the oxidation of hydrogen sulfide into elemental sulfur,

- with an O₂/H₂S ratio of 0.6, the amount of SO₂ formed during H₂S conversion is above 99.0% and depends on the water vapor content in the gas. With virtually no water vapor, the SO₂ concentration at the outlet is 0.15 vol.%, and with a water vapor content of 20 vol.%, the concentration of sulfur dioxide is 0.32 vol.%.

Thus, depending on the SO₂ content requirements in the exhaust gas, the issue of removing water from reaction mixture by concentrating it in special devices. Given the selected CO₂ catalyst, hydrogen and methane do not undergo any transformations.

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