INVESTIGATION OF GAS PURIFICATION PROCESSES FROM H₂S AND CO₂ USING MEA AND DEA AMINES

ABSTRACT

This article presents the results of comprehensive scientific research aimed at improving the quality of locally sourced natural gas to meet the requirements for commercial gas. The main objective of the study is the removal of acidic components from natural gas—namely hydrogen sulfide (H₂S) and carbon dioxide (CO₂)—using absorption-based purification methods.

Within the framework of the study, new-generation absorbent compositions intended for gas purification processes were developed and investigated. Monoethanolamine (MEA) and diethanolamine (DEA) were used as amine components, while dimethyl and monomethyl ethers of polyethylene glycol were applied as ether additives. At the initial stage, aqueous solutions of amines and ethers at various concentrations were prepared, and laboratory investigations of their absorption and operational characteristics were carried out.

АННОТАЦИЯ

В статье представлены результаты комплексных научных исследований, направленных на повышение качества природного газа местного происхождения до уровня требований, предъявляемых к товарным газам. Основной целью исследования является удаление кислых компонентов природного газа, в частности сероводорода (H₂S) и диоксида углерода (CO₂), с использованием абсорбционных методов очистки.

В рамках исследования разработаны и исследованы композиции абсорбентов нового поколения, применяемые в процессах газоочистки. В качестве аминных компонентов использованы моноэтаноламин (МЭА) и диэтаноламин (ДЭА), а в качестве эфирных добавок — диметиловый и монометиловый эфиры полиэтиленгликоля. На начальном этапе были получены водные растворы аминов и эфиров различной концентрации, проведены лабораторные исследования их абсорбционных и эксплуатационных характеристик.

Keywords: components, absorbents, acidic components, absorbent compositions, foaming, corrosion, technology, amines, esters.

Ключевые слова: компоненты, абсорбенты, кислые компоненты, композиции абсорбентов, вспенование, коррозии, технологии, амины, эфиры.

Introduction

In global industrial practice, the purification of gases from acidic components such as hydrogen sulfide (H₂S), carbon dioxide (CO₂), ethyl mercaptan (RSH), carbonyl sulfide (COS), and carbon disulfide (CS₂) is most commonly carried out using ethanolamines as absorbents. The most widely used ethanolamines include monoethanolamine (MEA), diethanolamine (DEA), and N-methyldiethanolamine (MDEA). The presence of COS and CS₂ in the gas composition represents a limiting factor, as these compounds react irreversibly with MEA, leading to significant solvent degradation and losses. Therefore, the development of technologies for producing new highly selective absorbent compositions for the removal of acidic components from natural gas is considered a relevant and pressing research task.

Aqueous solutions of monoethanolamine are commonly used as solvents in gas purification processes. According to operational regulations, the concentration of MEA in solution, when saturated with acidic gases, should not exceed 15–20% by volume. More highly concentrated solutions significantly intensify metal corrosion, whereas pure alkanolamine solutions do not exhibit corrosive properties [1, 4–8, 11].

MEA-Based Gas Purification Process

The existence of such a relationship between solution concentration and corrosion rate limits the possibility of improving the efficiency of chemisorption amine-based processes. However, in recent years, advances in the development of corrosion inhibitor technologies have made it possible to increase the concentration of the active component in the solution up to 30% (by volume). This development has rendered the MEA process more economically attractive and promising.

When designing MEA-based purification units, it is generally required that the concentration of acidic components in the solution leaving the bottom tray of the absorber should not exceed 65–70% of the equilibrium concentration relative to the primary raw gas. Under these conditions, the degree of solution loading should not exceed 0.3–0.4 mol/mol MEA. In recent years, at some plants engaged in the purification of synthesis gas from CO₂ under pressure, solution loadings of 0.6–0.7 mol/mol MEA have been achieved. Such operating conditions necessitate the use of alloyed steels in equipment manufacturing or the application of corrosion inhibitors during plant operation.

The MEA-based purification process is recommended for gas treatment when the partial pressure of hydrogen sulfide and carbon dioxide does not exceed 0.6–0.7 MPa.

Advantages of the process:

-deep removal of hydrogen sulfide and carbon dioxide from gases over a wide range of partial pressures;

-MEA exhibits high chemical stability, is easily regenerated, and possesses high reactivity;

-simplicity of technological and mechanical design, as well as high reliability of the process when the unit is properly operated;

-MEA solutions have relatively low absorption capacity for hydrocarbons, which increases the efficiency of sulfur recovery during acid gas treatment.

Disadvantages of the process:

• relatively low absorption capacity of the solution;
• high specific absorbent consumption and elevated operating costs;
• the presence of certain impurities in raw gas (CO₂, COS, CS₂, HCN, SO₂, and SO₃) leads to the formation of non-regenerable or poorly regenerable high-molecular compounds during interaction with the solvent, resulting in reduced absorbent activity, increased foaming, and enhanced corrosive behavior;
• the process is not applicable when COS and CS₂ are present in the gas;
• low efficiency in the removal of mercaptans and other organic sulfur compounds;

According to the data reported by Campbell [13], the irreversible reactions of monoethanolamine with CO₂, COS, and CS₂ result in the following MEA degradation rates: 3.35 kg per 1000 m³ of CO₂, 1 kg per 1 m³ of COS, and 1 kg per 1 m³ of CS₂. For DEA, the corresponding value is 3.68 kg per 1000 m³ of CO₂; moreover, DEA practically does not react with COS and CS₂, as these interactions lead to the formation of non-regenerable compounds.

Sulfur-containing compounds present in natural and associated petroleum gases—such as mercaptans, disulfides, thiophenes, and others—do not react with amines.

To prevent foaming in monoethanolamine solutions, antifoaming additives are introduced at concentrations of 0.001–0.0015 wt.%. Silicone-based antifoams or aqueous emulsions of high-boiling alcohols (oleyl alcohol and others) are commonly used. For example, at the Mubarek Gas Processing Plant, KE-10-12 (21-2A) and KE-10-21 antifoaming agents have been applied. Industrial testing of the KE-10-12 antifoaming agent demonstrated a reduction in solvent losses, improved operational stability of the unit, and enhanced performance of absorption and rectification equipment [1–3].

MEA-Based Gas Purification Process. The MEA-based gas purification process was implemented using the unit shown in Figure 1. Its main technological parameters are presented in Table 1.

Table 1.

Main technological parameters of the MEA process for hydrogen sulfide removal at the Mubarek Gas Processing Plant

* According to the design specifications, the temperature was 20–30 °C.

DEA-Based Gas Purification Process

An aqueous solution of diethanolamine (DEA) is used as the solvent in the DEA-based gas purification process. The concentration of DEA in the solution varies from 20 to 30 wt.% depending on the content of acidic gases in the primary raw gas and the degree of solution loading. When the concentration of acidic gases in the solution is 0.05–0.08 m³/L, a 20–25 wt.% DEA solution is applied; at an acidic gas concentration of 0.14–0.15 m³/L, a 25–27 wt.% DEA solution is used; and at acidic gas concentrations of 0.15–0.17 m³/L, a 25–30 wt.% DEA solution is applied within the SNPA–DEA process [1, 2, 8, 9].

The conventional DEA process employs a diethanolamine concentration of 25–27 wt.% when the partial pressure of acidic gases is 0.2 MPa or higher. The SNPA–DEA process, utilizing DEA with 25–30 wt.% active component, is applied when the partial pressure of acidic gases reaches 0.4 MPa or above.

These operating conditions enable the achievement of the required degree of solution loading and allow the advantages of the process to be realized. In the SNPA–DEA process, the solution loading reaches 1.0–1.3 mol/mol DEA, compared with 0.3–0.4 mol/mol for the MEA process [7]. However, despite the higher loading capacity, the absorption efficiency of DEA solutions in the SNPA–DEA process is lower than that of MEA solutions. This behavior is explained by the significantly lower molecular weight of monoethanolamine, which provides a higher absorption capacity at the same mass concentration.

Advantages of the Process

-deep purification of gas from H₂S and CO₂ even in the presence of COS and CS₂, since the reaction products of diethanolamine with COS and CS₂ are hydrolyzed to CO₂ and H₂S during solvent regeneration;

-high chemical stability of diethanolamine solutions under process conditions, easy regenerability, and low saturated vapor pressure;

-simplicity of technological and mechanical design, as well as high operational reliability when the unit is properly operated;

-the absorption process is carried out at temperatures 10–20 °C higher than those used in the MEA process, which prevents intensive foaming of the solution when the gas contains high concentrations of heavy hydrocarbons or when liquid hydrocarbons enter the solvent.

Disadvantages of the Process

-low absorption capacity of the solvent, resulting in higher specific absorbent consumption and increased operating costs;

-interaction of certain impurities present in the raw gas—partially CO₂ or completely HCN—with the solvent to form non-regenerable compounds;

-low efficiency in the removal of mercaptans and other organic sulfur compounds.

In practice, the technological flow diagrams of MEA and DEA processes do not differ significantly, except for the methods used to remove non-regenerable compounds from the circulating solution. In DEA-based units, solvent purification is performed by filtration, through which up to 10% of the circulating solution is passed. In MEA-based units, solvent purification involves both distillation and filtration, with up to 4% of the solution circulated through this treatment system.

An increase in amine concentration allows the circulating solution flow rate to be reduced while maintaining the same raw gas throughput. This, in turn, decreases heat consumption for the regeneration of loaded solutions and reduces electrical energy demand during solvent recirculation.

Pilot testing was carried out at the third processing train of the Orenburg Gas Processing Plant. The unit consists of two identical parallel operating trains, each equipped with an absorber of 3.8 m diameter and a single desorber with a variable diameter of 2.7/3.7 m (top/bottom), along with the corresponding heat exchange and cooling equipment.

The absorber and desorber are equipped with wire-mesh type tray internals. The absorber contains 25 trays, while the desorber is fitted with 33 trays (22 trays in the lower stripping section and 10 trays in the upper conditioning–cooling section).

The absorber operates with a two-stream solvent regeneration scheme, providing the same regeneration degree on the 15th and 25th trays, with flow split ratios of 40/60% of the total circulating solvent flow rate.

Experimental studies were conducted based on the main design specifications established for the operating conditions of the gas desulfurization unit. The obtained data indicate that increasing the DEA concentration from the design value of 25% to 40% made it possible to simultaneously reduce the steam consumption supplied for regeneration by more than 10% and to decrease the absorbent circulation rate by a factor of 1.5.

Absorptive purification of gas from acidic components (hydrogen sulfide and carbon dioxide) is applicable not only to produced natural gases, but also to the stabilization and degassing of low-pressure condensates containing up to 54 vol.% H₂S and 14 vol.% CO₂. These processes are carried out in absorber units using aqueous DEA solutions as absorbents under increased pressure conditions.

In the absorbers of the SO-1 design configuration, fourteen overflow pocket-type valve trays are installed. The schematic diagram of the specified equipment is shown in Figure 2.

During the operation of absorbers in gas processing units, the main operational problems are associated with severe metal erosion of the apparatus shell in the lower section beneath the valve trays, specifically in the zones of acidic gas inlet and discharge of the loaded absorbent.

Based on the results of the investigations, it was determined that, in addition to corrosion, cavitation-induced surface degradation also occurs on the walls of the lower section of the absorber shell.

When such a solution flows as a thin film along the absorber wall and comes into contact with the incoming gas undergoing purification, which has a lower temperature, film cooling occurs. This results in condensation of water vapor and rupture of gas bubbles.

As a consequence, cavitation phenomena develop, causing degradation of the lower section of the absorber shell, which in turn reduces the reliability and service life of the equipment.

Purified Gas Outlet

To reduce the rate of wall degradation of the equipment shell and to extend its service life, one of the absorbers was reconstructed, as shown in Figure 2. The reconstruction involved installing a square-section insert made of stainless steel in the lower part of the apparatus in order to eliminate direct contact between the raw gas and the apparatus shell, as well as to prevent the flow of the loaded absorbent along the shell walls [12].

The protective casing was installed in the zone of the feed gas inlet nozzle and the lowest valve trays (according to trays 1 and 4). For this purpose, the valves and support beams on the specified trays were covered with plates, and the downcomer and receiving box were dismantled in the central part of the tray (while the receiving pockets on the 4th tray were retained).

The use of such “activated” amines instead of DEA, which are selective toward CO₂ even without activators, makes it possible to reduce energy consumption during amine regeneration.

Studies of the corrosive activity of various absorbents (Table 2) showed that the addition of MEPEG St. to DEA and MDEA in amounts of 5–20% reduced the corrosion rate of St.10 carbon steel by 10–12%. Piperazine (PP) exhibited an even stronger effect: the addition of 2% PP to DEA and MDEA significantly reduced the corrosion rate, and a similar effect was observed for mixed MDEA/DEA systems [7, 8, 11].

The present research is aimed at improving the quality of locally sourced natural gas to meet the requirements specified for commercial gas. The primary objective of the study is the removal of acidic components from the gas composition, namely hydrogen sulfide and carbon dioxide. To achieve this goal, the development of new-generation absorbents for use in absorption processes and their subsequent industrial implementation was defined as the main research task.

In gas purification, MEA and DEA were used as amine components, while dimethyl and monomethyl ethers of polyethylene glycol were applied as ether components in the absorbent compositions. At the initial stage of the study, aqueous solutions of amines and ethers at various concentrations were prepared, and the obtained results are presented in Figure 2 [7, 8, 11].

The absorbent properties were investigated under laboratory conditions using a glass absorption column at the following operating parameters: gas flow rate of 8 L/h (nitrogen with added acidic gases), absorbent flow rate of 60 cm³/h, and temperature of 40 °C. Nitrogen was used as the model gas, into which the following components were introduced: H₂S, CO₂, COS, and RSH.

The experimental results are presented in Table 2. The addition of piperazine (PP) to MDEA and DEA in amounts of 2–10% had virtually no effect on the degree of RSH removal.

Table 2.

Equilibrium solubility of CO₂ in aqueous MDEA/DEA solutions containing MEPEG [4]

The results of corrosion studies, summarized in Table 3, demonstrate that piperazine, in contrast to other activators, not only enhances the absorption performance of the absorbents but also effectively reduces their corrosive properties.

Table 3.

 Corrosion rate of St.10 carbon steel in various absorbents [14]

Based on the above-mentioned issues, the present study investigates the activity and selectivity of absorbent compositions developed on the basis of MEA + DEA + PEGDME + PEGMME for the absorptive removal of acidic components from natural gas. As the feed gas, natural gas processed at the Mubarek Gas Processing Plant was used.

The results of studies aimed at determining the effect of the corrosion inhibitor “Kvatrmin 1001” on the foaming characteristics of absorbents used in gas absorption purification showed that an increase in the concentration of the corrosion inhibitor in the absorbent composition leads to an increase in foam height. When the concentration of the corrosion inhibitor in the absorbent was up to 30 ppm, the foam height reached 25 mm. In contrast, for the absorbent compositions DPP-1, MDPP-1, and MDPP-5, even at concentrations up to 50 ppm, the foam height did not reach 25 mm. It was also observed that at low initial concentrations of the corrosion inhibitor, the foam height increased rapidly, whereas further increases in concentration resulted in much smaller increments in foam height [6, 7, 8, 11, 13].

The dependence of foam stability of the absorbent compositions on the concentration of the Kvatrmin 1001 corrosion inhibitor showed that, at a concentration of 50 ppm in the DPP-1, MDPP-1, MDPP-2, and MDPP-5 absorbent systems, the foam collapse time was less than 60 s, indicating that these compositions fall into the medium foam stability class. In contrast, the DEA solution was found to belong to the high foam stability class [7, 8, 11, 13, 14].

Figure 3. Dependence of foam stability of absorbent compositions on the concentration of the “Kvatrmin 1001” corrosion inhibitor

Figure 4. Effect of mechanical particle content in absorbents on the foaming ability of absorbent compositions

At the next stage of the study, the foaming ability and foam stability of absorbent samples were investigated as a function of the concentration of mechanical particles present in their composition. The obtained results are presented in Figure 2. As shown in Figure 4, when the content of mechanical particles reached 0.005% in the DEA and MDPP-2 absorbents, a sharp increase in foam height was observed. For the DPP-1, MDPP-1, and MDPP-5 absorbents, a similar trend was detected; however, the increase in foam height occurred to a much lesser extent.

When the concentration of mechanical particles in amine solutions was increased up to 0.1%, the foam height continued to rise within a limited range. At concentrations above this level, the effect on foam height became insignificant. This behavior may be explained by a decrease in foam stability due to an increased amount of solid particles at the liquid–gas interfacial boundaries, which disrupts the structural integrity of the foam [7, 8, 11, 13, 14].

During the study, the corrosion activity of the developed absorbent compositions and DEA was initially determined in their aqueous solutions without additives. The obtained results are presented in Table 4.

Table 4.

Corrosion activity of absorbent compositions and DEA

In scientific studies aimed at investigating the factors influencing foam formation by amines, one of the most significant factors is the formation of degradation products resulting from absorbent decomposition. It is well known that during desorption, partial degradation of amines may occur under the influence of various external factors, leading to the formation of secondary compounds. At present, industrial practice allows the use of absorbents containing degradation products up to 25%, provided that their foaming tendency and corrosive activity remain within acceptable limits.

Conclusion

In general, the results of the studies conducted in the presence of substances influencing foam formation of absorbent compositions demonstrated that the DPP-1, MDPP-1, and MDPP-5 absorbent systems exhibited the best performance. Based on the investigated dependencies of foaming ability and foam stability on the concentrations of liquid hydrocarbons, corrosion inhibitors, mechanical particles, and degradation products formed as a result of absorbent decomposition, these absorbent compositions were proven to be fully suitable for industrial application.

The results obtained from the evaluation of corrosion activity showed that, among the investigated absorbent compositions, those based on MEA exhibited relatively lower corrosive properties. At the same time, the absorbents that demonstrated high efficiency in gas purification and favorable foaming characteristics were characterized by the following corrosion rates: DPP-1 — 0.06 mm/year, MDPP-1 — 0.05 mm/year, and MDPP-5 — 0.06 mm/year. These results indicate that the proposed absorbent compositions exhibit improved corrosion performance compared with conventional absorbents used in gas purification processes.

References:

1. Афанасьев А.И. Применение МДЭА для очистки природного газа / А.И. Афанасьев, С.П. Малютин, В.М. Стрючков // Газовая промышленность. - 1986. - № 4. - С. 20-21.
2. Стрючков В.М. Применение МДЭА для очистки газов от Н₂Б на установке Л24/6 в ООО «ПО Киришинефтеоргсинтез» / В. М. Стрючков, А.И. Афанасьев,
3. Н.Н. Кисленко // Научно-технический прогресс в технологии переработки природного газа и конденсата. - М.: ВНИИГАЗ, 2003. - С. 57-62.
4. Yuldashev, T. R., & Ashirov, O. N. (2026). TABIIY GAZNI MDEA (METALDIETANOLAMIN)+ DEA KOMPOZITTSION ABSORBENTLARI BILAN TOZALASH. Latin American journal of education, 6(1), 144-151.
5. Raxmanovish, Y. T., & Shermamato‘G‘Li, T. S. (2025). TABIIY GAZLARNI ALKANOLAMINLI ERITMALARNING KOMBINASIYALANGAN ABSORBENTLARI YORDAMIDA UGLEROD DIOKSIDI VA OLTINGUGURTDAN TOZALASH DARAJASINING BOSIM VA HARORATGA BOG ‘LIQLIGINI TADQIQ QILISH. Sanoatda raqamli texnologiyalar/Цифровые технологии в промышленности, 3(4), 159-166.
6. Tashmurza, Y., & Shahboz, T. (2025). STUDY OF THE TEMPERATURE DEPENDENCE OF THE DEGREE OF PURIFICATION OF NATURAL GASES FROM SOUR COMPONENTS USING COMBINATIONS OF MEA AND DEA ALKANOLAMINE SOLUTIONS. Universum: технические науки, 11(11 (140)), 75-81.
7. Юлдашев, Т. Р. (2023). Основа оборудования, используемого в процессе очистки газоабсорбционной технологии. Universum: технические науки, (5-6 (110)), 20-24.
8. Raxmanovish, Y. T., & Abdiraxmono‘G‘Li, A. S. (2025). METANOL VA TABIIY GAZDAN DIMETIL YOQILG ‘ISINI (DME) ISHLAB CHIQARISH VA UNI QAYTA ISHLASH TEXNOLOGIYASINI TANLASH. Sanoatda raqamli texnologiyalar/Цифровые технологии в промышленности, 3(3), 144-151.
9. T.R.Yuldashev (2023). TABIIY GAZNI NORDON KOMPONENTLARDAN TOZALASHDA SELEKTIVLIGI YUQORI BO‘LGAN AMINLI ERITMALARDAN FOYDALANISHNING SAMARADORLIGI. Sanoatda raqamli texnologiyalar / Цифровые технологии в промышленности, 1 (1), 86-92. doi: 10.5281/zenodo.8377015
10. Юлдашев, Т. Р. (2023). Актуальные проблемы аминной очистки природных газов и пути их использования. Universum: технические науки, (4-6 (109)), 24-27.
11. Yuldashev, T. R., Yuldashev, N. T., & Uralov, S. X. (2025). STUDY OF FOAMING AND CORROSION BASED ON THE USE OF COMPOSITIONS OF AMINES AND ETHERS IN THE PURIFICATION OF NATURAL GASES FROM ACIDIC COMPONENTS. AMERICAN JOURNAL OF EDUCATION AND LEARNING, 3(5), 984-992.
12. Yuldashev, T. R., & Мakhmudov M, J. (2023). Cleaninng of Natural from Sobe Component. Journal of Siberian Federal University. Engineeng & Technologies, 16(3), 296-306.
13. Makhmudov, M. J., & Yuldashev, T. R. (2023). Cleaning of Natural Gases from Sour Components.
14. Rakhmanovich, Y. T., Egamberdiyevich, A. P., & Raimovich, K. I. DISPOSAL OF FLARE ASSOCIATED GASES IN OIL AND GAS FIELDS.