COMPARISON OF ECONOMIC AND MATERIAL COSTS OF PURIFICATION OF SULFUR-CONTAINING COMPOUNDS AND POOR GASES IN GASES

ABSTRACT

To date, the processes of using amino solutions such as monoethanolamine (MEA-NH₂CH₂CH₂OH), diethanolamine (DEA-NH (CH₂CH₂OH)₂), and N-methyldiethanolamine (MDEA-NCH₃ (CH₂CH₂OH)₂) used in the absorption purification of natural gases from acidic components have been scientifically substantiated. Theoretical studies were conducted on the comparison of MDAA solution with MEA. Using the composite absorbent obtained during our research, the factors causing corrosion were assessed, and the absorbent composition with optimal indicators was selected. To date, the processes of using monoethanolamine (MEA) and diethanolamine (DEA) from amino solutions, mainly in industry, as absorption absorbents in natural gas purification units at the "Shurtan Oil and Gas Production Department," "MGPZ," "Shurtan Gas Chemical Complex," and "Ustyurt Gas Chemical Complex," due to their high selectivity in natural gas purification, have been studied. In this case, 26-30% MEA and MDEA compositions were used, and the obtained results were tested at the "MGPZ" and it was established that the MDEA solution is less susceptible to destructive thermal decomposition. Thus, due to the use of MDEA, energy consumption (electricity and heat) was reduced by up to 30%, and absorbent costs were reduced by 25-40%, which allowed for a reduction in equipment maintenance and repair costs.

АННОТАЦИЯ

На сегодняшний день научно обоснованы процессы использования аминных растворов, таких как моноэтаноламин (MEA-NH₂CH₂CH₂OH), диэтаноламин (DEA-NH (CH₂CH₂OH)₂) и N-метилдиэтаноламин (MDEA-NCH₃ (CH₂CH₂OH)₂), используемые при абсорбционной очистке природных газов от кислых компонентов. Проведены теоретические исследования по сравнению раствора МДЭА с МЭА. С помощью композиционных абсорбентов, полученных в ходе наших исследований, были оценены факторы, вызывающие коррозию, и выбрана композиция абсорбента с оптимальными показателями. На сегодняшний день изучены процессы применения моноэтаноламина (МЭА) и диэтаноламина (ДЭА) из аминовых растворов в основном в промышленности в качестве абсорбционных поглотителей в установках очистки кислых газов природного газа в "Шуртанском нефтегазодобывающем управлении," "МГПЗ," "Шуртанском газохимическом комплексе" и "Устюртском ГХК" в связи с высокой селективностью при очистке природного газа. При этом использовались 26-30%ные композиции МЭА и МДЭА и полученные результаты были апробированы на "МГПЗ" и установлено, что раствор МДЭА менее подвержен деструктивному термическому разложению. Таким образом, за счет применения МДЭА достигнута экономия энергопотребления (электроэнергии и теплоносителя) до 30%, а также достигнута экономия затрат на абсорбенты на 25-40%, что позволило снизить затраты на обслуживание и ремонт оборудования.

Keywords: Ethylene mercaptan, ethanolamines, non-selective, selective, corrosive, piperazine, polyethylene glycolin.

Ключевые слова: Этиленмеркаптан, этаноламины, неселективные, селективные, коррозионные, пиперазин, полиэтиленгликолин.

Introduction: In world practice, the most commonly used ethanolamines as absorbents for gas purification from acidic components (H₂S and CO₂, ethylene mercaptan (RSH), carbon disulfide (COS), carbon disulfide (CC₂)) are: monoethanolamine (MEA-NH₂CH₂CH₂OH), diethanolamine (DEA-NH (CH₂CH₂OH)2) and N-methyldiethanolamine (MDEA-NCH₃ (CH₂CH₂OH)2) [1, 2, 3]. We will analyze the results obtained during gas purification from hydrogen sulfide. The comparison of primary amine solution (MEA) with tertiary amine absorbent (MDEA) was theoretically investigated. In this case, the calculation of economic and material costs was carried out. In conclusion, the sequence of the main indicators of reducing economic costs is presented. The effectiveness of using an aqueous solution of methyldiethanolamine (MDEA) was evaluated. The main disadvantages of using monoethanolamine are described [4].

The main advantage of using chemical absorption processes is the high degree of purification of hydrocarbon gases from acidic components. At the same time, they are characterized by low absorption of hydrocarbon components of the raw gas. Chemosorbents such as caustic sodium and potassium, alkali metal carbonates, and alkanolamines were used.

One of the most common methods is the processes of amination. Their industrial use began in the 1930 s. The use of aqueous solutions of alkanolamines has been improved in the course of research. They are weak bases, therefore they react with acidic gases H₂S and CO₂. As a result, gas purification occurs. The obtained salts easily decompose when the saturated solution is heated. The most popular ethanolamines used in gas purification processes from H₂S and CO₂ include: monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diglycolamine (DGA), diisopropanolamine (DIPA), methyldiethanolamine (MDEA). [5, 6, 7].

Until now, monoethanolamine (MEA) and diethanolamine (DEA) have mainly been used in industry as absorption absorbents in devices for purifying acidic gases from natural gas. However, in recent years, a trend has been observed to replace MEA with a more effective absorbent - methyldiethanolamine (MDEA). For example, in the CIS, natural gas purification was used in large deposits of countries around the world, and later it is also used at the Mubarek Gas Processing Plant, the Gas Chemical Complex, the Shurtan Oil and Gas Production Department, and the Ustyurt Gas Production Complex in our republic.

Comparison of aqueous solutions of MEA and MDEA

As a result of studying many of our previous studies, as well as modeling the processes of purifying associated gas (AG) from acid gases H₂S and CO₂, data comparable to plant requirements were obtained..

An assessment of the economic costs of gas purification processes using a 19% aqueous solution of MEA and a 33% aqueous solution of MDEA was conducted [5, 6]. For the process of purifying associated gas from H₂S and CO₂ impurities using MDEA, 12 tons of amine per year are required for the initial filling of the system.

The hourly consumption to compensate for operational losses during gas purification is approximately 11*0.15=1.65 kg of MDEA 18200 kg/hour gas consumption, where 0.15 is the consumption rate per 1000 m³ of gas. This indicator is approximately 1.65*24*355 =14058 kg/year per year, where 355 is the number of operating days of the device. As a result, approximately 12 + 14 = 26 tons of methyldiethanolamine is consumed annually. The price of one ton of MDEA is $3,200. As a result, $3200*26 = $830,000 will be spent on MDEA in the first year [1.5.9]. When using MEA to replenish the system, 15.12 tons of MEA are required per year.

If the gas consumption is 18200 kg/h, then 1.82 kg of MEA is used to compensate for the operational losses of MEA due to large losses (0.0183%) due to irreversible formation, evaporation, and droplet liquid losses of chemical compounds of MEA with COS, CS₂, and O₂ (0.0084%), and other factors. Annually, 1.82*24*355=15506 kg of MEA is used for filling. The total annual consumption of MEA is 15.12+15.506=30.63 tons of monoethanolamine. The average price per ton of MEA is 90,000 rubles. As a result, 30.63*90000 = 275,6700 rubles are spent annually on MEA [3.6].

To replenish the system with an aqueous solution of methyldiethanolamine, 12*67/33 = 24.36 tons of water are required per year. To compensate for operating losses, 14*85/15=79.33 tons of water are consumed annually. Softened water is also fed into a scrubber located in an amine purification unit. Annual water requirement: - 174*24*355=1482.28 t/year, where 174 kg/hour is the softened water consumption.

When using MDEA, the total amount of softened [1,5] water prepared is 24.36+79.33+1482.28=1586.17 tons. The amount of water required to fill a 19% aqueous solution of MEA: - 15.12*81/19 = 64.46 t/year.

15.506 * 92/8 = 178.32 tons of water are used annually to compensate for operating losses. 205*24*355=1476.6 tons of softened water is used annually to retain the lost amine. As a result, 64.46 + 178.32 + 1476.6 = 1989.38 tons of softened water are used during the year when using MEA [6, 8].

The total cost of water preparation and its transportation to the facility is 39.84 + 9 = 48.84 rubles per ton of water, while the cost of water preparation is 39.84 [10].

Costs for water prepared when using MDEA: -3200*48.84=156,000 USD/year. Costs for the use of MEA: 2800*48.84 = 116,754 dollars/year [10]. 2AVG horizontal air cooling units are used for cooling a reconstituted aqueous solution of MDEA. These AVGs are designed for the condensation and cooling of steam, gas, and liquid media in the technological processes of the oil refining, petrochemical, and chemical industries.

The average power consumption of one engine is 11 kV t/h. These AVGs have two electric motors in their components. The total electricity consumption of AVG is 2*11 = 22k W/h. Since the process is continuous, the electricity consumption is 22*24*355= 187440 kW per year[1]. This type of AVG is also used for cooling an aqueous MEA solution, and the annual electricity consumption is 187,440 kWh.

This type of AVG is also used when MDEA is used as an absorber for cooling acidic vapors in the regeneration unit. Electricity consumption is 187,440 kW per year.

Gas turbine compressors GTK7 with an AZP 630/6000 electric motor are used for pumping sulfur-containing hydrocarbon gas. The annual electricity consumption of this electric motor is 630*24*355=5367600 kW/year. The number of compressors is 3, and the operating coefficient of the compressor is 1.4. Total electricity consumption: 5367600x1.4=7514640 kW/year. This gas compressor station also includes three Aerokom AA-117 compressors. The power consumption of one compressor is 630x24x355=5367600 kW/year. The compressor's efficiency coefficient is 1.5. Total consumption will be 5.367.600*1.5=8.051.400 kW/year [1, 5, 9, 10].

In GKS, D630/90 circulation pumps with a production capacity of 80 m³/hour are used for compressor cooling. There are 2 such pumps. The power consumption of one pump is 75*24*355=639000 kW per year. The operating factor of the pumps is 1.1. The total pump consumption is 639000*1.1=702900 kW [1, 5, 8, 9, 10] per year..

For the circulation of amine solution, AOM pumps with a production capacity of 1.1-1.5 m³ per hour are used. The pump's power consumption is 2.2*24*355=18744 kW/year.

A pump with a capacity of 50 m³/hour is used for pumping petroleum products from underground storage. The consumed electricity capacity is 18.5*24*355*0.7=110334 kW/year. An NV-E-50/50 pump with a capacity of 50 m3/hour is used for pumping amine from the underground tank. Electricity consumption also amounts to 128,000 kW per year.

The BEN-488 pump is used to pump MDEA into the desorption column. The capacity of one pump is 2.1 m³/hour. Two pumps are used in the process, which consume 2x2.2x24x355 kW of electricity per year.

1TsG25/80 pumps are used in the absorption column for irrigation. Three pumps consume 1.6x11x24x355 kW of electricity per year. For the circulation of the heat carrier, two 12CG100/80 pumps with a capacity of 100 m³/hour are used in the riboiler-evaporator. The total annual electricity consumption will be 1.4*37*24*355=441336 kW/year [1, 5, 9, 10].

The tariff for high-voltage electricity in the republic, taking into account VAT, is 1.27 rubles per kWh of electricity [12]. The saturation level of IEA is approximately 0.35 mol/mol. The saturation level of MEA is approximately 0.35 mol/mol. Consequently, the use of MDEA reduces energy consumption for circulation and regeneration by 1.5 times [1, 2, 3, 15].

Also, the use of MDEA allows saving heating steam. This is due to the lower heat of MDEA desorption. It is known that the amount of heat required for the reduction of MDEA solutions is 3.4 less than that of IEA [30-40%].

Due to low foaming on the inner surfaces of the devices, there is no sediment when using MDEA. This is associated with less structural disorders compared to MEA [4, 12, 13, 15]. Compared to MEA, MEA has higher corrosion activity and resin formation, which ultimately leads to pollution and, consequently, higher energy consumption (20-25% heating steam; 5-10% electricity) [12, 13, 15].

Table 1 shows the main costs of the H₂S purification unit and the regeneration unit. The use of MDEA reduces economic costs for the following reasons:

- reduction of the consumption of an aqueous solution of amine;

- increasing the saturation of the amine solution;

-reduction of heat consumption during α-amine reduction.

Also, due to low corrosion activity and resin formation, maintenance and repair costs are reduced, which can lead to equipment failure. MDEA solutions are less prone to destructive thermal decomposition. This serves to increase the service life of the amin. Complete replacement of MEA is carried out every 2-3 years, while the service life of MDEA can be 3-5 years [6]. Thus, by applying MDEA, it is possible to achieve savings in energy consumption (electricity and heat transfer) up to 30%; savings in absorber costs - 25 - 40%; savings in equipment maintenance and repair costs.

Table 1.

Types of expenses

Conclusion

The main costs of the natural gas purification unit and the regeneration unit are presented in the article. It was established that the use of MDEA in absorption leads to a reduction in economic costs, such as an increase in the consumption of an aqueous solution of amine, an increase in the saturation of the amine solution, and a reduction in heat consumption during the reduction of amine.

It was established that MDEA solutions are less prone to destructive thermal decomposition. As a result, it has been proven that the service life of amine has increased, full replacement of MEA is carried out every 2-3 years, and the service life of MDEA can be 3-5 years. Thus, by applying MDEA, energy savings of up to 30% were achieved, while absorbent costs were reduced by 25-40%, and the possibility of saving equipment maintenance and repair costs was revealed.

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