PRODUCTION OF AMINE ABSORBENTS ON THE BASIS OF LOCAL RAW MATERIALS

ABSTRACT

The article analyzes the technology of obtaining amine absorbents on the basis of local raw materials for oil and gas processing enterprises. Ethylene oxide (EO) and methylamine (MA) are used as raw materials in the synthesis of MDEA absorbent. Ethylene oxide (EO) synthesis uses ethylene produced at the Shurtan gas chemical complex and oxygen produced at the Uzbek GTL plant. Methylamine (MA) feedstock is produced at Navoiyazot JSC. By results of analysis and researches it is known that at use of MDEA the quantity of hydrogen sulfide in hydrocarbon gases can be reduced from 0,7% to 0,005%, the quantity of carbon oxide from 2,93% to 1,12%, steam consumption. in the process of desorption 30-40% saving of electric power consumption is reached, causes less corrosion, has high selectivity (selective separation) at separation of hydrogen sulfide from SO2 mixture, relatively low foaming in the process - the advantage of absorbent.

АННОТАЦИЯ

В статье проанализирована технология получения аминных абсорбентов на основе местного сырья для предприятий нефте- и газопереработки. Оксид этилена (ЭО) и метиламин (МА) используются в качестве сырья при синтезе абсорбента МДЭА. При синтезе оксида этилена (ЭО) используется этилен, производимый на Шуртанском газохимическом комплексе, и кислород, производимый на узбекском заводе GTL. Метиламиновое (МА) сырье производится на АО «Навоиязот». По результатам анализа и исследований известно, что при использовании МДЭА количество сероводорода в углеводородных газах может быть снижено с 0,7% до 0,005%, количество оксида углерода с 2,93% до 1,12%, расход пара. в процессе десорбции достигается 30-40% экономия расхода электроэнергии, вызывает меньшую коррозию, обладает высокой селективностью (селективным разделением) при отделении сероводорода от смеси SO2, сравнительно низким свойством пенообразования в процессе - преимуществом абсорбента.

Keywords: hydrocarbon gases, absorption purification, desorber-separator, methyldiethanolamine, diethanolamine, ethylene oxide, methylamine, hydrogen sulfide.

Ключевые слова: углеводородные газы, абсорбционная очистка, десорбер-сепаратор, метилдиэтаноламин, диэтаноламин, оксид этилена, метиламин, сероводород.

Introduction. Uzbekistan has a significant hydrocarbon potential that allows for the realization of long-term projects. It is estimated that one third of all Central Asian mineral reserves are located in Uzbekistan. Our country is among the twenty largest gas producers in the world. In our country, the main focus is on modernizing the economy, creating and expanding the production of import-substituting goods and high-tech, competitive products. The oil and gas sector has not only increased the production of raw materials, but also significantly increased the share of refined products. As a result of the implementation of the strategy aimed at the construction of complexes for deep processing of hydrocarbon raw materials, the oil and gas chemical industry based on advanced technologies has formed and is steadily developing in Uzbekistan [1].

Today amine absorbents used in the oil and gas industry are imported at the expense of foreign currency. With this in mind, technological methods are being developed to produce amine absorbents based on local raw materials for oil and gas refineries. In particular, methyldiethanolamine (MDEA) is imported from abroad by means of foreign currency. Rational use of hydrogen sulfide extracted from natural gas in various sectors of the national economy through its processing is one of the issues of rational use of modern resources. For sulfur-containing acid gases by absorption purification of natural gas, 30% methyldiethanolamine solution is widely used. This means that the use of local absorbents is one of the first reasons for the purification of sulfuric acid gases from natural gas.

Research materials and methods. The research divided it according to the principle of determining the most effective absorbent for natural gas purification. Ethanolamines, which belong to the group of amino alcohols, are used in natural gas purification. The absorbents used in gas desulfurization devices are:

Classification of methods of purification of natural gases from acidic components of hydrogen sulfide and carbon monoxide (IV) using methyldiethanolamines: Purification of gases from hydrogen sulfide is carried out by the method of cyclic absorption, in which as absorbers of hydrogen sulfide. In this case, 35-40% of the whole system in the gas desulfurization device is MDEA absorbent, and the viscosity of the absorbent is sufficient.

In the production industry, ethylene oxide (EO) and methylamine (MA) are used as raw materials for MDEA synthesis technologies. The process is organized on a synthesis basis. The synthesis of MDEA requires 0.3 tons of MA and 0.8 tons of EO, so that 1.0 tons of products are obtained from these raw materials. EO (ethylene oxide), which constitutes a large mass fraction, can be produced locally from the feedstock. For this purpose, ethylene produced at the Shurtan gas chemical complex owned by Uzbekneftegaz JSC and oxygen produced at the Uzbekistan GTL plant are used. If we look at the ethylene oxide production chain, ethane is first extracted from natural gas, the process is carried out in a de-ethanizer at low temperature. Ethylene is extracted by keeping the separated ethane in the de-ethanizer device at high temperature for a short time in pyrolysis furnaces followed by cooling [2].

Ethylene pyrolysis equation:

C₂ H₆= C₂ H₄ + H₂

Ethylene can be oxidized with air oxygen at 250  in the presence of catalysts containing silver:

The production of one ton of EO (ethylene oxide) requires 0.64 tons of ethylene and 0.37 (V=370/1.2=308 m³) tons of oxygen.

Ethylene oxide is a substance with a pungent odor that causes nausea. It has a solidification temperature of 115 . Ethylene oxide is a soluble substance that dissolves well in water, ethyl alcohol and other liquids.

The technological scheme is presented below (Fig.1). The technological device consists of 3 main blocks. 1- block is a tank block for collecting ethylene oxide and methylamine. 2- block is a block of reactors, where synthesis processes take place, and in this block chemical reactions are carried out. 3- block of extraction of product mixtures [3].

Figure 1. Methyldiethanolamine (MDEA) extraction technology:

1- mixer, 2- reactors, 3- separator, 4- heat exchangers, 5- pumps, 6- collecting tank, 7- condenser, 8- methylamine evaporation column, 9- distillation column of separation of initial fraction, 10-methyldiethanolamine (MDEA).) separation distillation column

The feedstock used in the process, ethylene oxide and methylamine, is fed into the reactor block at a predetermined rate. Methylamine from the separation stage is added to the feedstock stream. Mixing takes place in the reactor at a temperature of 40-70 and a pressure of 5-7 kgf/cm². MDEA is synthesized on the basis of reactor chemical reactions. The synthesis reactions are as follows:

The synthesis product is taken from the upper part of the reactor. Unreacted feedstock (3) from the lower part of the reactor is fed to the desorber-separator at a temperature of 100-120  and re-separated. Methylamine is extracted in the desorber-separator and cooled in the concentrator to the required temperature (7). The methylamine is collected in an intermediate tank (6) and fed back through the raw material pipeline. In the desorber-separator (3) the mixtures of methylamine (MA), methyl monoethanolamine (MMEA), methyldiethanolamine (MDEA) and OMDEA separated from the bottom part, i.e. from the cube part, are redirected for separation [4,5,6].

In this case, MA is evaporated through the evaporation column (8) and transferred to the MA collection vessel. The excess MA and the intermediate product, MMEA, are returned to the synthesis. The products are separated through a distillation column (9) to separate the remaining mixed intermediate fraction and through a distillation column (10) to separate methyldiethanolamine.

The material balance in the above synthesis method can be created as follows [7,8,].

Table 1.

Material balances of the process

The main advantages of the above production: the equipment and devices used are made in simple parts and are economical, the synthesis process is carried out at low temperature, i.e. up to 70 °C, operation of the reactor unit at low pressure - up to 7 kgf/cm², essentially because of the high productivity (for the synthesis of 1 ton of MDEA 800 kg of ethylene oxide and 300 kg of methylamine are consumed). Synthesized methyldiethanolamine is a colorless transparent liquid, the color on the platinum-cobalt scale is small, that is, it can be from light yellow to orange (in Hazen units), with a characteristic odor, corrosiveness and much similar in composition. compared to other amines does not form explosive mixtures with air, relatively safe, the effect on the human body refers to the 3rd class of hazard classes, meets the requirements of the state standard.

If we look at its physical and chemical properties.

Methyldiethanolamine is used as a more effective absorbent instead of diethanolamine as an absorbent in absorption purification of natural gases at modern industrial enterprises.

Methyldiethanolamine (MDEA) in concentration of 30-35% is used in gas desulfurization unit of Gas Treatment Plant of Oil and Gas Production Department of Uzbekneftegaz JSC. The annual demand of the unit is 700 tons.

Mass quantities before and after purification of hydrocarbon gases from sulfur compounds using 30-35% methyldiethanolamine (MDEA) absorbent were compared [9,10,11,12]:

Table 2.

Mass quantities of natural gases before and after desulfurization

Results and discussion. According to the analysis and research results as well as the study of practical application, the mdaa absorbent has the following advantages over DEA in industrial application:

- high selectivity of the process, due to high selectivity of MDEA it absorbs more hydrogen sulfide and less carbon dioxide;

- 30-40% saving of steam and electricity consumption in the desorption process;

15-25% increase in efficiency of gas desulfurization process;

- in accordance with the heat and humidity load of the low-pressure separation device when the temperature in the purified natural gases decreases;

- it is possible to improve the ecological situation in the working premises of enrichment plant employees by reducing the amount of hydrogen sulfide, carbon (IV) oxide burned in low-pressure furnaces into the atmosphere.

- methyldiethanolamine solution absorbing acid gases causes less corrosion of metals than diethanolamine.

- low consumption of steam, a source of heat required in the process of absorbent regeneration in the desorber.

It can be concluded that the absorbent methyldiethanolamine, which is used today in natural gas purification plants from sulfur components of Uzbekneftegaz JSC, is more effective than other absorbents and has high selectivity [13,14,15].

Advantages of methyldiethanolamine over other ethanolamine absorbents:

- Has high selectivity in separating hydrogen sulfide from SO2 mixture.

- absence of working volume in the system in the process of purification.

- relative consumption of water vapor in the desorption process is small.

- little influence on the hardware part of the device, i.e. it has small corrosive properties.

-relatively low foaming during the process.

Conclusion. The production method of MDEA using local raw materials was theoretically studied, and the advantages of this absorbent are presented based on the results of scientific research.

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