RU2232626C1 - Natural gas drier - Google Patents

Abstract

FIELD: absorption drying of natural gas.

SUBSTANCE: proposed natural gas drier is made on base of diethylene glycol including borax, foam suppressor, type 139-282 on base of silicon-organic liquids and anti-foamer; anti-foamer contains laprol and potassium carbonate, disodium phosphate and benzotrioazole at the following ratios of components, mass-%: borax, 0.3-1.0; potassium carbonate, 0.1-0.3; disodium phosphate, 0.5-1.2; benzotriazole, 0.05-0.1; laprol, 0.001-0.1; foam suppressor, type 139-282, 0.001-0.1; the remainder being diethylene glycol. Reduction of corrosion of field equipment in gas phase to 0.02-0.00493 mm/year and to 0.009-0.00015 mm/year in liquid phase.

EFFECT: enhanced efficiency.

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Description

The invention relates to the field of drying of natural gas using desiccants (absorbents) and can be used in the gas industry, where the drying of produced gas is necessary before transportation.

Various absorbents for drying gases are known, so, in particular, it is known to carry out drying of gases with an absorbent based on polyethylene glycol dimethyl ether (1). However, there is a high solubility of hydrocarbon gases and an insufficient degree of drying (dew point 4-5 ° C).

A number of glycol-based absorbents are known. So, the known composition used to dry natural gas, in preparing it for transportation, including, about. %:

Diethylene glycol 20-50

Polypropylene glycol 42-54

Dipropylene glycol 2-12

Propylene glycol 5-12

Tripropylene glycol 1-2

The absorbent allows you to get gas with a dew point of 16-25 °. The decomposition temperature is 200-220 ° С, losses during regeneration are 7 g / 1000 m ^{3 of} gas (2).

The disadvantage of this dehumidifier is that it does not contain anti-corrosion and anti-foam additives, and the given composition during operation will have a high corrosion rate of the field equipment and loss of the dehumidifier due to foaming.

Closest to the proposed absorbent for drying natural gas is a known desiccant based on diethylene glycol (3), including the following components, wt.%:

Borax 0.3-1.0

Laprol 251V 0.5-1.5

Phenosan 28 0.008-0.015

Laprol 5003-2-15 0.001-0.1

Pip defoamer 139-282 0.001-0.1

Diethylene glycol rest

In addition to the main component - diethylene glycol, the well-known desiccant includes a number of additives, in particular, it contains Laprol 251 V as an anti-corrosion additive, which is the product of the interaction of boric acid with a mixture of methyl esters of tri-, tetra- and pentaethylene glycols, borax, phenosan 28 - the product of the interaction diethylene glycol with 3,5-di-tert-butyl-4-hydroxyphenylpropylene alcohol. As an antifoam agent, the desiccant contains Laprol 5003-2-15, as well as an antifoam of type 139-282 based on organosilicon liquids.

The introduction of anticorrosion additives and antifoam agents into the dehumidifier leads to a decrease in the corrosion of field equipment and a decrease in foaming during the drying of natural gas, which allows to increase the service life of the equipment, reduce the consumption of the desiccant, and thereby increase the productivity of process equipment.

The corrosion rate in the liquid phase using a known desiccant is 0.16-0.48 mm / year and 0.1-0.25 mm / year in the gas phase, the height of the foam is 0.3-38 mm with a foam life of 0.4 -5 sec

The specified desiccant with the given composition reduces the corrosion rate, but its value remains relatively high, and the achieved effect of reducing foaming is insufficient and needs to be improved.

The objective of the invention is the creation of such a dehydrator of natural gas, which would provide, along with effective dehydration of the gas, a decrease in corrosion of field equipment and a decrease in foaming during operation of the desiccant.

To solve this problem, it is proposed to use as a desiccant of natural gas a composition that is a mixture of a certain composition of diethylene glycol (DEG), anti-corrosion and anti-foaming additives.

As anticorrosion additives, diethylene glycol is added: borax in an amount of 0.3-1.0 wt.%, Potassium carbonate in an amount of 0.1-0.3 wt.%, Sodium phosphate disubstituted in an amount of 0.5-1.2 wt. .%, benzotriazole in an amount of 0.05-0.1 wt.%

Laprol 6003-2B-18 and a defoamer of type 139-282 based on organosilicon liquids in an amount of 0.001-0.1 wt.% Each are introduced as antifoaming agent.

The proposed dehydrator of natural gas based on diethylene glycol containing (wt.%):

Borax 0.3-1.0

Potassium carbonate 0.1-0.3

Sodium Phosphate

Bisubstituted 0.5-1.2

Benzotriazole 0.05-0.1

Anti-foaming agent

Laprol 6003-2B-18 0.001-0.1

Defoamer type 139-282 0.001-0.1

Diethylene glycol rest

differs from the known one in that it contains Laprol 6003-2B-18 as an antifoam agent and includes potassium carbonate, disubstituted sodium phosphate and benzotriazole with the above quantitative ratios of the ingredients included in it.

Tests of the corrosion activity of the desiccant samples were carried out on a special device. Cells of the device are equipped with hermetically sealed “bombs” made of stainless steel, inside of which there are glass glasses equipped with a lid with a “herringbone” for fastening the test metal plates. During the tests, samples were used in the form of rectangular plates of size (20 ± 0.5) · (10 ± 0.5) · (2 ± 0.5) mm, made of steel St 40 with a surface finish of 8.

To simulate a real gas drying process, add 2 wt.% Water and 1 wt.% NaCl to the desiccant test sample. A sample of desiccant in an amount of 75 cm ³ and 6 test metal plates is placed in a glass beaker so that three of them are immersed in the desiccant and three are in the gas phase.

The tests were carried out by heating hermetically sealed “bombs” at a temperature of 170 ° C for 250 hours.

The corrosion rate was estimated by the change in the mass of the test samples before and after heating.

The calculation was carried out according to the formula

where n is the corrosion rate, mm / year;

m ₁ is the mass of the sample before the test, g;

m ₂ is the mass of the sample after the test, g;

s is the area of the sample after the test, cm ² ;

d is the density of the metal sample, g / cm ³ ;

τ is the test time, h

where 8760 is the number of hours per year, 10 is the conversion factor cm to mm, 10 ⁴ is the conversion factor m ² to cm ² .

The value of corrosion is defined as the arithmetic mean of three measurements.

The test results are shown in the table.

The foaming agent of the desiccant is determined by the method of GOST 28084. The method consists in blowing air through a porous filter at a given temperature through a porous filter with a set volumetric flow rate for a given time (5 min), and then the volume of foam formed and its stability are measured.

The stability of the foam is determined by the time it settles from the moment the air supply is cut off.

The experimental data on the determination of the expandability of the desiccant are given in the table.

As can be seen from the table, the introduction of the named anti-corrosion additives and anti-foaming agent into the dehumidifier dramatically improve its operational characteristics.

The addition to DEG of anticorrosive additives of borax, potassium carbonate, sodium phosphate disubstituted, benzotriazole in the amount of 0.3-1.0; 0.1-0.3; 0.5-1.2; 0.05-1.0 wt.%, Respectively (examples 1-3) leads to a significant reduction in the rate of corrosion compared with the prototype. The corrosion rate in the gas phase on average (examples 1-3) is reduced by more than 7 times.

The corrosion rate (in examples 1-3) in the liquid phase is on average 50 times lower than in the prototype.

When the concentration of anticorrosion additives in the desiccant decreases below the specified limit (Example 4), corrosion increases both in the liquid and in the gas phase in comparison with Examples 1-3.

As defoamers in the invention, Laprol 6003-2B-18 and type 139-282 antifoam based on organosilicon liquids in the amount of 0.001-0.1% of each are used (examples 1-3).

The introduction of these defoamers in this concentration and in this composition of additives provides a higher efficiency in reducing foam in a desiccant compared to the prototype.

In the case of a decrease in the concentration of antifoam agents below a predetermined concentration limit, an increase in the height of the foam and its lifetime occurs (example 4).

Determination of the effect of anticorrosion additives on the drying capacity of the modernized desiccant was carried out in comparison with pure diethylene glycol.

To this end, samples of aqueous solutions of the test substances are placed in a desiccator, where they are at the same pressure and temperature, and after establishing equilibrium with water, the concentration of water in the equilibrium liquid samples is determined. Having determined the final water content in the test samples, one can compare their drying capacity. Of the two samples of aqueous solutions of different substances with different final water contents, the best drying ability is considered to be the one in which the water concentration (expressed in wt.%) Will be greater.

In the initial samples was the following water content, wt.%:

pure deg 0.25

prototype 3.0

DEG with additives (proposed composition) 1.35

The equilibrium water content was as follows, wt.%:

pure deg 1.29

prototype 1.27

DEG with additives (proposed composition) 1.32

From the table it follows that the drying ability of the proposed desiccant and desiccant according to the method of the prototype and pure DEG within the experimental errors are the same.

Thus, the proposed dehumidifier based on diethylene glycol with a complex of anticorrosive and antifoam additives shows high efficiency in reducing the corrosion of field equipment and inhibits foaming during the drying of natural gas, which will increase the service life of the equipment, reduce the consumption of the desiccant by reducing its droplet entrainment and thereby increase process equipment performance.

Sources of information

1. US patent No. 3837143 for CL. 55-13.

2. Copyright certificate No. 799797 by class. B 01 D 53/28.

3. RF patent No. 2040959 for class. B 01 D 53/28.

Claims (1)

A diethylene glycol-based natural gas desiccant containing borax, an anti-foaming agent of type 139-282 based on organosilicon liquids and an antifoam agent, characterized in that it contains laprol 6003-2B-18 as an antifoam agent and additionally contains potassium carbonate, sodium phosphate disubstituted and benzotriazole in the following the ratio of components, wt.%: Borax 0.3-1.0 Potassium carbonate 0.1-0.3 Sodium phosphate disubstituted 0.5-1.2 Benzotriazole 0.05-0.1 Laprol 6003-2B-18 0.001-0.1 Defoamer type 139-282 0.001-0.1 Diethylene glycol rest