RU2246342C1 - Absorbent for removing hydrogen sulfide from gases - Google Patents

Abstract

FIELD: gas treatment.

SUBSTANCE: invention relates to compositions for oxidative removal of hydrogen sulfide from gases to produce elementary sulfur, which compositions can be used in oil and gas production, petroleum and gas processing, chemical, and other industries. Absorbent contains, g/L: iron chelate compound (on conversion to ferric ion) 2-12, alkali metal phosphate (on conversion to phosphate anion) 1-16, alkali metal carbonate or hydroxide 1-60, methyldiethanolamine and/or triethanolamine 10-30, monoethanolamine/formaldehyde reaction product 0.2-10, and water to 1 L. Monoethanolamine interacts with 37% formaldehyde solution at molar ratio 1:(1-3). Iron chelate compound is a complex of ferric compound with ethylenediaminetetraacetic acid disodium salt. To reduce foaming, absorbent may further contain 0.05-0.2 g/L aluminum sulfate.

EFFECT: increased stability and decreased corrosive activity of absorbent without loss in its high absorbing capacity regarding hydrogen sulfide.

4 cl, 2 tbl, 5 ex

Description

The invention relates to compositions for the oxidative purification of gases from hydrogen sulfide to produce elemental sulfur and can be used in the oil, gas, oil and gas processing, chemical and other industries.

Known absorbent (ed. Certificate. USSR No. 1031478, 1983) for the purification of hydrocarbon gas from hydrogen sulfide, containing the following components, g / l:

Ferric Chloride 7.9-49.4

Disodium salt of ethylenediamine -

tetraacetic acid (trilon B) 30.0-180.0

Caustic soda 12.5-35.0

Cadmium Chloride 2.24-13.44

Water up to 1.0 L

The main disadvantages of the known absorbent are high corrosiveness in relation to structural materials and low stability associated with the rapid destructive destruction of complexon - trilon B - with the formation of undesirable hydroxides and sulfides of iron during the cycles "absorption of hydrogen sulfide - regeneration of absorbent air". In addition, cadmium refers to toxic heavy metals, which narrows the scope of application of elemental sulfur obtained in the purification process, for example, does not allow its use in agriculture as an acaricide.

A known composition for the purification of hydrocarbon gases from hydrogen sulfide, including, wt.%: A complex of iron with ethylenediaminetetraacetate 2.0-10.0; sodium carbonate 0.1-0.5; sodium salt of di-2-ethylhexyl ether sulfosuccinic acid 0.01-0.05; mono- and diisobutylphenyl ethers of polyethylene glycol 0.005-0.02 and water - the rest (US Pat. RF No. 2050314, 1991, publ. BI No. 35, 1995).

The disadvantages of this composition are high corrosion activity and low stability, as well as the scarcity and high cost of the applied anti-adhesive additives - esters of sulfosuccinic acid and polyethylene glycol.

Known absorbent for cleaning gases from hydrogen sulfide to produce sulfur, which is an aqueous-alkaline solution of a chelate compound of a polyvalent metal, mainly iron, additionally containing 10-100 ppm (0.001-0.01%) of a bactericide (biocide). Moreover, as a bactericide (biocide) that inhibits the growth of bacteria (and other microorganisms), it contains quaternary ammonium compounds - alkylbenzylammonium chlorides and halo cyanoalkylamides (2,2-dibromo-2-cyanoacetamide) or glutaraldehyde (US Pat. No. 4,455,287, 1984) .).

According to the data given in the description, the additional introduction of the above bactericides (biocides) into the absorbent increases the stability of the circulating absorbent and reduces the loss of the expensive chelated iron compound by inhibiting the growth of bacteria and other microorganisms that cause the destruction of polyvalent metal chelates. The disadvantages of the known absorbent are high corrosion activity, insufficiently high stability, scarcity and high cost of the used bactericides and biocides.

Known absorbent for cleaning gases from hydrogen sulfide, including, g / l: chelated iron complex (in terms of iron) 1-12, alkali metal phosphate (in terms of phosphate anion) 10-35, alkali metal carbonate or hydroxide 0.1 -95, urea 10-50 and water up to 1 liter. (ed. certificate of the USSR No. 1401665, 1988).

The specified absorbent has low corrosion activity (corrosion rate of carbon steel in the range of 0.05-0.18 mm / year at 50 ° C), a sufficiently high absorption capacity and provides the required degree of gas purification from hydrogen sulfide. However, tests show that the known absorbent has low stability, is susceptible to bacterial infection, which leads to increased consumption of reagents and an increase in material costs for the gas purification process.

Closest to the proposed invention is an absorbent for the purification of gases from hydrogen sulfide, including a chelate compound of iron, sodium phosphate, or potassium, or ammonium, an alkali metal hydroxide or carbonate, an organic amine and water in the following ratio of components, g / l:

Chelate compound of iron (in terms of iron) 1-12

Sodium phosphate or potassium or ammonium

(in terms of phosphate anion) 1-32

Alkali metal hydroxide or carbonate 1-60

Organic Amine 2-60

Water up to 1 L

Moreover, as an organic amine, it contains dimethylaminopropionitrile, or monoethanolamine, or dibutylamine (US Pat. RF No. 1287346, 01 D 53/14, publ. BI No. 13, 1995).

The disadvantage of this absorbent is insufficient stability due to the destructive destruction of the used complexone - trilon B - with the formation of undesirable hydroxides and sulfides of iron, which leads to increased consumption of reagents (up to 0.15-0.17 g of trilon B per 1 g of sulfur obtained) . Other disadvantages of the absorbent are relatively high corrosion activity (corrosion rate of carbon steel 0.18-0.65 mm / year at 50 ° C) and foaming. In addition, the known composition provides for the use of scarce and expensive organic amines. These shortcomings lead to an increase in material costs for the gas purification process as a whole.

The objective of the invention is to increase the stability of the absorbent and reduce its corrosiveness while maintaining a high absorption capacity with respect to hydrogen sulfide. The invention also solves the problem of reducing the expandability of the absorbent.

The problem is solved in that the absorbent for the purification of gases from hydrogen sulfide, including the chelated iron compound (iron complexonate), alkali metal phosphate, carbonate and / or alkali metal hydroxide, organic amine and water, contains methyldiethanolamine and / or triethanolamine as an organic amine and additionally contains the product of the interaction of monoethanolamine with formaldehyde in the following ratio of components, g / l:

Chelate compound of iron in terms of

ferric iron 2-12

Alkali metal phosphate

in terms of phosphate anion 10-16

Carbonate and / or alkali metal hydroxide 1-60

Methyldiethanolamine and / or triethanolamine 10-30

The product of the interaction of monoethanolamine

with formaldehyde 0.2-10

Water up to 1 L

As a reaction product, the absorbent contains the reaction product of monoethanolamine with about 37% formaldehyde solution - formalin - in a molar ratio of monoethanolamine: formaldehyde 1: 1-3, preferably 1: 2-3.

In addition, in order to reduce foaming, the proposed absorbent may additionally contain aluminum sulfate in an amount of 0.05-0.2 g / l.

As an iron chelate, the absorbent mainly contains a complex of ferric iron with disodium salt of ethylenediaminetetraacetic acid (Trilon B), and trisodium phosphate and / or sodium tripolyphosphate as alkali metal phosphate.

The inventive absorbent for cleaning gases from hydrogen sulfide of the above composition is a moving transparent liquid from red to dark red (cherry) color with a pH value of 8.6-9.9 and a density of 1.05-1.23 g / cm ³ . As the starting material for the preparation of the proposed absorbent, iron sulfate (according to GOST 6981), disodium salt of ethylenediaminetetraacetic acid (Trilon B according to TU 113-04-260-87), trisodium phosphate (according to GOST 201) or sodium tripolyphosphate (according to GOST 13439) are mainly used , sodium carbonate (according to GOST 5100), methyldiethanolamine (according to TU 2423-005-11159873-2000) or triethanolamine (according to TU 6-02-916-79). The product of the catalytic interaction of monoethanolamine (MEA) with ~ 37% formaldehyde solution (formalin) used in the composition of the proposed absorbent as a bactericidal (biocidal) and anti-corrosion additive is a mobile transparent liquid from light yellow to red-brown in color with a hydrogen index (pH) in the range of 8.5-12, with a density of 1.08-1.11 g / cm ³ , pour point below minus 30 ° C. The specified product is manufactured by the domestic industry according to TU 2458-001-27815380-2002 and is used as n a catalyst for hydrogen sulfide and light mercaptans in oil during the extraction and preparation of sulfur oils and gas condensates. The industrial (trade) name is "NSMB-1" hydrogen sulfide neutralizer. It should be noted that methods for the purification of oils and gas condensates from hydrogen sulfide and light mercaptans using MEA with formalin as a neutralizer are described in US Pat. RF №№2092613, 2121492 and work: Fakhriev R.A. Field purification of hydrocarbon feedstocks (oils and gas condensates) from low molecular weight mercaptans and hydrogen sulfide. Diss. Candidate of Technical Science. Kazan. KSTU. 1999 .-- 156 p.

The proposed concentration of the added product of the interaction of MEA with formalin (0.2-10 g / l) is optimal, because at concentrations below 0.2 g / l, a sufficiently complete suppression of bacterial growth and an increase in the stability of the absorbent is not provided, and an increase in concentration above 10 g / l is not economically feasible due to unreasonably increased consumption of the product.

The absorbent in accordance with the invention is prepared by dissolving the above starting ingredients in water or steam condensate to adjust the pH of the medium to 8.6-10, after which it is blown with air to oxidize ferric complexonate to ferric. The prepared absorbent is fed to the absorber, where it is contacted with a hydrogen sulfide-containing gas to be purified with oxidation of the absorbed hydrogen sulfide to elemental sulfur. Subsequent regeneration of the spent absorbent is carried out by blowing air with the release of sulfur by filtration or centrifugation.

An analysis of the well-known technical solutions selected during the search showed that in science and technology there is no object similar in terms of the claimed combination of features and advantages, which allows us to conclude that its criteria are “novelty and inventive step”.

To prove the compliance of the claimed object with the criterion of "industrial applicability" below are specific examples of the preparation of the absorbent (examples 1-3) and tests for its absorption capacity with respect to hydrogen sulfide, stability and corrosion activity.

Example 1. The absorbent is prepared by dissolving the components in distilled water or in steam condensate. 20 g of iron sulfate (FeSO ₄ · 7H ₂ O) and 50 g of ethylenediaminetetraacetic acid disodium salt (Trilon B) are dissolved in 800 ml of water with stirring. An orange solution of a chelated iron compound with Trilon B (iron complexonate) is obtained. To the resulting solution, with stirring, add 50 g of trisodium phosphate (Na ₃ PO ₄ · 12H ₂ O) and 25 g of technical methyldiethanolamine (MDEA) according to TU 2423-005-11159873-2000. Then, 5 g of the reaction product of monoethanolamine (MEA) with a 37% solution of formaldehyde (formalin) in a molar ratio of MEA: formaldehyde 1: 2.5 (NSMB-1 hydrogen sulfide neutralizer according to TU2458-001-27815380-2002) is introduced into the solution . After stirring for 10-20 minutes, a 10% solution of sodium or potassium carbonate (soda or potash) is introduced dropwise into the resulting solution, adjusting the pH of the solution in the range of 9.0-9.5. Then the volume of the solution was adjusted to 1 L by adding water and purged with air for 20-30 minutes to oxidize the ferrous complexonate to ferric complexonate.

Thus prepared absorbent with a pH of 9.3 contains 4 g / l of ferric iron, 12.5 g / l of phosphate anion, 25 g / l of methyldiethanolamine, 5 g / l of the reaction product of MEA with formaldehyde, the rest is sodium carbonate and water.

Absorbents of the compositions of the claims are prepared in a similar manner.

Example 2. By the gravimetric method in an autoclave installation, the corrosion rate of St3sp carbon steel in a freshly prepared absorbent at 50 ° C is determined. The total duration of the experiment is 620 hours, of which heating at 50 ° C is carried out for 150 hours. The average results of determining the corrosion rate of steel in the absorbent is shown in table 1. Here, for comparison, the results of determining the corrosion rate of steel under the above conditions in known absorbents are shown (experiments 5 and 6).

Example 3 In a thermostated absorber (D = 40 mm, H = 400 mm) was charged with 150 ml of the absorbent at 25 ° C, atmospheric pressure is passed through the absorber at a space velocity of 150 hr ^-1 gas containing about 15% hydrogen sulfide until breakthrough hydrogen sulfide at the outlet of the absorber. The moment of breakthrough of hydrogen sulfide is controlled by passing the purified gas through a Drexel flask with a 10% aqueous solution of cadmium chloride. Then, the absorbent saturated with hydrogen sulfide is regenerated at 40 ° C for 30-40 minutes by blowing air. The resulting elemental sulfur is separated from the absorbent by filtration. The results of the experiments are shown in table 1. Here, for comparison, the results of determining the absorption capacity (sulfur intensity) of known absorbents are shown (experiments 5 and 6).

Example 4. To determine stability, in the absorber of example 3, 150 ml of absorbent of the composition of example 1 are loaded and a gas containing about 15 vol.% Hydrogen sulfide is passed until a breakdown of hydrogen sulfide appears at the outlet of the absorber. Then, the absorbent saturated with hydrogen sulfide is regenerated at 40 ° C for 30-40 minutes by blowing air. This cycle "absorption - regeneration" is repeated up to 50 times. Moreover, in the course of multi-cycle operation, every 10 cycles, the sulfur formed is separated from the regenerated absorbent by filtration, washed with water, dried to a constant mass and weighed. After 50 cycles of operation, the absorbent used is analyzed for the content of Trilon B by a known method, the difference between the initial mass of Trilon B and the mass after 50 cycles of operation is calculated, the losses of Trilon B per unit mass of the obtained elemental sulfur are determined. The loss of Trilon B is 0.07 g per 1 g of sulfur obtained.

A comparative experiment showed that when using the known absorbent of the composition according to experiment 5 (Table 1), the loss of Trilon B is 0.15 g per 1 g of sulfur obtained.

Example 5. Used in the composition of the proposed absorbent, the product of the interaction of monoethanolamine with formaldehyde is tested for bactericidal activity against sulfate reducing bacteria (SBB) according to the known method (RD 03-00147275-067-2001, Ufa, BashNIPIneft DOOO ANK Bashneft OJSC, 2001, - 16 p.).

SVB accumulative culture is isolated from the commercial fluid of the Romashkinskoye oil field (Republic of Tatarstan). After diluting the SSC, the sample is reseeded 3 more times in fresh culture medium. For testing, use a culture of SVB 4-5 daily exposure. The quantitative composition of SVB is determined by the method of limiting 10-fold dilution using the elective nutrient medium of Postgate (OST 39-151-83).

The investigated product of the interaction of MEA with formaldehyde in an amount providing the required concentration in mg / L is introduced into a series of labeled tubes with a nutrient medium.

The test tube with the culture culture culture mix is mixed, kept until the sulfide precipitate settles, a liquid is taken over the precipitate with a sterile pipette and 0.5 ml is introduced into each test tube containing the nutrient medium and the reaction product. The tubes are mixed and thermostated at 30-32 ° C. For each option, 3 replicates are made.

As control, similar samples are used without the addition of an interaction product.

Test tubes are observed for 15 days, noting the appearance of a black color. Reagents that do not give darkening or are slightly colored are considered effective.

The effectiveness of preventing the growth of bacteria is assessed by the degree of suppression of SVB, determined by the formula:

where C ₁ and C ₂ - the content of hydrogen sulfide in the control and test samples (mg / l), determined after 15 days from the start of the test.

Table 2 presents the results of the tests.

From the data presented in table 1, it can be seen that the proposed absorbent for the purification of gases from hydrogen sulfide, in comparison with the prototype, has low corrosion activity with almost the same absorption capacity with respect to hydrogen sulfide (sulfur intensity). The data presented in example 3 show that the proposed absorbent in comparison with the prototype also has higher stability, resulting in a reduction in loss and, consequently, the consumption of reagents for the process of gas desulfurization.

From the data of table 2 it is seen that the product of the interaction of MEA with formaldehyde used in the composition of the proposed absorbent has a sufficiently high bactericidal effect, therefore, in its presence (at concentrations of 0.2 g / l or more), the growth of bacteria in the circulating absorbent and the destruction of the chelate compound are prevented iron bacteria.

The experiments also show that the additional introduction of aluminum sulfate into the absorbent in concentrations of 0.05-0.2 g / l leads to a decrease in the foaming capacity of the absorbent, a decrease in the height of the sulfur foam formed during its regeneration, therefore, the losses of the absorbent with purified gas and exhaust air are reduced regeneration, conditions are improved and the degree of extraction of elemental sulfur is increased. In addition, the composition of the proposed absorbent uses more affordable and cheaper organic amines. So, for example, at present the factory price of triethanolamine is three times lower than monoethanolamine. The dimethylaminopropionitrile and dibutylamine used in the known absorbent are not currently available in the domestic industry.

The above advantages of the proposed absorbent compared with the prototype provide a reduction in material costs for the process of oxidative purification of gases from hydrogen sulfide to obtain elemental sulfur in general.

Table 1. No. of experiences The composition of the absorbent, g / l Corrosion rate, mm / year Absorbent absorption rate, g / l 1 Iron - 4; phosphate anion (as sodium phosphate) - 12.5; MDEA - 25; the product of the interaction of MEA with formaldehyde - 5; soda - 13; water - up to 1 liter. 0.06 5.2 2 Iron - 5; phosphate (sodium) - 13.3; triethanolamine (TEA) - 25; the product of the interaction of MEA with formaldehyde - 0.2; soda - 11; water - up to 1 liter. 0.08 6.5 3 Iron - 6; phosphate (sodium) - 15; MDEA-10; TEA - 15; the product of the interaction of MEA with formaldehyde - 0.5; soda - 15; water - up to 1 liter. 0.10 7.0 4 Iron - 12; phosphate (sodium) - 16; MDEA - 15; TEA - 15; the product of the interaction of MEA with formaldehyde - 10; aluminum sulfate - 0.1; soda - 60; water - up to 1 liter. 0.05 12.1 5 Iron - 5; MEA - 25; phosphate (sodium) - 8; sodium hydroxide - 1; water - up to 1 liter. (prototype) 0.23 6.5 6 Iron - 4; dibutylamine - 15; potassium carbonate (potash) - 5; phosphate (sodium) - 9; water - up to 1 liter. (prototype) 0.29 4.9

Table 2. The concentration of the product of the interaction of MEA with formaldehyde, g / l Bactericidal effect against SVB 0.1 incomplete suppression 0.2 complete suppression 0.5 complete suppression 1,0 complete suppression 10.0 complete suppression 15.0 complete suppression

Claims (4)

1. Absorbent for the purification of gases from hydrogen sulfide, including a chelate compound of iron, alkali metal phosphate, carbonate and / or alkali metal hydroxide, an organic amine and water, characterized in that it contains methyldiethanolamine and / or triethanolamine as an organic amine and additionally contains a product the interaction of monoethanolamine with formaldehyde in the following ratio of components, g / l: Iron Chelate in terms of ferric iron 2-12 Alkali metal phosphate in terms of phosphate anion 10-16 Carbonate and / or alkali metal hydroxide 1-60 Methyldiethanolamine and / or triethanolamine 10-30 Interaction product monoethanolamine with formaldehyde 0.2-10 Water Up to 1 L 2. The absorbent according to claim 1, characterized in that as the reaction product it contains the reaction product of monoethanolamine with about 37% formaldehyde solution - formalin in a molar ratio of monoethanolamine: formaldehyde 1: 1-3. 3. The absorbent according to claim 1, characterized in that as a chelate compound of iron, it contains a complex of ferric iron with disodium salt of ethylenediaminetetraacetic acid. 4. The absorbent according to claim 1, characterized in that to reduce foaming, it may additionally contain aluminum sulfate in an amount of 0.05-0.2 g / L.