RU2548655C2 - Method of neutralization of hydrogen sulfide and light mercaptans in stock oil and composition of mix of hemiformal and hydrocarbonic nitrocompound - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to treatment of stock oil, namely to the method of neutralization of hydrogen sulfide and light mercaptans in stock oil solution by supply of hemiformal by a tubular punched dispenser designed as a punched tube with holes which is inserted into process pipeline on the section downstream the desalting process and upstream the end separation unit. Also the invention relates to composition of the mix of hemiformal and hydrocarbonic nitrocompound for neutralization of hydrogen sulfide and methyl-ethyl mercaptans in stock oil.

EFFECT: invention allows to neutralize hydrogen sulfide and mercaptans in stock oil without formation of ballast and without disturbance of the treatment process.

2 cl, 2 tbl, 1 dwg

Description

The invention relates to the field of preparation of commercial oil.

In accordance with GOST R 51858-2002 "Oil. General Specifications" from January 1, 2007, the content of hydrogen sulfide (up to 20 ppm) and ethyl methyl mercaptans (up to 40 ppm) for the first type of oil is normalized in oil (1, p. 4 Table No. 4).

Meanwhile, analysis of the hydrogen sulfide and ethyl methyl mercaptans neutralizing reagents currently offered, as well as their pilot tests, show that their use causes disturbances either in the oil preparation processes or in the commercial transfer of oil to the Transneft system.

According to application No. 2003129715/15, a neutralizing agent based on dicarboxylic acid salts (adipic, succinic, glutaric, etc.) is known, when it is supplied to the oil preparation system, it disrupts the oil / water emulsion separation process, thereby increasing the oil content in water above normal. The reaction products of hydrogen sulfide with the main components of the reagent form ballast, i.e. insoluble in oil, precipitated impurity, which is normalized according to GOST R 51858-2002 (1, p. 3, table 3) to 0.05 wt.%. For example, the sodium salt of adipic acid, when reacted with hydrogen sulfide, forms sodium sulfide and adipic acid

According to the material balance of the reaction, 1 ppm of hydrogen sulfide forms 6.64 ppm of ballast upon neutralization. When using this converter in an oil and gas production department with an oil production of 10,000 tons per day and a hydrogen sulfide and light mercaptans content of 300 ppm (300 g / t), 20.0 tons of ballast per day will fall, which will be 0.2% of the total oil weight.

Known patents are No. 2002120783/04, 99104020/04, 2000128403/03, 2160761. All neutralizing agents based on ethanolamines form salts (2, p. 146); in oil they form a gel-like precipitate, i.e. in commercial oil form ballast.

When analyzing marketable oil for the content of chloride salts according to GOST 21534-76, ethanolamines, as well as amines containing an amino group —NH ₂ , color the titrated solution containing diphenylcarbazide indicator in bright yellow color, meanwhile, it is necessary to determine the border of titration of salts to achieve a weak Pink colour.

The error in determining the boundary of titration of chloride salts due to the additional color may be 50-180 mg / l. The norm for the I group of oil is 100 mg / l (1, p. 3, table 3).

According to the application No. 2003116365/04, known neutralizers consisting of solutions of nitrite salts (for example, NaNO ₂ ), form alkali and elemental sulfur upon reaction with hydrogen sulfide:

1 ppm of hydrogen sulfide forms 3.3 ppm of substances (alkali and sulfur), which are ballast for oil.

The introduction of reagent neutralizers into the oil stream at various stages of oil dehydration is useless due to losses of the reagent with separable formation water - all reagents, due to their properties, are water-soluble substances and in settlers pass into the aqueous phase - formation water.

Formation water, separated during oil dehydration, is returned (pumped) back to the formation through the reservoir pressure maintenance system. Thus, the reagent that has passed into the aqueous phase is lost irrevocably.

Putting the reagent into the commercial oil, as described above, forms ballast.

A method of neutralizing hydrogen sulfide and light mercaptans in commercial oil.

The proposed method for the neutralization of hydrogen sulfide and ethyl methyl mercaptans in crude oil is free from the above disadvantages.

In the neutralization reaction of hydrogen sulfide and ethyl methyl mercaptans with a neutralizing agent, oil-soluble substances are formed, do not form ballast and do not interfere with the preparation of marketable oil and transfer to the Transneft system. No special installations are required. The equipment uses standard reagent feed pumps and a simple input device.

The input of the neutralizing agent into the commercial oil is carried out using a specially designed dispersant, which is a perforated tube (see drawing) with holes D = 0.5 mm. The number of holes is calculated individually for a particular reagent supply mode; one hole, when pumped by a type ND pump, passes 3 l of reagent per hour.

The introduction of the catalyst through the dispersant is necessary for the following reasons:

a) there is relatively little hydrogen sulfide and mercaptans in oil - for oil with a content of hydrogen sulfide and light mercaptans in the amount of 300 ppm, it is 0.03 wt.% and they are distributed throughout, therefore it is also necessary to distribute the neutralizer;

b) a neutralization reaction does not occur without distribution of the reagent in the entire volume of oil - a heavier neutralizer (specific gravity of about 1.0 kg / dm ³ ), insoluble in oil, precipitates in pipelines or in a freight fleet. For comparison: the proportion of oil in regions where the process of neutralization is needed

Orenburgneft OJSC NGDU "Buguruslanneft" ρ _oil = 0.89 kg / dm ³ NGDU "Buzulukneft" ρ _oil = 0.85 kg / dm ³ OAO Tatneft NGDU "Leninogorskneft" ρ _oil = 0.89 kg / dm ³ NGDU "Nurlatneft" ρ _oil = 0.91 kg / dm ³ RITEK OJSC NGDU TatRITEKneft ρ _oil = 0.93 kg / dm ³

In the process of preparing the oil has a temperature of 40-60 ° C, thereby its specific gravity is reduced by another 10-15%.

c) the time for the neutralization reaction is limited by the fact that marketable oil is not delayed at the oil treatment facilities, but is usually sent immediately to the planned delivery to the system of Transneft.

Dispersant Description

The reagent-neutralizer is introduced into the marketable oil using a specially designed dispersant (see drawing), which is a perforated tube with D = 1/2 "(4) with holes D = 0.5 mm, which is introduced into the process pipeline (9) through the valve (6) and the glass (5) with the stuffing box (3). The holes in the tube are evenly distributed over the cross section of the pipeline (9).

The number of holes in the perforation zone (8) is calculated individually for a particular reagent supply mode; one hole, when pumped by an ND type pump, passes 3 l of reagent per hour.

The 1/2 "pipe (4) is inserted into the pipe (9) until it contacts the bottom surface, the end of the pipe (4) must be plugged.

To calculate the location of the centers of the holes, the inner diameter of the pipeline (9) is divided by the number of holes. If necessary, the holes can be arranged in two or more rows, vertically or in a spiral. When installing the tube (4) in the pipeline (9), the direction of the holes does not matter.

The height of the glass (5) should be equal to the sum: the diameter of the pipeline + the height of the pipe with flanges + the height of the valve with flanges - this is necessary so that the perforated tube can be pulled out over the valve without stopping the oil flow.

The reagent supply valve or valve (2) is mounted on quick couplings so that if necessary it is possible to quickly disassemble and pull out the tube (4) for revision or replacement.

The feed point of the converter is determined specifically for each oil treatment unit, but there are common determining factors:

- there should be no water in the oil - otherwise there will be a decrease in the efficiency of the neutralization process due to the transition of the neutralizer to the aqueous phase,

- the supply of the reagent-neutralizer should be carried out on the site after the process of desalination in the electric dehydrator, in front of the end separators. The feed in front of the end separators is very important due to the fact that oil rises vertically up to a height of 15 meters in this section. In the pipeline and further, in the end separator, oil boils due to the separation (release) of gas from oil. Thus, this site is a ready reactor for the neutralization process,

- the role of end separators can also be performed by other devices: tanks or technological, buffer tanks, in which case the converter must be fed in front of them.

The composition of the mixture of gemiformal and hydrocarbon nitro compounds

The basis of the neutralizing reagent is the product of the interaction of paraformaldehyde and methanol - hemiformal (3, p. 2730).

Formula: ONSN ₂ OCH ₃ , t _bale. = 111.0 ° C. The mass solubility of paraform in methanol can be up to 57.5 wt.% At 20 ° C (4, p. 150).

The reaction of hemiformal with hydrogen sulfide is similar to the reaction of formaldehyde with hydrogen sulfide (5, p. 7); the reaction product is substances remaining in the oil, actually turning into part of the oil:

reaction with hydrogen sulfide

reactions with methyl ethyl mercaptans

VI. By mat. the balance of reactions (III-V) 1 ppm of hemiformal neutralizes: Hydrogen sulfide - 34: 62 = 0.548 ppm Methyl mercaptans - 48: 62 = 0.774 ppm Ethyl mercaptans - 62: 62 = 1,000 ppm

Ballast in oil does not form with this form of neutralizing agent — a hemiformal solution. Thus, this reagent is designed to neutralize hydrogen sulfide and methyl ethyl mercaptans in commercial oil.

Laboratory tests (Table 1) show that the reaction rate of hemiformal with hydrogen sulfide (without dispersion) is low for real use as a neutralizer in oil treatment systems. The complete neutralization reaction at t = 40 ° C takes ≈48 hours.

Table 1 Name of analysis * Concentration change in 6 hours after 24 hours after 48 hours Initial hydrogen sulfide content 72 ppm 48.72 33.5 5.5 * The analysis was performed in the accredited laboratory of the commercial oil metering station PSP Geology CJSC

With dispersion, the neutralization time is at least 3 hours.

The residence time of commercial oil in oil treatment plants from the point of introduction of the reagent to the commercial metering unit is different, for example:

NGDU "Buguruslanneft" Bobrovsky stream 60 hours Pokrovsky stream 2 hours

The low reaction rate of hemiformal with hydrogen sulfide in oil is due to the fact that hemiformal is a hydrophilic substance, and oil is hydrophobic, they are insoluble in each other.

When nitrobenzene-C ₆ H ₅ NO ₃ (up to 5 wt%) is added to hemiformal, the process occurs in the entire medium treated with the reagent, does not depend on the area of the reagent drop and on the processes in the reaction zone, but depends on the concentration of H ₂ S and hemiformal (table 2).

table 2
Composition of a hydrogen sulfide and light mercaptan neutralizing agent with an accelerated neutralization reaction Name The content of paraform *, wt.% The content of nitrobenzene, wt.% The methanol content, wt.% The reaction time in the oil stream, h Reagent Composition up to 57.5 5,0 from 37.5 and higher up to 0.5 * Paraforms of brands A and C according to TU 6-09-141-03-89

The calculation of the required amount of a hydrogen sulfide neutralizer and light mercaptans is carried out according to the following procedure.

1. At the metering unit of a commercial oil preparation unit according to GOST R50802-95 (chromatographic method), the amount of hydrogen sulfide and light mercaptans is determined, for example:

H ₂ S content = 300 ppm methyl mercaptan content = 10 ppm ethyl mercaptan content = 20 ppm

2. The amount of hemiformal necessary to reduce hydrogen sulfide and ethyl methyl mercaptans in crude oil to a content of 20 ppm is equal to:

on

rounded 511 ppm,

where 0.548 is the hemiformal consumption per 1 ppm H ₂ S. (VI) Methyl and ethyl mercaptans will react in parallel with hydrogen sulfide, therefore, the consumption of the neutralizing reagent must be calculated on them:

rounded 13 ppm,

where 0.774 is the consumption of hemiformal at 1 ppm H ₂ S. (VI)

where 1,0 is the hemiformal consumption per 1 ppm H ₂ S. (VI)

In total, it is necessary to spend 511 + 13 + 20 = 544 ppm of the neutralizer or 544 g per 1 ton of oil. The calculation was made for a neutralizing agent with a hemiformal content = 100%. For an enterprise with a daily oil supply of 10,000 tons, the dosage of the neutralizing agent will be equal to:

daily 10,000 t × 544 g / t = 5440000 g or 5440 kg;

hourly 5440 kg: 24 h = 226.7 kg / h.

Information sources

1. GOST R 51858-2002 OIL "General Specifications" IPK Standards Publishing House, Moscow, Kolodezny per. 14.

2. Organic chemistry. A.A. Petrov, H.V. Balyan, A.T. Troshchenko. Third edition, "HIGHER SCHOOL", Moscow, 1973

3. L.V. Kogan. ZHPKh, No. 12, 1979. "The study of the state of water-methanol solutions of formaldehyde by NMR."

4. Formaldehyde. S.K. Ogorodnikov, Leningrad, Chemistry, 1984

02.02.13 - Petrochemistry / Gafiatullin, Rigat Rukhovich /. - Ufa, 2000 .-- 21 p.: Ill., Tab. - Bibliography: p. 19-20 (11 titles). - b / c. "Development of environmental and resource-saving processes for the processing of hydrogen sulfide."

Claims (2)

1. A method of neutralizing hydrogen sulfide and light mercaptans in salable oil by feeding a hemiformal solution with a tubular perforated dispersant, which is a perforated tube with holes that is introduced into the process pipe in the area after the desalination process before the end separation unit. 2. The composition of the mixture of hemiformal and a hydrocarbon nitro compound to neutralize hydrogen sulfide and methyl ethyl mercaptans in a commercial oil containing nitrobenzene in an amount of up to 5 wt.% As a hydrocarbon nitro compound accelerating the reaction.

Images