RU2237052C1 - Method of inhibiting clathrate-hydrates - Google Patents

Abstract

FIELD: petrochemical processes.

SUBSTANCE: invention relates to methods for preventing hydrate formation in various hydrocarbon-containing liquids and gases comprising hydrogen-containing molecules and can be used in production, transportation, and processing of hydrocarbon-containing raw materials. Inhibition of formation of clathrate-hydrates in liquid and gaseous hydrocarbon feedstock containing hydrate-forming components is carried out by adding water-soluble oxygenates as inhibitors. Oxygenates are added in amounts 0.01 to 3.29% with respect to known amount of C₁-C₆-hydrocarbons contained in feedstock. Optimal amount of utilized oxygenates is found from formula: C = MΔt_g/(K+Δt_g), where C is concentration of oxygenates in feed stream calculated on 1000 m³ of C₁-C₆-hydrocarbons, M molecular weight of oxygenates involved, Δt_g value of temperature drop caused by hydrate formation in feed stream, and K coefficient characterizing antihydrate potential of oxygenates. Method allows amount of oxygenate used as inhibitor to be considerable diminished (at least by a factor of 1.5). Duration of activity of inhibitor in hydrocarbon feedstock is twice prolonged as compared to known processes.

EFFECT: increased hydrate formation inhibition efficiency.

10 cl, 1 tbl, 6 ex

Description

This invention relates to methods for preventing hydrate formation of various hydrocarbon-containing liquids and gases containing water in various quantities, including micro quantities, and can be used in field preparation processes in the extraction, transportation and processing of hydrocarbon-containing raw materials.

Hydrocarbon-containing feed streams contain carbon dioxide, oxygen, nitrogen, hydrogen sulfide, paraffins and various hydrocarbons such as methane, ethane, propane, n-butane and isobutane, pentane, as well as unsaturated hydrocarbons, cyclic aromatic and non-aromatic. Under increased pressure or at a reduced temperature, clathrate hydrates can form in a mixture with water, which are aqueous crystals that form a cage-like structure around molecules capable of forming it, such as all of the above hydrocarbons or gases.

Hydrate crystals, or clathrate hydrates, cause clogging of pipelines when receiving and / or transporting liquid and gaseous streams containing water or water-containing compounds. For example, at a pressure of about 1 MPa, ethane forms hydrates at a temperature below 4 ° C, and at a pressure of 3 MPa ethane forms hydrates of a gas at a temperature below 14 ° C. Such temperatures and pressures are normal operating conditions used in the production and transportation of liquid and gaseous hydrocarbons.

A known method of preventing hydrate formation of hydrocarbon feedstocks, for example natural or associated petroleum gas, using methanol, ethanol, ethylene glycol in an amount of up to 70 wt.% Based on the feedstock, followed by separation of the inhibitors by separation (RU 2117854, 08.20.1998; 2175882, 11.20.2001 )

A disadvantage of the known methods is the significant consumption of the inhibitors used due to the inability to determine the maximum and minimum amounts needed, which leads to their excessive consumption.

The aim of this invention is to eliminate this drawback and, as a result, increase the efficiency of this invention by preventing the need for excessive consumption of inhibitors in the development of gas, gas condensate and oil fields, including offshore development in the North Seas and regions with the Far North with a sharp continental climate, and also increase the anti-hydrate properties for a longer time in hydrocarbon-containing feed streams to the required values or in the inhibitor used .

This goal is achieved by a method of inhibiting the formation of clathrate hydrates in liquid and gaseous hydrocarbon feeds containing hydrate-forming components by adding water-soluble oxygenates as inhibitors, the oxygenates being added in an amount of 0.01-3.29 wt.% Based on the amount contained in the feedstock light hydrocarbons C ₁ -C ₆ when determining the optimal amount of oxygenates used by the formula

C = MΔt _g / (K + Δt _g ),

where C is the concentration of oxygenates in the feed stream per 1000 cubic meters of C ₁ -C ₆ , wt.%,

M is the molecular weight of the oxygenates used,

Δt _g is the temperature of the necessary reduction during hydrate formation in the hydrocarbon stream as a result of the difference T _p -T _g , where T _p is the temperature of the hydrocarbon stream, and T _g is the temperature of hydrate formation in the stream,

K is the coefficient characterizing the antihydrate potential of the oxygenates used.

For methanol and ethanol, K = 1220, for ethylene glycol, propylene glycol and triethylene glycol, K = 2195, for diethylene glycol K-2425.

During the production and processing of hydrocarbon-containing feed streams, mixed types of hydrates are formed, the properties of which, if necessary, are specified by their physicochemical characteristics, which can be taken into account to adjust the concentration of oxygenates introduced into the stream, since the properties of the gas components of the stream composition and gas hydrates affect the hydrate formation temperature . The hydrate formation temperature of the hydrocarbon-containing feed stream allows us to determine the temperature of hydrate formation reduction in the gas phase by 1000 cubic meters when transporting it to 10 kilometers, which in turn affects the calculated value that determines the necessary concentration of oxygenate used in the stream.

Oxygenate can be added to hydrocarbon feeds by transporting it through a pipeline system from cluster wells to oil terminals or plants for the separation, compression and cooling of natural gas.

It is possible to use oil, gas condensate, natural gas, associated petroleum gases, liquid and gaseous refined products and their fractions as hydrocarbon feedstocks.

Aliphatic alcohols, mono-, di- or trialkylene glycols can be used as oxygenate.

As a hydrate inhibitor, all water-soluble oxygenates, for example, aliphatic alcohols, mono-, di- or trialkylene glycols, ethers, etc. can be used.

For economic reasons, it is preferable to use methanol or its rectificate as an aliphatic alcohol, obtained by gas-phase oxidation or steam reforming from natural gas or a hydrocarbon fraction boiling up to 470 ° С.

For a greater effect of lowering the crystallization temperature of water-containing compounds and increasing the duration of the inhibitor properties, a water-soluble polymer or copolymer, for example vinyl pyrrolidone or caprolactam, as well as polyacrylamides, cellulose ethers, etc., in the required quantities can be added to the oxygenate used.

For example, when caprolactam is added to oxygenate in an amount of up to 15 wt.%, The crystallization temperature of water-containing molecules decreases compared to its absence by no less than 10% with an increase in the duration of the inhibitor by more than 1.2 times.

To reduce the oxygenate consumption, a hydrocarbon fraction boiling in the range of 25-380 ° C, preferably a gasoline fraction boiling up to 210 ° C, as well as an electrolyte, for example, water-soluble alkali metal salts, including salts isolated from sea water in an amount up to 27 wt.%.

To reduce and neutralize the negative influence of molecules of heavy aromatic hydrocarbons contained in the hydrocarbon stream, it is recommended to add monomethylaniline or technical methylaniline in an amount of up to 13 wt.%.

Calculations determine the required concentration of oxygenate used as an inhibitor of hydrate formation in a hydrocarbon-containing feed stream by lowering the temperature in the hydrate formation zone, without taking into account the temperature and pressure adjustments of the hydrocarbon feed stream.

The calculation results by the formula (1) are shown in examples 1-6 and are summarized in the table.

Example 1

Oxygenate with a molecular weight of 106.1 units, realizing its antihydrate potential as an inhibitor of hydrate formation, in an amount of 0.55 wt.% When added to oil containing 5 wt.% Light hydrocarbons (C ₁ -C ₆ ), lowered the temperature by hydrate formation zone at 12.64 ° С (table).

Example 2

Oxygenate with a molecular weight of 150.2 units, realizing its antihydrate potential as an inhibitor of hydrate formation, in an amount of 0.5 wt.% When added to natural gas containing 98% light hydrocarbons (C ₁ -C ₆ ), lowered the temperature in the zone hydrate formation at 7.33 ° С (table).

Example 3

Oxygenate with a molecular weight of 76.1 units, realizing its antihydrate potential as an inhibitor of hydrate formation, in an amount of 0.3 wt.% When added to a gas condensate containing 10% light hydrocarbons (C ₁ -C ₆ ), lowered the temperature in the hydrate formation zone at 8.69 ° C (table).

Example 4

Oxygenate with a molecular weight of 62.1 units, realizing its antihydrate potential as an inhibitor of hydrate formation, in the amount of 0.08 wt.% When added to associated gas containing 96% light hydrocarbons (C ₁ -C ₆ ), lowered the temperature in the zone hydrate formation at 2.83 ° C (table).

Example 5

Oxygenate with a molecular weight of 52.0 units, realizing its antihydrate potential as an inhibitor of hydrate formation, in an amount of 0.55 wt.% When added to oil after its stabilization, containing 14% light hydrocarbons (C ₁ -C ₆ ), lowered the temperature in the hydrate formation zone at 13.04 ° С (table).

Example 6

Oxygenate with a molecular weight of 32.0 units, realizing its antihydrate potential as an inhibitor of hydrate formation, in an amount of 0.5 wt.% Per 1000 cubic meters when adding natural gas transported through the pipeline system to the stream, lowered the temperature in the hydrate formation zone by 19 , 37 ° C (table).

All other results are also shown in the table. Compared with known methods, the consumption of the inhibitor is reduced by at least 1.5 times.

The action of the inhibitor in the hydrocarbon feed is increased by at least 2 times compared with known methods.

Claims (10)

1. A method of inhibiting the formation of clathrate hydrates in liquid and gaseous hydrocarbon feeds containing hydrate-forming components by adding water-soluble oxygenates as inhibitors, characterized in that the oxygenates are introduced in an amount of 0.01-3.29 wt.% Based on the amount contained in the feedstock of light hydrocarbons C ₁ -C ₆ when determining the optimal amount of oxygenates used by the formula C = MΔt _g / (K + Δt _g ), where C is the concentration of oxygenates in the feed stream per 1000 m ³ C ₁ -C ₆ , wt.%; M is the molecular weight of the oxygenates used; Δt _g is the value of the temperature of lowering hydrate formation in the flow of hydrocarbons; K is the coefficient characterizing the antihydrate potential of the oxygenates used. 2. The method according to claim 1, characterized in that the oxygenate is added to the hydrocarbon stream of the feedstock when transporting it through a pipeline system from cluster wells to oil terminals or plants for the separation, compression and cooling of natural gas. 3. The method according to PP.1 and 2, characterized in that the hydrocarbon raw materials are oil, gas condensate, natural gas, associated petroleum gases, liquid and gaseous refined products and their fractions. 4. The method according to claims 1 and 2, characterized in that aliphatic alcohols, mono-, di- or trialkylene glycols and mixtures thereof are used as oxygenate. 5. The method according to claim 4, characterized in that methanol or its rectificate obtained by gas-phase oxidation or steam reforming from natural gas or a hydrocarbon fraction boiling up to 340 ° C is used as an aliphatic alcohol. 6. The method according to claims 1-5, characterized in that the oxygenate further comprises a water-soluble polymer or copolymer. 7. The method according to claim 6, characterized in that the oxygenate as a water-soluble polymer contains a copolymer of vinyl pyrrolidone or caprolactam. 8. The method according to claims 1 to 7, characterized in that the oxygenate further comprises a stable hydrocarbon fraction boiling up to 470 ° C. 9. The method according to claim 8, characterized in that the oxygenate additionally contains monomethylaniline or technical methylaniline in an amount of up to 13 wt.%. 10. The method according to claims 1 and 2 and 4-9, characterized in that the oxygenate further comprises an electrolyte in an amount of up to 27 wt.%.

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