RU2509271C2 - Method for obtaining gasolines and liquefied gas from associated gas - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: after condensate (oil and gasoline fractions) representing light gas fractions is separated from associated gas, the latter is cooled in a heat exchanger, subject to separation in a centrifugal separator, and as a result, the separated condensate together with condensate after primary separation is supplied for separation by rectification into oil and gasoline, and light fractions are subject to two-stage compression. After the first stage, gas is divided into two flows. The first flow is directed to a three-way vortex tube for energy separation so that cold, hot gaseous and liquid flows are formed. The second flow is cooled in a recuperative heat exchanger with a cold flow of the vortex tube and divided by separation into gas and liquid. Gas is supplied to the second compression stage, and liquid representing natural gas gasoline is then supplied for further processing. Gas compressed at the second stage is cooled in the recuperative heat exchanger by throttled liquid phase separated from hot flow of the vortex tube and supplied to a fuel-consumed separator for separation into dry and liquefied gas, which are removed from the plant in a marketable form.

EFFECT: use of the invention will allow improving separation efficiency of gaseous mixture.

2 cl, 1 dwg

Description

The invention relates to a technology for the preparation and processing of associated gas into commercial products, in particular, with the release of gasoline and oil fractions, as well as gaseous and liquefied gases. The problem of associated petroleum gas processing is very important, since this type of raw material can be an additional source for replenishing hydrocarbon resources for use in the gas and petrochemical industries.

Today in Russia up to 20 billion m ^{3 of} associated gas is burned in oil fields per year (Putin V.V. Message to the Federal Assembly of the Russian Federation dated April 26, 2007). Transportation of the undivided mixture is difficult, so a significant portion of the associated gas is simply flared. “Today it’s profitable to burn, but processing is not profitable, that’s what they burn” - V.V. Putin Meeting on the development of the oil and gas industry from 08/06/2007

This is harmful to the environment, therefore, the solution to this problem is also very important because it will satisfy the growing need for cheap, environmentally friendly energy resources - hydrocarbon raw materials.

However, a complex mixture consisting of an oil emulsion representing a mixture of oil, water and associated petroleum gas emerges from the wells. Therefore, preliminary preparation is required for separation of the mixture and, directly, separation into constituent components, including condensate, which is a mixture of oil and gasoline fractions and light hydrocarbons C ₁ -C ₃ .

The proposed technology includes a combination of highly efficient centrifugal separation, compression and vortex liquefaction of light hydrocarbon fractions by throttling them in a vortex tube using recuperative heat exchange of cold and hot vortex tube flows.

An analogue of the invention is a method that includes deep preparation of associated petroleum gas for processing into commercial products (See Kisin V.A., Tyurina L.A. Deep preparation of associated petroleum gas for processing into commercial products. Scientific and technical journal. Science and technology in the gas industry. 2008. No. 1 (33), pp. 4-10. - [1]).

According to this method, associated petroleum gas from a field separator enters a gas preparation unit - high-speed low-temperature separation of associated petroleum gas fractions using a low-pressure gas fractionation vortex fractionation apparatus (AVNF) - representing a multi-sectional design that, in addition to using the Rank-Hills effect, implements absorption separation technology own condensate (Lind's co-condensation effect), taking into account the directional formed ultrasonic action and the functions in two heat exchangers in one installation - for gas heating and heat recovery.

The use of the mentioned technological methods allows, while maintaining all the advantages of the vortex tube, to carry out a deeper separation of associated petroleum gas fractions at low pressure (from 0.3-0.4 MPa). AVNF is able to work autonomously, as well as as part of a unit for deep gas treatment (UGPG). The separation unit (working pressure 0.25 MPa) provides purification from water and mechanical impurities, as well as the separation of fractions: methane-ethane, propane-butane, light gasoline fraction (FR. C ₅ +).

In the present invention, despite the achievement of effective preparation for purification and fractionation of associated gas into dry stripped gas, propane-butane mixture and gasoline, it has the disadvantages of:

- the AVNF apparatus arriving for cleaning and fractionation operates at sound speeds, which is unacceptable at a pressure of 0.3-0.4 MPa, since the manifestation of the Rank effect is based on it, therefore unstable operation is possible, and therefore disruptions in operating modes are possible (it is known that the vortex tube effectively works when the pressure drop is reached before and after the vortex tube P ₁ / P ₂ ≤4-5);

- since the associated gases at the outlet of the field separator have a low initial pressure (0.1-0.3 MPa) and it is unstable in values, which will unsatisfactorily affect the operation of the vortex apparatus;

- the above arguments of the unstable operation of the vortex apparatus will also affect the supply of absorbent (condensate), since it is associated with the directed formation of ultrasonic action in the vortex apparatus.

The prototype of the invention is a method for the installation of vortex liquefaction of associated gas according to the patent of the Russian Federation: RLJ 2395763 from 07/27/2010, F25J 1/00, F25B 9/00 - [2], in which the source gas stream is previously separated from the water, cooled in regenerative heat exchangers and enters the turboexpander, and then into the vortex tube.

The dried associated gas is cooled by the “hot” methane fraction of the gas due to the hot stream of the vortex tube, then the cooled gas expands in the turboexpander with decreasing pressure and temperature and is fed into the vortex tube, in which two flows are formed - the axial cold one with a temperature below the condensation temperature of propane butane fractions and peripheral - hot.

The cold stream of expanded gas with a temperature of minus 65 ° C, representing a methane fraction with tiny droplets of condensed propane-butane fractions, is then separated into components: liquid propane-butane and methane.

The cold stream of the methane fraction after the regenerative heat exchanger, in which the initial flow of associated gas is cooled, enters the ejector for mixing with the dried hot stream of the vortex tube, which is supplied by a turbocompressor and then discharged as a commodity methane fraction.

The liquid phase separated from the cold vortex tube stream, as well as the moisture separated from the hot vortex tube stream, which is a liquid propane-butane mixture, are removed from the unit as a commercial product.

This method allows the separation of associated gas containing a significant amount (about 80%) of light methane and a small amount (about 10%) of heavy propane-butane fractions, however, it has disadvantages, which include:

- usually incoming associated gas contains a significant amount of various impurities, including both mechanical and hydrocarbon impurities, for example, oil emulsions, water, etc., therefore, more efficient cleaning of these impurities is required. This is especially important if devices such as a vortex tube, a turboexpander, a turbocompressor, an ejector are provided in the circuit (due to the possibility of clogging a nozzle in a vortex tube or a water hammer in compressors, etc.);

- the circuit provides an additional separator-water separator, but after it two recuperative heat exchangers are installed in series, in which cooling by hot and cold flows of the vortex tube is carried out, which naturally will cause condensation of the liquid phase from the gas stream, however, the resulting two-phase flow enters the turbine expander and the vortex pipes, which is unacceptable;

- similarly, the hot stream, after relative cooling in the first recuperative heat exchanger of the initial gas stream, is sent to the turbocharger, and then to the ejector. Despite the fact that the hot stream was separated from the liquid phase, secondary formation of moisture is possible after the heat exchanger, which must be released before the gas is directed to the turbocharger.

To eliminate the above disadvantages, the proposed method provides the following:

- preliminary preparation of incoming associated petroleum gas, including two-stage separation (so-called coarse and fine), which allows the condensed liquid, consisting mainly of oil and gasoline fractions, and light gaseous fractions to be isolated at the first stage (Block A - preparations);

- separation of water-hydrocarbon condensate, including oil emulsions, water condensate and gasoline fractions, using a stripping distillation column, with the necessary additional equipment, to obtain marketable: oil and gasoline (Block B - rectification block);

- compression and liquefaction of light hydrocarbon fractions using throttle regenerative liquefaction and energy separation in a three-stream vortex tube, and for normal operation of the vortex tube (the required minimum inlet pressure), the compressed gas stream is taken after the first compressor stage (1.5-2.0 MPa) and fed to the entrance of the vortex tube.

The presence of sufficient pressure allows you to include a vortex tube in the technological process (the lower boundary of the vortex tubes is equal to pressure values of 1.2-2.0 MPa), which allows the use of refrigeration cycles using the energy of the hot and cold vortex tube flows for regenerative exchange and efficient separation shared commodity gaseous and liquefied gases (Block C - compression and liquefaction).

Figure 1 shows a schematic flow chart for implementing the proposed method. The diagram shows: block A — associated gas preparation for separation, block B — rectification block, block C — gas compression and liquefaction block, as well as flows: I — initial gas flow; II - condensate of oil and gasoline fractions; III - light gaseous fractions; IV - separated gaseous fractions; V is the condensate of petroleum fractions; VI - oil; VII - gasoline; VIII - part of the compressed gas after the first stage of the compressor (first stream); IX - cold stream of a vortex tube; X is the hot stream of the vortex tube; XI is the separated liquid of the hot stream; XII - part of the compressed gas after the first stage of the compressor (second stream); XIII - separated gas; XIV - condensed gas gasoline; XV - gas gasoline; XVI - light hydrocarbon fraction compressed after the second stage of the compressor; XVII - methane gas fraction; XVIII - liquefied gases (fraction C ₃ -C ₄ ).

The apparatus and fittings are also shown in the diagram of FIG. 1: 1 — a primary separator in which light gas fractions are separated from the condensate of the oil-gasoline mixture; 2 - recuperative heat exchanger, used to cool light gas fractions (stream III) with a cold stream IX; 3 - multistage centrifugal separator for gas separation (stream III); 4 - capacity for petroleum-gas mixture; 5 - the first stage of the compressor for compressing the gas stream (stream IV); 6 - the second stage of the compressor for compressing the gas stream (stream XIII); 7 - vortex tube, serving for energy liquefaction and separation of light hydrocarbon fractions (FR. C ₁ -C ₅₊ ); 8 - recuperative heat exchanger, which serves to cool the compressed (second stream) - (stream XII) cold stream of the vortex tube; 9 - a separator used to separate the compressed (second stream XII) into gas XIII and liquid (stream XIV); 10 - capacity for collecting the separated liquid - gas gas condensate (+ stream XV); 11 - recuperative heat exchanger for cooling the compressed stream XVI - separated liquid (stream XI); 12 - consumable separator for the separation of the gaseous methane fraction (stream XVII) and liquefied gases fraction - C ₃ -C ₄ (stream XVIII); 13 - distillation stripping column for rectification (separation) of oil fractions (stream VI) from gasoline fractions (stream VII); 14 - a boiler for heating the still bottom of the distillation column 13; 15 - refrigerator for cooling and condensation of vapors leaving the top of the distillation column 13; 16 - capacity for collecting condensate of gasoline fractions; 17 - pump for supplying irrigation (phlegmy) to the top of the distillation column 13; 18 ... 37 - shut-off and control valves.

In this case, the valve 18 is placed on the exit line of the separated light gaseous fractions (stream III) entering the annulus of the recuperative heat exchanger 2; valve 19 - on the line of the outlet condensate of oil and gasoline fractions (stream II), leaving apparatus 1 and 4 to distillation stripping column 13; valve 20 - on the line of the separated gaseous fractions (stream IV) leaving the multi-stage centrifugal separator 3 and entering the input of the first stage of the compressor 5; valve 21 - on the output line (stream V) from the multi-stage centrifugal separator 3 of condensate of oil-gasoline fractions into the tank 4; valve 22 - on the exhaust line of the second stream (XII) of compressed gas after the first stage of the compressor 5 entering the pipe space of the regenerative heat exchanger 8; valve 23 - on the line of condensed gas gasoline (stream (XIV) coming from the separator 9 to the tank 10; valve 24 - on the line of the first stream of compressed gas (stream VIII) after the first stage of the compressor 5 entering the input of the vortex tube 7; valve 25 - on the line of the cold stream leaving their cold end of the vortex tube to enter the annular space of the recuperative heat exchanger 8; valve 26 - on the line (stream XI) of the output of the separated liquid from the hot stream of the vortex tube; valve 27 - on the line connecting the pipe a regenerative heat exchanger 11 with an entrance to the consumable separator 12; valve 28 is on the line connecting the hot end of the vortex tube 7 with the entrance to the multistage centrifugal separator 3; valve 29 is on the line connecting the upper part of the separator 9 with the entrance to the second stage of the compressor 6; valve 30 — on the line connecting the upper part of the consumable separator 12 with the main pipeline (stream XVII); valve 31 — on the outlet line from the lower part of the consumable separator 12 of a commodity liquefied gas fraction (fr. Sz-C4) - stream XVIII; valve 32 - on the output line from the lower part of the tank 10 gas gasoline (stream XV); valve 33 - on the condensate discharge line of oil and gasoline fractions from tank 4 (stream II); valve 34 - on the line of exit of the vapor phase of gasoline fractions for reflux (cooling) in the refrigerator 15; valve 35 - on the line of removal of the oil fraction from the bottom of the distillation column 13 (stream VI); 36 - on the supply line of irrigation (gasoline fractions) from the lower part of the tank 16 with a pump 17 to the upper part of the distillation column 13; 37 - on the line of removal of gasoline fractions (stream VII) from the bottom of the tank 16.

The associated gas I feed stream from the field gas separator enters a preliminary separator for separating light gas fractions from condensate II, which is a petrol-gas mixture. The input gas parameters are usually: pressure P = 0.2-0.4 MPa, temperature 20-30 ° C. The light gas fraction leaving the top of the separator 1 is cooled in a recuperative heat exchanger 2 by a cold stream of a vortex tube 7 and is subjected to highly efficient separation in a multi-stage centrifugal separator 3 to separate gas (stream IV) from the residual condensate and fine dispersed suspension and enters (Block C) to suction of the first stage 5 of a two-stage compressor, where it is compressed to a pressure of 1.5-2.0 MPa.

Compressed gas V of uniform composition after the first compressor stage, which is a gaseous fraction consisting of C ₁ -C ₃ hydrocarbons (methane-ethane-propane), is divided into two streams in the ratio (in volume percent): the first stream is from 10 to 30 and the second stream from 70 to 90. For example, the first stream VIII - 20% vol. and the second stream XII - 80% vol.

The first gas stream VIII enters the inlet of a three-stream vortex tube 7, in which cold IX, hot X gaseous and liquid XI flows are formed. The second gas stream XII after the first stage of the compressor 5 and the regenerative heat exchanger 8 is separated in the separator 9 into gas XIII and liquid XIV. Gas enters the second stage of compression, where it is compressed to a pressure of P = 5.0-5.5 MPa., And the liquid, which is gas gasoline, enters the tank 10, from where it is discharged for further processing into the final product.

Compressed gas XVI is cooled in a heat exchanger 11 throttled by a valve 26 with a liquid phase separated from a hot stream of a vortex tube, which is mixed with gas gas XIV in a tank 10, and stream XVI is fed to a separator 12 for separation, from the top of which dry methane gas is discharged XVII, and from the bottom of the separator the liquefied fraction C ₃ -C ₄ (stream XVIII), as commercial products.

The petrol-gas mixture (stream II) is separated in the rectification unit (block A), which includes: distillation stripping column 13, heat exchanger 15, capacity 16, pump 17.

Mixture II entering the distillation column is separated during the distillation process, including heating with steam in the heat exchanger 14 of the bottom part of the column and cooling (refluxing) the effluent from the top of the column in the refrigerator 15, collecting condensate in the vessel 16 and supplying the upper part of the distillation column 13 as irrigation condensate pump 17 to the top of the column. As a result of rectification, the mixture is separated (stream II) into oil VI and gasoline VII discharged as final products.

A method of producing gasoline and liquefied gas from associated gas, including crude associated gas coming from a gas pipeline, which is a mixture of oil residues, gasoline fractions and associated gas, is separated into condensed gasoline and oil residues by distillation, and associated gas consisting of light fractions C _1- C _{3 are} compressed and separated into dry and liquefied gases, characterized in that the associated gas, after separation of condensate (oil and gasoline fractions) from it, representing light gas fractions, is cooled to heat the exchanger is subjected to a highly efficient separation in a centrifugal separator, as a result of which the condensate separated together with the condensate after primary separation is separated by distillation into oil and gasoline, and the light fractions are subjected to two-stage compression, while after the first stage the gas is divided into two streams, the first stream is directed into a three-threaded vortex tube for energy separation with the formation of cold, hot gaseous and liquid streams, the second stream is cooled in a regenerative manner the heat exchanger with a cold vortex tube flow and is separated by gas and liquid separation, the gas enters the second stage of compression, and the gas gasoline liquid is then sent for further processing, the gas compressed in the second stage is cooled in a recuperative heat exchanger with a throttled liquid phase separated from the hot flow of the vortex tube, and enters the consumable separator for separation into dry and liquefied gas, which are removed from the installation as commodity.

The method, characterized in that the light fractions, after the first stage of compression, the gas is divided into two streams, in the ratio (in volume percent): the first stream from 10 to 30 and the second stream from 70 to 90.

Thus, in the proposed method for the processing of associated gas, which is processed as a crude hydrocarbon mixture having a relatively low pressure, technical and technological solutions for stabilizing the gas composition are given, and the rational use of compression allows the use of a vortex tube with which to obtain energy flows for use in gas separation processes refrigeration cycles.

This allows the use of recuperative heat exchangers for the condensation and gas separation processes of low molecular weight hydrocarbon mixtures of C ₁ -C ₄ fractions to produce individual hydrocarbon fractions (CH ₄ fractions and C ₃ -C ₄ fractions), as well as C ₅₊ gasoline fractions with separation of oil fractions.

The implementation of the method of producing gas and gas from associated gas in conjunction with the foregoing features (features of the claims) is new to the technology for the extraction of valuable hydrocarbons from associated gas for various industries, and therefore meets the criterion of "novelty."

The above set of distinctive features is not known at this level of technological development and does not follow from the well-known rules for the design of gas separation technological systems for the production of low molecular weight hydrocarbons from associated petroleum gases, which proves compliance with the criterion of "inventive step".

The constructive implementation of the claimed invention with the specified set of features does not present any structural, technical and technological difficulties, whence the compliance with the criterion of "industrial applicability" follows.

Information sources

1. Kisin V.A., Tyurina L.A. Deep preparation of associated petroleum gas for processing into commercial products. Scientific and technical journal. Science and technology in the gas industry. 2008. No. 1 (33), pp. 4-10.

2. RF patent: RU 2395763 from 07/27/2010, F25J 1/00, F25B 9/00 - prototype.

Claims (2)

1. A method of producing gasoline and liquefied gas from associated gas, in which crude associated gas coming from the gas pipeline, which is a mixture consisting of oil residues, gasoline fractions and associated gas, is separated into condensed gasoline and oil residues by distillation, and associated gas consisting of light fractions C ₁ -C _{3 are} compressed and separated into dry and liquefied gases, characterized in that the associated gas after separation of condensate (oil and gasoline fractions) from it, representing light gas fractions, is cooled to heat the exchanger is subjected to separation in a centrifugal separator, as a result of which the separated condensate, together with the condensate, is separated by distillation into oil and gas after primary separation, and the light fractions are subjected to two-stage compression, while after the first stage the gas is divided into two streams, the first stream is sent to three-stream vortex tube for energy separation, with the formation of cold, hot gaseous and liquid streams, the second stream is cooled in a recuperative heat exchanger x by a vortex tube flow boat and separated by gas and liquid separation, gas enters the second stage of compression, and gas gasoline liquid is then sent to further processing, the gas compressed in the second stage is cooled in a recuperative heat exchanger by a throttled liquid phase, separated from the hot stream vortex tube, and enters the consumable separator for separation into dry and liquefied gas, which are removed from the installation as commodity. 2. The method according to claim 1, characterized in that the light fractions, after the first stage of compression, the gas is divided into two streams, in the ratio (in volume percent): the first stream from 10 to 30 and the second stream from 70 to 90.

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