RU2812844C1 - Natural gas liquefaction system at compressor station of main gas pipeline - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: natural gas liquefaction system is mounted at the compressor station of the main gas pipeline and connected to a DN 200 gas pipeline running from the outlet collector of the dust collectors to the auxiliary block box. In the natural gas liquefaction system, adsorption-type natural gas drying and purification units, a heat exchange unit consisting of three preliminary heat exchangers for gas cooling, a turbine module consisting of injection and expansion turbines mounted on one working shaft, and an electric generator, the main cryogenic module were installed , adjustable chokes of the first and second stages, a separation unit consisting of a main and receiving separators, a weighing unit for liquefied natural gas, a unit for storing and dispensing liquefied natural gas, an ejector for supplying natural gas into the gas pipeline to receive the block box for the auxiliary needs of the compressor station, pipeline and reinforcement strapping.

EFFECT: development of an effective natural gas liquefaction system in the conditions of a compressor station, improved fire safety.

1 cl, 1 dwg

Description

The invention relates to the field of the gas industry, in particular, to the technology of liquefying natural gas and can be used in the operation of a compressor station of a main gas pipeline.

Various technical solutions are known for the technology of liquefying natural gas at gas pipeline facilities (in the conditions of autogas filling compressor and gas distribution stations) using a technologically closed throttle recuperative cycle with additional external cooling (RU 2295678 C2, 03.20.2007; RU 2665088 C1, 08.28.2018) , the general disadvantages of which are:

- precipitation of the solid phase of carbon dioxide in the cryogenic liquid and, as a consequence, a decrease in the reliability of throttling equipment;

- a smaller range of values between the inlet and outlet pressures of natural gas, compared to the compressor station of the main gas pipeline, and, accordingly, a smaller thermodynamic effect and, as a consequence, an increased level of energy and labor costs.

It is known to design a natural gas liquefaction system at a compressor station of a main gas pipeline (prototype), in which it is proposed to remove all present low-boiling components in distillation columns, and to increase the thermodynamic efficiency of the process of obtaining liquefied natural gas by generating additional electricity for its own technological needs and increasing the coefficient beneficial effect of the gas pumping unit of the compressor station by increasing the temperature of the fuel gas at the inlet to the gas turbine unit (RU 2694566, 07/16/2019).

The prototype natural gas liquefaction system includes a fuel and pulse gas preparation unit, a gas pumping unit with an oil cooling system and a fuel control system, complex cleaning units, controlled valves, a booster compressor, a liquefaction unit, an expander-generator, chokes, distillation columns, separators, a storage unit liquefied natural gas, heat exchangers connected to the oil cooling systems of the compressor and engine of the gas pumping unit.

The disadvantages of the prototype are:

1) excessive (non-design) thermodynamic load on the thermal resource of the main and auxiliary equipment of the compressor station included in the proposed natural gas liquefaction system:

- installation for the preparation of fuel, starting and pulse gas;

- oil cooling system in the compressor and engine of the gas turbine unit;

- fuel control system of the gas pumping unit;

2) diversion of a significant volume of already compressed commercial gas from the implementation of planned indicators of commodity and transport work (the main activity) to organize, in addition to the technological cycle, a “product flow”;

3) the need (in close proximity to objects and sections of gas pipelines of category “B”) to place, design piping and maintain rectification equipment that is unusual for the operation of a compressor station, which requires an additional supply of fuel or water vapor and is an additional potential source of explosion and fire hazard due to the events occurring in it processes of evaporation and gas formation;

4) the presence of additional costs for the installation, maintenance and operation of another booster compressor at the outlet of the liquefaction unit for supplying dry natural gas separated from the liquid phase with the required parameters to the gas turbine installation of the gas pumping unit.

The purpose of the invention is to produce liquefied natural gas at the compressor station of the main gas pipeline.

The technical result of the invention is the development of an effective natural gas liquefaction system in the conditions of a compressor station, during the operation of which, unlike the prototype, to ensure full-fledged commodity transport work, the design functionality of the main and auxiliary production is preserved without the use of additional thermodynamic loads on it and the presence of potentially explosive and fire hazards is excluded sources of dry natural gas in the form of compressor and gas fractionation distillation equipment at facilities and sections of gas pipelines of category “B”.

The technical result is achieved by the fact that the natural gas liquefaction system is mounted at the compressor station of the main gas pipeline and connected to a DN 200 gas pipeline running from the outlet collector of the dust collectors to the auxiliary block box. The following installations were carried out in the natural gas liquefaction system itself:

- adsorption-type natural gas drying and purification units;

- a heat exchange unit consisting of three preliminary heat exchangers for gas cooling;

- turbine module, consisting of injection and expansion turbines mounted on one working shaft, and an electric generator;

- main cryogenic module;

- adjustable throttles of the first and second stages;

- separation unit, consisting of main and receiving separators;

- liquefied natural gas weighing unit;

- liquefied natural gas storage and delivery unit;

- an ejector for supplying natural gas to the gas pipeline to receive the auxiliary block box of the compressor station;

- pipeline and fittings.

The figure shows a schematic diagram of the natural gas liquefaction system at the compressor station of the main gas pipeline.

The proposed system for liquefying natural gas at the compressor station of the main gas pipeline contains: inlet 1 and outlet 16 valves; block 2 of natural gas drying; injection turbine 3; preliminary heat exchangers for gas cooling 4, 6, 14; block 5 for purifying natural gas from carbon dioxide and hydrogen sulfide; cryogenic module 7; adjustable throttles of the first 8 and second 10 stages; a separation unit consisting of a main 9 and a receiving 11 separators; liquefied natural gas weighing unit 12 with electronic scales; unit 13 for storing and dispensing liquefied natural gas; ejector 15; expansion turbine 17 with electric generator 18.

The proposed natural gas liquefaction system at the compressor station of the main gas pipeline operates as follows. Flow I of natural gas (P=5.35 MPa, Q=67500 nm ³ /h, t=+10°C) from the gas pipeline DN 200, going from the output collector of the dust collectors to the auxiliary block box of the compressor station of the main gas pipeline, passes through inlet valve 1 and enters natural gas drying unit 2, where water vapor is removed to a concentration in natural gas of no more than 0.002 g/m ³ , corresponding to the dew point temperature t _{T. p} = -70°C. Natural gas dehydration is carried out in two adsorbers with NaA zeolite of 2.9 mm fraction. Stream III of dried natural gas (P=5.35 MPa, Q=45500 nm ³ /h, t=+10°C) then passes into injection turbine 3 (power 600 kW, working gas flow through the turbocompressor 25000 kg/h), from which the gas flow V (P = 6.55 MPa, Q = 45500 nm ³ / h, t = +35 ° C) enters the preliminary heat exchanger for gas cooling 4. Gas is sent to the same preliminary heat exchanger for gas cooling 4 for heat exchange flow II (P=5.35 MPa, Q=20000 nm ³ /h, t=+10°C). From the preliminary heat exchanger for gas cooling 4, gas stream VI (P=6.55 MPa, Q=5500 nm ³ /h, t=+15°C) is sent to block 5 for purifying natural gas from carbon dioxide and hydrogen sulfide from a concentration of 2500 to 50 ppm (0.005% by volume). Natural gas purification is carried out in two adsorbers with NaX zeolite of 2.9 mm fraction. The second interacting coolant is gas stream II (P=5.35 MPa, Q=20000 nm ³ /h, t=+10°C) from the preliminary heat exchanger for cooling gas 4 with gas stream XXII (P=5.35 MPa, Q=20000 nm ³ /h, t=+15°C) is sent to form and regulate technical parameters after ejection of the output gas flow XVII (P=0.6 MPa, Q=63500 nm ³ /h, t=+5°C). For ejection, gas flow IV (P=5.35 MPa, Q=2000 nm ³ /h, t=+10°C) entering after the ejector 15 into the output gas stream XVII (P=0.6 MPa, Q=63500 nm ³ /h, t=+5°C), directed after the outlet valve 16 in the form of gas flow XXIV (P=0.6 MPa, Q=63500 nm ³ /h, t=+5°C) with the required technical parameters into the auxiliary block box of the main gas pipeline compressor station. After block 5 for purifying natural gas from carbon dioxide and hydrogen sulfide, gas flow VII (P=6.55 MPa, Q=5500 nm ³ /h, t=+15°C) is sent for cooling in a preliminary heat exchanger for cooling gas 6. After preliminary cooling gas-liquid flow IX (P = 6.55 MPa, Q = 5500 nm ³ / h, t = -50 ° C) is sent to cryogenic module 7, consisting of two main heat exchangers for cooling and cryogenic equipment with cryogenic piping, shut-off -regulating and safety fittings, resistant thermal insulation and remote control. The second interacting coolant in the cryogenic module 7 is gas stream VIII (P=6.55 MPa, Q=40000 nm ³ /h, t=+15°C), cooled in a preliminary heat exchanger for gas cooling 14, converted into gas stream XVIII (P = 6.55 MPa, Q = 40,000 nm ³ / h, t = -55 ° C), supplied, in turn, to receive expansion turbine 17 (power 600 kW, working gas flow through the turboexpander 25,000 kg/h) for further sequential cooling, providing cold in the cryogenic module 7 and generating electricity for its own technological needs in the electric generator 18. Next, the cooled gas stream XIX (P = 0.6 MPa, Q = 40000 nm ³ / h, t = -115 ° C) is supplied sequentially as a refrigerant to the cryogenic module 7 and, having been converted into a gas stream XX (P=0.6 MPa, Q=40000 nm ³ /h, t=-55°C), into a preliminary heat exchanger for cooling gas 6, leaving which in the form of gas stream XXI (P=0.6 MPa, Q=40000 nm ³ /h, t=+5°C) is sent to the output gas stream XVII (P=0.6 MPa, Q=63500 nm ³ /h , t=+5°С). From the cryogenic module 7, the cooled gas-liquid flow X (P=6.55 MPa, Q=5500 nm ³ /h, t=-110°C) is supplied to the adjustable throttle of the first stage 8, in which additional cooling occurs due to the Joule effect -Thomson and conversion into gas-liquid stream XI (P=0.6 MPa, Q=5500 nm ³ /h, t=-130°C), which enters the main separator 9 for separation into gas and liquid phases. The separated gas stream XXIII (P=0.6 MPa, Q=1200 nm ³ /h, t=-130°C) is directed into gas stream XIX (P=0.6 MPa, Q=40000 nm ³ /h, t= -115°C), used as a refrigerant in cryogenic module 7. Liquid stream XII (P=0.6 MPa, Q=4300 nm ³ /h, t=-130°C) separated in the main separator 9 is fed into an adjustable throttle second stage 10, in which even more complete cooling occurs due to the Joule-Thomson effect and conversion into liquid stream XIII (P = 0.4 MPa, Q = 4300 nm ³ / h, t = -144 ° C) entering the receiving separator 11 for final separation of the gas phase present. Weight control is carried out by unit 12 for weighing liquefied natural gas with electronic scales. Storage and delivery to the consumer of liquid phase flow XIV (P=0.4 MPa, Q=4200 nm ³ /h, t=-144°C) is organized in block 13 for storing and dispensing liquefied natural gas. The gas phase from the receiving separator 11 by flow XV (P=0.4-0.6 MPa, Q=100 nm ³ /h, t=-144°C) is supplied as a refrigerant to the preliminary heat exchanger for cooling the gas 14 and further as passive gas flow XVI into the ejector 15, with the help of which the required technical parameters of the entire output gas flow XXIV (P = 0.6 MPa, Q = 63500 nm ³ / h, t = +5 ° C) directed to reception in the block are regulated -box for auxiliary needs of the main gas pipeline compressor station.

Example. At the compressor station (KS-3 "Arkaulovo"), normal operation of the main and auxiliary equipment is carried out. A natural gas liquefaction system is connected to the DN 200 gas pipeline running from the outlet collector of the dust collectors to the auxiliary block box of the main gas pipeline compressor station through an equal tee. Flow I of natural gas passes through inlet valve 1 and enters block 2 of natural gas drying, where water vapor is removed to the dew point temperature t _T . _p = -70°C. Flow III of the dried natural gas passes further into the injection turbine 3, from which gas flow V enters the preliminary heat exchanger for gas cooling 4. Gas flow P is sent to the same preliminary heat exchanger for gas cooling 4 for heat exchange. From the preliminary heat exchanger for gas cooling 4, gas stream VI is sent to unit 5 for purifying natural gas from carbon dioxide and hydrogen sulfide to a concentration of 50 ppm. The second interacting coolant gas stream II from the preliminary heat exchanger for cooling gas 4 with gas stream XXII is sent to form and regulate technical parameters after ejecting the output gas stream XVII. For ejection, gas flow IV is used as the active one, entering after the ejector 15 into the output gas flow XVII, directed after the outlet valve 16 in the form of gas flow XXIV with the required technical parameters into the auxiliary block box of the compressor station of the main gas pipeline. After block 5 for purifying natural gas from carbon dioxide and hydrogen sulfide, gas stream VII is sent for cooling in a preliminary heat exchanger for gas cooling 6. After pre-cooling, gas-liquid stream IX is sent to cryogenic module 7, consisting of two main heat exchangers for cooling and cryogenic equipment ( cryogenic pipeline, shut-off and control and safety valves) with resistant thermal insulation and remote control. The second interacting coolant in the cryogenic module 7 is gas stream VIII, which has been cooled in a preliminary heat exchanger for gas cooling 14, converted into gas stream XVIII and supplied to receive the expansion turbine 17 for further sequential cooling, providing cold in the cryogenic module 7 and generating electricity for its own technological needs in the electric generator 18. Next, the cooled gas stream XIX is supplied sequentially as a refrigerant to the cryogenic module 7 and, having been converted into a gas stream XX, into a preliminary heat exchanger for cooling the gas 6, leaving which in the form of a gas stream XXI is sent to the output gas stream XVII . From the cryogenic module 7, the cooled gas-liquid stream X is supplied to the adjustable throttle of the first stage 8, in which additional cooling occurs due to the Joule-Thomson effect and conversion into a gas-liquid stream XI, which enters the main separator 9 for separation into gas and liquid phases. The separated gas stream XXIII is directed into the gas stream XIX, used as a coolant in the cryogenic module 7. The liquid stream XII, separated in the main separator 9, is supplied to the adjustable throttle of the second stage 10, in which even more complete cooling occurs due to the Joule-Thomson effect and conversion into liquid stream XIII entering the receiving separator 11 for the final separation of the gas phase present. Weight control is carried out by unit 12 for weighing liquefied natural gas with electronic scales. Storage and delivery to the consumer of the liquid phase flow XIV is organized in block 13 for storing and dispensing liquefied natural gas. The gas phase from the receiving separator 11 by stream XV is supplied as a refrigerant to the preliminary heat exchanger for cooling the gas 14 and then as a passive gas stream XVI to the ejector 15, with the help of which the required technical parameters of the entire output gas stream XXIV sent to the receiving unit are regulated -box for auxiliary needs of the main gas pipeline compressor station.

The proposed invention makes it possible to produce liquefied natural gas in the conditions of a compressor station, ensuring full-fledged commodity transport operations, maintaining the design functionality of the main and auxiliary equipment and excluding additional sources of explosion and fire hazards.

The invention can find wide application in the gas industry during the operation of compressor stations and can be used in conjunction with or instead of block boxes for own needs, including to obtain the necessary resource of low-pressure natural gas.

Claims (1)

Natural gas liquefaction system at the compressor station of the main gas pipeline, including inlet and outlet valves, a natural gas drying unit, an injection turbine, preliminary heat exchangers for gas cooling, a unit for purifying natural gas from carbon dioxide and hydrogen sulfide, a cryogenic module, chokes, a separation unit, a weighing unit liquefied natural gas, a unit for storing and dispensing liquefied natural gas, an ejector, an expansion turbine with an electric generator, characterized in that it is connected at the compressor station of the main gas pipeline to a DN 200 gas pipeline running from the outlet collector of the dust collectors to the auxiliary block box, and for liquefaction natural gas, it was installed: adsorption-type natural gas drying and purification units with NaA and NaX zeolite grades of 2.9 mm fraction, respectively, a heat exchange unit consisting of three preliminary heat exchangers for gas cooling, a turbine module consisting of injection and expansion turbines, mounted on the same working shaft with an electric generator, a cryogenic module consisting of two main heat exchangers for gas cooling and cryogenic equipment with cryogenic pipeline, shut-off and control and safety valves, resistant thermal insulation and remote control, chokes made in the form of adjustable chokes of the first and second stages , a separation unit consisting of a main and receiving separators, a liquefied natural gas weighing unit with electronic scales, a unit for storing and dispensing liquefied natural gas, an ejector for supplying natural gas into the gas pipeline to receive the block box for the auxiliary needs of the compressor station, piping and fittings.

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