RU2642905C1 - Method for performing repair works on gas-distributing station of main gas pipeline without interruption of gas supply to consumer - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: station is brought into repair, natural gas is taken from the main pipeline, at the inlet of the operational gas distribution station is subjected to adiabatic expansion with external work for generation of cold, liquid natural gas is separated from gas phase to obtain liquefied natural gas which is delivered in a cryogenic transport tank to the gas distributing station to be repaired, re-gasified and supplied to a consumer.

EFFECT: uninterrupted supply to the consumer with gas during repairs by a low-cost method.

11 cl, 2 dwg

Description

The present invention relates to the gas industry, specifically to the transportation of natural gas (GHG) via gas pipelines (MG), to methods for providing a GHG to a consumer, and can be used in emergency, preventive and repair work at gas distribution stations (GDS).

Currently, during emergency, repair, and preventive maintenance, as a rule, the gas distribution station is shut down, with the obligatory notification of the consumer about the gas supply interruption. A known method of repair of gas distribution systems, in which uninterrupted gas supply to the consumer is provided from the neighboring (adjacent) gas distribution system. Such a scheme is applicable only in the case of a closed gas distribution system and only in the presence of GHGs in the supply gas pipeline.

There is a known method of repairing gas distribution systems, in which to prevent the gas supply to consumers being cut off, the gas flow is switched bypassing the gas distribution system through a bypass line (bypass) connecting the gas supply and output pipelines of the gas distribution station providing short-term gas supply to the consumer (paragraph 9.2.2 STO Gazprom 2-3.5- 051-2006). This scheme has several disadvantages: it is allowed to direct the gas flow through the bypass only for a short period of time, the gas supplied to the consumer is of inadequate quality (which can cause failures of the gas-using equipment of the consumer) and only in the presence of GHGs in the supply gas pipeline.

For uninterrupted gas supply to consumers for the period of repair work, it is possible to use temporary reduction units or “mobile Mini-GDS” (paragraph 9.1.11 STO Gazprom 2-3.5-051-2006), the disadvantage of this technical solution is the need for a sufficient site for it location, capacity limitations (not more than 10 thousand m ³ / h), as well as the presence of GHGs in the supply gas pipeline.

Closest to the claimed technical solution is, in our opinion, the method described in the book edited by Basniev K.S. Encyclopedia of the gas industry. Edition 4, Moscow, Joint-Stock Company TVANT, 1994, p. 480 - prototype. In this method, in order to ensure the possibility of supplying consumers with gas during repair work, liquefied natural gas (LNG) is delivered to the place of repair work in a mobile regasifier. Each regasifier is connected to a tank isolated on the basis of vacuum, and the entire installation is mounted on a caravan. The quality of the gas supplied is adjusted by supplying liquid nitrogen to the tank, and its odorization is ensured by supplying an odorant to the tank. The regasifiers used in the method are atmospheric: the heat source is atmospheric air. A large heat exchange surface is created by finned tubes, and the performance of the regasifier varies depending on atmospheric conditions (Fig. 1).

The disadvantages of the prototype include the relatively high cost of LNG produced in factories, usually located in fields quite remote from the place of use, with high energy costs for its production and delivery to the place of use. The disadvantage is also the method of adjusting the quality of regasified GHG, in which the addition of liquid nitrogen allows you to adjust the calorific value of GHG only in the direction of its decrease.

The technical problem to which the claimed invention is directed is the uninterrupted supply of gas to the consumer during repair work on the gas distribution system by simplifying and reducing the cost of production and transportation of LNG.

The problem is achieved due to the fact that in the method of performing repair work on the gas distribution system without interruption of gas supply to the consumer, in which the gas distribution station to be repaired is turned off, put into repair, the gas supply is delivered in a cryogenic transport tank, regasified, fed to the consumer through the insert, are provided following differences. GHGs are taken from the MG belonging to the same gas transmission network as the repaired GDS, at the inlet of the technically sound GDS, they undergo adiabatic expansion with external work to generate the cold necessary for the GHG to enter the liquid phase, and it is separated from the gas phase to produce LNG, which is loaded into a cryogenic transport capacity and transported to the GRS to be repaired,

In the proposed method, the GHG taken from the MG is throttled to generate the cold necessary for the GHG to transition to the liquid phase.

In this method, the GHG can be passed through the expander to generate the cold necessary for the GHG to transition into the liquid phase.

In the method, the imported LNG for injection through the regasifier into the distribution gas pipeline is pumped due to the pressure arising from the evaporation of part of the LNG in a special heat exchanger-evaporator. LNG can also be injected using a cryogenic pump.

In this method, the brought GHG can be regasified using an atmospheric regasifier. In addition, the GHG can be regasified using an external heat source (electric heater, combustion products of the GHG or an intermediate heat carrier, for example, from a district heating system).

Also in the method, the gas can be odorized before being fed into the network.

In the specified method regasified and heated gas can be reduced.

In addition, in the method, the outlet pressure of the regasified GHG before being fed into the network can be provided by the pressure of the gas pad in the cryogenic tank or by regulating the supply of the cryogenic pump.

The technical result is the uninterrupted supply of gas to the consumer during repair work in a low-cost way.

To clarify the essence of the proposed technical solutions are presented:

FIG. 1 - mobile regasification unit (prototype);

FIG. 2 is a diagram of a method for performing repair work on a gas distribution system, on which the following notation is adopted:

1 - main gas pipeline,

2 - valid serviceable GDS,

3 - pipe for removal of the steam generator,

4 - expander,

5 - cryogenic storage for LNG,

6 - cryogenic pump,

7 - cryogenic transport capacity,

8 - gas carrier,

9 - cryogenic pump,

10 - special evaporator-regasifier,

11 - regasifier,

12 - heater

13 - pressure regulator,

14 - odorizer

15 - subject to repair GDS,

16 - output crane GDS.

The proposed method is used in the following order. GDS 15 to be repaired is disconnected, taken out for repair. GHGs are taken from the main gas pipeline 1 at the entrance to the technically operational existing GDS 2, preferring the least remote from the GDS 15 being repaired and belonging to the same gas transmission network as the GDS being repaired 15. The selected GHG is passed through expander 4, where the GHG is subjected to adiabatic expansion with by performing external work to generate the cold necessary for the transition of the GHG to the liquid phase, it is separated from the gas phase to produce LNG. In this case, the accompanying gas fraction (the non-liquefied part of the stream) is sent through the pipe 3 to the gas network, after passing it through a heat exchanger to cool the NG going for liquefaction.

A significant part of the liquefied stream passes into the liquid phase, which is discharged into a cryogenic storage for LNG 5. Next, the LNG is transferred from storage 5 to a cryogenic transport tank 7 using a cryogenic pump 6 or under the action of a hydrostatic column of liquid, or under the influence of overpressure in the steam cushion of the storage 5 and on a gas carrier 8 are delivered to the GRS 15 to be repaired. Here, LNG from the transport cryogenic tank 7 to the atmospheric regasifier 11 is pumped due to the pressure arising from the evaporation of part of the joint venture G in a special heat exchanger-evaporator 10 or using a cryogenic pump 9. In the regasifier 11, the LNG is heated by atmospheric heat. In this case, the liquefied gas passes into the gaseous phase (regasified) and then heats up to a temperature close to the temperature of the surrounding atmosphere.

Then, to obtain the necessary temperature and pressure parameters, the regasified GHG is passed, if necessary, through the heater 12 and the reduction unit 13. After that, if necessary (gas is not required to odorize for industrial enterprises), gas is passed through the odorizer 14 and fed to the consumer gas distribution pipeline through the insert into the distribution gas pipeline (after the outlet valve ГРС 16).

The technical result provided by the above set of features is that with the method of repairing the gas distribution system described above, an uninterrupted gas supply to the consumer is ensured in a low-cost, economical way: the GHG is liquefied due to the pressure differential between the main and distribution gas pipelines to the gas distribution system and delivered over short distances. GHGs are selected from the same gas transmission system, so there is no need to adjust its calorific value, and the GHG composition is identical to that supplied earlier.

In addition, the described method does not require additional energy costs for regasification, since the imported LNG is regasified due to the heat of the environment; for uninterrupted gas supply to the consumer, there is no need to select a temporary reduction unit and prepare the site for its installation, and there is no need to use a bypass gas pipeline. The described method makes it possible to provide consumers in the absence of a looped gas network, as well as in the event of an accident at the supply gas pipeline for unlimited time.

According to the scheme described above, for several years now, the applicant’s enterprise has been actively using the patented method of performing repair work on gas distribution stations without interrupting gas supply to the consumer. During repair work on the gas distribution system of the applicant OOO Gazprom transgaz Yekaterinburg, over 650 tons of LNG were delivered to the consumer during the use of the method, which avoided the negative consequences for the technological processes at gas-supplying enterprises and confirmed the economic efficiency of the method. The repair work on the gas distribution system, carried out by the applicant, is currently underway imperceptibly for ordinary consumers of GHGs.

Claims (11)

1. A method of performing repair work at a gas distribution station of a main gas pipeline without interrupting gas supply to a consumer, in which the gas distribution station to be repaired is switched off, taken out for repair, natural gas is delivered to a cryogenic transport tank, regasified, supplied through an insert to a gas distribution pipeline, characterized in that natural gas is taken from the main gas pipeline belonging to the same gas transmission network as the gas distribution station under repair At the inlet of a technically sound gas distribution station, it is subjected to adiabatic expansion with external work to generate the cold necessary for the transition of natural gas to the liquid phase, it is separated from the gas phase to produce liquefied natural gas, which is loaded into a cryogenic transport tank and transported for repair gas distribution station. 2. The method according to p. 1, characterized in that the natural gas is throttled to generate the cold necessary for the transition of natural gas into the liquid phase. 3. The method according to p. 1, characterized in that the natural gas is passed through the expander to generate the cold necessary for the transition of natural gas into the liquid phase. 4. The method according to p. 1, characterized in that the liquefied natural gas brought in for supply through the regasifier to the distribution gas pipeline is pumped due to the pressure arising from the evaporation of part of the liquefied natural gas in a special heat exchanger-evaporator. 5. The method according to p. 1, characterized in that the liquefied natural gas brought in for supply through a regasifier to the distribution gas pipeline is pumped using a cryogenic pump. 6. The method according to claim 1, characterized in that the natural gas brought in is regasified using an atmospheric regasifier. 7. The method according to claim 1, characterized in that the natural gas brought in is regasified using an external heat source. 8. The method according to p. 1, characterized in that the gas odorize before feeding into the network. 9. The method according to p. 1, characterized in that the regasified and heated natural gas is reduced. 10. The method according to p. 1, characterized in that the outlet pressure of the regasified natural gas before being fed into the network is provided by the pressure of the gas pad in the cryogenic tank. 11. The method according to p. 1, characterized in that the outlet pressure of regasified natural gas before being fed into the network is ensured by controlling the supply of a cryogenic pump.

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