RU2742009C1 - Natural gas liquefaction device and method for the realization therof - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to the gas liquefaction and can be used in gas distribution stations. The device for natural gas liquefaction comprises a heat exchanger and a vortex cooler which are arranged in a two-sectional separator container. A vortex cooler chamber with a cold end is arranged in the lower section and is connected to a central pipe being the heat exchanger core, in which tubes are vertically arranged. There is a hollow space between the horizontal barrier and the top tube board, in which there is a vortex chamber with an inlet pipe connecting said chamber to the interpipe space of the heat exchanger. A hot end is arranged in the upper section and is enclosed in a cylindrospheric sleeve installed on a horizontal barrier. The horizontal barrier has throttle diaphragm apertures with an outlet into the lower hollow space. A separation device is arranged in the upper section of the cylindrospheric sleeve. A shut-off and control valve and a low-pressure gas discharge pipe are installed outside the upper section of the separator tank. An outlet pipe is arranged in the cubic part of the liquefied product gas collector.

EFFECT: technical result consists in increasing efficiency of natural gas liquefaction.

4 cl, 2 dwg

Description

The invention relates to low-temperature liquefaction of natural gas or other low molecular weight gas, such as associated petroleum or petrochemical gas, and can be used at gas distribution stations (GDS) in the production and storage of liquefied natural gases used in the gas industry.

There are known methods and installations for liquefying natural gas, for example, a liquefaction plant (patent RU 2103620, F25B 9/02, 1998 - [1]), in which natural gas is liquefied using independent expansion (throttling) of vortex cooler streams in a cryostat, with the division of the volume into zones, connected appropriately with the outlets of the vortex coolers flows.

In the invention [1], vortex coolers are placed in the liquefaction plant, with the help of which efficient use of the initial inlet pressure is achieved. This is achieved due to a branched high-pressure gas supply manifold located in the upper zone of the cryostat, a heat exchanger and vortex coolers, the gas outlets of which are connected to the lower zone of the cryostat, which is connected to the upper zone by means of a throttle diaphragm.

Despite the achieved goals, including the independent expansion of the separated streams of vortex coolers and the achievement of the technical effect of the natural gas liquefaction process, this device has the following disadvantages:

- cooling of the incoming gas flow is carried out according to a complex scheme, since the initial gas flow passes along the peripheral diametrical zone of the cryostat housing, where the tubular coil is located, after which it enters the tube space of the heat exchanger and, only after that, the incoming gas is cooled due to the recuperation of the generated cold flow passing through the shell side of the heat exchanger;

- the statement that the proposed design of the device will reduce the thickness of the protective casing, by throttling the gas pressure from the tubular coil placed between the protective casing and the inner shell, is not true, since the pressure drop affects the thickness of the pipes of the coil, and not the thickness of the protective casing, which houses a tubular heat exchanger;

- complicated design of structural elements, in particular, connecting transitions from the heat exchanger header in the lower zone of the cryostat with vortex coolers with a heat exchanger. This will lead to difficulties in the practical implementation of the manufacture of these units and assembly, in general, the design of the device.

The closest, according to the technical essence of the invention, which implements the device is a prototype of the device (patent RU 2500959, F25J, 1/00, 2013 - [2]).

The technical result of the prototype device is achieved by the fact that the initial flow of natural gas, after cleaning and drying, is directed to a vortex cooler, which is placed vertically in a three-section separator tank.

The proposed device contains an adsorber, a filter, a heat exchanger, a vortex tube with a cooled hot end of the tube. The hot end of the pipe has a separation device in the form of a coaxially mounted inner cone in the conical part of the hot end with the possibility of changing the gap between the conical surfaces. The compactness of the design and the ability to regulate the processes carried out inside the tank allows you to control the production, upon obtaining the required parameters and the quality of commercial products.

Despite the achieved technical result of the prototype of the device, it has disadvantages, in particular:

- cryogenic processes carried out in a three-section separator tank are most effective with minimal heat loss to the environment, which is not provided for in this design. This is, first of all, the lack of effective thermal insulation of the tank, heat exchanger and gas pipelines, which will lead to a decrease in the efficiency of the liquefaction process, due to possible heat influx from the outside;

- pre-cooling of the initial stream is carried out in a remote recuperative heat exchanger, i.e. located outside the vessel where the vortex tube is located, generated cold, which will lead to significant losses of cold;

- the complexity of the device for regulating the gas flow rate at the hot end of the vortex tube, and this is of great importance for obtaining a mode with optimal parameters of the cooler.

Thus, the indicated disadvantages of analogues and prototype pose the problem of their solution, on which the increase in the efficiency of natural gas liquefaction depends. The noted disadvantages are eliminated in the proposed invention of the device.

The essence of the inventive device for liquefying natural gas and the method for its implementation is shown in figure 1.

Figure 1 also presents the following data:

Technological streams: I - initial high-pressure gas flow; II - outlet of liquefied gas (LNG); III - low-pressure gas outlet; IV - the output of the separated C2 + fraction.

The device contains the following structural elements: 1 - heat exchanger; 2 - vortex cooler; 3 - separator tank; 4 - horizontal partition; 5 - lower section of the container; 6 - upper section of the tank; 7 - hot end of the vortex cooler; 8 - cold end of the vortex cooler; 9 - central pipe; 10 - heat exchanger tubes; 11 - upper tube sheet; 12 - lower tube sheet; 13 - hollow space between the upper and lower tube sheets; 14 - corner pipe; 15 - cylindrical spherical cup; 16 - auxiliary horizontal partition; 17 - the lower zone of the horizontal partition; 18 - the upper zone of the auxiliary partition; 19 - branch pipe; 20, 21 - through throttle holes of the diaphragm in the horizontal partition 4; 22 - cylindrical branch pipe with spherical edges; 23 - cylindrical-conical branch pipe; 24 - ball; 25 - spring; 26 - guide sleeve; 27 - plate with a central hole; 28 - vertical pipe; 29 - shut-off and control valve; 30 - pipe; 31 - shut-off and control valve; 32 - pipe; 33 - shut-off and control valve; 34 - pipe tie; 35 - shut-off and control valve; 36 - screen-vacuum, placed on the body 3 and bulk thermal insulation - pearlite chips; 37 - cantilever support.

The technical essence of the proposed invention of a device for liquefying natural gas lies in the fact that the heat exchanger and the vortex cooler are placed in a two-section separator tank, which is divided by a horizontal partition into a lower and an upper section, while the hot end is located in the upper section, and the cold end in the lower section , where a cooler chamber with a cold end is located, which is connected to the central tube, which is the core of the heat exchanger, in which tubes of a smaller diameter are vertically placed, and the tubes are fixed in the lower and upper tube sheets, the diameters of which are equal to the inner diameter of the vertical separator tank, and between the horizontal a baffle and an upper tube plate there is a hollow space, in which there is a vortex chamber with an inlet pipe connecting the heat exchanger to the annular space, in the upper section there is a hot end enclosed in a cylindrical spherical cup, which is mounted on a horizontal and the inner space formed between the outer surface of the hot end and the inner surface of the glass is divided by an auxiliary annular partition into upper and lower zones, in the upper zone of the upper space of the cylindrospherical glass, under the partition, in the wall of the cylindrospherical glass there is a through hole with a branch pipe, and in a horizontal partition, in the zone and outside the zone of placement of the cylindrospherical nozzle, there are throttling orifices-diaphragms with access to the lower hollow space, and in the upper zone of the cylindrospherical nozzle there is a separation device consisting of a cylindrical branch pipe with spherical edges, in the form of a baffle cap installed coaxially the hot end with a parallel gap to the inner wall of the hot end, and inside the baffle cap, also coaxially, a cylindrical-conical pipe is installed, in the transition from the cylindrical to the conical part of which a regulating device is installed, consisting of a ball and the spring adjoining it, a part of which with a tight fit is put on the end of the vertical pipe, and the pipe is brought out of the cylindrical spherical cup through the guide sleeve with a gap in relation to the pipe, and the guide sleeve is fixed in a plate covering the cone of the cylindrical-conical branch pipe, at the outgoing section of the pipe , outside the upper section of the separator tank, a shut-off and control valve and a pipe for low-pressure gas outlet are installed, as well as in the lower section of the tank in the area of the annular space above the tube sheet there is a branch pipe with a pipe coming out of the separator tank, at the outlet section it is installed a shut-off and control valve for the inlet of the initial flow of natural gas, from the bottom part of the collector of the product liquefied gas there is also a pipe from the bottom part of the separator tank with a pipe for the output of the product liquefied gas, as well as a tie-in pipe into the upper zone of the cylindrical spherical cup and the outlet pipe, a lock is installed but-control valve and outlet pipes from the collection of separated heavy fractions С2 +.

Compared with the known inventions, the proposed device has the following advantages:

- the presence of a separating device allows the separation of heavy hydrocarbon fractions contained in the gas, as well as moisture condensate and other undesirable impurities from the liquefied gas;

- the presence of a regulating device for the hot flow rate makes it possible to change the parameters of the vortex cooler operating mode, which makes it possible to achieve efficient operation of the vortex cooler and to achieve the maximum degree of gas liquefaction;

- the use of effective thermal insulation, due to the presence of a double layer of various heat-insulating materials, including screen-vacuum and bulk, allows the maximum preservation of the cryogenic temperature, and to achieve effective protection against heat loss of the vessel-separator body.

The claimed device operates as follows.

The initial gas flow I enters the shell side of the recuperative heat exchanger 1 for cooling with a cold flow. And then, the cooled gas flow enters through the corner pipe 14 to the inlet of the vortex cooler 2. The cold flow leaving the cold end of the cooler 2 first passes through the central pipe 9 to recuperate the cold in the heat exchanger 1, and then enters the bottom of the tank - separator 3 located below the tube sheet 12.

Non-condensed vapors of the cold flow of liquefied gas from the bottom of the tank are directed up the tube space 10 of the heat exchanger 1, enter the hollow space 13 between the upper tube sheet 11 and the horizontal baffle 4. From where, the vapor of the cold flow is throttled in the holes-diaphragms 20, 21 located in the horizontal partition 4 and enters the inner space of the lower zone 17 of the cylindrical spherical nozzle 15, where the vapor-liquid mixture is condensed to a liquefied state, which accumulates in height to the limiting level - the location of the branch pipe 19, cools the hot end 7 of the vortex cooler. Discharge of the liquefied gas fraction through the pipe 19 is carried out into the space of the upper section, into the hollow space, outside the cylindrical spherical cup.

The separation device, located in the upper zone of the cylindrical spherical cup 15, consisting of coaxially located pipes 22, 23 at the hot end, allows the separation of heavy hydrocarbons C2 + from the hot gas stream, which accumulates in the upper zone of the cylindrospherical cup, above the auxiliary partition 16, and then this the mixture is discharged through the pipe 30 and, installed on it, the shut-off and control valve 31, outside the tank-separator 3 (stream IV).

The hot flow rate is controlled by a device that is a ball-spring valve, which includes a cylindrical-conical pipe 23, a ball 24 and adjacent springs 25. The outlet of an adjustable hot gas flow is carried out by means of a pipe 28 and a shut-off and control device 29 installed on it by pipes 28 outlet of the low pressure gas stream (stream III).

In the lower section of the tank 3, in its bottom part, there is an insert of a pipe 32 with an outlet outside the container, a shut-off and control valve 33 is installed at the outlet section of the pipe, the outlet of liquefied gas (LNG) through a branch pipe 32 (stream II).

In the lower section 3, above the lower tube sheet 12, there is a pipe insert 34 with an outlet outside the container, at the outlet section of the tube 34, a shut-off and control valve 35 is installed for the inlet of the initial natural gas stream (stream I).

Two layers were used as thermal insulation: 3 screen-vacuum and 36 bulk - pearlite chips. The separator tank is installed on a cantilever support 37.

An analogue of the claimed invention of a method for liquefying natural gas, for implementing the device is a method (patent RU 2429434, F25J, 1/00, 2006 - [3]), in which a throttling recuperative method with an auxiliary cooling circuit is used for liquefying natural gas. Two vortex tubes are used: main and auxiliary. In this case, the auxiliary cooling circuit is used on the basis of the main vortex tube with the simultaneous use of the hot flow of the auxiliary tube to heat the equipment out of operation.

The energy separation chamber of the main vortex tube is subjected to additional cooling by a refrigerant undergoing phase transformations during boiling and heat removal from the vortex tube and condensation, when heat is transferred to an external coolant, and as a coolant to which heat is given off, during condensation of the refrigerant, the cold flow of the auxiliary vortex is used pipes. At the same time, due to external cooling of the energy separation chamber of the main vortex tube, its cold flow has the lowest possible temperature.

Despite the statement [3] that the proposed technical solution allows you to fully use the cold of a cold stream, the proposed method has disadvantages:

- the presence of two pipes and double heat exchangers - freezers (operating and standby), this complicates the technological scheme and complicates the control of technological processes to maintain normal operation;

The prototype of the claimed invention - a method for liquefaction is (patent RU 2500959, F25J, 1/00, 2013 - [4]), in which the vortex tube is placed vertically in a three-section separator tank, divided by horizontal partitions.

In the middle section, the hot end of the vortex tube is cooled by a cold flow entering tangentially into the separator vessel from the lower section after heat recovery while cooling the initial gas flow at the entrance to the vortex tube in the lower section.

A liquid phase is separated from the hot stream, which is mixed with the incoming liquid phase separated in the upper section of the separator vessel. The gaseous fraction is removed from the upper section, and the liquefied fraction is removed from the middle section as a commercial product (LNG). The hot end of the vortex tube has a separation device in the form of a coaxially mounted inner cone in the conical part of the hot end with the possibility of changing the gap between the conical surfaces.

The disadvantages of the prototype [4] as a method and as a device is that the technical result is aimed at increasing the efficiency of natural gas liquefaction. However, a partial loss of cold energy resources is possible due to the placement of an external recuperative heat exchanger, where energy losses are possible in the external communications of the heat exchanger and pipelines.

The disadvantages of the prototype can also be attributed to the absence of a separation device for the separation of heavy hydrocarbon impurities from the hot stream.

Thus, the indicated disadvantages of the analogue and the prototype set the task of fulfilling the technical result of the proposed method of gas liquefaction to solve the following tasks:

- maximum efficient use of the cold flow of the vortex cooler to cool the initial gas flow in the heat exchanger located in the closed volume of the separator tank;

- using the most efficient separation and control devices located inside the separator tank

- development of effective thermal insulation to reduce the heat of cryogenic processes occurring in a closed volume of a container, in contrast to the prototype, in which there is no thermal insulation.

Figure 1 shows a schematic section of a device for liquefying natural gas and a method for its implementation.

To perform the technical result and the essence of the gas liquefaction method, using the proposed device, the vortex cooler 2 and the recuperative heat exchanger 1 are placed in a two-section tank - separator 3, while the pre-cooling of the initial gas flow is performed by a cold flow in the annular space of the recuperative heat exchanger, where the flow enters from the vortex cooler, first into the central pipe 9, where the gas is partially condensed and accumulates in the bottom part of the tank - a collection of liquefied gas, and the uncondensed flow of cold gas passes countercurrently through the pipe space of the heat exchanger 1 and enters the hollow space 13 between the upper tube sheet 11 and the horizontal baffle 4, and then throttled through the holes - diaphragm 20 in the horizontal baffle and enters the upper section 6 of the separator tank, into the inner space of the cylindrical spherical cup 15, bounded from above by the auxiliary horizontal lane section 16, where condensate of liquefied gas accumulates, cooling the hot end of the cooler, the excess amount of liquefied gas is discharged through the hole in the wall of the cylindrical spherical cup and the discharge pipe 19 of the liquefied gas into the hollow space of the upper section of the separator tank, and the outgoing hot low pressure gas stream is separated from heavy hydrocarbon fractions С2 +, which are accumulated in the collector located on the auxiliary partition 6, bounded by the walls of the hot end 7 and the inner wall of the cylindrical spherical cup 15, and then are removed outside the separator tank by means of the pipe 30 in the side wall of the separator tank, the outlet of the controlled hot gas flow is carried out by means of a pipe 28 and a shut-off and control device 29 installed on it by means of a pipe 28, the low-pressure gas flow is output outside the separator tank, and the initial gas flow is introduced into the annular space of the recuperative heat exchanger at the bottom her section of the tank-separator by means of a pipe 34 with a shut-off and control valve 35, and the liquefied gas is discharged through a pipe 32 with a shut-off and control valve 33.

The technical result of the invention of a device for liquefying natural gas and a method for its implementation in more detail can be supplemented with the following explanations:

The main equipment, including a recuperative heat exchanger, vortex cooler, separation, regulating devices and pipeline communications, are compactly enclosed in a single block in a separator tank, which is a cryogenic block module.

The outer surface of the tank-separator must be carefully insulated, as shown in figure 1. The tank is located on the outer surface of two sealed "jackets" in which the thermal insulation is located.

A screen-vacuum thermal insulation must be placed in the "jacket" located on the container body. And, on top of it, a second layer of bulk thermal insulation (for example, pearlite chips) should be placed.

Particular attention should be paid to the lower part of the vessel, where the working lowest cryogenic temperature is of the order of minus (130-160) ° С.

Pipelines entering and leaving the cryogenic unit must also be carefully insulated with thermal insulation.

The vortex cooler operating mode is recommended under the condition μ = 0.4-0.7. Liquefied gas production mode, i.e. LNG production depends on pressure, the most preferable range of storage and use of liquefied gas in the pressure range from atmospheric to 0; MPa, which corresponds to a temperature from minus 135 to 160 ° C.

Of particular importance is the design of the recuperative heat exchanger located in the lower section of the separator vessel. The design of the heat exchanger must have a high efficiency of the special design, especially the design of the heat exchange tube bundle.

For example, the use of a vortex heat exchange element according to patent RU 2101643. This design is based on the use of a heat exchange element equipped with flow swirlers, which makes it possible to intensify heat exchange with increased heat exchange efficiency.

The proposed mode of natural gas liquefaction will make it possible to maintain the unit's operability at the initial pressure of high-pressure natural gas, which is typical for a main gas pipeline in the range of 3.5 -?, 0 MPa, which will allow using gas extraction from the main gas pipeline or from the gas distribution station of the GDS.

The above set of distinctive features is not known at this level of technical development and does not follow from the well-known rules of the known designs of devices and methods for liquefying natural gases, and technical solutions for the design of LNG devices and auxiliary equipment are not known, which proves the "inventive step".

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

Sources of information

1. Patent RU 2103620, F25B 9/02, 1998.

2. Patent RU 2500959, F25J, 1/00, 2013 - a prototype of the device.

3. Patent RU 2429434, F25J, 1/00, 2006.

4. Patent RU 2500959, F25J, 1/00, 2013 - a prototype of the method.

Claims (4)

1. A device for liquefying natural gas coming from a main gas pipeline or from a gas-reducing station (GDS), containing a heat exchanger, a vortex cooler with lines for supplying high-pressure source gas to the cooler and the ends of expanded cold and hot gaseous and liquid flows, located in a separator tank, in which there are separation and regulating devices for the hot gas flow, a liquefied gas collector, characterized in that the heat exchanger and the vortex cooler are placed in a two-section separator tank, which is divided by a horizontal partition into a lower and upper sections, while the hot end is located in the upper section, and the cold end in the lower section, where the vortex chamber of the cooler with the cold end is located, which is connected to the central tube, which is the core of the heat exchanger, in which tubes of a smaller diameter are vertically placed, and the tubes are fixed in the lower and upper tube sheets, the diameters of which are equal to the inner The same diameter of the vertical separator tank, and between the horizontal baffle and the upper tube sheet there is a hollow space in which there is a vortex chamber with an inlet pipe connecting it to the shell side of the heat exchanger, in the upper section there is a hot end enclosed in a cylindrical spherical cup, which is installed on a horizontal partition, and the inner annular space formed between the outer surface of the hot end and the inner surface of the glass is divided by an auxiliary annular partition into upper and lower zones, in the upper zone of the upper space of the cylindrical spherical glass, under the partition, in the wall of the cylindrospherical glass there is a through hole with a branch pipe, and in the horizontal partition, in the area and outside the area of the cylindrospherical cup, there are throttling orifices-diaphragms with access to the lower hollow space, and in the upper zone of the cylindrospherical cup there is a separation device unit, consisting of a cylindrical branch pipe with spherical edges, in the form of a baffle cap installed coaxially to the hot end with a parallel gap to the inner wall of the hot end, and inside the baffle cap, also coaxially, a cylindrical-conical branch pipe is installed, in the transition from the cylindrical to the conical part of which a regulating a device consisting of a ball and an adjoining spring, a part of which is fitted with a tight fit on the end of a vertical pipe, and the pipe is brought out of the cylindrical spherical cup through a guide sleeve with a gap in relation to the pipe, and the guide sleeve is fixed in a plate covering the bell of the cylindrical-conical cone a shut-off valve and a low-pressure gas outlet pipe are installed at the outlet section of the pipe, outside the upper section of the separator tank, and in the lower section of the tank in the area where the annular space is located above the lower tube sheet there is a branch pipe with it from the separator tank, a shut-off and control valve is installed at the outlet section for the input of the initial natural gas stream, in the bottom part of the product liquefied gas collector there is also an outlet pipe from the bottom of the separator tank with a pipe for withdrawing the product liquefied gas, as well as a pipe cut-in into the upper zone of the cylindrical spherical cup, at the outlet section of the pipe, a shut-off and control valve is installed to remove the separated heavy hydrocarbon fractions C2 + from the collector. 2. A device for liquefying natural gas according to claim 1, characterized in that, for example, a twisted heat exchanger with a pipe diameter of 10 × 1 or 8 × 1 mm is used as a heat exchanger, which are wound onto a central pipe. 3. A device for liquefying natural gas according to claim 1, characterized in that a plate-fin heat exchanger is used as a heat exchanger. 4. A method for liquefying natural gas for implementing the device according to claim 1, including pre-cooling and liquefying natural gas in a vortex cooler to obtain cold, hot gaseous and liquid streams located in a vertical separator vessel, and cooling the hot end of the cooler in a recuperative heat exchanger, characterized in that the vortex cooler and the recuperative heat exchanger are placed in a two-section separator tank, while the initial gas flow is pre-cooled by a cold flow in the annular space of the recuperative heat exchanger, where the flow enters from the vortex cooler first into the central pipe, where the gas is partially condensed and accumulated in the bottom part of the liquefied gas collection tank, and the uncondensed flow of cold gas flows countercurrently through the tube space of the heat exchanger and enters the hollow space between the upper tube sheet and the horizontal baffle, and then is throttled through the diaphragm openings in the horizontal baffle and enters the upper section of the separator tank, into the inner space of the cylindrical spherical cup, bounded from above by an auxiliary horizontal baffle, where liquefied gas condensate accumulates, cooling the hot end of the cooler, the excess amount of liquefied gas is discharged through the hole in the wall of the cylindrical spherical cup and a branch pipe for discharging liquefied gas into the hollow space of the upper section of the separator vessel, and the outgoing hot low-pressure gas stream is separated from heavy hydrocarbon fractions C2 +, which accumulate in a collector located on an auxiliary partition bounded by the walls of the hot end and the inner wall of the cylindrical spherical cup, and then are removed outside the tank-separator by means of a pipe in the side wall of the tank-separator, the outlet of an adjustable hot gas flow is carried out by means of a pipe and a shut-off and control device installed on it. by means of a branch pipe for outputting a low-pressure gas flow outside the separator tank, and the initial gas flow is introduced into the annular space of the recuperative heat exchanger in the lower section of the separator tank by means of a pipe with a shut-off and control valve, and the liquefied gas is removed through a pipe with a shut-off and control valve ...

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