CN106861222B

CN106861222B - Evaporated gas recondenser

Info

Publication number: CN106861222B
Application number: CN201510917334.XA
Authority: CN
Inventors: 赵广明; 李凤奇; 李明; 李海燕
Original assignee: Sinopec Engineering Inc; Sinopec Engineering Group Co Ltd
Current assignee: Sinopec Engineering Inc; Sinopec Engineering Group Co Ltd
Priority date: 2015-12-10
Filing date: 2015-12-10
Publication date: 2020-03-06
Anticipated expiration: 2035-12-10
Also published as: CN106861222A

Abstract

A BOG recondenser comprising: the LNG inlet (3) and the LNG outlet are arranged on the guide cylinder (4), a microporous pipe (5) is arranged in the guide cylinder, one end of the microporous pipe (5) is closed, the other end of the microporous pipe is communicated to the BOG inlet (1), and micropores are formed in the surface of the microporous pipe (5); and the mixing unit (7) is used for mixing, one end of the mixing unit (7) is communicated with the outlet of the guide shell (4), and the other end of the mixing unit (7) is provided with an LNG outlet (8). The BOG recondenser has the advantages of high recovery efficiency, compact structure, easy equipment operation and convenient maintenance.

Description

Evaporated gas recondenser

Technical Field

The present invention relates to Liquefied Natural Gas (LNG) boil-off gas (BOG) recovery processing, and in particular to a BOG recondenser for LNG storage, offloading and transfer.

Background

The treatment method of the BOG of the LNG storage tank can be divided into a direct output method and a re-condensation method. The direct output method is to compress the BOG to the output pressure and then directly send the BOG to a gas transmission pipe network; the recondensation process compresses the BOG to a lower pressure and mixes it with LNG from an LNG storage tank by an LNG low pressure transfer pump in a condenser. The BOG can be re-condensed because the LNG is in a supercooled state after being pressurized, and the condensed LNG is pressurized by an LNG high-pressure delivery pump and then is vaporized for outward delivery. The recondensing method can utilize the cold energy of the LNG, reduce the consumption of BOG compression work and save energy.

Typically, the BOG recondensation process employs a recondenser, which has a relatively large volume so as to allow the combination of BOG condensate with LNG sendout to form a subcooled liquid, if the buffer volume is insufficient, steam may be introduced into the high pressure pump, which may cause cavitation/cavitation in the pump, resulting in component damage, reduced efficiency, and ultimately shortened pump life. This makes the recondenser device too bulky and increases project investment.

At present, a recondenser of an LNG receiving station adopts a packing tower type design, and internal components mainly comprise a vortex breaker, a Raschig ring packing layer or a regular packing layer, a liquid distributor, a gas distribution disc, a liquid baffle plate, a gas baffle plate, a packing support plate and a flash evaporation disc. The liquid distributor and the gas distribution disc/packing layer are mainly used for increasing the contact area of BOG and LNG and improving the condensation effect. However, in the actual operation process, the recondenser is easily interfered by fluctuation of the low-pressure output header pipe, the BOG header pipe and the downstream pipe network, the fluctuation of any factor can interfere with the recondenser, and the control difficulty is high.

The BOG recondenser is the core of the LNG receiving station operation control, and is concerned with the smooth operation of the whole receiving station. Problems encountered with current conventional recondensors are: (1) in a limited equipment space, the contact time of BOG and the supercooled LNG is insufficient, and the BOG recondensation effect is poor; (2) the existing recondenser has a common treatment effect under a fluctuating working condition, so that the operation of equipment such as a downstream LNG pump is influenced; (3) the traditional BOG recondensor equipment is large in size and high in investment.

Disclosure of Invention

The invention aims to provide a BOG recondenser which can overcome the defects of insufficient contact between BOG and supercooled LNG and poor recondensing effect in the conventional recondenser.

The invention adopts the following solution:

a boil-off gas (BOG) recondenser, comprising:

the guide cylinder is provided with an LNG inlet and an LNG outlet, a microporous pipe is arranged in the guide cylinder, one end of the microporous pipe is closed, the other end of the microporous pipe is communicated to the BOG inlet, and micropores are formed in the surface of the microporous pipe; and

and the mixing unit is used for mixing, one end of the mixing unit is communicated with the outlet of the guide shell, and the other end of the mixing unit is provided with an LNG outlet.

Preferably, said one end of said microporous tube is fixed to a movable support grid and said other end is fixed to a tube sheet.

Preferably, the pore diameter of the micropores on the surface of the microporous tube is 5-100 micrometers.

Preferably, the microporous tube is formed by sintering or machining.

Preferably, the microporous pipe comprises a plurality of pipe bundles arranged in parallel, the projection of the central connecting line of adjacent pipe bundles on a plane perpendicular to the pipe bundles is an equilateral triangle, and the included angle between one side of the equilateral triangle and the axial direction of the LNG inlet is 30 ° or 60 °.

Preferably, the microporous pipe comprises a plurality of pipe bundles arranged in parallel, the projection of the central connecting line of adjacent pipe bundles on a plane perpendicular to the pipe bundles is square, and the included angle between one side of the regular triangle and the axial direction of the LNG inlet is 90 ° or 45 °.

Preferably, the ratio of the center distance of the adjacent tube bundles to the diameter of the tube bundles is 1.2-3.

Preferably, the mixing unit is a static mixer of the SK, SV, SX, SL or SH type.

Preferably, the BOG inlet is located at the bottom of the BOG recondenser and communicates to the microporous tube via a tapered interface.

Preferably, the BOG recondenser is mounted vertically or horizontally.

The BOG recondenser has the beneficial effects that the BOG passing through the microporous pipe is split into microbubbles with small diameters, so that the gas-liquid contact area is greatly increased, the BOG and the supercooled LNG are in full contact in the mixing unit and can be fully absorbed by the LNG, and the BOG recovery problem in an LNG receiving station is solved. In addition, the BOG recondenser has high recovery efficiency, compact structure, easy equipment operation and convenient maintenance.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings. Wherein like reference numerals generally refer to like parts throughout the exemplary embodiments of the invention.

FIG. 1 is a cross-sectional view of a BOG recondenser in accordance with an exemplary embodiment;

FIG. 2 is a schematic view of a regular triangular arrangement of microporous tubes of a BOG recondenser on a tube sheet, according to an exemplary embodiment;

FIG. 3 is a schematic view of a regular triangular arrangement of micro-bore tubes of a BOG recondenser in accordance with an exemplary embodiment;

FIGS. 4a and 4b are schematic views of a regular triangular arrangement of the micro-bore tubes of a BOG recondenser in accordance with an exemplary embodiment;

fig. 5a and 5b are schematic diagrams of a square arrangement of micro-bore tubes of a BOG recondenser according to an exemplary embodiment.

Description of the main reference numerals:

1: a BOG entrance; 2: a tube sheet; 3: an LNG inlet; 4: a draft tube; 5: a microporous tube; 6: a support grid; 7: a mixing unit; 8: and (4) LNG outlet.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The present disclosure provides a BOG recondenser comprising: the LNG inlet and the LNG outlet are arranged on the guide cylinder, a microporous pipe is arranged in the guide cylinder, one end of the microporous pipe is closed, the other end of the microporous pipe is communicated to the BOG inlet, and micropores are arranged on the surface of the microporous pipe; and the mixing unit is used for mixing, one end of the mixing unit is communicated with the outlet of the guide shell, and the other end of the mixing unit is provided with an LNG outlet.

In this public BOG recondenser, LNG gets into the draft tube through the LNG entry, and BOG gets into the micropore pipe through the BOG entry, and the micropore on micropore pipe surface splits BOG gas into the microbubble, and the micropore pipe of discharging is in the LNG in micropore pipe clearance and carries BOG microbubble and flow out the draft tube through the export of draft tube, gets into the mixing unit with the draft tube intercommunication.

The BOG forms micro-bubbles through the bubbling of the micropores on the surface of the microporous tube, enters the super-cooled LNG outside the microporous tube, and then the super-cooled LNG brings the micro-bubbles into the mixing unit for full mixing and condensation. Compared with the existing BOG recondensor technology, in the BOG recondensor disclosed by the invention, BOG passing through the microporous pipe is split into tiny microbubbles with small diameters, so that the gas-liquid contact area is greatly increased, the BOG and the supercooled LNG are fully contacted in the mixing unit and can be fully absorbed by the LNG, and therefore the problem of BOG recovery in an LNG receiving station is solved.

Preferably, the one end of the microporous tube is fixed to the movable support grid, and the other end is fixed to the tube sheet. The microporous tube may be secured to the tube sheet by a threaded connection or by welding. The support grating is movable, so that the microporous tube can be fixed, and the deformation problem of the microporous tube under large temperature difference can be solved.

As a preferable scheme, the aperture of the micropores on the surface of the microporous tube is 5-100 microns.

Preferably, the microporous tube is formed by sintering or machining.

Preferably, the microporous tube comprises a plurality of tube bundles arranged in parallel, and the projection of the central line of the adjacent tube bundles on a plane (for example, a tube plate) perpendicular to the plurality of tube bundles forms an equilateral triangle, and one side of the equilateral triangle forms an angle of 30 ° or 60 ° with the axial direction (indicated by the arrow in fig. 4a and 4 b) of the LNG inlet, as shown in fig. 2, 3, 4a and 4 b. Alternatively, the projection of the center line of adjacent tube bundles onto a plane perpendicular to the plurality of tube bundles (e.g. tube sheet) may also form a square, one side of which forms an angle of 90 ° or 45 ° with the axial direction of the LNG inlet (indicated by the arrow in fig. 5a and 5 b). The triangular arrangement mode has a compact structure and a good heat transfer effect, and the number of the tube bundles which can be arranged on the same tube plate is about 10 percent more than that of the tube bundles arranged in a square mode, so that the heat transfer area is larger for the same volume, and the triangular arrangement mode is suitable for occasions with less shell-side medium dirt and without mechanical cleaning. The square arrangement mode forms a straight line channel between the tube bundles through the tube bridge, and mechanical cleaning is facilitated. Therefore, when the dirt on the outer surface of the tube bundle needs to be cleaned frequently, a square arrangement mode is adopted.

As a preferred scheme, the ratio of the center distance of adjacent tube bundles to the diameter of the tube bundles is 1.2-3.

Preferably, the mixing unit is a static mixer of the SK, SV, SX, SL or SH type. The types "SK", "SV", "SX", "SL" and "SH" have established meanings in the art and will not be described in detail here. Most preferably, the mixing unit is an SK type static mixer, and the mixing insert unit includes a left spiral mixing unit and a right spiral mixing unit which are alternately arranged, and the twist angles of the left spiral mixing unit and the right spiral mixing unit are both 180 °. This openly uses micropore pipe and static mixing arrangement, compares with traditional BOG recondensing technique, compact structure, BOG recovery efficiency height, equipment operation are easy, easy maintenance.

The BOG recondenser can be mounted vertically or horizontally according to the specific requirements of the process and engineering. Accordingly, the flow direction of the LNG may be either transverse flow through the microporous tube (cross flow) or parallel flow through the microporous tube (co-flow).

Fig. 1 shows a schematic view of the construction of a BOG recondenser according to an exemplary embodiment. The BOG recondenser includes a guide cylinder 4 and a mixing unit 7. An LNG inlet 3 and an LNG outlet are arranged on the guide shell 4, a microporous tube 5 is arranged in the guide shell 4, one end of the microporous tube 5 is closed, the other end of the microporous tube is communicated to the BOG inlet 1, and micropores are arranged on the surface of the microporous tube 5. The mixing unit 7 is used for mixing, and one end of the mixing unit is communicated with the outlet of the guide shell 4, and the other end of the mixing unit is provided with an LNG outlet 8.

The BOG inlet 1 is positioned at the bottom of the BOG recondenser and communicated to the microporous tube 5 through a conical interface, and the BOG enters the microporous tube 5 through the BOG inlet 1.

One end of the microporous tube 5 is fixed on the tube plate 2, and the other end is fixed on the support grid 6. The microporous tubes 5 comprise a plurality of tube bundles arranged in parallel, and the projection of the central connecting line of the adjacent tube bundles on the vertical tube plate 2 is a regular triangle, as shown in fig. 2 and 3.

The mixing unit 7 is an SK type static mixer, and includes a left-hand spiral mixing unit and a right-hand spiral mixing unit which are alternately arranged, and the twist angles of the left-hand spiral mixing unit and the right-hand spiral mixing unit are both 180 °.

The operation of the BOG recondenser according to the exemplary embodiment is as follows: supercooling LNG with a certain flow rate flows into the guide shell 4 through an LNG inlet 3 arranged on the guide shell 4 and enters a tube bundle gap of the microporous tube 5. After the flow of the supercooled LNG is stable, BOG enters the microporous tube 5 through the BOG inlet 1, and the micropores on the surface of the microporous tube 5 divide BOG gas into micro bubbles to be discharged out of the microporous tube 5. The supercooled LNG in the gap of the micro-porous pipe 5 carries BOG micro-bubbles into the mixing unit 7 communicating with the guide shell 4. In the mixing unit 7, the LNG is thoroughly mixed with BOG, which is recondensed to LNG and flows out of the LNG outlet 8 at the top of the mixing unit.

While embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the illustrated embodiments. The terms used herein were chosen in order to best explain the principles of the embodiments and the practical application, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A boil-off gas (BOG) recondenser, comprising:

the LNG feed pump comprises a guide shell (4), wherein an LNG inlet (3) and an LNG outlet are arranged on the guide shell, a microporous pipe (5) is arranged in the guide shell, one end of the microporous pipe (5) is closed, the other end of the microporous pipe is communicated to a BOG inlet (1), and micropores are formed in the surface of the microporous pipe (5); the mixing unit (7) is used for mixing, one end of the mixing unit (7) is communicated with the outlet of the guide shell (4), and the other end of the mixing unit (7) is provided with an LNG outlet (8); wherein micropore pipe (5) are including parallel arrangement's a plurality of tube bundles, micropore pipe (5) are through sintering shaping or machining shaping, the aperture of the micropore on micropore pipe (5) surface is 5 ~ 100 microns, micropore pipe (5) one end is fixed in on portable support grid (6), the other end is fixed in on tube sheet (2), mixing unit (7) are SK, SV, SX, SL or SH type static mixer.

2. A BOG recondenser according to claim 1, wherein a projection of a line joining centers of adjacent bundles of the microporous tubes (5) onto a plane perpendicular to the plurality of bundles is a regular triangle having one side thereof at an angle of 30 ° or 60 ° to an axial direction of the LNG inlet (3).

3. A BOG recondenser according to claim 1, wherein a projection of a line joining centers of adjacent bundles of the microporous tubes (5) on a plane perpendicular to the plurality of bundles is square, and one side of the regular triangle is at an angle of 90 ° or 45 ° to an axial direction of the LNG inlet (3).

4. A BOG recondenser according to claim 2 or claim 3, wherein the ratio of the distance between adjacent tube bundle centres to the tube bundle diameter is from 1.2 to 3.

5. The BOG recondenser of claim 1, wherein the BOG inlet (1) is located at the bottom of the BOG recondenser, communicating to the micro-perforated tube (5) through a tapered interface.

6. The BOG recondenser of claim 1, wherein the BOG recondenser is mounted vertically or horizontally.