A BOG recovery recondenser for liquefied natural gas

Abstract

The present invention provides a BOG recovery recondenser for liquefied natural gas, comprising a vertical cylinder with heads at both ends, a first packing part, a second packing part and a spiral gas riser; an LNG inlet is provided at the center of the top of the cylinder, an LNG outlet is provided at the center of the bottom of the cylinder, and a BOG inlet is provided at the bottom of the side wall of the cylinder; the first packing part and the second packing part are installed in parallel and at intervals in the upper part of the cylinder from top to bottom; the spiral gas riser is located in the lower part of the cylinder, the lower part of the spiral gas riser is connected to the BOG inlet, and the upper part of the spiral gas riser is provided with an outlet pipe part, which passes through the second packing part and extends between the first packing part and the second packing part; a liquid level monitor is installed on the lower side wall of the cylinder. The BOG of the recondenser is precooled by indirect contact with LNG, and then condensed by direct contact with LNG in the first packing part and the second packing part, and condensed in multiple parts, with high condensation efficiency and good cooling effect, thereby reducing the waste of cold energy.

Description

Technical Field

[0001] The invention belongs to the technical field of liquefied natural gas (LNG) processing, and in particular relates to a BOG recovery recondenser for liquefied natural gas. Background Art

[0002] Liquefied natural gas (LNG) is a liquefied natural gas product stored and transported at normal pressure and low temperature (101.3kPa, -162℃). During the production, storage and transportation process, LNG will inevitably exchange heat with the outside world, and the temperature will rise, causing part of the liquid gas to evaporate and form BOG flash gas. After BOG is formed, the pressure of the storage container will increase. When the pressure is too high, it may cause the safety valve to open and increase the risk of explosion. Directly discharging BOG into the atmosphere will waste energy and increase the environmental burden. Therefore, the reasonable treatment of BOG directly affects the stability, safety and economy of daily operation. At present, the most common BOG treatment process is the BOG reliquefaction process, that is, BOG is compressed and pressurized by a compressor, enters the recondenser, mixes with supercooled LNG, and then reliquefies, and then is transported for use. The equipment of this process mainly involves BOG compressors and recondensers.

[0003] Among them, the recondenser exchanges heat between compressed BOG and supercooled LNG, cools it into LNG and then outputs it. The existing recondenser consists of two parts, the upper part is the contact section, which is equipped with a packing part, and the lower part is the liquid container part. The compressed BOG and the supercooled LNG contact at the upper part of the recondenser for condensation. Under the action of gravity, the condensed LNG flows into the liquid container part at the lower part, and then outputs it through the high-pressure LNG output pump. In the existing condensation tank, BOG and the supercooled LNG directly contact and condense after entering. There is a large temperature difference and pressure change, and it is difficult to accurately control the internal conditions (pressure, liquid level) of the recondenser; direct contact condensation, while running downward under the action of gravity, the contact time between BOG and LNG is limited, and the condensation efficiency is low, so a large amount of supercooled LNG is required, resulting in energy waste. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a BOG recovery recondenser for liquefied natural gas. The BOG of the recondenser is pre-cooled by indirect contact with LNG, and then condensed by direct contact with LNG in a first packing part and a second packing part. After condensation at multiple locations, the condensation efficiency is high, the cooling effect is good, and the waste of cold energy is reduced.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A BOG recovery recondenser for liquefied natural gas, characterized in that it comprises a vertical cylinder with heads at both ends, a first packing part, a second packing part and a spiral gas riser; an LNG inlet is provided at the center of the top of the cylinder, an LNG outlet is provided at the center of the bottom of the cylinder, and a BOG inlet is provided at the bottom of the side wall of the cylinder; the first packing part and the second packing part are installed in parallel and at intervals in the upper part of the cylinder body from top to bottom; the spiral gas riser is located in the lower part of the cylinder body, the lower part of the spiral gas riser is connected with the BOG inlet, and an outlet pipe part is provided at the upper part of the spiral gas riser, and the outlet pipe part passes through the second packing part and extends between the first packing part and the second packing part; a liquid level monitor is installed on the side wall of the lower part of the cylinder body.

[0007] Furthermore, a diffuser is installed at the LNG inlet, and the diffuser is located above the first packing part, so that the LNG can be fully dispersed and flow downward when entering the cylinder, and better contact with the BOG for condensation.

[0008] Furthermore, it also includes an injection plate, which is installed in the upper part of the cylinder, located above the first packing part and below the diffuser, and has a plurality of injection holes. The LNG dispersed by the diffuser is further dispersed by the injection plate, and then enters the first packing layer below, ensuring that the LNG in the first packing layer is evenly distributed and fully contacts and condenses with the rising BOG.

[0009] Furthermore, the thickness of the first filler portion is smaller than that of the second filler portion; the first filler portion includes a first filler bottom plate and a first filler top plate; the second filler portion is provided with a second filler bottom plate and a second filler top plate; the second filler bottom plate and the second filler top plate are provided with mounting holes for the air outlet pipe portion to pass through.

[0010] Furthermore, a plurality of flow holes are distributed on the first filler bottom plate, the first filler top plate, the second filler bottom plate and the second filler top plate.

[0011] Furthermore, the spiral air riser is arranged close to the inner wall of the cylinder, and its spiral outer diameter is slightly smaller than the inner diameter of the cylinder, and the air outlet pipe portion passes through the edge of the second filler portion.

[0012] Furthermore, the outlet of the gas outlet pipe extends to the central axis of the cylinder between the first filler part and the second filler part, and the outlet is equipped with a spray head with a dispersion function, so that the pre-cooled BOG is dispersed into the cylinder and fully mixed with the LNG to promote the condensation effect.

[0013] Furthermore, the injection head is provided with a plurality of nozzles, and a float valve is arranged at the nozzles, so that the BOG gas can be dispersed into the cylinder more easily.

[0014] Furthermore, the liquid level monitor includes a minimum liquid level monitor and a maximum liquid level monitor, the minimum liquid level monitor is located above the BOG inlet position, and the maximum liquid level monitor is located below the second filling part.

[0015] Furthermore, an LNG liquid replenishing port is provided at the lower part of the side wall of the cylinder, which is used to replenish LNG liquid, prevent the liquid level at the lower part of the cylinder from being too low, and ensure the stable operation of the recondenser.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The recondenser of the present invention is provided with a spiral riser at the lower part of the cylinder, so that BOG enters through the spiral riser and is precooled by indirect contact with LNG at the lower part of the cylinder; the precooled BOG is sprayed out between the first packing part and the second packing part and mixed with the supercooled LNG; most of the BOG directly contacts with LNG in the second packing part downwards to be condensed, and a small part of the BOG moves upwards to contact with LNG in the first packing part to be condensed. Through indirect precooling and direct condensation, it can be ensured that BOG is fully condensed and the condensation effect is good; the first packing part and the second packing part are provided, so that BOG and LNG can be fully dispersed and contacted, ensuring that heat exchange is fully carried out, ensuring that the cold energy of the supercooled LNG is fully utilized, the condensation efficiency is high, and the waste of cold energy is avoided. After being precooled, when BOG enters the cylinder and directly contacts with LNG, the temperature difference is reduced, the pressure change becomes smaller, and it is easier to control the changes in the conditions inside the cylinder. The liquid level monitor is provided to better control the liquid level at the lower part of the cylinder to prevent the LNG liquid level from being too high or too low, which affects the normal operation of the recondenser. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0020] Figure 2 It is a schematic diagram of the structure of the spiral air riser in the present invention.

[0021] Figure 3 for Figure 2 Schematic diagram of the enlarged structure of part A.

[0022] Figure 4 It is a schematic structural diagram of the second filler bottom plate and the second filler top plate in the present invention.

[0023] Reference numerals:

[0024] 1: Cylinder; 11: LNG inlet; 111: Diffuser; 12: LNG outlet; 13: BOG inlet; 14: LNG filling port; 2: First packing part; 21: First packing top plate; 22: First packing bottom plate; 3: Second packing part; 31: Second packing top plate; 311: Mounting hole; 312: Flow hole; 32: Second packing top plate; 4: Spiral riser; 41: Air outlet pipe; 42: Injection head; 421: Float valve; 5: Liquid level monitor; 51: Minimum liquid level monitor; 52: Maximum liquid level monitor; 6: Injection plate. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0026] like Figure 1 As shown, an embodiment of the present invention provides a BOG recovery recondenser for liquefied natural gas. The recondenser comprises a cylinder 1, a first packing part 2, a second packing part 3, a spiral riser 4 and a liquid level monitor 5.

[0027] The cylinder 1 is vertical, with heads at both ends; an LNG inlet 11 is provided at the center of the top head of the cylinder 1; an LNG outlet 12 is provided at the center of the bottom head of the cylinder 1, and a BOG inlet 13 is provided at the bottom of the side wall of the cylinder 1. The first packing part 2 and the second packing part 3 are provided at the upper part of the cylinder 1, the first packing part 2 is located on the upper side, and the second packing part 3 is located on the lower side. The first packing part 2 and the second packing part 3 are arranged in parallel, with a certain distance between them. The spiral riser 4 is provided at the lower part of the cylinder 1, and an inlet is provided at the bottom of the spiral riser 4, which is connected to the BOG inlet 13 at the bottom of the side wall of the cylinder 1, and BOG gas enters the spiral riser 4 from the BOG inlet 13; an outlet pipe part 41 is provided at the upper part of the spiral riser 4, and the outlet pipe part 41 passes through the second packing part 3 and extends into the interval space between the first packing part 2 and the second packing part 3. The liquid level monitor 5 is installed on the side wall of the lower part of the cylinder 1, and is used to monitor the liquid level change of LNG in the lower part of the cylinder 1.

[0028] In a preferred embodiment, a diffuser 111 is installed at the LNG inlet 11 in the upper part of the cylinder 1, and the diffuser 111 is located above the first packing part 2. The diffuser 111 has a structure similar to a shower head, so that the liquid entering from the LNG inlet 11 is dispersed and sprinkled on the first packing part 2 in the cylinder 1, and fully contacts with the BOG flash gas in the cylinder 1 for condensation.

[0029] Furthermore, an injection plate 6 is installed in the upper part of the cylinder 1. The injection plate 6 is located above the first packing part 2 and below the diffuser 111. The LNG solution dispersed by the diffuser 111 is further dispersed through the injection plate 6 and flows into the first packing part 2 below. A number of injection holes are evenly distributed on the injection plate 6. The injection plate 6 is fixed on the inner wall of the cylinder 1 and is spaced a certain distance from the upper and lower diffusers 111 and the first packing part 2.

[0030] like Figure 1 and Figure 4 As shown, the first packing part 2 includes a first packing bottom plate 22 located at the bottom for supporting and a first packing top plate 21 located at the top for pressing and fixing, and the space between the first packing bottom plate 22 and the first packing top plate 21 is filled with packing. The second packing part 3 includes a second packing bottom plate 32 located at the bottom for supporting and a second packing top plate 31 located at the top for pressing and fixing, and the space between the second packing bottom plate 32 and the first packing top plate 31 is filled with packing. The second packing bottom plate 32 and the second packing top plate 31 are provided with corresponding mounting holes 311 for the outlet pipe part 41 of the spiral air riser 4 to pass through, and the mounting holes 311 are sealed and connected with the outlet pipe part 41.

[0031] A number of flow holes 312 are evenly distributed on the first packing bottom plate 22, the first packing top plate 21, the second packing bottom plate 32 and the second packing top plate 31, and LNG and BOG can enter the first packing part 2 and the second packing part 3 through the flow holes 312 for direct contact condensation. Among them, the fillers in the first packing part 2 and the second packing part 3 are Raschig ring fillers. The aperture of the flow holes 312 on the first packing bottom plate 22 and the second packing bottom plate 32 is smaller than the particle size of the filler. The first packing bottom plate 22, the first packing top plate 21, the second packing bottom plate 32 and the second packing top plate 31 are detachably fixedly connected to the inner wall of the cylinder 1. Preferably, the thickness of the first packing part 2 is smaller than the thickness of the second packing part 3.

[0032] like Figures 1 to 3As shown, the spiral part of the spiral gas riser 4 is arranged close to the inner wall of the cylinder 1, and the outer diameter of the spiral is slightly smaller than the inner diameter 1 of the cylinder 1. The outlet pipe part 41 extends upward along the spiral pipe body, passes through the mounting hole 311 of the second packing part 3, and extends between the first packing part 2 and the second packing part 3. The connection part between the outlet pipe part 41 and the second packing part 3 is located at the edge of the second packing part 3. The outlet pipe part 41 bends and extends between the first packing part 2 and the second packing part 3 to the center of the cylinder 1, and the outlet part of the outlet pipe part 41 extends to the central axis position of the cylinder 1. The outlet part is equipped with a spray head 42, which has a dispersion function, and can disperse the pre-cooled BOG gas introduced by the spiral gas riser 4 into the inner cavity of the cylinder 1, so that the BOG is dispersed into the first packing part 2 and the second packing part 3, and is more fully contacted with LNG for condensation and mixing. Among them, a number of nozzles are evenly distributed on the spray head 42, and a float valve 421 is provided at the nozzle. The float valve 421 can change the direction of the gas sprayed from the nozzle and disperse it.

[0033] like Figure 1 As shown, the liquid level monitor 5 is installed on the side wall of the lower part of the cylinder 1, including a minimum liquid level monitor 51 located at the bottom and a maximum liquid level monitor 52 located at the top, wherein the minimum liquid level monitor 51 is located above the BOG inlet 13, and the maximum liquid level monitor 52 is located below the second packing part 3. When the recondenser is working, the LNG solution at the bottom of the cylinder 1 should be located between the minimum liquid level monitor 51 and the maximum liquid level monitor 52, which can ensure that the LNG solution at the bottom of the cylinder 1 is discharged at a stable pressure by the booster pump, and at the same time ensure that the BOG in the spiral riser 4 in the recondenser achieves a precooling effect, and the pressure in the recondenser is maintained stable and easy to control.

[0034] Preferably, an LNG replenishing port 14 is provided at the lower part of the side wall of the cylinder 1. When the LNG solution level at the bottom of the recondenser cylinder 1 is too low, it can be replenished through the LNG replenishing port 14 to ensure the normal temperature operation of the recondenser.

[0035] The recondenser is controlled and operated by a controller, which is connected to the switch solenoid valves and the liquid level monitor 5 at the LNG inlet 11, the LNG outlet 12, the BOG inlet 13 and the LNG replenishment port 14, and can coordinate and control the LNG inlet and outlet flow, the BOG addition flow, and the liquid level, etc., to ensure the intelligent and efficient operation of the recondenser.

[0036] In the above, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are considered to be exemplary and non-restrictive in nature.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when used, or are the orientations or positional relationships conventionally understood by those skilled in the art, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Claims

1. A BOG recovery recondenser for liquefied natural gas, characterized in that: The invention comprises a vertical cylinder (1) with sealed ends at both ends, a first packing part (2), a second packing part (3) and a spiral gas riser (4); an LNG inlet (11) is provided at the center of the top of the cylinder (1), an LNG outlet (12) is provided at the center of the bottom of the cylinder (1), and a BOG inlet (13) is provided at the bottom of the side wall of the cylinder (1); the first packing part (2) and the second packing part (3) are installed in parallel and at intervals in the upper part of the cylinder (1) from top to bottom; a diffuser (111) is installed at the LNG inlet (11), and the diffuser (111) is located above the first packing part (2); the spiral gas riser (4) is located in the lower part of the cylinder (1), the lower part of the spiral gas riser (4) is connected to the BOG inlet (13), and an outlet pipe part (41) is provided at the upper part of the spiral gas riser (4), and the outlet pipe part (41) passes through the second packing part (3). The recondenser (1) is a recondenser configured to be a liquid level monitor (5) and a liquid level monitor (5). The recondenser (1) is a liquid level monitor (5) and a liquid level monitor (5) configured to monitor the liquid level of the cylinder (1 ...

2. The BOG recovery recondenser of liquefied natural gas according to claim 1, characterized in that: It also comprises an injection plate (6), which is installed at the upper inner part of the cylinder (1), located above the first filler part (2) and below the diffuser (111), and is provided with a plurality of injection holes.

3. The BOG recovery recondenser of liquefied natural gas according to claim 1 or 2, characterized in that: The thickness of the first packing portion (2) is smaller than the thickness of the second packing portion (3); the first packing portion (2) comprises a first packing bottom plate (22) and a first packing top plate (21); the second packing portion (3) is provided with a second packing bottom plate (32) and a second packing top plate (31); the second packing bottom plate (32) and the second packing top plate (31) are provided with mounting holes (311) for the air outlet pipe portion (41) to pass through.

4. The BOG recovery recondenser of liquefied natural gas according to claim 3, characterized in that: A plurality of flow holes (312) are distributed on the first filler bottom plate (22), the first filler top plate (21), the second filler bottom plate (32) and the second filler top plate (31).

5. The BOG recovery recondenser of liquefied natural gas according to claim 1 or 4, characterized in that: The spiral air riser (4) is arranged close to the inner wall of the cylinder (1), and its spiral outer diameter is slightly smaller than the inner diameter of the cylinder (1).

6. The BOG recovery recondenser of liquefied natural gas according to claim 5, characterized in that: The injection head (42) is provided with a plurality of nozzles, and a float valve (421) is provided at the nozzles.

7. The BOG recovery recondenser of liquefied natural gas according to claim 1, characterized in that: The lower part of the side wall of the cylinder (1) is provided with an LNG liquid replenishing port (14).

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