LNG gas supply system for ships

Abstract

An LNG gas supply system for ships, comprising: an LNG storage tank (20), a BOG pipe (a), a low-pressure LNG treatment pipe (b), a high-pressure LNG treatment pipe (c) and an ethylene glycol aqueous solution heating pipe (d). The BOG pipe (a) comprises a first regulation valve and a first-stage compressor set (91), two branch pipes being provided at an outlet of the first-stage compressor set (91), wherein one of the branch pipes is communicated with a high-pressure unit (30) via a second-stage compressor set (92), and the other one of the branch pipes is communicated with a first heater (41) and a generator set (50) via a fifth regulation valve. The low-pressure LNG treatment pipe (b) and the high-pressure LNG treatment pipe (c) are both communicated with corresponding cold sources of a multi-stream vaporizer (10). The ethylene glycol aqueous solution heating pipe (d) comprises a medium storage tank (80), a low-pressure booster pump (72), a heat source of the multi-stream vaporizer (10), a fourth regulation valve and a second heater (42). The present application achieves the purpose of efficient utilization of LNG fuel on the basis of said gas supply system for high-pressure units of LNG ships.

Description

LNG gas supply system for ships Technical Field

[0001] The present invention belongs to the technical field of fuel vaporization in shipbuilding and ship design, and in particular relates to an LNG gas supply system for ships. Background Art

[0002] For LNG fuel-powered ships, natural gas fuel is convenient for storage and transportation when it exists in the form of liquid LNG. However, as a ship fuel supply, it needs to be further pressurized, gasified, and heated before it can be used by the main and auxiliary engines. The current LNG ship main engine gas supply process system mainly includes a high-pressure unit, a low-pressure unit, and an ethylene glycol aqueous solution heating pipeline; among them, the high-pressure unit and the low-pressure unit contain corresponding compressed gas processing modules, low-pressure LNG processing pipelines, and high-pressure LNG processing pipelines; the low-pressure LNG processing pipelines and the high-pressure LNG processing pipelines contain a large number of high-pressure vaporizers or low-pressure vaporizers. The defects of the above-mentioned traditional LNG gas supply system are: First, LNG fuel is stored in a storage tank. Although it exists in a liquid state at ordinary times, it will inevitably form natural gas boil-off gas, also known as BOG; if it is not handled properly, it will pose a severe test to the safety of equipment operation. Secondly, since the temperature of cryogenic LNG is -162°C, while the freezing point of ethylene glycol-water solution is typically around -40°C, the temperature of cryogenic LNG is far lower than the freezing point of ethylene glycol-water solution. Therefore, in many vaporizers, the ethylene glycol-water solution side is prone to freezing. Once the heat exchange flow channel on the ethylene glycol-water solution side partially freezes, it gradually blocks heat exchange and circulation in the heat exchange channel, and the freezing rate gradually accelerates. Eventually, the ethylene glycol-water solution flow channel in the vaporizer freezes completely, causing the vaporization function to fail and affecting the normal operation of the system. Currently, a common solution in the industry is to equip each vaporizer with an additional set of parallel vaporization systems. If the outlet temperature of the corresponding LNG side is significantly lower than the design temperature, or the resistance drop on the ethylene glycol-water solution side increases significantly, it can be determined that ice has occurred on the hot side of the corresponding vaporizer. At this time, the valve can be switched to switch and activate the other backup vaporization system, ensuring continuous operation of the equipment without interruption. Obviously, the aforementioned method of switching vaporization systems still has several drawbacks. For one thing, the additional vaporization system takes up more floor space, significantly increasing the weight of the entire equipment and, consequently, the production and maintenance costs. Furthermore, the icing detection and switching processes in the vaporization system currently still largely require manual assistance, requiring a high level of operator experience and technical skills. Furthermore, the operation and control logic of the computerized control system would become more complex, making it difficult to meet the current industry demands for simplicity, efficiency, and cost-effectiveness. Therefore, this issue urgently needs to be addressed. Technical issues

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an LNG gas supply system for ships, which realizes the lightweighting of the equipment and achieves the efficient utilization of LNG fuel based on the LNG ship high-pressure main engine gas supply process system while improving safety, reducing costs and facilitating the optimization of control logic. Technical Solutions

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The LNG gas supply system for ships includes an LNG storage tank, characterized in that: the LNG storage tank is connected to a BOG pipeline for outputting boil-off gas of natural gas, a low-pressure LNG processing pipeline, a high-pressure LNG processing pipeline, and an ethylene glycol aqueous solution heating pipeline, wherein:

[0006] The BOG pipeline includes a first regulating valve CV1 and a first-stage compressor unit arranged in sequence along the gas flow direction. Two branch pipelines are set at the outlet of the first-stage compressor unit, one of which is connected to the high-pressure main engine via the second-stage compressor unit, and the other branch pipeline is connected to the first heater and the generator unit in sequence via the fifth regulating valve CV5;

[0007] The low-pressure LNG processing pipeline includes a second regulating valve CV2, a first cold source of a multi-stream vaporizer, and a separator arranged in sequence along the gas flow direction, and then connected to the generator set via a first heater;

[0008] The high-pressure LNG processing pipeline includes a third regulating valve CV3, a high-pressure boosting pump, and a second cold source of a multi-stream vaporizer, which are arranged in sequence along the gas flow direction, and then connected to the high-pressure main engine;

[0009] The ethylene glycol aqueous solution heating pipeline includes a medium storage tank for storing ethylene glycol aqueous solution. After the ethylene glycol aqueous solution is discharged from the medium storage tank, it flows back to the medium storage tank through the low-pressure booster pump, the heat source of the multi-stream vaporizer, the fourth regulating valve CV4 and the second heater in sequence.

[0010] Preferably, the multi-stream vaporizer includes a pipe box and a core with built-in flow channels located in the pipe box, the flow channels include a low-pressure LNG flow channel constituting a first cold source, a heat exchange medium flow channel constituting a heat source, and a high-pressure LNG flow channel constituting a second cold source; the heat exchange medium flow channel is a sequential stacked structure of a first main channel, a first auxiliary flow channel, a second auxiliary flow channel and a second main channel, and the first main channel and the first auxiliary flow channel are connected to each other to form an upper heat source cavity, and the second main channel and the second auxiliary flow channel are connected to each other to form a lower heat source cavity; in the same layer of heat source cavity, the flow area of ​​the main channel is greater than the flow area of ​​the auxiliary flow channel, and the main channel and the auxiliary flow channel intersect with each other, so that the intersection constitutes a connection point that penetrates each other; along the stacking direction of the flow channels, the second auxiliary flow channel and the first main channel are adjacent to each other, and the second main channel and the first auxiliary flow channel are adjacent to each other.

[0011] Preferably, in the projection in the top view direction, the second auxiliary flow channel is located within the projection range of the first main flow channel, and the second main flow channel is located within the projection range of the first auxiliary flow channel.

[0012] Preferably, each auxiliary flow channel is formed by combining two or more independent flow channels side by side; each independent flow channel is independently connected to the corresponding main flow channel of the same layer of heat source cavity at the connection point.

[0013] Preferably, the two adjacent intersection points of the main flow channel and the auxiliary flow channel of the same layer of heat source cavity are taken as the two end points, and a section of the auxiliary flow channel between the two end points forms a single flow channel segment, and a partition is arranged in the single flow channel segment; the partition extends along the length direction of the single flow channel segment, thereby dividing the flow channel cavity of the single flow channel segment into two or more isolation cavities; there is a distance between both ends of the partition and the two end points.

[0014] Preferably, the bottom end of the first auxiliary flow channel and the top end of the second auxiliary flow channel intersect with each other along the stacking direction of the flow channels, and the intersection constitutes a confluence opening connecting the upper heat source cavity and the lower heat source cavity.

[0015] Preferably, the shapes of each main channel and each auxiliary channel are V-shaped, W-shaped or wavy, and in the same layer of heat source cavity, the openings of the main channel and auxiliary channel that cooperate with each other are opposite to each other, so that the openings of the main channel and auxiliary channel are matched to form a closed loop structure, and the connecting point is set at the matching point of the closed loop structure.

[0016] Preferably, the turning points of the V-shaped or W-shaped main channels and auxiliary channels, or the crests or troughs of the wavy main channels and auxiliary channels are used as the inflection points of each channel, and then the main channels and auxiliary channels of the same layer of heat source cavity cooperate with each other to form a column of channel units, and the adjacent inflection points of the current column of channel units and the adjacent column of channel units of the same layer of heat source cavity are connected to each other.

[0017] Preferably, the upper heat source cavity and the lower heat source cavity are formed by three layers of heat exchange plates; a first groove-shaped main channel is etched on the lower plate surface of the first heat exchange plate, a first groove-shaped auxiliary channel is etched on the upper plate surface of the second heat exchange plate, a second groove-shaped auxiliary channel is etched on the lower plate surface of the second heat exchange plate, and a second groove-shaped main channel is etched on the upper plate surface of the third heat exchange plate; the corresponding main channels and auxiliary channels are notched together at the connection points to form corresponding heat source cavities; an upper heat exchange plate with a low-pressure LNG flow channel is also arranged above the first heat exchange plate, and a lower heat exchange plate with a high-pressure LNG flow channel is arranged below the third heat exchange plate.

[0018] Preferably, the upper heat source cavity and the lower heat source cavity are formed by three layers of heat exchange plates, the lower plate surface of the first heat exchange plate is etched with a groove-shaped first main channel, the upper plate surface of the second heat exchange plate is etched with a groove-shaped first auxiliary channel, the lower plate surface of the second heat exchange plate is etched with a groove-shaped second auxiliary channel, and the upper plate surface of the third heat exchange plate is etched with a groove-shaped second main channel, and the corresponding main channels and auxiliary channels are notched together at the connection points to form corresponding heat source cavities; a side heat exchange plate with low-pressure LNG channels and high-pressure LNG channels that are independent of each other is also arranged above or below the first heat exchange plate.

[0019] Preferably, the angle formed between each main flow channel and the auxiliary flow channel and the length direction of each heat exchange plate is in the range of (0°, 15°].

[0020] Preferably, each main flow channel is a semicircular groove or a semi-elliptical groove with a radius of 0.5 to 2 mm, or a rectangular groove with a width of 0.5 to 2 mm; the junction of the main flow channel and the auxiliary flow channel that cooperate with each other has a smooth transition. Beneficial effects

[0021] The beneficial effects of the present invention are:

[0022] 1) This invention is used in the fuel vaporization process of the high-pressure main engine gas supply system of LNG ships. During operation, by optimizing pipeline connections, controlling valves, and adjusting pressure, it can flexibly and efficiently process LNG liquid fuel and BOG gaseous fuel within the LNG storage tank. This not only enhances the effective utilization of BOG gas and greatly improves the safety of the LNG storage tank, but also further simplifies the equipment size, reduces weight, and reduces the equipment footprint through the dual-cold source structure of the multi-stream vaporizer. This achieves efficient LNG fuel utilization while reducing costs and facilitating optimized control logic.

[0023] 2) Based on the above structure, the multi-stream vaporizer of the present invention also relies on the special design concept of "main and auxiliary flow diversion, temperature difference de-icing", relying on the cooperation between the main channel close to the cold source and the auxiliary channel relatively far away from the cold source. When in use, the dual cold sources naturally cause each main channel to form a specific stacking state of the first main channel, the first auxiliary channel, the second auxiliary channel, and the second main channel. At this time, due to the difference in the flow area of ​​the main channel and the auxiliary channel, during normal operation, the ethylene glycol aqueous solution will mainly travel along the main channel, thereby facilitating heat exchange with the LNG channel adjacent to the main channel. When severe icing occurs, it often occurs in the main channel; because the auxiliary channel is relatively farther away from the LNG channel and the temperature is relatively higher, it is less likely to freeze. At this time, as the ice becomes blocked, the flow rate in the main channel decreases, and the flow rate in the relative auxiliary channel gradually exceeds that in the main channel. At this time, more ethylene glycol aqueous solution begins to enter the auxiliary channel where the flow is relatively unobstructed; when the flow rate in the auxiliary channel is greater than that in the main channel, the auxiliary channel actually surpasses the main channel, that is, an alternative channel for the main channel is formed, thereby achieving the purpose of continuous circulation and heat exchange of ethylene glycol aqueous solution.

[0024] When the auxiliary flow channel functions as a replacement flow channel, a portion of the glycol-water solution still flows into the main flow channel, continuously flushing the ice in the main flow channel, achieving the effect of "mixing and melting ice." Meanwhile, the glycol-water solution that enters the auxiliary flow channel, because it is close to the corresponding main flow channel, achieves the purpose of inter-wall heat exchange with the main flow channel, achieving the effect of "heat exchange and ice melting." During this entire process, the equipment can continue to operate without stopping.

[0025] In summary, when localized ice forms, the present invention utilizes the ethylene glycol solution through serial contact heat exchange and interphase heat exchange at the front and rear sides of the specific ice formation location. This ingeniously utilizes the "heat differential" generated by the different distances between the main and auxiliary channels from the cold source, effectively enhancing the "ice melting effect" and fully ensuring the flowability of the ethylene glycol solution. The combined effects of "mixed ice melting" and "heat exchange ice melting" enable continuous ice melting at ice formations in the main and even auxiliary channels, ensuring self-cleaning of ice formations without affecting the normal operation of the vaporizer. Furthermore, the use of ethylene glycol solution for contact heat exchange and interphase heat exchange between the upper and lower heat source cavities, or even between two channels in the same heat source cavity, maintains the flowability of the ethylene glycol solution at the ice formation location, effectively suppressing the growth rate of ice, thereby ensuring the adaptability of the ethylene glycol solution in regulating the flow rate and temperature range.

[0026] Thus, the present invention can eliminate the need for a backup vaporization system while further eliminating the conventional parallel high-pressure vaporizer piping system and low-pressure vaporizer piping system, further saving floor space, weight, and investment; at the same time, the operation and control logic of the LNG ship high-pressure main engine gas supply process system using the present invention becomes simpler and more efficient.

[0027] 3) To maximize the "heat exchange and ice melting" effect, the optimized solution of the present invention can be used, that is, the second auxiliary channel is located within the projection of the first main channel, and the second main channel is also located within the projection of the first auxiliary channel. In this case, the second auxiliary channel is closest to the first main channel while being relatively farthest from the cold source, thus achieving a rapid heat exchange and ice melting effect on the first main channel. The same principle applies to the second main channel and the first auxiliary channel.

[0028] 4) In actual operation, the main and auxiliary flow channels of the present invention can be combined in various ways: the auxiliary flow channel can be formed by combining multiple independent flow channels, in which case the main flow channel simultaneously connects to each independent flow channel; or the inflection point of the auxiliary flow channel is the confluence point, while the other areas are separated by one or more partitions, which can also achieve the multi-channel effect of the auxiliary flow channel. Furthermore, the first and second auxiliary flow channels can even approach each other and intersect, thereby forming a three-dimensional connection relationship between the flow channels, thereby achieving a stronger connection effect.

[0029] The aforementioned flow channel structure, combined with multiple columns of flow channel units, offers the following benefits: First, the main and auxiliary flow channels within the same column of flow channel units consistently redistribute flow at the inflection point, ensuring the flowability of the ethylene glycol solution. Second, flow can be redistributed between adjacent columns of flow channel units. Furthermore, when the first and second auxiliary flow channels approach and intersect, an S-shaped, variable-thickness rotary cut surface forms at their intersection, further shearing the ethylene glycol solution as it circulates, enhancing the contact-type mixing and heat exchange effect. Furthermore, the ethylene glycol solution, through its own convergence, mixing, and diversion, further enhances its flowability and ensures resistance to ice and fouling blockage.

[0030] 5) The auxiliary flow channel adopts the method of multiple flow channels in parallel or single flow channel with partitions. Another reason is that the overall depth of the auxiliary flow channel is reduced to facilitate etching processing. In addition, the main flow channel groove and the auxiliary flow channel groove are opened respectively at the two heat exchange plates, and then rely on each other to form a corresponding heat source cavity. This not only increases the flow area of ​​the heat source cavity of the ethylene glycol aqueous solution, which is a medium that is easy to freeze or produce dirt, but also makes the heat source cavity surpass the conventional diffusion welding plate heat exchanger. The etching depth is difficult to exceed 2mm. The three-dimensional network formed by connecting a single heat source cavity or even multiple layers of heat source cavities to each other can enable the ethylene glycol aqueous solution to achieve continuous and intermittent combined flow forms in a three-dimensional continuously variable space, ensuring the uniformity of heat exchange efficiency in each flow channel and further reducing the risk of freezing.

[0031] 6) The angles formed between each main and auxiliary channel and the length of each heat exchange plate are limited. However, along the length of the heat exchange plate, the main and auxiliary channels of the same channel unit extend outward from the base point, moving away from each other. They then move closer to each other at the farthest point and finally converge at a certain inflection point, repeating this process. This design approach facilitates the formation of a three-dimensional network and is also more convenient for processing.

[0032] 7) For each level of compressor group, it can be set according to actual conditions. In the present invention, the first-stage compressor group and the second-stage compressor group each include two groups of compressors connected in series to ensure compression efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a diagram showing the arrangement of the pipelines of the present invention;

[0034] FIG2 is a diagram showing the flow channel arrangement of the upper heat source cavity and the lower heat source cavity in Example 1;

[0035] FIG3 is a front view of FIG2;

[0036] FIG4 is a top view of the structure shown in FIG2 ;

[0037] FIG5 is a diagram showing the flow channel arrangement of the upper heat source cavity and the lower heat source cavity in Example 2;

[0038] FIG6 is a front view of FIG5;

[0039] FIG7 is a top view of the structure shown in FIG5 ;

[0040] Figures 8 and 9 are diagrams showing the assembled structures of Example 1 and Example 2;

[0041] FIG10 is a diagram showing the flow channel arrangement of the upper heat source cavity and the lower heat source cavity in Example 3;

[0042] FIG11 is a front view of FIG10;

[0043] FIG12 is a schematic structural diagram of another embodiment of a multi-stream vaporizer.

[0044] The actual correspondence between the reference numerals and component names of the present invention is as follows:

[0045] a-BOG pipeline; b-low-pressure LNG processing pipeline; c-high-pressure LNG processing pipeline;

[0046] d-Ethylene glycol aqueous solution heating pipeline;

[0047] 10-multi-stream vaporizer; 10a-low-pressure LNG flow channel; 10b-heat exchange medium flow channel;

[0048] 10c - High-pressure LNG flow channel; 11a - First main flow channel; 11b - First auxiliary flow channel; 12a - Second auxiliary flow channel; 12b - Second main flow channel; 13 - Confluence port; 14 - Upper heat exchange plate; 15 - First heat exchange plate;

[0049] 16-second heat exchange plate; 17-third heat exchange plate; 18-lower heat exchange plate; 19-partition plate;

[0050] 20-LNG storage tank; 30-high-pressure main engine; 41-first heater; 42-second heater;

[0051] 50-generator set; 60-separator; 71-high-pressure booster pump; 72-low-pressure booster pump;

[0052] 80-Medium storage tank; 91-First stage compressor unit; 92-Second stage compressor unit. Modes for Carrying Out the Invention

[0053] For ease of understanding, the specific structure and working mode of the present invention are further described below with reference to FIG1 to FIG12 :

[0054] The specific implementation structure of the present invention is shown in Figures 1 to 11. The design purpose is mainly for the regulation between different pipelines and the switching adjustment between different working conditions. Specifically, it includes an LNG storage tank 20, and the LNG storage tank 20 is connected to a low-pressure LNG processing pipeline b, a high-pressure LNG processing pipeline c, an ethylene glycol aqueous solution heating pipeline d, and a BOG pipeline a for outputting natural gas boil-off gas, wherein:

[0055] 1. BOG pipeline a:

[0056] LNG storage tank 20 contains a large amount of cryogenic LNG, typically at -162°C and 0.1 MPa. Although the LNG storage tank 20 is covered with a highly insulating layer, the significant temperature difference from the surrounding environment inevitably produces a large amount of boil-off gas (BOG). In the present invention, this BOG can flow directly through BOG pipeline a. More specifically, the BOG flows through the first regulating valve CV1 and then enters the first-stage compressor unit 91, which consists of a first and second-stage compressor. The outlet is divided into two distinct flow paths. A portion of the NG, or natural gas in its natural state, passes through the second-stage compressor unit 92, consisting of a third and fourth-stage compressor, where it is compressed to a pressure above 20 MPa before entering the high-pressure main engine 30. The other portion of the NG passes through the fifth regulating valve CV5 and then enters the first heater 41, where it is heated to a higher temperature before entering the generator set 50.

[0057] 2. Low-pressure LNG processing pipeline b:

[0058] The -162°C low-temperature LNG stored in LNG storage tank 20 flows directly through second regulating valve CV2 and then through multi-stream vaporizer 10, absorbing heat from the ethylene glycol solution in ethylene glycol solution heating line d. At this point, the -162°C low-temperature LNG begins to absorb heat and vaporizes before entering separator 60, where heavy hydrocarbons are separated from light hydrocarbons, providing high-methane-number gas for subsequent processes. The LNG at the top of separator 60 then enters first heater 41, where it is heated to a higher temperature before entering generator set 50.

[0059] 3. High-pressure LNG processing pipeline c:

[0060] The low-temperature LNG at -162°C stored in the LNG storage tank 20 flows directly through the third regulating valve CV3 and enters the high-pressure boosting pump 71, where the low-temperature LNG is pressurized to above 20 MPa, and then enters the multi-stream vaporizer 10, absorbing heat from the ethylene glycol aqueous solution in the ethylene glycol aqueous solution heating pipeline d, and is fully vaporized into high-pressure and high-temperature NG, and then enters the high-pressure main engine 30.

[0061] 4. Ethylene glycol aqueous solution heating pipeline d:

[0062] The ethylene glycol aqueous solution in the medium storage tank 80 first enters the low-pressure booster pump 72, then flows through the multi-stream vaporizer 10, releasing heat to the high-pressure LNG in the high-pressure LNG processing line c and the low-pressure LNG in the low-pressure LNG processing line b. The ethylene glycol aqueous solution then enters the fourth regulating valve CV4 and then the second heater 42, absorbing heat, restoring the ethylene glycol aqueous solution to a relatively high temperature of approximately 50°C before returning to the medium storage tank 80.

[0063] The specific structure of the multi-stream vaporizer 10 is shown in Figures 2 to 11; it includes a pipe box and a core with built-in flow channels. The core includes an upper end plate and a lower end plate. The core is located between the two end plates, and the core includes one or more functional heat exchange structures. Each functional heat exchange structure has a built-in low-pressure LNG flow channel 10a, a high-pressure LNG flow channel 10c and a heat exchange medium flow channel 10b, as shown in Figure 8. Among them, the low-pressure LNG flow channel 10a and the high-pressure LNG flow channel 10c constitute the cold source, and the heat exchange medium flow channel 10b constitutes the heat source, as shown in Figures 1 and 8. In actual use, the multi-stream vaporizer 10 can also be increased as appropriate, such as two or even more groups, which will not be repeated here.

[0064] Furthermore, the low-pressure LNG flow channel 10a and the high-pressure LNG flow channel 10c can be arranged in the same heat exchanger type as shown in FIG12 , thereby placing both cold sources on the same side of the heat source. In this case, a side heat exchange plate with both low-pressure LNG flow channels and high-pressure LNG flow channels can be arranged above or below the first heat exchange plate. Of course, they can also be arranged on both sides of the heat source as shown in FIG1 and FIG2 to achieve the purpose of heat exchange.

[0065] For ease of description, the following description assumes that the low-pressure LNG flow channel 10a and the high-pressure LNG flow channel 10c are located on both sides of the heat source, that is, the embodiment shown in Figures 1 and 2.

[0066] Furthermore, the functional heat exchange structure is composed of multiple plates of different functional types stacked in a specific order, including at least an upper heat exchange plate 14, a first heat exchange plate 15, a second heat exchange plate 16, a third heat exchange plate 17, and a lower heat exchange plate 18. In actual arrangement, the heat exchange plates are stacked one on top of the other, forming channel-like flow cavities from the corresponding etched grooves. The combinations of functional heat exchange structures shown in Figures 8 and 9 are for reference only and may be adjusted as appropriate in actual operation.

[0067] The upper heat exchange plates 14 and the lower heat exchange plates 18 can be arranged in a straight channel, a wavy structure, or a zigzag structure along the flow direction. In a straight channel, the flow resistance is relatively small, while in a wavy structure or a zigzag structure, the heat exchange effect is better.

[0068] Figures 8 and 9 also illustrate the main and auxiliary channels formed by the first, second, and third heat exchange plates 15, 16, and 17. In actual design, the bottom dimension of each main channel, or a single large groove, is the sum of the top dimensions of each auxiliary channel, or multiple small grooves, and the dimensions of the solid connecting segment in the middle. Furthermore, each groove has a wavy or zigzag structure, bent along the length of the heat exchange plate. As can be seen in Figures 2, 5, and 10, on the same cross-section, the flow directions of the main channels intersect, the flow directions of the auxiliary channels also intersect, and adjacent main and auxiliary channels also form a cross structure, thus forming a three-dimensional grid-like flow channel structure.

[0069] Specifically, when the main flow channel and the auxiliary flow channel are combined to form a corresponding heat source cavity, there are at least three ways of matching them: Example

[0070] As shown in Figures 2 to 4, at this time, the upper heat source cavity is formed by a combination of the first main channel 11a as a large groove and the first auxiliary channel 11b as a parallel independent small groove; the lower heat source cavity is composed of the second auxiliary channel 12a as a parallel small independent groove and the second main channel 12b as a large groove; and in the projection direction or the top view, the first auxiliary channel 11b is located directly above the second main channel 12b and are arranged close to each other, while the first main channel 11a is located directly above the second auxiliary channel 12a and are arranged close to each other, thereby forming the above-mentioned cross structure.

[0071] Each single flow channel segment of the first main flow channel 11a at the bottom of the first heat exchange plate 15 and each single flow channel segment of the first auxiliary flow channel 11b at the top of the second heat exchange plate 16 are all the same length and have the same degree of deviation from the central axis. This makes the upper heat source cavity formed by the combination of the grooves present a regularly distributed diamond-shaped network flow channel structure as shown in Figures 2 and 4. The same is true for the lower heat source cavity formed by the second and third heat exchange plates 16 and 17. Example

[0072] The basic structure of Example 2 is shown in Figures 5 to 7. It can be seen that the structure is similar to that of Example 1. The difference is that the auxiliary flow channels of the parallel small grooves are not independent small grooves here, but the entire groove containing the discontinuous partition 19 is etched directly on the second heat exchange plate 16, thereby relying on the partition 19 to separate and form a parallel flow structure.

[0073] It should be noted here that, as shown in FIG7 , the partitions 19 can be any physical partition structure, such as a protruding plate or an arc-shaped arch. Furthermore, the number of partitions 19 can be determined based on the specific situation and can be one or more groups. Furthermore, a certain amount of space must be left at both ends of the partitions 19 to allow the ethylene glycol-water solution to converge and mix. Example

[0074] The basic structure of Example 3 is shown in Figures 10 and 11. Based on the structure of Example 1, the grooves etched on the upper and lower surfaces of the second heat exchange plate 16 are brought closer together until the first auxiliary flow channel 11b and the second auxiliary flow channel 12a intersect in spatial height. This intersection, commonly known as the intersection line within the cavity, forms an "S"-shaped variable thickness rotary cut surface, also known as the confluence port 13. After the ethylene glycol-water solution from the first heat exchange plate 15, the second heat exchange plate 16, and the third heat exchange plate 17 undergo interlayer heat exchange within their respective tortuous lengths, the ethylene glycol-water solution is further rotary cut at the "S"-shaped variable thickness rotary cut surface, further enhancing the contact-type mixed heat exchange effect.

[0075] For ease of understanding, the actual workflow of the present invention is further described below in conjunction with Example 1:

[0076] In actual use, the present invention can be divided into two conditions, according to the flow state of the heat exchange medium in the core, that is, the ethylene glycol aqueous solution, during use: a normal heat exchange condition in which the channels are not blocked by ice or dirt, and a heat exchange condition in which the channels are partially blocked by ice or dirt. The two conditions are described below respectively:

[0077] 1) Normal heat exchange conditions when there is no ice or dirt blocking the channels:

[0078] At this time, the grooves in the upper heat exchange plate 14 and the lower heat exchange plate 18, together with the corresponding first heat exchange plate 15 or the third heat exchange plate 17, respectively form two LNG flow channels of the cold source; the first heat exchange plate 15, the second heat exchange plate 16 and the third heat exchange plate 17 are aligned with each other to form the corresponding upper heat source cavity and the lower heat source cavity, and the upper heat source cavity and the lower heat source cavity together constitute the heat exchange medium flow channel 10b.

[0079] The upper and lower heat source cavities have wavy or zigzag flow structures, allowing not only the main and auxiliary flow channels within the same heat source cavity to connect at the inflection point, or connection point, but also interconnecting heat source cavities in different layers when necessary. This allows the ethylene glycol solution to flow freely within the current heat source cavity and between two layers of heat source cavities. At the core entrance, as shown in Figure 3, the cross-sectional dimensions of the first main channel 11a account for more than 60% of the total cross-sectional area of ​​the upper heat source cavity. As a result, the majority of the ethylene glycol solution enters the first main channel 11a, forming the primary flow channel; a smaller amount enters the first auxiliary channel 11b, forming the auxiliary flow channel. At this time, since the first main channel 11a is closer to the first cold source located above, it can fully perform inter-wall heat exchange, and the temperature of the ethylene glycol aqueous solution in the first main channel 11a is also lower; correspondingly, the first auxiliary channel 11b is farther away from the first cold source located above compared to the first main channel 11a, and performs insufficient inter-wall heat exchange, so the temperature of the ethylene glycol aqueous solution in the first auxiliary channel 11b is relatively higher. The same is true for the second main channel 12b and the second auxiliary channel 12a. The ethylene glycol aqueous solutions in each channel will converge and exchange heat at each inflection point, and then redistribute the flow, and then repeat the convergence and heat exchange until it finally flows out of the core.

[0080] 2) Conventional heat exchange conditions where ice or dirt blocks the channels:

[0081] When severe icing occurs, the frozen areas are often located in the main channels, where the temperature of the ethylene glycol solution is relatively low, namely, in the first main channel 11a and the second main channel 12b. Once the main channel is partially blocked, the ethylene glycol solution becomes difficult to pass through, and the ethylene glycol solution naturally begins to flow through the auxiliary channels as its primary channel. At this point, a portion of the ethylene glycol solution will continue to flow into the main channel, continuously flushing the frozen areas in the main channel, achieving a "mixed ice melting" effect. The remaining portion of the ethylene glycol solution that enters the auxiliary channels, due to their proximity to the corresponding main channels and the relatively high liquid temperature in the auxiliary channels, achieves the purpose of inter-wall heat exchange with the corresponding main channels, thus achieving a "heat exchange ice melting" effect. The combined effects of "mixed ice melting" and "heat exchange ice melting" ensure continuous ice melting in the frozen areas of the main channel, ensuring the self-cleaning function of the frozen areas without affecting the normal operation of the vaporizer.

[0082] Of course, if ice forms in one of the small grooves in the auxiliary flow channel, the presence of the other small grooves and the connection points at each inflection point allows the ice in the corresponding small groove to melt completely by the impact of the liquid and the heat exchange between the walls. This is one of the reasons why the auxiliary flow channel adopts a multi-groove parallel flow channel structure. In particular, for the structure of Example 3, the "S"-shaped variable thickness rotary cut surface can further enhance the rotary cutting of the ethylene glycol aqueous solution and further strengthen the contact mixing heat exchange function. This will not be repeated here.

[0083] It can be seen at this point that the design concept of the multi-stream evaporator 10 is to regard all the heat exchange plates as a whole, and increase the hydraulic diameter by etching grooves and then aligning them. At the same time, when local freezing occurs, the ethylene glycol aqueous solution is heat exchanged through series contact heat exchange and partition heat exchange on the front and rear sides of the specific freezing position, and cleverly utilizes the "heat difference" caused by the different distances between the main channel and the auxiliary channel and the cold source to generate different heat, effectively enhancing the "ice melting effect" and fully ensuring the passability of the ethylene glycol aqueous solution.

[0084] Of course, when dirt, such as endogenous dirt generated by the heat exchange process or the reaction process, blocks the flow channel, the above-mentioned design of the present invention can also prevent the flow channel from being completely blocked and unable to flow; that is, due to the existence of the three-dimensional flow system of the present invention, the blockage point only exists in a small area of ​​the huge system, especially in this area. The corresponding main flow channel and auxiliary flow channel can be automatically switched with each other, so the fluidity can still be guaranteed to ensure the continuous and reliable operation of the equipment.

[0085] Through the above design, the present invention can minimize the adverse effects of ice blockage or dirt blockage, ensuring the stable operation of the heat exchanger and the system.

[0086] Of course, it will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, but also encompasses the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and it is intended that all variations that fall within the meaning and range of equivalents of the claims be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0087] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0088] The technology, shape, and structure not described in detail in the present invention are all well-known technologies.

Claims

1. A LNG gas supply system for a ship, comprising an LNG storage tank (20), characterized in that: The LNG storage tank (20) is connected to a low-pressure LNG processing pipeline (b), a high-pressure LNG processing pipeline (c), an ethylene glycol aqueous solution heating pipeline (d), and a BOG pipeline (a) for outputting natural gas boil-off gas, wherein: The BOG pipeline (a) comprises a first regulating valve CV1 and a first-stage compressor unit (91) arranged in sequence along a gas flow direction, and two branch pipelines are arranged at the outlet of the first-stage compressor unit (91), one of the branch pipelines is connected to the high-pressure main engine (30) via the second-stage compressor unit (92), and the other branch pipeline is connected to the first heater (41) and the generator unit (50) in sequence via the fifth regulating valve CV5; The low-pressure LNG processing pipeline (b) comprises a second regulating valve CV2, a first cold source of a multi-stream vaporizer (10), and a separator (60) which are arranged in sequence along the gas flow direction, and is then connected to a generator set (50) via a first heater (41); The high-pressure LNG processing pipeline (c) comprises a third regulating valve CV3, a high-pressure boosting pump (71) and a second cold source of a multi-stream vaporizer (10) which are sequentially arranged along the gas flow direction, and is subsequently connected to the high-pressure main engine (30); The ethylene glycol aqueous solution heating pipeline (d) comprises a medium storage tank (80) for storing the ethylene glycol aqueous solution. After the ethylene glycol aqueous solution is discharged from the medium storage tank (80), it flows back to the medium storage tank (80) in sequence through the low-pressure booster pump (72), the heat source of the multi-stream vaporizer (10), the fourth regulating valve CV4 and the second heater (42); The multi-stream vaporizer (10) comprises a pipe box and a core body with built-in flow channels, wherein the flow channels comprise a low-pressure LNG flow channel (10a) constituting a first cold source, a heat exchange medium flow channel (10b) constituting a heat source, and a high-pressure LNG flow channel (10c) constituting a second cold source; the heat exchange medium flow channel (10b) is a sequentially stacked structure of a first main flow channel (11a), a first auxiliary flow channel (11b), a second auxiliary flow channel (12a), and a second main flow channel (12b), and the first main flow channel (11a) and the first auxiliary flow channel (12a) are stacked in sequence. The auxiliary flow channels (11b) are connected to each other to form an upper heat source cavity, and the second main flow channel (12b) and the second auxiliary flow channel (12a) are connected to each other to form a lower heat source cavity; in the same layer of heat source cavity, the flow area of ​​the main flow channel is greater than the flow area of ​​the auxiliary flow channel, and the main flow channel and the auxiliary flow channel intersect with each other so that the intersection constitutes a connection point that penetrates each other; along the stacking direction of the flow channels, the second auxiliary flow channel (12a) and the first main flow channel (11a) are adjacent to each other, and the second main flow channel (12b) and the first auxiliary flow channel (11b) are adjacent to each other.

2. The LNG gas supply system for ships according to claim 1, characterized in that: In a projection in a top-down direction, the second auxiliary flow channel (12a) is located within the projection range of the first main flow channel (11a), and the second main flow channel (12b) is located within the projection range of the first auxiliary flow channel (11b).

3. The LNG gas supply system for ships according to claim 2, characterized in that: Each auxiliary flow channel is formed by combining two or more independent flow channels side by side; each independent flow channel is independently connected to the corresponding main flow channel of the same layer of heat source cavity at the connecting point.

4. The LNG gas supply system for ships according to claim 3, characterized in that: The bottom end of the first auxiliary flow channel (11b) and the top end of the second auxiliary flow channel (12a) intersect with each other along the stacking direction of the flow channels, and the intersection forms a confluence opening (13) connecting the upper heat source cavity and the lower heat source cavity.

5. The LNG gas supply system for ships according to claim 2, characterized in that: Two adjacent intersections of the main flow channel and the auxiliary flow channel of the same layer of heat source cavity are taken as two end points, a section of the auxiliary flow channel between the two end points forms a single flow channel segment, and a partition (19) is arranged in the single flow channel segment; the partition (19) extends along the length direction of the single flow channel segment, thereby dividing the flow channel cavity of the single flow channel segment into two or more isolation cavities; there is a distance between both ends of the partition (19) and the two end points.

6. The LNG gas supply system for ships according to claim 1, 2, 3, 4 or 5, characterized in that: The shapes of each main flow channel and each auxiliary flow channel are V-shaped, W-shaped or wavy, and in the same layer of heat source cavity, the openings of the main flow channel and the auxiliary flow channel that cooperate with each other are opposite to each other, so that the openings of the main flow channel and the auxiliary flow channel are matched to form a closed-loop structure, and the connecting point is set at the matching point of the closed-loop structure.

7. The LNG gas supply system for ships according to claim 6, characterized in that: The turning points of V-shaped or W-shaped main and auxiliary flow channels, or the crests or troughs of wavy main and auxiliary flow channels are used as inflection points of each flow channel, and then the main and auxiliary flow channels of the same layer of heat source cavity that cooperate with each other form a column of flow channel units, and the adjacent inflection points of the current column of flow channel units and the adjacent column of flow channel units of the same layer of heat source cavity are connected to each other.

8. The LNG gas supply system for ships according to claim 1, 2, 3, 4 or 5, characterized in that: The upper heat source cavity and the lower heat source cavity are formed by three layers of heat exchange plates; a first main flow channel (11a) in the shape of a groove is etched on the lower plate surface of the first heat exchange plate (15), a first auxiliary flow channel (11b) in the shape of a groove is etched on the upper plate surface of the second heat exchange plate (16), a second auxiliary flow channel (12a) in the shape of a groove is etched on the lower plate surface of the second heat exchange plate (16), and a second main flow channel (12b) in the shape of a groove is etched on the upper plate surface of the third heat exchange plate (17); the corresponding main flow channels and auxiliary flow channels are notched together at the connection points to form corresponding heat source cavities; an upper heat exchange plate (14) provided with a low-pressure LNG flow channel (10a) is also arranged above the first heat exchange plate (15), and a lower heat exchange plate (18) provided with a high-pressure LNG flow channel (10c) is arranged below the third heat exchange plate (17).

9. The LNG gas supply system for ships according to claim 1, 2, 3, 4 or 5, characterized in that: The upper heat source cavity and the lower heat source cavity are formed by three layers of heat exchange plates. A first main flow channel (11a) in the shape of a groove is etched on the lower plate surface of the first heat exchange plate (15), a first auxiliary flow channel (11b) in the shape of a groove is etched on the upper plate surface of the second heat exchange plate (16), a second auxiliary flow channel (12a) in the shape of a groove is etched on the lower plate surface of the second heat exchange plate (16), and a second main flow channel (12b) in the shape of a groove is etched on the upper plate surface of the third heat exchange plate (17). The corresponding main flow channels and auxiliary flow channels are notched together at the connection points to form corresponding heat source cavities. A side heat exchange plate having low-pressure LNG flow channels (10a) and high-pressure LNG flow channels (10c) that are independent of each other is also arranged above or below the first heat exchange plate (15).

10. The LNG gas supply system for ships according to claim 9, characterized in that: The range of the angle formed between each main flow channel and the auxiliary flow channel and the length direction of each heat exchange plate is (0°, 15°].

11. The LNG gas supply system for ships according to claim 9, characterized in that: Each main flow channel is a semicircular groove or a semi-elliptical groove with a radius of 0.5 to 2 mm, or a rectangular groove with a width of 0.5 to 2 mm.

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