JP6347004B1 - LNG ship evaporative gas reliquefaction method and system - Google Patents

Abstract

An evaporative gas reliquefaction method for an LNG ship is disclosed.
A method for reliquefying an evaporative gas of an LNG ship according to the present invention includes: 1) a step of compressing the evaporative gas; 2) heat-exchanging the evaporative gas compressed in the step 1) with a heat exchanger using evaporative gas as a refrigerant. 3) a step of expanding the fluid cooled in the step 2); and 4) a flow rate of the reliquefied evaporation gas supplied to the heat exchanger after being compressed in the step 1). A step of stably maintaining reliquefaction performance even if it fluctuates, and the amount of evaporative gas reliquefied through steps 1) to 3) is maintained at 50% or more of the value calculated by HYSYS.
[Selection] Figure 1

Description

  The present invention relates to a method and system for re-liquefying surplus evaporative gas that has not been used in an engine out of evaporative gas generated inside a storage tank of an LNG ship using the evaporative gas itself as a refrigerant.

  In recent years, consumption of liquefied gas such as liquefied natural gas (LNG) has been rapidly increasing worldwide. The liquefied gas obtained by liquefying the gas at a low temperature has an advantage that the storage and transfer efficiency is improved because the volume is greatly reduced as compared with the gas. In addition, liquefied gas such as LNG is an environmentally friendly fuel in which air pollutants are removed or reduced during the liquefaction process, and the amount of air pollutants discharged is small during combustion.

  LNG is a colorless and transparent liquid obtained by cooling and liquefying natural gas mainly composed of methane to about −163 ° C., and its volume is about 1/600 compared to natural gas. Therefore, when natural gas is liquefied and transferred, very efficient transfer becomes possible.

  However, the liquefaction temperature of natural gas is an extremely low temperature of −163 ° C. at normal pressure, and LNG is easily evaporated because it is sensitive to temperature changes. Therefore, the storage tank for storing LNG is thermally insulated, but external heat is continuously transmitted to the storage tank, and LNG is naturally vaporized in the storage tank during the LNG transport process, resulting in evaporation gas. (BOG) occurs.

  Evaporative gas is one of the losses and is an important issue in transportation efficiency. In addition, if evaporative gas accumulates in the storage tank, the tank internal pressure rises excessively, and in extreme cases, the tank may be damaged. Therefore, various methods for treating the evaporative gas generated in the storage tank have been studied. Recently, in order to process the evaporative gas, the evaporative gas is re-liquefied and returned to the storage tank, the evaporative gas is returned to the ship engine, etc. The method of using as an energy source of the fuel consumption destination is used.

  The method for re-liquefying the evaporative gas includes a refrigeration cycle using another refrigerant and re-liquefying the evaporative gas by exchanging heat with the refrigerant, or re-liquefying the evaporative gas itself as a refrigerant without using another refrigerant. There are methods. In particular, a system that employs the latter method is referred to as a partial re-liquefaction system (PRS).

  Further, among engines generally used in ships, engines that can use natural gas as fuel include gas fuel engines such as DFDE, X-DF engine, and ME-GI engine.

  The DFDE is a four-stroke engine and employs an Otto cycle in which natural gas having a relatively low pressure of about 6.5 bar is injected into the combustion air inlet and the piston is compressed while rising.

  The X-DF engine is a two-stroke engine that uses natural gas of about 16 bar as fuel and adopts the Otto cycle.

  The ME-GI engine is a two-stroke engine and employs a diesel cycle in which high-pressure natural gas of about 300 bar is directly injected into the combustion chamber near the top dead center of the piston.

  The present invention provides an evaporative gas reliquefaction method and system for an LNG ship that can stabilize the reliquefaction performance and increase the efficiency and amount of reliquefaction.

  In order to achieve the above object, in the embodiment of the present invention, 1) a step of compressing the evaporative gas; 2) using the evaporative gas as a refrigerant, the evaporative gas compressed in the step 1) is heat-exchanged by a heat exchanger and cooled. 3) a step of expanding the fluid cooled in the step 2); and 4) even if the flow rate of the reliquefied evaporative gas supplied to the heat exchanger after the compression in the step 1) fluctuates. And the step of stably maintaining the reliquefaction performance, and the amount of the evaporated gas reliquefied through the steps 1) to 3) is maintained at 50% or more of the value calculated by HYSYS. A gas reliquefaction method is provided.

  The LNG ship evaporative gas reliquefaction method may further include 5) gas-liquid separation of the fluid expanded in step 3).

  The gas component separated in the gas-liquid step in the step 5) is combined with the evaporating gas and used as a heat exchange refrigerant in the step 2).

  In the evaporative gas reliquefaction method of the LNG ship, the operation speed of the LNG ship is 10 to 17 knots.

  Part of the evaporative gas compressed in step 1) is used as engine fuel, and the flow rate of evaporative gas used as the engine fuel is 1,100 to 2,660 kg / h.

  The engine includes a propulsion engine and a power generation engine.

  The LNG ship evaporative gas reliquefaction method is characterized in that a flow rate of the reliquefied evaporative gas is 1,900 to 3,300 kg / h.

  In the evaporative gas reliquefaction method of the LNG ship, the flow rate ratio of the evaporative gas to be reliquefied is 0.42 to 0.72 based on the flow rate of the evaporative gas used as the heat exchange refrigerant in the step 2). It is the range of these.

  Of the evaporated gas compressed in the step 1), the evaporated gas not sent to the engine is further compressed and then sent to the heat exchanger.

  In order to achieve the above object, in another embodiment of the present invention, 1) a step of compressing the evaporative gas; 2) a step of cooling the evaporative gas compressed in the step 1) by heat exchange using the evaporative gas as a refrigerant; 3) The step of expanding the fluid cooled in the step 2); and 4) The liquefaction performance is stably maintained even when the flow rate of the evaporative gas used as the heat exchange refrigerant in the step 2) fluctuates. An LNG ship evaporative gas reliquefaction method in which the amount of evaporative gas reliquefied through steps 1) to 3) is maintained at 50% or more of the value calculated by HYSYS.

  The evaporative gas reliquefaction method of the LNG ship further includes 5) a step of gas-liquid separation of the fluid expanded in step 3), and the gas component separated in the step 5) joins the evaporative gas. And used as a heat exchange refrigerant in step 2).

  In order to achieve the above object, in another embodiment of the present invention, the evaporative gas discharged from the storage tank is compressed at a high pressure, and all or a part of the high-pressure compressed evaporative gas is discharged from the storage tank; In a method for reliquefying an evaporative gas of an LNG ship equipped with a high-pressure gas injection engine, the method further comprises: changing the operating conditions of the LNG ship, re-exchanging the heat-exchanged high-pressure compressed evaporative gas in the heat exchanger; A high pressure gas injection engine that includes a step of stably maintaining the reliquefaction performance even when the flow rate of the liquefied target evaporative gas varies, and the amount of the reliquefied evaporative gas is maintained at 50% or more of the value calculated by HYSYS An LNG ship evaporative gas reliquefaction method is provided.

  The high-pressure compressed evaporative gas is in a supercritical state.

  The pressure of the high-pressure compressed evaporative gas is 100 to 400 bara.

  The pressure of the high-pressure compressed evaporative gas is 150 to 400 bara.

  The pressure of the high-pressure compressed evaporative gas is 150 to 300 bara.

  The present invention stably maintains the reliquefaction performance even if the flow rate of the reliquefied evaporation gas changes.

  In one embodiment of the present invention, the fluid supplied to the heat exchanger or the fluid discharged from the heat exchanger is dispersed to alleviate the phenomenon that the refrigerant concentrates on a specific block.

  In one embodiment of the present invention, the refrigerant is evenly distributed not only between a plurality of blocks but also within each block, and the separation between the porous plate and the core can be maintained. In particular, the perforated plate and the core are in contact with each other, and the flow path is blocked to prevent the fluid from flowing into the core.

  In one embodiment of the present invention, the perforated plate is combined with a heat exchanger so that thermal expansion and contraction can be eliminated. To prevent damage to the connecting parts.

  In one embodiment of the present invention, since the heat exchanger includes a channel shaped to resist the fluid, the phenomenon that the refrigerant concentrates on a specific block can be alleviated without adding another member that disperses the fluid. To prevent.

It is a figure which shows the basic model for demonstrating the concept of the evaporative gas reliquefaction which concerns on one Embodiment of this invention. In the evaporative gas reliquefaction system according to an embodiment of the present invention, each heat of the high temperature fluid and the low temperature fluid when the pressure of the revaporization target evaporative gas is each pressure of 10 bara in the range of 39 bara and 50 bara to 120 bara. It is the graph which showed the temperature change by flow volume. In the evaporative gas reliquefaction system according to the embodiment of the present invention, each pressure of 10 bara in the range of 130 bara to 200 bara, and each of the high temperature fluid and the low temperature fluid when the pressure of the evaporative gas to be reliquefied is 300 bara. It is the graph which showed the temperature change by a heat flow rate. It is the schematic of the evaporative gas reliquefaction system which concerns on one Embodiment of this invention in case the pressure of revaporization object evaporative gas is 39 bara. It is the schematic of the evaporative gas reliquefaction system which concerns on one Embodiment of this invention in case the pressure of evaporative gas for reliquefaction is 150 bara. It is the schematic of the evaporative gas reliquefaction system which concerns on one Embodiment of this invention in case the pressure of evaporative gas for reliquefaction is 300 bara. It is the graph which showed the "reliquefaction amount" of Table 1 in the pressure range of 39 bara-300 bara. It is the graph which showed the "reliquefaction amount" of Table 1 in the pressure range of 39 bara-300 bara. It is the schematic of conventional PCHE. It is the schematic of the heat exchanger which concerns on 1st Embodiment of this invention. It is the schematic of the 1st partition or the 2nd partition with which the heat exchanger concerning a 2nd embodiment of the present invention is provided. It is the schematic of the 1st partition and 1st perforated plate with which the heat exchanger which concerns on 2nd Embodiment of this invention is provided. It is the schematic of the 2nd partition and 2nd perforated panel with which the heat exchanger which concerns on 2nd Embodiment of this invention is provided. It is the schematic of the 3rd partition or the 4th partition with which the heat exchanger which concerns on 2nd Embodiment of this invention is provided. It is the schematic of the 3rd partition and the 3rd perforated panel with which the heat exchanger concerning a 2nd embodiment of the present invention is provided. It is the schematic of the 4th partition and the 4th perforated panel with which the heat exchanger concerning a 2nd embodiment of the present invention is provided. (A) is the schematic which showed the flow of the refrigerant | coolant of the conventional heat exchanger. (B) is the schematic which showed the flow of the refrigerant | coolant of the heat exchanger which concerns on preferable 1st Embodiment of this invention. (C) is the schematic which showed the flow of the refrigerant | coolant of the heat exchanger which concerns on preferable 2nd Embodiment of this invention. (A) is the schematic which showed the position of the temperature sensor installed in order to measure the internal temperature of a heat exchanger. (B) is the graph which showed the temperature distribution inside the heat exchanger which the temperature sensor measured in the position illustrated in (a), respectively. It is the schematic which shows a part of heat exchanger which concerns on preferable 3rd Embodiment of this invention. It is the schematic which expanded the A part of FIG. It is the schematic which shows a part of heat exchanger which concerns on preferable 4th Embodiment of this invention. It is the schematic which expanded the B section of FIG. (A) is the schematic of the whole shape of a heat exchanger. (B) is a schematic diagram of a block. (C) is a schematic view of a channel plate. (A) is the schematic of a mode that the channel plate for low-temperature fluids illustrated in FIG.23 (c) was seen from C direction. (B) is the schematic of the channel of the channel plate for the cryogenic fluid of the conventional heat exchanger. (C) is the schematic of the channel of the channel plate for the cryogenic fluid of the heat exchanger which concerns on preferable 5th Embodiment of this invention. (D) is the schematic of the channel of the channel plate for the cryogenic fluid of the heat exchanger which concerns on preferable 6th Embodiment of this invention.

  Hereinafter, the configuration and operation of an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The present invention can be applied to various applications and applications such as a ship equipped with an engine using natural gas as a fuel and a ship equipped with a liquefied gas storage tank. The following embodiments can be modified in various other forms, and the scope of the present invention is not limited to the following embodiments.

  The evaporative gas treatment system of the present invention to be described later includes all kinds of ships and offshore structures equipped with storage tanks for storing low-temperature liquid cargo or liquefied gas, such as LNG carrier, liquefied ethane gas carrier (Liquid Ethane carrier). It can be applied to marine structures such as LNG FPSO and LNG FSRU, as well as ships such as Gas Carrier) and LNG RV. However, in the embodiment described later, for the sake of convenience of explanation, liquefied natural gas that is a typical low-temperature liquid cargo will be described as an example, and the LNG ship is a concept including an LNG carrier ship, LNG RV, LNG FPSO, LNG FSRU, and the like. .

  The fluid in each line of the present invention is in a liquid state, a gas-liquid mixed state, a gas state, or a supercritical fluid state, depending on the operating conditions of the system.

  FIG. 1 shows a basic model for explaining the concept of evaporative gas reliquefaction according to an embodiment of the present invention.

  Referring to FIG. 1, in the present invention, evaporative gas (1) discharged from a storage tank is sent to a heat exchanger and used as a refrigerant, and then compressed by a compressor. The evaporative gas compressed by the compressor is used as fuel for an engine. (2), surplus evaporative gas (3) surpassing the required amount of the engine is sent to the heat exchanger, and evaporative gas (1) discharged from the storage tank is heat-exchanged as a refrigerant for cooling. .

  The re-liquefied evaporative gas that has been compressed by the compressor and then cooled by the heat exchanger passes through a decompression means (for example, an expansion valve or an expander), and then is separated into a liquid component and a gas component by a gas-liquid separator. . The liquid component separated by the gas-liquid separator is returned to the storage tank, and the gas component separated by the gas-liquid separator merges with the evaporated gas (1) discharged from the storage tank and is supplied to the heat exchanger again as a refrigerant. Is done.

  The invention is characterized in that, instead of using another additional cycle to reliquefy the evaporative gas, the evaporative gas discharged from the storage tank itself is used as a refrigerant to reliquefy the evaporative gas. A separate refrigeration cycle can be provided to ensure re-liquefaction of all evaporated gas as required. The provision of a separate cycle is disadvantageous in that it requires additional equipment and additional power, but re-liquefaction of almost the entire amount of evaporative gas is guaranteed.

  The reliquefaction performance of a system that reliquefies evaporative gas using the evaporative gas itself as a refrigerant as in the present invention is greatly dependent on the pressure of the reliquefied evaporative gas (hereinafter referred to as “reliquefied target evaporative gas”). The results of an experiment (hereinafter referred to as “Experiment 1”) for examining the reliquefaction performance by the pressure of the reliquefied target evaporating gas are as follows.

(Experiment 1)
The conditions of the reliquefaction performance evaluation experiment by the pressure of the reliquefied target evaporating gas are as follows.

  1. Target ship: An LPG carrier equipped with a high-pressure gas injection engine that is a propulsion engine and a low-pressure engine that is a power generation engine.

  2. Process calculation program: Aspen HYSYS V8.0

  3. Formulas for calculating physical properties: Peng-Robinson equation

  4). Amount of evaporation gas: Since an evaporation gas of about 3,500 kg / h to 4,000 kg / h is generated in a 170,000 CBM (cubic meter) class LPG carrier, 3,800 kg / h is applied in this experiment.

5. Evaporative gas components: A composition of 10% nitrogen (N ₂ ) and 90% methane (CH ₄ ) is applied to both the evaporated gas discharged from the storage tank and the evaporated gas compressed by the compressor.

  6). Temperature and pressure of the evaporative gas discharged from the storage tank: a pressure of 1.06 bara and a temperature of −120 ° C. are applied.

  7). Engine fuel consumption: In actual ship operation, considering the economy, the engine is operated at a low load. In this experiment, the total amount of evaporative gas used in the propulsion engine and the power generation engine is Assume 2,660 kg / h, which is 70% of the evaporative gas (3,800 kg / h) generated in the storage tank.

  8). Compressor capacity: The normal compressor capacity does not exceed 150% of the evaporation gas generated in the storage tank, but in this calculation, 120% of the evaporation gas generated in the storage tank (based on the suction flow rate of the compressor) 3,800 kg / h × 120% = 4,650 kg / h) is applied.

  9. Performance of heat exchanger: logarithmic mean temperature difference (LMTD) 13 ° C or higher, minimum square method (Minimum Approach) 3 ° C or higher is applied.

  When designing a heat exchanger, the temperature and heat flow of the low-temperature fluid and the high-temperature fluid flowing into the heat exchanger are fixed, and the temperature of the fluid used as the refrigerant should not be higher than the temperature of the cooling fluid. In other words, a logarithmic mean temperature difference (LMTD) is made as small as possible (so that the graph of the temperature by heat flow does not intersect the graph of the cold fluid and the graph of the hot fluid).

  The logarithm mean temperature difference (LMTD) is the temperature before the low temperature fluid passes through the heat exchanger when the high temperature fluid and the low temperature fluid are in opposite directions of the heat exchange system in which the high temperature fluid and the low temperature fluid are injected from opposite directions and discharged to the opposite side. Tc1, the temperature after the low temperature fluid passes through the heat exchanger, tc2, the temperature before the high temperature fluid passes through the heat exchanger, th1, the temperature after the high temperature fluid passes through the heat exchanger, th2, d1 = Assuming that th2−tc1 and d2 = th1−tc2, this is a numerical value expressed by (d2−d1) / ln (d2 / d1), and the efficiency of the heat exchanger increases as the logarithmic average temperature difference decreases. .

  The logarithm mean temperature difference (LMTD) in the graph showing the temperature by heat flow is expressed by the interval between the low-temperature fluid used as the refrigerant and the high-temperature fluid that is cooled by heat exchange with the refrigerant, and the interval between the low-temperature fluid and the high-temperature fluid is narrow. This means that the logarithm average temperature difference (LMTD) is small, and a low logarithm average temperature difference (LMTD) means that the efficiency of the heat exchanger is high.

  The thermodynamic calculation of the experimental conditions 1 to 9 was performed in order to quantitatively present the influence of high pressure compression of the reliquefied evaporation gas on the reliquefaction performance. In order to verify the characteristics of the reliquefaction performance by the pressure of the evaporating gas and the cooling curve of the heat exchanger, the pressure of the evaporating gas to be reliquefied is 39 bar, 50 bara to 200 bara, each 10 bara pressure, 250 bara and 300 bara. The reliquefaction amount for each pressure and the cooling curve of the heat exchanger were calculated thermodynamically.

  FIG. 2 is a schematic view of the evaporative gas reliquefaction system according to an embodiment of the present invention, in which the high temperature fluid and the low temperature fluid when the pressure of the revaporization target evaporative gas is 39 bara or 10 bara in a range of 50 bara to 120 bara. It is the graph which showed the temperature change by each heat flow. FIG. 3 is a schematic diagram of the evaporative gas reliquefaction system according to an embodiment of the present invention. It is the graph which showed the temperature change by each heat flow rate.

  FIG. 4 is a schematic diagram of an evaporative gas reliquefaction system according to an embodiment of the present invention when the pressure of the reliquefied evaporative gas is 39 bara. FIG. 5 is a schematic diagram of an evaporative gas reliquefaction system according to an embodiment of the present invention when the pressure of the reliquefied target evaporative gas is 150 bara. FIG. 6 is a schematic diagram of an evaporative gas reliquefaction system according to an embodiment of the present invention when the pressure of the reliquefied evaporative gas is 300 bara.

  Table 1 shows the calculated value of the reliquefaction performance depending on the pressure of the reliquefied target evaporative gas in the evaporative gas reliquefaction system according to the embodiment of the present invention.

  7 and 8 are graphs showing the “reliquefaction amount” in Table 1 in a pressure range of 39 bara to 300 bara.

  As a result of referring to FIGS. 2 to 8 and Table 1, in the cooling curve of the evaporative gas to be reliquefied, even if the compression pressure of the evaporative gas is in the supercritical state, it is 39 bara in the range of 50 bara to 100 bara. It was confirmed that the horizontal section such as the latent heat section that was observed was gradually decreasing, and the maximum liquefaction amount (cooling temperature before expansion—122.4 ° C., reliquefaction amount 1,174. 6 kg / h, a relative ratio of reliquefaction amount of 208.4%) was confirmed.

  The largest difference between the case where the reliquefied evaporation gas is low pressure and high pressure is the cooling temperature before expansion. As can be seen from FIG. 8, due to the difference in the cooling curve due to pressure, in the case of low pressure, a limit occurs in the cooling temperature before expansion and the cooling temperature cannot be lowered significantly, whereas in the case of high pressure Cooling is possible to near the temperature of the evaporated gas discharged from the storage tank.

This difference is due to the characteristics of the physical properties of methane (methane, CH ₄ ), which is the main component of the evaporative gas. It can be seen that there is a section similar to the latent heat section, but it is decreasing. Therefore, from the viewpoint of the amount of reliquefaction, when revaporizing the evaporation gas, it is preferable to carry out at a critical pressure of 47 bara or higher.

  On the other hand, the ME-GI engine has a fuel gas supply pressure in the range of 150 bara to 400 bara (mainly operated at 300 bara), but as shown in FIG. When re-liquefying evaporative gas while supplying fuel to the ME-GI engine, the re-liquefaction amount shows the maximum value in the vicinity of 170 bara and there is almost no change in the liquefaction amount between 150 and 300 bara. Has the advantage of easy reliquefaction and control of fuel supply.

  The “reliquefaction amount” in Table 1 was separated by the gas-liquid separator (40) after passing through the compressor (10), the heat exchanger (20), and the decompression device (30) in FIGS. Indicates the flow rate of the liquefied liquefied natural gas, and the “relative ratio of the liquefied amount” indicates the relative ratio (% ).

  On the other hand, it is also possible to indicate the reliquefaction performance by the “reliquefaction rate”, and the reliquefaction rate indicates a value obtained by dividing the flow rate of the reliquefied liquefied natural gas by the flow rate of the entire reliquefied evaporation gas. That is, “reliquefaction amount” represents the absolute amount of liquefied liquefied natural gas, and “reliquefaction rate” represents the proportion of liquefied natural gas that has been reliquefied out of the entire reliquefied evaporation gas.

  As an example, when the speed of the ship is low and the amount of evaporative gas used in the propulsion engine decreases, the amount of evaporative gas to be reliquefied increases and the “reliquefaction amount” also increases. However, under the conditions of Experiment 1, the total of the gas components separated by the gas-liquid separator and the evaporated gas discharged from the storage tank, which is the fluid used as the refrigerant, is almost constant due to the capacity limit of the compressor. The “reliquefaction rate” decreases.

  In the experiment 1, the flow rate of the refrigerant flowing into the compressor is 4,560 kg / h, which is 120% of the 3,800 kg / h of the evaporating gas generated in the storage tank. Among these, the engine usage amount is 2,660 kg. 1,900 kg / h excluding / h (ME-GI engine 2,042 kg / h + DFDG 618 kg / h) is the reliquefied target evaporating gas.

  Even when the experiment was carried out by increasing the pressure of the re-liquefied evaporation gas to 400 bara, there was no significant difference from the case of 300 bara, and the difference in reliquefaction flow rate between 150 bara and 400 bara was within 4%.

  On the other hand, in each graph of FIG.2 and FIG.3, the high temperature fluid displayed with the broken line (upper) means the re-liquefied evaporation gas, and the low temperature fluid displayed with the solid line (lower) is the evaporation discharged from the storage tank. It means gas, that is, refrigerant.

  In each graph of FIG. 2 and FIG. 3, the straight section where the heat flow changes but the temperature does not change is the latent heat section, and methane is a supercritical fluid and has no latent heat section, so it is a supercritical fluid. The amount of reliquefaction varies greatly depending on whether or not That is, when the reliquefied target evaporating gas is a supercritical fluid, there is no latent heat section at the time of heat exchange, so the reliquefaction flow rate and reliquefaction rate are increased.

  Summarizing the above results, the reliquefaction performance is high when the reliquefied evaporation gas is in a supercritical state, particularly in the range of 100 bara to 400 bara, preferably in the range of 150 bara to 400 bara, more preferably in the range of 150 bara to 300 bara. Reliquefaction performance was high in the range.

  Considering that the required pressure of the ME-GI engine is 150 bara to 400 bara, the reliquefaction performance is high when the evaporated gas compressed to satisfy the required pressure of the ME-GI engine is used as the reliquefied target evaporative gas as it is. Therefore, it can be confirmed that there is a very advantageous advantage when the system for supplying fuel to the ME-GI engine and the evaporative gas reliquefaction system using the evaporative gas itself as a refrigerant are linked.

  On the other hand, in Experiment 1 described above, the reliquefaction performance due to the pressure of the reliquefied target evaporative gas was evaluated by a simulation program, and then whether this result shows the same result in an actual reliquefaction apparatus using a heat exchanger? In order to investigate whether or not, an experiment (hereinafter, referred to as “Experiment 2”) was performed using PCHE (Printed Circuit Heat Exchanger).

(Experiment 2)
Under actual operating conditions, the amount of evaporative gas generated is constant, but the amount of evaporative gas used in the engine changes, so the flow rate of the remaining reliquefied evaporative gas that is not used in the engine changes. Therefore, in Experiment 2, the reliquefaction performance of the actual reliquefaction apparatus was evaluated while changing the flow rate of the reliquefaction target evaporative gas. For convenience of experiment, instead of explosive methane, nitrogen, which is generally used, is used as a refrigerant, and the temperature of the nitrogen used is adjusted in the same manner as the evaporative gas discharged from the storage tank, and other conditions Was also adjusted in the same manner as the conditions 1 to 9 in Experiment 1.

  Moreover, since the fuel consumption of the ME-GI engine used according to the operating conditions changes, the experiment was conducted assuming an actual LNG carrier. Assuming that the size of the ME-GI engine of the LNG carrier is 25 MW (12.5 MW, 2 aircraft) under the conditions of Experiment 1 above, it is about 19.5 knots (the fuel consumption of the engine is It can be operated at about 3,800 kg / h), and if operated at an economic speed, it will operate at about 17 knots (engine fuel consumption is about 2,660 kg / h). Therefore, considering the actual operating conditions, the maximum operating speed is 19.5 knots, the economic operating speed is 17 knots, and the berthing state (ME-GI engine fuel consumption 0, DFDG fuel consumption 618 kg / h) It becomes operational conditions. In Experiment 2, each reliquefaction performance was tested under these conditions.

  When nitrogen was used as the refrigerant and the reliquefication target evaporative gas, it was confirmed that the reliquefaction performance was almost the same level as the calculated value of Experiment 1 regardless of the flow rate of the reliquefaction target evaporative gas. That is, the amount of evaporative gas consumed by the propulsion engine varies depending on the operating speed of the LNG carrier, so the flow rate of the evaporative gas subject to reliquefaction also changes. However, when nitrogen is used as the refrigerant and the evaporative gas subject to reliquefaction, Regardless of the flow rate of the target evaporative gas, the reliquefaction performance was stably maintained.

  However, in an actual evaporative gas reliquefaction system, when methane (that is, evaporative gas generated in an actual storage tank) is applied to the refrigerant and evaporative gas to be reliquefied instead of nitrogen, the LNG carrier is In the vicinity of the maximum operation speed (most evaporative gas generated in the LNG storage tank may be used as fuel under the conditions of the maximum operation speed), the reliquefaction performance is almost the same as the calculated value in Experiment 1 above. When operating a ship at 70% of the fuel consumption of the maximum operating speed, which is the economic operating speed, and when operating a ship at a lower speed, the reliquefaction performance will be 70% or less of the theoretical expected value. It was confirmed that the reliquefaction performance was lower depending on the operation speed section. That is, when methane (that is, evaporation gas generated in an actual storage tank) is used instead of nitrogen as the refrigerant and reliquefaction target evaporation gas, the reliquefaction performance is theoretically determined by the flow rate of the reliquefaction target evaporation gas. There was an interval that did not reach the calculated value.

  Specifically, an example of a section where the reliquefaction performance of the actual evaporative gas reliquefaction system does not reach the theoretical calculation value is as follows.

  An LNG carrier using a 1.25 MW ME-GI engine operates at a speed of 10 to 17 knots.

  2. The flow rate of evaporative gas generated in the storage tank is 3,800 kg / h, and the flow rate of evaporative gas used as fuel in the engine (ME-GI engine for propulsion engine + DFDG for power generation engine) is 1,100 to When it is 2,660 kg / h.

  3. When the flow rate of the evaporative gas generated in the storage tank is 3,800 kg / h and the flow rate of the reliquefied evaporative gas is 1,900-3,300 kg / h.

  4). The ratio of the flow rate of the re-liquefied evaporative gas to the flow rate of the evaporating gas (including the gas component separated by the gas-liquid separator) used as the refrigerant is in the range of 0.42 to 0.72.

  Since there is a large difference between the reliquefaction amount actually measured and the theoretical calculation value depending on the ship operating conditions or the flow rate of the evaporative gas to be reliquefied, it is necessary to solve this problem. If the re-liquefaction performance becomes low and the amount of evaporative gas that is not re-liquefied increases, there is a problem that additional measures such as waste of energy due to external discharge of evaporative gas and combustion, and re-liquefaction by another re-liquefaction cycle are required. Thus, unlike nitrogen, the reliquefaction performance of evaporative gas is significantly different from the theoretically expected value because of the difference in the physical property values of nitrogen and evaporative gas.

  From the above results, it can be seen that even if the operating conditions of the LNG carrier change, that is, even if the flow rate of the reliquefied evaporative gas fluctuates, a step for stably maintaining the reliquefaction performance is necessary.

  Therefore, in the embodiment of the present invention, the step of compressing the evaporative gas discharged from the storage tank at high pressure, branching all or part of the high-pressure compressed evaporative gas and exchanging heat with the evaporated gas discharged from the storage tank, In the LNG ship evaporative gas reliquefaction method including the step of decompressing the heat exchanged high pressure compressed evaporative gas, the operating condition of the LNG ship is changed or the flow rate of the reliquefied evaporative gas is changed. The present invention also provides a method for re-liquefying an evaporative gas of an LNG ship equipped with a high-pressure gas injection engine, the method including a step of stably maintaining re-liquefaction performance.

  In addition, when the engine mounted on the LNG ship uses a relatively low-pressure evaporative gas such as an X-DF engine as a fuel instead of a high-pressure gas injection engine, the engine is compressed to be supplied as fuel for the low-pressure engine. The present invention has an advantage in the case of re-liquefaction after further pressurizing excess evaporative gas passing through the re-liquefaction process.

  In the reliquefaction method, the LNG ship operates at a speed of 10 to 17 knots, and the flow rate of evaporative gas used as fuel for the engine (propulsion engine + power generation engine) is 1,100 to 2,660 kg / h. That is, the reliquefaction target evaporative gas flow rate is 1,900-3,300 kg / h, or the reliquefaction target with respect to the evaporative gas flow rate (including gas components separated by the gas-liquid separator) used as the refrigerant. The ratio of the flow rate of the evaporation gas is in the range of 0.42 to 0.72.

  The step of stably maintaining the reliquefaction performance is that the reliquefaction performance is stably maintained when the specific heat ratio of the heat exchanger is in the range of 0.7 to 1.2. It is characterized by.

The specific heat ratio is CR, the flow rate of the high temperature fluid (evaporation gas to be reliquefied in the present invention) is m1, the specific heat of the high temperature fluid is c1, the flow rate of the low temperature fluid (evaporation gas used as a refrigerant in the present invention) is m2, and the flow rate of the low temperature fluid When the specific heat is c2, the following formula (1) is satisfied.
CR = (m1 × c1) / (m2 × c2) (1)

  In Experiment 2, when the amount of evaporating gas (including gas components generated in the gas-liquid separator) used as the refrigerant is kept constant and the amount of evaporating gas to be reliquefied changes, that is, 1) m2 was kept constant, and it was confirmed that the reliquefaction performance did not reach the calculated value when m1 changed. Not only that, but evaporative gas used as refrigerant (generated in gas-liquid separator) It was confirmed that the reliquefaction performance did not reach the calculated value even if the amount of gas component was changed), that is, even if m2 was changed in the equation (1).

  Therefore, the step of stably maintaining the reliquefaction performance of the present invention includes the amount of evaporating gas used as a refrigerant (including gas components generated in the gas-liquid separator) and the amount of evaporating gas to be reliquefied. When any one or more fluctuates, the reliquefaction performance is stably maintained even when the specific heat ratio of the heat exchanger is in the range of 0.7 to 1.2.

  The step of stably maintaining the reliquefaction performance is characterized in that the reliquefaction amount under the calculation condition of Experiment 1 is maintained at 50% or more of the calculated value. Preferably, the calculated value is maintained at 60%, more preferably 70% or more. When the amount of reliquefaction is 50% or less of the calculated value, there is a problem in that excess evaporative gas must be burned and discarded by a gas combustion unit (GCU) depending on the operating conditions during operation of the LNG carrier.

  From the above results, it can be seen that even if the operating conditions of the LNG carrier change, that is, even if the flow rate of the reliquefied evaporative gas fluctuates, a step for stably maintaining the reliquefaction performance is necessary.

  In addition, it has been found that one of the reasons why the reliquefaction performance has a large difference from the theoretically expected value is due to a heat exchanger in which two or more blocks are combined.

  The heat exchanger applied to the actual LNG evaporative gas reliquefaction system is PCHE, which is advantageous when the evaporative gas to be reliquefied is high pressure, manufactured by KOBELCO, ALfa Laval, Heatlic, etc. There is a limit in one block due to processing capacity, and it is necessary to use two or more blocks in combination.

  When the evaporative gas treatment capacity when two or more blocks need to be used in combination is “A or more and B or less”, A is 1,500 kg / h, 2,000 kg / h, 2, It may be any one of 500 kg / h, 3,000 kg / h, and 3,500 kg / h, and B is any one of 7,000 kg / h, 6,000 kg / h, and 5,000 kg / h. Sometimes it is. As an example, the evaporative gas treatment capacity when two or more blocks need to be used in combination may be 2,500 kg / h or more and 5,000 kg / h or less.

  FIG. 10 is a schematic view of a conventional PCHE.

  Referring to FIG. 10, a conventional PCHE includes a hot fluid inlet pipe (Hot Gas Inlet Pipe, 110), a hot fluid inlet head (Hot Gas Inlet Header, 120), a core (Core, 190), a hot fluid outlet head (Hot). Gas Outlet Header, 130), High Temperature Fluid Discharge Pipe (Hot Gas Outlet Pipe, 140), Low Temperature Fluid Inflow Pipe (Cold Gas Inlet Pipe, 150), Low Temperature Fluid Inflow Head (Cold Gas Inlet Header, 160), Low Temperature Fluid Discharge Head (Cold Gas Outlet Header, 170), and a cold fluid outlet pipe (Cold Gas Outlet Pipe, 180).

  The hot fluid supplied to the heat exchanger flows into the heat exchanger through the hot fluid inflow pipe (110), and then is dispersed by the hot fluid inflow head (120) and sent to the core (190). The high-temperature fluid sent to the core (190) is cooled by exchanging heat with the low-temperature fluid in the core (190), and then accumulated in the high-temperature fluid discharge head (130) to be heated through the high-temperature fluid discharge pipe (140). It is discharged outside the exchanger.

  The cryogenic fluid supplied to the heat exchanger flows into the heat exchanger through the cryogenic fluid inflow pipe (150), and then is dispersed by the cryogenic fluid inflow head (160) and sent to the core (190). The low-temperature fluid sent to the core (190) is used as a heat exchange refrigerant for cooling the high-temperature fluid in the core (190), and then is accumulated in the low-temperature fluid discharge head (170) to be connected to the low-temperature fluid discharge pipe (180). And discharged to the outside of the heat exchanger.

  The low-temperature fluid used as the refrigerant of the heat exchanger in the present invention is evaporative gas (including gas components separated by the gas-liquid separator) discharged from the storage tank, and the high-temperature fluid cooled by the heat exchanger is Compressed re-liquefied evaporation gas.

  On the other hand, the core (190) can include a plurality of blocks (FIG. 9 illustrates a case where three blocks are provided. Hereinafter, a case where the core of the heat exchanger includes three blocks will be described in the present specification. However, when the core of the heat exchanger includes two or more blocks, a space exists between the blocks, and the air existing in the space between the blocks serves as a heat insulating layer. The thermal conductivity between the blocks will decrease.

  Referring to the graph of FIG. 18B described later, it can be confirmed that the temperature distribution between the blocks is non-uniform due to the heat insulating layer or the heat insulating portion (gap, barrier air, etc.) between the blocks.

  In addition, when evaporating gas is used as a refrigerant, if the refrigerant flows into a specific block first, a phenomenon occurs in which the refrigerant supplied later is biased to the block into which the refrigerant has flowed first, and the refrigerant has flowed first. The temperature of the block is lower than the temperature of the other blocks.

  If the phenomenon in which the refrigerant is biased to the block into which the refrigerant has previously flown overlaps with the phenomenon in which the thermal conductivity between the blocks decreases, the temperature difference between the blocks increases, and eventually the reliquefaction performance decreases. That is, even if the refrigerant is biased to a specific block, if the thermal conductivity between the blocks is high, the temperature difference between the blocks will not increase, but if the air between the blocks acts as a heat insulating layer, the temperature difference between the blocks will be large. Become.

  FIG. 10 is a schematic view of the heat exchanger according to the first embodiment of the present invention.

  Referring to FIG. 10, the heat exchanger of the present embodiment has a first PC installed between the high-temperature fluid inflow head (120) and the core (190) in addition to the configuration of the conventional PCHE illustrated in FIG. 9. Perforated plate (210), second perforated plate (220) installed between high temperature fluid discharge head (130) and core (190), installed between low temperature fluid inflow head (160) and core (190) And at least one of a third perforated plate (230) and a fourth perforated plate (240) installed between the cryogenic fluid discharge head (170) and the core (190).

  The heat exchanger according to this embodiment includes means for dispersing fluid supplied to or discharged from the heat exchanger, and uses means for imparting resistance to the flow of fluid to disperse the fluid. can do. The porous plate (210, 220, 230, 240) of this embodiment is an example of a means for dispersing fluid or a means for imparting resistance to the flow of fluid, and the heat exchanger of this embodiment is limited to including a porous plate. Not.

  The perforated plates (210, 220, 230, 240) of the present embodiment are thin plate members in which a plurality of holes are formed, and the first perforated plate (210) is the same size as the cross section of the high-temperature fluid inflow head (120). The second perforated plate (220) preferably has the same size and shape as the cross section of the high temperature fluid discharge head (130), and the third perforated plate (230) has a low temperature fluid inflow head (160). ) And the fourth perforated plate (240) preferably has the same size and shape as the cross section of the cryogenic fluid discharge head (170).

  The plurality of holes formed in the perforated plates (210, 220, 230, 240) of the present embodiment may have the same cross-sectional area, and pipes (110, 140, 150, 180) in the vicinity of the cross-sectional area is narrow, and it is possible to form a hole having a wider cross-sectional area as the distance from the pipe (110, 140, 150, 180) increases.

  The plurality of holes formed in the perforated plates (210, 220, 230, 240) of the present embodiment may have a uniform formation density, and pipes (110, 140) through which fluid flows in or out are provided. , 150, 180), the formation density is low, and the formation density can be increased as the distance from the pipe (110, 140, 150, 180) increases. A low formation density means that fewer holes are formed in the same area, and a high formation density means that more holes are formed in the same area.

  Further, in the porous plate (210, 220, 230, 240) of the present embodiment, the fluid that has passed through the first porous plate (210) and the third porous plate (230) is effectively dispersed in the core (190). A predetermined distance from the core (190) so that the fluid discharged from the core (190) can be effectively dispersed and pass through the second perforated plate (220) and the fourth perforated plate (240). It is preferable that they are installed apart from each other. The distance between the perforated plates (210, 220, 230, 240) and the core (190) is, for example, about 20 to 50 mm.

  In the heat exchanger of the present embodiment, the fluid is dispersed by at least one of the first to fourth perforated plates (210, 220, 230, 240), so that the phenomenon that the refrigerant is biased to a specific block is alleviated.

  The heat exchanger according to the second embodiment of the present invention is provided with the heat exchanger according to the first embodiment illustrated in FIG. 10, and between the first perforated plate (210) and the core (190). The first partition (310) installed, the second partition (320) installed between the core (190) and the second porous plate (220), the third porous plate (230) and the core (190) A third partition wall (330) disposed between the cores (190) and the fourth porous plate (240) is provided.

  FIG. 11 is a schematic view of the first partition or the second partition provided in the heat exchanger according to the second embodiment of the present invention. FIG. 12 is a schematic view of the first partition and the first perforated plate included in the heat exchanger according to the second embodiment of the present invention. FIG. 13 is a schematic view of the second partition and the second perforated plate provided in the heat exchanger according to the second embodiment of the present invention.

  The first to fourth partition walls (310, 320, 330, 340) of the present embodiment prevent the fluid dispersed by the first to fourth perforated plates (210, 220, 230, 240) from collecting again. .

  Referring to FIGS. 11 and 12, the first partition (310) of the present embodiment surrounds the peripheral edge of the first perforated plate (210) at a predetermined height, and divides the enclosed internal space into a plurality of regions. Shape. 11 (a) and 12 (a) show a shape in which the internal space surrounding the peripheral portion of the first perforated plate (210) at a predetermined height is divided into four parts, and FIG. 11 (b). FIG. 12B shows a shape divided into eight pieces.

  11 (b) and 12 (b), the first partition wall (310) has an internal space surrounding the periphery of the first perforated plate (210) at a predetermined height, as shown in FIG. 11 (a) and FIG. As shown in FIG. 12 (a), not only the lattice in one direction is divided but also the lattice in the other direction is divided. That is, in the first partition wall (310) shown in FIGS. 11 (a) and 12 (a), the member that divides the inner space by surrounding the periphery of the first perforated plate (210) at a predetermined height is vertical. If it is a member (1), the 1st partition (310) illustrated in FIG.11 (b) and FIG.12 (b) is not only several vertical members (1) but each vertical member (1). The horizontal space (2) which divides | segments the space between is provided, the grating | lattice of one direction and the grating | lattice of another direction cross | intersect mutually, and divide | segment an interior space.

  As shown in FIG. 11 (b) and FIG. 12 (b), when the internal space of the first perforated plate (210) is further divided in the other direction, the fluid can be more dispersed, especially between a plurality of blocks. In addition, the refrigerant is prevented from collecting again in one block.

  Further, when the internal space of the first perforated plate (210) is further divided in the other direction, there is an advantage that the separation between the first perforated plate (210) and the core (190) can be more stably maintained. In particular, it is possible to prevent the first porous plate (210) from being bent and coming into contact with the core (190) by the pressure of the fluid passing through the first porous plate (210). When the first perforated plate (210) and the core (190) are in contact with each other, there is a possibility that the fluid cannot be normally supplied at the contacted portion and the heat exchange efficiency is lowered.

  Referring to FIGS. 11 and 12, the hot fluid flowing in through the hot fluid inlet pipe (110) sequentially passes through the hot fluid inlet head (120), the first perforated plate (210), and the first partition wall (310). And flows into the core (190).

  Referring to FIGS. 11 and 13, the second partition (320) of the present embodiment surrounds the peripheral portion of the second porous plate (220) at a predetermined height, and divides the enclosed internal space into a plurality of regions. Shape. 11 (a) and 13 (a) show a shape in which the inner space surrounding the peripheral portion of the second porous plate (220) at a predetermined height is divided into four parts, and FIG. 11 (b). FIG. 13B shows a shape divided into eight pieces.

  The second partition wall (320) shown in FIGS. 11 (b) and 13 (b) has an internal space that surrounds the peripheral edge of the second perforated plate (220) at a predetermined height, as shown in FIGS. As shown in FIG. 13 (a), not only the lattice in one direction is divided but also the lattice in another direction is also divided. That is, in the second partition wall (320) shown in FIGS. 11 (a) and 13 (a), a member that divides the internal space surrounding the peripheral portion of the second perforated plate (220) at a predetermined height is vertically arranged. In the case of the member (1), the second partition wall (320) shown in FIGS. 11 (b) and 13 (b) is not only a plurality of vertical members (1) but also each vertical member (1). A plurality of horizontal members (2) that divide the space between them are provided, and the lattice in one direction and the lattice in the other direction intersect with each other to divide the internal space.

  As shown in FIG. 11 (b) and FIG. 13 (b), when the internal space of the second porous plate (220) is further divided in the other direction, the fluid can be more dispersed, and in particular, a plurality of blocks Refrigerant is prevented from collecting again in one block as well as in between.

  In addition, when the internal space of the second porous plate (220) is further divided in the other direction, there is an advantage that the separation between the second porous plate (220) and the core (190) can be more stably maintained. In particular, it is possible to prevent the second porous plate (220) from being bent and coming into contact with the core (190) by the pressure of the fluid passing through the second porous plate (220). When the second perforated plate (220) and the core (190) are in contact with each other, the fluid may not be discharged normally at the contacted portion, and the heat exchange efficiency may be reduced.

  Referring to FIGS. 10 and 13, the hot fluid discharged from the core (190) sequentially passes through the second partition (320), the second perforated plate (220), and the hot fluid discharge head (130). It is discharged via a hot fluid discharge pipe (140).

  FIG. 14 is a schematic view of the third partition wall or the fourth partition wall included in the heat exchanger according to the second embodiment of the present invention. FIG. 15 is a schematic view of a third partition and a third perforated plate included in the heat exchanger according to the second embodiment of the present invention. FIG. 16 is a schematic view of the fourth partition and the fourth porous plate provided in the heat exchanger according to the second embodiment of the present invention.

  Referring to FIGS. 14 and 15, the third partition wall (330) of the present embodiment surrounds the peripheral edge of the third perforated plate (230) at a predetermined height, and divides the enclosed internal space into a plurality of regions. Shape. 14 (a) and 15 (a) show a shape in which the internal space surrounding the peripheral portion of the third porous plate (230) at a predetermined height is divided into four parts, and FIG. 14 (b). FIG. 15B shows a shape divided into eight pieces.

  The third partition wall (330) shown in FIGS. 14 (b) and 15 (b) has an internal space surrounding the peripheral portion of the third porous plate (230) at a predetermined height as shown in FIG. 14 (a). Further, as shown in FIG. 15A, not only the lattice in one direction is divided but also the lattice in another direction is also divided. That is, in the third partition wall (330) shown in FIGS. 14 (a) and 15 (a), a member that divides the internal space surrounding the peripheral portion of the third porous plate (230) with a predetermined height is provided. In the case of the vertical member (1), the third partition wall (330) shown in FIGS. 14 (b) and 15 (b) includes not only the plurality of vertical members (1) but also each vertical member (1). A plurality of horizontal members (2) that divide the space between them are provided, and the lattice in one direction and the lattice in the other direction intersect with each other to divide the internal space.

  As shown in FIGS. 14 (b) and 15 (b), when the internal space of the third porous plate (230) is further divided in the other direction, the fluid can be more dispersed, especially with a plurality of blocks. The refrigerant is prevented from collecting again not only during the period but also within one block.

  Further, when the internal space of the third porous plate (230) is further divided in the other direction, there is an advantage that the separation between the third porous plate (230) and the core (190) can be more stably maintained. In particular, it is possible to prevent the third porous plate (230) from being bent and coming into contact with the core (190) by the pressure of the fluid passing through the third porous plate (230). When the third perforated plate (230) and the core (190) are in contact with each other, the fluid cannot be normally supplied at the contacted portion, and the heat exchange efficiency may be reduced.

  Referring to FIGS. 10 and 15, the cryogenic fluid flowing along the cryogenic fluid inflow pipe (150) passes through the cryogenic fluid inflow head (160), the third perforated plate (230), and the third partition wall (330). It flows through the core (190) sequentially.

  Referring to FIGS. 14 and 16, the fourth partition wall (340) of the present embodiment surrounds the periphery of the fourth porous plate (240) at a predetermined height, and divides the enclosed internal space into a plurality of regions. Shape. 14 (a) and 16 (a) show a shape in which the inner space surrounding the peripheral portion of the fourth porous plate (240) at a predetermined height is divided into four parts, and FIG. 14 (b). FIG. 16B shows a shape divided into eight parts.

  The fourth partition wall (340) shown in FIGS. 14 (b) and 16 (b) has an internal space that surrounds the peripheral edge of the fourth porous plate (240) at a predetermined height as shown in FIG. 14 (a). In addition, as shown in FIG. 16A, not only the lattice in one direction is divided but also the lattice in another direction is also divided. That is, in the fourth partition wall (340) shown in FIGS. 14 (a) and 16 (a), a member that divides the internal space surrounding the peripheral portion of the fourth perforated plate (240) with a predetermined height is provided. In the case of the vertical member (1), the fourth partition wall (340) illustrated in FIGS. 14 (b) and 14 (b) is connected not only to the plurality of vertical members (1) but also to each vertical member (1). A plurality of horizontal members (2) that divide the space between them are provided, and the lattice in one direction and the lattice in the other direction intersect with each other to divide the internal space.

  As shown in FIG. 14 (b) and FIG. 16 (b), when the internal space of the fourth porous plate (240) is further divided in the other direction, the fluid can be more dispersed, especially between a plurality of blocks. In addition, the refrigerant is prevented from collecting again in one block.

  In addition, when the internal space of the fourth porous plate (240) is divided again in the other direction, there is an advantage that the separation between the fourth porous plate (240) and the core (190) can be more stably maintained. In particular, it is possible to prevent the fourth porous plate (240) from being bent and coming into contact with the core (190) by the pressure of the fluid passing through the fourth porous plate (240). When the fourth perforated plate (240) and the core (190) are in contact with each other, the fluid may not be discharged normally at the contacted portion, and the heat exchange efficiency may be reduced.

  Referring to FIGS. 10 and 16, the cryogenic fluid discharged from the core (190) passes through the fourth partition wall (340), the fourth perforated plate (240), and the cryogenic fluid discharge head (170) in this order. It is discharged through a fluid discharge pipe (180).

  FIG. 17A is a schematic diagram showing the flow of refrigerant in a conventional heat exchanger. FIG. 17B is a schematic diagram showing the flow of refrigerant in the heat exchanger according to the first embodiment of the present invention. FIG. 17C is a schematic diagram showing the flow of the refrigerant in the heat exchanger according to the second embodiment of the present invention.

  Referring to FIG. 17 (a), in the case of the conventional heat exchanger, the low temperature fluid flowing into the low temperature fluid inflow pipe (150) is concentrated on the central block located near the low temperature fluid inflow pipe (150). It can be seen that it is supplied. In the case of a conventional heat exchanger with three blocks, about 70% of refrigerant is supplied in the block located near the cryogenic fluid inflow pipe (150), and about 15% of refrigerant is supplied to the other blocks. It was confirmed that the difference in refrigerant flow rate between the block and the block reached 4 times or more.

  Referring to FIG. 17B, in the heat exchanger according to the first embodiment of the present invention, the low temperature fluid flowing into the low temperature fluid inflow pipe (150) is dispersed by the third perforated plate (230). It turns out that it flows equally into a some block relatively compared with a heat exchanger. However, it can be confirmed that the phenomenon that the cryogenic fluid is concentrated remains in the central block located near the cryogenic fluid inflow pipe (150) to some extent.

  Referring to FIG. 17 (c), in the heat exchanger according to the second embodiment of the present invention, after the low temperature fluid flowing into the low temperature fluid inflow pipe (150) is dispersed by the third perforated plate (230), the third temperature is changed. It can be seen that it passes through the partition wall (330) and flows relatively evenly into the plurality of blocks as compared with the conventional heat exchanger, and evenly flows from the heat exchanger of the first embodiment.

  The heat exchanger of the present embodiment is characterized in that the difference in the flow rate of the fluid supplied to each of the plurality of blocks or the fluid discharged from each of the plurality of blocks is less than four times.

  FIG. 18A is a schematic view showing the position of a temperature sensor installed to measure the internal temperature of the heat exchanger. FIG. 18B is a graph showing the temperature distribution inside the heat exchanger measured by each temperature sensor at the position shown in FIG. Moreover, the broken line (1) illustrated in FIG. 18B shows the temperature distribution inside the conventional heat exchanger, and the solid line (2) shows the temperature distribution inside the heat exchanger according to the second embodiment of the present invention. Indicates.

  Referring to FIG. 18B, in the case of the conventional heat exchanger, it is confirmed that the temperature of the central block is very low compared to the temperature of the other blocks, and the temperature difference between the plurality of blocks is large. it can. In the case of the conventional heat exchanger, it was confirmed that the temperature difference between the lowest temperature portion and the highest temperature portion is about 130 to 140 ° C.

  On the other hand, in the case of the heat exchanger of the second embodiment, it can be confirmed that the temperature difference between the plurality of blocks is relatively small. In the case of the heat exchanger of this embodiment, the temperature difference between the lowest temperature portion and the highest temperature portion is about 40 to 50 ° C., and it was confirmed that the temperature difference between the blocks was reduced as compared with the conventional heat exchanger. .

  The present invention uses evaporative gas as the refrigerant of the heat exchanger, and even if the heat exchanger includes a plurality of blocks, the flow rate of the refrigerant supplied to each block can be maintained relatively evenly. The heat exchange efficiency can be increased by reducing the temperature difference between them, and stable reliquefaction performance can be ensured even if the flow rate of the reliquefied target evaporative gas changes.

  In addition, the perforated plate can be formed of a SUS material and contracted by contact with a cryogenic evaporating gas so that it can return to its original state after the refrigerant has passed. The heat capacity is much less than the heat exchanger with a thin porous plate. Since a small perforated plate has a large shrinkage rate when it comes into contact with evaporating gas, the perforated plate may break.

  Therefore, it is necessary to couple the perforated plate with a heat exchanger so that the thermal expansion and contraction can be eliminated. In the fourth and fifth embodiments of the present invention, an example of the perforated plate joined so that the thermal expansion and contraction can be eliminated. Will be explained.

  FIG. 19 is a schematic view showing a part of a heat exchanger according to the third embodiment of the present invention, and FIG. 20 is an enlarged schematic view of portion A of FIG.

  Similarly to the first embodiment, the heat exchanger of this embodiment is installed between the high-temperature fluid inflow head (120) and the core (190) in addition to the configuration of the conventional PCHE illustrated in FIG. The first perforated plate (210), the second perforated plate (220) installed between the high temperature fluid discharge head (130) and the core (190), the low temperature fluid inflow head (160) and the core (190) And at least one of a third perforated plate (230) disposed between the second perforated plate (230) and a fourth perforated plate (240) disposed between the cryogenic fluid discharge head (170) and the core (190). .

  Referring to FIGS. 19 and 20, the fourth porous plate (240) of the present embodiment is installed in the cryogenic fluid discharge head (170), and the fourth porous plate (240) is directly welded to the cryogenic fluid discharge head (170). Instead, the two support members (420) are welded (410) to the cryogenic fluid discharge head (170) at a predetermined interval, and the fourth perforated plate (240) is attached to the two support members (420). Sandwiched between them.

  The fourth perforated plate (240) is sandwiched between the two support members (420), and is not completely fixed. Therefore, even if the fourth perforated plate (240) contracts due to contact with the cryogenic evaporating gas. It does not bend or break, and the connecting part is not damaged.

  The support member (420) is preferably of a minimum size that can accommodate the shrinkage of the fourth porous plate (240), and the spacing between the support members (420) is somewhat due to the shrinkage of the fourth porous plate (240). It is preferable that the distance is the smallest possible distance.

  Similarly to the fourth porous plate (240), the first to third porous plates (210, 220, 230) of the present embodiment are separated from the high-temperature fluid inflow head (120) at a predetermined interval. The second perforated plate (220) is sandwiched between the two support members welded at a predetermined interval to the high temperature fluid discharge head (130). The third perforated plate (230) is sandwiched between two support members welded to the cryogenic fluid inflow head (160) at a predetermined interval.

  FIG. 21 is a schematic view showing a part of a heat exchanger according to the fourth embodiment of the present invention, and FIG. 22 is an enlarged schematic view of a portion B in FIG.

  Similarly to the first embodiment, the heat exchanger of this embodiment is installed between the high-temperature fluid inflow head (120) and the core (190) in addition to the configuration of the conventional PCHE illustrated in FIG. The first perforated plate (210), the second perforated plate (220) installed between the high temperature fluid discharge head (130) and the core (190), the low temperature fluid inflow head (160) and the core (190) And at least one of a third perforated plate (230) disposed between the second perforated plate (230) and a fourth perforated plate (240) disposed between the cryogenic fluid discharge head (170) and the core (190).

  Referring to FIGS. 21 and 22, the fourth porous plate (240) of the present embodiment is installed in the low temperature fluid discharge head (170) as in the third embodiment, but the low temperature fluid discharge head (170). Not welded directly.

  However, unlike the third embodiment, the fourth porous plate (240) of the present embodiment has a shape in which both end portions extend in parallel with the core (190) and have a step in a direction away from the core (190). Yes, not between two support members (420), but between one support member (420) and the core (190).

  That is, one support member (420) is welded (410) to the cryogenic fluid discharge head (170) at a predetermined interval from the core (190), and the fourth porous plate (240) extending in parallel with the core (190). ) Are sandwiched between the support member (420) and the core (190), and the fourth porous plate (240) is formed from the both ends located between the support member (420) and the core (190). It is a shape which has a level | step difference in the direction away from (190).

  Since the fourth porous plate (240) of the present embodiment is not in a state of being completely fixed by being sandwiched between the support member (420) and the core (190), it contracts due to contact with the cryogenic evaporating gas. Even if it is not bent or damaged, the connection part is not damaged.

  The support member (420) of the present embodiment preferably has a minimum size that can accommodate the shrinkage of the fourth porous plate (240), and the distance between the support member (420) and the core (190) is also the fourth. It is preferable that the perforated plate (240) has a minimum distance that allows some movement by contraction. In addition, both end portions of the fourth porous plate (240) extending in parallel with the core (190) are sandwiched between the support member (420) and the core (190), and are the smallest that can allow deformation and free movement due to contraction. The length is preferred.

  Similarly to the fourth perforated plate (240), the first to third perforated plates (210, 220, 230) of the present embodiment are separated from the core (190) after both end portions extend in parallel with the core (190). The first perforated plate (210) has a shape with a step in the direction, and the first perforated plate (210) is sandwiched between the support member welded to the high-temperature fluid inflow head (120) and the core (190), and the second perforated plate (220) is sandwiched between the support member welded to the high temperature fluid discharge head (130) and the core (190), and the third perforated plate (230) is welded to the low temperature fluid inflow head (160). Both ends are sandwiched between the support member and the core (190).

  FIG. 23 (a) is a schematic diagram of the overall shape of the heat exchanger, FIG. 23 (b) is a schematic diagram of a block, and FIG. 23 (c) is a schematic diagram of a channel plate. The block illustrated in FIG. 23B may be a diffusion block.

  Referring to FIG. 23, the core (190) in which heat exchange between the cryogenic fluid and the hot fluid is performed includes a plurality of blocks (192), and the block (192) includes a plurality of channel plates (194) for the cryogenic fluid; A plurality of high-temperature fluid channel plates (196) are alternately stacked. Each channel plate (194, 196) has a plurality of channels through which fluid flows.

  24A is a schematic view of the channel plate for cryogenic fluid shown in FIG. 23C as viewed from the C direction, and FIG. 24B is a channel plate for cryogenic fluid of a conventional heat exchanger. 24 (c) is a schematic view of the channel plate of the channel plate for the cryogenic fluid of the heat exchanger according to the fifth embodiment of the present invention, and FIG. 24 (d) is a schematic view of the channel of the present invention. It is the schematic of the channel of the channel plate for the cryogenic fluid of the heat exchanger which concerns on 6th Embodiment.

  Referring to FIG. 24, the channel (198) formed in the channel plate is generally constant in width and straight as shown in FIG. 24 (b). The heat exchanger which concerns on 6th Embodiment is provided with the channel of the shape which gives resistance to a fluid.

  Referring to FIG. 24 (c), the heat exchanger of the fifth embodiment includes a plurality of channels (198) in which the width of the inflow portion is narrower than the width of other portions. That is, the channel (198) of the present embodiment is formed so that the cross-sectional area of the inflow portion is narrower than other portions when the channel plate is viewed from the direction C in FIG.

  When the cross-sectional area of the inflow portion of the channel (198) is reduced, the inflowing fluid receives resistance and the flow is dispersed, thereby mitigating or preventing the phenomenon of fluid concentration in a specific block among the plurality.

  Referring to FIG. 24 (d), the heat exchanger of the sixth embodiment includes a plurality of zigzag shaped channels (198). When the channel (198) is formed in a zigzag shape, the fluid is subjected to resistance and the flow is dispersed, and the phenomenon of the fluid concentrating on a specific block among the plurality can be reduced or prevented.

  Since the heat exchangers of the fifth embodiment and the sixth embodiment of the present invention include a channel having a shape that provides fluid resistance, a specific one of the plurality of the heat exchangers can be used without adding another member that disperses the fluid. There is an advantage that the phenomenon of refrigerant concentration on the block can be reduced or prevented.

  The present invention is not limited to the above-described embodiment, and various modifications or variations can be made without departing from the technical scope of the present invention. Those skilled in the art to which the present invention belongs have ordinary knowledge. It is self-explanatory.

DESCRIPTION OF SYMBOLS 10 ... Compressor, 20 ... Heat exchanger, 30 ... Depressurization device, 40 ... Gas-liquid separator, 110 ... High temperature fluid inflow pipe, 120 ... High temperature fluid inflow head, 130 ... High temperature fluid discharge head, 140 ... High temperature fluid discharge pipe 150 ... Cryogenic fluid inlet pipe, 160 ... Cryogenic fluid inlet head, 170 ... Cryogenic fluid outlet head, 180 ... Cryogenic fluid outlet pipe, 190 ... Core, 192 ... Block, 194 ... Channel plate for cryogenic fluid, 196 ... Hot fluid 198 ... channel, 210, 220, 230, 240 ... perforated plate, 310, 320, 330, 340 ... partition wall, 420 ... support member.

Claims (18)

1) compressing the evaporative gas discharged from the LNG storage tank ;
2) A step of cooling the evaporative gas compressed in the step 1) with a heat exchanger using the evaporative gas as a refrigerant;
3) The step of expanding the fluid cooled in the step 2); and 4) The operating condition of the LNG ship is changed, and after the compression in the step 1), the reliquefied evaporation gas supplied to the heat exchanger Maintaining the reliquefaction performance stably even if the flow rate of the liquid fluctuates;
An evaporative gas reliquefaction method for an LNG ship in which the amount of evaporative gas reliquefied through the steps 1) to 3) is maintained at 50% or more of the value calculated by HYSYS.   5) The method for re-liquefying an evaporative gas of an LNG ship according to claim 1, further comprising the step of gas-liquid separating the fluid expanded in step 3).   The vapor component of the LNG carrier according to claim 2, wherein the gas component separated in the gas-liquid separation in the step 5) is combined with the evaporation gas and used as a heat exchange refrigerant in the step 2). Liquefaction method.   The evaporative gas reliquefaction method for an LNG ship according to any one of claims 1 to 3, wherein an operating speed of the LNG ship is 10 to 17 knots. Part of the evaporated gas compressed in step 1) is used as engine fuel,
The evaporative gas reliquefaction method for an LNG ship according to any one of claims 1 to 3, wherein the flow rate of the evaporative gas used as fuel for the engine is 1,100 to 2,660 kg / h. .   6. The evaporative gas reliquefaction method for an LNG ship according to claim 5, wherein the engine includes a propulsion engine and a power generation engine.   The evaporative gas reliquefaction method for an LNG ship according to any one of claims 1 to 3, wherein a flow rate of the reliquefied target evaporative gas is 1,900 to 3,300 kg / h.   The ratio of the flow rate of the evaporating gas to be reliquefied is in the range of 0.42 to 0.72 based on the flow rate of the evaporating gas used as the heat exchange refrigerant in the step 2). The evaporative gas reliquefaction method of the LNG ship of any one of 1-3.   The evaporative gas reliquefaction method for an LNG ship according to claim 5, wherein the evaporative gas not sent to the engine among the evaporative gas compressed in step 1) is further compressed and then sent to the heat exchanger. . 1) compressing the evaporative gas discharged from the LNG storage tank ;
2) Using the evaporating gas as a refrigerant, the step of cooling the evaporating gas compressed in the step 1) by exchanging heat;
3) The step of expanding the fluid cooled in the step 2); and 4) Even if the operating condition of the LNG ship changes and the flow rate of the evaporative gas used as the heat exchange refrigerant in the step 2) fluctuates. Stably maintaining reliquefaction performance;
An evaporative gas reliquefaction method for an LNG ship in which the amount of evaporative gas reliquefied through steps 1) to 3) is maintained at 50% or more of the value calculated by HYSYS. 5) further comprising gas-liquid separation of the fluid expanded in step 3),
11. The LNG ship evaporative gas re-use according to claim 10, wherein the gas component separated in the gas-liquid separation in step 5) joins the evaporative gas and is used as a heat exchange refrigerant in step 2). Liquefaction method. A step of compressing evaporative gas discharged from the LNG storage tank at high pressure, and exchanging all or a part of the high-pressure compressed evaporative gas with evaporative gas discharged from the LNG storage tank by a heat exchanger; A method for reliquefying an evaporative gas of an LNG ship equipped with a high-pressure gas injection engine, comprising: depressurizing compressed evaporative gas;
Changing the operating conditions of the LNG ship, maintaining the reliquefaction performance stably even if the flow rate of the reliquefied evaporation gas fluctuates;
An evaporative gas reliquefaction method for an LNG ship equipped with a high pressure gas injection engine in which the amount of reliquefied evaporative gas is maintained at 50% or more of the value calculated by HYSYS.   The method of claim 12, wherein the high pressure compressed evaporative gas is in a supercritical state.   The method of claim 12, wherein the pressure of the high-pressure compressed evaporative gas is 100 to 400 bara.   The method of claim 14, wherein the pressure of the high-pressure compressed evaporative gas is 150 to 400 bara.   The method of claim 15, wherein the pressure of the high-pressure compressed evaporative gas is 150 to 300 bara. The heat exchanger includes a core for heat exchange between a high temperature fluid and a low temperature fluid,
The method of claim 1, wherein the core includes a plurality of blocks. The evaporative gas reliquefaction method for an LNG ship according to claim 17, wherein a heat insulating layer or a heat insulating portion exists between the plurality of blocks of the core.

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