JP2015105810A - Condensing mixing device and boil-off gas re-liquefying apparatus having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a condensing mixing device for effectively re-liquefying boil-off gas, and a boil-off gas re-liquefying apparatus having the same.SOLUTION: The condensing mixing device includes a mixture flow tube portion 2B having a Venturi tube-type flow tube 7 in which a diameter-reduced portion 7A, a throat portion 7B and a diameter-enlarged portion 7C are formed, and the condensing mixing device injects steam to a liquid flowing in the flow tube to condense the steam and mix the same into the liquid. In the condensing mixing device, a swirl flow forming portion 2A is provided which is positioned in an extension of an axis X of the flow tube at an upstream side with respect to the flow tube 7 and which accords the liquid of low temperature to flow toward the flow tube communicated and connected with the diameter-reduced portion. In the swirl flow forming portion 2A, the liquid of a kind same as the liquid of low temperature in the flow tube is injected from the tangential direction. In the diameter-enlarged portion 7C of the mixture flow tube portion 2B, stepped portions 10B-1, 10B-2 are formed in a plurality of axial-direction positions and stepped diameter-enlarged portions 7C-1, 7C-2 successively diametrically enlarged at the stepped portions and extended toward the downstream side are provided, and the steam holes 10-1, 10-2 are formed on an upstream-side position in a region of the stepped diameter-enlarged portions.

Description

  The present invention relates to a condensing and mixing apparatus for bringing vapor into contact with a low-temperature liquid, condensing and liquefying the vapor, and mixing it into a low-temperature liquid, and an evaporative gas reliquefaction apparatus having the same.

  When low temperature liquid such as liquefied natural gas (LNG) is stored in a tank, a part of the low temperature liquid in the tank evaporates due to heat input to the tank from the outside, and evaporated gas is generated in the tank. When the low-temperature liquid is LNG, an evaporating gas mainly composed of methane is generated.

  The generated evaporative gas can be compressed as it is and supplied to the demand side as city gas, but the compression power becomes very large. Therefore, in order to reduce such power, it can be considered that the evaporated gas is re-liquefied and pressurized in a liquid state and then gasified again to be supplied as city gas. In order to reliquefy, evaporative gas is compressed and cooled, and as a cooling method, evaporative gas is cooled by the cold heat of LNG discharged as a low temperature liquid from the tank, that is, compressed. Patent Documents 1 and 2 disclose a method of cooling evaporative gas by exchanging heat with LNG.

  Patent Document 1 discloses a method (indirect heat exchange method) in which compressed evaporative gas is cooled by heat exchange with LNG in a heat exchanger. However, in this indirect heat exchange method that requires a heat exchanger, a large heat exchanger is required to secure a sufficient heat transfer area for heat exchange, and there is a problem that the equipment becomes large and costs increase. . Furthermore, since heat transfer is indirect through the heat transfer surface, improvement in heat transfer performance on this heat transfer surface is also required.

  On the other hand, Patent Document 2 discloses a method (direct contact heat exchange method) in which compressed evaporative gas is blown into an LNG pipe and directly brought into contact with LNG to exchange heat, and evaporative gas is blown into LNG. As an injection method, an apparatus is disclosed in which one evaporative gas supply nozzle is arranged in the LNG pipe so as to be in a direction orthogonal to the flow direction of the discharge LNG flowing in the LNG pipe or in a direction opposite to the flow direction of the LNG. The evaporative gas supply nozzle is bent in an L shape in the LNG pipe, and the discharge port of the nozzle is located on the center line of the LNG pipe so that the evaporative gas is directed in the direction opposite to the flow of LNG. Is discharged. The discharged evaporative gas is cooled by heat exchange with LNG, condensed, liquefied and mixed with LNG.

  Since the direct contact heat exchange method of Patent Document 2 exchanges heat without passing through the heat transfer surface, the heat transfer performance at the interface where both the LNG and the evaporation gas are in contact with each other is improved. However, in the direct contact heat exchange system, the liquefaction efficiency is poor due to insufficient contact and mixing of the evaporating gas and the low temperature liquid due to the difference in density between the evaporating gas as the gas and the LNG as the low temperature liquid. Prone. In order to improve the efficiency, there is a demand for an efficient apparatus that mixes gas evaporative gas and low-temperature liquid LNG to condense and mix evaporative gas. It is difficult to say that contact and mixing of gas and liquid LNG can be sufficiently ensured, and desired liquefaction performance can be ensured.

  On the other hand, as a direct contact heat exchange system, a condensing and mixing device that condenses and mixes steam by injecting steam into a low-temperature liquid flowing in a venturi-type flow tube and directly contacting it is patented. It is disclosed in documents 3 and 4. In the apparatus of the type disclosed in Patent Documents 3 and 4, steam holes for injecting steam from the radial direction are formed in the flow pipe, and the steam is a venturi of a low-temperature liquid flowing in the flow pipe. It is sucked into the flow tube from the vapor hole by the phenomenon. The vapor immediately after being sucked is present as bubbles in the cryogenic liquid, and then condensed and mixed with the cryogenic liquid.

  First, in Patent Document 3, a large number of small-diameter steam holes are formed in a plurality of positions in the circumferential direction and in the liquid flow direction in the enlarged diameter portion that is downstream of the throat portion of the venturi tube. Yes. Since the steam is dispersed from the plurality of steam holes and sucked into the enlarged diameter portion, the bubble diameter of the steam immediately after being sucked is small. As a result, the condensation of the steam is completed in a short time, and the water hammer action in the enlarged diameter portion is suppressed.

  Next, in Patent Document 4, a section having a constant channel cross-sectional area is formed by forming a section with a constant diameter and extending downstream with a step immediately after the throat portion of the venturi tube and having a stepped diameter. Is provided at one position at the step where the flow path is rapidly expanded by the step.

  As another type of condensing and mixing apparatus, Patent Document 5 discloses that vapor as evaporating gas is injected into water as low-temperature liquid flowing through a mixing chamber in a pipe, and the vapor is condensed and mixed with water. Discloses a condensing and mixing device that produces hot water. This condensing and mixing device is provided with a fixed swirl vane for imparting swirl to water in the mixing chamber, and the efficiency of mixing water and steam is improved by the fixed swirl vane.

JP 55-145897 JP 08-173781 JP 04-045832 A JP2013-039497A JP 7-116486 A

  However, even in an apparatus such as Patent Documents 3 and 4, when the pressure of gaseous evaporative gas is increased and brought into direct contact with LNG as a low-temperature liquid, if sufficient condensing and mixing performance is not ensured, evaporative gas merged with LNG If the liquid is not liquefied completely and supplied to the liquid feed pump in a state where bubbles remain without being liquefied, not only liquid feeding becomes difficult, but also the liquid feeding pump may be broken.

  In this way, in order to suck a predetermined amount of vapor more efficiently with the liquid venturi phenomenon, the arrangement of the vapor holes for sucking the vapor, the optimal shape and structure for reducing the pressure loss in the venturi pipe, etc. An optimum structure as a condensing and mixing apparatus is required. Further, in the condensing and mixing apparatus provided with the swirl imparting mechanism that improves the condensing and mixing performance as in Patent Document 5, the fluid in the condensing and mixing apparatus passes through the fixed swirling blades, so that the pressure loss of the condensing and mixing apparatus increases. There is a problem.

  In view of such circumstances, the present invention increases the pressure of gaseous evaporative gas, and when this evaporative gas is brought into direct contact with a low temperature liquid such as LNG for reliquefaction, the evaporative gas is effectively condensed to a low temperature liquid. It is an object of the present invention to provide a condensing and mixing apparatus for mixing and an evaporative gas reliquefying apparatus having the apparatus and capable of effectively realizing reliquefaction.

  According to the present invention, the above-described problems are solved by a condensing and mixing apparatus having the following configuration and an evaporative gas reliquefaction apparatus having the same.

<Condensation mixer>
Mixing having a venturi-type flow tube in which a diameter-reduced portion that gradually decreases from the upstream side toward the downstream side is followed by a throat portion that has the smallest diameter, and then a diameter-expanded portion that gradually increases from the throat portion. In order to provide a flow tube portion and inject steam into the flow tube from the outside of the flow tube, the steam holes directed in the radial direction and downstream direction of the flow tube have a plurality of positions in the axial direction of the flow tube. In a condensing and mixing apparatus that is formed to have an injection opening on an inner diameter surface, injects steam from an injection opening of a vapor hole into a low-temperature liquid that flows downstream in a flow tube, condenses the vapor, and mixes it with the low-temperature liquid A swirl flow forming portion that is located upstream of the flow tube and on an extension of the axis of the flow tube and that is connected to the reduced diameter portion to allow low temperature liquid to flow toward the flow tube. The swirl flow forming part is in contact with the same kind of liquid as the low temperature liquid in the flow tube. The diameter-enlarged portion of the mixed flow pipe portion is formed with a plurality of step portions in the axial direction, and the diameter is gradually increased at the step portion and downstream in the axial direction. A condensing and mixing apparatus comprising a step-shaped enlarged portion having an inner peripheral surface extending in a direction, and an injection opening for a vapor hole provided at an upstream position in the region of each step-shaped enlarged portion.

  In the present invention, the swirl flow forming portion divides a part of the low-temperature liquid supplied to the reduced diameter portion of the flow tube at a position upstream of the swirl flow formation portion, and is tangential to the swirl flow formation portion. Inject in the direction.

  In the present invention, the stepped portion has a radius difference between a preceding stepped diameter-enlarged portion adjacent to the stepped portion on the upstream side and a succeeding stepped diameter-expanded portion adjacent downstream on the stepped portion. The size is preferably 12 to 30% of the inner diameter of the part.

  In the present invention, it is preferable that the stepped enlarged portion extends in the axial direction over a section length of 2.5 to 8 times the radius of the stepped enlarged portion.

<Evaporative gas reliquefaction device>
Evaporative gas generated from cryogenic liquid stored in the storage tank is mixed with the low-temperature liquid discharged from the storage tank to condense and re-liquefy. An evaporative gas compressor, and a delivery pump for delivering cryogenic liquid from the storage tank. The evaporative gas is supplied from the upstream side to the flow pipe of the condensing and mixing device by the delivery pump, and the evaporative gas is condensed by the evaporative gas compressor. An evaporative gas reliquefaction apparatus, wherein the evaporative gas reliquefaction apparatus is adapted to inject into the flow pipe from a vapor hole of a mixing apparatus.

  When not using the condensing and mixing apparatus and evaporative gas reliquefaction apparatus of the present invention, the vapor immediately after being sucked from the vapor hole cannot be condensed due to the small contact time and contact area with the low temperature liquid, and is present as bubbles in the liquid. However, in the condensing and mixing apparatus and the evaporative gas reliquefaction apparatus according to the present invention, a swirl flow forming unit is provided in the previous stage to generate a swirl flow in the low-temperature liquid before flowing into the mixed flow tube unit, In the downstream mixed flow pipe section, the steam hole is positioned upstream in the region of the step-shaped expanded diameter portion formed in the flow pipe of the mixed flow pipe section, that is, the steam hole is positioned at the expanded diameter section of the venturi pipe. The space immediately after the sudden expansion at the stepped portion can be secured as a sufficiently large space through which vapor bubbles are mixed in the cryogenic liquid. Sufficient contact time between vapor and cryogenic liquid in space It can be coercive, can be mixed and the vapor is cooled by a cryogenic liquid condensate. Further, the vapor is efficiently sucked by the venturi phenomenon efficiently without being affected by the flow of the low-temperature liquid in the flow tube in the space of the stepped enlarged diameter portion. Further, since the low temperature liquid flows into the mixed flow pipe portion while forming a swirling flow, the vapor and the low temperature liquid are sufficiently mixed both in the circumferential direction and in the radial direction.

  Further, in the present invention, a plurality of step-shaped enlarged diameter portions are provided in the flow tube of the mixed flow tube portion, and steam holes are formed in each step-shaped enlarged diameter portion. Since the liquid can be dispersedly arranged in the flow direction of the liquid, the bubble diameter of the vapor is reduced, the condensation of the vapor and the mixing with the low-temperature liquid are promoted, and the water hammer action is suppressed.

  In the present invention, as described above, the cryogenic liquid is swirled in the swirling flow forming section in the former stage, and then, in the latter stage, a plurality of step-shaped enlarged diameter sections are provided in the flow tube in the mixing flow tube section of the condensing and mixing apparatus. The diameter of the vapor hole is gradually increased and the injection opening of the vapor hole is positioned upstream in the region of each step-shaped enlarged portion, so that the evaporative gas can be generated in the space of the portion expanded with respect to the preceding step-shaped enlarged portion. Since it is reliably introduced into the cryogenic liquid, condensed and mixed, and the cryogenic liquid flows into the mixing flow pipe as a swirling flow, and the vapor and the cryogenic liquid are sufficiently mixed both in the circumferential direction and in the radial direction. The evaporative gas can be effectively reliquefied in the low-temperature liquid, and the evaporative gas can be prevented from flowing into the pump as a gas and causing trouble in the pump. Moreover, in the evaporative gas reliquefaction apparatus having the condensing and mixing apparatus having such a configuration, the reliquefaction of the evaporative gas can be completed efficiently in a short time, and as a result, the apparatus configuration can be made compact.

1 is a schematic configuration diagram of an evaporative gas reliquefaction apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view of a condensing and mixing apparatus used in the apparatus, (A) is the entire apparatus, (B) is a BB cross-sectional view in (A), and (C) is an enlarged cross-sectional view of a part of (A). is there. 2 is a graph showing the experimental results regarding the efficiency improvement rate by providing a stepped diameter-enlarged portion for the device, (A) shows the step size ratio, (B) shows the efficiency improvement rate for the section length dimension ratio. Yes. It is a schematic block diagram which shows the structure for controlling the flow volume of the cryogenic liquid in 2nd embodiment. It is a figure which shows the relationship between the minimum value of the supercooling degree of a mixed low temperature liquid, and a secondary flow rate ratio (swirl strength).

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<First embodiment>
FIG. 1 is a schematic configuration diagram of an evaporative gas reliquefaction apparatus including a condensing and mixing apparatus as an embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes an evaporative gas reliquefaction device according to the present embodiment, which has a condensing and mixing device 2 having a structure shown in detail in FIG. Connected to the left side) are a delivery pump 3 for delivering the cryogenic liquid 11 to the condensing and mixing device 2 and an evaporative gas compressor 4 for injecting the evaporative gas 12.

  The cryogenic liquid 11 is, for example, a part of liquefied natural gas (LNG) stored in a tank (not shown), and the evaporative gas 12 is, for example, a part of liquefied natural gas in the tank. Is a boil-off gas (BOG) generated by evaporation.

  As seen in FIG. 1, the cryogenic liquid 11 is delivered by the delivery pump 3 and flows into the condensation and mixing device 2. The evaporative gas 12 compressed by the evaporative gas compressor 4 is injected into the low-temperature liquid 11 flowing in the condensing and mixing apparatus 2.

  A booster pump 5 is connected to the outlet side of the condensing and mixing device 2 and condenses and mixes evaporative gas 12 condensed after being injected into the low temperature liquid 11 and mixed with the low temperature liquid 11 in a liquefied state. The mixed cryogenic liquid 11A discharged from the apparatus 2 is pressurized. For example, if the low-temperature liquid is liquefied natural gas, the mixed low-temperature liquid 11A whose pressure has been increased is brought to the vaporizer, gasified again, and then sent to the demand side as city gas.

  As shown in FIG. 2 (A), the condensing and mixing apparatus 2 includes a swirl flow forming portion 2A disposed at a position for receiving the cryogenic liquid 11 delivered from the delivery pump 3, and subsequently the downstream side thereof. It has the mixed flow pipe part 2B located. The swirl flow forming portion 2A and the mixed flow tube portion 2B are located on one axis X and are formed as one device.

  As shown in FIG. 2A, the swirl flow forming portion 2A is a straight pipe having an inner diameter equal to the inner diameter on the inlet side of a mixed flow pipe portion 2B of a venturi tube type to be described later, and at least one place in the circumferential direction. Is provided with a tangential inlet 2A-1 for injecting a cryogenic liquid in the tangential direction (see also FIG. 2B). In the present embodiment, the tangential inlet 2A-1 is connected to a branch pipe 2A-2 provided at an upstream position of the tangential inlet 2A-1, and is sent out by the delivery pump 3 and swirled. A part of the cryogenic liquid 11 flowing into the forming section 2A is extracted by the branch pipe 2A-2, and then injected into the swirling flow forming section 2A through the tangential inlet 2A-1, and the tangential direction generated by the injection The low-temperature liquid in the swirl flow forming portion 2A is swirled flow S. The cryogenic liquid flowing in the branch pipe 2A-2 can be injected into the tangential inlet 2A-1 with the flow momentum originally provided by the delivery pump 3, but to obtain the momentum more reliably. It is preferable to provide a pump in the branch pipe 2A-2.

  In the present embodiment, the cryogenic liquid extracted by the branch pipe 2A-2 is injected into the tangential inlet 2A-1, but the present invention is not limited to this, and the same kind of liquid as the cryogenic liquid is injected. It is good as well. The liquid to be injected is sufficient if it is completely the same liquid as the low-temperature liquid flowing through the swirl flow forming portion 2A, and is supplied from another supply source regardless of the branch pipe 2A-2. There may be.

  The mixed flow pipe portion 2B connected to the swirl flow forming portion 2A on the wake side has a venturi-type flow tube 7 housed in a horizontal cylindrical casing 6, and the casing 6 and the flow Between the pipes 7, an insert 8 made of a woven or knitted fiber metal fine wire such as stainless steel is inserted.

  The casing 6 has an inlet portion 6A on the upstream side in the flow direction of the cryogenic liquid 11, an outlet portion 6B on the downstream side, and a flow tube housing portion 6C in which the flow tube 7 is housed and disposed at an intermediate position therebetween. The inlet portion 6A and the outlet portion 6B have the same inner diameter, and the inner diameter is increased in the flow tube housing portion 6C. The axis X that is the center of the inlet portion 6A, the outlet portion 6B, and the flow tube accommodating portion 6C is located on the same straight line. The flow tube accommodating portion 6C has an inner diameter larger than the outer diameter of the flow tube 7, forms a space around the flow tube 7, is dispersed in this space, and the insert 8 is inserted therein. Yes. Further, an evaporative gas injection part 6D that opens upward is formed at the upper upstream side position of the flow tube accommodating part 6C, and the evaporative gas 12 pumped from the evaporative gas compressor 4 is injected into the evaporative gas. Part 6D accepts it. In the condensing and mixing apparatus 2 shown in FIG. 2 (A), the evaporative gas injection part 6D is formed at an upper upstream side position of the flow tube accommodating part 6C, but the position of the evaporative gas injection part 6D is limited to this. Instead of this, an opening may be formed at a position upstream of the side portion of the flow tube accommodating portion 6C. In the embodiment shown in FIG. 2A, the condensing and mixing apparatus 2 is arranged in the horizontal direction, but may be arranged in the vertical direction. Since the condensing and mixing apparatus 2 is arranged in the vertical direction, the cryogenic liquid 11 is circulated downward in the vertical direction, and the evaporative gas 12 flows in from the horizontal direction. Evaporative gas condensation and mixing is performed more stably.

  The venturi-type flow tube 7 has mounting flanges 9A and 9B projecting radially outward on both sides in the direction of the axis X, and the mounting flanges 9A and 9B are provided in the flow tube housing portion 6C of the casing 6. In addition, the flow tube 7, the inlet 6A of the casing 6 and the axis X of the outlet 6B are attached so that they are aligned and located on one straight line.

  The inner diameter of the flow tube 7 is a reduced diameter portion 7A located on the inlet portion 6A side of the casing 6, a throat portion 7B located immediately after the reduced diameter portion 7A, and an expansion extending from the throat portion 7B toward the outlet portion 6B. The diameter portion 7C is sequentially formed. The diameter-reduced portion 7A has a curved surface and the inner diameter is relatively abruptly reduced to narrow the cross-sectional area of the flow path, and the diameter-expanded portion 7C is expanded so as to recover the inner diameter over a long distance in the axis X direction. The throat portion 7B connects the reduced diameter portion 7A and the enlarged diameter portion 7C with a smooth curve so as to be low resistance to the flow of the low-temperature liquid, and is formed to have a minimum diameter so as to have a minimum flow path cross-sectional area. Has been.

  The diameter-expanded portion 7C is divided into a range from the position immediately after the throat portion 7B to the position of the right flange portion 9B in the direction of the axis X, and a plurality of step-shaped diameter-expanded portions 7C-1, 7C-2 ..., 7C-N. Each of the stepped enlarged portions 7C-1, 7C-2,..., 7C-N has a cylindrical inner diameter surface, and the inner diameter does not change within the same stepped enlarged portion. Stepped portions 10B-1, 10B-2, in which the next stepped enlarged portion 7C-2 and the next stepped enlarged portion 7C-3 are formed at the upstream side of the shaped expanded portion 7C-1, respectively. The diameter is expanded in a step shape.

  FIG. 2 (C) shows a stepped enlarged portion 7C-1, as a part of the plurality of stepped enlarged portions 7C-1, 7C-2, ..., 7C-N of the enlarged portion 7C. 7C-2 and 7C-3 are shown enlarged.

  In FIG. 2 (C), the stepped enlarged portion 7C-2 located in the middle in the axial direction has a stepped portion 10B with respect to the radius R of the stepped enlarged portion 7C-1 adjacent on the upstream side. A cylindrical inner surface having a section length L extending in the axial direction is formed with a radius of R + ΔR expanded by a step size of ΔR so as to form −2. On the other hand, the stepped enlarged portion 7C-3 adjacent on the downstream side is similarly expanded in diameter than the stepped enlarged portion 7C-2 and extends by the section length L. In FIG. 2C, the section length L of the stepped enlarged portions 7C-1, 7C-2,..., 7C-N is a constant length, but the section increases toward the downstream stepped enlarged portion. The length L may be increased. In addition, the radius of the stepped diameter-enlarged portion has a constant dimension in the axial direction and forms the inner surface of the cylinder. Good. By doing so, the space volume of the step-shaped enlarged diameter portion is further increased, and the space for introducing and condensing the evaporative gas into the low-temperature liquid can be further increased, so that the evaporative gas can be condensed more reliably. Mixing can be performed.

  In the stepped enlarged diameter portion 7C-2, an injection opening 10A-2 of the steam hole 10-2 is located at an upstream position in the region. In the example of FIG. 2C, the upstream side edge of the injection opening 10A-2 is formed at the position of the stepped portion 10B-2. The steam hole 10-2 is formed so as to penetrate the tube wall of the flow tube 7 in the radial direction, and is inclined inward in the axial direction toward the radial inward. The other steam holes 10-1, 10-3,..., 10-N are similarly upstream of the corresponding step-shaped enlarged diameter portions 7C-1, 7C-3,. The injection openings 10A-1, 10A-3, 10A-N are provided on the side.

  In the present invention, the steam holes 10-1, 10-2,..., 10-N are positioned immediately after the sudden expansion at the stepped portions 10B-1, 10B-2,. The space over the section length L immediately after the sudden expansion at the stepped portions 10B-1, 10B-2,... Can be secured as a sufficiently large space through which bubbles of the evaporative gas flow in the low temperature liquid. A sufficient contact time between the evaporative gas and the low-temperature liquid can be ensured in the space, and the evaporative gas can be cooled, condensed, and mixed with the low-temperature liquid. Further, the evaporative gas is efficiently sucked by the venturi phenomenon efficiently without being affected by the flow of the low-temperature liquid in the flow tube within the space of the stepped diameter-expanded portion.

  The form of the stepped enlarged portion having the stepped portion described above is effective for condensing and mixing the evaporative gas in the low-temperature liquid, but this effect can be achieved by appropriately setting the size of the stepped enlarged portion. Can be played more reliably. For example, if the step size ΔR of the step portions 10B-1, 10B-2,... That rapidly expands the inner diameter of the venturi-type flow tube 7 is too large, the flow of the cryogenic liquid is disturbed from the position of this step portion. , The vapor holes 10-1, 10-2,. As a result, the efficiency of sucking the vapor due to the venturi phenomenon of the low temperature liquid decreases. Accordingly, it is necessary to optimally set the step size for rapidly expanding the inner diameter of the venturi expanded portion.

  Therefore, the inventor conducted various experiments to determine what step size the efficiencies of sucking the evaporative gas into the low-temperature liquid are good. FIG. 3A shows the result of examining the efficiency of suction based on the step size and the venturi phenomenon based on the experiment. The step size ratio is expressed as a ratio (%) of the step size to the immediately preceding radius, that is, a ratio (%) of the step size to the radius of the step-shaped enlarged diameter portion located on the upstream side of the step portion. The efficiency improvement rate is the ratio at which the flow rate of the evaporative gas sucked by the low temperature liquid venturi phenomenon increases compared to when no step is provided, assuming that the power required to flow the low temperature liquid to the venturi pipe is the same. It is expressed as an efficiency improvement rate (%). As shown in FIG. 3A, the efficiency improvement rate is increased by setting the step size in the range of 5 to 40% of the immediately preceding radius compared to when no step is provided, and the step size is set immediately before the step size. It can be seen that when the radius is in the range of 12 to 30%, the efficiency improvement rate is 70% or more and the suction efficiency is high.

  Furthermore, in the present invention, not only the above step radius but also the section length (the length of one section which is the length in the axial direction) of the stepped diameter enlarged portion in which the inner diameter of the venturi expanded portion is rapidly expanded is an appropriate range. We thought that there was, and experimented about this. If the length of one section is short, the transition to the next step-shaped enlarged diameter portion occurs while mixing of the evaporating gas and the cryogenic liquid is insufficient, so that the temperature of only the cryogenic liquid near the vapor hole rises. As a result, since the temperature difference between the evaporative gas and the low-temperature liquid becomes small in the downstream, the evaporative gas is difficult to condense. On the other hand, if the section length is too long, the pressure loss in the venturi tube increases, so that more power is required, and the apparatus becomes larger, leading to an increase in cost. As a result of an experiment on the ratio of the section length dimension, which is the ratio of the section length dimension to the radius of the stepped enlarged portion, and the venturi tube suction efficiency improvement rate (%), as shown in FIG. It has been found that the appropriate size is 2.5 to 8 times the radius of the stepped enlarged portion.

  Next, the evaporative gas reliquefaction apparatus of this embodiment configured as described above and its operation will be described with reference to FIGS.

  First, a part of a cryogenic liquid (for example, LNG) 11 in a tank (not shown) is sent out by the delivery pump 3 and introduced into the condensing and mixing apparatus 2. The evaporative gas generated in the tank is boosted to a pressure (intermediate pressure) between the atmospheric pressure and the city gas operating pressure (4 to 7 MPa) by the evaporative gas compressor 4 and then introduced into the condensing and mixing apparatus 2. Is done.

  The cryogenic liquid 11 introduced into the condensing and mixing apparatus 2 directly flows into the swirl flow forming unit 2A and a part thereof is injected from the tangential inlet 2A-1 via the branch pipe 2A-2. The cryogenic liquid 11 that has directly flowed into the swirling flow forming portion 2A flows in the direction of the axis X, and the cryogenic liquid injected from the tangential inlet 2A-1 flows in the circumferential direction, and flows through the swirling flow forming portion 2A. Will form a swirl flow.

  The cryogenic liquid 11 that has turned into a swirl flow in the swirl flow forming portion 2A flows into the flow tube 7 via an inlet portion 6A provided in the casing 6 of the condensing and mixing device 2 containing the mixed flow tube portion 2B. It flows through the reduced diameter portion 7A, the throat portion 7B, and the expanded diameter portion 7C, and reaches the outlet portion 6B of the casing 6. The cryogenic liquid 11 flowing in the flow tube 7 increases the flow velocity at the reduced diameter portion 7A, reaches the maximum flow velocity at the throat portion 7B, and then gradually decreases the flow velocity at the expanded diameter portion 7C, but the right end at the expanded diameter portion 7C. Since the maximum inner diameter is smaller than the inner diameter of the inlet portion 6A, the flow velocity at the enlarged diameter portion 7C is higher than the flow velocity at the time of inflow of the inlet portion 6A. -Suction power is provided for 2, ...

  On the other hand, the evaporative gas 12 is pressurized by the evaporative gas compressor 4 and injected into the casing 6 through the evaporative gas injection part 6D provided in the casing 6 of the condensing and mixing apparatus 2. An insertion material 8 is inserted into the outer periphery of the flow tube 7 in the flow tube accommodating portion 6C of the casing 6 that accommodates the flow tube 7, and the evaporative gas injection portion is pumped by the evaporative gas compressor 4. The evaporative gas 12 injected from 6D is buffered by the insert 8 and diffuses over the entire circumference and the entire length of the flow tube 7 in the flow tube housing 6C.

  As described above, the low-temperature liquid 11 flowing through the enlarged diameter portion 7C of the flow tube 7 provides a suction force to the vapor holes 10-1, 10-2,. The evaporative gas 12 diffusing in the gas is sucked and introduced into the enlarged diameter portion 7C from the vapor holes 10-1, 10-2,. For example, in the vapor hole 10-2 shown in FIG. 2B, the evaporative gas 12 is sucked from the vapor hole 10-2 and passes through the injection opening 10A-2, and then the step-shaped enlarged diameter portion 7C-. 2 flows in. The injection opening 10A-2 is located on the upstream side in the region of the stepped enlarged diameter portion 7C-2, and the vapor hole 10-2 is inclined upstream toward the radius inward. Are joined under low resistance without countering the flow of the cryogenic liquid 11 in the flow tube 7. At that time, since the cryogenic liquid 11 forms a swirling flow, the evaporative gas 12 is sufficiently mixed with the cryogenic liquid 11 both in the circumferential direction and in the radial direction.

  The stepped diameter-enlarged portion 7C-2 has a diameter that is abruptly increased by ΔR at the stepped portion 10B-2 relative to the preceding stepped diameter-increased portion 7C-1 located on the upstream side. A space over the section length L is formed on the downstream side of the portion 10B-2, and this space can be secured as a sufficiently large space through which bubbles of the evaporative gas 12 flow in the cryogenic liquid 11, A sufficient contact time between the evaporative gas 12 and the cryogenic liquid 11 can be secured in the space, and the evaporative gas 12 can be easily mixed into the cryogenic liquid 11, and the evaporative gas 12 is cooled and condensed by the cryogenic liquid 11 and mixed. Can be made. As a result, the evaporation gas 12 is condensed and reliably liquefied, and flows downstream as a part of the low temperature liquid 11. In this way, the merging due to the inflow of evaporative gas from the vapor hole and mixing into the low-temperature liquid is performed in the same manner in the stepped enlarged portion other than the stepped enlarged portion 7C-2. Thus, the mixed cryogenic liquid 11A containing the re-liquefied evaporative gas is boosted by the booster pump 5 and brought to the vaporizer, then vaporized by the vaporizer and sent to the demand side as city gas.

<Second embodiment>
In the first embodiment, the flow rate of the cryogenic liquid is not particularly controlled. However, in the second embodiment, the degree of supercooling of the generated mixed cryogenic liquid can be adjusted by controlling the flow rate of the cryogenic liquid. This is different from the first embodiment. FIG. 4 is a schematic diagram showing a configuration for controlling the flow rate of the cryogenic liquid in the second embodiment. Hereinafter, the difference from the first embodiment will be mainly described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

  The condensing and mixing apparatus 2 shown in FIG. 4 is the same apparatus as the condensing and mixing apparatus 2 of the first embodiment shown in FIG. 2, and the same reference numerals as those of the first embodiment are given to the respective parts. As shown in FIG. 4, the condensing and mixing apparatus 2 is connected to the upstream end of the swirl flow forming portion 2A, the main flow pipe 25 for circulating the cryogenic liquid 11 flowing from the upstream side toward the downstream side as the main flow. In addition, a subflow pipe 26 that branches from the main flow pipe 25 and distributes the cryogenic liquid 11 as a subflow is connected to the tangential inlet 2A-1 of the swirl flow forming portion 2A. In this embodiment, a part of the low-temperature liquid (for example, LNG) 11 in the tank (not shown) is sent out by the delivery pump 3 and circulates in the main flow pipe 25 as the main flow to the swirl flow forming unit 2A. Direct inflow. A part of the mainstream low-temperature liquid flowing through the main flow pipe 25 flows as a subflow through the subflow pipe 26 and is injected in the tangential direction from the tangential inlet 2A-1 of the swirl flow forming portion 2A. The swirl flow forming portion 2A receives the low-temperature liquid of the main flow and the sub flow, and generates a swirl flow with respect to the main flow by the sub flow flowing in the circumferential direction in the swirl flow formation portion 2A. Further, in the condensing and mixing apparatus 2, a mixed liquid pipe 10 through which the mixed cryogenic liquid flowing out from the outlet portion 6B flows toward the downstream side, that is, the booster pump 5 side, is connected to an end portion on the downstream side of the outlet portion 6B. Yes.

  The condensing and mixing apparatus 2 further includes a main flow meter 27 and a main flow adjusting valve 28 provided in the main flow tube 25, a sub flow meter 13 and a sub flow adjusting valve 14 provided in the sub flow tube 26, and a mixed liquid tube. 10 stores a mixed liquid pressure gauge 15 and a mixed liquid thermometer 16, a control unit 17 for controlling the flow rates of the main flow and the substream, and data referred to in the control by the control unit 17. Storage means 18.

  As described above, the main flow meter 27 and the main flow regulating valve 28 are provided in the main flow pipe 25, respectively. The mainstream flow meter 27 measures the flow rate of the mainstream cryogenic liquid 11 flowing in the mainstream pipe 25 and flowing into the swirl flow forming unit 2A. The main flow regulating valve 28 can adjust the main flow rate by adjusting the opening degree under the control of the control means 17 described later. Further, the secondary flow meter 13 and the secondary flow adjustment valve 14 are provided in the secondary flow pipe 26, respectively. The side flow meter 13 measures the flow rate of the low temperature liquid 11 in the side flow that flows through the side flow pipe 26 and is injected into the swirl flow forming unit 2A. The subflow adjusting valve 14 can adjust the flow rate of the subflow by adjusting the opening degree under the control of the control means 17 described later. Further, as described above, the mixed liquid pressure gauge 15 and the mixed liquid thermometer 16 are provided in the mixed liquid pipe 10, respectively, and the pressure of the mixed low-temperature liquid flowing out from the outlet portion 6B and flowing in the mixed liquid pipe 10 and Each temperature is measured.

  The storage means 18 uses the data of the correspondence between the pressure of the mixed cryogenic liquid and the saturation temperature at that pressure as the first correspondence A, and the allowable minimum value of the subcooling degree of the mixed cryogenic liquid and the side flow rate ratio. Data on the correspondence with (turning strength) is stored in advance as the second correspondence B (see FIG. 5). The data of the first correspondence relationship A and the second correspondence relationship B is referred to by the control means 17 when controlling the flow rate of the secondary flow, as will be described later. Here, the “minimum value of the degree of supercooling” is the smallest value of the degree of supercooling that prevents vapor from being present in the mixed low-temperature liquid. As the minimum value of the degree of supercooling is smaller, the temperature at which the mixed cryogenic liquid is cooled so that there is no vapor in the mixed cryogenic liquid is closer to the saturation temperature. The degree of supercooling is calculated by the supercooling degree calculating means as the difference between the derived value of the saturation temperature and the measured value of the temperature of the mixed cryogenic liquid. The “substream flow rate ratio” is the ratio of the substream flow rate to the sum of the mainstream flow rate and the substream flow rate. It is calculated by dividing the measured value of the flow rate of the secondary flow by the sum of the measured value of the flow rate. Further, it is desirable that the storage means 18 stores the first correspondence relationship A as, for example, a relational expression between the pressure of the mixed cryogenic liquid and the saturation temperature, a relationship diagram, or a form of a vapor table.

  FIG. 5 is a diagram showing the relationship between the minimum value of the degree of supercooling of the mixed low-temperature liquid and the side flow rate ratio (swirl strength), that is, the second correspondence relationship B. As shown in FIG. 5, the minimum value of the degree of supercooling of the mixed cryogenic liquid is reduced when the side flow rate ratio is 0, that is, when there is a swirling, and the subcooling of the mixed cryogenic liquid is reduced. The minimum value of the degree of flow and the secondary flow rate ratio (swirl strength) have a relation that the minimum value of the degree of supercooling decreases as the secondary flow rate ratio increases. In other words, the larger the side flow rate ratio, the smaller the minimum value of the degree of supercooling, the temperature of the mixed cryogenic liquid in the liquid state in which no vapor exists in the mixed cryogenic liquid is close to the saturation temperature, and the mixing performance of the condensing and mixing device is improved. To do.

  As shown in FIG. 4, the control means 17 includes a supercooling degree calculating means 22 for calculating the degree of supercooling of the mixed cryogenic liquid, a subflow flow rate ratio calculating means 23 for calculating a subflow flow rate ratio, and a main flow regulating valve. 28 and a flow rate adjusting means 24 for adjusting the respective opening degrees of the auxiliary flow adjusting valve 14. The supercooling degree calculation means 22 refers to the first correspondence A stored in the storage means 18 and derives the saturation temperature corresponding to the measured value of the pressure of the mixed cryogenic liquid, and then derives the saturation temperature derived value. And the difference between the measured value of the temperature of the mixed cryogenic liquid and the degree of supercooling of the mixed cryogenic liquid. The secondary flow rate ratio calculating means 23 calculates the secondary flow rate ratio by dividing the measured value of the secondary flow by the sum of the measured value of the primary flow and the measured value of the secondary flow. The flow rate adjusting unit 24 compares the calculated value of the degree of supercooling with the minimum value of the degree of supercooling in the second correspondence B stored in the storage unit 18 (see FIG. 5), When the calculated value is equal to or less than the minimum value, the second correspondence relationship B is referred to, and a subflow rate ratio in which the calculated value of the degree of supercooling is larger than the minimum value is derived as a target value. The flow rate of the secondary flow is increased by increasing the opening of the secondary flow adjustment valve 14 so that the calculated value of the secondary flow rate ratio follows the target value.

  Next, the control operation of the side flow rate by the control means 17 will be described. In this embodiment, when the evaporative gas reliquefaction apparatus 1 is operated with the main flow adjustment valve 28 open and the sub flow adjustment valve 14 closed, the sub flow adjustment valve 14 is opened as necessary. A control operation when a side flow is injected into the swirl flow forming unit 2A to form a swirl flow will be described.

  The supercooling degree calculation means 22 of the control means 17 refers to the first correspondence relationship A stored in the storage means 18 and corresponds to the measured value of the pressure of the mixed cryogenic liquid measured by the mixed liquid pressure gauge 15. The saturation temperature is calculated, and then the difference between the calculated saturation temperature and the measured value of the mixed cryogenic liquid temperature measured by the mixed liquid thermometer 16 is calculated as the degree of supercooling. Further, the side flow rate ratio calculating means 23 is the sum of the measurement value of the main flow rate measured by the main flow meter 27 and the measurement value of the sub flow rate measured by the sub flow meter 13. The measured value of the flow rate is divided to calculate the side flow rate ratio (turning strength).

  The flow rate adjusting unit 24 compares the calculated value of the degree of supercooling calculated by the degree of supercooling calculating unit 22 with the minimum value of the degree of supercooling in the second correspondence B stored in the storage unit 18. As a result of this comparison, when the calculated value of the degree of supercooling is larger than the minimum value, it can be said that the evaporated gas is mixed in the low temperature liquid without being present as bubbles in the low temperature liquid. Therefore, the flow rate adjusting means 24 does not perform control for opening the subflow adjusting valve 14. That is, since the subflow is not injected into the swirl flow forming portion 2A, the state where the swirl flow is not formed with respect to the main flow is maintained.

  On the other hand, when the calculated value of the degree of supercooling is less than or equal to the minimum value, bubbles of evaporative gas remain in the mixed low-temperature liquid flowing out from the outlet 6B, and the mixed low-temperature liquid becomes a gas-liquid two-phase flow. I can say that. In such a state, if the evaporative gas is condensed on the downstream side of the condensing and mixing device 2, the safe operation of the entire evaporative gas reliquefaction device 1 is hindered, such as the occurrence of a water hammer action.

  Therefore, the flow rate adjusting means 24 refers to the second correspondence B, derives the subflow flow rate ratio so that the calculated value of the degree of supercooling is larger than the minimum value, and sets the subflow flow rate ratio as a target value. The opening degree of the secondary flow adjustment valve 14 is adjusted so that the calculated value of the secondary flow rate ratio calculated by the calculation means 23 follows the target value. As a result, the sub-flow low-temperature liquid adjusted to an appropriate flow rate is injected tangentially into the swirl flow forming portion 2A, and forms a swirl flow with respect to the main flow, thereby reducing the degree of supercooling of the mixed low-temperature liquid. . Accordingly, the evaporated gas can be reliably condensed and mixed with the low temperature liquid without remaining in the low temperature liquid.

  As a specific example of the above-described control operation, the flow rate of the mixed cryogenic liquid is changed from the state in which the swirling flow is not formed (the swirl strength is 0%) and the supercooling degree of the mixed cryogenic liquid is operating at 5 ° C. A case where the temperature of the mixed cryogenic liquid is increased without changing much will be described. In this case, it is necessary to increase the flow rate of the evaporating gas blown into the flow pipe 7, but as can be seen from FIG. 5 showing the second correspondence B, the degree of supercooling of the mixed cryogenic liquid is the minimum value (5 ° C.). Therefore, if it remains as it is, bubbles of the evaporative gas in the mixed low temperature liquid remain, and the flow rate of the evaporative gas cannot be increased.

  Therefore, the secondary flow regulating valve 14 is opened to inject the secondary flow low temperature liquid into the swirl flow forming section 8 in the tangential direction to form a swirl flow, thereby reducing the minimum value of the degree of supercooling and mixing the low temperature liquid. Increase the temperature. As shown in FIG. 5, when the temperature of the mixed cryogenic liquid is increased by 2 ° C. (when the degree of supercooling is raised from 5 ° C. to 3 ° C.), the side flow rate ratio (swirl strength) is about 35%. By adjusting the flow rate of the side flow, the condensation mixing performance of the evaporative gas is enhanced, so that the bubbles of the evaporative gas do not remain in the mixed low temperature liquid. The application of such swirling causes an increase in the pressure loss of the fluid in the condensing and mixing apparatus 2 and increases the power of the pump to be supplied. Therefore, the swirling is performed only when the degree of supercooling of the mixed cryogenic liquid is reduced. It is desirable. In this way, by providing swirl only when necessary, it is possible to suppress an increase in pressure loss to a minimum as compared with the case where a device such as a fixed swirl blade is provided, and unnecessarily reduce energy consumption. An increase can be prevented.

  As described above, the turning control as described above is performed when the amount of evaporating gas to be condensed and mixed in the low temperature liquid is increased. In addition, this swirl control is performed by increasing the temperature of the obtained mixed low temperature liquid, for example, when water as evaporative gas is mixed with water as low temperature liquid to generate hot water as mixed low temperature liquid. This is also effective when desired.

  In the present embodiment, since the flow rate of the low-temperature liquid in the secondary flow is controlled so that the degree of supercooling of the mixed low-temperature liquid is always greater than the minimum value, the evaporative gas is effectively mixed into the low-temperature liquid. The liquid can be reliquefied, and it is possible to prevent the evaporative gas from flowing into the pump as a gas and causing a failure of the pump. In addition, since it is not necessary to provide a device such as a conventional fixed swirl blade for imparting swirl, the pressure loss of the condensing and mixing device can be minimized, and the reliquefaction of the evaporative gas can be efficiently performed in a short time. In addition, the apparatus configuration can be made compact.

  Further, in the present embodiment, the control means 17 controls both the main flow regulating valve 28 and the sub flow regulating valve 14, but instead, only the sub flow regulating valve 14 may be controlled. Good.

  Moreover, in this embodiment, although the condensation mixing apparatus 2 is arrange | positioned in the horizontal direction, you may arrange | position in the vertical direction. Since the condensing and mixing device 2 is arranged in the vertical direction, the cryogenic liquid 11 is circulated downward in the vertical direction, and the evaporative gas flows in from the horizontal direction. Gas condensation and mixing is performed more stably.

  Further, in the present embodiment, the calculated value of the degree of supercooling is compared with the minimum value of the degree of supercooling in the second correspondence B, and the side flow rate ratio is set such that the calculated value of the degree of supercooling is larger than the minimum value. The flow rate of the secondary flow is adjusted as the target value, but the target system is required to set the secondary flow rate ratio that is larger than the value obtained by adding a constant value to the minimum value of the degree of subcooling. The safety factor may be reflected.

DESCRIPTION OF SYMBOLS 1 Evaporative gas reliquefaction apparatus 2 Condensation mixing apparatus 2A Swirling flow formation part 2B Mixed flow pipe part 3 Delivery pump 4 Evaporative gas compressor 7 Flow pipe 7A Reduced diameter part 7B Throat part 7C Expanded diameter part 7C-1, 7C-2 Stage 9A Mounting flange 9B Mounting flange 10-1, 10-2 Steam hole 10A-1, 10A-2 Injection opening 10B-1, 10B-2 Step portion L Section length R Radius of step-like enlarged portion ΔR Radius Difference (step size)

Claims (5)

Mixing having a venturi-type flow tube in which a diameter-reduced portion that gradually decreases from the upstream side toward the downstream side is followed by a throat portion that has the smallest diameter, and then a diameter-expanded portion that gradually increases from the throat portion. In order to provide a flow tube portion and inject steam into the flow tube from the outside of the flow tube, the steam holes directed in the radial direction and downstream direction of the flow tube have a plurality of positions in the axial direction of the flow tube. In a condensing and mixing apparatus that is formed to have an injection opening on an inner diameter surface, injects steam from an injection opening of a vapor hole into a low-temperature liquid that flows downstream in a flow tube, condenses the vapor, and mixes it with the low-temperature liquid ,
A swirl flow forming portion is provided upstream of the flow tube and on the extension of the axial line of the flow tube and connected to the reduced diameter portion to allow low temperature liquid to flow toward the flow tube. ,
The swirl flow forming portion is formed so as to inject a liquid of the same type as the low temperature liquid in the flow tube from a tangential direction,
The expanded diameter portion of the mixed flow pipe section is formed with stepped portions at a plurality of positions in the axial direction, and has a stepped diameter expansion having an inner peripheral surface that is sequentially expanded in diameter in the stepped section and extends toward the downstream side in the axial direction. A condensing and mixing apparatus, characterized in that a steam hole injection opening is provided at a position upstream of each step-shaped enlarged diameter portion.   The swirl flow forming unit is configured to divide a part of the low-temperature liquid supplied to the reduced diameter portion of the flow tube at a position upstream of the swirl flow forming unit and to inject the swirl flow forming unit in a tangential direction. The condensing and mixing apparatus according to claim 1, wherein   The stepped portion has a radius difference between a preceding stepped enlarged portion adjacent upstream on the upstream side and a succeeding stepped enlarged portion adjacent downstream on the inner diameter of the preceding stepped enlarged portion. The condensing and mixing apparatus according to claim 1, which has a size of 12 to 30%.   The condensing and mixing apparatus according to claim 2 or 3, wherein the stepped enlarged diameter portion extends in the axial direction over a section length of 2.5 to 8 times the radius of the stepped enlarged diameter portion. In the evaporative gas reliquefaction device that mixes the condensed gas generated from the cryogenic liquid stored in the storage tank with the cryogenic liquid dispensed from the storage tank, condenses and reliquefies it,
5. A condensing and mixing apparatus according to claim 1, an evaporative gas compressor for compressing evaporative gas, and a delivery pump for delivering a cryogenic liquid from a storage tank, wherein the cryogenic liquid is supplied by the delivery pump. The evaporative gas reliquefaction is characterized in that the evaporative gas is supplied from the upstream side to the flow tube of the condensing and mixing device, and the evaporative gas is injected into the flow tube from the vapor hole of the condensing and mixing device by the evaporative gas compressor. apparatus.

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