JP5855298B1 - LNG evaporator and LNG evaporation method using LNG evaporator - Google Patents

Abstract

When cold and hot water of about 20 to 30 ° C. is used in a conventional LNG evaporator, icing may occur on the surface of a heat transfer tube coil, and the LNG evaporator may become blocked. A heat transfer tube coil is arranged in an outer cylinder, and is divided from the entire flow flowing in the outer cylinder by the heat transfer tube coil itself or by a spiral flow forming member spirally provided in the outer cylinder. A spiral flow with an increased flow velocity is formed along the heat transfer tube coil, and heat exchange is performed between the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil. Freezing on the outer surface is suppressed. [Selection] Figure 2

Description

  The present invention relates to an LNG evaporator and an LNG evaporation method using the LNG evaporator.

  In recent years, natural gas has attracted attention as an energy resource to replace oil and coal. Natural gas generates very little sulfur oxides and dust during combustion, and emits less carbon dioxide, which causes global warming, and nitrogen oxides, which causes air pollution and acid rain, compared to oil and coal. Therefore, it can be said that it is an energy source that can contribute to global environmental problems. In particular, the emergence of new technologies related to the extraction of natural gas (shale gas) collected from the shale layer has made it possible to stably supply a large amount of natural gas at a relatively low cost. Are expected to become increasingly large. The fuel conversion to natural gas has a great effect on the reduction of carbon dioxide emissions that promote global warming. If fuel oil is simply converted to natural gas, it can be reduced by about 30%, and a great effect can be achieved in suppressing global warming. (Considering the use of fuel in satellite construction, the reduction effect of carbon dioxide emissions is about 25%) With this aspect, fuel conversion has been actively promoted for several years, and the shale gas revolution LNG conversion is expected to be promoted more and more in the future.

  Except for areas where natural gas can be directly supplied through pipelines, the natural gas supply method consists mainly of liquefied natural gas (hereinafter referred to as LNG) storage tanks, evaporators, and pressure regulators. It is common to construct a land-based LNG supply facility (hereinafter referred to as LNG satellite) at each natural gas consumption place, and to transport and supply LNG to the LNG satellite by an LNG lorry vehicle.

In the LNG satellite facility, LNG is stored in a storage tank, vaporized by an evaporator, and consumed as gaseous fuel. As an evaporator system for vaporizing LNG, which is a cryogenic gas, it is also possible to use an air temperature evaporator (star fin type) that exchanges heat with the atmosphere used to evaporate oxygen or nitrogen gas. is there. This method does not require a compulsory heat source, but because the heat exchange rate is low, it is large in terms of securing the heat transfer area of the heat exchanger, resulting in a very large installation space, foundation work, extension of piping length, etc. This has led to an increase in construction costs. In view of this, the latent heat of vaporization of LNG requires three times the amount of heat as compared to nitrogen, and since sensible heat is large, the use of an evaporation method other than an air temperature evaporator is increasing as examples. Other evaporation methods include a hot water circulation evaporator that circulates hot water by putting an evaporation pipe in hot water at about 60 to 75 ° C., and an evaporation pipe in hot water at about 60 ° C. Steam-heating evaporators that use heat as a heat source are currently used. In both cases of these hot water evaporators, the temperature of the hot water is increased to about 60 ° C. using a heat source in order to prevent the ice from adhering to the surface of the evaporator tube.
About the conventional LNG evaporation method 1) Air temperature evaporator method The LNG evaporation method by the air temperature evaporator takes out the LNG stored in the LNG storage tank,
In this system, heat is exchanged with the atmosphere using an aluminum star fin, and evaporated natural gas (hereinafter sometimes referred to as NG) is pressure-regulated by a pressure regulator and supplied.

Although a heat source is not required, it is affected by the outside air temperature, and since the heat exchange rate is low, the heat exchanger has a large size and a large installation area from the viewpoint of securing the heat transfer area. Two units are installed in order to thaw the ice icing on the fins, and they are used alternately to ensure thawing time. In addition, it is necessary to select the capacity with a large safety factor for the actual usage amount in consideration of icing. There are more points to consider than equations.
2) Warm water circulation evaporator method The LNG evaporation method by the warm water circulation evaporator takes out LNG stored in the LNG storage tank, exchanges heat with a vaporization tube in the warm water tank filled with warm water, and evaporates the evaporated NG. This is a method of supplying after pressure regulation with a pressure regulator.

It is necessary to produce hot water as a heat source with a hot water boiler or a hot water heater. LNG will be used as a heat source for hot water boilers, and overall efficiency will be reduced accordingly. Hot water produced by a hot water boiler or the like is supplied to the evaporator by a hot water pump, and a cold circulation water whose temperature has been lowered by using it for heat exchange is heated by a hot water boiler or the like.
3) Steam hot water evaporator method The LNG evaporation method using the steam hot water evaporator takes out the LNG stored in the LNG storage tank, exchanges heat with the vaporization tube in the hot water tank heated by the steam, and evaporates NG Is supplied after pressure regulation with a pressure regulator.

  Warm water as a heat source is generated by blowing steam into the hot water tank.

  It is effective when there is excess steam, but it is difficult to use because there is usually no room for production facilities. In addition, it is not very efficient to use steam only for heating other than production facilities. In some cases, a steam generator is installed for the evaporator. In this case, LNG is used as a heat source for the steam generator (steam boiler, etc.), and the overall efficiency is reduced accordingly. .

  Patent Document 1 describes a vaporizer in which the arrangement of the spiral tube and the heater is improved to reduce the size of the hot water tank and to improve the thermal efficiency.

JP 2003-214596 A

  The invention described in Patent Document 1 does not form a swirling flow and does not solve icing on the surface of the spiral tube.

  There has been a problem with the use of cold and hot water in conventional hot water evaporators.

  When cold and hot water of about 20 ° C. is used in a conventional hot water evaporator, ice is generated on the vaporization tube surface. According to the result of earnest examination of the generation state, it has been found that the generation of ice depends on the flow rate of hot water (heat medium) on the surface of the heat transfer tube, but this flow rate was not considered. It has been found that the faster the flow velocity outside the tube, the less the ice adheres. However, the conventional hot water evaporator currently used has a slow flow velocity outside the tube and heat transfer tubes when cold / hot water is circulated. It is clear that ice is formed on the surface. When ice is generated, the tube becomes blocked and an accident occurs, making it impossible to operate. The present invention provides an LNG evaporator and an evaporation method that solve this problem.

The present invention includes a cylindrical outer cylinder that is long in the longitudinal direction and a heat transfer tube coil that is wound around the outer cylinder in a coil shape, and that flows through the first medium flowing in the outer cylinder and the heat transfer tube coil. Heat exchange is performed with the second medium. The first medium flowing in the outer cylinder is cold / hot water flowing from a hot water source, and the second medium flowing in the heat transfer tube coil is liquefied LNG. In the LNG evaporator in which liquefied LNG is evaporated by cold / hot water,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is disposed at the center of the outer tube, and the heat transfer tube coil is disposed around the center tube tube, or by the heat transfer tube coil itself or The spiral flow forming member provided in a spiral shape in the outer cylinder is divided from the entire flow flowing in the outer cylinder to form a spiral flow having a higher flow velocity along the heat transfer tube coil. The LNG evaporator is characterized in that heat exchange is performed between the chilled / warm water and the liquefied LNG flowing in the heat transfer tube coil to suppress icing on the outer surface of the heat transfer tube coil.

  The present invention provides the above-described LNG evaporator, wherein the cylindrical body is a cylindrical center tube.

The present invention comprises a cylindrical outer cylinder that is long in the longitudinal direction and a heat transfer tube coil disposed in a coil shape in the outer cylinder, and a first medium that flows in the outer cylinder and a heat transfer tube coil that flows in the heat transfer tube coil. Heat exchange is performed between the second medium, the first medium flowing in the outer cylinder is hot water flowing from a hot water source, and the second medium flowing in the heat transfer tube coil is liquefied LNG. In an LNG evaporator in which liquefied LNG is evaporated by hot water,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is disposed in the center of the outer tube, and the sub-warm water divided from the hot water source is passed through the center tube tube. The heat transfer tube coil is disposed by winding the center tube tube, and the heat transfer tube coil is disposed by the heat transfer coil itself or a spiral flow forming member provided in a spiral shape in the outer cylinder. A spiral flow with an increased flow velocity is formed along the heat transfer tube coil from the entire flow flowing in the cylinder, and between the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil. Provided is an LNG evaporator, characterized in that heat exchange is performed and sub-warm water flowing through a center tube tube heats the heat transfer tube coil and ice formation on the outer surface of the heat transfer tube coil is suppressed.

  The present invention is the above-described LNG evaporator, in which the spiral flow forming member is provided on the outer surface of the center tube tube, the spiral fin is provided on the inner wall surface of the outer cylinder, or Provided is an LNG evaporator, wherein the spiral flow forming member is a plurality of cold / hot water inlets arranged on the inner wall surface of the outer cylinder in a spiral shape.

The present invention includes a cylindrical outer cylinder that is long in the longitudinal direction and a heat transfer tube coil that is wound around the outer cylinder in a coil shape, and that flows through the first medium flowing in the outer cylinder and the heat transfer tube coil. Heat exchange is performed with the second medium, the first medium flowing in the outer cylinder is warm water flowing from the hot water source, and the second medium flowing in the heat transfer tube coil tube is liquefied LNG. In the evaporation method of liquefied LNG by the LNG evaporator in which liquefied LNG is evaporated by hot water,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is disposed at the center of the outer tube, and the heat transfer tube coil is disposed around the center tube tube, or by the heat transfer tube coil itself or The spiral flow forming member provided in a spiral shape in the outer cylinder is divided from the entire flow flowing in the outer cylinder to form a spiral flow with an increased flow velocity along the heat transfer tube coil. A method for evaporating liquefied LNG using an LNG evaporator is provided, in which heat exchange is performed between cold / warm water to be liquefied and liquefied LNG flowing in the heat transfer tube coil to suppress icing on the outer surface of the heat transfer tube coil.

The present invention includes a cylindrical outer cylinder that is long in the longitudinal direction and a heat transfer tube coil that is wound around the outer cylinder in a coil shape, and that flows through the first medium flowing in the outer cylinder and the heat transfer tube coil. Heat exchange is performed with the second medium. The first medium flowing in the outer cylinder is hot water flowing from the hot water source, and the second medium flowing in the heat transfer tube coil is liquefied LNG. In the evaporation method of liquefied LNG by the LNG evaporator in which liquefied LNG is evaporated by hot water,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is disposed in the center portion of the outer tube, and the sub cold / hot water separated from the cold / hot water source flows through the center tube tube. The heat transfer tube coil is arranged by winding a tube, the heat transfer tube coil is arranged by winding the center tube tube, the heat transfer tube coil itself, or by the spiral flow forming member provided spirally in the outer cylinder, The entire flow flowing in the outer cylinder is divided from the entire flow to form a spiral flow whose flow velocity is increased along the heat transfer tube coil, and between the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil. The LNG evaporator is used to exchange liquefied LNG by heat exchange in the LNG evaporator, which suppresses icing on the outer surface of the heat transfer tube coil by heating the spiral flow with sub-cold hot water flowing through the center tube. An evaporation method is provided.

  The present invention provides a heat exchange method in an LNG evaporator, characterized in that in the heat exchange method using the LNG evaporator described above, the cold / hot water is cold / hot water of a cold / hot water source generally provided in the office. provide.

  According to the present invention, the heat flow tube coil itself or a spiral flow forming member provided in a spiral shape in the outer cylinder is divided from the entire flow flowing in the outer cylinder, and the flow velocity along the heat transfer tube coil is changed. Is formed, heat exchange is performed between the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil, and icing on the outer surface of the heat transfer tube coil is suppressed. By suppressing the formation of icing, a tube blockage accident is prevented, and a situation where operation is impossible is avoided. The hot water discharged from the cooling tower generally provided in the office is usually in the range of 20 to 38 ° C., and the temperature before being connected to the LNG evaporator is maintained, and the LNG is evaporated as cold / hot water. Therefore, the present invention can solve the problems of the conventional LNG evaporator.

The figure which shows the structure of the LNG evaporation system which is an Example of this invention. The figure which shows the structure of the LNG evaporator which is an Example of this invention. The figure which shows the plane of the structure shown by FIG. The figure explaining the function of a warm water inlet part. The figure explaining spiral flow. The figure which shows the form of the center tube pipe provided with fin. The figure which shows typically the virtual long cross-sectional area of the spiral flow formed. Figure that examines freezing at the time of calculation The figure which shows calculation result data. The figure which shows calculation result data. The figure which shows calculation result data.

  The present invention provides a cold / hot water type LNG evaporator that can use the cold / warm water of the cooling water circulation system used in each business site without using hot water. The cooling water used in the workplace is returned to the cooling device such as a cooling tower after cooling the object to be cooled, and is cooled and circulated to cool the object again. The return of the cooling water is used as a heat source for the LNG cold / hot water evaporator. The temperature of the cold / hot water from the cooling tower is usually about 20 ° C to 38 ° C. If a conventional hot water evaporator is used at this temperature, the surface of the heat transfer tube coil, which is the evaporation tube, will freeze and be used continuously. Difficult to do. In the present invention, a cold / hot water type LNG evaporator having a structure capable of continuously evaporating and evaporating LNG by providing a spiral flow forming member while partially utilizing the cold / hot water and partially accelerating the flow of the flowing cold / hot water. I will provide a.

  By using the cold / hot water type LNG evaporator of the present invention, a heat source for generating hot water, which is necessary for the use of the hot water type evaporator, becomes unnecessary, and furthermore, in the existing cooling water circulation system, by the cold heat recovery of LNG Cooling efficiency will increase, and using LNG will not only prevent global warming, but will also save energy and build environment-friendly equipment.

  FIG. 1 is a diagram showing a configuration of an LNG evaporation system 300 that is an embodiment of the present invention.

In FIG. 1, the LNG evaporation system 300 has a configuration in which a liquefied LNG evaporator (hereinafter, referred to as LNG evaporator) 100 forming a cold / warm evaporator and a cold / warm water circulation system 200 are combined. A typical example of the cold / hot water circulation system 200 is a system provided with a cooling tower. Hereinafter, a cooling system provided with a cooling tower (hereinafter referred to as a cooling tower system 200) will be described as an example.
The LNG evaporator 100 includes a cylindrical evaporator outer cylinder 10 (hereinafter referred to as an outer cylinder) that is long in the longitudinal direction, an outer cylinder 10, and a heat transfer tube coil (tube) that is wound around the outer cylinder and disposed in a coil shape. Tube) 11 and is configured as an LNG evaporator in which heat is exchanged between a first medium flowing in the outer cylinder and a second medium flowing in the heat transfer tube coil, and the first flowing in the outer cylinder This medium is cold / hot water flowing from the cold / hot water source, and the second medium flowing in the heat transfer tube coil is liquefied LNG.

  The cooling tower system 200 includes a circulation system 13 formed between the cooling tower system 200 and the LNG evaporator 100. The cooling tower system 200 includes a cooling tower 201, a pump 202, and a cooling object 203. The cold / hot water discharged from the cold / hot water outlet 45 of the LNG evaporator 100 is guided to the cooling tower 201 via the LNG side pipe 14 and the cooling tower system side pipe 42 connected to the cold / hot water outlet 12. The cooling tower 201 is a general cooling tower installed in a factory building or a general building. The cold / warm water cooled by the cooling tower 201 is boosted by the pump 202 and guided to the object to be cooled 203, cools the object to be cooled 203, increases its temperature, and becomes cold / warm water of 20 to 38 ° C. as before. . The cold / warm water heated to about 20 to 38 ° C. is led to the lower part of the LNG evaporator 100 through the cooling tower side pipe 41 and the LNG side pipe 13. A part of the warm / warm water that has been heated is branched from the pipe 13, led to the lower part of the LNG evaporator 100 through the pipe 13 </ b> A disposed in the center tube pipe 16, and led out from the outlet 23.

  In FIG. 1, a cold / hot water circulation system 1 is configured. The circulation system 1 is formed by the LNG side pipe introduction system 13, the cooling tower side pipe 41 connected thereto, the cooling tower 201, the cooling tower side pipe 42, the LNG side pipe 14 connected thereto, and the LNG evaporator 100.

  FIG. 2 shows details of the configuration of the LNG evaporator 100. In FIG. 2, the outer cylinder 10 is sectioned in the vertical direction so that the inside can be seen, and the arrangement configuration of FIG. 1 is shown rotated 180 degrees. The outer cylinder 10 is formed of SUS.

  The LNG evaporator 100 forms a sealed container sealed with a lid 15, and a center tube pipe 16 that extends through the center of the lid 15 to the lower side of the outer cylinder 10 is disposed at the center. FIG. 2 shows an example in which the center tube 16 passes through the bottom of the outer cylinder 10 and the tip is blocked. Therefore, in this example, the branched pipe 13A shown in FIG. 1 is not provided, but a part of the lower portion of the center tube pipe 16 is opened inside the LNG evaporator 100, so that FIG. The example shown in FIG.

  A heat transfer tube coil 11 is wound around the center tube tube 16. The winding pitch of the heat transfer tube coil 11 is typically the same between the windings. In FIG. 1 and FIG. 2, the heat transfer tube coils 11 are displayed at intervals, but typically the pitch between the heat transfer tube coils 11 is reduced and closely arranged.

  The inlet 18 of the heat transfer tube coil 11 is provided on the lower side of the outer cylinder 10, and the outlet 19 is provided on the upper side of the outer cylinder 10. The inlet 18 serves as an inlet for the liquid LNG, and the outlet 19 serves as an outlet for the evaporated LNG. The liquid LNG introduced from the inlet 18 flows through the heat transfer tube coil 11 and is led out from the outlet 19. The LNG on the gas led out from the outlet 19 flows through the pipe 31, the pressure of the pressure regulator 32 is adjusted, and the LNG is guided to a device (not shown). The heat transfer tube coil 11 is replaceable.

  The inner diameter of the center tube 16 is much larger than that of the heat transfer tube coil 11. Therefore, the heat transfer tube coil 11 is wound around the center tube tube 16 having a large diameter.

  A gap 20 is provided between the center tube 16 and the heat transfer tube coil 11.

  A hot water inlet portion 21 is provided on the lower side of the outer cylinder 10 below the inlet portion 18, and a hot water outlet portion 22 is provided on the upper side of the outer cylinder 10 and above the inlet portion 18.

  FIG. 3 shows the arrangement of the LNG inlet 18, the LNG outlet 19, the hot water inlet 21, and the hot water outlet 22, which are arranged in the same direction and spaced apart from the center lines A and B. The part 19, the hot water inlet part 21, and the hot water outlet part 22 are arranged in the horizontal direction. The hot water inlet portion 21 is inserted to the inner depth, and the hot water outlet portion 22 is inserted shallowly inside.

  FIG. 4 shows the function of the hot water inlet 22, and the cold / hot water introduced depends on the insertion angle, as shown in FIG. 4 (b) by the arrangement of the cold / hot water inlet 21 according to FIG. Therefore, it turns inside. In this way, the chilled / warm water is given kinetic energy for turning in the outer cylinder and is led out from the chilled / warm water inlet 21 and swirls spirally. The spiral flow is strong at the lower part of the LNG evaporator 100 in relation to the kinetic energy and becomes weaker as it goes upward.

    FIG. 5 shows a situation in which the pitch in the vertical direction of the cold / hot water flow increases as it is wound. A and B in FIG. 3 are expanded and illustrated as A, B, and A in FIG.

  As shown in FIG. 5, the winding pitch of the coil 11 is the same between the windings, but the pitch of the cold / hot water flow gradually increases upward as L1 <L2 <L3 <L4 <L5.

  The warm water flow rate is preferably 0.05 m / s to 0.2 m / s, and a warm water temperature of 20 to 35 ° C. The temperature is slightly lower than the temperature of the cold / hot water flowing through the pipe 41.

  As shown in FIGS. 2 to 4, hot water is supplied from the side surface of the outer cylinder 10, and at that time, the hot water is jetted deep inside the cylinder as shown in FIG. 4. At the time of jetting, a spiral flow is formed using the jet angle and the inner wall of the hot water. A spiral flow is formed by the wound heat transfer tube coil 11 installed in the outer cylinder, the spiral flow at the time of hot water introduction is maintained, and flows upward.

  A center tube 16 is disposed at the center of the outer tube 10, and the heat transfer tube coil 11 around which the center tube 16 is wound includes cold and hot water flowing spirally around the outside of the heat transfer tube coil 11. Heat is exchanged with cold and hot water flowing inside. Also in the gap 20 formed between the center tube tubes, a spiral flow that makes contact with the heat transfer tube coil 11 is formed, but the amount of heat exchange with the cold / hot water that flows by rotating outside the heat transfer tube coil 11 is small. It is much larger than the amount of heat exchange with cold / hot water flowing inside.

  A cylindrical body having an outer diameter larger than the diameter of the heat transfer tube coil tube is disposed at the center of the outer tube of the LNG evaporator 100, and the heat transfer tube coil 11 is disposed by winding the outer tube shape body. In addition to the formation of the spiral flow by the coil 11, or in the case of a structure in which the formation of the spiral flow by the heat transfer tube coil 11 is not performed, the spiral flow may be formed by a wound spiral flow forming member alone. . As described above, the heat transfer tube coil 11 arranged in close proximity is wound, or the wound spiral flow forming member is provided in the outer cylinder so that the center tube tube 16 and the center tube tube 16 are spirally formed around the center tube tube 16. The provided spiral flow forming portion can be formed to form a spiral flow.

  The same applies to the swirling spiral flow formed in the gap between the heat transfer tube coil 11 and the center tube tube 16 which is a cylindrical body. A diverted spiral flow is formed in the gap, which is divided from the swirling outer spiral flow and has a lower flow velocity than the swirling spiral flow, and heat exchange is performed between the divided spiral flow and the liquefied LNG flowing in the heat transfer tube coil. A spiral flow in a form of being divided from the entire flow is formed on the outside along the spiral flow forming member by the spiral flow forming member provided in a spiral shape.

  A typical case of a cylindrical body is the center tube 16 shown in FIG. The cylindrical body need only be cylindrical and does not have to be round. However, the use of a round tubular center tube 16 is recommended in design.

  FIG. 6 shows a spiral fin 31 provided on the outer surface of the center tube 16 as an example of the spiral flow forming member. A swirling spiral flow can also be formed by these fins. One of the designs is to provide the fin 31 on the inner wall of the outer cylinder 10.

  The spiral flow forming member is a fin having a spiral arrangement provided on the outer surface of the center tube, a fin having a spiral arrangement provided on the inner wall surface of the outer cylinder, or a spiral flow forming member provided on the inner wall surface of the outer cylinder. It can also be formed by forming a plurality of cold / hot water inlets arranged in a jumping manner so that the arrangement position is spiral in the vertical direction. Naturally, a cold / hot water source is connected to the cold / hot water inlet, and the cold / hot water is introduced into the outer body through the cold / hot water inlet. The spiral flow forming member can also be configured by a combination of these members and a heat transfer tube coil.

  As described above, the spiral flow can be formed by the flow formation by the equipment or by using the kinetic energy of the inflowing hot / cold water. It includes a form in which a shunt state is formed between the spiral flow outside the coil and the spiral flow inside the heat transfer tube coil.

  By providing the spiral flow forming member, a spiral flow is formed in the entire flow that flows upward in the interior of the LNG evaporator 100, that is, in the outer cylinder 10. A split spiral flow is formed in the overall flow. Thus, a laminar flow and a spiral flow are formed inside the LNG evaporator 100, and as shown in FIG. 5, the cross-sectional area in the flow direction is the pitch arrangement of the heat transfer tube coils 11 ( In this example, it is constant), and gradually increases in proportion to the virtual long cross-sectional area of the spiral flow that gradually expands as the kinetic energy decreases. The velocity of the spiral flow is faster at the lower part. The spirally arranged fins 31 provided on the outer surface of the center tube tube are arranged on the upper side of the heat transfer tube coil 11 in the vicinity of the heat transfer tube coil 11 so that a spiral flow having a virtual long cross-sectional area described below is formed. All or part of the heat transfer tube coil 11 can be disposed therein.

  FIG. 7 schematically shows a virtual long cross-sectional area of the formed spiral flow. The spiral flow is assumed to have a virtual long cross-sectional area, and the swirling spiral flow having the virtual long cross-sectional area is arranged along the heat transfer tube coil 11 on the side on which cold / hot water collides as the introduced hot water. It is formed. The entire flow consists of a laminar flow that swirls as such a spiral flow but does not become the amount of spiral, and in relation to the applied kinetic energy, the spiral flow has a small hypothetical cross section at the bottom and a velocity. Is fast. The virtual long cross-sectional area increases as it goes upwards, and the speed decreases. The high-speed spiral flow exchanges heat with LNG flowing in the heat transfer tube coil 11. At this time, the spiral flow is cold / hot water, but heat exchange is efficiently performed, and freezing to the outer surface of the heat transfer tube coil is prevented.

  The shape of the spiral flow is determined by the insertion angle of the hot water inlet 21, the injection flow velocity, the inner diameter of the outer cylinder 10, the center tube tube 16, and the shape of the heat transfer tube coil 11 to be wound.

  If the inner diameter of the outer tube 10 is too large compared to the coil outer shape of the heat transfer tube coil 11, the hot water cannot flow through the surplus inside to form a spiral flow, or even if it is made, the formation of a swirling flow with a slight flow rate remains. . In the present embodiment, as shown in FIG. 2, the heat transfer tube coil 11 is disposed close to the inner wall of the outer cylinder 10.

  Here, the spiral flow formed on the outer side of the heat transfer tube coil 11 is referred to herein as a virtual long tubular spiral flow as described above. Since each pitch of the heat transfer tube coil 11 is small, a spiral flow formed outside along the heat transfer tube coil 11 between the heat transfer tube coils 11 forms a cylindrical shape. The spiral flow formed outside the heat transfer tube coil 11 has a long cylindrical shape in the entire flow, and the lower the cross-sectional area is, the faster the flow velocity is. The cross-sectional area of the virtual elongated tubular spiral flow gradually increases upward as the kinetic energy decreases. This causes a decrease in flow rate. Even if the flow velocity decreases, the temperature on the LNG side increases as it goes upward, and the possibility of icing is reduced, so there is no practical problem.

  The gap 20 between the wound heat transfer tube coil 11 and the center tube tube 16 is maintained at a constant width, and in the gap 20 formed between the wound heat transfer tube coil 11 and the center tube tube 16, In the same manner as the relationship between the outer cylinder 10 and the heat transfer tube coil 11, a part of the cold / hot water flows.

  The cross-sectional area of the formed virtual elongated tubular spiral flow is very small compared to the cross-sectional area of the entire flow. The ratio is large in the lower part and decreases as it goes upward. For this reason, the flow rate of hot water on the surface of the heat transfer tube coil 11 is remarkably fast, and the flow rate of hot water of the virtual long tubular spiral flow is faster in the lower part.

  The rapid warm water flow velocity of the virtual long tubular spiral flow with respect to the heat transfer tube coil surface improves the heat exchange rate with the liquid LNG flowing in the heat transfer tube coil 11. For this reason, even if the hot water is cold / hot water, heat exchange is sufficiently performed, and freezing can be suppressed even on the outer surface of the heat transfer tube coil 11. Moreover, the warm water flow rate is faster in the lower part, and the fast warm water flow rate improves the heat exchange rate with the liquid LNG flowing in the heat transfer tube coil 11, and heat exchange is sufficiently performed even if the hot water is cold / hot water. Freezing can be reliably suppressed even on the outer surface of the lower part of the coil 11.

  Thus, a low temperature type LNG evaporator can be provided. In addition, in this method, if LNG exceeding the design flow rate flows, even if freezing occurs on the surface of the heat transfer tube coil, the area of the spiral flow conduit is reduced along with freezing, and the flow velocity is increased accordingly. , It will be possible to cope with some fluctuations in the flow rate of LNG, especially an increase in the flow rate in a short time.

  The cross-sectional area of the hypothetical long tubular spiral flow of cold / hot water that is formed increases in relation to kinetic energy as it goes upward, and the flow rate of the cool / warm water of the hypothetical long tubular spiral flow gradually decreases. The LNG flowing in the heat transfer tube coil 11 has already received the latent heat of vaporization and sensible heat at the portion where the flow rate of the hot water of the virtual long tubular spiral flow in the lower part is high, and the temperature has risen. Freezing is suppressed even when the flow rate of the hot water in the spiral flow gradually decreases.

  In this way, the swirling spiral flow in the outer cylinder is prevented from being blocked, and the flow velocity is maintained.

  Compared to the previous example, in the conventional hot water circulation type LNG evaporator, when supplying hot water from the lower part of the hot water tank and returning the cold and hot water derived from the upper part to the clean tower etc., the internal space in the hot water tank It was a structure in which cold / hot water was allowed to flow to the upper side using the entire part. The interior space is designed with a large diameter from the viewpoint of securing the total heat capacity, and the entire hot water flow is almost laminar in the upper part, and the flow rate is very slow. Although there was a fear, in the structure of the present embodiment, there is no fear of blockage in the tube.

  Next, when the LNG is evaporated by cold / hot water by exchanging heat between the spiral flow, that is, the virtual long tubular spiral flow and the liquefied LNG flowing in the heat transfer tube coil 11, The test which suppresses freezing was done. This test will be described.

The inventors of the present application conducted a study calculation and a verification experiment on the suppression of icing formation on the surface of the heat transfer coil in the low temperature LNG evaporator.
-Study calculation-
○ Examination of ice thickness on the surface of the heat transfer tube coil in the low temperature type LNG evaporator ○ Objective: The hot water temperature of the hot water type LNG evaporator is usually about 75 ° C in the previous example, but the hot water temperature is about 30 ° C. In this case, freezing is expected on the surface of the heat transfer tube coil. A study calculation was conducted on the ice thickness.
○ Assumptions: Assumed conditions are as follows.

        1) The medium (fluid) is LNG.

        2) The LNG flow rate is 100 kg / h.

        3) Set to a steady state.

4) The low-temperature water temperature is constant.
○ Cross section of heat transfer coil: as shown in FIG.
○ Ice thickness calculation method (outline)
1) Obtain the overall thermal resistance _Rtotal .

        2) Obtain the heat transfer amount Q.

3) Obtain the temperature T ₃ at the interface between ice and low-temperature water.

4) Find r ₃ such that T ₃ = 0 ° C.

5) Obtain the ice thickness r ₃ -r ₂ .
○ Result: The expected ice thickness when the flow rate and temperature of hot water are used as parameters is shown in the table, and the results of the table are shown in the figure.

Fig. 9: Expected ice thickness in supercooled state Fig. 10: Expected ice thickness in liquid saturated state Fig. 11: Expected ice thickness in gas saturated state-Verification experiment-
○ Experiment for suppressing freezing formation on the surface of a heat transfer tube coil in a low temperature type LNG evaporator ○ Purpose: The hot water temperature of a hot water LNG evaporator is usually about 75 ° C, but when the temperature of the hot water is about 30 ° C, the heat transfer tube Ice formation is expected on the coil surface. It is verified whether or not freezing on the outer surface of the heat transfer tube coil can be suppressed by performing heat exchange between the split flow spiral flow, that is, the virtual long tubular spiral flow and the liquefied LNG flowing in the heat transfer tube coil.
○ Test conditions
1) The test fluid is liquid nitrogen (LN2).
2) The temperature of cold / hot water shall be 20-38 degreeC.
3) The capacity of the cold / hot water evaporator shall be LNG 100kg / h.
4) The test contents are as follows.
Case 1: Constant enthalpy test
A test in which LN2 equivalent to enthalpy of LNG 100kg / h is supplied at a constant flow rate, and the cold / hot water flow rate and cold / hot water temperature are changed as parameters.
Case 2: Constant flow rate test
A test in which LNG 100 kg / h is supplied with a constant flow rate of LN2 equivalent to the flow rate through the evaporator tube, and the cold / hot water flow rate and cold / hot water temperature are changed as parameters.
Case 3: Constant enthalpy test with low-temperature brine solution
Test with the same content as Case 1 but using cold / hot water as brine solution.
Case 4: Cold / hot water flow rate change test
A test that changes the flow rate of cold and hot water with the same contents as Case 1.
○ Consideration of results:
Case 1
(1) The flow rate of low-temperature water tends to increase, and it tends to be difficult for icing to occur as the temperature increases.

  (2) The inside of the low temperature water type LNG evaporator is a swirling flow from the low temperature water inlet to the outlet.

  (3) This low temperature water type LNG evaporator is expected to have an LNG evaporation capacity of 100 kg / h.

(4) When the low-temperature water flow rate is four times the design flow rate, vibration occurs in the heat transfer coil tube.
Case 2
(1) When the supply flow rate is decreased, the icing thickness decreases.

  (2) The position where icing is likely to occur on the surface of the heat transfer coil tube does not depend on the flow rate.

However, the hot water flow rate and temperature are the same.
Case 3
(1) If the low temperature water LNG evaporator outlet gas temperature is allowed to be about 0 ° C., the evaporator will have an LNG evaporation capacity of 100 kg / h when used at a brine liquid temperature of 0 ° C. and a flow rate of 63900 kg / h. expected to have h.
Case 4
(1) There is a tendency for the icing thickness and range to increase as the low-temperature water flow rate decreases.

  (2) There is a tendency that icing is likely to be generated and grow on the surface of the heat transfer coil tube on the center tube tube side.

  (3) Supply flow rate 208.2kg / h (LNG conversion flow rate 100kg / h) ・ Low limit value of low-temperature water supply flow rate under the condition of low-temperature water inlet temperature 20 ° C is the stability of the low-temperature water type LNG evaporator outlet gas temperature Judging from sex alone, it is estimated to be about 6600 kg / h.

  (4) The icing thickness and range tend to decrease as the low-temperature water flow rate increases.

(5) When used at a low-temperature water flow rate of 18600 kg / h and a low-temperature water inlet temperature of 15 ° C., it is expected to have an LNG evaporation capacity of 100 kg / h.
Thus, heat exchange between the split spiral flow and the liquefied LNG flowing in the heat transfer tube coil is effective in suppressing the formation of icing on the outer surface of the heat transfer tube coil.

From the relationship between the hot water temperature T _{h /} hot water flow rate U _h and ice thickness, t, as shown in FIG. 9, the hot and cold water in this embodiment, it is possible to prevent icing by accelerating the hot water flow rate U _h 15 to 55 Hot water in the range of ° C. is applicable, and hot water having a temperature of 20 to 38 ° C. is preferably used as cold and hot water. The hot water temperature of the conventional hot water type LNG evaporator is usually about 75 ° C., and 55 ° C. can be said to be considerably cooler than 75 ° C. The hot water discharged from the cooling tower generally provided in the office is usually in the range of 20 to 38 ° C., and the temperature before being connected to the LNG evaporator is maintained, and the LNG is evaporated as cold / hot water. Introduced into the vessel.

  In the outer cylinder, the heat transfer tube coil is arranged, and by the heat transfer tube coil itself or by the spiral flow forming member provided in a spiral shape in the outer cylinder, the entire flow flowing in the outer cylinder is made into a diversion state, A spiral flow with an increased flow velocity is formed outside the heat transfer tube coil, and heat is exchanged between the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil.

  The effect by flowing sub warm water through the center tube 16 will be described.

  It has been described that heat exchange between the split spiral flow and the liquefied LNG flowing in the heat transfer tube coil is effective in suppressing icing on the outer surface of the heat transfer tube coil. Although this effect is large outside the heat transfer tube coil tube where the cold / hot water collides, it is expected that the flow velocity becomes slow inside the opposite heat transfer tube coil. Considering this, in order to surely prevent the formation of icing, cold / hot water from the cooling tower system is divided in the middle of the pipe 13 and supplied to the lower part of the sentiment tube 16 through the pipe 13A. Do.

  As a result, the heat energy of the sub-cooled / warm water is supplied to the center tube 16 to increase the temperature of the spiral flow. The heat transfer tube temperature can be raised. For the center tube 16, it is recommended to use an aluminum material having a high thermal conductivity.

By attaching a spiral fin 31 as shown in FIG. 6 to the center tube 16, the hot water flow rate can be increased and the heat exchange rate can be improved.

In this way, the cylindrical center tube pipe 16 having a diameter larger than the diameter of the heat transfer tube coil pipe is arranged at the central portion in the outer cylinder, and the sub cold / hot water divided from the cold / hot water circulation system into the center tube pipe 16. To supply heat energy. The sub-cooled / warm water flowing through the center tube 16 heats the heat transfer tube coil 11 and the formation of icing on the outer surface of the heat transfer tube coil is reliably suppressed.

  According to the present embodiment, the formation of freezing is suppressed, so that even if cold / hot water is used or cold / hot water of 20 to 38 ° C. from the cooling tower is introduced, a tube blockage accident is prevented and operation is impossible. Is avoided. According to the present embodiment, cold / hot water can use cold / hot water from a cooling tower generally provided in the office, and the amount of LNG required to evaporate the liquefied LNG can be completely consumed. Is an effective measure for energy saving. Thus, the present invention can solve the problems of the conventional LNG evaporator.

  FIG. 1 shows a heat exchange heat source utilization method.

A heat source utilization method comprising using cold / warm water discharged from a cooling tower system used in an office as a heat source for warming liquid LNG flowing inside the LNG evaporator,
In the LNG evaporator,
A first medium flowing in the outer cylinder and a second medium flowing in the heat transfer tube coil, comprising a cylindrical outer cylinder that is long in the longitudinal direction and a heat transfer tube coil that is wound in a coil shape in the outer cylinder The first medium flowing in the outer cylinder is cold / warm water discharged from the cooling tower system, and the second medium flowing in the heat transfer tube coil is liquefied LNG. And
The temperature of the cold / hot water discharged from the cooling tower system is maintained at a temperature within the range of 20 to 38 ° C., which is the temperature after cooling in the conventional cooling tower, and the LNG evaporation from the cooling tower system of this embodiment is performed. By introducing the cold / hot water into the inside of the vessel, the low-temperature hot water in which the temperature from the cooling tower system is maintained as before is introduced as the low-temperature heated water of the LNG evaporator,
In the outer tube of the LNG evaporator, the entire flow flowing in the outer tube is divided by the heat transfer tube coil itself or by a spiral flow forming member provided spirally in the outer tube, along the heat transfer tube coil. A spiral flow with an increased flow velocity is formed on the outside, and heat exchange is performed between the low temperature heating water of the cold / hot water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil, and the LNG evaporator is derived. Compared to the case where the temperature of the heating water to the LNG evaporator is assumed to be 75 ° C., the cooled / warm water can be returned to the cooling tower system at a low temperature of several degrees C. A heat exchange heat source utilization method characterized in that a system is formed is proposed.
The hot water temperature of the hot water LNG evaporator is usually about 75 ° C., and the temperature of 20 to 38 ° C. described above can be said to be considerably colder than 75 ° C. Further, the cool / warm water introduced into the cooling tower 201 via the pipes 14 and 42 can be considerably lower than the warm water of the previous system led to the cooling tower 201. In this way, by recovering cold energy by using the LNG evaporator 100 as cold / warm water cooled to the limit of the warm water returning to the cooling tower, it is possible to perform cooling in the cooling tower very easily and increase the cooling efficiency. In addition, since it is not necessary to provide a separate heat source for the LNG evaporator, the operator can easily install the LNG evaporator.

  DESCRIPTION OF SYMBOLS 1 ... Circulation system, 10 ... Outer cylinder, 11 ... Heat transfer tube coil, 16 ... Center tube pipe, 20 ... Gap, 100 ... LNG evaporator, 200 ... Cold / hot water circulation system (cooling tower system), 300 ... LNG evaporation system.

Claims (7)

A long tube-shaped outer tube in the longitudinal direction and a heat transfer tube coil arranged in a coil shape in the outer tube, a first medium flowing in the outer tube and a second medium flowing in the heat transfer tube coil, The first medium flowing in the outer cylinder is cold / warm water flowing from the hot water source, and the second medium flowing in the heat transfer tube coil is liquefied LNG, In the LNG evaporator where the liquefied LNG is evaporated,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is disposed at the center of the outer tube , a heat transfer tube coil is disposed around the center tube tube, and an arrangement position is provided on the inner wall surface of the outer tube. A spiral flow is formed by a spiral flow forming portion formed by a plurality of spiral hot / cold water inlets, and heat exchange is performed between the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil. The LNG evaporator is characterized in that icing on the outer surface of the heat transfer tube coil is suppressed. In LNG evaporator according to claim 1, the Center tube pipe, LNG evaporator, characterized in that hot water is introduced. A long tube-shaped outer tube in the longitudinal direction and a heat transfer tube coil arranged in a coil shape in the outer tube, a first medium flowing in the outer tube and a second medium flowing in the heat transfer tube coil, The first medium flowing in the outer cylinder is hot water flowing from the hot water source, and the second medium flowing in the heat transfer tube coil is liquefied LNG, which is liquefied by the hot water. In the LNG evaporator where LNG is evaporated,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is disposed in the center portion of the outer tube, and the sub-cold hot / cold water separated from the cold / hot water source is passed through the center tube tube. are disposed heat transfer tubes coil by winding a tube, is disposed heat transfer tubes coil by winding the center tube pipe, the heat transfer tube coil itself, or in a spiral flow forming member provided spirally within the outer tube thus A spiral flow having a flow velocity increased along the heat transfer tube coil is formed from the entire flow flowing in the outer cylinder, and the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil The LNG evaporator is characterized in that heat is exchanged between them, and the sub-cooled hot water flowing through the center tube tube heats the spiral flow to prevent icing on the outer surface of the heat transfer tube coil. 4. The LNG evaporator according to claim 1, wherein the spiral flow forming portion forms a spiral arrangement fin provided on the outer surface of the center tube tube or a spiral flow provided on the inner wall surface of the outer cylinder. 5. LNG evaporator, characterized in that it comprises a. A first medium flowing in the outer cylinder and a second medium flowing in the heat transfer tube coil, comprising a cylindrical outer cylinder that is long in the longitudinal direction and a heat transfer tube coil that is wound in a coil shape in the outer cylinder The first medium flowing in the outer cylinder is hot water flowing from the hot water source, and the second medium flowing in the heat transfer tube coil tube is liquefied LNG, which is liquefied by hot water. In the evaporation method of liquefied LNG by an LNG evaporator in which LNG is evaporated,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is arranged at the center of the outer tube , a heat transfer tube coil is arranged around the center tube tube, and the arrangement position is located on the inner wall surface of the outer tube. the spiral flow forming portion formed by spirally and have been several hot and cold water inlet, form a helical flow, by heat exchange with the liquefied LNG flowing through the helical flow to become cold and hot water and the heat transfer tube in the coil A method for evaporating liquefied LNG using an LNG evaporator, wherein icing is suppressed on the outer surface of the heat transfer tube coil. A first medium flowing in the outer cylinder and a second medium flowing in the heat transfer tube coil, comprising a cylindrical outer cylinder that is long in the longitudinal direction and a heat transfer tube coil that is wound in a coil shape in the outer cylinder The first medium flowing in the outer cylinder is warm water flowing from the hot water source, and the second medium flowing in the heat transfer tube coil is liquefied LNG, and is heated by the hot water. In the evaporation method of liquefied LNG by the LNG evaporator in which liquefied LNG is evaporated,
A cylindrical center tube tube having a diameter larger than the diameter of the heat transfer tube coil tube is disposed in the center portion of the outer tube, and the sub cold / hot water separated from the cold / hot water source flows through the center tube tube. are disposed heat transfer tubes coil by winding a tube, is disposed heat transfer tubes coil by winding the center tube pipe, the heat transfer coil itself, or within the outer cylinder in a spiral flow forming member provided spirally Therefore The spiral flow having a flow velocity increased along the heat transfer tube coil is divided from the entire flow flowing in the outer cylinder, and the cold / warm water that becomes the spiral flow and the liquefied LNG flowing in the heat transfer tube coil The LNG evaporator evaporates liquefied LNG by heat exchange between them and heating the spiral flow with sub-cold hot and cold water flowing through the center tube to suppress icing on the outer surface of the heat transfer tube coil Method. In the heat exchanger the method according LNG evaporator according to claim 5 or 6, has been hot water discharged from the cooling tower provided in the office, in a state where the temperature before being connected to the LNG evaporator is maintained, A heat exchange method in an LNG evaporator, wherein the heat is introduced into the LNG evaporator as cold / hot water.

Images