JP3551063B2 - Method and apparatus for producing hydrate slurry - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for producing a hydrate slurry by cooling an aqueous solution containing a guest compound. More specifically, the present invention provides a method and an apparatus for efficiently producing a hydrate slurry having stable properties when a guest compound that produces two hydrates having different hydration numbers is used. About.
[0002]
[Prior art]
It has been known that clathrate hydrates are produced by cooling an aqueous solution containing a guest compound such as various salts. Such a hydrate can be formed at a temperature of 0 ° C. or higher, and can be dispersed as fine particles in an aqueous solution to form a hydrate slurry having a high fluidity. It has excellent properties as a cold storage material for equipment or as a transport medium for cold heat.
[0003]
By the way, according to researches and investigations by the present inventors, when cooling an aqueous solution as described above to generate a hydrate, two or more types of hydrates may be generated in some cases. found.
[0004]
For example, when tetra-n-butylammonium bromide (TBAB) is used as the guest compound, as the aqueous solution of TBAB is cooled, the number of water molecules bonded to one molecule of TBAB, that is, the hydration number Is a hydrate of 26 (hereinafter, this hydrate is referred to as a primary hydrate) and a hydrate having a hydration number of 36 (hereinafter, this hydrate is referred to as a second hydrate) Turned out to be generated.
[0005]
The first hydrate and the second hydrate are different in the amount of latent heat, density, and other physical properties. FIG. 1 shows the difference between the aqueous solution concentration and the formation temperature characteristics of the first hydrate and the second hydrate. In FIG. 1, the curve indicated by EBGH is the characteristic of the first hydrate, and the curve indicated by GCF is the characteristic of the second hydrate.
[0006]
As is apparent from FIG. 1, the second hydrate is formed at a temperature of about 8 ° C. or less. The second hydrate has a larger latent heat and a lower density than the first hydrate.
[0007]
At a temperature of 8 ° C. or lower, the first hydrate and the second hydrate do not coexist stably, and only one of them exists depending on the conditions of the concentration of the aqueous solution and the temperature. However, at the time of manufacture, etc., both may be mixed transiently.
[0008]
For example, in the case of producing a hydrate by cooling an aqueous solution, as the aqueous solution is cooled, a first hydrate having a low hydration number is first generated, and the first hydrate is mixed with surrounding water. And a peritectic reaction occurs to change to a second hydrate having a large hydration number. When the second hydrate melts, the second hydrate first changes to the first hydrate, and then the first hydrate tends to melt.
[0009]
Therefore, during the production of this hydrate slurry, the particles of the first hydrate and the second hydrate may be mixed together. As described above, the particles of the first hydrate undergo peritectic reaction with the water of the surrounding aqueous solution to change to the second hydrate. Since the density is smaller than that of the first hydrate, the volume expands when the first hydrate changes to the second hydrate.
[0010]
Therefore, if the particles of the first hydrate are mixed in the hydrate slurry at the time of production, before the particles of the first hydrate change to the second hydrate, the piping and the It is conceivable that the data will be distributed in various devices or devices on the load side. In such a case, when the particles of the first hydrate are changed into the particles of the second hydrate and expanded in these pipes and devices, the pipes and devices may be blocked.
[0011]
In particular, in a hydrate slurry manufacturing apparatus of a type in which a hydrate layer formed on a heat transfer surface is mechanically peeled off, a large amount of the above-described first hydrate particles is generated during manufacturing. There is a problem.
[0012]
That is, when cooling the aqueous solution, the aqueous solution is cooled via the heat transfer surface of the heat exchanger. In this case, the produced hydrate adheres in a layer on the heat transfer surface. Since such a hydrate layer reduces the efficiency of heat exchange on the heat transfer surface, for example, the heat transfer surface is formed in a cylindrical shape, and the scraping blade rotates while sliding on the cylindrical heat transfer surface. The hydrate layer is peeled off by a peeling member such as.
[0013]
In this case, the primary hydrate is formed on the heat transfer surface. Therefore, when the layer of the first hydrate is mechanically peeled and dispersed in the aqueous solution, a large amount of particles of the first hydrate float in the aqueous solution. For this reason, there is a problem in that the particles of these first hydrates flow into the pipes and devices as described above, and the possibility of blocking these particles increases.
[0014]
[Problems to be solved by the invention]
The present invention has been made based on the above circumstances, and a method for producing a hydrate slurry having a more stable characteristic by reducing the generation of hydrate particles having a small hydration number during production of a hydrate slurry. And an apparatus.
[0015]
[Means for Solving the Problems]
The method of the present invention according to claim 1 is a method for producing a hydrate slurry by cooling an aqueous solution containing a guest compound, wherein the aqueous solution is cooled via a heat transfer surface, and the heat transfer is performed. Generating a layer of hydrate on the surface; and forming a layer of hydrate having a high hydration number on the layer of hydrate generated on the heat transfer surface; Exfoliating the hydrate having a high hydration number generated on the surface portion of the hydrate layer and leaving at least a part of the hydrate layer on the heat transfer surface. It is characterized by the following.
[0016]
As described above, the first hydrate formed on the heat transfer surface is a hydrate having a small hydration number. However, the hydrate that is further formed on the layer of the hydrate having a low hydration number is a large hydrate of the hydrate. The reason for this is that the surface of the hydrate having a low hydration number changes to a hydrate having a high hydration number by peritectic reaction with the surrounding water, It is considered that a hydrate having a higher hydration number is generated from the beginning because a hydrate further formed on the material is generated using the nucleus as a nucleus.
[0017]
Therefore, if the hydrate is left on the heat transfer surface, the hydrate formed on the heat transfer surface becomes a hydrate having a large hydration number. A hydrate slurry containing almost no hydrate particles having a small sum number can be produced.
[0018]
Further, in the method according to claim 2, the step of peeling off the hydrate having a high hydration number is performed by mechanically peeling off the vicinity of the surface of the hydrate layer attached on the heat transfer surface. The hydrate having a high hydration number near the surface of the hydrate layer is peeled off.
[0019]
Therefore, only the hydrate part near the surface of the hydrate layer, that is, only the hydrate part having a large hydration number can be peeled off accurately and reliably. In addition, this method has an advantage that it can be implemented only by adding a small modification to an existing hydrate slurry manufacturing apparatus.
[0020]
According to the third aspect of the present invention, there is provided a heat transfer surface in contact with an aqueous solution containing a guest compound, and a hydrate layer moving along the heat transfer surface and adhering to the heat transfer surface. And a peeling mechanism provided with a peeling member for leaving at least a part of the hydrate layer on the heat transfer surface.
[0021]
Therefore, since the hydrate layer is mechanically peeled off, it is possible to peel off the hydrate portion near the surface of the hydrate layer, that is, the hydrate portion having a large hydration number accurately and reliably, and the structure is simple and Reliable operation and high reliability.
[0022]
According to a fourth aspect of the present invention, in the apparatus, the heat transfer surface has a cylindrical shape, and the aqueous solution comes into contact with the inner peripheral surface of the heat transfer surface. It is characterized in that it comprises a separating blade member that rotates along the inner peripheral surface of the hot surface. Therefore, the structure is simple and the operation is reliable.
[0023]
Further, in the apparatus according to claim 5, a predetermined gap is formed between the peeling member of the peeling mechanism and the heat transfer surface, and the gap is formed on the heat transfer surface by the gap. This is to leave at least a part of the material layer.
[0024]
Therefore, the structure is simple and the operation is highly reliable. In addition, by appropriately setting the gap, the hydrate portion having a large hydration number near the surface of the hydrate layer on the heat transfer surface can be accurately separated. In addition, since a thin layer of hydrate remains on the entire surface of the heat transfer surface, the area of this layer is large, and the amount of hydrate with a large hydration generated on this layer is large and the efficiency is high.
[0025]
In the apparatus according to claim 6, the peeling member of the peeling mechanism has flexibility and moves along the heat transfer surface to peel off the hydrate layer on the heat transfer surface. The hydrate layer is bent by the resistance at the time, thereby leaving at least a part of the hydrate layer on the heat transfer surface.
[0026]
Therefore, by appropriately setting the flexibility and elastic modulus of the peeling member, it is not necessary to adjust the gap between the peeling member and the heat transfer surface, and the hydrate layer is always kept in a stable state. A predetermined portion of the surface can be reliably peeled off.
[0027]
Further, in the apparatus according to claim 7, the heat transfer surface has an uneven portion, and when the hydrate layer on the heat transfer surface is peeled off by the peeling member, the above-mentioned structure is obtained. At least a part of the hydrate layer remains in the concave portion of the uneven portion.
[0028]
Therefore, even if the peeling member is slid on the heat transfer surface, a predetermined amount of the hydrate layer always remains in the concave portion, so that the adjustment work and the like are easy and the reliability is high. .
[0029]
Further, in the apparatus according to claim 8, a plurality of notches are formed in a portion of the peeling member of the peeling mechanism which faces the heat transfer surface, and the heat transfer surface is formed by the peeling member. At the time of peeling off the upper hydrate layer, at least a part of the hydrate layer on the heat transfer surface is left in a portion corresponding to the notch.
[0030]
Therefore, a predetermined amount of the hydrate layer always remains on the heat transfer surface corresponding to the cutout portion, so that the reliability is high and the adjustment work and the like are easy. In addition, there is no need to process irregularities or grooves on the heat transfer surface, and the manufacturing cost of the device is low.
[0031]
Further, in the apparatus according to claim 9, a net member is attached to the heat transfer surface, and when the hydrate layer on the heat transfer surface is separated by the separation member of the separation mechanism. In addition, at least a part of the hydrate layer remains in the mesh of the mesh member.
[0032]
Therefore, a predetermined amount of the hydrate layer can be reliably left on the heat transfer surface. Further, since the net member is embedded in the remaining hydrate layer, by forming the net member with a metal material, the thermal conductivity of the remaining hydrate layer can be increased and the efficiency can be improved. . Further, this net member has an advantage that it can be easily replaced when worn.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method and an apparatus according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 shows a schematic configuration of the apparatus according to the first embodiment. This embodiment is an apparatus for producing a hydrate slurry by cooling an aqueous solution containing TBAB as a guest compound as described above.
[0034]
Reference numeral 1 in the figure is a generated heat exchanger for producing a hydrate slurry. The generated heat exchanger 1 has a cylindrical shape, and its inner peripheral surface is formed as a heat transfer surface 2. Further, a cooling jacket 3 through which a refrigerant flows is arranged around the heat transfer surface 2. In the cooling jacket 3, a refrigerant or brine is circulated from a refrigerating device 4 by a pump 5, and the heat transfer surface 2 is cooled to a temperature of 8 ° C. or less, for example, 4 ° C. or less, at which the above-mentioned dihydrate is formed. Cool to a temperature below ° C.
[0035]
Reference numeral 6 denotes a hydrate tank for storing the above-mentioned aqueous solution of TBAB and for storing the generated hydrate slurry. Then, from the hydrate tank 6, an aqueous solution is sent to the above-described heat exchanger 1 by a pump 7, and the hydrate slurry generated in the heat exchanger 1 is again transferred to the hydrate tank 6. Returned and stored.
[0036]
In the actual apparatus, for example, a mechanism for supplying the hydrate slurry to the load side and other parts are added, but the one shown in FIG. 2 is simplified for explanation.
[0037]
In addition, a peeling mechanism is provided inside the cylindrical heat exchanger 1. In this embodiment, the peeling mechanism includes a peeling blade 8. The peeling blade body 8 is rotatably provided in the generating heat exchanger 1, and is driven to rotate at a predetermined rotation speed by a rotation driving mechanism 9.
[0038]
A plurality of peeling blade members 10 are radially protruded from the outer periphery of the rotating blade body 8. In this embodiment, these stripping blade members 10 have a linear shape along the axial direction of the cylindrical generating heat exchanger 1, but may have a spiral shape or another shape. As shown in FIG. 3, the leading edge portions of these peeling blade members 10 face the inner peripheral surface of the cylindrical heat transfer surface 2 with a predetermined gap therebetween. The hydrate layer formed on the surface 2 is configured to be mechanically peeled off.
[0039]
Next, the operation of the above-described device and the method performed by this device will be described. FIG. 3 is a cross-sectional view of a part of the generated heat exchanger 1. As described above, a layer of the first hydrate S1 is first formed on the heat transfer surface 2 of the heat exchanger 1, and the second hydrate S2 is further formed on the layer S1 as described above. Is formed.
[0040]
The rotation of the peeling blade body 8 causes the peeling blade member 10 to move along the heat transfer surface 2 and mechanically peels off the hydrate layer. In this case, since a predetermined gap is formed between the leading edge of the peeling blade member 10 and the heat transfer surface 2, the surface portion of the hydrate layer, that is, the second hydration layer, is formed. Only the part of the material layer S2 is peeled off and dispersed in the aqueous solution. Then, a hydrate layer is left on the heat transfer surface 2 with a thickness corresponding to the gap.
[0041]
The hydrate layer remaining on the heat transfer surface 2 is the base portion of the hydrate layer, that is, the first hydrate layer. As described above, the second hydrate layer S2 is generated. After the second hydrate layer S2 is formed, the next separating blade member 10 separates the second hydrate layer S2 in the same manner as described above, and the first water The hydrate layer S1 remains.
[0042]
By repeating such an operation, of the hydrate layer on the heat transfer surface 2, only the portion of the second hydrate layer S2 near the surface is peeled off and dispersed in an aqueous solution to form particles. A hydrate slurry is formed, the first hydrate layer S1 always remains on the heat transfer surface 2, and the second hydrate layer is formed thereon.
[0043]
In the above description, the initial state of the operation of this apparatus has been described for easy understanding. However, in the steady state of operation of this apparatus, the hydrate layer remaining on the heat transfer surface 2 Is peritectically reacted with the water in the surrounding aqueous solution and gradually changes to a second hydrate. Therefore, in the steady operation state, the remaining hydrate layer is not the first hydrate, but at least the vicinity of the surface is changed to the second hydrate.
[0044]
In addition, since the thermal conductivity of a hydrate is generally low, the heat exchange efficiency is reduced by the remaining hydrate layer. However, as described above, the thickness of the remaining hydrate layer may be small. In an actual apparatus, the remaining hydrate layer may be about 1 mm or several mm, and the heat exchange efficiency is extremely low, although it depends on the structure and dimensions of the generated heat exchanger 1. The thickness of the remaining hydrate layer can be arbitrarily adjusted by setting a gap between the above-described peeling blade member 10 and the heat transfer surface 2.
[0045]
Further, as described above, when the surface of the remaining hydrate layer changes to the second hydrate, the hydrate formed thereon is formed with the second hydrate as a nucleus. The second hydrate is formed directly. The temperature at which this second hydrate is formed directly is higher than the temperature at which the first hydrate is formed. Therefore, the cooling temperature of the heat transfer surface 2 can be increased by that much, and the efficiency of the refrigerating device 4 can be increased by that much, so that the efficiency of the entire hydrate slurry production device can be increased. Is also possible.
[0046]
FIG. 5 shows the results of an experiment performed to confirm the above effects. In this experiment, the above-mentioned TBAB aqueous solution was used as an aqueous solution, and an apparatus having the same structure as that of the above-described embodiment was used. The experiment was started from the initial temperature of the aqueous solution of 13 ° C. without circulation. The curve a in FIG. 5 is a case where all the hydrates generated on the heat transfer surface are peeled off by the peeling blade member, and the curve b is a thin layer of the hydrate remaining on the heat transfer surface. Is the case. The point P1 in the figure is a temperature change due to supercooling of the aqueous solution when a hydrate is first generated.
[0047]
As is apparent from FIG. 5, when no hydrate remains on the heat transfer surface (curve a), the temperature of the aqueous solution drops to about 3 ° C. even after the first hydrate starts to be formed at point P1. Until the first hydrate is formed, and the first hydrate changes to the second hydrate at the point P2. However, since the first hydrate continues to be generated, the temperature of the aqueous solution decreases. Continue. This indicates that hydrates are not formed unless cooled to lower temperatures.
[0048]
On the other hand, when the hydrate remains on the heat transfer surface (curve b), after the first hydrate is generated on the heat transfer surface at point P1, the remaining hydrate layer Since the surface changes to a dihydrate, the temperature of the aqueous solution decreases little (a hydrate is formed at a higher temperature), and the primary hydrate layer remaining at the point P2 is completely converted to the secondary water. It has been shown that the second hydrate continues to form directly on this layer at steady state. Therefore, according to the above method and apparatus, the second hydrate can be stably produced at a high temperature of the aqueous solution of about 8 ° C.
[0049]
Note that the present invention is not limited to the above embodiment. For example, FIG. 4 shows a second embodiment of the present invention. In this example, the peeling blade member 11 is a flexible member. The flexible peeling blade member 11 is made of a material such as a thin steel plate, a synthetic resin, a synthetic rubber, or the like, and is configured to bend with a predetermined elasticity. This embodiment is the same as the first embodiment except for the above points.
[0050]
In this embodiment, the peeling blade member 11 is curved as shown in FIG. 4 due to the resistance when the hydrate layer on the heat transfer surface 2 is peeled off, and the hydrate Is left. In this embodiment, since the hydrate layer having a predetermined thickness is automatically left on the heat transfer surface 2 due to the curvature of the peeling blade member 11, the adjustment work and the like are easy and the reliability is high. .
[0051]
FIG. 6 shows a third embodiment of the present invention. FIG. 6 is a vertical cross-sectional view of a part of the above-mentioned generated heat exchanger. In this embodiment, a large number of fine circumferential grooves 13 are formed on the heat transfer surface 2 and the heat transfer surface 2 is formed as an uneven surface. This embodiment has the same configuration as the first embodiment except for the above points.
[0052]
In this embodiment, a hydrate layer remains in the groove 13. Then, when the hydrate changes to the second hydrate S2 as described above, the second hydrate is directly generated on the heat transfer surface 2 near the grooves 13 with the hydrate as a nucleus.
[0053]
In this embodiment, even if the peeling blade member 10 is brought into sliding contact with the heat transfer surface 2 and the hydrate on the heat transfer surface 2 other than the groove 13 is completely stripped off, as described above, The second hydrate can be produced directly. Therefore, a decrease in the heat transfer efficiency of the heat transfer surface 2 is prevented, and the efficiency can be further increased.
[0054]
In this embodiment, it is not always necessary to form a groove in the heat transfer surface, and the heat transfer surface may be formed in a rough surface to form irregularities, or may be formed in other forms of irregularities. You may.
[0055]
FIG. 7 shows a fourth embodiment of the present invention. In this embodiment, a large number of fine notches 14 are formed at the leading edge of the peeling blade member 10. In this embodiment, a hydrate layer remains on the heat transfer surface 2 at a portion corresponding to the cutout portion 14, and the operation and the like are the same as those in the third embodiment.
[0056]
FIG. 8 shows a fifth embodiment of the present invention. This is obtained by attaching a fine mesh member 16 to the heat transfer surface 2. This net member 16 is preferably formed of a metal material having high thermal conductivity.
[0057]
In this embodiment, the hydrate layer remains in the eyes of the mesh member 16. In this embodiment, since it is not necessary to process the heat transfer surface into an uneven surface as in the third embodiment, the manufacturing cost of the device can be reduced. In addition, since the net member 16 is embedded in the remaining hydrate layer, there is an advantage that the thermal conductivity of the hydrate layer is increased and the heat exchange efficiency is improved.
[0058]
Note that the present invention is not limited to the above embodiments. For example, the apparatus of the above embodiment uses a cylindrical heat exchanger, but may use another heat exchanger.
[0059]
【The invention's effect】
As described above, according to the method of the present invention, by leaving hydrate on the heat transfer surface, the hydrate formed thereon becomes a hydrate having a large hydration number. By exfoliating the hydrate, it is possible to produce a stable hydrate slurry containing almost no hydrate particles having a small hydration number, and to improve the efficiency.
[0060]
Further, according to the apparatus of the present invention, since the hydrate layer is mechanically peeled off, it is possible to peel off the hydrate part near the surface of the hydrate layer, that is, the hydrate part having a large hydration number accurately and reliably. The effect is great, as well as simple structure, reliable operation and high reliability.
[Brief description of the drawings]
FIG. 1 is a diagram showing characteristics of the concentration of an aqueous solution of a first hydrate and a second hydrate and the formation temperature.
FIG. 2 is a schematic diagram of an apparatus according to the first embodiment.
FIG. 3 is a cross-sectional view of a part of the generating heat exchanger of the apparatus of the first embodiment.
FIG. 4 is a cross-sectional view of a part of a production heat exchanger of the device of the second embodiment.
FIG. 5 is a diagram showing the results of an experiment for confirming the effects of the present invention.
FIG. 6 is a longitudinal sectional view of a part of a generating heat exchanger of the device according to the third embodiment.
FIG. 7 is a longitudinal sectional view of a part of a production heat exchanger of an apparatus according to a fourth embodiment.
FIG. 8 is a longitudinal sectional view of a part of a production heat exchanger of an apparatus according to a fifth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat generator 2 Heat transfer surface 4 Refrigerator 10 Peeling blade member

Claims (9)

A method for producing a hydrate slurry by cooling an aqueous solution containing a guest compound,
Cooling the aqueous solution through the heat transfer surface to form a hydrate layer on the heat transfer surface;
Generating a layer of hydrate having a higher hydration number on the layer of hydrate generated on the heat transfer surface;
Exfoliating the hydrate having a high hydration number generated on the surface portion of the hydrate layer and leaving at least a part of the hydrate layer on the heat transfer surface. A method for producing a hydrate slurry. The step of exfoliating the hydrate having a high hydration number includes mechanically exfoliating the vicinity of the surface of the hydrate layer attached on the heat transfer surface and hydrating the vicinity of the surface of the hydrate layer 2. The method for producing a hydrate slurry according to claim 1, wherein the hydrate having a high number is exfoliated. A heat transfer surface in contact with the aqueous solution containing the guest compound; and a heat transfer surface that moves along the heat transfer surface, mechanically peels off the hydrate layer attached to the heat transfer surface, and at least removes the hydrate layer. An apparatus for producing a hydrate slurry, comprising: a peeling mechanism having a peeling member that partially leaves the heat transfer surface. The heat transfer surface has a cylindrical shape, and the aqueous solution contacts the inner peripheral surface, and the peeling mechanism rotates along the inner peripheral surface of the cylindrical heat transfer surface. The apparatus for producing a hydrate slurry according to claim 3, further comprising a peeling blade member. A predetermined gap is formed between the peeling member of the peeling mechanism and the heat transfer surface, and at least a part of the hydrate layer remains on the heat transfer surface by the gap. 4. The apparatus for producing a hydrate slurry according to claim 3, wherein: The peeling member of the peeling mechanism has flexibility, and moves along the heat transfer surface to be curved by resistance when the hydrate layer on the heat transfer surface is peeled off. 4. The hydrate slurry producing apparatus according to claim 3, wherein at least a part of the hydrate layer is left on the heat transfer surface. On the heat transfer surface, an uneven portion is formed, and when the hydrate layer on the heat transfer surface is separated by the release member, a hydrate layer is formed in the concave portion of the uneven portion. An apparatus for producing a hydrate slurry, at least a part of which remains. A plurality of notches are formed in a portion of the peeling member of the peeling mechanism facing the heat transfer surface, and when the hydrate layer on the heat transfer surface is peeled by the peeling member, 4. The hydrate slurry producing apparatus according to claim 3, wherein at least a part of the hydrate layer on the heat transfer surface is left in a portion corresponding to the notch. A mesh member is attached to the heat transfer surface, and when the hydrate layer on the heat transfer surface is separated by the separation member of the separation mechanism, the mesh member is placed in the mesh of the mesh member. The hydrate slurry producing apparatus according to claim 3, wherein at least a part of the hydrate layer remains.

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