JP4303666B2 - Fluidized bed reactor for gas hydrate slurry - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a fluidized bed reaction tower for reacting water adhering to a physically dehydrated gas hydrate and a raw material gas to increase the hydrate.

  A gas hydrate is a solid hydrate having a structure in which a gas is taken into a cage formed by water molecules, and is relatively stable under atmospheric pressure of about −20 ° C., so that liquefied natural gas (LNG) Research is underway to use it as a means of transporting and storing natural gas as an alternative.

  In general, the gas hydrate is generated by, for example, reacting a raw material gas such as natural gas, methane gas, and carbon dioxide with water in a low-temperature and high-pressure vessel. Since the gas hydrate thus generated contains a large amount of unreacted water, it is necessary to purify the product gas hydrate by separating the water.

  As a method for separating water from gas hydrate generated in a container, according to the method described in Patent Document 1, gas hydrate and water are extracted from a generator as a slurry, and first a mesh processed inner cylinder It is led to a double-structure screw press-type dewatering device having a physical dehydration. After that, the product is dehydrated by a hydration reaction in which the gas hydrate adhering water and raw material gas are reacted with a twin screw type dehydrator to obtain a product with less adhering water, that is, a product with a high gas hydrate concentration. .

Japanese Patent Laid-Open No. 2003-64385 (see FIG. 1 and pages 2-4)

  However, Patent Document 1 does not describe a specific method for controlling the gas hydrate concentration in a twin-screw type dehydrator.

  An object of the present invention is to realize control of gas hydrate concentration in hydration dehydration.

  In order to solve the above problems, a fluidized bed reaction tower of the present invention includes a vertical container, a dispersing device provided between the position where the gas hydrate of the vertical container is introduced and the bottom, and a vertical container. A suction port connected to the upper part of the vertical container, sucks the raw material gas at the upper part of the vertical container, cools it and circulates it to the lower part of the vertical container, and discharges the gas hydrate above the dispersing device Detecting the load of the discharge machine and the discharge machine, and the amount of circulating gas circulated by the circulating gas blower, the temperature of the circulating gas, and the discharge volume of the discharge machine so that the detected load is within the set range. It is characterized by comprising control means for controlling at least one.

  That is, the fluidized bed reaction tower forms a fluidized bed by fluidizing the gas hydrate discharged from the dehydrating apparatus that performs physical dehydration with the raw material gas, and reacts the adhering water of the gas hydrate with the raw material gas by the fluidized bed reaction. Thus, the concentration of the gas hydrate is increased to the concentration level required for the product. The gas hydrate concentration discharged from the fluidized bed reaction tower correlates with the load of the discharger as shown in FIG. That is, in a granular gas hydrate with relatively little water after hydration and dehydration, if the amount of adhering water decreases, that is, the gas hydrate concentration increases, the fluidity improves and the load on the discharger decreases. Therefore, the load amount of the discharger, for example, the torque or the current of the drive motor of the discharger is detected, and the circulating gas amount, the temperature of the circulating gas, and the discharge amount of the discharger are adjusted so that those values are within the set range. Control at least one. That is, the concentration of the product gas hydrate can be set to a desired value by controlling the fluidized bed reaction and controlling the residence time of the fluidized bed reaction.

  In this case, if the temperature of the circulating gas, that is, the temperature in the tower is lowered too much, the particle size of the gas hydrate becomes smaller, and if it is further lowered, the adhering water of the gas hydrate tends to become ice without being hydrated. is there. Moreover, when the amount of gas circulation is changed, the state of the fluidized bed in the tower will change. Therefore, usually, the control is performed by the discharge amount of the discharger, and the circulation gas amount and the circulation gas temperature can be controlled as necessary.

  According to the present invention, a suitable dehydrator and control of gas hydrate concentration can be realized.

  Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the whole block diagram of the hydrate manufacturing plant to which the fluidized bed reaction tower of the present invention is applied is shown. Although the present embodiment shows a plant for producing a hydrate of natural gas (hereinafter abbreviated as NGH), the present invention is not limited to natural gas and can be applied to hydrate production of other raw material gases.

  As shown in FIG. 1, the hydrate manufacturing plant of this embodiment includes a generator 1 that generates an NGH slurry, and a dehydration that generates high-concentration NGH by separating moisture from the NGH slurry generated by the generator 1. It comprises a tower 2, a fluidized bed reaction tower 3 for reacting NGH adhering water dehydrated in the dehydration tower 2 and natural gas to increase the concentration of NGH to the product level, and a hopper 4 for storing the product NGH. ing. The generator 1, the dehydration tower 2, the fluidized bed reaction tower 3, and the hopper 4 are all maintained at a predetermined high pressure (for example, 3 to 10 MPa).

  The generator 1 is formed of a cylindrical container, and a natural gas introduced into the generator 1 by supplying a certain amount of high-pressure raw material gas (natural gas) and high-pressure water from a supply device (not shown) Water reacts under conditions of low temperature (for example, 1 to 5 ° C.) to produce NGH. The generator 1 is provided with a stirrer 11 for stirring water and a circulating gas blower 12 for extracting natural gas. The discharge port of the circulating gas blower 12 is connected to a nozzle 13 disposed at the bottom of the container via a flow control valve 14 equipped with a flow meter. Since the generation of NGH is accompanied by heat generation, a circulating slurry pump 15 is connected to the bottom of the container to extract NGH slurry containing NGH, a slurry density meter 19, a flow control valve 17 equipped with a slurry flow meter, a cooler 16 and the thermometer 18 so as to return to the upper part of the container, and the amount of refrigerant in the cooler 16 is controlled according to the detection value of the thermometer 18 so that the temperature in the generator 1 is maintained at the set temperature. I have to. Furthermore, depending on the concentration of NGH in the NGH slurry, fluidity may be lowered and transfer may be difficult, or problems may occur in the dewatering process on the downstream side. For example, by controlling at least one of the circulating gas amount, the circulating slurry temperature, and the circulating slurry amount so as to be within 20% by weight), the NGH concentration of the NGH slurry is accurately and stably continuous to a desired value. Control. The NGH slurry generated in the generator 1 in this way is continuously extracted from the bottom of the generator 1 by the slurry transfer pump 20 and supplied to the bottom of the dehydration tower 2.

  The dehydrating tower 2 is formed of a cylindrical vertical container, and a water draining portion 21 is provided in the middle of the tower. The inner wall of the tower corresponding to the water draining portion 21 is a porous wall 22 formed of, for example, a metal mesh or a perforated plate, and water in the dehydration tower 2 is separated into the water draining portion 21 through the porous wall 22. The water in the drain part 21 is extracted by the dehydration circulation pump 24 via the flow control valve 23 and returned to the generator 1. In the vicinity of the top in the dewatering tower 2, a screw conveyor 26 having an opening in a casing (for example, a lower surface) at a position located in the tower is provided. As a result, the water in the NGH slurry introduced into the dehydration tower 2 is separated and removed by the drainage section 21, reaches the top of the tower and is discharged as a dehydrated NGH slurry with a high NGH concentration.

  The NGH concentration in the process of reaching the top of the tower changes from a state where water is filled in the voids of the finely packed powdery NGH to a state where water is attached to the surface of the powdered NGH. If this NGH concentration is too low, that is, if there is too much NGH adhering water, the fluidity of NGH in the fluidized bed reaction tower 3 in the next step is lowered, and the reaction between the NGH adhering water and the raw material gas becomes worse.

  Therefore, in the dehydration tower 2, the concentration of NGH (NGH / (NGH + attached water)) is controlled to, for example, 45 to 70% by weight, preferably 50 ± 5% by weight. The NGH concentration is controlled by controlling the amount of extracted water with the flow rate control valve 23 so that the water level meter 25 holds the water level in the water draining portion 21 at the set water level. That is, the position where the water holding force held in the gap between the NGH and the gravity of the water in the tower is balanced from the water level of the drainage portion 21 to a certain height position. Is adjusted as appropriate based on the water level of the drainage section 21 so that the concentration of NGH carried out by the screw conveyor 26 is controlled to a desired value.

  The fluidized bed reaction tower 3 includes a cylindrical vertical container, and a perforated plate 31 serving as a dispersing device is provided between the position where the gas hydrate of the vertical container is introduced and the bottom. The vertical container has a suction port at an upper portion thereof, and the suction port of the circulation blower 32 is communicated with the suction port. The discharge port of the circulation blower 32 is connected to the bottom of the vertical container, for example, the lower side surface of the container or the bottom of the container. An NGH discharger 38 is provided above the perforated plate 31 in the vertical container so that the dehydrated NGH is carried out to the hopper 4. The ejector 38 is provided with a load detector 39 for detecting the load amount. Then, at least one of the circulating gas amount circulated by the circulating gas blower 32, the temperature of the circulating gas, and the discharge amount of the discharger 38 is controlled so that the load amount detected by the load detector 39 falls within the set range. It has become so.

  The NGH carried out by the discharger 38 is temporarily stored in the hopper 4. The powdery NGH stored in the hopper 4 is appropriately cut out through the gate valve 41 and processed as a product NGH or NGH pellets. In addition, since the inside of the hopper 4 is high pressure (for example, 3-10 Mpa), although not shown in figure, normally, the depressurization apparatus is provided in the downstream of the gate valve 41. FIG.

  Next, the fluidized bed reaction tower 3 which is a characteristic part of this embodiment will be described in detail. The suction port at the top of the fluidized bed reaction tower 3 communicates with the suction port of the circulating gas blower 32 through a cyclone 34. In addition, a cooler 35 and a thermometer 36 are provided in a conduit from the cyclone 34 to the suction port of the circulating gas blower 32. A thermometer 40 is provided in the fluidized bed reaction tower 3. Based on the temperature detected by the thermometer 36 and the thermometer 40, the flow rate of the refrigerant in the cooler 35 is controlled so that the temperature of the fluidized bed reaction tower 3 is maintained at the set temperature. The discharge port of the circulating gas blower 32 is connected between the bottom and the perforated plate 31 via a flow rate control valve 33. The discharger 38 is constituted by, for example, a screw conveyor, one end of the screw conveyor is disposed above the porous plate 31 in the fluidized bed reaction tower 3, and an opening is provided in a casing (for example, the upper surface) located in the tower. The configuration is as follows. This screw conveyor is driven by a motor 37. The motor 37 is provided with a torque detector that detects the torque of the output shaft as a load detector 39. The flow rate control valve 33 is controlled so that the torque of the screw conveyor detected by the torque detector falls within the set range, and at least the circulating gas amount, the carry-out amount of the screw conveyor 38, and the refrigerant flow rate of the cooler 35 are at least. One is to control.

  With this configuration, according to the present embodiment, when natural gas is ejected through the porous plate 31 to the NGH layer formed by being charged into the fluidized bed reactor 3, the upper portion of the porous plate 31. An NGH fluidized bed is formed. In this fluidized bed, NGH adhering water reacts with natural gas to produce NGH, and the NGH concentration is increased to 90% by weight or more, for example. Further, since there is a correlation as shown in FIG. 2 between the NGH concentration in the fluidized bed reaction tower and the load (torque) of the screw conveyor, the detected value detected by the torque detector is used to control the NGH concentration. At least one of the circulating gas amount, the screw conveyor carry-out amount, and the refrigerant flow rate of the cooler 35 is controlled so as to be in a desired range. The NGH discharged from the fluidized bed reaction tower has a relatively low amount of water, for example, an NGH concentration of, for example, 90% by weight. Therefore, the load on the discharger tends to increase as the amount of water increases, that is, as the NGH concentration decreases. It has become. As a result, the control for promoting the fluidized bed reaction or the residence time of the fluidized bed reaction is controlled, the concentration of the product gas hydrate can be controlled to a desired value, and finally the high quality product NGH can be produced stably and continuously. can do.

  By the way, when controlling the NGH concentration, if the temperature of the circulating gas is lowered too much, the temperature in the tower may be lowered too much to generate a gas hydrate having a small particle size. On the other hand, when the amount of gas circulation is changed, the state of the fluidized bed in the tower may become unstable. Therefore, when controlling the NGH concentration, it is preferable to first control by the discharge amount of the discharger 38 and control the circulation gas amount and the circulation gas temperature as necessary.

  In this embodiment, a screw conveyor is used as the discharger 38. However, the present invention is not limited to this, and a known discharge mechanism used for a fluidized bed can be applied. In addition, although what controlled based on the torque of a screw conveyor was mentioned in this embodiment, it can also control based on the electric current value of the motor 37 instead of this as a load of a screw conveyor.

  As described above, according to the present embodiment, the NGH concentration at the time of hydration and dehydration can be adjusted, so that finally a high-quality product NGH can be stably and continuously manufactured.

  In the above-described embodiment, the example in which the vertical container is formed in a cylindrical shape has been described. However, the present invention is not limited thereto, and the vertical container can be formed in an arbitrary shape such as a rectangle. Further, although the porous plate 31 is used as the dispersing device, a diffuser tube or the like can be used instead.

It is a whole block diagram of the hydrate manufacturing plant of one embodiment to which the fluidized bed reaction tower of the gas hydrate slurry of one embodiment of the present invention is applied. It is a graph which shows the relationship between the rotational torque of a screw conveyor in a fluidized bed reaction tower, and a NGH density | concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generator 2 Dehydration tower 3 Fluidized bed reaction tower 4 Hopper 31 Perforated plate 33 Flow control valve 34 Cyclone 35 Cooler 37 Motor 38 Ejector (screw conveyor)
39 Load detector

Claims (1)

A vertical container, a dispersing device provided between a position where the gas hydrate of the vertical container is introduced and a bottom, and a suction port connected to an upper part of the vertical container; A circulating gas blower that sucks and cools the raw material gas at the upper part of the mold container and circulates it in the lower part of the vertical container; a discharger that discharges the gas hydrate above the dispersing device; and a load of the discharger Control means for detecting and controlling at least one of the circulating gas amount circulated by the circulating gas blower, the temperature of the circulating gas, and the discharge amount of the discharger so as to keep the detected load amount within a set range And a fluidized bed reaction tower.

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