Maintenance method for the discharge pump in the ammonia tank

Abstract

To prevent ammonia gas from being diffused to the atmosphere, to perform maintenance work for a dispensing pump in an ammonia tank safely.SOLUTION: An ammonia tank 1 comprises a tank 2 that stores liquid ammonia 100, a pump barrel 3 inserted from a top part 2a of the tank 2 to near a bottom part 2b, a foot valve 4 provided at the lower end part of the pump barrel 3, and a dispensing pump 5 suspended inside the pump barrel 3 and whose weight can open the foot valve 4. A maintenance method for a dispensing pump in the ammonia tank comprises: pulling up the dispensing pump 5 to close the foot valve 4; suctioning ammonia gas from the pump barrel 3 while introducing purge gas into the pump barrel 3; and extracting the dispensing pump 5 from the upper end part of the pump barrel 3 while detoxifying the ammonia gas by a detoxification device 8.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a maintenance method for an ammonia tank discharge pump. [Background technology]

[0002] Patent Document 1 below discloses a cryogenic tank for storing liquefied gas such as LNG. A pump barrel is inserted through the roof of this cryogenic tank, and a liquid discharge line is attached to the upper end of the pump barrel. A foot valve is provided at the lower end of the pump barrel, and the foot valve is opened by the weight of a discharge pump suspended inside the pump barrel. When the discharge pump is driven with the foot valve open, the liquefied gas in the cryogenic tank is discharged via the pump barrel and the liquid discharge line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 63-30700 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, as a measure against global warming, ammonia, which does not generate carbon dioxide when burned, has attracted attention as a fuel, and it has been considered to store large amounts of liquid ammonia using the above-mentioned cryogenic tank. In such an ammonia tank, in order to perform maintenance on the discharge pump suspended inside the pump barrel, it is necessary to open the top end of the pump barrel and lift the discharge pump. When the top end of the pump barrel is opened, ammonia gas vaporized inside is released into the atmosphere, so workers must wear special protective equipment to avoid inhaling toxic ammonia gas.

[0005] The present invention has been made in consideration of the above problems, and has an object to suppress the emission of ammonia gas into the atmosphere and to safely perform maintenance work on the discharge pump in the ammonia tank. [Means for solving the problem]

[0006] A maintenance method for a discharge pump in an ammonia tank according to one aspect of the present invention includes: an ammonia tank including a tank for storing liquid ammonia; a pump barrel inserted from the top of the tank to near the bottom; a foot valve provided at the lower end of the pump barrel; and a discharge pump suspended inside the pump barrel and opening the foot valve by its own weight; the method comprises: lifting up the discharge pump, closing the foot valve, and introducing a purge gas into the pump barrel while sucking ammonia gas from the pump barrel; and removing the discharge pump from the upper end of the pump barrel while detoxifying the ammonia gas with a detoxification device.

[0007] In one aspect of the present invention, a gas suction position of the ammonia gas in the pump barrel may be set lower than a gas introduction position of the purge gas.

[0008] In one aspect of the present invention, the internal space of the pump barrel may be partitioned into upper and lower spaces below a gas suction position of the ammonia gas in the pump barrel, and the dispensing pump may be dried in the internal space above the partition position.

[0009] In one aspect of the present invention, suction of the ammonia gas may be stopped until the liquid ammonia inside the pump barrel is pushed out from the lower end of the pump barrel into the tank by introducing the purge gas.

[0010] In one aspect of the present invention, after the cables connected to the dispensing pump are pulled out from the upper end of the pump barrel, the cables are washed on a liquid receiving pan, and the post-wash liquid received in the liquid receiving pan is stored in a liquid collection tank installed outside the tank via piping and disposed of. [Effects of the Invention]

[0011] According to the above aspect of the present invention, it is possible to suppress the emission of ammonia gas into the atmosphere and to perform maintenance work on the ammonia tank discharge pump safely. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic view showing a main part of an ammonia tank according to a first embodiment. [Figure 2] 1 is an explanation for explaining a first step of a maintenance method for an ammonia tank discharge pump according to a first embodiment. [Figure 3] FIG. 4 is an explanatory view illustrating a second step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. [Figure 4] FIG. 10 is an explanatory view illustrating a third step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. [Figure 5] FIG. 10 is an explanatory view illustrating a fourth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. [Figure 6] FIG. 10 is an explanatory view illustrating a fifth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. [Figure 7] FIG. 10 is an explanatory view illustrating a sixth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. [Figure 8] FIG. 10 is an explanatory view illustrating a seventh step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. [Figure 9] FIG. 10 is an explanatory view illustrating a sixth step of the maintenance method for the ammonia tank discharge pump according to the second embodiment. [Figure 10] FIG. 10 is an explanatory view illustrating a fifth step of the maintenance method for the ammonia tank discharge pump according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] (First embodiment) FIG. 1 is a schematic diagram showing a main part of an ammonia tank according to the first embodiment. As shown in FIG. 1, the ammonia tank 1 includes a tank 2 for storing liquid ammonia 100, a pump barrel 3 inserted from a top 2a of the tank 2 to near the bottom 2b, a foot valve 4 provided at the lower end of the pump barrel 3, and a discharge pump 5 suspended inside the pump barrel 3 and opening the foot valve 4 by its own weight.

[0015] The tank 2 is, for example, a large-scale low-temperature PC wall-type or underground low-temperature tank. The tank 2 has a cold insulation material such as granular perlite filled between an inner tank (not shown) about 50 meters high and an outer tank made of PC dike, or between the wall of an underground cavity.

[0016] The pump barrel 3 is a cylindrical tubular member (also called a pump column) inserted vertically downward from the top 2a of the tank 2, and a liquid dispensing line (not shown) and the like are connected to the side of its upper end. The upper opening of the pump barrel 3 is closed by a head plate 3a.

[0017] The foot valve 4 includes a closure plate 4a that closes the opening at the bottom end of the pump barrel 3, and a plurality of spring rods 4b that support the closure plate 4a. When the dispensing pump 5 is placed on the closure plate 4a inside the pump barrel 3, the weight of the pump 5 moves the closure plate 4a downward against the spring force of the spring rods 4b, and the opening at the bottom end of the pump barrel 3 is opened.

[0018] The dispensing pump 5 is suspended within the pump barrel 3. The dispensing pump 5 is, for example, a column-type (cylindrical) submerged pump, and lifts liquid ammonia from the lower end to the upper end of the pump barrel 3. The dispensing pump 5 is suspended from a lifting wire 9 extending downward from the head plate 3a.

[0019] Cables 10 are connected to the dispensing pump 5. The cables 10 include, for example, a power cable 10a and an instrumentation cable 10b. The instrumentation cable 10b is connected to a terminal header 12 installed on the head plate 3a. In addition, a storage cover 13 that covers the end of the lifting wire 9 is installed on the head plate 3a.

[0020] A gas inlet line 6 and a gas suction line 7 are connected to the pump barrel 3 for maintenance of the dispensing pump 5. The gas inlet line 6 introduces an inert gas such as nitrogen gas as a purge gas into the pump barrel 3. The gas suction line 7 sucks in and discharges ammonia gas and the like vaporized inside the pump barrel 3.

[0021] The gas inlet line 6 is connected to the side of the upper end of the pump barrel 3 that protrudes outside the tank 2. The gas suction line 7 is connected to the upper end of the pump barrel 3 that protrudes outside the tank 2, below the gas inlet line 6. In other words, the gas suction position 7a of the ammonia gas in the pump barrel 3 is set below the gas introduction position 6a of the purge gas.

[0022] The gas suction line 7 is connected to a detoxification device 8 that detoxifies the ammonia gas. The detoxification device 8 includes a blower 8a that sucks gas from inside the pump barrel 3 via the gas suction line 7, and a detoxification tank 8b that processes the ammonia gas contained in the gas discharged from the blower 8a. The detoxification tank 8b includes, for example, a scrubber that absorbs ammonia into water, and a tank that stores the generated aqueous ammonia solution.

[0023] Next, a maintenance method (hereinafter referred to as the present method) for the discharge pump 5 installed inside the ammonia tank 1 described above will be described with reference to FIGS.

[0024] FIG. 2 is an explanatory view illustrating a first step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. In this method, as shown in Fig. 2, the dispensing pump 5 is raised and the foot valve 4 is closed. Specifically, first, the storage cover 13 covering the end of the lifting wire 9 is removed.

[0025] Next, the end of the lifting wire 9 is slightly lifted up with a crane 14, and the foot valve 4 is closed. During this time, purge gas is introduced into the pump barrel 3 through the gas inlet line 6. Also, ammonia gas inside the pump barrel 3 is sucked through the gas suction line 7, and the ammonia gas is detoxified by the detoxification device 8.

[0026] FIG. 3 is an explanatory view illustrating a second step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. Next, in this method, as shown in FIG. 3, the liquid ammonia 100 inside the pump barrel 3 is pushed out from the lower end of the pump barrel 3 into the tank 2 by introducing a purge gas.

[0027] That is, by introducing purge gas from the gas inlet line 6, the internal pressure of the pump barrel 3 is increased, and the liquid ammonia 100 inside the pump barrel 3 is pushed out into the tank 2 through the gap between the lower end opening of the pump barrel 3 and the closure plate 4a. During this time, it is recommended that the blower 8a be stopped. This makes it easier to increase the internal pressure of the pump barrel 3.

[0028] FIG. 4 is an explanatory view illustrating a third step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. Next, in this method, the terminal header 12 installed on the head plate 3a is removed as shown in Fig. 4. At this time, the introduction of purge gas into the pump barrel 3 and the suction of ammonia gas from the pump barrel 3 are resumed.

[0029] Specifically, in the second step described above, once the liquid ammonia 100 inside the pump barrel 3 is pushed into the tank 2, the liquid pressure of the liquid ammonia 100 presses the closure plate 4a against the lower end of the pump barrel 3. Therefore, even if the blower 8a is driven and the internal pressure of the pump barrel 3 decreases, the liquid ammonia 100 in the tank 2 will hardly infiltrate into the pump barrel 3.

[0030] FIG. 5 is an explanatory view illustrating a fourth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. Next, in this method, as shown in Fig. 5, the head plate 3a of the pump barrel 3 is removed. At this time, the introduction of purge gas into the pump barrel 3 and the suction of ammonia gas from the pump barrel 3 continue.

[0031] Here, the gas suction position 7a of the ammonia gas in the pump barrel 3 is set lower than the gas introduction position 6a of the purge gas, so that the purge gas functions like an air curtain, and it is possible to suppress the diffusion of the ammonia gas from the upper end opening of the pump barrel 3.

[0032] FIG. 6 is an explanatory view illustrating a fifth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. Next, in this method, as shown in Fig. 6, the dispensing pump 5 is lifted up to the gas layer part of the pump barrel 3. Specifically, the lifting wire 9 is wound up from the upper end opening of the opened pump barrel 3 with a hoist or the like (not shown), thereby lifting the dispensing pump 5.

[0033] Here, the position to which the dispensing pump 5 is pulled up is preferably above the liquid level of the liquid ammonia 100 inside the tank 2 and below the gas introduction position 6a. A more preferable position to pull up the dispensing pump 5 is above the liquid level of the liquid ammonia 100 inside the tank 2 and below the gas suction position 7a. As a result, even if the liquid ammonia adhering to the outer surface of the dispensing pump 5 vaporizes, it can be immediately sucked and discharged from the gas suction line 7 directly above.

[0034] FIG. 7 is an explanatory view illustrating a sixth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. Next, in this method, as shown in FIG. 7, the dispensing pump 5 is removed from the upper end of the pump barrel 3 and stored in a dry pot 15.

[0035] FIG. 8 is an explanatory view illustrating a seventh step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. Next, in this method, as shown in Figure 8, the cables 10 are unwound and the dry pot 15 containing the dispensing pump 5 is closed. At the same time or in parallel with this, the upper opening of the pump barrel 3 is closed with the head plate 3a.

[0036] As a result, the discharge pump 5 can be safely lifted up from the ammonia tank 1, and the lifted discharge pump 5 can be lowered to the top 2a of the tank 2 or to the ground for maintenance.

[0037] As described above, according to the first embodiment described above, in an ammonia tank 1 including a tank 2 for storing liquid ammonia 100, a pump barrel 3 inserted into the tank 2 from the top 2a to near the bottom 2b, a foot valve 4 provided at the lower end of the pump barrel 3, and a discharge pump 5 suspended inside the pump barrel 3 and opening the foot valve 4 by its own weight, the discharge pump 5 is pulled up, the foot valve 4 is closed, and ammonia gas is sucked from the pump barrel 3 while introducing a purge gas into the pump barrel 3, and the discharge pump 5 is removed from the upper end of the pump barrel 3 while the ammonia gas is detoxified by the detoxification device 8. This method prevents ammonia gas from being released into the atmosphere, and allows for safe maintenance of the discharge pump 5 installed inside the ammonia tank 1.

[0038] In the first embodiment, the ammonia gas suction position 7a in the pump barrel 3 is set lower than the purge gas introduction position 6a. This technique effectively prevents ammonia gas from escaping from the upper end of the pump barrel 3.

[0039] Furthermore, in the first embodiment, suction of ammonia gas is stopped until the liquid ammonia 100 inside the pump barrel 3 is pushed out from the lower end of the pump barrel 3 into the tank 2 by introducing the purge gas. According to this method, the internal pressure of the pump barrel 3 is increased by introducing the purge gas, and the liquid ammonia 100 can be quickly pushed out from inside the pump barrel 3 into the tank 2.

[0040] (Second embodiment) Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0041] FIG. 9 is an explanatory view illustrating a sixth step of the maintenance method for the ammonia tank discharge pump according to the second embodiment. In the sixth step of the second embodiment, as shown in FIG. 9, the internal space of the pump barrel 3 is divided into upper and lower parts below the gas suction position 7a of the ammonia gas in the pump barrel 3, and the dispensing pump 5 is dried in the internal space above the partition position.

[0042] Specifically, a partition plate 16 is inserted into the pump barrel 3 to separate the internal space of the pump barrel 3 into upper and lower spaces. Alternatively, the internal space of the pump barrel 3 may be separated into upper and lower spaces by providing a valve (not shown) in the pump barrel 3 and closing the valve.

[0043] According to the second embodiment described above, instead of using the dry pot 15 of the first embodiment, the inside of the pump barrel 3 is partitioned into upper and lower sections, and the dispensing pump 5 pulled up inside the pump barrel 3 can be dried.

[0044] (Third embodiment) Next, a third embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0045] FIG. 10 is an explanatory view illustrating a fifth step of the maintenance method for the ammonia tank discharge pump according to the third embodiment. In the fifth step of the third embodiment, as shown in Fig. 10, the cables 10 pulled out together with the dispensing pump 5 are washed on a liquid receiving pan 22, and the post-washing liquid received in the liquid receiving pan 22 is stored in a liquid collection tank 25 installed outside the tank 2 via a pipe 24 and disposed of. Note that reference numeral 20 shown in Fig. 10 denotes a hoist that lifts the dispensing pump 5. Reference numeral 21 denotes a take-up drum that takes up the cables 10.

[0046] The liquid receiving pan 22 is installed on, for example, a maintenance stage on the top 2a of the tank 2, a short distance from the pump barrel 3. A cleaning device 23 is disposed above the liquid receiving pan 22. The cleaning device 23 includes, for example, a plurality of spray nozzles 23a connected to an industrial water line. It is preferable that the direction of each spray nozzle 23a be adjusted toward the winding drum 21 above the liquid receiving pan 22.

[0047] A pipe 24 extending from the top 2a of the tank 2 to the ground is connected to the liquid receiving pan 22. The liquid collection tank 25 receives the post-cleaning liquid received in the liquid receiving pan 22 from the lower end of the pipe 24. The cleaning liquid sprayed onto the cables 10 from the spray nozzle 23a may be water (industrial water in the third embodiment) in which ammonia is easily dissolved.

[0048] Because the cables 10 are covered with, for example, a metal-coated flexible hose, liquid ammonia may be entrained in the metal coating. In the third embodiment, in order to prevent ammonia gas from escaping into the atmosphere from the cables 10, a spray nozzle 23a and a liquid receiving pan 22 are installed near the pump barrel 3, and the cables 10 are washed with water as soon as they are pulled out. The aqueous ammonia solution once received in the liquid receiving pan 22 is allowed to drip down the pipe 24 below the tank 2, collected in a liquid collection tank 25, and then disposed of after undergoing appropriate processing.

[0049] While preferred embodiments of the present invention have been described and illustrated, it should be understood that these are illustrative of the present invention and should not be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Accordingly, the present invention should not be deemed limited by the foregoing description, but rather by the scope of the claims. [Explanation of symbols]

[0050] 1...ammonia tank, 2...tank, 2a...top, 2b...bottom, 3...pump barrel, 3a...head plate, 4...foot valve, 4a...closure plate, 4b...spring rod, 5...discharge pump, 6...gas inlet line, 6a...gas inlet position, 7...gas suction line, 7a...gas suction position, 8...detoxification device, 8a...blower, 8b...detoxification tank, 9...lifting wire, 10...cables, 10a...power cable, 10b...instrumentation cable, 12...terminal header, 13...storage cover, 14...crane, 15...dry pot, 16...plate, 20...symbol, 21...symbol, 21...winding drum, 22...liquid receiving pan, 23...cleaning device, 23a...spray nozzle, 24...piping, 25...liquid collection tank, 100...liquid ammonia

Claims

1. An ammonia tank comprising: a tank for storing liquid ammonia; a pump barrel inserted into the tank from the top to near the bottom; a foot valve provided at the lower end of the pump barrel; and a discharge pump suspended inside the pump barrel for opening the foot valve by its own weight, the dispensing pump is pulled up, the foot valve is closed, and ammonia gas is sucked from the pump barrel while a purge gas is introduced into the pump barrel, and the dispensing pump is removed from the upper end of the pump barrel while the ammonia gas is detoxified by a detoxification device; a gas suction position of the ammonia gas in the pump barrel is set lower than a gas introduction position of the purge gas. A maintenance method for an ammonia tank discharge pump.

2. An ammonia tank comprising: a tank for storing liquid ammonia; a pump barrel inserted into the tank from the top to near the bottom; a foot valve provided at the lower end of the pump barrel; and a discharge pump suspended inside the pump barrel for opening the foot valve by its own weight, the dispensing pump is pulled up, the foot valve is closed, and ammonia gas is sucked from the pump barrel while a purge gas is introduced into the pump barrel, and the dispensing pump is removed from the upper end of the pump barrel while the ammonia gas is detoxified by a detoxification device; an internal space of the pump barrel is divided into upper and lower spaces below a gas suction position of the ammonia gas in the pump barrel, and the dispensing pump is dried in the internal space above the partition position; A maintenance method for an ammonia tank discharge pump.

3. 3. The maintenance method for an ammonia tank internal discharge pump according to claim 1, wherein suction of the ammonia gas is stopped until the liquid ammonia inside the pump barrel is pushed out from the lower end of the pump barrel into the tank by introducing the purge gas.

4. The maintenance method for the discharge pump in the ammonia tank according to any one of claims 1 to 3, characterized in that after cables connected to the discharge pump are pulled out from the upper end of the pump barrel, the cables are washed on a liquid receiving pan, and the washed liquid received in the liquid receiving pan is stored in a liquid collection tank installed outside the tank via piping and disposed of.

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