JP7824764B2 - Maintenance method for the discharge pump in the ammonia tank - Google Patents

Description

The present invention relates to a maintenance method for an ammonia tank discharge pump.

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 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 inside the cryogenic tank is discharged via the pump barrel and the liquid discharge line.

Japanese Unexamined Patent Publication No. 63-30700

In recent years, ammonia, which does not emit carbon dioxide when burned, has been attracting attention as a fuel in order to combat global warming, and it is being considered to use the above-mentioned cryogenic tanks to store large quantities of liquid ammonia. In such ammonia tanks, to perform maintenance on the discharge pump suspended inside the pump barrel, it is necessary to open the top of the pump barrel and lift the discharge pump. When the top 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.

The present invention was developed in consideration of the above-mentioned problems, and aims to prevent ammonia gas from escaping into the atmosphere and enable safe maintenance work on the ammonia tank discharge pump.

One aspect of the present invention relates to a maintenance method for an internal ammonia tank discharge pump, which includes an ammonia tank that stores liquid ammonia, a pump barrel inserted from the top of the tank to near the bottom, a foot valve attached to the lower end of the pump barrel, and a discharge pump suspended inside the pump barrel that opens the foot valve by its own weight. The method involves: lifting the discharge pump, closing the foot valve, and introducing 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 neutralizing the ammonia gas with a detoxification device.

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

In one aspect of the present invention, the internal space of the pump barrel may be divided into upper and lower sections below the 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.

In one aspect of the present invention, the suction of the ammonia gas may be stopped until the introduction of the purge gas pushes the liquid ammonia inside the pump barrel out from the lower end of the pump barrel into the inside of the tank.

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.

According to one aspect of the present invention, the dispersion of ammonia gas into the atmosphere can be suppressed, allowing maintenance work on the ammonia tank discharge pump to be performed safely.

FIG. 2 is a schematic view showing a main part of the ammonia tank according to the first embodiment. 1 is a diagram illustrating a first step of a maintenance method for an ammonia tank discharge pump according to a first embodiment. FIG. 10 is an explanatory diagram illustrating a second step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. FIG. 10 is an explanatory diagram illustrating a third step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. FIG. 10 is an explanatory diagram illustrating a fourth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. FIG. 10 is an explanatory diagram illustrating a fifth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. FIG. 10 is an explanatory diagram illustrating a sixth step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. FIG. 10 is an explanatory diagram illustrating a seventh step of the maintenance method for the ammonia tank discharge pump according to the first embodiment. FIG. 10 is an explanatory diagram illustrating a sixth step of the maintenance method for the ammonia tank discharge pump according to the second embodiment. FIG. 10 is an explanatory diagram illustrating a fifth step of the maintenance method for the ammonia tank discharge pump according to the third embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a main part of an ammonia tank according to a 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 2 a of the tank 2 to near the bottom 2 b, 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.

Tank 2 is, for example, a large, low-temperature PC-walled or underground low-temperature tank. Tank 2 has a cooling 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 walls of an underground cavity.

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, with a liquid dispensing line (not shown) connected to the side of its upper end. The upper opening of the pump barrel 3 is closed by a head plate 3a.

The foot valve 4 comprises a closure plate 4a that closes the lower opening of the pump barrel 3, and multiple 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, its weight causes the closure plate 4a to move downward against the spring force of the spring rods 4b, opening the lower opening of the pump barrel 3.

The discharge pump 5 is suspended within the pump barrel 3. The discharge 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 discharge pump 5 is suspended from a lifting wire 9 extending downward from the head plate 3a.

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.

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 into the pump barrel 3 as a purge gas. The gas suction line 7 sucks in and discharges ammonia gas and other vaporized gases inside the pump barrel 3.

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 for ammonia gas in the pump barrel 3 is set below the gas introduction position 6a for purge gas.

The gas suction line 7 is connected to a detoxification device 8, which neutralizes the ammonia gas. The detoxification device 8 includes a blower 8a that draws 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 resulting aqueous ammonia solution.

Next, with reference to Figures 2 to 8, we will explain the maintenance method (hereinafter referred to as the present method) for the discharge pump 5 installed inside the above-mentioned ammonia tank 1.

FIG. 2 is an explanatory diagram illustrating a first step of the maintenance method for the ammonia tank discharge pump according to the first embodiment.
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.

Next, the end of the lifting wire 9 is slightly lifted with the 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. Furthermore, ammonia gas inside the pump barrel 3 is sucked out through the gas suction line 7, and the ammonia gas is detoxified by the detoxification device 8.

FIG. 3 is an explanatory diagram 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.

In other words, 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. It is recommended that the blower 8a be stopped during this time. This makes it easier to increase the internal pressure of the pump barrel 3.

FIG. 4 is an explanatory diagram 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.

Specifically, once the liquid ammonia 100 inside the pump barrel 3 is pushed into the tank 2 in the second step described above, 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, there is almost no chance of the liquid ammonia 100 in the tank 2 infiltrating into the pump barrel 3.

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

Here, the ammonia gas suction position 7a in the pump barrel 3 is set lower than the purge gas introduction position 6a, so the purge gas functions like an air curtain, suppressing the emission of ammonia gas from the upper opening of the pump barrel 3.

FIG. 6 is an explanatory diagram 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 portion of the pump barrel 3. Specifically, the lifting wire 9 is wound up from the upper end opening of the opened pump barrel 3 using a hoist or the like (not shown), thereby lifting the dispensing pump 5.

Here, the position to which the dispensing pump 5 is raised 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 raise 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. This allows for immediate suction and discharge from the gas suction line 7 directly above, even if liquid ammonia adhering to the outer surface of the dispensing pump 5 vaporizes.

FIG. 7 is an explanatory diagram 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 the dry pot 15.

FIG. 8 is an explanatory diagram 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 Fig. 8, the cables 10 are unwound and the dry pot 15 housing 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.

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

As described above, according to the first embodiment, an ammonia tank 1 includes a tank 2 for storing liquid ammonia 100, a pump barrel 3 inserted from the top 2a of the tank 2 to near the bottom 2b, a foot valve 4 attached to 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 then raised, the foot valve 4 is closed, and ammonia gas is sucked from the pump barrel 3 while purge gas is introduced into the pump barrel 3. The ammonia gas is then detoxified by the detoxification device 8, while the discharge pump 5 is removed from the upper end of the pump barrel 3. This method prevents ammonia gas from escaping into the atmosphere, allowing for safe maintenance of the discharge pump 5 installed inside the ammonia tank 1.

In addition, 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 suppresses the emission of ammonia gas from the upper end of the pump barrel 3.

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 purge gas. According to this method, the internal pressure of the pump barrel 3 is increased by introducing purge gas, and the liquid ammonia 100 can be quickly pushed out from inside the pump barrel 3 into the tank 2.

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.

FIG. 9 is an explanatory diagram 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 partitioned into upper and lower spaces below the gas suction position 7 a of the ammonia gas in the pump barrel 3, and the dispensing pump 5 is dried in the internal space above the partition position.

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

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

(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.

FIG. 10 is an explanatory diagram 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.

The liquid receiving pan 22 is installed on the top 2a of the tank 2, a short distance from the pump barrel 3, for example, on a maintenance stage. A cleaning device 23 is located above the liquid receiving pan 22. The cleaning device 23 is equipped with, for example, multiple spray nozzles 23a connected to an industrial water line. It is recommended that each spray nozzle 23a be oriented toward the take-up drum 21 above the liquid receiving pan 22.

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.

The cables 10 are covered, for example, by a metal-coated flexible hose, and liquid ammonia may be entrained in the metal coating. In the third embodiment, 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 piping 24 below the tank 2, collected in the liquid collection tank 25, and then disposed of after appropriate processing.

While preferred embodiments of the present invention have been described and illustrated above, 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.

DESCRIPTION OF SYMBOLS 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 introduction line, 6a...gas introduction 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 (4)

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. 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. 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. 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 an 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 a pipe and disposed of.