JPH06277643A - Washing method - Google Patents

Abstract

PURPOSE:To peel and wash off the black film generated in a tank or piping when caustic soda (NaOH) or caustic potash (KOB) is especially stored as a chemical agent in storage facilities having the tank and piping formed using a stainless steel material. CONSTITUTION:After a pre-washing process washing a previously stored chemical agent with water, a main washing process using a washing soln. composed of water containing at least 1-30% of nitric acid and at least 0.1-10% of hydrofluoric acid and held to the temp. range of 20-90 deg.C is performed. A post-washing process removing the washing soln. used in the main washing process is provided after the main washing process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning tanks for storing chemicals and pipes for delivering chemicals or valves attached to them.

[0002]

2. Description of the Related Art In oil tanks for storing chemicals, it is necessary to clean the inside of accessories such as tanks, pipes and valves when changing the chemicals to be stored. This cleaning work is often performed manually by an operator after discharging the chemicals stored in the tank.To carry out the cleaning work of the tank, a scaffold is assembled inside the tank and the worker It is common to climb onto the scaffold, rub the wall surface with a wire brush to which detergent is attached, and then wash it off with washing water.

[0003]

In particular, caustic soda (N
When storing aOH) or caustic potash (KOH), it is common to use stainless steel materials for tanks and pipes, but if the chemicals are stored in stainless steel tanks for a long time, the inner walls of the tanks and pipes A black film was generated in the state where it was baked, and it was difficult to peel off the black film even if the wall surface was rubbed with a wire brush to which a detergent was attached during cleaning. In addition, since the inside of the piping is inaccessible, in many cases, it was impossible to wash and was often discarded.

The object of the present invention is to provide a storage facility in which tanks and pipes are made of stainless steel, as a chemical, especially caustic soda (NaOH) or caustic potash (K).
When storing the above chemicals in a stainless steel tank for a long period of time, a black film is formed on the inner wall surfaces of the tank and the pipes, which makes it difficult for the operator to clean the tanks and pipes. It is to provide a cleaning method that enables cleaning without entering the inside of the tank and completely cleans the black film generated on the inner wall surface of the tank in a short time. Another object of the present invention is to provide a cleaning method for completely cleaning the inner wall surface of a pipe and the inner wall surface of an accessory such as a valve that cannot be cleaned.

[0005]

In order to solve the above-mentioned problems, a cleaning method according to the present invention is a cleaning method for a tank for storing chemicals and a pipe for delivering the chemicals, a valve attached to them, and the like. After storing caustic soda (NaOH) or caustic potash (KOH) as a chemical in a storage facility where tanks and pipes or valves attached to them are made of stainless steel, the chemical is stored when changing the chemical to be stored. It is a method of cleaning the tanks and piping for delivering chemicals or valves attached to them.

The cleaning method will be described step by step for each cleaning step. First, there is a pre-cleaning step of the object to be cleaned. The purpose of this step is to flush away the previously stored chemicals. Since caustic soda (NaOH) and caustic potash (KOH) are water-soluble and have a property of being extremely well dissolved in water, normal temperature water is used for pre-cleaning. It should be noted that it is desirable to use a cleaning means such as jetting high-pressure water in the form of a shower when washing the tank, or jetting high-pressure water such as a jet water stream when washing the pipes.

Next is the main cleaning step. The purpose of this process is to remove dirt that cannot be removed by the pre-cleaning process, that is, caustic soda (NaO).
H) or caustic potash (KOH) is to wash away the black film generated on the inner wall surface of the tank and the pipe when the stainless steel tank is stored for a long time. Cleaning solution containing at least 1% to 30% nitric acid, at least 0.1% to 10% hydrofluoric acid, the remaining components consisting of water, and keeping the temperature in the range of at least 20 ° C to 90 ° C. Wash with.

In the cleaning step, it is preferable to provide a heater for heating the cleaning liquid and keeping the temperature substantially constant in the cleaning liquid supply path. Furthermore, the temperature of the cleaning environment is at least 20 ° C to 9 ° C which is the temperature of the cleaning liquid.
It is preferably in the range of 0 ° C. In addition, when cleaning the tank, you can spray pressurized cleaning liquid in the form of a shower,
In the case of cleaning the pipe, it is desirable to use a cleaning means such as circulating a cleaning liquid under high pressure.

Finally, there is a post-cleaning step. The purpose of this step is to wash away the washing liquid used in the main washing step and rinse it. In order to carry out the washing without affecting the components of the chemical to be stored next, water at room temperature is used for the post-washing, as in the case of the pre-washing. The cleaning liquid has a hydrogen ion concentration index of 4
It is an acidic aqueous solution of a certain degree, and it is necessary to recover and neutralize this. As in the case of the pre-cleaning step, it is possible to use a cleaning means such as spraying high-pressure water in a shower when cleaning the tank, or spraying high-pressure water such as a jet water stream when cleaning the piping. desirable.

[0010]

According to the above cleaning method, in the pre-cleaning step,
By washing away with normal temperature water, caustic soda (NaOH) and caustic potash (KOH) are extremely soluble in water, so they are completely washed out and do not affect the washing liquid used in the next main washing step.

In this cleaning step, the cleaning liquid used contains at least 1% to 30% nitric acid and at least 0.1% to 10% hydrofluoric acid, and the other components are composed of water. The black film generated on the surface to be cleaned is peeled off by immersing the cleaning liquid in the surface to be cleaned while keeping the temperature of the cleaning liquid substantially constant in the range of at least 20 ° C. to 90 ° C. by heating.

Further, in the post-cleaning step, the cleaning liquid used in the main cleaning is completely rinsed out by rinsing with water at room temperature, and the chemicals to be stored next are not affected. In addition, by using only the chemical action for cleaning, it is possible to perform uniform cleaning without causing countless fine scratches on the surface to be cleaned by the wire brush as in the conventional case.

[0013]

EXAMPLE An example of the cleaning method will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a cleaning device for cleaning the inner wall surface of the tank. FIG. 2 is a diagram illustrating a configuration of a cleaning device for cleaning the inner wall surface of the pipe.
FIG. 3 is a diagram illustrating the configuration of a cleaning device for cleaning the inner wall surface of a small accessory such as a valve.

In FIG. 1, the tank 1 is constructed as a cylindrical tank having a peripheral wall 1a and a ceiling 1b, and has a height and an inner diameter according to the accommodation volume. For example, 30
A tank with a volume of 0 kiloliters is about 10m high,
The inner diameter is about 7.8 m. A ladder 2 for raising and lowering is provided inside the tank 1, a hole 3 is formed in the center of the ceiling, and a manhole 4 is formed below the peripheral wall 1a.

The cleaning water spray pipe 5 is arranged inside the tank 1 and sprays cleaning water or cleaning steam onto the peripheral wall 1a. The cleaning water spray pipe 5 is configured by connecting two stainless steel pipes having a length shorter than the radius of the tank 1 minus the size of the ladder 2, and a nozzle 6 for injecting high pressure water at both ends. Are attached via a union joint 5a.

A wash water supply hose 8 is connected to a tee 5b at the center of the wash water spray pipe 5 via a swivel joint 7. Therefore, the tee 5b of the wash water spray pipe 5 is arranged so as to coincide with the center of gravity of the spray pipe 5, and when the wash water spray pipe 5 is suspended by the wash water supply hose 8, the left and right balance can be maintained. Is configured. The wash water spray pipe 5 and the wash water supply hose 8 are rotatably connected to each other.

The washing water supply hose 8 supplies the washing water to the washing water spray pipe 5, and the spray pipe 5 is connected to the ceiling 1 of the tank 1.
It has the function of hanging from b. Therefore, the cleaning water supply hose 8 is composed of the cleaning water spray pipe 5 and the cleaning liquid spray pipe 12, which will be described later.
It is necessary to have a strength capable of supporting the cleaning liquid supply hose 16.

For this reason, in the embodiment, a protective wire 8a is provided along with the washing water supply hose 8 and the both are bound by a band (not shown) or the like to reduce the weight of the washing water spray pipe 5 and other pipes and hoses. It is constructed so that it can be supported by the protective wire 8a.

A guide roller 9a for guiding the movement of the wash water supply hose 8 during winding and unwinding is arranged in the hole 3 provided in the ceiling 1b of the tank 1, and also at a predetermined position on the upper surface of the ceiling 1b of the tank 1. A guide roller 9b is arranged. The wash water supply hose 8 is wound around a drum 10 provided outside the tank 1 and is attached to each guide roller 9
After passing through a and 9b, it is arranged inside the tank 1 through the hole 3.

The washing water supply hose 8 is wound around a drum 10 driven by a motor 10a such as an air motor. Therefore, by rotating the drum 10 in a desired direction, the wash water supply hose 8 is rolled up to raise the wash water spray pipe 5 connected to the hose 8 in the tank 1, or the wash water supply hose 8 is fed out. It is possible to lower the washing water spray pipe 5 in the tank 1.

The other end of the wash water supply hose 8 is a pump
It is connected to the nozzle 11, and is configured to be able to supply the cleaning water having a pressure of up to 150 atm to the nozzle 6 by driving the pump 11 in the pre-cleaning step and the post-cleaning step.

The nozzle 6 has a function of spraying cleaning water in the shape of a curtain having a preset angle and spraying it onto the peripheral wall 1a of the tank 1. The jet direction of the wash water in the horizontal plane by the nozzle 6 is set to be inclined in only one direction from the axis of the wash water spray pipe 5.

For this reason, a force for rotating the tee 5b in the direction opposite to the inclination direction of the nozzle 6 acts on the wash water spray pipe 5 by the reaction when the high-pressure wash water is jetted from the nozzle 6, and this By the force, it is possible to rotate the wash water spray pipe 5 suspended by the wash water supply hose 8 horizontally about the swivel joint 7.

A cleaning liquid spraying pipe 12 having a length substantially equal to that of the cleaning water spraying pipe 5 is arranged in parallel with the cleaning water spraying pipe 5, and the cleaning liquid spraying pipe 12 is fixed by a fixing member 13 such as a band. It is attached integrally to 5. The cleaning liquid spray pipe 12 has a function of spraying the cleaning liquid on the peripheral wall 1a of the tank 1, and a nozzle for spraying the cleaning liquid on both ends.
14 is attached.

A tee 12a is provided at the center of the cleaning liquid spray pipe 12, and a swivel joint 15 is attached to the tee 12a. A cleaning liquid supply hose 16 is connected to the cleaning liquid spray pipe 12 via a swivel joint 15.

The other end of the cleaning liquid supply hose 16 is connected to a pump 20 via a heater 17, and the cleaning liquid supplied with a pressure of up to 5 atm is driven by driving the pump 20 in the main cleaning process. It is configured so that it can be supplied to the nozzle 14.

The nozzle 14 has a function of spraying the cleaning liquid in a curtain shape having a preset angle and spraying it on the peripheral wall 1a of the tank 1. The injection direction of the cleaning liquid in the horizontal plane by the nozzle 14 is set so as to be inclined in only one direction from the axis of the cleaning liquid spray pipe 12.

Therefore, due to the reaction of the pressurized cleaning liquid sprayed from the nozzle 14 to the cleaning liquid spray pipe 12,
A force for rotating the tee 5b in the direction opposite to the inclination direction of the nozzle 14 acts, and this force causes the cleaning liquid distribution pipe 5 integrally attached to the cleaning water distribution pipe 5 suspended by the cleaning water supply hose 8. It is possible to rotate 12 around the swivel joint 7 in the horizontal direction.

The cleaning liquid supply hose 16 is connected to the cleaning liquid spraying pipe 12, is guided to the outside of the tank 1 through the manhole 4, and is connected to the container 18 containing the cleaning liquid via the heater 17 and the pump 20. The heater 17 has a function of heating the supplied cleaning liquid. Pump 20 is a container
The cleaning liquid stored in 18 is supplied to the cleaning liquid spraying pipe 12, and the cleaning liquid accumulated in the groove 1d formed in the bottom plate 1c of the tank 1 is sucked in through the hose 19 and is again washed by the cleaning liquid spraying pipe 12.
Is to be supplied to.

In the cleaning apparatus constructed as described above, the integrated cleaning water spray pipe 5 and cleaning liquid spray pipe 12 are inserted into the tank 1 from the manhole 4 and the respective spray pipes 5, 12 are inserted.
The cleaning preparation is completed by connecting the cleaning water supply hose 8 and the cleaning liquid supply hose 16 to.

The cleaning method of the present invention will be described using the tank cleaning apparatus configured as described above. [Pre-cleaning process] First, in the pre-cleaning process of the tank 1, the cleaning water supply hose 8 is connected to the pump 11. In addition, the pump
After connecting the water supply pipe (not shown) to the pumping part of 11, pump 11
When water is driven, water is absorbed from the water supply pipe to become high-pressure water via the pump 11, and the high-pressure water passes through the wash water supply hose 8 and is sprayed from the nozzle 6 of the wash water distribution pipe 5 in a shower shape.

When the cleaning water supply hose 8 is wound by driving the drum 10 at the same time as the injection of the cleaning water, the integrated cleaning water spray pipe 5 and the cleaning liquid spray pipe 12 rotate while rising. In this ascending process, the cleaning water is sprayed over the entire surface of the peripheral wall 1a of the tank 1, and the pre-cleaning work is performed. At this time, the previously stored chemicals are completely washed out. After the cleaning water spray pipe 5 and the cleaning liquid spray pipe 12 reach the ceiling 1b of the tank 1, the pump 11 is stopped to complete the pre-cleaning process.

[Main Cleaning Step] Next, in the main cleaning step of the tank 1, first, when the heater 17 and the pump 20 are driven, the cleaning liquid is supplied from the container 18 to the pump 20 through the liquid supply pipe 16 a and the pump 20. It becomes a pressure washing liquid. The pressurized cleaning liquid is supplied to the heater 17 through the cleaning liquid supply hose 16 and heated to at least 20 ° C to 90 ° C. The cleaning solution thus warmed passes through the cleaning solution supply hose 16 and the cleaning solution spray pipe.
It sprays from 12 nozzles 14 like a shower.

When the drum 10 is driven and the washing water supply hose 8 is fed simultaneously with the jetting of the washing liquid, the washing water spray pipe 5 and the washing liquid spray pipe 12 which are integrated are rotated while descending.
In this descending process, the cleaning liquid is sprayed over the entire surface of the peripheral wall 1a of the tank 1, and the main cleaning work is performed. At this time, the black film generated on the inner wall of the tank is completely peeled off. After the cleaning water spray pipe 5 and the cleaning liquid spray pipe 12 reach the bottom plate 1c of the tank 1, the pump 20 and the heater 17 are stopped to complete the main cleaning process.

[Post-Washing Step] Finally, in the post-washing step of the tank 1, first, when the pump 11 is driven, water is absorbed from the water supply pipe connected to the pumping section of the pump 11, and high-pressure water is passed through the pump 11. Change to. The high-pressure water passes through the wash water supply hose 8 and is sprayed in a shower shape from the nozzle 6 of the wash water spray pipe 5.

When the cleaning water supply hose 8 is wound by driving the drum 10 at the same time as the injection of the cleaning water, the integrated cleaning water spray pipe 5 and the cleaning liquid spray pipe 12 rotate while rising. In this ascending process, the cleaning water is sprayed over the entire surface of the peripheral wall 1a of the tank 1, and the post-cleaning work is performed.

At this time, the acidic cleaning liquid used in the main cleaning step is washed out and does not affect the chemicals to be stored next. After the cleaning water spray pipe 5 and the cleaning liquid spray pipe 12 reach the ceiling 1b of the tank 1, the pump 11 is stopped to complete the post-cleaning process.

In FIG. 2, the pipe 21 is 3B (inner diameter 80 m).
m) to 6B (inner diameter 150 mm) and a length of about 8 m are connected by a flange 22 to a pipe 21 having a total length of about 60 m and fixed to a fixed leg 30 so that the pipe 21 is horizontally fixed. To be done. A packing 23 is inserted between the flanges 22 so that liquid does not leak from the joint.

Elbows 24 are joined to both ends of the pipe 21 in an upward direction to form a U-shaped pipe A. A blind flange 25 is joined to the opening surface of the elbow 24 via a packing 23, and a pipe joint 26 for supplying a cleaning liquid is attached to the blind flange 25.

A cleaning liquid circulation hose 27 for circulating and supplying the cleaning liquid to the inside of the pipe 21 is attached to the pipe joint 26, and a circulation pump 28 for circulating the cleaning liquid and a cleaning liquid are further provided in the cleaning liquid circulation hose 27. A heater 29 for heating is connected in series.

The cleaning method of the present invention will be described using the pipe cleaning apparatus configured as described above. [Pre-cleaning step] First, in the pre-cleaning step of the pipe 21, after connecting the water supply pipe to the pumping part of the pump 28 (not shown), when the pump 28 is driven, water is absorbed from the water supply pipe and the water passes through the hose 27a. It flows into the U-shaped pipe A through the pipe joint 26. When the water surface reaches the upper end surface of the elbow 24, the inner wall surface of the pipe 21 is uniformly filled with water due to the property of the U-shaped pipe structure.

Next, after stopping the pump 28,
Remove the water pipe connected to the pumping section of 28 and
b is connected to the pumping section of the pump 28 without the heater 29. Then, when the pump 28 is driven, the water filled in the U-shaped pipe A circulates through the circulation hose 27. At this time, the inner volume of the elbow 24 has a sufficient inner volume to fill the insides of the empty circulation hose 27 and the pump 28, and it is possible to uniformly fill the inner wall surface of the pipe 21 with water.

By the circulation of the water, the cleaning water flows over the entire inner wall surface of the pipe 21 to perform the pre-cleaning. At this time, the previously stored chemicals are completely washed out. When the cleaning is completed, the pump 28 is stopped, and then the hose 27a is removed from the pipe joint 26 and the hose 27a is connected to a waste liquid container (not shown). When the pump 28 is driven, the cleaning water filled in the pipe 21 is sucked and collected in the waste liquid container. When the collection is completed, the pump 28 is stopped. With the above, the pre-cleaning step is completed.

[Main Cleaning Step] Next, in the main cleaning step of the pipe 21, the hose 27a removed in the pre-cleaning step is connected to the pipe joint 26.
Although not shown, a liquid supply pipe for supplying the cleaning liquid from the container containing the cleaning liquid to the pump 28 is connected to the pumping section of the pump 28, though not shown. When the pump 28 is driven, the cleaning liquid is sucked from the liquid supply pipe, and the cleaning liquid passes through the hose 27a and the pipe joint 26 to U.
It flows into the letter tube A. When the liquid surface reaches the upper end surface of the elbow 24, the inner wall surface of the pipe 21 is uniformly filled with the cleaning liquid due to the property of the U-shaped pipe structure.

Next, after stopping the pump 28,
Remove the liquid supply pipe connected to the pumping part of 28, and connect the circulation hose 27
Connect b to the pumping section of pump 28 via heater 29.
Then, when the heater 29 and the pump 28 are driven, the cleaning liquid filled in the U-shaped pipe A circulates through the circulation hose 27 and is heated by the heater 29 to at least 20 ° C to 90 ° C.

By the circulation of the heated cleaning liquid, the cleaning liquid flows over the entire inner wall surface of the pipe 21, and the main cleaning is performed. At this time, the black film generated on the inner wall surface is peeled off. When the cleaning is completed, the heater 29 and the pump 28 are stopped, and then the hose 27a is removed from the pipe joint 26 and the hose 27a is connected to a detergent container (not shown). When the pump 28 is driven, the cleaning liquid filled in the pipe 21 is sucked and collected in the detergent container. When the collection is completed, the pump 28 is stopped. This completes the main cleaning step.

[Post-Washing Step] Finally, in the post-washing step of the pipe 21, the hose 27 a removed in the main washing step is connected to the pipe joint 26, and the liquid supply pipe connected to the pumping section of the pump 28 is removed to remove the water supply pipe. Connect. After that, when the pump 28 is driven, water is absorbed from the water supply pipe and flows into the U-shaped pipe.

Pump when the water surface reaches the upper end surface of the elbow 24
Stop 28. Next, the water supply pipe connected to the pumping section of the pump 28 is removed, and the circulation hose 27b is connected to the pumping section of the pump 28 without the heater 29. Then, when the pump 28 is driven, the water filled in the U-shaped pipe A circulates through the circulation hose 27.

By the circulation of the water, the washing water flows over the entire inner wall surface of the pipe 21, and the post-washing is performed. At this time, the acidic cleaning liquid used in the main cleaning step is washed out and does not affect the chemicals to be stored next. When the washing is completed, the hose 27a is removed from the pipe joint 26 and the hose 27a is connected to a waste liquid container (not shown). pump
When 28 is driven, the washing water filled in the pipe 21 is sucked and collected in the waste liquid container, and the pump 28 is stopped when the collection is completed. The post-cleaning process is completed as described above.

In FIG. 3, the cleaning method of the present invention will be described for a small accessory such as a valve using a container with a heater filled with a cleaning liquid. [Pre-cleaning step] First, in the pre-cleaning step of the small article B, the small article B is put into a container C provided with a heater to fill water.
At this time, the small article B is below the water surface and is completely immersed in the water. At this time, the previously stored chemicals are completely washed out. When the pre-cleaning is completed, the outlet is opened and the water in the container C is collected in the waste liquid container.

[Main Cleaning Step] Next, in the main cleaning step of the small object B, the outlet is closed and the container C is filled with the cleaning liquid. At this time,
The small object B is below the liquid surface and is completely immersed in the cleaning liquid. Next, the heater provided in the container C is driven to perform cleaning at a temperature of the cleaning liquid of at least 20 ° C to 90 ° C. At this time, the black film generated on the inner wall surface is peeled off. When the cleaning is completed, stop the heater and open the outlet to collect the cleaning liquid in the detergent container.

[Post-Washing Step] Next, in the post-washing step of the small item B, the drain port is closed and the container C is filled with water. At this time, the small article B is below the water surface and is completely immersed in the water. At this time, the acidic cleaning liquid used in the main cleaning step is washed out and does not affect the chemicals to be stored next. When the cleaning is completed, the outlet is opened and the water in the container C is collected in the waste liquid container.

[0053]

EFFECTS OF THE INVENTION According to the above cleaning method, in a storage facility in which a tank, a pipe and the like are made of a stainless material, the tank is used especially when caustic soda (NaOH) or caustic potash (KOH) is stored as a chemical. It is possible to completely clean the black film generated on the inner wall surface of the pipe in a short time.

By using water at room temperature as the cleaning liquid in the pre-cleaning process and the post-cleaning process, it is possible to reduce the cleaning cost without using an expensive cleaning liquid. Further, it does not affect the components of the drug to be stored next.

In addition, since the detergent used as the washing liquid in the main washing step is generally widely marketed, there is no need to mix it in particular, it is easy to obtain, and the washing cost can be reduced. Niru.

Further, by washing only with the detergent, it is possible to perform uniform washing without innumerable minute scratches on the surface to be washed by the wire brush as in the conventional case. Moreover, the inner wall surface of the pipe and the inner wall surface of the accessory such as the valve, which cannot be cleaned, can be thoroughly cleaned so that the inner wall surface can be reused without being discarded.

Further, by using the cleaning means shown in the above embodiment, it is possible for an operator to carry out the cleaning without entering the inside of the tank, and it is not necessary to perform the cleaning work in a bad working environment. .

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a cleaning device for cleaning an inner wall surface of a tank.

FIG. 2 is a diagram illustrating a configuration of a cleaning device for cleaning an inner wall surface of a pipe.

FIG. 3 is a conceptual diagram for cleaning the inner wall surface of a small accessory such as a valve.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tank 1a ... Peripheral wall 1b ... Ceiling 1d ... Groove 2 ... Ladder 3 ... Hole 4 ... Manhole 5 ... Wash water spray pipe 5a ... Union joint 6 ... Nozzle 7 ... Swivel joint 8 ... Wash water supply hose 8a ... Protective wire 9a, 9b ... Guide roller 10 ... Drum 10a ... Motor 11 ... Pump 12 ... Cleaning liquid spraying pipe 13 ... Fixing member 14 ... Nozzle 15 ... Swivel joint 16 ... Cleaning liquid supply hose 16a ... Liquid supply pipe 17 ... Heater 18 ... Container 19 ... Hose 20 ... Pump 21 ... Piping 22 ... Flange 23 ... Packing 24 ... Elbow 25 ... Blind flange 26 ... Pipe joint 27, 27a, 27b ... Cleaning liquid circulation hose 28 ... Circulation pump 29 ... Heater 30 ... Fixed leg A ... U pipe B ... Small article C …container

Claims (2)

[Claims] 1. A cleaning method for cleaning an inner wall surface of a tank for storing caustic soda or potassium hydroxide, wherein a pre-cleaning step of cleaning the inner wall surface of the tank by making water into a high pressure state and spraying it in a shower shape from a nozzle member, At least 1% to 3
A cleaning liquid containing 0% nitric acid and at least 0.1% to 10% hydrofluoric acid, the remaining components consisting of water, and having a temperature kept in the range of at least 20 ° C to 90 ° C under pressure. Including a main cleaning step of spraying in a shower shape from the nozzle member to clean the inner wall surface of the tank, and a post-cleaning step of spraying water from the nozzle member in a shower shape to clean the inner wall surface of the tank. A cleaning method characterized by: 2. A cleaning method for cleaning an inner wall surface of a pipe through which caustic soda or caustic potash is circulated, wherein a pre-cleaning step of circulating water in the pipe to clean the inner wall surface of the pipe,
At least 1% to 30% nitric acid and at least 0.1
% To 10% hydrofluoric acid, the rest of which consists of water, and a cleaning solution whose temperature is kept at least in the range of 20 ° C. to 90 ° C. is circulated in the cleaning solution, and the cleaning solution is circulated in the piping. And a post-washing step of washing water on the inner wall surface of the pipe by circulating water in the pipe.