JPH0762573A - Cleaning solution - Google Patents

Abstract

PURPOSE:To obtain a cleaning soln. capable of cleaning the inner wall surface of chemical storage tanks and delivery pipelines in a short time and with the erosion of a base material reduced by specifying a composition consisting of nitric acid, hydrofluoric acid and water. CONSTITUTION:The coating film formed on the inner wall surface of chemical storage tanks, chemical delivery pipelines or the valves attaching on them is cleaned off by a cleaning soln. The soln. contains 1-30% nitric acid, 0.1-10% hydrofluoric acid and the balance water. The soln. is sprayed on the surface to be cleaned or the surface is dipped in the soln. to efficiently clean off the film, and the surface is excellently cleaned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning liquid for cleaning a tank for storing chemicals and a pipe for delivering the 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 done manually by the operator after discharging the chemicals stored in the tank.It is recommended that the wall surface be rubbed with a wire brush to which general detergent is attached, and then rinsed with cleaning water. It is general.

[0003]

A chemical that forms a film on the inner surface of a tank or a chemical that has a viscosity when stored for a long period of time,
For example, caustic soda (NaOH) or caustic potash (KO)
When storing H) etc., it is common to use stainless steel materials for tanks and pipes, but when the chemicals are stored in stainless steel tanks for a long time, it seems that they are burned on the inner wall surfaces of tanks and pipes. It was difficult to remove the coating even if the wall surface was rubbed with a wire brush to which a general 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.

It is an object of the present invention to provide a drug storage facility,
When storing caustic soda, caustic potash, and viscous chemicals or chemicals that generate a film, etc. as chemicals,
When the above chemicals are stored in a stainless steel tank for a long period of time, a film or a film such as a black or brown striped pattern is formed on the inner wall surface of the tank and the pipe, and it is difficult to clean the tank and the pipe. An object of the present invention is to provide a cleaning liquid for cleaning the above-mentioned film and the like generated on the wall surface, the inner wall surface of the pipe, and the inner wall surface of an accessory such as a valve in a short time.

[0005]

In order to solve the above problems, the cleaning solution according to the present invention contains 1% to 30% nitric acid,
A cleaning liquid containing 0.1% to 10% of hydrofluoric acid and the remaining component consisting of water.

[0006]

According to the above cleaning solution, as shown in the experimental data in the examples described below, 1% to 30% nitric acid and 0.1%
To 10% of hydrofluoric acid, and the others are sprayed or dipped on the surface to be cleaned with a cleaning liquid having a composition of components to form a film or black or brown stripes on the surface to be cleaned. A film such as a pattern can be peeled off and efficiently washed.

[0007]

EXAMPLES An example of washing using the above washing solution will be described below using experimental data. Experiment 1-Experiment 10
Was performed on parts used in storage facilities such as stainless steel pipes where a film was formed on the inner wall surface by storing caustic potash.

[Experiment 1] Material to be cleaned: SUS304,
Parts to be cleaned: 80% cleaning liquid consisting of 30% nitric acid, 10% hydrofluoric acid and the balance water for the lap joint
As a result of spraying the surface to be cleaned for 25 minutes while maintaining the temperature at ℃, the finished state of cleaning was good.

[Experiment 2] Material to be cleaned: SUS304,
Parts to be cleaned: Lap joint, for nitric acid 13.5
%, Hydrofluoric acid 4.5%, and the balance water, the cleaning solution was sprayed on the surface to be cleaned for 40 minutes while maintaining the temperature at 85 ° C., and the finished state of cleaning was good.

[Experiment 3] Material to be cleaned: SUS304,
Parts to be cleaned: Pipes were sprayed on the surface to be cleaned for 40 minutes while maintaining a cleaning liquid consisting of 13.5% nitric acid, 4.5% hydrofluoric acid and the balance water at 85 ° C. As a result, the finished state of washing was good.

[Experiment 4] Material to be cleaned: SUS304,
Parts to be cleaned: Lap joint, for nitric acid 13.5
%, Hydrofluoric acid 4.5%, and the balance water, the cleaning liquid was sprayed on the surface to be cleaned for 60 minutes while being kept at a temperature of 60 ° C., and the finished state of cleaning was good.

[Experiment 5] Material to be cleaned: SUS304,
Parts to be cleaned: T-joint 4B (inner diameter 105.3 mm) x 3B (inner diameter 80.7 mm), nitric acid 10%, hydrofluoric acid 1%,
As a result of spraying the cleaning liquid composed of the rest with water at a temperature of 80 ° C. for 40 minutes on the surface to be cleaned, the finished state of cleaning was good.

[Experiment 6] Material to be cleaned: SUS304,
Parts to be cleaned: 8% cleaning liquid consisting of 10% nitric acid, 0.5% hydrofluoric acid and the balance water for the lap joint
As a result of spraying the surface to be cleaned for 30 minutes while maintaining the temperature of 0 ° C., the finished state of cleaning was good.

[Experiment 7] Material to be cleaned: SUS304,
Parts to be cleaned: 80% cleaning liquid consisting of 1% nitric acid, 0.1% hydrofluoric acid and the balance water for the lap joint
As a result of spraying the surface to be cleaned for 90 minutes while keeping the temperature at ℃, it took time, but the finished state of cleaning was good.

[Experiment 8] Material to be cleaned: SUS304,
Parts to be cleaned: Lap joint, 0.5% nitric acid,
As a result of spraying a cleaning liquid composed of hydrofluoric acid of 0.05% and the balance of water at a temperature of 80 ° C. for 90 minutes on the surface to be cleaned, the finished state of cleaning was poor and almost no cleaning was performed. .

[Experiment 9] Material to be cleaned: SUS304,
Parts to be cleaned: Lap joint, a cleaning liquid consisting of 10% nitric acid, 0% hydrofluoric acid and the balance water at 80 ° C
As a result of spraying the surface to be cleaned for 90 minutes in the state of being kept at the temperature, the cleaning state was poor and there was almost no change from the state before cleaning.

[Experiment 10] Material to be cleaned: SUS30
4, parts to be cleaned: lap joint, for nitric acid 10
%, Hydrofluoric acid 0.5%, and the rest water, sprayed on the surface to be cleaned for 73 minutes with the temperature kept at 80 ° C. It was

Experiments 11 to 13 were carried out on parts used for storage facilities such as iron pipes having rust on the inner wall surface.

[Experiment 11] Material to be cleaned: SS, parts to be cleaned: piping, nitric acid 13.5%, hydrofluoric acid 4.
As a result of immersing the surface to be cleaned for 30 minutes in a state where a cleaning liquid composed of 5% and the remaining water was kept at a temperature of 80 ° C., powder rust was generated although the finished state of cleaning was good.

[Experiment 12] A cleaning liquid composed of 13.5% nitric acid, 4.5% hydrofluoric acid, and the balance of water for a material to be cleaned: SS and parts to be cleaned: drum was heated to a temperature of 80 ° C. As a result of spraying on the surface to be cleaned for 30 minutes while maintaining the same, powder rust was generated although the finished state of cleaning was good.

[Experiment 13] Material to be cleaned: SS, Parts to be cleaned: Drum, Nitric acid 10%, Hydrofluoric acid 0.5
%, The cleaning liquid consisting of water was sprayed on the surface to be cleaned for 40 minutes with the temperature kept at 80 ° C., and the finished state of cleaning was good.

The grounds for specifying the concentration ranges of the respective constituents of the cleaning liquid based on the experimental data of Experiments 1 to 13 described above will be explained in detail. First, Experiments 1 to 4
Since the results of cleaning the stainless steel parts were good, it was possible to obtain a maximum concentration of 30% of nitric acid and a maximum concentration of 10% of hydrofluoric acid, which are components of the cleaning liquid, from Experiment 1. I can.

Although it is possible to clean with a cleaning liquid exceeding these upper limits of concentration, since nitric acid and hydrofluoric acid are strong acids, the base material of the part to be cleaned itself is melted and cleaned. Considering that there is a possibility that the service life of parts will be significantly reduced due to aging, and that raising the concentration of the cleaning liquid more than necessary increases the cost of the cleaning liquid, The above values are suitable as the values.

In addition, among Experiments 5 to 8, in Experiments 5 and 6, the results of cleaning and finishing the stainless steel parts were good. In Experiment 7, the cleaning liquid contained 1% nitric acid and 0.1% hydrofluoric acid, and in Experiment 8, the cleaning liquid contained 0.1% nitric acid.
5% and 0.05% hydrofluoric acid were contained respectively, and although the cleaning time was 90 minutes in Experiment 7, the finished state of cleaning was good, but in Experiment 8, almost no cleaning was performed.
From these results, it is possible to obtain the value adopted in Experiment 7, that is, the minimum value of 1% of the concentration of nitric acid and the minimum value of 0.1% of the concentration of hydrofluoric acid constituting the components of the cleaning liquid.

If cleaning is performed with a cleaning liquid having a concentration lower than the lower limit of these concentrations, the cleaning time will be long and the workability will be poor. As a result, it will take a long time to complete the cleaning of one component constituting the storage facility. There is a risk of waste such as having to wait for a time, or providing with a substitute for the part to be cleaned.

In Experiments 9 and 10, nitric acid 10 was used in Experiment 9.
%, The rest is water, and then the stainless steel parts are washed once, and then 0.5% hydrofluoric acid is added to the washing liquid.
% Was additionally washed in Experiment 10, and it was proved from the results of these washing finishes that at least hydrofluoric acid was indispensable in the washing liquid.

Further, the results of cleaning and finishing the iron material parts in Experiments 11, 12, and 13 proved that although the powder rust was generated, it could be cleaned in a short time. Therefore, the cleaning liquid of the present invention can also be used for cleaning iron parts,
It is not necessary to limit the cleaning to stainless steel parts.
Further, as shown in Experiments 1 to 13, it is desirable that the cleaning liquid of the present invention is cleaned while being heated to about 20 ° C to 90 ° C.

In this embodiment, SUS304 is used as the stainless material, but the invention is not limited to this and other kinds of stainless materials may be used. Furthermore, although the process was performed using the parts storing caustic potash as a chemical, the parts storing the caustic soda may be washed. Further, it can be used for various general cleaning such that a film is formed on the surface of a metal depending on the stored chemical, and the material to be cleaned and the type of the stored chemical need not be limited to this embodiment. .

[0029]

EFFECTS OF THE INVENTION If the above cleaning liquid is used for cleaning, in a storage facility where tanks and pipes are made of stainless steel material, especially when caustic soda and caustic potash are stored as chemicals, The coating generated on the wall surface can be peeled off and cleaned in a short time, and the maximum and minimum concentrations of each component that makes up the cleaning solution have been experimentally determined, so that the parts to be cleaned are cleaned more than necessary by the cleaning solution. It is possible to reduce the cost of the cleaning liquid and to perform the cleaning in the minimum necessary time without abrasion.

Claims (1)

[Claims] 1. A cleaning liquid for cleaning an inner wall surface of a tank for storing a chemical and a pipe for delivering the chemical or a valve attached to the pipe or the like, containing 1% to 30% nitric acid and 0.1% by weight of nitric acid.
% To 10% hydrofluoric acid, the remaining component consisting of water, a cleaning liquid.