KR20060129670A - Method of clearance of scale using chlorite - Google Patents

Abstract

A method for removing scale by using chlorine dioxide is provided to remove the scale completely by contacting chlorine dioxide, ammonium ion, and hydroxyl ion with a probe during a short time. The scale of a silicon tube is removed by the first cleansing process. The commercially received chlorine dioxide of 8 % is diluted with water so that the first cleansing solution is produced. The browned silicon tube having the scale is processed by the first cleansing solution during 15 minutes so that the scale is removed through the first cleansing. The firstly cleaned silicon tube is contacted with water. Thereafter the color of the firstly cleaned silicon tube is changed into brown after 48 hours.

Description

Method of Clearance of Scale Using Chlorite

Figure 1a shows a simplified representation of the surface of a sample on which scale has been produced prior to treatment in accordance with the present invention.

Figure 1b is a simplified illustration of the surface of the sample after the first cleaning in accordance with the present invention, the scale is partially removed and the residual coating is formed.

Figure 1c briefly shows the surface of the sample after the second cleaning in accordance with the present invention the scale is completely removed.

2A shows an inner surface of a silicon tube that has been scaled before being processed in accordance with one aspect of the present invention.

Figure 2b shows a state in which the scale is removed from the inner surface after the first cleaning of the silicon tube according to the present invention.

Figure 2c shows the phenomenon of brown discoloration again as a result of contacting the silicon tube completed the first cleaning with water.

3A illustrates an inner surface of a silicon tube that has been scaled before being processed in accordance with another aspect of the present invention.

Figure 3b shows a state in which the scale is removed on the inner surface after the first cleaning of the silicon tube according to the present invention.

Figure 3c shows a state in which the scale is removed from the inner surface after the second cleaning of the silicon tube according to the present invention.

FIG. 3D illustrates a phenomenon in which the silicon tubes having completed the first and second cleanings are not discolored as a result of contacting with water.

4A shows an inner surface of a silicon tube that has been scaled before being processed in accordance with another aspect of the present invention.

Figure 4b shows the scale removed on the inner surface after the first and second cleaning of the silicon tube according to the present invention.

Figure 4c shows the phenomenon of discoloration as a result of contacting the silicon tube of the first and second cleaning is completed with water.

Figure 5a shows the results of analyzing the state of the new unused silicon tube using EDAX.

Figure 5b shows the results of the analysis of the state of the silicon tube scale is generated using EDAX.

Figure 5c shows the results of the analysis using EDAX after the first and second cleaning the scale-generated silicone tube according to the present invention.

According to the present invention, the scale-generated sample is first washed by contacting with a primary washing solution containing chlorine dioxide, and the first washed sample is second washed by contacting with a secondary washing solution containing ammonium ions and hydroxide ions. It relates to a method for removing scale from the sample.

Industrial water-soluble systems, such as boiler systems, cooling tower systems, heat exchange systems, desalination systems, papermaking, fire fighting water, and reactors, tend to accumulate deposits on the inner surfaces in contact with the circulating water. As the deposit is oxidized by dissolved oxygen contained in water, it accumulates and adsorbs on the metal surface to form scale. In addition, scale may be additionally created by chemical reactions between the metal surface of the piping and other components of the system and water.

Scale can affect heat transfer efficiency and can clog piping and limit water flow. If the scale is not removed, oxidation by water may be promoted, causing oxidation and corrosion to the inside of the metal. When this happens, the system is usually leaked and must be removed from the line for repair or replacement. Accordingly, there have been several attempts in the art to remove scale.

U. S. Patent No. 5,183, 673 discloses a method for removing certain cations such as iron using chelating agents. According to this, chelating agents work essentially by fixing metals to soluble free ring structures, especially chelating agents such as ethylene diamine tetraacetyl acid (EDTA), which can be used to remove iron more effectively when used with dispersants. . Although a clean system piping surface can be obtained by this method, the metal can continue to dissolve even after the scale has been completely removed since the chelating agent does not spontaneously terminate the action of removing the oxidized metal. This can, in severe cases, lead to perforation of the metal which causes damage to the tube or leakage of the joint by the chelating agent.

Another method is the use of high concentrations of aminoalkylphosphonates, which are expensive and have the disadvantage that the removed oxide foil remains on the metal surface. Carboxyalkyl, aminoalkyl hydroarylsulfonic acids can also be used, but several weeks of time are required for these detergents to remove sufficient scale. In addition, organic compounds such as hydroquinone and quinone have been used as iron oxide dispersants, but their use has been limited due to their high cost and alkaline hydrogen ion concentration range. In addition, acidic detergents such as hydrochloric acid and sulfamic acid have been used, but there is a problem that handling is dangerous and difficult to treat due to low pH value.

In particular, the inside of the water purifier is composed of silicon tubes connecting the respective storage tanks and the inside, and even though the scale generated inside these products is required to be removed, there is currently no other way than to separate and replace them. It is required.

On the other hand, chlorine dioxide (ClO ₂ ) is a water treatment agent for sterilization, the use of the chlorine (Cl ₂ ) has been limited to use as it was found to produce trihalomethanes (THM's), which is a widely used chlorine (Cl ₂ ) As a substitute material that has been used since then, it has an oxidation capacity of 2.5 times that of chlorine and is widely used for sterilizing water due to its advantages of not generating harmful substances such as trihalomethane, which is harmful to the human body. have.

To date, research and patents related to chlorine dioxide have focused on the method of producing chlorine dioxide and sterilizing water using the chlorine dioxide thus produced. In Korea, a method of generating chlorine dioxide using electrolysis (Korea Patent 10-0445756), a method of generating chlorine dioxide from sodium chlorite (NaClO ₂ ) (Korea Patent Publication No. 2004-0039276), activation of stabilized chlorine dioxide Most of the methods related to the production of chlorine dioxide, such as methods and apparatus (Korean Patent 10-0472566).

Overseas, the patent also relates to a method of generating chlorine dioxide at a constant concentration in water by reacting metal chlorite with acid (US 6676850), chloric acid and alkali metal chlorate. Method of generating chlorine dioxide by electrolysis (US 5296108), a method of safely producing chlorine dioxide by carrying powder components which dissolve in water to generate chlorine dioxide in tablet form having pores (US 6432322) It is concentrated in the manufacturing method, and its use is also concentrated in sterilization for water sterilization, odor removal, and long-term preservation of fruits and vegetables.

Thus, the inventors of the present invention treated the scaled sample with an aqueous solution of chlorine dioxide, and most of the scale was removed. As a result, the scaled sample was once again treated with an aqueous solution containing ammonium ion and hydroxide ion. It was confirmed that browning does not occur even when it is removed and brought into contact with water, and the present invention has been completed.

Therefore, in one aspect, the present invention, (a) the first step of contacting the scale-produced sample with the primary rinse containing chlorine dioxide and (b) the first rinsed sample is ammonium ion and hydroxide ion Provided is a method for removing scale from a sample comprising contacting with a secondary cleaning solution containing the secondary cleaning.

The present invention comprises the steps of (a) washing the sample produced with the scale with a primary washing liquid containing chlorine dioxide, and (b) washing the first washed sample with ammonium ions and hydroxide ions. It relates to a method for removing the scale from the sample, including the step of second cleaning in contact with, and will be described in detail below.

"Samples" subject to the treatment according to the invention are not only industrial water-soluble systems such as boiler systems, cooling tower systems, heat exchange systems, desalination systems, papermaking, heating / cooling systems, fire water, reactors, etc., but also sinks, sinks and sewage treatment plants. These pipes and any objects that are easily formed on scale, such as refrigerators, air conditioners, air purifiers, water purifiers, humidifiers and bidets, which are easily formed in scale, especially tubes that act as waterways.

According to the present invention, since the scale can be removed not only by chlorine dioxide but also a sterilization effect can be achieved, the sample is preferably a sink, a sink and a sewage treatment pipe and pipes thereof, and a refrigerator, an air conditioner, an air purifier, a water purifier, a humidifier and a bidet. Do. In addition, the sample of the present invention may be a substrate requiring cleaning to remove the metal oxide during the semiconductor manufacturing process. On the other hand, the material of the sample is not particularly limited and may be organic, inorganic, metal or non-metal.

Step (a) of the method according to the invention is a step of first cleaning the scaled sample in contact with the primary cleaning liquid containing chlorine dioxide. In the first washing step, chlorine dioxide acts as a powerful oxidant, as shown in Scheme 1 below, where the redox level is about E0 = + 0.954 V at 25 ° C.

^{_{ClO 2 + e - → ClO 2}} -

Therefore, chlorine dioxide dissolves the scale of the sample through the bleaching action of oxidizing the scale generated in the sample.

The "primary cleaning liquid" used in the step (a) is a solution in which chlorine dioxide is dissolved, and the primary cleaning liquid is, for example, a chlorine dioxide solution made by dissolving chlorine dioxide gas in water; Chlorine dioxide solutions prepared by a method of generating chlorine dioxide in water using sodium chlorate, sodium chlorite or sodium hypochlorite or a combination thereof and an acid; Prepared by a method of generating chlorine dioxide in water using a mechanical or electrical device from a chlorine dioxide solution made by dissolving chlorine dioxide in solid state in water and sodium chloride, sodium chlorate, sodium chlorite or sodium hypochlorite or a combination thereof Selected from the group consisting of chlorine dioxide solution.

Although the concentration of chlorine dioxide in the primary cleaning liquid depends on the contact time with the sample, when the concentration of chlorine dioxide is 30 ppm or less, even if the contact time with the scale is extended, the concentration of chlorine dioxide is low to achieve the desired scale removal effect. If the concentration of chlorine dioxide is more than 25,000ppm, the contact time with the scale is reduced, but there may be a problem in safety. Therefore, in the present invention, the concentration of chlorine dioxide in the primary cleaning solution is preferably 30 to 25,000 ppm, preferably 50 to 500 ppm. Moreover, 1 minute-60 minutes are suitable for the contact time of a primary wash liquid and a sample, and 3 minutes-30 minutes are preferable.

Table 1 shows an example of the contact time between the concentration of chlorine dioxide and the scale in the primary washing solution preferred in the present invention.

 Chlorine Dioxide Concentration and Contact Time with Scale Concentration of chlorine dioxide Contact time with scale 50 ppm or less 30 minutes 50 to 100 ppm 20 minutes 100 to 200 ppm 15 minutes 200 to 300 ppm 10 minutes 300 ppm or more 3 minutes

On the other hand, when a small amount of scale is formed in the sample, the scale can be completely removed through primary washing with chlorine dioxide. However, when a large amount of scale is formed, as shown in FIG. 1B even after the first washing. The scale remains in the form of residual coating. This coating is inconspicuous, but when the specimens in which the primary cleaning is completed are brought into contact with water, the ions in the water become brown or gray in combination with the residual coating (browning phenomenon) and can be easily distinguished by the naked eye. Therefore, when the specimen is brought into contact with water after washing, browning may occur, indicating that the scale has not been completely removed.

Residual coatings of such a scale that have not been removed can be removed according to step (b) of the method according to the invention. Step (b) of the method according to the invention is a step of secondary cleaning of the first washed sample in contact with a secondary cleaning liquid containing ammonium ions and hydroxide ions. In the secondary cleaning step, ammonium ions and hydroxide ions as well as ammonia, which can be produced as a by-product of these, can substantially completely dissolve the scale remaining on the surface of the sample through etching.

"Secondary cleaning liquid" used in step (b) is a solution in which ammonium ions and hydroxide ions are dissolved, and can generally be prepared by dissolving an ammonium salt and a basic substance in water. Of course, the secondary cleaning solution may be obtained by preparing a solution in which ammonium ions are dissolved and a solution in which hydroxide ions are dissolved, respectively, or by mixing or dissolving both ammonium salts and basic substances in water. Examples of the ammonium salt include, but are not limited to, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium sulfate, and the like. Examples of the basic material include, but are not limited to, sodium hydroxide, potassium hydroxide, calcium hydroxide, and the like. In particular, the secondary cleaning solution is preferably prepared by dissolving ammonia or ammonium hydroxide in water because it can form both hydroxide and ammonium ions without dissolving a single substance in water to form other additional ions. .

The concentration of ammonium ion in the secondary cleaning solution is suitably 0.01% to 30.0%, preferably 0.1% to 2.0%. In addition, the concentration of hydroxide ions in the secondary cleaning liquid is preferably 0.01% to 30.0%, preferably 0.1% to 2.0%. When the ammonia solution is used as the secondary cleaning liquid, the concentration of the ammonia solution is preferably 0.01% to 30.0%, and preferably 0.1% to 2.0%. Moreover, 1 minute-60 minutes are suitable for the contact time of a secondary washing | cleaning liquid and a sample, and 5 minutes-30 minutes are preferable.

Table 2 shows an example of the concentration of ammonium and hydroxide ions and the contact time of the scale in the secondary cleaning liquid suitable for use in the present invention.

Contact time between the concentration of ammonium ion and hydroxide ion and scale Concentrations of Ammonium and Hydroxide Contact time 0.6% ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) + 0.6% sodium hydroxide (NaOH) 5 minutes 0.4% Ammonium Chloride (NH ₄ Cl) + 0.4% Sodium Hydroxide (NaOH) 10 minutes 0.4% ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) + 0.3% calcium hydroxide (Ca (OH) ₂ ) 10 minutes 0.4% ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) + 0.2% magnesium hydroxide (Mg (OH) ₂ ) 15 minutes 0.4% ammonium chloride (NH ₄ Cl) + 0.4% calcium hydroxide (Ca (OH) ₂ ) 10 minutes 5% aqueous ammonium hydroxide solution (NH ₄ OH) 10 minutes

In step (b) according to the present invention, not only the scale of the residual coating is removed, but also the hydroxide ions in the secondary cleaning solution may be stabilized in combination with the metal ions activated by chlorine dioxide during the first cleaning to prevent discoloration. In addition, since the first washing is performed in acid (pH 1.5 to 4.5), it is necessary to neutralize it. Since the second washing liquid contains ammonium ion and hydroxide ion and shows basicity (pH 9.0 to 14.0), no separate neutralization process is required. The neutralization can proceed simultaneously with the secondary washing.

Hereinafter, the examples are only for illustrating the present invention in more detail, and the scope of the present invention is not limited by these examples in accordance with the gist of the present invention, those skilled in the art. Will be self-evident.

<Example 1>

Descaling of the Silicone Tube by Primary Cleaning

First, the primary cleaning solution shown in Table 3 was prepared by diluting a commercially obtained 8% chlorine dioxide solution (trade name: Duozone, manufacturer: Shinwang Chemical) with water so that the final concentration was 200 ppm.

The scale was removed and the scale was removed through a primary wash in which a brownish silicone tube (FIG. 2A) was treated with the primary wash for 15 minutes (FIG. 2B). Then, the first cleaned silicon tube was brought into contact with water and then changed color again to brown after 48 hours (FIG. 2C). This phenomenon occurred because the scale which was not removed through the primary cleaning was reduced to brown again by contact with water.

Composition and contact time of cleaning solution Cleaning solution Concentration and composition Contact time  Primary cleaning liquid 200 ppm chlorine dioxide aqueous solution 15 mins  Secondary cleaning solution - -

<Example 2>

Descaling of Silicone Tubes by Primary and Secondary Cleaning

The first cleaning solution shown in Table 4 was prepared by diluting a commercially available 8% chlorine dioxide solution (trade name: Duozone, manufacturer: Shinwang Chemical) to a final concentration of 200 ppm. The secondary cleaning solution was prepared by dissolving 0.4 g of ammonium sulfate (three electrochemical, reagent grade) and 0.2 g of sodium hydroxide (three electrochemical, reagent grade) after filling a beaker with 100 ml of water.

The scale produced a brownish silicon tube (FIG. 3A) treated with the primary cleaning solution for 15 minutes for first cleaning (FIG. 3B), and the first cleaned silicon tube was treated with the secondary cleaning solution for 10 minutes. The scale was removed through a second wash (FIG. 3C). As a result of contacting the silicon tube with water after the first and second cleaning as described above, it was confirmed that the phenomenon of brown discoloration did not occur (FIG. 3D). This is because the scale has been substantially completely removed through two washes.

Cleaning solution composition and contact time Cleaning solution Concentration and composition Contact time  Primary cleaning liquid 200 ppm chlorine dioxide aqueous solution 15 mins  Secondary cleaning solution 0.4% ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) + 0.2% sodium hydroxide (NaOH) 10 minutes

<Example 3>

Descaling of Silicone Tubes by Primary and Secondary Cleaning

The first cleaning solution shown in Table 5 was prepared by diluting a commercially available 8% chlorine dioxide solution (trade name: Duozone, manufacturer: Shinwang Chemical) to a final concentration of 300 ppm. The secondary cleaning solution was prepared by dissolving 0.4 g of ammonium chloride (three electrochemical, reagent grade) and 0.2 g of potassium hydroxide (three electrochemical, reagent grade) after filling a beaker with 100 ml of water.

The scale produced a brownish silicon tube (FIG. 3A) treated with the primary cleaning solution for 15 minutes for first cleaning (FIG. 3B), and the first cleaned silicon tube was treated with the secondary cleaning solution for 10 minutes. The scale was removed through a second wash (FIG. 3C). As a result of contacting the silicon tube subjected to the first and second cleaning with water as described above, it was confirmed that the phenomenon of brown discoloration did not occur (FIG. 3D). This is because the scale has been completely removed through two washes.

Cleaning solution composition and contact time Cleaning solution Concentration and composition Contact time  Primary cleaning liquid 300 ppm chlorine dioxide aqueous solution 10 minutes  Secondary cleaning solution 0.4% ammonium chloride (NH ₄ Cl) + 0.2% potassium hydroxide (KOH) 10 minutes

<Example 4>

Qualitative analysis of descaling results by primary and secondary washes

A black brown silicon surface scale was analyzed using EDAX (Energy Dispersive Spectrometer, model name: EDAX-9100 Multichannel-Analyzer, Philips), and the main component was silver oxide (Ag ₂ O).

Meanwhile, the primary cleaning solution shown in Table 6 was prepared by diluting a commercially available 8% chlorine dioxide solution (trade name: Duozone, manufacturer: Shinwang Chemical) to a final concentration of 300 ppm. The secondary cleaning solution was prepared by dissolving 0.4 g of ammonium sulfate (three electrochemical, reagent grade) and 0.4 g of potassium hydroxide (three electrochemical, reagent grade) after filling a beaker with 100 ml of water.

Cleaning solution composition and contact time Cleaning solution Concentration and composition Contact time  Primary cleaning liquid 300 ppm chlorine dioxide aqueous solution 10 minutes  Secondary cleaning solution 0.4% ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) + 0.4% sodium hydroxide (NaOH) 15 mins

In this case, EDAX was used to analyze the state of the new silicon tube surface and the state of the silicon tube surface in which the scale was generated, and the results are shown in FIGS. 5A and 5B. In addition, the scaled silicone tube was treated with the primary and secondary cleaning solutions shown in Table 6 and analyzed using EDAX, and the results were similar to those of the new silicone tube. That is, it was confirmed that the scale in the silicon tube is substantially completely removed through the first and second cleaning methods according to the present invention.

According to the method of the present invention, it is possible not only to completely remove the scale but also to sterilize by contacting the sample with chlorine dichloride, ammonium ion, hydroxide ion for a short time step without using the physical method of separating and dismantling the sample. .

Claims (10)

(a) subjecting the scaled sample to a first rinse containing chlorine dioxide and (b) contacting the first rinsed sample with a second rinse containing ammonium and hydroxide ions. Removing the scale from the sample including a second rinse. The method of claim 1, wherein the primary cleaning liquid is a chlorine dioxide solution made by dissolving chlorine dioxide gas in water; Chlorine dioxide solutions prepared by a method of generating chlorine dioxide in water using sodium chlorate, sodium chlorite or sodium hypochlorite or a combination thereof and an acid; Prepared by a method of generating chlorine dioxide in water using a mechanical or electrical device from a chlorine dioxide solution made by dissolving chlorine dioxide in solid state in water and sodium chloride, sodium chlorate, sodium chlorite or sodium hypochlorite or a combination thereof Chlorine dioxide solution selected from the group consisting of chlorine dioxide solution. The method according to claim 1 or 2, wherein the concentration of chlorine dioxide in the primary cleaning liquid is 30 to 25,000 ppm. The method of claim 1, wherein step (a) comprises contacting the scaled sample with a primary cleaning solution for 1 to 60 minutes. The method of claim 1, wherein the secondary cleaning liquid is prepared by dissolving ammonia or ammonium hydroxide in water. The method of claim 1 or 5, wherein the concentration of ammonium ions in the secondary cleaning liquid is 0.01% to 30.0%, characterized in that the concentration of the hydroxide ion is 0.01% to 30.0%. The method of claim 1, wherein step (b) comprises contacting the first washed sample with a second cleaning solution for 1 to 60 minutes. The method of claim 1, wherein the secondary cleaning liquid is characterized in that the pH of 9.0 to 14.0. The method of claim 1, wherein the sample is any one of a substrate, a sink, a sink and a sewage treatment port and pipes thereof, and a refrigerator, an air conditioner, an air purifier, a water purifier, a humidifier, and a bidet that require cleaning to remove metal oxides during a semiconductor manufacturing process. Method characterized in that. The method of claim 1 or 10, wherein the sample is made of an organic material, an inorganic material, a metal, or a nonmetal material.

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