KR20080041416A - Water treating method for open recirculating cooling system - Google Patents

Abstract

A water treatment method is provided to control both corrosion and scale excellently by maximally preventing a corrosion reaction generated on a surface of metal in a high hardness water quality condition and substantially suppressing scale of bivalent metal salts at the same time, and to use the phosphorous safely by lowering the concentration of phosphorous to less than 2 ppm. A water treatment method comprises the step of adding phosphorous(P), an acrylate copolymer, an azole-based compound, and a zinc ion into cooling water such that a concentration of the phosphorous(P) is controlled to a range of 0.1 to 2 ppm, concentration of the acrylate copolymer is controlled to a range of 0.1 to 15 ppm, a concentration of the azole-based compound is controlled to a range of 0.1 to 5 ppm, and concentration of the zinc ion is controlled to a range of 0.1 to 5 ppm relative to cooling water, and maintaining the concentrations of the respective components. The phosphorous(P) is derived from a compound selected from the group consisting of phosphoric acid, sodium phosphate(mono-basic, di-basic, tri-basic), potassium phosphate(mono-basic, di-basic, tri-basic), tetrapotassium pyrophosphate, sodium hexametaphosphate, 1-hydroxyethylidene-1,1-diphosphonic acid, hydroxyphosphono carboxylic acid, aminotrimethylene phosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, ethylenediamine tetramethylidene phosphonic acid, and mixtures thereof. The azole-based compound is selected from the group consisting of tolyltriazole, 20mercapto benzothiazole, benzotriazole, imidazole, and mixtures thereof. The zinc ion is provided from a zinc salt selected from the group consisting of zinc chloride, zinc sulfate, zinc nitrate, zinc oxide, and mixtures thereof.

Description

Water treatment method for open recirculating cooling system

The present invention relates to a water treatment method for suppressing corrosion and scale formation caused by cooling water in an open circulation cooling system, and more particularly, to a water treatment method suitable for high hardness water and low in phosphorus usage.

Major industrial facilities, such as petrochemical, oil refining, textiles, steel, electronics, and power plants, use cooling systems to cool the heat generated during the process. Most of the materials that make up the open-circulation cooling system are metals. On metal surfaces, various metal ions present in deposits or water due to corrosion are combined with anionic chemicals to generate scale. These scales form porous deposits on heat transfer surfaces such as heat exchangers, which hinder the smooth flow of water or, in severe cases, block the water pipes, and in some cases cause local corrosion due to differences in the concentration of dissolved oxygen in the water. .

Scale problems can be easily found in various industrial installations using water pipes, including heat exchangers for cooling and air conditioning installed in actual industrial sites, which not only impair the cooling circulation system seriously, but also cause serious problems in thermal efficiency, resulting in enormous economic losses. It is occurring.

In order to solve the above problems, the use of a coolant treatment agent is indispensable, and is currently widely used in all industrial fields. Conventionally, the water treatment agent containing high concentration of phosphate is widely used as the cooling water treatment agent. However, such water treatment agent maintains relatively high phosphorus content, which increases red tide and green algae by phosphorus when the cooling water is discharged from the system. When applied to a cooling system in water conditions, there is a problem of generating a scale composed of calcium phosphate.

Hard water contains calcium and magnesium cations and is less corrosive because a protective carbonate film is formed on the surface [Principles and Prevention of corrosion, second edition, denny A. Jones]. Therefore, since the risk of corrosion is not high in high hardness water, even if the phosphorus content is relatively low, there is no risk of corrosion.

Accordingly, it is an object of the present invention to provide a safe water treatment method that is excellent in corrosion and scale suppression effects and has a low phosphorus (P) concentration in a cooling system under high hardness water quality, and thus has low risk of problem occurrence.

In order to achieve the above object, the present invention provides (a) 0.1 to 2 ppm of phosphorus (P) with respect to cooling water, (b) 0.1 to 15 ppm of acrylate copolymer, and (c) 0.1 to 5 ppm of azole compound. And (d) adding each component to the cooling water so as to have a concentration of zinc ion of 0.1 to 5 ppm, and maintaining the concentration.

Hereinafter, the present invention will be described in detail.

Phosphorus (P) used in the water treatment method according to the present invention serves to inhibit the corrosion reaction and scale formation of the cooling water, to provide the phosphorus, that is, the compound from which the phosphorus is derived from phosphoric acid (phosphoric acid) ), Sodium phosphate (mono-basic, di-basic, tri-basic), potassium phosphate (mono-basic, di-basic, tri-basic), tetrapotassium pyrophosphate, sodium hexa metaphosphate, hydr Hydroxyethylidene diphosphonic acid, hydroxyl phosphono carboxylic acid, amino trimethylene phosphonic acid, phosphonobutane tricarboxylic acid, ethylenediamine tetra methylidine phosphonic acid or Preference is given to using mixtures thereof. The concentration of phosphorus in the cooling water is preferably 0.1 to 2 ppm, more preferably 0.5 to 1.5 ppm. If the concentration of phosphorus is less than 0.1 ppm, the effect of water treatment is lowered, and if it exceeds 2 ppm, the risk of calcium phosphate scale generation is increased.

The acrylate copolymer has a function of suppressing scale formation in water, and preferably has a structure represented by the following Chemical Formula 1.

In the above formula, R ₁ and R ₂ may be the same or different from each other, hydrogen, an alkyl group, a hydroxyl group or a phosphono group, X and Y are each independently an integer of 1 to 15. The concentration of the acrylate copolymer in the cooling water is preferably 0.1 to 15 ppm, more preferably 1.0 to 10 ppm. If the concentration of the acrylate copolymer is less than 0.1 ppm, the effect of water treatment is insignificant, and if it exceeds 15 ppm, it is not economical, and when the cooling water is discharged into the river, the COD of the effluent is increased.

The azole compound is particularly excellent in the ability to inhibit corrosion of copper and copper compounds, the azole compound is used tolyltriazole, mercapto benzothiazole, benzotriazole, imidazole or a mixture thereof It is desirable to. The concentration of the azole compound in the cooling water is preferably 0.1 to 5 ppm, more preferably 0.5 to 3 ppm. If the concentration of the azole compound is less than 0.1 ppm, the anticorrosive effect is insufficient. If the concentration of the azole compound exceeds 5 ppm, the economic efficiency is low.

The zinc ions function to inhibit the corrosion reaction of the metal, and in the present invention, it is preferable to use zinc chloride, zinc sulfate, zinc nitrate, zinc oxide, or a mixture thereof as the zinc salt for providing zinc ions. The concentration of the zinc ions in the cooling water is preferably 0.1 to 5 ppm, more preferably 0.5 to 3 ppm. If the concentration of zinc ions is less than 0.1 ppm, the effect is negligible. If the concentration of zinc ions exceeds 5 ppm, river and shellfish may be dangerous.

The water treatment method according to the present invention can be carried out by adding each component compound to the cooling water to a desired concentration. Applying the water treatment method of the present invention can effectively suppress the corrosion and scale formation that can occur in various industrial water pipes, such as cooling towers, heat exchangers, in particular, the high hardness of more than 800 ppm total hardness of calcium (Ca) and magnesium (Mg) It is also effective in water quality conditions.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. The following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by the following examples.

[Examples 1-3]

To the test water (A ~ C) having the characteristics shown in Table 1 below, each component was added to the content shown in Table 2 to prepare Examples 1 to 3.

In Table 1, pH was adjusted with 0.1N sodium hydroxide solution and 0.05N sulfuric acid aqueous solution, calcium hardness (Ca-H) was adjusted to calcium chloride, methyl orange-alkalinity (M-Alkalinity) was adjusted to sodium bicarbonate, Magnesium hardness (Mg-H) was adjusted to magnesium sulfate.

In Table 2, phosphorus (P) -1 is phosphonobutane tricarboxylic acid (PBTC, manufactured by BAYER) (indicates the concentration of phosphorus), and phosphorus (P) -2 is hydroxyethylidene diphosphonic acid (HEDP). , Manufactured by LONZA Co., Ltd. (indicated phosphorus concentration), zinc ions used zinc chloride (indicated zinc ion concentration), and azole-based compounds used benzotriazole (manufactured by PMC Co., Ltd.). Belkren 400 (manufactured by BIOLAB) was used. Each of these components was diluted to 10,000ppm and then re-diluted to an appropriate concentration.

[Comparative Example 1-5]

Comparative Examples 1 to 5 were prepared by adding each component to the same test water (A to C) used in the Examples so as to have the contents shown in Table 3 below.

In Table 3, phosphorus (P) -1 is phosphonobutane tricarboxylic acid (PBTC, manufactured by BAYER) (indicator of phosphorus concentration), and phosphorus (P) -2 is hydroxyethylidene diphosphonic acid (HEDP). , Manufactured by LONZA Co., Ltd. (indicated phosphorus concentration), zinc ions used zinc chloride (indicated zinc ion concentration), and azole-based compounds used benzotriazole (manufactured by PMC Co., Ltd.). Belkren 400 (manufactured by BIOLAB) was used. Each of these components was diluted to 10,000ppm and then re-diluted to an appropriate concentration.

Experimental Example 1 Corrosion Test

For the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 5, the carbon steel test specimen (0.218dm ² ) was rotated at a rotational speed of 170 rpm for 3 days at a temperature of 30 ° C. for each corrosion rate [mpy, mils per year (mils: 1 / 1000 inch)] and the results are shown in Table 4 below.

As shown in Table 4, in Examples 1 to 3 according to the present invention, it can be seen that the corrosion rate of the carbon steel is significantly reduced compared to Comparative Examples 1 to 5.

Experimental Example 2 Scale Performance Test

After the samples prepared in Examples 1-3 and Comparative Examples 1-5 were each sealed and held for 24 hours at 70 ° C., the sample solution was filtered with a 0.45 micro filter. After measuring the total hardness of the filtered sample, the scale inhibition rate (%) was calculated using Equation 1 below, and the results are shown in Table 5 below.

 [Equation 1]

% Inhibition = {Ce / Ct} * 100

In Equation 1, Ce is the total hardness of the sample after the test, Ct is the total hardness of the sample before the test.

As shown in Table 5, in Examples 1 to 3 treated with water according to the present invention, it can be seen that the scale inhibition rate is significantly improved compared to Comparative Examples 1 to 5.

As described above, the water treatment method according to the present invention prevents corrosion reactions that may occur on metal surfaces under high hardness water conditions, and at the same time, has an excellent ability to suppress the scale of divalent metal salts. Excellent control at the same time. In addition, since the concentration of phosphorus (P) is less than 2ppm, there is less risk of problems compared to the conventional can be used safely.

Claims (5)

(A) 0.1 to 2 ppm of phosphorus (P) relative to cooling water, (b) a concentration of 0.1 to 15 ppm of the acrylate copolymer, (c) 0.1 to 5 ppm of an azole compound, and (d) adding each component to the cooling water to maintain a concentration of 0.1 to 5 ppm of zinc ions and maintaining the concentration. The method of claim 1, wherein the phosphorus (P) is phosphoric acid, sodium phosphate (mono-basic, di-basic, tri-basic), potassium phosphate (mono-basic, di-basic, tri-basic), tetra potassium Pyrophosphate, sodium hexa metaphosphate, hydroxy ethylidene diphosphonic acid, hydroxy phosphono carboxylic acid, amino trimethylene phosphonic acid, phosphonobutane tricarboxylic acid, ethylenediamine tetra methylidine phosphonic acid and these A water treatment method derived from a compound selected from the group consisting of a mixture of The method of claim 1, wherein the acrylate copolymer has a structure represented by the following Chemical Formula 1. [Formula 1]

Wherein R ₁ and R ₂ may be the same as or different from each other, and are hydrogen, an alkyl group, a hydroxyl group, or a phosphono group, and X and Y are each independently an integer of 1 to 15. The method of claim 1, wherein the azole compound is selected from the group consisting of tolyltriazole, mercapto benzothiazole, benzotriazole, imidazole and mixtures thereof. The method of claim 1, wherein the zinc ions are provided from zinc salts selected from the group consisting of zinc chloride, zinc sulfate, zinc nitrate, zinc oxide, and mixtures thereof.