KR100289416B1 - Method for restraining scale formation and corrosion - Google Patents

Abstract

PURPOSE: Provided is a method for inhibiting scale formation and corrosion on the inner surface of pipe, which is suitable to a water with a hardness lower than 1,500ppm and a chlorine ion concentration higher than 1,500ppm, a turbidity lower than 20NTU, M-alkalinity lower than 500ppm, a silica ion concentration lower than 1,500ppm. CONSTITUTION: The method is characterized in that an anti-scale agent is injected in a water in such a concentration that the water contains Zn¬2+ 0.05-5.0ppm, orthophosphate ion 0.5-30.0ppm, polyphosphate ion 0.5-30ppm, organic phosphate ion 0.5-30.0ppm, azole compounds 0.1-10.0ppm, acrylate copolymer 0.1-30.0ppm represented by chemical formula I, wherein n and m is an integer of 5 to 1000, respectively; R1 and R6 represents hydrogen, alkyl or hydroxyl, respectively; R2 and R3 represents hydrogen, methyl, ethyl; R4 is C1-C5 alkyl; R5 represents C1-C10 alkyl or C8-C10 aralkyl; X and Y represent hydrogen, monovalent metal ion or N(R1)(R") respectively, wherein R1 and R" are hydrogen, C1-C5 alkyl or C1-C5 hydroxyl alkyl.

Description

Corrosion and Scale Inhibition Method of Wastewater Effluent and Cooling Water Metals

The present invention relates to a method for inhibiting corrosion and scale of wastewater effluent and cooling water-based metal, in particular, a water treatment agent composition containing zinc salt, orthophosphate, polyphosphate, phosphonate, azole compound and acrylate copolymer The present invention relates to a method for preventing corrosion and scale formation of a drain pipe and recycling wastewater discharged to cooling water.

In general, when an electrolyte material such as water comes into contact with a metal, the state of the electrolyte in contact with the metal surface becomes uneven to form a potential difference on the metal surface, and when a corrosion product, scale, or slime adheres to the metal surface, Since local corrosion occurs according to the amount, corrosion and scale occur in industrial facilities using various water pipes including cooling towers, heat exchangers, etc., which are installed in actual industrial sites, thus causing a great obstacle to the circulation system. In particular, since the open-circulating cooling water system operates at a high concentration, dissolved salts form a porous precipitate on the heat transfer surface of a heat exchanger, thereby causing local corrosion or generating scales such as calcium salts and magnesium salts.

In particular, the water quality of the wastewater discharged water has a high value such as chlorine ion and electrical conductivity, so that there are many factors that can affect the corrosion and scale differently from industrial water, so the management of industrial sites is important.

Previous water treatment composition used a chromium salt, phosphate and azole compound, acrylic polymer, maleic polymer and phosphate, lignin, tannin and the like.

In particular, zinc salts are known to inhibit cathodic reactions during corrosion reactions and are useful for preventing corrosion even in small amounts. US Pat. No. 4,149,969 discloses zinc salts, molybdates, manganese salts, nickel salts, azole compounds and phosphonates. Compositions of zinc salts, chromium salts, phosphates, acrylate copolymers are described in US Pat. Nos. 4,324,684 and 4,411,865, and US Pat. No. 4,530,955 describes the composition of zinc salts and maleic anhydride polymers. The composition is described.

However, the conventional water treatment composition as described above is somewhat different in the effect of preventing corrosion or the ability to suppress scale, but can not expect a satisfactory effect, especially in the case of chromium salts, such as pollution, human toxicity, stability, etc. The problem is regulated.

Therefore, the present invention solves the conventional problems and at the same time provides a method of suppressing corrosion and scale by adding a simple and safe water treatment composition to the wastewater effluent and the cooling water system to recycle wastewater effluent and to be used as cooling water. There is a purpose.

In order to achieve the above object, the present invention adds a composition containing zinc salt, orthophosphate, polyphosphate, phosphonate, azole compound, acrylate copolymer to wastewater and cooling water system, 0.05 to 5 ppm on the basis of orthophosphate, 0.5 to 30 ppm on the basis of orthophosphate ions, 0.5 to 30 ppm on the basis of polyphosphate ions, 0.5 to 30 ppm on the basis of organic phosphate ions, and azole compounds It is a method of suppressing corrosion and scale, characterized in that 0.1 to 10ppm, acrylate copolymer can be maintained at a concentration of 0.1 to 30ppm.

Hereinafter, the present invention will be described in detail.

In the water treatment agent composition according to the present invention, zinc chloride, zinc sulfate, zinc nitrate, and the like, zinc orthophosphate, first sodium phosphate, second sodium phosphate, third sodium phosphate, and phosphoric acid, Sodium hexametaphosphate, sodium pyrophosphate, potassium pyrophosphate, etc., phosphonates include hydroxyethyl diphosphonic acid, hydroxyphosphonocarboxylic acid, aminotrimethylene phosphonic acid, phosphonobutane tricarboxylic acid, and the like. The azole compound may be used tolyltriazole, mercaptobenzothiazole, benzothiazole, and the like, and the acrylate copolymer is used to suppress scale formation of divalent metal salts including zinc salts and carbonate salts. And the structure shown in the following formula (1).

M and n are each an integer of 5 to 1,000, and Each represents a hydrogen atom, an alkyl group or a hydroxy group, , Each represents a hydrogen atom, a methyl group or an ethyl group, Represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, Represents an alkyl group having 1 to 10 carbon atoms or an aralkyl group having 8 to 10 carbon atoms, and X and Y each represent a hydrogen atom, a monovalent metal atom, or N (R ′) (R ″), wherein R ′ and R Represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a hydroxy alkyl group having 1 to 5 carbon atoms, respectively.

The content of zinc salt having a function of inhibiting cathodic reaction during corrosion reaction is preferably 0.05 to 5 ppm, preferably 0.1 to 4.5 ppm, based on zinc ions when the water treatment program is applied. Corrosion may occur and exceeding 5ppm may pose a risk to fish and shellfish during stream discharge.

The content of orthophosphate having the function of suppressing the positive and negative reactions during the corrosion reaction is 0.5 to 30 ppm, preferably 1.0 to 25 ppm, based on orthophosphate ions when the water treatment program is applied, and the content is less than 0.5 ppm. If the anticorrosive ability is lowered and exceeds 30ppm, the risk of calcium salt scale is included.

The content of the polyphosphate having the function of inhibiting cathodic reaction and scale suppression during the corrosion reaction is 0.5 to 30 ppm, preferably 1.0 to 30 ppm, based on polyphosphate ions when the water treatment program is applied, and the content is less than 0.5 ppm. If the anticorrosive ability is lowered, and it exceeds 30ppm, it is economical.

The content of phosphonate which is excellent in inhibiting cathodic reaction and calcium salt scale suppression during corrosion reaction is 0.5 to 30ppm, preferably 1.0 to 25ppm, based on organic phosphate ions when the water treatment program is applied. If it is less than 0.5 ppm, the effect will fall, and if it exceeds 30 ppm, economic efficiency will fall.

In particular, the azole compound having excellent corrosion inhibiting ability of copper and copper compounds is preferably 0.1 to 10 ppm, preferably 0.3 to 8 ppm, based on the concentration of the water treatment program. If exceeded, the economy is lowered.

The acrylate copolymer having a scale inhibiting function in water has a good concentration of 0.1 to 30 ppm, preferably 0.5 to 25 ppm, based on the concentration of the water treatment program. If the content is less than 0.1 ppm, the scale inhibiting effect is lowered. This has the disadvantage of falling.

As described above, the water treatment agent composition of the present invention may be more effectively used to prevent corrosion and to suppress scale that may occur in various industrial water pipes, so that an open or closed circulation cooling water system and a transient cooling water system may be used. Among them, the salt is concentrated in the concentration operation, and therefore, it is particularly effective when used as a water treatment agent of an open circulation cooling water system having high corrosion tendency and scale tendency.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the Examples.

<Examples 1-3, Comparative Examples 1-3>

The corrosion rate was measured by rotating a carbon steel test piece (0.218dm ² ) at a temperature of 45 ° C. for 5 days at a rotational speed of 170 rpm.

At this time, after maintaining each concentration of the water treatment agent components shown in Table 2 in the test water quality of Table 1, the results of the corrosion rate of the test piece is shown in Table 3.

<Examples 4-6, Comparative Examples 4-6>

The test solution was sealed and allowed to stand at 50 ° C. for 25 hours, and then filtered through No. 5 C filter paper to measure total hardness to determine scale inhibition.

At this time, after maintaining each concentration of the water treatment agent components shown in Table 2 in the test water quality of Table 1, the results of the scale inhibition rate is shown in Table 4.

Inhibition rate (%) = (total hardness in the test solution before the test / total hardness in the test solution after the test) x 100

division # One # 2 # 3 pH 8.7 8.2 7.7 Conductivity (μmho / cm) 1,480 2,945 4,890 Ca-H (ppm) 150 300 500 Mg-H (ppm) 50 100 170 Cl ^- (ppm) 200 400 670

Note) pH: adjusted with 0.5N sodium hydroxide solution and 0.5N sulfuric acid solution

Ca-H (calcium hardness): controlled by calcium chloride

Mg-H (magnesium hardness): controlled by magnesium sulfate

Cl ^-: adjusting with sodium chloride

ingredient Content (ppm) Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Orthophosphate 10 12 14 0 10 10 Polyphosphate 4 8 8 0 12 0 Organic Phosphate 4 4 4 0 0 4 Tolyltriazole 2 3 3 0 2 Acrylate copolymer 5 10 10 0 4 5 Zinc ions 2.5 2.0 1.5 0 0 2

Acrylate copolymer: Acumer 2000 by Rohm & Haas

division Corrosion Rate (mdd, mg / (dm ² · day)) # One # 2 # 3 Example 1 5.2 8.4 12.5 Example 2 4.6 6.4 9.2 Example 3 6.8 8.5 11.0 Comparative Example 1 257.8 275.2 266.1 Comparative Example 2 22.9 32.1 54.1 Comparative Example 3 10.1 14.7 17.4

Scale Suppression Ratio (%) # One # 2 # 3 Example 1 87 82 79 Example 2 95 93 90 Example 3 93 91 85 Comparative Example 1 33 27 24 Comparative Example 2 75 67 58 Comparative Example 3 84 79 73

According to Table 3, the corrosion rate of Examples 1 to 3 according to the present invention for the water quality of Table 1 was much slower than that of Comparative Examples 1 to 3, and according to Table 4, Example 4 according to the present invention. The scale suppression rate of -6 showed the higher numerical value in the case of the comparative examples 4-6. Therefore, the water treatment agent according to the present invention was found to have a very good effect of preventing corrosion and scale generation of the metal.

Since the present invention has an oxide film type and a precipitation film type, it is possible to expect an excellent anticorrosive effect by suppressing the anode and cathode reactions, which are electrochemical reactions that may occur on the metal surface, to minimize the conditions where corrosion can occur. The rate copolymer and the phosphonate are excellent in suppressing the scale of the divalent metal salt, especially the total hardness is 1,500 ppm, the electrical conductivity is 6,000 μmho / cm, the M-alkalinity is 500 ppm, the chlorine ion is 1,500 ppm, the silica ion is 150 ppm, and the turbidity is 20 NTU. It has an excellent function of simultaneously suppressing corrosion and scale that may occur in the following water quality.

Claims (6)

A composition containing zinc salt, orthophosphate, polyphosphate, phosphonate, azole compound, and acrylate copolymer is added to the wastewater discharge water and the cooling water system, and the zinc salt is 0.05 to 5 ppm based on zinc ions, orthophosphate 0.5-30 ppm on the basis of orthophosphate ions, 0.5-30 ppm on the basis of polyphosphate ions, 0.5-30 ppm on the basis of organic phosphate ions, 0.1-10 ppm on the azole compound, and acrylate copolymer Corrosion and scale suppression method characterized in that to be maintained at a concentration of 0.1 to 30ppm. The method according to claim 1, wherein the zinc salt is zinc chloride, zinc sulfate or zinc nitrate. The method for inhibiting corrosion and scale according to claim 1, wherein the phosphonate is phosphonobutanetricarboxylic acid, hydroxyethyl diphosphonic acid, hydroxyphosphonocarboxylic acid or aminotrimethylene phosphonic acid. . The method for inhibiting corrosion and scale according to claim 1, wherein the polyphosphate is sodium hexametaphosphate, sodium pyrophosphate or potassium pyrophosphate. The method for inhibiting corrosion and scale according to claim 1, wherein the azole compound is tolyltriazole, mercapto benzothiazole or benzothiazole. The method for suppressing corrosion and scale according to claim 1, wherein the acrylate copolymer has a structure as shown in the following formula (1). M and n are each an integer of 5 to 1,000, and Each represents a hydrogen atom, an alkyl group or a hydroxy group, , Each represents a hydrogen atom, a methyl group or an ethyl group, Represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, Represents an alkyl group having 1 to 10 carbon atoms or an aralkyl group having 8 to 10 carbon atoms, and X and Y each represent a hydrogen atom, a monovalent metal atom, or N (R ′) (R ″), wherein R ′ and R Represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a hydroxy alkyl group having 1 to 5 carbon atoms, respectively.