DD249253A1 - METHOD FOR THE WATER TREATMENT OF REFRIGERATED CIRCUITS - Google Patents

Abstract

The process for water treatment concerns the corrosion inhibition of Kuehlwasserkreislaeufen with simultaneous stabilization of Haertebildnern. The goal is an economical and application-technically simple procedure. The invention solves the problem of simultaneous corrosion-inhibiting, hair-stabilizing and complex-forming water treatment by the use of 1-500 ppm of phosphonic N (diphosphonoethyl) acetamidine and / or its tautomeric form Iminoacetylaminoethandiphosphonsaeure.

Description

CH ^ C = NH

and alkali and (subst.) ammonium salts thereof, optionally mixed with other water treatment components, are added to the cooling water. 2. The method according to claim 1, characterized in that I or I and / or Il in amounts of 1 to 500 ppm, preferably 2-25 ppm are added to the cooling water.

Field of application of the invention

The process for water treatment relates to the corrosion inhibition with simultaneous stabilization of hardness formers.

Characteristic of the known technical solutions

In water-bearing cooling systems, deposition of hardness constituents of the cooling water leads to deposits on the heat exchanger surfaces. This leads to reduced heat transfer, impaired flow through cross-sectional constriction and formation of ventilation elements under the deposits, which strongly promote corrosion. To alleviate or eliminate the described negative effects, depending on the quality of the cooling water, chemicals (corrosion inhibitors, hardness stabilizers, dispersants and biocides) are added.

For lack of suitable substances with simultaneous corrosion-inhibiting and hardness-stabilizing properties, mixtures or the individual components must be added separately, which reduces the effectiveness of the cooling water treatment.

Most known polyphosphonic acids which have good hardness stabilizing and / or complexing properties are not good corrosion inhibitors. This also applies to nitrogen-containing polyphosphonic acids.

The known hardness stabilizer hydroxyethanediphosphonic acid (HEDP) shows unsatisfactory effectiveness as a corrosion inhibitor, under certain conditions it even promotes corrosion. Although mixing with aminotrimethylenephosphonic acid (ATMP) achieves an improved corrosion-inhibiting effect at certain water ratios (US Pat. No. 4,206,45), the achievable protective values are not yet sufficient. Therefore, other alkane diphosphonic acids (eg, 1,2-ethane diphosphonic acid: DE 2624572) and the phosphonocarboxylic acids have been proposed for use. They have the disadvantage that they are either too high in manufacturing costs and / or require too high application rates.

Corrosion inhibiting properties in addition to hardness-stabilizing and / or complexing effectiveness are for

Mixtures of dimethylaminomethanediphosphonic acid with polymeric water-soluble polycarboxylic acids (BE 863904),

Phosphonoadipic acid (US 4208344) and

- For mixtures of ATMP and Diethylentriaminopentamethylenphosphonsäure according to DE 2800457 for mild steel and aluminum

given. The disadvantage of these proposed solutions is that at least one of the required components must be produced with considerable cost burdens or that there are only limited effectiveness or fields of application for the proposed solutions using ATMP.

For further N-containing on the basis of PCI ₃ or H3PO3 or P ₄ O ₆ and cheap organic reaction components such as acetic acid, urea or acetamide produced diphosphonic acids or phosphonic acid mixtures

Ureidoethanediphosphonic acid according to DE 2446749

- N (phosphonomethylene) monoaminoethanmono- and polyphosphonic acids or N (phosphonomethylene) diaminoethanpolyphosphonsäuren according to DE 2737410

- N (diphosphonoethyl) acetamidine according to DE 2316396

- Substituted aminoethane diphosphonic acid according to DE 2203340

- N-acetylaminoethanediphosphonic acid according to DE 2519264

- Aminoalkandiphosphonic according to DE 2625767

Only hardness-stabilizing and / or complex-forming properties have been described.

Object of the invention

The aim of the invention is an economical and application-technically simple method for water treatment of systems and plants, in particular for cooling water treatment.

Explanation of the essence of the invention

The object of the invention is to use a phosphonic acid which, in addition to the corrosion-inhibiting activity, also has simultaneously hardness-stabilizing and complex-forming properties.

It has been found that when using the phosphonic acid N (diphosphonoethyl) -acetamine

for X = H, alkali, (subst.) ammonium

and / or their tautomeric form Iminoacetylaminoethandiphosphonsäure

CH ₃ -C = NH

and alkali metal salts and (subst.) ammonium salts which can be prepared therefrom in cooling-water circulation systems in amounts of from 1 to 500 ppm, preferably from 2 to 25 ppm, optionally in admixture with other water treatment components, effective corrosion inhibition is achieved with simultaneous hardness stabilization. The phosphonic acids or their salts reduce or prevent the corrosion in open as well as in closed cooling circuits. I and / or Il can also be used in a variety of hot water or hot water systems. The corrosion-inhibiting properties are not limited to iron and steel, but also to copper, its alloys and other metals.

I and / or II are alone as well as in admixture with other corrosion inhibiting substances, eg. B.

N-Acetylaminoethandiphosphonsäure Zn and phosphate ions, hardness-stabilizing compounds and dispersants used. The advantageous effectiveness is achieved with substance quantities which are sufficient for an effective hardness stabilization of the water: normally 2-25 ppm. The simultaneous effectiveness as a corrosion inhibitor as well as a hardness stabilizer promotes economic use. Compared to known water treatment agents such as ATMP and HEDP significantly improved effects.

In the phase of pretreatment of a cooling circuit system is advantageously carried out with increased concentration, for. B.

five times the amount of the permanent concentration otherwise used.

I and / or II can also be used in already corrosion-damaged circulatory systems. They prevent further corrosion and limit these to values that are also achieved in newly commissioned circulatory systems.

In higher concentrations, the good complexing effect of I and / or II can be used to remove or dissolve already formed precipitates and deposits.

embodiment

The process of the invention is illustrated by the following examples:

example 1

In this example, the hardness-stabilizing activity is demonstrated. Water with a calcium hydrogen carbonate content of 2.5 mmol / l is mixed with an appropriate amount of hardness stabilizer (eg 2.5 mg / l). This water is heated with intensive aeration to 40,60 or 80 ⁰ C. The decrease of the calcium bicarbonate content after 48 h becomes analytical

determined and compared to the initial concentration of calcium bicarbonate (100%) indicated.

Sample A: without additive

Sample B: Hydroxyethanediphosphonic Acid (HEDP)

Sample C: Aminotrimethanephosphonic Acid (ATMP)

Sample D: Monoammonium salt of N (diphosphonoethyl) acetamine χ H ₂ O

Sample E: Sample D in a mixture with orthophosphate in a molar ratio of about 3: 1

Sample F: iminoacetylaminoethanediphosphonic acid

sample P content amount Hardness stabilization (%) 80 ° C / 48h 12 d. sample 40 ° C / 48h 60 ° C / 48h 20 58 A - 24 95 46 B 30.1% 2.5 mg / l 100 72 46 C 25.3% 2.5 mg / l - 85 43 D 20.1% 2.5 mg / l 100 77 65 e 22.4% 2.5 mg / l 100 96 46 F 25.0% 2.5 mg / l 100 85 2.0 mg / l 100

Example 2

In this example, the corrosion-inhibiting activity is demonstrated. For this purpose, flow tests were carried out over 28 days on tube samples made of unalloyed steel ST 35 with gravimetric evaluation. The calculated from corrosion rates after 28 days, GKG ^28, and in the second half of the experiment, TKG ^14, allow on the determination of the corresponding protection values, S ^GKG and S ^TKG, and the amount of deposits obtained, + At ^28, a comparison of the effectiveness of used compounds

 Table 1 characterizes the different synthetic cooling waters used in the examples.

Table 1: Coolant compositions Composition

Cooling water designation KWV KWVI

KWVII

(mg / l СГ) ) ) GKG ²⁸ 150 15m / s TKG ¹⁴ 400 _s tkg 700 + On ²⁸ (mg / l SO ₄ "" (Mm / a) 150 (Mm / a) 600 (%) 1500 (G) (mg / ICa ⁺⁺ ) 0.422 2 0.486 40 0 87 3,074 (mg / IMg ⁺⁺ Flow rate: 0, 0,432 5 0,350 25 28 50 1,853 (Mmol / l) Conc. 0.1 2.0 4.2 (Mg / l) 0,041 7.9 0.023 8.1 95 8.2 0.108 chloride - sulfate 37 0,039 0,014 _s gkg 97 0,095 calcium 2 (%) magnesium 22 0 Ks, 4.3 2 0 PH value 26 a) cooling water V, 35 ° C, 2 90 sample 91 without inhibitor Sample B + Zn ⁺⁺ Sample E + Zn ⁺⁺ Sample F + Zn ⁺⁺

v) cooling water Vl, 35 ° C, flow rate 0.15m / s

sample

Conc. (Mg / l)

GKG ²⁸ (mm / a)

TKG ¹⁴ (mm / a)

GKG

_s tkg

+ On ²⁸

(G)

without inhibitor - 0.334 0,383 0 0 2,179 Sample C 10 0,430 0,581 -29 -20 2,266 Sample F 8th 0,049 0,040 85 93 0,159 Sample B 37 0.063 0.074 81 81 0,575 + Zn ⁺⁺ 2 Sample F 20 0,015 0,015 96 96 0.112 + Zn ⁺⁺ 2

с) cooling water VII, 35 ° С, flow rate 0,15m / s

sample Conc. GKG ²⁸ TKG ¹⁴ gGKG _s tkg + On ²⁸ (Mg / l) (Mm / a) (Mm / a) (%) (%) (G) without inhibitor - 0.370 0,280 0 0 1,845 Sample B 15 0,133 0.096 64 66 0.605 Sample E 9 0.031 0,021 92 93 0,122 Sample F 8th 0,051 0,042 86 85 0,160 Sample E 9 0,030 0,018 92 94 0,065 + Zn ⁺⁺ 2 Sample E 22 0,012 0,012 97 96 0.046 + Zn ⁺⁺ 2

Claims (1)

1. A process for the water treatment of cooling circuits with simultaneous corrosion inhibition and stabilization of hardness formers, characterized in that the phosphonic acid N (diphosphonoethyl) acetamidine но ^ S CH ₃ -C-NH ₂ for X = H, alkali, (subst.) ammonium and / or their tautomeric form Iminoacetylaminoethandisphosphonsäure